The antitumour antibiotic actinomycin D normally binds to DNA by intercalation at sequences containing the CpG step, but in the presence of daunomycin it has been reported to interact with poly(dA-dT). This observation has neither been confirmed nor explained. Here we have used a photoreactive 7-azido derivative of actinomycin to study the effect of daunomycin on its binding to three DNA fragments. Daunomycin did indeed alter the binding of actinomycin to the DNA, such that the antibiotic was displaced from its primary GpC sites onto secondary sites in the DNA, though not to AT regions especially. These findings suggest a possible scientific explanation for the increased toxicity seen during combination chemotherapy with these two drugs.
Periodontal disease is characterized by both inflammation and bone loss. Advances in research in both these areas have led to a new appreciation of not only each field but also the intimate relationship between inflammation and bone loss. This relationship has resulted in a new field of science called osteoimmunology and provides a context for better understanding the pathogenesis of periodontal disease. In this review, we discuss several aspects of the immuno-inflammatory host response that ultimately results in loss of alveolar bone. A proposal is made that periodontal inflammation not only stimulates osteoclastogenesis but also interferes with the uncoupling of bone formation and bone resorption, consistent with a pathologic process. Furthermore, arguments based on experimental animal models suggest a critical role of the spatial and temporal aspects of inflammation in the periodontium. A review of these findings leads to a new paradigm to help explain more fully the impact of inflammation on alveolar bone in periodontal disease so that it includes the effects of inflammation on uncoupling of bone formation from resorption.
adaptive immunity; bone matrix; cytokine; innate immunity; IL-1; osteoblast; osteoclast; RANK ligand; TNF
Fracture healing and distraction osteogenesis have important applications in orthopedic, maxillofacial, and periodontal treatment. In this review, the cellular and molecular mechanisms that regulate fracture repair are contrasted with bone regeneration that occurs during distraction osteogenesis. While both processes have many common features, unique differences are observed in the temporal appearance and expression of specific molecular factors that regulate each. The relative importance of inflammatory cytokines in normal and diabetic healing, the transforming growth factor beta superfamily of bone morphogenetic mediators, and the process of angiogenesis are discussed as they relate to bone repair. A complete summary of biological activities and functions of various bioactive factors may be found at COPE (Cytokines & Cells Online Pathfinder Encyclopedia), http://www.copewithcytokines.de/cope.cgi.
Fracture healing; distraction osteogenesis; morphogens; cytokines
Although it is known that diabetes impairs oral wound healing, relatively little is known about the cellular parameters affected, particularly in connective tissue. This study investigated the hypothesis that diabetes impairs connective tissue formation in healing gingiva, and that impaired healing is associated with factors that decrease fibroblast numbers. Full-thickness wounds were created in the palatal gingiva of type 1 and type 2 diabetic and normoglycemic mice. Five days after wounding, diabetic mice had less epithelial wound coverage, less new connective tissue formation, and reduced fibroblast density (p < 0.05). This occurred with increased numbers of caspase-3- and TUNEL-positive fibroblasts, decreased fibroblast proliferation, increased nuclear translocation of the pro-apoptotic transcription factor FOXO1, and increased numbers of polymorphonuclear leukocytes, all of which were significant (p < 0.05). The results suggest that diabetes may decrease fibroblast numbers through increased apoptosis and reduced proliferation, both of which may be mediated through increased activation of FOXO1.
diabetes; wound healing; apoptosis; fibroblast; FOXO1
Variations in the balance between cell proliferation and apoptosis could contribute to the etiology of gingival overgrowth. The aim of this study was to test the hypothesis that, in fibrotic gingival lesions, fibroblast proliferation is stimulated and apoptosis is decreased. Apoptotic index, caspase 3 expression, the proliferative index, FOXO1 expression, and histological inflammation were measured in situ. Analysis of data showed that apoptosis decreased in all forms of gingival overgrowth examined (p < 0.05), and inflammation caused a small but significant increase compared with non-inflamed tissues (p < 0.05). The greatest decrease of apoptosis occurred in the most fibrotic tissues. Cell proliferation was elevated in all forms of gingival overgrowth tested, independent of inflammation (p < 0.05). To identify potential mechanisms of transcriptional regulation of apoptosis, we assessed FOXO1 and caspase 3 expression levels and found them to correlate well with diminished apoptosis. Analysis of data suggests that increased fibroblast proliferation and a simultaneous decrease in apoptosis contribute to gingival overgrowth.
gingival overgrowth; fibrosis; fibroblast; apoptosis; FOXO1
Using a ligature-induced model in type-2 Zucker diabetic fatty (ZDF) rat and normoglycemic littermates, we investigated whether diabetes primarily affects periodontitis by enhancing bone loss or by limiting osseous repair. Diabetes increased the intensity and duration of the inflammatory infiltrate (P < 0.05). The formation of osteoclasts and percent eroded bone after 7 days of ligature placement was similar, while four days after removal of ligatures, the type 2 diabetic group had significantly higher osteoclast numbers and activity (P < 0.05). The amount of new bone formation following resorption was 2.4- to 2.9- fold higher in normoglycemic vs. diabetic rats (P < 0.05). Diabetes also increased apoptosis and decreased the number of bone-lining cells, osteoblasts, and periodontal ligament fibroblasts (P < 0.05). Thus, diabetes caused a more persistent inflammatory response, greater loss of attachment and more alveolar bone resorption, and impaired new bone formation. The latter may be affected by increased apoptosis of bone-lining and PDL cells.
bone coupling; cell death; bacteria; gingiva; hyperglycemia; inflammation; infection; in vivo; periodontitis
Episodic ataxia type 1 (EA1) is a monogenic channelopathy caused by mutations of the potassium channel gene KCNA1. Affected individuals carrying the same mutation can exhibit considerable variability in the severity of ataxia, neuromyotonia, and other associated features. We investigated the phenotypic heterogeneity of EA1 in 2 sets of identical twins to determine the contribution of environmental factors to disease severity. One of the mutations was also found in a distantly related family, providing evidence of the influence of genetic background on the EA1 phenotype.
We evaluated 3 families with an EA1 phenotype, 2 of which included monozygotic twins. We sequenced the KCNA1 gene and studied the biophysical consequences of the mutations in HEK cells.
We identified a new KCNA1 mutation in each pair of twins. Both pairs reported striking differences in the clinical severity of symptoms. The F414S mutation identified in one set of twins also occurred in a distantly related family in which seizures complicated the EA1 phenotype. The other twins had an R307C mutation, the first EA1 mutation to affect an arginine residue in the voltage-sensor domain. Both mutants when expressed exerted a dominant-negative effect on wild-type channels.
These results broaden the range of KCNA1 mutations and reveal an unexpectedly large contribution of nongenetic factors to phenotypic variability in EA1. The occurrence of epilepsy in 1 of 2 families with the F414S mutation suggests an interplay of KCNA1 with other genetic factors.
= episodic ataxia type 1.
The role of TNF-α in impaired wound healing in diabetes was examined by focusing on fibroblasts.
Small excisional wounds were created in the db/db mice model of type 2 diabetes and normoglycaemic littermates, and in a streptozotocin-induced type 1 diabetes mouse model and control mice. Fibroblast apoptosis was measured by the TUNEL assay, proliferation by detection of proliferating cell nuclear antigen, and forkhead box O1 (FOXO1) activity by DNA binding and nuclear translocation. TNF-α was specifically inhibited by pegsunercept.
Diabetic wounds had increased TNF-α, fibroblast apoptosis, caspase-3/7 activity and activation of the pro-apoptotic transcription factor FOXO1, and decreased proliferating cell nuclear antigen positive fibroblasts (p<0.05). TNF-α inhibition improved healing in the diabetic mice and increased fibroblast density. This may be explained by a decrease in fibroblast apoptosis and increased proliferation when TNF-α was blocked (p <0.05). Although decreased fibroblast proliferation and enhanced FOXO1 activity were investigated in type 2 diabetes, they may also be implicated in type 1 diabetes. In vitro, TNF-α enhanced mRNA levels of gene sets related to apoptosis and Akt and p53 but not mitochondrial or cell-cycle pathways. FOXO1 small interfering RNA reduced gene sets that regulate apoptosis, Akt, mitochondrial and cell-cycle pathways. TNF-α also increased genes involved in inflammation, cytokine, Toll-like receptor and nuclear factor-kB pathways, which were significantly reduced by FOXO1 knockdown.
These studies indicate that TNF-α dysregulation in diabetic wounds impairs healing, which may involve enhanced fibroblast apoptosis and decreased proliferation. In vitro, TNF-α induced gene sets through FOXO1 that regulate a number of pathways that could influence inflammation and apoptosis.
Diabetes; Fibroblast; FOXO; Nuclear translocation; PCNA; Proliferation; TNF-α
The m.8993T→C MTATP6 mutation of mitochondrial DNA (mtDNA) usually causes mitochondrial disease in childhood, but was recently described in a family with adult onset ataxia and polyneuropathy. Cytochrome c oxidase muscle histochemistry, which is the standard clinical investigation for mitochondrial disease in adults, is usually normal in patients with MTATP6 mutations. This raises the possibility that these cases have been missed in the past. We therefore studied 308 patients with unexplained ataxia and 96 patients with suspected Charcot–Marie–Tooth disease to determine whether the m.8993T→C MTATP6 mutation is common in unexplained inherited ataxia and/or polyneuropathy. We identified a three‐generation family with the m.8993T→C mutation of mtDNA. One subject had episodic ataxia (EA) and transient hemipareses, broadening the phenotype. However, no further cases were identified in an additional cohort of 191 patients with suspected EA. In conclusion, m.8993T→C MTATP6 should be considered in patients with unexplained ataxia, CMT or EA, but cases are uncommon.
Monocyte chemoattractant protein 1 (MCP-1) is an important chemokine that induces monocyte recruitment in a number of different pathologies, including infection. To investigate the role of MCP-1 in protecting a host from a chronic interstitial polymicrobial infection, dental pulps of MCP-1−/− mice and controls were inoculated with six different oral pathogens. In this model the recruitment of leukocytes and the impact of a genetic deletion on the susceptibility to infection can be accurately assessed by measuring the progression of soft tissue necrosis and osteolytic lesion formation. The absence of MCP-1 significantly impaired the recruitment of monocytes, which at later time points was threefold higher in the wild-type mice than in MCP-1−/− mice (P < 0.05). The consequence was significantly enhanced rates of soft tissue necrosis and bone resorption (P < 0.05). We also determined that the MCP-1−/− mice were able to recruit polymorphonuclear leukocytes (PMNs) to a similar or greater extent as controls and to produce equivalent levels of Porphyromonas gingivalis-specific total immunoglobulin G (IgG) and IgG1. These results point to the importance of MCP-1 expression and monocyte recruitment in antibacterial defense and demonstrate that antibacterial defense is not due to an indirect effect on PMN recruitment or modulation of the adaptive immune response.
We have developed a method to study the primary sequence specificities of protein kinases by using an oriented degenerate peptide library. We report here the substrate specificities of eight protein Ser/Thr kinases. All of the kinases studied selected distinct optimal substrates. The identified substrate specificities of these kinases, together with known crystal structures of protein kinase A, CDK2, Erk2, twitchin, and casein kinase I, provide a structural basis for the substrate recognition of protein Ser/Thr kinases. In particular, the specific selection of amino acids at the +1 and -3 positions to the substrate serine/threonine can be rationalized on the basis of sequences of protein kinases. The identification of optimal peptide substrates of CDK5, casein kinases I and II, NIMA, calmodulin-dependent kinases, Erk1, and phosphorylase kinase makes it possible to predict the potential in vivo targets of these kinases.
Chemokines are a family of low-molecular-weight proinflammatory cytokines that stimulate recruitment of leukocytes. The chemokines interleukin-8 (IL-8) and monocyte chemoattractant protein 1 (MCP-1) are relatively specific chemoattractants for neutrophils and monocytes, respectively. Chemokine expression contributes to the presence of different leukocyte populations observed in normal and pathologic states. In the present studies, peripheral blood mononuclear cells (PBMC) were stimulated by microbes (Candida albicans, Streptococcus mutans, Porphyromonas gingivalis, and Actinobacillus actinomycetemcomitans) selected based upon their importance as oral pathogens. IL-8 and MCP-1 gene expression and protein release were determined by Northern blot (RNA blot) analysis and enzyme-linked immunosorbent assay. C. albicans, P. gingivalis, and A. actinomycetemcomitans induced high levels of production of both MCP-1 and IL-8. S. mutans was a strong inducer of MCP-1, but it did not stimulate significant production of IL-8. C. albicans, S. mutans, and A. actinomycetemcomitans were 500 to 5,000 times more potent than P. gingivalis in terms of MCP-1 production. In general, the microbe-to-PBMC ratios required for maximum gene expression of MCP-1 were lower than those for IL-8. However, for actual protein release of MCP-1 versus IL-8, differences in the effects of various microbe concentrations were observed only for A. actinomycetemcomitans. These results demonstrate that different oral pathogens induce specific dose-dependent patterns of chemokine gene expression and release. Such patterns may help explain the immunopathology of oral infections, particularly with regard to inflammatory leukocyte recruitment.
Pneumocystis carinii has been shown to cause extra-alveolar infections in humans, but the lack of a reproducible animal model has hindered the elucidation of mechanisms of P. carinii dissemination. In the present study, PCR and the immunosuppressed rat model were used to gain further insight into the dissemination of P. carinii organisms in extrapulmonary (EP) tissues. Primer sequences specific to major surface glycoprotein (MSG) and dihydrofolate reductase (DHFR) were used to detect P. carinii in lungs and EP tissues. Sprague-Dawley rats were grouped into two classes: one group included rats that had primary episodes of pneumocystosis and the other group included rats that had undergone treatment for P. carinii infection and that had second episodes of pneumocystosis. PCR analysis with MSG primers with tissues obtained from both groups of rats showed the presence of P. carinii DNA in adrenal tissue, bone marrow, blood, and heart, kidney, liver, lymph node, spleen, and thyroid tissues. Reverse transcriptase-PCR (RT-PCR) analysis was carried out with DHFR primers with lung, spleen, heart, kidney, and liver tissues from both groups of rats. Only those tissues that showed a positive PCR result and hybridization signal for the MSG gene were used for the RT-PCR experiments. RT-PCR analysis showed that the P. carinii DHFR gene is actively transcribed in these tissues, thereby indicating the presence of viable P. carinii organisms in EP tissues. Our observations suggest that P. carinii dissemination is influenced by factors other than P. carinii chemotherapy and that heavy organism load and destruction of lung tissue may contribute to the dissemination of P. carinii. The study provides an animal model that can be used for further investigations of the causes of EP pneumocystosis.
Gingival inflammation is initiated by bacterial colonization on the tooth surface. It is characterized by infiltration of mononuclear cells, a common feature of many forms of chronic inflammation. Monocyte chemoattractant protein 1 (MCP-1) is the predominant monocyte chemoattractant secreted by a variety of different cells in vitro. For this report, we examined MCP-1 expression in bacterially induced gingival inflammation by immunohistochemistry and in situ hybridization. The cell types expressing MCP-1 are identified as vascular endothelial cells and monocytes/macrophages. Correlation analysis shows that the number of cells expressing MCP-1 is related to the degree of inflammation. Our finding that MCP-1 is expressed in inflamed gingival tissue suggests that MCP-1 plays an important role in the recruitment of monocytes and amplification of inflammatory signals in bacterially induced inflammation.
A repetitive genomic DNA clone (B12-2) that specifically hybridizes to Pneumocystis carinii DNA has been identified. No cross-hybridization to genomic DNA prepared from bacteria, other fungi, protozoa, or mammals was observed. Clone B12-2 is multiply represented in the P. carinii genome. By direct hybridization to DNA prepared from the lungs of immunosuppressed rats, the probe can detect the equivalent of fewer than 1,000 P. carinii organisms. A hybridization assay employing clone B12-2 has been developed to quantitate organism load in the rat model for P. carinii. Application of the assay to track the accumulation of organisms during the immunosuppression regimen as well as to monitor the efficacy of two drug therapies used clinically for the treatment of P. carinii pneumonia is described here. The clone B12-2 hybridization assay for the determination of P. carinii organism load possesses several advantageous features and thus should serve to complement conventional staining and immunohistochemical methods.
Ceftazidime is widely used in the therapy of infectious complications in neutropenic patients. We studied an outbreak of ceftazidime-resistant gram-negative bacillary infections in pediatric cancer patients receiving empirical ceftazidime therapy for neutropenic fever. Fourteen isolates (12 Klebsiella pneumoniae and 2 Escherichia coli) from 13 patients were studied. Specimens were obtained from multiple clinical sites including blood, urine, throat, and lung. The organisms were resistant to ceftazidime, aztreonam, and penicillins but remained susceptible to cephamycins and imipenem. All resistant isolates produced a novel beta-lactamase (TEM-26) with a pI of approximately 5.58, which was transferred by transformation to E. coli on a 7.9-kb nonconjugative plasmid which cotransferred resistance to trimethoprim-sulfamethoxazole. This enzyme readily hydrolyzed ceftazidime, aztreonam, and penicillins in a spectrophotometric assay. DNA sequencing data suggest that TEM-26 is derived from TEM-1.
Simple enzymatic assays to detect heat-labile enterotoxins whose modes of action are similar to that of cholera toxin were evaluated. The assays are performed by using an artificial substrate, diethylamino benzylidine-aminoguanidine, which is an ADP-ribose acceptor. The product, formed in the presence of NAD+, can be quantitated by spectrofluorometric, spectrophotometric, or high-performance liquid chromatographic (HPLC) methods. As little as 25 ng (spectrofluorometry) or 125 ng (spectrophotometry or HPLC) of cholera toxin can be detected in an assay volume of 250 microliters. The detection limit for heat-labile enterotoxin by either the spectrophotometric or HPLC methods was 125 ng/250 microliters. Because the results are quantitative, the enzymatic methods can be used for medium development, determination of factors that influence toxin production, and other applications that heretofore could be accomplished only with difficulty. The enzymatic methods add a new dimension to the assay of toxins that ribosylate arginine residues of proteins. Sensitivities of the assays might be improved by developing better synthetic substrates, and applications could be broadened by the development of artificial substrates containing other functional groups.
We developed a modified double-antibody sandwich enzyme-linked immunosorbent assay (ELISA) that detected relatively low concentrations of known Pneumocystis carinii antigen added to buffer or rat sera. Artificial immunization-derived polyclonal rabbit anti-P. carinii antibody was used on the solid phase to capture the antigen. Infection-derived (after P. carinii pneumonia) polyclonal rat anti-P. carinii antibody or a mixture of five murine monoclonal antibodies was used as the antigen detector antibody. Rabbit anti-rat immunoglobulin G antibody or goat anti-mouse immunoglobulin G antibody conjugated to alkaline phosphatase was used as the final antibody. After standardization and optimization of the various reactants in this ELISA system, approximately 53 ng of known P. carinii antigen per ml suspended in phosphate-buffered saline-Tween 20 buffer or 210 ng of antigen per ml suspended in normal rat serum diluted 1:4 could be detected. In addition, an indirect ELISA for P. carinii antibody measurement was developed, using as the antigen a soluble supernatant from a sonicated preparation of Percoll-purified whole cysts and trophozoites to coat the solid phase. Limited studies with sera from a small number of caesarian-obtained, barrier-sustained rats from Charles River Breeding Laboratories, Inc., and the National Institutes of Health and sera from normal and heavily infected rats indicated that the caesarian-obtained, barrier-sustained rats had negligible levels of antibody. The normal and heavily infected rats had variable antibody titers. A significantly high level of P. carinii antigenemia was detected in only 2 (11%) of 18 heavily infected rats. Extensive studies of the P. carinii pneumonia rat model with the ELISA did not reveal significant serum P. carinii antigenemia during the acute stage of infection. However, soluble P. carinii antigen was detected by the ELISA and Western blot assays in the supernatant of lavage fluid after centrifugation to sediment intact organisms. As expected, P. carinii antigens were detected by these assays in the lavage pellet recovered after centrifugation. In conclusion, the antigen assay used in this study detected P. carinii antigen in lung lavage but failed to detect P. carinii antigen in rat serum during the acute phase of infection.
The major Pneumocystis carinii antigens inducing antibody responses in infected hosts were identified by Western immunoblotting techniques. The biochemical nature of these antigens was also elucidated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by protein staining revealed a major component with a molecular weight (MW) of greater than 205,000. This major component disappeared and a new major protein staining component of approximately 110,000 to 116,000 MW appeared when electrophoresis was done in the presence of beta-mercaptoethanol. Periodic acid-Schiff staining revealed that this major component contains carbohydrate moieties. A major component in the 55,000- to 60,000-MW region was visible with periodic acid-Schiff stain, but not with a protein stain, after electrophoresis in the presence of beta-mercaptoethanol. The majority of sera tested from humans with diagnosed pneumocystosis and from rats allowed to recover from steroid-induced pneumocystosis reacted strongly with 110,000- to 116,000-, and 55,000- to 60,000-MW components. These sera often, but not always, detected antigens with MWs of approximately 170,000, 125,000, and 30,000 to 32,000. The data suggest that the antigenic composition of P. carinii is relatively complex and that rat and human P. carinii probably share antigenic determinants. Competitive studies between infection-derived human and rat antisera for the major rat P. carinii components revealed competition; rat antisera appeared to recognize a greater range of antigenic epitopes than did human antisera. Protease treatment of the antigenic components that had been immobilized on nitrocellulose paper destroyed their antigenic reactivity with rat antibody. Treatment with sodium periodate decreased reactivity of this 110,000- to 116,000-MW component and completely destroyed the reactivity of the 55,000- to 60,000-MW component with rat antibody.
Hybridoma-producing monoclonal antibodies against Pneumocystis carinii were produced by the fusion of nonsecreting mouse myeloma cells (P3X63-Ag8.653) with splenocytes from BALB/c mice that had been immunized with partially purified preparations of P. carinii. Of 227 hybridoma clones producing antibodies against P. carinii, as measured by an enzyme-linked immunosorbent assay, 12 monoclonal antibodies showing the highest reactivity in the enzyme-linked immunosorbent assay were further characterized. The majority (11 of 12) of the monoclonal antibodies did not cross-react with Candida albicans, Cryptococcus neoformans, Histoplasma capsulatum, or Mycobacterium avium as determined by absorption experiments. By using the indirect immunofluorescence assay, serological reactivity was shown for these antibodies with titers ranging from 1:40 to 1:10,240. By using a competitive binding assay, these 12 monoclonal antibodies could be divided into seven groups, each group reacting with a different antigenic determinant of P. carinii. Sodium dodecyl sulfate-polyacrylamide gradient gel electrophoresis of P. carinii, followed by Western immunoblot analysis, allowed the identification of one major antigen with an apparent molecular weight of 110,000 by all 12 monoclonal antibodies. Other minor bands with molecular weights of approximately 116,000, 90,000, 55,000, and 35,000 were recognized by several of the monoclonal antibodies.
Monoclonal antibodies were produced against parainfluenza virus type 3 (PI-3) and used to identify PI-3 clinical isolates in cell culture and PI-3 antigen in cells obtained from nasopharyngeal (NP) washes of patients. Two (2E9 and 4G5) of the three monoclonal antibodies characterized reacted by immunoblotting with a 67,000-dalton PI-3 protein, and one antibody (4E5) reacted with two viral proteins in the range of 29,000 to 31,000 daltons. The three monoclonal antibodies did not cross-react by indirect immunofluorescence (IFA) with PI-1 or PI-2 and identified by IFA 18 isolates of PI-3 in cell culture. The 2E9 antibody reacted with PI-3 antigen in cells of 8 NP wash specimens that also yielded PI-3 in cell culture. Cells from 12 specimens reactive by IFA for respiratory syncytial virus, 1 specimen yielding adenovirus in cell culture, and 5 specimens yielding influenza virus were not reactive.
Ten selected murine hybridoma cell lines that produce monoclonal antibodies against M type 5 Streptococcus pyogenes and human heart antigen were isolated. All of the monoclonal antibodies studied were determined to be the immunoglobulin M isotype. The antibodies were characterized on the basis of their reactions with Triton X-100-extracted whole human heart antigens, sodium dodecyl sulfate-extracted sarcolemmal antigens, and whole streptococci or their membranes. Enzyme-linked immunosorbent assays and Western immunoblotting techniques were used to compare the reactivity of the monoclonal antibodies. All 10 of the antibodies were first selected for their reactivity with Triton X-100-extracted heart antigens and whole group A, M type 5 streptococci. These antibodies were then divided into two categories: strong reactors or weak reactors with human sarcolemmal and streptococcal membranes. Among the strong reactors, two different types of monoclonal antibodies were observed on the basis of their immunobanding patterns with sarcolemmal and streptococcal membranes on Western blots. Monoclonal antibodies that were strong reactors with sarcolemmal and group A streptococcal membrane antigen were directed against a determinant on a family of proteins. The major reactants of sarcolemmal extracts were high-molecular-weight proteins near 200,000. Some monoclonal antibodies demonstrated more specificity for the heart than did others when reacted with separated Triton X-100-extracted tissue antigens from the heart, kidney, and skeletal muscle. One of the monoclonal antibodies that reacted with group A streptococci reacted with a Triton X-100-extracted heart antigen ca. 40,000 daltons in size. None of these monoclonal antibodies opsonized type 5 Streptococcus pyogenes, and in enzyme-linked immunosorbent assays most of the antibodies were found to react to a lesser degree with other groups of streptococci. Monoclonal antibody was used to probe normal and rheumatic sarcolemma for differences in reactivity. Although the rheumatic heart reacted more intensely, no major differences between the immunobanding patterns of normal and rheumatic hearts were observed.
A comparison of the direct agglutination test and the indirect hemagglutination test for the detection of blood serum antibodies to Escherichia coli organisms indicated that these serological tests were comparable. In some instances the indirect hemagglutination test provided higher endpoint readings. Preparation of the antigens for the indirect hemagglutination test was more time consuming than for the direct agglutination test. Crude extract and purified polysaccharides were comparable as red blood cell sensitizing agents.
The DNA photoaffinity ligands, 7-azidoactinomycin D and 8-azidoethidium, form DNA adducts that cause chain cleavage upon treatment with piperidine. Chemical DNA sequencing techniques were used to detect covalent binding. The relative preferences for modifications of all possible sites defined by a base pair step (e.g. GC) were determined within all quartet contexts such as (IGCJ). These preferences are described in terms of 'effective site occupations', which express the ability of a ligand to covalently modify some base in the binding site. Ideally, the effective site occupations measured for photoaffinity agents can also be related to site-specific, non-covalent association constants of the ligand. The sites most reactive with 7-azidoactinomycin D were those preferred for non-covalent binding of unsubstituted actinomycin D. GC sites were most reactive, but next-nearest neighbors exerted significant influences on reactivity. GC sites in 5'-(pyrimidine)GC(purine)-3' contexts, particularly TGCA, were most reactive, while reactivity was strongly suppressed for GC sites with a 5'-flanking G, or a 3'-flanking C. High reactivities were also observed for bases in the first (5') GG steps in TGGT, TGGG and TGGGT sequences recently shown to bind actinomycin D with high affinity. Pyrimidine-3',5'-purine steps and GG steps flanked by a T were most preferred by 8-azidoethidium, in agreement with the behavior of unsubstituted ethidium. The good correspondence between expected and observed covalent binding preferences of these two azide analogs demonstrates that photoaffinity labeling can identify highly preferred sites of non-covalent DNA binding by small molecules.
The equilibrium binding of the antitumor agent m-AMSA (4'-(9-acridinylamino) methane-sulfon-m-ansidide) has been examined by optical methods. These studies which have focused on the low bound drug concentrations (r values less than 0.02, base pairs) reveal m-AMSA to bind calf thymus DNA in a highly cooperative manner as indicated by the initial positive slope of the Scatchard plot. In contrast, the studies on the parent 9-aminoacridine under identical conditions demonstrate that this compound binds DNA in a noncooperative (neighbor exclusion) manner. The positive cooperative binding phenomenon of m-AMSA is probed as a function of ionic concentration and shown to exist over the range of salt concentrations examined (0.01 to 0.1 M); however, the magnitude of the cooperative binding is altered. This observation of cooperativity is consistent with earlier studies on biologically active compounds and may be related to such binding parameters as binding sequence selectivity and/or structural perturbations to the DNA structure.