Mesenchymal stem-cell based therapies have been
proposed as novel treatments for intervertebral disc degeneration,
a prevalent and disabling condition associated with back pain. The
development of these treatment strategies, however, has been hindered
by the incomplete understanding of the human nucleus pulposus phenotype
and by an inaccurate interpretation and translation of animal to
human research. This review summarises recent work characterising
the nucleus pulposus phenotype in different animal models and in
humans and integrates their findings with the anatomical and physiological
differences between these species. Understanding this phenotype
is paramount to guarantee that implanted cells restore the native
functions of the intervertebral disc.
Cite this article: Bone Joint Res 2013;2:169–78.
Intervertebral disc; Disc degeneration; Nucleus pulposus; Phenotype; Cell-based therapies; Mesenchymal stem cells; Animal models
Mortality risk across metabolic health-by-BMI categories in NHANES-III was examined. Metabolic health was defined as: (1) homeostasis model assessment-insulin resistance (HOMA-IR) <2.5; (2) ≤2 Adult Treatment Panel (ATP) III metabolic syndrome criteria; (3) combined definition using ≤1 of the following: HOMA-IR ≥1.95 (or diabetes medications), triglycerides ≥1.7 mmol/L, HDL-C <1.04 mmol/L (males) or <1.30 mmol/L (females), LDL-C ≥2.6 mmol/L, and total cholesterol ≥5.2 mmol/L (or cholesterol-lowering medications). Hazard ratios (HR) for all-cause mortality were estimated with Cox regression models. Nonpregnant women and men were included (n = 4373, mean ± SD, age 37.1 ± 10.9 years, BMI 27.3 ± 5.8 kg/m2, 49.4% female). Only 40 of 1160 obese individuals were identified as MHO by all definitions. MHO groups had superior levels of clinical risk factors compared to unhealthy individuals but inferior levels compared to healthy lean groups. There was increased risk of all-cause mortality in metabolically unhealthy obese participants regardless of definition (HOMA-IR HR 2.07 (CI 1.3–3.4), P < 0.01; ATP-III HR 1.98 (CI 1.4–2.9), P < 0.001; combined definition HR 2.19 (CI 1.3–3.8), P < 0.01). MHO participants were not significantly different from healthy lean individuals by any definition. While MHO individuals are not at significantly increased risk of all-cause mortality, their clinical risk profile is worse than that of metabolically healthy lean individuals.
Juvenile myoclonic epilepsy (JME) is characterized by myoclonic jerks of the upper limbs, often triggered by cognitive stressors. Here we aim to reconcile this particular seizure phenotype with the known frontal lobe type neuropsychological profile, photosensitivity, hyperexcitable motor cortex, and recent advanced imaging studies that identified abnormal functional connectivity of the motor cortex and supplementary motor area (SMA).
We acquired fMRI and diffusion tensor imaging (DTI) in a cohort of 29 patients with JME and 28 healthy control subjects. We used fMRI to determine functional connectivity and DTI-based region parcellation and voxel-wise comparison of probabilistic tractography data to assess the structural connectivity profiles of the mesial frontal lobe.
Patients with JME showed alterations of mesial frontal connectivity with increased structural connectivity between the prefrontal cognitive cortex and motor cortex. We found a positive correlation between DTI and fMRI-based measures of structural and functional connectivity: the greater the structural connectivity between these 2 regions, the greater the observed functional connectivity of corresponding areas. Furthermore, connectivity was reduced between prefrontal and frontopolar regions and increased between the occipital cortex and the SMA.
The observed alterations in microstructural connectivity of the mesial frontal region may represent the anatomic basis for cognitive triggering of motor seizures in JME. Changes in the mesial frontal connectivity profile provide an explanatory framework for several other clinical observations in JME and may be the link between seizure semiology, neurophysiology, neuropsychology, and imaging findings in JME.
Erectile dysfunction mechanisms in diabetic patients are multifactorial and often lead to resistance to current therapy. Animal toxins have been used as pharmacological tools to study penile erection. Human accidents involving the venom of Phoneutria nigriventer spider are characterized by priapism. We hypothesize that PnTx2-6 potentiates cavernosal relaxation in diabetic mice by increasing cGMP. This effect is nNOS dependent. Cavernosal strips were contracted with phenylephrine (10−5 M) and relaxed by electrical field stimulation (EFS, 20V, 1–32 Hz) in the presence or absence of PnTx2-6 (10−8 M).Cavernosal strips from nNOS and eNOS knocaut (KO) mice, besides nNOS inhibitor (10−5M), were used to evaluate the role of this enzyme in the potentiation effect evoked by PnTx2-6. Tissue cGMP levels were determined after stimulation with PnTx2-6 in presence or absence of L-NAME (10−4M) and ω-conotoxin GVIA (10−6M), an N-type calcium channel inhibitor. Results showed PnTx2-6 enhanced cavernosal relaxation in diabetic mice (65%) and eNOS KO mice, but not in nNOS KO mice. The toxin effect in the cavernosal relaxation was abolished by nNOS inhibitor. cGMP levels are increased by PnTx2-6, however L-NAME abolished this enhancement as well as ω-conotoxin GVIA. We conclude PnTx2-6 facilitates penile relaxation in diabetic mice through a mechanism dependent on nNOS, probably via increasing NO/cGMP production.
Phoneutria nigriventer; erectile dysfunction; PnTx2-6 toxin; NO; cGMP
Characteristic cardiac valve abnormalities and left ventricular hypertrophy are present in untreated patients with mucopolysaccharidosis type VI (MPS VI). Cardiac ultrasound was performed to investigate these findings in subjects during long-term enzyme replacement therapy (ERT) with recombinant human arylsulfatase B (rhASB, rhN-acetylgalactosamine 4-sulfatase, galsulfase, Naglazyme®). Studies were conducted in 54 subjects before ERT was begun and at specific intervals for up to 96 weeks of weekly infusions of rhASB at 1 mg/kg during phase 1/2, phase 2, and phase 3 trials of rhASB. At baseline, mitral and aortic valve obstruction was present and was significantly greater in those ≥12 years of age. Mild mitral and trace aortic regurgitation were present, the former being significantly greater in those <12 years. Left ventricular hypertrophy, with averaged z-scores ranging from 1.6–1.9 SD greater than normal, was present for ages both <12 and ≥12 years. After 96 weeks of ERT, ventricular septal hypertrophy regressed in those <12 years. For those ≥12 years, septal hypertrophy was unchanged, and aortic regurgitation increased statistically but not physiologically. Obstructive gradients across mitral and aortic valves remained unchanged. The results suggest that long-term ERT is effective in reducing intraventricular septal hypertrophy and preventing progression of cardiac valve abnormalities when administered to those <12 years of age.
Experiments in animal models have identified specific subcortical anatomic circuits, which are critically involved in the pathogenesis and control of seizure activity. However, whether such anatomic substrates also exist in human epilepsy is not known.
We studied 2 separate groups of patients with focal epilepsies arising from any cortical location using either simultaneous EEG-fMRI (n = 19 patients) or [11C]flumazenil PET (n = 18).
Time-locked with the interictal epileptiform discharges, we found significant hemodynamic increases common to all patients near the frontal piriform cortex ipsilateral to the presumed cortical focus. GABAA receptor binding in the same area was reduced in patients with more frequent seizures.
Our findings of cerebral blood flow and GABAergic changes, irrespective of where interictal or ictal activity occurs in the cortex, suggest that this area of the human primary olfactory cortex may be an attractive new target for epilepsy therapy, including neurosurgery, electrical stimulation, and focal drug delivery.
To assess whether weekend admissions to hospital and/or already being an inpatient on weekend days were associated with any additional mortality risk.
Retrospective observational survivorship study. We analysed all admissions to the English National Health Service (NHS) during the financial year 2009/10, following up all patients for 30 days after admission and accounting for risk of death associated with diagnosis, co-morbidities, admission history, age, sex, ethnicity, deprivation, seasonality, day of admission and hospital trust, including day of death as a time dependent covariate. The principal analysis was based on time to in-hospital death.
National Health Service Hospitals in England.
Main Outcome Measures
30 day mortality (in or out of hospital).
There were 14,217,640 admissions included in the principal analysis, with 187,337 in-hospital deaths reported within 30 days of admission. Admission on weekend days was associated with a considerable increase in risk of subsequent death compared with admission on weekdays, hazard ratio for Sunday versus Wednesday 1.16 (95% CI 1.14 to 1.18; P < .0001), and for Saturday versus Wednesday 1.11 (95% CI 1.09 to 1.13; P < .0001). Hospital stays on weekend days were associated with a lower risk of death than midweek days, hazard ratio for being in hospital on Sunday versus Wednesday 0.92 (95% CI 0.91 to 0.94; P < .0001), and for Saturday versus Wednesday 0.95 (95% CI 0.93 to 0.96; P < .0001). Similar findings were observed on a smaller US data set.
Admission at the weekend is associated with increased risk of subsequent death within 30 days of admission. The likelihood of death actually occurring is less on a weekend day than on a mid-week day.
Management of upper gastrointestinal anastomotic leaks is an inter-disciplinary challenge. We present a case of late pyloroplasty leak following 3-stage oesophagectomy. We describe a novel, combined endoscopic and fluroscopic procedure to introduce a T-tube into the anastomotic leak proving an ideal plug at the site of leak which enabled the patient to consume a normal diet and return home safely.
The aging heart undergoes well characterized structural changes associated with functional decline, though the underlying mechanisms are not understood. The aim of this study was to determine to what extent ventricular myocardial protein expression was altered with age and which proteins underwent protein nitration. Fischer 344 X Brown Norway F1 hybrid (FBN) rats of four age groups were used, 4, 12, 24, and 34 months. Differential protein expression was determined by 2-DE and proteins were identified by peptide mass fingerprinting. Altered protein nitration with age was assessed by immunoblotting. Over 1,000 protein spots per sample were detected, and 255 were found to be differentially expressed when all aged groups were compared to young rats (4 months) (p ≤ 0.05). A strong positive correlation between differential protein expression and increasing age (p=0.03, R2=0.997) indicated a progressive, rather than abrupt, change with age. Of 46 differentially expressed proteins identified, 17 have roles in apoptosis, 10 in hypertrophy, 7 in fibrosis, and 3 in diastolic dysfunction, aging-associated processes previously reported in both human and FBN rat heart. Protein expression alterations detected here could have beneficial effects on cardiac function; thus, our data indicate a largely adaptive change in protein expression during aging. In contrast, differential protein nitration increased abruptly, rather than progressively, at 24 months of age. Altogether, the results suggest that differential myocardial protein expression occurs in a progressive manner during aging, and that a proteomic-based approach is an effective method for the identification of potential therapeutic targets to mitigate aging-related myocardial dysfunction.
aging; F344 X BN hybrid; heart; MALDI-TOF; nitrosylation; peptide mass fingerprinting; proteomics; two-dimensional electrophoresis
To determine the pharmacokinetic and pharmacodynamic dose-response effects of insulin glargine administered subcutaneously in individuals with type 2 diabetes.
RESEARCH DESIGN AND METHODS
Twenty obese type 2 diabetic individuals (10 male and 10 female, aged 50 ± 3 years, with BMI 36 ± 2 kg/m2 and A1C 8.3 ± 0.6%) were studied in this single-center, placebo-controlled, randomized, double-blind study. Five subcutaneous doses of insulin glargine (0, 0.5, 1.0, 1.5, and 2.0 units/kg) were investigated on separate occasions using the 24-h euglycemic clamp technique.
Glargine duration of action to reduce glucose, nonessential fatty acid (NEFA), and β-hydroxybutyrate levels was close to or >24 h for all four doses. Increases in glucose flux revealed no discernible peak and were modest with maximal glucose infusion rates of 9.4, 6.6, 5.5, and 2.8 μmol/kg/min for the 2.0, 1.5, 1.0, and 0.5 units/kg doses, respectively. Glargine exhibited a relatively hepatospecific action with greater suppression (P < 0.05) of endogenous glucose production (EGP) compared with little or no increases in glucose disposal.
A single subcutaneous injection of glargine at a dose of ≥0.5 units/kg can acutely reduce glucose, NEFA, and ketone body levels for 24 h in obese insulin-resistant type 2 diabetic individuals. Glargine lowers blood glucose by mainly inhibiting EGP with limited effects on stimulating glucose disposal. Large doses of glargine have minimal effects on glucose flux and retain a relatively hepatospecific action in type 2 diabetes.
The aim of this study was to determine if there were focal cortical abnormalities in juvenile myoclonic epilepsy (JME) using neuropsychological investigations and MRI.
Twenty-eight patients with JME and a large sample of healthy controls were assessed using a series of neuropsychological tests as well as structural and diffusion tensor MRI (DTI). DTI measures assessed fractional anisotropy (FA) within a white matter skeleton.
Neuropsychological testing indicated subtle dysfunctions in verbal fluency, comprehension, and expression, as well as nonverbal memory and mental flexibility. Utilizing whole-brain voxel-based morphometry for gray matter MRI data and tract-based spatial statistics for white matter diffusion MRI data, we found reductions in gray matter volume (GMV) in the supplementary motor area and posterior cingulate cortex and reductions in FA in underlying white matter of the corpus callosum. Supplementary motor area FA predicted scores in word naming tasks and expression scores. Posterior cingulate cortex GMV and FA predicted cognitive inhibition scores on the mental flexibility task.
The neuropsychological, structural, and tractography results implicate mesial frontal cortex, especially the supplementary motor area, and posterior cingulate cortex in JME.
The venom of the spider Phoneutria nigriventer contains several toxins that have bioactivity in mammals and insects. Accidents involving humans are characterized by various symptoms including penile erection. Here we investigated the action of Tx2-6, a toxin purified from the P. nigriventer spider venom that causes priapism in rats and mice. Erectile function was evaluated through changes in intracavernosal pressure/mean arterial pressure ratio (ICP/MAP) during electrical stimulation of the major pelvic ganglion (MPG) of normotensive and deoxycorticosterone-acetate (DOCA)-salt hypertensive rats. Nitric oxide (NO) release was detected in cavernosum slices with fluorescent dye (DAF-FM) and confocal microscopy. The effect of Tx2-6 was also characterized after intracavernosal injection of a non-selective nitric oxide synthase (NOS) inhibitor, L-NAME. Subcutaneous or intravenous injection of Tx2-6 potentiated the elevation of ICP/MAP induced by ganglionic stimulation. L-NAME inhibited penile erection and treatment with Tx2-6 was unable to reverse this inhibition. Tx2-6 treatment induced a significant increase of NO release in cavernosum tissue. Attenuated erectile function of DOCA-salt hypertensive rats was fully restored after toxin injection. Tx2-6 enhanced erectile function in normotensive and DOCA-salt hypertensive rats, via the NO pathway. Our studies suggest that Tx2-6 could be important for development of new pharmacological agents for treatment of erectile dysfunction.
Phoneutria nigriventer; Tx2-6 toxin; Nitric oxide; Erectile function
Several experimental studies have shown that human grasping behavior exhibits a transition from one-handed to two-handed grasping when to-be-grasped objects become larger and larger. The transition point depends on the relative size of objects measured in terms of human body-scales. Most strikingly, the transitions between the two different behavioral ‘modes’ of grasping exhibit hysteresis. That is, one-to-two hand transitions and two-to-one hand transitions occur at different relative object sizes when objects are scaled up or down in size. In our study we approach body-scaled hysteresis and mode transitions in grasping by exploiting the notion that human behavior in general results from self-organization and satisfies appropriately-defined order parameter equations. To this end, grasping transitions and grasping hysteresis are discussed from a theoretical perspective in analogy to cognitive processes defined by Haken’s neural network model for pattern recognition. In doing so, issues such as the exclusivity of grasping modes, biomechanical constraints, mode-mode interactions, single subject behavior and population behavior are explored.
Order parameters; Hysteresis; Grasping
Interferon α (IFN‐α) activated cellular signalling is negatively regulated by inhibitory factors, including the suppressor of cytokine signalling (SOCS) family. The effects of host factors such as obesity on hepatic expression of these inhibitory factors in subjects with chronic hepatitis C virus (HCV) are unknown.
To assess the independent effects of obesity, insulin resistance, and steatosis on response to IFN‐α therapy and to determine hepatic expression of factors inhibiting IFN‐α signalling in obese and non‐obese subjects with chronic HCV.
A total of 145 subjects were analysed to determine host factors associated with non‐response to antiviral therapy. Treatment comprised IFN‐α or peginterferon alpha, either alone or in combination with ribavirin. In a separate cohort of 73 patients, real time‐polymerase chain reaction was performed to analyse hepatic mRNA expression. Immunohistochemistry for SOCS‐3 was performed on liver biopsy samples from 38 patients with viral genotype 1 who had received antiviral treatment.
Non‐response (NR) to treatment occurred in 55% of patients with HCV genotypes 1 or 4 and 22% with genotypes 2 or 3. Factors independently associated with NR were viral genotype 1/4 (p<0.001), cirrhosis on pretreatment biopsy (p = 0.025), and body mass index ⩾ 30 kg/m2 (p = 0.010). Obese subjects with viral genotype 1 had increased hepatic mRNA expression of phosphoenolpyruvate carboxy kinase (p = 0.01) and SOCS‐3 (p = 0.047), in comparison with lean subjects. Following multivariate analysis, SOCS‐3 mRNA expression remained independently associated with obesity (p = 0.023). SOCS‐3 immunoreactivity was significantly increased in obesity (p = 0.013) and in non‐responders compared with responders (p = 0.014).
In patients with chronic HCV viral genotype 1, increased expression of factors that inhibit interferon signalling may be one mechanism by which obesity reduces the biological response to IFN‐α.
insulin resistance; tumour necrosis factor; phosphoenolpyruvate carboxy kinase; suppressor of cytokine signalling; obesity; antiviral therapy; hepatitis C
To determine whether polymorphic variations in the apolipoprotein E gene (APOE) are associated with increased risk of frontotemporal lobar degeneration (FTLD) when mutation in tau gene is absent.
The APOE gene was genotyped by polymerase chain reaction from DNA routinely extracted from blood or brain tissues. The APOE ε4 allele frequency in 198 patients with FTLD not associated with mutations in tau gene was compared with that of a control group of 756 normal individuals drawn from the same geographical region. Analyses were done according to clinical subtype or sex.
The APOE ε4 allele frequency (19.4%) was increased (p = 0.01) in FTLD v the whole control group (14.1%), while the APOE ε2 allele frequency in FTLD (6.5%) was slightly lower than in controls (8.0%) (NS). The APOE ε4 allele frequency in men with FTLD (22.3%) was greater (p = 0.002) than in male controls (12.3%); the frequency in women (16.3%) was similar to that in female controls (14.8%) (NS). The APOE ε2 allele frequency in men with FTLD was 4.9% while in male controls it was 9.5% (p = 0.06), but there was no difference in women (7.5% v 7.9%, NS). Neither the APOE ε2 nor APOE ε4 allele frequency varied significantly between any of the clinical subtypes.
In FTLD not associated with mutations in tau gene, possession of APOE ε4 allele in men roughly doubles the chances of developing disease, whereas this has no impact upon disease risk in women.
frontotemporal lobar degeneration; apolipoprotein E gene; dementia; genetic risk; gender
Background: There is increasing interest in the influence of host genetic factors on hepatic fibrosis, and whether genetic markers can reliably identify subjects at risk of developing severe disease. We hypothesised that hepatitis C virus (HCV) infected subjects with progressive fibrosis, classified using strict criteria based on histology at biopsy in addition to disease duration would be more likely to inherit several genetic polymorphisms associated with disease progression compared with subjects with a low rate of disease progression.
Methods: We examined polymorphisms in eight genes that have been reported to have an association with hepatic fibrosis.
Results: Associations between polymorphisms in six genes and more rapidly progressing fibrosis were observed, with individual adjusted odds ratios ranging from 2.1 to 4.5. The relationship between rapidly progressing fibrosis and possession of ⩾3, ⩾4, or ⩾5 progression associated alleles was determined and the adjusted odds ratios increased with increasing number of progression associated alleles (9.1, 15.5, and 24.1, respectively). Using logistic regression analysis, a predictive equation was developed and tested using a second cohort of patients with rapidly progressing fibrosis. The predictive equation correctly classified 80% of patients in this second cohort.
Conclusions: This approach may allow determination of a genetic profile predictive of rapid disease progression in HCV and identify patients warranting more aggressive therapeutic management.
Anterior temporal lobe resection (ATLR) benefits many patients with refractory temporal lobe epilepsy (TLE) but may be complicated by material specific memory impairments, typically of verbal memory following left ATLR, and non-verbal memory following right ATLR. Preoperative memory functional MRI (fMRI) may help in the prediction of these deficits.
To assess the value of preoperative fMRI in the prediction of material specific memory deficits following both left- and right-sided ATLR.
We report 15 patients with unilateral TLE undergoing ATLR; eight underwent dominant hemisphere ATLR and seven non-dominant ATLR. Patients performed an fMRI memory paradigm which examined the encoding of words, pictures and faces.
Individual patients with relatively greater ipsilateral compared with contralateral medial temporal lobe activation had greater memory decline following ATLR. This was the case for both verbal memory decline following dominant ATLR and for non-verbal memory decline following non-dominant ATLR. For verbal memory decline, activation within the dominant hippocampus was predictive of postoperative memory change whereas activation in the non-dominant hippocampus was not.
These findings suggest that preoperative memory fMRI may be a useful non-invasive predictor of postoperative memory change following ATLR and provide support for the functional adequacy theory of hippocampal function. They also suggest that fMRI may provide additional information, over that provided by neuropsychology, for use in the prediction of postoperative memory decline.
Methods: 20 healthy subjects and 25 patients with known hippocampal sclerosis (HS) were studied using a dual echo CSE sequence on a 1.5T MRI GE scanner. The T2 relaxation time of the amygdala was calculated and measured using a previously validated method.
Results: The mean control AT2 was 88.1 ms (SD 2 ms). The coefficient of reliability was good at 6.3% test-retest and 7.4% inter-rater. The upper limit of normal AT2 was 92 ms. AT2 was abnormal ipsilaterally in six, and bilaterally in three, of 20 patients with unilateral HS. Two of five patients with bilateral HS had unilateral abnormal AT2.
Conclusion: Reliable T2 measurements can be obtained in the amygdala, and may be useful in the detection of amygdala abnormality.
Knowledge of the clonal expansion of Mycobacterium tuberculosis and accurate identification of predominant evolutionary lineages in this species remain limited, especially with regard to low-IS6110-copy-number strains. In this study, 170 M. tuberculosis isolates with ≤6 IS6110 insertions identified in Cape Town, South Africa, were characterized by principal genetic grouping, restriction fragment length polymorphism analysis, spoligotyping, IS6110 insertion site mapping, and variable-number tandem repeat (VNTR) typing. These analyses indicated that all but one of the isolates analyzed were members of principal genetic group 2 and of the same low-IS6110-copy-number lineage. The remaining isolate was a member of principal genetic group 1 and a different low-IS6110-copy-number lineage. Phylogenetic reconstruction suggests clonal expansion through sequential acquisition of additional IS6110 copies, expansion and contraction of VNTR sequences, and the deletion of specific direct-variable-repeat sequences. Furthermore, comparison of the genotypic data of 91 representative low-IS6110-copy-number isolates from Cape Town, other southern African regions, Europe, and the United States suggests that certain low-IS6110-copy-number strain spoligotypes and IS6110 fingerprints were acquired in the distant past. These clones have subsequently become widely disseminated and now play an important role in the global tuberculosis epidemic.
Previous studies have described IS6110-mediated polymorphism as an important driving force in Mycobacterium tuberculosis genome evolution and have provided indirect evidence for IS6110-driven deletion events. This study provides the first description of an IS6110-mediated deletion event in truly isogenic strains. We also provide further support for the hypothesis that the region from Rv1754 to Rv1765 is a hot spot for IS6110 insertion and deletion events.
The stability of the genotypic marker IS6110, used to define the epidemiology of Mycobacterium tuberculosis, is one of the most important factors influencing the interpretation of DNA fingerprint data. We propose that evolved strains should be considered together with clustered strains to represent chains of ongoing transmission. For the present study we used a large set of fingerprint data for strains collected between 1992 and 1998 from residents of a community with a high incidence of tuberculosis in Cape Town, South Africa. Interstrain genetic distances were calculated by counting the banding pattern mismatches in the IS6110 DNA fingerprints of different isolates. These data demonstrate that the propensity to change by one or two bands is independent of the IS6110 copy number. Hence, the genetic distance between pairs of isolates can be simply expressed as the number of differences in the banding patterns. From this foundation, a data set which identifies newly evolved strains has been generated. Inclusion of these evolved strains into various molecular epidemiological calculations significantly increased the estimate of ongoing transmission in this study setting. The indication is that nearly all cases of tuberculosis in this community are due to ongoing transmission. This has important implications for tuberculosis control, as it indicates that the control measures used at present are unable to reduce the level of transmission. This technique may also be applicable to the study of low-incidence tuberculosis outbreaks as well as the analysis of epidemiological data from other disease epidemics.
This study investigates the phenomenon of IS6110-mediated deletion polymorphism in the direct repeat (DR) region of the genome of Mycobacterium tuberculosis. Clinical isolates and their putative predecessors were compared using a combination of DR region restriction fragment length polymorphism, IS6110 DNA fingerprinting, spoligotyping, and DNA sequencing, which allowed the mapping of chromosome structure and deletion junctions. The data suggest that adjacently situated IS6110 elements mediate genome deletion. However, in contrast to previous reports, deletions appear to be mediated by inversely oriented IS6110 elements. This suggests that these events may occur via mechanisms other than RecA-mediated homologous recombination. The results underscore the important role of IS6110-associated deletion hypervariability in driving M. tuberculosis genome evolution.
BACKGROUND/AIMS—To measure cerebral benzodiazepine receptor binding using 11C-flumazenil positron emission tomography in patients with stable chronic hepatic encephalopathy, who were also characterised by proton magnetic resonance spectroscopy.
METHODS—Six abstinent patients of mean age 61 years with alcohol related cirrhosis and grade I-II hepatic encephalopathy and 11 matched healthy volunteers were studied. Each patient's encephalopathy was defined according to clinical, psychometric, electroencephalographic, and magnetic resonance spectroscopy criteria. Using positron emission tomography, the brain volume of distribution of 11C-flumazenil was obtained; this reflects benzodiazepine receptor availability. Proton magnetic resonance spectra were acquired at 1.5 T using a multivoxel technique; peak area ratios were calculated for choline, glutamine/glutamate, N-acetylaspartate, and creatine resonances.
RESULTS—The mean volume of distribution of 11C-flumazenil was significantly higher in the cortex, cerebellum, and the basal ganglia in the patients compared with controls (p<0.001). In the patient group, the mean glutamine/glutamate to creatine ratio was significantly increased and the mean choline to creatine ratio was significantly decreased in all brain areas, compared with healthy volunteers. However, the N-acetylaspartate to creatine ratio was unchanged compared with controls.
CONCLUSIONS—The spectroscopy results reflect the cerebral metabolic derangement associated with hepatic encephalopathy. Stable grade I-II chronic hepatic encephalopathy in alcohol related cirrhosis may be associated with increased cerebral benzodiazepine receptor availability. However, a direct effect of previous chronic exposure to alcohol cannot be excluded.
Keywords: benzodiazepine receptors; chronic hepatic encephalopathy; 11C-flumazenil; in vivo proton magnetic resonance spectroscopy; positron emission tomography