Cell death is a critically important biological process. Disruption of homeostasis, either by excessive or deficient cell death, is a hallmark of many pathological conditions. Recent research advances have greatly increased our molecular understanding of cell death and its role in a range of diseases and therapeutic treatments. Central to these ongoing research and clinical efforts is the need for imaging technologies that can locate and identify cell death in a wide array of in vitro and in vivo biomedical samples with varied spatiotemporal requirements. This review article summarizes community efforts over the past five years to identify useful biomarkers for dead and dying cells, and to develop molecular probes that target these biomarkers for optical, radionuclear, or magnetic resonance imaging. Apoptosis biomarkers are classified as either intracellular (caspase enzymes, mitochondrial membrane potential, cytosolic proteins) or extracellular (plasma membrane phospholipids, membrane potential, surface exposed histones). Necrosis, autophagy, and senescence biomarkers are described, as well as unexplored cell death biomarkers. The article discusses possible chemotherapeutic and theranostic strategies, and concludes with a summary of current challenges and expected eventual rewards of clinical cell death imaging.
Apoptosis; necrosis; autophagy; senescence; molecular imaging; optical imaging; nuclear imaging; magnetic resonance imaging; contrast agent; theranostic
As a classic neuromodulator, dopamine has long been thought to modulate, rather than trigger, synaptic plasticity. In contrast, our present results demonstrate that within the parallel projections of dopaminergic and GABAergic terminals from the ventral tegmental area (VTA) to nucleus accumbens core (NAcCo), action potential-activated release of dopamine heterosynaptically triggers LTD at GABAergic synapses, which is likely mediated by activating presynaptically-located dopamine D1 class receptors and expressed by inhibiting presynaptic release of GABA. Moreover, this dopamine-mediated heterosynaptic LTD is abolished after withdrawal from cocaine exposure. These results suggest that action potential-dependent dopamine release triggers very different cellular consequences from those induced by volume release or pharmacological manipulation. Activation of the VTA-to-NAcCo projections is essential for emotional and motivational responses. This dopamine-mediated LTD allows a flexible output of NAcCo neurons, whereas disruption of this LTD may contribute to the rigid emotional and motivational state observed in addicts during cocaine withdrawal.
ventral tegmental area; inhibitory synapse; cocaine; accumbens; addiction; IPSC
Rationale and Objectives
Magnetic resonance elastography (MRE) can non-invasively measure the stiffness of liver tissue and display this information in anatomic maps. Magnetic resonance imaging (MRI)-guidance has not previously been used to biopsy segments of heterogeneous stiffness identified on MRE. Dedicated study of MRE in post-liver transplant patients is also limited. In this study, the ability of real-time MRI to guide biopsies of segments of the liver with different MRE stiffness values in the same post-transplant patient was assessed.
Materials and Methods
MRE was performed in 9 consecutive post-transplant patients with history of hepatitis C. Segments of highest and lower stiffness on MRE served as targets for subsequent real-time MRI-guided biopsy using T2-weighted imaging. The ability of MRI-guided biopsy to successfully obtain tissue specimens was assessed. The Wilcoxon Signed Rank Test was used to compare mean stiffness differences for highest and lower MRE stiffness segments, with α = 0.05.
MRI-guidance allowed successful sampling of liver tissue for all (18/18) biopsies. There was a statistically significant difference in mean MRE stiffness values between highest (4.61 ± 1.99 kPa) and lower stiffness (3.03 ± 1.75 kPa) (P=0.0039) segments biopsied in the 9 post-transplant patients.
Real-time MRI can guide biopsy in patients after liver transplantation based upon MRE stiffness values. This study supports the use of MRI-guidance to sample tissue based upon functional information.
magnetic resonance elastography; MRI-guidance; image-guided biopsy; liver biopsy; liver transplantation
Although alcohol use has long been a significant cause of hospital presentations, little is published regarding the long-term demographic changes that have occurred at a single hospital site. To address this deficit, we prospectively studied all acute alcohol-related presentations to Bellevue Hospital Center (New York, NY) and compared this contemporary data set with one from the same institution from 1902 to 1935. We prospectively identified all patients presenting to the emergency department because of acute alcohol use over an 8-week period in 2009. We described the basic attributes of patients presenting currently because of alcohol and compared these data to those previously described between 1902 and 1935. We also compared our census data with contemporaneous data from all patients presenting to this hospital site. During the study period, 560 patients presented because of acute alcohol use which extrapolated to an estimated 3,800 patients over the calendar year. This compares to 7,600 presentations recorded annually early in the twentieth century. Twelve percent of patients in 2009 were female as compared to 18 % of patients between 1934 and 1935. Patients with alcohol-related presentations in 2009 were more likely to be admitted than contemporaneous patients without an alcohol-related presentation (30 vs. 19 % admitted; p < 0.001). Since first measured 110 years ago at one large New York City hospital, alcohol-related presentations remain common representing 5 % of all emergency department visits. This demonstrates alcoholism's continuing toll on society's limited medical resources and on public health as a whole.
Alcohol; Demographics; Emergency department; Emergency medicine; Urban
Francisella tularensis is a facultative intracellular bacterial pathogen and the causative agent of tularemia. After infection of macrophages, the organism escapes from its phagosome and replicates to high density in the cytosol, but the bacterial factors required for these aspects of virulence are incompletely defined. Here, we describe the isolation and characterization of Francisella tularensis subsp. tularensis strain Schu S4 mutants that lack functional iglI, iglJ, or pdpC, three genes of the Francisella pathogenicity island. Our data demonstrate that these mutants were defective for replication in primary human monocyte-derived macrophages and murine J774 cells yet exhibited two distinct phenotypes. The iglI and iglJ mutants were similar to one another, exhibited profound defects in phagosome escape and intracellular growth, and appeared to be trapped in cathepsin D-positive phagolysosomes. Conversely, the pdpC mutant avoided trafficking to lysosomes, phagosome escape was diminished but not ablated, and these organisms replicated in a small subset of infected macrophages. The phenotype of each mutant strain was reversed by trans complementation. In vivo virulence was assessed by intranasal infection of BALB/c mice. The mutants appeared avirulent, as all mice survived infection with 108 CFU iglJ- or pdpC-deficient bacteria. Nevertheless, the pdpC mutant disseminated to the liver and spleen before being eliminated, whereas the iglJ mutant did not. Taken together, our data demonstrate that the pathogenicity island genes tested are essential for F. tularensis Schu S4 virulence and further suggest that pdpC may play a unique role in this process, as indicated by its distinct intermediate phenotype.
A zinc(II)-dipicolylamine coordination complex selectively associates with anionic liposomes, including sterically protected PEGylated liposomes, and causes rapid leakage of encapsulated contents.
Evolution balances DNA replication speed and accuracy to optimize replicative fitness and genetic stability. There is no selective pressure to improve DNA replication fidelity beyond the background mutation rate from other sources, such as DNA damage. However, DNA polymerases remain amenable to amino-acid substitutions that lower intrinsic error rates. Here, we review these ‘antimutagenic’ changes in DNA polymerases and discuss what they reveal about mechanisms of replication fidelity. Pioneering studies with bacteriophage T4 DNA polymerase (T4 Pol) established the paradigm that antimutator amino-acid substitutions reduce replication errors by increasing proofreading efficiency at the expense of polymerase processivity. The discoveries of antimutator substitutions in proofreading-deficient ‘mutator’ derivatives of bacterial Pols I and III and yeast Pol δ suggest there must be additional antimutagenic mechanisms. Remarkably, many of the affected amino-acid positions from Pol I, Pol III, and Pol δ are similar to the original T4 Pol substitutions. The locations of antimutator substitutions within DNA polymerase structures suggest that they may increase nucleotide selectivity and/or promote dissociation of primer termini from polymerases poised for misincorporation, leading to expulsion of incorrect nucleotides. If misincorporation occurs, enhanced primer dissociation from polymerase domains may improve proofreading in cis by an intrinsic exonuclease or in trans by alternate cellular proofreading activities. Together, these studies reveal that natural selection can readily restore replication error rates to sustainable levels following an adaptive mutator phenotype.
DNA replication fidelity; mutator; genetic adaptation; protein structure/function; genetic instability; cancer
Genotypic surveys suggest that human immunodeficiency virus type 1 (HIV-1) and HIV-2 evolve different sets of mutations in response to nucleoside reverse-transcriptase inhibitors (NRTIs). We used site-directed mutagenesis, culture-based phenotyping, and cell-free assays to determine the resistance profiles conferred by specific amino acid replacements in HIV-2 reverse transcriptase. Although thymidine analogue mutations had no effect on zidovudine sensitivity, the addition of Q151M together with K65R or M184V was sufficient for high-level resistance to both lamivudine and zidovudine in HIV-2, and the combination of K65R, Q151M, and M184V conferred classwide NRTI resistance. These data suggest that current NRTI-based regimens are suboptimal for treating HIV-2 infection.
Traumatic brain injury is characterized by initial tissue
which then can lead to secondary processes such as cell death and
blood-brain-barrier disruption. Clinical and preclinical studies of
traumatic brain injury typically employ anatomical imaging techniques
and there is a need for new molecular imaging methods that provide
complementary biochemical information. Here, we assess the ability
of a targeted, near-infrared fluorescent probe, named PSS-794, to
detect cell death in a brain cryolesion mouse model that replicates
certain features of traumatic brain injury. In short, the model involves
brief contact of a cold rod to the head of a living, anesthetized
mouse. Using noninvasive whole-body fluorescence imaging, PSS-794
permitted visualization of the cryolesion in the living animal. Ex
vivo imaging and histological analysis confirmed PSS-794 localization
to site of brain cell death. The nontargeted, deep-red Tracer-653
was validated as a tracer dye for monitoring blood-brain-barrier disruption,
and a binary mixture of PSS-794 and Tracer-653 was employed for multicolor
imaging of cell death and blood-brain-barrier permeability in a single
animal. The imaging data indicates that at 3 days after brain cryoinjury
the amount of cell death had decreased significantly, but the integrity
of the blood-brain-barrier was still impaired; at 7 days, the blood-brain-barrier
was still three times more permeable than before cryoinjury.
Traumatic brain injury; multicolor fluorescence imaging; cell death imaging; blood-brain-barrier; annexin
Youth suicide is a national public health priority, with policymakers highlighting schools as an ideal setting in which to deliver suicide prevention programs. Over the past decade, the number of schools implementing such programs has grown substantially, yet little is known about how successfully such programs are being implemented. This study examines the implementation of a district-wide suicide prevention program through key informant interviews with school personnel. Schools with higher rates of implementing district protocols for at-risk students had an organized system to respond to at-risk students, a process for effectively responding to students who were at-risk for suicide, and strong administrative support. In contrast, schools that had lower rates of implementing district protocols relied on a handful of individuals for suicide prevention activities and had limited administrative support. Attention to organizational factors leading to successful implementation of school-based suicide prevention programs may enhance schools’ role in national adolescent suicide prevention efforts.
suicide prevention; school mental health; dissemination
A series of fluorescent phosphatidylserine and phosphatidylcholine derivatives were prepared and evaluated by cell microscopy for ability to translocate across mammalian plasma membranes via the putative aminophospholipid flippase. Phosphatidylserine derivatives, with either a neutral 7-nitrobenz-2-oxa-1,3-diazol-4-yl (NBD) or a coumarin fluorophore appended to the 2-acyl chain, entered the cytosol of all three cell lines tested and control experiments showed that the translocation was due to flippase activity. In contrast, a phosphatidylserine conjugate containing a charged and polar carboxyfluorescein was not translocated and remained in the cell plasma membrane. The phosphatidylserine-coumarin derivative exhibits bright fluorescence and higher photostability than the NBD analogues, and thus is a promising new fluorescent probe for extended-imaging studies of flippase action in living cells using laser confocal microscopes.
Fluorescent probes; cell microscopy; phosphatidylserine; aminophospholipid flippase
Francisella tularensis is a Gram-negative bacterium and the causative agent of the disease tularemia. Escape of F. tularensis from the phagosome into the cytosol of the macrophage triggers the activation of the AIM2 inflammasome through a mechanism that is not well understood. Activation of the AIM2 inflammasome results in autocatalytic cleavage of caspase-1, resulting in the processing and secretion of interleukin-1β (IL-1β) and IL-18, which play a crucial role in innate immune responses to F. tularensis. We have identified the 5-formyltetrahydrofolate cycloligase gene (FTL_0724) as being important for F. tularensis live vaccine strain (LVS) virulence. Infection of mice in vivo with a F. tularensis LVS FTL_0724 mutant resulted in diminished mortality compared to infection of mice with wild-type LVS. The FTL_0724 mutant also induced increased inflammasome-dependent IL-1β and IL-18 secretion and cytotoxicity in macrophages in vitro. In contrast, infection of macrophages with a F. tularensis LVS rluD pseudouridine synthase (FTL_0699) mutant resulted in diminished IL-1β and IL-18 secretion from macrophages in vitro compared to infection of macrophages with wild-type LVS. In addition, the FTL_0699 mutant was not attenuated in vivo. These findings further illustrate that F. tularensis LVS possesses numerous genes that influence its ability to activate the inflammasome, which is a key host strategy to control infection with this pathogen in vivo.
To compare the diagnostic accuracy of MR elastography and anatomic MR imaging features in the diagnosis of severe hepatic fibrosis and cirrhosis.
Materials and Methods
Three readers independently assessed presence of morphological changes associated with hepatic fibrosis in 72 patients with liver biopsy including: caudate to right lobe ratios, nodularity, portal venous hypertension (PVH) stigmata, posterior hepatic notch, expanded gallbladder fossa and right hepatic vein caliber. Three readers measured shear stiffness values using quantitative shear stiffness maps (elastograms). Sensitivity, specificity and diagnostic accuracy of stiffness values and each morphological feature were calculated. Inter-reader agreement was summarized using weighted kappa statistics. Intra-class correlation coefficient was used to assess inter-reader reproducibility of stiffness measurements. Binary logistic regression was used to assess inter-reader variability for dichotomized stiffness values and each morphological feature.
Using 5.9 kPa as a cut-off for differentiating F3–F4 from F0–2 stages, overall sensitivity, specificity and diagnostic accuracy for MR elastography were 85.4%, 88.4 % and 87% respectively. Overall inter-reader agreement for stiffness values was substantial, with insignificant difference (p=0.74) in the frequency of differentiating F3–4 from F0–2 fibrosis. Only hepatic nodularity and PVH stigmata showed moderately high overall accuracy of 69.4% and 72.2%. Inter-reader agreement was substantial only for PVH stigmata, moderate for C/R m, deep notch and expanded gallbladder fossa. Only posterior hepatic notch (p=0.82) showed no significant difference in reader rating.
MR elastography is a non-invasive, accurate and reproducible technique compared with conventional features of detecting severe hepatic fibrosis.
liver; fibrosis; cirrhosis; magnetic resonance elastography; morphological features
The present study investigated the process of second-order change among a group of individuals recovering from substance abuse problems. Data were collected from 56 individuals who were current or past members of Oxford Houses, which are democratically operated recovery homes that have no professional staff and where there is no limit on length of stay. We collected data on individual and house demographics, per week involvement in the community, house involvement in the community, and types of community involvement while residing in the Oxford House. Findings reveal a significant positive relationship between the length of time living in an Oxford House and level of participant involvement in the community. Participants reported multiple factors that increased their community involvement and reported the type of impact that their involvement had on their neighborhoods. Findings from the present study indicate that not only do residents help themselves stay abstinent by living in the Oxford Houses, but residents report that they also make important contributions to their neighborhoods and communities.
Despite the importance of migratory birds in the ecology and evolution of avian influenza virus (AIV), there is a lack of information on the patterns of AIV spread at the intra-continental scale. We applied a variety of statistical phylogeographic techniques to a plethora of viral genome sequence data to determine the strength, pattern, and determinants of gene flow in AIV sampled from wild birds in North America. These analyses revealed a clear isolation-by-distance of AIV among sampling localities. In addition, we show that phylogeographic models incorporating information on the avian flyway of sampling proved a better fit to the observed sequence data than those specifying homogeneous or random rates of gene flow among localities. In sum, these data strongly suggest that the intra-continental spread of AIV by migratory birds is subject to major ecological barriers, including spatial distance and avian flyway.
avian influenza; phylogeography; evolution; gene flow; ecological barriers; flyways; spatial distance
The title compound, C60H76Si2, a formally anti-aromatic system containing 20-π electrons, contains a rare p-xylylene motif. This is displayed by the alternating short and long bonds. The outer rings possess nearly homogenous bond lengths. In the crystal, the molecules forms layers perpendicular to the c axis and within these layers there are two one-dimensional stacks with one stack that has a sp
2 carbon contact of 3.283 (6) Å, less than the sum of the van der Waals radii. The center of the molecule sits on an inversion center.
Incidence estimates for pituitary adenomas vary widely, suggesting the effects of numerous risk factors or varying levels of tumor surveillance. We studied the epidemiology of pituitary adenomas using 2004–2007 data collected by 17 Surveillance, Epidemiology, and End Results (SEER) Programs in the United States (N = 8,276). We observed that incidence rates generally increased with age and were higher in females in early life and higher in males in later life. Males are diagnosed with larger tumors on average than females. Diagnosis may be delayed for males, giving tumors a chance to grow larger before clinical detection. We also observed that American Blacks have higher incidence rates for pituitary adenomas compared with other ethnic groups. There are several potential explanations for this finding with some evidence that at least part of the effect may be due to differential diagnosis between races.
pituitary; adenoma; incidence; race; sex
Alu RNA accumulation due to DICER1 deficiency in the retinal pigmented epithelium (RPE) is implicated in geographic atrophy (GA), an advanced form of age-related macular degeneration that causes blindness in millions of individuals. The mechanism of Alu RNA-induced cytotoxicity is unknown. Here we show that DICER1 deficit or Alu RNA exposure activates the NLRP3 inflammasome and triggers TLR-independent MyD88 signaling via IL-18 in the RPE. Genetic or pharmacological inhibition of inflammasome components (NLRP3, Pycard, Caspase-1), MyD88, or IL-18 prevents RPE degeneration induced by DICER1 loss or Alu RNA exposure. These findings, coupled with our observation that human GA RPE contains elevated amounts of NLRP3, PYCARD and IL-18, and evidence of increased Caspase-1 and MyD88 activation, provide a rationale for targeting this pathway in GA. Our findings also reveal a function of the inflammasome outside the immune system and an immunomodulatory action of mobile elements.
To evaluate if electronic health records (EHR) have observable effects on care outcomes, we examined quality and efficiency measures for patients presenting to emergency departments (ED).
Materials and methods
We conducted a retrospective study of 5166 adults with heart failure in three metropolitan EDs. Patients were termed internal if prior information was in the EHR upon ED presentation, otherwise external. Associations of internality with hospitalization, mortality, length of stay (LOS), and numbers of tests, procedures, and medications ordered in the ED were examined after adjusting for age, gender, race, marital status, comorbidities and hospitalization as a proxy for acuity level where appropriate.
At two EDs internals had lower odds of mortality if hospitalized (OR 0.55; 95% CI 0.38 to 0.81 and 0.45; 0.21 to 0.96), fewer laboratory tests during the ED visit (−4.6%; −8.9% to −0.1% and −14.0%; −19.5% to −8.1%) as well as fewer medications (−33.6%; −38.4% to −28.4% and −21.3%; −33.2% to −7.3%). At one of these two EDs, internals had lower odds of hospitalization (0.37; 0.22 to 0.60). At the third ED, internal patients only experienced a prolonged ED LOS (32.3%; 6.3% to 64.8%) but no other differences. There was no association with hospital LOS or number of procedures ordered.
EHR availability was associated with salutary outcomes in two of three ED settings and prolongation of ED LOS at a third, but evidence was mixed and causality remains to be determined.
An EHR may have the potential to be a valuable adjunct in the care of heart failure patients.
Electronic health records; emergency department; evaluation; heart failure; clinical outcomes; YT; health IT adoption; people and organizational issues; emergency medicine; medical informatics; measuring/improving patient safety and reducing medical errors; classical experimental and quasi-experimental study methods (lab and field); methods for integration of information from disparate sources; supporting practice at a distance (telehealth); data models; data exchange; communication; aintegration across care settings (inter- and intra-enterprise); human-computer interaction and human-centered computing
A versatile deep-red fluorescent imaging probe is described that is comprised of a bis(zinc(II)-dipicolylamine) targeting unit covalently attached to a pentamethine carbocyanine fluorophore with Cy5-like spectroscopic properties. A titration assay based on fluorescence resonance energy transfer is used to prove that the probe selectively associates with anionic vesicle membranes whose composition mimics bacterial cell membranes. Whole-body optical imaging experiments show that the probe associates with the surfaces of both Gram-positive and Gram-negative bacteria cells, and it can target the site of bacterial infection in a living mouse. In vivo accumulation at the infection site and subsequent clearance occurs more quickly than a structurally related near-infrared bis(zinc(II)-dipicolylamine) probe. The fact that the same deep-red probe molecule can be used for spectroscopic assays, cell microscopy, and in vivo imaging studies, is an important and attractive technical feature.
fluorescent molecular probe; imaging bacterial infection; zinc dipicolylamine; in vivo imaging; optical imaging; FRET
A major goal in the application of hydrogels for tissue engineering scaffolds, especially for load-bearing tissues such as cartilage, is to develop hydrogels with high mechanical strength. In this study, a double-network (DN) strategy was used to engineer strong hydrogels that can encapsulate cells. We improved upon previously studied double-network (DN) hydrogels by using a processing condition compatible with cell survival. The DN hydrogels were created by a two-step photocrosslinking using gellan gum methacrylate (GGMA) for the rigid and brittle first network, and gelatin methacrylamide (GelMA) for the soft and ductile second network. We controlled the degree of methacrylation of each polymer so that they obtain relevant mechanical properties as each network. The DN was formed by photocrosslinking the GGMA, diffusing GelMA into the first network, and photocrosslinking the GelMA to form the second network. The formation of the DN was examined by diffusion tests of the large GelMA molecules into the GGMA network, the resulting enhancement in the mechanical properties, and the difference in mechanical properties between GGMA/GelMA single networks (SN) and DNs. The resulting DN hydrogels exhibited the compressive failure stress of up to 6.9 MPa, which approaches the strength of cartilage. It was found that there is an optimal range of the crosslink density of the second network for high strength of DN hydrogels. DN hydrogels with a higher mass ratio of GelMA to GGMA exhibited higher strength, which shows promise in developing even stronger DN hydrogels in the future. Three dimensional (3D) encapsulation of NIH-3T3 fibroblasts and the following viability test showed the cell-compatibility of the DN formation process. Given the high strength and the ability to encapsulate cells, the DN hydrogels made from photocrosslinkable macromolecules could be useful for the regeneration of load-bearing tissues.
hydrogel; IPN; photopolymerization; cell encapsulation; mechanical properties
Cell death is a fundamental biological process that is present in numerous disease pathologies. Fluorescent probes that detect cell death have been developed for a myriad of research applications ranging from microscopy to in vivo imaging. Here we describe a synthetic near infrared conjugate of zinc(II)-dipicolylamine (Zn2+-DPA) for in vivo imaging of cell death. Chemically induced in vivo models of myopathy were established using an ionphore, ethanol, or ketamine as chemical cytotoxins. The Zn2+-DPA fluorescent probe or corresponding control was subsequently injected and whole animal fluorescence imaging demonstrated probe uptake at the site of muscle damage, which was confirmed by ex vivo and histological analyses. Further, a comparative study with a near-infrared fluorescent conjugate Annexin V showed less intense uptake at the site of muscle damage and high accumulation in the bladder. The results indicate that the fluorescent Zn2+-DPA conjugate is an effective probe for in vivo cell death detection and in some cases may be an appropriate alternative to fluorescent Annexin V conjugates.
in vivo imaging; cell death; near-infrared probe; zinc-dipicolylamine; annexin V; ketamine
The Adirondacks of New York State, USA is a region that is sensitive to atmospheric mercury (Hg) deposition. In this study, we estimated atmospheric Hg deposition to the Adirondacks using a new scheme that combined numerical modeling and limited experimental data. The majority of the land cover in the Adirondacks is forested with 47% of the total area deciduous, 20% coniferous and 10% mixed. We used litterfall plus throughfall deposition as the total atmospheric Hg deposition to coniferous and deciduous forests during the leaf-on period, and wet Hg deposition plus modeled atmospheric dry Hg deposition as the total Hg deposition to the deciduous forest during the leaf-off period and for the non-forested areas year-around. To estimate atmospheric dry Hg deposition we used the Big Leaf model. The average atmospheric Hg deposition to the Adirondacks was estimated as 17.4 g m yr with a range of −3.7–46.0 g m yr. Atmospheric Hg dry deposition (370 kg yr) was found to be more important than wet deposition (210 kg yr) to the entire Adirondacks (2.4 million ha). The spatial pattern showed a large variation in atmospheric Hg deposition with scattered areas in the eastern Adirondacks having total Hg deposition greater than 30 μg m−2 yr−1, while the southwestern and the northern areas received Hg deposition ranging from 25–30 μg m−2 yr−1.