Post-mortem MRI-based volumetry of the hippocampus in forensic cases of decedents with severe mental illness.

A decrease in the volume of the hippocampus is associated with severe mental illness, especially schizophrenia, and has been studied extensively in the living using magnetic resonance imaging. Autopsy cohorts also represent a valuable data source for imaging studies. However, post-mortem magnetic resonance imaging (PMMRI) is subject to unique challenges, such as the lower core temperature of scanned subjects and the influence of decomposition processes. This study aimed to determine if results from in vivo studies could be replicated on a post-mortem cohort of decedents who suffered from severe mental illness. We included 96 decedents with either schizophrenia (n = 34), depressive disorder (n = 17), or no known psychiatric diagnosis (n = 45) from April 2015 to January 2017. All cases underwent a T2-weighted cerebral MRI less than 24 h before autopsy. We used a manual segmentation algorithm to define the hippocampus on coronal images and subsequently estimate the volume of the region. The group with schizophrenia had a statistically significant 9.5% decrease in mean hippocampal volume compared with control subjects, while the group with depression trended towards a reduced volume, but this difference was not statistically significant. Thus we were able to replicate previous results from in vivo studies. PMMRI has unique potential for research in that it can be combined with procedures possible only in the research fields of clinical pathology and forensic science, e.g. histopathological sampling.

Gradual onset and recovery of the Younger Dryas abrupt climate event in the tropics.

Proxy records of temperature from the Atlantic clearly show that the Younger Dryas was an abrupt climate change event during the last deglaciation, but records of hydroclimate are underutilized in defining the event. Here we combine a new hydroclimate record from Palawan, Philippines, in the tropical Pacific, with previously published records to highlight a difference between hydroclimate and temperature responses to the Younger Dryas. Although the onset and termination are synchronous across the records, tropical hydroclimate changes are more gradual (>100 years) than the abrupt (10-100 years) temperature changes in the northern Atlantic Ocean. The abrupt recovery of Greenland temperatures likely reflects changes in regional sea ice extent. Proxy data and transient climate model simulations support the hypothesis that freshwater forced a reduction in the Atlantic meridional overturning circulation, thereby causing the Younger Dryas. However, changes in ocean overturning may not produce the same effects globally as in Greenland.

Investigating groundwater flow between Edwards and Trinity aquifers in central Texas.

Understanding the nature of communication between aquifers can be challenging when using traditional physical and geochemical groundwater sampling approaches. This study uses two multiport wells completed within Edwards and Trinity aquifers in central Texas to determine the degree of groundwater inter-flow between adjacent aquifers. Potentiometric surfaces, hydraulic conductivities, and groundwater major ion concentrations and Sr isotope values were measured from multiple zones within three hydrostratigraphic units (Edwards and Upper and Middle Trinity aquifers). Physical and geochemical data from the multiport wells were combined with historical measurements of groundwater levels and geochemical compositions from the region to characterize groundwater flow and identify controls on the geochemical compositions of the Edwards and Trinity aquifers. Our results suggest that vertical groundwater flow between Edwards and Middle Trinity aquifers is likely limited by low permeability, evaporite-rich units within the Upper and Middle Trinity. Potentiometric surface levels in both aquifers vary with changes in wet vs. dry conditions, indicating that recharge to both aquifers occurs through distinct recharge areas. Geochemical compositions in the Edwards, Upper, and Middle Trinity aquifers are distinct and likely reflect groundwater interaction with different lithologies (e.g., carbonates, evaporites, and siliceous sediments) as opposed to mixing of groundwater between the aquifers. These results have implications for the management of these aquifers as they indicate that, under current conditions, pumping of either aquifer will likely not induce vertical cross-formational flow between the aquifers. Inter-flow between the Trinity and the Edwards aquifers, however, should be reevaluated as pumping patterns and hydrogeologic conditions change.

Postmortem genetic testing of the ryanodine receptor 2 (RYR2) gene in a cohort of sudden unexplained death cases.

The aim of this investigation was to identify pathogenic variants of the ryanodine receptor 2 (RYR2) gene in a cohort of persons aged 0-40 years who died of sudden unexpected death syndrome (SUD), including a cohort of infants who died of sudden infant death syndrome (SIDS). We genetically screened 29 of the 105 exons of the RYR2 gene associated with catecholaminergic polymorphic ventricular tachycardia (CPVT) in 74 cases of SUD without reported structural abnormalities of the heart. Cases were selected from the case database at the Institute of Forensic Medicine, and subsequent mutational screening by DNA sequencing was performed to detect variants in DNA samples extracted from blood samples of deceased persons. A total of 7 of the examined 74 cases were heterozygous for a rare sequence variant in the RYR2 gene. We identified five novel missense variants (p.Q486H, p.D1872N, p.G2367R, p.E4213D, and p.H4579Y), one synonymous variant (p.L4767L), and one previously reported missense variant (p.G4315E). Follow-up studies were possible in family members of three probands (p.Q486H, p.D1872N, and p.H4579Y), and clinical examinations were conducted in family members of two of these probands (p.Q486H and p.H4579Y). In conclusion, we identified a higher prevalence of variants in the CPVT-associated gene RYR2 than in a previously reported cohort of SIDS (9.4% vs. 1-2%). Segregation studies show that one variant (p.H4579Y) co-segregates with CPVT and is presumed to be pathogenic.

Molecular autopsy in young sudden cardiac death victims with suspected cardiomyopathy.

The aim of this investigation was to identify and characterise pathogenic mutations in a sudden cardiac death (SCD) cohort suspected of cardiomyopathy in persons aged 0-40 years. The study material for the genetic screening of cardiomyopathies consisted of 41 cases and was selected from the case database at the Institute of Forensic Medicine. Mutational screening by DNA sequencing was performed to detect mutations in DNA samples from deceased persons suspected of suffering from hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), and arrhythmogenic right ventricle cardiomyopathy (ARVC). A total of 9 of the examined 41 cases had a rare sequence variant in the MYBPC3, MYH7, LMNA, PKP2 or TMEM43 genes, of which 4 cases (9.8%) were presumed to be pathogenic mutations. The presumed pathogenic mutations were distributed with one case of suspected HCM and DCM (MYH7; p.R442H), one case of suspected DCM (LMNA; p.R471H), and two cases of suspected ARVC (PKP2; p.R79X and LMNA; p.R644C). The presented data adds important information on the genetic elements of SCD in the young, and calls for expert pathological evaluation and molecular autopsy in the post-mortem examination of SCD victims with structural anomalies of the heart.

Case management model for a community-based multiple sclerosis clinic.

This article describes the process from inception to successful operation of a case management model of a community-based multiple sclerosis clinic. The article includes information regarding the pathophysiology, diagnosis, and clinical manifestations of multiple sclerosis. The assessment, planning, and intervention stages of the process are explained, and a case study of one clinic patient is provided.

The slowing of visual processing by hypoxia.

An additive factors method (AFM) experiment was undertaken to determine whether the preprocessing and identification stages of information processing are implicated in the slowing of reaction time (RT) by hypoxia. The subjects (n = 14) responded at two levels of light intensity to pairs of lines that differed in length while breathing a low oxygen mixture that produced arterial oxyhaemoglobin saturations ranging between 64%-66%. The results showed a relatively large interaction between light intensity and hypoxia that was interpreted as evidence for slowing of the preprocessing stage. Differences in line length were plotted in terms of Crossman's confusion function and relatively small interactions with both hypoxia and light intensity were found, reflecting increases in slope. The light intensity x confusion level interaction was interpreted as evidence that AFM assumptions may not have been met completely in this experiment. This leads to the possibility that hypoxia slowed the identification stage indirectly rather than directly, although the latter hypothesis cannot be ruled out entirely at present. It is argued that visual slowing probably plays an important role in the disruption of perceptual-motor tasks by hypoxia.

Regional ground-water mixing and the origin of saline fluids: midcontinent, United States.

Ground waters in three adjacent regional flow systems in the midcontinent exhibit extreme chemical and isotopic variations that delineate large-scale fluid flow and mixing processes and two distinct mechanisms for the generation of saline fluids. Systematic spatial variations of major ion concentrations, H, O, and Sr isotopic compositions, and ground-water migration pathways indicate that each flow system contains water of markedly different origin. Mixing of the three separate ground waters exerts a fundamental control on ground-water composition. The three ground waters are: (i) dilute meteoric water recharged in southern Missouri; (ii) saline Na-Ca-Cl water in southeastern Kansas of far-traveled meteoric origin that acquired its salinity by halite dissolution; and (iii) Na-Ca-Cl brines in north-central Oklahoma that may have originated as Paleozoic seawater.