The emotional and mental health impact of the murder of George Floyd on the US population.

On May 25, 2020, George Floyd, an unarmed Black American male, was killed by a White police officer. Footage of the murder was widely shared. We examined the psychological impact of Floyd's death using two population surveys that collected data before and after his death; one from Gallup (117,568 responses from n = 47,355) and one from the US Census (409,652 responses from n = 319,471). According to the Gallup data, in the week following Floyd's death, anger and sadness increased to unprecedented levels in the US population. During this period, more than a third of the US population reported these emotions. These increases were more pronounced for Black Americans, nearly half of whom reported these emotions. According to the US Census Household Pulse data, in the week following Floyd's death, depression and anxiety severity increased among Black Americans at significantly higher rates than that of White Americans. Our estimates suggest that this increase corresponds to an additional 900,000 Black Americans who would have screened positive for depression, associated with a burden of roughly 2.7 million to 6.3 million mentally unhealthy days.

An Australian Brain Bank: a critical investment with a high return!

Research into neuropsychiatric disorders, including alcohol-related problems, is limited in part by the lack of appropriate animal models. However, the development of new technologies in pathology and molecular biology means that many more questions can be addressed using appropriately stored human brain tissues. The New South Wales Tissue Resource Centre (TRC) in the University of Sydney (Australia) is a human brain bank that can provide tissues to the neuroscience research community studying alcohol-related brain disorders, schizophrenia, depression and bipolar disorders. Carefully standardised operational protocols and integrated information systems means that the TRC can provide high quality, accurately characterised, tissues for research. A recent initiative, the pre-mortem donor program called "Using our Brains", encourages individuals without neuropsychiatric illness to register as control donors, a critical group for all research. Community support for this program is strong with over 2,000 people registering their interest. Discussed herein are the protocols pertaining to this multifaceted facility and the benefits of investment, both scientific and financial, to neuroscience researchers and the community at large.

Joint estimation of migration rate and effective population size using the island model.

Using the island model of population demography, I report that the demographic parameters migration rate and effective population size can be jointly estimated with equilibrium probabilities of identity in state calculated using a sample of genotypes collected at a single point in time from a single generation. The method, which uses moment-type estimators, applies to dioecious populations in which females and males have identical demography and monoecious populations with no selfing and requires that offspring genotypes are sampled following reproduction and prior to migration. I illustrate the estimation procedure using the infinite-island model with no mutation and the finite-island model with three kinds of mutation models. In the infinite-island model with no mutation, the estimators can be expressed as simple functions of estimates of the F-statistic parameters F(IT) and F(ST). In the finite-island model with mutation among k alleles, mutation rate, migration rate, and effective population size can be simultaneously estimated. The estimates of migration rate and effective population size are somewhat robust to violations in assumptions that may arise in empirical applications such as different kinds of mutation models and deviations from temporal equilibrium.

Brain donation for research: who donates and why?

Understanding what influences people to donate or not donate body organs is critical for the future of transplant surgery and medical research. Are people involved with a brain donor program for research influenced by the same factors, and are they also donors for organ transplantation? Using web-based technology, people involved in an Australian brain donation program (for research) were asked to complete a questionnaire designed to elicit demographic information, motivational factors and information about involvement in organ transplantation programs. The response rate was 82%. The majority of people involved in the program are young, well-educated Australian females. Seventy-eight percent are involved in other organ and tissue donation programs. People involved in the 'Using our Brains' program are the same group as those who are organ and tissue donors. An improvement in the overall donation rate might be possible if the resources of the research and transplant organisations were combined.

Brain donation for research: strong support in Australia.

Permission by families for transplant donation has decreased in Australia. We do know that Australians are interested in donating organs. What has not been explored is how people feel about donating brain tissue for medical research. This study examines the verbal responses of the next of kin, on the day of autopsy of the deceased, to the question of brain donation for medical research. On the day of autopsy a telephone call was made to the next of kin. Families were asked to consider donating the brain tissue of the deceased to medical research. All responses were recorded. Fifty-eight per cent of families contacted by telephone gave permission for the brain donation. The main reasons given for donating the brain to research were wanting to help others, and the family knowing the deceased's wishes. This is an excellent response from families and more encouraging than the literature would predict. Further education and awareness about brain donation is needed and may be achieved effectively by combining donation options with the Australian Organ Donor Register.

Evaluation of DNA pooling for the estimation of microsatellite allele frequencies: a case study using striped bass (Morone saxatilis).

Using striped bass (Morone saxatilis) and six multiplexed microsatellite markers, we evaluated procedures for estimating allele frequencies by pooling DNA from multiple individuals, a method suggested as cost-effective relative to individual genotyping. Using moment-based estimators, we estimated allele frequencies in experimental DNA pools and found that the three primary laboratory steps, DNA quantitation and pooling, PCR amplification, and electrophoresis, accounted for 23, 48, and 29%, respectively, of the technical variance of estimates in pools containing DNA from 2-24 individuals. Exact allele-frequency estimates could be made for pools of sizes 2-8, depending on the locus, by using an integer-valued estimator. Larger pools of size 12 and 24 tended to yield biased estimates; however, replicates of these estimates detected allele frequency differences among pools with different allelic compositions. We also derive an unbiased estimator of Hardy-Weinberg disequilibrium coefficients that uses multiple DNA pools and analyze the cost-efficiency of DNA pooling. DNA pooling yields the most potential cost savings when a large number of loci are employed using a large number of individuals, a situation becoming increasingly common as microsatellite loci are developed in increasing numbers of taxa.

Characterization of gabaergic neurons within the human medial mamillary nucleus.

The morphology, distribution and relative frequency of GABAergic neurons in the medial mamillary nucleus (MMN) of normal human individuals was studied using a glutamic acid decarboxylase (GAD) antiserum. GAD-immunoreactive (GAD-IR) neurons were found sparsely distributed throughout the MMN and most displayed a simple bipolar morphology. A small population of large diameter GAD-IR neurons was found in the white matter capsule adjacent to the ventral border of the MMN. Results of double-labeling experiments revealed no evidence of calretinin, parvalbumin or calbindin immunoreactivities co-localizing with GAD-IR neurons. GAD-IR neurons of the MMN had an average somal area of 138+/-41 microm2, compared with the average somal area of 384+/-137 microm2 for the population of MMN neurons as a whole. GAD-IR neurons had a tendency to cluster in groups of two (and occasionally three) and showed a distribution gradient across the MMN with higher densities being found near the insertion of the fornix, the origin of the mamillo-thalamic tract and toward the medial MMN border. Quantitative estimates of GAD-IR neuron frequency revealed the GAD-IR phenotype to constitute an average of 1.7% percent of the total neuron population within the human MMN. These findings suggest that inhibitory activity within the human MMN is regulated in part by a small population of intrinsic GABAergic interneurons.

The diffusive spread of alleles in heterogeneous populations.

The spread of genes and individuals through space in populations is relevant in many biological contexts. I study, via systems of reaction-diffusion equations, the spatial spread of advantageous alleles through structured populations. The results show that the temporally asymptotic rate of spread of an advantageous allele, a kind of invasion speed, can be approximated for a class of linear partial differential equations via a relatively simple formula, c = 2 square root of (rD), that is reminiscent of a classic formula attributed to R. A. Fisher. The parameters r and D represent an asymptotic growth rate and an average diffusion rate, respectively, and can be interpreted in terms of eigenvalues and eigenvectors that depend on the population's demographic structure. The results can be applied, under certain conditions, to a wide class of nonlinear partial differential equations that are relevant to a variety of ecological and evolutionary scenarios in population biology. I illustrate the approach for computing invasion speed with three examples that allow for heterogeneous dispersal rates among different classes of individuals within model populations.

A diffusion-based theory of organism dispersal in heterogeneous populations.

We develop a general theory of organism movement in heterogeneous populations that can explain the leptokurtic movement distributions commonly measured in nature. We describe population heterogeneity in a state-structured framework, employing advection-diffusion as the fundamental movement process of individuals occupying different movement states. Our general analysis shows that population heterogeneity in movement behavior can be defined as the existence of different movement states and among-individual variability in the time individuals spend in these states. A presentation of moment-based metrics of movement illustrates the role of these attributes in general dispersal processes. We also present a special case of the general theory: a model population composed of individuals occupying one of two movement states with linear transitions, or exchange, between the two states. This two-state "exchange model" can be viewed as a correlated random walk and provides a generalization of the telegraph equation. By exploiting the main result of our general analysis, we characterize the exchange model by deriving moment-based metrics of its movement process and identifying an analytical representation of the model's time-dependent solution. Our results provide general and specific theoretical explanations for empirical patterns in organism movement; the results also provide conceptual and analytical bases for extending diffusion-based dispersal theory in several directions, thereby facilitating mechanistic links between individual behavior and spatial population dynamics.

Banking for the future: an Australian experience in brain banking.

The New South Wales (NSW) Tissue Resource Centre (TRC) has been set up to provide Australian and international researchers with fixed and frozen brain tissue from cases that are well characterised, both clinically and pathologically, for projects related to neuropsychiatric and alcohol-related disorders. A daily review of the Department of Forensic Medicine provides initial information regarding a potential collection. If the case adheres to the strict inclusion criteria, the pathologist performing the postmortem examination is approached regarding retention of the brain tissue. The next of kin of the deceased is then contacted requesting permission to retain the brain for medical research. Cases are also obtained through donor programmes, where donors are assessed and consent to donate their brain during life. Once the brain is removed at autopsy, the brain is photographed, weighed and the volume determined, the brainstem and cerebellum are removed. The two hemispheres are divided, one hemisphere is fresh frozen and one fixed (randomised). Prior to freezing, the hemisphere is sliced into 1-cm coronal slices and a set of critical area blocks is taken. All frozen tissues are kept bagged at -80 degrees C. The other hemisphere is fixed in 15% buffered formalin for 2 weeks, embedded in agar and sliced at 3-mm intervals in the coronal plane. Tissue blocks from these slices are used for neuropathological analysis to exclude any other pathology. The TRC currently has 230 cases of both fixed and frozen material that has proven useful in a range of techniques in many research projects. These techniques include quantitative analyses of brain regions using neuropathological, neurochemical, neuropharmacological and gene expression assays.

Feeding under predation hazard: testing models of adaptive behavior with stream fish.

Many empirical studies support the premise that animals consider both the benefits of feeding and the cost of mortality when making behavioral decisions, and many theoretical studies predict animal behavior in the presence of a feeding-mortality trade-off. However, empirical work is lacking in studies that quantitatively assess alternative models. Using data from two sets of behavioral experiments examining stream minnows (bluehead chubs) foraging in the presence of sunfish predators (green sunfish), we assess, via statistical model fitting, the utility of four basic optimization models of foraging behavior. Our analysis of feeding and mortality of the minnows indicates that mortality is incurred so as to feed above maintenance requirements, that feeding rate is suppressed in response to the presence of predators, and that the balance of feeding against mortality can be estimated using a life-history parameter theta, interpreted theoretically as the marginal rate of substitution of mortality rate for growth rate. Our results indicate that both body size and age are probably involved in determining the value of theta, and we suggest that future studies should focus on estimating and understanding this parameter.

Stress-induced enhancement of auditory startle: an animal model of posttraumatic stress disorder.

An innovative animal model of posttraumatic stress disorder (PTSD) is proposed in which nonhabituation of the acoustic startle response is developed in rats subsequent to tailshock exposure. Subjects (n = 31) received 30 minutes of intermittent tail shock on 2 days followed by exposure to the tailshock apparatus on the third day. Compared to baseline startle reactions, 9 of 31 tailshock-exposed rats developed nonhabituation of startle response reactions during the subsequent 3 weeks of testing. No control rats developed nonhabituation of startle reactions over a similar time period. These data suggest that this system models useful aspects of clinical PTSD emphasizing nonhabituation of startle reactions as a dependent variable. The method consistently identifies a subgroup of rats that develop persistent nonhabituation of startle in response to a tailshock-stress paradigm.

Heroin-related deaths in Sydney, Australia. How common are they?

The objective of this article was to determine the number of recent deaths caused by accidental illicit drug overdoses seen at the NSW Institute of Forensic Medicine, Glebe (Sydney). All Forensic cases (3559) were reviewed during the period July 1995-February 1997. Any that were classified as accidental illicit drug overdose were followed up, and demographic and toxicological data were collected for analysis. Our results found that one hundred and forty three accidental illicit drug overdoses were identified from 3359 autopsies during the 20 month data collection period (4%). Male to female ratio was 5:1, but females predominated in the methadone toxicity group. Most of the cases were under 40 years of age. Toxicological results showed that 80% of the deaths were associated with morphine (heroin) levels in the toxic range, although 91% had morphine present at some level. Only 35% of cases had significant levels of bile morphine, suggesting "chronic" usage. In many cases, multiple illicit substances and/or alcohol were thought to be important contributing factors. Cocaine was found in 13% of cases, and all of these had morphine (heroin) in their blood. Methadone was found in 13% of cases, and 13/19 had toxic levels--9/19 also had morphine in their blood. Only two cases had amphetamines or methamphetamines in their blood. The authors conclude that Heroin overdose is by far the most common cause of accidental illicit drug overdose. Those at greatest risk are naive users and those who are not tolerant. There is an urgent need for increased awareness and further education concerning the dangers of heroin use, particularly of multiple drug use (including alcohol). Only about one-third of these cases appear to be "chronic" users.

Actuarial risk assessment models: a review of critical issues related to violence and sex-offender recidivism assessments.

Risk assessment in the area of identification of violence has been dichotomized by several prominent researchers as the "clinical approach" versus the "actuarial method". The proponents of the actuarial approach argue for actuarially derived decisions to replace existing clinical practice. The actuarial method requires no clinical input, just a translation of the relevant material from the records to calculate the risk score. A risk appraisal approach based upon a sole actuarial method raises several questions: those of public safety, peer-accepted standards of practice, liability issues, and concordance with evidence-based medicine practice. We conclude that the sole actuarial approach fails to satisfy these critical issues.

Size of mamillary bodies in health and disease: useful measurements in neuroradiological diagnosis of Wernicke's encephalopathy.

BACKGROUND: As the resolution of noninvasive neuroimaging techniques improves, small structures such as the mamillary bodies can be visualized and measured. The mamillary bodies are pathologically small in a number of neurological disorders, the most common and important is chronic Wernicke's encephalopathy (WE), or the Wernicke-Korsakoff syndrome (WKS), as it is often called. This disorder is caused by vitamin B1 deficiency (thiamin) and is seen most commonly in people who drink excessive amounts of alcohol. The disorder is easily preventable by using oral or parenteral thiamin. The aim of this study was to establish a range for the volume of the mamillary bodies in normal and in various disease states, particularly WE. METHODS: Brains were taken from 2212 sequential autopsies performed at the New South Wales Institute of Forensic Medicine from 1996 through 1997. After fixation in 10% formalin, the brains were sectioned coronally and a block containing the mamillary bodies was dissected. The maximum vertical and transverse diameters of the mamillary bodies were measured using Mitutoyo vernier callipers and the volume calculated (V = 4/3 (a2b), where a and b are the vertical and transverse radii, respectively). RESULTS: There were 164 cases with significant pathological changes in the mamillary bodies. These included cases with WE (25), Alzheimer's discase (10), infarction (11), and trauma (55). All but two of the WE cases were chronic or acute on chronic. The mean volume of the mamillary bodies was reduced by 60% in cases with chronic WE and by 25% in cases with Alzheimer's disease. In normal cases, there was a significant age-related reduction in volume, and males had larger mamillary bodies than females. Cases with alcoholic cirrhosis of the liver had normal mamillary body volumes. CONCLUSIONS: There is a gross shrinkage of the mamillary bodies in cases of chronic WE, but clinicians need to consider other diagnoses, such as Alzheimer's disease, which can also result in shrinkage. These quantitative data will be helpful in the neuroradiological diagnosis of some of these disorders, particularly WE.