STP position paper: Recommended practices for sampling and processing the nervous system (brain, spinal cord, nerve, and eye) during nonclinical general toxicity studies

The Society of Toxicologic Pathology charged a Nervous System Sampling Working Group with devising recommended practices to routinely screen the central nervous system (CNS) and peripheral nervous system (PNS) in Good Laboratory Practice-type nonclinical general toxicity studies. Brains should be weighed and trimmed similarly for all animals in a study. Certain structures should be sampled regularly: caudate/putamen, cerebellum, cerebral cortex, choroid plexus, eye (with optic nerve), hippocampus, hypothalamus, medulla oblongata, midbrain, nerve, olfactory bulb (rodents only), pons, spinal cord, and thalamus. Brain regions may be sampled bilaterally in rodents using 6 to 7 coronal sections, and unilaterally in nonrodents with 6 to 7 coronal hemisections. Spinal cord and nerves should be examined in transverse and longitudinal (or oblique) orientations. Most Working Group members considered immersion fixation in formalin (for CNS or PNS) or a solution containing acetic acid (for eye), paraffin embedding, and initial evaluation limited to hematoxylin and eosin (H&E)-stained sections to be acceptable for routine microscopic evaluation during general toxicity studies; other neurohistological methods may be undertaken if needed to better characterize H&E findings. Initial microscopic analyses should be qualitative and done with foreknowledge of treatments and doses (i.e., "unblinded"). The pathology report should clearly communicate structures that were assessed and methodological details. Since neuropathologic assessment is only one aspect of general toxicity studies, institutions should retain flexibility in customizing their sampling, processing, analytical, and reporting procedures as long as major neural targets are evaluated systematically.

IntelliCage Automated Behavioral Phenotyping Reveals Behavior Deficits in the 3xTg-AD Mouse Model of Alzheimer's Disease Associated With Brain Weight

Transgenic rodent models of Alzheimer's disease (AD) were designed to study mechanisms of pathogenesis and connect these mechanisms with cognitive decline. Measurements of cognition in rodents can be confounded, however, by human handling and interaction; the IntelliCage was created to circumvent these issues while measuring various facets of cognition in a social environment with water consumption as the primary motivator for task completion. Here, for the first time, we examined the behavioral performance of 3xTg-AD mice in the IntelliCage. Seven- to 9-month-old female 3xTg-AD and non-transgenic (NonTg) mice were tested for 29 days in the IntelliCage to measure prefrontal cortical and hippocampal function. We found that a higher percentage of NonTg mice (86.96%) were able to successfully complete the training (adaptation) phases compared to their 3xTg-AD (57.14%) counterparts. Furthermore, the 3xTg-AD mice showed impairments in attention and working memory. Interestingly, we found that differences in body and brain weight between NonTg and 3xTg-AD mice were associated with whether mice were able to complete the IntelliCage tasks. 3xTg-AD mice that completed IntelliCage tasks had lower cortical insoluble amyloid-β40 fractions than their 3xTg-AD counterparts who failed to complete the tasks. Collectively, these results demonstrate deficits in cognition in the 3xTg-AD mouse and inform scientists of important factors to consider when testing this transgenic model in the IntelliCage.

Organ weights and ratios for postmortem identification of fetal growth restriction: utility and confounding factors

OBJECTIVES

The postmortem fetal brain:liver weight ratio is commonly used as a marker of nutrition for diagnosis of fetal growth restriction (FGR). However, there are limited data regarding the effects of intrauterine retention, fetal maceration and postmortem interval on organ weights and their ratios at autopsy. Our aims were to examine the relationships between gestational-age-adjusted and sex-adjusted fetal organ weights at autopsy, cause of intrauterine death and effects of intrauterine retention, and to determine whether the brain:liver weight ratio is a reliable marker of FGR in intrauterine death.

METHODS

As part of a larger study examining autopsy findings in intrauterine death, data from two specialist centers in London were collated in a specially designed database. Autopsy and clinical information for > 1000 intrauterine deaths between 2005 and 2013 were extracted. Adjusted (delta) organ weights were calculated by plotting against gestational age female and male brain, liver, thymus, heart, combined kidney, combined lung, spleen and combined adrenal gland weights. Polynomial regression was used to determine best fit and to calculate expected (50^th centile) organ weights and deviations from expected. We compared adjusted organ weights and body:organ weight ratios in fetuses which were small-for-gestational age (SGA) at autopsy (birth weight < 10^th centile for normal live births) vs those in fetuses which were not, and in macerated vs non-macerated fetuses.

RESULTS

The majority of fetal organs (brain, liver, heart, thymus, lungs, kidneys and thyroid) in SGA fetuses were significantly lighter than those in non-SGA fetuses. Body:organ weight ratios for thymus, liver and spleen were significantly greater in SGA fetuses, indicating these organs to be disproportionately small. The majority of organs were significantly lighter in macerated compared with non-macerated fetuses and body:organ weight ratios for most organs (liver, thymus, lung, pancreas, adrenal gland, kidney, heart) were significantly greater in macerated compared with non-macerated fetuses. When SGA cases with demonstrable placental histological abnormalities were compared with other SGA cases, there was a significant difference in the brain:liver weight ratio (median, 6 vs 3.5).

CONCLUSION

Changes after intrauterine death lead to loss of fetal weight, with preferential weight loss of visceral organs such as the liver. Maceration therefore affects the brain:liver weight ratio and adjustment should be made for such changes during interpretation of ratios. Fetal organ weights may be affected significantly by mechanism of death and postmortem changes. The fetal brain:liver weight ratio may provide useful information regarding intrauterine growth status at time of death, provided that adjustment is made for effects of intrauterine retention and that appropriate cut-off values are used. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Brain weight in sudden unexpected death in infancy: experience from a large single-centre cohort

AIMS

Published reports of brain weight in sudden infant death syndrome (SIDS) are contradictory, although several have concluded that brain weight is increased in SIDS compared with controls or reference data. This is important as, if brain weight is significantly different, it may be of diagnostic use or provide insights into the aetiology of SIDS. The aim of this study was to use a large series of well-characterized sudden unexpected infant deaths from a single centre to provide definitive data regarding this issue.

METHODS

A retrospective review identified 1100 infants who had died suddenly and undergone a comprehensive autopsy at Great Ormond Street Hospital between 1996 and 2011. They were split into two groups: those in whom death could be explained and those whose deaths remained unexplained despite full investigation (SIDS/unexplained sudden unexpected death in infancy).

RESULTS

There were 1100 cases of whom 573 (52%) were unexplained and 527 (48%) explained. Multiple regression analysis, which adjusted for sex, age and post-mortem interval, showed no difference in the ratio of brain weight : body weight between those infants dying of explained causes and those in whom no cause could be found. This finding remained true when restricting analysis to those with macroscopically normal brains.

CONCLUSIONS

In this large series of infants dying of both explained and unexplained causes, brain weight, once corrected for body weight, did not vary consistently with the cause of death. Brain weight cannot be used as a diagnostic indicator of the cause of death or to inform hypothetical models of the pathogenesis of SIDS.

Genetic basis of thermal nociceptive sensitivity and brain weight in a BALB/c reduced complexity cross

Thermal nociception involves the transmission of temperature-related noxious information from the periphery to the CNS and is a heritable trait that could predict transition to persistent pain. Rodent forward genetics complement human studies by controlling genetic complexity and environmental factors, analysis of end point tissue, and validation of variants on appropriate genetic backgrounds. Reduced complexity crosses between nearly identical inbred substrains with robust trait differences can greatly facilitate unbiased discovery of novel genes and variants. We found BALB/cByJ mice showed enhanced sensitivity on the 53.5°C hot plate and mechanical stimulation in the von Frey test compared to BALB/cJ mice and replicated decreased gross brain weight in BALB/cByJ versus BALB/cJ. We then identified a quantitative trait locus (QTL) on chromosome 13 for hot plate sensitivity (LOD = 10.7; p < 0.001; peak = 56 Mb) and a QTL for brain weight on chromosome 5 (LOD = 8.7; p < 0.001). Expression QTL mapping of brain tissues identified H2afy (56.07 Mb) as the top transcript with the strongest association at the hot plate locus (FDR = 0.0002) and spliceome analysis identified differential exon usage within H2afy associated with the same locus. Whole brain proteomics further supported decreased H2AFY expression could underlie enhanced hot plate sensitivity, and identified ACADS as a candidate for reduced brain weight. To summarize, a BALB/c reduced complexity cross combined with multiple-omics approaches facilitated identification of candidate genes underlying thermal nociception and brain weight. These substrains provide a powerful, reciprocal platform for future validation of candidate variants.

Anti-Aging Activity of Andaliman (Zanthoxylum Acanthopodium DC) Fruit Ethanol Extract on Brain Weight and p16INK4a Expression of Hippocampus in Aging Model Rats

BACKGROUND

Physiological aging and due to oxidative stress in long term will have an impact on cellular response disorders, can caused aging of hippocampus and senility. Brain weight is known to decrease with age and p16INK4a as aging biomarkers have been investigated. Andaliman is one of typical herbal plants from North Sumatra has been widely used as an antioxidant, anti-inflammatory and anti-aging.

OBJECTIVE

This study was evaluated effect of andaliman (Zanthoxylum acanthopodium DC) fruit ethanol extract (AEE) on brain weight and p16INK4a expression in aging model rats.

METHODS

This study was carried out experimentally of 24 male wistar rats. The treatment group consisted of 4 groups; KN= negatif control (normal), KP= positif control (aging model rat), P1 and P2= aging model rat + AEE at dose 150 and 300mg/kgbw, respectively. The aging model rats were D-galactose-induced at dose of 150mg/kgbw for 8 weeks. Brain weigth were recorded by digital scales. p16INK4a expression using immunohistochemical methods. The data analysis with Anova test.

RESULTS

This study showed differences brain weight between groups (p=0.523). Brain weight in P1 (1.34±0,06) and P2 (1.30±0.09) tendency increased than KP (1.29±0.62). The p16INK4a expression between groups significant difference (p=0.041), continued with post hoc Least Significant Difference (LSD) showed p16INK4a expression in KN significant decreased than KP (p=0.027). Likewise, p16INK4a expression in P2 was significant decreased than KP (p=0.010).

CONCLUSION

Andaliman ethanol extract at a dose 300mg/kgbw for 8 weeks was improved aging process caused D-galactose induced.

Gender-Specific Effects of Two Treatment Strategies in a Mouse Model of Niemann-Pick Disease Type C1

In a mouse model of Niemann-Pick disease type C1 (NPC1), a combination therapy (COMBI) of miglustat (MIGLU), the neurosteroid allopregnanolone (ALLO) and the cyclic oligosaccharide 2-hydroxypropyl-β-cyclodextrin (HPßCD) has previously resulted in, among other things, significantly improved motor function. The present study was designed to compare the therapeutic effects of the COMBI therapy with that of MIGLU or HPßCD alone on body and brain weight and the behavior of NPC1^−/− mice in a larger cohort, with special reference to gender differences. A total of 117 NPC1^−/− and 123 NPC1^+/+ mice underwent either COMBI, MIGLU only, HPßCD only, or vehicle treatment (Sham), or received no treatment at all (None). In male and female NPC1^−/− mice, all treatments led to decreased loss of body weight and, partly, brain weight. Concerning motor coordination, as revealed by the accelerod test, male NPC1^−/− mice benefited from COMBI treatment, whereas female mice benefited from COMBI, MIGLU, and HPßCD treatment. As seen in the open field test, the reduced locomotor activity of male and female NPC1^−/− mice was not significantly ameliorated in either treatment group. Our results suggest that in NPC1^−/− mice, each drug treatment scheme had a beneficial effect on at least some of the parameters evaluated compared with Sham-treated mice. Only in COMBI-treated male and female NPC^+/+ mice were drug effects seen in reduced body and brain weights. Upon COMBI treatment, the increased dosage of drugs necessary for anesthesia in Sham-treated male and female NPC1^−/− mice was almost completely reduced only in the female groups.

Three-dimensional ultrasound virtual organ computer-aided analysis to monitor fetal intracranial volume development characteristics: A multi-center study in a Chinese population

OBJECTIVES

This study aimed to evaluate the feasibility of monitoring fetal intracranial volume using three-dimensional ultrasound virtual organ computer-aided analysis (VOCAL) technology and to analyze normal fetal brain growth.

METHODS

This multi-center prospective cross-sectional study included 821 pregnant women (18-40 gestational weeks) divided into 23 groups according to gestational week. We used transabdominal three-dimensional ultrasound VOCAL to monitor fetal intracranial volume; explore the correlation between intracranial volume and gestational age, biparietal diameter (BPD), and head circumference (HC); and analyze the proportion of brain weight to body weight.

RESULTS

The intracranial volume of normal fetuses conformed to the normal distribution, gradually increased with gestational age, and was highly correlated with gestational age (r = 0.977), BPD (r = 0.975), and HC (r = 0.953; p < 0.001). The median percentage of brain weight (BW) to estimated fetal weight (EFW) was between 13% and 21%, and the BW/EFW ratio showed a significant downward trend in the third trimester. The VOCAL technology monitored the fetal intracranial volume with good repeatability.

CONCLUSIONS

VOCAL technology is feasible for monitoring the fetal intracranial volume, and the intracranial volume increases more than 10-times in the second and third trimesters.

Genetic and environmental control of variation in retinal ganglion cell number in mice

How much of the remarkable variation in neuron number within a species is generated by genetic differences, and how much is generated by environmental factors? We address this problem for a single population of neurons in the mouse CNS. Retinal ganglion cells of inbred and outbred strains, wild species and subspecies, and F1 hybrids were studied using an unbiased electron microscopic method with known technical reliability. Ganglion cell numbers among diverse types of mice are highly variable, ranging from 32,000 to 87,000. The distribution of all cases (n = 252) is close to normal, with a mean of 58,500 and an SD of 7800. Genetic factors are most important in controlling this variation; 76% of the variance is heritable and up to 90% is attributable to genetic factors in a broad sense. Strain averages have an unanticipated bimodal distribution, with distinct peaks at 55,500 and 63,500 cells. Three pairs of closely related strains have ganglion cell populations that differ by > 20% (10,000 cells). These findings indicate that different alleles at one or two genes have major effects on normal variation in ganglion cell number. Nongenetic factors are still appreciable and account for a coefficient of variation that averages approximately 3.6% within inbred strains and isogenic F1 hybrids. Age- and sex-related differences in neuron number are negligible. Variation within isogenic strains appears to be generated mainly by developmental noise.

Mammalian Life History: Weaning and Tooth Emergence in a Seasonal World

The young of toothed mammals must have teeth to reach feeding independence. How tooth eruption integrates with gestation, birth and weaning is examined in a life-history perspective for 71 species of placental mammals. Questions developed from high-quality primate data are then addressed in the total sample. Rather than correlation, comparisons focus on equivalence, sequence, the relation to absolutes (six months, one year), the distribution of error and adaptive extremes. These mammals differ widely at birth, from no teeth to all deciduous teeth emerging, but commonalities appear when infants transit to independent feeding. Weaning follows completion of the deciduous dentition, closest in time to emergence of the first permanent molars and well before second molars emerge. Another layer of meaning appears when developmental age is counted from conception because the total time to produce young feeding independently comes up against seasonal boundaries that are costly to cross for reproductive fitness. Mammals of a vast range of sizes and taxa, from squirrel monkey to moose, hold conception-to-first molars in just under one year. Integrating tooth emergence into life history gives insight into living mammals and builds a framework for interpreting the fossil record.

Natural variation in neuron number in mice is linked to a major quantitative trait locus on Chr 11

Common genetic polymorphisms-as opposed to rare mutations-generate almost all heritable differences in the size and structure of the CNS. Surprisingly, these normal variants have not previously been mapped or cloned in any vertebrate species. In a recent paper (), we suggested that much of the variation in retinal ganglion cell number in mice, and the striking bimodality of strain averages, are caused by one or two quantitative trait loci (QTLs). To test this idea, and to map genes linked to this variable and highly heritable quantitative trait, we have counted ganglion cells in 38 recombinant inbred strains (BXD and BXH) derived from parental strains that have high and low cell numbers. A genome-wide search using simple and composite interval-mapping techniques revealed a major QTL on chromosome (Chr) 11 in a 3 cM interval between Hoxb and Krt1 (LOD = 6.8; genome-wide p = 0.001) and possible subsidiary QTLs on Chr 2 and Chr 8. The Chr 11 locus, neuron number control 1 (Nnc1), accounts for one third of the genetic variance among BXH strains and more than half of that among BXD strains, but Nnc1 has no known effects on brain weight, eye weight, or total retinal cell number. Three strong candidate genes have been mapped previously to the same region as Nnc1. These genes-Rara, Thra, and Erbb2- encode receptors for retinoic acid, thyroxine, and neuregulin, respectively. Each receptor is expressed in the retina during development, and their ligands affect the proliferation or survival of retinal cells.