David Groth

Reduction of inclusion body pathology in ApoE-deficient mice fed a combination of antioxidants

Clinical studies have shown that the antioxidant vitamin E can slow the progression of Alzheimers disease (AD). Other antioxidants reported to affect cognitive function include ginkgo biloba, vitamin C, and lipoic acid. To examine the effects of combination antioxidant therapy (CAT) on longevity and neuropathology in mice, we supplemented the diet of ApoE-deficient mice with vitamin E, ginkgo biloba, pycnogenol, and ascorbyl palmitate. ApoE-deficient mice normally exhibit increased numbers of PAS-positive inclusion bodies with aging. However, supplementation with CAT resulted in a significant increase in life span and a marked reduction of inclusion body histopathology in the hippocampus. In addition, while untreated apoE-deficient mice exhibited increased levels of TUNEL staining, a marker of DNA fragmentation, supplementation with CAT resulted in a significant reduction in the levels of TUNEL staining. These findings suggest that oxidative mechanisms, perhaps related to neuronal apoptosis, are integral to inclusion body formation in aging mice. The association between the reduced number of apoptotic cells and the reduction in inclusion bodies may explain in part the increased longevity of mice fed CAT, and supports the contention that the combined actions of selected antioxidants may be therapeutically effective against neurodegenerative diseases.

The structure and function of Alzheimer’s gamma secretase enzyme complex

The production and accumulation of the beta amyloid protein (Aβ) is a key event in the cascade of oxidative and inflammatory processes that characterizes Alzheimer’s disease (AD). A multi-subunit enzyme complex, referred to as gamma (γ) secretase, plays a pivotal role in the generation of Aβ from its parent molecule, the amyloid precursor protein (APP). Four core components (presenilin, nicastrin, aph-1, and pen-2) interact in a high-molecular-weight complex to perform intramembrane proteolysis on a number of membrane-bound proteins, including APP and Notch. Inhibitors and modulators of this enzyme have been assessed for their therapeutic benefit in AD. However, although these agents reduce Aβ levels, the majority have been shown to have severe side effects in pre-clinical animal studies, most likely due to the enzymes role in processing other proteins involved in normal cellular function. Current research is directed at understanding this enzyme and, in particular, at elucidating the roles that each of the core proteins plays in its function. In addition, a number of interacting proteins that are not components of γ-secretase also appear to play important roles in modulating enzyme activity. This review will discuss the structural and functional complexity of the γ-secretase enzyme and the effects of inhibiting its activity.

Evaluation of Color Preference in Zebrafish for Learning and Memory

There is growing interest in using zebrafish (Danio rerio) as a model of neurodegenerative disorders such as Alzheimers disease. A zebrafish model of tauopathies has recently been developed and characterized in terms of presence of the pathological hallmarks (i.e., neurofibrillary tangles and cell death). However, it is also necessary to validate these models for function by assessing learning and memory. The majority of tools to assess memory and learning in animal models involve visual stimuli, including color preference. The color preference of zebrafish has received little attention. To validate zebrafish as a model for color-associated-learning and memory, it is necessary to evaluate its natural preferences or any pre-existing biases towards specific colors. In the present study, we have used four different colors (red, yellow, green, and blue) to test natural color preferences of the zebrafish using two procedures: Place preference and T-maze. Results from both experiments indicate a strong aversion toward blue color relative to all other colors (red, yellow, and green) when tested in combinations. No preferences or biases were found among reds, yellows, and greens in the place preference procedure. However, red and green were equally preferred and both were preferred over yellow by zebrafish in the T-maze procedure. The results from the present study show a strong aversion towards blue color compared to red, green, and yellow, with yellow being less preferred relative to red and green. The findings from this study may underpin any further designing of color-based learning and memory paradigms or experiments involving aversion, anxiety, or fear in the zebrafish.

Latrepirdine: Molecular mechanisms underlying potential therapeutic roles in Alzheimer’s and other neurodegenerative diseases

Latrepirdine (DimebonTM) was originally marketed as a non-selective antihistamine in Russia. It was repurposed as an effective treatment for patients suffering from Alzheimer’s disease (AD) and Huntington’s disease (HD) following preliminary reports showing its neuroprotective functions and ability to enhance cognition in AD and HD models. However, latrepirdine failed to show efficacy in phase III trials in AD and HD patients following encouraging phase II trials. The failure of latrepirdine in the clinical trials has highlighted the importance of understanding the precise mechanism underlying its cognitive benefits in neurodegenerative diseases before clinical evaluation. Latrepirdine has shown to affect a number of cellular functions including multireceptor activity, mitochondrial function, calcium influx and intracellular catabolic pathways; however, it is unclear how these properties contribute to its clinical benefits. Here, we review the studies investigating latrepirdine in cellular and animal models to provide a complete evaluation of its mechanisms of action in the central nervous system. In addition, we review recent studies that demonstrate neuroprotective functions for latrepirdine-related class of molecules including the β-carbolines and aminopropyl carbazoles in AD, Parkinson’s disease and amyotrophic lateral sclerosis models. Assessment of their neuroprotective effects and underlying biological functions presents obvious value for developing structural analogues of latrepirdine for dementia treatment.

Regular care and maintenance of a Zebrafish (Danio rerio) laboratory: An introduction

This protocol describes regular care and maintenance of a zebrafish laboratory. Zebrafish are now gaining popularity in genetics, pharmacological and behavioural research. As a vertebrate, zebrafish share considerable genetic sequence similarity with humans and are being used as an animal model for various human disease conditions. The advantages of zebrafish in comparison to other common vertebrate models include high fecundity, low maintenance cost, transparent embryos, and rapid development. Due to the spur of interest in zebrafish research, the need to establish and maintain a productive zebrafish housing facility is also increasing. Although literature is available for the maintenance of a zebrafish laboratory, a concise video protocol is lacking. This video illustrates the protocol for regular housing, feeding, breeding and raising of zebrafish larvae. This process will help researchers to understand the natural behaviour and optimal conditions of zebrafish husbandry and hence troubleshoot experimental issues that originate from the fish husbandry conditions. This protocol will be of immense help to researchers planning to establish a zebrafish laboratory, and also to graduate students who are intending to use zebrafish as an animal model.

Genetic evidence for mixed parentage in nests of the emu (Dromaius novaehollandiae)

Abstract Parentage in emus (Dromaius novaehollandiae) was examined by microsatellite analysis using four independent loci. Of 106 chicks sampled in one breeding season from 18 nests, 54 (51%) were not fathered by the nesting male, 12 (11%) were not from the observed mate of the sitting male, and 9 (8%) represented intra-specific brood parasitism, having no alleles in common with either nest parent. Some males (11%) fathered all chicks in their nests, but the majority showed high levels of cuckoldry. Those males commencing incubation earliest in the season tended to have the highest levels of paternity in their own nests. These results reveal a high frequency of extra-pair fertilisations and resultant cuckoldry in a predominantly socially monogamous bird and support recent reports which have described the emu mating system as a complexity of polyandrous, promiscuous and monogamous behaviour. Parentage assignment of chicks resulting from extra-pair fertilisations revealed an evenly scattered pattern of paternity that did not show any particular male dominance in reproductive success. These results lead to a reassessment of behavioural observations of emus, the consequences of parentage distribution, and theories about mating systems and sexual selection. The frequency of extra-pair copulations and intra-specific brood parasitism suggests patterns of descent that differ greatly from those implied by social monogamy.

Gender balance in patients with systemic lupus erythematosus

Factors are reviewed that contribute to the contemporary view of a disproportionate prevalence and incidence of SLE in females. Recent studies on the epidemiology of SLE report that global incidences and prevalences of SLE for Caucasian and Black populations are of the order of 5.5 and 13.1 per year and 81 and 212 per 100,000 persons respectively. Both parameters displayed age dependent variation over a 90-year lifespan. The female to male (F:M) incidence of SLE varied with age, being approximately 1 during the first decade of life, followed by a sharp increase to 9 during the 4th decade, thence declining in subsequent decades before an increase during the 7th or 8th decade. A cognate review of SLE diagnosis in neonates revealed a F:M ratio of ≈1.2, consistent with the epidemiology review and the sporadic nature of SLE. Notional estimates of disease duration showed a steady increase from a base level for both males and females. The linear trend line for males was always lower than the trend line for females, supporting clinical experience that SLE is a more severe disease in males. Over a 14-year interval ending in 2012, the notional duration of SLE increased from 10-15years to 20-25years, probably reflecting advances in diagnosis and clinical practice. A metastudy of SLE concordance in twins revealed a 75% discordance in monozygotic twins compared to a 95% discordance in dizygotic twins confirming the importance of environmental factors in susceptibility to SLE. The elevated discordance in dizygotic SLE twins (and between siblings) suggests a role for the intrinsic genomic sexual dimorphism due to divergence of Y chromosome regulatory loci from their X chromosome homologues due to lack of recombination of mammalian sex chromosomes over evolutionary time. Estimates were made of the incidences of SLE in males and females based on population data for nine autosomal deficiency loci of major effect, plus expected male prevalence associated with Klinefelters syndrome and female prevalence associated with Triple X syndrome. These genetic abnormalities accounted for ≈4% of female and ≈23% of male Caucasoid prevalence and for SLE resulting in a F:M ratio of ≈0.17. It may be deduced therefore that the impressive preponderance of SLE in females arises from a combination of environmental triggers and susceptibility loci of relatively small effect acting between the interval from the mini-puberty of childhood to the peak of reproductive adulthood. It is in this cohort of females, and especially in the Black population, that combinations of loci of minor effect acting together with environmental factors initiate defective apoptosis resulting in consequential autoimmune disease especially SLE. We postulate that because apoptosis is itself a very complex process, and defective apoptosis is an important contributor to SLE, there will be many combinations of susceptibility loci and environmental stimuli that can result in SLE (and other autoimmune disease(s)), of varying severity.

The influence of MHC and immunoglobulins a and e on host resistance to gastrointestinal nematodes in sheep.

Gastrointestinal nematode parasites in farmed animals are of particular importance due to their effects on production. In Australia, it is estimated that the direct and indirect effects of parasite infestation cost the animal production industries hundreds of millions of dollars each year. The main factors considered by immunologists when studying gastrointestinal nematode infections are the effects the hosts response has on the parasite, which immunological components are responsible for these effects, genetic factors involved in controlling immunological responses, and the interactions between these forming an interconnecting multilevel relationship. In this paper, we describe the roles of immunoglobulins, in particular IgA and IgE, and the major histocompatibility complex in resistance to gastrointestinal parasites in sheep. We also draw evidence from other animal models to support the involvement of these immune components. Finally, we examine how IgA and IgE exert their influence and how methods may be developed to manage susceptible animals.

Isolation and detection of ingested DNA from the immature stages of Calliphora dubia (Diptera: Calliphoridae): A forensically important blowfly

The forensic entomologist frequently bases time since death (TSD) estimation on fly larvae. In some cases, the food source on which these larvae have completed their development may be questionable, and requires verification to ensure the accuracy of the TSD estimation. Ingested DNA may be isolated from the alimentary canal of immature insects. Previous studies have confirmed the ability to extract ingested DNA from the alimentary tract of third instar blowfly larvae. This study considers the potential to detect ingested DNA from immature stages of the blue-bodied blowfly Calliphora dubia (Macquart) that had fed on sheep liver. Individuals from early first instar larvae through day 3 pupae were surface decontaminated, followed by DNA isolation and detection by amplifying the sheep satellite I region. Fragments of 197 basepairs (bp) and 87 bp were successfully isolated and detected in all stages of immatures until 2-day-old pupae, with detection at this stage being unsuccessful on 3-day-old pupae. This study presents a suitable protocol for the isolation and detection of ingested DNA from immature stages of C. dubia.

Multiple incursions and putative species revealed using a mitochondrial and nuclear phylogenetic approach to the Trogoderma variabile (Coleoptera: Dermestidae) trapping program in Australia.

The Warehouse beetle, Trogoderma variabile (Coleoptera: Dermestidae), is an internationally significant invasive pest of packed goods and stored grain. When it was first documented in Australia at Griffith, New South Wales, in 1977, an eradication campaign was initiated. After several years and considerable effort, the eradication campaign was abandoned. To monitor the presence and spread of T. variabile, surveys were carried out by government agencies in 1992 and 2002. When survey data was compared, it was concluded that the distribution of morphologically identified T. variabile had doubled in most Australian states. Here, we used samples from the 2002 survey to conduct a phylogenetic study using partial sequences of mitochondrial genes Cytochrome oxidase I and Cytochrome B, and the nuclear gene 18S, to examine the distribution and dispersal of T. variabile and detect the presence of misidentified species. Based on our molecular results, we show that only 47% of the samples analysed were T. variabile, and the remaining were a mixture of six putative species. In addition, T. variabile was found in only 78% of the trapping sites. We discuss the importance of correct diagnosis in relation to the eradication campaign.