Possible role of metal ionophore against zinc induced cognitive dysfunction in <Emphasis Type="SmallCaps">d-</Emphasis>galactose senescent mice

Metal ionophores are considered as potential anti-dementia agents, and some are currently undergoing clinical trials. Many metals are known to accumulate and distribute abnormally in the aging brain. Alterations in zinc metal homeostasis in the glutaminergic synapse could contribute to ageing and the pathophysiology of Alzheimer’s disease (AD). The present study was designed to investigate the effect of metal ionophores on long term administration of zinc in D-galactose induced senescent mice. The ageing model was established by combined administration of zinc and D-galactose to mice for 6 weeks. A novel metal ionophore, PBT-2 was given daily to zinc-induced d-galactose senescent mice. The cognitive behaviour of mice was monitored using the Morris Water Maze. The anti-oxidant status and amyloidogenic activity in the ageing mouse was measured by determining mito-oxidative parameters and deposition of amyloid β (Aβ) in the brain. Systemic administration of both zinc and D-galactose significantly produced memory deficits, mito-oxidative damage, heightened acetylcholinesterase enzymatic activity and deposition of amyloid-β. Treatment with PBT-2 significantly improved behavioural deficits, biochemical profiles, cellular damage, and curbed the deposition of APP in zinc-induced senescent mice. These findings suggest that PBT-2, acting as a metal protein attenuating compound, may be helpful in the prevention of AD or alleviation of ageing.     

Characterization and partial purification of <Emphasis Type="Italic">Candida albicans</Emphasis> Secretory IL-12 Inhibitory Factor

Background  

We have previously shown that supernatant from Candida albicans (CA) culture contains a Secretory Interleukin (IL)-12 Inhibitory Factor (CA-SIIF), which inhibits IL-12 production by human monocytes. However, the effect of CA-SIIF on secretion of other cytokines by monocytes is unknown, and detailed characterization of this factor has not been performed.     

Generalized linear models with random effects; salamander mating revisited.

In recent years much effort has been devoted to extending regression methodology to non-Gaussian data, where responses are not independent. These methods for dependent responses are suitable for data from longitudinal studies or nested designs. However, use of these methods for crossed designs seems to have serious limitations due to the intensive computations involved because of the intractable nature of the joint distribution. In this paper, we cast the problem in a Bayesian framework and use a Monte Carlo method, the Gibbs sampler, to avoid current computational limitations. The flexibility of this approach is illustrated by analyzing the interesting salamander mating data reported by McCullagh and Nelder (1989, Generalized Linear Models, 2nd edition, London: Chapman and Hall).     

Intracellular regulation of cell signaling cascades: how location makes a difference

Organelles such as endosomes and the Golgi apparatus play a critical role in regulating signal transmission to the nucleus. Recent experiments have shown that appropriate positioning of these organelles within the intracellular space is critical for effective signal regulation. To understand the mechanism behind this observation, we consider a reaction-diffusion model of an intracellular signaling cascade and investigate the effect on the signaling of intracellular regulation in the form of a small release of phosphorylated signaling protein, kinase, and/or phosphatase. Variational analysis is applied to characterize the most effective regions for the localization of this intracellular regulation. The results demonstrate that signals reaching the nucleus are most effectively regulated by localizing the release of phosphorylated substrate protein and kinase near the nucleus. Phosphatase release, on the other hand, is nearly equally effective throughout the intracellular space. The effectiveness of the intracellular regulation is affected strongly by the characteristics of signal propagation through the cascade. For signals that are amplified as they propagate through the cascade, reactions in the upstream levels of the cascade exhibit much larger sensitivities to regulation by release of phosphorylated substrate protein and kinase than downstream reactions. On the other hand, for signals that decay through the cascade, downstream reactions exhibit larger sensitivity than upstream reactions. For regulation by phosphatase release, all reactions within the cascade show large sensitivity for amplified signals but lose this sensitivity for decaying signals. We use the analysis to develop a simple model of endosome-mediated regulation of cell signaling. The results demonstrate that signal regulation by the modeled endosome is most effective when the endosome is positioned in the vicinity of the nucleus. The present findings may explain at least in part why endosomes in many cell types localize near the nucleus.     

Ultrastructure of the pineal gland of the tropical bat Rousettus leschenaulti

The ultrastructure of the pineal organ was studied in the tropical megachiropteran Rousettus leschenaulti. The pineal lies deep beneath the hemispheres adjacent to the third ventricle and is traversed by the habenular commissure anteriorly. Its parenchyma consists of a uniform population of light and occasional dark pinealocytes which appear to differ only in the degree of cytoplasmic staining. Pinealocytes are characterized by well developed Golgi bodies associated with numerous small vesicles, many mitochondria and polyribosomes, and frequent subsurface cisternae. Lipid droplets and elements of smooth endoplasmic reticulum are scant. Cisternae of granular endoplasmic reticulum are occasionally dilated. A distinct feature is the abundance of clear vesicles in the pinealocyte pericapillary terminals, which also frequently contain granular vesicles and a very large vacuole. The pineal is further characterized by the presence of a small number of glial cells and myelinated nerve fibers. A broad perivascular space investing numerous capillaries contains glial-cell and pinealocyte processes, collagen fibrils and abundant unmyelinated nerve fibers. Tortuous extensions of the perivascular space enter the pineal parenchyma where they come in close proximity to branched intercellular channels or canaliculi characterized by specialized junctions and microvilli. Differences between the pineal of the non-hibernating megachiropteran Rousettus and that of the hibernating microchiropteran bats, and structural similarities to the pineal of tropical rodents are discussed.     

Signal processing, glycosylation, and secretion of mutant hemagglutinins of a human influenza virus by Saccharomyces cerevisiae.

We investigated the nature of signal recognition, transport, and secretion of mutant hemagglutinins (HAs) of a human influenza virus by the yeast Saccharomyces cerevisiae. The cDNA sequences encoding variant forms of influenza HA were expressed in S. cerevisiae. The HA polypeptides (HA500 and HA325) that were synthesized with their N-terminal signal peptides were correctly targeted to the membrane compartment where they were glycosylated. In contrast, the HA polypeptides (HA484 and HA308) lacking the signal peptide were expressed in the cytoplasm and did not undergo any glycosidic modification, demonstrating the importance of the heterologous signal sequence in the early steps of translocation in S. cerevisiae. The analysis of the N-terminal amino acid sequence of HA500 and HA325 polypeptides demonstrated the correct cleavage of the signal peptide, indicating the structural compatibility of a heterologous signal peptide for efficient recognition and processing by the yeast translocation machinery. The membrane-sequestered and glycosylated HA polypeptides were relatively stable in S. cerevisiae compared with the signal-minus, nonglycosylated HA molecules. Although both the anchor-minus HA (HA500) and HA1 (HA325) polypeptides were targeted efficiently to the membrane, their glycosylation and transport patterns were shown to be different. During pulse-chase, the HA500 remained cell-associated with no detectable secretion into the extracellular medium, whereas the HA325 secreted into the medium. Furthermore, only the cell-associated and secreted forms of HA325 and not HA500 appeared to have undergone hyperglycosylation with the extensive addition of high-molecular-weight outer-chain mannans. Possible reasons for the observed phenotypic behavior of these two mutant HAs are discussed.     

Compatability of Metarhizium anisopliae var. anisopliae with chemical pesticides

The effects of various insecticides on the mycelial growth, sporulation and conidial germination of Metarhizium anisopliae var. anisopliae isolate E₉ were studied in the laboratory. Chlorpyrifos was the most toxic organophosphate to mycelial growth and sporulation at all concentrations. Temephos, malathion and leptophos were highly toxic to sporulation while malathion was the most inhibitory to germination. The carbamates, carbofuran, methomyl and oxamyl were moderately toxic to mycelial growth and sporulation while oxamyl had an adverse effect on germination. The pyrethroids (pyrethrin, permethrin and resmethrin) and the insect growth regulators (diflubenzuron and methoprene) were not inhibitory to the various developmental stages of isolate E₉. The chlorinated hydrocarbons (chlordane, lindane and toxaphene) were more deleterious than all other insecticide groups tested. Among the fungicides, benomyl and maneb produced the greatest inhibition.     

The effect of age on the response of the detrusor to intracellular mechanical stimulus: DNA replication and the cell actin matrix.

Benign prostatic hypertrophy and posterior urethral valves present at both extremes of the age spectrum. Both disease processes can obstruct the urinary stream and ultimately have pathophysiological effects on detrusor structure and function. The mechanisms regulating the structural reorganization of the detrusor to a mechanical outflow obstruction are not known. In an attempt to identify maturational differences in myocyte ultrastructure and consequent effects these might have in modifying the response of the detrusor to mechanical stimulus, we studied differences in dynamic nuclear-cytoskeletal interactions in detrusor tissue in an animal model. Using a drug which specifically severs actin, cytochalasin D (CD), as an intracellular mechanical stimulus, we measured changes in nuclear area and the rate of DNA synthesis in detrusor myocytes from young (2-3 week) and old (8-12 mon) guinea pigs. We found that there were age specific differences to intracellular mechanical stimuli in detrusor muscle. Nuclei of myocytes from young animals showed elastic recoil on severing the cell actin matrix and the tissue from young animals increased replicative DNA synthesis with an intracellular stimulus. In contrast, nuclear shape changes in myocytes from old animals suggested less elasticity, and there was no increase in DNA synthesis with disruption of the cell actin matrix. Anti-alpha-smooth muscle actin antibody and rhodamine phalloidin staining of actin in cytochalasin D treated primary explants of detrusor myocytes showed dose dependent disruption of the actin component of the cytoskeleton. These results suggest that there are fundamental modifications in detrusor myocyte ultrastructure with age. These maturational changes might result in differences in the pathophysiological and structural reorganization of the detrusor in response to outflow obstruction in infancy and adulthood. Furthermore, they suggest that 1) a tensile equilibrium exists between the myocyte nucleus and cytoskeleton; 2) there appears to be a decrease in myocyte nuclear elasticity with ageing; 3) release of nuclear template restrictions increases activity of DNA polymerase alpha in young, but not old, detrusor myocytes; and 4) mechanico-chemical signal transduction in detrusor myocytes may be mediated via the cytoskeleton. In addition, based on previous reports of actin within the nucleus, the results suggest that 1) nuclear actin may have a homeostatic structural role, maintaining the tensile equilibrium between nucleus and cytoskeleton, and 2) integrity of nuclear actin may function to maintain the spatial template restriction on DNA polymerase alpha activity.