Modulation of phorbol ester-elicited events in mouse epidermis by dietary n-3 and n-6 fatty acids

Because arachidonic acid-derived eicosanoids are potent modulators of hyperproliferation and inflammation during skin tumor promotion with the phorbol ester, 12-0-tetradecanoylphorbol-13-acetate (TPA) (17, 18), it was hypothesized that dietary modification of epidermal fatty acids might modulate TPA-induced biochemical events in mouse skin. Semipurified diets containing 10% total fat composed of corn oil (CO) or a combination of CO and menhaden oil (MO) or coconut oil (CT) were fed to SENCAR mice for 4 weeks. Fatty acid composition of epidermal phospholipids generally reflected fatty acid composition of dietary oils fed to the mice. Since fatty acid-derived eicosanoids are thought to be essential in tumorigenesis, we compared the effects of dietary fats on prostaglandin E (PGE) production in epidermis treated with a single dose of TPA. TPA-induced PGE production in mouse epidermis from mice fed the MO diet was significantly reduced compared to PGE production in epidermal homogenates from mice fed the CO or CT diets. Type of dietary fats did not appear to modulate TPA-induced vascular permeability, however hyperplasia was slightly elevated in skins of mice fed MO. The subcellular distribution of protein kinase C, the plasma membrane receptor for TPA predominantly located in the cytosol (80%), was altered in epidermis from mice fed the MO diet compared to preparations from mice fed CO or CT diets which exhibited normal protein kinase C distribution. Our results suggest that n-3 rich dietary lipids modulate TPA-elicited events in mouse skin to a greater extent than diets containing higher proportions of saturated or n-6 fatty acids.     

Vacuolar reticulum in oomycete hyphal tips: An additional component of the Ca2+Regulatory system?

Cultures of Achlya sp., Phytophthora cinnamomi, Saprolegnia diclina, S. ferax, and S. parasitica, treated with 6-carboxyfluorescein diacetate solution, accumulate 6-carboxyfluorescein in a reticulate system of fine tubules. The network shows longitudinal polarity within the hyphae, tubules being finest toward the hyphal tips. In more mature subapical regions the network is connected with large vacuoles that also accumulate 6-carboxyfluorescein. A morphologically similar system has also been identified in freeze-substituted hyphae of S. ferax. The network is considered to be vacuolar, but differs from the tubular vacuole system of true fungi in that tubules are less motile, more frequently branched, and do not alternate with clusters of spherical vacuoles. The appearance of the network resembles patterns of calcium-sensitive dye staining and it is suggested that the vacuolar reticulum in the tip region of oomycete hyphae may act as a Ca2+ sink. The tubular reticulum in oomycetes is very fragile and can be shown with 6-carboxyfluorescein in only those hyphal tips with a motility and organelle distribution characteristic of growing hyphae with normal morphology. Diverse abnormal hyphae show a range of other fluorochrome localizations. These include large irregular compartments filled with fluorochrome, and fluorescent cytoplasm with organelles and vacuoles standing out in negative contrast. These localizations in abnormal hyphae are correlated with other structural changes indicative of damage. Special care is required in experiments with oomycetes to avoid such artefacts of localization. Copyright 1997 Academic Press. Copyright 1997 Academic Press     

A queueing model for chronic recurrent conditions under panel observation

In many chronic conditions, subjects alternate between an active and an inactive state, and sojourns into the active state may involve multiple lesions, infections, or other recurrences with different times of onset and resolution. We present a biologically interpretable model of such chronic recurrent conditions based on a queueing process. The model has a birth-death process describing recurrences and a semi-Markov process describing the alternation between active and inactive states, and can be fit to panel data that provide only a binary assessment of the active or inactive state at a series of discrete time points using a hidden Markov approach. We accommodate individual heterogeneity and covariates using a random effects model, and simulate the posterior distribution of unknowns using a Markov chain Monte Carlo algorithm. Application to a clinical trial of genital herpes shows how the method can characterize the biology of the disease and estimate treatment efficacy.     

Molecular mechanism of ligand recognition by membrane transport protein,Mhp1

The hydantoin transporter Mhp1 is a sodium‐coupled secondary active transport protein of the nucleobase‐cation‐symport family and a member of the widespread 5‐helix inverted repeat superfamily of transporters. The structure of Mhp1 was previously solved in three different conformations providing insight into the molecular basis of the alternating access mechanism. Here, we elucidate detailed events of substrate binding, through a combination of crystallography, molecular dynamics, site‐directed mutagenesis, biochemical/biophysical assays, and the design and synthesis of novel ligands. We show precisely where 5‐substituted hydantoin substrates bind in an extended configuration at the interface of the bundle and hash domains. They are recognised through hydrogen bonds to the hydantoin moiety and the complementarity of the 5‐substituent for a hydrophobic pocket in the protein. Furthermore, we describe a novel structure of an intermediate state of the protein with the external thin gate locked open by an inhibitor, 5‐(2‐naphthylmethyl)‐L‐hydantoin, which becomes a substrate when leucine 363 is changed to an alanine. We deduce the molecular events that underlie acquisition and transport of a ligand by Mhp1.     

Excitatory and inhibitory neuron imbalance in the intrauterine growth restricted fetal guinea pig brain: Relevance to the developmental origins of schizophrenia and autism

Neurodevelopmental disorders such as schizophrenia and autism are thought to involve an imbalance of excitatory and inhibitory signaling in the brain. Intrauterine growth restriction (IUGR) is a risk factor for these disorders, with IUGR onset occurring during critical periods of neurodevelopment. The aim of this study was to determine the impact of IUGR on excitatory and inhibitory neurons of the fetal neocortex and hippocampus. Fetal brains (n = 2) were first collected from an unoperated pregnant guinea pig at mid-gestation (32 days of gestation [dg]; term ∼67 dg) to visualize excitatory (Ctip2) and inhibitory (calretinin [CR] and somatostatin [SST]) neurons via immunohistochemistry. Chronic placental insufficiency (CPI) was then induced via radial artery ablation at 30 dg in another cohort of pregnant guinea pigs (n = 8) to generate IUGR fetuses (52 dg; n = 8); control fetuses (52 dg; n = 7) were from sham surgeries with no radial artery ablation. At 32 dg, Ctip2- and CR-immunoreactive (IR) cells had populated the cerebral cortex, whereas SST-IR cells had not, suggesting these neurons were yet to complete migration. At 52 dg, in IUGR versus control fetuses, there was a reduction in SST-IR cell density in the cerebral cortex (p = .0175) and hilus of the dentate gyrus (p = .0035) but not the striatum (p > .05). There was no difference between groups in the density of Ctip2-IR (cortex) or CR-IR (cortex, hippocampus) neurons (p > 0.05). Thus, we propose that an imbalance in inhibitory (SST-IR) and excitatory (Ctip2-IR) neurons in the IUGR fetal guinea pig brain could lead to excitatory/inhibitory dysfunction commonly seen in neurodevelopmental disorders such as autism and schizophrenia.     

Using aggregate data to estimate the standard error of a treatment–covariate interaction in an individual patient data meta‐analysis

Subgroup analyses are important to medical research because they shed light on the heterogeneity of treatment effectts. A treatment–covariate interaction in an individual patient data (IPD) meta‐analysis is the most reliable means to estimate how a subgroup factor modifies a treatment's effectiveness. However, owing to the challenges in collecting participant data, an approach based on aggregate data might be the only option. In these circumstances, it would be useful to assess the relative efficiency and power loss of a subgroup analysis without patient‐level data. We present methods that use aggregate data to estimate the standard error of an IPD meta‐analysis’ treatment–covariate interaction for regression models of a continuous or dichotomous patient outcome. Numerical studies indicate that the estimators have good accuracy. An application to a previously published meta‐regression illustrates the practical utility of the methodology.     

Serologically detected lymphocyte antigens in Holstein cattle1

Lymphocytes from 103 Holstein cattle were tested with 11 antilymphocytotoxic sera. Four of these sera were produced by whole blood immunization; these generally yielded lymphocytotoxicity against a large number of animals in each test panel. The majority of the sera were collected from parous cows which had never been immunized. Observations about this latter group of sera are (1) lymphocyte antibodies may occur by alloimmunization in foetal-maternal interaction, (2) normal sera from non-immunized parous cows generally had a narrower specificity of antibodies than from parous cows immunized with blood from unrelated animals and in some cases these antisera may be monospecific, and (3) these sera from parous cows are easy to obtain without the need for laborious immunizations. Analysis of these lymphocytotoxic sera indicate several reagents were obtained which possessed different antibodies; these were useful in detecting polymorphism of cattle lymphocyte antigens. Using these 11 sera, an analysis of the reactions patterns among 103 Holsteins, including parent-offspring data resulted in the postulation of several alleles. These data suggest that cattle lymphocyte antigens are very polymorphic and inherited.     

Breed differences in frequency of BoLA specificities*

A total of 675 cattle of five purebred and one crossbred group were tested for lymphocyte antigens. The purebred animals represented progeny of 107 sires. Lymphocytotoxicity sera obtained from parous cows were used to detect six antigens which are controlled by codominant alleles at the BoLA-TxA locus. Gene frequencies for the six alleles varied within breeds and large differences were observed between breeds for a given allele.