Effects of estradiol and FSH on maturation of the testis in the hypogonadal (hpg) mouse

Background  

The hypogonadal (hpg) mouse is widely used as an animal model with which to investigate the endocrine regulation of spermatogenesis. Chronic treatment of these GnRH-deficient mice with estradiol is known to induce testicular maturation and restore qualitatively normal spermatogenesis. The aim of the current studies was to investigate whether these effects of estradiol are direct effects in the testis, or indirect actions via paradoxical stimulation of FSH secretion from the pituitary gland.     

Oculocutaneous Albinism Type 1: The Last 100 Years

Research on human albinism has been central to many of the major discoveries in human genetics. These include the first evidence that Mendel's rules of genetic segregation apply to humans, first published in 1903. Contrary to initial thought that albinism is caused by mutations in a single gene, we now know that the genetics of albinism are complex. The complexity of albinism was hinted at, in early publications, but has only recently been fully appreciated with the advent of molecular techniques. Currently, 12 different genes have been identified, that when mutated, result in a different type of albinism. Oculocutaneous albinism type 1 (OCA1), resulting from mutations of the tyrosinase gene, is genetically and biochemically the best understood type of albinism. Though much of the research in albinism has involved OCA1, there are many unanswered questions about OCA1 and albinism, in general. The next 100 yr should still provide many surprises as did the first 100 yr.     

Delayed blockade of the kinin B1 receptor reduces renal inflammation and fibrosis in obstructive nephropathy

Renal fibrosis is the common histological feature of advanced glomerular and tubulointerstitial disease leading to end-stage renal disease (ESRD). However, specific antifibrotic therapies to slow down the evolution to ESRD are still absent. Because persistent inflammation is a key event in the development of fibrosis, we hypothesized that the proinflammatory kinin B1 receptor (B1R) could be such a new target. Here we show that, in the unilateral ureteral obstruction model of renal fibrosis, the B1R is overexpressed and that delayed treatment with an orally active nonpeptide B1R antagonist blocks macrophage infiltration, leading to a reversal of the level of renal fibrosis. In vivo bone marrow transplantation studies as well as in vitro studies on renal cells show that part of this antifibrotic mechanism of B1R blockade involves a direct effect on resident renal cells by inhibiting chemokine CCL2 and CCL7 expression. These findings suggest that blocking the B1R is a promising antifibrotic therapy.     

C. botulinum inactivation kinetics implemented in a computational model of a high‐pressure sterilization process

High‐pressure, high‐temperature (HPHT) processing is effective for microbial spore inactivation using mild preheating, followed by rapid volumetric compression heating and cooling on pressure release, enabling much shorter processing times than conventional thermal processing for many food products. A computational thermal fluid dynamic (CTFD) model has been developed to model all processing steps, including the vertical pressure vessel, an internal polymeric carrier, and food packages in an axis‐symmetric geometry. Heat transfer and fluid dynamic equations were coupled to four selected kinetic models for the inactivation of C. botulinum; the traditional first‐order kinetic model, the Weibull model, an nth‐order model, and a combined discrete log‐linear nth‐order model. The models were solved to compare the resulting microbial inactivation distributions. The initial temperature of the system was set to 90°C and pressure was selected at 600 MPa, holding for 220 s, with a target temperature of 121°C. A representation of the extent of microbial inactivation throughout all processing steps was obtained for each microbial model. Comparison of the models showed that the conventional thermal processing kinetics (not accounting for pressure) required shorter holding times to achieve a 12D reduction of C. botulinum spores than the other models. The temperature distribution inside the vessel resulted in a more uniform inactivation distribution when using a Weibull or an nth‐order kinetics model than when using log‐linear kinetics. The CTFD platform could illustrate the inactivation extent and uniformity provided by the microbial models. The platform is expected to be useful to evaluate models fitted into new C. botulinum inactivation data at varying conditions of pressure and temperature, as an aid for regulatory filing of the technology as well as in process and equipment design. © 2009 American Institute of Chemical Engineers Biotechnol. Prog., 2009     

HLA-Associated Clinical Progression Correlates with Epitope Reversion Rates in Early Human Immunodeficiency Virus Infection

Human immunodeficiency virus type 1 (HIV-1) can evade immunity shortly after transmission to a new host but the clinical significance of this early viral adaptation in HIV infection is not clear. We present an analysis of sequence variation from a longitudinal cohort study of HIV adaptation in 189 acute seroconverters followed for up to 3 years. We measured the rates of variation within well-defined epitopes to determine associations with the HLA-linked hazard of disease progression. We found early reversion across both the gag and pol genes, with a 10-fold faster rate of escape in gag (2.2 versus 0.27 forward mutations/1,000 amino acid sites). For most epitopes (23/34), variation in the HLA-matched and HLA-unmatched controls was similar. For a minority of epitopes (8/34, and generally associated with HLA class I alleles that confer clinical benefit), new variants appeared early and consistently over the first 3 years of infection. Reversion occurred early at a rate which was HLA-dependent and correlated with the HLA class 1-associated relative hazard of disease progression and death (P = 0.0008), reinforcing the association between strong cytotoxic T-lymphocyte responses, viral fitness, and disease status. These data provide a comprehensive overview of viral adaptation in the first 3 years of infection. Our findings of HLA-dependent reversion suggest that costs are borne by some escape variants which may benefit the host, a finding contrary to a simple immune evasion paradigm. These epitopes, which are both strongly and frequently recognized, and for which escape involves a high cost to the virus, have the potential to optimize vaccine design.The dynamics of viral replication in acute and early human immunodeficiency virus (HIV) infection are not well understood as longitudinal data from large cohorts of seroconverters are hard to assemble. Recent studies have shown that new HIV infections may be the result of a single transmitted variant, that new env gene mutations can be detected within a few weeks (25), and that early immune escape can be detected at sites across the HIV genome (9). These data add to a body of work showing that cytotoxic T cells act early, contributing to the early reduction in viremia (8, 30).Whether early cytotoxic T-lymphocyte (CTL) immune responses influence longer-term clinical outcome is not clear. Antigen-specific CTLs capable of producing gamma interferon and other cytokines are detectable at all stages of HIV infection (1, 3, 24, 41). Much weight is placed on the macaque/simian immunodeficiency virus model in which nearly total peripheral blood CD8⁺ T-cell elimination using monoclonal antibodies results in rising viremia (42). The role of other forms of host immunity (e.g., neutralizing antibodies, natural killer cells, and macrophages) has, to some extent, been pursued with less intensity in light of persuasive evidence that CTLs can control retrovirus infection (46). The extent to which the simian model mirrors HIV infection has been questioned (5) and, despite exhaustive cellular assays of T-cell function—from gamma interferon enzyme-linked immunospot assays(1, 27, 38) to polyfunctional cytokine matrices (2, 6)—no CTL function correlates robustly with HIV plasma viral load or viral dynamics. Moreover, analyses of evolutionary data suggest that CTLs are inefficient at killing HIV-infected cells (4).However, statistical analysis of data from large cross-sectional studies link HLA class I alleles with specific genome-wide HIV polymorphisms, suggestive of a pervasive selection pressure enacted by CTLs (7, 10, 18, 36, 40). It is clear that associations between some HLA class I alleles and particular amino acid polymorphisms are robust although it is disputed whether immune escape influences disease progression. The viral fitness costs resulting from immune escape may even contribute to better clinical outcomes associated with the possession of HLA class I alleles such as B*27, B*57, and B*58 (18).Evolutionary studies of HIV require longitudinal data from large cohorts of patients sampled since seroconversion to detect adaptation in new hosts as it accrues. HIV is one of the few pathogens where it is possible to do this within individuals because of the high viral turnover and rapid intrahost evolution. Here, we investigate a cohort of 189 acute seroconverters—the largest cohort reported to date—followed for up to 3 years to study the rates of viral mutation in individual epitopes within internal HIV proteins and to determine the association between HLA class I alleles and rates of immune escape and reversion.     

Whole genome sequencing of a natural recombinant Toxoplasma gondii strain reveals chromosome sorting and local allelic variants

Background  

Toxoplasma gondii is a zoonotic parasite of global importance. In common with many protozoan parasites it has the capacity for sexual recombination, but current evidence suggests this is rarely employed. The global population structure is dominated by a small number of clonal genotypes, which exhibit biallelic variation and limited intralineage divergence. Little is known of the genotypes present in Africa despite the importance of AIDS-associated toxoplasmosis.     

Does diurnal temperature variability affect growth in juvenile Atlantic salmon Salmo salar?

This study investigated the effects of diurnal temperature variability (>7° C) on the growth of 1+ year Atlantic salmon Salmo salar. Experimental manipulation of water temperature was used to simulate: (1) constant and (2) naturally varying thermal regimes with similar daily mean values. Data from two replicates of four treatments (two thermal and two feeding regimes) were collected over 6 months corresponding to the main spring to summer growth period. Fish growth was assessed at fortnightly intervals. Small but significant differences in mean fork length (L(F) ) and mass were observed between temperature treatments, with smaller, lighter fish under the variable temperature regime. The effects of temperature regime on growth were independent of food ration. At termination of the experiment, the median L(F) and mass of fish exposed to the variable temperature regime were estimated, respectively, to be 2· 6 and 8· 0% less than those under the constant regime. Given the relatively small differences in growth attributable to variable temperature regime in these experiments, it is suggested that mean daily temperatures are adequate to inform juvenile growth models for field-based studies.     

ABCA1 is required for normal central nervous system ApoE levels and for lipidation of astrocyte-secreted apoE

ABCA1 is an ATP-binding cassette protein that transports cellular cholesterol and phospholipids onto high density lipoproteins (HDL) in plasma. Lack of ABCA1 in humans and mice causes abnormal lipidation and increased catabolism of HDL, resulting in very low plasma apoA-I, apoA-II, and HDL. Herein, we have used Abca1-/- mice to ask whether ABCA1 is involved in lipidation of HDL in the central nervous system (CNS). ApoE is the most abundant CNS apolipoprotein and is present in HDL-like lipoproteins in CSF. We found that Abca1-/- mice have greatly decreased apoE levels in both the cortex (80% reduction) and the CSF (98% reduction). CSF from Abca1-/- mice had significantly reduced cholesterol as well as small apoE-containing lipoproteins, suggesting abnormal lipidation of apoE. Astrocytes, the primary producer of CNS apoE, were cultured from Abca1+/+, +/-, and -/- mice, and nascent lipoprotein particles were collected. Abca1-/- astrocytes secreted lipoprotein particles that had markedly decreased cholesterol and apoE and had smaller apoE-containing particles than particles from Abca1+/+ astrocytes. These findings demonstrate that ABCA1 plays a critical role in CNS apoE metabolism. Since apoE isoforms and levels strongly influence Alzheimer's disease pathology and risk, these data suggest that ABCA1 may be a novel therapeutic target.     

Regulation of fermentative capacity and levels of glycolytic enzymes in chemostat cultures of Saccharomyces cerevisiae

Regulation of fermentative capacity was studied in chemostat cultures of two Saccharomyces cerevisiae strains: the laboratory strain CEN.PK113-7D and the industrial bakers’ yeast strain DS28911. The two strains were cultivated at a fixed dilution rate of 0.10 h⁻¹ under various nutrient limitation regimes: aerobic and anaerobic glucose limitation, aerobic and anaerobic nitrogen limitation on glucose, and aerobic ethanol limitation. Also the effect of specific growth rate on fermentative capacity was compared in glucose-limited, aerobic cultures grown at dilution rates between 0.05 h⁻¹ and 0.40 h⁻¹. Biomass yields and metabolite formation patterns were identical for the two strains under all cultivation conditions tested. However, the way in which environmental conditions affected fermentative capacity (assayed off-line as ethanol production rate under anaerobic conditions) differed for the two strains. A different regulation of fermentative capacity in the two strains was also evident from the levels of the glycolytic enzymes, as determined by in vitro enzyme assays. With the exception of phosphofructokinase and pyruvate decarboxylase in the industrial strain, no clear-cut correlation between the activities of glycolytic enzymes and the fermentative capacity was found. These results emphasise the need for controlled cultivation conditions in studies on metabolic regulation in S. cerevisiae and demonstrate that conclusions from physiological studies cannot necessarily be extrapolated from one S. cerevisiae strain to the other.