Male reproductive toxicity of vincristine: ultrastructural changes in the epididymal epithelial apical cell

The toxic effect of vincristine on the apical cells of the rat caput epididymis was investigated. The drug was administered at 20 and 40 microg/kg body weight daily for 15 days. Light microscopy using semithin sections, and transmission electron microscopy, of the caput epididymis were undertaken. The results revealed that the basal region of the apical cell was in contact with the basement membrane and the luminal end took part in endocytosis. The apical cells reflected a dose-dependent response to vincristine (VCR) treatment. In general the changes included protrusion of the apical ends deep into the lumen, with the nucleus of the cell located in such protruded ends, and an increase in the abundance of lysosomal bodies and multivesicular bodies. These changes reflected the physiological response of the apical cell to VCR treatment rather than toxic manifestations.     

Golgi matrix protein gene, Golga3/Mea2, rearranged and re-expressed in pachytene spermatocytes restores spermatogenesis in the mouse

In a transgenic mouse, Golga3/Mea2 gene (human homolog: GOLGA3/golgin-160) was disrupted by a translocation at the site of the transgene integration. Exons 8-24 of the disrupted gene remained intact and formed a fusion gene (DeltaMea2) with the antisense strand of E. coli-derived transgene by means of a cryptic splice signal in there. The protein product of DeltaMea2, virtually a form truncated to 2/3 of the normal size, localized to Golgi apparatus of pachytene spermatocytes and round spermatids. DeltaMea2 expression was specific to the testis, but varied among separate seminiferous tubules. It also showed variation among homozygous individuals from 0.5 to 4.3% of the wild type (wt) level. At the lowest levels, neither spermatids nor spermatozoa were present in the homozygous testes, but when the expression of DeltaMea2 increased to 4.3% of the wt level, high sperm production was restored and a sporadic (1/22) fertile homozygous male was obtained. The earliest apoptotic degeneration of pachytene spermatocytes evidenced at 17 dpp in homozygous testes in some discrete seminiferous tubules was preceded by DeltaMea2 expression in a variegated fashion at 16 dpp. These results consistently indicated that in homozygous testes, the pachytene spermatocytes which failed to express DeltaMea2 may undergo apoptotic degeneration. Golga3/Mea2, and DeltaMea2 in homozygotes, in a certain excessive amount may be important for survival of pachytene spermatocytes in the mouse.     

Setaria cervi: kinetic studies of filarial glutathione synthetase by high performance liquid chromatography

The bovine filarial worm Setaria cervi was found to have abundance of glutathione synthetase (GS; EC 6.3.2.3) activity, the enzyme being involved in catalysing the final step of glutathione (GSH) biosynthesis. A RP-HPLC method involving precolumn derivatization with o-phthalaldehyde has been followed for the estimation of GS activity in crude filarial preparations. Subcellular fractionation of the enzyme was undertaken and it was confirmed to be a soluble protein residing mainly in cytosolic fraction. Attempts to determine the Km value for L-gamma-glutamyl-L-cysteine gave a distinctly nonlinear double-reciprocal plot in which data obtained at relatively high dipeptide concentrations (>1 mM) extrapolate to a Km value of about 400 microM whereas data obtained at lower concentrations (<0.1 mM) extrapolate to a value of about 33 microM. Km was determined to be around 950 and 410 microM for ATP and glycine, respectively. The effect of various amino acids was studied on enzyme activity at 1mM concentration. L-cystine caused a significant enzyme inhibition of 11%. Preincubation with N-ethylmaleimide also resulted in significant inhibition of GS activity.     

Temporal transmission studies of mouse parvovirus 1 in BALB/c and C.B-17/Icr-Prkdc(scid) mice

Fecal shedding and transmission of mouse parvovirus 1 (MPV) to naive sentinels, breeding mates, and progeny were assessed. Neonatal SCID and BALB/c mice inoculated with MPV were evaluated over 24 wk; several mice from each strain were mated once during this period. Fecal MPV loads for each cage were determined weekly by quantitative polymerase chain reaction (PCR) analysis, and all mice were evaluated by quantitative PCR analysis of lymphoid tissues and seroconversion to MPV antigens in immunocompetent mice. Results indicated persistently high fecal shedding of MPV in SCID mice throughout the evaluation period sufficient to allow transmission to sentinels, naive breeding partners, and the progeny of infected male mice and naive partners. Lymphoid tissue viral loads in the progeny of infected female SCID mice were high at weaning but low at 6 wk of age. Infected BALB/c mice shed high levels of MPV in feces for 3 wk postinoculation, with seroconversion only in sentinels exposed during the first 2 wk postinoculation. Thereafter the feces of infected BALB/c mice and the lymphoid tissues of sentinels, naive breeding partners, and progeny intermittently contained extremely low levels of MPV DNA. Although pregnancy and lactation did not increase viral shedding in BALB/c mice, MPV exposure levels were sufficient to induce productive infection in some BALB/c progeny. These data indicate that the adaptive immune response suppresses, but does not eliminate, MPV shedding; this suppression is sufficient to inhibit infection of weanling and adult mice but allows productive infection of some progeny.     

Tenascin-R: role in the central nervous system

Tenascin-R (TN-R), a member of the tenascin family of extracellular matrix glycoproteins, is exclusive to the nervous system. It affects cell migration, adhesion and differentiation, although no remarkable clinical consequences have been shown in knock-out animal models. TN-R's expression pattern suggests a possible primary or secondary role in certain neurological problems including malformations, tumors and neurodegenerative disorders. This review summarizes the structure and molecular interactions of this molecule and discusses its function and possible roles in the central nervous system.     

Leptin concentration in breast milk and its relationship to duration of lactation and hormonal status

Mass media content likely influences the decision of women to breastfeed their newborn children. Relatively few studies have empirically assessed such a hypothesis to date, however. Most work has tended to focus either on specific interventions or on broad general commentary about the role of media. In this study, we examined infant feeding advertisements in 87 issues of Parents' Magazine, a popular parenting magazine, from the years 1971 through 1999. We then used content analysis results to predict subsequent changes in levels of breastfeeding among U.S. women. When the frequency of hand feeding advertisements increased, the percentage change in breastfeeding rates reported the next year generally tended to decrease. These results underscore the need to acknowledge the potential role of popular media content in understanding breastfeeding patterns and public health trends.     

The Role of Conformational Dynamics and Allostery in the Disease Development of Human Ferritin

Determining the three-dimensional structure of myoglobin, the first solved structure of a protein, fundamentally changed the way protein function was understood. Even more revolutionary was the information that came afterward: protein dynamics play a critical role in biological functions. Therefore, understanding conformational dynamics is crucial to obtaining a more complete picture of protein evolution. We recently analyzed the evolution of different protein families including green fluorescent proteins (GFPs), β-lactamase inhibitors, and nuclear receptors, and we observed that the alteration of conformational dynamics through allosteric regulation leads to functional changes. Moreover, proteome-wide conformational dynamics analysis of more than 100 human proteins showed that mutations occurring at rigid residue positions are more susceptible to disease than flexible residue positions. These studies suggest that disease-associated mutations may impair dynamic allosteric regulations, leading to loss of function. Thus, in this study, we analyzed the conformational dynamics of the wild-type light chain subunit of human ferritin protein along with the neutral and disease forms. We first performed replica exchange molecular dynamics simulations of wild-type and mutants to obtain equilibrated dynamics and then used perturbation response scanning (PRS), where we introduced a random Brownian kick to a position and computed the fluctuation response of the chain using linear response theory. Using this approach, we computed the dynamic flexibility index (DFI) for each position in the chain for the wild-type and the mutants. DFI quantifies the resilience of a position to a perturbation and provides a flexibility/rigidity measurement for a given position in the chain. The DFI analysis reveals that neutral variants and the wild-type exhibit similar flexibility profiles in which experimentally determined functionally critical sites act as hinges in controlling the overall motion. However, disease mutations alter the conformational dynamic profile, making hinges more loose (i.e., softening the hinges), thus impairing the allosterically regulated dynamics.