Mutagenic effects of carbosulfan,a carbamate pesticide

The genotoxic effects of carbosulfan were evaluated using chromosome aberration (CA), bone marrow micronucleus (MN) and sperm abnormality assays in mice. All the three acute doses (1.25, 2.5 and 5mg/kg) of carbosulfan induced significant dose-dependent increase in the frequency of CA (P<0.02), micronucleated polychromatic erythrocytes (PCEs) (P<0.05) and sperm head abnormalities (P<0.05) but did not affect the total sperm count. The highest acute dose of carbosulfan induced >7-fold increase in the frequency of CA, >3.5-fold increase in the frequency of micronucleated PCEs and >4.6-fold increase in the frequency of sperms with abnormal head morphology following intraperitoneal exposure as compared to the untreated controls. The present findings suggest that carbosulfan is a potent genotoxic agent and may be regarded as a potential germ cell mutagen also.     

Molecular analysis of a carbohydrate antigen involved in the structure and function of zona pellucida glycoproteins

A lactosaminoglycan-associated antigen is associated with a carbohydrate moiety of all three zona pellucida (ZP) glycoproteins of pig and rabbit but is absent in the mouse and rat. A monoclonal antibody (PS1) recognizing this determinant was obtained by immunizing mice with a porcine ZP glycoprotein isoform purified by two-dimensional polyacrylamide gel electrophoresis. Conditions known to remove O-linked or sialic acid carbohydrate moieties (alkaline reduction; O-glycanase or neuraminidase enzymatic cleavage) did not remove the carbohydrate epitope. However, treatment with endo-beta-glycosidase, endoglycosidase F, or combinations of neuraminidase plus beta-galactosidase, totally removed the determinant, indicating that it is associated with a poly-N-acetyllactosaminoglycan structure present on an N-linked oligosaccharide. Molecular morphology studies using immunofluorescence and confocal microscopy techniques demonstrate that the PS1 antigen is localized at the surface of the ZP. Confirmation of this localization was obtained through studies that show that this antibody will inhibit homologous sperm binding to the pig ZP. Additional analyses using modular contrast microscopy and immunocytochemistry demonstrate that this carbohydrate-associated antigen is localized in discrete layers throughout the ZP matrix. These studies are the first to demonstrate the presence of a lactosaminoglycan type carbohydrate moiety in all three ZP proteins using a monoclonal antibody that appears to be involved in sperm recognition and structural organization.     

Characterization of Serine Proteinase Inhibitor from Subabul (Leucaena leucocephala Lam) Seeds

Partially purified subabul trypsin inhibitor (STI) showed high level of thermotolerance and pH stability with a molecular weight of -15 kD. Bioassay results showed that STI is a strong inhibitor of Helicoverpa armigera larval gut proteinases. In vitro feeding experiments revealed 40% mortality in inhibitor fed larvae followed by 12 days extension in larval growth period and significant reduction in pupal weight. Differential activity staining for the larval gut proteolytic enzymes did not show any difference in the isoprotease pattern between the control and the larvae fed with STI.     

An intermediate polymer in the assembly of clathrin baskets

Clathrin (8 S) is known to polymerize into two varieties of basket structures (150 S or 300 S) under the normal buffer conditions [100 mM 2-(N-morpholino)ethanesulfonic acid (Mes), pH 5.9-6.7] used for the isolation of coated vesicles. However, it is now observed that under very low salt conditions (2 mM Mes, pH 5.9), it forms a homogeneous species with a sedimentation coefficient of 27 S. Increasing the salt concentration to 50 mM Mes completely converts all the 27S species into 150S baskets. Sedimentation equilibrium data show that this 27S species has a molecular weight that is 6 times that of the clathrin protomer and is the result of highly cooperative reversible self-association of the 8S protomer. Light-scattering studies show that the stabilities of 27S species and baskets (150 S or 300 S) are comparable. Fluorescent labeling of sulfhydryl groups with N-(1-anilinonaphthalenyl)maleimide indicates that the conformation of clathrin in 27S species and baskets (150 S or 300 S) is similar. Trypsin digestion reveals that in the 27S species clathrin has a conformation differing from that in both the 8S species and baskets.     

Free and total thyroid hormones in humans at extreme altitude

Alterations in circulatory levels of total T₄ (TT₄), total T₃ (TT₃), free T₄ (FT₄), free T₃ (FT₃), thyrotropin (TSH) and T₃ uptake (T₃U) were studied in male and female sea-level residents (SLR) at sea level, in Armed forces personnel staying at high altitude (3750 m) for prolonged duration (acclimatized lowlanders, ALL) and in high-altitude natives (HAN). Identical studies were also performed on male ALL who trekked to an extreme altitude of 5080 m and stayed at an altitude of more than 6300 m for about 6 months. The total as well as free thyroid hormones were found to be significantly higher in ALL and HAN as compared to SLR values. Both male as well as female HAN had higher levels of thyroid hormones. The rise in hormone levels in different ALL ethnic groups drawn from amongst the southern and northern parts of the country was more or less identical. In both HAN and ALL a decline in FT₃ and FT₄ occurred when these subjects trekked at subzero temperatures to extreme altitude of 5080 m but the levels were found to be higher in ALL who stayed at 6300 m for a prolonged duration. Plasma TSH did not show any appreciable change at lower altitudes but was found to be decreased at extreme altitude. The increase in thyroid hormones at high altitude was not due to an increase in hormone binding proteins, since T₃U was found to be higher at high altitudes. A decline in TSH and hormone binding proteins and an increase in the free moiety of the hormones is indicative of a subtle degree of tissue hyperthyroidism which may be playing an important role in combating the extreme cold and hypoxic environment of high altitudes.     

Mitotic factors from mammalian cells: A preliminary characterization

The objective of this study was the preliminary characterization of the factors from mitotic HeLa cells that can induce meiotic maturation in Xenopus laevis oocytes. We found that this factor is a heat-labile, Ca²⁺-sensitive, nondialyzable protein with a sedimentation value of 4-5S. Furthermore, no new protein synthesis was found to be required for this mitotic factor to induce maturation in the amphibian oocytes. These data suggest that the factors involved in the breakdown of nuclear membrane and the condensation of chromosomes that are associated with three different phenomena, mitosis, meiosis, and premature chromosome condensation, are very similar in different animal species.