Immunochemical studies on shigella dysenteriae type 9 bacterial polysaccharide

On graded hydrolysis and Smith degradation, the O-somatic polysaccharide isolated from Shigella dysenteriae type 9 bacteria, strain NCTC 7919, yielded five oligosaccharides which were characterized. The positions of the O-acetyl and pyruvic acetal groups in the repeating unit were identified. Immunochemical studies indicated that d-galactose is the immunodominant sugar in the polysaccharide, and one of the oligomers, having the structure Gal-(1→3)-GlcNAc-(1→3)-Gal-(1→4)-Man, showed maximum inhibition of the homologous precipitation.     

Cell Wall Composition of Neurospora crassa Under Conditions of Copper Toxicity

The mycelia of Neurospora crassa grown in the presence of high concentrations of copper were blue in color, but only on a medium containing inorganic nitrate and phosphate as the nitrogen and phosphate sources, respectively. The cell wall isolate of the blue mycelia contained large amounts (12%) of copper and higher amounts of chitosan, phosphate, and amino groups, with a 42% decrease in the chitin content. Although all the glucosamine of the cell wall of control cultures could be released within 6 h of hydrolysis with acid, that of the blue mycelium required prolonged hydrolysis for 24 h. On removal of copper, the cell wall of the blue mycelium could quantitatively bind again to copper as well as to zinc. Although zinc binding was fivefold greater, copper alone was preferentially bound from a mixture of the two metal ions. Supplementation of iron along with copper in the culture medium resulted in the disappearance of the blue color of the mycelium and restoration of normal growth and composition of the cell wall, probably by limiting the uptake of copper from the medium. The possibility of the cell wall being a specific site of lesion in copper toxicity in the mold is discussed.     

Blood pressure levels of Rellis (India) with special reference to variations with age

The paper presents a survey of arterial blood pressures measured in 193 adult males and females of Relli community, selected at random from Visakhapatnam City, Andhra Pradesh. Age shows more influence on the rise of systolic than diastolic blood pressure. Females show a higher rate of rise in both pressures with advancing age. The incidence of hypertension is also found to be higher in females than in males.     

Fluidity,permeability and antioxidant behaviour of model membranes incorporated with α-tocopherol and vitamin E acetate

Magnetic resonance studies reveal a marked difference between the binding of α-tocopherol and that of the corresponding acetate (vitamin E acetate) with dipalmitoylphosphatidylcholine (DPPC) vesicles. This is reflected in differences in the phase-transition curves of the DPPC vesicles incorporated with the two compounds, as well as in the ¹³C relaxation times and line widths. A model for the incorporation of these molecules in lipid bilayers has been suggested. α-Tocopherol binds strongly with the lipids, possibly through a hydrogen bond formation between the hydroxyl group of the former and one of the oxygen atoms of the latter. The possibility of such a hydrogen bond formation is excluded in vitamin E acetate, which binds loosely through the normal hydrophobic interaction. The model for lipid-vitamin interaction explains the in vitro decomposition of H₂O₂ by α-tocopherol. α-Tocopherol in conjuction with H₂O₂ can also act as a free-radical scavenger in the lipid phase. The incorporation of α-tocopherol and vitamin E acetate in DPPC vesicles enhances the permeability of lipid bilayers for small molecules such as sodium ascorbate.     

beta-N-gamma-glutamyl diaminopropionic acid, a convulsant and an inhibitor of brain glutamate decarboxylase

The different isomers of the dipeptide beta-N-gamma-glutamyl diaminopropionate inhibit L-glutamate-1-carboxylyase (GAD, EC-4.1.1.15) activity in mouse brain homogenates. The L-D isomer is the most effective as an inhibitor, while the D-D isomer is least inhibitory. The different isomers are neurotoxic to mice and the chick, the L-D isomer being the most toxic. The neurotoxicity of the isomers in mice was also associated with a significant lowering in GAD activity in the brains of convulsing mice.     

Comparison of vascular hemodynamics in experimental models of microvascular anastomoses

Blood flow was measured in the canine saphenous artery using electromagnetic flowmetry. Significant increase in blood flow was noted after occlusion of the distal femoral artery. However, after raising a saphenous island flap there was no significant change in the blood flow before and after distal femoral artery occlusion. The flap peripheral resistance and blood flow were compared after end-to-end and end-to-side anastomosis and no statistical difference was noted.     

Evidence for the presence of inhibitors of mitotic factors during G1 period in mammalian cells

Our earlier studies indicated that the mitotic factors, which induce germinal vesicle breakdown and chromosome condensation when injected into fully grown Xenopus oocytes, are preferentially associated with metaphase chromosomes and that they bind to chromatin as soon as they are synthesized during the G2 phase. In this study, we attempted to determine the fate of these factors as the cell completes mitosis and enters G1. Extracts from HeLa cells at different points during G1, S, and G2 periods were mixed with mitotic extracts in various proportions, incubated, and then injected into Xenopus oocytes to determine their maturation-promoting activity. The maturation-promoting activity of the mitotic extracts was neutralized by extracts of G1 cells during all stages of G1 but not by those of late S and G2 phase cells. Extracts of quiescent (G0) human diploid fibroblasts exhibited very little inhibitory activity. However, UV irradiation of G0 cells, which is known to cause decondensation of chromatin, significantly enhanced the inhibitory activity of extracts of these cells. These factors are termed inhibitors of mitotic factors (IMF). They seem to be activated, rather than newly synthesized, as the cell enters telophase when chromosomes begin to decondense. The IMF are nondialyzable, nonhistone proteins with a molecular weight of greater than 12,000. Since mitotic factors are known to induce chromosome condensation, it is possible that IMF, which are antagonistic to mitotic factors, may serve the reverse function of the mitotic factors, i.e., regulation of chromosome decondensation.     

Cuticular lesions induced in grass shrimp exposed to hexavalent chromium

Adult grass shrimp were exposed to four concentrations (0.5, 1.0, 2.0 and 4.0 ppm) of hexavalent chromium for 28 days. At the end of the exposure period, over 50% of the surviving shrimp possessed cuticular lesions that had many of the gross characteristics of “shell disease.” These lesions were usually associated with articulations of the appendages and abdomen. Furthermore, it was found that at increasing levels of chromium exposure, there was a proportionate increase in the loss of limbs such that nearly 50% of the limbs were lost in grass shrimp exposed to the highest test concentration of chromium. Histological and ultrastructural examination of numerous lesions demonstrated a range of degenerative features within the subcuticular epithelium that included cytoplasmic vacuolization, mitochondrial swelling, chromatin emargination, and the presence of unusual nuclear inclusions that appear to indicate direct chromium toxicity. Additionally, a marked retardation in new epicuticle and exocuticle formation was observed in viable tissues associated with lesions in late premolt shrimp. It is proposed that chromium interferes with the normal functions of subcuticular epithelium, particularly cuticle formation, and subsequently causes structural weaknesses or perforations to develop in the cuticle of newly moted shrimp. Because of these chromium-induced exoskeletal deficiencies, a viaduct for pathogenic organisms (e.g., bacteria) and direct chromium influx is formed that perpetuates lesion development.     

Disparate functional properties of two interleukin 1-responsive Ly-1+2- T cell clones: distinction of T cell growth factor and T cell-replacing factor activities

We describe the properties of two Ly-1+2- T cell clones (Ly-1.14 and Ly-1.21), which are maintained in long-term culture in the absence of other cell types. The clones require media containing a source of interleukin 1 as well as interleukin 2. They retain physiologic responses to interleukin 1, which is required for optimal production of T cell lymphokines by these clones in response to concanavalin A (Con A). The two Ly-1+2- T cell clones differ in their production of lymphokines after stimulation by Con A. The supernatant of clone Ly-1.21 promotes the proliferation of T cells maintained in long-term culture, induces antibody synthesis in cultures of B cells and antigen, and induces the differentiation of cytolytic cells in cultures of thymocytes and antigen; these assays define the properties of T cell growth factor (TCGF), T cell-replacing factor for B cells (TRF-B), and T cell-replacing factor for cytolytic cells (TRF-C), respectively. In contrast, the supernatant of clone Ly-1.14 contains only TCGF activity and does not promote antibody synthesis by B cells or differentiation of cytolytic cells from thymocytes. The results indicates that TCGF and TRF activities reside on independent, although perhaps related, molecules.