Barotolerant variant of Streptococcus faecalis with reduced sensitivity to glucose catabolite repression

Physiological characterization of the APR-11 variant of Streptococcus faecalis ATCC 9790 revealed that the variant has reduced sensitivity to glucose catabolite repression. This reduced sensitivity was indicated by the synthesis of enzymes for catabolism of lactose or arginine in cultures growing at 0.1, 40, or 70 MPa in media with levels of glucose highly repressive for the parent strain. Reduced catabolite repression appeared to be due to reduced activity of the glucose-specific, phosphotransferase system in APR-11 cells. Conversion of pyruvate to lactate or to acetate and ethanol did not appear to be altered in the variant. The APR-11 variant produced a greater final yield of biomass than the parent at all pressures tested, and its barotolerance was especially marked in media with low levels of glucose and high levels of lactose in which derepression of the lactose catabolic system was necessary for full growth. Overall, the greater barotolerance of the APR-11 strain appeared to be due to its enhanced capacity for catabolism related to its reduced sensitivity to catabolite repression by glucose.     

Geminate recombination of CO in rabbit, opossum, and adult hemoglobins

The geminate recombination of CO with Hb following dissociation by a 10-ns laser pulse has been studied as a function of pH (9.2 and 7.0 without inositol hexaphosphate and 6.0 with inositol hexaphosphate) and temperature (5-35 degrees C). The hemoglobins studied included adult, Rothschild, rabbit, opossum, and carp. Despite significant differences in their structural and functional properties, the first four of these hemoglobins show similar trends in the yields, rates, and activation energies of the geminate recombination. The nature of the "cage recombination" in hemoglobin is discussed in the light of such findings. Neither a slow diffusion model nor a model based upon a specific non-heme binding site accounts for the observations.     

Relationship between progesterone receptor binding and progestin biological activity

The binding affinities of a series of steroidal compounds for the hamster uterine progesterone receptor were determined using two sets of incubation conditions. These competitive binding conditions were designed to deduce the relative rates of ligand dissociation from the progesterone receptor. The progestin activity of these compounds was also determined in a bioassay employing the measurement of diamine oxidase in the traumatized hamster uterus. Steroids could be classified into two categories based on either an increase or decrease in relative binding affinity (RBA) with increasing time of competitive incubation. The mean (+/- SEM) progestin biopotency for the compounds having an increase in RBA was 120 +/- 18 (progesterone = 100), while the biopotency for compounds having a decrease in RBA was only 44 +/- 17. This difference was significant (P less than 0.01). Linear regression analyses revealed significant correlations between the RBAs and progestin biopotencies. Compounds showing a decrease in RBA with increasing time of incubation did not have antiprogestin activity. Kinetic studies of this type should be useful for selecting compounds with potent agonistic activity, but cannot unequivocally predict antihormonal activity.     

Ivermectin: an update

Ivermecan was introduced as an antiparasitic agent in 1981. It is now registered for animal-health use in 35 countries and is being evaluated for possible use in man. This review summarises its antiparasitic efficacy and apparent mode of action. Additional information is given in previous review articles.     

Enhanced enzymatic hydrolysis of lignocellulosic biomass pretreated by low-pressure steam autohydrolysis

Summary The use of low-pressure steam autohydrolysis in the pretreatment of corn stover and hybrid poplar has been assessed. In terms of yield of prehydrolyzed solids, minimal by-product formation and extent of subsequent enzymatic saccharification, the results of low-pressure steam pretreatment were found to be as good as or better than those reported for more severe pretreatment processes. Almost complete saccharification of the cellulose in the prehydrolyzed biomass solids was obtained within 24h with a commercial cellulase preparation — Celluclast. The presence of grinding elements (glass beads) during the enzymatic hydrolysis was found to increase the extent of saccharification by 40% to 50% over controls without any grinding elements.     

Intracellular Ca and cell injury: A paradoxical role of Ca in complement membrane attack

Disturbances in intracellular Ca2+ are known to be important in cell injury caused by a wide range of toxic factors. The complement system is a major effector of immune damage in vivo, and is known to be involved in the pathogenesis of many immune diseases. We present here evidence that the potentially lethal membrane attack complex of complement causes a rapid increase in intracellular free Ca2+ concentration before any other detectable biochemical changes in the cell. In nucleated cells the increased intracellular free Ca2+ concentration initially stimulates recovery processes, allowing the cell to escape mild complement attack and also activates the production of inflammatory mediators, which may amplify an ongoing inflammatory response. More severe complement membrane attack causes a more rapid rise in intracellular free Ca2+ concentration allowing a threshold to be breached above which recovery processes are overwhelmed, and cell death occurs. The importance of non-lytic effects and recovery processes mediated by Ca2+, and the molecular basis of these effects are discussed, and the hypothesis proposed that the cell-injuring effects of other "pore-forming" toxins are also caused by increases in intracellular free Ca2+.     

Processing of the Encephalomyocarditis Virus Capsid Precursor Protein Studies in Rabbit Reticulocyte Lysates Incubated with N-Formyl-[35S]Methionine-tRNAfMet

Translation of encephalomyocarditis virus RNA in rabbit reticulocyte lysates in the presence of N-formyl-[(35)S]methionine-tRNA(f) (Met) revealed that a small polypeptide is cleaved from the N-terminus of the capsid protein precursor, preA, by virus-coded protease activity. Therefore, this N-terminal segment comprising the translation initiation site is not conserved in any of the mature capsid proteins.     

Primitive erythropoiesis in early chick embryogenesis. II. Correlation between hemoglobin synthesis and the mitotic history

Primitive erythroblasts in the circulating blood of the chick embryo continue to divide while synthesizing hemoglobin (Hb). Hb measurements on successive generations of erythroblasts show that there is a progressive increase in the Hb content of both interphase and metaphase cells. Furthermore, for any given embryo the Hb content of metaphase cells is always significantly greater than that of interphase cells. The distribution of Hb values for metaphase cells suggests that there are six Hb classes corresponding to the number of cell cycles in the proliferative phase. The location of erythroblasts in the cell cycle was determined by combining Feulgen cytophotometry with thymidine radioautography on the same cells. Measurements of the Hb content for erythroblasts in different compartments of the cell cycle (G1, S, G2, and M) show a progressive increase through the cycle. Thus, the amount of Hb per cell is a function of the number of cell divisions since the initiation of Hb synthesis and, to a lesser degree, the stage of the cell cycle. Earlier generations of erythroblasts synthesize Hb at a faster rate than the terminal generation. Several models have been proposed to explain these findings.     

Urinary Concentrating Ability in Women with Asymptomatic Bacteriuria in Pregnancy

The incidence of impaired renal concentrating ability in pregnant women with asymptomatic significant bacteriuria is significantly less than previously reported when osmolality readings are performed on every urine specimen obtained during the 24 hours'' deprivation of fluids. The concentrating defect is more considerable as pregnancy progresses. The lower the maximum urinary osmolality the more difficult is the treatment of the patient, and the higher the incidence of acute pyelonephritis.