Co-purification of soluble human galactosyltransferase and immunoglobulins

Preparations of human malignant effusion galactosyltransferase activity purified according to previously published techniques using enzyme-specific affinity chromatography consistently produced antibodies directed toward immunoglobulins with no detectable antigalactosyltransferase. Double immunodiffusion analysis of the antigen showed the presence of both IgG and IgA. Affinity chromatography with anti-human IgG-Sepharose and anti-human serum-Sepharose resulted in a 48,000-fold purification of galactosyltransferase activity with no detectable IgG by radioimmunoassay. Immunization of rabbits with this preparation produced antibodies directed against galactosyltransferase activity and minimal anti-Ig. The persistence of immunoglobulins during the purification of soluble galactosyltransferase activity through two enzyme-specific affinity chromatographic steps suggests an association of immunoglobulins with galactosyltransferase activity.     

Assimilation of ammonia inParacoccus denitrificans

Two pathways serve for assimilation of ammonia inParacoccus denitrificans. Glutamate dehydrogenase (NADP⁺) catalyzes the assimilation at a high NH₄ ⁺ concentration. If nitrate serves as the nitrogen source, glutamate is synthesized by glutamate-ammonia ligase and glutamate synthase (NADPH). At a very low NH₄ ⁺ concentration, all three enzymes are synthesized simultaneously. No direct relationship exists between glutamate dehydrogenase (NADP⁺) and glutamate-ammonia ligase inP. denitrificans, while the glutamate synthase (NADPH) activity changes in parallel with that of the latter enzyme. Ammonia does not influence the induction or repression of glutamate dehydrogenase (NADP⁺). The inner concentration of metabolites indicates a possible repression of glutamate dehydrogenase (NADP⁺) by the high concentration of glutamine or its metabolic products as in the case when NH₄ ⁺ is formed by assimilative nitrate reduction. No direct effect of the intermediates of nitrate assimilation on the synthesis of glutamate dehydrogenase (NADP⁺) was observed.     

Spontaneous occurrence of heat-stable somatic antigen variants in Bacillus thuringiensis

Heat-stable somatic antigen (HSSA) variants were isolated from Bacillus thuringiensis strain T84A1-A by antiserum-mediated selection. Substantial differences in HSSAs were clearly shown between variants and the parent strain by HSSA agglutination tests, Ouchterlony tests and precipitin-halo-formation (PHF) tests of extracellular HSSAs, although a 'one way'cross-reaction was evident. The frequency of HSSA variants in the population was < 10^-4, as determined by PHF tests on antiserum-agar plates. Heat-stable somatic antigen variants showed no alteration in flagellar antigenic structure and in 30 phenotypic characteristics. The insecticidal activity of HSSA variants was on the level with that of the parent strain, when tested with larvae of three lepidopterous species.     

Nitrogen fixation by the benthic freshwater cyanobacterium Lyngbya wollei

The ability of the benthic cyanobacterium Lyngbya wollei to fix nitrogen was studied using field samples and axenic cultures. L. wollei was collected and isolated from Lake Okeechobee, Florida, where it forms extensive mats. Rates of acetylene reduction up to 39.1 nmol mg dry wt⁻¹ h⁻¹ were observed for field samples. The maximum observed rate of acetylene reduction in axenic laboratory cultures was 200 nmol mg dry wt⁻¹ h⁻¹. Aerobic conditions limited nitrogen fixation activity, but dark/light cycles promoted the development of activity. Reduced oxygen levels appeared to be required for the development of significant levels of nitrogenase activity. The level of irradiance also had a significant impact on the level of activity. The potential significance of nitrogen fixation to Lyngbya production is discussed.     

Pregnancy termination by prostaglandin F2α stimulates maternal behavior in the rat

Treatment with PGF_2α resulted in the termination of pregnancy in 16- and 19-day pregnant rats, but not in 10- or 13-day pregnant rats. Rats that aborted displayed a rapid onset of maternal behavior when tested with foster pups. Aborted rats also displayed sexual receptivity and ovulation: these phenomena resemble the sequence of events following hysterectomy on the same days of pregnancy. Both can be related to the events surrounding normal parturition in the rat. The results are interpreted as due to a pregnancy-induced deactivation of the factor in the uterus that prevents estrogen from stimulating maternal behavior in nonpregnant females. In the absence of this factor, the PGF_2α-induced rise in estrogen secretion facilitates maternal behavior and sexual behavior and induces ovulation.     

Discrete regions of simian virus 40 large T antigen are required for nonspecific and viral origin-specific DNA binding.

The nondefective adenovirus type 2 (Ad2)-simian virus 40 (SV40) hybrid viruses, Ad2+ND2 and Ad2+ND4, have been used to determine which regions of the SV40 genome coding for the large tumor (T) antigen are involved in specific and nonspecific DNA binding. Ad2+ND2 encodes 45,000 M4 (45K) and 56,000 Mr (56K) T antigen-related polypeptides. The 45K polypeptide did not bind to DNA, but the 56K polypeptide bound nonspecifically to calf thymus DNA, Ad2+ND4 encodes 50,000 Mr (60K), 66,000 Mr (66K), 70,000 Mr (70K), 74,000 Mr (74K), and 90,000 Mr (90K) T antigen-related polypeptides, all of which bound nonspecifically to calf thymus DNA. However, in more stringent assays, where tight binding to viral origin sequences was tested, only the 90K protein specified by Ad2A+ND4 showed specific high affinity for sequences at the viral origin of replication. From these results and previously published experiments describing the SV40 DNA integrated into these hybrid viruses, it was concluded that SV40 early gene sequences located between 0.39 and 0.44 SV40 map units contribute to nonspecific DNA binding, whereas sequences located between 0.50 and 0.63 SV40 map units are necessary for specific binding to the viral origin of replication.     

Regional CNS Levels of Acetylcholine and Choline During Hypoglycemic Stupor and Recovery

During insulin stupor in mice, acetylcholine levels in cerebral cortex, cerebellum. brainstem, striatum, and hippocampus were unchanged from control values despite brain glucose concentrations 3-10% of normal, whereas choline levels rose 2.4-3.6-fold in all five CNS regions. Brain acetylcholine and choline levels did not change during recovery following glucose injection. The data suggest that. in hypoglycemic stupor, (1) overall rates of acetylcholine synthesis and degradation remain balanced within each of the CNS regions studied: (2) the biochemical mechanism that elevates brain choline levels is unlikely to be related only to cholinergic synaptic processes: and (3) brain choline levels need not rise for stupor to occur.