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Biomedical subjects

R R Schmidt

Publications and source records attributed to R R Schmidt.

At least 109 records · Page 6Linked to original sources
PubMed1978

Purification and properties of the inducible nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase from Chlorella sorokiniana.

The nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (NADP-GDH) of Chlorella sorokiniana was purified 260-fold to electrophoretic homogeneity in six steps. Depending on the techniques used, the native enzyme appeared to have a molecular weight of 290,000 or 410,000 and to be composed of five to seven identical subunits with a molecular weight of 58,000. The amino acid composition of this enzyme was shown to differ considerably from that of the NAD-GDH in this organism. The NH2-terminal amino acid was unavailable to dansylation. All six cysteines in the native enzyme were in the free sulfhydryl form. The pH optima for the aminating and deaminating reactions were 7.2 and 9.2, respectively. The Km values for NH4+, alpha-ketoglutarate, NADPH, L-glutamate, and NADP+ were 68, 12, 0.13, and 0.038 mM, respectively. At low substrate concentrations, no cooperativity was seen; however, severe inhibition of enzyme activity was observed at high alpha-ketoglutarate concentrations. Nucleotides did not affect enzyme activity. Antiserum produced in rabbits to the subunits of the enzyme yielded a single precipitin band with the purified enzyme in Ouchterlony double-diffusion analysis. Immunoelectrophoresis was used to confirm the purity of the enzyme and also to quantify the amount of enzyme antigen. These studies indicate that the NADPH-GDH and NAD-GDH isozymes are distinct molecular species in this organism.

Amino Acids↗
PubMed1978

Regulation of initial rate of induction of nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase during the cell cycle of synchronous Chlorella.

When synchronous cells of the eucaryotic microorganism Chlorella sorokiniana growing in nitrate medium were challenged to synthesize an ammonium-inducible nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (NADP-GDH) at frequent intervals during the cell cycle the initial rate of induction (i.e., enzyme potential) of this enzyme increased in an approximately linear manner until the period of DNA replication (i.e., S phase). During the S phase, NADP-GDH potential exhibited a positive rate change proportional to the step increase in DNA level. The timing of this rate change was insensitive to large changes in cellular growth rate. This rate change could be blocked within the first cell cycle by specific inhibition of DNA replication with 2'-deoxyadenosine. The approximately linear increase in NADP-GDH potential and also of total cellular protein observed before and after the S phase is proposed to be a result of the increasing photosynthetic capacity of the cell during the cell cycle.

Cell Cycle↗
PubMed1978

Effects of the teratogenic folic acid antagonist, 9-methyl pteroylglutamic acid on uronic acid levels in fetal rat limbs.

Experimental pregnant rats were placed on a transitory folic acid-deficient regimen, i.e. dietary restriction of folic acid plus the teratogen and folic acid antagonist, 9-methyl pteroylglutamic acid; a regimen resulting in multiple congenital skeletal malformations. Controls received a folic acid-supplemented regimen. Accumulation of a primary component of the extracellular matrix, glycosaminoglycans (GAG), was quantitatively evaluated by measuring uronic acid concentrations in fetal limbs. On days 16 and 18 of gestation, fetal limbs were removed, pooled from each litter, and prepared for uronic acid, protein, and DNA quantitation. The treatment results in (1) a decreased rate of protein and DNA accumulation prior to day 16 of gestation, the rate not being affected from day 16 to day 18 of gestation; (2) a trend toward an increased rate of uronic acid accumulation prior to day 16 of gestation, and (3) a decreased rate of uronic acid accumulation from day 16 to day 18 of gestation. Furthermore, our observations confirm our earlier suggestion that there is a decreased rate of accumulation of some nonprotein component(s) in fetal limbs obtained from folic acid-deficient mothers from day 16 to day 18 of gestation.

Animals↗
PubMed1977

Coordinate and non-coordinate accululation of aspartate transcarbamylase and dihydroorotase in synchronous Chlorella cells growing on different nitrogen sources.

Regulation of the levels of aspartate transcarbamylase (carbamoylphosphate:L-aspartate carbamoyltransferase, EC 2.1.3.2) and dihydroorotase (L-5,6-dihydro-orotate amidohydrolase, EC 3.5.2.3) was studied in synchronous cultures of the eucaryotic microorganism Chlorella. Analytical polyacrylamide gel electrophoresis and sucrose density-gradient centrifugation studies revealed that these cells contain a single aspartate transcarbamylase and a dihydroorotase with apparent molecular weights of 160 000 and 80 000, respectively. In synchronous cells cultured in nitrate medium, these two enzymes accumulated in single step-patterns over different periods of the cell cycle. In contrast, these enzymes accumulated in a coordinate manner throughout the cell cycle in ammonium medium. Experiments with inhibitors of protein and RNA synthesis indicated that dihydroorotase is stable in vivo and suggested that cell cycle changes in the turnover rate of aspartate transcarbamylase might determine whether or not these enzymes accumulate in a coordinate manner. Although uracil and uridine could be absorbed and metabolized by the cells, synthesis of these two enzymes could not be repressed by culturing synchronous cells in medium, containing high concentrations (29-40 mM) of uracil or uridine, for an entire cell cycle.

Amidohydrolases↗
PubMed1977

Recording urethral pressure profile: comparison of methods and clinical implications.

Urodynamic evaluation of urethral sphincter efficiency can be carried out by constant carbon dioxide perfusion, constant water perfusion, or the use of membrane catheters. A comparison of these three techniques was made in in vitro and in vivo experiments. Results, and advantages and disadvantages of each method are discussed. From all factors considered in this study--responsiveness to pressure changes sensitivity to pressures at various levels along the urethra, and reproducibility and accuracy of the profile--the membrane catheter system was by far superior to either of the flow systems.

Animals↗
PubMed1977

Regulation of accumulation and turnover of an inducible glutamate dehydrogenase in synchronous cultures of Chlorella.

Earlier studies indicated that the gene of an ammonium-inducible glutamate dehydrogenase (GDH) was inducible throughout the cell cycle and was expressible shortly after replication early in the S-phase in synchronous Chlorella cells growing at a rate of 13% per h in the absence of inducer. In the present study, synchronous cells cultured at the same growth rate in the continuous presence of inducer accumulated this enzyme in a linear manner, with a positive rate change observed late instead of early in the S-phase. At a growth rate of 26% per h, the positive rate change appeared to be displaced to 1.5 h before the S-phase in the next cell cycle. With 2'-deoxyadenosine, an in vivo inhibitor of deoxyribonucleic acid (DNA) synthesis, the magnitude of the positive rate change was shown to be proportional to the relative increase in DNA in the previous cell cycle. Collectively, these data support the idea that expression of newly replicated genes of this enzyme can be delayed into the subsequent cell cycle in cells in the continuous presence of inducer. Studies with cycloheximide indicated that the inducible GDH and another GDH isozyme were stable in fully induced cells in the absence of protein synthesis. However, after ammonium was removed from the culture medium, the activity of the inducible GDH decreased rapidly in vivo, with a half-time of 5 to 10 min at 38.5 degrees C, whereas the rate of accumulation of the other GDH isozyme did not change. Addition of cycloheximide, at the time of inducer removal, prevented this loss in activity of the inducible GDH. The inability to rescue the activity of the inducible GDH, by readdition of ammonium during the deinduction period, indicates that this enzyme probably underwent irreversible inactivation and/or proteolytic degradation.

Chlorella↗
PubMed1976

Factors involved in immunization program for swine influenza.

The decision to undertake a nationwide program of vaccination against swine influenza requires assessment of the status of immunity of those in various age groups in our population against this agent. Pools of serum were collected from persons born in the years from 1889 to 1943; they were tested for hemaggultinin inhibiting (HI) antibody against the HSW 1N1 influenza virus strains isolated in 1931 and 1976. The titers secured serve as an indication of the average level of immunity of those of different ages. Persons less than 43 years of age are found to be without antibody protection. The need for vaccination of people in different age groups based on mortality statistics of previous epidemics is evaluated. It is realized that no epidemic may occur and that a reduced virulence of the viral agent and use of antibiotics may reduce the death rate if the infection recurs. The extraordinary high mortality in 1918 in people between 15 and 44 years of age deserves recognition together with the fact that those in the same age group are now without protection. The fact that women of childbearing age fall into this group deserves special consideration in view of increased mortality in puerperal women observed in the pandemics of 1918 and 1957. The degree of protection afforded the newborn by transplacental transmission of maternal antibodies is discussed. The need of increasing the level of immunity in those who have varying titers of HI antibodies is considered in relation to the prevalence of cardiopulmonary complications and other chronic diseases in older subjects.

Adolescent↗
PubMed1975

Acute hemiphegia of childhood associated with Coxsackie A9 viral infection.

A 16-mo-old girl is described with acute hemiplegia associated with virologic and serologic evidence of Coxsackie A9 infection. Possibilities of pathogenesis are discussed. It is suggested that the present hemiplegia may have been the result of a focal vasculitis due to Coxsachie A9 viral infection in the region of the middle cerebral artery.

Acute Disease↗