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R R Schmidt

Publications and source records attributed to R R Schmidt.

At least 91 records · Page 5Linked to original sources
PubMed1985

Evaluation of two immunofluorescence assays with monoclonal antibodies for typing of herpes simplex virus.

An indirect immunofluorescence assay and a direct immunofluorescence assay were evaluated for typing clinical isolates of herpes simplex virus (HSV). The indirect immunofluorescence assay (Electro-Nucleonics, Inc.) correctly identified 16 HSV type 2 (HSV-2) isolates, but failed to identify 4 of 14 HSV-1 isolates because of background fluorescence and instability of reagents. Forty-nine HSV-1 isolates were correctly typed by direct immunofluorescence assay (Kallestad Laboratories, Inc.), but 1 of 39 HSV-2 isolates did not react with the HSV-2 type-specific antibody conjugate.

Antibodies, Monoclonal↗
PubMed1985

Longitudinal assessment of immunologic abnormalities of mice with the autosomal recessive mutation, "wasted".

Mice homozygous for the autosomal recessive mutation wasted (wst/wst) undergo a progressive wasting beginning at the third week of postnatal life, when body weight declines in the mutants. The wst/wst mice do not survive past 30 days of age. The present report describes histologic and functional abnormalities in a longitudinal analysis (17 to 29 days postpartum) of wst/wst mice. In addition to a marked age-dependent decline in wst/wst body weight as well as spleen and thymus wet weight to body weight ratios, we have observed a significant decline in spleen and thymus cell number in these organs, compared with phenotypically normal (+/+ or +/wst) littermates. Histologic analysis of the wst/wst thymus revealed marked cortical pyknosis at 23 days of age and significant cortical depletion by 26 days postpartum. The wst/wst spleen at 23 days of age and later was characterized by a marked reduction in the content of red pulp. Lymphoproliferative responsiveness to Con A was markedly altered in the wst/wst thymus and spleen, in an age-dependent fashion, compared with normal littermates. The wst/wst spleen LPS responsiveness was also markedly altered in an age-dependent fashion. Hypotheses are presented concerning the possible site(s) of gene action in the wst/wst mutant which may mediate the observed morphologic and functional abnormalities.

Age Factors↗
PubMed1983

Effect of a synthetic folic acid analogue, 9-methyl-pteroylglutamic acid, on fetal chondrogenesis: ultrastructural observations.

Maternally administered folic acid antagonists (x-methyl-PGA and 9-methyl-PGA) are known to produce various skeletal malformations in the neonate. These defects are thought to be due in part to abnormal metabolism and/or deposition of various extracellular matrix components, i.e., collagen and glycosaminoglycans. Experimental reduction of glycosaminoglycan biosynthesis in vitro has been shown previously to alter the spatial orientation and normal pattern of collagen fibrillogenesis. Furthermore, dietary withdrawal of folic acid concomitant with maternal administration of 9-methyl-PGA has been shown to result in abnormal collagen, uronic acid, and hexosamine metabolism by fetal limbs. In the present study pregnant rats were exposed to a transitory folic acid deficiency from day 11 to 14 of gestation and fetal tibias (mid-diaphyseal region) were examined with the electron microscope on day 18 of gestation. Although we were unable to ascertain any aberrant patterns of fibrillogenesis and orientation with respect to collagen, this particular teratogenic regimen resulted in an altered pattern of chondrocyte development when observed at the ultrastructural level.

Abnormalities, Drug-Induced↗
PubMed1983

Macromolecular insoluble cold globulin (MICG): a marker for pluripotential hemopoietic stem cells.

In embryonic mice pluripotential hemopoietic stem cells (PHSC) originate in the yolk sac and migrate to the fetal liver and from there to the bone marrow. Hemopoietic cells from yolk sac and fetal liver also migrate to the thymic primordium, and within the thymic environment these prothymocytes differentiate into mature T cells. We have recently demonstrated that macromolecular insoluble cold globulin (MICG), a T cell marker, is synthesized and inserted into the plasma membrane of embryonic prothymocytes as soon as these cells appear in the early thymus. In addition, we have shown that MICG+ cells are present within the fetal liver before the thymus has fully formed. In the present study we show that pluripotential hemopoietic stem cells in the fetal liver and bone marrow have MICG on their surface and represent a subpopulation of these MICG+ cells. The implications of these findings in relationship to stem cell differentiation and isolation are discussed.

Animals↗
PubMed1982

In vitro effects of the teratogen and folic acid antagonist, 9-methyl pteroylglutamic acid, on glycosaminoglycan accumulation in fetal rat limbs.

Fetal rat limbs were obtained from pregnant females on the 14th day of gestation. Forelimbs and hindlimbs were pooled separately and preincubated for 22 hours at 37 degrees C in Eagle's MEM containing the teratogen and folic acid antagonist, 9-methyl pteroylglutamic acid (9-mePGA). Following removal of old medium, fresh medium together with the teratogen were added at the same concentration as before. Tritiated glucosamine (10 micro Ci) was added to each vial and the incubation continued for 4 hours at 37 degrees C. Tissues were homogenized, digested with pronase, and glycosaminoglycans (GAG) selectively precipitated with cetylpyridinium chloride. In vitro exposure of fetal limbs to various doses of 9-mePGA resulted in a significant increase in the accumulation of labeled GAG by fetal forelimbs at the high and intermediate dosage levels. No effect was observed at the lowest dose. Accumulation of labeled GAG by fetal hindlimbs although similar to fetal forelimbs in control incubations, was unaffected by in vitro exposure to 9-mePGA at any of the dosage levels studied.

Animals↗
PubMed1982

9-methyl pteroylglutamic acid, a synthetic analogue of folic acid: its effects on hexosamine levels in fetal rat limbs and other fetal tissues.

Pregnant rats were administered the teratogen and synthetic analogue of folic acid, 9-methyl pteroylglutamic acid, on the 11th day of gestation and placed on a semisynthetic diet containing the antagonist but lacking the vitamin until the 14th gestational day. This transitory maternal folic acid deficiency results in multiple congenital skeletal malformations. Control animals were administered a folic acid-supplemented regimen. Hexosamine levels were measured in fetal tissues, i.e. limbs, livers, and yolk sacs, in order to monitor the accumulation of a primary constituent of the extracellular matrix, i.e. glycosaminoglycans. Fetal tissues were obtained for hexosamine analysis on the 16th and 18th days of gestation. The teratogenic and transitory folic acid-deficient regimen resulted in (1) a significant reduction in the accumulation of hexosamine in fetal limbs by the 16th day of gestation, and (2) a significant increase in the accumulation of hexosamine in fetal livers by the 16th day of gestation. The regimen was observed to have had no effect on hexosamine accumulation by the yolk sac. Furthermore, no significant effect on hexosamine accumulation from the 16th to the 18th day of gestation was observed in any of the tissues studied.

Animals↗
PubMed1982

Rapid isolation of intact, viable fetal cartilage models.

A rapid procedure is described for the isolation of viable, intact, femoral cartilage models (humeri and femora) obtained from pregnant rats on the 18th day of gestation. Viability of these models is demonstrated in an in vitro system where the incorporation of 35S-sulfate was linear with time of incubation and with numbers of cartilage models utilized. Treatment of cartilage models with ice-cold trichloroacetic acid and a boiling water bath prior to incubation with radiolabel, reduced the amount of radioactivity incorporated to 1.3% of that observed for models incubated by routine procedures. Furthermore, digestion of cartilage model homogenates with protease yielded a supernatant from which 51% to 57% of the radioactivity was precipitated as GAG. This method may also be used to isolate fetal cartilage models as early as the 16th day of gestation. with this system, specific biochemical parameters of mammalian fetal chondrogenesis may be surveyed in normally and abnormally developing fetal cartilage free of surrounding soft tissue.

Animals↗
PubMed1981

Light requirement for induction and continuous accumulation of an ammonium-inducible NADP-specific glutamate dehydrogenase in chlorella.

The ammonium-inducible NADP-specific glutamate dehydrogenase of Chlorella sorokiniana was shown to require light for both its induction by ammonia in uninduced cells, and its continuous accumulation in fully induced cells. Addition of ammonia to uninduced cells in the light resulted in a 35-minute induction lag followed by linear and coincident increases in enzyme activity and antigen. Enzyme activity was not induced in the dark; however, transfer of these cells to the light resulted in an immediate increase in enzyme activity and antigen. The absence of an induction lag suggested that mRNA sequences and/or an enzyme precursor with different antigenic properties than the active holoenzyme accumulated in cells in the dark in ammonium medium. When fully induced cells were transferred to the dark, the activity of the enzyme quickly ceased to accumulate. In contrast to the NADP-specific isozyme, the cells also contain a constitutive NAD-specific isozyme which was shown to accumulate in cells in the dark in either ammonium or nitrate medium.

Journal Article↗
PubMed1981

Turnover of ammonium-inducible glutamate dehydrogenase during induction and its rapid inactivation after removal of inducer from Chlorella sorokiniana cells.

When ammonia was removed from Chlorella sorokiniana cells, which contain an ammonium-inducible nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (NADP-GDH), the activity of this enzyme decayed with a half-life of approximately 8 min. By use of rocket immunoelectrophoresis, indirect immunoprecipitation, and indirect immunoadsorption (coupled with pulse-chase experiments with 35S-labeled sulfate), the rapid initial loss in activity was shown to be due to enzyme inactivation rather than degradation of NADP-GDH antigen. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of immunoprecipitates obtained with anti-NADP-GDH immunoglobulin G showed that enzyme inactivation is accompanied by the conversion of enzyme subunits (Mr = 59,000) to a protein with a molecular weight of 118,000. Because this protein was stable during boiling and in the presence of sodium dodecyl sulfate and high concentrations of mercaptoethanol or dithiothreitol, it was tentatively assumed to be a covalently linked dimer of enzyme subunits. Pulse-chase experiments showed that total NADP-GDH antigen was subject to rapid degradation (t 1/2 = 88 min) in induced cells, and the same degradation rate was maintained after removal of ammonia from induced cells.

Chlorella↗
PubMed1981

Regulation of accumulation of ammonium-inducible glutamate dehydrogenase catalytic activity and antigen during the cell cycle of fully induced, synchronous Chlorella sorokiniana cells.

By use of a rocket immunoelectrophoresis-activity stain procedure, it was shown that catalytic activity of an ammonium-inducible nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (NADP-GDH) was accompanied by a coincident increase in enzyme antigen during the cell cycle of preinduced synchronous Chlorella sorokiniana cells growing in the continuous presence of ammonia. Between the fourth and fifth hours of the G-1 phase of the cell cycle, a three- to fourfold increase in linear accumulation of enzyme antigen was observed. Pulse-chase studies with [35S]sulfate, coupled with a specific indirect immunoadsorption procedure for enzyme antigen, showed that NADP-GDH antigen undergoes continuous degradation (i.e., a half-life of 88 to 110 min) during its linear pattern of accumulation during the cell cycle. The apparent half-life of the enzyme increased by approximately 23% of the 4.5-h positive rate change in antigen accumulation during the cell cycle. This increase in half-life is insufficient in itself to account for the large change in rate of NADP-GDH antigen accumulation. The data from immunoelectrophoresis, pulse-chase, and initial 35S incorporation rate experiments taken together support the inference that changes in the rate of NADP-GDH synthesis are primarily responsible for the accumulation patterns of NADP-GDH activity during the C. sorokiniana cell cycle.

Ammonium Sulfate↗
PubMed1981

Evidence for messenger ribonucleic acid of an ammonium-inducible glutamate dehydrogenase and synthesis, covalent modification, and degradation of enzyme subunits in uninduced Chlorella sorokiniana cells.

The cells of Chlorella sorokiniana cultured in nitrate medium contain no detectable catalytic activity of an ammonium-inducible nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase (NADP-GDH). However, several lines of experimental evidence indicated that the NADP-GDH messenger ribonucleic acid was present at high levels and was being translated in uninduced cells. First, binding studies with 125I-labeled anti-NADP-GDH immunoglobulin G and total polysomes isolated from uninduced and induced cells showed that NADP-GDH subunits were being synthesized on polysomes from both types of cells. Second, when polyadenylic acid-containing ribonucleic acid was extracted from polysomes from uninduced and induced cells and placed into a messenger ribonucleic acid-dependent in vitro translation system, NADP-GDH subunits were synthesized from the ribonucleic acid from both sources. Third, when ammonia was added to uninduced cells, NADP-GDH antigen accumulated without an apparent induction lag. Fourth, by use of a specific immunoprecipitation procedure coupled to pulse-chase studies with [35S]sulfate, it was shown that the NADP-GDH subunits are rapidly synthesized, covalently modified, and then degraded in uninduced cells.

Ammonium Sulfate↗
PubMed1981

Macromolecular insoluble cold globulin (MICG): a marker for embryonic prothymocytes in the mouse.

Adult thymocytes and peripheral T cells synthesize and insert a glycoprotein into their plasma membrane that is termed macromolecular insoluble cold globulin (MICG). This protein, in contrast to other T cell markers, was shown to be present in embryonic prothymocytes as soon as they appear in the thymic rudiment. Furthermore, some hematopoietic cells in the fetal liver were shown to contain MICG at a period in gestation before the completion of lymphocyte migration to the thymus. These results are discussed in terms of the requirements for embryonic cell migration.

Animals↗
PubMed1979

Oxygen consumption by chick embryos exposed to mechanical (shaking) stress.

Stage 34 (8-day) and 41 (15-day) chick embryos (Gallus gallus; in ovo) were exposed (3 min) to two separate amounts of mechanical (shaking) stress. Oxygen consumption determinations, following a temperature equilibration period (60 min), were made on entire, intact eggs using a Warburg apparatus equipped with 130-ml flasks modified to hold the egg. Shaking at 300 excursions per minute (epm) resulted in depressed O2 consumption by stages 34 and 41. Only stage 34 embryos had markedly depressed O2 consumption values when shaken at 100 epm. When exposed to 300 epm and reincubated for either 1, 2, or 4 hr prior to O2 consumption determinations stage 34 embryos, following an early return to control levels exhibited a marked fall in O2 consumption by 4 h reincubation. The stage 41 embryos, on the other hand, demonstrated a gradual rise to control O2 consumption levels by 4 h reincubation. Oxygen consumption has now been shown for the first time in an embryonic system (at two distinct developmental stages) to be functionally impaired by mechanically induced stress.

Animals↗
PubMed1979

Neonatal herpes simplex infection possibly acquired via maternal breast milk.

A newborn infant with disseminated herpes simplex virus type 1 (HSV-1) infection was determined serologically to have acquired the infection postnatally; his mother was found to have HSV-1 in her breast milk but had no history of genital lesions and negative viral cultures of cervix, vagina, and throat. We suggest that HSV-infected maternal breast milk may be a source of this infection for susceptible infants.

Female↗
PubMed1978

Physical and Kinetic Properties of the Nicotinamide Adenine Dinucleotide-specific Glutamate Dehydrogenase Purified from Chlorella sorokiniana.

The nicotinamide adenine dinucleotide-specific glutamate dehydrogenase (l-glutamate:NAD(+) oxidoreductase, EC 1.4.1.2) of Chlorella sorokiniana was purified 1,000-fold to electrophoretic homogeneity. The native enzyme was shown to have a molecular weight of 180,000 and to be composed of four identical subunits with a molecular weight of 45,000. The N-terminal amino acid was determined to be lysine. The pH optima for the aminating and deaminating reactions were approximately 8 and 9, respectively. The K(m) values for alpha-ketoglutarate, NADH, NH(4) (+), NAD(+), and l-glutamate were 2 mm, 0.15 mm, 40 mm, 0.15 mm, and 60 mm, respectively. Whereas the K(m) for alpha-ketoglutarate and l-glutamate increased 10-fold, 1 pH unit above or below the pH optima for the aminating or deaminating reactions, respectively, the K(m) values for NADH and NAD(+) were independent of change in pH from 7 to 9.6. By initial velocity, product inhibition, and equilibrium substrate exchange studies, the kinetic mechanism of enzyme was shown to be consistent with a bi uni uni uni ping-pong addition sequence. Although this kinetic mechanism differs from that reported for any other glutamate dehydrogenase, the chemical mechanism still appears to involve the formation of a Schiff base between alpha-ketoglutarate and an epsilon-amino group of a lysine residue in the enzyme. The physical, chemical, and kinetic properties of this enzyme differ greatly from those reported for the NH(4) (+)-inducible glutamate dehydrogenase in this organism.

Journal Article↗