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Biomedical subjects

M W Pariza

Publications and source records attributed to M W Pariza.

90 records · Page 5Linked to original sources
PubMed1979

Effects of temperature and time on mutagen formation in pan-fried hamburger.

Mutagenic activity generated in hamburger during pan-frying is dependent upon both temperature and time, with temperature appearing to be the more important variable. Uniformly prepared frozen hamburger pattie (115 g; 19% fat) were fried under carefully controlled conditions at 143 degrees C, 191 degrees C and 210 degrees C. Mutagenic activity assayed with the Ames test was not detected in uncooked hamburger, and in hamburger fried at 143 degrees C mutagenic activity remained low at all times studied (4--20 min). In contrast, frying at 191 degrees C or 210 degrees C for up to 10 min resulted in the generation of considerably higher levels of mutagenic activity. Mutagenic activity in fried hamburgers sold at selected restaurants ranged from very low to moderately high. Evidence is also presented for mutagenic inhibitory activity in uncooked and fried hamburger. Mutagenic inhibitory activity decreased mutagenesis mediated by liver S-9 from normal rats but not from Aroclor 1254-treated rats.

Animals↗
PubMed1978

Effects of dietary butylated hydroxytoluene and phenobarbital on the activities of ornithine decarboxylase and thymidine kinase in rat liver and lung.

Rats were entrained to a 12 h dark/12 h light cycle with food (60% protein +/- 0.5% butylated hydroxytoluene or 0.05% phenobarbital) available only during the first 2 h of the dark period. Under these conditions liver ornithine decarboxylase (ODC) activity in control animals displayed a characteristic diurnal oscillation. In livers of rats fed butylated hydroxytoluene or phenobarbital ODC activity was not increased whereas thymidine kinase (TK) activity was stimulated 4--10 fold at 3 days. In lungs from the same animals ODC and TK activities were unchanged. In rats fed butylated hydroxytoluene for 3 days [3H]thymidine incorporation into DNA was increased in liver but decreased in lung.

Animals↗
PubMed1977

3':5'-cyclic AMP: independent induction of amino acid transport by epinephrine in primary cultures of adult rat liver cells.

Liver cells were obtained from adult rats by a collagenase perfusion technique and cultured as monolayers in serum-free media. Epinephrine and isoproterenol both induced large increases in intracellular adenosine 3':5'-monophosphate (cAMP) within 1-2 min whereas epinephrine (but not isoproterenol) induced 2- to 3-fold increases in the rate of alpha-aminoisobutyric acid transport within 2-4 hr after a 1 hr lag. Propranolol abolished the increase in cAMP elicited by epinephrine and isoproterenol, but did not block the induction of alpha-aminoisobutyric acid transport by epinephrine. In contrast, dihydroergotamine abolished and phentolamine diminished the induction of alpha-aminoisobutyric acid transport by epinephrine but did not decrease the stimulation of cAMP levels by epinephrine. Epinephrine dose response curves for cAMP and alpha-aminoisobutyric acid transport were similar. Once exposed to epinephrine, cells became refractory to further stimulation of cAMP levels by epinephrine.

Adrenergic alpha-Antagonists↗
PubMed1976

Induction of amino acid transport in primary cultures of adult rat liver parenchymal cells by insulin.

Amino acid transport was studied in primary cultures of parenchymal cells isolated from adult rat liver by a collagenase perfusion technique and maintained as a monolayer in a serum-free culture medium. Amino acid transport was assayed by measuring the uptake of the nonmetabolizable amino acid, alpha-aminoisobutyric acid. Rat liver parenchymal cells transported alpha-aminoisobutyric acid by an energy-dependent Na+-requiring system which displayed Michaelis-Menten kinetics. Addition of insulin to cultured rat liver parenchymal cells resulted in an increased influx of alpha-aminoisobutyric acid which was reflected in a higher initial rate of alpha-aminoisobutyric acid transport as well as an increased accumulation of alpha-aminoisobutyric acid at later time points. Cycloheximide effectively blocked the increase while results with actinomycin D were equivocal. Insulin at concentrations as low as 50 pM was effective in stimulating alpha-aminoisobutyric acid transport while the maximal response was observed at 80 nM.

Aminoisobutyric Acids↗
PubMed1976

Hormonal regulation of amino acid transport and gluconeogenesis in primary cultures of adult rat liver parenchymal cells.

Amino acid transport was studied in primary cultures of parenchymal cells isolated from adult rat liver by a collagenase perfusion technique and maintained as a monolayer in a serum-free culture medium. These cells carried out gluconeogenesis from three carbon precursors (alanine, pyruvate, and lactate) in response to glucagon addition. Amino acid transport was assayed by measuring the uptake of the nonmetabolizable amino acid, alpha-aminoisobutyric acid (AIB). Addition of insulin or glucagon to culture rat liver parenchymal cells resulted in an increased influx of AIB transport. The glucocorticoid, dexamethasone, when added alone to cultures did not affect AIB transport. However, prior or simultaneous addition of dexamethasone to glucagon-treated cells caused a strong potentiation of the glucagon induction of AIB transport. Kinetic analysis of the effects of insulin and glucagon demonstrated that insulin increased the Vmax for transport without changing the Km while glucagon primarily decreased the Km for AIB transport. The effect of dexamethasone was to increase the Vmax of the low Km system.

Alanine↗
PubMed1976

Induction and decay of glucagon-induced amino acid transport in primary cultures of adult rat liver cells: paradoxical effects of cycloheximide and puromycin.

Liver parenchymal cells were isolated from adult rats and cultured in collagen-coated plastic petri dishes in serum-free medium. Glucagon induced 4- to 5-fold increases in alpha-aminoisobutyric acid (AIB) transport within 6 hr. Dexaemthasone had no direct effect on AIB transport but greatly potentiated the induction by glucagon ("permissive effect"). Levels of 3':5'-cyclic AMP increased 30- to 100-fold within 30 min after glucagon addition to cultures that had been treated with dexamethasone, and dibutyryl cyclic AMP mimicked the glucagon induction of AIB transport. Additionally, dexamethasone exerted a "permissive" effect on induction of AIB transport by dibutyryl cyclic AMP, whereas the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine induced AIB transport only in cultures that had been treated with dexamethasone. Induction of AIB transport was not dependent upon the continued presence of glucagon, but induced AIB transport activity decayed to uninduced levels within 3-4 hr after glucagon removal. The protein syntesis inhibitors puromycin and cycloheximide inhibited both induction and decay of glucagon induced AIB transport, but had a stabilizing effect if added once induction or decay had commenced. Unlike cycloheximide, the inhibitory effect of puromycin on the glucagon induction of AIB transport was reversible.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1974

Base ratio and deoxyribonucleic acid homology studies of six Staphylococcus aureus typing bacteriophages.

Genetic relatedness among Staphylococcus aureus typing bacteriophages 80, 47, 81, 71, 77, and 187 was investigated by using base ratio determinations and deoxyribonucleic acid (DNA)-DNA hybridization. Guanine/cytosine (G/C) content, as determined by thermal denaturation and chromatographic analysis of the purines released by acid hydrolysis of the DNA, was between 31 and 36%. No pattern correlating G/C content with serological or lytic group was discernible. DNA-DNA hybridization studies indicated high degrees of homology (43% or more) among the genomes of phages in the same serological group. Less homology (29% or less) was observed between the genomes of phages belonging to different serological groups. These findings implied a positive correlation between serological and genetic relatedness.

Bacteriophage Typing↗
PubMed1972

Ribosome synthesis in thermally shocked cells of Staphylococcus aureus.

Thermally shocked cells of Staphylococcus aureus rapidly synthesized ribonucleic acid (RNA) during the early stages of recovery. During this period, protein synthesis was not observed and occurred only after RNA had reached a maximum level. Even in the absence of coordinated protein synthesis, a large portion of the RNA appeared in newly synthesized ribosomes. Although the 30S subunit was specifically destroyed by the heating process, both ribosomal particles were reassembled during recovery. The addition of chloramphenicol did not inhibit the formation of the ribosomal subunits, nor was the presence of immature chloramphenicol particles detected. Extended recovery with highly prelabeled cells showed that the original ribosomal proteins present before heating are conserved and recycled. Furthermore, the data indicate that the 50S subunit is turned over and used as a source of protein for new ribosome assembly. Kinetic studies of the assembly process by pulse labeling have not revealed the presence of the normally reported precursor particles. Rather, the data suggest that assembly may occur, in this system, in a manner similar to that reported for in vitro assembly of Escherichia coli subunits.

Arginine↗
PubMed1969

Coagulase production by injured Staphylococcus aureus MF-31 during recovery.

Suspensions of Staphylococcus aureus MF-31 injured by heat treatment at 54 C for 15 min produced coagulase during recovery in Trypticase Soy Broth. Coagulase also was produced by injured cells during recovery in a medium that did not support growth. Coagulase synthesis during recovery was independent of the molar strength of the buffer in which the cells were injured, the age of the cells, and the degree of injury. Return of salt tolerance and coagulase production required glucose, amino acids, and phosphate in the recovery medium. Vitamins stimulated coagulase production, but did not affect recovery. Although coagulase production was not necessary for repair of thermal injury to S. aureus MF-31, its detection was interpreted as an indicator of protein synthesis.

Buffers↗