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Biomedical subjects

R E Smith

Publications and source records attributed to R E Smith.

At least 19 recordsLinked to original sources
PubMed1979

The role of cysteine residues in the catalytic activity of glycerol-3-phosphate dehydrogenase.

Glycerol-3-phosphate dehydrogenase (sn-glycerol-3-phosphate:NAD+ 2-oxido-reductase, EC 1.1.1.8) has been shown to be sensitive to inhibition by iodoacetate. The reaction of the enzyme with iodoacetate, which appears to be a simple bimolecular process, is accompanied by a corresponding loss of enzyme activity. In addition to changes in activity, the alkylation reaction was monitored by the incorporation of radioactivity from iodo[2-14C]acetate, by changes in amino acid composition, and by changes in the content of free sulfhydryl groups. It is concluded that there are two cysteine residues in the native dimeric enzyme which are essential for enzymic activity. The rate of inactivation was relatively insensitive to the presence of various compounds with the exception of NADH which markedly inhibited the reaction. Kinetic and binding studies showed that the binding of NADH prevents alkylation and, conversely, alkylation prevents NADH binding. From the pH dependence of the alkylation reaction, the pKa of the essential sulfhydryl groups was calculated to be 8.5 and it is suggested that the binding of coenzyme is independent of the state of ionization of these groups.

Alkylation↗
PubMed1979

Effect of capping upon the mRNA properties of satellite tobacco necrosis virus ribonucleic acid.

The mRNA guanyltransferase-mRNA methyltransferases of vaccinia virions can be used to introduce a 5'-terminal m7g(5')pp(5')Apm... capping group onto the RNA of satellite tobacco necrosis virus (STNV RNA) to yield intact capped STNV RNA. Studies with an in vitro system from wheat germ and limiting quantities of capped and uncapped STNV RNA show that the rates and extents of formation of initiation complexes of protein synthesis by intact capped and uncapped STNV RNA are identical, suggesting that 5'-terminal cap groups cannot function in the translation of STNV RNA. Also, the cap analogue pm7G equally inhibits the initiation and the translation of limiting quantities of both capped and uncapped STNV RNA. These contrasting observations suggest that the wheat germ system contains a pm7G sensitive protein and that STNV RNA has a tertiary structure that restricts the function of an added 5'-terminal capping group. This theory is supported by observations that fragmented capped STNV RNA is better at forming initiation complexes than is equally fragmented uncapped STNV RNA.

Adenine Nucleotides↗
PubMed1979

Effect of cefamandole nafate on blood coagulation and platelet function.

Platelet function and coagulation were tested after brief in vivo exposure to cefamandole nafate and in the presence of various concentrations of the drug in vitro. Alterations in hemostatic function were observed only with exposure to drug concentrations severalfold higher than those expected to prevail clinically.

Adenosine Diphosphate↗
PubMed1979

Elevated proteinase activities in mouse lung tumors quantitated by synthetic fluorogenic substrates.

Proteinase activities in malignant and normal lung tissues were measured using two synthetic substrates that consist of a fluorophor coupled to a peptide moiety. The hydrolysis of CBZ-Val-Lys-Lys-Arg-4-methoxy-2-naphthylamide and BZ-Gly-Gly-Arg-4-methoxy-2-naphthylamide were studied in homogenates of two types of mouse lung tumors, the Lewis lung tumor of the C57 black mouse and the KHT tumor of the C3H mouse. The activity of CBZ-Val-Lys-Lys-Arg-4-methoxy-2-naphthylamide hydrolysis had a pH optimum of 6.3 and a Km of 2.1 x 10(-4) M, required a thiol activator, and was inhibited by leupeptin suggesting the activity of a cathepsin B-like enzyme. The activity of BZ-Gly-Gly-Arg-4-methoxy-2-naphthylamide hydrolysis had a pH optimum of 6.7 and a Km of 3 x 10(-5) M. Lung tumor homogenates contained higher hydrolytic activities for both substrates than normal lung homogenates.

Animals↗
PubMed1979

A study of acid phosphatase and dipeptidyl aminopeptidase II in monodispersed anterior pituitary cells using flow cytometry and electron microscopy.

A brief historical review of cytoenzymology is presented from the time of introduction into electron microscopy to the present, where the direction for quantification of an enzyme in single cells appears most promising by fluorescent staining. First attempts are reported to quantitate acid phosphatase (AcPase) and dipeptidyl aminopeptidase II (DAP-II) in monodispersed anterior pituitary cells from lactating and postlactating rats by flow cytometry, fluorescent, and electron microscopy. 3-Hydroxy-flavone is introduced as a new fluorescent cytochemical stain for AcPase, useful in flow cytometry but of only limited use in fluorescent microscopy. Histograms for AcPase indicate a single peak of cells staining more intensely in cell preparations from postlactating over lactating animals. Histograms for DAP-II staining indicate two distinct populations of cells present in the lactating and only one in the postlactating rat anterior pituitary gland. The application of dual laser staining indicates that not all cells stain for both enzymes. Electron microscopy shows the subcellular localization of DAP-II to be limited to lytic bodies and in mammotrophic cells to some secretion granules.

Acid Phosphatase↗
PubMed1979

Electrocardiographic voltage changes during hyperthyroidism.

Electrocardiograms of 67 thyrotoxic patients were studied. Subsequent electrocardiograms during euthyroidism in 16 patients permitted an analysis of voltage changes. Decreases in voltages after radioiodine therapy were significant (P less than 0.01) for the P wave in lead, V1, R wave in leads II, AVF, V4, V5, and V6, maximal RS wave, and maximal R wave and were present in all but one patient. Criteria for left ventricular hypertrophy (sum of S wave in V1 plus R wave in V5 or V6 greater than 35 mm), present in 21% of patients, regressed in all five patients who had later electrocardiograms during euthyroidism. Left ventricular hypertrophy or high-voltage R waves in the absence of usual causes may suggest the presence of hyperthyroidism. The concept that cardiac voltage is determined in part by thyroid hormone is reviewed; this relationship may be the basis for increased voltage in hyperthyroidism as well as decreased voltage in hypothyroidism.

Adult↗
PubMed1979

A new technique for isolation of Descemet's membrane: preliminary studies.

The structure and function of basement membranes have been the subject of extensive investigation. The present study takes advantages of a new experimental procedure to yield ultrastructurally pure basement membranes and applies this methodology to Descemet's membrane, a highly specialized ocular basement membrane. Rabbit Descemet's membranes and associated endothelial cells were mechanically isolated without contaminating stromal elements. The endothelial cells were then solubilized and removed by treatment with detergents as verified by light microscopy and scanning and transmission electron microscopy. The Descemet's membrane remained intact and retained its fibrillar fine structure. Therefore purity of starting material for ongoing morphological and biochemical studies of isolated Descemet's membranes is demonstrated. These investigations will provide a valuable data base for comparison with disease-altered Descemet's membranes.

Animals↗
PubMed1979

A comparison of three methods for the measurement of corneal thickness.

Four subjects who had never worn contact lenses underwent measurement of their corneal thickness by each of three measurement methods: Haag-Streit pachometer with/and without Mishima-Hedby attachment and the Syber specular microscope. Data were collected on three separate sessions, and at each session triplicate measurement trials were made for each method. The resulting 108 measurements were analyzed statistically. Significant differences were found among the measurement methods. Two of the methods were found to be consistent from session to session. In addition, the specular microscope was found to be the most precise method within a session. It was concluded that the specular microscope, which highly trained technicians can utilize to make the measurements, offers a valuable alternative to the measurement of corneal thickness in long-term prospective studies.

Adult↗
PubMed1978

Vectorcardiographic identification of myocardial scar: a discriminative study with automatically processed vectorcardiographic information.

A multivariate discriminative procedure for the vectorcardiographic identification of ischemic myocardial scarring was performed utilizing data from 1,162 vectorcardiograms (VCGs) obtained in clinically normal subjects and 90 VCGs obtained from patients proved at autopsy to have ischemic myocardial scars. The VCGs from patients with myocardial scars were divided into two groups, a design group of 50 cases and an evaluation group of 40 cases. The best vectorcardiographic variables to discriminate the clinically normal group from the design group with scars were identified by stepwise linear discrimination. Sixteen vectorcardiographic variables were then used for discriminative analysis. This analysis correctly identified myocardial scars in 45 of the 50 VCGs in the design group (sensitivity 90%); among the 1,162 VCGs from clinically normal subjects, 32 were misidentified as myocardial scar (specificity 97.2). The sensitivity of these defining criteria was then tested in the 40 cases of myocardial scar in the evaluation group and found to be reproducible; 34 of the 40 cases of this group (85.0%) were correctly identified as having a myocardial scar. The multivariate discriminative criteria developed in this study had greater sensitivity and specificity than standard methods usually employed in electrocardiography and vectorcardiography. The criteria defined need to be evaluated in a large series that includes instances of cardiac pathology of nonischemic nature.

Adolescent↗
PubMed1978

Characterization of anemia induced by avian osteopetrosis virus.

Chickens infected intravenously at 8 days after hatching with an avian osteopetrosis virus developed a severe, progressive anemia in the absence of osteopetrosis. The anemia was characterized as a pancytopenia, in which erythrocytes, granulocytes, and thrombocytes decreased concomitantly. Serum bilirubin levels were normal, whereas erythrocytes from infected chickens demonstrated a slightly elevated osmotic fragility. A negative Coombs test indicated that there was no evidence for erythrocyte-bound antibody. Erythrocytes from infected animals had slightly decreased 51Cr-labeled erythrocyte survival time when compared with normal. Examination of marrow histological preparations, together with ferrokinetic studies with 59Fe, indicated that marrow failure occurred during the acute phase of the anemia. Circulating virus was present during the development and acute phases of the anemia, but disappeared during the recovery phase of the disease. Neutralizing antibody appeared after the disappearance of circulating virus. It is concluded that virus infection induced both marrow failure (aplastic crisis) and decreased erythrocyte survival.

Alpharetrovirus↗
PubMed1978

Variations in acute multifocal histoplasmic choroiditis in the primate.

Experimental histoplasmic choroiditis was produced in primates by intracarotid injections of living H. capsulatum organisms. The severity of the choroiditis varied with inoculum size, as well as with site of injection (common carotid vs. internal carotid artery). A reproducible model of histoplasmic choroiditis in primates was produced with an internal carotid injection of 5,000 to 10,000 organisms/lb. The clinical and histopathological course of this acute choroiditis over the first 30 days is presented.

Acute Disease↗