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Biomedical subjects

M W Smith

Publications and source records attributed to M W Smith.

At least 253 records · Page 14Linked to original sources
PubMed1981

Distinguishing transport systems having overlapping specificities for neutral and basic amino acids in the rabbit ileum.

1. The kinetic parameters of lysine and alanine uptake by rabbit ileal mucosa have been measured in the presence and absence of Na. 2. Using lysine as an inhibitor of part of alanine uptake in the absence of Na it has been possible to define two mediated systems for alanine entry. One of these systems (Km 14.2 mM; Jmax 41.3 n-mole cm-2 min-1) is inhibited by lysine (Ki 0.96 mM) while the other (Km 115 mM; Jmax 323 n-mole cm-2 min-1) is not. 3. Methionine is an effective inhibitor of both Na-independent uptake mechanisms for alanine. 4. Na-independent lysine uptake also takes place through two mediated systems. One of these systems (Km 1.0 mM; Jmax 12.8 n-mole cm-2 min-1) is inhibited by alanine (Ki 4.3 mM) while the other (Km 108 mM; Jmax 194 n-mole cm-2 min-1) is not. 5. The use of a naturally occurring basic amino acid to inhibit a portion of neutral amino acid uptake extends considerably the ability to distinguish multiple acid transport systems present in the same cell membrane. The physiological implications of these findings are discussed.

Alanine↗
PubMed1981

Cellular distribution of neutral and basic amino acid transport systems in rabbit ileal mucosa.

1. An autoradiographic technique is described whereby the cellular location of tritiated amino acids can be determined following uptake by rabbit ileal mucosa. 2. Stirring solutions in contact with the intestinal mucosa during measurement of rapid influx changes the quantity, but not the distribution, of alanine taken up by the tissue. 3. Conditions predicted to favour either a high affinity system (Ly1) or a low affinity system (Ly2) were used to measure lysine distribution following uptake. Maximal uptake for both transport systems occurred in fully differentiated enterocytes at the tips of villi. Initial maturation of the Ly1 system, which was slow, was followed by a rapid phase of development. The Ly2 system lacked this rapid phase of late development. 4. The cellular distribution of alanine entering on a low affinity Na-independent neutral amino acid carrier closely resembles that determine for Ly1 system for lysine entry. 5. Arginine is a potent inhibitor of lysine uptake through the Ly2 system. Little or no diffusion of lysine appears to take place into rabbit ileal enterocytes. 6. The different distribution of the high and low affinity systems for lysine transport provides further support for their independent existence. It also suggests that more than one message exists fo the switching on of amino acid transport function in differentiating enterocytes.

Alanine↗
PubMed1981

Identity of the B56.5 protein, the A-protein, and the groE gene product of Escherichia coli.

Protein B56.5 is a major Escherichia coli protein, originally identified on two-dimensional gels as an abundant cellular protein with unique regulation. The groE gene product is a bacterial protein essential for the assembly of many diverse bacteriophages. The ribosomal A-protein is a large, acidic protein of unknown function associated with isolated, washed ribosomes. On the basis of comigration in two-dimensional gels, oligopeptide map patterns, amino acid composition, immunological specificity, physical properties, and genetic analysis, protein B56.5 has now been shown to be the groE gene product and to be identical with the A-protein.

Bacterial Proteins↗
PubMed1981

Aryl hydrocarbon hydroxylase in human bronchial epithelium and blood monocyte.

The inducibility of aryl hydrocarbon hydroxylase (AHH) in human bronchial epithelium and blood monocyte was studied in 11 immediate autopsy patients without lung cancer. When the bronchus was exposed to 10 microgram of benz[a]anthracene (BA)/ml medium in explant culture, the levels of AHH induction in the bronchus were 3- to 29-fold above control levels. The specific enzyme activity ranged from not detectable (i.e., < 0.14) to 2.9 nmol/hour/mg DNA in untreated tissue and from 1.2 to 30 nmol/hour/mg DNA in BA-treated bronchus. The optimum pH for the bronchus AHH was 7.7. Control AHH and BA-induced AHH in bronchus were both inhibited by 100 microM 7,8-benzoflavone in vitro. Induction of AHH in monocytes ranged from 1.5- to 30-fold above that of controls when the cells were exposed to 2 microgram of BA/ml medium in culture. The specific enzyme activity ranged from 1.6 to 19 pmol/hour/10(6) cells in untreated monocytes and from 5.8 to 53 pmol/hour/10(6) cells in BA-treated monocytes. The extent of AHH induction in monocytes depended on BA concentration (from 0.1 to 10.0 microgram) in a dose-related manner. AHH activity increased linearly with the number of monocytes (from 0.5 to 2x10(6)) in the assay system. 7,8-Benzoflavone inhibited the BA-induced but not the basal levels of monocyte AHH activity. The data are consistent with a correlation between the inducibility of AHH in human bronchus and blood monocyte from the same individual.

Adolescent↗
PubMed1980

Stoichiometry versus coupling ratio in the cotransport of Na and different neutral amino acids.

The stoichiometry of Na coupling to amino acid movement across the brush border membrane of the rabbit distal ileum has been determined under initial rate conditions. The coupling ratio, defined as the amino acid-dependent Na influx/the Na-dependent amino acid influx, was equal to unity for alanine, measured over a 10-fold range of Na and alanine concentrations. Coupling ratio values determined under a single set of conditions for a number of amino acids varied from 1 for serine to 4.6 for methionine. Reducing the methionine concentration from 12.5 to 1.5 mM caused the coupling ratio value to fall from 4.6 to 1.2. These results are explained by assuming a fixed stoichiometry of 1 : 1 under all conditions, with initial binding of the amino acids (A) to the Na-dependent carrier (E) but with some amino acids being able to cross on the Na-dependent carrier in the absence of Na. The variation in coupling ratio values can be used to calculate KA, the apparent dissociation constant of amino acid from the Na-dependent carrier in the absence of Na, and the ratio kappa 1/kappa 2, where kappa 1 and kappa 2 are first-order rate constants for translocation of the complexes EA and EANa, respectively. This method of processing results has been defined as delta analysis. The value of KA for methionine is 3.6 +/- 1.1 mM and the kappa 1/kappa 2 ratio is 1.01 +/- 0.07. The constant coupling ratio value for 1 for alanine indicates that the value for KA is extremely high or that the kappa 1 value is extremely low.

Alanine↗
PubMed1980

A phosphatidylinositol-containing derivative of Lactobacillus casei ATCC 7469.

A derivative of Lactobaccillus casei ATCC 7469, characterized by limited growth in liquid media and an unusual phospholipid composition, has been isolated. Grown to early stationary phase on a lipid-free and inositol-free medium, the organism produces phosphatidylinositol phosphatidylglycerol, and diphosphatidylglycerol. The phosphatidylinositol was identified by thin-layer, paper, and gas chromatography, and by mass spectrometry. In agreement with published data, the conventional strain produced phosphatidylglycerol, diphosphatidylglycerol, and lysylphosphatidylglycerol, but no phosphatidylinositol. The phospholipid/glycolipid molar ratio, calculated on the basis of published glycolipid analyses, is 1.3 : 1 for the derivative and 1.5 : 1 for the conventional strain.

Lacticaseibacillus casei↗
PubMed1980

Changes in mitochondrial lipids of rat kidney during ischemia.

Lipid changes in mitochondria isolated from rat kidney after various periods of ischemia were analysed by thin-layer chromatography and gas-liquid chromatography. Free fatty acids were increased at 30 min and more so thereafter. Total phospholipid fatty acids decreased steadily. The proportion of diphosphatidylglycerol (cardiolipin) in the total phospholipid fraction decreased at 30 min, but the proportion of phosphatidylcholine and phosphatidylethanolamine in the total phospholipid fraction did not change until the irreversible phase of ischemic injury. We have shown that decrease of cardiolipin in mitochondrial membrane occurs early during ischemia, and only during the irreversible phase of ischemia are phosphatidylethanolamine and phosphatidylcholine broken down. It is postulated that these phenomena are due to activation of phospholipase in the mitochondrial membrane.

Animals↗
PubMed1980

Animal variation in alanine uptake by rabbit ileal mucosa.

Alanine uptake by rabbit ileal mucosa has been measured in the presence and absence of Na+ to establish the characteristics of biological variation. Common Km values, calculated for two systems of alanine entry, were used for estimation of two Jmax values for individual rabbits. The distribution of Jmax1 and Jmax2 within the population was normal and there was minimal interaction between these two parameters, judged by a cross-correlation analysis. Ways of processing data to account for this type of animal variation are discussed.

Alanine↗
PubMed1980

Amino acid transport by small and large intestine of newborn pig.

Unidirectional fluxes of different amino acids have been determined across newborn pig small intestine and colon. The systems responsible for amino acid transport are present in the same proportion in both tissues. Colonic transport of amino acids appears to represent a transient overspill function of the small intestine.

Amino Acids↗
PubMed1980

Electroacoustic assessment of the semipermeable tympanic ventilating tube. A physical model.

The semipermeable membrane ventilating tube has been in use for the past few years. Initial evaluation of this tube indicated that electroacoustic impedance measurements could be used to measure in situ patency. Our clinical experience seemed to question this assumption. A physical model was developed to evaluate the validity of using electroacoustic impedance measurements to test patency of membrane-type ventilating tubes. Our results indicate that volume impedance measurements cannot be used to evaluate patency. Pressure clearance studies validated the efficacy of the membrane tubes but would not appear to be a reliable method for in vivo evaluation of patency.

Acoustic Impedance Tests↗
PubMed1980

Cell proliferation in follicle-associated epithelium of mouse Peyer's patch.

Follicle-associated epithelium (FAE) from the mouse Peyer's patch consists of a dome part containing goblet as well as columnar epithelial cells and a crypt part, containing Paneth as well as goblet and undifferentiated epithelial cells. The proportions of columnar epithelial, goblet and Paneth cells in the FAE are similar to those found in normal crypt/villus complexes. Mitosis is confined to the crypts of the FAE. The cell-renewal time for FAE columnar epithelial cells, estimated from experiments using tritiated thymidine, is approximately 60 hours. Large numbers of lymphoid cells are also present in the FAE, particularly in regions distal to the crypts. The similarity between follicle-associated and villus epithelial structure is discussed, together with its possible relevance to "M" cell formation within the FAE.

Animals↗
PubMed1980

"M" cell distribution in follicle-associated epithelium of mouse Peyer's patch.

The distribution of "M" cells within the follicle-associated epithelium (FAE) of mouse Peyer's patches has been estimated from a series of SEM micrographs. "M" cells are found generally to be distributed evenly throughout the higher regions of the FAE. The frequency with which "M" cells occur decreases in the lower regions of the FAE. No "M" cells are found in the follicle-associated crypts. "M" cell microvilli are longer than those of enterocytes found at the base of the follicle-associated crypts and shorter than those found on enterocytes in other parts of the FAE. No lymphoid cells occur within the epithelium of the follicle-associated crypt. Lymphoid cells in the higher regions of the FAE are associated closely with "M" cells. There is, in the lower regions of the FAE, a transitional zone where lymphoid cells occur both free within the epithelium and closely associated with "M" cells. It is suggested that an initial close association of lymphoid cells with young, fully differentiated enterocytes is responsible for the latter's subsequent transformation to "M" cells.

Animals↗
PubMed1980

Use of differential interference contrast microscopy to determine cell renewal times in mouse intestine.

Pieces of mouse mid jejunum have been cleared in glycerin and examined by differential interference contrast microscopy at low powers of magnification. The position and number of crypts and villi can be determined in the same specimen using this technique. The calculated value for crypt/villus ratio 4.53 +/- 0.99 (mean +/- SD) is less than a previously published value obtained using indirect techniques. A revised estimate of cell renewal time, based on this newly determined value for crypt/villus ratio, is 45 h. This agrees with earlier estimates derived from entirely different methods of analysis. The general usefulness of this form of light microscopy in helping one appreciate some three-dimensional problems in mucosal architecture is emphasized.

Animals↗