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Biomedical subjects

R A Reynolds

Publications and source records attributed to R A Reynolds.

At least 37 records · Page 2Linked to original sources
PubMed1992

Responsivity to cognitive therapy as a function of treatment format and client personality dimensions.

The effects of treatment format and client personality dimensions upon responsivity to cognitive therapy were investigated. Depressed subjects were assigned to either 12 weeks of individual or group cognitive therapy. The two formats were found to be equally effective in significantly reducing depression. Subjects were categorized at pretreatment using Beck's Sociotropy/Autonomy Scale in conducting a post hoc analysis of the impact of client personality dimensions upon responsivity to treatment. Consistent with Beck's (1983) interactional model, sociotropic subjects who received group therapy and autonomous subjects assigned to individual therapy showed greater improvement than subjects whose predominant personality dimension did not match the type of treatment received.

Adult↗
PubMed1991

The influence of pH on cystine and dibasic amino acid transport by rat renal brushborder membrane vesicles.

The uptake of cystine and lysine by rat renal brushborder membrane vesicles was examined at various intravesicular and extravesicular hydrogen ion concentrations to discern whether ionic species are determinants of specificity for the shared transport system and whether hydrogen ion gradients play a role in determining uptake values. When intravesicular and extravesicular pH are identical, the highest uptake of cystine occurred at pH 7.4, with lesser uptake at pH 6.0 and 8.3. Since cystine is electroneutral at pH 6.0 and 90% anionic at pH 8.3, it appears that neither form of the amino acid is a preferred species for transport. A similar relationship between pH and uptake occurs for lysine, which is cationic at pH below 8.5. This suggests that pH affects the functioning of the membrane carrier system independent of ionic species of the substrate. There is no apparent relationship of cystine uptake to hydrogen ion gradients across the membrane. Over the range of extravesicular pH studied, optimal cystine uptake occurred whenever the intravesicular pH was 7.4. Competitive interactions between unlabeled amino acids and labeled cystine were not affected by the extravesicular pH and, therefore, did not seem determined by the ionic species of cystine.

Amino Acids, Diamino↗
PubMed1990

Pseudomonas cepacia 2,2-dialkylglycine decarboxylase. Sequence and expression in Escherichia coli of structural and repressor genes.

A 3969-base pair PstI-PstI fragment of Pseudomonas cepacia DNA containing the gene for the pyridoxal 5'-phosphate dependent 2,2-dialkylglycine decarboxylase (pyruvate) (EC 4.1.1.64) was cloned in Escherichia coli. The insert was sequenced by the dideoxy method using nested deletions from both ends, revealing a central 1302-base pair region that codes for the decarboxylase subunit. The recombinant enzyme was expressed in E. coli, purified to homogeneity, and sequenced at the amino terminus. Also, a cofactor-labeled active site peptide was sequenced. The carboxyl terminus of the deduced amino acid sequence is homologous with the carboxyl terminus of mammalian ornithine aminotransferase; the active site sequence is similar to the active site sequences of several other aminotransferases. No homologies with known decarboxylase sequences could be found. Expression of the decarboxylase gene is negatively controlled by a 687-nucleotide sequence upstream of and diverging from the structural gene. Expression is induced by S-isovaline, 2-methylalanine, and D-2-aminobutanoic acid, but not by glycine, D- or L-alanine, L-2-aminobutanoic acid, R-isovaline, or other alkyl amino acids.

Amino Acid Sequence↗
PubMed1989

Characteristics of L-proline and sodium transport in renal brush border membranes isolated from 7-day-old and adult rats.

To explore the nature of differences in uptake by renal brush border vesicles from animals of different ages, vesicles were isolated from 7-day old and adult rats by a Mg-aggregation method. A number of criteria were compared in vesicles from the young and mature animals. The vesicles isolated from animals of both ages appear similar on electron microscopy, in response to osmotic changes, and in uptake kinetics for L-glucose. Despite these parameters which indicate no basic differences between the membranes of young and mature kidney, differences in proline and sodium handling are seen. When compared to the uptake pattern seen in vesicles from adult animals, the height of the sodium gradient-stimulated proline overshoot is diminished and sodium entry is faster in vesicles of the 7-day old rats. These are the same differences which were found in vesicles prepared by differential centrifugation from 7-day old animals. In addition, although sodium efflux was faster from vesicles of immature kidney and mirrored the faster sodium entry, proline efflux was slower. The data indicate a dissociation of proline and sodium fluxes in brush borders of the young rat kidney.

Aging↗
PubMed1989

Cystinuria in dogs: comparison of the cystinuric component of the Fanconi syndrome in basenji dogs to isolated cystinuria.

Two animal models for cystinuria have been examined: the Basenji dog with Fanconi syndrome and cystine stone-forming dogs of various breeds. Brush-border membranes were isolated from these animals and uptake of D-glucose and L-cystine was characterized. Experiments with isolated brush-border vesicles from Basenji dogs with cystinuria as a component of the Fanconi syndrome showed diminished sodium-dependent D-glucose uptake but no decrease in L-cystine uptake even though the cystine defect in vivo was as high as 94% (ie, 6% reabsorption). In contrast, brush-border vesicles isolated from the kidney of a cystine stone-forming dog (Welsh Corgi) with a cystine defect of only 16% (ie, 84% reabsorption) had decreased uptake of cystine compared to values found for Beagle and Basenji vesicles. Thus, cystinuria found in Basenji dogs with the Fanconi syndrome differs from that in classic stone-forming cystinuric dogs. The alteration responsible for the cystinuria of Basenji dogs with Fanconi syndrome does not appear to have a membrane locus and may reflect altered energetics for transport, which are not detected in isolated vesicles. The cystine defect in cystinuric stone-forming dogs does appear to be reflected in the isolated membrane.

Amino Acids↗
PubMed1988

The structure of rat mast cell protease II at 1.9-A resolution.

The structure of rat mast cell protease II (RMCP II), a serine protease with chymotrypsin-like primary specificity, has been determined to a nominal resolution of 1.9 A by single isomorphous replacement, molecular replacement, and restrained crystallographic refinement to a final R-factor of 0.191. There are two independent molecules of RMCP II in the asymmetric unit of the crystal. The rms deviation from ideal bond lengths is 0.016 A and from ideal bond angles is 2.7 degrees. The overall structure of RMCP II is extremely similar to that of chymotrypsin, but the largest differences between the two structures are clustered around the active-site region in a manner which suggests that the unusual substrate specificity of RMCP II is due to these changes. Unlike chymotrypsin, RMCP II has a deep cleft around the active site. An insertion of three residues between residues 35 and 41 of chymotrypsin, combined with concerted changes in sequence and a deletion near residue 61, allows residues 35-41 of RMCP II to adopt a conformation not seen in any other serine protease. Additionally, the loss of the disulfide bridge between residues 191 and 220 of chymotrypsin leads to the formation of an additional substrate binding pocket that we propose to interact with the P3 side chain of bound substrate. RMCP II is a member of a homologous subclass of serine proteases that are expressed by mast cells, neutrophils, lymphocytes, and cytotoxic T-cells. Thus, the structure of RMCP II forms a basis for an explanation of the unusual properties of other members of this class.

Amino Acid Sequence↗
PubMed1987

Transcutaneous electrical nerve stimulation for reducing narcotic use after cesarean section.

This study evaluated the potential efficacy of transcutaneous electrical nerve stimulation in reducing narcotic requirements following cesarean section. The total required dose of postoperative analgesic (meperidine) was found to be 511 mg in the experimental group and 456 mg in the control group. There was no significant difference in narcotic use or hospital stay between the experimental and control groups.

Adult↗
PubMed1987

Cervical incompetence. A review.

Cervical incompetence is one of the main contributors to repeated pregnancy loss, accounting for approximately 25% of the cases. Typically it results in progressive cervical dilatation, leading to a painless second- or early-third-trimester abortion. In most instances cervical incompetence is the result of previous obstetric or gynecologic trauma; a congenital etiology is unusual. Despite the various reported diagnostic procedures, the obstetric history and frequent visual and digital examinations during pregnancy remain the most important factors in arriving at the correct diagnosis. In spite of the fact that numerous procedures have been advocated as treatment, the McDonald purse string closure technique is by far the most simple and effective corrective surgical technique, yielding an overwhelming number of successful pregnancies.

Female↗
PubMed1983

Effect of acidosis on glutamine transport by isolated rat renal brush-border and basolateral-membrane vesicles.

Glutamine uptake was examined in isolated renal brush-border and basolateral-membrane vesicles from control and acidotic rats. In brush-border vesicles from acidotic animals, there was a significant increase in the initial rate of glutamine uptake compared with that in controls. Lowering the pH of the medium increased the initial rate of glutamine uptake in brush-border vesicles from acidotic, but not from control, rats. In brush-border vesicles from both groups of animals, two saturable transport systems mediated glutamine uptake. There was a 2-fold increase in the Vmax. of the low-affinity high-capacity system in the brush-border vesicles from the acidotic animals compared with that from control animals, with no alteration in the other kinetic parameters. There was no difference in glutamine uptake by the two saturable transport systems in basolateral vesicles from control and acidotic animals. Lowering the incubation-medium pH increased the uptake of glutamine by basolateral vesicles from both control and acidotic rats to a similar extent. The data indicate that during acidosis there are alterations in glutamine transport by both the basolateral and brush-border membrane which could enhance its uptake by the renal-tubule cell for use in ammoniagenesis.

Acidosis↗
PubMed1982

Glutamine uptake by rat renal basolateral membrane vesicles.

The presence of a sodium-dependent, saturable uptake process is described in basolateral membranes of rat renal cortex for L-glutamine. Concentration-dependence studies indicate the presence of multiple transport systems with Km1 of 0.032 mM and V1 of 0.028 nmol/mg of protein per min, and Km2 of 17.6 mM and V2 of 17.6 nmol/mg of protein per min. Lysine completely inhibits the high-affinity, low-capacity Km system and partially inhibits the low-affinity, high-capacity system. Cystine and other dibasic amino acids also affect glutamine uptake.

Amino Acids↗
PubMed1981

Amino acid uptake by isolated renal brush border membrane vesicles in various buffers.

The uptake of amino acids by isolated rat renal brush border membrane vesicles in a modified Krebs-Ringer bicarbonate buffer and a phosphate buffer was compared to the uptake in the standard membrane vesicle buffer, Tris-Hepes-mannitol. The uptake in the modified Krebs-Ringer bicarbonate buffer was similar to that in the Tris-Hepes-mannitol buffer. Removal of the ionic constituents other than NaCl and NaHCO3 in the modified Krebs-Ringer bicarbonate buffer (KCl, CaCl2, KH2PO4 and MgSO4) did not affect the amino acid uptake by the isolated membrane vesicles. The timed uptake of proline under sodium gradient conditions in a phosphate buffer had a markedly dampened overshoot. Kinetic analysis of the initial rate of proline uptake in a phosphate buffer compared to a Tris-Herpes-mannitol buffer showed two entry systems for proline in each buffer with similar Km values, but the maximal rate of transport (V) for each system in the phosphate buffer was much lower than that in the Tris-Hepes-mannitol buffer. From these data, phosphate buffer does not appear to be a suitable medium for the study of amino acid uptake by isolated brush border membrane vesicles.

Amino Acids↗
PubMed1976

Regulatory characteristics of amino acid transport in newborn rat renal cortex cells.

The uptaken of alpha-aminoisobutyric acid by slices of kidney cortex from newborn rats is enhanced by a preliminary incubation of the tissue in buffer at 37 degrees C. This effect is abolished by anaerobiosis, the presence of dinitrophenol or the removal of Na+ during the preliminary incubation. Cycloheximide (50 muM) and purimycin (1 mM) as well as alpha-aminoisobutyric acid, glycine and proline (5 mM) in the preincubation buffer also abolish the effect, while actinomycin D (0.8 muM) partially the phenomenon indicates that the enhanced uptake is due to an increased entry rate into the cells without a change in effux. There is no alteration in the apparent transport Km but an increase in the V for entry. The effect is dependent on tissue age being observed between birth and 22 days, after which there is a decrease in response to preliminary incubation with no effect seen in adult tissues.

Aging↗