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Biomedical subjects

R M Kay

Publications and source records attributed to R M Kay.

At least 55 records · Page 3Linked to original sources
PubMed1985

The cellular defect in alpha 1-proteinase inhibitor (alpha 1-PI) deficiency is expressed in human monocytes and in Xenopus oocytes injected with human liver mRNA.

To determine the basis for low serum concentrations of alpha 1-proteinase inhibitor (alpha 1PI) in individuals with homozygous alpha 1PI deficiency (hereafter referred to as PiZZ), biosynthesis and secretion of alpha 1PI were studied in Xenopus oocytes microinjected with hepatic mRNA and in blood monocytes (an extrahepatic site of alpha 1PI gene expression). Although both the usual alpha 1PI (hereafter referred to as PiMM) and PiZZ alpha 1PI were secreted in functionally active form, the rate of secretion of alpha 1PI was significantly and selectively decreased in Xenopus oocytes injected with PiZZ liver mRNA and in monocytes from PiZZ individuals. The apparent size of alpha 1PI in the intracellular compartment of Xenopus oocytes injected with PiZZ liver mRNA was different from the corresponding intracellular PiMM alpha 1PI in oocytes injected with PiMM liver mRNA. There were also differences in the relative ratio of native and complexed alpha 1PI secreted by monocytes from individuals with PiMM and PiZZ phenotypes.

Animals↗
PubMed1985

Coamplification and coexpression of human tissue-type plasminogen activator and murine dihydrofolate reductase sequences in Chinese hamster ovary cells.

Expression of human tissue-type plasminogen activator (t-PA) at high levels has been achieved in Chinese hamster ovary (CHO) cells by cotransfection and subsequent coamplification of the transfected sequences. Expression vectors containing the t-PA cDNA gene and dihydrofolate reductase (DHFR) cDNA gene were cotransfected into CHO DHFR-deficient cells. Transformants expressing DHFR were selected by growth in media lacking nucleosides and contained low numbers of t-PA genes and DHFR genes. Stepwise selection of the DHFR+ transformants in increasing concentrations of methotrexate generated cells which had amplified both DHFR genes and t-PA genes over 100-fold. These cell lines expressed elevated levels of enzymatically active t-PA. To optimize both t-PA sequence amplification and t-PA expression, various modifications of the original procedure were used. These included alterations to the DHFR expression vector, optimization of the molar ratio of t-PA to DHFR sequences in the cotransfection, and modification of the methotrexate resistance selection procedure. The structure of the amplified DNA, its chromosomal location, and its stability during growth in the absence of methotrexate are reported.

Animals↗
PubMed1985

Isolation of cDNAs encoding human and gibbon GM-CSF.

We have used a mammalian cell expression cloning system to identify cDNA clones encoding human granulocyte-macrophage colony stimulating factor. The human clone was used as a hybridization probe to identify the corresponding sequence from a cDNA library prepared from a gibbon T-cell line. The human cDNA has been used to produce recombinant GM-CSF in monkey COS-1 cells. The purified protein from COS cells is very similar to the GM-CSF isolated from a continuous human T-cell line.

Amino Acid Sequence↗
PubMed1984

Human T-cell growth factor: partial amino acid sequence, cDNA cloning, and organization and expression in normal and leukemic cells.

The partial amino acid sequences of human T-cell growth factors (TCGFs) isolated from normal peripheral blood lymphocytes and from a leukemia T-cell line (Jurkat) show that the amino-terminal sequences of the two proteins (15 residues) are identical. Oligonucleotides based on the published Jurkat TCGF DNA sequence were used to isolate six cDNA clones of TCGF mRNA from normal lymphocytes. The predicted amino acid sequence of normal lymphocyte TCGF was identical to the sequence of the Jurkat protein, showing that the differences in biochemical properties of the two proteins result from post-translational events. Amino acid and nucleotide sequence data suggest that TCGF is derived from a precursor polypeptide that is cleaved at the amino terminus but not at the carboxyl terminus. Hybridization of the cloned lymphocyte TCGF cDNA to cellular DNA and RNA strongly suggested that the TCGF gene is expressed as a single mRNA species from a single-copy gene. No differences in the organization of the TCGF gene in normal, leukemic, and human T-cell leukemia/lymphoma virus-infected cells was detected regardless of whether they produce TCGF or not.

Amino Acid Sequence↗
PubMed1983

The nucleotide sequence of the mRNA encoding a tadpole beta-globin polypeptide of Xenopus laevis.

We have determined the nucleotide sequence of a cloned cDNA derived from the mRNA encoding an abundant Xenopus laevis tadpole beta-globin polypeptide. The cloned sequence contains the entire coding region of the mRNA as well as most of its 5'- and 3' -noncoding regions. The complete amino acid sequence of the protein has been deduced. Comparison of this sequence with that of the major adult beta-globin polypeptide of X. laevis shows that the two gene products are highly diverged from each other, the tadpole sequence actually displaying a somewhat greater homology to the human beta-like globin sequences than to the adult frog sequence. An unusual feature of the predicted tadpole beta-globin polypeptide is the presence of a phenylalanine residue at its carboxyl terminus. All known amphibian, avian, and mammalian beta-globin polypeptides have a COOH-terminal histidine residue, and this amino acid is known to play a major role in the alkaline Bohr effect. This observation suggests that, as has been found for two fish hemoglobins which also have a COOH-terminal phenylalanine residue, the tadpole hemoglobin of X. laevis will display a much reduced alkaline Bohr effect.

Amino Acid Sequence↗
PubMed1983

Complete nucleotide sequence of a cloned cDNA derived from the major adult alpha-globin mRNA of X. laevis.

The complete sequence of a cloned cDNA derived from the major adult alpha-globin mRNA of Xenopus laevis (the South African Clawed Toad) is presented. The sequence contains the complete coding and 3' non-coding regions of the mRNA and part of the 5' non-coding region. The amino acid sequence of the encoded alpha-globin polypeptide has been deduced and is compared to other alpha-globin polypeptides. We find that the sequence is equally diverged from a bullfrog tadpole alpha-globin polypeptide and human alpha-globin polypeptide suggesting that these three sequences may have diverged from a common ancestral sequence several hundred million years ago.

Amino Acid Sequence↗
PubMed1983

Sustained alterations in lipoprotein cholesterol concentrations dependent on the daily distribution of lipid intake.

Since the fat content of a single meal influences chylomicron size and hence intestinal apoprotein synthesis, we determined the chronic effects of the daily distribution of fat intake on plasma concentrations of total cholesterol (TC), high density lipoprotein cholesterol (HDL-C) and low density lipoprotein cholesterol (LDL-C). Eight normal male subjects ingested 100 g of fat (a) as a bolus at the evening meal (SL) or (b) equally distributed over 4 meals (q4h) (DL). Each diet was consumed for 7 days; studies were performed 14 days apart using a crossover design and paired comparisons. Nutrient intake and body weight were held constant. At the end of the DL dietary regimen, fasting plasma concentrations of TC, LDL-C and HDL-C were significantly increased as compared to the SL phase of study (TC: 174 +/- 2.9 (mean +/- SEM) vs 161 +/- 2.7; LDL-C: 108 +/- 3.2 vs 98 +/- 3.3 and HDL-C: 53 +/- 1.1 vs 48 +/- 0.8) (P less than 0.05). The consumption of 100 g/day of fat in several small meals results in a sustained increase in LDL-C and HDL-C. This may be due to increased synthesis of lipoprotein components (e.g. apoprotein A-I) or to altered metabolism of intestinal and hepatic TG-rich lipoproteins dependent on size, number and apoprotein composition.

Adult↗
PubMed1983

[Indications for the surgical correction of patients with transposition of the great arteries associated with an interventricular defect. Analysis of 98 cases operated on using the Mustard technic].

At the Hospital for Sick Children, London, between Jan. 1965 and Jan. 1980, 98 patients, ranging in age from 22 days to 20.8 years (mean = 29.6 months), with a clinical diagnosis of transposition of the great arteries (TGA) associated with a ventricular septal defect (VSD) found at cardiac catheterization, underwent Mustard procedure at the atrial level, whether or not associated with the VSD closure. Twenty-nine other patients, with irreversible obstructive pulmonary vascular disease in whom a "palliative" Mustard was performed, have been excluded from this report. At operation, in 8 cases, the VSD was found to have closed spontaneously during the interval between the cardiac catheterization and the surgical repair, while, in 13 patients, the VSD was judged to be too small to influence the hemodynamic results and, accordingly, was left open. In 35 cases the VSD was closed with mattress stitches buttressed with dacron pledgets and in 42 patients a dacron patch was used. The defects were accessible through the tricuspid valve in all but 10 cases. There were 24 early deaths (24%) and these did not correlate either with the year of operation or with the age at the time of operation. The mortality rate was higher in the cases who had required previous pulmonary artery banding (37%), than in those who had not (21.5%), but this difference was not statistically significant. The early results were related to the size of the VSD. In the 21 patients in whom the VSD was partially or completely closed, the early mortality was 9.5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Biosynthesis and postsynthetic processing of human C-reactive protein.

Human C-reactive protein (CRP) is one of several plasma proteins that increase after tissue injury or inflammation. The magnitude of the increase in CRP (100 to 1000-fold over the resting state) makes this an excellent model for studies of eukaryotic gene control. Accordingly, the biosynthesis and postsynthetic processing of human CRP was examined under cellfree conditions and in Xenopus oocytes injected with liver mRNA. The primary translation product is larger than native serum CRP by an 18-amino acid amino terminal extension. The sequence of this signal peptide was derived from nucleotide sequencing of a 1.8-kilobase (Kb) CRP-specific cDNA clone. Northern blot analysis revealed a CRP mRNA of approximately 2.2 Kb, a size more than three times that required (615 bases) to code for the primary translation product. These data form the basis for study of molecular control of the acute phase response.

Amino Acid Sequence↗
PubMed1982

Dietary fiber.

Dietary fiber is plant-derived material that is resistant to digestion by human alimentary enzymes. Fiber may be divided into two broad chemical classes: 1) non-alpha-glucan polysaccharides (cellulose, hemicelluloses, and pectins) and 2) lignins. Dietary fiber behaves within the gastrointestinal tract as a polymer matrix with variable physicochemical properties including susceptibility to bacterial fermentation, water-holding capacity, cation-exchange, and adsorptive functions. These properties determine physiological actions of fiber and are dependent on the physical and chemical composition of the fiber. Fiber undergoes compositional changes as a consequence of bacterial enzymatic action in the colon. Dietary fiber is of clinical significance in certain disorders of colonic function and in glucose and lipid metabolism. Dietary fiber increases stool bulk by acting as a vehicle for fecal water and by increasing fecal bacterial volume. Use of fiber in the treatment of constipation and uncomplicated diverticular disease is well established. By increasing stool bulk, fiber also reduces the fecal concentration of bile acids and other substances. Certain types of fiber decrease the rate of glucose absorption and attenuate postprandial rises in blood glucose and insulin. Plasma cholesterol levels are reduced by mucilaginous forms of fiber. This effect appears to be mediated in part by an increase in fecal acidic sterol excretion.

Adsorption↗
PubMed1981

Towards an improved lipid-lowering diet: additive effects of changes in nutrient intake.

To identify diets that are more effective than existing ones in reducing lipoprotein-mediated risk of atherosclerotic heart disease, the serum lipids and lipoprotein response to three modified diets was studied in twelve normal men living in an institution. The "Western" reference diet (40% energy from fat, P/S ratio 0.27) was compared in Latin square design with a fat-modified diet (diet B, 27% energy from fat, P/S 1.0, reduced cholesterol content); with a fat-modified diet supplemented with fruit, vegetable, and cereal fibre (diet C); and with a diet providing 40% energy from fat, having P/S ratio 1.0 and supplemented by fibre (diet D). The effects of fat modification and fibre-supplementation (diets C and D) were strongly additive-a fall serum cholesterol by 24-29%, in low-density-lipoprotein (LDL) cholesterol by 31-34%, and in serum triglyceride by 21-26%; and the reduction, by diet C, of the ratio of serum cholesterol to high-density-lipoprotein (HDL)-cholesterol by 21%, and that of LDL-cholesterol to HDL2-cholesterol by 26%. The additive effects of multiple changes in nutrient intake, each moderate in extent, permits the design of diets which are remarkably effective in reducing serum-cholesterol level.

Adult↗
PubMed1981

Diets rich in natural fibre improve carbohydrate tolerance in maturity-onset, non-insulin dependent diabetics.

The influence of low and high fibre diets upon carbohydrate tolerance was examined in five maturity-onset, non-insulin dependent diabetics. After 14 days on a diet rich in natural fibre (30 g/day), the subjects consumed a high fibre (13 g) test meal. They then ate a low fibre diet (10 g/day) followed by a low fibre (1 g) test meal. Mean basal plasma glucose concentrations were similar after both fibre diets; however, both mean basal plasma insulin and gastric inhibitory polypeptide (GIP) were significantly lower after the high fibre diet. After the high fibre test meal, significantly lower mean plasma glucose, insulin and GIP concentrations were measured. This study is the first study to demonstrate the ability of an institutionally supervised diet of natural foodstuffs rich in fibre to improve carbohydrate tolerance in maturity-onset, non-insulin dependent diabetics. This findings is relevant to the dietary management of diabetics.

Aged↗
PubMed1981

Oat-bran intake selectively lowers serum low-density lipoprotein cholesterol concentrations of hypercholesterolemic men.

To evaluate selected metabolic effects of plant fibers, we fed control and oat-bran diets in an alternating sequence to eight men with previously documented hypercholesterolemia. The two solid diets differed only in the inclusion of 100 g of oat bran in the test diet. We randomized diet sequences and the measured intakes of carbohydrate, protein, fat, and cholesterol were virtually identical on the two diets. Serum total cholesterol concentrations were stable on control diets whereas a progressive reduction was observed in seven men on oat-bran diets. On oat-bran diets, average reductions in serum total cholesterol concentrations were 13% (p less than 0.01, N = 8); plasma low-density lipoprotein cholesterol concentrations were 14% lower (p less than 0.05) while high-density lipoprotein cholesterol concentrations were not changed. Fasting and postprandial serum glucose, insulin, and triglyceride concentrations were similar on the two diets. Fecal excretion of total bile acids was 54% higher (p less than 0.001) on oat-bran diets than on control diets but neutral steroid excretion was slightly lower while on oat bran. Palatable and inexpensive high-fiber foods such as oat bran may have a role in the treatment of certain patients with hypercholesterolemia.

Adult↗
PubMed1981

Effects of diet on the fecal excretion and bacterial modification of acidic and neutral steroids, and implications for colon carcinogenesis.

Diet-induced changes in the excretion and fecal concentration of bile acids have been associated with enhancement or reduction of chemically initiated colon carcinogenesis in experimental animals. Dietary lipid increases the excretion and fecal concentration of bile acids. Certain types of dietary fiber such as pectin and lignin also increase fecal sterol output. However, the predominant effect of food-derived fiber (e.g., wheat brain) is to increase stool bulk and, hence, reduce the concentration of fecal sterols. Although it has been suggested that the tumor-promoting activity of bile acids is enhanced following bacterial dehydroxylation, dietary factors appear to have limited effect on bacterial flora or acidic sterol degradation in the colon.

Bacteria↗
PubMed1981

Prevention of cholesterol gallstones by lignin and lactulose in the hamster.

The effect on prevention of cholesterol gallstones by a nonfermentable type of fiber, lignin, and a fermentable fiber analogue, lactulose, was studied in hamsters fed an essential fatty acid deficient diet. Control animals had a high incidence of cholesterol gallstones (21 of 24) and lithogenic bile (lithogenic index 1.08). Animals fed lignin had significantly fewer gallstones (11 of 25), improved cholesterol saturation of gallbladder bile, and increased fecal bile acid excretion. Lactulose-fed animals had significantly fewer gallstones (12 of 24) but no significant change in cholesterol saturation of gallbladder bile or in fecal bile acid excretion. Serum cholesterol concentration was reduced, however, and fecal neutral steroid excretion was increased. Gallstones were completely prevented in animals fed both lignin and lactulose (0 of 22), but gallbladder bile cholesterol saturation was not significantly different from the lignin-fed group. Gallbladder bile mucopolysaccharide concentrations did not differ among groups. Lignin appears to prevent cholesterol gallstones in this model by improving cholesterol saturation of bile. The mechanism of action of lactulose is not yet clear.

Animals↗
PubMed1980

Effects of dietary fibre on serum lipid levels and fecal bile acid excretion.

Epidemiologic studies have suggested that dietary fibre protects humans against coronary heart disease, but interpretation of the data is confounded by coexisting differences in both dietary and environmental variables. The hypocholesterolemic action of dietary fibre varies: in general mucilaginous fibres such as pectin and oat bran are more effective than particulate fibres such as wheat bran. Although the mechanism of action of mucilaginous fibres is not completely understood, there is evidence that they induce small increases in the fecal excretion of bile acids and neutral steroids that are not fully compensated for by de novo cholesterol synthesis.

Animals↗
PubMed1980

The nucleotide sequence of the major beta-globin mRNA from Xenopus laevis.

The nucleotide sequence of a cloned fragment containing an almost complete copy of the mRNA encoding the major adult beta-globin polypeptide in Xenopus laevis, the South African Clawed Toad, is presented. A procedure for strand separation by hybridization to complementary mRNA was used to determine some of the sequence and this technique is described. The complete amino acid sequence of the polypeptide has been deduced and comparison with other vertebrate beta-globins reveals several highly conserved, and therefore potentially important, regions of the protein. The sequence of beta-globin mRNA has been determined in several mammals, and in the chicken. Thus we have searched for conserved regions in the non-coding portions of these mRNA sequences, which encode the same protein, but which have been evolving separately for several hundred million years.

Amino Acid Sequence↗