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K Kaul

Publications and source records attributed to K Kaul.

34 records · Page 2Linked to original sources
PubMed1988

Ascorbate peroxidase in bovine retinal pigment epithelium and choroid.

Peroxidase, catalyzing hydrogen peroxide reduction concurrent with ascorbate oxidation, was demonstrated in the extract of retinal pigment epithelium and choroid. The peroxidase in the choroid, RPE, and retina are 236.1, 25.1, and 0.5 units/mg protein respectively. Ammonium sulfate fractionation and high pressure liquid chromatography showed that the peroxidase in the RPE-choroid is associated with a group of heme proteins with absorption maxima at 410 nm, and optimal activity at pH 4.5. The high peroxidase activity in the RPE-choroid explains the observation of dehydroascorbate in these tissues and indicates a possible role of this enzyme in the removal of H2O2.

Ammonium Sulfate↗
PubMed1987

Sequence of MET protooncogene cDNA has features characteristic of the tyrosine kinase family of growth-factor receptors.

We isolated overlapping cDNA clones corresponding to the major MET protooncogene transcript. The cDNA nucleotide sequence contained an open reading frame of 1408 amino acids with features characteristic of the tyrosine kinase family of growth factor receptors. These features include a putative 24-amino acid signal peptide and a candidate, hybrophobic, membrane-spanning segment of 23 amino acids, which defines an extracellular domain of 926 amino acids that could serve as a ligand-binding domain. A putative intracellular domain 435 amino acids long shows high homology with the SRC family of tyrosine kinases and within the kinase domain is most homologous with the human insulin receptor (44%) and v-abl (41%). Despite these similarities, however, we found no apparent sequence homology to other growth factor receptors in the putative ligand-binding domain. We conclude from these results that the MET protooncogene is a cell-surface receptor for an as-yet-unknown ligand.

Amino Acid Sequence↗
PubMed1987

c-mos proto-oncogene RNA transcripts in mouse tissues: structural features, developmental regulation, and localization in specific cell types.

c-mos RNA transcripts have been previously detected in mouse gonadal tissue and in late-term embryos. Here, we show that they are also present at low levels in placenta and in adult mouse brain, kidney, mammary gland, and epididymis. Marked differences are observed in the size of the mos RNA transcripts detected in different tissues. All transcripts appear to end at the same 3' position, and the tissue-specific size variations appear to be due to the use of different promoters. For example, the testicular and ovarian RNA transcripts initiate approximately 280 and approximately 70 base pairs, respectively, upstream from the first initiation codon, but both end at a common site downstream from the mos open reading frame. The expression of mos is developmentally regulated in gonadal tissue. Thus, the level of mos transcripts in testes is low for the first 3 weeks after birth, increases at least 10-fold around day 25, and reaches adult levels by day 30. In contrast, ovaries from preweaning mice contain a higher level of mos mRNA compared to ovaries from adult mice. In cell fractionation experiments we show that mos transcripts are present in haploid germ cells. We find that these transcripts are associated with monosomes and polysomes. The peculiar pattern of mos expression in mouse gonadal tissue suggests a role for the c-mos proto-oncogene in germ cell differentiation.

Age Factors↗
PubMed1985

Identification of renin inhibitors in normal and uremic plasma.

The enzymatic activity of renin is increased in plasma of patients with renal failure, possibly because of the deficiency of a renin inhibitor. Our study was undertaken to identify renin inhibitors and to compare their activities in plasma of 10 normal humans and 10 patients with renal failure. In vitro, both human renal renin and purified mouse submaxillary renin were inhibited by intact plasma and by a high molecular weight (greater than 65,000 daltons) and a lower molecular weight (55,000 daltons) plasma fraction (HMF and LMF, respectively) obtained by Sephadex chromatography. Most plasma proteins were recovered in HMF, and LMF also contained a small amount of protein; however, renin inhibition by HMF and LMF was not dependent on the presence of intact protein. HMF extracted from normal and uremic plasma inhibited renin to a comparable extent. However, LMF from uremic plasma inhibited renin to a lesser extent (p less than 0.01) than LMF from normal plasma. HMF-free plasma of normal subjects contained a specific renin-inhibiting neutral lipid component that was absent in uremic plasma. Thus, circulating renin inhibitors may contribute to the overall activity of the renin-angiotensin system, and increased enzymatic activity of renin in plasma of patients with renal failure may be related to the deficiency of a normally occurring neutral lipid renin inhibitor.

Adult↗
PubMed1978

Isolation of six novel phosphoinositol-containing sphingolipids from tobacco leaves.

A concentrate of phosphosphingolipids from tobacco leaves has been resolved into two groups by chromatography on diethylaminoethylcellulose. The first group eluted contains no acetyl residues, whereas the second group contains one N-acetyl/mol of phosphorus. Three lipids from each group have been purified by chromatography on Porasil columns. The chemical composition of these six novel lipids shows them to be related to the previously characterized phosphosphingolipids PSL-I, N-acetylglucosamine[glucuronic acid, inositol phosphate]ceramide and PSL-II, glucosamine[glucuronic acid, inositol phosphate] ceramide [Kaul, K.,and Lester,R. L. (1975), Plant Physiol. 55, 120]. The novel lipids are: PSL-IA, PSL-I-[Ara2Gal2]; PSL-IB, PSL-I-[Ara3Gal2]; PSL-IC, PSL-I-[Ara4Gal2]; PSL-IIA, PSL-II-[Ara3Gal]; PSL-IIB, PSL-II-[Ara2or3Gal2]; PSL-IIC, PSL-II-[Ara2Gal2Man]. The unusual finding of unacetylated hexosamine in the PSL-II group of lipids appears not to be an artifact, as suggested by experiments involving rapid harvesting and processing of the tobacco leaves. Some of the fractions obtained by chromatography on diethylaminoethylcellulose appear to contain phosphosphingolipids with 16 or more sugar residues.

Phosphatidylinositols↗
PubMed1978

Structure of a major glycophosphoceramide from tobacco leaves, PSL-I: 2-deoxy-2-acetamido-D-glucopyranosyl(alpha1 leads to 4)-D-glucuronopyranosyl(alpha1 leads to 2)myoinositol-1-O-phosphoceramide.

The chemical structure of a major glycophosphoceramide from tobacco leaves, called PSL-I [K. Kaul and R. L. Lester (1975), Plant Physiol. 55, 120], has now been characterized as 2-deoxy-2-acetamido-D-glucopyranosyl(alpha1 leads to 4)D-glucuronopyranosyl(alpha1 leads to 2)myoinositol-1-O-phosphoceramide. Sites of glycoside linkage were determined by (1) methylation analysis on a trisaccharide isolated by degradation of carboxyl-reduced PSL-I and (2) periodate oxidation experiments on PSL-I. The resulting products were identified with gas chromatography/mass spectrometry. Anomeric configurations were determined by resistance of the sugars in the peracetylated trisaccharide to chromium trioxide treatment.

Glycosphingolipids↗
PubMed1975

Characterization of Inositol-containing Phosphosphingolipids from Tobacco Leaves: Isolation and Identification of Two Novel, Major Lipids: N-Acetylglucosamidoglucuronidoinositol Phosphorylceramide and Glucosamidoglucuronidoinositol Phosphorylceramide.

A method for a large scale extraction of phosphoglycosphingolipids from the leaves of Nicotiana tabacum L. has been developed. The phosphosphingolipid concentrate consists of a dozen or more polar lipids as judged by thin layer chromatography. Two of these lipids were purified by chromatography on porous silica beads and partially characterized. These lipids are formulated as: N-acetylglucosamidoglucuronidoinositol phosphorylceramide and glucosamidoglucuronidoinositol phosphorylceramide. Although not fully characterized, the other lipids in the concentrate are inositol-containing phosphosphingolipids with a higher carbohydrate content.

Journal Article↗
PubMed1974

Kinetin-induced Changes in delta-Aminolevulinic Acid Dehydratase of Tobacco Callus.

Kinetin-induced changes in dry weight, soluble protein content, delta-aminolevulinic acid dehydratase activity, and chlorophyll content of two clones of Nicotiana tabacum L. callus were studied. Kinetin brought about a marked increase in the delta-aminolevulinic acid dehydratase activity of nongreen tissue just before induction of greening. The experimental data suggested a possible induction of specific chloroplast protein(s) during the kinetin-induced greening of nongreen tobacco tissue. Kinetin caused a decline in the delta-aminolevulinic acid dehydratase activity and chlorophyll content of the green callus used in the present study.

Journal Article↗
PubMed1971

Effects of sucrose and kinetin on growth and chlorophyll synthesis in tobacco tissue cultures.

Investigations were carried out on the effects of various combinations of sucrose and kinetin concentrations on growth and chlorophyll production in a green and a nongreen clone of pith callus of Nicotiana tabacum L. It was found that 2 milligrams per liter or higher amounts of kinetin induced greening in the nongreen tissue. The observations suggested that growth of the callus and synthesis of chlorophyll and soluble protein are controlled by relative concentrations of sucrose and kinetin in the medium. Kinetin was found to be inhibitory for chlorophyll synthesis in the green callus.

Journal Article↗