Search PubMed⌕ Search

Biomedical subjects

R Kaplan

Publications and source records attributed to R Kaplan.

At least 109 records · Page 6Linked to original sources
PubMed1990

Cloning of three human tyrosine phosphatases reveals a multigene family of receptor-linked protein-tyrosine-phosphatases expressed in brain.

A human brainstem cDNA library in bacteriophage lambda gt11 was screened under conditions of reduced hybridization stringency with a leukocyte common antigen (LCA) probe that spanned both conserved cytoplasmic domains. cDNA encoding a receptor-linked protein-tyrosine-phosphatase (protein-tyrosine-phosphate phosphohydrolase, EC 3.1.3.48), RPTPase alpha, has been cloned and sequenced. Human RPTPase alpha consists of 802 amino acids. The extracellular domain of 150 residues includes a hydrophobic signal peptide and eight potential N-glycosylation sites. This is followed by a transmembrane region and two tandemly repeated conserved domains characteristic of all RPTPases identified thus far. The gene for RPTPase alpha has been localized to human chromosome region 20pter-20q12 by analysis of its segregation pattern in rodent-human somatic cell hybrids. Northern blot analysis revealed the presence of two major transcripts of 4.3 and 6.3 kilobases. In addition to RPTPase alpha, two other RPTPases (beta and gamma), identified in the same screen, have been partially cloned and sequenced. Analysis of sequence comparisons among LCA, the LCA-related protein LAR, and RPTPases alpha, beta, and gamma reveals the existence of a multigene family encoding different RPTPases, each containing a distinct extracellular domain, a single hydrophobic transmembrane region, and two tandemly repeated conserved cytoplasmic domains.

Amino Acid Sequence↗
PubMed1990

Renal vasoconstriction caused by short-term cholesterol feeding is corrected by thromboxane antagonist or probucol.

Recent studies indicate that short-term cholesterol feeding causes vascular hyperreactivity and/or increased tone in certain vascular beds. The present study in rats examined the effect of 3 wk of cholesterol-supplemented diet (CSD) on renal hemodynamics. We tested the hypothesis that LDL oxidized in vivo is causally related to increased renal vascular tone by adding the antioxidant drug probucol to the CSD (CSD + P). Micropuncture of surface nephrons in the CSD rats demonstrated that single nephron glomerular filtration rate (SNGFR) and single nephron afferent plasma flow (QA) were markedly lower than in normal rats, whereas glomerular capillary pressure (PGC), afferent arteriolar resistance (RA), and single nephron filtration fraction (SNFF) were higher. In the CSD + P animals, almost all of these hemodynamic abnormalities were absent. TXB2 and PGE2 were increased in proximal tubule fluid and urine in the CSD rats, but normal in the CSD + P group. Infusion of a TXA2 receptor antagonist into the suprarenal aorta of CSD rats caused a rapid return to normal of RBF (renal blood flow), GFR (glomerular filtration rate), SNGFR, QA, RA, PGC, and Kf (ultrafiltration coefficient). Our observations demonstrate that cholesterol feeding leads to renal vasoconstriction, which appears to be mediated largely by increased TXA2 production. The fact that probucol prevented the hemodynamic abnormalities as well as the increased TX production is consistent with the hypothesis that LDL oxidized in vivo initiates events leading to TX mediated vasoconstriction.

Animals↗
PubMed1990

Chromosome assignment by polymerase chain reaction techniques: assignment of the oncogene FGF-5 to human chromosome 4.

We describe a new chromosomal assignment method based on the polymerase chain reaction mediated amplification of target sequences in DNAs from somatic cell hybrids. The new method is faster, much more sensitive and less labor intensive than the standard method of chromosome assignment by Southern hybridization analysis of somatic cell hybrid DNAs. The feasibility of the new approach was demonstrated by verifying the assignment of the previously mapped acidic fibroblast growth factor gene to human chromosome 5. The method was employed to assign the related oncogene, FGF-5, to human chromosome 4.

Animals↗
PubMed1989

Increased frontal and reduced parietal glucose metabolism in acute untreated schizophrenia.

Frontal and parietal lobe metabolism was measured by [18F] fluorodeoxyglucose positron emission tomography in 8 never-medicated DSM-III schizophrenic patients and in 10 control subjects. Patients were in a psychotic episode at the time of this scan. Seven of eight had been ill less than 2 years and had only mild neurocognitive impairment. Frontal lobe glucose metabolism was significantly greater in schizophrenic patients than in controls. This finding differs from that of hypofrontality reported in chronic patients previously treated with neuroleptics. Relative glucose metabolism in the interior parietal lobe was significantly lower in schizophrenic patients than in controls. The frontal/parietal ratios were significantly greater in patients than in controls.

Acute Disease↗
PubMed1989

The human endonexin II (ENX2) gene is located at 4q28----q32.

A relatively recently identified family of structurally similar Ca2(+)-dependent phospholipid binding proteins is called the annexin gene family. At least seven genes are known, although their exact functions are unclear. The endonexin II gene (ENX2), one member of the gene family, is assigned to 4q28----q32 using both Southern transfer analysis of human x rodent somatic cell hybrid DNAs and in situ chromosome hybridization. One of the lipocortin II genes, another annexin, had previously been assigned to the long arm of chromosome 4.

Animals↗
PubMed1989

Survival of human immunodeficiency virus-infected patients on maintenance dialysis.

It has recently been reported that patients on maintenance dialysis with the acquired immune deficiency syndrome (AIDS) survive only 1 to 3 months. We studied all patients on maintenance dialysis at the Baumritter Kidney Center who were known to be infected with the human immunodeficiency virus (HIV). Five patients met the criteria for AIDS; another ten had anti-HIV antibodies but no opportunistic infections. The AIDS patients survived 8 to 18 months, and two are still alive. Mean survival in the AIDS group was 13.2 +/- 1.9 months, while the HIV(+) non-AIDS group survived 15.7 +/- 3.0 months. While these data are not statistically different, the survival curve in the AIDS group predicted a shorter survival than for the HIV(+) patients without AIDS. In fact, the survival of our dialyzed AIDS patients was similar to that reported for AIDS patients in general. Our experience suggests that dialysis may have no adverse effect on survival in AIDS. We conclude that dialysis patients with AIDS may survive 8 to 12 months or more and that the approach to such patients should be individualized.

Acquired Immunodeficiency Syndrome↗
PubMed1988

Cloning and expression of cDNA for human endonexin II, a Ca2+ and phospholipid binding protein.

Endonexin II is a member of the family of Ca2+-dependent phospholipid binding proteins known as annexins. We cloned human endonexin II cDNA and expressed it in Escherichia coli. The apparent size and Ca2+-dependent phospholipid binding properties of purified recombinant endonexin II were indistinguishable from those of the placental protein. A single mRNA of approximately 1.6 kilobase pairs was found to be expressed in human cell lines and placenta and was in close agreement with the length of the cDNA clone (1.59 kilobase pairs). The cDNA predicted a 320-amino acid protein with a sequence that was in agreement with the previously determined partial amino acid sequence of endonexin II isolated from placenta. Endonexin II contained 58, 46, and 43% sequence identity to protein II, calpactin I (p36, protein I), and lipocortin I (p35), respectively. The partial sequence of bovine endonexin I was aligned with the sequence of endonexin II to give 63% sequence identity. Like these other proteins, endonexin II had a 4-fold internal repeat of approximately 70 residues preceded by an amino-terminal domain lacking similarity to the repeated region. It also had significant sequence identity with 67-kDa calelectrin (p68), a protein with an 8-fold internal repeat. Comparing the amino-terminal domains of these four proteins of known sequence revealed that, in general, only endonexin II and protein II had significant sequence identity (29%). Endonexin II was not phosphorylated by Ca2+/phospholipid-dependent enzyme (protein kinase C) even though it contained a threonine at a position analogous to the protein kinase C phosphorylation sites of lipocortin I, calpactin I, and protein II.

Amino Acid Sequence↗
PubMed1988

Effect of diet restriction on glucose metabolism and insulin responsiveness in aging rats.

The effect of age and of prolonged caloric restriction on glucose tolerance and insulin responsiveness has been studied in male Fischer 344 rats. Beginning at 1 month of age dietary intake of an experimental group (R) was limited to 60% of that of the control group (AL) which was allowed to eat ad libitum. Studies were carried out at intervals up to 24 months of age. In AL rats the oral glucose tolerance curve showed progressively higher peak levels of plasma glucose with age, and a decrease in the plasma insulin concentration at the time of the glucose peak. The R group did not show the increase in peak value with age and the corresponding insulin concentration was lower than that of the AL group. These results are compatible with a delay in the first phase of insulin secretion in aging AL rats. Insulin-stimulated glucose disposal was assessed by the method of Reaven et al. [Diabetes, 32 (1983) 175], at ages 4, 12, 18 and 24 months; using infusions of 2 mU of insulin and 1 mg of glucose/min per kg, the steady-state plasma glucose level (SSPG) was slightly lower in R than in AL rats, while the steady-state plasma insulin level was reduced by 40-60%. In rats aged 18-24 months the hepatic glucose output, measured with [3-3H]glucose, was the same for AL and R rats in the basal state and was reduced to the same extent by insulin. In the presence of epinephrine and propranolol, infusion of glucose and insulin at various rates demonstrated that the plasma glucose clearance rate increased linearly with increasing SSPI, and at comparable SSPI levels was lower in R than in AL rats. The ability of insulin to stimulate glycogenesis from glucose was measured in primary hepatocyte cultures. Insulin increased glycogenesis 3-fold in cells from AL rats and 4-6-fold in cells from R rats. There was no effect of age. The increased insulin responsiveness of R rats was not due to an increase in insulin binding or to a decrease in insulin degradation (measured with intact cells or as cytosolic insulinase activity).(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1988

Growth disadvantage of 45,X and 46,X,del(X)(p11) fibroblasts.

We have previously shown that cell generation time (CGT) is prolonged in 45,X and certain X-deletion fibroblast lines (Simpson & Le Beau 1981). A consequence of that finding should be that cells with 45,X or an X-structural abnormality are at a competitive disadvantage when cocultivated with 46,XX cells. To test this hypothesis we prepared 15 minutes of cells from combinations of 9 different cell lines: four 45,X; one 46,Xdel(X)(p11); and four 46,XX. Each culture was monitored cytogenetically at frequent passage intervals for the percentage of the two cell lines. Significant differences were found between normal and abnormal lines in culture predominance, in the order predicted by our hypothesis (p less than 0.01). The specific mechanism by which absence of an X chromosome confers growth disadvantage is unknown, but is consistent with prolongation of CGT. Prolongation of CGT could also be responsible for the embryonic lethality, intrauterine growth retardation, short stature, and somatic anomalies commonly observed in individuals with absent or aberrant X chromosomes.

Cell Division↗
PubMed1988

A new and simple method of measuring menstrual blood loss.

Although it is difficult for women to make reliable judgments about their menstrual blood loss, the direct measurement of such blood loss is useful in diagnosis and in evaluation of therapy. We developed a new and simple procedure for measuring blood on sanitary materials. The procedure is a modification of previous alkaline hematin methods but overcomes some of their major drawbacks. The method involves the separate extraction of blood using a detergent solution and color development of sample aliquots with sodium carbonate. The standard curves obtained for four products tested--regular maxi pads, thin maxi pads and two brands of tampons--were significantly linear over the range of 1-10 mL of blood. The extraction efficiency varied with the four products; tampons exhibited the highest extraction efficiency and thin maxi pads the lowest. Blood loss in normally menstruating women was estimated to be 41.8 +/- 3.9 mL, which correlates well with other estimates reported. Furthermore, the procedure can be used to measure both very low and very concentrated levels of blood on pads or tampons and thus can be used to assess both functional and dysfunctional uterine bleeding.

Female↗
PubMed1987

Decreases in REM sleep after phentolamine depend on the ambient temperature.

According to monoaminergic theories of rapid-eye-movement (REM) sleep, phentolamine (PHEN), an alpha-adrenoceptor antagonist that diminishes noradrenergic activity, should decrease REM sleep. However, PHEN also causes a fall in body temperature (Tb) that depends on the ambient temperature (Ta). When REM sleep and Tb were recorded in the same rats at 4 Ta's, after intraperitoneal injections of either PHEN or saline, the two measures were highly correlated. When PHEN lowered Tb, at Ta 20 degrees C, latency to REM sleep increased and total REM time decreased compared to controls. At Ta 32 degrees C, where PHEN had no effect on Tb, drug-treated rats had as much REM sleep as did controls.

Animals↗
PubMed1987

Transient global amnesia: the electroencephalogram at onset.

A middle-aged man experienced onset of transient global amnesia while undergoing an electroencephalogram. No important change in electroencephalographic activity occurred. This case provides evidence against the hypothesis that epileptic discharge is responsible for transient global amnesia.

Amnesia↗
PubMed1987

Comparative in vitro activity of A-56268 (TE-031) against gram-positive and gram-negative bacteria and Chlamydia trachomatis.

The in vitro activity of A-56268 (TE-031) was determined and compared with that of 13 antibiotics against 401 gram-positive and gram-negative bacteria and 11 strains of Chlamydia trachomatis. A-56268 was very active against methicillin-susceptible Staphylococcus aureus and Neisseria gonorrhoeae, and was among the most active of the agents tested against Listeria monocytogenes, streptococci and Chlamydia trachomatis. It was moderately active against Haemophilus spp., Vibrio spp., Campylobacter jejuni and Campylobacter fetus subsp. fetus. It was inactive against enterococci, methicillin-resistant Staphylococcus aureus, Staphylococcus epidermidis, Campylobacter coli, Salmonella spp., Shigella spp. and Yersinia enterocolitica. A-56268 was not consistently bactericidal or more active than erythromycin for any organism except Chlamydia trachomatis.

Animals↗