PubMed Health⌕ Search

Biomedical subjects

D B Martin

Publications and source records attributed to D B Martin.

14 recordsLinked to original sources
PubMed1991

Dioctanoylglycerol regulation of cytosolic Ca2+ by protein kinase C-independent mechanism in HIT T-15 islet cells.

The effect of activators of protein kinase C (PKC) on cytosolic concentration of free Ca2+ [( Ca2+]i) was assessed in insulin-secreting islet cell line HIT T-15. Dioctanoylglycerol (DiC8) and 12-O-tetradecanoylphorbol-13-acetate (TPA) evoked activation of PKC. Basal [Ca2+]i was 65-160 nM. DiC8 induced triphasic increases in [Ca2+]i; phase 2 was the most prominent and consistent one. With 25-150 microM DiC8, [Ca2+]i increased in a dose-dependent manner during phase 2; half-maximal stimulatory dose was 53 microM. TPA did not evoke any increase in [Ca2+]i. Staurosporine, sphingosine, and H7, which are inhibitors of PKC, did not block DiC8-induced rise in [Ca2+]i. DiC8-induced rise in [Ca2+]i was also seen in cells that had been depleted of PKC by prior exposure to TPA. DiC8-induced rise in [Ca2+]i still occurred in the presence of the Ca(2+)-channel blocker verapamil or when the extracellular Ca2+ had been reduced from 2.5 mM to 30 nM by EGTA. Three immediate metabolites of DiC8, monooctanoylglycerol, octanoate, and glycerol, did not evoke any change in [Ca2+]i. Monooleoylglycerol and R59022, which induce increases in endogenous diacylglycerol (DAG) by inhibiting DAG kinase, evoked increases in [Ca2+]i. DiC8 did not cause any change in inositol 1,4,5-trisphosphate levels. DiC8 evoked biphasic increases in insulin release; the second-phase increase in [Ca2+]i preceded the late phase of insulin secretion. Exogenous DAGs should be used with caution in assessing PKC function. Changes in the generation in DAGs must be included among the mechanisms by which Ca2+ homeostasis is regulated in islet cells.(ABSTRACT TRUNCATED AT 250 WORDS)

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1979

Atypical measles in adolescents and young adults.

Seven patients, aged 12 to 19 years, had atypical measles. Prodromal symptoms of fever, malaise, myalgia, headache, nausea, and vomiting were commonly followed by coryza, sore throat, conjunctivitis, photophobia, nonproductive cough, and pleuritic pain. The characteristic rash was erythematous, maculopapular, and progressed frequently to vesicular, petechial, or purpuric lesions. It initially involved palms and soles with subsequent spread to proximal extremities and the trunk, sparing the face. Six of six chest roentgenograms showed infiltrates. Findings not previously described in atypical measles included liver enzyme elevations, thrombocytopenia, disseminated intravascular coagulation, possible transmission among three siblings, and suspected cardiac involvement. Measles complement fixation titers compatible with recent infection were seen in all patients. All patients had previously received killed measles vaccine. A substantial number of persons who are older adolescents or young adults may be at risk of developing atypical measles.

Adolescent↗
PubMed1976

Identification and subcellular distribution of adipocyte peptides and phosphopeptides.

Subcellular fractions of high purity (including plasma membrane, endoplasmic reticulum, mitochondria, nuclei, and cytoplasm) were prepared from isolated adipocytes, and the peptide components were examined by detergent gel electrophoresis. Each fraction except the endoplasmic reticulum exhibited a unique and reproducible complement of major peptides. Although the endoplasmic reticulum was distinctive in its enzymic markers, its peptide components showed striking homologies with certain species in the plasma membrane and cytoplasm. The two major adipocyte glycopeptides appear to be contained in the plasma membrane, inasmuch as they followed the distribution of 5'-nucleotidase. Incubation of adipocytes with extracellular 32Pi led to a uniform rate of incorporation of 32P into cellular peptides, with steady-state incorporation reached by 2 hours. Plasma membrane, mitochondria, nuclei, and cytoplasm all contained a distinctive complement of from two to five major phosphopeptides of different molecular weights. The majority of endoplasmic reticulum phosphopeptides exhibited molecular weights closely similar to those of certain species in the plasma membrane and cytoplasm. The phosphopeptides of the plasma membrane exhibited the highest absolute 32P incorporation of all phosphopeptides, next was the single major mitochondiral phosphopeptide. All fractions except the mitochondria contained, in addition to the few major phosphopeptides, numerous minor 32P-labeled phosphopeptides.

Adipose Tissue↗
PubMed1976

Effects of epinephrine and insulin on phosphopeptide metabolism in adipocytes.

Isolated adipocytes, incubated in the presence of extracellular 32Pi to steady state 32P incorporation into cellular phosphopeptides, were exposed to hormones for 5 min. Epinephrine (10(-6) M) stimulated 32P incorporation into at least 12 major phosphopeptides, distributed in the cytoplasm, endoplasmic reticulum, and plasma membrane. Quantitatively pre-eminent among these were peptides of molecular weight 123,000 and 69,000, each located both in the cytoplasm and endoplasmic reticulum. The effect of epinephrine (10(-7) M) on 32P incorporation into these two peptides was augmented by theophylline (10(-3) M) in a synergistic fashion. Norepinephrine, dibutyryl N6,O2'-dibutyryl adenosine 3':5'-monophosphate, adrenocorticotropic hormone (ACTH) (synthetic 1 to 24 fragment), and glucagon mimicked the effect of epinephrine. Insulin modified adipocyte peptide phosphorylation in two ways. When present as the sole hormone, insulin (100 microunits/ml) consistently and selectively stimulated the 32P incorporation into a peptide of molecular weight 123,000 (endoplasmic reticulum, cytoplasm) without significant alteration in the 32P content of any other major peptide. A second effect of insulin was evident when epinephrine (10(-6) M) was present simultaneously. Insulin significantly inhibited the epinephrine-stimulated phosphorylation of the molecular weight 69,000 (endoplasmic reticulum, cytoplasm) and 26,000 (plasma membrane) peptides. Nevertheless, persistence of insulin-stimulated phosphorylation of the 123,000 peptide in the presence of epinephrine was shown by a 32P content of this peptide that was greater in the presence of both hormones than with either individually. These findings indicate that in intact adipocytes: (a) epinephrine acutely alters the phosphorylation of a large number of adipocyte peptides, partly at least, via activation of adenosine 3':5'-monophosphate (cyclic AMP)-dependent protein kinase; (b) insulin opposes several epinephrine-stimulated phosphorylations in a manner consitent with its ability to lower epinephrine-stimulated intracellular cyclic AMP accumulation in adipocytes; and (c) insulin, in addition, exerts a unique stimulatory effect on adipocyte peptide phosphorylation that is independent of its effects on cyclic AMP metabolism and may be medicated by the generation of an as yet undefined intracellular "messenger" unique to insulin.

Adipose Tissue↗
PubMed1976

Glucagon secretion from the perfused pancreas of streptozotocin-treated rats.

One hour following intravenous streptozotocin, rat pancreases were perfused in situ, and , in contrast to saline-injected controls a marked decrease of insulin secretion was observed. In these streptozotocin-treated animals, baseline glucagon secretion was enhanced when the perfusate glucose concentration was either 80 mg./100 ml. or 300 mg./100 ml. In addition there was hypersecretion of glucagon in response to arginine. Exogenous insulin (20,000 muU./ml.) could suppress glucagon secretion when endogenous secretion was plentiful. Baseline and arginine-stimulated glucagon secretion of the streptozotocin treated animals was not suppressed by large amounts of glucose and insulin to the degree seen in control animals. The glucagon rise in response to an abrupt fall of glucose from 80 mg./100 ml. to 25 mg./100 ml. was not significantly higher in the control group than in the streptozotocin group. The results seen with epinephrine were in sharp contrast to those found with arginine. Epinephrine-stimulated glucagon secretion was not enhanced in the streptozotocin group. In addition, epinephrine-induced secretion could be suppressed by exogenous insulin in both the control and streptozotocin groups. The differences may be secondary to differences of endogenous insulin secretion. The present results are compatible with the hypothesis that local insulin secretion can exert a significant suppressive effect upon the alpha cell and that the inhibition of glucagon secretion by glucose is partially mediated by this mechanism. Furthermore, anomalous local insulin secretion may contribute to the abnormal glucagon secretion of diabetes mellitus.

Animals↗
PubMed1975

Nucleotide and nucleoside stimulation of glucagon secretion.

The effects of various nucleosides and nucleotides upon glucagon secretion from the isolated perfused rat pancreas were studied. Increasing glucagon secretion was found with increasing concentrations of exogenous cyclic AMP (2 X 10(-4) M, 2 X 10(-3) M and 1 X 10(-2) M). Stimulation of alpha cell secretion was also found with 2 X 10(-3) M 2'AMP, 3'AMP, 5'AMP, ADP, Adenosine, NADP, and NADPH. One X 10(-3) M cyclic GMP elicited significant glucagon secretion. The pattern of glucagon release was similar in all cases with peak secretion occurring during the 30- to 90-s time period following initiation of the stimulus. No significant increase of glucagon secretion was found in response to ATP, guanosine, 2'GMP, 3'GMP, 5'GMP, GTP, xanthosine, inosine, adenine, xanthine, thymidine, cytidine, ribose, nicotinamide, and uric acid. On the basis of the above results, the structural requirement for stimulation of glucagon secretion appears to be adenine linked to ribose, with phosphate groups being unnecessary. The conclusion of this study is that a new class of compounds capable of stimulating glucagon secretion has been identified, and important questions are thus raised about the mechanism of the action of exogenous cyclic AMP.

Animals↗
PubMed1975

High molecular weight glucagon-like immunoreactivity in plasma.

An "interference factor" has been shown to be present in human plasma, which can cause artifactual elevation of pancreatic glucagon values as conventionally determined by radioimmunoassay using antiserum 30K. A method of correcting for this problem was developed and used to measure glucagon levels in 60 diabetic and 30 nondiabetic subjects. No significant difference was found between the two groups. Twelve percent of the diabetic subjects had evidence of glucagon binding in their plasma which prevented valid measurement of their glucagon levels. Characterization of the "interference factor" was undertaken with G-200 sephadex column chromatography. Large amounts of glucagon-like immunoreactivity were found in fractions indicating an approximate molecular weight of 160,000. It was demonstrated that this "factor" was not an artifact of charcoal treatment of plasma. The original source of this material is unknown.

Blood Proteins↗
PubMedDate not supplied

Beta hemolytic streptococcal endocarditis: predominance of non-group A organisms.

Identification of beta hemolytic streptococci (BHS) as group A or non-group A on the basis of bacitracin sensitivity rather than Lancefield serogrouping may lead to misidentification of the pathogen. In four recent cases of endocarditis due to BHS, the pathogens initially were identified as group A; Lancefield serogrouping showed all four to be group G. All four patients presented with a syndrome characteristic of acute bacterial endocarditis. Review of all cases of endocarditis at our institution for the past five years showed none due to group A BHS. In 166 previously reported cases of endocarditis due to BHS, 68 pathogens were serogrouped: 53 belonged to groups B, C, G, or H; only five were group A. Our four cases and review of the literature demonstrate the need for Lancefield serogrouping in serious beta hemolytic streptococcal infections, rather than reliance on bacitracin sensitivity.

Acute Disease↗