Cimetidine-resistant Zollinger-Ellison syndrome: successful management with ranitidine.

In a patient with the Zollinger-Ellison syndrome who had undergone vagotomy, pyloroplasty and, later, gastrojejunostomy, epigastric pain and stomal ulceration recurred despite the use of high doses (2700 mg/d) of cimetidine. Ranitidine, a new histamine H2-receptor antagonist, reversed all symptoms and healed the stomal ulcer without side effects, thus obviating the need for further surgery. Ranitidine may prove to be the drug of choice in the medical management of patients with the Zollinger-Ellison syndrome.     

Regulation of cardiac cyclic GMP-dependent protein kinase

An assay method based on the ability of high concentrations of Mg²⁺ to stimulate phosphorylation of histone in the presence of low concentrations of ATP was developed for the measurement of cyclic GMP-dependent protein kinase activity ratios (activity -cyclic GMP/activity + cyclic GMP). In tissues which contain only trace amounts of cyclic GMP-dependent protein kinase, the basal activity ratios were high due to interference from a cyclic nucleotide-independent protein kinase. In order to study the regulation of the cardica cyclic GMP-dependent protein kinase, factors affecting the equilibrium between the active and inactive forms of the enzyme were determined. Since the rate of dissociation of cyclic GMP from its binding site(s) was relatively slow at 0–4°C at pH 7.0, the amount of time required to process tissue samples was the major limiting factor for preserving the equilibrium between active and inactive forms of the enzyme. Dilution of heart tissue extracts at 0–4°C did not significantly alter the activity ratio of the enzyme under conditions of basal or elevated cyclic GMP levels. Experiments using charcoal or exogenous cyclic GMP-dependent protein kinase in the homogenizing medium demonstrated that the release of sequestered cyclic GMP was not responsible for the elevation of the cyclic GMP-dependent protein kinase activity ratios by agents like acetylcholine. Therefore, the assay reflected in part, at least, the retention of kinase-bound cyclic GMP in the tissue extracts. The effects of acetylcholine and sodium nitroprusside on cyclic GMP levels, the cyclic GMP-dependent protein kinase activity ratios, and force of contraction were studied in the perfused rat heart. Both agents produced rapid, dose-dependent increases in cardiac cyclic GMP. Optimal concentrations of acetylcholine produced a 2–3-fold increase in the levels of cyclic GMP and an increase in the cyclic GMP-dependent protein kinase activity ratio. No significant effect of acetylcholine on cyclic nucleotide-independent protein kinase activity was observed. Associated witth the acetylcholine-induced protein kinase, factors affecting the equilibrium between the active and inactive forms of the enzyme were determined. Since the rate of dissociation of cyclic GMP from its binding site(s) was relatively slow at 0–4°C at pH 7.0, the amount of time required to process tissue samples was the major limiting factor for preserving the equilibrium between active and inactive forms of the enzyme. Dilution of heart tissue extracts at 0–4°C did not significantly alter the activity ratio of the enzyme under conditions of basal elevated cyclic GMP levels. Experiments using charcoal or exogenous cyclic GMP-dependent protein kinase in the homogenizing medium demonstrated that the release of sequestered cyclic GMP was not responsible for the elevation of the cyclic GMP-dependent protein kinase activity ratios by agents like acetylcholine. Therefore, the assay reflected in part, at least, the retention of kinase-bound cyclic GMP in the tissue extracts. The effects of acetylcholine and sodium nitroprusside on cyclic GMP levels, the cyclic GMP-dependent protein kinase activity ratios, and force of contraction were studied in the perfused rat heart. Both agents produced rapid, dose-dependent increases in cardiac cyclic GMP. Optimal concentrations of acetylcholine produced a 2–3-fold increase in the levels of cyclic GMP and an increase in the cyclic GMP-dependent protein kinase activity ratio. No significant effect of acetylcholine on cyclic nucleotide-independent protein kinase activity was observed. Associated with the acetylcholine-induced increase in cyclic GMP and the cyclic GMP-dependent protein kinase activity ratio was a reduction in the force of contraction. In contrast, nitroprusside produced little or no increase in the cyclic GMP-dependent protein kinase activity ratio despite increasing the level of cyclic GMP 8–10-fold. Nitroprusside also had no effect on contractile force. In combination, nitroprusside and acetylcholine produced additive effects on cyclic GMP levels, but protein kinase activation and force of contraction were similar to those seen with acetylcholine alone. The results suggest that the cyclic GMP produced by acetylcholine in the rat heart is coupled to activation of the cyclic GMP-dependent protein kinase, while that produced by nitroprusside is not.     

Screening costramid libraries for chromosomal genes: an alternative interspecific hybridization method

Abstract Broad host-range RK2-based cosmid vectors ('costramids') are increasingly used in molecular genetic studies of Gram-negative soil bacteria such as Rhizobium spp. we describe a simple modification of existing methods, whereby a genomic library constructed in a stringently replicated vector can be screened for genes which are undetectable by colony hybridization due to background cross-hybridization. This method allows the use of 'heterologous' probes (interspecies hybridization) to isolate several presumptive genes of interest from a gene bank of Rhizobium sp. NGR234 made in the costramid pRK7813. These are a gene with homology to the citrate synthase gene ( gltA ) or Escherichia coli , the gene encoding δ-aminol evulinic acid synthase ( hemA ), and a gene or genes regulating dicarboxylate transport.     

Familial DiGeorge syndrome and associated partial monosomy of chromosome 22

Summary Partial monosomy of 22q due to an unbalanced 4;22 translocation was seen in a 2-month-old male with Type I truncus arterious, dysmorphic features, and T-cell abnormalities. The family history revealed a previous sib with Type I truncus arteriosus, thymic aplasia, and parathyroid hypoplasia noted on postmortem examination, consistent with DiGeorge syndrome. Evaluation of the asymptomatic mother of these two patients revealed partial T-cell deficiency and the same unbalanced translocation with deletion of proximal 22qll. These findings provide further evidence that some cases of complete or partial DiGeorge syndrome are associated with monosomy of the proximal long arm of chromosome 22, and they may explain many, if not all, familial cases of the syndrome.Supported in part by National Foundation-March of Dimes Grant No. 2-161/C-331. Funds from the Texas Department of Health through PL94-278 National Genetic Diseases Act, from the Robert J. Kleberg, Jr. Center for Human Genetics, and USPHS Grant No. RR-05425.     

Subcellular Localization of Enzymes of Carbon and Nitrogen Metabolism in Nodules of Medicago sativa

Alfalfa (Medicago sativa L. cv. Vernal) nodules were separatedinto host plant fractions and fractions of rhizobial originby differential centrifugation and sedimentation equilibriumcentrifugation. Both NAD- and NADP-linked isocitrate dehydrogenase(70%, 90%) and glutamate dehydrogenase activities (90%, 83%)were located primarily (percent total nodule activity) in thefractions of plant origin and their specific activities werehighest in the fractions of plant origin. More than 50% of thenodules' total activity of both glutamine synthetase and NAD-glutamatesynthase and greater than 90% of the total glutamate oxaloacetatetransaminase activity was located in plant fractions. However,the fractions of rhizobial origin had the highest specific activitiesof glutamine synthetase and glutamate synthase. (Received September 5, 1981; Accepted December 7, 1981)     

Simultaneous determination of 4-hydroxy-3-methoxy-phenylacetic (homovanillic) acid and other monoamine metabolites in human lumbar cerebrospinal fluid : An improved high-performance liquid chromatographic study with electrochemical detection

We describe a direct analysis for the simultaneous quantitative determination of 4-hydroxy-3-methoxyphenylacetic (homovanillic) acid and other monoamine metabolites in human lumbar cerebrospinal fluid, utilizing reversed-phase high-performance liquid chromatography with amperometric detection. In addition, a rapid isocratic separation was developed for homovanillic acid in the presence of other endogenous compounds.Twenty-five unselected diagnostic specimens of human lumbar cerebrospinal fluid were extracted with ethyl acetate and subsequently analyzed using the described method. Chromatographic peaks were identified on the basis of retention behavior and ratio of responses at several oxidation potentials.Although our quantitative results correlate well with the literature values, the data were not interpreted clinically since samples were obtained from routine, diagnostic testing of patients admitted to the medical or neurologic services at the Mount Sinai Hospital.     

Glycoalkaloids of Solanum Series Megistacrolobum and related potato cultigens

Glycoalkaloids were used as evidence of the affinities of nine taxa of Solanum Series Megistacrolobum and related potato cultigens from western Bolivia. S. boliviense, S. sanctae-rosae and S. toralapanum contain the commertetraose sugar moiety and appear to represent a relatively wild group within the Series. S. megistacrolobum, S. sogarandinum and S. raphanifolium show anomolous glycoalkaloid profiles that probably reflect hybridization associated with human disturbance. Primitive forms of the S. χ ajanhuiri cultigen are indistinguishable chemicaliy from conspecific weeds that were previously classified as S. megistacrolobum. Variation in total glycoalkaloid content within Series Megistacrolobum likely reflects direct selection by humans for reduced glycoalkaloid levels during the domestication process.     

Identification of the milk fat globule membrane proteins. II. Isolation of major proteins from electrophoretic gels and comparison of their amino acid compositions

The fat globule membranes of milk are derived from the apical plasma membrane of the mammary secretory cells. The nature of the membrane proteins, as isolated from cows' milk, has been studied by the use of discontinuous and continuous SDS-gel electrophoresis. Six methods of preparation of milk fat globule membrane suggested by various authors were tested; gel electrophoresis showed that five major bands were present, independent of the method of preparation. The apparent molecular masses of these proteins as determined on SDS-gels (15% T) were 167, 142, 64, 49 and 46 kDa, respectively. The 167 kDa band stained only with periodic acid-Schiff reagent, while the 142 kDa band stained only with Coomassie blue; the last three bands stained with both. Delipidated membranes were extracted stepwise with water, 0.02 M NaCl and 0.6 M NaCl. The 64 kDa band appears to be nearly insoluble, while the bands of 142, 49 and 46 kDa are fractionated by this procedure. The resolution of all of these proteins by electrophoresis was superior to that achieved by molecular sieve chromatography, and so electrophoretic extraction was used to isolate the major proteins. Dansyl chloride derived proteins were used as markers. Amino acid compositions of the recovered proteins were obtained and are compared.