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  • Cell & Developmental Biology  (14)
  • fluid secretion  (8)
  • linkage analysis  (4)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 94 (1986), S. 143-152 
    ISSN: 1432-1424
    Keywords: fluid secretion ; exocrine gland ; chloride transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Sodium (22Na) transport was studied in a basolateral membrane vesicle preparation from rabbit parotid. Sodium uptake was markedly dependent on the presence of both K+ and Cl− in the extravesicular medium, being reduced 5 times when K+ was replaced by a nonphysiologic cation and 10 times when Cl− was replaced by a nonphysiologic anion. Sodium uptake was stimulated by gradients of either K+ or Cl− (relative to nongradient conditions) and could be driven against a sodium concentration gradient by a KCl gradient. No effect of membrane potentials on KCl-dependent sodium flux could be detected, indicating that this is an electroneutral process. A KCl-dependent component of sodium flux could also be demonstrated under equuilibrium exchange conditions, indicating a direct effect of K+ and Cl− on the sodium transport pathway. KCl-dependent sodium uptake exhibited a hyperbolic dependence on sodium concentration consistent with the existence of a single-transport system withK m =3.2mm at 80mm KCl and 23°C. Furosemide inhibited this transporter withK 0.5=2×10−4 m (23°C). When sodium uptake was measured as a function of potassium and chloride concentrations a hyperbolic dependence on [K] (Hill coefficient =1.31±0.07) were observed, consistent with a Na/K/Cl stoichiometry of 1∶1∶2. Taken together these data provide strong evidence for the electroneutral coupling of sodium and KCl movements in this preparation and strongly support the hypothesis that a Na+/K+/Cl− cotransport system thought to be associated with transepithelial chloride and water movements in many exocrine glands is present in the parotid acinar basolateral membrane.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-0428
    Keywords: Glucagon-like peptide-1 receptor ; non-insulin-dependent diabetes mellitus ; maturity onset diabetes of the young ; polymerase chain reaction ; linkage analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Glucagon-like peptide-1 (GLP-1) is a hormone derived from the preproglucagon molecule that is secreted by intestinal L cells and stimulates insulin secretion from betacells. The GLP-1 receptor is a candidate gene for diabetes mellitus, as mutations may induce the impaired insulin response that is a characteristic feature of NIDDM. To study the relationship between the GLP-1 receptor gene and NIDDM, linkage of a microsatellite polymorphism flanking the GLP-1 receptor gene with diabetes was investigated in three Caucasian families with MODY and in the nuclear families of 12 NIDDM probands. A cumulative LOD score −8.50 excludes linkage in these MODY pedigrees. A LOD score of −1.24 in the NIDDM nuclear pedigrees makes linkage improbable. Mutations in or near the GLP-1 receptor gene are unlikely to be the major cause of the inherited predisposition to NIDDM in Caucasian pedigrees, but we cannot exclude a role for this locus in a polygenic model or a major role in some pedigrees.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Diabetologia 31 (1988), S. 407-414 
    ISSN: 1432-0428
    Keywords: Genetics ; Type 2 (non-insulin-dependent) diabetes ; linkage analysis ; restriction fragment length polymorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In the last five years, genetic markers for a large number of diseases have been localised using linkage analysis of DNA polymorphisms in affected families. The site of the genetic defect or defects leading to Type 2 (non-insulin-dependent) diabetes mellitus, a common illness with a major genetic component, remains unknown. This is due, at least in part, to the lack of large well-defined Type 2 diabetic pedigrees suitable for linkage analysis. There are several features of the disease which make large pedigrees difficult to find. The late age of onset of most probands means that informative older generations are often dead, while there is difficulty in detecting disease in younger generations. The diagnostic criteria for diabetes are, as yet, dependent on an arbitrary cut-off along a continuum of plasma glucose. The high prevalence of the disease may also produce problems as, in any given family, diabetogenic genes may be contributed by more than one parent. Varieties of the disease with a well-defined inheritance, such as maturity onset diabetes of youth, are more suitable for linkage analysis but might be due to defects at a different gene locus. Despite these difficulties, once large well-defined pedigrees have been found, linkage analysis using both candidate genes and random highly polymorphic markers is the strategy most likely to find genetic markers for the disease.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1432-0428
    Keywords: Genetics ; Type 2 (non-insulin-dependent) diabetes ; insulin receptor ; linkage analysis ; maturity onset diabetes of the young
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The possibility of linkage between the human insulin receptor gene locus and diabetes was examined in three Type 2 (non-insulin-dependent) diabetic families and one family with maturity onset diabetes of the young. Insulin receptor gene haplotypes were established using BglII, Rsal and Sstl restriction enzyme digests of genomic DNA from all available family members. The digested DNA was subjected to agarose gel electrophoresis, Southern blotted, and hybridised to 32P-labelled human insulin receptor gene cDNA. In the pedigree with maturity onset diabetes of the young, formal linkage analysis allowed exclusion of close linkage between the insulin receptor locus and diabetes (logarithm of the odds for linkage versus non-linkage was −5.35 at recombination fraction of 0.01). This confirms the absence of linkage between insulin receptor and diabetes which has been reported in two similar pedigrees. In the three Type 2 diabetic families there were a minimum of 4 recombinants between the insulin receptor locus and diabetes, which makes a direct role for insulin receptor defects unlikely. The importance of using realistic estimates of penetrance when performing linkage analysis in a disease with a late age of onset is emphasised. In contrast to the one previous linkage analysis study of the insulin receptor gene, no specific association of diabetes with the rare Sstl Sl(-) allele was observed in either the maturity onset diabetes of the young or the Type 2 diabetic families.
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1432-0428
    Keywords: Maturity-onset diabetes of the young ; glucokinase ; adenosine deaminase ; pituitary adenylate cyclase-activation polypeptide receptor ; hexokinase II ; glucagon-like peptide-1 receptor ; polymerase chain reaction ; linkage analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Maturity-onset diabetes of the young (MODY) is a form of non-insulin-dependent diabetes mellitus characterised by an early age of onset and an autosomal dominant mode of inheritance. Only a proportion of cases are due to mutations in the glucokinase gene. We have studied five Caucasian MODY families, including the first MODY family to be described, with five candidate genes implicated in regulation of insulin secretion. The affected subjects showed more marked hyperglycaemia than that found in subjects with glucokinase mutations. We assessed polymorphic markers close to the genes for glucokinase, hexokinase II, adenosine deaminase, pituitary adenylate cyclase-activating polypeptide receptor, and glucagon-like peptide-1 receptor. Linkage analysis with diabetes gave cumulative log of the odds (LOD) scores of less than -3, implying that mutations in these genes are unlikely to provide a major genetic contribution to this form of MODY.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-4919
    Keywords: salivary glands ; volume regulation ; fluid secretion ; osmoregulation ; stimulus-secretion coupling ; intracellular signalling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract The application of Ca2+ mobilizing secretagogues to rat parotid acini results in a significant decrease in cell volume (15-30%) due to isotonic salt loss. It is often assumed that the effects of such an isotonic volume decrease can be mimicked by anisotonic cell shrinkage. We demonstrate that the Na+-K+-2Cl- cotransporter in these cells is up-regulated by Ca2+ mobilizing secretagogues as well as by cell shrinkage in hypertonic media. However, we find that although the protein kinase inhibitors staurosporine (0.3 μM) and K252a (0.6 μM) significantly blunt the latter up-regulation, they are without effect on the former. These observations suggest that hypertonic and isotonic shrinkage do not result in the activation of the same intracellular signalling pathways, and indicate that anisotonic volume perturbations may not provide good experimental models of physiologic isotonic volume changes.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 111 (1989), S. 191-198 
    ISSN: 1432-1424
    Keywords: exocrine gland ; pH regulation ; Na+/H+ exchange ; fluid secretion ; muscarinic agonist
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The present studies were designed to test our previous suggestion that Na+/H+ exchange was activated by muscarinic stimulation of rat parotid acinar cells. Consistent with this hypothesis, we demonstrate here that intact rat parotid acini stimulated with the muscarinic agonist carbachol in HCO 3 − -free medium show an enhanced recovery from an acute acid load as compared to similarly challenged untreated preparations. Amiloride-sensitive22Na uptake, due to Na+/H+ exchange, was also studied in plasma membrane vesicles prepared from rat parotid acini pretreated with carbachol. This uptake was stimulated twofold relative to that observed in vesicles from control (untreated) acini. This stimulation was time dependent, requiring ∼15 min of acinar incubation with carbachol to reach completion, and ws blocked by the presence of the muscarinic antagonist atropine (2×10−5 m) in the pretreatment medium. The effect of carbachol was dose dependent withK 0.5∼3×10−6 m. Stimulation of the exchanger was also seen in vesicles prepared from acini pretreated with the α-adrenergic agonist epinephrine, but not with the β-adrenergic agonist isoproterenol, or with substance P. Kinetic analysis indicated that the stimulation induced by carbachol was due to an alkaline shift in the pH responsiveness of the exchanger in addition to an increasedapparent transport capacity. Taken together with previous results from this and other laboratories, these results strongly suggest that the Na+/H+ exchanger and its regulation are intimately involved in the fluidsecretory response of the rat parotid.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 112 (1989), S. 51-58 
    ISSN: 1432-1424
    Keywords: loop diuretics ; exocrine gland ; fluid secretion ; parotid ; acinar cell ; ion transport ; chloride secretion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary The inactivation of the rabbit parotid Na/K/Cl cotransporter by the irreversible sulfhydryl reagent N-ethylmaleimide (NEM) is studied by monitoring its effect on high affinity bumetanide binding to the carrier. NEM reduces the number of bumetanide binding sites with no significant change in the affinity of those remaining. NEM also reduces KCl-dependent22Na flux via the cotransporter by the same factor as the reduction in bumetanide binding sites. Both bumetanide and its analogue furosemide can protect against the effect of NEM. The concentration range over which this protection occurs is in good agreement with affinities of these two compounds for the high affinity bumetanide binding site (2.6 and 85 μm, respectively), indicating an association of this site with the site of action of NEM. Also consistent with this hypothesis are the observations that (i) sodium and potassium, both of which are required for high affinity bumetanide binding, increase the rate of inactivation of binding by NEM and (ii) chloride, at concentrations previously shown to competitively inhibit bumetanide binding, protects the cotransporter against NEM. The effects of NEM on bumetanide binding are mimicked by another highly specific sulfhydryl reagent, methyl methanethiolsulfonate. The apparent rate constant for inactivation of high affinity bumetanide binding by NEM is a hyperbolic function of NEM concentration consistent with a model in which the inactivation reaction is first order in [NEM] and proceeds through an intermediate adsorptive complex. The data indicate that the presence of a reduced sulfhydryl group at or closely related to the bumetanide binding site is essential for the operation of the parotid Na/K/Cl cotransporter.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 113 (1990), S. 203-210 
    ISSN: 1432-1424
    Keywords: loop diuretics ; exocrine gland ; fluid secretion ; parotid ; acinar cell ; ion transport ; chloride secretion ; detergent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary We demonstrate that the high affinity bumetanide binding site of the rabbit parotid acinar cell can be extracted from a basolateral membrane fraction using relatively low concentrations (0.07%, wt/vol; 1 mg membrane protein/ml) of the nonionic detergent Triton X-100. This extracted site cannot be sedimented by ultracentrifugation at 100,000 ×g × 1 hr. Bumetanide binding to this site retains the ionic characteristics of bumetanide binding to native membranes but shows a fivefold increase in binding affinity (K d=0.57±0.15 μm vs.K d=3.3±0.7 μm for native membranes). Inactivation of the extracted bumetanide binding site observed at detergent/protein ratios〉1 can be prevented or (partially) reversed by the addition of exogenous lipid (0.2% soybean phosphatidylcholine). When the 0.07% Triton extract is fractionated by sucrose density gradient centrifugation in 0.24% Triton X-100, 0.2% exogenous lipid and 200mm salt, the high affinity bumetanide binding site sediments as a single band withS 20,w =8.8±0.8 S. This corresponds to a molecular weight ∼200 kDa for the bumetanide binding protein-detergent-lipid complex and represents a sevenfold purification of this site relative to the starting membrane fraction. In contrast to previous attempts to purify Na/K/Cl cotransport proteins and their associated bumetanide binding sites, the present method avoids harsh detergent treatment as well as direct covalent modification (inactivation) of the transporter itself. As a consequence, one can follow the still active protein through a series of extraction and purification steps by directly monitoring its bumetanide binding properties.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    The journal of membrane biology 120 (1991), S. 125-130 
    ISSN: 1432-1424
    Keywords: loop diuretics ; exocrine gland ; fluid secretion ; lipid ; acinar cell ; ion transport ; chloride secretion ; detergent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary It was recently reported (Turner, R.J., George, J.N., 1990,J. Membrane Biol. 113:203–210) that the high affinity bumetanide binding site of the rabbit parotid Na/K/Cl cotransporter could be extracted from a basolateral membrane preparation from this gland using relatively low concentrations of the non-ionic detergent Triton X-100. At the detergent: protein ratios required for complete membrane solubilization bumetanide binding activity in this extract was lost but could be recovered by the addition of crude soybean lipids. In the present paper the ability of various purified lipids to restore high affinity bumetanide binding activity in detergent solubilized rabbit parotid basolateral membranes is studied. We show that the effect of exogenous lipid on the detergent-inactivated bumetanide binding site is to increase the affinity of binding without affecting the number of binding sites. Of the 11 lipid species tested, several relatively minor, negatively charged membrane phospholipids are the most effective in restoring binding activity (phosphatidylserine ≈ phosphatidylglycerol 〉 phosphatidylinositol 〉 cardiolipin). while the major mammalian plasma membrane lipid components phosphatidylcholine, phosphatidylethanolamine, sphingomyelin and cholesterol are without effect. In addition, we show that in the presence of these minor lipids the affinity of bumetanide binding is considerably increased over that observed in the native membrane (e.g.,K d ≈0.06 μm in membranes extracted with 0.3% Triton and treated with 0.15% wt/vol phosphatidylserine,vs. K d ≈3 μm in native basolateral membranes). This dramatic dependence of bumetanide binding affinity on the presence of certain lipid species suggests that the properties of the bumetanide binding proteinin situ may be quite dependent on the minor lipid content of the plasma membrane. This effect may account for the relatively large variations in bumetanide binding affinity observed from tissue to tissue.
    Type of Medium: Electronic Resource
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