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R J Turner

Publications and source records attributed to R J Turner.

At least 109 records · Page 6Linked to original sources
PubMed1995

Inflammation and matrix metalloproteinases in the enlarging abdominal aortic aneurysm.

The risk of rupture of an abdominal aortic aneurysm increases with aortic diameter. To obtain insight into the pathological processes associated with the vascular remodeling that accompanies aortic dilatation, we compared the histological features and the activity of matrix metalloproteinases (MMPs) in biopsies from 21 small (4.0 to 5.5 cm in diameter) and 45 larger abdominal aortic aneurysms. The histological feature most clearly associated with enlarging aneurysm diameter was a higher density of inflammatory cells in the adventitia, P = .018. This inflammation was nonspecific, principally macrophages and B lymphocytes. Fibrosis of the adventitia provided compensatory thickening of the aortic wall as the aneurysm diameter increased. A combination of zymography and immunoblotting identified gelatinase A (MMP-2) as the principal metallogelatinase in small aneurysms, whereas zymography indicated an increasing activity of gelatinase B (MMP-9) in large aneurysms. Homogenates prepared from both small and large aneurysms had similar total activity against gelatin or type IV collagen. However, the concentration of gelatinase A, determined by immunoassay, was highest for small aneurysms: median concentrations, 385, 244, and 166 ng/mg protein for small aneurysms, large aneurysms, and atherosclerotic aorta, respectively. Immunolocalization studies indicated that gelatinase A was concentrated along fibrous tissue of both the acellular media and the atherosclerotic plaque. The recruitment of inflammatory cells into the adventitia, with subsequent elaboration of metalloproteinases, including gelatinase B, may contribute to the rapid growth and rupture of larger aneurysms.

Amino Acid Sequence↗
PubMed1995

Lifetime traumas and mental health: the significance of cumulative adversity.

This paper reports the community prevalence of 20 life traumas and considers their individual relevance as risk factors for psychiatric disorder. Also presented is the first evidence on the mental health significance of cumulative adversity as indexed by a count of lifetime exposure to a wide array of potentially traumatic events. The question of the importance of considering such events within efforts to assess variations in life stress is also examined. Our results demonstrate clear relationships between many traumatic events and, especially, accumulated lifetime trauma experience and both psychological distress and psychiatric disorder. That these relationships persist with temporal priority controlled - and net of the effects of parental psychopathology - suggest the causal relevance of major lifetime events and the conclusion that they represent on important dimension of increased mental health risk. From these findings and from evidence for the significance of traumas in disorder recurrence, it is contended that failure to take account of such events has resulted in the systematic underestimation of the role of stress exposure in accounting for variations in emotional distress and disorder.

Adult↗
PubMed1994

Characterization of the three different states of the cholecystokinin (CCK) receptor in pancreatic acini.

By measuring binding of [125I]CCK-8 and [3H]L-364,718 to rat pancreatic acini we demonstrated directly that the pancreatic CCK receptor can exist in three different affinity states with respect to CCK--high affinity, low affinity and very low affinity. Binding of [125I]CCK-8 reflects interaction of the tracer with the high and low affinity states, whereas binding of [3H]L-364,718 reflects interaction of the tracer with the low and very low affinity states. Treating acini with carbachol abolished the high affinity state of the CCK receptor and converted approximately 25% of the low affinity receptors to the very low affinity state. Carbachol treatment was particularly useful in establishing the values of Kd for the high and low affinity states for different CCK receptor agonists and antagonists. Of the various CCK receptor agonists tested, CCK-8 had the highest affinity for the high affinity state (Kd approximately 1 nM), whereas CCK-JMV-180 had the highest affinity for the low (Kd 7 nM) and very low affinity (Kd 200 nM) states. Gastrin and de(SO4)CCK-8 had affinities for the high and low affinity states of the receptor that were 100- to 400-fold less than those of CCK-8 but had affinities for the very low affinity state that were only 3- to 10-fold less than that of CCK-8. CCK receptor antagonists showed several patterns in interacting with the different states of the CCK receptor. L-364,718 had the same affinity for each state of the CCK receptor. CR1409 and Bt2cGMP each had similar affinities for the high and low affinity states and lower affinity for the very low affinity state. L-365,260 and CCK-JMV-179 had the highest affinity for the low affinity state and lower affinities for the high and very low affinity states. Different CCK receptor agonists caused the same maximal stimulation of amylase secretion but showed different degrees of amplification in terms of the relationship between their abilities to stimulate amylase secretion and their abilities to occupy the low affinity state of the CCK receptor. When amplification was expressed quantitatively as the value of Kd for the low affinity state divided by the corresponding EC50 for stimulating amylase secretion the values were CCK-8 (1000), de(SO)CCK-8 (1500), gastrin (100) and CCK-JMV-180 (Menozzi, D., Vinayek, R., Jensen, R.T. and Gardner, J.D. (1991) J. Biol. Chem. 266, 10385-1091).(ABSTRACT TRUNCATED AT 400 WORDS)

Amylases↗
PubMed1994

A new gonadotropin-releasing hormone (GnRH) superagonist in goldfish: influence of dialkyl-D-homoarginine at position 6 on gonadotropin-II and growth hormone release.

The two native forms of gonadotropin-releasing hormones (GnRH) present in goldfish, salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II), stimulate gonadotropin-II (GTH-II) and growth hormone (GH) release both in vivo and in vitro. In our previous study using perifused goldfish pituitary fragments, many mammalian GnRH antagonists, especially those with D-Arg6, showed weak to strong stimulation of GTH-II and GH release. In the present study, the dose-related stimulation of GTH-II and GH release by [Ac-D(2)-Nal1, 4Cl-D-Phe2, D-Trp3, D-Arg6, Trp7, D-Ala10] mGnRH (analog J) and [Ac-D(2)-Nal1, 4Cl-D-Phe2, D-Trp3, D-hArg(Et2)6, D-Ala10] mGnRH (analog K) was demonstrated; the stimulatory potency of both analogs was significantly lower than that of native sGnRH. In the presence of analogs J and K, cGnRH-II stimulated GTH-II release was significantly suppressed. Further, GTH-II and GH stimulation by 2 microM of analog K was significantly suppressed by a 'true' GnRH antagonist, [Ac-delta 3-Pro1, 4FD-Phe2, D-Trp3,6] mGnRH (analog E). These results indicate that analogs J and K increase GTH-II and GH release in goldfish by acting on GnRH receptors on gonadotrophs and somatotrophs. Since analog K, having [D-hArg(Et2)6], strongly stimulated GTH-II release, the potency of [D-hArg(Et2)6] or [D-hArg(CH2CF3)2(6)] substituted analogs to stimulate GTH-II and GH release from the perifused goldfish pituitary fragments was tested. Among the peptides tested, [D-hArg(Et2)6, Pro9-NHEt] sGnRH had a higher potency in stimulating GTH-II release than any other analog tested in the present or in previous studies. For stimulation of GH release, [D-hArg(Et2)6, Pro9-NHEt] sGnRH and [D-Arg6, Pro9-NHEt] sGnRH were the most potent analogs tested; analogs of mGnRH were less potent than sGnRH, indicating the importance of Trp7, Leu8 residues in the native peptide. These results suggest the importance of [D-Arg6] or alkylated [D-Arg6] in determining the intrinsic activity and potency of GnRH peptides in goldfish.

Amino Acid Sequence↗
PubMed1994

Effect of inhibition of microsomal Ca(2+)-ATPase on cytoplasmic calcium and enzyme secretion in pancreatic acini.

We used thapsigargin (TG), 2,5-di-tert-butyl-1,4-benzohydroquinone (BHQ) and cyclopiazonic acid (CPA), each of which inhibits microsomal Ca(2+)-ATPase, to evaluate the effects of this inhibition on cytoplasmic free calcium ([Ca2+]i) and secretagogue-stimulated enzyme secretion in rat pancreatic acini. Using single-cell microspectrofluorimetry of fura-2-loaded acini we found that all three agents caused a sustained increase in [Ca2+]i by mobilizing calcium from inositol-(1,4,5)-trisphosphate-sensitive intracellular calcium stores and by promoting influx of extracellular calcium. Concentrations of all three agents that increased [Ca2+]i potentiated the stimulation of enzyme secretion caused by secretagogues that activate adenylate cyclase but inhibited the stimulation of enzyme secretion caused by secretagogues that activate phospholipase C. With BHQ, potentiation of adenylate cyclase-mediated enzyme secretion occurred immediately whereas inhibition of phospholipase C-mediated enzyme secretion occurred only after several min of incubation. In addition, the effects of BHQ and CPA on both [Ca2+]i and secretagogue-stimulated enzyme secretion were reversed completely by washing whereas the actions of TG could not be reversed by washing. Concentrations of BHQ in excess of those that caused maximal changes in [Ca2+]i inhibited all modes of stimulated enzyme secretion by a mechanism that was apparently unrelated to changes in [Ca2+]i. Finally, in contrast to the findings with TG and BHQ, CPA inhibited bombesin-stimulated enzyme secretion over a range of concentrations that was at least 10-fold lower than the range of concentrations over which CPA potentiated VIP-stimulated enzyme secretion.

Amylases↗
PubMed1994

A novel form of pectinesterase in tomato.

The pectinesterases in tomato pericarp were fractionated by cation exchange into four forms (A-D). Form A was the most abundant and C the second most abundant. Forms A-C were further purified by gel filtration, and antibodies were raised against A and C. Comparison of the different forms by dot blots and Western blots showed that although all three forms shared common immunological characteristics, there were also differences in their behaviour, indicative of structural differences. Form A had an N-terminal sequence identical to that published previously for the major pectinesterase in tomato fruit. In contrast, form C had a completely novel N-terminal sequence. Form A was absent from hypocotyls and roots. Forms B and C were present in comparable amounts in hypocotyls, while from C predominated in roots.

Amino Acid Sequence↗
PubMed1994

Pseudomembranous enterocolitis after gynecologic endoscopy.

A 21-year-old nulligravida underwent diagnostic hysteroscopy and laparoscopic potassium-titanyl-phosphate laser ablation of pelvic peritoneal endometriosis (revised American Fertility score of 10) for dysmenorrhea, dyspareunia, and dyschezia. Preoperatively the patient had an electrolyte bowel preparation but no antibiotic prophylaxis. Six days postoperatively she developed symptoms of nausea, vomiting, and diarrhea, which were not affected by diet and over-the-counter bowel medications. Examination of stool samples for culture, ova, parasites, and Clostridium difficile toxin led to the diagnosis of C. difficile pseudomembranous enterocolitis. The patient was referred to a gastroenterologist. She required 4 months of metronidazole therapy, including two hospitalizations, before her symptoms resolved. The stool assay became negative for C. difficile toxin 6 months after surgery. Pseudomembranous enterocolitis may occur rarely in patients without the usual risk factors of antibiotic therapy. The role of electrolyte bowel preparation is uncertain, but it may have permitted overgrowth of C. difficile.

Adult↗
PubMed1994

In vivo complementation and site-specific mutagenesis of the tellurite resistance determinant kilAtelAB from IncP alpha plasmid RK2Ter.

The IncP alpha plasmid RK2 carries a cryptic tellurite resistance (Ter) determinant. This determinant from RK2Ter has been previously cloned into a pUC8 plasmid (pDT1558). The Ter determinant identified as the kilA locus comprises an operon of three genes: kilA, telA and telB [also referred to as klaA, klaB and klaC on RK2(Tes)]. Each of the genes was subcloned into the expression vector pJF118EH behind an inducible tac-promotor using PCR. The PCR primers were used to engineer an efficient ribosome-binding site and adjacent sequence to improve protein expression. Expression plasmids were modified by inclusion of different resistance markers for selection during complementation. The tellurite-resistance phenotype was studied with the overexpressing plasmids. The study provides further evidence that all three genes within the kilAtelAB operon are required for cells to show resistance to potassium tellurite. Additionally, site-directed mutagenesis was carried out on the two cysteine residues in TelB. Changing either Cys125 or Cys132 to a Ser or Ala residue decreased the resistance mediated by the operon. These mutants demonstrate the requirement of cysteine residues within TelB for expression of tellurite resistance.

Amino Acid Sequence↗
PubMed1994

Regulation of the Bacillus subtilis pyrimidine biosynthetic (pyr) gene cluster by an autogenous transcriptional attenuation mechanism.

A complete transcript of the Bacillus subtilis pyr operon contains the following elements in 5' to 3' order: a 151-nucleotide (nt) untranslated leader; pyrR, encoding a 20-kDa protein; a 173-nt intercistronic region; pyrP, encoding a 46-kDa protein; a 145-nt intercistronic region; and eight overlapping cistrons encoding all of the six enzymes for de novo pyrimidine biosynthesis. Transcription is controlled by the availability of pyrimidines via an attenuation mechanism. There are three transcription terminators within the operon, each of which is preceded by another stem-loop structure, the antiterminator, whose formation would prevent formation of the terminator stem-loop. These are located in the leader, the pyrR-pyrP intercistronic region, and the pyrP-pyrB intercistronic region. Northern (RNA) blot analysis has identified transcripts of lengths which coincide with termination at these proposed attenuation sites and whose relative abundances vary in the expected pyrimidine-dependent manner. Each antiterminator contains a 50-base conserved sequence in its promoter-proximal half. Various transcriptional fusions of the pyr promoter and surrounding sequences to promoterless reporter genes support an attenuation mechanism whereby when pyrimidines are abundant, the PyrR protein binds to the conserved sequence in the pyr mRNA and disrupts the antiterminator, permitting terminator hairpin formation and promoting transcription termination. Deletion of pyrR from the chromosome resulted in the constitutive, elevated expression of aspartate transcarbamylase, which is encoded by pyrB, the third gene in the operon. Complementation of an E. coli upp mutant, as well as direct enzymatic assay, has demonstrated that pyrR also confers uracil phosphoribosyltransferase activity. Analysis of pyrR and upp deletion mutants demonstrated that upp, not pyrR, encodes the quantitatively important uracil phosphoribosyltransferase activity. The pyrP gene probably encodes an integral membrane uracil permease.

Amino Acid Sequence↗
PubMed1994

Ion transport mechanisms in rat parotid intralobular striated ducts.

The intracellular pH (pHi) indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein and microfluorimetry were used to characterize several ion transport mechanisms in rat parotid striated ducts. The recovery of ductal pHi from an acute acid load was Na+ dependent and inhibited by the amiloride analogue ethylisopropylamiloride with 50% inhibitory concentration 4.7 +/- 0.8 microM, indicating the presence of a Na(+)-H+ exchanger of the amiloride-insensitive type. The rate of this recovery was stimulated approximately 20% in ducts pretreated with the muscarinic agonist carbachol (10(-5) M) and inhibited approximately 20% in ducts pretreated with the beta-adrenergic agonist isoproterenol (10(-6) M). Upon removal of extracellular K+, ductal pHi rapidly decreased (0.19 +/- 0.02 pH units/min), consistent with a coupling between K+ and H+ (or OH-) fluxes in this tissue. In HCO(3-)-containing medium, the acidification due to K+ removal was blunted, arguing against ductal K(+)-HCO3- cotransport. However, the effect of K+ removal was inhibited by the K+ channel blocker Ba2+ (1 mM) and by the H+ channel blocker Zn2+ (25 microM), consistent with the involvement of electrically coupled K+ and H+ channels. The effect of K+ removal was unaffected by pretreatment of ducts with isoproterenol (10(-6) M) but markedly inhibited (approximately 50%) by pretreatment with carbachol (10(-5) M). No evidence for a significant component of Cl(-)-HCO3- exchange was found in striated ducts. The properties of the Na(+)-H+ exchanger and K(+)-H+ exchange mechanism identified here are consistent with their involvement in ductal salt reabsorption and secretion.

Animals↗
PubMed1994

K(+)-induced alkalinization in mouse cerebral astrocytes mediated by reversal of electrogenic Na(+)-HCO3- cotransport.

Raising extracellular K+ concentration ([K+]o) induces an alkaline shift of intracellular pH (pHi) in astrocytes. The mechanism of this effect was examined using the fluorescent pHi indicator 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein in primary cultures of mouse cerebral astrocytes. Raising [K+]o from 3 to 12 mM increased pHi by 0.28 pH units in 26 mM HCO(3-)-buffered solution. In nominally HCO(3-)-free solution (containing approximately 95 microM HCO3-), the alkalinization fell to 0.21 pH units and further to 0.08 pH units on removal of atmospheric CO2, suggesting a process with high affinity for HCO3-. This effect was Na+ dependent, Cl- independent, and inhibited by 0.5 mM 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid, indicating the involvement of Na(+)-HCO3- cotransport. The relationship between pHi and log[K+]o was found to be linear and to predict a stoichiometry of at least two HCO3- transported with each Na+. After removal of exogenous CO2/HCO3-, the direction of changes in pHi elicited by adding 1 mM HCO3- showed that net flux of HCO3- via the Na(+)-HCO3- cotransporter was outward at rest and was reversed by depolarization.

Animals↗
PubMed1994

Microfluorometric studies of intracellular Ca2+ and Na+ concentrations in normal human labial gland acini.

The responses of human labial salivary acini to muscarinic, adrenergic, and substance P peptidergic stimulation were studied using the fluorescent indicators fura 2 for intracellular Ca2+ concentration ([Ca2+]i) and sodium-binding benzofuran isophthalate for intracellular Na+ concentration ([Na+]i). Of the agents tested (carbachol, epinephrine, isoproterenol, and substance P) only the muscarinic agonist carbachol increased [Ca2+]i substantially above basal levels (three to fourfold; half-maximal effect approximatley 1 microM). Experiments with the Ca(2+)-adenosinetriphosphatase inhibitor thapsigargin indicated the presence of both thapsigargin-sensitive and thapsigargin-insensitive intracellular Ca2+ stores, both of which were mobilized by carbachol. [Na+]i in resting labial acini was approximately 20 mM. On stimulation with carbachol, [Na+]i rose transiently to more than three times this value and then partially recovered. This carbachol-induced rise in [Na+]i was largely blocked by bumetanide, a specific inhibitor of the Na(+)-K(+)-2Cl- cotransporter. These results are consistent with an intact muscarinic fluid secretory response in human labial acini with transepithelial Cl- secretion driven via Na(+)-K(+)-2Cl- cotransport and the secretion of fluid presumably following Cl- loss via an apical Ca(2+)-dependent anion channel, as observed in salivary acini from other species.

Adult↗
PubMed1994

Differential actions of a mammalian gonadotropin-releasing hormone antagonist on gonadotropin-II and growth hormone release in goldfish, Carassius auratus.

In goldfish the two native forms of gonadotropin-releasing hormone (GnRH), salmon GnRH (sGnRH) and chicken GnRH-II (cGnRH-II), stimulate both gonadotropin-II (GTH-II) and growth hormone (GH) release. Modifications of GnRH structure at positions 1, 2, 3, and 6 often result in an antagonist in goldfish, an observation well documented in mammalian studies. In a preliminary study in goldfish, a mammalian GnRH antagonist, [Ac-D(2)Nal1, 4Cl-D-Phe2, D(3)-Pal3,6, Arg5, D-Ala10]-mGnRH (analog L) weakly stimulated GTH-II release, and strongly inhibited GH release. The objectives of the present study were to study the dose-related actions of analog L on GTH-II and GH release in the goldfish, the specificity of inhibition of native GnRH actions, and to test whether analog L can act directly on goldfish pituitary cells. In a goldfish pituitary fragments perifusion system, analog L at different concentrations, given as 2-min pulses or as 30-min prolonged treatments, stimulated GTH-II and inhibited GH release in a dose-dependent manner. Analog L at 2 microM concentration (45 min) significantly suppressed sGnRH- and cGnRH-II-stimulated GTH-II as well as GH release. Analog L specifically inhibited GnRH-stimulated GH release, without having any significant effects on the GH release induced by either SKF38393, a dopamine D1 receptor agonist, or thyrotropin-releasing hormone. The GTH-II stimulatory and GH-inhibitory actions of analog L were significantly suppressed by a 'true' GnRH antagonist (Ac-delta 3-Pro1, 4FD-Phe2, D-Trp3,6)-mGnRH. Further, analog L stimulated GTH-II release and suppressed GH release from the enzymatically dispersed goldfish pituitary cells, indicating the direct actions of analog L at the pituitary cell level. Analog L also displaced 125I-(D-Arg6, Pro9 NHEt)-sGnRH bound to crude goldfish pituitary membrane preparations in a dose-related manner. In conclusion, contrary to its action as a potent GnRH antagonist in mammals, analog L has GTH-II stimulatory action in goldfish. Analog L by acting via GnRH receptors at the pituitary cell level differentially acts on GTH-II and GH release, suggesting functional differences in the properties of the GnRH receptors on GTH and GH cells. Analog L also specifically inhibits sGnRH and cGnRH-II actions on GTH-II and GH release.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗
PubMed1994

Social support and social structure: a descriptive epidemiology.

Despite a very large and growing literature demonstrating the significance of social support for health and well-being, surprisingly little is known about the social distribution of this crucial resource. This paper presents data on the distribution of social support and support resources across social class, marital status, age and gender, with the aims of contributing toward an understanding of the impact of social structures on processes of social support, and of assessing the hypothesis that epidemiological variations in mental health arise partially from social support differences. The epidemiology of perceived social support was found to correspond closely to the epidemiology of psychological distress and disorder. The single exception involved gender, where a positive rather than negative relationship was observed, with women demonstrating the highest levels of both social support and psychological distress. The observed patterns of variation in social support link this significant adaptive resource to one's locations in the social structure and reinforce the conclusion that it represents a promising intervention target. The practical importance of these results, however, are not matched by theoretical significance. Except in the case of marital status, our findings largely discount the hypothesis that the social distribution of mental health is partially attributable to social support differences.

Adult↗
PubMed1993

Extracellular potassium regulates the glutamine content of astrocytes: mediation by intracellular pH.

Based upon previous evidence that glutamine formation in astrocytes is pH-sensitive and that raised extracellular K+ alkalinizes astrocytic cytoplasm, it was hypothesized that extracellular K+ might regulate glutamine formation. In this study, the free glutamine content of mouse cerebral astrocytes incubated with 0.1 mM glutamate and 0.1 mM ammonium increased by 80-90% when the extracellular K+ concentration was raised from 3 to 12 mM. The corresponding K(+)-induced intracellular alkalinization of +0.13 pH units only partially reversed a glutamate-induced intracellular acidification of -0.24 pH units. By comparison, adjustment of extracellular pH from 7.4 to 7.8 shifted intracellular pH by +0.25 pH units, fully reversing the glutamate-induced acidification and increasing glutamine content by 120-180%. The effect of K+ on intracellular pH increased to +0.25 pH units in bicarbonate-buffered solution, suggesting that the regulation of glutamine formation by extracellular K+ is enhanced in the presence of bicarbonate.

Ammonia↗
PubMed1993

Evaluation of transmembrane helix prediction methods using the recently defined NMR structures of the coat proteins from bacteriophages M13 and Pf1.

Currently, there are a large number of hydropathy scales available to predict the presence of transmembrane segments within integral membrane proteins. These scales and their subsequent numerical manipulations provide an aid in the determination of topology in transmembrane proteins. In order to analyse the accuracy of these procedures to correctly identify the boundaries of a transmembrane segment, 13 methods were applied to the amino-acid sequence of the coat proteins from the bacteriophages Pf1 and M13. These monotopic integral membrane proteins have been incorporated into detergent micelles and their structures have recently been solved using NMR. The predicted regions were then compared to their NMR-determined structures. All methods used were able to detect a transmembrane region within the protein sequence. However, there was considerable differences in their accuracy in determining the boundaries of the main transmembrane alpha-helix. Surprisingly, the methods which worked the best for Pf1 coat protein had poor accuracy in identifying the transmembrane region correctly in the M13 protein. It was concluded that a number of methods should be utilized in order to obtain a clear model of transmembrane protein topology, and that regardless of how closely related two proteins are, a different conclusion may be obtained from different prediction procedures.

Amino Acid Sequence↗