Biomedical subjects

S A Price

Publications and source records attributed to S A Price.

At least 19 recordsLinked to original sources

PubMed2004

Expression of axotomy-inducible and apoptosis-related genes in sensory nerves of rats with experimental diabetes.

In diabetes, peripheral nerves suffer deficient neurotrophic support-a situation which resembles axotomy. This raises the question: does inappropriate establishment of an axotomised neuronal phenotype contribute to diabetic neuropathy, and in extremis, does this provoke apoptosis? We hybridized reverse-transcribed RNA, from the dorsal root ganglia (DRG) of 8-week streptozotocin (STZ)-induced diabetic rats, to Affymetrix Rat Genome U34A chips and scanned the array for expression of (a) genes that are upregulated by axotomy, (b) proapoptotic and (c) anti-apoptotic genes. Expression of the axotomy-responsive genes coding for growth-associated protein 43 (GAP-43), galanin, neuropeptide Y (NPY), pre-pro-vasoactive intestinal polypeptide (pre-pro-VIP), neuronal nitric oxide synthase (nNOS), protease nexin 1, heat-shock protein 27 (HSP 27) and myosin light chain kinase II (MLCK II) was unaffected in ganglia from diabetic rats compared to controls; thus, no axotomised phenotype was established. The expression of the majority of proapoptotic genes in the DRG was also unaltered (bax, bad, bid, bok, c-Jun, p38, TNFR1, caspase 3 and NOS2). Similarly there was no change in expression of the majority of antiapoptotic genes (bcl2, bcl-xL, bcl-w, NfkappaB). These alterations in gene expression make it clear that neither axotomy nor apoptotic phenotypes are established in neurones in this model of diabetes.

Animals↗

PubMed2001

Modulation of adipocyte G-protein expression in cancer cachexia by a lipid-mobilizing factor (LMF).

Adipocytes isolated from cachectic mice bearing the MAC 16 tumour showed over a 3-fold increase in lipolytic response to both low concentrations of isoprenaline and a tumour-derived lipid mobilizing factor (LMF). This was reflected by an enhanced stimulation of adenylate cyclase in plasma membrane fractions of adipocytes in the presence of both factors. There was no up-regulation of adenylate cyclase in response to forskolin, suggesting that the effect arose from a change in receptor number or G-protein expression. Immunoblotting of adipocyte membranes from mice bearing the MAC16 tumour showed an increased expression of Galphas up to 10% weight loss and a reciprocal decrease in Galpha. There was also an increased expression of Galphas and a decrease in Galpha in adipose tissue from a patient with cancer-associated weight loss compared with a non-cachectic cancer patient. The changes in G-protein expression were also seen in adipose tissue of normal mice administered pure LMF as well as in 3T3L1 adipocytes in vitro. The changes in G-protein expression induced by LMF were attenuated by the polyunsaturated fatty acid, eicosapentaenoic acid (EPA). This suggests that this tumour-derived lipolytic factor acts to sensitize adipose tissue to lipolytic stimuli, and that this effect is attenuated by EPA, which is known to preserve adipose tissue in cancer cachexia.

Adenylyl Cyclases↗

PubMed2001

Uterine quiescence: the role of cyclic AMP.

It is accepted that whilst hormones such as oxytocin, vasopressin and prostaglandin F2alpha induce myometrial contractions, essentially via an elevation of intracellular calcium, other ligands, such as beta-adrenoceptor agonists, calcitonin gene-related peptide, and prostaglandin E2, promote uterine quiescence via their ability to increase intracellular cyclic AMP levels. At present, the exact factors initiating human parturition remain unknown, and labour may occur due to a loss of uterine quiescence, an increase in uterine contractility, or a combination of both. Whilst many studies have aimed to understand the mechanisms underlying uterine contractility there is a relative paucity of data regarding myometrial relaxation. We have verified the presence of mRNA encoding adenylyl cyclase (AC) isoforms I, II, III, V, VI, VII, VIII and IX in both non-pregnant and pregnant human myometrium, and in isolated myometrial cells maintained in cell culture. Furthermore, by means of immunoblotting and immunocytochemistry, we have demonstrated the expression of these isoforms as membrane-associated AC proteins, and identified changes in individual AC isoform expression during gestation. These findings illustrate the diversity of potential cAMP generating pathways in human myometrium, and the complexity of the signal transduction systems underlying uterine quiescence. Experimental Physiology (2001) 86.2, 265-272.

Adenylyl Cyclases↗

PubMed2001

Characterization of adenylyl cyclases in cultured human granulosa cells.

Granulosa cells play an essential role in follicular development and formation of corpora lutea. Many functions of granulosa-lutein cells are controlled by activation of G protein-coupled receptors and the formation of cyclic AMP (cAMP) by adenylyl cyclase. There are at least nine mammalian adenylyl cyclase isoenzymes, which show different sensitivities towards other signalling systems. The aim of this study was to identify the types of adenylyl cyclase present in human granulosa cells and to investigate its functional regulation by G proteins, calcium and the protein kinase C and A pathways. Granulosa cells were obtained from women undergoing IVF. The cells were maintained in primary culture and they consistently expressed mRNA coding for adenylyl cyclase I, III, VI, VII and IX. The signals for adenylyl cyclase V and VIII were more variable among patients and there was no signal for adenylyl cyclase II. The expression of multiple adenylyl cyclase proteins was confirmed by immunochemistry with subtype-specific antibodies. The formation of cAMP in cultured cells was stimulated many times by hCG (EC(50) value 4.2 iu ml(-1)) and by prostaglandin E(2) (PGE(2); EC(50) = 0.75 micromol l(-1)) in a concentration-dependent manner, thus confirming the presence of receptors coupled positively to G(s). The diterpene forskolin, which stimulates all isoforms of adenylyl cyclase except for adenylyl cyclase IX, increased cAMP formation to higher levels than hCG or PGE(2). The strong stimulation by forskolin indicates that adenylyl cyclase IX is unlikely to be the major source of cyclase activity in these cells. Basal and forskolin- or PGE(2)-stimulated adenylyl cyclase activity was amplified 1.5-2.0 times by phorbol-12,13-dibutyrate, indicating that protein kinase C-sensitive enzymes (for example, adenylyl cyclase types IV, V, VI or VII) may be active in the cells. In contrast, hCG-stimulated activity was inhibited (76 +/- 6%) by phorbol ester. Stimulation of G(i) with the alpha-adrenoceptor agonist clonidine inhibited hCG-induced cyclase activity. This finding indicates that adenylyl cyclase II and IV subtypes, which are stimulated by betagamma subunits released from G(i), are not predominant. Increases in intracellular free calcium concentrations by the ionophore A23187, the calcium-ATPase inhibitor thapsigargin or by fluprostenol, a selective prostanoid FP receptor agonist, which is known to open calcium channels in granulosa cells, or removal of calcium by EGTA, had no significant effects on basal or forskolin-stimulated formation of cAMP. These results indicate that subtypes adenylyl cyclase I, III and VIII, which are activated by calcium, and adenylyl cyclase V and VI, which are inhibited by calcium, are not dominant isoforms in granulosa-lutein cells. The protein kinase A inhibitor H89 had no effects on formation of cAMP; this finding rules out the involvement of adenylyl cyclase V and VI subtypes, which are subjected to negative feedback by protein kinase A. These results indicate that adenylyl cyclase VII is the dominant functional isoenzyme in human granulosa-lutein cells.

Adenylyl Cyclases↗

PubMed2000

Adenylyl cyclase isoforms in pregnant and non-pregnant human myometrium.

The precise factors involved in the transition of the relaxed pregnant uterus to the contractile state at the onset of parturition remain unclear, but it is accepted that cAMP-generating pathways contribute to uterine relaxation. We have previously reported an increased expression of the adenylyl cyclase (AC)-stimulating protein Galphas in human myometrium during gestation, with a corresponding increase in GTP-stimulated AC activity. However, little is known about the predominating AC isoforms expressed during pregnancy. This information is important, because although all AC isoforms are stimulated by Galphas, their regulation by other signalling molecules is very different. In the present study we have identified the isoforms of AC expressed in both pregnant and non-pregnant myometrium by mRNA analysis and immunoblotting. mRNA encoding for AC I, II, III, VIII and IX was present in non-pregnant and pregnant myometrium, and in cultured myometrial cells. Differing levels of AC protein could be detected in myometrial plasma membranes, with decreased levels of Group 1 (isoforms I, III and VIII) and Group 4 (IX) ACs allied with increased levels of Group 2 (II, IV and VII) and 3 (V and VI) ACs during pregnancy. These findings imply a role for Group 2-activating pathways, e.g. G-protein betagamma-subunits and protein kinase C, in the maintenance of uterine quiescence, whilst suggesting a lesser involvement of calcium-calmodulin complex, an activator of Group 1 AC isoforms, in uterine relaxation during gestation. These data may provide an alternative pharmacological approach for the attenuation of preterm labour.

Adenylyl Cyclases↗

PubMed1999

Subacute sepsis impairs vascular smooth muscle contractile machinery and alters vasoconstrictor and dilator mechanisms.

INTRODUCTION: Sepsis results in hyporesponsiveness to alpha-adrenergic stimulation. This is thought to be mediated by the release of vasoactive compounds from the septic endothelium or by the direct effect of sepsis on vascular smooth muscle (VSM) contractile mechanics and machinery. Previous studies have used lethal models of sepsis or endotoxemia to examine this phenomenon. The present study utilizes a clinically relevant, nonlethal model of soft tissue infection to determine the effects of sepsis on alpha-adrenergic mechanisms. We hypothesize that subacute sepsis causes impaired alpha-adrenergic vascular responsiveness by a combination of effects on adrenergic constrictor mechanisms, endogenous dilator tone, and VSM contractile function. METHODS: Male Sprague-Dawley rats underwent implantation of a 2 x 2-cm2 gauze sponge into a subcutaneous pocket created at the base of the tail. Five days after implantation, sepsis (S) was induced by inoculation of the sponge with 10(9) CFU Escherichia coli and Bacteroides fragilis. Controls (C) were inoculated with saline. Thoracic aortic harvest was performed 24 and 48 h after sponge inoculation for organ bath ring studies. Receptor-mediated (phenylephrine) and nonreceptor-mediated (KCl) maximum force of contraction (Fmax) was measured. Vessel sensitivity (pD2) to phenylephrine, acetylcholine, and KCl was calculated from dose-response curves. RESULTS: At 24 h, sepsis resulted in a lower Fmax to phenylephrine (1.15 for C vs 0.5 for S, P < 0.05 by ANOVA), despite an increase in vessel sensitivity (pD2) to alpha-adrenergic stimulation (6.70 for C vs 6.88 for S, P < 0.05 by ANOVA). Fmax to KCl was lower in septic animals at 24 h (3. 50 for C vs 2.77 for S, P < 0.05 by ANOVA) and sensitivity to acetylcholine (pD2) was markedly increased (6.56 for C vs 7.23 for S, P < 0.05 by ANOVA). At 48 h, the impairment in Fmax to alpha-adrenergic stimulation (2.29 for C vs 1.72 for S, P < 0.05 by ANOVA) and KCl (3.5 for C vs 3.08 for S. P < 0.05 vs 24 h C by ANOVA) persisted without any change in sensitivity to phenylephrine or acetylcholine. CONCLUSIONS: Subacute sepsis results in an early suppression of maximum contractile force despite an increase in adrenergic receptor sensitivity (pD2). This may be secondary to an elevation in dilator sensitivity combined with a direct effect of sepsis on VSM contractile mechanisms. Later in the septic process, however, alpha-adrenergic hyporesponsiveness ( downward arrow Fmax) is primarily due to changes in VSM contractile machinery.

Acetylcholine↗

PubMed1999

Prophylactic and therapeutic use of antibiotics in pelvic surgery.

The abiding principles of antibiotic use in the surgical patient vary in the complicated pelvic surgery setting only in that some microbes likely to be encountered warrant minor variation in drug choice. Very early antibiotic administration, relatively large doses, and prompt association when the reason for therapy has been accomplished, are the keystones for treatment. Tissue levels of antimicrobial activity are the uniform therapeutic goal. We also prefer consistent selection of drugs known to be safe and believe that continuous infusion may enhance the overall protective effect. Preservation of normal host defenses enhances the action of all antibiotics.

Antibiotic Prophylaxis↗

PubMed1999

Altered vasoconstrictor and dilator responses after a "two-hit" model of sequential hemorrhage and bacteremia.

BACKGROUND: The "two-hit" theory of multiple organ dysfunction (MOD) proposes that an initial insult, such as hemorrhage (HEM), primes the host for an abnormal response to a second stress such as infection. The immunologic/inflammatory component of this theory has been well examined; however, the effects on vascular responsiveness are poorly understood. We hypothesized that HEM primes the vasculature for an altered response to a second pathophysiologic stress. METHODS: Male Sprague-Dawley rats underwent a fixed-volume HEM with resuscitation (H/R) or sham procedure (Sham). At 48 h, animals were given iv E. coli or saline and followed for 1 h. Thoracic aortic rings were then placed in organ baths containing Krebs buffer aerated with 95% O2, 5% CO2. Cumulative dose-response curves to phenylephrine (PHE) and acetylcholine (ACH) were obtained. Maximum force of contraction (Fmax) was measured and pD2 values (receptor sensitivity) were derived. RESULTS: H/R alone resulted in heightened constrictor tone and blunted dilator tone. E. coli reduced Fmax in response to PHE by 50% in Sham vs 76% in H/R. Receptor sensitivity (pD2) to PHE was reduced to a greater degree in H/R (3-fold vs 2-fold). These animals also had a more pronounced enhancement of ACH receptor sensitivity (7-fold vs 2-fold). CONCLUSIONS: Hemorrhage primes the vasculature for an altered response to a subsequent stress. When infection is added as a "second hit," responsiveness to adrenergic agents is diminished and dilator tone is increased. These data may explain the cardiovascular derangements seen clinically in patients who develop MODS after major hemorrhage followed sequentially by infection.

Acetylcholine↗

PubMed1999

Pretesting Spanish-language educational radio messages to promote timely and complete infant immunization in California.

California's Hispanic infants have lower immunization levels than non-Latino white infants, 53.7% versus 65.2%, respectively. Spanish-language radio is an effective mass media venue for imparting information to Latino populations. It has been demonstrated that lack of parental knowledge of infant immunization timing is associated with delayed immunization coverage. In an effort to improve Latino parent knowledge of immunization timing, two Spanish-language radio commercials were developed to be used in conjunction with community-based educational efforts. In order to gage the potential educational impact of the two commercials, they were pretested with a group of low-income Spanish-speaking Latino parents who represented members of the target population for whom the commercials were created. Both commercials were rated favorably by parents, and elicited immunization-specific responses. Although correct recall of the simplified, basic immunization schedule was low, the level of immunization response consistency and overall approval of both commercials appear to support their use as part of Latino infant immunization educational outreach in California.

Adult↗

PubMed1999

Expression of G-protein-coupled receptor kinases in pregnant term and non-pregnant human myometrium.

There is evidence for hormonal receptor desensitisation in human myometrium, but little is known about the mechanisms involved in the loss of myometrial response to agonists such as beta(2)-adrenergic agonists, prostaglandin gamma and oxytocin. It is well known that the receptors for these hormones are coupled to G-proteins. The first step of receptor desensitisation is the phosphorylation of activated receptors by a G-protein-coupled receptor kinase (GRK). GRKs are members of a multigene family and the various subtypes differ in their localisation, regulation and mode of action. We have used Western blotting and reverse transcription PCR to identify the GRKs present in human myometrium from pregnant and non-pregnant women as well as in cultured human myometrial cells. We have found that human myometrium expresses the GRK subtypes 2, 4gamma, 5 and 6. On the other hand, GRK3 and the isoforms GRK4alpha, beta and delta were not found in myometrial tissue. Our data indicate that GRK2 is only expressed in pregnant term myometrium and is not found in non-pregnant tissue. Moreover, GRK6 appears to be expressed at a much higher level in pregnant term tissue than in non-pregnant myometrium. Our observations suggest that GRK2 and GRK6 may contribute to the regulation of uterine contractility at term. Further work is necessary to determine whether GRKs and receptor desensitisation play a role in disorders of uterine contractility.

Blotting, Western↗

PubMed1998

Mechanism of inhibition of a tumor lipid-mobilizing factor by eicosapentaenoic acid.

Stimulation of lipolysis or adenylate cyclase activity by either isoprenaline or a tumor-derived lipid-mobilizing factor was effectively attenuated in isolated white adipocytes or in adipocyte plasma membranes pretreated with eicosapentaenoic acid (EPA) dissolved in ethanol or from mice dosed p.o. with EPA (1.25 g/kg). A similar effect was observed with docosahexanoic acid (DHA) that may be partly due to retroconversion to EPA. Stimulation of adenylate cyclase activity by forskolin, which acts directly on the enzyme without the involvement of a receptor, was also decreased in membranes of mice treated with EPA, suggesting a direct interaction between EPA and adenylate cyclase. Pertussis toxin eliminated the inhibition of lipolysis and the stimulation of adenylate cyclase by isoprenaline and lipid-mobilizing factor in the presence of EPA, but not DHA. This suggests that the attenuation of hormonal stimulation of adenylate cyclase by EPA was due, at least in part, to an inhibitory guanine nucleotide-binding protein-mediated inhibition of adenylate cyclase activity. The effect of DHA may be due to a direct inhibition of the cyclase catalytic component. The ability of EPA to preserve fat stores during the process of cachexia seems to arise from the attenuation of the stimulation of adenylate cyclase.

Adenylyl Cyclase Inhibitors↗

PubMed1998

Biological evaluation of a lipid-mobilizing factor isolated from the urine of cancer patients.

We have previously shown human lipid-mobilizing factor (LMF) to be homologous with the plasma protein Zn-alpha2-glycoprotein in amino acid sequence, electrophoretic mobility, and immunoreactivity. In this study, both LMF and Zn-alpha2-glycoprotein have been shown to stimulate glycerol release from isolated murine epididymal adipocytes with a comparable dose-response profile. Both LMF and Zn-alpha2-glycoprotein caused a stimulation of adenylate cyclase in murine adipocyte plasma membranes in a GTP-dependent process, with maximum stimulation at 0.1 microM GTP and with saturation at protein concentrations of >5 microg/assay. Administration of LMF to exbreeder male mice over a 89-h period produced a decrease in body weight without a change in food and water intake. Body composition analysis showed a 42% reduction in carcass lipid when compared with controls. Treatment of ob/ob mice with human LMF over a 160-h period also produced a decrease in body weight, with a 19% reduction in carcass fat, without a change in body water or nonfat mass. Serum levels of glycerol and 3-hydroxybutyrate were significantly increased, as was oxygen uptake by interscapular brown adipose tissue, providing evidence of increased lipid mobilization and utilization. Human white adipocytes responded to both LMF and isoprenaline to the same extent, although the maximal response was lower than that for murine white adipocytes. These results suggest that LMF not only has the capacity to induce lipid mobilization and catabolism in mice, but it also has the potential to exert similar effects in cachectic cancer patients.

Adenylyl Cyclases↗

PubMed1998

Amyloid beta protein increases Ca2+ currents in rat cerebellar granule neurones.

The effects of amyloid beta protein on voltage-sensitive Ca2+ channels were measured in cultured rat cerebellar granule neurones using the whole-cell patch-clamp technique. Incubation of cells for 24 h with 1 microM amyloid beta protein resulted in a 40-60% increase in the Ca2+ channel current at potentials positive to 0 mV. The increase in current was accompanied by a 5 mV shift in channel activation in the positive direction and an increase in the rate of channel deactivation. Inhibition of L-type channels with 2 microM nifedipine did not prevent the rise in Ca2+ channel current or effects on current activation and deactivation. The N-type Ca2+ channel antagonist omega-conotoxin GVIA (1 microM) abolished the current increase and increase in the rate of channel deactivation but did not prevent the shift in the current activation curve. These data suggest that amyloid beta protein may exert its effects on cell survival by increasing Ca2+ influx through N-type Ca2+ channels in central neurones.

Amyloid beta-Peptides↗

PubMed1998

Flunitrazepam rapidly reduces GABA(A) receptor subunit protein expression via a protein kinase C-dependent mechanism.

Acute flunitrazepam (1 microM) exposure for 1 h reduced GABA(A) receptor alpha1 (22+/-4%, mean+/-s.e.mean) and beta2/3 (21+/-4%) subunit protein levels in cultured rat cerebellar granule cells. This rapid decrease in subunit proteins was completely prevented by bisindolymaleimide 1 (1 microM), an inhibitor of protein kinase C, but not by N-[2-((p-bromocinnamyl)amino)ethyl]-5-isoquinolinesulfonamide (H-89, 4.8 microM), an inhibitor of protein kinases A and G. These results suggest the existence of a benzodiazepine-induced mechanism to rapidly alter GABA(A) receptor protein expression, that appears to be dependent on protein kinase C activity.

Animals↗

PubMed1997

Lack of association between schizophrenia and a polymorphism close to the cytosolic phospholipase A2 gene.

Biochemical studies have shown that a proportion of schizophrenics have an abnormal fatty acid composition in their red blood-cell membrane phospholipids and it has been suggested that this might be due to altered levels of the enzyme phospholipase A2 (PLA2). A recent report indicated that there was an association between schizophrenia and alleles of a poly-A repeat polymorphism close to the 5' end of the PLA2 gene. We report the analysis of this polymorphism in a series of 58 schizophrenic patients and 56 controls and find no evidence for allelic association.

Alleles↗

PubMed1996

Mechanisms controlling egg size and number in the rainbow trout, Oncorhynchus mykiss.

Female rainbow trout (Oncorhynchus mykiss) produce a single batch of eggs each year; synchronous growth of oocytes, all of which are ovulated at the same time, occurs in the two ovaries. To examine the regulatory mechanisms controlling egg size and number, virgin female rainbow trout were subjected to unilateral ovariectomy (ULO) during early vitellogenesis, and oocyte recruitment and growth in the remaining ovary were monitored. The study also set out to determine whether the presence of a second population of smaller oocytes in the maturing pool (induced by ULO) affected the timing of ovulation and/or the size of the eggs ovulated. Two months after ULO, there was no difference in the gonadosomatic index between ULO fish and controls. Compensatory ovarian hypertrophy resulted from the recruitment of a second population of primary oocytes into the vitellogenic pool. This population of smaller maturing oocytes in the ULO fish displayed growth rates up to twice those of the population of larger oocytes in the same ovary and of oocytes in controls. The growth rate of the population of larger oocytes in the ULO fish was not altered by the recruitment of a second maturing population. One month after ULO, fish had a lower concentration of plasma estradiol-17 beta than did controls; subsequently the concentrations of plasma estradiol-17 beta in the ULO and control groups were similar. After ULO, plasma levels of vitellogenin in the ULO fish did not differ from those in the control group throughout the study. At or close to ovulation, the fecundity of ULO fish was 75-80% that of controls. In the control group, oocytes appeared to reach a certain critical size before they were ovulated, and fish with higher fecundity ovulated later than their less fecund counterparts. ULO did not affect the timing of ovulation, and ULO fish ovulated eggs with a considerably greater size-range than did controls.

Animals↗

PubMed1996

Valuing authority/responsibility relationships. The essence of professional practice.

Central to the practice of professional nursing are the elements of accountability, autonomy, direct communication, and authority. The value that nursing work groups place on authority affects their level of acceptance of responsibility and accountability for clinical decision making. The authors examined the value that nurse managers and staff nurses on primary nursing and total patient care units place on authority/responsibility relationships. Results indicated that nurse managers and staff nurses on primary nursing units valued accountability, authority, and autonomy more than the nurse managers and staff nurses on total patient care units, a finding consistent with the professional practice model of primary nursing.

Attitude of Health Personnel↗

PubMed1996

The unit nurse executive: a changing perspective.

A study describes the perception of unit nurse managers (head nurses/nurse executives) as to what constituted their role functions, activities and responsibilities. Four major components were used to clarify this description: administration, clinical practice, education and research.

Adult↗