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Biomedical subjects

P A Gray

Publications and source records attributed to P A Gray.

At least 19 recordsLinked to original sources
PubMed2002

Effects of non-steroidal anti-inflammatory drugs on cyclo-oxygenase and lipoxygenase activity in whole blood from aspirin-sensitive asthmatics vs healthy donors.

1. Cyclo-oxygenase (COX) and lipoxygenase (LO) share a common substrate, arachidonic acid. Aspirin and related drugs inhibit COX activity. In a subset of patients with asthma aspirin induces clinical symptoms associated with increased levels of certain LO products, a phenomenon known as aspirin-sensitive asthma. The pharmacological pathways regulating such responses are not known. 2. Here COX-1 and LO activity were measured respectively by the formation of thromboxane B(2) (TXB(2)) or leukotrienes (LT) C(4), D(4) and E(4) in whole blood stimulated with A23187. COX-2 activity was measured by the formation of prostaglandin E(2) (PGE(2)) in blood stimulated with lipopolysaccharide (LPS) for 18 h. 3. No differences in the levels of COX-1, COX-2 or LO products or the potency of drugs were found in blood from aspirin sensitive vs aspirin tolerant patients. Aspirin, indomethacin and nimesulide inhibited COX-1 activity, without altering LO activity. Indomethacin, nimesulide and the COX-2 selective inhibitor DFP [5,5-dimethyl-3-(2-isopropoxy)-4-(4-methanesulfonylphenyl)-2(5H)-furanone] inhibited COX-2 activity. NO-aspirin, like aspirin inhibited COX-1 activity in blood from both groups. However, NO-aspirin also reduced LO activity in the blood from both patient groups. Sodium salicylate was an ineffective inhibitor of COX-1, COX-2 or LO activity in blood from both aspirin-sensitive and tolerant patients. 4. Thus, when COX activity in the blood of aspirin-sensitive asthmatics is blocked there is no associated increase in LO products. Moreover, NO-aspirin, unlike other NSAIDs tested, inhibited LO activity in the blood from both aspirin sensitive and aspirin tolerant individuals. This suggests that NO-aspirin may be better tolerated than aspirin by aspirin-sensitive asthmatics.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed2001

Normal breathing requires preBötzinger complex neurokinin-1 receptor-expressing neurons.

The normal breathing rhythm in mammals is hypothesized to be generated by neurokinin-1 receptor (NK1R)-expressing neurons in the preBötzinger complex (preBötC), a medullary region proposed to contain the kernel of the circuits generating respiration. If this hypothesis is correct, then complete destruction of preBötC NK1R neurons should severely perturb and perhaps even fatally arrest breathing. Here we show that specific and near complete bilateral (but not unilateral) destruction of preBötC NK1R neurons results in both an ataxic breathing pattern with markedly altered blood gases and pH, and pathological responses to challenges such as hyperoxia, hypoxia and anesthesia. Thus, these approximately 600 neurons seem necessary for the generation of normal breathing in rats.

Animals↗
PubMed2000

Macrophage-derived chemokine (MDC).

Macrophage-derived chemokine (MDC) is a CC chemokine paradigmatic of emerging aspects of chemokine immunobiology. It is constitutively expressed, yet microbial products and cytokines regulate its expression with divergent effects of type II (IL-4 and IL-13) and type I (interferon) cytokines. Processing of the mature protein by dipeptidyl peptidase IV/CD26 provides a further level of regulation. It acts on diverse cellular targets including dendritic cells (DC), NK cells, and T cell subsets. Among these, MDC is a potent attractant for CCR4 expressing polarized Th2 and Tc2 cells, and evidence is consistent with a role of this chemokine as an amplification loop of polarized type II responses. Emerging indications on the involvement of MDC in diverse pathologies, ranging from allergic reactions to HIV infection and neoplasia, are discussed.

Chemokine CCL22↗
PubMed1999

Modulation of respiratory frequency by peptidergic input to rhythmogenic neurons in the preBötzinger complex.

Neurokinin-1 receptor (NK1R) and mu-opioid receptor (muOR) agonists affected respiratory rhythm when injected directly into the preBötzinger Complex (preBötC), the hypothesized site for respiratory rhythmogenesis in mammals. These effects were mediated by actions on preBötC rhythmogenic neurons. The distribution of NK1R+ neurons anatomically defined the preBötC. Type 1 neurons in the preBötC, which have rhythmogenic properties, expressed both NK1Rs and muORs, whereas type 2 neurons expressed only NK1Rs. These findings suggest that the preBötC is a definable anatomic structure with unique physiological function and that a subpopulation of neurons expressing both NK1Rs and muORs generate respiratory rhythm and modulate respiratory frequency.

Animals↗
PubMed1998

Differential expression of chemokine receptors and chemotactic responsiveness of type 1 T helper cells (Th1s) and Th2s.

T helper cells type 1 (Th1s) that produce interferon-gamma predominantly mediate cellular immune responses and are involved in the development of chronic inflammatory conditions, whereas Th2s which produce large amounts of IL-4 and IL-5 upregulate IgE production and are prominent in the pathogenesis of allergic diseases. The precise factors determining whether Th1- or Th2-mediated immune responses preferentially occur at a peripheral site of antigen exposure are largely unknown. Chemokines, a superfamily of polypeptide mediators, are a key component of the leukocyte recruitment process. Here we report that among four CXC (CXCR1-4) and five CC (CCR1-5) chemokine receptors analyzed, CXCR3 and CCR5 are preferentially expressed in human Th1s. In contrast, Th2s preferentially express CCR4 and, to a lesser extent, CCR3. In agreement with the differential chemokine receptor expression, Th1s and Th2s selectively migrate in response to the corresponding chemokines. The differential expression of chemokine receptors may dictate, to a large extent, the migration and tissue homing of Th1s and Th2s. It may also determine different susceptibility of Th1s and Th2s to human immunodeficiency virus strains using different fusion coreceptors.

Cell Movement↗
PubMed1998

Calbindin-D28k fails to protect hippocampal neurons against ischemia in spite of its cytoplasmic calcium buffering properties: evidence from calbindin-D28k knockout mice.

Cytoplasmic calcium-binding proteins are thought to shield neurons against damage induced by excessive Ca2+ elevations. Yet, in theory, a mobile cellular Ca2+ buffer could just as well promote neuronal injury by facilitating the rapid dispersion of Ca2+ throughout the cytoplasm. In sharp contrast to controls, in mice lacking the gene for calbindin-D28k, synaptic responses of hippocampal CA1 pyramidal neurons which are normally extremely vulnerable to ischemia, recovered significantly faster and more completely after a transient oxygen-glucose deprivation in vitro, and sustained less cellular damage following a 12 min carotid artery occlusion in vivo. Other cellular and synaptic properties such as the altered adaptation of action potential firing, and altered paired-pulse and frequency potentiation at affected synapses in calbindin-D28k-deficient mice were consistent with a missing intraneuronal Ca2+ buffer. Our findings provide direct experimental evidence against a neuroprotective role for calbindin-D28k.

Animals↗
PubMed1994

Blood concentrations of dopexamine in patients during and after orthotopic liver transplantation.

Blood concentrations of dopexamine were measured in five female patients during and after orthotopic liver transplantation. Each patient received a continuous infusion of the drug (2 micrograms kg-1 min-1), starting at induction of anaesthesia and finishing 48 h afterwards. Blood concentrations of dopexamine increased rapidly at the start of the infusion, to a mean (range) value of 64 (40-150) ng ml-1 after 20 min. Blood concentrations of dopexamine increased further during the anhepatic period of surgery, to 236 (180-410) ng ml-1. On reperfusion of the donor liver, concentrations of dopexamine decreased rapidly, reaching similar values to the maximum seen during the dissection period. Steady-state was not reached during either the dissection or anhepatic periods. From 1-2 h after revascularisation the mean (range) steady-state concentration was 85 (69-102) ng ml-1 corresponding to a mean (range) clearance of 24 (20-29) ml min-1 kg -1. These results suggest that the liver plays a significant role in the clearance of dopexamine.

Adult↗
PubMed1993

Midazolam-induced amnesia: implications for the implicit/explicit memory distinction.

In order to examine how the distinction between implicit and explicit memory might relate to theories regarding the organization of memory, two types of memory tests were administered in conjunction with the amnesia-inducing benzodiazepine midazolam. Performance on an implicit task (perceptual facilitation in identifying degraded pictures and words) was relatively unimpaired by midazolam, whereas performance on an explicit task (recognition memory) was severely impaired. Interpreting the results in both the implicit/explicit framework and an independent stage analysis suggests that the terms implicit and explicit may reflect something about the nature of the memory representation and need not be reserved solely to describe classes of memory tasks.

Adolescent↗
PubMed1993

Comparison of the sedative and amnesic effects of midazolam and propofol.

We have compared the sedative and amnesic effects of midazolam and propofol in 35 volunteers. Sedation was measured by simple reaction time immediately before and after a bolus injection and 1 h after the commencement of a subsequent continuous infusion. Memory was measured three times using two memory tests: perceptual facilitation provided an implicit memory measure and recognition provided an explicit memory measure. Propofol and midazolam had similar sedative effects both immediately after bolus doses and after 1-h continuous infusions of the drugs. In contrast, midazolam had a more profound amnesic effect than propofol on the recognition memory test. The drugs had little effect on performance with the implicit memory test. Performance on the memory tests was unrelated to sedation.

Adolescent↗
PubMed1992

Renal effect of dopexamine hydrochloride in patients with chronic renal dysfunction.

Dopexamine hydrochloride, a dopamine analogue, has been reported, both experimentally and clinically, to increase renal blood flow (RBF) and improve renal function in normal kidneys. The availability of computer-enhanced radionuclide scintigraphy, which provides accurate non-invasive measurement of changes in RBF, enabled us to study the renographic effects of dopexamine hydrochloride in patients with chronic renal dysfunction (CRD). Ten patients suffering from CRD and ten normal kidney donors were the study population. Renography was performed, heart rate (HR) and blood pressure (BP) measured, and hematological and biochemical tests carried out before and after intravenous infusion of dopexamine 2 micrograms kg-1 min-1 for 60 min. The patient population displayed significant increases in total cortical and medullary RBF and renographic clearance rate (CR), while in kidney donors the RBF was increased in all kidney regions with no change in CR. HR increased in both groups, while BP showed no significant changes. The hematological and biochemical changes were transient and returned to preinfusion levels after 24 h. It is concluded that dopexamine hydrochloride 2 micrograms kg-1 min-1 increases RBF and CR in patients with CRD.

Adult↗
PubMed1992

Propofol metabolism in man during the anhepatic and reperfusion phases of liver transplantation.

1. An i.v. dose of 14C-propofol (0.53 mg/kg) was administered to three male and three female patients during the anhepatic phase of liver transplantation, which lasted 30-56 min after dosing. Arterial and venous blood samples, bile (T-tube drainage) and urine were collected at various times afterwards and submitted to h.p.l.c. and radioassay or specific fluorescence detection for the unchanged drug. 2. Extrahepatic metabolism was apparent during the anhepatic phase, since at 30 min post-dose, unchanged propofol comprised only 42-89% of the blood radioactivity. 3. Examination of the plasma radioactivity during the anhepatic phase in two subjects showed evidence of propofol glucuronide and 4-quinol sulphate, confirming extrahepatic metabolism of the drug. Quinol glucuronides were only detected in the liver reperfusion phase. 4. There was no evidence that the lungs contribute to the extrahepatic metabolism of propofol, since drug concentrations in the arterial blood were not less than in central venous samples. 5. During the first 24 h period, urine collected from five patients contained 7-74% dose, whilst the bile contained 0.1-0.9%. In three patients with normal renal function recovery in urine was 66-74% dose. Examination of urinary radioactivity in one subject showed the main component to be propofol glucuronide during the anhepatic phase.

Adult↗
PubMed1991

A comparison of dopexamine and dopamine to prevent renal impairment in patients undergoing orthotopic liver transplantation.

The efficacy of low-dose dopamine as a renal protective agent was compared with that of dopexamine in patients who underwent orthotopic liver transplantation. Twelve patients who received a continuous infusion of dopexamine (1-3 micrograms/kg/minute) were matched for age, diagnosis, pre-operative creatinine clearance and blood loss with 12 patients who received a low-dose infusion of dopamine (2 micrograms/kg/minute). The catecholamine infusion was started after induction of anaesthesia and continued for 48 hours after surgery. Patients in the dopexamine group had less evidence of renal impairment and failure than those in the dopamine group during 7 days after the operation, although the differences between groups did not achieve statistical significance. Similarly there were no significant differences between the two groups in peri-operative urine output, urine/plasma osmolality ratio or creatine clearance. Dopexamine is at least as effective as dopamine for renal protection in patients who undergo liver transplantation.

Acute Kidney Injury↗
PubMed1990

Dopexamine: studies in the general intensive care unit and after liver transplantation.

1. It has been suggested that the use of dopaminergic agents in the critically ill patient may reduce the incidence of renal failure and hence mortality. 2. Dopexamine hydrochloride is a new synthetic catecholamine. Like dopamine, it stimulates dopaminergic receptors. It also stimulates beta 2-adrenoceptors. Unlike dopamine, dopexamine has minimal effect at beta 1-adrenoceptors and no alpha-adrenoceptor activity. 3. Stimulation of renal dopaminergic and beta 2-adrenoceptors independently results in dilation of the renal vasculature. A natriuresis and diuresis is also promoted by dopaminergic stimulation. 4. A comparison between the administration of low dose dopamine and dopexamine in patients undergoing orthotopic liver transplantation resulted in less renal impairment and failure in the dopexamine group, although this did not achieve statistical significance. 5. Dopexamine elimination is reduced in the absence of hepatic function. 6. A patient with terminal liver failure was treated with dopexamine and although oxygen delivery was unchanged, oxygen consumption doubled. This suggests that dopexamine affects other organs as well as the kidneys.

Critical Care↗