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S Rees

Publications and source records attributed to S Rees.

At least 73 records · Page 4Linked to original sources
PubMed1997

A cysteine-3 to serine mutation of the G-protein Gi1 alpha abrogates functional activation by the alpha 2A-adrenoceptor but not interactions with the beta gamma complex.

Pertussis toxin-resistant (C351G) and also palmitoylation-negative (C3S/C351G), myristoylation-negative (G2A/C351G) and combined acylation-negative (G2A/C3S/C351G) forms of the G-protein Gi1 alpha were expressed in COS-7 cells along with the porcine alpha 2A-adrenoceptor. G2A/C3S/C351G Gi1 alpha and G2A/C351G Gi1 alpha were largely cytosolic and failed to interact with the agonist-occupied alpha 2A-adrenoceptor in membrane preparations. In contrast, C351G Gi1 alpha was almost entirely particulate and the alpha 2-adrenoceptor agonist UK14304 caused a marked stimulation of its GTPase activity and binding of [35S]GTP gamma S which was not prevented by pertussis toxin treatment of the cells. C3S/C351G Gi1 alpha was present in both the particulate and cytosolic fractions but the GTPase activity of the membrane bound fraction was only slightly activated by the alpha 2A-adrenoceptor. Coexpression of C3S/C351G Gi1 alpha and the alpha 2A-adrenoceptor along with beta 1 and gamma 2 subunits increased the P2 membrane complement of the alpha subunit and increased substantially the ratio of membrane bound to cytosolic protein. However, this also failed to allow marked stimulation of high-affinity GTPase activity by the alpha 2A-adrenoceptor despite the increased proportion of G-protein in the P2 membrane fraction. Despite the low fractional activation of C3S/C351G Gi1 alpha by the alpha 2A-adrenoceptor compared to C351G Gi1 alpha, the palmitoylation-resistant G-protein caused a marked reduction in pertussis toxin-resistant, agonist (UK14304)-mediated stimulation of adenylyl cyclase activity. UK14304 caused the same degree of effect on adenylyl cyclase activity in pertussis toxin-treated cells following transfection of the same amounts of C351G Gi1 alpha and C3S/C351G Gi1 alpha, as both appear to act to sequester beta gamma subunits. By contrast, neither G2A/C351G Gi1 alpha nor G2A/C3S/C351G Gi1 alpha resulted in effective regulation of adenylyl cyclase activity.

Adenylate Cyclase Toxin↗
PubMed1997

Chronic placental insufficiency in the fetal guinea pig affects neurochemical and neuroglial development but not neuronal numbers in the brainstem: a new method for combined stereology and immunohistochemistry.

This study has examined the development of the brainstem in a suboptimal intrauterine environment induced via chronic placental insufficiency in the fetal guinea pig. Placental insufficiency was produced by unilateral ligation of the maternal uterine artery at mid-gestation (term = 66-68 days) resulting in the production of growth-retarded fetuses that are chronically hypoxic and malnourished. The structural and neurochemical development of brainstem nuclei either directly or indirectly related to cardiorespiratory control were analysed by using new stereological methods and immunohistochemistry. A technique was devised to enable the procedures to be performed on alternate frozen sections. There were no significant differences between control and growth-retarded fetuses in the total number of neurons, area of neuronal somata or volume of the hypoglossal nucleus. Quantitative densitometry was used to measure immunohistochemical staining in the brainstem of growth-retarded fetuses compared to controls and revealed a significant (P < 0.02) decrease in substance P(SP)-immunoreactivity in the spinal trigeminal nucleus and a significant (P < 0.05) increase in met-enkephalin-immunoreactivity in the hypoglossal nucleus. Counts of stained neurons demonstrated a significant increase in the density of SP-positive neurons in the nucleus tractus solitarius (P < 0.05) and of met-enkephalin-positive neurons in the ventral medullary reticular formation (P < 0.05). There was also a proliferation of astrocytes, as determined by immunoreactivity to glial fibrillary acidic protein in the dorsal motor nucleus of the vagus, nucleus tractus solitarius and more generally around blood vessels throughout the brainstem. Thus, these results have been shown that although chronic intrauterine deprivation does not alter neuronal numbers, at least in the hypoglossal nucleus, there is a proliferation of astrocytes, and the expression of neurotransmitters/neuromodulators is markedly effected in some of the nuclei involved with cardiorespiratory control.

Animals↗
PubMed1997

Identification of brainstem neurons responding to hypoxia in fetal and newborn sheep.

Hypoxia causes a reversible decrease in the level of respiratory, oculomotor and postural muscle activity in fetal sheep, an effect not seen in newborn lambs. We have used Fos immunohistochemistry to identify neurons which are activated by hypoxia and which may mediate this motor inhibition in the fetus. Pregnant sheep of either 117 or 138 days gestation were made hypoxic by allowing them to breathe 8-9% O2 for 2 h. Compared to age-matched control fetuses, hypoxia caused a significant increase in Fos-immunoreactivity in several medullary nuclei including the nucleus tractus solitarius, lateral reticular nucleus and the rostral ventrolateral medulla and also in the lateral parabrachial nucleus, locus coeruleus and subcoeruleus region in the pons. Hypoxia in newborn lambs, 7-18 days old, resulted in Fos staining in the same medullary and pontine nuclei with the exception of the subcoeruleus region which was devoid of Fos-immunoreactivity. In newborn lambs in which the carotid sinus nerves had been sectioned bilaterally, Fos-immunoreactivity was increased in the nucleus tractus solitarius in the medulla and in the locus coeruleus, lateral parabrachial and Kölliker-Fuse nuclei in the pons when compared to intact control newborn lambs. When carotid sinus nerve denervated-lambs were subjected to hypoxia the pattern of Fos-ir was similar to the pattern seen in the denervated control lambs but in addition staining was present in the subcoeruleus. These results suggest that a specific set of pontine neurons are activated by low oxygen levels in the fetus but not in the newborn lamb in the presence of an intact innervation from the carotid sinus. We hypothesise that: (a) in the fetus hypoxia activates neurons in the region of the subcoeruleus and this causes cessation of breathing movements and muscle atonia; and (b) that after birth stimulation of the carotid chemoreceptors by hypoxia normally inhibits activation of these subcoeruleus neurons.

Aging↗
PubMed1997

Interactions of the alpha2A-adrenoceptor with multiple Gi-family G-proteins: studies with pertussis toxin-resistant G-protein mutants.

The alpha2A-adrenoceptor is the prototypic example of the family of G-protein-coupled receptors which function by activation of 'Gi-like' pertussis toxin-sensitive G-proteins. A number of members of this subfamily of G-proteins are often co-expressed in a single cell type. To examine the interaction of this receptor with individual Gi-family G-proteins the porcine alpha2A-adrenoceptor was transiently transfected into COS-7 cells either alone or with each of wild-type Gi1alpha, Gi2alpha and Gi3alpha or mutations of each of these G-proteins in which the cysteine residue which is the target for pertussis toxin-catalysed ADP-ribosylation was exchanged for a glycine residue. The alpha2-adrenoceptor agonist UK14304 stimulated both high-affinity GTPase activity and the binding of guanosine 5'-[gamma-35thio]-triphosphate (GTP[35S]), when expressed without any additional G-protein. These effects were greatly reduced by pretreatment of the cells with pertussis toxin. Co-expression of each of the wild-type Gi-like G-protein alpha-subunits resulted in enhanced agonist activation of the cellular G-protein population which was fully prevented by pretreatment with pertussis toxin. Co-expression of the receptor along with the cysteine-to-glycine mutations of Gi1alpha, Gi2alpha and Gi3alpha resulted in agonist stimulation of these G-proteins, which was as great as that of the wild type proteins, but now the agonist stimulation produced over that due to the activation of endogenously expressed Gi-like G-proteins was resistant to pertussis toxin treatment. The Cys --> Gly mutations of Gi1alpha, Gi2alpha and Gi3alpha were each also able to limit agonist-mediated stimulation of adenylate cyclase activity. The degree of agonist-mediated activation of the pertussis toxin-resistant mutant of Gi1alpha was correlated highly both with the level of expression of this G-protein and with the level of expression of the alpha2A-adrenoceptor. Half-maximal stimulation of high-affinity GTPase activity of the Cys --> Gly mutants of Gi1alpha, Gi2alpha and Gi3alpha required 10-15-fold higher concentrations of agonist than did stimulation of their wild-type counterparts, consistent with a model in which the affinity of functional interactions of the alpha2A-adrenoceptor with the wild-type G-protein is greater than with the pertussis toxin-resistant mutant G-protein.

Adenylate Cyclase Toxin↗
PubMed1997

Ways forward for shared learning between nursing and social work students.

This paper is based on the work of Connor (1995) which examined the potential for shared learning on qualifying programmes of social work and nurse education in Wales. The research was carried out mainly by interviewing 44 providers of social work and nurse education in the 13 colleges delivering qualifying courses throughout Wales. The main findings indicate that: nursing and social work educators have a positive attitude to shared learning, provided that the focus is on sharing appropriate areas of learning and not on joint training; there are considerable areas of commonality between social work and nurse education that could be shared; obstacles to shared learning mainly concern structural and resource issues which would require the appropriate political will to implement shared learning programmes; and there are a wide variety of models that could be used to implement future shared learning. The management of this project with its commitment to collaboration between the two professional groups throughout the process of enquiry is offered as a model for further research projects.

Curriculum↗
PubMed1997

The Bentham Unit: a pilot remand and assessment service for male mentally disordered remand prisoners. II: Report of an independent evaluation.

BACKGROUND: Findings are presented from an evaluation of a pilot remand and assessment service--the Bentham Unit. The aims of the Bentham Unit are to provide rapid assessment, identify mentally disordered remand prisoners, and speed their transfer from prison to NHS care, where a need is indicated. METHOD: The number, rate and speed of referral, assessment and transfer to NHS care of offenders remanded to Wormwood Scrubs prison during periods before and after the Bentham Unit opened were compared. RESULTS: The service attracted a large volume of referrals. Between the two periods, significant increases in the numbers of referrals and hospital disposals, and major reductions in the interval between reception on remand into the prison, NHS assessment and transfer to NHS care, were observed. CONCLUSIONS: The aims of the unit were met. Implications for service configurations are discussed.

England↗
PubMed1996

Experimental hydranencephaly in the ovine fetus.

Hydranencephaly is defined as the replacement of a previously normal brain, in whole or in part, by membranous fluid-filled sacs. The etiology is not well understood, and the time course of development is unknown. Fifteen ovine fetuses were chronically cannulated and had both carotid arteries ligated at 100 days of gestation (term is 145-150 days). They were killed at 1 (n = 4), 2 (n = 6) and 4 (n = 5) weeks post-surgery, and the findings compared with those of 25 age-matched controls. By 2 weeks post-surgery the entire cerebral hemispheres and diencephalon had been replaced by fluid closely resembling cerebrospinal fluid. The choroid plexus, pituitary and brain stem remained outwardly normal, but the cerebellum showed signs of damage. Fetuses maintained normal values for blood gases and hematocrit up to 4 weeks post-surgery, and grew normally. Light microscopy of the brain stem showed significant losses of cell populations in the medulla by 4 weeks. Vascular casting and acute blood flow studies in an additional group of fetuses showed that the entire brain was perfused via the vertebral-occipital anastomosis immediately after acute bilateral carotid clamping, but that the blood flow rate was insufficient to maintain adequate oxygen delivery.

Animals↗
PubMed1996

Which cardiac potassium channel subtype is the preferable target for suppression of ventricular arrhythmias?

Prolongation of the cardiac action potential duration is the hallmark of Class III antiarrhythmic activity. Action potential duration prolongation may be achieved by several means: enhancement of inward current and, more commonly, blockade of one or more of the many outward currents that are carried by K+. However, it is far from clear whether blockade of one particular K+ channel is more efficacious than blockade of another. The objective of this review is to consider this question with particular reference to ischaemic heart disease, a condition for which effective prevention of ventricular arrhythmias continues to be sought.

Animals↗
PubMed1996

The development of diurnal rhythmicity in fetal suprachiasmatic neurons as demonstrated by fos immunohistochemistry.

Using Fos immunohistochemistry as a marker of cellular activity, we have shown that neurons in the suprachiasmatic nucleus of fetal sheep are active by 75 days gestation. From at least 90 days gestation (term is 146 days), these neurons are more active during the day (12.00) than at night (03.00) when pregnant ewes are exposed to a 12-h light-dark cycle with lights on at 07.00. The day-night difference in Fos immunoreactivity persisted when the lighting schedule was extended by 8 h to 03.00, although neurons were now more active at 03.00 than they were in fetuses maintained on the normal light-dark cycle. When ewes were maintained in constant light from 133 to 138 days, the day-night difference in Fos immunoreactivity in the fetal suprachiasmatic nucleus was abolished, suggesting that diurnal activity of the fetal suprachiasmatic nucleus is maintained by a signal related to the external lighting regime. In a twin pregnancy where one fetus was optically enucleated at 100 days gestation, the density of Fos-immunoreactive neurons in the suprachiasmatic nucleus during the day at 138 days was similar to the unoperated twin. This suggests that the effects of dim light in the uterus on the fetal retina do not account for the high level of Fos immunoreactivity in the suprachiasmatic nucleus in the daytime. We propose that a chemical messenger of maternal origin, possibly melatonin, suppresses the activity of fetal suprachiasmatic neurons during the night, and that fetal suprachiasmatic neurons have endogenous activity which is expressed fully during the daytime.

Animals↗
PubMed1996

Bicistronic vector for the creation of stable mammalian cell lines that predisposes all antibiotic-resistant cells to express recombinant protein.

We have developed an improved vector for the stable expression of recombinant protein in mammalian cells. In this vector, designated pCIN, both the recombinant cDNA and the neomycin phosphotransferase selection marker are transcribed from a single promoter element. To facilitate translation of the second open reading frame, the encephalomyocarditis virus internal ribosome entry site has been inserted into the expression cassette immediately before the start codon of this sequence. We report the use of this vector to generate stable cell lines expressing the human 5-HT1Da serotonin receptor and show that following transfection and clonal selection, all ten cell lines characterized express similar and high levels of receptor (1.5-11.9 pmol receptor/mg protein). Use of pCIN should permit the rapid and efficient production of stable mammalian cell lines for the characterization of recombinant protein, as this vector appears to predispose all transfected cells to express such protein.

Animals↗
PubMed1996

Pharmacokinetics of extended relief vs regular release Tylenol in simulated human overdose.

BACKGROUND: The purpose of this trial was to compare the pharmacokinetics of the two available acetaminophen dosage forms in simulated human overdose. METHODS: Ten healthy volunteers received acetaminophen, 75 mg/kg orally, either as the regular release or extended relief formulation in a random, crossover fashion. Blood samples were analyzed using a TDx assay and a best fit correlation of data points was determined by PCNONLIN. RESULTS: The area under the curves for extended relief acetaminophen and regular release acetaminophen were 426 mg h/L and 432 mg h/L, respectively (p = 0.768). The mean half times for extended relief acetaminophen and regular release acetaminophen were 4.02 h and 2.56 h, respectively (p < 0.001). The mean maximum serum acetaminophen concentrations were 62.6 mg/L (414.4 mmol/L:) and 94.3 mg/L (624.3 mmol/L) for extended relief acetaminophen and regular release acetaminophen, respectively (p < 0.001) and the mean time to maximum serum acetaminophen concentrations were 0.87 h and 0.75 h for extended relief acetaminophen and regular release acetaminophen, respectively (p = 0.508). CONCLUSIONS: Although the formulations appear to have equal bioavailability, their half-lives and peak concentrations were significantly different. Further study is required to determine whether these differences affect the assessment and management of poisoned patients.

Acetaminophen↗
PubMed1995

Nitric oxide synthase immunoreactivity and NADPH diaphorase staining are co-localised in neurons closely associated with the vasculature in rat and human retina.

Nitric oxide synthase (NOS) is widely distributed throughout the nervous system and is found in neurons which produce nitric oxide (NO). In attempting to elucidate the biological roles of NO in neurotransmission, vasodilation, and in neurodegeneration, nicotinamide adenine dinucleotide phosphate diaphorase (NADPHd) histochemistry has been widely used. NADPHd histochemistry and NOS immunoreactivity (NOS-IR) have been assumed to stain the same population of neurons. However, there have been numerous reports which suggest that this may not always be the case, and in all neuronal populations investigated, the coincidence of NOS and NADPHd must be unequivocally demonstrated. We have examined NADPHd histochemistry and NOS immunoreactivity in the human and rat retina and shown that these are 100% co-localised. Further, we have described the morphology of NADPHd and NOS-IR neurons in the human and rat retina and shown a close association of these neurons and their processes to the retinal vasculature. We have taken the NOS-IR to the ultrastructural level and have identified NOS-IR cells in close association with the basal lamina covering endothelial cells and pericytes of the retinal capillaries. We suggest that NO released from these neurons may be involved in the regulation of retinal microcirculation.

Aged↗
PubMed1995

Prenatal development of somatosensory primary afferent connections in the sheep.

A summary is presented of recently published studies on the structural and functional development of cutaneous and muscle receptors and the connections of their afferent fibres in fetal sheep (n = 26) aged between 67 and 143 days gestation (term, 146 days). In these studies it was shown that primary afferent fibres projected to, and made synaptic connections with, dorsal horn neurons in lumbosacral spinal cord by 56-61 days gestation. Sensory innervation of the skin occurred later by about 75 days gestation and, at this age, stimulation of the skin first activated cutaneous afferent fibres and evoked a discharge in dorsal root ganglion and dorsal horn neurons. Muscle stretch first activated muscle spindles and evoked a discharge in dorsal root ganglion cells by about 75 days. Prior to this (by about 67 days) primary afferent fibres had begun to innervate motoneuron pools in the spinal cord, and motor nerves had begun to innervate muscle fibres. Both muscle spindle and cutaneous innervation were relatively simple at mid gestation indicating that the structure of sensory receptors need not be complex in order to generate a response. Neural pathways necessary for reflex activity involving muscle spindles are therefore present and functional by mid gestation as are cutaneous pathways projecting from the skin to the spinal cord.

Afferent Pathways↗
PubMed1994

Cloning and characterisation of the human 5-HT5A serotonin receptor.

The human 5-HT5A serotonin receptor has been cloned. As with the mouse and rat 5-HT5A receptors, the gene consists of two coding exons separated by a large intron. The deduced amino acid sequence of the gene reveals a protein of 357 residues which shares 93% (nucleotide) and 84% (amino acid) identity to the cloned mouse 5-HT5A receptor. We have determined the tissue distribution of the receptor by reverse transcriptase-PCR and found expression in all regions of the brain examined with little or no expression in peripheral tissues. The receptor has been transiently expressed in Cos M6 cells and exhibits a pharmacological profile closely resembling the mouse and rat 5-HT5A receptors with high, specific binding for ergotamine and methiothepin.

Amino Acid Sequence↗