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D Murphy

Publications and source records attributed to D Murphy.

At least 19 recordsLinked to original sources
PubMed1992

The identification of a cis-acting element involved in cyclic 3',5'-adenosine monophosphate regulation of bovine vasopressin gene expression.

Cyclic adenosine 3',5'-monophosphate (cAMP) has been implicated as an intracellular messenger mediating osmotic regulation of expression of the gene encoding the neuropeptide vasopressin (VP) in the hypothalamus. We have used a heterologous transient transfection system to demonstrate that cAMP regulates the bovine VP gene promoter following transfection into CV1 cells. Mutational analysis identified a bovine VP cAMP-responsive element (BVP-CRE) 120-112 base-pairs upstream of the start of transcription. DNase I footprint analysis using nuclear protein extract from CV1 cells showed protection at the site of the BVP-CRE. Protection of the BVP-CRE was also observed using purified AP1 protein, while there was a weak interaction with the BVP-CRE using purified rat CREB protein. Nuclear proteins purified from the rat supraoptic nucleus bind to the BVP-CRE. As transgenic mouse studies have shown that the bovine VP gene is subject to appropriate physiological regulation in the mouse hypothalamus (Ang, H. L., Funkhouser, J., Carter, D. A., Ho, M. Y., and Murphy, D. (1991) Soc. Neurosci. Abstr. 513, 12), these data indicate a role for the BVP-CRE element in mediating VP gene expression in vivo. These data demonstrate that cAMP regulates bovine VP gene expression in vitro via a cis-acting element within the VP promoter, and this activation may be mediated by members of the AP1/ATF/CREB family of transcription factors.

Animals↗
PubMed1992

Equine hyperlipaemia in the United Kingdom: clinical features and blood biochemistry of 18 cases.

The background, clinical signs, blood biochemistry and management of 18 cases of equine hyperlipaemia are described. Eleven of the animals were Shetland ponies, four were Welsh mountain ponies or their crosses, one was a fell pony and two were riding ponies of mixed breeding. Their average age was nine years. Fourteen of the cases were mares, of which nine were in foal and two were lactating; the remainder were geldings. Underlying or concurrent diseases were identified in only six animals, but in one other animal the hyperlipaemia appeared to have been precipitated by stress, and in another by undernutrition to prevent laminitis. Twelve of the animals were considered obese. There was no age, seasonal, or geographic bias to the distribution of cases. Plasma triglyceride concentrations were increased by between five- and 80-fold, and ranged from 4.7 to 78.8 mmol/litre. There was biochemical evidence of hepatic damage in 17 cases, of renal insufficiency in 15, and pancreatic pathology in three cases. Four animals were euthanased without therapy. The others were treated with oral glucose solutions, which were supplemented with injections of insulin and heparin in four cases, and insulin alone in two cases. Eight of the treated animals died, to give an overall mortality of 67 per cent. The outcome of the treatment was unrelated to the degree of hypertriglyceridaemia, to the presence and severity of hepatic, renal or pancreatic pathology or to the therapeutic regimen.

Alkaline Phosphatase↗
PubMed1992

Decrease in hypothalamic vasopressin mRNA poly(A) tail length following physiological stimulation.

1. The vasopressin mRNA in the adult male rat hypothalamus is modulated in two distinct ways by a dehydration stimulus. In addition to the well-established increase in transcript abundance, it has recently been demonstrated that the vasopressin mRNA poly(A) tail increases in length. 2. We have studied the ontogeny of poly(A) tail length modulation in neonates in response to milk deprivation and found that poly(A) tail length changes are age dependent. In neonates older than 12 days of age, the vasopressin mRNA poly(A) tail length increased with milk deprivation and this effect became more marked in older animals. However, in rats 5 to 9 days old, milk deprivation resulted in a detectable though not significant decrease in vasopressin mRNA poly(A) tail length. 3. As milk deprivation is a combination of dehydration and starvation, we investigated the effect of the latter stimulus in more mature animals. We found that starvation modifies the length of the vasopressin mRNA poly(A) tail in a manner opposite that due to dehydration. 4. Our data indicate a novel mode of regulation of the vasopressin mRNA, namely, poly(A) tail shortening. This system provides a model for future studies concerning the adaptive role of poly(A) tail length modulation in response to physiological stimuli.

Adaptation, Physiological↗
PubMed1992

Surgically created Wolff-Parkinson-White syndrome after Fontan operation.

The Wolff-Parkinson-White syndrome is caused by a congenital accessory connection between the atrium and ventricle. We describe a case of symptomatic Wolff-Parkinson-White syndrome that arose after a Björk modification of the Fontan operation. Invasive electrophysiologic and intraoperative mapping indicated that the surgically created atrioventricular connection was functioning as an accessory pathway. Surgical dissection and cryoablation abolished the symptoms and the preexcitation.

Adolescent↗
PubMed1992

Ricin and lentil lectin-affinity chromatography reveals oligosaccharide heterogeneity of thyrotropin secreted by 12 human pituitary tumors.

Some patients with thyrotropin (TSH)-producing pituitary tumors are more hyperthyroid than others despite similar TSH levels in serum, suggesting that qualitatively different TSH molecules with differing bioactivities may be secreted by different tumors. We used ricin and lentil lectin-affinity chromatography to test whether the TSH oligosaccharides varied among 12 patients with TSH-producing tumors. We found that each tumor secreted heterogeneous isoforms of TSH that differed in their extents of exposed galactose (Gal) residues, and their degrees of sialylation and core fucosylation. These biochemical parameters also varied markedly for TSH secreted by different tumors. Isoforms appeared to reflect poor sialyltransferase activity in two tumors and efficient sialyltransferase in the remainder. TSH secreted by tumors was more fucosylated than TSH secreted by control euthyroid persons. There was an inverse relationship between the sialylation and fucosylation of tumor TSH. No simple relationship between TSH oligosaccharide structures and bioactivity was evident, although mixtures of isoforms having the least and most sialylated TSH seemed to be the most bioactive clinically. In three patients from whom serum and medium TSH were both available, TSH in serum was more sialylated than TSH secreted by the tumor in vitro, perhaps reflecting slow clearance of sialylated isoforms from the circulation. Core fucosylation of serum TSH was less than that of medium TSH. These data prove that human tumors secrete TSH with heterogeneous oligosaccharide structures.

Adult↗
PubMed1992

Nuclear mechanisms mediate rhythmic changes in vasopressin mRNA expression in the rat suprachiasmatic nucleus.

Vasopressin (VP) gene expression in the rat suprachiasmatic nucleus (SCN) is subject to a cyclical mode of regulation which is indicative of a close association with the circadian clock intrinsic to this area of the hypothalamus. Previous studies show that both the amount and size (due to differential polyadenylation) of VP mRNA are reduced during the dark phase of the daily cycle. We have now identified the cellular site wherein these changes are mediated. By transcriptional run-on analysis of nuclei isolated at different time points from the SCN we have shown that an attenuation of transcriptional activity can account for the dark-phase reduction in VP mRNA levels; by comparison with other genes expressed in this tissue, a significant, VP gene-specific reduction was observed which resulted in dark-phase transcriptional activity at 30% of light-phase activity (P less than 0.005). A similar diurnal variation was not found in the supraoptic nucleus. In addition, by Northern analysis of sub-cellular RNA pools, we have demonstrated that the smaller, dark-phase-specific VP RNA species is located, in abundance, within the nuclear fraction. These results provide clear evidence that the cyclical changes in SCN VP mRNA expression are primarily regulated within the nucleus, indicating that any potential regulation in the cytoplasm is of secondary importance. Further analysis of the molecular components which mediate the cyclical changes in transcriptional activity of the VP gene may identify fundamental aspects of neuronal timing mechanisms.

Animals↗
PubMed1992

Transgenic approaches to modifying cell and tissue function.

As our knowledge of cell regulation pathways becomes increasingly sophisticated, the tools and techniques that have emerged from in vitro studies are being applied to the whole organism through transgenesis. With the development of new ways of modifying cellular signalling in intact animals comes the ability to analyse physiological systems and their pathologies with greater spatial and temporal precision.

Animals↗
PubMed1992

Phase I/II study of intraperitoneal iproplatin in patients with minimal residual disease following platinum-based systemic therapy for epithelial ovarian carcinoma.

13 patients with minimal residual disease following platinum-based systemic therapy for epithelial ovarian cancer were treated with intraperitoneal iproplatin. A total of three cycles were given at monthly intervals. All patients had minimal residual disease (defined as less than 2 cm in diameter) or positive cytology documented at second look laparotomy following systemic chemotherapy. Iproplatin was administered via a temporary dialysis catheter (n = 11) or a semi permanent Tenckhoff peritoneal dialysis catheter (n = 2). The dose of iproplatin ranged from 150 to 450 mg/m2. No responses to therapy were documented. In this trial the major toxic side effects of iproplatin were thrombocytopenia, diarrhoea, nausea and vomiting. The maximum tolerated dose was 300 mg/m2.

Adult↗
PubMed1992

Neuropeptide gene expression in transgenic animals.

Transgenic animal techniques offer today's neuroscientist the ability to experimentally manipulate neurosecretory systems with a precision undreamt of by our predecessors. The range of techniques now available, building as it does on our growing knowledge of physiological systems at the inter- and intercellular level, allows us to critically define molecular lesions and ask about their consequences to the whole organism. Neuroscientist should grasp the opportunities afforded by these recent developments.

Animals↗
PubMed1992

Glutathione S-transferase activity and isoenzyme distribution in ovarian tumour biopsies taken before or after cytotoxic chemotherapy.

A study involving the measurement of glutathione S-transferase activities and isoenzyme distributions in human ovarian tumours has been carried out. These tumours have been obtained either at initial debulking surgery, prior to cytotoxic chemotherapy, or at second look laparotomy following chemotherapy. The response rates of these two groups to chemotherapy differ markedly, with patients who have relapsed following initial chemotherapy showing a reduction in response rates to subsequent chemotherapy. Analysis of these data show no statistically significant differences between the glutathione S-transferase activity or isoenzyme distribution in these two groups of patients. Significant differences were observed in the glutathione-S-transferase activities (GST) between tumours and normal ovaries. GST activities in pre-chemotherapy tumours (n = 33, P = 0.01) and post-chemotherapy tumours (n = 20, P = 0.001) where significantly higher than the GST activity in normal ovaries (n = 15). One feature was the expression of the basic isoenzyme which is expressed more in normal ovaries than in tumours. No differences in these parameters were observed in normal peritoneal tissue taken from patients before or after chemotherapy. These data do not support the hypothesis that changes in glutathione S-transferase enzyme activity or isoenzyme expression are major determinants of response to chemotherapy in ovarian tumours.

Adult↗
PubMed1992

Posttranscriptional regulation of rat growth hormone gene expression: increased message stability and nuclear polyadenylation accompany thyroid hormone depletion.

In thyroid hormone-depleted rats, the rate of transcription of the growth hormone (GH) gene in the anterior pituitary gland is lower than the rate in euthyroid controls, and there is a corresponding reduction in the abundance of the GH mRNA. Concomitantly, the poly(A) tail of the GH mRNA increases in length. Examination of nuclear RNA from anterior pituitary glands of control and thyroid hormone-depleted rats revealed no difference in the length of pre-mRNAs containing the first and last introns of the GH gene. However, mature nuclear GH RNA is differentially polyadenylated in euthyroid and hypothyroid animals. We suggest that the extent of polyadenylation of the GH transcript is regulated in the cell nucleus concomitant with or subsequent to the splicing of the pre-mRNA. Experiments with anterior pituitary gland explant cultures demonstrated that the GH mRNA from thyroid hormone-depleted rats is more stable than its euthyroid counterpart and that the poly(A) tail may contribute to the differential stability of free GH ribonucleoproteins.

Animals↗
PubMed1992

Morphology of adenohypophysial tumors in mice transgenic for vasopressin-SV40 hybrid oncogene.

Transgenic mice for the promoter sequence of bovine arginine vasopressin (AVP) gene fused to large SV40 T-antigen coding sequence develop pituitary tumors and insulin-producing pancreatic tumors. In order to establish the cellular composition of the pituitary tumors, histological, immunocytochemical, in situ hybridization, and electron microscopic technics were applied. Pituitary anterior lobe tumors were identified in 10 out of 14 glands examined. In 2 of these cases, intermediate lobe tumors were also found. The anterior lobe tumors contained a variable number of GH immunoreactive cells. In situ hybridization performed in 7 cases revealed a diffuse distribution of GH messenger RNA over all tumor cells. Ultrastructurally, the tumors contained undifferentiated cells with very small secretory granules and rare cells showing some resemblance to somatotrophs. The results indicate that these pituitary tumors are composed of undifferentiated somatotrophs. The presence of a few PRL immunoreactive cells in four tumors and scattered TSH immunoreactive cells in two tumors supports the view that somatotrophs have the potential to produce PRL and TSH. The intermediate lobe tumors were immunoreactive for ACTH and intensely positive for POMC mRNA. In the nontumorous adenohypophyses, no hyperplasia of any cell type was noted. Several GH immunoreactive cells exhibited pleomorphic, giant nuclei and mitoses. In conclusion, the majority of transgenic mice for AVP/large T-antigen develop pituitary tumors originating in and composed of somatotrophs. Less frequently, intermediary lobe tumors were present as well. AVP/SV40 transgenic mice provide a unique experimental model for somatotroph tumors that are neither preceded by, nor associated with somatotroph hyperplasia.

Animals↗
PubMed1992

Pituitary-specific transcriptional initiation sites of the rat carboxypeptidase-H gene and the influence of thyroid hormone status.

Carboxypeptidase-H (CPH) is a metallocarboxypeptidase implicated in the processing of peptide hormones. Consistent with such a role, the gene for CPH is expressed in cells that secrete regulatory peptides, such as those of the brain and endocrine tissues. In the rat brain, CPH is transcribed from a single transcriptional start site associated with the initiator-type element first described in the gene encoding lymphocyte-specific terminal deoxynucleotidyltransferase. We have used a combination of Northern blot analysis and S1 nuclease protection mapping to describe the expression and transcription initiation pattern of the gene for CPH in the peripheral tissues and brain regions of the normal rat. The single transcriptional start site is used in all tissues examined, except the pituitary, where two additional specific initiation sites are found. The expression of the CPH gene is up-regulated in the anterior pituitary gland as a consequence of systemic thyroid hormone depletion, and this increase is associated with a preferential utilization of the novel upstream transcriptional initiation sites. Thus, the use of different major transcriptional initiation sites of the CPH gene in the pituitary gland is subject to differential direct or indirect thyroid hormone regulation.

Amino Acid Sequence↗
PubMed1992

Computed tomographic assessment of intraperitoneal fluid distribution prior to intraperitoneal chemotherapy for ovarian cancer.

Intraperitoneal chemotherapy (IPCT) is under evaluation in patients with ovarian cancer. Computed tomographic peritoneography (CTP) prior to IPCT establishes the distribution of the infusate, which if complete, demonstrates the patient's suitability for this method of treatment. We report our method of CTP and describe the intraperitoneal fluid distribution and complications encountered in 28 patients with advanced ovarian carcinoma being considered for IPCT.

Adult↗
PubMed1992

Opiate addiction in Iowa.

Where do opiate addicts obtain drugs? Interviews with patients in an Iowa methadone clinic reveal some surprising responses with definite implications for physicians who prescribe.

Adult↗