Search PubMed⌕ Search

Biomedical subjects

J C Porter

Publications and source records attributed to J C Porter.

At least 37 records · Page 2Linked to original sources
PubMed1994

Tuberculous bronchoesophageal fistulae in patients infected with the human immunodeficiency virus: three case reports and review.

To our knowledge, < 30 patients with tuberculous bronchoesophageal fistulae have been described in the English-language literature. However, the overall incidence of infection due to Mycobacterium tuberculosis has been increasing during the epidemic of human immunodeficiency virus (HIV) infection. We describe three HIV-infected patients who presented with tuberculous esophagomediastinal fistulae during their initial illness. Fistulous connections appeared to be secondary to mycobacterial mediastinal adenopathy. All fistulae healed with antituberculous therapy and nasogastric feeding, and surgical intervention was not necessary. The combination of mediastinal lymphadenopathy, cough, and retching or vomiting should alert clinicians treating HIV-infected patients to the possibility of tuberculous bronchoesophageal fistulae.

Adult↗
PubMed1993

Twelve new polymorphic microsatellites on human chromosome 22.

A strategy directed at constructing polymorphic STSs from human chromosome 22 has yielded 15 poly(TG) microsatellite markers. A short insert plasmid library containing flow-sorted chromosome 22 DNA was screened with a labeled poly(AC) probe. A combination of sequencing techniques was used to identify the poly(TG) targets, primers were designed to flank these targets, and PCR screening was carried out on a panel of genomic and hybrid DNAs to determine heterozygosity and regional localization on chromosome 22. Twelve of the STSs are polymorphic. Markers with high heterozygosity have been localized to three subregions of 22q, with seven in the Giemsa-dark 22q12 band. The new chromosome 22 loci will be useful for mapping disease loci, for linkage analysis, and for PCR-based contig construction in the ongoing effort to map human chromosome 22.

Animals↗
PubMed1993

The interleukin-2 receptor gamma chain maps to Xq13.1 and is mutated in X-linked severe combined immunodeficiency, SCIDX1.

The gene encoding the gamma chain of the lymphocyte interleukin-2 receptor has been cloned and shown to be required to associate with the beta chain in order for IL-2 internalization and cell activation to occur (1). We considered this gene, IL2RG, a candidate for the X-linked form of severe combined immunodeficiency at the SCIDX1 locus, in which affected males have impaired lymphocyte development. Using fluorescence in situ hybridization and PCR amplification of somatic cell hybrid DNAs, we mapped IL2RG to human Xq13.1, a location within the SCIDX1 critical region established by linkage analysis. The 4.2 kb IL2RG gene was sequenced, and its genomic organization was elucidated. Seven of 19 transformed B-lymphocyte cell lines with independent SCIDX1 mutations had absent or minimal IL2RG mRNA. Unique point mutations were documented to be specifically associated with the disease and the carrier state in four unrelated affected males and their family members: one in a boy with no detectable IL2RG mRNA, in which the mutation ablated a splice donor site; one causing premature chain termination; and two causing distinct amino acid changes. The demonstration of impaired IL2RG mRNA expression in males with X-linked SCID and of unique point mutations in SCIDX1 pedigrees constitutes powerful evidence that the SCIDX1 gene is IL2RG. Noguchi et al. (2) have independently published IL2RG mapping to Xq13 and discovery of mutations in three affected males. The specific pathogenesis of IL2RG mutations and approaches to gene therapy can now be addressed in the X-linked form of SCID.

Amino Acid Sequence↗
PubMed1993

Localization of a defect in hypothalamic dopaminergic neurons of the aged brain that results in impaired PKA-dependent activation of tyrosine hydroxylase.

Using an in vitro incubation system, the role of the cyclic AMP-dependent protein kinase A (PKA) pathway in the regulation of the in situ activity of tyrosine hydroxylase (TH) was studied in the hypothalamuses of young and aged ovariectomized rats. Hypothalamic tissue was incubated for 60 min in medium containing 3-hydroxybenzylhydrazine dihydrochloride, a dihydroxyphenylalanine (DOPA) decarboxylase inhibitor, and various agents that modify the activity of the PKA pathway. At the end of the incubation, the tissue was homogenized and analyzed for DOPA and TH mass. The in situ molar activity of TH was expressed as the moles of DOPA accumulating in the tissue per mole of TH per hour. Forskolin, an activator of adenylyl cyclase and the cyclic AMP agonist, (Sp)-cyclic adenosine 3',5'-monophosphothioate, significantly (P < .01) increased the in situ molar activity of TH in the hypothalamic dopaminergic (DAergic) neurons of both young and aged rats. Theophylline, a phosphodiesterase inhibitor, did not affect the TH molar activity in the hypothalamuses of aged animals but did significantly (P < .001) increase its activity in those of young rats. When vasoactive intestinal peptide was evaluated, the TH molar activity was significantly (P < .005) increased in the hypothalamuses of young rats but not in those of aged rats. It was suggested that the deficiency of DA secretion by hypothalamic DAergic neurons of aged rats may be the result of insufficient activation of PKA caused by failure of transduction of an extracellular signal to activate adenylyl cyclase and produce cyclic AMP.

Aging↗
PubMed1992

Dopa accumulates in the hypothalamic-hypophysial portal vessels and is taken into the anterior pituitary of NSD-1015-treated rodents.

DOPA was measured in the anterior pituitary and hypothalamic-hypophysial portal blood after treatment with NSD-1015, a DOPA decarboxylase inhibitor. NSD-1015 caused DOPA to accumulate in the anterior pituitary of mice and rats, and increased DOPA in the hypothalamic-hypophysial portal blood of rat. Serum prolactin was also increased. Interruption of the anterior pituitary blood supply from the hypothalamic-hypophysial system by cannulation of the entire pituitary stalk eliminated the NSD-1015-induced DOPA accumulation in the rat pituitary. We conclude that DOPA can be taken into the anterior pituitary from the portal blood of NSD-1015-treated rodents and that the anterior pituitary lacks tyrosine hydroxylase activity in both mice and rats.

Animals↗
PubMed1991

Incertohypothalamic A13 dopamine neurons: effect of gonadal steroids on tyrosine hydroxylase.

In this study the effect of gonadectomy and steroid treatment on the dorsal component of the incertohypothalamic dopamine system or nucleus A13 was assessed by immunocytochemistry using an antibody raised to tyrosine hydroxylase (TH). A computer graphic system interfaced to a microscope was used to count and measure the diameters of TH-positive neurons and display the data in the three-dimensional space of the nucleus. In males, castration resulted in a dramatic decrease in the reaction product representative of TH. The number of TH-positive cells in the A13 DA nucleus decreased to 25% of intact levels. In females, ovariectomy also caused an impressive loss in the TH-immunostainable material, but this was not indicated by a change in the total number of TH-positive neurons. In both sexes the loss in TH immunostain was confined mainly to the mid-portion of the nucleus. Hormone treatment restored the TH immunostain (cell number and size) to and/or above intact levels in both sexes. These data suggest that A13 TH immunostain is stimulated by gonadal steroids in male and female rats.

Animals↗
PubMed1991

Effects of acute hypercapnia on maternal and fetal vasopressin and catecholamine release.

Although fetal asphyxia, i.e. hypoxemia, acidosis, and hypercapnia, increases plasma arginine vasopressin (AVP) greater than 40-fold, hypoxemia and metabolic acidosis occurring independently cause only 5-fold and 2-fold increases, respectively. To determine the effects of hypercapnia on AVP release, we examined the effects of acute hypercapnia on AVP secretion in six pregnant sheep and their fetuses at 135 +/- 4 d (chi +/- SD), exposing the ewe successively to room air, 30% O2, 30% O2 plus 10% CO2, 30% O2, and room air, and monitoring uterine blood flow, as well as maternal and fetal mean arterial pressure, heart rate, arterial blood gases, and plasma AVP and catecholamines. Oxygen exposure had no effect on the ewe or fetus. During O2 plus CO2 exposure, the ewes and fetuses developed hypercapnia in the absence of hypoxia, arterial CO2 tension increasing to 8.38 +/- 0.87 kPa (62.9 +/- 6.5 mm Hg) and 10.0 +/- 0.61 kPa (75.2 +/- 4.6 mm Hg) (p less than 0.001), respectively, at 30 min of exposure. Although fetal heart rate and mean arterial pressure were unchanged, maternal values rose 61 and 30% (p less than 0.001), respectively. At 30 min of O2 + CO2 exposure, maternal norepinephrine increased from 2.23 +/- 0.74 to 8.52 +/- 3.97 nmol/L (p = 0.15) and fetal epinephrine increased from 0.27 +/- 0.10 to 2.271 +/- 0.90 nmol/L (p = 0.01); plasma AVP was not significantly increased in the ewe or fetus, although levels rose from approximately 45 to 127 +/- 48 and 137 +/- 64 pmol/L (p = 0.10), respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Effect of cerebroventricular anterior pituitary grafts on in situ expression of tyrosine hydroxylase in dopaminergic neurons of the aged animal.

The effect of cerebroventricular anterior pituitary (AP) grafts on brain tyrosine hydroxylase (TH) expression in the median eminence (ME), substantia nigra (SN), and corpus striatum (CS) has been investigated in young and aged female rats. TH expression was studied using the following indices: in situ TH activity, TH mass, and quantity of TH mRNA. The rate of synthesis of dihydroxyphenylalanine (DOPA) was evaluated by measuring its accumulation in the ME, SN, and CS. TH mRNA and TH mass were quantified by an S1 nuclease protection assay and an immunoblot assay, respectively. Viability of the grafts was demonstrated by histological examination and by their ability to secrete PRL into the cerebrospinal fluid (CSF). Liver grafts served as controls. In castrated young and castrated aged animals with AP grafts, the PRL concentrations in the CSF were 204 +/- 49 (mean +/- SE) and 345 +/- 83 ng/ml, respectively, compared to control values of 14 +/- 9 and 23 +/- 9. In intact aged animals, the concentration of PRL was 729 +/- 180 ng/ml in CSF of rats with AP grafts and 223 +/- 62 ng/ml in the controls. DOPA synthesis in the ME of castrated young rats and castrated aged rats with AP grafts was significantly (P less than 0.01) greater than that in controls with liver grafts. AP grafts did not stimulate DOPA synthesis in the ME of intact aged animals. The synthesis of DOPA in the SN and CS was not affected by AP grafts, regardless of the status of the animal. The amount of TH mRNA and the quantity of TH were not influenced by the AP grafts in any of the animal models. However, the in situ molar activity of TH in the ME was significantly greater in castrated young rats and castrated aged rats bearing AP grafts than in animals with liver grafts. The in situ molar activity of TH in the ME of castrated young rats was greater than that of castrated or intact aged animals. It is concluded that AP grafts secrete a substance that stimulates DOPA synthesis in the ME of young as well as aged castrated animals, but not in the nigrostriatal system. This stimulation is due to increased catalytic activity of a fixed number of TH molecules rather than an increase in the mass of TH.

Aging↗
PubMed1991

Testicular inhibition of tyrosine hydroxylase expression in tuberoinfundibular and nigrostriatal dopaminergic neurons.

We have investigated, in young and aged rats, tuberoinfundibular dopaminergic (TIDA) and nigrostriatal neurons of the brain, and the role of the testes and anterior pituitary (AP) on 1) the in situ activity of tyrosine hydroxylase (TH), 2) translation of TH mRNA, as reflected by the mass of TH, and 3) transcription of the TH gene, as revealed by the mass of TH mRNA. The median eminence (ME) and corpus striatum (CS) were used as the sources of proximal neurites of the TIDA neurons and nigrostriatal neurons, respectively. The arcuate-periventricular nuclei of the ventral hypothalamus were used as the source of perikarya of the TIDA neurons, and substantia nigra (SN) nuclei of the midbrain were used as the source of perikarya of nigrostriatal neurons. The in situ activity of TH was calculated using the rate of accumulation of dihydroxyphenylalanine after pharmacological inhibition of dihydroxyphenylalanine decarboxylase activity. TH mass and TH mRNA were measured using an immunoblot assay and an S1 nuclease protection assay, respectively. Compared to intact animals, orchidectomized young and aged male rats had significantly (P less than 0.001) increased in situ activity of TH in the ME and CS, but not the SN. Orchidectomy also caused a significant (P less than 0.01) increase in the quantity of TH in the ME and a 2- to 3-fold increase in TH in the CS and SN. In contrast to castration, AP grafts, implanted in the lateral ventricles of the brain, caused a significant (P less than 0.001) increase only in TH activity in the ME. No effect of AP grafts was seen on TH activity of the CS or SN. AP grafts had no effect on the amount of TH in the ME, CS, or SN. In the TIDA neurons of young males and in the nigrostriatal neurons of young and aged castrates, the amount of TH mRNA was not different from that in intact males. AP grafts had no effect on TH mRNA in these dopaminergic neurons. These studies show that TIDA neurons and nigrostriatal neurons share some common aspects in their regulation and are dissimilar in others. AP grafts stimulate TH activity in young as well as aged TIDA neurons, but not in nigrostriatal neurons. Castration leads to an increase in TH mass in both TIDA and nigrostriatal neurons. The increase in TH mass is not associated with an increase in the amount of TH mRNA. It is suggested that castration results in increased translation of TH mRNA, but not transcription of the TH gene.(ABSTRACT TRUNCATED AT 400 WORDS)

Aging↗
PubMed1991

Tyrosine hydroxylase expression in hypothalamic cells: analysis of the roles of adenosine 3',5'-monophosphate- and Ca2+/calmodulin-dependent protein kinases in the action of pituitary cytotropic factor.

We investigated the involvement of second messenger systems in the control by pituitary cytotropic factor (CTF) of tyrosine hydroxylase (TH) expression in primary cultures of hypothalamic cells. Forskolin, an activator of adenylyl cyclase, as well as Sp-cAMP[S] [(Sp)-cyclic adenosine 3',5'-monophosphothioate], a cAMP agonist, and theophylline, an inhibitor of phosphodiesterase activity, stimulate the secretion of dihydroxyphenylalanine (DOPA) and dopamine (DA), suggesting a role for cAMP-dependent protein kinase in the secretion of catecholamines by hypothalamic dopaminergic cells. When cells were cultured with either CTF or forskolin for 14 days, a progressive increase in the secretion of DOPA and DA was observed throughout the period of incubation. At the end of the 2-week culture period, the amount of TH in the cells, determined by immunoblot analysis, was appreciably increased compared to controls. When the cells were analyzed immunocytochemically for TH, the TH-positive cells that had been incubated with CTF or forskolin for 2 weeks were found to have neurites that appeared larger than those of TH-positive cells in the controls. The diameters of the perikarya of TH-positive cells in cultures incubated with CTF also appeared larger than the controls. After incubation of hypothalamic cells with CTF for 96 h, the amount of TH mRNA in the cultures was significantly increased. When membranes isolated from PC12 cells were incubated for 10 min with 50 microM forskolin, the specific activity of adenylyl cyclase was increased 20-fold; CTF had no effect on adenylyl cyclase activity of PC12 cell membranes. Yet, CTF significantly (P less than 0.001) stimulated the secretion of DOPA and DA by PC12 cells. When hypothalamic cells were incubated with both forskolin and CTF, using doses of each that stimulated maximal secretion, the secretion of DOPA and DA was equal to sum of the secretions with each stimulant alone. These additive actions of forskolin and CTF and the failure of CTF to activate adenylyl cyclase in membranes of PC12 cells suggest that forskolin and CTF stimulate catecholamine secretion by hypothalamic dopaminergic cells through different mechanisms, perhaps through different protein kinases. When hypothalamic cells were incubated with CTF and W-7 [N-(6-aminohexyl)5-chloro-1-naphthalenesulfonamide], an inhibitor of calmodulin, the secretion of DOPA was significantly (P less than 0.001) less than that in cultures that were not incubated with W-7. The findings of this study suggest that TH expression in hypothalamic dopaminergic cells is controlled by redundant protein kinases, including cAMP-dependent protein kinase and Ca2+/calmodulin-dependent protein kinase.

Adenylyl Cyclases↗
PubMed1991

Stress hormones and acid-base status of human fetuses at delivery.

The relationship of plasma concentrations of arginine vasopressin (AVP), ACTH, cortisol, and PRL in the human fetus to mode of delivery and acid-base status has been investigated in 91 term pregnancies consisting of 4 groups based on mode of delivery, type of anesthesia, and use of ephedrine prophylaxis for maternal blood pressure control. Infants delivered vaginally after uncomplicated labors had higher umbilical cord plasma concentrations of AVP, ACTH, and cortisol than infants delivered without labor. Use of ephedrine, an alpha-agonist, during regional anesthesia was associated with elevated plasma AVP and ACTH concentrations compared to those in women receiving general anesthesia. At the time of delivery, 12 infants had acidemia (pH less than 7.20), as judged by pH of umbilical arterial blood. Their plasma AVP, ACTH, and cortisol levels did not differ from those of infants delivered by uncomplicated vaginal delivery, but were greater than those of infants delivered by cesarean section under general anesthesia. Moreover, in infants with acidemia, plasma concentrations of AVP and ACTH were significantly correlated, but PRL levels were unaffected by mode of delivery or acidemia. Elevated umbilical cord plasma concentrations of AVP, ACTH, and cortisol characterize term vaginal deliveries and are associated with intrauterine stress, demonstrating activation of the fetal hypothalamic-pituitary-adrenal axis and suggesting that AVP is important in ACTH release in the human fetus; however, PRL does not appear to be an important stress hormone.

Acid-Base Equilibrium↗
PubMed1991

A novel non-enzymatic procedure for removing DNA template from RNA transcription mixtures.

A novel, simplified procedure for the removal of DNA template from newly synthesized RNA is described. The method avoids the use of DNase and involves extraction of the RNA transcription products at acid pH using either phenol or phenol: chloroform:guanidinium thiocyanate mixture. Both procedures are as effective as DNase digestion in removing DNA template, but are free of the hazard of RNA degradation, are highly reproducible and remove proteins at the same time.

Chloroform↗
PubMed1990

The tuberoinfundibular dopaminergic neurons of the brain: hormonal regulation.

The role of prolactin and of estradiol and progesterone in the control of the biosynthetic and secretory activity of TIDA neurons has been investigated in the following animal models: young female rats, aged female rats, and young male rats. The indices of TIDA neuronal function employed were a) mass of TH in neurites in the ME, b) total in situ activity of TH in the ME, c) in situ molar activity of TH in the ME, and d) secretion of dopamine into hypophysial portal blood. It was found that prolactin in high concentration in the circulation and in the CSF had little, if any, effect on the mass of TH in the ME. However, a high concentration of prolactin in either the circulation or in the CSF stimulated significantly the in situ TH activity in the ME whether expressed in terms of total activity per ME or activity per mole of TH. The stimulation of TH activity with prolactin was prevented by immunoneutralization of circulating prolactin. A high concentration of prolactin in the CSF was as effective in stimulating TH activity in the ME of rats with intact pituitary glands as in hypophysectomized rats. In addition to prolactin, treatment of animals with intact pituitaries with a combination of estradiol and progesterone markedly stimulated the total in situ activity of TH of the ME as well as the in situ molar activity of TH of the ME, but neither estradiol nor progesterone alone had an effect on TH activity. Hypophysectomy abolished the stimulatory action of estradiol and progesterone on TH activity of the ME. In addition to the in situ activity of TH in the ME, estradiol-progesterone treatment stimulated the secretion of dopamine into hypophysial portal blood. Neither estradiol nor progesterone alone affected dopamine secretion by TIDA neurons. We conclude that exposure to high concentrations of prolactin or to both estradiol and progesterone stimulate the biosynthetic and secretory activity of TIDA neurons. These hormones are effective in old rats and well as young rats and in males as well as females.

Animals↗
PubMed1990

Quantitative study of tyrosine hydroxylase mRNA in catecholaminergic neurons and adrenals during development and aging.

Using a solution hybridization-S1 nuclease protection assay, we quantitatively studied tyrosine hydroxylase mRNA (mRNATH) in catecholaminergic cells of the substantia nigra, hypothalamus, superior cervical ganglion, and adrenal of male rats from early neonatal life to old age. Throughout this time, the lowest level of mRNATH in any tissue was found in the youngest animals, and their development was associated with an increase in the quantity of mRNATH. However, the extent of the increase as well as the pattern of change was dependent on the tissue. The amount of mRNATH in the substantia nigra of 1-day-old pups was 162 +/- 7 attomoles (mean and S.E.M.), increasing to 877 +/- 39 amol at 14 days of age. Then, the amount fell to 480 +/- 25 amol at 6 weeks of age, but changed little between 6 weeks and 23 months of age. In the hypothalamus of 1-day-old pups, the quantity of mRNATH was 24 +/- 3 amol, increasing to 60 +/- 6 amol at 2 weeks and changed little thereafter. mRNATH in the superior cervical ganglion increased gradually until 10 months of age; at which time the amount was 3 times that of neonatal animals. In the adrenal, mRNATH increased continuously throughout the period of observation. The amount of mRNATH in the adrenal of 23-month-old animals was 25 times that in the adrenal of 4-day-old pups. These data suggest that tyrosine hydroxylase gene expression does not diminish in aged rats.

Adrenal Glands↗
PubMed1990

Ontogeny of plasma, CSF and brainstem ACTH in piglets: effects of hypoxia and anesthesia.

This study was designed to assess the postnatal maturation of adrenocorticotropin (ACTH) levels in piglets under basal conditions and in response to single, acute stressors. ACTH levels were measured by radioimmunoassay in plasma, cerebrospinal fluid (CSF) and in a dorsal medullary slice containing the nucleus tractus solitarii (dmscNTS) of young and older piglets (1.5-6 and 35-43 days old, respectively) under the following experimental conditions: (1) normoxia (both groups); (2) hypoxia, 10% O2/N2 for greater than or equal to 30 min (both groups); (3) sham anesthesia, i.p. saline in normoxia (young group); (4) anesthesia, 25 mg/kg i.p. pentobarbital in normoxia (young group), and (5) anesthesia combined with hypoxia (young group). During normoxia, ACTH levels in young, as compared to older piglets, were higher in CSF (p less than 0.01) and plasma (0.05 less than p less than 0.10) and not different in dmscNTS. Hypoxia produced no ACTH changes in CSF, increased ACTH in plasma of young (p = 0.03) and older piglets (p = 0.09), and decreased ACTH in dmscNTS of older (p = 0.01) and young piglets (p = 0.07). As compared to sham anesthesia, anesthesia did not alter any ACTH levels. Combined hypoxia and anesthesia increased ACTH levels in plasma when compared to normoxia (p less than 0.05), sham anesthesia (p less than 0.05) or anesthesia alone (p less than 0.05), but not when compared to hypoxia alone. We conclude that neonatal swine have high basal ACTH levels and mount significant plasma ACTH responses to a single, acute hypoxic stressor. The presence of ACTH in the region of the NTS supports its possible role as a neuromodulator in the brain.

Adrenocorticotropic Hormone↗