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Biomedical subjects

J W Ryan

Publications and source records attributed to J W Ryan.

At least 19 recordsLinked to original sources
PubMed1999

HIV prevalence at reception into Australian prisons, 1991-1997.

OBJECTIVE: To measure the extent and outcome of HIV antibody testing at reception into Australian prisons. DESIGN: Cross-sectional survey at reception into prison. PARTICIPANTS AND SETTING: People received into Australian prisons from 1991 to 1997. MAIN OUTCOME MEASURES: Number of people tested for HIV infection and prevalence of diagnosed HIV infection. RESULTS: In 1991-1997, HIV antibody testing was carried out for 72% of prison entrants in Australia; the percentage tested declined significantly from 76% in 1991 to 67% in 1997 (P < 0.001). In New South Wales, the percentage of entrants tested at reception into prison dropped from almost 100% in 1991-1994 to 45% in 1997, whereas in the Northern Territory, South Australia and Western Australia the extent of testing increased significantly (P < 0.001). HIV prevalence was 0.2% among people received into Australian prisons in 1991-1997, and did not differ by sex. Most people with HIV infection (242/378; 64%) received into prison in 1991-1997 had been diagnosed at a previous entry; 136 people (36% of the total number of diagnoses) were newly diagnosed at reception into prison. CONCLUSIONS: A national monitoring system in place from 1991 indicates generally high rates of HIV antibody testing and a low prevalence of HIV infection among people entering Australian prisons. In each year, people not previously known to the prison health service to have HIV infection were received into prison, indicating continuing HIV infection in the population entering Australian prisons.

Australia↗
PubMed1999

Pulmonary capillary endothelium-bound angiotensin-converting enzyme activity in humans.

BACKGROUND: Pulmonary endothelium has metabolic functions including the conversion of angiotensin I to angiotensin II by angiotensin-converting ectoenzyme (ACE). In this study, we have validated an indicator-dilution technique that provides estimations of dynamically perfused capillary surface area (DPCSA) in humans, and we have characterized pulmonary endothelial ACE in vivo. METHODS AND RESULTS: In 12 adults, single-pass transpulmonary (one or both lungs) hydrolysis of the specific ACE substrate 3H-benzoyl-Phe-Ala-Pro (3H-BPAP) was measured and expressed as % metabolism (%M) and v=-ln(1-M). We also calculated Amax/Km, an index of DPCSA. %M (70.1+/-3.2 vs 67.9+/-3.1) and v (1.29+/-0.14 vs 1. 20+/-0.12) were similar in both lungs and the right lung, respectively, whereas Amax/Km//body surface area decreased from 2460+/-193 to 1318+/-115 mL/min per square meter. CONCLUSIONS: Pulmonary endothelial ACE activity can be assessed in humans at the bedside by means of indicator-dilution techniques. Our data suggest homogeneous pulmonary capillary ACE concentrations and capillary transit times (tc) in both human lungs, and similar tc within the normal range of cardiac index. Amax/Km in the right lung is 54% of total Amax/Km in both lungs, suggesting that Amax/Km is a reliable and quantifiable index of DPCSA in humans.

Adult↗
PubMed1999

An innovative approach to the medical management of the nursing home resident: the EverCare experience.

Providing quality medical care to the frail elderly who reside permanently in nursing homes is associated with a variety of problems and impediments. This article describes the solution devised by two geriatric nurse practitioners who created a program of care called EverCare. This program, now a Health Care Financing Administration (HCFA) demonstration project, incorporates the nurse practitioner in a collaborative relationship with the primary care physician to provide early detection and intervention for myriad health and medical problems found in the nursing home population and to enhance the care of the frail elderly overall.

Aged↗
PubMed1997

Cloning and tissue distribution of human membrane-bound aminopeptidase P.

Complementary DNA clones encoding human membrane-bound aminopeptidase P (AmP) were isolated by reverse transcription-polymerase chain reaction (RT-PCR) of human kidney and lung poly (A)+ RNA. Comparison of the human AmP sequence to that of the pig shows significant evolutionary divergence with only 83% amino acid sequence identity between the two species. Northern hybridization analysis and RT-PCR suggests that the soluble and membrane-bound forms of human AmP are products of two distinct genes or, through alternative splicing, have different C-terminal sequences.

Alternative Splicing↗
PubMed1997

Subunit interactions of endothelial nitric-oxide synthase. Comparisons to the neuronal and inducible nitric-oxide synthase isoforms.

Endothelial nitric-oxide synthase (eNOS) is comprised of two identical subunits. Each subunit has a bidomain structure consisting of an N-terminal oxygenase domain containing heme and tetrahydrobiopterin (BH4) and a C-terminal reductase domain containing binding sites for FAD, FMN, and NADPH. Each subunit is also myristoylated and contains a calmodulin (CaM)-binding site located between the oxygenase and reductase domains. In this study, wild-type and mutant forms of eNOS have been expressed in a baculovirus system, and the quaternary structure of the purified enzymes has been analyzed by low temperature SDS-PAGE. eNOS dimer formation requires incorporation of the heme prosthetic group but does not require myristoylation or CaM or BH4 binding. In order to identify domains of eNOS involved in subunit interactions, we have also expressed eNOS oxygenase and reductase domain fusion proteins in a yeast two-hybrid system. Corresponding human neuronal NOS (nNOS) and murine inducible NOS (iNOS) fusion proteins have also been expressed. Comparative analysis of NOS domain interactions shows that subunit association of eNOS and nNOS involves not only head to head interactions of oxygenase domains but also tail to tail interactions of reductase domains and head to tail interactions between oxygenase and reductase domains. In contrast, iNOS subunit association involves only oxygenase domain interactions.

Antioxidants↗
PubMed1997

The influence of xenotransplant immunogenicity and immunosuppression on host MHC expression in the rat CNS.

During the early stages following neural transplantation, host immune responses are initiated that are not normally found in the CNS including the induction of major histocompatibility antigens (MHC I and II). Previous laboratory findings have demonstrated prolonged survival of bovine chromaffin cells (BCC) in the rat CNS following transient immunosuppression with cyclosporin A (CSA) providing chromaffin cells are isolated from highly immunogenic passenger cells. To assess the influence of passenger and chromaffin cells on host MHC I and II expression, either BCC, nonchromaffin cell adrenal constituents (NCC), or adrenal medullary endothelial cells (EC) were implanted into the host. At 2 weeks postimplantation, robust BCC survival was obtained in CSA-treated animals. This correlated with low expression of MHC I at the host-graft border and the virtual absence of MHC II. Good BCC survival with reduced MHC I expression only was seen at 6 weeks postimplantation in animals transiently immunosuppressed (4 weeks). In contrast, poor survival was seen in the EC group (even with CSA treatment). In addition, marked MHC I and II expression was found in and around these grafts at 2 weeks, and was particularly intense in EC implanted animals. The results of this study suggest that nonchromaffin passenger cells in BCC preparations, most notably endothelial cells, can induce strong immune responses even in the presence of immunosuppression. Based on MHC staining, removal of these passenger cells can reduce host responses and improve long term survival of xenogeneic chromaffin cells in the CNS.

Adrenal Medulla↗
PubMed1997

Endopeptidase 24.11 activity in the human prostate cancer cell lines LNCaP and PPC-1.

Human endopeptidase 24.11 (EP) occurs in greatest abundance on terminally differentiated prostate cells; thus, loss of EP could mark dedifferentiation of prostate epithelium. To identify laboratory models that would permit continuous work on the biochemistry and hormonal regulation of EP, we examined the well-differentiated LNCaP and poorly differentiated PPC-1 human prostate cancer cell lines. Ultrastructural analysis revealed that LNCaP secretes electron-dense material that resembles the particulate matter of seminal plasma, which is associated with endopeptidase activity. LNCaP medium contained EP activity while PPC-1 medium did not. Whether the apparent deletion of EP from the PPC-1 cell line is characteristic of poorly differentiated prostate adenocarcinoma is not yet clear. However, it may be relevant to the carcinogenic process that EP can limit growth of lung small carcinomas by inactivating cell growth-promoting bombesin-like peptides. Because bombesin has been identified in aggressive human prostate cancers, loss of EP in PPC-1 could represent a necessary step in transformation to aggressive phenotype. The combination of LNCaP and PPC-1, which offers well-differentiated and poorly differentiated cancer phenotypes, appears well suited to studying the relevance of EP in prostate cancer biology.

Adenocarcinoma↗
PubMed1997

The orally active ET(A) receptor antagonist (+)-(S)-2-(4,6-dimethoxy-pyrimidin-2-yloxy)-3-methoxy-3,3-diphe nyl-propionic acid (LU 135252) prevents the development of pulmonary hypertension and endothelial metabolic dysfunction in monocrotaline-treated rats.

Pulmonary hypertension is associated with endothelial dysfunction that may mediate or contribute to the disease process; among those abnormalities is an increase in circulating endothelin-1 levels. We investigated the effect of the orally active endothelin A receptor antagonist LU 135252 (LU) on the development of monocrotaline (MCT)-induced pulmonary hypertension and endothelial metabolic dysfunction. Rats were assigned to four groups by receiving a single dose of MCT or saline, followed by once-daily gavage with LU (50 mg/kg) or saline for 3 weeks. Plasma immunoreactive endothelin-1 levels doubled after MCT and were unaffected by LU therapy. The MCT-induced increase in right ventricular systolic pressure (72.5 +/- 15.9 mmHg) and hypertrophy (right ventricle/[left ventricle plus septum weight]; 0.58 +/- 0.08) were reduced by LU to 42.7 +/- 8.5 mmHg (P < .01) and 0.42 +/- 0.05 (P < .01), respectively. LU, however, did not modify MCT-induced pulmonary artery medial hypertrophy. Pulmonary vascular endothelial metabolic activity was evaluated in isolated lungs by measuring endothelium-bound angiotensin-converting enzyme activity using a synthetic angiotensin-converting enzyme substrate, 3H-benzoyl-phenylalanly-glycyl-proline. MCT reduced fractional 3H-benzoyl-phenylalanly-glycyl-proline hydrolysis (0.488 +/- 0.051, P < .01) which was normalized by LU therapy (0.563 +/- 0.050). LU treatment alone had no significant effect on any of these parameters. We conclude that the endothelin A antagonist LU reduces MCT-induced pulmonary hypertension and right ventricular hypertrophy and restores endothelial metabolic function. These results support the development of endothelin antagonists for the treatment of pulmonary hypertension and associated endothelial metabolic abnormalities.

Administration, Oral↗
PubMed1996

Monocyte- and cytokine-induced downregulation of angiotensin-converting enzyme in cultured human and porcine endothelial cells.

We investigated the effects of monocytes on endothelial cell (EC) ectoenzyme activity. Coculture of human aortic ECs with human monocytes (2 x 10(5) monocytes per 2-cm2 well) led to a decrease in EC angiotensin-converting enzyme (ACE) activity (64.5 +/- 3.5% of control) but not aminopeptidase N, aminopeptidase P, and 5'-nucleotidase activities. Similar results were obtained using human umbilical vein EC-human monocyte and porcine aortic EC-porcine monocyte cocultures. The decrease in ACE activity was monocyte concentration and coculture time dependent, reaching a maximum of 65% decrease in activity at 120 hours. Monocyte-mediated reduction in ACE activity did not require cell to cell contact, since exposure of ECs to conditioned medium from cocultures (CCCM) or from monocyte cultures (MCM) produced a decrease in ACE activity similar to that observed in EC-monocyte cocultures. Exogenously added tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 alpha, two known secretory products of monocytes, simulated the effects of monocytes on ACE activity. Western blot analysis revealed a decrease in the amount of ACE protein in TNF-alpha-treated and CCCM-treated ECs compared with control ECs. Both TNF-alpha and IL-1 alpha were present in CCCM and MCM but not EC-conditioned medium. Incubation of the cocultures with a mixture of neutralizing antibodies against TNF-alpha and IL-1 totally abolished the monocyte-induced decrease in ACE activity. In conclusion, monocytes decrease ACE activity in cultured ECs through the release of cytokines such as TNF-alpha and IL-1.

5'-Nucleotidase↗
PubMed1996

Implementing strategies to decrease risk of falls in older women.

1. Seventy-three percent of older women attending a fall prevention program made at least one low cost change in either their personal behavior or living environment to decrease their likelihood of falls. 2. Older women educated in small group sessions made more fall prevention changes than those educated individually. 3. When conducting a fall prevention program, having examples of safety devices available for participants to examine enhances the presentation.

Accidental Falls↗
PubMed1995

Hypoxia sensitive neurons in the caudal hypothalamus project to the periaqueductal gray.

Previous studies have demonstrated that the caudal hypothalamus modulates the respiratory responses to hypoxia and hypercapnia. In addition, many of the neurons in this area have a basal discharge related to the cardiac and/or respiratory cycles and are stimulated by hypoxia or hypercapnia. The purpose of the present study was to determine if these hypothalamic neurons project to a known cardiorespiratory area, the periaqueductal gray in the rat. In a first set of experiments, rhodamine-tagged microspheres were injected into the periaqueductal gray (PAG) to determine the areas of the caudal hypothalamus that project to the PAG. These studies revealed that the caudal hypothalamus sends strong ipsilateral and weak contralateral projections to the PAG. In a second set of experiments, single unit recordings were made from neurons in the caudal hypothalamus; the basal discharge of these neurons were examined with signal averaging techniques. Each neuron (n = 79) was tested for a response to inhalation of a hypoxic (10% O2) and a hypercapnic (5% CO2) gas. Antidromic activation techniques were then used to determine if neurons in the caudal hypothalamus send projections to or through the PAG. Nineteen percent (n = 15) of the hypothalamic neurons studied could be activated from the PAG; approximately 53% (n = 8) of these were excited by hypoxia and 27% (n = 4) by hypercapnia. Most of these neurons tested (42 of 64 neurons) had a basal discharge related temporally to the cardiac and/or respiratory cycles. These findings suggest that a caudal hypothalamic to periaqueductal gray projection is involved in the integrated response to hypoxia.

Animals↗
PubMed1994

Guinea pig membrane-bound aminopeptidase P is a member of the proline peptidase family.

Members of the newly recognized proline peptidase family share the ability to hydrolyze imide bonds and share six blocks of highly homologous amino acid sequences. We have found that guinea pig lung and kidney forms of aminopeptidase P, both forms bound to membranes via glycosyl phosphatidylinositol lipid anchors, share at least three of the six conserved blocks of amino acid sequences. In addition, aminopeptidase P acts as an aminoacylproline hydrolase and thus appears to be a member of the proline peptidase family.

Amino Acid Sequence↗
PubMed1994

Immunoaffinity purifications of aminopeptidase P from guinea pig lungs, kidney and serum.

Previously, aminopeptidase P (AmP) has been purified from mammalian tissues by highly laborious multistep chromatography procedures. To simplify purifications, we raised a monoclonal antibody to guinea pig serum AmP and used the antibody to prepare an immunoaffinity matrix. The immunoaffinity matrix was used to obtain highly purified forms of AmP from guinea pig lungs, kidney and serum. The antibody is reactive with rat and human forms of AmP and may simplify procedures needed for their purifications.

Amino Acid Sequence↗
PubMed1994

Assay of pulmonary microvascular endothelial angiotensin-converting enzyme in vivo: comparison of three probes.

We monitored the activity of pulmonary microvascular endothelial-bound angiotensin-converting enzyme (ACE) in vivo by means of multiple indicator-dilution-type techniques, utilizing three different probes: the hydrolysis of two substrates, [3H]-benzoyl-Phe-Ala-Pro (BPAP) and [14C]benzoyl-Ala-Gly-Pro (BAGP), and the binding of the inhibitor [3H]RAC-X-65 (RAC), all measured during a single transpulmonary passage in anesthetized rabbits, placed on total heart bypass, so that both systemic and pulmonary circulations were fully supported by means of a two-channel extracorporeal pump. Experiments were performed at pulmonary blood flows (Qb) of 250, 400, 560, and 800 ml/min in control or indomethacin-pretreated rabbits. ACE activity was also compared to that of pulmonary microvascular endothelial-bound 5'-nucleotidase, by measuring the dephosphorylation of its natural substrate 5'-[14C]AMP. We calculated substrate utilization, mean lung transit time (t), and volume of distribution (i.e., central blood volume) of all substrates, as well as inhibitor binding. We also calculated Amax/Km and Bmax products of enzyme mass and kinetic constants for substrates and inhibitor, respectively. As Qb increased, Amax/Km values for all three substrates and Bmax increased linearly, indicating microvascular recruitment. In experiments in which either BPAP and 5'-AMP metabolism or BAGP metabolism and RAC binding were studied concomitantly, a linear relationship was observed between Qb-induced changes in Amax/Km values of BPAP vs 5'-AMP as well as in Amax/Km of BAGP vs Bmax of RAC. Similarly, increasing Qb increased central blood volume and decreased t. Indomethacin had no effect on most of the hemodynamic or enzyme parameters measured. We conclude that in vivo assays of ACE proceed as predicted by Michaelis-Menten kinetics and offer insights into pulmonary endothelial pathophysiology.

Animals↗