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Biomedical subjects

C J Foster

Publications and source records attributed to C J Foster.

At least 19 recordsLinked to original sources
PubMed2006

Neurodevelopmental outcomes in children with HIV infection under 3 years of age.

Following the introduction of combination antiretroviral therapy, children vertically infected with the human immunodeficiency virus (HIV-1) living in the developed world are surviving into adult life. This paper reviews the neurodevelopmental outcomes of 62 consecutively-presenting children with HIV-1 infection diagnosed before 3 years of age (32 males, 30 females; median age at presentation 6 mo). Neurological and developmental data are presented with immunological and virological responses to antiretroviral therapy. Fourteen children (22%) had abnormal neurological signs and 25 (40%) demonstrated significant developmental delay on standardized developmental assessments. Children presenting with more severe HIV-1 disease and immune compromise had significantly more abnormal neurological signs and developmental delays than children presenting with milder HIV-1 symptomatology. Immune function, control of HIV-1 viral replication, and growth parameters improved with antiretroviral therapy (median age at last follow-up 7 y 3 mo); however, abnormal neurological signs and significant gross motor difficulties persisted.

AIDS Dementia Complex↗
PubMed2006

HIV in pregnancy: evolution of clinical practice in the UK.

Prior to the introduction of interventions reducing mother-to-child transmission of HIV-1 natural history data reports vertical transmission rates in the order of 25%. The risk of transmission from mother-to-child has been associated with advanced maternal HIV disease, maternal plasma HIV viral load and CD4 lymphocyte count, mode of delivery, length of rupture of membranes, prematurity and breast feeding. During the last 10-15 years the introduction of prelabour cesarean section, formula feeding and antiretroviral therapy has reduced transmission to less than 1% for pregnant women in the UK who are aware of their HIV status. Attention is now turning to the minimization of possible drug side effects for both mother and infant as women are increasingly conceiving on combination antiretroviral therapy. The evolution of current UK guidelines on the prevention of mother-to-child transmission of HIV-1 are discussed.

Anti-HIV Agents↗
PubMed2001

Molecular identification and characterization of the platelet ADP receptor targeted by thienopyridine antithrombotic drugs.

ADP plays a critical role in modulating thrombosis and hemostasis. ADP initiates platelet aggregation by simultaneous activation of two G protein-coupled receptors, P2Y1 and P2Y12. Activation of P2Y1 activates phospholipase C and triggers shape change, while P2Y12 couples to Gi to reduce adenylyl cyclase activity. P2Y12 has been shown to be the target of the thienopyridine drugs, ticlopidine and clopidogrel. Recently, we cloned a human orphan receptor, SP1999, highly expressed in brain and platelets, which responded to ADP and had a pharmacological profile similar to that of P2Y12. To determine whether SP1999 is P2Y12, we generated SP1999-null mice. These mice appear normal, but they exhibit highly prolonged bleeding times, and their platelets aggregate poorly in responses to ADP and display a reduced sensitivity to thrombin and collagen. These platelets retain normal shape change and calcium flux in response to ADP but fail to inhibit adenylyl cyclase. In addition, oral clopidogrel does not inhibit aggregation responses to ADP in these mice. These results demonstrate that SP1999 is indeed the elusive receptor, P2Y12. Identification of the target receptor of the thienopyridine drugs affords us a better understanding of platelet function and provides tools that may lead to the discovery of more effective antithrombotic therapies.

Adenosine Diphosphate↗
PubMed2001

Is coronary angioplasty safe in the elderly?

OBJECTIVE: To evaluate the use of percutaneous transluminal coronary angioplasty (PTCA) and the immediate procedural outcomes in the elderly at a tertiary care centre. PATIENTS AND METHODS: Between January 1992 and December 1997, a total retrospective cohort study of 2322 consecutive patients aged 60 years or older underwent PTCA. Patients were categorized into three age groups: group A (60 to 69 years of age), which included 1294 patients; group B (70 to 79 years), which included 895 patients; and group C (80 years of age or older), which included 133 patients. PTCA was performed using the newest catheter technology as it became available. RESULTS: Men comprised 63% of the patients in groups A and B combined, and 44% of group C (P<0.001). Canadian Cardiovascular Society angina class IV was present in 45% of group C compared with 30% and 35% in groups A and B, respectively (P<0.001). The proportion of patients with diabetes mellitus and hypertension was similar among the three groups. Acute myocardial infarction before PTCA was twice as common at 4.5% (95% CI 3.7% to 5.3%) in group C, compared with 2.9% (95% CI 2.7% to 3.1%) and 2.2% (95% CI 2.0% to 2.3%) in groups A and B, respectively. The procedural success rate was similar at 93%, 92.7% and 91.7% in groups A, B and C, respectively. A total of five (0.2%) deaths and eight (0.34%) myocardial infarctions occurred in groups A and B combined, while none occurred in group C (not significant). More patients in groups A and B underwent emergency coronary artery bypass graft than in group C: group A - 22, 3.4% (95% CI 3.2% to 3.6%); group B - 16, 3.4% (95% CI 3.2% to 3.6%) and group C - one, 0.75% (95% CI 0.6% to 0.9%). CONCLUSIONS: In this retrospective series of patients, it was shown that PTCA may be performed in the very elderly with high procedural success and acceptable risk. Age alone should not be the criterion to limit the use of PTCA.

Aged↗
PubMed1998

Exclusion of a p53 germline mutation in a classic Li-Fraumeni syndrome family.

Li-Fraumeni syndrome (LFS) is characterized by a high risk of sarcomas, early onset of breast cancer, and a diversity of other cancers occurring as multiple primary tumors in multiple family members. In many families with LFS, germline mutations within the tumor-suppressor gene p53 have been identified. However, mutations in p53 have not been detected in approximately 30% of LFS families. To address the possibility either that p53 mutations were being missed or that another predisposing gene is altered in LFS, we used a variety of methods to accurately determine the p53 status in a large LFS kindred. A transcriptional activation assay on exons 4-10 of p53 excluded a mutation within the DNA-binding domain of p53. Single-stranded conformational-polymorphism analysis, using intronic primers and sequencing of all the coding exons and intron/exon junctions, also yielded no mutations. Finally, linkage analysis excluded potential mutations in the noncoding regions of p53. Our findings exclude the presence of a p53 germline mutation in a classic LFS family.

Adult↗
PubMed1994

Mercaptoacyl amino acid inhibitors of atriopeptidase. 1. Structure-activity relationship studies of methionine and S-alkylcysteine derivatives.

A broad series of N-(3-mercaptoacyl) amino acid derivatives was evaluated for their ability to inhibit atriopeptidase (neutral endopeptidase, EC 3.4.24.11) in vitro and in vivo. Structural parameters studied were (i) the substituent on the 2-position of the 3-mercaptopropionyl moiety, (ii) the amino acid component, (iii) the S-terminal derivative, and (iv) the C-terminal derivative. Optimum activity was observed for derivatives of methionine and S-alkylcysteines. N-[3-Mercapto-2(S)-[(2-methylphenyl)methyl]-1-oxopropyl]-L-methionine was identified as a highly effective inhibitor of atriopeptidase meriting evaluation as a potential cardiovascular therapeutic agent.

Amino Acid Sequence↗
PubMed1994

Does the speed of balloon deflation affect the complication rate of coronary angioplasty?

Two hundred consecutive coronary arteries in 157 patients undergoing angioplasty were randomized to fast or slow balloon deflation. Angioplasty was successful in 188 cases (101 with slow and 87 with fast deflation). There was no significant difference between the 2 groups with regard to the total number of dissections, although there was a greater number in the slow deflation group, and no difference in the number of minor dissections (National Heart, Lung, and Blood Institute types A and B). There was a significantly greater number of more severe dissections (types C to F) in the slow deflation group (20 vs 5; p = 0.013). It is proposed that the greater number of severe dissections is due to either increased turbulence or movement of the partially deflated balloon during slow deflation. Thus, slow balloon deflation during coronary angioplasty is associated with a higher complication rate than is conventional rapid deflation.

Aged↗
PubMed1994

Comparison of fixed-wire and over-the-wire balloon dilatation systems for percutaneous transluminal coronary angioplasty.

There is controversy concerning the relative safety and efficacy of the 2 currently available percutaneous transluminal coronary angioplasty dilatation systems--fixed-wire (FW) and over-the-wire (OW). A randomized, prospective trial comparing the 2 systems was performed to examine this controversy. Of 1,513 patients undergoing percutaneous transluminal coronary angioplasty at 3 centers between June 1990 and October 1991, 602 (40%) fulfilled the eligibility criteria for the study. There were 643 lesions, of which 327 were randomized to FW and 316 to OW systems. There was no difference in the success rate between FW (92%) and OW (94%) systems. Inability to cross with a wire was infrequent with either system (FW: 1.8%; and OW: 1.6%). Inability to cross with a balloon when the wire crossed the lesion did not occur. An FW system was successful in 6 cases (1.9%) in which the OW system had been unsuccessful, whereas an OW system succeeded in 14 (4.3%) after the FW system had been unsuccessful (p = NS). Time to cross stenoses was 200 +/- 21 and 233 +/- 22 seconds, procedural time was 21 +/- 1.3 and 21 +/- 1.0 minutes, fluoroscopy time was 6.7 +/- 0.4 and 7.1 +/- 0.4 minutes, contrast used was 89.0 +/- 4.2 and 84.0 +/- 3.5 ml, and number of cine runs was 5.9 +/- 3.0 and 6.3 +/- 3.4 in the FW and OW systems, respectively. Complications were infrequent with either system (FW: 10.4%; and OW: 9.5%). Acute closure occurred in 1.8 and 2.2% of cases in the FW and OW systems, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1994

Anaesthesia for the patient with neonatal adrenoleukodystrophy.

The authors present and discuss the care of a nine-month-old with neonatal adrenoleukodystrophy who required general anaesthesia for gastrointestinal endoscopy. Neonatal adrenoleukodystrophy is an inherited disorder of peroxisomal enzymes. Anaesthetic care may be affected by the presence of hypotonia, liver function abnormalities, gastroesophageal reflux, and impaired adrenocortical function. Preoperative sedation is contraindicated because of the risk of precipitating airway obstruction due to pre-existing hypotonia. Anaesthetic induction and tracheal intubation should be performed to minimize the risk for aspiration of gastric contents. The choice of muscle relaxant should take into account the pre-existing hypotonia as well as the possibility of hyperkalaemia in response to succinylcholine. Anaesthetic agents known to decrease the seizure threshold should be avoided in patients with a seizure disorder. In addition, anaesthetic agents that rely on the liver for metabolism should be used with caution in patients with cirrhosis. When time permits, these patients should be screened for adrenocortical insufficiency before surgery, and perioperative steroid coverage is advisable when preoperative testing of adrenocortical function is not feasible. While these patients eventually die after progressive deterioration, full recovery from the effects of anaesthesia and surgery can be achieved with attention to neurological, metabolic, and physical problems.

Adrenoleukodystrophy↗
PubMed1991

Modulation of circulating endothelin levels in hypertension and endotoxemia in rats.

We have developed separate radioimmunoassays to measure circulating ET-1 and ET-3 levels in normotensive and different hypertensive rat models so that the role of endothelin in the regulation of vasomotor function can be studied. We also assessed the stimulatory effects of endotoxin on plasma and liver lymph ET-1 and ET-3 levels. The circulating ET-1 levels in normotensive rats, SHRs, and DOCA-salt hypertensive rats were 2.3 +/- 0.5, 2.1 +/- 0.4, and 2.1 +/- 0.9 pg/ml, respectively. Similarly, the plasma ET-3 levels in normotensive and different hypertensive rats were similar, ranging from 19.7 +/- 1.5 to 24.7 +/- 2.2 pg/ml. The data indicate that steady-state circulating levels of endothelins are a poor correlate of the hypertensive state. Endotoxin (30 mg/kg i.v. over 15 min) reduced blood pressure significantly and augmented plasma ET-1 levels by sevenfold (29.1 +/- 3.7 vs. 4.1 +/- 0.6 pg/ml in the vehicle group; p less than 0.05) and ET-3 levels by twofold (47.7 +/- 7.0 vs. 22.7 +/- 4.0 pg/ml in the vehicle group; p less than 0.05). Human TNF-alpha (30 ng/kg/min x 30 min), a putative mediator of endotoxin shock, enhanced plasma ET-1 (18.3 +/- 1.0 vs. 2.7 +/- 0.4 pg/ml in the vehicle group; p less than 0.05) by sevenfold and ET-3 levels by twofold (45.7 +/- 2.0 vs. 27.1 +/- 4.0 pg/ml in the vehicle group; p less than 0.05) without affecting blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Influence of C-ANF receptor and neutral endopeptidase on pharmacokinetics of ANF in rats.

The role of C-atrial natriuretic factor (ANF) receptors and neutral endopeptidase (NEP) in the pharmacokinetics and hydrolysis of 125I-labeled ANF was evaluated in rats by using C-ANF and SCH 39370 to block the nonenzymatic and enzymatic pathways, respectively. After a bolus injection of 125I-ANF, the resulting area under the plasma concentration curve (AUC) with C-ANF treatment was seven times the control value with regard to trichloroacetic acid-precipitable (TCA-ppt) radioactivity (intact ANF). SCH 39370 tended to increase AUC, but the changes were not significant. Nevertheless, SCH 39370 suppressed the appearance of TCA-soluble radioactivity (hydrolytic products), indicating that in vivo inhibition of ANF degradation had occurred. SCH 39370 plus C-ANF produced a 15-fold increase in AUC for TCA-ppt radioactivity and a reduction in plasma TCA-soluble radioactivity. High-performance liquid chromatography (HPLC) analysis confirmed that combination treatment increased intact ANF and reduced hydrolytic products in the plasma. SCH 39370 reduced clearance (C) without altering volume of distribution in steady state (Vss) and half-life (t1/2). C-ANF decreased both C and Vss leading to a fourfold increase in t1/2, which was further prolonged by SCH 39370 (7.5 times control). Bilateral nephrectomy caused a proportionally similar decrease in Vss and C without changing t1/2, suggesting significant extrarenal metabolism of ANF. SCH 39370 systemically inhibits ANF hydrolysis; the resulting increase in ANF, however, is masked by the great capacity of ANF clearance receptors but can be revealed with excess C-ANF, suggesting that the plasma ANF concentrations are determined by the interplay of the C-ANF receptor and NEP systems.

Animals↗
PubMed1990

Potent peptide inhibitors of smooth muscle myosin light chain kinase: mapping of the pseudosubstrate and calmodulin binding domains.

Smooth muscle myosin light chain kinase (MLCK) is activated by calcium-calmodulin and, in turn, phosphorylates and activates the smooth muscle actomyosin ATPase, resulting in muscle contraction. The amino acid sequence of the regulatory domain of MLCK is known, and it contains a region that binds calmodulin and also bears a strong homology to the phosphorylation site in the substrate. Thus, it has been called the "pseudosubstrate". It has been proposed that calmodulin activates MLCK by binding to and reversing the autoinhibitory function of the pseudosubstrate. Synthetic peptides based on this sequence inhibit MLCK both by binding to calmodulin and by competing with the substrate at the active site. In the work reported here, we have synthesized a large number of peptides from the regulatory region of MLCK (MLCK 480-516). The region was systematically analyzed by dividing it into fragments of two to six amino acids, each containing one or more basic residues, in order to map in detail the calmodulin binding site and the autoinhibitory region. It was observed that both calmodulin binding and autoinhibition are mediated by several different fragments of the regulatory sequence. Two nonoverlapping peptides, MLCK 480-493 and MLCK 494-504, are similar in potency in inhibiting the enzyme (IC50's of 2 and 6 microM, respectively). Larger fragments, combining multiple inhibitory regions, are more potent inhibitors. For example, MLCK 480-504 is extremely potent, with an IC50 of 13 nM. The calmodulin binding site and active site directed inhibitory regions overlap, but are not identical. Residues 505-512 are important only for calmodulin binding.

Amino Acid Sequence↗
PubMed1990

Rapid receptor-mediated catabolism of 125I-atrial natriuretic factor by vascular endothelial cells.

The binding, internalization and degradation of 200 pM monoiodinated human atrial natriuretic factor-(99-126) (125I-hANF) by cultured bovine aortic endothelial cells (BAECs) were studied at 37 degrees C. 125I-hANF was rapidly cleared from the extracellular medium (t1/2 approximately 10 min), whereas preincubation of the cells in the presence of 20 mM-NH4Cl or 0.2 mM-chloroquine resulted in a significant inhibition of this process. The BAECs rapidly produce three major degradation products of 125I-hANF, namely [125I]iodotyrosine 126 (125I-Y), Arg125-[125I]iodotyrosine126 (125I-RY) and Phe124-Arg125-[125I]iodotyrosine126(125I-FRY), which were detected in the extracellular medium. NH4Cl and chloroquine acted to inhibit the generation of 125I-Y and 125I-RY, but not that of 125I-FRY. Furthermore, excess unlabelled hANF (300 nM) completely blocked the rapid production of 125I-Y and 125I-RY in the first 5 min, but only partially (49%) inhibited the generation of 125I-FRY. Thus, in contrast with our previous findings with cultured smooth-muscle cells [Johnson, Arik & Foster (1989) J. Biol. Chem. 264, 11637-11642], BAECs bind, internalize and rapidly degrade 125I-hANF, resulting in the release of 125I-Y and 125I-RY into the extracellular medium. Similarly to smooth-muscle cells, the BAECs generate 125I-FRY from 125I-hANF via an extracellular proteolytic event. The rapidity of the receptor-mediated process and its sensitivity to NH4Cl and chloroquine suggest that the 125I-hANF is proteolytically processed in the endosomes of BAECs and that its receptors cycle between the cell surface and intracellular stores.

Ammonium Chloride↗
PubMed1990

Partial characterization of a metalloendopeptidase activity produced by cultured endothelial cells that removes the COOH-terminal tripeptide from 125I-atrial natriuretic factor.

The presence of the COOH-terminal region of human atrial natriuretic factor-(99-126) (hANF) is necessary for the full expression of its biological activity. Here, we report on the partial characterization of a proteolytic activity in the conditioned medium from cultured bovine aortic endothelial cells that cleaves the Ser123-Phe124 bond of 125I-hANF generating the COOH-terminal tripeptide. The concentrated conditioned medium was fractionated by gel filtration high performance liquid chromatography and fractions were assayed for the ability to generate the COOH-terminal tripeptide from 125I-hANF. This analysis indicated that the protein responsible for this activity had an approximate molecular weight of 200,000 daltons. Of 16 protease inhibitors tested, only 1,10 phenanthroline, EDTA, EGTA and N-ethylmaleimide significantly inhibited the endopeptidase activity. Thus, we conclude that cultured bovine aortic endothelial cells produce a potentially novel phosphoramidon-insensitive metalloendopeptidase that removes the COOH-terminal tripeptide from 125I-hANF.

Animals↗
PubMed1989

Metabolism of 125I-atrial natriuretic factor by vascular smooth muscle cells. Evidence for a peptidase that specifically removes the COOH-terminal tripeptide.

The addition of 200 pM monoiodinated human atrial natriuretic factor-(99-126) (125I-hANF) to cultured bovine aortic smooth muscle cells at 37 degrees C resulted in a rapid clearance from the medium (t1/2 approximately 7.5 min). Within 5 min, [125I]iodotyrosine126 (125I-Y), Arg125-[125I]iodotyrosine126 (125I-RY) and Phe124-Arg-[125]iodotyrosine126 (125I-FRY) appeared in the medium. The identities of these degradation products were confirmed by 1) retention time on high performance liquid chromatography (HPLC) relative to standards, 2) products generated by digestion with aminopeptidase M, and 3) the absence of the Met110. Preincubation of the cells with ammonium chloride or chloroquine resulted in a significant increase in the intracellular accumulation of radiolabel, indicative of endocytosis and rapid delivery of 125I-hANF to an acidic intracellular compartment (endosome and/or lysosome). Neither ammonium chloride, chloroquine, nor excess unlabeled hANF blocked the rapid appearance in the medium of 125I-RY or 125I-FRY. Bestatin inhibited the generation of 125I-RY, with a concomitant increase in 125I-FRY, suggesting that the 125I-RY is produced by aminopeptidase action on 125I-FRY. The endopeptidase 24.11 (enkephalinase) inhibitor, SCH 39370, did not inhibit the formation of 125I-FRY. These results provide evidence of a peptidase capable of specifically removing the COOH-terminal tripeptide from 125I-hANF. The COOH-terminal tripeptide, Phe124-Arg-Tyr126, was also isolated from cell digests of hANF by HPLC and its identity confirmed by amino acid analysis. Since it is generally believed that the COOH-terminal tripeptide is critical to many of atrial natriuretic factor-(99-126)'s bioactivities, this enzyme may be involved in the inactivation of atrial natriuretic factor-(99-126) in target tissues.

Amino Acids↗