Biomedical subjects
A Phillips
Publications and source records attributed to A Phillips.
Screening urine for exogenous testosterone by isotope ratio mass spectrometric analysis of one pregnanediol and two androstanediols.
We propose a new screening method for testosterone (T) doping in sport. The current method for detecting T administration is based on finding a T to epitestosterone ratio (T/E) in urine that exceeds six. The difficulties with T/E are that T administration does not always result in a T/E>6 and that a rare individual will have T/E>6 in the absence of T administration. Our previous studies reveal that carbon isotope ratio helps to determine the origin of the urinary T because the values for T and its metabolites decrease after the administration of exogenous T. In this study, we present a rapid and efficient screening sample preparation method based on three successive liquid-solid extractions, deconjugation with E. coli beta-glucuronidase after the first extraction, acetylation after the second extraction, and a final extraction of the acetates. The 13C/12C of two T metabolites (5beta-androstane-3alpha,17beta-diol and 5alpha-androstane-3alpha,17beta-diol) and one pregnanediol as endogenous reference (5beta-pregnane-3alpha,20alpha-diol) was measured by gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) on 10 ml of urine collected from 10 healthy men before and after T administration. Following T administration, the 13 C/12C of 5beta-androstane-3alpha,17beta-diol diacetate and 5alpha-androstane-3alpha,17beta-diol diacetate declined significantly from -26.2 per thousand to -30.8 per thousand and from -25.2 per thousand to -29.9 per thousand, respectively and the 13C/12C of 5beta-pregnane-3alpha,20alpha-diol diacetate was unchanged. In addition, the ratio of androstanediols to pregnanediol increased in the post-T urines.
Virological response to protease inhibitor therapy in an HIV clinic cohort.
OBJECTIVE: New antiretroviral strategies aim to reduce plasma HIV RNA (viral load) to below the limits of detectability of assays with the objective of reducing viral replication in order to stop or reverse the pathogenic process and prevent development of drug resistance. First use of a protease inhibitor might offer the most realistic chance of achieving this aim. Our objective was to study the virological response to protease inhibitors in patients taking them for the first time. METHODS: A total of 901 patients from a large outpatient clinic were followed a mean of 15 months from the time of starting a protease inhibitor until 1 May 1998. Viral load and CD4 cell count measurements were made on average every 34 days. RESULTS: Overall there was a 79% [95% confidence interval (CI), 76-82] probability of the patients achieving a viral load < 500 copies/ml by 24 weeks after starting the protease inhibitor. In a multiple Cox regression model, those with lower initial viral load [relative hazard (RH), 0.72; P < 0.0001], higher CD4 cell count (RH, 1.07; P = 0.002), those starting other new drugs at same time as the protease inhibitor (RH, 1.46 for two versus none; P = 0.003), those who were antiretroviral-naive, and those using indinavir or nelfinavir were more likely to achieve such levels. In those 651 patients achieving viral load < 500 copies/ml within 24 weeks, there was an estimated 53% (95% CI, 51-55) probability of rebound of viral load to > 500 copies/ml by 52 weeks from the first undetectable value. Again, those who had started other new drugs at the same time as the protease inhibitor (RH, 0.57; P = 0.003 for starting two versus none) tended to experience a lower probability of viral load rebound, as did those with higher initial CD4 cell count (RH, 0.87 per 100 x 10(6)/l higher; P = 0.0007). Those who took saquinavir achieved less durable virological responses than those who took other protease inhibitors. CONCLUSIONS: Starting protease inhibitor therapy with two other new antiretroviral drugs simultaneously with protease inhibitor therapy offers a better best chance of achieving sustained viral load < 500 copies/ml than starting fewer new drugs.
Stabilization of poly-L-lysine/DNA polyplexes for in vivo gene delivery to the liver.
We are developing a self-assembling non-viral in vivo gene delivery vehicle based on poly-l-lysine and plasmid DNA. We have characterized poly-l-lysines of different chain lengths for DNA condensation and strength of DNA binding. Poly-l-lysine chains >20 residues bound DNA efficiently in physiological saline, while shorter chains did not. Attachment of asialoorosomucoid to PLL increased the PLL chain length required for efficient DNA binding in saline and for efficient DNA condensation. By electron microscopy, poly-l-lysine/DNA polyplexes appeared as toroids 25-50 nm in diameter or rods 40-80 nm long; conjugation of asialoorosomucoid to the polylysine component increased the size of resulting polyplexes to 50-90 nm. In water, poly-l-lysine and asialoorosomucoid-PLL polyplexes have effective diameters of 46 and 87.6 nm, respectively. Polyplexes containing only poly-l-lysine and DNA aggregated in physiological saline at all charge ratios and aggregated at neutral charge ratios in water. Attachment of asialoorosomucoid lessened, but did not eliminate, the aggregation of PLL polyplexes, and did not result in efficient delivery of polyplexes to hepatocytes. Conjugation of polyethylene glycol to poly-l-lysine sterically stabilized resulting polyplexes at neutral charge ratios by shielding the surfaces. For efficient in vivo gene delivery, polyplexes will need to be sterically stabilized to prevent aggregation and interaction with serum components.
The prevalence of non-B subtype HIV-1 in a London HIV/AIDS outpatient clinic.
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Effect of laser welding with human serum albumin on the expression of P-selectin on platelets.
BACKGROUND AND OBJECTIVE: Artery repair by means of laser energy induces activation of platelets with a risk of thrombosis and local inflammatory reactions. The aim of this study was to investigate the effect of human serum albumin, the most common solder in laser surgery, on platelet activation. STUDY DESIGN/MATERIALS AND METHODS: Platelet activation was evaluated in canine blood by using two-color flow cytometry with a phycoerythrin-labeled antibody to a common platelet marker, glycoprotein IIb/IIIa and fluorescein isothiocyanate-labeled antibody to a platelet activation molecule, P-selectin. Human serum albumin was applied in vitro and in vivo, as a solder during laser reconstruction of canine arteries. RESULTS: In vitro, albumin significantly (P < 0.01) reduces the expression of P-selectin on platelets. This is most likely related to the blockage of P-selectin by albumin, which binds to the platelet surface, as confirmed by flow cytometry with fluorescein isothiocyanate-labeled albumin. In vivo, application of albumin solder tended to result in a lower percentage of P-selectin-expressing platelets in laser-repaired arteries compared to suture-repaired arteries. CONCLUSION: Albumin decreases the percentage of P-selectin-expressing platelets in vitro. Further research may allow the platelet activation inhibiting properties of albumin to be further optimized in vivo.
Tissue plasminogen activator and plasminogen activator inhibitor in patients with acute ischemic stroke: relation to stroke etiology.
Recent studies suggest that high plasma levels of tissue-type plasminogen activator (tPA) and its inhibitor (plasminogen activator inhibitor-1, PAI-1) are markers of an increased risk of atherothrombotic ischemic events such as stroke and myocardial infarction. In this prospective study, we measured tPA antigen, PAI-1 antigen and activity, as well as tPA/PAI-1 complex in patients with acute stroke. Stroke subtypes were classified according to the TOAST criteria. From 132 consecutively screened patients, 89 (100%) were enrolled in this study, including 42 patients (47%) with large artery atherosclerosis (LAA), 32 (36%) with small vessel occlusion (SVO), and 15 (17%) with cardioembolism (CE). Nineteen age-matched neurologic patients without manifestations of cerebrovascular disease served as control subjects (CS). Patients with acute stroke had significantly higher plasma levels of tPA antigen (p < 0.001), PAI-1 antigen (p < 0.05) and PAI activity (p < 0.05) than patients in the control group. t-PA antigen, PAI activity and tPA/PAI-1 complex levels were similar regardless of stroke etiology. Only PAI-1 antigen was lower in patients with cardioembolic stroke than in stroke patients with LAA (p < 0.05). Plasma tPA antigen, PAI-1 antigen, and PAI activity are significantly increased in patients with acute ischemic stroke. Except for PAI-1 antigen, this increase appears not to be related to the underlying stroke etiology.
Broiler stunning and meat quality.
The effects of electrical and concussion stunning on meat and carcass quality of broilers were compared. Broiler chickens (n = 165) were subjected to treatments: 1) electrical stunning with no fibrillation, 2) electrical stunning with fibrillation, 3) concussion stunning with restraint, or 4) concussion stunning with no restraint. Electrical stunning (100 V, 80 mA, 50 Hz sinusoidal waveform alternating current) was applied for 3 s. Concussion was applied using a nonpenetrative captive bolt gun with or without restraint. We assessed broken bones, hemorrhages, meat quality defects, blood loss, pH at 10 min and 24 h, and texture from breasts filleted 3 h and 24 h postmortem. Electrically stunned birds showed a significantly higher incidence of broken bones (P < 0.0001), coracoid and furculum bone hemorrhages (P < 0.0001), and nonbone hemorrhages (P < 0.0001) than birds stunned by concussion. However, the incidence of red wing tips (P < 0.005) and shoulder hemorrhages was significantly higher (P < 0.05) in concussion-stunned birds than electrically stunned birds. Electrically stunned and nonfibrillated birds had the fastest blood loss rate. The pH value at 10 min was the lowest in concussion-stunned and unrestrained birds. Breast muscles from concussion-stunned birds that were filleted at 3 h postmortem were more tender than those from birds stunned electrically (P < 0.05). We concluded that concussion stunning could be advantageous for early filleting.
Are endoscopic biopsies of small bowel as good as suction biopsies for diagnosis of enteropathy?
BACKGROUND: Endoscopy is increasingly used in paediatric practice for diagnosis of enteropathy, although the quality of grasp forceps-obtained biopsy specimens required for reliable diagnosis has been questioned in comparison with suction capsule biopsy specimens. This study prospectively compared the diagnostic suitability of grasp forceps biopsy versus suction biopsy in the same patient during the same procedure. METHODS: A double-port paediatric suction biopsy capsule was front-loaded onto an endoscope and directed to the fourth part duodenum-proximal jejunum for biopsy sampling. Subsequently, three grasp biopsy specimens were taken from the same region. All biopsies were coded, photographed, and measured for area, using computed morphometry. A single blinded histopathologist assessed sample adequacy for diagnosis. Twenty-nine patients were enrolled (age range, 8-185 months). RESULTS: On three occasions the suction capsule failed to fire, and on four occasions only one sample was obtained. Three grasp biopsy specimens were obtained on each occasion by endoscopy, and the first two were used for comparison with suction biopsy samples. Median total area of individual biopsy samples obtained by the two procedures was not different (21.3 vs. 22.5 mm2; P = 0.027). Muscularis mucosae was obtained more commonly with grasp biopsies (P<0.001), and no difference was observed for the presence of three or more villus-crypt units, degree of haemorrhage, or optimal orientation. Two suction biopsy procedures and one grasp biopsy procedure were inadequate for diagnosis. CONCLUSIONS: Endoscopic grasp biopsies are perfectly adequate for the assessment of small intestinal histology. In addition, endoscopy affords advantage in diagnosis of other upper gastrointestinal disease with avoidance of radiologic screening involved with the suction capsule technique.
Resection rates in lung cancer.
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Acute anaphylaxis following midline catheterisation in a patient with cystic fibrosis.
A 16 year old male with cystic fibrosis experienced an acute life threatening anaphylactic reaction following the insertion of an Ohmeda Hydrocath(TM) midline peripheral venous catheter. The catheter was immediately withdrawn and treatment with intravenous adrenaline, hydrocortisone, chlorpheniramine, and colloid over a 24 hour period resulted in a gradual resolution of symptoms.
Progression of diabetic nephropathy. Insights from cell culture studies and animal models.
Nephropathy in patients with type I and II diabetes mellitus is a rapidly increasing problem worldwide. Studies using both glomerular and tubular cells have delineated some of the consequences induced by acute hyperglycemia. In vitro studies have clearly demonstrated that exposure of cultured renal cells, such as glomerular mesangial cells and proximal tubular epithelial cells, to elevated glucose concentrations, may alter cell proliferation and/or extracellular matrix turnover. The latter is effected both directly and indirectly by the alteration of cytokine generation. Furthermore, these in vitro studies have allowed detailed examination of the mechanisms by which exposure of these cells to high ambient glucose concentrations may alter cell function. Extension of these studies to the experimental in vivo situation has confirmed most of the in vitro findings. Important insights gained from models of type I diabetes (i.e. streptocotocin-induced diabetes) as well as type II diabetes (i.e. Goto-Kakizaki (GK) rats and obese Zucker rats) include: (1) The demonstration that increased glomerular cell proliferation and renal matrix accumulation, driven by TGF-beta and/or PDGF, occur in streptocotocin-induced diabetes, yet that nephropathy in these rats does not progress to renal failure. (2) The demonstration that prolonged mild type II diabetes does induce morphological changes characteristic of pre-clinical diabetic nephropathy in GK-rats but does not result in albuminuria or progressive renal disease. (3) The demonstration that the association of type II diabetes with hyperlipidemia in obese Zucker rats results in early podocyte damage and subsequent progression to glomerulosclerosis, tubulointerstitial damage, and renal insufficiency. Identification of the mediators involved in the above processes and in particular of the conditions that will determine progression of subclinical morphological changes to overt nephropathy and renal failure will likely result in future novel therapeutic approaches to diabetic nephropathy.
Cellular expression of a leech netrin suggests roles in the formation of longitudinal nerve tracts and in regional innervation of peripheral targets.
Netrins are secreted, diffusible proteins that direct axonal growth. To study the functions of netrins in the relatively simple and easily accessible nervous system of the leech Hirudo medicinalis, we have cloned a leech netrin and have characterized its expression during embryogenesis. By probing a leech cDNA library at low stringency with chick netrin probes, we have identified a complete cDNA clone that bears significant sequence similarity to netrins of other species. In situ hybridization and dye filling of individual neurons show that this leech netrin is expressed by several identifiable central neurons in every segmental ganglionic primordium during early stages of embryogenesis. Some of these neurons, including the bipolar cells which are thought to be involved in setting up longitudinal tracts, express this gene only transiently during embryogenesis, while others continue to express it in the adult. In addition, leech netrin is expressed by ventral but not dorsal longitudinal muscle cells in each segment before central neurons project their axons to the periphery. These highly specific expression patterns are consistent with the hypothesis that leech netrin plays a role in forming the major interganglionic neuronal tracts and in defining ventral versus dorsal domains of peripheral innervation.
Disease progression and survival in HIV-1-infected Africans in London.
OBJECTIVE: To examine differences in progression to AIDS and death between HIV-1-positive Africans (most infected in sub-Saharan Africa and therefore with non-B subtypes) and HIV-1-positive non-Africans in London. DESIGN: Retrospective cohort study of 2048 HIV-1-positive individuals. SETTING: HIV-1-infected individuals attending 11 of the largest HIV/AIDS units in London. PATIENTS: Subjects were 1056 Africans and 992 non-Africans seen between 1982-1995. RESULTS: There were no differences in crude survival from presentation to death between Africans and non-Africans (median 82 and 78 months, respectively; P = 0.22). Africans progressed more rapidly to AIDS [hazard ratio (HR), 1.21; 95% confidence interval (CI), 1.02-1.45] but after adjustment for age, sex, Centers for Disease Control and Prevention category B symptoms and CD4+ lymphocyte count at presentation, year of HIV diagnosis and hospital attended, this difference was no longer significant (adjusted HR, 1.15; 95% CI, 0.93-1.43). Africans with AIDS had a reduced risk of death compared with non-Africans (HR, 0.78; 95% CI, 0.63-0.96) but not after adjustment for age, CD4+ lymphocyte count at AIDS, initial AIDS-defining conditions (ADC) and hospital attended (HR, 0.98; 95% CI, 0.76-1.27). Tuberculosis as the first ADC was associated with a 64% reduction in the risk of death. CD4+ lymphocyte decline was not significantly different between Africans and non-Africans (P = 0.18). CONCLUSIONS: Differences in progression to AIDS and death and CD4+ lymphocyte decline between HIV-1-infected Africans and non-Africans in London could not be attributed to ethnicity or different viral subtypes. Age and the clinical and immunological stage at presentation, or AIDS, were the major determinants of outcome. Compared with other diagnoses, tuberculosis as the initial ADC was associated with increased survival. Lack of access to health care and exposure to environmental pathogens are the most likely causes of reduced survival with AIDS in Africa, rather than inherently different rates of progression of immune deficiency due to racial differences or viral subtypes.
Dual resistance to zidovudine and lamivudine in patients treated with zidovudine-lamivudine combination therapy: association with therapy failure.
Human immunodeficiency virus type 1 (HIV-1) strains dually resistant to zidovudine and lamivudine (3TC) may arise during zidovudine-3TC combination therapy. The objective of this cross-sectional study (n = 43 patients) was to test the association between therapy response (clinical and immunologic) to zidovudine-3TC and the level of phenotypic zidovudine resistance and zidovudine resistance-associated genotype of 3TC-resistant isolates. Other variables included were baseline CD4+ cell count, baseline Centers for Disease Control and Prevention (CDC) classification, virus load, and time receiving zidovudine. Phenotypic resistance was assessed using a recombinant virus assay. Genotypic analysis was based on population sequencing of plasma HIV-1. In a univariate analysis using a logistic regression model, it was found that therapy response was significantly associated with phenotypic and genotypic zidovudine resistance, baseline CD4+ cell count, and virus load. After adjustment for all variables, phenotypic resistance to zidovudine remained the only significantly associated factor, independent of baseline CD4+ cell count, baseline CDC classification, and virus load.
Intraventricular quinupristin/dalfopristin for the treatment of vancomycin-resistant Enterococcus faecium shunt infection.
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