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Biomedical subjects

R Williams

Publications and source records attributed to R Williams.

At least 307 records · Page 17Linked to original sources
PubMed1998

A 20.7 kb deletion within the factor VIII gene associated with LINE-1 element insertion.

Large deletions within the factor VIII gene account for approximately 5% of the mutations causing haemophilia A. The characterization of such mutations can provide insights into the molecular mechanisms of these and other deletions in man. We have analyzed a 20.7 kb deletion spanning exons 15 to 20 within the factor VIII gene in a patient with severe haemophilia A. Long range PCR was used to investigate the extent of the deletion and to provide a template for sequencing across the deletion breakpoint. A 38-base insertion homologous to the 3' region of a LINE-1 (L1) element was detected at the breakpoint of the deletion. Normal sequence at the 5' breakpoint in intron 14 was homologous to an L1 flanking region and normal sequence at the 3' breakpoint in intron 20 was homologous to an adjacent sequence within the same L1 flanking region. A molecular mechanism for the deletion involving retrotransposition of a readthrough product of an L1 element plus its 3' flanking region is suggested.

Base Sequence↗
PubMed1998

Cutaneous lesions in swine after decompression: histopathology and ultrastructure.

A detailed histopathologic description of skin lesions from a porcine model of decompression sickness (DCS) is presented. Pigs were dived in a dry chamber on a variety of profiles over an 11-mo period, with a 0.1-0.6 (10-60%) incidence of cutaneous lesions. The clinical appearance of the lesions evolved from irregular, sharply demarcated areas of erythema to violaceous and, eventually, darkly mottled macules. The lesions were biopsied under deep, sedative anesthesia. Histologic abnormalities were found in 91% (20/22) of the biopsies from clinically apparent cutaneous lesions. Vascular congestion was the most common finding. Focal areas of vasculitis were noted in 45% (10/22) of the lesions. Perivascular neutrophil infiltrates, edema, and occasionally, hemorrhage were also noted. Ultrastructural abnormalities were found in all of the lesions studied. Acute inflammation affecting the dermal vasculature was the most common finding. Platelets were rarely observed aggregating within vessels. The clinical and histologic features of cutaneous lesions in pigs after decompression are compared with previous accounts in humans. The model provides a useful tool for the study of cutaneous lesions in DCS and may be a means of exploring interventions in the disease.

Animals↗
PubMed1998

Halothane-induced acute liver failure: continuing occurrence and use of liver transplantation.

BACKGROUND/AIMS: This study was aimed at determining if the frequency and pattern of acute liver failure (ALF) following halothane anaesthesia had decreased during the last 11 years in comparison with a previous series of 48 patients referred between 1965 and 1984 and whether clinical outcome had been altered by the introduction of liver transplantation. METHODS: Between January 1985 and December 1995, all patients with halothane-induced ALF admitted to the Liver Failure Unit at King's College Hospital were identified. Four other European liver transplant centres with a known interest in acute liver failure also provided data. RESULTS: Of the 18 patients admitted, the clinical data were complete in 15. Ten of these patients had at least one previous halothane anaesthesia with documented clinical complications following the earlier exposure in six. Four patients had been re-exposed to halothane within 1 month of the penultimate halothane anaesthesia. Of the 15 patients four survived with medical management alone and 11 patients fulfilled transplant criteria. Four of the latter group were not listed because of rapidly deteriorating medical state and died, and of the seven patients who were listed, three died without a liver becoming available and four were transplanted, one of whom survived. No patient who had grade 4 encephalopathy and a prothrombin time > 50 s survived without a transplant. The survey of the other European liver centres recorded a total of 19 patients with halothane-induced ALF including three cases reported in the literature. Of those, 13 patients had been transplanted with nine survivors. CONCLUSION: Cases of halothane-induced acute liver failure still occur, albeit at a lower frequency than previously, and the Committee on Safety of Medicines guidelines are not being followed. The results of transplantation in these patients are encouraging.

Adult↗
PubMed1998

Algorithm for nutritional support: experience of the Metabolic and Infusion Support Service of St. Jude Children's Research Hospital.

The Metabolic and Infusion Support Service (MISS) at St. Jude Children's Research Hospital was established in 1988 to improve the quality of nutritional support given to children undergoing therapy for cancer. This multidisciplinary group, representing each of the clinical services within the hospital, provides a range of services to all patients requiring full enteral or parenteral nutritional support. In 1991, the MISS developed an algorithm for nutritional support which emphasized a demand for a compelling rationale for choosing parenteral over enteral support in patients with functional gastrointestinal tracts. Compliance with the algorithm was monitored annually for 3 years, with full compliance defined as meeting all criteria for initiating support and selection of an appropriate type of support. Compliance rates were 93% in 1992, 95% in 1993 and 100% in 1994. The algorithm was revised in 1994 to include criteria for offering oral supplementation to patients whose body weight was at least 90% of their ideal weight and whose protein stores were considered adequate. Full support was begun if no weight gain occurred. Patients likely to tolerate and absorb food from the gastrointestinal tract were classified into groups defined by the absence of intractable vomiting, severe diarrhea, graft-vs.-host disease affecting the gut, radiation enteritis, strictures, ileus, mucositis and treatment with allogeneic bone marrow transplant. Overall, the adoption of the algorithm has increased the frequency of enteral nutritional support, particularly via gastrostomies, by at least 3-fold. Our current emphasis is to define the time points in therapy at which nutritional intervention is most warranted.

Algorithms↗
PubMed1997

Stimulatory effect of a specific substance P antagonist (RPR 100893) of the human NK1 receptor on the estradiol-induced LH and FSH surges in the ovariectomized cynomolgus monkey.

Utilizing a human NK1 receptor antagonist (RPR 100893), the present in vivo study was designed to test the hypothesis that endogenous substance P (SP) modulates the action of 17beta-estradiol in inducing luteinizing hormone (LH) and follicle stimulating hormone (FSH) surges in ovariectomized cynomolgus monkey. Plasma concentrations of LH and FSH as well as NK1 receptor antagonist and SP were measured during the development of the negative and positive feedback phases which follow a single administration of estradiol benzoate (50 microg/kg) to long-term ovariectomized monkeys. Daily administration by gastric intubation of 1 mg/kg or 10 mg/kg of the NK1 receptor antagonist (RPR 100893) leads to detectable levels of the antagonist in the blood of treated animals for at least 6 hr after its administration. These levels are in agreement with the experimentally determined IC50 value of the antagonist. The most striking finding of this study is that LH and FSH releases are enhanced during the descending arm of the estradiol benzoate-induced LH and FSH surges, which suggests that endogenous SP normally has an inhibitory role during this time. The enhancement of LH release is approximately 50%, regardless of the amount of the NK1 antagonist used. However, the enhanced FSH release is more important. Furthermore, blockade of the NK1 receptor with the smaller dose of the antagonist leads to a small, but significant, increase in plasma levels of SP, indicating that blockade of SP receptors leads to an increased release of SP. Collectively, these results further substantiate the link which exists between the ovarian steroid 17beta-estradiol and SP systems. Also, for the first time, these results demonstrate an inhibitory involvement of the human NK1 receptor in the 17beta-estradiol-induced pseudo-ovulatory gonadotropin surges in the ovariectomized monkey.

Animals↗
PubMed1997

Clinical characteristics affecting the outcome of liver retransplantation.

BACKGROUND: The outcome of retransplantation remains unsatisfactory when compared with primary transplantation of the liver. The aim of the present study was to determine which preoperative clinical and laboratory risk variables are implicated in the poorer outcome. METHODS: The preoperative status of 70 retransplanted patients was compared with a group of 303 time-matched recipients receiving their first graft. RESULTS: Survival at 1 year was reduced in the retransplant versus the primary transplant group (50% vs. 80%, P<0.001). Preoperatively older age, high United Network of Organ Sharing score, inpatient status, elevated bilirubin, and creatinine levels were associated with increased mortality after a second transplant. Preoperatively, the retransplant group had higher encephalopathy grades, were more likely to be inpatients, and had higher serum creatinine, bilirubin, and white cell levels than the primary recipients (P<0.05 in all cases). The median length of inpatient stay was longer after the second transplant (25 vs. 19 days, P<0.001). CONCLUSIONS: These factors assist in the stratification of patients awaiting retransplantation; however, the outcome of this procedure is only likely to be improved with an earlier identification of the patients who require it, along with an increased priority in organ allocation.

Adolescent↗
PubMed1997

Air pollution exposure-DNA adduct dosimetry in humans and rodents: evidence for non-linearity at high doses.

The impact of air pollution exposure on the level of total DNA adducts in human white blood cells (WBCs) was evaluated in two populations in the Czech Republic and compared to the exposure-DNA adduct relationship in other populations in the US and China in human lung cells and rodent lung tissue. The human populations examined were exposed to respirable particles (< 2.5 microm) (PM2.5) in urban, rural, and occupational settings where the particles originated from coal and petroleum fuel combustion, coke production, and other coal-tar aerosols (e.g., used in aluminum production). These particles contain carcinogenic polycyclic aromatic hydrocarbons (PAHs) that are known to form DNA adducts through covalent binding. Personal exposure to PM2.5 and PAHs were measured prior to collection of blood samples for DNA adduct analysis by 32P-postlabeling. Coke oven workers (n = 76), in 10 job categories on the top and side of a coke oven in Ostrava, CZ, were studied and compared to a different population exposed to environmental levels of PAHs from air pollution in Teplice, CZ. Personal exposures to airborne particles ranged from < 1 to more than 15,000 microg/m3 and carcinogenic PAHs exposure ranged from < 5 to > 200,000 ng/m3. At low to moderate environmental exposures to carcinogenic PAHs, DNA adduct levels in the WBCs were significantly correlated with exposure. However, at the higher occupational levels found on the coke oven, the exposure-DNA adduct relationship became non-linear. Under these high exposure conditions, the relative DNA adduct level per unit of exposure (DNA-binding potency) was significantly lower than measured at environmental exposures. This finding is consistent with observations in lung cells from bronchoalveolar lavage of humans exposed to a wide range of PAH. This same high exposure-dose non-linearity was also observed in lung DNA from rats exposed by inhalation to a coal-tar pitch aerosol. DNA adduct levels in all these cases show evidence of a form of non-linearity at high doses that has been described by Lutz (W.K. Lutz, Dose-response relationship and low dose extrapolation in chemical carcinogenesis, Carcinogenesis, 11 (1990) 1243-1247) as a superlinear dose response. This superlinear response may be due to saturation of metabolic activation enzymes, induction of either DNA repair processes or detoxification enzymes, or other mechanisms. Regardless of the mechanism, this decrease in the DNA-binding potency at moderate to high doses of PAH has important implications for dose-response extrapolation in risk assessment.

Air Pollutants↗
PubMed1997

PHLS mycobacteriology reference services in England and Wales.

Tuberculosis (TB) is the most important cause of infectious disease in the world, with eight million new cases and three million deaths each year. The increasing incidence of TB in the developed and the developing world, increasing drug resistance, and the occurrence of nosocomial outbreaks of drug sensitive as well as drug resistant TB has led the PHLS to establish TB as a priority area. This article reviews the enhanced reference services for mycobacteriology provided by the PHLS in England and Wales. These include microscopy and culture on solid and liquid media, rapid culture systems, identification of mycobacteria using macroscopic, microscopic, growth, and biochemical characteristics, and molecular DNA analysis. The Mycobacterium Reference Unit (MRU) provides rapid molecular DNA amplification techniques to identify Mycobacterium tuberculosis in specimens. All four PHLS Regional Centres test isolates for drug susceptibility. This work is quality controlled by MRU, which is one of the World Health Organisation's reference centres for global surveillance on drug resistance in tuberculosis. National data on drug resistance are collated through 'Mycobnet', a surveillance scheme run through the collaboration of PHLS and other UK reference centres and the PHLS Communicable Disease Surveillance Centre.

Bacteriological Techniques↗
PubMed1997

Comparison of a new quantitative cytomegalovirus DNA assay with other detection methods.

OBJECTIVE: We assessed a new cytomegalovirus (CMV) DNA hybridization assay. We also compared the assay with other currently used assays to determine its use in the early detection of active CMV infection. PATIENTS AND METHODS: Sequential whole blood samples collected from 109 patients who had undergone orthotopic liver transplantation were tested using the Murex hybrid capture system, cell culture, antigen detection, and serology. Liver biopsies performed during the study period for graft dysfunction in 84 patients were examined for histological features of CMV hepatitis. The biopsies were also immunostained for the presence of CMV antigens. RESULTS: Fifteen patients developed clinically significant CMV disease (CMV syndrome in six patients and CMV hepatitis in nine patients, including two patients with disseminated CMV disease). In all 15, CMV DNA was detected by the hybrid capture assay between 1 and 20 days before other CMV assays. Fourteen of the 15 patients had CMV DNA levels greater than 50 pg/ml; the other patient had a value of 48 pg/ml. Of the remaining 94 patients with no evidence of CMV disease, 86 were negative by the hybrid capture assay and 8 were positive; all but one patient had values less than 50 pg/ml. DNA levels fell rapidly in all patients during antiviral therapy. CONCLUSION: Unlike conventional CMV detection methods, this hybridization assay is an early predictor of clinically significant CMV infection after liver transplantation and also provides quantitation of viral load, allowing monitoring of antiviral therapy.

Antibodies, Viral↗
PubMed1997

Identification of a chicken homologue in the Brn-3 subfamily of POU-transcription factors.

Among the many transcription factors thus far identified several are found to be expressed almost exclusively in the nervous system. The Brn-3 subfamily of POU-transcription factors constitutes a highly conserved group of such factors showing expression predominantly in sensory neurons. We now describe the nucleotide sequence and proposed amino acid sequence of a chicken homologue to the murine and human Brn-3 genes. Furthermore we characterise the early embryonic expression pattern of this chicken Brn-3 gene and show it to be expressed in peripheral sensory ganglia as well as in retinal ganglion cells. Based on these findings we conclude that the chicken homologue to the murine and human Brn-3a genes has been cloned. We have begun to examine possible regulatory pathways of Brn-3a by stimulating chick embryonic peripheral ganglia with trophic factors and assaying resulting levels of Brn-3a with a quantitative PCR approach. Trigeminal and dorsal root ganglia stimulated in culture by NGF and NT-3 embryonic day 9 (E9) produce neurites without raising the Brn-3a mRNA levels.

Amino Acid Sequence↗
PubMed1997

Interleukin-12 induction of Th1 cytokines is important for viral clearance in chronic hepatitis B.

Interleukin-12, a cytokine with an important role against intracellular pathogens, promotes Th1 cell development, cellmediated cytotoxicity, and interferon-gamma production. We investigated the immunoregulatory role of IL-12 in 72 chronic hepatitis B virus (HBV) carriers, 33 of whom were monitored longitudinally during interferon-alpha treatment. Serum levels of IL-12 heterodimer, IL-12 p40 subunit, IL-4, and Th1 cytokines were determined by specific ELISAs, and hepatitis B core antigen-specific T cell response by a proliferation assay. Chronic HBV carriers had higher serum levels of IL-12 and IL-12 p40 in comparison with controls (P < 0.01), suggesting that IL-12 production is not impaired. The longitudinal analysis revealed a further substantial increase (> 2.5x baseline level) of bioactive IL-12 and Th1 cytokines in patients who cleared HBV and seroconverted to anti- hepatitis B e, unlike the 23 nonresponders with persistent HBV replication (P < 0.01). The IL-12 peak followed the peak of hepatocytolysis by 9.8+/-2.8 wk and occurred either before or simultaneously with hepatitis B e seroconversion. Hepatitis B core antigen-specific T cell proliferation closely correlated with hepatocytolysis and increased significantly in all patients (8 responders and 15 nonresponders) who developed hepatitis flare, irrespective of the virological outcome. These results provide in vivo evidence that IL-12 may have an important role for viral clearance in chronic HBV infection.

Adult↗
PubMed1997

Intrasplenic hepatocyte allotransplantation in dalmation dogs with and without cyclosporine immunosuppression.

Hepatocyte allotransplantation has been performed successfully in several small animal models for the amelioration of inborn metabolic errors. Before a human clinical trial of hepatocyte allotransplantation can be attempted, preliminary experience in a large animal model is needed. We transplanted isolated mongrel hepatocytes into the spleen of dalmatians in the attempt to cure their inborn error of uric acid metabolism. Of 10 dalmatian recipients, two that received 9-10 x 10(9) mongrel hepatocytes died early after surgery of acute portal hypertension and hemorrhage. The eight long-term survivors received 5-6 x 10(9) hepatocytes and were randomized either to no treatment or to oral cyclosporine (CsA). Levels of CsA were adjusted to maintain trough levels between 400 and 800 ng/ml. In the four nonimmunosuppressed dalmatians, a reproducible average reduction in urinary uric acid excretion (UUAEx) of 23.7% was achieved; values returned to baseline within 14 days. In the CsA-immunosuppressed dalmatians, the average decline in UUAEx was 30%. The partial correction of the metabolic defect persisted for an average of 25 days in three immunosuppressed dogs, whereas in one dog, the partial correction lasted for over 90 days. No change in UUAEx was observed in two dalmatians that underwent sham laparotomy and intrasplenic injection of saline solution; CsA given alone to dalmatians did not modify UUAEx. We conclude that the dalmatian dog is a valuable large animal model for studies of the role of hepatocyte transplantation in the cure of inborn hepatic metabolic errors.

Animals↗
PubMed1997

Some DNA targets of the yeast CYP1 transcriptional activator are functionally asymmetric--evidence of two half-sites with different affinities.

CYP1 protein is a yeast transcriptional regulator which contains a zinc cluster in its DNA-binding domain. It was recently shown by selecting random CYP1 binding sites that CYP1 protein recognizes with a higher affinity targets containing the CGGNNNTANCGG consensus sequence. Notably, this ideal sequence is however not found in wild-type CYP1 target sites. In order to investigate how CYP1 protein actually binds to its targets, mutations were introduced in three of them (UAS1-A/CYC1, UAS1-A/CYB2, UAS/CYC7) and the consequences towards the binding of purified CYP1-(1-200)-peptide were analyzed. Our data support the following conclusions: (a) When the sequence element contains two CGGs and no TA, both CGGs are essential for binding. (b) If the sequence element contains only the right CGG and the TA, both are sufficient but indispensable for the binding of CYP1. (c) When two CGCs and the TA are present, the right CGC, and not the left one, is essential for the binding of CYP1. (d) CYP1-(1-200)-peptide is usually a monomer in solution but binds DNA as a dimer. Finally, we found evidence for the presence of two half-sites with different measured affinities in the asymmetric sequences of some CYP1 targets.

Base Sequence↗