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Biomedical subjects

P Clark

Publications and source records attributed to P Clark.

At least 91 records · Page 5Linked to original sources
PubMed1999

Topiramate pharmacokinetics in infants.

PURPOSE: This study's goal was to provide preliminary data on the pharmacokinetics of topiramate (TPM) in a cohort of infants (younger than 4 years) participating in an open-label trial of TPM in refractory infantile spasms. METHODS: The pharmacokinetics of TPM were assessed in infants receiving a stable TPM dose for >7 days during the extension phase of this trial. Blood samples were drawn just before and 0.5. 1, 1.5, 2, 4, 6, 8, and 12 h after the morning TPM dose. TPM plasma concentrations were determined by fluorescence polarization immunoassay. The noncompartmental analysis module of WinNonlin was used to calculate individual patient pharmacokinetics profiles. RESULTS: Five infants (ages, 23.5-29.5 months) formed the study cohort. These infants had been given TPM for a median of 9 months (range, 6-11 months) and were currently receiving between 11 and 38.5 mg/kg/day TPM. One was receiving TPM monotherapy, whereas four were taking concomitant antiepileptic medications (AEDs; n = 2, enzyme-inducing agents; n = 2, non-enzyme-inducing drugs). TPM pharmacokinetics in infants appears to be linear. In this cohort, mean TPM plasma clearance (CL/F, 66.6+/-27.4 ml/h/kg) was slightly higher than that reported for children and adolescents and therefore substantially higher than that reported for adults. TPM CL/F was higher and the calculated half-life shorter in the infants receiving concomitant enzyme-inducing AEDs. CONCLUSIONS: Based on this small cohort of patients, it appears that infants may require significantly larger TPM doses, based on weight, than children, adolescents, or adults. Titration to effect and not absolute TPM dose should guide therapy in this age group.

Adolescent↗
PubMed1999

Missense mutations in the insulin promoter factor-1 gene predispose to type 2 diabetes.

The transcription factor insulin promoter factor-1 (IPF-1) plays a central role in both the development of the pancreas and the regulation of insulin gene expression in the mature pancreatic beta cell. A dominant-negative frameshift mutation in the IPF-l gene was identified in a single family and shown to cause pancreatic agenesis when homozygous and maturity-onset diabetes of the young (MODY) when heterozygous. We studied the role of IPF-1 in Caucasian diabetic and nondiabetic subjects from the United Kingdom. Three novel IPF-1 missense mutations (C18R, D76N, and R197H) were identified in patients with type 2 diabetes. Functional analyses of these mutations demonstrated decreased binding activity to the human insulin gene promoter and reduced activation of the insulin gene in response to hyperglycemia in the human beta-cell line Nes2y. These mutations are present in 1% of the population and predisposed the subject to type 2 diabetes with a relative risk of 3.0. They were not highly penetrant MODY mutations, as there were nondiabetic mutation carriers 25-53 years of age. We conclude that mutations in the IPF-1 gene may predispose to type 2 diabetes and are a rare cause of MODY and pancreatic agenesis, with the phenotype depending upon the severity of the mutation.

Adult↗
PubMed1998

Impaired activation of NFkappaB in T cells from a subset of renal cell carcinoma patients is mediated by inhibition of phosphorylation and degradation of the inhibitor, IkappaBalpha.

Activation of the transcription factor NFkappaB in peripheral blood T cells from patients with renal cell carcinoma (RCC) is compromised. This impaired signaling function results from a failure of RelA and c-Rel to translocate to the nucleus though normal levels of Rel proteins are present in the cytoplasm. We demonstrate here in a subset of RCC patients that the defect in NFkappaB activation is attributable to the absence of phosphorylation and degradation of the inhibitor IkappaBalpha. In patient T cells there was no stimulus dependent decrease in the cytoplasmic level of IkappaBalpha. Coimmunoprecipitation studies showed that RelA was in complex with IkappaBalpha and was not released after stimulation. Moreover, the phosphorylated form of IkappaBalpha detected in normal T cells after activation is absent in patient T cells. Additional experiments showed that soluble products from RCCs (RCC-S) can reproduce the same phenotype in T cells from healthy individuals. Supernatant fluid from cultured explants of RCC, but not normal kidney, inhibited the stimulus dependent nuclear translocation of NFkappaB without altering the cytoplasmic levels of RelA, c-Rel, and NFkappaB1. Phosphorylation and degradation of IkappaBalpha was also blocked by RCC-S. The mechanistic similarities between patient-derived T cells and normal T cells cultured with RCC-S suggest that the tumor-derived products may be the primary mediators of impaired T-cell function in this tumor system.

Biological Transport↗
PubMed1998

The association of asymptomatic bacterial vaginosis with upper genital tract infection.

Objective: To determine whether asymptomatic bacterial vaginosis (BV) is associated with upper genital tract inflammation or bacterial colonization.Methods: Fifty nonpregnant women with intact uteri who planned to undergo gynecologic surgery and had no recent symptoms of vaginal infection were enrolled. We obtained a vaginal swab for Gram stain, endocervical swab for chlamydia and gonorrhea DNA probe testing, and Pipelle endometrial biopsy for aerobic and anaerobic cultures and histology. We correlated surgical findings and histology of available surgical specimens with the microbiologic results. The diagnosis of BV was made according to Speigel's criteria. Bacteria isolated from the uterus were classified as high virulence versus low virulence. Contingency tables were analyzed using the chi-square or Fisher Exact tests.Results: Twenty-one of 50 patients had BV on Gram stain, 3 had intermediate BV, and 3 had unreadable slides. Eleven patients had histologic endometritis, including 7 of the 21 with BV. The association between BV and endometritis was not statistically significant. Thirty-eight patients had a positive endometrial culture; 18 of these also had BV and 3 had intermediate BV. Of patients with a positive endometrial culture, isolates from those who also had BV or intermediate BV were more likely to be highly virulent pathogens compared to those who tested negative for BV (P <.05). No patients had positive gonorrhea or chlamydia tests. Of the 37 patients who underwent abdominal surgery, 20 had visible adhesions. The association between adhesions and endometritis, BV, or positive endometrial cultures was not significant.Conclusion: Patients with asymptomatic BV are more likely than patients without BV to have highly virulent bacteria isolated from the endometrium. BV may predispose to upper genital tract infection.

Journal Article↗
PubMed1998

The novel combination of fat clearance and immunohistochemistry improves prediction of the outcome of patients with colorectal carcinomas: a preliminary study.

To evaluate the significance of micrometastases in relation to survival rate, specimens from 48 colorectal carcinoma patients were analysed after fat clearance. The number and size of the lymph nodes harbouring metastases and the significance of micrometastases for patients' survival were assessed. We found that although the majority of metastatic lymph nodes (71.8%) were 5 mm or less in diameter, their size had no effect on survival. Immunohistochemical staining of lymph nodes revealed that 15 of 25 patients with Dukes' stage B diagnosed by routine staining had micrometastases, 86% of these lymph nodes being less than 5 mm in diameter. The survival rate of this subgroup was found to be considerably poorer than that of Dukes' stage B patients with no micrometastases. None of the three patients with Dukes' stage A carcinoma had micrometastases. Since most of the metastases and micrometastases occur in lymph nodes of 5 mm and less and can be easily missed by routine examination, we suggest that fat clearance and routine immunohistochemical analysis of Dukes' stage B improve the prediction of outcome of colorectal cancer patients.

Aged↗
PubMed1998

A randomized trial comparing methotrexate and vinblastine (MV) with cisplatin, methotrexate and vinblastine (CMV) in advanced transitional cell carcinoma: results and a report on prognostic factors in a Medical Research Council study. MRC Advanced Bladder Cancer Working Party.

Transitional cell carcinomas may arise at any site within the urinary tract and are a source of considerable morbidity and mortality. In particular, patients with metastatic disease have a poor prognosis, with less than 5% alive at 5 years. A multicentre randomized trial comparing methotrexate and vinblastine (MV) with cisplatin, methotrexate and vinblastine (CMV) in advanced or metastatic transitional cell carcinoma was conducted in the UK. From April 1991 to June 1995, 214 patients were entered by 16 centres, 108 randomized to CMV and 106 to MV. A total of 204 patients have died. The hazard ratio (relative risk of dying) was 0.68 (95% CI 0.51-0.90, P-value = 0.0065) in favour of CMV. This translates to an absolute improvement in 1-year survival of 13%, 16% in MV and 29% in CMV. The median survival for CMV and MV was 7 months and 4.5 months respectively. Two hundred and eight patients objectively progressed or died. The hazard ratio was 0.55 (95% CI 0.41-0.73, P-value = 0.0001) in favour of CMV. Two hundred and nine patients symptomatically progressed or died. The hazard ratio was 0.48 (95% CI 0.36-0.64, P-value = 0.0001) in favour of CMV. The most important pretreatment factors influencing overall survival were WHO performance status and extent of disease. These two factors were used to derive a prognostic index which could be used to categorize patients into three prognostic groups. We conclude that the addition of cisplatin to methotrexate and vinblastine should be considered in patients with transitional cell carcinoma, taking into account the increased toxicity.

Aged↗
PubMed1998

Allogeneic bone marrow transplantation vs filgrastim-mobilised peripheral blood progenitor cell transplantation in patients with early leukaemia: first results of a randomised multicentre trial of the European Group for Blood and Marrow Transplantation.

In a multicentre trial involving 20 transplant centres from 10 countries haematopoietic stem cells were obtained either from the bone marrow of 33 sibling donors or from the peripheral blood of 33 such donors after administration of filgrastim (10 microg/kg/day). The haematopoietic stem cells were infused into their HLA-identical recipients suffering from acute leukaemias in remission or chronic myeloid leukaemia in chronic phase. PBPC donors tolerated filgrastim administration and leukapheresis well with the most frequent side-effects being musculoskeletal pain, headache, and mild increases of LDH, AP, Gamma-GT or SGPT. Pain and haematoma at the harvest site and mild anaemia were the most frequent complaints of BM donors. Severe or life-threatening complications were not seen with any type of harvest procedure. Time to platelet recovery greater than 20 x 10(9)/l was 15 days (95% confidence interval (CI) 13-16 days) in the PBPCT group and 19 days (CI 16-25) in the BMT group. Time to neutrophil recovery greater than 0.5 x 10(9)/l was 14 days (CI 12-15 days) in the PBPCT group as compared to 15 days (CI 15-16 days) in the BMT group. The numbers of platelet transfusions administered to PBPCT and BMT patients were 12 (range: 1-28) and 10 (range: 3-39), respectively. Sixteen patients (48%) transplanted with bone marrow and 18 patients (54%) transplanted with PBPC developed acute GVHD of grades II-IV; acute GVHD of grades III or IV developed in six (18%) and seven (21%) patients, respectively. Kaplan-Meier plots for transplant-related mortality until day 100 and leukaemia-free survival at a median of 400 days after BMT or PBPCT showed no significant differences. Administration of filgrastim and leukapheresis in normal donors were feasible and well tolerated. The number of days with restricted activity and of nights spent in hospital was lower in donors of PBPC. Transplantation of PBPC to HLA-identical siblings with early leukaemia resulted in earlier platelet engraftment. The incidence of moderate to severe acute GVHD, transplant-related mortality, and leukaemia-free survival did not show striking differences. Further investigation of allogeneic PBPCT as a substitute for allogeneic BMT is warranted.

Adolescent↗
PubMed1998

The neutrophil and preeclampsia.

Endothelial injury is common to all pathological features of preeclampsia. Neutrophil activation has been implicated in the pathophysiology of preeclampsia and requires binding and transmigration of neutrophils through the endothelium. This occurs via an interaction of endothelial adhesion molecules and surface receptors on neutrophils. Upon activation, neutrophil granules are released, the contents of which are capable of mediating vascular damage. In addition, leukotrienes are synthesized, and superoxide is generated in a respiratory burst. These products also provoke vascular damage. Neutrophil recruitment to the endothelium involves express of P-selectin and released of platelet activating factor from the endothelium. In preeclampsia there is evidence of an increase in neutrophil activation with up-regulation of neutrophil integrin expression and increased regulation of the protease elastase. Furthermore, these markers of neutrophil activation correlate with established markers of disease severity. The primary mechanism of neutrophil activation is unknown, but neutrophils in preeclampsia appear to have normal motor activity. Several potential mechanisms of neutrophil activation have been identified. They include up-regulation of cellular adhesion molecules on the endothelial surface, increased generation of tumor necrosis factor-alpha, and endothelial activation from hyperlipidemia. In additional to activation of neutrophils in preeclampsia, there may be involvement of the interleukin-6 and endothelin-1 in "priming" neutrophils for subsequent superoxide production. Activated neutrophils are likely to play a large part in the arteriopathy and endothelial damage associated with preeclampsia, but it is unclear whether neutrophil activation is the cause or the consequence of endothelial damage.

Biomarkers↗
PubMed1998

Capsular polysaccharide types of group B streptococcal isolates from neonates with early-onset systemic infection.

The distribution of serotypes of group B streptococci (GBS) isolated from 67 infants with early-onset sepsis are described. Case-infants were assembled from 13 hospitals across the United States from 15 July 1995 to 5 February 1997 through prospective active surveillance. The distribution of GBS serotypes was Ia, 40%; Ib, 9%; II, 6%; III, 27%; V, 15%; and nontypeable, 3%. Type V occurred more frequently in the northeast region (New York and New Jersey) than in other regions (29% vs. 9%, P = .06). Conversely, type III occurred significantly less frequently in the northeast region than other regions (10% vs. 35%, P = .04). GBS types Ia, III, and V accounted for 82% of the isolates. This report supports previous observations about the emergence of GBS type V, but our data caution that conclusions about serotype distributions based on one geographic location or on a small number of patients may not be generally applicable. Continued monitoring seems necessary for the design of a GBS vaccine.

Bacterial Capsules↗
PubMed1998

Activated protein C sensitivity, protein C, protein S and coagulation in normal pregnancy.

A prospective study of activated protein C sensitivity, protein C, protein S, and other coagulation factors in 239 women during normal pregnancy was carried out. Protein C activity appeared unaffected by gestation, although an elevation of protein C activity was observed in the early puerperium. A fall in total and free protein S with increasing gestation was observed. Activated protein C sensitivity ratio (APC:SR) showed a progressive fall through pregnancy. This fall correlated with changes in factor VIIIc, factor Vc and protein S. 38% of subjects, with no evidence of Factor V Leiden or anticardiolipin antibodies, showed a low APC:SR (APC:SR <2.6) in the third trimester of pregnancy. Aside from a significant reduction in birth weight, no difference in pregnancy outcome was observed between these subjects and those with a normal APC:SR. Activated protein C sensitivity ratio, modified by pre-dilution of patient samples with factor V depleted plasma, showed no consistent trend with gestation.

Birth Weight↗
PubMed1998

Risk factors for osteoporotic hip fractures in Mexicans.

BACKGROUND: Osteoporosis (OP) and its fractures are a major problem due to their impact in morbidity and mortality in the elderly. Although this entity is well studied in other countries, OP and its fractures have not been evaluated carefully in our population. The objective was to assess risk factors for osteoporotic hip fracture in Mexicans. METHODS: A total of 295 subjects, 152 cases and 143 controls, were studied. Cases were patients with hip fracture, of both sexes and 45 years of age or older. Controls were healthy subjects who were in hospital waiting rooms accompanying patients without hip fractures. A questionnaire covering known possible risk factors for osteoporotic hip fracture was administered by the same evaluator to all subjects. Pelvic roentgenograms, anterior-posterior view, were obtained in both cases and controls to perform the Singh index and the cortical index of the femur. RESULTS: Fractures were present in (72.2%) of women. Weight and any alcohol ingestion were associated with an increased risk of hip fracture. The odds ratio (OR) for low weight by the Quetelet Index was 4.03 (95% CI 1.93-8.39) p < 0.001. Any alcohol intake was associated with an OR of 1.73 (95% CI 1.04-2.90) p < or = 0.03 for the total group, and 2.78 (95% CI 1.25-6.14) p < or = 0.003 for women. Controls had a significantly higher mean daily calcium intake compared to cases (mean, SD 575.9 +/- 297.2 vs. 490.4 +/- 245.5, p < or = (0.007). Family history, smoking, physical activity, pregnancies, breastfeeding or concomitant diseases were not associated with risk of hip fracture. CONCLUSIONS: This study confirmed the risk factors for osteoporotic hip fracture in Mexicans, previously shown for other ethnic groups. Further research in different factors, such as rate of bone turnover, anthropometric dimensions, and genetic studies (osteoporosis gene) are needed in order to define the differences among ethnic groups.

Aged↗
PubMed1998

Prevalence of fibromyalgia in children: a clinical study of Mexican children.

OBJECTIVE: To determine the prevalence of fibromyalgia (FM) in schoolchildren according to the 2 stage classification process proposed by the 1990 American College of Rheumatology (ACR) Multicenter Criteria Committee on Fibromyalgia. METHODS: Stage 1: we administered a pain questionnaire to a sample of 548 schoolchildren (264 boys, 284 girls; mean age 11.9 yrs, range 9-15). Stage 2: two rheumatologists examined all children with diffuse pain. Using thumb palpation, they examined 18 fibromyalgia tender points and 3 pairs of controls points followed by dolorimetry. Additionally, a random sample of 79 children with no pain were selected as controls, following the same procedures (thumb palpation and dolorimetry). The Wilcoxon test was used to compare the distribution of tenderness thresholds between FM and non-FM groups. Kappa statistics for multiple raters was used to assess interobserver agreement. RESULTS: Seven children, all girls, fulfilled the ACR diagnostic criteria for FM. Thus, the prevalence of FM in this group of schoolchildren reached only 1.2%. The girls with FM had a mean of 14 tender points, whereas controls (n = 79) had 2.4. Pain thresholds were 3.4 kg in children with FM and 5.1 kg in controls (p = 0.004). CONCLUSION: The prevalence of FM in our study was 5-fold lower than a previous report. This variance may be due to (1) racial and sociocultural differences between populations; and (2) differences in methodological approach. The difficulties of making accurate estimates of FM across different studies are highlighted.

Adolescent↗