Metabolic effects of ritodrine in the fetal lamb.

Ritodrine infusion to fetal lambs causes numerous metabolic perturbations including hypoxemia. To investigate these changes further and to elucidate a mechanism for the development of hypoxemia, ritodrine was infused at rate of 2.6 micrograms/min into nine chronically catheterized fetal lambs for 8, 12 or 24 hr. Plasma levels of ritodrine (20.0 +/- 2.7 ng/ml) were within the range of those reported in human fetuses exposed to ritodrine tocolysis. Fetal arterial glucose levels nearly doubled (0.72 +/- 0.07 to 1.29 +/- 0.18 mM), whereas lactate levels rose more than 5-fold (1.54 +/- 0.11 to 8.67 +/- 1.12 mM), with the latter change leading to a decline in fetal arterial pH from 7.370 +/- 0.004 to 7.273 +/- 0.033. Fetal oxygen consumption (VO2) rose from 342 +/- 35 to 407 +/- 30 mumol/min.kg via an increase in fetal fractional O2 extraction (32.0 +/- 1.1 to 49.0 +/- 1.7%). The rise in fetal O2 extraction contributed to concurrent declines in fetal arterial PO2 (21.9 +/- 0.6 to 17.0 +/- 0.5 mm Hg) and O2 content (3.7 +/- 0.2 to 2.1 +/- 0.1 mM). Umbilical venous PO2 and O2 content also fell resulting in a decline in fetal O2 delivery (DO2) from 1115 +/- 97 to 838 +/- 68 mumol/min.kg. The rise in fetal VO2 was reflected by a similar rise uterine VO2 (not significant), with the latter being accompanied by a significant increase in uterine O2 extraction and decrease in uterine venous PO2 and O2 content, perhaps contributing to the fall in fetal DO2. In conclusion, fetal hypoxemia during the infusion of ritodrine results from an increase in fetal VO2 that is not compensated for by a similar increase in umbilical or uterine DO2. These metabolic effects may put the fetus at risk, particularly in situations in which fetal DO2 is already reduced, as may occur in compromised pregnancies.     

A novel approach to data processing of the QT interval response in the conscious telemetered beagle dog

INTRODUCTION: Drug-induced QT interval prolongation may lead to ventricular arrhythmias. The aim of the study was to optimize QT interval data processing to quantify drug-induced QT interval prolongation in the telemetry instrumented conscious dog model. METHODS: The test substances cisapride, dofetilide, haloperidol, and terfenadine and corresponding vehicles were given to male and female beagle dogs during two consecutive 90-min intravenous infusions. Cardiovascular parameters were recorded for 24 h and exposure to the drugs was measured. The delayed response in the QT interval after an abrupt change in heart rate was investigated. Eight mathematical models to describe the QT interval-heart rate relationship were compared and different sets of covariates were used to quantify the drug-induced effect on the QT interval. RESULTS: After an abrupt decrease in heart rate, a 75% adaptation of the QT interval was reached after 54+/-9 s. A linear model was preferred to correct the drug-induced effect on the QT interval for heart rate, vehicle effect, serial correlation, plasma concentration and time of day. All test substances significantly prolonged the QT interval. DISCUSSION: To optimize the processing of QT interval data, the delay in QT interval response after an abrupt change in heart rate should be considered. The QT interval-heart rate relationship and vehicle response were individual-specific and corrections were therefore made individually. When estimating the drug-induced effect on the QT interval it is considered advantageous to use plasma concentration as a covariate, as well as adjusting for vehicle effect and serial correlation in measurements. The conscious dog model detected significant increases in the QT interval for all test substances investigated.     

rd1 mouse retina shows imbalance in cellular distribution and levels of TIMP-1/MMP-9, TIMP-2/MMP-2 and sulfated glycosaminoglycans

BACKGROUND: The rd1 mouse retina displays fast degeneration of photoreceptors resulting in a depletion of almost all rod photoreceptors by postnatal day 21 (PN21). To evaluate the role of proteinases in the pathophysiology of this animal model of retinitis pigmentosa, C3H rd1 and congenic wild-type (wt) mice retinas were analyzed. MATERIAL AND METHODS: The cellular localization and levels of proteins, matrix metalloproteinases (MMPs), their endogenous inhibitors (TIMPs), total sulfated glycosaminoglycans (sGAG) and nature of saccharides in rd1 and wt retinal extracts were compared. RESULTS: MMP-2/TIMP-2 and MMP-9/TIMP-1 were predominantly localized in the interphotoreceptor matrix (IPM) of both genotypes, but MMP-2/TIMP-2 also appeared in the Muller cell fibers of rd1 retina. In rd1 retinal extracts the levels of total proteins were lower and those of active MMP-9, MMP-2, TIMP-1 and total sGAG were higher than those of wt extracts. Despite an increase in TIMP-1, active MMP-9/MMP-2 were disproportionately elevated in rd1 compared to wt retina. With increasing age, MMPs in wt retinas were decreased but were increased in rd1. The sialylation of proteoglycans in PN2 and PN7 rd1 retinas was lower, and galactosylation was higher than that in wt retinas. CONCLUSIONS: MMP-9/MMP-2 and TIMP-1/TIMP-2 are associated with IPM, possibly after secretion by retinal pigmented epithelial cells. In degenerating rd1 retina, MMP-2/TIMP-2 are associated with the Muller cell fibers, which apparently play a central role in modifying the balance between MMPs and TIMPs. Elevated sGAG and proteolysis due to an imbalance in the levels of TIMPs and active MMP-9/MMP-2 in rd1 retina possibly contribute to retinal degeneration in the rd1 mouse.     

Epidemiology and heritability of astigmatism in Norwegian twins: an analysis of self-reported data

PURPOSE: To describe the occurrence and heritability of astigmatism in a population-based sample of Norwegian twins. METHODS: Self-reported history of astigmatism based on questionnaire responses was used to estimate the prevalence and incidence rates of astigmatism from birth through 31 years in 8,045 twins. Kaplan-Meier analysis and log-binomial regression were used to study the conditional and relative risk of astigmatism in twin pairs by sex and zygosity. Tetrachoric correlations and structural equation models were applied to estimate the genetic and environmental sources of variations in liability for astigmatism. RESULTS: Altogether 21.1% of males and 29.3% of females (p < 0.001) reported a positive history of astigmatism. Estimated incidence rates peaked in both sexes in the group aged 16-19 years and then decreased. Both conditional and relative risks of developing astigmatism were considerably higher in monozygotic than in dizygotic twins if a cotwin reported a positive history of astigmatism. The best-fitting biometrical model suggested that additive genetic, dominant genetic, and individual environmental effects explained 9% (95% CI: 0-40), 54% (95% CI: 20-69), and 38% (95% CI: 31-45) of the variation in the liability to astigmatism, respectively. No differences in heritability of astigmatism between the genders were found. CONCLUSIONS: The prevalence of self-reported astigmatism in twins is comparable with previous findings from Norway. Our results suggest considerable genetic contribution to the development of astigmatism in young adult Norwegian twins mainly due to dominant genetic effects, which are similar in both males and females.     

Clinical phenotype in a Swedish family with a mutation in the IMPDH1 gene

PURPOSE: Mutations in the inosine monophosphate dehydrogenase 1 gene (IMPDH1) have recently been discovered to cause a form of autosomal dominant retinitis pigmentosa (adRP). Such mutations are estimated to account for approximately 2-5% of the adRP cases among Americans of European origin and Europeans. Aiming towards an understanding of the molecular background of retinitis pigmentosa, this paper describes the phenotype of a Swedish family with a mutation in IMPDH1. METHODS: Venous blood samples were obtained from 12 family members and screened for mutations in IMPDH1. Six individuals with the mutation were examined clinically and with full-field electroretinography (ERG), dark adaptometry, multifocal electroretinography (mfERG), and optical coherence tomography (OCT). Also reviewed were the clinical findings and ERGs obtained 14 years earlier. RESULTS: The proband and eight other relatives from three generations were found to harbor the Asp226Asn mutation in IMPDH1. These individuals, from three generations, showed clinical and electrophysiological signs of retinitis pigmentosa. The cone responses to the full-field, 30-Hz flicker ERG demonstrated an unusual pattern, with implicit times within normal limits or only slightly prolonged. Rod ERG responses, however, were undetectable. OCT showed intraretinal fluid and swelling, changes that were more pronounced in younger individuals. mfERG showed residual preserved central function. The older the individual, the smaller the area of preserved central function. CONCLUSION: In this family with a mutation in IMPDH1, we found a specific phenotype with rod function affected more than cone function, foveal edema, and central retinal function preserved for a long period of time. Foveal edema could be a pathogenic feature in this form of retinal degeneration.     

Metoclopramide pharmacokinetics in pregnant and nonpregnant sheep

The pharmacokinetics of metoclopramide was studied in chronically instrumented pregnant and nonpregnant sheep. Metoclopramide was administered to the ewe by intravenous bolus injections (on a crossover basis) of 10, 20, and 40 mg, with an additional 80-mg dose to the nonpregnant animals. Transfer of the drug to the fetus was rapid with significant concentrations in fetal plasma 1 min after maternal dosing. The ratio of fetal-to-maternal area under the plasma concentration-time curves averaged 0.74, indicating significant fetal exposure to the drug. Maternal metoclopramide administration resulted in minimal fetal effects, with no change in arterial pressure, heart rate, or arterial pH or PCO2, and only a small (approximately 1.8 mmHg) transient decline in PO2. Plasma concentrations in maternal and fetal plasma in most animals were best described by a biexponential equation with rapid distribution and elimination phases. The terminal elimination half-lives in maternal and fetal plasma averaged 71.3 and 86.8 min, respectively, with fetal half-life being significantly longer. The number of fetuses present had no consistent effects on either maternal or fetal pharmacokinetic parameters. Total body clearance and volume of distribution averaged 3.5 L/h/kg and 5.8 L/kg, respectively, in the pregnant ewe, and 4.5 L/h/kg and 6.9 L/kg, respectively, in the nonpregnant animals. The terminal elimination half-life in the nonpregnant ewes averaged 67.5 min. Pharmacokinetic parameters were compared in the pregnant and nonpregnant ewes at the 10-, 20-, and 40-mg doses, and no significant differences were observed in the distribution or elimination rate constants, elimination half-life, or volume of distribution.(ABSTRACT TRUNCATED AT 250 WORDS)     

Linearity of metoclopramide kinetics at doses of 5-20 mg.

The disposition of metoclopramide was studied on a four-way crossover basis in six healthy non-smoking volunteers. The linearity of kinetic parameters and absolute bioavailability of metoclopramide were examined. In contrast to previous reports, metoclopramide obeyed linear kinetics over oral doses ranging from 5 to 20 mg. The absolute bioavailability of metoclopramide was 0.76 +/- 0.38 (mean +/- s.d.) from the oral dosage forms examined in this study.     

Neuroblastoma cell death in response to docosahexaenoic acid: sensitization to chemotherapy and arsenic-induced oxidative stress

Docosahexaenoic acid (DHA) is an omega-3 polyunsaturated fatty acid vital for the developing nervous system and significantly decreased in neuroblastoma cells compared to nontransformed nervous tissue. We investigated whether supplementation of DHA affects the susceptibility of neuroblastoma cells to oxidative stress generated endogenously and in response to cytotoxic therapy. DHA, but not the monounsaturated oleic acid (OA), induced dose- and time-dependent neuroblastoma cell death. DHA supplementation was associated with depolarization of the mitochondrial membrane potential, production of reactive oxygen species (ROS) and accumulation of DNA in sub-G1 phase of the cell cycle. The antioxidant, vitamin E, inhibited mitochondrial depolarization and subsequent cell death induced by DHA, whereas, the mitochondrial pore inhibitor, cyclosporin A, partly inhibited DHA-induced neuroblastoma cell death. Depletion of glutathione by L-buthionine-sulfoximine significantly enhanced the cytotoxic effects of DHA. Nontransformed fibroblasts were not substantially affected by DHA. DHA, but not OA, significantly enhanced the cytotoxicity of cisplatin, doxorubicin and irinotecan both in chemosensitive and in multidrug-resistant neuroblastoma cells. DHA potently sensitized neuroblastoma cells to a clinically relevant concentration (1 microM) of arsenic trioxide (As2O3) and enhanced the effect of the nonsteroidal antiinflammatory drug (NSAID), diclofenac. These findings provide experimental evidence that the omega-3 fatty acid, DHA, is cytotoxic to drug-resistant neuroblastoma. The potent action of DHA with arsenic trioxide, NSAID and chemotherapeutic agents suggests clinical testing of this therapeutic concept in children with neuroblastoma.     

Diagnostic accuracy of p16INK4a immunohistochemistry in oropharyngeal squamous cell carcinomas: A systematic review and meta‐analysis

The accurate diagnosis of human papillomavirus (HPV) causality in oropharyngeal squamous cell carcinomas (OPSCC) is likely to influence therapeutic decisions in affected patients in the near future. We conducted a systematic review and meta‐analysis to determine the diagnostic accuracy of p16^INK4a immunohistochemistry (IHC) to identify HPV‐induced OPSCC. We identified all studies that performed p16^INK4a IHC (index test) and HPV E6/E7 mRNA detection using an amplification‐based method (gold standard to indicate a transforming relevance of HPV) in OPSCC. Testing with one or more comparator tests (HPV DNA PCR, HPV DNA in situ hybridization (ISH) and p16^INK4a IHC/HPV DNA PCR combined testing) was an optional criterion for inclusion. Among 1,636 retrieved studies 24 fulfilled the inclusion criteria. The pooled sensitivity of p16^INK4a IHC, HPV DNA PCR, HPV DNA ISH and p16^INK4a IHC/HPV DNA PCR combined testing was 94% (95%‐confidence interval (CI) 91–97%), 98% (CI 94–100%), 85% (CI 76–92%) and 93% (CI 87–97%), respectively. The pooled specificity was 83% (CI 78–88%), 84% (CI 74–92%), 88% (CI 78–96%) and 96% (CI 89–100%), respectively. p16^INK4a IHC/HPV DNA PCR combined testing was as sensitive as either p16^INK4a IHC or HPV DNA PCR alone but significantly more specific than either separate test. In conclusion, p16^INK4a IHC is highly sensitive but moderately specific to diagnose HPV‐transformed OPSCC when used as a single test. Combined p16^INK4a IHC and HPV DNA PCR testing significantly enhances specificity while maintaining high sensitivity. This diagnostic test combination thus represents an attractive testing strategy for the reliable diagnosis of HPV‐induced OPSCC in the clinical setting and may constitute an inclusion criterion for future therapeutic trials.