The role of size, sequence and haplotype in the stability of FRAXA and FRAXE alleles during transmission

Factors involved in the stability of trinucleotide repeats during transmission were studied in 139 families in which a full mutation, premutation or intermediate allele at either FRAXA or FRAXE was segregating. The transmission of alleles at FRAXA, FRAXE and four microsatellite loci were recorded for all individuals. Instability within the minimal and common ranges (0-40 repeats for FRAXA, 0-30 repeats for FRAXE) was extremely rare; only one example was observed, an increased in size at FRAXA from 29 to 39 repeats. Four FRAXA and three FRAXE alleles in the intermediate range (41-60) repeats for FRAXA, 31-60 for FRAXE) were unstably transmitted. Instability was more frequent for FRAXA intermediate alleles that had a tract of pure CGG greater than 37 although instability only occurred in two of 13 such transmissions: the changes observed were limited to only one or two repeats. Premutation FRAXA alleles over 100 repeats expanded to a full mutation during female transmission in 100% of cases, in agreement with other published series. There was no clear correlation between haplotype and probability of expansion of FRAXA premutations. Instability at FRAXA or FRAXE was more often observed in conjunction with a second instability at an independent locus suggesting genomic instability as a possible mechanism by which at least some FRAXA and FRAXE mutations arise.      

Nitric oxide mediates inhibitory nerve effects in human esophagus and lower esophageal sphincter

The effect of inhibition of nitric oxide synthase on nonadrenergic, noncholinergic nerve-mediated responses in circular smooth muscle of the human esophageal body and lower esophageal sphincter (LES) was examinedin vitro. Tissues were obtained from 10 patients (eight esophageal resection for cancer, two transplant donors). Muscle strips from the LES developed significant spontaneous tension (11.6 ± 2.1 mN/mm²,N=6) and relaxed in response to electrical stimulation. The nitric oxide synthase inhibitor,N -nitro-l-arginine (NNA), at 10^–5 M, inhibited the relaxation, but had no significant effect on the spontaneous tension (13.0 ± 2.6 mN/mm²,P=0.07). Esophageal body strips developed little spontaneous tension, demonstrated an off contraction following the cessation of the electrical stimulus, and when contracted with 10^–5 M carbachol, relaxed during electrical stimulation. NNA (10^–5 M) inhibited the off contraction and the relaxation seen after carbachol and unmasked a prominent intrastimulus contraction. This intrastimulus contraction was enhanced by eserine and inhibited by atropine and tetrodotoxin. NNA showed similar potency in the esophageal body and LES and its effects were reversed byl-arginine, but notd-arginine. The results indicate that nitric oxide is an important mediator for nonadrenergic, noncholinergic nerve effects in the human esophagus and lower esophageal sphincter.This research was supported in part by an ICI Pharma/Medical Research Council of Canada Research Fellowship grant awarded to H.G. Preiksaitis and a Medical Research Council Program Grant PG8.     

Tunicamycin Dissociates Depolarization-induced Calcium Entry From Transmitter Release. Involvement of Glycosylated Protein(s) in the Process of Neurosecretion in PC-12 Cells

The process of regulated secretion in PC-12 cells is tightly coupled to calcium entry, which is absolutely dependent on extracellular Ca2+([Ca2+]ex). Tunicamycin treatment of the cells dissociated depolarization-triggered Ca2+ influx from depolarization (high K+)-induced transmitter release into two distinct and independent phases. Deplarization-evoked Ca2+ influx was not affected by tunicamycin treatment (1 microg/ml, 72 h), whereas depolarization-evoked transmitter release was strongly inhibited (> 60%), suggesting at least a two-step process, and the participation of glycosylated protein(s) in the actual fusion/secretion step. Similarly, bradykinin-mediated transmitter release was linearly related to and absolutely dependent on Ca2+ entry, and was inhibited by tunicamycin treatment (> 80%), whereas bradykinin-evoked Ca2+ entry was not impaired, indicating that glycosylated protein(s) are essential for bradykinin-evoked release at a step subsequent to Ca2+ influx. The heavily glycosylated alpha2 subunit of the dihydropyridine-sensitive channel, which was used to monitor tunicamycin inhibition of glycosylation, was not expressed in the tunicamycin-treated cells, as shown by Western blot analysis. This observation allowed us to conclude that the alpha1 subunit of the heteromeric dihydropyridine voltage-sensitive Ca2+ channel, which is responsible for Ca2+ entry, is also fully functional when not assembled with its corresponding alpha2 subunit. The molecular properties of the alpha2 subunit, whose role in the complex structure of the channel is not yet understood, are shown for the first time for the L-type Ca2+ channel of PC-12 cells. Similar to cardiac and skeletal muscle cells, the alpha2 subunit appears to be a glycosylated polypeptide of molecular weight 170 kD and to display a characteristic mobility shift to 140 kD under reducing conditions.     

Muscle mass effect on arterial desaturation after maximal exercise.

We measured arterial oxygen saturation before and immediately after randomly allocated 6 min of "all-out" maximal arm cranking, treadmill running, and ergometer rowing in 10 men and women with a median maximal oxygen uptake of 4.47 (range 3.22-5.34) 1.min-1. Arterial saturation for oxygen was unaltered after arm cranking, but decreased 1.7 (-2.5-6.0) % (P less than 0.05) after running, and 2.2 (1.0-8.7) % (P less than 0.01) after rowing. Arterial saturation was inversely related to capillary blood lactate, which reached 11.8 (7.4-14.0), 12.6 (8.9-18 2), and 14.3 (12.0-19.3) mmol.l-1 (P less than 0.01), respectively, and arterial bicarbonate fell to 15.0 (13.0-23.6), 12.4 (7.2-20.4), and 10.8 (0.0-12.5) mmol.l-1 (P less than 0.01). Thus, pH decreased to 7.25 (7.22-7.40), 7.17 (6.95-7.35), and 7.09 (6.84-7.19) (P less than 0.01). When measured immediately post-exercise, arterial oxygen tension was unchanged or elevated from rest, eliminating the possibility that the arterial desaturation was caused by a pulmonary diffusion limitation. The results of this investigation show that arterial desaturation associated with maximal exercise takes place in proportion to the involved muscle mass, as do deviations in blood lactate, bicarbonate, and hydrogen concentrations.     

Nosocomial respiratory syncytial virus infection in Canadian pediatric hospitals: a Pediatric Investigators Collaborative Network on Infections in Canada Study

OBJECTIVE: To determine nosocomial transmission of respiratory syncytial virus (RSV) in Canadian pediatric hospitals, outcomes associated with nosocomial disease, and infection control practices. DESIGN: A prospective cohort study in the 1992 to 1994 winter respiratory seasons. SETTING: Nine Canadian pediatric university-affiliated hospitals. PARTICIPANTS: Hospitalized children with symptoms of lower respiratory tract infection (at least one of cough, wheezing, dyspnea, tachypnea, and apnea) and RSV antigen identified in a nasopharyngeal aspirate. RESULTS: Of 1516 children, 91 (6%) had nosocomial RSV (NRSV), defined as symptoms of lower respiratory tract infection and RSV antigen beginning >72 hours after admission. The nosocomial ratio (NRSV/[com-munity-acquired RSV {CARSV})] + NRSV) varied by site from 2.8% to 13%. The median length of stay attributable to RSV for community-acquired illness was 5 days, but 10 days for nosocomial illness. Four children with NRSV (4. 4%) died within 2 weeks of infection, compared with 6 (0.42%) with CARSV (relative risk = 10.4, 95% confidence interval: 3.0, 36.4). All sites isolated RSV-positive patients in single rooms or cohorted them. In a multivariate model, no particular isolation policy was associated with decreased nosocomial ratio, but gowning to enter the room was associated with increased risk of RSV transmission (incidence rate ratio 2.81; confidence interval: 1.65, 4.77). CONCLUSIONS: RSV transmission risk in Canadian pediatric hospitals is generally low. Although use of barrier methods varies, all sites cohort or isolate RSV-positive patients in single rooms. Children with risk factors for severe disease who acquire infection nosocomially have prolonged stays and excess mortality.     

Dynamic multistage scheduling for patient-centered care plans

We investigate the scheduling practices of multistage outpatient health programs that offer care plans customized to the needs of their patients. We formulate the scheduling problem as a Markov decision process (MDP) where patients can reschedule their appointment, may fail to show up, and may become ineligible. The MDP has an exponentially large state space and thus, we introduce a linear approximation to the value function. We then formulate an approximate dynamic program (ADP) and implement a dual variable aggregation procedure. This reduces the size of the ADP while still producing dual cost estimates that can be used to identify favorable scheduling actions. We use our scheduling model to study the effectiveness of customized-care plans for a heterogeneous patient population and find that system performance is better than clinics that do not offer such plans. We also demonstrate that our scheduling approach improves clinic profitability, increases throughput, and decreases practitioner idleness as compared to a policy that mimics human schedulers and a policy derived from a deep neural network. Finally, we show that our approach is fairly robust to errors introduced when practitioners inadvertently assign patients to the wrong care plan.

     

Intermittent fasting during Ramadan causes a transient increase in total,LDL, and HDL cholesterols and hs-CRP in ethnic obese adolescents

The radical change of lifestyle during Ramadan fast has shown to affect cardiometabolic risk variables in adults. In youth, however, no studies are available. We aimed to evaluate the effect of Ramadan fast on Body Mass Index (BMI) and the cardiometabolic profile of obese adolescents. A prospective cohort study was conducted. We measured weight, height, body composition, blood pressure, heart rate, glucose, insulin, total cholesterol, low-density lipoprotein (LDL) cholesterol and high-density lipoprotein (HDL) cholesterol, triglycerides, and high sensitivity C-reactive protein (hs-CRP) levels before, during the last week of and at 6 weeks after Ramadan. Twenty-five obese adolescents were included. BMI and glucose metabolism did not change after Ramadan or at 6 week after cessation of Ramadan. At the end of Ramadan, a significant decrease in body fat percentage was observed, while significant increases in heart rate, total cholesterol, LDL cholesterol, HDL cholesterol, and hs-CRP were found (all P?<?0.05). Six weeks after Ramadan, all parameters returned to baseline levels. Conclusion: In this sample of 25 ethnic obese adolescents transient cardiometabolic changes were observed during Ramadan fasting. Since most of these changes were reversible within 6 weeks, there seems no harm or benefit for obese adolescents to participate in Ramadan.