Separation of gating properties from permeation and block in mslo large conductance Ca-activated K+ channels

In this and the following paper we have examined the kinetic and steady-state properties of macroscopic mslo Ca-activated K+ currents in order to interpret these currents in terms of the gating behavior of the mslo channel. To do so, however, it was necessary to first find conditions by which we could separate the effects that changes in Ca2+ concentration or membrane voltage have on channel permeation from the effects these stimuli have on channel gating. In this study we investigate three phenomena which are unrelated to gating but are manifest in macroscopic current records: a saturation of single channel current at high voltage, a rapid voltage-dependent Ca2+ block, and a slow voltage-dependent Ba2+ block. Where possible methods are described by which these phenomena can be separated from the effects that changes in Ca2+ concentration and membrane voltage have on channel gating. Where this is not possible, some assessment of the impact these effects have on gating parameters determined from macroscopic current measurements is provided. We have also found that without considering the effects of Ca2+ and voltage on channel permeation and block, macroscopic current measurements suggest that mslo channels do not reach the same maximum open probability at all Ca2+ concentrations. Taking into account permeation and blocking effects, however, we find that this is not the case. The maximum open probability of the mslo channel is the same or very similar over a Ca2+ concentration range spanning three orders of magnitude indicating that over this range the internal Ca2+ concentration does not limit the ability of the channel to be activated by voltage.     

Large scale identification of genes involved in cell surface biosynthesis and architecture in Saccharomyces cerevisiae

The sequenced yeast genome offers a unique resource for the analysis of eukaryotic cell function and enables genome-wide screens for genes involved in cellular processes. We have identified genes involved in cell surface assembly by screening transposon-mutagenized cells for altered sensitivity to calcofluor white, followed by supplementary screens to further characterize mutant phenotypes. The mutated genes were directly retrieved from genomic DNA and then matched uniquely to a gene in the yeast genome database. Eighty-two genes with apparent perturbation of the cell surface were identified, with mutations in 65 of them displaying at least one further cell surface phenotype in addition to their modified sensitivity to calcofluor. Fifty of these genes were previously known, 17 encoded proteins whose function could be anticipated through sequence homology or previously recognized phenotypes and 15 genes had no previously known phenotype.     

Acute hemorrhagic pulmonary infarction and necrotizing pneumonia in horses: 21 cases (1967-1993)

Specimens of formalin-fixed, paraffin-embedded non-small-cell lung carcinomas (NSCLCs; n = 187) were analysed immunohistochemically for expression of cyclin A. The analysis was intended to determine whether cyclin A has additional prognostic value for predicting patients' survival and drug response. Of the 187 NSCLCs, 141 cases (75%) showed expression of cyclin A. Patients with cyclin A-positive carcinomas had significantly shorter median survival times than patients with cyclin A-negative carcinomas (79 vs 129 weeks, P = 0.045). Similar results were obtained with more homogeneous groups of patients: patients with only T3 tumours, patients with epidermoid carcinomas and patients with lymph node involvement. The clinical parameters (age, stage, histology, extent of tumour size, lymph node involvement) had no influence on expression of cyclin A. A direct correlation between cyclin A and the proportion of S-phase cells (P = 0.08) and an inverse relationship between cyclin A and the proportion of G0/G1-phase cells (P = 0.04) were found. Furthermore, a significant correlation between the expression of cyclin A and the response of NSCLC to doxorubicin in vitro was detected (P = 0.026).     

Effect of a nitric oxide synthase inhibitor and a glucocorticosteroid on exhaled nitric oxide

Nitric oxide (NO) is produced by a variety of cells within the respiratory tract, including inflammatory epithelial cells. NO has been detected in the exhaled air of normal human subjects, and its concentration is raised in asthmatic patients. To study whether exhaled NO arises from the respiratory tract, we administered a NO synthase (NOS) inhibitor, NG-monomethyl-L-arginine (L-NMMA), by inhalation (490 mg) in a double-blind randomized manner in nine normal and six asthmatic subjects. Because exhaled NO may arise from an inducible isoform of NO synthase that may be inhibited by glucocorticosteroids, we also studied the effects of oral prednisolone (30 mg orally for 3 d) in seven normal and six asthmatic subjects in a separate double-blind crossover study with matched placebo. After nebulized L-NMMA, there was a significant fall in peak exhaled NO compared with saline control values, with a mean fall of 43.6 +/- 5.6% in normal subjects (p < 0.01) and of 39.7 +/- 6.5% (p < 0.01) in asthmatic subjects, which persisted for 4 h. There were no effects of L-NMMA inhalation on heart rate, blood pressure, or FEV1 in either normal or asthmatic patients. Administration of oral prednisolone (30 mg) resulted in a fall in exhaled NO concentrations in asthmatic subjects by 21.6 +/- 5.0% at 48 h (p < 0.01) but no significant change in normal subjects. These data suggest that NOS inhibitors may be safely given in normal and asthmatic patients and that the increased exhaled NO seen in asthmatic patients is likely to be caused by induction of inducible NOS.     

Endometriosis in monozygotic twins

OBJECTIVE: To describe the occurrence of endometriosis in monozygotic twins. DESIGN: Postal questionnaire plus confirmation of disease status. SETTING: Twins were recruited via the American Endometriosis Association and the National Endometriosis Society of Great Britain and via British gynecologists. RESULT(S): Fourteen twin pairs were concordant for endometriosis, and two were discordant. Nine pairs of twins had moderate-severe endometriosis. CONCLUSION(S): These findings contribute to the growing body of literature that suggests endometriosis has a genetic basis.     

Evaluation of alpine skiing and snowboarding injury in a northeastern state

BACKGROUND: To demonstrate the injury patterns of Alpine skiing and snowboarding in a northeastern state and evaluate potential risk factors. METHODS: The medical records of a single pediatric and adult Level I trauma center were evaluated from January 1, 1990, through December 31, 1995. All admissions with injuries caused by Alpine skiing or snowboarding were reviewed. Those patients arriving from two local ski resorts, all of whose injuries are referred to the institution for care, were separated out for consideration. Age, sex, type of injury, date of injury, Injury Severity Score, operations performed, and outcome (including mortality) were evaluated. In addition, resort utilization for the study period was obtained from the two resorts included in the evaluation. Mortality data was obtained from the Vermont office of the Chief Medical Examiner for the same time period. RESULTS: For the 6-year period of the study approximately 2,978,000 skier and snowboarder days were recorded at the study sites. Approximately 447,000 of those days were attributed to snowboarders (15%). In all, 279 patients were admitted for injuries (0.01%), 238 were related to Alpine skiing (incidence 0.01%) and 40 to snowboarding (incidence 0.01%). Snowboarders were statistically younger (20 years; range, 4-44 years) than skiers (29 years; range, 6-70 years) (p < 0.001) and had a significantly lower Injury Severity Score (15 in snowboarders vs. 27 in skiers, p < 0.03). Two female patients were injured snowboarding and 68 female patients were injured skiing. Eight percent of injured snowboarders and 16% of injured skiers sustained multiple injuries (p < 0.01). Injury patterns were significantly different. Upper extremity injuries were almost exclusively found in snowboarders (24% vs. 7%, p < 0.003), whereas cruciate ligament injuries occurred far more commonly in skiers (45% vs. 4%, p < 0.001 Lower extremity injuries in general were more common in skiers (78% vs. 38%, p < 0.001). Central nervous system injuries, including head and spine, were evenly distributed over the two groups, although the snowboarders with central nervous system injuries were younger. In addition, splenic injuries were more common in snowboarders (13% vs. 2%, p < 0.01). Snowboarding accidents were far more common in December, March, and April than other months. Fifty-one patients sustained abdominal or chest injuries and only two of these required operative intervention (two splenectomies). Other operative interventions were limited to extremity injuries, injuries of the spine, or placement of an intracranial pressure monitor. There were no fatalities recorded in this population, although over the 6.5 years, there were 25 deaths related to alpine skiing and one to snowboarding in the State (incidence 0.0000009 skier days). Victims tended to be male: 96% of the skiers and the one snowboarder. The predominant cause of death was blunt head trauma followed by blunt chest trauma. Helmets were not worn by those sustaining head injuries or fatalities. Spine injuries were recorded only in extremely young snowboarders and skiers out of control. CONCLUSION: Snowboarders and Alpine skiers are equally prone to injury. Snowboarding accidents are typically less severe and show significantly different injury patterns than skiing accidents. Abdominal and chest injuries in this population are generally amenable to nonoperative management. Prevention programs are best targeted at safe skiing and snowboarding practices, not skiing or snowboarding in poor conditions, use of helmets for skiers, and restraint of snowboard use in very young children.