Mobile genetic elements, chiasmata, and the unique organization of beta-heterochromatin

Beta-heterochromatin in Drosophila and the Syrian hamster share a similar DNA organization, few unique sequences, and scrambled repeats of mobile elements without tandem repetition. DNA in alpha-heterochromatin is tandemly repetitious, and we now show that the repeat unit can either contain or lack a mobile element. The tandem repeat organization of alpha-heterochromatin is presumably due to a concertina-like mechanism of unequal exchange between repeat units. Although both heterochromatin types are late replicating and can incorporate mobile retroposons, the sequence distinction between the two heterochromatins appears to be due to a property conferred by chiasmata upon the process of homologous recombination in beta-heterochromatin but not in alpha-heterochromatin. Chiasmata seem to suppress the concertina mechanism of unequal exchange and impart to beta-heterochromatin its nontandem, scrambled repeat organization.     

Optimization of hydrolysis of protein substrates by yeast proteases from Saccharomyces carlsbergenis

Maximizing efficiency of staff and resources is one method of reducing costs without affecting quality. Using a methodology similar to that used to maximize efficiency of airline-gate use, we developed a model with which to evaluate nursing support staff and clinical examining-room resources in a general otolaryngology clinic. For 144 patients over 7 consecutive clinic days, with four otolaryngologists and various combinations of support staff and examining rooms, we measured space and staff resource use, including total clinic time, number of patients seen, patient waiting time, physician and nurse productivity, and examining-room use. A simulation model was used as the medium of analysis to define parameters of the patient encounter. We identified optimal efficiency when there were three examining rooms and one and one-half nursing staff per physician or five examining rooms and three nursing staff for two simultaneously practicing physicians. Compared with a model of two rooms and one nursing staff member, our ideal model increased the percentage of the physicians' time spent in direct contact with patients from 84% to 92%. Visit length decreased from 81 minutes to 57 minutes, the average time from check-in to examination decreased from 47 to 16 minutes, and it became possible for three additional patients to be seen each day. Additional rooms and support staff, in comparison with the optimally efficient distribution, did not significantly affect these parameters. Maximizing efficiency with the use of this methodology can decrease waiting times for patients, resulting in greater patient satisfaction, improved physician productivity, total number of patients seen, and increased total contact time between physicians and patients.     

Circulating leptin levels during acute experimental endotoxemia and antiinflammatory therapy in humans

Leptin, a newly discovered adipose tissue-derived weight-reducing hormone, is increased in acute inflammation and may be involved in the anorexia and wasting syndrome associated with infection. To determine whether this hormone responds to an acute inflammatory stimulus, plasma leptin concentrations were measured in 12 healthy subjects after intravenous administration of endotoxin. These subjects were randomized to receive concurrently ibuprofen or placebo normal saline (6 in each group). Endotoxin administration resulted in fever, leukocytosis, and an increase in plasma levels of the stress hormones adrenocorticotropic hormone (3.2 +/- 0.3 to 132.6 +/- 75.5 pmol/L, P = .001) and cortisol (431.6 +/- 44 to 796.9 +/- 99 mmol/L, P = .001). Plasma leptin levels, however, did not change significantly from baseline values after administration of endotoxin (0 h: 6.9 +/- 3.1 ng/mL; 6 h: 6.0 +/- 2.2; 24 h: 6.5 +/- 2.8). While ibuprofen suppressed fever and symptoms associated with endotoxemia, it had no effect on the plasma levels of leptin. In conclusion, acute experimental human endotoxinemia is not associated with acute changes in circulating leptin levels.     

Induction of early and bioeffective antibody response in rodents with the luteinizing hormone-releasing hormone vaccine given as a single dose in biodegradable microspheres along with alum

Total urinary incontinence is a difficult problem faced by the urologist. Several techniques to increase ureteral resistance have been described. The majority of them rely on intermittent catheterization for bladder emptying, especially in neurogenic incontinence. We have developed a new procedure in which a bladder flap is used to create a neourethra. This urethral extension acts as a flap valve to provide continence. Bladder emptying is accomplished by clean intermittent catheterization. Urethral lengthening with an anterior bladder-wall flap was performed in 18 patients aged a mean of 8.9 years who had neurogenic incontinence (14) or exstrophy (4). Patients with previous bladder interventions received a lateralized anterior flap. Bladder augmentation was performed in 14 of the 18 patients [detubularized ileum (11), detubularized colon (3)]. The average follow-up period is currently 29.3 months. Continence was achieved in 13 of the 18 patients (72%). Complications included urethrovesical fistulae, which developed in two patients. Two patients could not perform catheterization due to pain but had no obstruction to passage of catheter (exstrophy). Ureteral lengthening with an anterior bladder-wall flap is a useful alternative for the surgical treatment of urinary incontinence. This technique achieves a good continence rate and presents few problems with catheterization.     

Myoblast city, the Drosophila homolog of DOCK180/CED-5, is required in a Rac signaling pathway utilized for multiple developmental processes

The Rac and Cdc42 GTPases share several regulators and effectors, yet perform distinct biological functions. The factors determining such specificity in vivo have not been identified. In a mutational screen in Drosophila to identify Rac-specific signaling components, we isolated 11 alleles of myoblast city (mbc). mbc mutant embryos exhibit defects in dorsal closure, myogenesis, and neural development. DOCK180, the mammalian homolog of Mbc, associates with Rac, but not Cdc42, in a nucleotide-independent manner. These results suggest that Mbc is a specific upstream regulator of Rac activity that mediates several morphogenetic processes in Drosophila embryogenesis.     

The laboratory diagnosis of spring-summer infections in Yekaterinburg in the epidemic season for tick-borne encephalitis

The authors propose a comprehensive approach to laboratory diagnosis of seasonal transmissible infections, based on modern methods permitting etiological deciphering of disease. A universal diagnostic algorithm notably accelerated the laboratory diagnosis due to cutting the period between collection of material from a patient and consecutive screening for antibodies to agents of tick-borne encephalitis, Lyme disease, and California encephalitis.     

A genetic system involving superoxide causes F1 necrosis in wheat (T. aestivum L.)

A genetic system in wheat is described in which F1 produced by crossing a drought tolerant cultivar C306 and high yielding cultivar WL711 exhibits leaf necrosis leading to the death of the plant. The mechanism underlying hybrid necrosis is not yet known. The hybrid exhibited a higher level of superoxide anion compared to the healthy leaves of parents at similar developmental stages. This increase in superoxide generation preceded necrotic lesion formation and displayed a gradient from the leaf tip to base. The leaf tip where necrotic lesions make their first appearance exhibited a higher level of superoxide compared to the base. Superoxide anion thus appears to play a vital role in necrosis of leaves in F1 hybrid. This genetic system can be a model system for understanding cell death in higher plants.     

Cytotoxicity-associated effects of reactive oxygen species on endothelin-1 secretion by pulmonary endothelial cells

In this study bovine pulmonary artery endothelial cells (BPAEC) were used as a model system to investigate the effects of the hypoxanthine-xanthine oxidase (HXXO) oxygen radical donor system on ET-1 secretion into pulmonary vasculature. Incubation of BPAEC with HXXO for 4 h caused a significant reduction in ET-1 secretion, which was significantly offset by allopurinol or catalase, but not by Cu/Zn superoxide dismutase (SOD). ET-1 secretion was also reduced by H2O2, and this effect was again significantly offset by catalase. XO alone also reduced ET-1 secretion, but to a significantly lesser degree than did HXXO, and this effect was not offset by allopurinol, catalase, or SOD. None of the oxidant treatments were associated with a loss of immunoreactive ET-1 from endothelial cell medium containing synthetic peptide. The HXXO- and H2O2-mediated reductions in ET-1 secretion were accompanied by evidence of reduced cell viability. This loss of viability was absent when cells were treated with HXXO + catalase, allopurinol, or mercaptopropionyl glycine, but not when SOD was present. We conclude that under conditions of oxidative stress, the pulmonary vascular endothelium responds by secreting less ET-1. This may be relevant to its vasodilator functions in the pulmonary vasculature, which would therefore be compromised when the endothelium is exposed to oxidant stress.     

Hypohydration effects on skeletal muscle performance and metabolism: a 31P-MRS study

The purpose of this study was to determine whether hypohydration reduces skeletal muscle endurance and whether increased H+ and Pi might contribute to performance degradation. Ten physically active volunteers (age 21-40 yr) performed supine single-leg, knee-extension exercise to exhaustion in a 1.5-T whole body magnetic resonance spectroscopy (MRS) system when euhydrated and when hypohydrated (4% body wt). 31P spectra were collected at a rate of one per second at rest, exercise, and recovery, and were grouped and averaged to represent 10-s intervals. The desired hydration level was achieved by having the subjects perform 2-3 h of exercise in a warm room (40 degrees C dry bulb, 20% relative humidity) with or without fluid replacement 3-8 h before the experiment. Time to fatigue was reduced (P < 0.05) by 15% when the subjects were hypohydrated [213 +/- 12 vs. 251 +/- 15 (SE) s]. Muscle strength was generally not affected by hypohydration. Muscle pH and Pi/beta-ATP ratio were similar during exercise and at exhaustion, regardless of hydration state. The time constants for phosphocreatine recovery were also similar between trials. In summary, moderate hypohydration reduces muscle endurance, and neither H+ nor Pi concentration appears to be related to these reductions.     

Expression of aquaporin-4 in fast-twitch fibers of mammalian skeletal muscle

OBJECT: Ependymomas in children continue to generate controversy regarding their histological diagnosis and grading. optimal management, and possible prognostic factors. To increase our knowledge of these tumors the authors addressed these issues in a cohort of children with prospectively staged ependymomas treated with radiotherapy and chemotherapy. METHODS: Children between the ages of 2 and 17.3 years harboring an intracranial ependymoma confirmed by a central review of the tumor's pathological characteristics were treated according to Children's Cancer Group Protocol 921 from 1986 to 1992. Treatment following surgery and postoperative tumor staging (including brain computerized tomography or magnetic resonance [MR] imaging, spinal MR imaging or myelography, and cerebrospinal fluid cytological investigation) included craniospinal irradiation with a local boost to the primary tumor and patient randomization to receive adjuvant chemotherapy with either 1) CCNU, vincristine, and prednisone, or 2) the eight-drugs-in-1-day regimen. Centralized review of the tumor pathological characteristics revealed 20 ependymomas and 12 anaplastic ependymomas in the 32 children included in the study. Diagnoses made at the individual institutions included anaplastic (malignant) ependymoma (15 patients), ependymoma (four patients), ependymoblastoma (nine patients), ependymoastrocytoma (one patient), and primitive neuroectodermal tumor (three patients), which were discordant with the centralized review diagnosis in 22 of 32 cases. Only three of the 32 patients had metastatic disease (two with M and one with M3 stages). At surgery, 47% of tumors were estimated to be totally resected. Among the 14 of 17 patients who suffered a relapse and were evaluated for site of relapse, 10 (71%) had an isolated local relapse, three (21%) had concurrent local and metastatic relapse, and only one (7%) had an isolated metastatic relapse. Kaplan-Meier estimates of 5-year progression-free survival (PFS) and overall survival rates were 50 +/- 10% and 64 +/- 9%, respectively. CONCLUSIONS: Predictors of PFS duration included an estimate of the extent of resection made at surgery (total compared with less than total, p = 0.0001) and the amount of residual tumor on postoperative imaging as verified by centralized radiological review (< or = 1.5 cm2 compared with > 1.5 cm2, p < 0.0001). No other factors, including centrally reviewed tumor histopathological type, location, metastasis and tumor (M and T) stages, patient age, race, gender, or chemotherapy treatment regimen significantly correlated with PFS duration. The pattern of predominantly local relapse and the important influence of residual tumor or the extent of resection on PFS duration confirms a prevailing impression that local disease control is the major factor in the prediction of outcome of ependymoma. Survival rates were comparable with those reported by other investigators who have treated patients with similar doses of radiation and no chemotherapy.