Crystallization study of chemically vapour-deposited amorphous silicon films by in situ x-ray diffraction

The solid phase crystallization kinetics of chemically vapour-deposited amorphous silicon films were studied by in situ X-ray diffraction. We determined the crystalline volume directly from the Bragg peak intensities at various times during isothermal annealing in the temperature range 578 °C < T < 658 °C. From these experiments we deduced that the crystallization was due to nucleation predominantly at the substrate-film interface followed by crystal growth perpendicular to this interface. The crystal growth rate was thermally activated with an activation energy E_v of 3.1 eV. A strong 〈111〉 preferred orientation of the growing polycrystal was observed and the grain size remained constant at about 60 nm. Evidence of stresses at the amorphous-crystalline interface during the early stages of crystallization was observed. A comparison with previous conductivity measurements is also carried out.     

Artefactual cleavage of E coli H-NS by OmpT

In the bacterium Escherichia coli, H-NS-(H1, H1a) is a heat-stable protein with a molecular mass of 15.5 kDa involved in nucleoid organisation and gene regulation linked to certain signal transduction pathways. We have shown that, following addition of preparations of everted inner membrane vesicles, heat-stable cleavage products of approximately 10 kDa of H-NS are formed in vitro from newly synthesised, radio-labelled H-NS and from purified H-NS. The 15.5 kDa protein and its cleavage products were also recovered from a minicell system. These results raised the possibility that cleavage of H-NS is physiologically significant. However, the cleavage of H-NS observed appears to occur during cell breakage and to depend on the method of protein extraction and the presence of the outer membrane protease, OmpT. Nevertheless, the results indicate that H-NS may contain at least two separate domains with cleavage occurring between these domains at a preferred OmpT site. Failure to take account of H-NS cleavage in sample preparation and analysis can lead to serious underestimation of H-NS levels.     

Analysis of molecular determinants in native AMPA receptors

For this study, 194 respondents completed a biographical data sheet, the Templer (1970) Death Anxiety Scale and the Constantinople (1973) Inventory of Psychosocial Development to help assess the relationship among death anxiety, age, and psychosocial maturity. Findings showed that psychosocial maturity was a better predictor of death anxiety than age was. However, both variables were significantly negatively correlated with death anxiety, revealing that as psychosocial maturity and age increase, death anxiety decreases.     

Identification of a gene that causes primary open angle glaucoma

Glaucoma is a major cause of blindness and is characterized by progressive degeneration of the optic nerve and is usually associated with elevated intraocular pressure. Analyses of sequence tagged site (STS) content and haplotype sharing between families affected with chromosome 1q-linked open angle glaucoma (GLC1A) were used to prioritize candidate genes for mutation screening. A gene encoding a trabecular meshwork protein (TIGR) mapped to the narrowest disease interval by STS content and radiation hybrid mapping. Thirteen glaucoma patients were found to have one of three mutations in this gene (3.9 percent of the population studied). One of these mutations was also found in a control individual (0.2 percent). Identification of these mutations will aid in early diagnosis, which is essential for optimal application of existing therapies.     

Na/K pump current in guinea pig cardiac myocytes and the effect of Na leak

INTRODUCTION: Steady-state Na/K pump current (Ip) in adult guinea pig ventricular myocytes was studied to determine the effect on the Na/K pump of transmembrane Na leak, membrane potential, and pipette Na concentration. METHODS AND RESULTS: Using conventional whole cell, patch clamp techniques, Ip was identified as either Ko-sensitive or ouabain-sensitive current when most other membrane currents were inhibited. Control experiments showed that there were no Ko-sensitive currents other than Ip under the conditions of our experiments. Ip was found to be similar to that reported by others being voltage dependent between -130 and 0 mV and having a half maximal activation by Nai of 28 mM. Ouabain sensitivity was also measured, and it was found that there were two binding sites with the high affinity site comprising 5% to 10% of the total and having an apparent affinity 1000-fold higher than the low affinity site. Apparent affinity of both sites was shifted about 10-fold (higher affinity) by increasing Nai from 10 to 85 mM. When internally perfused with 0 Na solution, Na leak through the membrane was found to be linearly related to Na/K pump activity. In contrast to prior suggestions, Ip was not correlated with series resistance when there was a large transmembrane Na gradient. CONCLUSION: These data suggest that, under conditions of high transmembrane Na gradient, Na leak through the membrane plays a significant role in determining Na/K pump activity.     

Gastric ECL-cell hyperplasia produces enhanced basal and stimulated gastric acid output but not gastric erosion formation in the rat

Cervical involvement is one of the major prognostic factors in carcinoma of the endometrium confined to the uterus. The purpose of this study was to determine whether intrauterine ultrasound with a high-frequency miniature probe can depict the degree of cervical involvement of the disease. Thirty-two women with endometrial carcinoma underwent preoperative transvaginal and intrauterine sonography. By both scans, the degree of cervical involvement was prospectively evaluated. Sonograms were compared with the findings from histologic examination. Intrauterine sonography was completed in 30 of the 32 patients. In these 30 patients, the degree of cervical involvement (none, endocervical gland, or cervical stroma) based on transvaginal scan was correct in 23 cases (77%), and that based on intrauterine scan was correct in 26 cases (87%). Three tumors with endocervical glandular involvement were correctly diagnosed by intrauterine sonography, whereas they were incorrectly diagnosed by transvaginal scan. The specificity and positive predictive value of intrauterine sonography for the assessment of the presence of cervical stromal invasion are 100% (26/26 and 3/3, respectively). Although this study is preliminary, our experience with intrauterine sonography shows that it has potential for assessing cervical stromal invasion in endometrial carcinoma.     

Mechanomyography and oxygen consumption during incremental cycle ergometry

Brucella abortus strain RB51 was recently approved as an official brucellosis calfhood vaccine for cattle by the Animal and Plant Health Inspection Service branch of the United States Department of Agriculture. Currently available serologic surveillance tests for B. abortus do not detect seroconversion following SRB51 vaccination. The purpose of this study was to evaluate a dot-blot assay using gamma-irradiated strain RB51 bacteria for its specificity and sensitivity to detect antibody responses of cattle vaccinated with strain RB51. Dot-blot titers of sera at a recommended dosage (10(10) colony-forming units) were similar to those of sera from cattle vaccinated with similar numbers of B. abortus strain 19 and greater (P < 0.05) than titers of nonvaccinated cattle. In the first 12 weeks after vaccination with 10(10) colony-forming units of strain RB51, the RB51 dot-blot assay had 100% specificity for titers of 80 or less and a 53% sensitivity for titers of 160 or greater. Sensitivity of the RB51 dot-blot assay peaked at 4 weeks after vaccination with 10(10) colony-forming units of strain RB51. Dot-blot responses of sera from cattle vaccinated with a reduced dosage of strain RB51 (10(9) colony-forming units) did not differ (P > 0.05) from titers of sera from nonvaccinated cattle. Following intraconjunctival challenge with B. abortus strain 2308, titers on the RB51 dot-blot assay did not differ (P > 0.05) between nonvaccinated cattle and cattle vaccinated at calfhood with strain 19 or strain RB51.     

Disulfide bond assignment in human interleukin-7 by matrix-assisted laser desorption/ionization mass spectroscopy and site-directed cysteine to serine mutational analysis

Interleukin-7 (IL-7) is a proteinaceous biological response modifier that has a bioactive tertiary structure dependent on disulfide bond formation. Disulfide bond assignments in human (h)IL-7 are based upon the results of matrix-assisted laser desorption/ionization (MALDI) mass spectroscopy and Cys to Ser mutational analyses. A gene encoding the hIL-7 was synthesized incorporating Escherichia coli codon usage bias and was used to express biologically active protein as determined by stimulation of precursor B-cell proliferation. MALDI mass spectroscopic analysis of trypsin-digested hIL-7 was performed and compared with the anticipated results of a simulated tryptic digestion. Many of the anticipated hIL-7 tryptic fragments were detected including one with a molecular mass equivalent to the sum of two polypeptides linked through a disulfide bond formed from Cys residues (Cys3 and Cys142). Subsequently, Cys to Ser substitution mutational analyses were performed. A hIL-7 variant with all six Cys substituted with Ser was found to be biologically inactive (EC50 > 1 x 10(-7) M). In contrast, a family of single disulfide bond-forming variants of hIL-7 were constructed by reintroducing Cys pairs (Cys3-Cys142, Cys35-Cys130, and Cys48-Cys93), and each could stimulate cell proliferation with an EC50 of 4 x 10(-9), 2 x 10(-8), and 2 x 10(-9) M, respectively. In single disulfide bond-forming mutants of hIL-7, the ability to stimulate cell proliferation was abolished in the presence of 2 mM dithiothreitol. The results presented strongly suggest that only a single disulfide bond is required for hIL-7 to form a tertiary structure capable of stimulating precursor B-cell proliferation.