Effect of barrier width on performance of long wavelengthGaInAs/InP multi-quantum-well lasers

It is demonstrated that lasing thresholds in GaInAs/InP MQW lasers under electrical injection are sensitive to the InP barrier thickness and that reducing the barrier width contributes significantly to achieving low-threshold, room temperature operation. In contrast, lasing thresholds under optical pumping show a relative insensitivity to the barrier width. The authors show that this behaviour is consistent with preferential hole capture in the leading wells     

Role of endoproteolytic dibasic proprotein processing in maturation of secretory proteins in Trichoderma reesei

Cell extracts of Trichoderma reesei exhibited dibasic endopeptidase activity toward the carboxylic side of KR, RR, and PR sequences. This activity was stimulated by the presence of Ca2+ ions and localized in vesicles of low bouyant density; it therefore exhibited some similarity to yeast Kex2. Analytical chromatofocusing revealed a single peak of activity. The dibasic endopeptidase activity was strongly and irreversibly inhibited in vitro as well as in vivo by 1 mM p-amidinophenylmethylsulfonyl fluoride (pAPMSF) but not by PMSF at concentrations up to 5 mM. We therefore used pAPMSF to study the role of the dibasic endopeptidase in the secretion of protein by T. reesei. Secretion of xylanase I (proprotein processing sequence -R-R- downward arrow-R- downward arrow-A-) and xylanase II (-K-R- downward arrow-Q-) was strongly inhibited by 1 mM pAPMSF, and a larger, unprocessed enzyme form was detected intracellularly under these conditions. Secretion of cellobiohydrolase II (CBH II; -E-R- downward arrow-Q-) was only slightly inhibited by pAPMSF, and no accumulation of unprocessed precursors was detected. In contrast, secretion of CBH I (-R-A- downward arrow-Q-) was stimulated by pAPMSF addition, and a simultaneous decrease in the concentration of intracellular CBH I was detected. Similar experiments were also carried out with a single heterologous protein, ShBLE, the phleomycin-binding protein from Streptoalloteichus hindustanus, fused to a series of model proprotein-processing sequences downstream of the expression signals of the Aspergillus nidulans gpdA promoter. Consistent with the results obtained with homologous proteins, pAPMSF inhibited the secretion of ShBLE with fusions containing dibasic (RK and KR) target sequences, but it even stimulated secretion in fusions to LR, NHA, and EHA target sequences. Addition of 5 mM PMSF, a nonspecific inhibitor of serine protease, nonspecifically inhibited the secretion of heterologous proteins from fusions bearing the NHA and LR targets. These data point to the existence of different endoproteolytic proprotein processing enzymes in T. reesei and demonstrate that dibasic processing is obligatory for the secretion of the proproteins containing this target.     

Confirmation of the human-pathogenic microsporidia Enterocytozoon bieneusi, Encephalitozoon intestinalis, and Vittaforma corneae in water

Microsporidia, as a group, cause a wide range of infections, though two species of microsporidia in particular, Enterocytozoon bieneusi and Encephalitozoon intestinalis, are associated with gastrointestinal disease in humans. To date, the mode of transmission and environmental occurrence of microsporidia have not been elucidated due to lack of sensitive and specific screening methods. The present study was undertaken with recently developed methods to screen several significant water sources. Water concentrates were subjected to community DNA extraction followed by microsporidium-specific PCR amplification, PCR sequencing, and database homology comparison. A total of 14 water concentrates were screened; 7 of these contained human-pathogenic microsporidia. The presence of Encephalitozoon intestinalis was confirmed in tertiary sewage effluent, surface water, and groundwater; the presence of Enterocytozoon bieneusi was confirmed in surface water; and the presence of Vittaforma corneae was confirmed in tertiary effluent. Thus, this study represents the first confirmation, to the species level, of human-pathogenic microsporidia in water, indicating that these human-pathogenic microsporidia may be waterborne pathogens.     

Surgical management of third nerve palsy

AIMS: A surgical technique has been developed in order to obtain ocular alignment in the primary position in patients with third nerve palsy. METHODS: A method for surgically correcting the vertical deviation and the pseudoptosis is described in three patients with longstanding third nerve palsy. By decreasing the ability of the non-involved eye to elevate, a fixation duress was created which eliminated the secondary deviation that characteristically occurs in such patients when the involved eye fixates. As a result of this technique, both eyes in all patients on attempted fixation were under similar duress, therefore requiring equal amounts of stimulation to move into the primary position. When the fixation duress was sufficient, elimination of the hypotropia and ptosis was achieved. Additionally, in order to correct the exotropia, generous recession and resection procedures in the involved eye and recession of the lateral rectus in the noninvolved eye were performed. RESULTS: Between 8 and 10 prism dioptres of esotropia were achieved and maintained in two patients. One patient had 20 prism dioptres of exotropia. Two patients had no residual ptosis and one required an additional anterior levator resection to achieve a satisfactory result. CONCLUSION: Patients with a third nerve palsy and a pseudoptosis may be candidates for this approach.     

Urine but not plasma nitric oxide metabolites are decreased in women with preeclampsia

OBJECTIVE: Nitric oxide is a potent vasorelaxant produced by endothelial cells. We tested the hypothesis that urinary and perhaps plasma nitric oxide metabolites would be reduced in women with preeclampsia. STUDY DESIGN: Plasma and urine from 14 women meeting strict clinical criteria for the diagnosis of preeclampsia and 20 normal nulliparous women were assayed for the stable metabolites of nitric oxide, nitrate and nitrite. RESULT: There was no significant difference of plasma concentrations of nitrate and nitrite between women with preeclampsia and women with normal pregnancies (32.7 +/- 3.1 vs 25.8 +/- 2.4 micromol/L). Plasma creatinine levels were elevated in women with preeclampsia (0.85 +/- 0.09 vs 0.66 +/- 0.02 mg/dl, p<0.01), indicating a reduced glomerular filtration rate. Urine concentrations of nitrate and nitrite normalized by creatinine excretion were significantly lower in women with preeclampsia compared with normal pregnant women (0.37 +/- 0.06 vs 0.69 +/- 0.11 micromol of nitrite per milligram creatinine, p. <0.05). CONCLUSIONS: Our study using concomitant measurement of plasma and urine nitrate and nitrite suggests a reduced production of nitric oxide in women with preeclampsia compared with normal pregnant women.     

Therapeutic node dissections in malignant melanoma

BACKGROUND: Therapeutic lymphadenectomies involve the dissection and removal of clinically enlarged, histologically positive nodes at the regional nodal basin, in the absence of detectable distant disease. METHODS: The literature dealing with therapeutic lymphadenectomies in malignant melanoma was reviewed. RESULTS: The rate of wound complications varies with the particular nodal basin. The 5-year survival varies from 19% to 38%, with an average of 26%. Survival is affected primarily by the number of histologically positive nodes and extracapsular spread, and secondarily by the extent of disease at the various levels of the nodal basin, fixation of the nodes, and, probably, the preceding disease-free interval. Prognostic parameters of the primary lesion, e.g., thickness, ulceration, and location, also may have an effect on survival. The rate of local recurrence at the nodal basin after lymphadenectomy has varied from 0.8% to 52%. Adjuvant therapy with interferon alfa-2b has improved the 5-year disease-free survival from 26% to 37%. CONCLUSIONS: Therapeutic node dissections in melanoma provide an appreciable 5-year survival rate, which is further augmented by adjuvant therapy. Many series report a significant rate of local recurrence at the nodal basin following therapeutic dissection. Complete lymphadenectomy reduces the rate of local failure with its attendant morbidity.     

Attentional effects of single dose triazolam

1. While the effects of benzodiazepines on human memory have been extensively studied little is known about the effects of these agents on attentional processes. The authors studied the effects of a single dose of triazolam on selective visual-spatial attention using a double blind, placebo controlled design. 2. In each of 2 sessions 12 normal volunteers ingested either 0.25 mg of triazolam or placebo. Attentional performance was evaluated using two versions of the covert orienting paradigm which measured automatic (exogenous) and controlled (endogenous) aspects of attentional orienting, respectively. 3. Triazolam selectively modified performance on automatic orienting to exogenous cues. Specifically, triazolam increased the facilitation of target detection seen at shorter (150 msec) SOA's. This may indicate an increase in facilitation and a reduction in inhibition or a slowing of the time course of the biphasic attentional effect normally resulting from exogenous cuing. 4. These results indicate the importance of using experimental paradigms which effectively dissociate endogenous and exogenous mechanisms of spatial orienting in studies evaluating the effects of pharmacological agents on visual-spatial attention.     

Structure and properties of ethylene—methacrylic acid copolymers and their sodium salts: Dielectric and proton magnetic relaxation studies

Dielectric and proton magnetic relaxation data have been obtained for an ethylene-methacrylic acid copolymer (containing about 4 mole% methacrylic acid units) and its 53% ionised sodium salt. The degrees of crystallinity and percentage ionisation of the samples investigated were estimated by infra-red methods. The dielectric results were obtained principally in the frequency range 100 Hz to 10 kHz and at temperatures ranging from 80° to – 120°. A few results are also reported at frequencies down to 0·1 Hz and up to 100 MHz. For the acid copolymer, two dielectric loss regions are observed and these are correlated with the reported mechanical β′- and γa-processes respectively. The partly ionised copolymer exhibits three dielectric relaxation regions which correlate with the mechanical α-, β- and γa-relaxations respectively. In addition, a dielectric peak appears at about —40° in the presence of absorbed water, a result similar to that found in the polyamides. The proton magnetic relaxation results were obtained by pulse methods which yielded the spin-lattice relaxation times T₁ (at 30 MHz) and T_1p (at kilohertz frequencies) as a function of temperature from ?180° to 100°. Two components were generally observed for T_1p. For the acid copolymer the β′- and γ-processes have been observed from these results, as well as a lower-temperature (δ) process which has not been detected by the mechanical or dielectric methods. For the sodium salt the γ- and δ-processes are also found, in addition to a high-temperature process in the region of the merged α- and β-processes. The present data are consistent with previous assignments for the β′-, α-, β- and γ-processes. The ‘water’ relaxation appears to involve some rotation of water molecules, or of ionic segments to which water molecules are attached, in the proposed ionic domains. The δ-process is ascribed to the rotations of methyl groups present in the methacrylic acid units.