Diameter of the mammalian porin channel in open and "closed" states: direct measurement at the single channel level in planar lipid bilayer

Porin isolated from bovine skeletal muscle was reconstitute in planar lipid bilayers under voltage clamp conditions. A set of non-electrolytes were used as molecular probes for determining the pore diameter. The maximal diameter of the open channel was estimated to be 3.02 +/- 0.26 nm. As observed for other porin channels, a large transmembrane potential drove the channel into a "closed" state. The channel transition to the low conductance (closed) state was followed by a decrease in the maximal diameter of the channel to 2.4 +/- 0.08 nm.     

Effect of stimulus intensity on prolactin and cortisol release induced by unilateral electroconvulsive therapy

The corneal wound-healing properties of fibronectin (FN) and a fibronectin hydrolysate (FNH) have been evaluated in comparison with commonly used drugs. Nonpenetrating bilateral surgical keratectomy was performed in male albino rabbits. The left eye was treated with the active product, whereas the right eye served as a control (vehicle). The healing area was measured by planimetry after fluorescein staining at 0, 24, 48, and 72 h after keratectomy. Histological and immunohistochemical analysis of the healing process was also performed. Results were as follows: (a) Nandrolone (p < 0.005) and asiaticoside (p < 0.001), both at 10 mg/ml, in eyedrops delayed the healing process. (b) An ointment containing vitamin A and amino acids also delayed the process but at the limit of statistical significance (p = 0.055). (c) FNH (20-80 mg prot/ml) significantly improved the quality and shortened the time of the healing process at 60 mg prot/ml and above. (d) Human FN (100-800 micrograms/ml) did not affect the healing process. Immunohistochemical analysis demonstrated that FNH accelerated the appearance of endogenous FN in the damaged cornea earlier than in the control eyes. It is concluded that FNH may be useful in the management of corneal wounds, whereas the effectiveness of FN is doubtful.     

Self-reported effects of alcohol use on symptoms of schizophrenia

Forty-two acute inpatients with schizophrenia, 23 of whom had a past or current alcohol use disorder, were given a structured interview that focused on reasons for alcohol use and changes in perceived effects of alcohol on psychiatric symptoms from the first episode of illness to the current episode. Drinking for sociability or celebration decreased over time, while drinking to relieve depression or problems increased. Subjects who experienced hallucinations, paranoia, or both significantly more often reported an increase in these symptoms after drinking. Subjects with an alcohol-related diagnosis were significantly more likely than those without such a diagnosis to cite relief of depression and problems or worries as a reason for alcohol use.     

Alpha-helical, but not beta-sheet, propensity of proline is determined by peptide environment

Proline is established as a potent breaker of both alpha-helical and beta-sheet structures in soluble (globular) proteins. Thus, the frequent occurrence of the Pro residue in the putative transmembrane helices of integral membrane proteins, particularly transport proteins, presents a structural dilemma. We propose that this phenomenon results from the fact that the structural propensity of a given amino acid may be altered to conform to changes imposed by molecular environment. To test this hypothesis on proline, we synthesized model peptides of generic sequence H2N-(Ser-LyS)2-Ala- Leu-Z-Ala-Leu-Z-Trp-Ala-Leu-Z-(Lys-Ser)3-OH (Z = Ala and/or Pro). Peptide conformations were analyzed by circular dichroism spectroscopy in aqueous buffer, SDS, lysophosphatidylglycerol micelles, and organic solvents (methanol, trifluoroethanol, and 2-propanol). The helical propensity of Pro was found to be greatly enhanced in the membrane-mimetic environments of both lipid micelles and organic solvents. Proline was found to stabilize the alpha-helical conformation relative to Ala at elevated temperatures in 2-propanol, an observation that argues against the doctrine that Pro is the most potent alpha-helix breaker as established in aqueous media. Parallel studies in deoxycholate micelles of the temperature-induced conformational transitions of the single-spanning membrane bacteriophage IKe major coat protein, in which the Pro-containing wild type was compared with Pro30 --> Ala mutant, Pro was found to protect the helix, but disrupt the beta-sheet structure as effectively as it does to model peptides in water. The intrinsic capacity of Pro to disrupt beta-sheets was further reflected in a survey of porins where Pro was found to be selectively excluded from the core of membrane-spanning beta-sheet barrels. The overall data provide a rationale for predicting and understanding the structural consequences when Pro occurs in the context of a membrane.     

Hypervascular tumor of the buccal space in an adult as a late recurrence of juvenile angiofibroma

We describe an adult patient with recurrent juvenile angiofibroma, which presented as a rapidly enlarging, hypervascular mass in the anterior part of the cheek. The case is unusual because of the extreme delay (greater than 30 years) and the anatomic location of the recurrence.     

L-2-Hydroxyglutaric aciduria: neuropathological correlations and first report of severe neurodegenerative disease and neonatal death

Chromolaena odorata (formerly Eupatorium odoratum) is used as a traditional medicine in Vietnam (Nghiem, 1992), where its Vietnamese common name is "co hoi." While it has been widely considered a weed by agriculturalists (Holm et al., 1991), the aqueous extract and the decoction from the leaves of this plant have been used throughout Vietnam for the treatment of soft tissue wounds, burn wounds, and skin infections. A number of clinical studies done by Vietnamese as well as foreign medical workers has demonstrated the efficacy of this extract on the wound-healing process. In this article, the effect of the Eupolin extract on hydrated collagen lattice contraction by human dermal fibroblasts, an in vitro model of wound contraction, is described. The significant inhibition of collagen gel contraction by Eupolin extract at 50 to 200 micrograms/ml is demonstrated in various concentrations of collagen. When the extract at 50 to 150 micrograms/ml was washed out of the lattices and replaced by fresh medium without Eupolin, the contraction of collagen by cells was resumed. The visualization of cells in the lattices by incubation in a tetrazolium salt for 2 h showed live cells at 50 to 150 micrograms/ml of extract. In contrast, all cells were killed in the higher extract doses of 300 or 400 micrograms/ml. These preliminary results showing the inhibitory effect of Eupolin extract on collagen contraction suggest that a clinical evaluation of its effect on wound contraction and scar quality should be made. This work illustrates that traditional remedies that are used by folk practitioners to improve healing can be examined in a scientific manner using in vitro wound-healing models. It could be that the synergistic properties of components of the natural extract contribute to the positive effects demonstrated on various wound-healing mechanisms.     

Role of Ca2+ in differentiation mediated by nerve growth factor and dibutyryl cyclic AMP in PC12 cells

Nerve growth factor (NGF) and dibutyryl cyclic AMP (dbcAMP) have synergistic effects on the neurite outgrowth of rat pheochromocytoma PC12 cells. The sites of interaction between NGF and dbcAMP have been studied extensively; however, the role of Ca2+ in differentiation induced by the two agents remains unclear. To understand whether intracellular Ca2+ is involved in the differentiation induced by the two agents, PC12 cells were treated with NGF, dbcAMP, or NGF plus dbcAMP for 2 days, and then effects on neurite outgrowth, ATP-induced Ca2+ influx, and Ca2+ mobilization from intracellular Ca2+ pools were examined. NGF or dbcAMP alone enhanced neurite outgrowth and Ca2+ accumulation by nonmitochondrial Ca2+ pools or the thapsigargin (TG)-sensitive Ca2+ pool. The dbcAMP acted synergistically with NGF to increase neurite outgrowth and to enlarge the TG-sensitive Ca2+ pool. The synergistic effect occurred within the first hour of treatment with dbcAMP plus NGF. On the other hand, dbcAMP abolished NGF's ability to enhance ATP-induced influx of extracellular Ca2+ . Therefore, NGF and dbcAMP induced different effects on Ca2+ signaling pathways through two different but interacting pathways. In PC12 cells pretreated with TG to deplete the TG-sensitive Ca2+ pool, the dbcAMP- or dbcAMP plus NGF-mediated neurite outgrowth was significantly inhibited, whereas NGF-mediated neurite outgrowth was not affected by TG pretreatment. Our results suggest that the intracellular nonmitochondrial Ca2+ pools were changed in the differentiation process and were necessary for the synergistic effect of NGF and dbcAMP.     

A population-based study of tractor-related injuries: Regional Rural Injury Study-I (RRIS-I)

Although tractors account for the majority of fatal farming-related injuries, little is known about the magnitude of this problem. The study population in this article was obtained from the five state Regional Rural Injury Study-I (RRIS-I) database that included 3939 farm households and 13,144 persons interviewed during 1990. Rates were calculated for sociodemographic variables and various exposures; logistic regression was used to calculate the relative risks and respective confidence intervals. Among the total farming-related injury events (n = 764), 65 (8.4%) were related to regular tractor (> or = 20 horsepower) use (495 injured persons per 100,000 persons per year). The rates increased incrementally for those persons working between 20 to 39 and 60 to 79 hours per week (range, 529 to 1430 per 100,000 persons). Among the 12 rollover events, there were only three injuries. The majority of injury events occurred while persons were mounting or dismounting the tractor (42%). Although only 7% of the cases were hospitalized, 83% required some type of health care. Among all injured persons, 43% were restricted from regular activities for 1 week or more and 20% were restricted for 1 month or more; 28% continued to have persistent problems. The finding of the large proportion of events associated with activities of mounting and dismounting suggests a need to investigate specific design characteristics of the tractors associated with these events and, in general, the tractors to which the population is exposed.     

Effect of intracellular acidity and ionomycin on apoptosis in HL-60 cells

The aim was to investigate in detail the influence of intracellular pH (pHi) and intracellular Ca2+ concentration ([Ca2+]i) on apoptosis in HL-60 human promyelocytic leukaemia cells. The pHi was controlled by changing the pH of media as well as by interfering with the pHi regulatory mechanisms with 3-amino-6-chloro-5-(1-homopiperidyl)-N-(diaminomethylene) pyrazincarboxamide (HMA; an inhibitor of Na+/H+ antiport), 4-diiosothiocyanatostilbene-2,2'disulfonic acid, (DIDS; an inhibitor of Na(+)-dependent HCO3-/Cl- exchange) and nigericin (a K+ ionophore). The [Ca2+]i was increased with ionomycin, a Ca2+ ionophore. The apoptosis of HL-60 cells was measured with conventional agarose gel electrophoresis for DNA fragmentation and also with the release of 3H from 3H-thymidine-labelled DNA. Based on the magnitude of DNA fragmentation and 3H release at different pHi, it was shown that apoptosis occurred in HL-60 cells when the pHi was lowered from normal pHi of 7.4 to about 7.2-6.7 with a peak increase at pHi 6.8-6.9. Addition of 4 microM ionomycin to RPMI 1640 medium, which contained 615 microM Ca2+, elevated the apoptosis in the cells. Such an increase in apoptosis by ionomycin in HL-60 cells appeared to result from both an increase in [Ca2+]i and from a decline in pHi. The results indicate that the acidic intratumour environment may greatly affect the response of neoplastic tissues to hyperthermia, radiation and chemotherapeutic drugs which cause apoptosis.