Discrete conductance fluctuations in lipid bilayer protein membranes

Discrete fluctuations in conductance of lipid bilayer membranes may be observed during the initial stages of membrane interaction with EIM ("excitability inducing material"), during destruction of the EIM conductance by proteolysis, and during the potential-dependent transitions between low and high conductance states in the "excitable" membranes. The discrete conductance steps observed during the initial reaction of EIM with the lipid membranes are remarkably uniform, even in membranes of widely varying lipid composition. They range only from 2 to 6 x 10_-10 ohm_-1 and average 4 x 10_-10 ohm_-1. Steps found during destruction of the EIM conductance by proteolysis are somewhat smaller. The transition between high conductance and low conductance states may involve steps as small as 0.5 x 10_-10 ohm_-1. These phenomena are consistent with the formation of a stable protein bridge across the lipid membrane to provide a polar channel for the transport of cations. T6he uniform conductance fluctuations observed during the formation of these macromolecular channels may indicate that the ions in a conductive channel, in its open state, are largely protected from the influence of the polar groups of the membrane lipids. Potential-dependent changes in conductance may be due to configurational or positional changes in the protein channel. Differences in lipid-lipid and lipid-macromolecule interactions may account for the variations in switching kinetics in various membrane systems.     

Cancer of the Nasopharynx

Of 75 consecutive patients with nasopharyngeal cancer treated at UCLA Center for Health Sciences, 42 were eligible for long-term study. Fourteen (33 percent) survived five years, and one survived ten years. Since the management of nasopharyngeal cancer is primarily irradiation, a well-planned aggressive treatment program using supravoltage therapy is recommended. In spite of cranial nerve involvement or skull erosion, radiation therapy occasionally may offer long term control of the disease.     

Chromosome Replication in Salmonella typhimurium

The replication of the Salmonella typhimurium chromosome was studied. As with E. coli 15T(-), replication was sequential. After amino acid starvation, replication proceeded from a unique and heritable region of the chromosome. 5-Bromouracil, when substituted for thymine, did not disturb the sequence of replication nor did it initiate extra replication cycles. By labeling the origin and the terminus of the chromosome with (3)H- and (14)C-thymine, respectively, it was possible to determine that the rate of chain elongation decreases as the growth rate decreases. No gap in the replication cycle could be observed.     

Seasonal changes in the distribution of gonadal lipids and spermatogenetic tissue in the male phase of Monopterus albus (Pisces: Teleostei)

The gonad of Monopterus albus undergoes cyclical changes after the reversal of sex from female to male. The seasonally variable events include a prenuptial accumulation of cholesterol-positive lipid droplets in the cytoplasm of the interstitial cells when spermatogenetic activity is resumed in late February and early March. The development of the interstitial Leydig cells reaches a maximum in May just before spawning. There occurs a sudden depletion of the interstitial lipids during the breeding season in June at a time when the male animals exhibit active nuptial behaviour. After spermiation, the old interstitial cells degenerate, and during the succeeding phase of gonadal inactivity, become replaced by a new generation from connective tissue cells in the interstitium of the gonadal lamellae which gradually accumulate lipoidal material.
The lobular cycle comprises a postnuptial accumulation of amorphous intralobular lipids which become completely cleared in February when active spermatogenesis is restored. Spermatogenesis resumes shortly after spawning, but only advances as far as primary spermatocytes during the postnuptial period of inactivity.
The authors conclude that, as far as the seasonal variations in gonadal lipid distribution is concerned, the cycles in the gonad of the hermaphroditic teleost, M. albus , conform to the same pattern as those of the gonochoristic seasonal breeders studied.     

Magnetic resonance study of renal transplantation

In the last few years, we have focused our research effort on the magnetic resonance spectroscopic (NMR) studies of organ transplantation in the rat. P-31 NMR was employed to study changes in high-energy phosphates, intracellular pH in vivo of transplanted kidneys either during normal function, while undergoing the rejection process or subjected to other insults (e.g. ischemia, cyclosporine nephrotoxicity, urinary obstruction) which may also cause graft dysfunction. Nuclear magnetic resonance (NMR) parameters, specifically relative peak areas and intracellular pH, accurately distinguished among the different causes of graft dysfunction. Ureteral obstruction was clearly identified by elevations in the phosphodiester/urine phosphate peak. Ischemia and rejection were both associated with increases in inorganic phosphates and phosphomonesters and decreases in the beta-phosphate peak of adenosine triphosphate but were distinguishable from each other by differences in intracellular pH which was normal in rejected allografts (7.33 +/- 0.07, n = 3) and low in ischemic allografts (7.00 +/- 0.05, n = 3, p less than 0.05). Grafts insulted with cyclosporine toxicity were not distinguishable from normal allografts by any of the parameters studied. To determine the temporal relationship of NMR changes in allograft rejection, similar studies were performed serially in a group of rejecting (R) kidneys (n = 7) and compared with a control group of nonrejecting (NR) kidneys (n = 7). Major decrease in adenosine triphosphate (ATP) with increases in Pi and a marked increase in the Pi/ATP ratio were noted in the R allografts over time. The R allografts could be completely segregated from the NR allografts on the basis of the Pi/ATP ratio by day 7. These data suggest that 31P NMR spectroscopy may have potential clinical application in differentiating among the causes of graft failure of human renal allografts.     

Integration and expression of theEscherichia coli xylose isomerase gene inSchizosaccharomyces pombe

Summary The xyclose isomerase gene inEscherichia coli was cloned complementarily into a Leu2-negativeSchizosaccharomyces pombe mutant (ATCC 38399). The subsequent integration of the plasmid into the chromosomal DNA of the host yeast was verified by using the dot blot and southern blot techniques. The expressed xylose isomerase showed activity on a nondenaturing polyacrylamide gel. The expression of xylose isomerase gene was influenced by the concentration of nutrients in the fermentation broth. The yeast possessed a xylose isomerase activity of 20 nmol/min/mg by growing in an enriched medium containing yeast extract-malt extract-peptone (YMP) andd-xylose. The conversion ofd-xylose tod-xylulose catalyzed by xylose isomerase in the transformed yeast cells makes it possible to fermentd-xylose with ethanol as a major product. When the fermentation broth contained YMP and 5% (w/v)d-xylose, the maximal ethanol yield and productivity reached 0.42 g/g and 0.19 g/l/h, respectively.     

Vasoactive properties of dihomo-gamma-linolenic acid and series one prostaglandins in a freshwater teleost, Channa maculata

1. Prostaglandins A1, B1, E1 and F1 alpha (2-120 micrograms/kg), arachidonic acid and dihomo-gamma-linolenic acid (0.1-2 mg/kg) were injected intravenously into Channa maculata and changes in arterial blood pressure were recorded. 2. Injection of PGF1 alpha had no significant effect on arterial blood pressure. Injection of PGA1 and PGE1 was followed by dose-dependent hypotension whereas injection of PGB1 elicited significant dose-dependent increase in arterial blood pressure. 3. Both dihomo-gamma-linolenic acid and arachidonic acid were also depressor agents but dihomo-gamma-linolenic acid was more potent. 4. A single bolus intravenous injection of indomethacin (5 mg/kg) or 4 daily intraperitoneal injections (4 x 10 mg/kg) significantly lowered arterial blood pressure. One hour after pre-treatment of indomethacin, the vascular effects of both prostaglandin precursors were abolished. 5. It appears that the vascular effects of prostaglandins in Channa maculata are qualitatively different from those reported for mammals.     

Randomised controlled trial of lymphoblastoid interferon alfa in Europid men with chronic hepatitis B virus infection.

OBJECTIVE--To confirm the findings of pilot studies that interferon alfa is an effective treatment of Europid men with chronic hepatitis B virus infection. DESIGN--Randomised controlled trial of three months treatment with interferon alfa followed by 12 months of observation. SETTING--Outpatient clinic of a tertiary referral centre. PATIENTS--37 Treated men (six anti-HIV positive) and 34 untreated men (nine anti-HIV positive) who met the criteria for the trial. Four controls failed to complete follow up. INTERVENTIONS--The treated group received subcutaneous injections of 5-10 MU interferon alfa/m2 daily for five days, then 10 MU/m2 thrice weekly for 11 weeks. Follow up continued at monthly intervals for 12 months. Untreated controls were monitored over the same period. MAIN OUTCOME MEASURE--Hepatitis B e antigen and hepatitis B virus DNA state after 15 months of observation. RESULTS--12 Of the 37 treated patients cleared hepatitis B e antigen and hepatitis B virus DNA, whereas only one of 30 untreated controls seroconverted over the same period--an increased response rate of 29% (95% confidence interval 13% to 45%). The life table estimate of response at 15 months was 35% in treated patients, an increase of 32% above controls (95% confidence interval 16% to 48%). The response rates in groups by predictive pretreatment variables were 12 of 31 anti-HIV negative patients (excess response 34%; 95% confidence interval 14% to 54%), 12 of 26 with chronic active hepatitis before treatment (excess response 46%; 27% to 65%), and 12 of 21 with a pretreatment serum aspartate aminotransferase activity greater than 70 IU/l (excess response 46%; 16% to 76%). The combination of these factors predicted response with a sensitivity of 100% and a specificity of 80%. Four of the 12 responders, who had all been infected for less than two years, also lost hepatitis B surface antigen. Treatment was well tolerated. CONCLUSIONS--Interferon alfa is effective in the treatment of a proportion of Europid men with chronic hepatitis B virus infection, who might be identified before treatment. Additional strategies are required to improve the rate of response.     

Expression and function of the UM4D4 antigen in human thymus

UM4D4 is a newly identified T cell surface molecule, distinct from the Ag receptor and CD2, which is expressed on 25% of peripheral blood T cells, resting or activated. Monoclonal anti-UM4D4 is mitogenic for T cells and T cell clones. Since alternative activation pathways independent of Ag/MHC recognition may be important in thymic differentiation, the expression and function of UM4D4 was examined in human thymus. UM4D4 was found on the surface of 6% of thymocytes. All thymocyte subsets contained UM4D4+ cells but expression was greatest on thymocytes that were CD1- (12%), CD3+ (11%) and especially CD4-CD8- (18%). CD3+CD4- CD8- cells, most of which bear the gamma delta-receptor, were greater than or equal to 50% + for UM4D4. Moreover, anti-UM4D4 was comitogenic for thymocytes together with PMA or IL-2. Anti-UM4D4 also reacted strongly with a subset of thymic epithelial cells in both cortex and medulla. Dual color fluorescence microscopy, with anti-UM4D4 and antibodies to other thymic epithelial Ag, showed UM4D4 expression on neuroendocrine thymic epithelium but not on thymic fibrous stroma. Thus, UM4D4 is expressed on, and represents an activation pathway for, a subset of thymic T cells. In addition, this determinant, initially identified as a novel T cell activating molecule, is broadly expressed by neuroendocrine thymic epithelium. Although the function of UM4D4 on the thymic epithelial cells is not yet clear, it is possible that UM4D4 represents a pathway for the functional activation of a subset of the thymic epithelium as well as a subset of thymocytes, thus playing a dual role in T cell differentiation.