Superoxide dismutase: fluctuations in the structure and solvation of the active site channel studied by molecular dynamics simulation

The molecular dynamics (MD) simulation of superoxide dismutase (SOD) in water is carried out for a total of 23 ps. The simulation system is a 26 A sphere centered at the active site of SOD, including 1602 atoms from SOD and 1761 water molecules. There is no gross deviation from the x-ray structure for the average MD structure. The structure and potential fluctuations around the active site are examined. The results provide new insight to the interactions between SOD and its substrate superoxide.

A comparison of the digestion and absorption of cocoa butter and palm kernel oil and their effects on cholesterol absorption in rats

Digestion and absorption of cocoa butter and palm kernel oil and their effect on cholesterol absorption were studied in adult male rats. Duodenal and thoracic duct catheters were inserted surgically into the anesthetized rats. After an overnight fast, animals were given a single duodenal dose of an aqueous emulsion containing [1,2-3H]cholesterol and one of the following: corn oil, cocoa butter or palm kernel oil. Digestion and absorption were estimated by recovering the total fatty acids in the thoracic duct lymph over a 24-h collection period (after subtraction of the baseline "endogenous fatty acids" in the lymph). Intestinal absorption of cholesterol into the thoracic duct lymph was reduced significantly (P less than 0.05) in the presence of cocoa butter, compared to absorption when palm kernel oil or corn oil was administered. Compared to the absorption of corn oil (arbitrarily defined as 100%), the absorption of palm kernel oil and cocoa butter was 82 and 63%, respectively. The present study suggests that palm kernel oil absorption was not significantly different from that of corn oil. The lower absorbability of cocoa butter and its inhibitory effect on cholesterol absorption may explain in part why cocoa butter is less hypercholesterolemic and atherogenic than other equally saturated fats.

Water and polypeptide conformations in the gramicidin channel. A molecular dynamics study

Theoretical studies of ion channels address several important questions. The mechanism of ion transport, the role of water structure, the fluctuations of the protein channel itself, and the influence of structural changes are accessible from these studies. In this paper, we have carried out a 70-ps molecular dynamics simulation on a model structure of gramicidin A with channel waters. The backbone of the protein has been analyzed with respect to the orientation of the carbonyl and the amide groups. The results are in conformity with the experimental NMR data. The structure of water and the hydrogen bonding network are also investigated. It is found that the water molecules inside the channel act as a collective chain; whereas the conformation in which all the waters are oriented with the dipoles pointing along the axis of the channel is a preferred one, others are also accessed during the dynamics simulation. A collective coordinate involving the channel waters and some of the hydrogen bonding peptide partners is required to describe the transition of waters from one configuration to the other.

Replacement of aspartic residues 85, 96, 115, or 212 affects the quantum yield and kinetics of proton release and uptake by bacteriorhodopsin

Recently, a number of aspartic acid mutants of bacteriorhodopsin have been shown to be defective in steady-state proton transport. Here we report time-resolved measurements of light-induced proton release and uptake for these mutants. Proton transfers between the protein and the aqueous phase were directly monitored by measuring changes in the bulk conductivity of a micellar solution of bacteriorhodopsin. For the Asp-96----Asn mutant, proton uptake was slowed by greater than 1 order of magnitude with no observable effect on the release step. For Asp-85----Asn, H+ uptake occurred with normal kinetics, but the yield was significantly lower compared with either the Asp-96----Asn mutant or wild type, especially at pH 6. Substitution of glutamate for Asp-85 or Asp-96 had smaller but detectable effects on the kinetics and quantum yield of proton movements. Both asparagine and glutamate substitutions of aspartates at positions 115 and 212 lowered the proton quantum yields. Of these, only the Asp-115----Asn mutant showed an effect on the proton release step, and only the Asp-212----Glu mutation decreased the proton uptake rate. These experiments imply an obligatory role for Asp-96 in H+ uptake in the normal operation of the bacteriorhodopsin proton pump. The results also indicate that the amino acid substitutions affect the kinetics of either H+ release or H+ uptake, but not both. This implies that the two steps occur independently of each other after initiation of the photocycle.

Engineering, mosquitoes and filariasis: a case report

The results of larval surveys were used to assess the relative numbers of mosquitoes breeding in different types of habitat and in different parts of the town of Pondicherry, India. The results illustrate an effective method to set priorities for mosquito control by identifying the most significant breeding sites in a town, and show that they are not necessarily the most obvious, the most extensive or those intuitively most likely.

Reduction of colonic carcinogenesis by wheat bran independent of fecal bile acid concentration

It has been reported previously that populations with a decreased concentration of fecal bile acids have a lower incidence of colon cancer. We examined the importance of fecal bile acid dilution by wheat bran (WB) in inhibiting colonic tumorigenesis in an experimental animal model. Male F344 rats received oral doses of the colon carcinogen 1,2-dimethylhydrazine [CAS: 540-73-8] and were assigned randomly to groups fed one of four semipurified diets for 26 weeks. The diets were fiber-free (FF), 10% WB, FF + bile salts, or WB + bile salts. The amount of bile salts added was adjusted to produce a fecal bile acid concentration in the group fed WB + bile salts equal to that found in the FF groups. Fecal bile acid concentrations at 12 and 24 weeks in the WB + bile salts group were similar to those in the FF group. Gross and microscopic findings at necropsy revealed a reduced total number and multiplicity of colon tumors in both bran-fed groups. Although the fecal bile acid concentrations of the FF and WB + bile salts groups were equal, the latter showed a significant reduction in tumor yield.

Comparison of rice water, rice electrolyte solution, and glucose electrolyte solution in the management of infantile diarrhoea

150 infants aged under 6 months and admitted to hospital with acute gastroenteritis were treated with rice water (RW), rice-based electrolyte solution (RES), and the glucose electrolyte solution (GES) recommended by the World Health Organisation. Two-thirds of the patients were moderately dehydrated and only 8% had positive stool culture. Vomiting, present in 11%, did not interfere with successful oral rehydration. Before treatment serum electrolytes and other biochemical variables were similar in the three groups. After 48 h of treatment the blood urea nitrogen and serum creatinine were lower (p less than 0.05) in the RW and RES group than in the GES group. Serum potassium was also lower in the RW than in the RES group. RW and RES were superior to GES in reducing the frequency and volume of stool output and in producing weight gain.

Lateral diffusion of specific antibodies bound to lipid monolayers on alkylated substrates

We have measured the lateral mobility of fluoresceinated monoclonal IgG antibodies bound specifically to a spin label lipid hapten in phospholipid monolayers supported on alkylated silicon oxide surfaces. Dimyristoyl phosphatidylcholine and dipalmitoyl phosphatidylcholine monolayers containing 5 mol% of the lipid hapten were transferred by conventional Langmuir-Blodgett techniques onto substrates alkylated with hydrocarbon chains containing 10, 16, and 18 carbon atoms. We show that the diffusion of the bound antibodies depends on their lateral density, the composition of the lipid monolayer, and the nature of lipid coupling to hydrocarbon chains on the alkylated substrate. Antibody diffusion coefficients at low antibody densities are within a factor of 2 of those displayed by the lipid hapten in the absence of the bound antibody. High antibody densities result in reduced antibody mobility, but the lateral diffusion of unbound lipids is unaffected.

Specific Skin Involvement in Leukaemias and Lymphomas

Four cases of leukemia, 5 cases of non-Hodgkin's lymphoma and 3 cases of Hodgkin's lymphoma, developed maculo-papular rashes, papules, nodules, urticarial skin lesions and a plaque. Each of these on histopathology, showed a specific skin infiltrate corresponding to the malignancy.

Intestinal absorption and lipoprotein transport of (omega-3) eicosapentaenoic acid

Adult male rats were surgically provided with a drainage catheter in the left thoracic lymphatic channel and an indwelling gastric catheter for constant infusion of saline-glucose. After an overnight fast, animals were given a single gastric dose of an aqueous emulsion containing one of the following 1-14C-labeled fatty acids: oleic, arachidonic or eicosapentaenoic acid, and [1,2-3H]cholesterol. Absorption was estimated by the appearance of radioactivity in lymph over a 24-h collection period, and the lymph lipoprotein distributions and lipoprotein lipid distribution were determined in the 24-h samples. Although there were apparent differences in the rates of eicosapentaenoic and arachidonic acid absorption, the overall appearance (after 24 h) of these acids in lymph was quantitatively equivalent to that of oleate. Furthermore, cholesterol absorption from each fatty acid medium was quantitatively similar. The distributions of each fatty acid among major lymph lipoproteins were similar with 93-95% recovered in chylomicrons and very low density lipoprotein (VLDL) fractions. Furthermore in these lipoproteins, 85-91% of each of the three fatty acids was recovered as triglycerides. With both polyunsaturated fatty acids, there was greater incorporation into phospholipids and their precursor partial glycerides than with oleate. These studies suggest that unesterified eicosapentaenoic acid is absorbed efficiently into the lymphatic system, and has lymph lipoprotein and lipid distribution comparable to those of the more typical mono- and polyunsaturated fatty acids.

Suicide in a northern town of Sri Lanka

Suicide mortality in a northern town of Sri Lanka for the year 1982 is examined. The rate was 53.5 per 100,000 general population and shows an increasing trend amongst the 15-34 age group. The commonest method was self-poisoning by agrochemicals and insecticides of organophosphorus type. Psychiatric diagnosis, social, economic and political factors are presented. Easy availability of dangerous agrochemicals and rapid social and political changes appear to be of equal importance in producing a high rate of suicide.

Comparative lymphatic absorption of sitosterol, stigmasterol, and fucosterol and differential inhibition of cholesterol absorption

Studies have been conducted on the lymphatic absorption of sitosterol (24 alpha-ethyl cholesterol), stigmasterol (delta 22, 24 alpha-ethyl cholesterol), and fucosterol (24-ethylidine cholesterol) when administered intragastrically to rats. In addition, the effect of each sterol on absorption of endogenous cholesterol has been assessed by including tracer cholesterol in the administered test emulsion. Analysis of 24-h lymph collections by GLC-mass spectrometry demonstrated that all three sterols were poorly absorbed to the extent of only 3 to 4% of the administered dose of 50 mg. In contrast, cholesterol absorption under similar conditions was about 42% of the administered dose. Administration of either sitosterol or stigmasterol resulted in an equally effective inhibition of cholesterol absorption (54%). Under identical conditions fucosterol had no effect on absorption of luminal cholesterol. The data suggest that the mechanism(s) for intestinal discrimination of sterols for absorption may be independent of the mechanism for interference with efficient cholesterol uptake by the intestine.

Kinetics of protein-mediated transfer of rat pancreatic microsomal phosphatidylinositol to liposomes

Pancreatic microsomes were isolated from fasted and pilocarpine-injected rats and the microsomal phosphatidylinositol radiolabelled with myo-[2-3H]inositol by isotopic exchange. A standard reaction mixture was established in which partially purified rat liver phosphatidylinositol exchange proteins sustain a maximal rate of phosphatidylinositol transfer from rat pancreatic microsomes to liposomes. Determination of the transfer kinetics shows (1) that pancreatic microsomal phosphatidylinositol is partitioned approximately equally between a non-exchangeable and a single exchangeable pool and (2) that cholinergic stimulation does not significantly change the relative sizes of the two pools nor the exchange half-life of the latter pool.

Effects of acupuncture in bronchial asthma: preliminary communication

Twenty patients randomly assigned to an experimental and a control group participated in a double blind study to assess the effectiveness of acupuncture in bronchial asthma, using the peak expiratory flow rate (PEFR) as an index of bronchial patency. All patients in the control group showed a significant improvement in their PEFR while only 3 patients in the treated group showed an improvement. A subjective improvement and a reduction in drug dosages were observed in both groups. It is concluded that acupuncture has a placebo effect in bronchial asthma.

Effects of Acupuncture in Bronchial Asthma: Preliminary Communication

Twenty patients randomly assigned to an experimental and a control group participated in a double blind study to assess the effectiveness of acupuncture in bronchial asthma, using the peak expiratory flow rate (PEFR) as an index of bronchial patency. All patients in the control group showed a significant improvement in their PEFR while only 3 patients in the treated group showed an improvement. A subjective improvement and a reduction in drug dosages were observed in both groups. It is concluded that acupuncture has a placebo effect in bronchial asthma.

Antigenic subtypes of HBsAg: their distribution and pattern of occurence among blood donors and patients with liver diseases and leprosy in Tamilnadu, India

One hundred and seventy hepatitis B Surface antigen positive sera derived from blood donors, patients with liver diseases and leprosy were antigenically subtyped by Rheophoresis and 107 of them by agar-gel diffusion. For the first time in India HBsAg/adr as a predominant subtype (64.0%) is documented. Of the two methods adopted, Rheophoresis showed a greater sensitivity of typing, namely 82.3% in contrast to 39.2% only by agar-gel diffusion (p less than 0.001). Analysis of the Hepatitis Be antigen and antibody (anti HBe) positive sera for subtype predeliction revealed the same pattern as in HBe system negative sera.

In vitro sensitivity of enteric bacteria to epicillin, chloramphenicol, ampicillin and furazolidone

Strains of Salmonella typhi (148) and Salmonella paratyphi A (27) isolated from the blood of patients with clinical features of enteric fever were tested in vitro for their sensitivity to epicillin, ampicillin, chloramphenicol and furazolidone. Results from both the disc and tube dilution methods showed that greater percentages of the two strains were sensitive to epicillin than to the other antibiotics.