Lipid and protein contributions to the membrane surface potential of vesicular stomatitis virus probed by a fluorescent pH indicator, 4-heptadecyl-7-hydroxycoumarin

The surface potential of membranes of vesicular stomatitis virus and liposomes was determined by shift of ionization over a wide pH range of the membrane-inserted fluorophore, 4-heptadecyl-7-hydroxycoumarin. Incorporation into sonicated vesicles of negatively charged phosphatidylserine markedly increased the surface potential of uncharged phosphatidylcholine, but no significant effect on surface potential was produced by polar but uncharged glucocerebroside incorporated in phosphatidylcholine vesicles. The membrane of vesicular stomatitis virus was found to have a moderately high surface potential. Contributing to this viral membrane surface potential were glycoprotein spikes and phospholipid headgroups as determined by lowered charge after treatment of intact virions with thermolysin to remove glycoprotein or phospholipase C to remove phospholipid headgroups. The role of viral glycoprotein was confirmed by demonstrating increased surface charge of vesicles reconstituted with both viral glycoprotein and lipids compared with vesicles reconstituted with viral lipids alone. An unexpected finding was the large contribution to surface potential of cholesterol present in viral membrane. Increasing cholesterol concentration in virions by interaction with cholesterol-complexed serum lipoproteins resulted in a marked decrease in surface potential, whereas 75% depletion of virion cholesterol by interaction with sphingomyelin-complexed serum lipoproteins resulted in a significant increase in virion membrane surface potential. Although removal of glycoprotein spikes or depletion of cholesterol causes reduction in infectivity of vesicular stomatitis virus, no direct correlation could be found between alteration in surface charge and infectivity.

Thiomethylation and thiohydroxylation--a new pathway of metabolism of heterocyclic compounds

1. G.l.c.--mass spectral analysis of t.l.c. fractions of urine samples of patients treated with 5-(2-chloroethyl)-4-methylthiazole (clomethiazole), has revealed two minor metabolites, each with two sulphur atoms. 2. Their structures were found to be 2-methylthio-clomethiazole and 5-acetyl-4-methyl-2-mercapto-thiazole, formed by thiomethylation and thiohydroxylation, respectively, of the original compound. 3. The structures of six other minor metabolites resulting from side-chain degradation have been elucidated. 4. The occurrence of metabolites with substituents at position 2 of the heterocyclic nucleus is assumed to be initiated by oxidative attack at the nitrogen, followed by nucleophilic substitution in position 2.

Pardaxin, a hydrophobic toxin of the Red Sea flatfish, disassembles the intact membrane of vesicular stomatitis virus

Reaction of vesicular stomatitis virus with pardaxin, the hydrophobic toxin of the Red Sea flatfish, resulted in a profound morphological change of many virions and dissociation of their membrane and nucleocapsid into components readily separable by density gradient centrifugation. The basic matrix protein and acidic pardaxin segregated largely with the high density nucleocapsid. The dissociated virion membrane formed lipoprotein vesicles which retained glycoprotein spikes and a certain amount of N protein but no appreciable amounts of other nucleocapsid proteins and little if any RNA. Iodination of the tyrosine residue of the glycoprotein tail fragment provided supporting evidence that the COOH terminus of the glycoprotein extends beyond the inner layer of the membrane into the interior of the virion. These data indicate that pardaxin may serve as a probe for studying the organization of viral membranes, and, hopefully, other biological membranes.

Transcription of vesicular stomatitis virus activated by pardaxin, a fish toxin that permeabilizes the virion membrane

The toxic protein, Pardaxin, of the Red Sea flatfish Pardachirus marmoratus readily induced transcription of vesicular stomatitis virus by making the virion membrane permeable to nucleoside triphosphates in the absence of nonionic detergents. Virion transcription was activated over a wide range of Pardaxin concentrations, but at optimal concentrations, the rate of transcription exceeded that induced by Triton X-100. The inhibitory effect of M protein was manifested for both Pardaxin-induced and Triton-induced transcription at high concentrations of vesicular stomatitis virions; however, unlike the Triton-induced reaction, the inhibitory effect of M protein was not reversed by polyglutamic acid added to the Pardaxin-induced transcription reaction. We propose that activation of virion transcription by Pardaxin resembles more closely intracellular transcription initiated by virion penetration than does detergent-activated transcription of vesicular stomatitis virus.

Fluorescence studies of dipalmitoylphosphatidylcholine vesicles reconstituted with the glycoprotein of vesicular stomatitis virus

The vesicular stomatitis virus glycoprotein (G) was reconstituted into dipalmitoylphosphatidylcholine (DPPC) vesicles by detergent dialysis. The DPPC gel to liquid-crystalline phase transition of the DPPC-G protein vesicles was monitored by the fluorescence anisotrophy of trans-paranaric acid, 16-(9-anthroyloxy)palmitoylglucocerebroside, 1,6-diphenyl-1,3,5-hexatriene, and 4-heptadecyl-7-hydroxycoumarin. The DPPC transition temperature measured by all four fluorescent probes was lowered in the presence of the G protein and the DPPC gel state was disordered by the G protein as evidenced by a decreased fluorescence anisotropy for all four probes below the phase-transition temperature. A possible ordering of the DPPC liquid-crystalline state by the G protein was indicated by an increased anisotropy of trans-paranaric acid and 16-(9-anthroyloxy)palmitoylglucocerebroside in the liquid-crystalline state of DPPC-G protein vesicles. The G protein in addition affected the ionization of the 4-heptadecyl-7-hydroxycoumarin in lipid vesicles, increasing the apparent pK of the probe from 9.05 to 9.45.

Fluorescence anisotropy of a fatty acid covalently linked in vivo to the glycoprotein of vesicular stomatitis virus

The covalently-attached fatty acid of the membrane glycoprotein (G) of vesicular stomatitis virus was fluorescently labeled biologically by isolating vesicular stomatitis virus from infected baby hamster kidney clone 21 cells that had been grown in the presence of 16(9-anthroyloxy)palmitate. The fluorescent labeling was specific for the G protein; the other viral membrane protein, the matrix (M) protein, was not labeled. Steady state fluorescence anisotropy of the 16(9-anthroyloxy)palmitate-labeled G protein reconstituted into dipalmitoylphosphatidylcholine vesicles indicated that the fatty acid attached to G protein is located in a dipalmitoylphosphatidylcholine domain that does not undergo the gel to liquid-crystalline phase transition.

Depletion and exchange of cholesterol from the membrane of vesicular stomatitis virus by interaction with serum lipoproteins or poly(vinylpyrrolidone) complexed with bovine serum albumin

Cholesterol was depleted from the membrane of vesicular stomatitis virus by exposing virion suspensions to serum lipoproteins enriched with phospholipids. Unlike the reaction of virions with phospholipid vesicle, nonspecific adherence of lipoproteins and exogenous lipids to the envelope of the virus was found to be minimal. The extent of cholesterol depletion was dependent upon the type of phospholipid complexed with interacting lipoprotein; sphingomyelin and dipalmitoyllecithin were found to be highly effective depleters of cholesterol compared to egg phosphatidylcholine, phosphatidylethanolamine, or phosphatidylserine. Similar depletion of cholesterol from the virion membrane was also observed when vesicular stomatitis virus was exposed to a complex of poly(vinylpyrrolidone) and bovine serum albumin coated with egg phosphatidylcholine or dioleoylphosphatidylcholine. Cholesterol depletion was found to alter the morphology but not the membrane integrity of the virus. Directly correlated with depletion of cholesterol was a substantial loss in the anisotropy of the viral membrane as determined by fluorescence depolarization of the lipophilic probe 1,6-diphenyl-1,3,5-hexatriene. Interaction with poly(vinylpyrrolidone) complexed with albumin, phosphatidylcholine, and cholesterol resulted in exchange of cholesterol from the virion membrane which following biphasic kinetics with a rapid and a slow phase; these data indicate that 75-85% of viral membrane cholesterol is present in the outer monolayer, and 15-25% is located in the inner monolayer. Depletion of cholesterol from the virion membrane resulted in a significant drop in the infectivity of the virus as measured by plating efficiency on L-cell monolayers. Such an effect was not observed when virion cholesterol was exchanged without net reduction in the concentration of viral membrane cholesterol. Part of the loss in infectivity following depletion of cholesterol could be restored by reincorporation of cholesterol in the membrane, thus demonstrating that membrane cholesterol partly contributes to the infectivity of vesicular stomatitis virus.

Alteration of the membrane lipid composition and infectivity of vesicular stomatitis virus by growth in a Chinese hamster ovary cell sterol mutant and in lipid-supplemented baby hamster kidney clone 21 cells

The cholesterol and phospholipid composition of the membrane of vesicular stomatitis (VS) virus was altered by growth in a sterol auxotroph Chinese hamster ovary (CHO MI) host cell and by infection of CHO MI and baby hamster kidney (BHK)-21 cells supplemented with fatty acids and dimethylethanolamine. VS virus released from infected CHO MI sterol auxotroph cells grown in delipidated serum had a 50% lower ratio of cholesterol to phospholipid and an 80% drop in infectivity measured by plaque formation on L-929 cells compared with VS virus released from infected CHO MI cells grown in fetal calf serum. When VS virus was harvested from infected BHK-21 cells fed the choline analogue dimethylethanolamine, 29% of the membrane phospholipids were phosphatidyldimethylethanolamine (PDME); 87% of the PDME was located in the external monolayer of the virus membrane as determined by phospholipase C hydrolysis. Exogenous fatty acids added to the medium of cells infected with VS virus comprised up to 30% of the fatty acyl chains of the viral glycerophospholipids. The presence of PDME or unusual fatty acyl chains in the viral membrane had no effect on viral infectivity. These data indicate that the lipid composition of the VS virus membrane is determined primarily by the lipids available in the host cell and that only cholesterol content affects the biological activity of the virus membrane.

Thermotropic behavior of dipalmitoylphosphatidylcholine vesicles reconstituted with the glycoprotein of vesicular stomatitis virus

The vesicular stomatitis virus glycoprotein reconstituted into dipalmitoylphosphatidylcholine (DPPC) vesicles exerts a profound effect upon the DPPC gel to liquid-crystalline phase transition. The glycoprotein was reconstituted into DPPC vesicles by octyl glucoside dialysis. The gel to liquid-crystalline phase transition of these vesicles was monitored by differential scanning calorimetry. Vesicles formed in the absence of glycoprotein (600--2100-A diameter) underwent the phase transition at 41.0 degrees C and had an associated enthalpy change of 8.0 +/- 1.6 kcal/mol. Increasing the mole ratio of glycoprotein to DPPC in the vesicles to 0.15 mol % reduced both the transition temperature and the transition enthalpy change. The enthalpy change as a function of the mole percent glycoprotein could be fit to a straight line by a least-squares procedure. Extrapolation of the results to the glycoprotein concentration where the enthalpy change was zero indicated one glycoprotein molecule bound 270 +/- 150 molecules of DPPC.

Aircraft disinsecting: the effectiveness of Freon-based and water-based phenothrin and permethrin aerosols

In Miami, Florida, USA, passenger compartments of jet aircraft were disinsected at "blocks away". An application of a 20 g/litre Freon-based or water-based permethrin formulation at 35 mg of aerosol per 100 m(3) was 100% effective against caged mosquitos and flies. The flammability hazard of the sprays from water-based hydrocarbon aerosols was evaluated.

Species complexes in the Simuliidae

The recent discovery that Simulium damnosum in Africa is not a single species but a complex of sibling species has important implications for the epidemiology and control of onchocerciasis. This paper sets out the current situation with regard to classification within the S. damnosum complex and the smaller S. neavei group. The nomenclature of the S. damnosum complex and current morphological and enzyme electrophoretic methods of differentiating among sibling species are discussed. Finally, recommendations are made on priorities for future research.

A comparison of Freon- and water-based insecticidal aerosols for aircraft disinsection

In Miami, USA, passenger compartments of wide-bodied jet aircraft were disinsected at "blocks away" or while parked. The application of 2% Freon- and water-based formulations of (+)-phenothrin at about 35 g/100 m(3) was highly effective against mosquitos and flies in all instances. More basic research is needed on water-based aerosols.

Possible Surface Reactions on Mars: Implications for Viking Biology Results

The results of two of the three biology experiments carried out on the Viking Mars landers have been simulated. The mixture of organic compounds labeled with carbon-14 used on Mars released carbon dioxide containing carbon-14 when reacted with a simulated martian surface and atmosphere exposed to ultraviolet light (labeled release experiment). Oxygen was released when metal peroxides or superoxides were treated with water (gas exchange experiment). The simulations suggest that the results of these two Viking experiments can be explained on the basis of reactions of the martian surface and atmosphere.

Antileukemic and other constituents of Tithonia tagitiflora Desf

Phytochemical investigation of Tithonia tagitiflora has led to isolation of six new germacranolides, tagitinins A, B, C, D, E, AND F, beta-sitosterol, and its beta-D-glucoside. Among these, tagitinin F possesses antileukemic activity.

Aircraft disinfection: the physical and insecticidal characteristics of (+)-phenothrin applied by aerosol at "blocks away"

A 2% formulation of (+)-phenothrin dispensed from 340-g or break-off tip aerosol cans was highly effective against mosquitos in aircraft disinsection trials. Two minutes after application at "blocks away", the mass median diameter of the dispersed drops was 5.1-6.2 mum. The concentration of the insecticide in the cabin fell to 10% of the original concentration after 9.2 min. No odour or irritation was caused by the use of this insecticide.

Worldwide studies on aircraft disinsection at "blocks away"

During 1971 worldwide experiments on the disinsection of passenger cabins at "blocks away" (as the aircraft starts taxiing for take-off) were conducted in several types of jet aircraft. A procedure was developed whereby the high capacity Boeing 747 could be disinsected by four stewardesses in less than 1 minute. The favourable results of these and previous trials indicate that this method is suitable as a standard procedure for aircraft disinsection for international quarantine purposes.The biological effectiveness against resistant and non-resistant mosquitos of a 2% concentration of a pyrethroid, resmethrin, in Freon 11+Freon 12 (1:1) (without kerosine) and a favourable passenger response make it suitable as a standard formulation for aircraft disinsection.

The impact of insecticide-resistance on control of vectors and vector-borne diseases

A questionnaire inquiring into the nature of schemes for the insecticidal control of disease vectors, the development of resistance in these vectors, and the effect of any such resistance on their control and on the extent of disease was sent to more than 100 health authorities throughout the world. The replies to the questionnaire are summarized in this paper.Until recently, the use of insecticides in public health has been largely based on three organochlorine compounds-DDT, HCH and dieldrin. However, in some countries resistance to these has now severely affected control both of many insect species and of the diseases they transmit (e.g., malaria, yellow fever, filariasis, typhus, plague). Certain other public health problems (onchocerciasis, Chagas' disease, trypanosomiasis, leishmaniasis) have not so far been greatly affected by resistance, but it is difficult to be sure of the continued reliability of the organochlorines.Research in the past 5 years, much of it sponsored by WHO, has shown the value of various organophosphorus and carbamate insecticides as replacements for the organochlorines, although resistance to them, too, can occur. Attention must therefore be focused on all facets of the use of these newer compounds and particular scrutiny made of possible instances of resistance to them.

Ortho-isopropoxphenyl methylcarbamate (OMS-33) as a residual spray for control of anopheline mosquitos. With special reference to its evaluation in the WHO programme for evaluating and testing new insecticides

More than 1300 compounds have so far been included in the WHO Programme for Evaluating and Testing New Insecticides, which is designed to disclose compounds that may satisfactorily replace those to which insect vectors of disease have become resistant. The authors describe the successful passage of o-isopropoxyphenyl methylcarbamate (OMS-33) through the first 6 stages of the 7-stage programme that has been established for compounds intended for use against anopheline mosquitos and conclude that this product is suitable for testing in the final stage-large-scale epidemiological evaluation.In operational field trials (at 2 g/m(2)) OMS-33 has been shown capable of controlling Anopheles stephensi (in Iran), An. gambiae and An. funestus (in Nigeria) for 3-4 months, An. albimanus (in El Salvador) for 2-4 months and An. dthali (in Iran) for 2(1/2) months. It has an airborne effect by which anophelines are killed for a considerable time after OMS-33 has been sprayed, even though they do not make contact with a sprayed surface; this quality would appear advantageous in areas where anophelines enter houses and bite man but do not rest long enough on sprayed surfaces to acquire a lethal dose of insecticide or where significant outdoor biting occurs. The observance of simple safety precautions protects occupants of sprayed houses, spraymen and others from danger. Chemical studies have indicated that commercially produced water-dispersible powders of OMS-33 are stable under field conditions of storage and use.

Genetic control of insects of public health importance

During recent years many advances have been made in the development of insect control by genetic manipulation. These methods include the sterile-male technique, now well known, which depends on ionizing radiation or chemosterilization. The recent field experiment carried out by WHO in Rangoon, Burma, on Culex fatigans has demonstrated that naturally occurring cytogenetic mechanisms such as cytoplasmic incompatibility can be used successfully without the use of radiations or chemosterilants. The paper not only describes the experiment on Culex fatigans but also discusses basic concepts and theoretical considerations involved in genetic control of insects of public health importance. The possibility of using genetic mechanisms for the control of other vector species is also discussed. There are a number of problems which require study before genetic control can be used on an operational scale. These problems and suggestions for future research in this field are also outlined.

Second survey of insecticid-resistance in body-lice, 1958-63

Between 1953 and 1956 the World Health Organization carried out a global survey of the susceptibility of body-lice to insecticides. A second survey was organized in 1958; this paper summarizes the results of susceptibility tests done in 22 countries over the period 1958-63.Resistance to DDT has been found in a number of countries. The LC(100) for resistant body-lice has been found to be over 5% DDT, the LC(100) for hybrids to be between 1% and 5% DDT; and the LC(50) for susceptible genotypes has been estimated to be less than 0.04% DDT.Body-lice continue to be susceptible to gamma-HCH and pyrethrins in most countries, although they show increased tolerance to gamma-HCH in Egypt. Their susceptibility to malathion in various localities in Egypt has been assessed, and the LC(50) found to range from 0.02% to 0.032%.