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Biomedical subjects

M Guy

Publications and source records attributed to M Guy.

53 records · Page 3Linked to original sources
PubMed1985

Delays in the primary vaccination of children.

The results of a population-based survey of 170 children's vaccination records were used to calculate the cumulative distributions of the ages (in months) at which each dose of vaccine had been received. Considerable delays in the administration of measles-mumps-rubella (MMR) vaccine and of the fourth dose of diphtheria-pertussis-tetanus vaccine were observed, particularly in children vaccinated by private physicians rather than at public health clinics. The delay before MMR vaccination causes concern because of the frequency of measles in children aged 1 to 2 years, particularly those attending day-care centres, and the fragility of the herd immunity against this disease. Physicians should follow up patients who have missed appointments for MMR vaccination if a voluntary measles control program is to succeed.

Age Factors↗
PubMed1983

[Tularemia].

Explore the source record for details and available documents.

Disease Outbreaks↗
PubMed1982

[Interactions of 2 associated parasitoses in the rat: Plasmodium berghei and Strongyloides ratti].

When Plasmodium berghei and Strongyloides ratti are associated, each one of these parasites can modify development of the other one. This repercussion is subordinated to the respective periods of contamination and strength of influential parasitism. It lies in an inhibition of Protozoosis or intensification of helminthiasis. When severe, palustral infection releases two hypercosticosteronemy phases; the more important one is situated at the peak of the parasitemia. These hypercorticosteronemiae reactions to a severe malaria enable the interpretation of the variations of an associateds trongyloïdiasis. They may be regarded as one of the inducer elements of immunological depression which takes place in the course of malaria in rodents.

Animals↗
PubMed1981

Protonation and light synergistically convert plasmalemma sugar carrier system in mesophyll protoplasts to its fully activated form.

The course of sugar fluxes into and out of protoplasts isolated from the mesophyll of Pisum sativum L. has been followed over brief time intervals (minutes). Light strongly stimulated net sugar influx at pH 8 as well as at pH 5.5. The proton conductor carbonyl cyanide m-chlorophenylhydrazone (CCCP) inhibited initial influx in the light, both at pH 8.0 and at pH 5.5. CCCP was without effect in the dark at either pH. All these results applied both to sucrose and to the nonmetabolizable glucose analog 3-O-methyl-d-glucose.When protoplasts at pH 5.5 were transferred from light to darkness, "stored" light driving force maintained uptake in the dark at the full light rate for the first 7 minutes. At pH 8, however, even 4 minutes after transfer to dark, uptake was well below the light rate. Initial uptake rates over a range of external concentrations were derived from progress curves obtained in the light and in the dark, both at pH 5.5 and at 7.7. When initial rate was plotted against concentration, simple Michaelis-Menten kinetics were observed only under the condition pH 5.5, light. In the dark at both pH values, and in the light at pH 7.7, complex curves with intermediate plateaus were obtained, strongly resembling curves reported for systems where mixed negative and positive cooperativity is operating.The same "K(m) for protons" was observed in the dark and in the light (10(-7) molar). Switching protoplasts in the dark from pH 8 to 5.5 failed to drive sugar transport by imposed protonmotive force, as judged by lack of sensitivity to CCCP. Switching protoplasts which had taken up sugar in the dark at pH 5.5 to pH 7 induced net efflux of sugar. Flux analysis showed that this effect was entirely due to the prompt fall in influx.It is concluded from the kinetic experiments that protonation alone is not sufficient to convert the sugar transport system to its fully activated high affinity form. A further light-dependent factor which acts synergistically with protonation is required.

Journal Article↗
PubMed1980

Energization of the sugar transport mechanism in the plasmalemma of isolated mesophyll protoplasts.

The mechanism of 3-O-methyl-d-glucose transport through the plasmalemma has been investigated in protoplasts isolated from the mesophyll of Pisum sativum L. var. Dan.Analysis of the fluxes after 50 minutes of uptake showed that the gradual decrease in slope of the net uptake curve with time was not due to any decline in uptake capacity; it represented the approach to flux equilibrium of a small compartment of the protoplast, probably the cytoplasm.The energy of activation for initial flux into this compartment was 20 kilocalories per mole between 17 and 27 C. Very high discrimination was shown with regard to sugar isomers. Light strongly promoted flux (by a factor of 2.5 in the case of methyl glucose). Initial flux showed sharply contrasting inhibitor sensitivity in the light and the dark. Light uptake was sensitive to the proton conductor carbonyl cyanide m-chlorophenylhydrazone (CCCP), but stable for at least the first 10 minutes to the ATPase inhibitors quercetin, rutin, and diethylstilbestrol, as well as to arsenate. Dark uptake, on the other hand, was stable to CCCP but was immediately depressed by quercetin, rutin, diethylstilbestrol, and arsenate.Protoplasts which received a light pretreatment before incubation in the dark took up methyl glucose at the accelerated light rate for the first 7 minutes. Moreover, the light pretreatment sensitized subsequent initial dark uptake to CCCP, and conferred on it the stability to ATPase inhibitors and arsenate characteristic of light uptake. After about 7 minutes the characteristic inhibitor responses of dark uptake were resumed.It is proposed that more than one mode of energy-coupling for sugar transport may operate in these protoplasts.

Journal Article↗
PubMed1979

Direct evidence for a sugar transport mechanism in isolated vacuoles.

Sugar transport has been directly observed in isolated higher plant vacuoles for the first time. The latter were released from protoplasts isolated from the mesophyll of Pisum sativum L.Uptake of l-glucose by the vacuoles was very slight in comparison with that of the d-glucose analog 3-O-methyl glucose (MeG), indicating, first, that a highly selective sugar uptake mechanism is seated in the tonoplast; and, second, that the mechanism was functioning in the isolated vacuoles.MeG uptake was markedly sensitive to the pH of the medium, falling as the external pH rose. Addition of MgATP to buffered medium strongly promoted MeG uptake by vacuoles, but not by the protoplasts from which they were released. Treatment with the proton ionophore SF(6847) drastically reduced uptake by the vacuoles, but had a lesser effect on uptake by the protoplasts. The inhibitory effect of SF(6847) on uptake by the vacuoles was countered to a substantial degree by the addition of MgATP.The influence of pH, the stimulatory effect of ATP, and the ATP-reversible inhibition by SF(6847) all strengthen the conclusion that the observed sugar uptake reflected membrane function and was not due to a diffusional inward leak through damaged membranes.The results are discussed in the light of currently held concepts regarding the driving force for sugar transport.

Journal Article↗
PubMed1978

Membrane transport of sugars and amino acids in isolated protoplasts.

A method has been developed for observing membrane transport in isolated protoplasts. Transport of sugars and amino acids has been studied in protoplasts isolated from the mesophyll of Pisum sativum L. That uptake was not due to passive diffusion through damaged membranes was demonstrated by supplying simultaneously two sugar stereoisomers, the one (3)H-labeled and the other (14)C-labeled. The protoplast membranes were sufficiently functional to discriminate strongly between these stereoisomers.To characterize transport the nonmetabolized glucose analogue 3-O-methyl glucose (MeG) and amino acid analogue alpha-aminoisobutyric acid (AIB) were employed. When uptake was compared per unit of protein as between leaf strips and protoplasts prepared from the same tissue, it was estimated that the protoplasts had retained approximately 40 to 50% of the uptake ability of the whole cells. Uptake of neither MeG nor AIB by protoplasts was linear with time, but the tendency to flatten was more marked for AIB. Addition of Mg-ATP to buffered medium significantly promoted AIB uptake, an effect not ascribable to either chelation or pH. Transport of both MeG and AIB was markedly pH-dependent, uptake falling with rise in pH.The stimulatory effect of Mg-ATP and the pH dependence confirm that uptake was not due to a diffusional inward "leak" but involved membrane function.This work demonstrates the feasibility of using isolated protoplasts for membrane transport studies. The potential advantages of using protoplasts for such studies are pointed out.

Journal Article↗
PubMed1978

Neonatal transport.

Communication and teamwork are the keynotes to a successful transport system. This requires a team not only trained in transport details but also able to give emergency care to stabilize the infant prior to transport. The effectiveness of neonatal transport in lowering infant mortality depends on the efficiency of team care before and during transport.

Ambulances↗
PubMedDate not supplied

Animal models of arthritis: relevance to human disease.

Animal models of arthritis are used to evaluate potential antiarthritis drugs for clinical use. Therefore capacity of the model to predict efficacy in human disease is one of the most important criteria in model selection. Animal models of rheumatoid arthritis (RA) with a proven track record of predictability include rat adjuvant arthritis, rat type II collagen arthritis, mouse type II collagen arthritis, and antigen-induced arthritis in several species. Agents currently in clinical use (or trials) that are active in these models include corticosteroids, methotrexate, nonsteroidal anti-inflammatory drugs, cyclosporin A, leflunomide, interleukin-1 receptor antagonist, and soluble tumor necrosis factor receptors. For some of these agents, the models also predict that toxicities seen at higher doses for prolonged periods would preclude dosing in humans at levels that might provide disease-modifying effects. Animal models of osteoarthritis (OA) include mouse and guinea pig spontaneous OA, meniscectomy and ligament transection in guinea pigs, meniscectomy in rabbits, and meniscectomy and cruciate transection in dogs. None of these models have a proven track record of predictability in human disease because there are no agents that have been proven to provide anything other than symptomatic relief in human OA. Efficacy data and features of the various models of RA and OA are discussed with emphasis on their proven relevance to human disease.

Animals↗