Challenges of nanotechnology in cosmetic permeation with caffeine.

The evolution of beauty market and personal care is constant in Brazil as well in the rest of the world. Technological advances have brought up nanotechnology to the cosmetological field, employing active principles at atoms enveloped by vesicles, in order to take the active principle precisely to the target tissue to optimize the results achieved because of the considerable ease to cross skin barriers. Manufacturing of nanotechnology cosmetics is confronted with low absorption capacity. One of the many active principle found in cosmetic industry is caffeine, a pseudoalkaloid from the xanthine group used as a stimulant with the mechanism of the lipolytic action. This active is widely used in ​​a esthetics and cosmetics field in treatments involving dysfunctions such as localized fat and fibroedema geloid. To work out perfectly, the principle active need to interact and create a set of factors that includes lipolysis intensification. The caffeine encapsulation in gel-based nanocosmetics has the purpose of taking this active up to the adipocyte, the target cell, for mentioned dysfunctions treatment. Thus, we aim to present a review of how has been, the use of caffeine in the production of cosmetics.

Quality of cosmetics with active caffeine in cream and gel galenic bases prepared by compounding pharmacies.

As there is a great scarcity of studies on the importance of good compounding practices in the preparation of cosmetics, this study aimed to evaluate the quality control of cosmetics with active ingredient caffeine for the treatment of cellulite prepared by magistrals pharmacies. Microbiological analyzes, pH determination, color measurement, quantification of the percentage of the active ingredient caffeine and viscosity in creams and gels with 5% of the active ingredient caffeine were performed. In the microbiological analysis, the presence of molds and yeasts was verified above the permitted level according to the Brazilian pharmacopoeia. The pH decreased over time, contributing to the formulations becoming more acidic. In the color parameters, it was found that pharmacy F4 showed a brownish color, both for the gel and for the cream. The percentage of caffeine was within specifications in all formulations and the viscosity remained unchanged during the shelf life of the samples. It is important that the compounding pharmacies demand more effectively the commitment of the team, as well as the analysis of the raw material according to the microbiological control regulations to translate into the quality of the products prepared by the pharmacies and favor the consumer in the effective objective that the product you want to achieve.

GaAs Clusters in the Quantum Size Regime: Growth on High Surface Area Silica by Molecular Beam Epitaxy.

Molecular beam epitaxy has been used to grow microcrystalline clusters of gallium arsenide (GaAs) in the size range from 2.5 to 60 nanometers on high-purity, amorphous silica supports. High-resolution transmission electron microscopy reveals that clusters as small as 3.5 nanometers have good crystalline order with a lattice constant equal to that of bulk GaAs. Study of the microcrystallite surfaces by x-ray photoelectron spectroscopy shows that they are covered with a shell (1.0 to 1.5 nanometers thick) of native oxides of gallium and arsenic (Ga(2)O(3) and As(2)O(3)), whose presence could explain the low luminescence efficiency of the clusters. Optical absorption spectra of the supported GaAs are consistent with the blue-shifted band edge expected for semiconductor microcrystallites in the quantum size regime.

Challenges of nanotechnology in cosmetic permeation with caffeine / Desafios da nanotecnologia na permeação cosmética com cafeína

The evolution of beauty market and personal care is constant in Brazil as well in the rest of the world. Technological advances have brought up nanotechnology to the cosmetological field, employing active principles at atoms enveloped by vesicles, in order to take the active principle precisely to the target tissue to optimize the results achieved because of the considerable ease to cross skin barriers. Manufacturing of nanotechnology cosmetics is confronted with low absorption capacity. One of the many active principle found in cosmetic industry is caffeine, a pseudoalkaloid from the xanthine group used as a stimulant with the mechanism of the lipolytic action. This active is widely used in a esthetics and cosmetics field in treatments involving dysfunctions such as localized fat and fibroedema geloid. To work out perfectly, the principle active need to interact and create a set of factors that includes lipolysis intensification. The caffeine encapsulation in gel-based nanocosmetics has the purpose of taking this active up to the adipocyte, the target cell, for mentioned dysfunctions treatment. Thus, we aim to present a review of how has been, the use of caffeine in the production of cosmetics.

A evolução do mercado de beleza e cuidados pessoais é constante no Brasil e no resto do mundo. Os avanços tecnológicos trouxeram a nanotecnologia para o campo cosmetológico, empregando princípios ativos em átomos envolvidos por vesículas, a fim de levar o princípio ativo precisamente ao tecido alvo para otimizar os resultados alcançados devido à considerável facilidade de atravessar barreiras cutâneas. A fabricação de cosméticos nanotecnológicos é confrontada com baixa capacidade de absorção. Um dos muitos princípios ativos encontrados na indústria cosmética é a cafeína, um pseudoalocalóide do grupo xantina usado como estimulante no mecanismo da ação lipolítica. Este ativo é amplamente utilizado no campo da estética e dos cosméticos em tratamentos que envolvem disfunções, como gordura localizada e fibroedema gelóide. Para funcionar perfeitamente, o princípio ativo precisa interagir e criar um conjunto de fatores que inclui a intensificação da lipólise. O encapsulamento de cafeína em nanocosméticos à base de gel tem o objetivo de levar esse ativo até o adipócito, a célula alvo, para o tratamento de disfunções mencionado. Assim, objetivamos apresentar uma revisão de como tem sido o uso de cafeína na produção de cosméticos.

Quality of cosmetics with active caffeine in cream and gel galenic bases prepared by compounding pharmacies / Qualidade de cosméticos com cafeína ativa em bases galênicas em creme e gel preparadas por farmácias de manipulação

As there is a great scarcity of studies on the importance of good compounding practices in the preparation of cosmetics, this study aimed to evaluate the quality control of cosmetics with active ingredient caffeine for the treatment of cellulite prepared by magistrals pharmacies. Microbiological analyzes, pH determination, color measurement, quantification of the percentage of the active ingredient caffeine and viscosity in creams and gels with 5% of the active ingredient caffeine were performed. In the microbiological analysis, the presence of molds and yeasts was verified above the permitted level according to the Brazilian pharmacopoeia. The pH decreased over time, contributing to the formulations becoming more acidic. In the color parameters, it was found that pharmacy F4 showed a brownish color, both for the gel and for the cream. The percentage of caffeine was within specifications in all formulations and the viscosity remained unchanged during the shelf life of the samples. It is important that the compounding pharmacies demand more effectively the commitment of the team, as well as the analysis of the raw material according to the microbiological control regulations to translate into the quality of the products prepared by the pharmacies and favor the consumer in the effective objective that the product you want to achieve.

Como há uma grande escassez de estudos sobre a importância de boas práticas de manipulação na elaboração de cosméticos, o presente estudo teve como objetivo avaliar o controle de qualidade de cosméticos com princípio ativo cafeína para o tratamento de celulite, elaborados por farmácias de manipulação de Campo Mourão. Foram realizadas análises microbiológicas, determinação do pH, mensuração da coloração, quantificação da porcentagem do princípio ativo cafeína e viscosidade em cremes e geís com 5% do princípio ativo cafeína. Nas análises microbiológicas foi verificada a presença de bolores e leveduras acima do pemitido segundo a farmacopéia brasileira. O pH diminuiu ao longo do tempo, contribuindo para que as formulações ficassem mais ácidas. Nos parâmetros de cor averiguou-se que a farmácia F4 apresentou uma coloração amarronzada, tanto para o gel quanto para o creme. A porcentagem de cafeína estava dentro das especificações em todas as formulações e a viscosidade se manteve inalterada durante o prazo de validade das amostras. Com o propósito de um melhor preparo magistral é importante que as farmácias de manipulação exijam de forma mais eficaz o comprometimento da equipe, bem como a análise da matéria-prima segundo as regulamentações de controle microbiológico. Além disso, a implementação de normas mais rígidas e o melhor controle da matéria-prima e das formulações finais fazem com que a qualidade dos produtos manipulados pelas farmácias magistrais seja aumentada significativamente, favorecendo o consumidor na efetiva finalidade a que o produto objetiva atingir.

Challenges of nanotechnology in cosmetic permeation with caffeine

Abstract The evolution of beauty market and personal care is constant in Brazil as well in the rest of the world. Technological advances have brought up nanotechnology to the cosmetological field, employing active principles at atoms enveloped by vesicles, in order to take the active principle precisely to the target tissue to optimize the results achieved because of the considerable ease to cross skin barriers. Manufacturing of nanotechnology cosmetics is confronted with low absorption capacity. One of the many active principle found in cosmetic industry is caffeine, a pseudoalkaloid from the xanthine group used as a stimulant with the mechanism of the lipolytic action. This active is widely used in a esthetics and cosmetics field in treatments involving dysfunctions such as localized fat and fibroedema geloid. To work out perfectly, the principle active need to interact and create a set of factors that includes lipolysis intensification. The caffeine encapsulation in gel-based nanocosmetics has the purpose of taking this active up to the adipocyte, the target cell, for mentioned dysfunctions treatment. Thus, we aim to present a review of how has been, the use of caffeine in the production of cosmetics.

Resumo A evolução do mercado de beleza e cuidados pessoais é constante no Brasil e no resto do mundo. Os avanços tecnológicos trouxeram a nanotecnologia para o campo cosmetológico, empregando princípios ativos em átomos envolvidos por vesículas, a fim de levar o princípio ativo precisamente ao tecido alvo para otimizar os resultados alcançados devido à considerável facilidade de atravessar barreiras cutâneas. A fabricação de cosméticos nanotecnológicos é confrontada com baixa capacidade de absorção. Um dos muitos princípios ativos encontrados na indústria cosmética é a cafeína, um pseudoalocalóide do grupo xantina usado como estimulante no mecanismo da ação lipolítica. Este ativo é amplamente utilizado no campo da estética e dos cosméticos em tratamentos que envolvem disfunções, como gordura localizada e fibroedema gelóide. Para funcionar perfeitamente, o princípio ativo precisa interagir e criar um conjunto de fatores que inclui a intensificação da lipólise. O encapsulamento de cafeína em nanocosméticos à base de gel tem o objetivo de levar esse ativo até o adipócito, a célula alvo, para o tratamento de disfunções mencionado. Assim, objetivamos apresentar uma revisão de como tem sido o uso de cafeína na produção de cosméticos.

Quality of cosmetics with active caffeine in cream and gel galenic bases prepared by compounding pharmacies

Abstract As there is a great scarcity of studies on the importance of good compounding practices in the preparation of cosmetics, this study aimed to evaluate the quality control of cosmetics with active ingredient caffeine for the treatment of cellulite prepared by magistrals pharmacies. Microbiological analyzes, pH determination, color measurement, quantification of the percentage of the active ingredient caffeine and viscosity in creams and gels with 5% of the active ingredient caffeine were performed. In the microbiological analysis, the presence of molds and yeasts was verified above the permitted level according to the Brazilian pharmacopoeia. The pH decreased over time, contributing to the formulations becoming more acidic. In the color parameters, it was found that pharmacy F4 showed a brownish color, both for the gel and for the cream. The percentage of caffeine was within specifications in all formulations and the viscosity remained unchanged during the shelf life of the samples. It is important that the compounding pharmacies demand more effectively the commitment of the team, as well as the analysis of the raw material according to the microbiological control regulations to translate into the quality of the products prepared by the pharmacies and favor the consumer in the effective objective that the product you want to achieve.

Resumo Como há uma grande escassez de estudos sobre a importância de boas práticas de manipulação na elaboração de cosméticos, o presente estudo teve como objetivo avaliar o controle de qualidade de cosméticos com princípio ativo cafeína para o tratamento de celulite, elaborados por farmácias de manipulação de Campo Mourão. Foram realizadas análises microbiológicas, determinação do pH, mensuração da coloração, quantificação da porcentagem do princípio ativo cafeína e viscosidade em cremes e geís com 5% do princípio ativo cafeína. Nas análises microbiológicas foi verificada a presença de bolores e leveduras acima do pemitido segundo a farmacopéia brasileira. O pH diminuiu ao longo do tempo, contribuindo para que as formulações ficassem mais ácidas. Nos parâmetros de cor averiguou-se que a farmácia F4 apresentou uma coloração amarronzada, tanto para o gel quanto para o creme. A porcentagem de cafeína estava dentro das especificações em todas as formulações e a viscosidade se manteve inalterada durante o prazo de validade das amostras. Com o propósito de um melhor preparo magistral é importante que as farmácias de manipulação exijam de forma mais eficaz o comprometimento da equipe, bem como a análise da matéria-prima segundo as regulamentações de controle microbiológico. Além disso, a implementação de normas mais rígidas e o melhor controle da matéria-prima e das formulações finais fazem com que a qualidade dos produtos manipulados pelas farmácias magistrais seja aumentada significativamente, favorecendo o consumidor na efetiva finalidade a que o produto objetiva atingir.

Quality of cosmetics with active caffeine in cream and gel galenic bases prepared by compounding pharmacies / Qualidade de cosméticos com cafeína ativa em bases galênicas em creme e gel preparadas por farmácias de manipulação

As there is a great scarcity of studies on the importance of good compounding practices in the preparation of cosmetics, this study aimed to evaluate the quality control of cosmetics with active ingredient caffeine for the treatment of cellulite prepared by magistrals pharmacies. Microbiological analyzes, pH determination, color measurement, quantification of the percentage of the active ingredient caffeine and viscosity in creams and gels with 5% of the active ingredient caffeine were performed. In the microbiological analysis, the presence of molds and yeasts was verified above the permitted level according to the Brazilian pharmacopoeia. The pH decreased over time, contributing to the formulations becoming more acidic. In the color parameters, it was found that pharmacy F4 showed a brownish color, both for the gel and for the cream. The percentage of caffeine was within specifications in all formulations and the viscosity remained unchanged during the shelf life of the samples. It is important that the compounding pharmacies demand more effectively the commitment of the team, as well as the analysis of the raw material according to the microbiological control regulations to translate into the quality of the products prepared by the pharmacies and favor the consumer in the effective objective that the product you want to achieve.

Como há uma grande escassez de estudos sobre a importância de boas práticas de manipulação na elaboração de cosméticos, o presente estudo teve como objetivo avaliar o controle de qualidade de cosméticos com princípio ativo cafeína para o tratamento de celulite, elaborados por farmácias de manipulação de Campo Mourão. Foram realizadas análises microbiológicas, determinação do pH, mensuração da coloração, quantificação da porcentagem do princípio ativo cafeína e viscosidade em cremes e geís com 5% do princípio ativo cafeína. Nas análises microbiológicas foi verificada a presença de bolores e leveduras acima do pemitido segundo a farmacopéia brasileira. O pH diminuiu ao longo do tempo, contribuindo para que as formulações ficassem mais ácidas. Nos parâmetros de cor averiguou-se que a farmácia F4 apresentou uma coloração amarronzada, tanto para o gel quanto para o creme. A porcentagem de cafeína estava dentro das especificações em todas as formulações e a viscosidade se manteve inalterada durante o prazo de validade das amostras. Com o propósito de um melhor preparo magistral é importante que as farmácias de manipulação exijam de forma mais eficaz o comprometimento da equipe, bem como a análise da matéria-prima segundo as regulamentações de controle microbiológico. Além disso, a implementação de normas mais rígidas e o melhor controle da matéria-prima e das formulações finais fazem com que a qualidade dos produtos manipulados pelas farmácias magistrais seja aumentada significativamente, favorecendo o consumidor na efetiva finalidade a que o produto objetiva atingir.

Challenges of nanotechnology in cosmetic permeation with caffeine / Desafios da nanotecnologia na permeação cosmética com cafeína

The evolution of beauty market and personal care is constant in Brazil as well in the rest of the world. Technological advances have brought up nanotechnology to the cosmetological field, employing active principles at atoms enveloped by vesicles, in order to take the active principle precisely to the target tissue to optimize the results achieved because of the considerable ease to cross skin barriers. Manufacturing of nanotechnology cosmetics is confronted with low absorption capacity. One of the many active principle found in cosmetic industry is caffeine, a pseudoalkaloid from the xanthine group used as a stimulant with the mechanism of the lipolytic action. This active is widely used in a esthetics and cosmetics field in treatments involving dysfunctions such as localized fat and fibroedema geloid. To work out perfectly, the principle active need to interact and create a set of factors that includes lipolysis intensification. The caffeine encapsulation in gel-based nanocosmetics has the purpose of taking this active up to the adipocyte, the target cell, for mentioned dysfunctions treatment. Thus, we aim to present a review of how has been, the use of caffeine in the production of cosmetics.

A evolução do mercado de beleza e cuidados pessoais é constante no Brasil e no resto do mundo. Os avanços tecnológicos trouxeram a nanotecnologia para o campo cosmetológico, empregando princípios ativos em átomos envolvidos por vesículas, a fim de levar o princípio ativo precisamente ao tecido alvo para otimizar os resultados alcançados devido à considerável facilidade de atravessar barreiras cutâneas. A fabricação de cosméticos nanotecnológicos é confrontada com baixa capacidade de absorção. Um dos muitos princípios ativos encontrados na indústria cosmética é a cafeína, um pseudoalocalóide do grupo xantina usado como estimulante no mecanismo da ação lipolítica. Este ativo é amplamente utilizado no campo da estética e dos cosméticos em tratamentos que envolvem disfunções, como gordura localizada e fibroedema gelóide. Para funcionar perfeitamente, o princípio ativo precisa interagir e criar um conjunto de fatores que inclui a intensificação da lipólise. O encapsulamento de cafeína em nanocosméticos à base de gel tem o objetivo de levar esse ativo até o adipócito, a célula alvo, para o tratamento de disfunções mencionado. Assim, objetivamos apresentar uma revisão de como tem sido o uso de cafeína na produção de cosméticos.

Adrenergic nerves mediate the venoconstrictor response to PVN stimulation.

Veins play an important role in the control of venous return, cardiac output and cardiovascular homeostasis. However, the central nervous system sites and effector systems involved in modulating venous function remain to be fully elucidated. The hypothalamic paraventricular nucleus (PVN) is an important site modulating autonomic outflow to the cardiovascular system. Venous tone can be modulated by sympathetic nerves or by adrenal catecholamines. The present study assessed the relative contribution of these autonomic effector systems to the venoconstrictor response elicited by stimulation of the hypothalamic paraventricular nucleus. Male Sprague-Dawley rats were subjected to sham operation or bilateral adrenal demedullation fitted with PVN guide cannulae and fitted with catheters for recording arterial pressure (AP) and intrathoracic vena caval pressure (VP). A latex balloon was advanced into the right atrium. MCFP was calculated from the AP and VP recorded after 4 s of right atrial occlusion. MCFP = VP + (AP - VP)/60. Mean arterial pressure (MAP), heart rate (HR), VP and MCFP responses to injections of BMI (25 ng/side) into the PVN were recorded from conscious rats to avoid the complicating effects of anesthesia. In sham-operated rats, injection of BMI into the PVN increased MAP by 13 +/- 3 mm Hg and HR by 56 +/- 6 bpm. MCFP was also increased significantly by 0.98 +/- 0.15 mm Hg indicating an increase in venomotor tone. Adrenal medullectomy did not affect the pressor (DeltaMAP = 12 +/- 2 mm Hg), tachycardic (DeltaHR = 48 +/- 7 bpm) or venoconstrictor (DeltaMCFP = 0.73 +/- 0.11 mm Hg) responses. Ganglionic blockade abolished the PVN-induced responses in both groups of rats. In a separate group, pretreatment with the adrenergic neuron blocker, guanethidine (20 mg/kg), also abolished the PVN-mediated venoconstrictor responses. Conversely, selective beta2 adrenergic receptor blockade did not affect MCFP responses to BMI. These data indicate that adrenomedullary catecholamines are not necessary for full expression of the venoconstrictor response to PVN stimulation.

[Continuous subcutaneous infusion in palliative care, an undervalued method]. / Continue subcutane infusie in de palliatieve zorg, een ondergewaardeerde methode.

Three patients, 2 men aged 55 and 54 years and a woman aged 86 years, were admitted to hospital for treatment of symptoms resulting from terminal disease (pain, agitation, nausea etc.). In all three patients, continuous subcutaneous infusion (CSI) of medication was successfully used to control the symptoms. Compared with intravenous infusion, the technique of CSI is easy to learn and is associated with fewer complications. Its reliability and ease-of-use make it a technique that can be used not only in a hospital setting, but also in general practice and nursing homes. Medication used in palliative care (e.g. morphine, haloperidol, metoclopramide, levomepromazine, midazolam) can often be administered safely by CSI. In palliative care, where goals should be accomplished with minimal burden to the patient, CSI must be considered the technique of choice in patients who are unable to swallow their medication.

Ion-exchanged optical waveguides for all-optical switching.

Current interest in all-optical waveguide devices has created a need for suitable nonlinear materials and fabrication techniques. To meet this need, we have made optical waveguides using ion exchange in two glasses, which were designed both to have large optical nonlinearities and to be compatible with the ion-exchange processing. We find that the choice of alkali metal ion in the glass has a major effect on the exchange process and on the optical quality of the ensuing guides. Guides made in one of these glasses have been used for demonstrations of spatial soliton propagation, which can be used as the basis of an all-optical switch.

Crossover studies are a better format for comparing equivalent treatments than parallel-group studies.

BACKGROUND: In controlled clinical trials the new treatment may be a slight modification of the standard or be equivalent to it with the addition of a new component. In this situation there is a positive correlation between the response to the new and the standard treatment. OBJECTIVE: The influence of the correlation between the treatment responses on the statistical sensitivity of testing was studied. Randomized trials of equivalent treatments in psychiatry and hypertension research were studied for their design in relation to their level of correlation. RESULTS: With equivalent treatments and, thus, a positive correlation a paired analysis provides better power than an unpaired one. CONCLUSIONS: Crossover studies are a better format than parallel-group studies for comparing equivalent treatments. The scientific community is technically largely unaware of the mechanisms by which correlation levels influence or lack to influence the statistical power of controlled clinical trials.

Neodymium-doped tellurite single-mode fiber laser.

A single-mode Nd(3+)-doped tellurite glass fiber laser operating at 1.061 microm is described. We believe this is the first demonstration of a single-mode fiber laser in tellurite glass. A lasing threshold of 27 mW of 818-nm absorbed pump power and a slope efficiency output power versus pump power of 23% emitted from one end were observed in the fiber cavity with 11.9% Fresnel reflection at both ends.

Guided blue and green upconversion fluorescence in an erbium-ytterbium-containing silicate glass.

We observe guided blue and green upconversion fluorescence in an ion-exchanged waveguide that is fabricated in an erbium-ytterbium-codoped silicate laser glass. The guides are optically pumped at room temperature by using a Ti:sapphire laser with lambda = 880-980 nm; the observed fluorescence is in two bands, 480-490 and 520-560 nm, and results from multiphoton excitation.

Observation of spatial optical solitons in a nonlinear glass waveguide.

We report the observation of spatial optical solitons due to the Kerr nonlinearity in a planar glass waveguide and present measurements of the nonlinear response obtained by placing a pinhole at the output of the waveguide. For input intensities greater than that required for the fundamental soliton, we observe breakup of the output owing to the effect of two-photon absorption.

Silver resistance in Pseudomonas stutzeri.

Silver resistance was studied in a silver-resistant Pseudomonas stutzeri AG259 strain and compared to a silver-sensitive P. stutzeri JM303 strain. Silver resistance was not due to silver complexation to intracellular polyphosphate or the presence of low molecular weight metal-binding protein(s). Both the silver-resistant and silver-sensitive P. stutzeri strains produced H2S, with the silver-resistant AG259 strain producing lower amounts of H2S than the silver-sensitive JM303 strain. However, intracellular acid-labile sulfide levels were generally higher in the silver-resistant P. stutzeri AG259 strain. Silver resistance may be due to formation of silver-sulfide complexes in the silver-resistant P. stutzeri AG259 strain.

Effects of deletion of tropomyosin overlap on regulated actomyosin subfragment 1 ATPase.

The role of the overlap region at the ends of tropomyosin molecules in the properties of regulated thin filaments has been investigated by substituting nonpolymerizable tropomyosin for tropomyosin in a reconstituted troponin-tropomyosin-actomyosin subfragment 1 ATPase assay system. A previous study [Heeley, Golosinka & Smillie (1987) J. Biol. Chem. 262, 9971-9978] has shown that at an ionic strength of 70 mM, troponin will induce full binding of nonpolymerizable tropomyosin to F-actin both in the presence and absence of calcium. At a myosin subfragment 1-to-actin ratio of 2:1 ([actin] = 4 microM) and an ionic strength of 50 mM, comparable levels of ATPase inhibition were observed with increasing levels of tropomyosin or the truncated derivative in the presence of troponin (-Ca2+). Large differences were noted, however, in the activation by Ca2+. Significantly lower ATPase activities were observed with nonpolymerizable tropomyosin and troponin (+Ca2+) over a range of subfragment 1-to-actin ratios from 0.25 to 2.5. The concentration of subfragment 1 required to generate ATPase activities exceeding those seen with actomyosin subfragment 1 alone under these conditions was 3-4-fold greater when nonpolymerizable tropomyosin was used. Similar effects were seen at the much lower ionic strength of 13 mM and are consistent with the reduced ATPase activity with nonpolymerizable tropomyosin observed previously [Walsh, Trueblood, Evans & Weber (1985) J. Mol. Biol. 182, 265-269] at low ionic strength and a subfragment 1-to-actin ratio of 1:100. Little cooperativity in activity as a function of subfragment 1 concentration with either intact tropomyosin or its truncated derivative was observed under the present conditions. Further studies are directed towards an understanding of these effects in terms of the two-state binding model for the attachment of myosin heads to regulated thin filaments.

Phosphorus-31 and carbon-13 nuclear magnetic resonance studies of glucose and xylose metabolism in Candida tropicalis cell suspensions.

The metabolism of glucose and xylose was studied as a function of oxygenation in suspensions of Candida tropicalis by 31P and 13C nuclear magnetic resonance spectroscopy. Both the rate of carbohydrate metabolism and the cytoplasmic pH were independent of the rate of oxygenation in cells metabolizing glucose. However, these two parameters were markedly dependent on the rate of oxygenation in C. tropicalis cells metabolizing xylose. For example, the cytoplasmic pH in fully oxygenated xylose-metabolizing cells was 7.8 but decreased to 6.3 in anoxic cells. In general, suspensions of cells consuming xylose had a lower rate of sugar uptake, a more acidic cytoplasmic pH, lower levels of sugarphosphomonoesters (SP) and ATP, higher levels of intracellular Pi, a more alkaline vacuolar pH, and a lower rate of extracellular Pi assimilation and polyphosphate synthesis than cells consuming glucose. These observations indicate that C. tropicalis metabolizing xylose is less energized than glucose-metabolizing cells. On both carbon sources, however, an inverse correlation between intracellular levels of SP and Pi was observed. Also, uptake of extracellular Pi correlated with the synthesis of polyphosphates within the cells. During anoxia, Pi was not taken up, and polyphosphates were hydrolyzed instead to fulfill the cells' requirements for phosphate.