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1.
S D Med ; 75(6): 258-262, 2022 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-36206566

RESUMO

Dermatologic conditions account for a large proportion of healthcare visits in the United States, yet there continues to be barriers to dermatologic care particularly among the rural and underserved populations. Patients among these populations are particularly vulnerable to poor outcomes and increased morbidity. Teledermatology offers a potential solution to increase access to high-quality dermatologic care. Studies have previously examined the convenience, cost-effectiveness, and clinical efficacy of teledermatology compared to in-person dermatology visits. There is a need to assess which populations are appropriate and in what settings teledermatology can be most effective. We surveyed patients of a South Dakota dermatology practice to assess perceptions and experiences with teledermatology visits in the context of the COVID-19 pandemic. Significant factors leading patients to prefer in-person visits compared to teledermatology were being over the age 65 (OR 2.9 95 percent CI 1.9,3.8 and p-value 0.036) or experiencing technical difficulties during the visit (OR 2.9 95 percent CI 1.9,3.9 and p-value 0.048). We found the chief complaint played an important role in patient preference for visit modality. Patients with acne or acne follow up compared to all other chief complaints had a strong preference for teledermatologic visits (OR 4.7 95 percent CI 4.0,5.4 and p-value 0.000018) whereas patients with possible malignant lesions strongly preferred having an in-person visit (OR 6.6 95 percent CI 5.5,7.8 and p-value 0.0004). Based on these results, we suggest a targeted use of teledermatology with pre-visit screening measures to maintain a patient center approach and avoid redundant visits.


Assuntos
Acne Vulgar , COVID-19 , Dermatologia , Dermatopatias , Telemedicina , Idoso , Dermatologia/métodos , Humanos , Pandemias , Assistência Centrada no Paciente , Dermatopatias/diagnóstico , Dermatopatias/epidemiologia , Dermatopatias/terapia , South Dakota , Estados Unidos
2.
Tetrahedron ; 66(14): 2561-2569, 2010 Apr 03.
Artigo em Inglês | MEDLINE | ID: mdl-20305832

RESUMO

A series of colored hydrocarbon and fluorocarbon tagged 1-fluoro-4-alkylamino-anthraquinones and 1,4-bis-alkylamino-anthraquinone probe molecules were synthesized from a (fluorinated) alkyl amine and 1,4-difluoroanthraquinone to aid in the development of fluorous separation applications. The anthraquinones displayed stacking of the anthraquinone tricycle and interdigitation of the (fluorinated) alkyl chains in the solid state. Furthermore, intramolecular N-H···O hydrogen bonds forced the hydrocarbon and fluorocarbon tags into a conformation pointing away from the anthraquinone tricycle, with the angle of the tricycle plane normal and the main (fluorinated) alkyl vector ranging from 1 to 39°. Separation of the probe molecules on fluorous silica gel showed that the degree of fluorination of the probe molecules plays only a minor role with most eluents (e.g., hexane-ethyl acetate and methyl nonafluorobutyl ethers-ethyl acetate). However, toluene as eluent caused a pronounced separation by degree of fluorination for fluorocarbon, but not hydrocarbon tagged probe molecules on both silica gel and fluorous silica gel. These studies suggest that hydrocarbon and fluorocarbon tagged anthraquinones are useful probe molecules for the development of laboratory scale fluorous separation applications.

3.
Colloids Surf B Biointerfaces ; 51(1): 25-9, 2006 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-16814996

RESUMO

Perfluorooctane-1-sulfonic acid (PFOS) is emerging as an important persistent environmental pollutant. To gain insight into the interaction of PFOS with biological systems, the mixing behavior of dipalmitoylphosphatidylcholine (DPPC) with PFOS was studied using differential scanning calorimetry (DSC) and fluorescence anisotropy measurements. In the DSC experiments the onset temperature of the DPPC pretransition (Tp) decreased with increasing PFOS concentration, disappearing at XDPPC < or = 0.97. The main DPPC phase transition temperature showed a depression and peak broadening with increasing mole fraction of PFOS in both the DSC and the fluorescence anisotropy studies. From the melting point depression in the fluorescence anisotropy studies, which was observed at a concentration as low as 10 mg/L, an apparent partition coefficient of K = 5.7 x 10(4) (mole fraction basis) was calculated. These results suggest that PFOS has a high tendency to partition into lipid bilayers. These direct PFOS-DPPC interactions are one possible mechanism by which PFOS may contribute to adverse effects, for example neonatal mortality, in laboratory studies and possibly in humans.


Assuntos
1,2-Dipalmitoilfosfatidilcolina/química , Ácidos Alcanossulfônicos/química , Fluorocarbonos/química , Varredura Diferencial de Calorimetria , Sistemas de Liberação de Medicamentos , Polarização de Fluorescência , Bicamadas Lipídicas/química , Lipossomos , Estrutura Molecular , Temperatura
4.
J Neurosci ; 21(16): RC159, 2001 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-11459880

RESUMO

Comparative studies have implicated the nucleus accumbens (NAcc) in the anticipation of incentives, but the relative responsiveness of this neural substrate during anticipation of rewards versus punishments remains unclear. Using event-related functional magnetic resonance imaging, we investigated whether the anticipation of increasing monetary rewards and punishments would increase NAcc blood oxygen level-dependent contrast (hereafter, "activation") in eight healthy volunteers. Whereas anticipation of increasing rewards elicited both increasing self-reported happiness and NAcc activation, anticipation of increasing punishment elicited neither. However, anticipation of both rewards and punishments activated a different striatal region (the medial caudate). At the highest reward level ($5.00), NAcc activation was correlated with individual differences in self-reported happiness elicited by the reward cues. These findings suggest that whereas other striatal areas may code for expected incentive magnitude, a region in the NAcc codes for expected positive incentive value.


Assuntos
Intuição/fisiologia , Núcleo Accumbens/fisiologia , Recompensa , Adulto , Mapeamento Encefálico , Núcleo Caudado/anatomia & histologia , Núcleo Caudado/irrigação sanguínea , Núcleo Caudado/fisiologia , Sinais (Psicologia) , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Núcleo Accumbens/anatomia & histologia , Núcleo Accumbens/irrigação sanguínea , Oxigênio/sangue , Tálamo/anatomia & histologia , Tálamo/irrigação sanguínea , Tálamo/fisiologia
5.
Biol Psychiatry ; 50(9): 685-90, 2001 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-11704075

RESUMO

BACKGROUND: Brain volume decreases with normal aging. We sought to determine whether, in addition to age, individual differences in stress reactivity (i.e., neuroticism) would also predict reductions in brain volume. METHODS: Brain volume ratios were calculated for a sample of 86 healthy volunteers, based on segmented brain volumes taken from T(1)-weighted magnetic resonance imaging and corrected for intracranial volume. Standardized self-reported measures of dispositional neuroticism were concurrently obtained by administering the Revised NEO Personality Inventory. RESULTS: After statistically controlling for age and sex, neuroticism showed a significant negative association with the ratio of brain to the remainder of the intracranial volume, but was not related to intracranial volume itself. In particular, subfactors of neuroticism related to the chronic experience of arousing negative emotions were associated with reduced brain ratio. CONCLUSIONS: These results suggest that individual differences in stress reactivity contribute to reductions in brain volume observed during adulthood.


Assuntos
Encéfalo/anatomia & histologia , Transtornos Neuróticos/etiologia , Adulto , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Transtornos Neuróticos/diagnóstico , Determinação da Personalidade
6.
Am J Psychiatry ; 155(3): 373-9, 1998 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9501748

RESUMO

OBJECTIVE: The authors sought to test the causal hypothesis that serotonergic function modulates aspects of the normal spectrum of individual differences in affective experience and social behavior in humans. METHOD: A selective serotonin reuptake inhibitor (SSRI), paroxetine, 20 mg/day (N = 26), or placebo (N = 25) was administered to normal volunteers in a double-blind manner for 4 weeks, and personality variables and social behavior were assessed at baseline and at weeks 1 and 4 of treatment. RESULTS: Relative to placebo, SSRI administration reduced focal indices of hostility through a more general decrease in negative affect, yet did not alter indices of positive affect. In addition, SSRI administration increased a behavioral index of social affiliation. Changes in both negative affect and affiliative behavior were significantly related to volunteers' plasma SSRI levels at the end of the experiment. CONCLUSIONS: Central serotonergic function may modulate a dimension of normal personality characterized by reduced negative affective experience and increased affiliative behavior. SSRI administration has significant and detectable effects on these measures even in the absence of baseline clinical depression or other psychopathology.


Assuntos
Paroxetina/farmacologia , Personalidade/efeitos dos fármacos , Inibidores Seletivos de Recaptação de Serotonina/farmacologia , Comportamento Social , Adulto , Agressão/efeitos dos fármacos , Encéfalo/efeitos dos fármacos , Encéfalo/fisiologia , Método Duplo-Cego , Emoções/efeitos dos fármacos , Feminino , Hostilidade , Humanos , Masculino , Paroxetina/sangue , Personalidade/fisiologia , Inventário de Personalidade , Placebos , Serotonina/fisiologia , Inibidores Seletivos de Recaptação de Serotonina/sangue
7.
Drugs ; 31 Suppl 3: 55-63, 1986.
Artigo em Inglês | MEDLINE | ID: mdl-3488198

RESUMO

The plasmid-mediated beta-lactamase in Branhamella catarrhalis (BRO-1), also occurring in Moraxella nonliquefaciens, differs from other known plasmid-mediated beta-lactamases in Gram-negative bacteria regarding substrate profile and isoelectric point. B. catarrhalis strains previously reported to produce beta-lactamases deviating from BRO-1 were tested, and the beta-lactamases did not differ significantly from BRO-1 in substrate profile, isoelectric point or relative substrate affinity index (RSAI). Further investigations of strains of various geographic origin should be undertaken. RSAI seems to be a useful tool for screening of beta-lactamases in B. catarrhalis since values for a large number of strains can easily be determined. The previously reported conjugational transfer of BRO-1 production within species B. catarrhalis and from M. nonliquefaciens to B. catarrhalis was confirmed. Four bands of extrachromosomal DNA were regularly detected by agarose gel electrophoresis in beta-lactamase-producing as well as in beta-lactamase-negative strains of B. catarrhalis and M. non-liquefaciens, provided that the excessive nuclease activity in the preparations was inhibited.


Assuntos
Neisseriaceae/enzimologia , Plasmídeos , beta-Lactamases/metabolismo , DNA Bacteriano/genética , Eletroforese em Gel de Ágar , Focalização Isoelétrica , Neisseriaceae/genética , Especificidade por Substrato
8.
Behav Neurosci ; 114(2): 320-7, 2000 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-10832793

RESUMO

Adult rats emit increased rates of 50-kHz ultrasonic vocalizations (USVs) before receiving social and pharmacological rewards. This study sought to determine whether anticipation of rewarding electrical stimulation of the brain (ESB) would also elicit these vocalizations. In Experiments 1 and 2, rats showed increased 50-kHz USVs before receiving experimenter-delivered ventral tegmental area (VTA) and lateral hypothalamic (LH) ESB on a fixed time 20-s schedule. In Experiments 3 and 4, rats increased their rate of 50-kHz USVs in response to cues that predicted the opportunity to self-stimulate the VTA or LH. Interestingly, unexpected termination of either type of ESB evoked 20-kHz, rather than 50-kHz, USVs. In Experiment 5, a cue that predicted daily 1-hr feeding sessions increased 50-kHz USVs, whereas a cue that predicted footshock decreased 50-kHz USVs. These effects could not be explained simply by changes in locomotor activity or general arousal. Together, these findings support the hypothesis that short 50-kHz USVs may selectively index a state of reward anticipation in rats.


Assuntos
Nível de Alerta/fisiologia , Região Hipotalâmica Lateral/fisiologia , Motivação , Autoestimulação/fisiologia , Área Tegmentar Ventral/fisiologia , Vocalização Animal/fisiologia , Animais , Sinais (Psicologia) , Estimulação Elétrica , Masculino , Ratos , Ratos Long-Evans , Esquema de Reforço , Espectrografia do Som
9.
Behav Neurosci ; 115(4): 940-4, 2001 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-11508733

RESUMO

The authors have hypothesized that, in adult rats, 50-kHz ultrasonic vocalizations (USVs) index a state characterized by high arousal and expectations of reward. This study was conducted to investigate whether dopamine agonism of the nucleus accumbens (NAcc) could evoke such an appetitive state, by examining the effects of NAcc amphetamine (AMPH) microinjections on USVs. Intra-NAcc AMPH injections (0.3, 1.0, 3.0, 10.0 microg unilaterally) produced robust, dose-dependent increases in 50-kHz USVs, which could not be accounted for by concomitant increases in locomotor activity (LA). However, AMPH injections into dorsal control caudate putamen sites produced a modest, dose-dependent increase in LA without significant increases in 50-kHz USVs. These findings indicate that NAcc AMPH microinjections selectively evoke 50-kHz USVs in rats, supporting the notion that dopamine elevations in the NAcc may unconditionally elicit a state of reward anticipation.


Assuntos
Anfetamina/farmacologia , Estimulantes do Sistema Nervoso Central/farmacologia , Dopaminérgicos/farmacologia , Núcleo Accumbens/efeitos dos fármacos , Vocalização Animal/efeitos dos fármacos , Anfetamina/administração & dosagem , Animais , Comportamento Apetitivo/efeitos dos fármacos , Estimulantes do Sistema Nervoso Central/administração & dosagem , Dopaminérgicos/administração & dosagem , Masculino , Microinjeções , Núcleo Accumbens/patologia , Núcleo Accumbens/fisiologia , Distribuição Aleatória , Ratos , Ratos Sprague-Dawley , Ultrassom
10.
Psychopharmacology (Berl) ; 155(1): 35-42, 2001 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-11374334

RESUMO

RATIONALE: Since cues that predict aversive outcomes can elicit both avoidance and 20 kHz ultrasonic vocalizations (USVs) in adult rats, 20 kHz USVs may also index the conditioned aversive effects of drugs. OBJECTIVE: We evaluated whether exposure to compartments associated with drugs with aversive effects would selectively increase 20 but not 50 kHz USVs in rats. METHOD: Rats were injected with naloxone (NAL) or lithium chloride (LiCl) and placed in one compartment or with saline (VEH) and placed in another compartment for three 50-min conditioning sessions. 20 kHz USVs, 50 kHz USVs, and time spent in each chamber were recorded during subsequent 15-min testing sessions during which rats had access to both compartments (expt 1) or were confined to the drug- or VEH-paired compartment (expt 2). RESULTS: In expt 1, animals conditioned either with NAL (0.3 and 3.0 mg/kg) or LiCl (10 and 30 mg/kg) emitted increased 20 kHz USVs in the drug-paired compartment, relative to VEH-conditioned controls. Conditioning with high doses of both drugs also increased conditioned place aversion and decreased emission of 50 kHz USVs. In expt 2, restriction of animals to the compartment paired with high doses of NAL and LiCl also increased emission of 20 kHz USVs and decreased 50 kHz USVs, relative to VEH-conditioned controls. CONCLUSIONS: In rats, cues associated with drugs with aversive effects increase 20 kHz USVs and decrease 50 kHz USVs, suggesting that USVs may provide a useful model for predicting the conditioned aversive effects of drugs.


Assuntos
Antimaníacos/farmacologia , Condicionamento Psicológico/efeitos dos fármacos , Cloreto de Lítio/farmacologia , Naloxona/farmacologia , Antagonistas de Entorpecentes/farmacologia , Ultrassom , Vocalização Animal/efeitos dos fármacos , Analgésicos Opioides/farmacologia , Animais , Condicionamento Psicológico/fisiologia , Sinais (Psicologia) , Masculino , Morfina/farmacologia , Ratos , Ratos Sprague-Dawley , Vocalização Animal/fisiologia
11.
Neuroreport ; 12(17): 3683-7, 2001 Dec 04.
Artigo em Inglês | MEDLINE | ID: mdl-11726774

RESUMO

Reward processing involves both appetitive and consummatory phases. We sought to examine whether reward anticipation vs outcomes would recruit different regions of ventral forebrain circuitry using event-related fMRI. Nine healthy volunteers participated in a monetary incentive delays task in which they either responded to a cued target for monetary reward, responded to a cued target for no reward, or did not respond to a cued target during scanning. Multiple regression analyses indicated that while anticipation of reward vs non-reward activated foci in the ventral striatum, reward vs non-reward outcomes activated foci in the ventromedial frontal cortex. These findings suggest that reward anticipation and outcomes may differentially recruit distinct regions that lie along the trajectory of ascending dopamine projections.


Assuntos
Comportamento/fisiologia , Motivação , Vias Neurais/fisiologia , Núcleo Accumbens/fisiologia , Córtex Pré-Frontal/fisiologia , Recompensa , Adulto , Mapeamento Encefálico , Sinais (Psicologia) , Feminino , Lateralidade Funcional/fisiologia , Humanos , Imageamento por Ressonância Magnética , Masculino , Inibição Neural/fisiologia , Vias Neurais/anatomia & histologia , Núcleo Accumbens/anatomia & histologia , Córtex Pré-Frontal/anatomia & histologia , Putamen/anatomia & histologia , Putamen/fisiologia , Tempo de Reação/fisiologia
12.
Physiol Behav ; 66(4): 639-43, 1999 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-10386908

RESUMO

We have proposed that short (<0.5 s), high-frequency (approximately 50 kHz) ultrasonic vocalizations ("50-kHz USVs") index a positive affective state in adult rats, because they occur prior to rewarding social interactions (i.e., rough-and-tumble play, sex). To evaluate this hypothesis in the case of nonsocial stimuli, we examined whether rats would make increased 50-kHz USVs in places associated with the administration of rewarding pharmacological compounds [i.e., amphetamine (AMPH) and morphine (MORPH)]. In Experiment 1, rats made a greater percentage of 50-kHz USVs on the AMPH-paired side of a two-compartment chamber than on the vehicle-paired side, even after statistical correction for place preference. In Experiment 2, rats made a higher percentage of 50-kHz USVs on the MORPH-paired side than on the vehicle-paired side, despite nonsignificant place preference. These findings support the hypothesis that 50-kHz USVs mark a positive affective state in rats and introduce a novel and rapid marker of pharmacological reward.


Assuntos
Afeto/efeitos dos fármacos , Anfetamina/farmacologia , Condicionamento Clássico/efeitos dos fármacos , Morfina/farmacologia , Motivação , Comportamento Social , Animais , Nível de Alerta/efeitos dos fármacos , Aprendizagem por Associação/efeitos dos fármacos , Feminino , Masculino , Ratos , Ratos Long-Evans , Meio Social , Espectrografia do Som , Ultrassom
13.
J Comp Psychol ; 112(1): 65-73, 1998 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9528115

RESUMO

The authors provide initial documentation that juvenile rats emit short, high-frequency ultrasonic vocalizations (high USVs, approximately 55 kHz) during rough-and-tumble play. In an observational study, they further observe that these vocalizations both correlate with and predict appetitive components of the play behavioral repertoire. Additional experiments characterized eliciting conditions for high USVs. Without prior play exposure, rats separated by a screen vocalized less than playing rats, but after only 1 play session, separated rats vocalized more than playing rats. This findings suggested that high USVs were linked to a motivational state rather than specific play behaviors or general activity. Furthermore, individual rats vocalized more in a chamber associated with play than in a habituated control chamber. Finally, congruent and incongruent motivational manipulations modulated vocalization expression. Although play deprivation enhanced high USVs, an arousing but aversive stimulus (bright light) reduced them. Taken together, these findings suggest that high USVs may index an appetitive motivation to play in juvenile rats.


Assuntos
Nível de Alerta , Motivação , Jogos e Brinquedos , Vocalização Animal , Animais , Comportamento Apetitivo , Feminino , Masculino , Ratos , Espectrografia do Som , Ultrassom
14.
J Pharm Sci ; 85(6): 586-94, 1996 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-8773954

RESUMO

Supercritical CO2 was used as an antisolvent to form protein particles that exhibited minimal loss of activity upon reconstitution. Organic protein solutions were sprayed under a variety of operating conditions into the supercritical fluid, causing precipitation of dry, microparticulate (1-5 microns) protein powders. Three proteins were studied: trypsin, lysozyme, and insulin. Amide I band Raman spectra were used to estimate the alpha-helix and beta-sheet structural contents of native and precipitate powders of each protein. Analysis of the Raman spectral revealed minimal (lysozyme), intermediate (trypsin), and appreciable (insulin) changes in secondary structure with respect to the commercial starting materials. The perturbations in secondary structure suggest that the most significant event during supercritical fluid-induced precipitation involved the formation of beta-sheet structures with concomitant decreases of alpha-helix. Amide I band Raman and Fourier-transform infrared (FTIR) spectra indicate that higher operating temperatures and pressures lead to more extensive beta-sheet-mediated intermolecular interactions in the precipitates. Raman and FTIR spectra of redissolved precipitates are similar to those of aqueous commercial proteins, indicating that conformational changes were reversible upon reconstitution. These results suggest that protein precipitation in supercritical fluids can be used to form particles suitable for controlled release, direct aerosol delivery to the lungs, and long-term storage at ambient conditions.


Assuntos
Dióxido de Carbono/química , Estrutura Secundária de Proteína , Proteínas/química , Fenômenos Químicos , Precipitação Química , Físico-Química , Dimetil Sulfóxido , Muramidase/química , Soluções , Espectroscopia de Infravermelho com Transformada de Fourier , Análise Espectral Raman , Tripsina/química
17.
Neuroimage ; 12(1): 20-7, 2000 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-10875899

RESUMO

Comparative studies have implicated striatal and mesial forebrain circuitry in the generation of autonomic, endocrine, and behavioral responses for incentives. Using blood oxygen level-dependent functional magnetic resonance imaging, we sought to visualize functional activation of these regions in 12 normal volunteers as they anticipated and responded for monetary incentives. Both individual and group analyses of time-series data revealed significant activation of striatal and mesial forebrain structures (including insula, caudate, putamen, and mesial prefrontal cortex) during trials involving both monetary rewards and punishments. In addition to these areas, during trials involving punishment, group analysis revealed activation foci in the anterior cingulate and thalamus. These results corroborate comparative studies which implicate striatal and mesial forebrain circuitry in the elaboration of incentive-driven behavior. This report also introduces a new paradigm for probing the functional integrity of this circuitry in humans.


Assuntos
Encéfalo/fisiologia , Imageamento por Ressonância Magnética , Recompensa , Adulto , Encéfalo/anatomia & histologia , Mapeamento Encefálico , Circulação Cerebrovascular/fisiologia , Corpo Estriado/fisiologia , Giro do Cíngulo/fisiologia , Humanos , Masculino , Oxigênio/sangue , Estimulação Luminosa , Prosencéfalo/fisiologia , Punição , Tempo de Reação , Tálamo/fisiologia
18.
Biotechnol Bioeng ; 65(3): 258-64, 1999 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-10486123

RESUMO

An important advantage of carrying out enzymatic catalysis in organic media is the increased solubility of hydrophobic substrates. This study compares a model lipase catalyzed esterification of cholesterol using vinyl acetate (VA) in two such nontraditional media: high-pressure hexane and supercritical (SCF) ethane. The effect of using one of the reactants (VA) as a cosolvent to increase the solubility of the other reactant (cholesterol) in SCF ethane has been investigated. The thermodynamic activity of water (a(w)) in the reaction media was controlled by the direct addition of the salt hydrate pair Na(4)P(2)O(7)/Na(4)P(2)O(7).10H(2)O. The a(w) of the salt hydrate system is shown to be a function of pressure and its variation over the pressure range 104-173 bar has been estimated. The initial reaction rate in pressurized hexane was found to vary linearly with the cholesterol concentration. The reaction rate was also a function of pressure-the effect being more pronounced in ethane than in hexane. This is consistent with the large negative partial molar volumes observed in SCFs, although the sign of the resulting activation volume differs from previous investigations of lipase-catalyzed reactions in SCFs. When corrected for substrate concentration, the initial rate of catalysis in SCF ethane was determined to be greater than in pressurized hexane over the conditions investigated. This study shows that proper solvent choice can be used to regulate reaction rates in pressurized solvents.


Assuntos
Lipase/química , Solventes/química , Catálise , Colesterol/química , Esterificação , Indicadores e Reagentes , Concentração Osmolar , Pressão
19.
Appl Microbiol Biotechnol ; 65(2): 149-57, 2004 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-14752579

RESUMO

The continuous culture of Clostridium thermocellum, a thermophilic bacterium capable of producing ethanol from cellulosic material, is demonstrated at elevated hydrostatic pressure (7.0 MPa, 17.3 MPa) and compared with cultures at atmospheric pressure. A commercial limitation of ethanol production by C. thermocellum is low ethanol yield due to the formation of organic acids (acetate, lactate). At elevated hydrostatic pressure, ethanol:acetate (E/A) ratios increased >10(2) relative to atmospheric pressure. Cell growth was inhibited by approximately 40% and 60% for incubations at 7.0 MPa and 17.3 MPa, respectively, relative to continuous culture at atmospheric pressure. A decrease in the theoretical maximum growth yield and an increase in the maintenance coefficient indicated that more cellobiose and ATP are channeled towards maintaining cellular function in pressurized cultures. Shifts in product selectivity toward ethanol are consistent with previous observations of hydrostatic pressure effects in batch cultures. The results are partially attributed to the increasing concentration of dissolved product gases (H2, CO2) with increasing pressure; and they highlight the utility of continuous culture experiments for the quantification of the complex role of dissolved gas and pressure effects on metabolic activity.


Assuntos
Reatores Biológicos/microbiologia , Celobiose/metabolismo , Clostridium/crescimento & desenvolvimento , Hidrogênio/metabolismo , Ácido Acético/metabolismo , Monóxido de Carbono/farmacologia , Clostridium/metabolismo , Meios de Cultura , Etanol/metabolismo , Hidrogênio/farmacologia , Pressão Hidrostática
20.
Biotechnol Bioeng ; 70(5): 491-7, 2000 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-11042545

RESUMO

Selection of biocompatible solvents is critical when designing bioprocessing applications for the in situ biphasic extraction of metabolic end-products. The prediction of the biocompatibility of supercritical and compressed solvents is more complicated than for liquid solvents, because their properties can change significantly with pressure and temperature. The activity of the anaerobic thermophilic bacterium, Clostridium thermocellum, was studied when the organism was incubated in the presence of compressed nitrogen, ethane, and propane at 333 K and multiple pressures. The metabolic activity of the organisms in contact with compressed solvents was analyzed using traditional indicators of solvent biocompatibility, such as log P, interfacial tension, and solvent density. The toxicity of the compressed solvents was compared with the phase and molecular toxicity effects measured in liquid alkanes at atmospheric pressure. Inactivation increased with time in the presence of the compressed solvents, but was constant in the presence of atmospheric liquid solvents. Knowledge of molecular and phase toxicity provides a framework for the interpretation of C. thermocellum metabolism in contact with atmospheric and compressed solvents.


Assuntos
Clostridium/efeitos dos fármacos , Clostridium/metabolismo , Solventes/química , Solventes/toxicidade , Etano/toxicidade , Fermentação , Nitrogênio/toxicidade , Pressão , Propano/toxicidade
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