RESUMO
Our objectives were to measure net fluxes of free AA (FAA) and peptide-bound AA (PBAA) across portal-drained viscera, liver, splanchnic tissues, and mammary tissues, and milk AA output of lactating Holstein cows (n = 8, 86 +/- 8 d in milk). Cows were fed an alfalfa-based total mixed ration containing 40% steam-flaked (SFS) or dry-rolled (DRS) sorghum grain. The total mixed rations were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in portal, hepatic, and mammary veins and from mesenteric or costoabdominal arteries every 2 h from each cow and diet. Intake of dry matter was 17.9 and 18.6 kg/d of the SFS and DRS diets, respectively, but dropped to 16.3 kg/d for cows fed the SFS diet in the last 3 experimental days, sampling day included. Milk and milk crude protein yields (kg/12-h sampling) were 13.85 vs. 13.25 and 0.425 vs. 0.396 for cows fed SFS or DRS, respectively, and were not affected by the considerable drop in dry matter intake of cows fed the SFS diet during the last 3 experimental days. The portal-drained visceral flux of total essential FAA was 417 and 442 g/12 h (SEM 63) in cows fed SFS and DRS, respectively. However, the portal-drained visceral flux of 7 essential PBAA out of the 9 determined was numerically greater in cows fed the SFS diet, and total essential PBAA in that treatment was 77.4 +/- 22.2 compared with 35.4 +/- 50.2 g/12 h for cows fed the DRS diet. This phenomenon was again observed in a greater total splanchnic flux (FAA + PBAA) of 462 and 371 g/12 h in SFS- and DRS-fed cows, respectively. Mammary uptake of essential AA from both pools (free and peptide bound), and recovery of essential AA in milk, was again numerically higher in SFS-fed cows. In addition to FAA, quantifying the contribution of PBAA may improve our understanding of tissue use of AA substrates, and this may ultimately lead to improved diet formulations with respect to intestinal absorption and mammary uptake of AA.
Assuntos
Aminoácidos/farmacocinética , Ração Animal , Bovinos/metabolismo , Lactação , Fígado/metabolismo , Glândulas Mamárias Animais/metabolismo , Sorghum , Animais , Estudos Cross-Over , Feminino , Veias Hepáticas/fisiologia , Absorção Intestinal/fisiologia , Fígado/irrigação sanguínea , Leite/metabolismo , Proteínas do Leite/metabolismo , Veia Porta/fisiologia , Distribuição AleatóriaRESUMO
Objectives were to measure net fluxes of free (FAA) and peptide bound amino acids (AA) (PBAA) across portal-drained viscera (PDV), liver, splanchnic, and mammary tissues, and of milk AA output of lactating Holstein cows (n = 6, 109 +/- 9 d in milk) as influenced by flaking density of corn grain. Cows were fed alfalfa-based total mixed ration (TMR) containing 40% steam-flaked (SFC) or steam-rolled corn (SRC) grain. The TMR were offered at 12-h intervals in a crossover design. Six sets of blood samples were obtained from indwelling catheters in portal, hepatic, and mammary veins and mesenteric or costoabdominal arteries every 2 h from each cow and diet. Intake of dry matter (18.4 +/- 0.4 kg/d), N, and net energy for lactation were not altered by corn processing. Milk and milk crude protein yields (kg/12-h sampling) were 14.2 vs. 13.5 and 0.43 vs. 0.39 for cows fed SFC or SRC, respectively. The PDV flux of total essential FAA was greater (571.2 vs. 366.4 g/12 h, SEM 51.4) in cows fed SFC. The PDV flux of total essential PBAA was 69.3 +/- 10.8 and 51.5 +/- 13.2 g/12 h for cows fed SFC and SRC, respectively, and differed from zero, but fluxes of individual PBAA rarely differed between treatments. Liver flux of essential FAA was greater in cows fed SRC, but only the PBAA flux in cows fed SRC differed from zero. Splanchnic flux of FAA and PBAA followed the pattern of PDV flux, but variation was greater. Mammary uptake (g/12 h) of total essential FAA was greater in cows fed SFC than SRC (224.6 vs. 198.3, SEM 7.03). Mammary uptake of essential PBAA was 25.0 vs. 15.1, SEM 5.2, g/12 h for cows fed SFC or SRC, respectively, and differed from zero in half of the PBAA. Milk output of EAA was 187.8 vs 175.4, SEM 4.4 g/12 h in cows fed SFC and SRC, respectively, and output of most essential AA consistently tended to be greater in cows fed SFC. It is apparent that PBAA comprise a portion of total AA flux across PDV and are affected by grain processing. Further, this pool supplies an important component of AA taken up by the mammary gland. Quantifying the contribution of PBAA may improve diet formulation with respect to intestinal absorption and mammary uptake of AA.
Assuntos
Aminoácidos/metabolismo , Bovinos/metabolismo , Dieta , Fígado/metabolismo , Glândulas Mamárias Animais/metabolismo , Leite/metabolismo , Aminoácidos/sangue , Animais , Artérias , Proteínas Sanguíneas/metabolismo , Feminino , Manipulação de Alimentos/métodos , Veias Hepáticas , Absorção Intestinal , Cinética , Lactação , Glândulas Mamárias Animais/irrigação sanguínea , Medicago sativa , Artérias Mesentéricas , Sistema Porta , Veia Porta , Circulação Esplâncnica , Veias , Vísceras/irrigação sanguínea , Vísceras/metabolismo , Zea maysRESUMO
Objectives were to determine net release or uptake of alpha-amino N, ammonia N, and urea N across portal-drained viscera, liver, splanchnic, and mammary tissues of lactating Holstein cows (n = 8, 86 +/- 8 d in milk) fed alfalfa hay-based total mixed rations containing 40% dry-rolled or steam-flaked sorghum grain. The total mixed rations were offered at 12-h intervals in a crossover design. Blood samples were obtained from indwelling catheters in the portal, hepatic, and mammary veins and mesenteric or costoabdominal arteries, every 2 h for each cow and diet. Steam-flaking increased in vitro rate of starch hydrolysis compared with dry-rolled sorghum (66 vs. 25%). Diet did not alter dry matter intake (18.2 +/- 0.3 kg). Daily milk yield (27.6 +/- 0.8 kg), efficiency of production, and most milk components did not differ between diets, but fat yield was reduced (0.86 vs. 0.91 kg/d) by steam-flaked sorghum, and lactose concentration was increased (4.99 vs. 4.82%). Blood flows in portal and hepatic veins did not differ between diets. Steam-flaking tended to increase urea N cycling to the gut (162 vs. 95 g/d) compared with dry-rolling of sorghum, whereas net absorption of ammonia N and alpha-amino N across portal-drained viscera were decreased. Net mammary uptake of a-amino N increased more than 20% (83 vs. 67 g/d), resulting in a higher mammary extraction ratio (15 vs. 11%) for steam-flaked versus dry-rolled sorghum. Flaking of sorghum improved the efficiency of postabsorptive N metabolism by increasing urea N cycled to the gut and alpha-amino N uptake by the mammary gland.
Assuntos
Ração Animal/classificação , Bovinos/fisiologia , Lactação/fisiologia , Leite/metabolismo , Nitrogênio/metabolismo , Fenômenos Fisiológicos da Nutrição Animal , Animais , Nitrogênio da Ureia Sanguínea , Bovinos/metabolismo , Estudos Cross-Over , Dieta/veterinária , Ingestão de Alimentos/fisiologia , Grão Comestível , Feminino , Manipulação de Alimentos/métodos , Absorção Intestinal , Lactação/metabolismo , Lactose/análise , Lipídeos/análise , Fígado/irrigação sanguínea , Fígado/metabolismo , Glândulas Mamárias Animais/irrigação sanguínea , Glândulas Mamárias Animais/metabolismo , Leite/química , Sistema Porta/fisiologia , Distribuição Aleatória , Circulação EsplâncnicaRESUMO
The behaviour of solutions of pure myosin, of pure F-actin and of the equimolar mixture of myosin and of F-actin is studied. It is found that the chemical potential of the two proteins, in separate solutions, increases monotonically with the increase of protein osmotic pressure. A method is presented to determine the chemical potential of the 1:1 actin-myosin complex formed from equimolar solutions of myosin and of F-actin (as monomer). This is the first evaluation of the chemical potential of actomyosin under conditions similar to those of skeletal muscle. It is found that the filament suspensions of myosin and of the 1:1 actin-myosin complex display a high non-ideal behavior as well as distinctly different energy profiles as a function of protein osmotic pressure. This supports the hypothesis that, in muscle: (a) detached cross-bridge change significantly their free energy when sarcomere is shifting from the relaxed to the active or to the rigor state; and (b) the cross-bridge attachment-detachment process is accompanied by changes of muscle protein osmotic pressure.
Assuntos
Actinas/química , Actomiosina/química , Miosinas/química , Pressão Osmótica , Trifosfato de Adenosina/química , Animais , Matemática , Músculo Esquelético/química , Coelhos , Soluções/química , TermodinâmicaRESUMO
The objective of this study was to determine effects of processing method, dry-rolled (DR) vs steam-flaked (SF), and degree of processing (flake density, FD) of SF sorghum grain on splanchnic (gut and liver) N metabolism by growing steers. Diets contained 77% sorghum grain either DR or SF at densities of 437, 360, and 283 g/L (SF34, SF28, and SF22, respectively). Eight crossbred steers (340 kg initial BW), implanted with indwelling catheters into portal, hepatic, and mesenteric veins and the mesenteric artery, were used in a randomized complete block design. Blood flows and net output or uptake of ammonia N, urea N (UN), and alpha-amino N (AAN) were measured across portal-drained viscera, hepatic, and splanchnic tissues. Plasma arterial, portal, and hepatic concentrations of individual amino acids were also measured. Decreasing FD linearly increased (P = .04) net absorption of AAN (51, 73, and 78 g/d for SF34, SF28, and SF22, respectively) and transfer (cycling) of blood UN to the gut (49, 48 and 64 g/d; P = .02). Net UN cycling averaged 38% of N intake across all diets. Hepatic uptake of AAN or UN synthesis, and splanchnic output of AAN and UN, were not altered by FD. Lowering FD linearly increased (P < or = .02) portal-arterial concentration differences for blood AAN and UN and plasma arterial concentrations for alanine. Steers fed SF compared to DR tended to have greater (P = .11) blood UN cycling (percentage of hepatic synthesis; 64 vs 50%) and decreased (P = .03) net splanchnic UN output (30 vs 50 g/d), but other net fluxes of N were not altered across splanchnic tissues. Steam-flaking compared to dry-rolling tended to decrease (P = .12) portal, but not hepatic, blood flow and increased (P < .01) hepatic-arterial concentration differences for blood UN. Except for a decrease (P = .01) in hepatic-arterial concentration differences of glutamine, plasma amino acid concentrations were not altered by feeding SF vs DR sorghum. Processing method (steam-flaking vs dry-rolling) or increasing the degree of processing (by decreasing FD) of SF sorghum grain resulted in greater transfer of blood UN to the gut. Reducing FD also linearly increased the absorption of AAN by growing steers, which explains (in part) published responses of superior performance by steers fed SF grains.
Assuntos
Bovinos/crescimento & desenvolvimento , Dieta , Grão Comestível , Nitrogênio/sangue , Circulação Esplâncnica , Animais , Nitrogênio da Ureia Sanguínea , Bovinos/sangue , Digestão , Ingestão de Energia , Absorção Intestinal , Masculino , Nitrogênio/metabolismoRESUMO
We determined the effect of processing method (dry-rolled [DR] vs steam-flaked [SF]) and degree of processing (flake density; FD) of SF sorghum grain on splanchnic (gut and liver) metabolism of energy-yielding nutrients by growing steers. Diets contained 77% sorghum grain, either DR or SF, with SF at densities of 437, 360, or 283 g/L (SF34, SF28, or SF22). Eight multicatheterized steers (340 kg initial BW) were used in a randomized complete block design. Net output or uptake of glucose, L-lactate, VFA, and beta-hydroxybutyrate (BHBA) were measured across portal-drained viscera (PDV), liver, and splanchnic (PDV plus liver) tissues. Net absorption of glucose across PDV was negative and similar for all treatments (average of -104 g/d). Decreasing FD of SF sorghum grain linearly increased (P < or = .04) net absorption and splanchnic output of L-lactate by 20 and 130%, respectively, and hepatic synthesis (P = .06) and splanchnic output (P = .01) of glucose by 50%. Reducing FD did not alter output or uptake of acetate or n-butyrate by gut and liver tissues, but linearly decreased (P = .06) splanchnic output of BHBA by 40%. Net absorption (P = .18) and splanchnic output (P = .15) of propionate tended to be increased linearly by 50% with decreasing FD. Neither processing method (SF vs DR) nor degree of processing (varying FD) altered hepatic nutrient extraction ratios or estimated net absorption and splanchnic output of energy. Maximal contribution of propionate, L-lactate, and amino acids (alpha-amino N) to gluconeogenesis averaged 49, 11, and 20%, respectively. Feeding steers SF compared to DR diets did not alter net output or uptake of energy-yielding nutrients across splanchnic tissues, except net absorption of acetate tended to be greater (P = .13) for steers fed DR. Increasing degree of grain processing in the present study, by incrementally decreasing FD, tended to linearly increase the net absorption of glucose precursors (propionate and lactate), resulting in linear increases in synthesis and output of glucose by the liver to extrasplanchnic tissues (e.g., muscle).
Assuntos
Ração Animal , Bovinos/metabolismo , Grão Comestível/metabolismo , Ácidos Graxos Voláteis/farmacocinética , Glucose/farmacocinética , Ácido Láctico/farmacocinética , Fígado/metabolismo , Ácido 3-Hidroxibutírico/metabolismo , Animais , Carboidratos da Dieta/metabolismo , Digestão , Gluconeogênese , Hidrólise , MasculinoRESUMO
A method is presented to determine the energy of formation of the myosin-ADP complexes at the muscle protein osmotic pressure. It is found that, at 18 kP, the putative protein osmotic pressure in skeletal muscle, the increase of MgADP from 0.05 to 2 mmolal, increases the free energy of myosin-ADP and of myosin-(ADP)2 by 0. 756 and by 9.85 kJ/mol, respectively, and decreases the free energy of myosin by 8.34 kJ erg/mol. It is pointed out that the local changes of water chemical potential, induced by the binding of MgADP to myosin, can be sensed by other structures of the contractile machinery, which per se may even be insensitive to MgADP. Cross talking between macromolecules can thus be achieved by changes of the water chemical potential.
Assuntos
Difosfato de Adenosina/química , Proteínas Musculares/química , Miosinas/química , Pressão Osmótica , Difosfato de Adenosina/análise , Animais , Cloretos/análise , Contração Muscular/fisiologia , Músculo Esquelético/fisiologia , Ligação Proteica , Coelhos , Termodinâmica , Água/químicaRESUMO
Thin filaments were prepared from rabbit and beef skeletal muscle with three different procedures, both at high and low ionic strength. Nebulin was always found to be associated with the myosin fraction and was always absent from the thin filament fraction.
Assuntos
Citoesqueleto de Actina/química , Proteínas Musculares/análise , Miofibrilas/química , Actomiosina/análise , Animais , Bovinos , Concentração Osmolar , CoelhosRESUMO
We have studied the osmotic properties of the calcium-regulated actomyosin complexes from skeletal muscle at the protein osmotic pressure of 18 kPa and a different actin-to-myosin molar ratios. Essentially, protein solutions were equilibrated against a solution of poly(ethylene glycol) 40,000 of known macromolecular osmotic pressure. At the end of the equilibration the water and the protein masses of the protein solutions were determined gravimetrically and the protein molar concentration was calculated. In this reconstructed system we have found following, at the actin-to-molar ratio of 2.6 (the most likely stoichiometry of these two proteins in the dense region of the A band) the average distance between the myosin filaments is 34.2 nm, this equals the interfilament distance in the intact fibre of muscle in rigor, at the sarcomere length of 3.38 micrograms. The formation of the F-actin-myosin and of the tropomyosin-F-actin-myosin rigor complexes involves the largest free energy changes, -5.38 kJ/mol myosin and -5.67 kJ/mol myosin, respectively. The formation of the troponin-tropomyosin-F-actin-myosin(Ca) rigor complex from myosin and troponin-tropomyosin-F-actin(Ca) occurs with the free energy change of -3.43 kJ/mol myosin. Of these -3.43 kJ, -1.81 kJ are provided by the endergonic conversion of troponin-tropomyosin-F-actin(EGTA) into troponin-tropomyosin-F-actin (Ca). The transition of myosin and of troponin-tropomyosin-F-actin(EGTA) into the -F-actin-myosin(Ca) rigor complex is accompanied by a 5.8% increase of volume. The increase of volume is due to a large influx of water, which is essentially protein-hydration water.
Assuntos
Actomiosina/química , Músculo Esquelético/química , Actinas/química , Trifosfato de Adenosina/química , Animais , Cálcio/química , Ácido Egtázico/química , Miosinas/química , Pressão Osmótica , Coelhos , Tropomiosina/químicaRESUMO
We have compared the osmotic properties of the hydrated, native actin filament and of hydrated phalloidin-F-actin. We have found that phalloidin-F-actin interacts much more strongly with water than native F-actin. It is therefore very likely that the interaction with myosin (that requires the expulsion of the protein solvation water) is more problematic for phalloidin-F-actin that for native F-actin. We conclude that phalloidin-F-actin is not a bona fide substitute for native F-actin in the "in vitro motility assay".
Assuntos
Actinas/química , Faloidina/química , Actinas/metabolismo , Animais , Músculo Esquelético/metabolismo , Pressão Osmótica , Faloidina/metabolismo , Polietilenoglicóis , Ligação Proteica , Coelhos , SoluçõesRESUMO
Indwelling central venous catheters obviate many problems in the care of children with malignancies, but they also are a well-known source of infection. We are reviewed the history of 584 Broviac catheters inserted from January 1984 to December 1991, in 475 children with cancer in order to assess the etiology of bacteremias, their association with neutropenia and their relationship with the presence of the catheters. The overall duration-time of the catheters, employed for blood tests, drug and blood infusions and parenteral nutrition, was 1-835 days (median 263, mean 186). Total catheter courses was 108.678 days. In this period 226 episodes of sepsis were observed in 180 patients: 157 in neutropenic patients and 69 in non neutropenic. Catheter related bacteremias were diagnosed in 65/226 episodes (29%): 23 (35%) were observed in neutropenic patients and 42 (65%) in non neutropenic (P < 0.005). Gram-positive pathogens were isolated in 28/65 (43%) episodes, Gram-negatives in 15/65 (23%), fungi in 9/65 (14%), and the remaining 13 (20%) were polymicrobial. In the last years we observed an increase of catheter related bacteremias due to Gram-negative rods no change was observed in pathogens causing catheters unrelated bacteremias. The high incidence of catheters related bacteremias in non neutropenic, non hospitalized patients, stress on the home-care of the catheters; a high level of suspicion of Gram-negative infections should be maintained in cancer patients with an indwelling central venous catheters.
Assuntos
Cateterismo Venoso Central/efeitos adversos , Cateteres de Demora/efeitos adversos , Neoplasias/terapia , Sepse/etiologia , Antineoplásicos/administração & dosagem , Cateterismo Venoso Central/instrumentação , Criança , Feminino , Bactérias Gram-Negativas/isolamento & purificação , Bactérias Gram-Positivas/isolamento & purificação , Humanos , Infusões Intravenosas , Masculino , Neutropenia/etiologia , Nutrição Parenteral/instrumentação , Sepse/microbiologiaRESUMO
The effect of alpha-actinin from chicken gizzard on the properties of F-actin solutions at 37 degrees C and at 4 degrees C was investigated. Beside the well-known increase of the gelling activity of alpha-actinin, it was found that lowering temperature to 4 degrees C: (a) modifies the shape of the alpha-actinin-F-actin binding isotherm; (b) increases the light scattering of the alpha-actinin-F-actin mixtures; (c) induces the formation of ribbons and bundles of F-actin. It was also observed that, by warming to 37 degrees C, the bundles of F-actin formed at 4 degrees C were dissociated into quasi-parallel actin filaments running at a distance of 25-42 nm from each other. On subsequent cooling to 4 degrees C, these parallel filaments were rapidly assembled into bundles. As at 37 degrees C, alpha-actinin displays a potent gelling activity on bundles but not on filaments of actin, and as the gelling activity at 4 degrees C is accompanied by the formation of actin bundles, it is concluded that actin bundling is a necessary condition to promote the actin-gelling activity.
Assuntos
Actinina/metabolismo , Actinas/metabolismo , Moela das Aves/metabolismo , Actinina/ultraestrutura , Actinas/ultraestrutura , Animais , Galinhas , Temperatura Baixa , Géis , Temperatura Alta , Luz , Microscopia Eletrônica , Coelhos , Espalhamento de Radiação , ViscosidadeRESUMO
In a cross-sectional investigation of the properties of DSM-III-R panic disorder (PD), panic disorder with agoraphobia (PDA), and agoraphobia without history of panic disorder (AWOPD), we analyzed demographic, descriptive, comorbidity, treatment, and course data for 562 subjects with PD, PDA, or AWOPD in a multicenter anxiety-disorders study. In general, AWOPD subjects had the worst functioning and PD subjects the best, as measured by length of intake episodes, education attained, likelihood of receiving financial assistance, depressive comorbidity, and likelihood of having experienced 8 weeks symptom-free. Panic disorder with agoraphobia was the most common disorder and emerged as a condition intermediate in severity between the other two. Treatments received varied little by diagnosis. Most subjects received medication, usually benzodiazepines. Psychodynamic psychotherapy was the most frequently received psychosocial treatment; cognitive and behavioral approaches were less common. Subjects classified with AWOPD were the most likely to have received exposure therapies.
Assuntos
Agorafobia/epidemiologia , Transtorno de Pânico/epidemiologia , Adulto , Idoso , Agorafobia/diagnóstico , Agorafobia/terapia , Benzodiazepinas/uso terapêutico , Comorbidade , Estudos Transversais , Diagnóstico Diferencial , Feminino , Seguimentos , Humanos , Masculino , Pessoa de Meia-Idade , Transtorno de Pânico/diagnóstico , Transtorno de Pânico/terapia , Estudos Prospectivos , Escalas de Graduação Psiquiátrica , Psicoterapia , Índice de Gravidade de Doença , Resultado do TratamentoRESUMO
The interaction of alpha-actinin from chicken gizzard with F-actin is quite complex. The apparent dissociation constant, C, increases with the increase of actin concentration according to the following expression: C = Ko + a[actin] - c[actin]5/2. At pH 7.5 and 37 degrees C, in the presence of 0.1 M KCl and 2 mM MgCl2, the dissociation constant at infinite actin dilution, Ko, is 2.17 microM. The binding of alpha-actinin to actin is related by the term a[actin] to the diffusion of actin filaments and by the term c[actin]5/2 to the crossing number concentration of the F-actin network. Especially at low actin concentration, the binding of alpha-actinin to actin is increased by gelsolin, which fragments actin filaments and increases their diffusion. The different binding isotherms of alpha-actinin to actin filaments and to actin bundles are discussed.
Assuntos
Actinina/metabolismo , Actinas/metabolismo , Moela das Aves/metabolismo , Actinina/química , Actinas/química , Animais , Proteínas de Ligação ao Cálcio/farmacologia , Galinhas , Difusão , Gelsolina , Proteínas dos Microfilamentos/farmacologia , Ligação Proteica/efeitos dos fármacos , CoelhosRESUMO
BACKGROUND: There are abundant data to justify the use of behavioral methods in treating patients with anxiety disorders. Yet there also is evidence that these methods have been underutilized in treating these patients. In this study we examined a large sample of patients with anxiety disorders to determine the extent to which behavior therapy methods were used in their treatment. METHOD: As part of a multicenter longitudinal study of patients with anxiety disorders in New England, we analyzed data pertinent to the type of treatment received by 231 patients at nine study sites. Study subjects received a battery of interview and self-report instruments administered by trained study interviewers at intake and at 6-month follow-up. A Psychosocial Treatments Interview designed by study personnel and administered by study interviewers at 6 months after intake provided data as to types of psychosocial treatment received by study subjects. RESULTS: Behavioral methods were used less frequently than supportive psychotherapy. medication, or psychodynamic psychotherapy. Among behavioral treatments, relaxation and imaginal exposure were used more frequently than in vivo exposure. Obsessive compulsive disorder and agoraphobia without panic were the diagnoses most likely to be treated behaviorally. Behavioral methods were used more frequently in combination with other modalities than they were alone. CONCLUSION: When compared with previous studies, the frequency of utilization of behavioral methods appears to have increased moderately. But our data are still consistent with a pattern of inappropriately low utilization of these effective treatment methods.
Assuntos
Transtornos de Ansiedade/terapia , Terapia Comportamental , Adolescente , Adulto , Idoso , Agorafobia/terapia , Terapia Comportamental/estatística & dados numéricos , Terapia Cognitivo-Comportamental/estatística & dados numéricos , Terapia Combinada , Interpretação Estatística de Dados , Dessensibilização Psicológica/estatística & dados numéricos , Feminino , Seguimentos , Humanos , Estudos Longitudinais , Masculino , Pessoa de Meia-Idade , Transtorno Obsessivo-Compulsivo/terapia , Transtorno de Pânico/terapia , Escalas de Graduação Psiquiátrica , Psicoterapia/estatística & dados numéricos , Terapia de Relaxamento/estatística & dados numéricosRESUMO
At pH 7.14 and 37 degrees C, in 7.2% (w/v) poly(ethylene glycol) 6000, tropomyosin-regulated actin filaments are converted into filament bundles by increasing the free Mg2+ concentration to 1.7-2.0 mM. When free Mg2+ concentration is decreased below 1.7 mM, bundles dissociate back into tropomyosin-regulated actin filaments. Pure actin filaments are insensitive to this mechanism of control and are found as filament bundles in all the range of free Mg2+ concentrations tested (1.37-2.2 mM). The mechanism of regulation described above is likely to operate in the cell, where the concentration of free Mg2+ is linked to the energy charge of the adenine nucleotide system.
Assuntos
Citoesqueleto de Actina/fisiologia , Magnésio/fisiologia , Proteínas dos Microfilamentos/fisiologia , Músculos/citologia , Tropomiosina/fisiologia , Citoesqueleto de Actina/metabolismo , Actinas/biossíntese , Actinas/fisiologia , Difosfato de Adenosina/farmacologia , Trifosfato de Adenosina/farmacologia , Animais , Movimento Celular/fisiologia , Tamanho Celular/fisiologia , Galinhas , Cinética , Substâncias Macromoleculares , Proteínas dos Microfilamentos/biossíntese , Músculos/fisiologia , Polietilenoglicóis/farmacologia , Coelhos , Tropomiosina/metabolismoRESUMO
At 37 degrees C, the alpha-actin-F-actin binding isotherm is anomalous. In 6.7% polyethylene glycol 6000, concomitantly with the formation of actin bundles, the binding isotherm becomes hyperbolic (Kdiss. = 11.3 microM). alpha-Actinin increases the rigidity of the networks formed by actin bundles in polyethylene glycol and by paracrystalline actin in 16 mM MgCl2 but not by F-actin. It is proposed that in the cell alpha-actinin functions are mostly carried on by interaction with actin bundles.
Assuntos
Actinina/metabolismo , Actinas/metabolismo , Actinas/química , Animais , Cristalografia , Cloreto de Magnésio/farmacologia , Polietilenoglicóis/farmacologia , CoelhosRESUMO
A comprehensive set of speech reception measures were obtained in a group of about 20 postlingually deafened adult users of the Ineraid multichannel cochlear implant. The measures included audio, visual, and audiovisual recognition of words embedded in two types of sentences (with differing degrees of difficulty) and audio-only recognition of isolated monosyllabic words, consonant identification (12 alternatives, /Ca/), and vowel identification (8 alternatives, /bVt/). For most implantees, the audiovisual gains in the sentence tests were very high. Quantitative relations among audio-only scores were assessed using power-law transformations suggested by Boothroyd and Nittrouer [J. Acoust. Soc. Am. 84, 101-114 (1988)] that can account for the benefit of sentence context (via a factor k) and the relation between word and phoneme recognition (via a factor j). Across the broad range of performance that existed among the subjects, substantial order was observed among measures of speech reception along the continuum from recognition of words in sentences, words in isolation, speech segments, and the retrieval of underlying phonetic features. Correlations exceeded 0.85 among direct and sentence-derived measures of isolated word recognition as well as among direct and word-derived measures of segmental recognition. Results from a variety of other studies involving presentation of limited auditory signals, single-channel and multichannel implants, and tactual systems revealed a similar pattern among word recognition, overall consonant identification performance, and consonantal feature recruitment. Finally, improving the reception of consonantal place cues was identified as key to producing the greatest potential gains in speech reception.
Assuntos
Implantes Cocleares , Surdez/reabilitação , Teste do Limiar de Recepção da Fala , Adulto , Idoso , Idoso de 80 Anos ou mais , Feminino , Humanos , Leitura Labial , Masculino , Pessoa de Meia-Idade , Fonética , Desenho de Prótese , Percepção da FalaRESUMO
We propose that, in the cell, the reversible conversion of actin filaments into actin bundles is controlled by the concentration of the macromolecules [we have employed poly(ethylene glycol) 6000 to mimic the macromolecules of the cell] as well as by the nature of the ancillary cytoskeletal proteins that decorate actin filaments. The proposal is based on the following evidence. (1) Under our experimental conditions the transition from filaments into bundles occurs at increasing concentrations of poly(ethylene glycol), with the following sequence: caldesmon-actin, 3%; filamin-actin, 4-5%; caldesmon-tropomyosin-actin, 5-7%; actin, 6-7%; tropomyosin-actin, 9-10%. (2) Under conditions of low osmoelastic stress [3% poly(ethylene glycol)], preformed caldesmon-actin bundles are dissociated by the addition of either tropomyosin or tropomyosin-decorated actin. The dissociation of the bundles promoted by the addition of tropomyosin-decorated actin is faster than that promoted by the addition of tropomyosin.
Assuntos
Actinas/fisiologia , Citoesqueleto/fisiologia , Actinas/ultraestrutura , Animais , Proteínas de Ligação a Calmodulina/metabolismo , Proteínas de Ligação a Calmodulina/fisiologia , Centrifugação , Citoesqueleto/ultraestrutura , Cinética , Luz , Substâncias Macromoleculares , Microscopia Eletrônica , Polietilenoglicóis , Coelhos , Espalhamento de Radiação , Tropomiosina/metabolismo , Tropomiosina/fisiologiaRESUMO
Solation of actin gel by gelsolin is much less efficient in the presence of a high concentration of macromolecular solutes. The rigidity of the gel formed by 12 microM actin is lowered from 4 to 0.33 dynes/cm2 by 15 nM gelsolin, while in 6% (w/v) polyethylene glycol, rigidity is lowered only from 20 to 11 dynes/cm2 by 64 nM gelsolin. Owing to the large concentration of protein, transitions in the fluid- and gel-like properties of the cytoplasm are expected to be problematic when promoted by gelsolin alone.