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1.
Musculoskeletal Care ; 16(1): 222-232, 2018 03.
Artigo em Inglês | MEDLINE | ID: mdl-28401656

RESUMO

INTRODUCTION: Chronic knee and hip pain is prevalent, impairing mobility, function and quality of life. Allied health professions (AHPs) are better trained and have more time than general practitioners in primary care to advise and support people to adopt healthier lifestyles (maintain healthy weight, increase physical activity) that reduce joint pain. We evaluated whether AHP-led primary care delivering person-centred, practical lifestyle coaching was a feasible, effective way to manage chronic knee and/or hip pain. METHODS: At initial assessment the 'Joint Pain Advisor' assessed pain, function, quality of life, physical activity, waist circumference and body mass, taught simple self-management strategies and used behaviour change techniques (motivational interviewing, goal setting, action/coping planning) to alter participants' lifestyles. Participants were invited for 6-week and 6-month reviews, when the Advisor reassessed clinical outcomes, fed back progress and reinforced health messages. Feasibility and effectiveness of the service was evaluated using quantitative and qualitative methods. RESULTS: Uptake of the service was good: 498 people used the service. Between initial assessment and reviews, participants' pain, function, quality of life, weight, waist circumference and physical activity improved (p < 0.005). Service user satisfaction was high; they reported easier access to advice and support tailored to their needs that translated into clinical benefits and a more efficient pathway reducing unnecessary consultations and investigations. Relatively few people returned for a 6-month review as they considered they had received sufficient advice. CONCLUSIONS: AHP-led care is a popular, effective, efficient and sustainable way to manage joint pain, without compromising safety or quality of care.


Assuntos
Pessoal Técnico de Saúde , Artralgia/terapia , Osteoartrite do Quadril/terapia , Osteoartrite do Joelho/terapia , Atenção Primária à Saúde , Adulto , Idoso , Idoso de 80 Anos ou mais , Artralgia/etiologia , Estudos de Viabilidade , Feminino , Grupos Focais , Pesquisa sobre Serviços de Saúde , Humanos , Masculino , Pessoa de Meia-Idade , Osteoartrite do Quadril/complicações , Osteoartrite do Joelho/complicações , Satisfação do Paciente
2.
Nutr Cancer ; 30(1): 69-73, 1998.
Artigo em Inglês | MEDLINE | ID: mdl-9507516

RESUMO

Thermally oxidized animal fat (beef tallow) was assessed for colon cancer-promoting and -initiating activity in F-344 rats and CF-1 mice with the use of the aberrant crypt focus (ACF) assay. In two promotion studies, extensively oxidized beef tallow (110 degrees C for 144-168 h, peroxide value approx 200 meq/kg, with > 80% loss of allylic and olefinic protons) had relatively little effect on the growth of ACF in F-344 rats. The multiplication constant for treatment/control of ACF size in aberrant crypts per ACF at 100 days was 1.07 (95% confidence interval = 1.01-1.14) and 0.98 (95% confidence interval = 0.91-1.06). ACF size was not affected by less extensively oxidized beef tallow or by a 10-fold reduction of dietary alpha-tocopherol during the growth of the ACF. In initiation studies, extensively oxidized beef tallow administered by gavage increased the number of animals with ACF and the number of ACF per colon (11 of 23 and 5 of 29 animals with ACF; 1.09 +/- 0.29 and 0.21 +/- 0.09 ACF/colon, respectively). Less severely oxidized beef tallow was without effect. Further studies with CF-1 mice confirmed that extensively oxidized beef tallow increased numbers of animals with ACF and average ACF per colon. The unsaturated aldehyde acrolein was without effect in the ACF assay. These data suggest that highly thermolyzed beef tallow contains an uncharacterized initiator or leads to conditions in which spontaneously initiated ACF are increased.


Assuntos
Neoplasias do Colo/induzido quimicamente , Gorduras na Dieta/administração & dosagem , Gorduras/química , Temperatura Alta , Acroleína/administração & dosagem , Acroleína/toxicidade , Animais , Apoptose , Bovinos , Colo/patologia , Óleo de Milho/química , Gorduras/administração & dosagem , Gorduras/toxicidade , Masculino , Camundongos , Oxirredução , Peróxidos/química , Ratos , Ratos Endogâmicos F344
3.
Nutr Cancer ; 23(3): 271-81, 1995.
Artigo em Inglês | MEDLINE | ID: mdl-7603887

RESUMO

Thermolyzed casein is known to promote the growth of aberrant crypt foci (ACF) and colon cancer when it is fed to rats that have been initiated with azoxymethane. We speculated that the promotion was a consequence of increased colonic protein fermentation (i.e., that the thermolysis of the casein decreases its digestibility, increases the amount of protein reaching the colon, and increases colonic protein fermentation and that the potentially toxic products of this fermentation promote colon carcinogenesis). We found that the thermolysis of casein reduces its digestibility and increases colonic protein fermentation, as assessed by fecal ammonium and urinary phenol, cresol, and indol-3-ol. Thermolysis of two other proteins, soy and egg white protein, also increases colonic protein fermentation with increased fecal ammonia and urinary phenols, and thermolysis of all three proteins increases the levels of ammonia and butyric, valeric, and i-valeric acids in the cecal contents. We found, however, that the increased protein fermentation observed with thermolysis is not associated with promotion of colon carcinogenesis. With casein, the kinetics of protein fermentation with increasing thermolysis time are clearly different from the kinetics of promotion of ACF growth. The formation of the fermentation products was highest when the protein was thermolyzed for one hour, whereas promotion was highest for protein that had been thermolyzed for two or more hours. With soy and egg white, thermolysis increased colonic protein fermentation but did not promote colon carcinogenesis. Thus, although thermolysis of dietary casein increases colonic protein fermentation, products of this fermentation do not appear to be responsible for the promotion of colon carcinogenesis. Indeed, the results suggest that protein fermentation products do not play an important role in colon cancer promotion.


Assuntos
Caseínas/metabolismo , Colo/metabolismo , Neoplasias do Colo/induzido quimicamente , Fermentação , Proteínas/metabolismo , Animais , Digestão , Feminino , Temperatura Alta , Cinética , Ovalbumina/metabolismo , Proteínas de Vegetais Comestíveis/metabolismo , Ratos , Ratos Endogâmicos F344 , Proteínas de Soja
4.
Caring ; 14(2): 16-8, 20-2, 1995 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-10140642

RESUMO

Tuberculosis has found its way back into the mainstream after decades of slow decline. The Centers for Disease Control and Prevention and the Occupational Safety and Health Administration have implemented standards for all health care providers in an effort to prevent and control this disease before it reaches epidemic levels.


Assuntos
Visitadores Domiciliares , Controle de Infecções/organização & administração , Exposição Ocupacional/prevenção & controle , Tuberculose/prevenção & controle , Centers for Disease Control and Prevention, U.S. , Aconselhamento , Educação em Saúde , Visitadores Domiciliares/educação , Visitadores Domiciliares/normas , Humanos , Transmissão de Doença Infecciosa do Paciente para o Profissional/prevenção & controle , Teste Tuberculínico , Tuberculose/transmissão , Estados Unidos , United States Occupational Safety and Health Administration
5.
Caring ; 13(10): 81-5, 87, 1994 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-10137694

RESUMO

The expansion of managed care into the home care industry necessitates change to prepare for different systems of payment and cost containment. One home care provider learned from what hospitals were doing how it could improve its own day-to-day workings and outcomes.


Assuntos
Serviços de Assistência Domiciliar/organização & administração , Programas de Assistência Gerenciada/organização & administração , Inovação Organizacional , Atitude do Pessoal de Saúde , Capacitação em Serviço , Cultura Organizacional , Planejamento de Assistência ao Paciente , Equipe de Assistência ao Paciente , Técnicas de Planejamento , Rhode Island
6.
Mutat Res ; 290(1): 111-8, 1993 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-7694090

RESUMO

We have used the aberrant crypt focus (ACF) assay to test and develop hypotheses linking diet and colon cancer. The hypotheses were suggested by epidemiological studies that identified possible dietary factors associated with colorectal cancer risk. The ACF assay was used to quantitate the effect of the dietary factors on the initiation and growth of these putative precursors of colon cancers in experimental animals. Using this approach we have developed 3 new hypotheses for the role of diet in colorectal cancer. These are (1) a risk associated with 5-hydroxymethyl-2-furaldehyde in caramelized sugar, (2) a risk associated with some factor in thermolyzed casein, and (3) a risk associated with single nutrient boluses of sucrose and fructose. The importance of these hypotheses has still to be tested in long term carcinogenesis experiments, in analytic epidemiology studies and then, perhaps, in intervention trials.


Assuntos
Neoplasias Colorretais/etiologia , Dieta/efeitos adversos , Animais , Testes de Carcinogenicidade , Humanos
7.
Carcinogenesis ; 14(4): 773-5, 1993 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-8472346

RESUMO

We have previously shown that thermolyzed sucrose in the diet promotes the growth of aberrant crypt foci (ACF) in the rat. HPLC analysis of the light caramel colored product showed that it contained 1% 5-hydroxymethyl-2-furaldehyde (HMF), confirmed by mass and NMR spectroscopy. To determine whether HMF was responsible for the promotion of ACF by thermolyzed sucrose, 45 F344 female rats were initiated with the colon carcinogen azoxymethane (AOM), and a week later were randomized to four groups receiving AIN-76 diets containing untreated sucrose, 20% thermolyzed sucrose, 20% butanol extracted thermolyzed sucrose (HMF free) or 1% HMF. Thermolyzed sucrose in the diet led to larger ACF as previously observed. Thermolyzed sucrose extracted to remove HMF, did not affect ACF size, but 1% HMF added to the diet led to a larger ACF both with relation to average size and number of ACF of larger sizes (P < 0.05). To determine whether HMF had initiating effects, 172 female F344 rats were given water, HMF (at doses to 300 mg/kg) or AOM (5 mg/kg) by gavage twice and the total number of ACF was scored 30 days later. The results demonstrated that HMF induces ACF in a dose-dependent manner (P < 0.02), though the effect was much weaker than that of AOM. We conclude that sugar heated under household cooking conditions may act as both an initiator and a promoter of colon cancer because of the presence of HMF.


Assuntos
Colo/efeitos dos fármacos , Neoplasias do Colo/induzido quimicamente , Furaldeído/análogos & derivados , Lesões Pré-Cancerosas/induzido quimicamente , Sacarose , Animais , Azoximetano , Feminino , Furaldeído/toxicidade , Temperatura Alta , Ratos , Ratos Endogâmicos F344 , Sacarose/administração & dosagem , Sacarose/química , Sacarose/toxicidade
8.
Carcinogenesis ; 14(4): 777-9, 1993 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-8472347

RESUMO

The association of refined sugars and colorectal cancers and polyps in three recent case-control studies led us to investigate the effects of sucrose, fructose and glucose on colonic epithelial proliferation and sensitivity to carcinogenesis. CF1 and C57BL/6J mice were used; proliferation was assessed as vincristine-accumulated mitotic figures per crypt section; sensitivity to carcinogenesis was assessed as the number of aberrant crypt foci (ACF) per colon observed following the colon carcinogen, azoxymethane (AOM, 3 mg/kg and 5 mg/kg). Oral gavages of sucrose and fructose in CF1 mice (10 g/kg) increased colonic proliferation 16 h later (2.8 +/- 0.6 and 4.1 +/- 0.7 (mean +/- SEM) accumulated mitotic figures/crypt section), compared with glucose and water (1.0 +/- 0.2 and 0.4 +/- 0.1). Sucrose and fructose given 14 h prior to the AOM (5 mg/kg) increased the sensitivity of the colon to carcinogenesis (18.4 +/- 1.5 and 13.1 +/- 1.8 ACF/colon), compared with glucose and water (11.4 +/- 2.0 and 8.6 +/- 1.1). Similar results were observed with C57BL/6J mice. We conclude that dietary sucrose and fructose may represent risk factors for colorectal cancer through a direct effect of the sugars on colonic epithelial proliferation.


Assuntos
Neoplasias do Colo/induzido quimicamente , Glucose/efeitos adversos , Lesões Pré-Cancerosas/induzido quimicamente , Sacarose/efeitos adversos , Animais , Azoximetano , Divisão Celular/efeitos dos fármacos , Cocarcinogênese , Feminino , Frutose/administração & dosagem , Frutose/efeitos adversos , Glucose/administração & dosagem , Camundongos , Camundongos Endogâmicos C57BL , Mitose/efeitos dos fármacos , Especificidade da Espécie , Sacarose/administração & dosagem
9.
Environ Health Perspect ; 98: 195-7, 1992 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-1486848

RESUMO

Foci of aberrant crypts similar to those seen in experimental animals exposed to colon carcinogens have been identified and quantified on the mucosal surface of fixed resections of human colon after methylene blue staining. Many of the foci in humans showed dysplasia on histologic examination and were considered to be microadenoma (MA). These lesions may be precursors for adenomatous polyps and colorectal cancer. Rats and mice initiated with azoxymethane, then fed diets containing sucrose or casein heated at 180 degrees C to stimulate normal cooking conditions, had three to five times more large MA after 100 days than controls. Thus, cooked sugar and protein contain promoters of the growth of colonic MA. 5-Hydroxymethylfuraldehyde was identified as a promoter in cooked sugar.


Assuntos
Adenoma/patologia , Neoplasias do Colo/patologia , Dieta/efeitos adversos , Temperatura Alta , Lesões Pré-Cancerosas/patologia , Adenoma/etiologia , Animais , Azoximetano , Cocarcinogênese , Neoplasias do Colo/etiologia , Camundongos , Distribuição Aleatória , Ratos , Ratos Endogâmicos F344
10.
J Natl Cancer Inst ; 84(13): 1026-30, 1992 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-1608054

RESUMO

BACKGROUND: We have previously shown that thermolyzed protein (casein) cooked with fat in the diet of the rat promotes the growth of aberrant crypt foci (putative precursors of colon cancer) assessed at 100 days. PURPOSE: To determine how thermolysis affects this promotion, we examined thermolysis conditions, quantity of thermolyzed protein in the diet, and duration of thermolysis. To determine whether the previous finding of promotion of aberrant crypt foci corresponds to promotion of cancers assessed much later, we carried out promotion studies until colon cancers appeared. METHODS: F344 rats were given an initiating dose of azoxymethane and were then randomly allocated to groups receiving diets differing in their quantity and quality of casein. The groups were examined for aberrant crypt foci and tumors in the colon. RESULTS: Aberrant crypt foci were promoted by diets containing thermolyzed casein (180 degrees C, 2 hours). Promotion increased with increasing level of thermolyzed casein in the diet (to 20%) and with increasing thermolysis time (to 4 hours). The number of animals with polyps and cancers was higher in the animals receiving thermolyzed protein (2 hours), 16/23 versus 9/26 (P less than .05) and 10/26 versus 3/27 (P less than .05), respectively. The number of aberrant crypts per focus and the number of large aberrant crypt foci were higher in the tumor-bearing animals. CONCLUSIONS: Thermolyzed casein promotes early colonic precursor lesions in a dose-dependent and thermolysis time-dependent manner; thermolyzed casein also promotes colon cancer. IMPLICATIONS: The promoter formed on thermolysis could be involved in colon cancers associated with diets cooked at elevated temperatures, such as can occur with high-fat diets.


Assuntos
Caseínas/toxicidade , Neoplasias do Colo/induzido quimicamente , Animais , Caseínas/administração & dosagem , Relação Dose-Resposta a Droga , Feminino , Temperatura Alta , Masculino , Distribuição Aleatória , Ratos , Ratos Endogâmicos F344 , Fatores de Tempo
11.
Hum Pathol ; 22(3): 287-94, 1991 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-1706308

RESUMO

The objective of the present study was to determine whether aberrant crypt foci (ACF) similar to those observed in the colons of experimental animals exposed to colon carcinogens could be identified and quantified in the human colon. Twenty-seven colon resections from patients affected by familial adenomatous polyposis (FAP, five cases), colorectal cancer (CRC, 12 cases), and benign diseases of the large bowel (BD, 10 cases) were collected from a pathology repository or immediately after operation. Ten or more 1-cm2 formalin-fixed, methylene-blue--stained samples of colonic mucosa from each colon were scored under light microscopy for ACF. The number of ACF per cm2 and the number of crypts per ACF for each colon were calculated. The average number of ACF per cm2 in the FAP group (20 +/- 19, mean +/- SD) was significantly higher (P less than 0.01) than those of the CRC (0.37 +/- 0.41) and BD (0.18 +/- 0.35) groups. At least one ACF was found in every colon resection from CRC patients and in six out of 10 colon resections from the BD group. The average number of crypts per ACF ranged from five to 35 with absolute values from 1 to over 100. Fifty-five histologic specimens, 43 with ACF of various size and 12 without, were prepared by sectioning the colon parallel to the mucosal surface. There was a close correlation between the number of crypts per ACF in each specimen as scored by methylene-blue and histologic examination. Twenty-six aberrant crypt foci displayed dysplasia as evident by histologic analysis. In these instances we feel the term microadenoma is appropriate and, using this unique approach of examining the human colon, they can be easily identified and quantified. These lesions may well be precursors for adenomatous polyps and colorectal cancer.


Assuntos
Adenoma/patologia , Colo/ultraestrutura , Neoplasias do Colo/patologia , Microvilosidades/ultraestrutura , Adenoma/diagnóstico , Adenoma/ultraestrutura , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias do Colo/diagnóstico , Neoplasias do Colo/ultraestrutura , Feminino , Histocitoquímica/métodos , Humanos , Mucosa Intestinal/patologia , Mucosa Intestinal/ultraestrutura , Masculino , Pessoa de Meia-Idade , Coloração e Rotulagem/métodos
12.
Cancer Res ; 50(21): 6955-8, 1990 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-2208161

RESUMO

We studied the effect of cooked food components on the promotion of microadenoma growth in the colons of mice and rats. CF1 mice and Fisher 344 rats were initiated with azoxymethane, with 152 mice receiving four weekly i.p. injections of 5 mg/kg, 59 rats receiving a single injection of 20 mg/kg, and 24 rats receiving 30 mg/kg. A week after the last injection, the animals were randomly assigned to one of eight diets with identical ingredients, but the three components, sucrose, casein, and beef tallow, either uncooked or cooked. Control animals were given diets with uncooked ingredients. Experimental animals were fed diets in which one, two, or three of the components were cooked in an oven at 180 degrees C until golden brown before they were added to the diet. After 100 days on the diets, the colons were fixed, stained with methylene blue, and scored for microadenomas. The mice and the rats fed cooked sucrose, or casein and beef tallow cooked together, had three to five times more large microadenomas than did the controls (P ranging from 0.02 to 0.0001). No significant increase was observed with the five other cooked diets. Two rats fed the casein and beef tallow cooked together had adenocarcinomas. Thus, a diet containing 20% of cooked sucrose, or 40% of casein and beef tallow cooked together, promotes the growth of colonic microadenomas in initiated mice and rats, and would appear to contain promoters for colon cancer.


Assuntos
Adenoma/etiologia , Caseínas/efeitos adversos , Neoplasias do Colo/etiologia , Carboidratos da Dieta/efeitos adversos , Gorduras na Dieta/efeitos adversos , Adenoma/induzido quimicamente , Animais , Azoximetano , Peso Corporal , Neoplasias do Colo/induzido quimicamente , Feminino , Temperatura Alta , Camundongos , Ratos , Ratos Endogâmicos F344 , Fatores de Tempo
13.
Carcinogenesis ; 7(10): 1657-61, 1986 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-3757168

RESUMO

The effect of dietary calcium on the cholic acid-induced colon cell proliferative response was investigated with C57BL/6J mice. The control diets were formulated on the basis of the AIN-76 diet with the levels of calcium set at 0.1, 0.5 or 1.0% by weight and the ratio of Ca:P at approximately 1:1. Cholic acid was added at 0.1% and 0.25% by weight. The cytokinetic parameters of the colons were evaluated after 2 weeks of feeding by the metaphase arrest technique and by autoradiography. Mitotic activity was found to monotonically decrease with increasing calcium level from 0.1 to 1.0% for both the cholic acid and control groups, cholic acid-fed groups exhibiting significantly higher mitotic activity than the control groups. The effect of calcium (0.1 versus 1.0%) was evident throughout the 24-h period with both the control and cholic acid-supplemented diets. Autoradiographic analyses of the colons yielded similar results. Among the controls, the 0.1% Ca group exhibited significantly higher (P less than or equal to 0.05) crypt height, higher whole crypt labelling index and higher labelling indices at various positions along the crypt height than the 1.0% Ca group. Cholic acid-fed groups had higher values for crypt height, whole crypt labelling indices and the position of the uppermost labelled cells than the control groups. The level of calcium affected the bile acid-induced cell proliferation in the colonic epithelium; the groups fed 0.1% Ca + cholic acid had a markedly higher whole crypt labelling index, a higher position of the uppermost labelled cells and higher labelling indices at various cell positions along the crypt column compared with the 1.0% Ca + cholic acid group. The present study thus demonstrated that increased dietary calcium alleviates the mitogenic effect of a cholic acid supplemented diet on the colonic epithelium.


Assuntos
Cálcio da Dieta/farmacologia , Ácidos Cólicos/farmacologia , Colo/efeitos dos fármacos , Animais , Divisão Celular/efeitos dos fármacos , Ácido Cólico , Colo/patologia , Neoplasias do Colo/etiologia , Epitélio/efeitos dos fármacos , Epitélio/patologia , Camundongos , Camundongos Endogâmicos C57BL
14.
Cancer Lett ; 31(1): 61-7, 1986 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-3697955

RESUMO

The present study investigated the effect of low (5%) and high (23.5%) corn oil diets on the cytokinetic parameters of colonic crypts. C57BL/6J mice were fed the designated diets for 10 or 15 weeks. In comparison to the low corn oil group, the high corn oil group had an increased number of labelled cells per crypt, with increased labelling indices and crypt heights and larger proliferative compartments in their colons at both time periods. The findings of the present study suggest that a high corn oil diet may exert an enhanced tumorigenic effect by altering the cell diversion parameters of the colonic crypts.


Assuntos
Colo/citologia , Gorduras na Dieta , Animais , Divisão Celular/efeitos dos fármacos , Colo/efeitos dos fármacos , Feminino , Masculino , Camundongos , Camundongos Endogâmicos C57BL
17.
Neurochem Res ; 7(8): 953-64, 1982 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-7144999

RESUMO

A TLC procedure which resolves two molecular species of ethanolamine plasmalogen, Pl-PE-1 and Pl-PE-2, was used to compare the ratio of these was species in myelin isolated from normal appearing white matter from brains of 17 multiple sclerosis (MS) patients, 17 normal (N) individuals, 1 patient with subacute sclerosing panencephalitis (SSPE) and 1 patient with a non-demyelinating neurological disease (OND). One of these species (Pl-PE-2) has been reported to be unique to myelin and has primarily 18:1 in both the 1 and 2 positions of glycerol. The other species (Pl-PE-1) is also present in other membranes and has primarily a saturated chain in the 1 position and a polyunsaturated chain in the 2 position. The Pl-PE-1 to Pl-PE-2 ratio was quantitated by scanning the plates with a densitometer. The ratio was similar to normal in most of the MS samples, 0.88 +/- 0.09, but was much less th an normal in 4 of the MS samples and the SSPE sample. This is attributed to increased decomposition or hydrolysis of Pl-PE-1 relative to Pl-PE-2 at some stage, either during the disease process or due to post-mortem decomposition. Although the reason for the enhanced decomposition of Pl-PE-1 is not known it suggests that Pl-PE-2 is more stable chemically. This may be related to the unique occurrence of Pl-PE-2 in myelin.


Assuntos
Esclerose Múltipla/metabolismo , Bainha de Mielina/metabolismo , Plasmalogênios/metabolismo , Cromatografia em Camada Fina , Humanos , Plasmalogênios/isolamento & purificação
18.
Biochemistry ; 21(6): 1208-14, 1982 Mar 16.
Artigo em Inglês | MEDLINE | ID: mdl-6176267

RESUMO

The basic protein of myelin binds electrostatically to acidic lipids but has several hydrophobic segments which may penetrate into the lipid bilayer. Calorimetric and spin-label evidence suggests that below the phase transition temperature, Tc, several phase states occur in the complex of phosphatidylglycerol with basic protein, possibly due to differences in the degree of penetration of the protein and/or interdigitation of the lipid acyl chains. One of these states is a metastable state which starts to melt 10 degrees C below the Tc of the pure lipid and then refreezes, with release of heat, into a stable state. The stable state melts near the Tc of the pure lipid but restricts the motion of fatty acid spin-labeled near the terminal methyl much more than does the pure lipid. The relationship between the rate of conversion to the stable state and the degree of penetration of the protein at varying pH, in the range 4--8, and the lipid acyl chain length, in the range 14 to 18 carbons, was investigated. Altering the pH in this range affects protonation of the histidines of the protein but has no effect on the lipid at pH 4 and above. The rate of conversion of the sample to both the metastable state and the stable state decreased with increase in pH for phosphatidylglycerol with all lipid chain lengths. It also decreased with decreasing chain length at constant pH. This suggested that the lipid could refreeze into the stable state more readily if a smaller proportion of the total bilayer thickness was occupied by the hydrophobic segments of the protein. The consistency of these results with the concept of penetration of portions of the protein partway into the bilayer lends support to this hypothesis.


Assuntos
Proteína Básica da Mielina , Fosfatidilgliceróis , Sítios de Ligação , Varredura Diferencial de Calorimetria , Fenômenos Químicos , Química , Espectroscopia de Ressonância de Spin Eletrônica , Ácidos Graxos , Concentração de Íons de Hidrogênio , Ligação Proteica , Relação Estrutura-Atividade
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