Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 119
Filtrar
1.
Ir Med J ; 113(7): 124, 2020 Jul 30.
Artigo em Inglês | MEDLINE | ID: mdl-35575604

RESUMO

Aim To assess breastfeeding intention, initiation and duration up to three months postnatal and associated factors. Methods Secondary data from 131 healthy pregnant women participating in an RCT in a Dublin hospital who recorded intention to breastfeed were included. Demographic and breastfeeding data were collected. Results Of the 131 women, 91.6% (n=120) reported intending to breastfeed. 91.7% of those subsequently initiated breastfeeding (n=110/120). Of those intending to breastfeed, 78.9% (n=86/109) and 68.9% (n=73/106) remained breastfeeding at one and three months postnatal respectively. Higher education (p<0.05) and lower BMI (p<0.05) were significantly associated with initiation and duration of breastfeeding. Ethnicity, age, parity or mode of delivery were not significantly associated with breastfeeding. Conclusion Many factors are associated with breastfeeding intention and duration including education and BMI. It is important to develop tailored support measures to encourage initiation and continuation of breastfeeding.

2.
Nature ; 493(7433): 501-3, 2013 Jan 24.
Artigo em Inglês | MEDLINE | ID: mdl-23344359

RESUMO

It is now apparent that there are at least two heating mechanisms in the Sun's outer atmosphere, or corona. Wave heating may be the prevalent mechanism in quiet solar periods and may contribute to heating the corona to 1,500,000 K (refs 1-3). The active corona needs additional heating to reach 2,000,000-4,000,000 K; this heat has been theoretically proposed to come from the reconnection and unravelling of magnetic 'braids'. Evidence favouring that process has been inferred, but has not been generally accepted because observations are sparse and, in general, the braided magnetic strands that are thought to have an angular width of about 0.2 arc seconds have not been resolved. Fine-scale braiding has been seen in the chromosphere but not, until now, in the corona. Here we report observations, at a resolution of 0.2 arc seconds, of magnetic braids in a coronal active region that are reconnecting, relaxing and dissipating sufficient energy to heat the structures to about 4,000,000 K. Although our 5-minute observations cannot unambiguously identify the field reconnection and subsequent relaxation as the dominant heating mechanism throughout active regions, the energy available from the observed field relaxation in our example is ample for the observed heating.

4.
J Anim Physiol Anim Nutr (Berl) ; 98(1): 56-64, 2014 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-23298172

RESUMO

Previous studies from our laboratory have shown positive benefits of linoleic acid (LA) feeding for attenuation of rat heart failure (HF). However, another research group concluded LA feeding was detrimental to cardiac function, using the American Institute of Nutrition 76A (AIN) diet as a background diet for the experimental animals only. To reconcile these conflicting results and determine whether (i) AIN has effects on cardiovascular function, and (ii) AIN reverses the positive effects of LA feeding, studies were performed using spontaneously hypertensive heart failure (SHHF) rats in both a survival study with lifetime feeding of AIN (control: Purina 5001) and a 2 × 2 factorial design for 6 weeks in young male SHHF rats with background diet and LA as variables. During a lifetime of AIN feeding, mortality from heart failure is significantly accelerated, cardiolipin altered and triglycerides increased. In young rats, 6 weeks on the AIN diet promoted increased systolic and diastolic blood pressure, increased fed and fasting blood glucose, increased serum inflammatory eicosanoids, decreased docosahexanoic acid, increased posterior wall thickness in diastole and an altered cardiolipin subspecies profile. The addition of LA to the AIN diet was able to rescue blood pressure. However, the combination increased retroperitoneal fat mass, body weight and fed blood glucose beyond the levels with the AIN diet alone. Because the AIN diet has wide ranging effects on cardiovascular parameters, our results suggest that it should not be used in animal studies involving the cardiovascular system unless induction of cardiac dysfunction is the desired outcome.


Assuntos
Ração Animal/análise , Dieta , Insuficiência Cardíaca/induzido quimicamente , Animais , Pressão Sanguínea , Peso Corporal , Feminino , Masculino , Estado Nutricional , Ratos , Ratos Endogâmicos SHR
5.
J Dairy Sci ; 95(11): 6242-51, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22981572

RESUMO

Skim milk, butter-derived aqueous phase, butter oil, and fish oil (3 levels) were used to produce UHT pasteurized n-3 fatty acid-fortified beverages (3.1% fat, 3.9% protein, and 11.5% total solids) with targeted deliveries of 200, 500, and 800 mg of eicosapentaenoic acid and docosahexaenoic acid (combined total) per 250 mL (8 fl oz) serving. Microbial quality, emulsion stability, and oxidation of lipids over 35 d of storage at 4 °C were evaluated. Conjugated diene hydroperoxides were below 1% throughout storage and were found at highest concentrations around d 21 of storage for all formulations. Volatile analysis indicated an increase in 1-penten-3-ol in the n-3 fortified dairy-based beverage systems during storage. Triangle tests were conducted to determine if consumers could detect a difference in aroma, compared with commercially processed aseptically packaged milk. The beverage system with targeted delivery of 500 mg of eicosapentaenoic acid + docosahexaenoic acid per 250-mL serving was not different in aroma compared with commercially available UHT processed milk. This formulation delivered 432 mg of heart-healthy n-3 fatty acids per 250-mL serving on d 35 and was microbiologically and physically stable throughout the 35-d refrigerated storage period.


Assuntos
Laticínios , Leite/química , Animais , Bovinos , Laticínios/análise , Ácidos Docosa-Hexaenoicos/análise , Ácido Eicosapentaenoico/análise , Ácidos Graxos Ômega-3/análise , Óleos de Peixe/análise , Qualidade dos Alimentos , Armazenamento de Alimentos , Alimentos Fortificados/análise , Alimentos Fortificados/normas , Oxirredução , Pasteurização/métodos
6.
J Clin Invest ; 104(4): 469-81, 1999 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-10449439

RESUMO

Multiple mutations in cardiac troponin T (cTnT) can cause familial hypertrophic cardiomyopathy (FHC). Patients with cTnT mutations generally exhibit mild or no ventricular hypertrophy, yet demonstrate a high frequency of early sudden death. To understand the functional basis of these phenotypes, we created transgenic mouse lines expressing 30%, 67%, and 92% of their total cTnT as a missense (R92Q) allele analogous to one found in FHC. Similar to a mouse FHC model expressing a truncated cTnT protein, the left ventricles of all R92Q lines are smaller than those of wild-type. In striking contrast to truncation mice, however, the R92Q hearts demonstrate significant induction of atrial natriuretic factor and beta-myosin heavy chain transcripts, interstitial fibrosis, and mitochondrial pathology. Isolated cardiac myocytes from R92Q mice have increased basal sarcomeric activation, impaired relaxation, and shorter sarcomere lengths. Isolated working heart data are consistent, showing hypercontractility and diastolic dysfunction, both of which are common findings in patients with FHC. These mice represent the first disease model to exhibit hypercontractility, as well as a unique model system for exploring the cellular pathogenesis of FHC. The distinct phenotypes of mice with different TnT alleles suggest that the clinical heterogeneity of FHC is at least partially due to allele-specific mechanisms.


Assuntos
Cardiomiopatia Hipertrófica/genética , Mutação de Sentido Incorreto , Troponina T/genética , Alelos , Animais , Fator Natriurético Atrial/genética , Sequência de Bases , Cardiomiopatia Hipertrófica/patologia , Cardiomiopatia Hipertrófica/fisiopatologia , Tamanho Celular , Primers do DNA/genética , Modelos Animais de Doenças , Ventrículos do Coração/patologia , Humanos , Técnicas In Vitro , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Endogâmicos CBA , Camundongos Transgênicos , Microscopia Eletrônica , Contração Miocárdica , Cadeias Pesadas de Miosina/genética , Fenótipo , Sarcômeros/ultraestrutura
7.
J Clin Invest ; 101(12): 2800-11, 1998 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-9637714

RESUMO

Mutations in multiple cardiac sarcomeric proteins including myosin heavy chain (MyHC) and cardiac troponin T (cTnT) cause a dominant genetic heart disease, familial hypertrophic cardiomyopathy (FHC). Patients with mutations in these two genes have quite distinct clinical characteristics. Those with MyHC mutations demonstrate more significant and uniform cardiac hypertrophy and a variable frequency of sudden death. Patients with cTnT mutations generally exhibit mild or no hypertrophy, but a high frequency of sudden death at an early age. To understand the basis for these distinctions and to study the pathogenesis of the disease, we have created transgenic mice expressing a truncated mouse cTnT allele analogous to one found in FHC patients. Mice expressing truncated cTnT at low (< 5%) levels develop cardiomyopathy and their hearts are significantly smaller (18-27%) than wild type. These animals also exhibit significant diastolic dysfunction and milder systolic dysfunction. Animals that express higher levels of transgene protein die within 24 h of birth. Transgenic mouse hearts demonstrate myocellular disarray and have a reduced number of cardiac myocytes that are smaller in size. These studies suggest that multiple cellular mechanisms result in the human disease, which is generally characterized by mild hypertrophy, but, also, frequent sudden death.


Assuntos
Cardiomiopatia Hipertrófica/genética , Coração/fisiopatologia , Mutação , Troponina/genética , Animais , Sequência de Bases , Cardiomiopatia Hipertrófica/fisiopatologia , Humanos , Camundongos , Camundongos Transgênicos , Dados de Sequência Molecular , Troponina T
8.
J Clin Oncol ; 15(3): 1239-43, 1997 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-9060568

RESUMO

PURPOSE: To determine whether a sucralfate oral solution can prevent/alleviate radiation-induced esophagitis. PATIENTS AND METHODS: Patients included on this clinical trial were beginning thoracic radiation therapy to the mediastinum. Following stratification, they were randomized, in a double-blind manner, to receive a sucralfate solution or an identical-appearing placebo solution. Esophagitis was measured by physicians who used standard criteria and also by patients who used short questionnaires completed weekly during the course of the trial. RESULTS: A total of 97 assessable patients were entered onto this clinical trial. During the first 2 weeks of the study, two placebo patients (4%) stopped their study medication, compared with 20 sucralfate patients (40%). This was related to substantially increased incidences of gastrointestinal toxicity (58% of sucralfate patients v 14% of placebo patients; P > .0001). There was no substantial benefit from the sucralfate in terms of esophagitis scores. CONCLUSION: This oral sucralfate solution does not appear to inhibit radiation-induced esophagitis and is associated with disagreeable gastrointestinal side effects in this patient population.


Assuntos
Antiulcerosos/uso terapêutico , Esofagite/tratamento farmacológico , Lesões por Radiação/tratamento farmacológico , Sucralfato/uso terapêutico , Administração Oral , Idoso , Esofagite/prevenção & controle , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Lesões por Radiação/prevenção & controle
9.
Diabetes ; 49(3): 431-5, 2000 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10868965

RESUMO

We previously reported that adiposity and serum leptin levels increase with age in male F-344xBN rats and that when physiological levels of serum leptin are manipulated by fasting, there is a corresponding reciprocal change in hypothalamic neuropeptide Y (NPY) mRNA in young rats, but there are no changes in older rats. These findings suggest that the regulation of hypothalamic NPY mRNA by leptin may be impaired with age. To test this hypothesis, we infused saline or leptin for 7 days into ad libitum-fed rats and compared these with saline-infused rats that were pair-fed the amount of food consumed by the leptin-treated rats. We examined daily food consumption, body weight, whole-body oxygen consumption, serum leptin, and NPY mRNA in the hypothalamus. Food consumption decreased by 50% in the leptin-infused compared with the saline-infused young rats but only decreased by 20% in the aged rats. In the leptin-treated young rats, there was a 24% increase in oxygen consumption compared with the pair-fed rats, but there were no changes in oxygen consumption in the aged rats. Leptin infusion diminished hypothalamic NPY levels by nearly 50% compared with pair-fed young rats, whereas there were no changes in the hypothalamic NPY mRNA levels in senescent rats. In summary, aged rats demonstrate a reduced responsiveness to leptin, including a diminished decrease in food intake and no increase in energy expenditure. These diminished responses to leptin were associated with and may be the result of an impaired suppression of hypothalamic NPY mRNA levels. This leptin resistance may be due to either the elevated obesity and serum leptin with age or due to age itself, or both.


Assuntos
Envelhecimento/fisiologia , Leptina/farmacologia , Tecido Adiposo/efeitos dos fármacos , Animais , Peso Corporal/efeitos dos fármacos , Ingestão de Alimentos/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Hipotálamo/efeitos dos fármacos , Hipotálamo/fisiologia , Masculino , Neuropeptídeo Y/genética , Consumo de Oxigênio/efeitos dos fármacos , Ratos , Ratos Endogâmicos BN , Ratos Endogâmicos F344
10.
Genetics ; 117(4): 645-55, 1987 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-2828155

RESUMO

The two yeast genes for 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase, HMG1 and HMG2, each encode a functional isozyme. Although cells bearing null mutations in both genes are inviable, cells bearing a null mutation in either gene are viable. This paper describes a method of screening for recessive mutations in the HMG1 gene, the gene encoding the majority of HMG-CoA reductase activity in the cell. This method should be applicable to the isolation of mutations in other recovered in HMG1. These mutations exhibited intragenic complementation: one allele is in one complementation group and three alleles are in a second complementation group. Assays of HMG-CoA reductase activity indicated that the point mutations destroy most if not all of the activity encoded by HMG1. Intragenic complementation occurred with partial restoration of enzymatic activity. HMG1 was mapped to the left arm of chromosome XIII near SUP79, and HMG2 was mapped to the right arm of chromosome XII near SST2. A slight deleterious effect of a null mutation in either HMG-CoA reductase gene was detected by a co-cultivation experiment involving the wild-type strain and the two single mutants.


Assuntos
Genes Fúngicos , Genes Recessivos , Genes , Hidroximetilglutaril-CoA Redutases/genética , Mutação , Saccharomyces cerevisiae/genética , Enzimas de Restrição do DNA , Genótipo , Plasmídeos , Saccharomyces cerevisiae/enzimologia
11.
Int J Radiat Oncol Biol Phys ; 36(2): 345-9, 1996 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-8892458

RESUMO

PURPOSE: Considerable pilot data and clinical experience suggested that an aloe vera gel might help to prevent radiation therapy-induced dermatitis. METHODS AND MATERIALS: Two Phase III randomized trials were conducted. The first one was double blinded, utilized a placebo gel, and involved 194 women receiving breast or chest wall irradiation. The second trial randomized 108 such patients to aloe vera gel vs. no treatment. Skin dermatitis was scored weekly during both trials both by patients and by health care providers. RESULTS: Skin dermatitis scores were virtually identical on both treatment arms during both of the trials. The only toxicity from the gel was rare contact dermatitis. CONCLUSIONS: This dose and schedule of an aloe vera gel does not protect against radiation therapy-induced dermatitis.


Assuntos
Aloe , Neoplasias da Mama/radioterapia , Fármacos Dermatológicos/administração & dosagem , Plantas Medicinais , Protetores contra Radiação/administração & dosagem , Radiodermite/prevenção & controle , Adulto , Idoso , Método Duplo-Cego , Feminino , Géis , Humanos , Pessoa de Meia-Idade , Placebos , Índice de Gravidade de Doença
12.
Int J Radiat Oncol Biol Phys ; 35(2): 299-303, 1996 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-8635937

RESUMO

PURPOSE: A randomized clinical trial from Great Britain suggested a possible beneficial effect of acetylsalicylate in the prevention of radiation-induced bowel toxicity. Olsalazine is an orally administered drug designed to deliver 5-aminosalicylate to the large bowel with minimal systemic absorption. A randomized clinical trial was undertaken to assess the effectiveness of olsalazine in preventing acute diarrhea in patients receiving pelvic radiation therapy. METHODS AND MATERIALS: Patients receiving pelvic radiation therapy were randomized, in double-blind fashion, to olsalazine 250 mg, two capsules twice daily, or an identical appearing placebo, two capsules twice daily. Patients were then evaluated weekly during radiation therapy for the primary study endpoint, diarrhea, as well as rectal bleeding, abdominal cramping, and tenesmus. RESULTS: The study was closed early, after entry of 58 evaluable patients, when a preliminary analysis showed excessive diarrhea in patients randomized to olsalazine. The incidence and severity of diarrhea were worse in patients randomized to olsalazine (p = 0.0036). Sixty percent of the patients randomized to olsalazine experienced Grade 3 or 4 diarrhea compared to only 14% randomized to placebo. There was also a trend toward higher incidence and greater severity of abdominal cramping in patients who were randomized to olsalazine (p = 0.084). CONCLUSION: Administration of olsalazine during pelvic radiation therapy resulted in an increased incidence and severity of diarrhea. Olsalazine is contraindicated in patients receiving pelvic radiation therapy.


Assuntos
Ácidos Aminossalicílicos , Diarreia/prevenção & controle , Neoplasias Pélvicas/radioterapia , Idoso , Contraindicações , Defecação/efeitos dos fármacos , Diarreia/induzido quimicamente , Diarreia/epidemiologia , Método Duplo-Cego , Esquema de Medicação , Feminino , Humanos , Incidência , Masculino , Espasmo/induzido quimicamente
13.
Am J Cardiol ; 62(8): 20E-24E, 1988 Sep 09.
Artigo em Inglês | MEDLINE | ID: mdl-3414534

RESUMO

In an effort to produce significant systemic circulatory training effects, including adaptations of the heart, myocardial infarcted (MI) rats were subjected to 2 training regimens: low-intensity endurance training (LIET) and high-intensity endurance training (HIET). When compared with sedentary controls, the MI rats subjected to LIET had small but significant beneficial systemic circulatory training effects exclusive of any training effects on the heart. MI rats subjected to HIET had similar but more extensive and quantitatively greater circulatory adaptations than those found in MI rats subjected to LIET. Unlike LIET MI rats, the HIET MI rats had an increase in maximal heart rate when compared with sedentary MI rats. However, despite the reversal of this chronotropic incompetence, the HIET MI rats did not have significant increases in parameters indicative of increased left ventricular pump function (maximal cardiac output) and maximal stroke volume. To further study the effect of incrementally increasing exercise intensity, a high-intensity sprint training (HIST) regimen was developed and studied in normal rats. In response to HIST, normal rats had central myocardial adaptations (increases in maximal cardiac output and stroke volume) in response to training that were not found in the MI rats subjected to LIET and HIET. Although the effects of HIST in normal rats is now known, the question of whether a training paradigm consisting of HIET and HIST will produce increases in maximal cardiac output and stroke volume in the MI rat has yet to be determined.


Assuntos
Insuficiência Cardíaca/fisiopatologia , Hemodinâmica , Infarto do Miocárdio/fisiopatologia , Esforço Físico , Animais , Débito Cardíaco , Insuficiência Cardíaca/sangue , Frequência Cardíaca , Hemoglobinas/análise , Músculos/irrigação sanguínea , Infarto do Miocárdio/sangue , Oxigênio/sangue , Resistência Física , Ratos , Fluxo Sanguíneo Regional , Circulação Esplâncnica , Volume Sistólico
14.
AIDS Res Hum Retroviruses ; 9(1): 51-9, 1993 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-7678972

RESUMO

The V3 loop of human immunodeficiency virus (HIV) glycoprotein gp160 is of interest as a possible site for protective immune responses. This article examines the murine T cell response to peptide 315-329 derived from HIV gp160. Surprisingly, immunization with peptide in complete Freund's adjuvant induced class I-restricted T cells as well as class II-restricted T cells. These data suggest that this peptide may have the unusual ability to enter the class I antigen processing pathway. Strategies that employ V3 loop peptides to induce protective immunity must generate T cells that can recognize epitopes derived from whole molecules in vivo. Therefore, peptide-induced T cells were tested for their ability to respond to naturally processed forms of gp120 and gp160 whole-molecule preparations. Peptide induced class I-restricted cells were capable of recognizing transfectants expressing gp160. However, only one of two class II-restricted T cell lines was capable of recognizing soluble whole molecules. This indicates that peptide immunization induces T cells that recognize a class II-restricted determinant that is not generated during normal processing of whole molecules. We have also examined the response of peptide primed T cells to lipidated peptide antigens. Lipidated peptides are generally considered to have increased antigenicity and immunogenicity as compared to normal peptides. However, lipidation of peptide 315-329 damaged both the class I- and II-restricted determinants, indicating that lipidation is not always desirable. The data presented here highlight a potential serious problem in the use of peptide vaccines, in that peptide immunization may not always induce T cells that can protect against a viral challenge.


Assuntos
Produtos do Gene env/imunologia , Antígenos HIV/imunologia , HIV/imunologia , Antígenos de Histocompatibilidade Classe II/imunologia , Antígenos de Histocompatibilidade Classe I/imunologia , Precursores de Proteínas/imunologia , Linfócitos T/imunologia , Animais , Linhagem Celular , Epitopos , Proteína gp160 do Envelope de HIV , Imunização , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos , Ácido Palmítico , Ácidos Palmíticos/metabolismo , Fragmentos de Peptídeos/imunologia
15.
J Endocrinol ; 164(3): 331-7, 2000 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-10694373

RESUMO

We recently reported that the leptin-induced increase in uncoupling protein 1 (UCP1) mRNA in brown adipose tissue (BAT) is prevented by the denervation of BAT. We also reported that retinoic acid (RA) increases UCP1 mRNA in BAT. To extend these finding to UCP2 and UCP3 in BAT, we examined UCP2 and UCP3 mRNA after unilateral denervation of BAT, as well as after leptin, beta(3)-adrenergic agonist, RA, and glucocorticoid administration to rats. UCP3 mRNA was 20% less in the denervated compared with the intact BAT, whereas UCP2 mRNA was unchanged with denervation. The beta(3)-adrenergic agonist, CGP-12177 (0.75 mg/kg), increased UPC3 mRNA by 40% in the innervated and by 85% in the denervated BAT. Leptin (0.9 mg/day for 3 days) increased both UCP2 and UCP3 mRNA by 30% in the innervated and, surprisingly, in the denervated BAT. RA (7.5 mg/kg) increased UCP1 mRNA but decreased UCP2 and UCP3 mRNA by 50%, whereas methylprednisolone (65 mg/kg, two doses 24 h apart) suppressed all three uncoupling proteins by greater than 60%. The present findings indicate that: sympathetic innervation is necessary to maintain basal levels of UCP3 mRNA; beta(3)-adrenergic agonist stimulation induces UCP3 mRNA; leptin induces UCP2 and UCP3 mRNA and this induction is not dependent on sympathetic innervation; RA increases UCP1 but decreases UCP2 and UCP3 mRNA; and methylprednisolone suppresses UCP1, UCP2, and UCP3 mRNA equally. These data suggest that there are distinct patterns of regulation between UCP1, UCP2, and UCP3, and there may be at least two modes by which leptin could modulate thermogenesis in BAT; first, by increasing sympathetic stimulation of BAT and induction of UCP1 mRNA and, secondly, by increasing UCP2 and UCP3 mRNA by a mechanism independent of sympathetic stimulation.


Assuntos
Tecido Adiposo Marrom/inervação , Proteínas de Transporte/genética , Regulação da Expressão Gênica/efeitos dos fármacos , Leptina/farmacologia , Proteínas de Membrana Transportadoras , Proteínas Mitocondriais , Proteínas/genética , Agonistas Adrenérgicos beta/farmacologia , Análise de Variância , Animais , Denervação , Glucocorticoides/farmacologia , Canais Iônicos , Masculino , Metilprednisolona/farmacologia , Propanolaminas/farmacologia , RNA Mensageiro/análise , Ratos , Ratos Endogâmicos F344 , Tretinoína/farmacologia , Proteína Desacopladora 2 , Proteína Desacopladora 3
16.
J Appl Physiol (1985) ; 91(4): 1545-54, 2001 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-11568135

RESUMO

In this study, we sought to determine whether there was any evidence for the idea that cardiac ATP-sensitive K+ (K(ATP)) channels play a role in the training-induced increase in the resistance of the heart to ischemia-reperfusion (I/R) injury. To do so, the effects of training and an K(ATP) channel blocker, glibenclamide (Glib), on the recovery of left ventricular (LV) contractile function after 45 min of ischemia and 45 min of reperfusion were examined. Female Sprague-Dawley rats were sedentary (Sed; n = 18) or were trained (Tr; n = 17) for >20 wk by treadmill running, and the hearts from these animals used in a Langendorff-perfused isovolumic LV preparation to assess contractile function. A significant increase in the amount of 72-kDa class of heat shock protein was observed in hearts isolated from Tr rats. The I/R protocol elicited significant and substantial decrements in LV developed pressure (LVDP), minimum pressure (MP), rate of pressure development, and rate of pressure decline and elevations in myocardial Ca(2+) content in both Sed and Tr hearts. In addition, I/R elicited a significant increase in LV diastolic stiffness in Sed, but not Tr, hearts. When administered in the perfusate, Glib (1 microM) elicited a normalization of all indexes of LV contractile function and reductions in myocardial Ca(2+) content in both Sed and Tr hearts. Training increased the functional sensitivity of the heart to Glib because LVDP and MP values normalized more quickly with Glib treatment in the Tr than the Sed group. The increased sensitivity of Tr hearts to Glib is a novel finding that may implicate a role for cardiac K(ATP) channels in the training-induced protection of the heart from I/R injury.


Assuntos
Glibureto/farmacologia , Hipoglicemiantes/farmacologia , Contração Miocárdica/efeitos dos fármacos , Isquemia Miocárdica/fisiopatologia , Condicionamento Físico Animal/fisiologia , Canais de Potássio , Transportadores de Cassetes de Ligação de ATP , Animais , Cálcio/metabolismo , Circulação Coronária/efeitos dos fármacos , Circulação Coronária/fisiologia , Feminino , Proteínas de Choque Térmico/metabolismo , Técnicas In Vitro , Canais KATP , Reperfusão Miocárdica , Miocárdio/metabolismo , Bloqueadores dos Canais de Potássio/farmacologia , Canais de Potássio Corretores do Fluxo de Internalização , Ratos , Ratos Sprague-Dawley
17.
J Appl Physiol (1985) ; 59(1): 127-31, 1985 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-4030555

RESUMO

The response of hypertrophied soleus and plantaris muscle of rats to endurance training was studied. Hypertrophy was produced by bilateral extirpation of the gastrocnemius muscle. A 13-wk training program of treadmill running initiated 30 days after removal of the gastrocnemius muscle accentuated (P less than 0.01) the hypertrophy. Succinate dehydrogenase activities of the enlarged muscles of sedentary rats were similar to those of normal animals, as were the increases associated with training. Phosphorylase and hexokinase activities were unaltered as a result of the experimental perturbations. Rates of glycogen depletion during exercise were lower (P less than 0.01) in the liver and soleus and plantaris muscles of endurance-trained animals. No difference existed in the rate of glycogen depletion of normal and hypertrophied muscle within the sedentary or trained groups. These data demonstrate that extensively hypertrophied muscle responds to training and exercise in a manner similar to that of normal muscle.


Assuntos
Adaptação Fisiológica , Músculos/patologia , Condicionamento Físico Animal , Resistência Física , Animais , Feminino , Glicogênio/metabolismo , Hexoquinase/metabolismo , Hipertrofia/fisiopatologia , Fígado/metabolismo , Músculos/enzimologia , Músculos/metabolismo , Fosforilases/metabolismo , Ratos , Ratos Endogâmicos , Succinato Desidrogenase/metabolismo
18.
J Appl Physiol (1985) ; 65(6): 2752-6, 1988 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-3215875

RESUMO

Measurements of hemodynamics and blood metabolites in rats are often made by insertion of a small polyethylene (PE-50) catheter into the aorta via the carotid artery. Although the effect of this type of procedure on animal body weight has been described, little information exists regarding the quantitative and temporal effects of this procedure on liver and skeletal muscle glycogen concentration. Relative to the control group (group C), liver glycogen concentration was reduced by 56% 24 h after catheterization (group CN). With respect to liver glycogen concentration, it was apparent that a postcatheterization recovery period of variable duration (2-8 days; group CNR) based on attainment of a normal food consumption-to-body weight ratio (FdWt/BdWt) was more effective than was a fixed 6-day recovery period (group CN6). This was probably due to the large between-animal variability in recovery times required to reach normal FdWt/BdWt values. After aortic catheterization, FdWt/BdWt was a reasonable predictor of postprocedural liver (y = 2,601x + 43.9; r = 0.72; P less than 0.01) and diaphragm muscle glycogen concentration (y = 146.3x + 14.0; r = 0.57; P less than 0.05). Aortic catheterization did not affect the glycogen concentration in the other skeletal muscles examined. Since the results of certain types of experiments can be significantly influenced by liver glycogen concentration, the use of FdWt/BdWt on 24-h food intake as a general indicator of recovery after instrumentation via aortic catheterization is proposed.


Assuntos
Cateterismo Periférico/efeitos adversos , Glicogênio/metabolismo , Animais , Aorta , Artérias Carótidas , Feminino , Glicogênio Hepático/metabolismo , Músculos/metabolismo , Ratos , Ratos Endogâmicos
19.
J Appl Physiol (1985) ; 66(1): 195-201, 1989 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-2917921

RESUMO

The hemodynamic response to maximal exercise was determined in rats that were subjected to high-intensity sprint training (HIST) and rats that served as sedentary controls. Training consisted of five 1-min bouts of treadmill running at work loads (15% grade, 97 m/min) in excess of the animals' maximal O2 uptake (VO2max) interspersed with 90 s of rest. Training was performed 6 days/wk for 6 wk. After the training regimen, all rats were acutely instrumented with catheters in the right carotid artery and right ventricle. O2 uptakes, hemodynamic parameters, arterial and mixed venous O2 concentrations, blood gases, and acid-base status were determined at rest and during submaximal and maximal exercise. Results demonstrated that VO2max of HIST rats was significantly greater than that found for sedentary control rats. This increase in VO2max was due to an increase in maximal cardiac output (Qmax), since maximal arteriovenous O2 difference was similar between trained and sedentary rats. The increase in Qmax was due to an increase in maximal stroke volume (SVmax), because maximal heart rate in trained rats was similar to that in sedentary control rats. Citrate synthase and phosphofructokinase activities measured in the white gastrocnemius, plantaris, and soleus muscles of trained and sedentary rats were similar. These results suggest that the increase in VO2max produced with HIST in rats is strongly linked to an increase in central cardiac function as indicated by an increase in Qmax and SVmax.


Assuntos
Consumo de Oxigênio , Corrida , Animais , Peso Corporal , Débito Cardíaco , Feminino , Frequência Cardíaca , Condicionamento Físico Animal , Ratos , Ratos Endogâmicos , Volume Sistólico
20.
J Appl Physiol (1985) ; 66(2): 712-9, 1989 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-2523373

RESUMO

The hemodynamic response to maximal exercise was determined in sedentary and trained rats with a chronic myocardial infarction (MI) produced by coronary artery ligation and in rats that underwent sham operations (SHAM). Infarct size in the MI groups of rats comprised 28-29% of the total left ventricle and resulted in both metabolic and hemodynamic changes that suggested that these animals had moderate compensated heart failure. The training regimen used in the present study produced significant increases in maximal O2 uptake (VO2max) when expressed in absolute terms (ml/min) or when normalized for body weight (ml.min-1.kg-1) and consisted of treadmill running at work loads that were equivalent to 70-80% of the animal's VO2max for a period of 60 min/day, 5 days/wk over an 8- to 10-wk interval. This training paradigm produced two major cardiocirculatory adaptations in the MI rat that had not been elicited previously when using a training paradigm of a lower intensity. First, the decrement in the maximal heart rate response to exercise (known as "chronotropic incompetence") found in the sedentary MI rat was completely reversed by endurance training. Second, the downregulation of cardiac myosin isozyme composition from the fast ATPase V1 isoform toward the slower ATPase (V2 and V3) isoforms in the MI rat was partially reversed by endurance training. These cardiac adaptations occurred without a significant increase in left ventricular pump function as an increase in maximal cardiac output (Qmax) and maximal stroke volume (SVmax) did not occur in the trained MI rat.(ABSTRACT TRUNCATED AT 250 WORDS)


Assuntos
Adaptação Fisiológica , Hemodinâmica , Infarto do Miocárdio/fisiopatologia , Resistência Física , Animais , Débito Cardíaco , Masculino , Miocárdio/enzimologia , Miosinas/metabolismo , Consumo de Oxigênio , Ratos , Ratos Endogâmicos , Volume Sistólico
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA