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1.
Pediatr Blood Cancer ; 67(9): e28475, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32589365

RESUMO

BACKGROUND: Hyperglycemia is a complication of induction chemotherapy in 10%-50% of pediatric patients with acute lymphoblastic leukemia (ALL). Though hyperglycemia in ALL patients is usually transient, it may be associated with adverse health outcomes. However, the risk factors for and consequences of hyperglycemia are poorly understood. We hypothesized that hyperglycemia significant enough to require insulin therapy during induction chemotherapy would be associated with increased morbidity and mortality in pediatric ALL patients during induction chemotherapy and in subsequent care. METHODS: We abstracted clinical and resource utilization data from the Pediatric Health Information System (PHIS) database utilizing ICD-9 codes and medication charges. We used logistic regression analysis to predict the development of hyperglycemia. The effects of hyperglycemia on binary and count adverse outcomes following induction chemotherapy were modeled using mixed-effect regression models. RESULTS: An increased risk of hyperglycemia requiring insulin was associated with older age, female sex, higher risk group and trisomy 21. Patients on insulin for hyperglycemia had increased mortality following induction chemotherapy. These patients were more likely to have subsequent infectious complications, need for bone marrow transplant, and risk of disease relapse. They also had greater length of inpatient stay, higher cost of care, and were more likely to require intensive care unit admission during induction chemotherapy. CONCLUSIONS: Hyperglycemia requiring insulin during induction chemotherapy in pediatric ALL is associated with an increased risk of short-term and long-term complications. Prospective studies are needed to analyze formal screening, preventive measures, and optimal management practices for hyperglycemia during ALL induction chemotherapy.


Assuntos
Hiperglicemia , Quimioterapia de Indução , Insulina , Leucemia-Linfoma Linfoblástico de Células Precursoras , Adolescente , Adulto , Criança , Pré-Escolar , Custos e Análise de Custo , Feminino , Humanos , Hiperglicemia/induzido quimicamente , Hiperglicemia/tratamento farmacológico , Hiperglicemia/economia , Quimioterapia de Indução/efeitos adversos , Quimioterapia de Indução/economia , Lactente , Insulina/administração & dosagem , Insulina/economia , Masculino , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Leucemia-Linfoma Linfoblástico de Células Precursoras/economia
2.
J Pediatr Hematol Oncol ; 39(5): 370-375, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28538500

RESUMO

The prevalence of obesity and related comorbidities in survivors of childhood acute lymphoblastic leukemia (ALL) is well established and ranges anywhere from 29% to 69% depending on the study. We sought to explore the awareness of parents of survivors of childhood ALL regarding the increased risk of obesity and their perceptions regarding the overall health of their child. One hundred twenty-one parents of 99 survivors of pediatric ALL completed surveys regarding perceptions of obesity risk in survivors. Eighty percent of parents of overweight and obese survivors correctly identified their child as "a little overweight" or "overweight." Few parents recalled discussing weight gain (21%) or obesity risk (36%) with their practitioner. Parents that did recall having these discussions and/or reported a decreased level of posttherapy activity in their child were more likely to be concerned about their child's weight status. Improved awareness and education regarding the risk of obesity and associated comorbid conditions may provide an avenue for future prevention of obesity in survivors of pediatric ALL. Discussion and education regarding a healthy lifestyle, including proper diet and exercise, should be incorporated early in routine patient visits.


Assuntos
Relações Familiares , Obesidade , Leucemia-Linfoma Linfoblástico de Células Precursoras/complicações , Adolescente , Criança , Pré-Escolar , Comorbidade , Humanos , Lactente , Pais , Percepção , Risco , Inquéritos e Questionários , Sobreviventes
3.
Pediatr Diabetes ; 17(6): 398-406, 2016 09.
Artigo em Inglês | MEDLINE | ID: mdl-26377593

RESUMO

OBJECTIVE: To test the hypothesis that HbA1c variability, as measured by standard deviation (SD), is associated with increased risk for incident microalbuminuria and persistent microalbuminuria in pediatric type 1 diabetes (T1D). METHODS: A retrospective analysis using data from electronic health records was performed on 1195 patients from a pediatric diabetes clinic network in the Midwest USA from 1993 to 2009 with ≥1 yr of T1D, ≥4 total HbA1c values, ≥2 HbA1c values/yr, ≥1 urine microalbumin. Microalbuminuria, the main outcome was defined as albumin excretion rate ≥20 mcg/min or 2 of 3 consecutive urine microalbumin/creatinine ≥30 mg/gm. Patients who had persistently high microalbumin or who were treated with an angiotensin-converting-enzyme inhibitor within 1 yr were considered to have persistent microalbuminuria. Sex, race, age, diagnosis age, and duration were covariates. RESULTS: Median numbers of per-patient HbA1c and microalbumin results were 14 and 3, respectively. Median intrapersonal mean HbA1c and SD were 8.62% (70.72 mol/mol) and 1.47% (16.07 mmol/mol), respectively. The median interquartile range (IQR) of diagnosis age was 9.4 yr (6.26-12.02) and diabetes duration was 4.97 yr (2.93-7.64). A total of 172 patients (14.4%) developed microalbuminuria; 55 (4.6%) had persistent microalbuminuria. Patients with higher SD of HbA1c had shorter time to microalbuminuria. In time-dependent Cox Proportional Hazard models, updated SD of HbA1c was significantly associated with microalbuminuria [univariate hazard ratio (HR) 1.48 (1.25-1.76); multivariable HR 1.28 (1.04-1.58)], whereas updated mean HbA1c was not [univariate HR 1.08 (0.97-1.22); multivariable HR 1.05 (0.92-1.2)]. Patients with persistent microalbuminuria had similar HRs. CONCLUSIONS: HbA1c variability is independently associated with development of microalbuminuria in children with T1D, highlighting the importance of maintaining stable glycemic control in pediatric patients.


Assuntos
Albuminúria/sangue , Diabetes Mellitus Tipo 1/urina , Hemoglobinas Glicadas/metabolismo , Adolescente , Criança , Pré-Escolar , Diabetes Mellitus Tipo 1/sangue , Feminino , Humanos , Masculino , Modelos de Riscos Proporcionais , Estudos Retrospectivos
4.
JAMA ; 314(21): 2241-50, 2015 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-26624824

RESUMO

IMPORTANCE: Previous studies assessing the effect of metformin on glycemic control in adolescents with type 1 diabetes have produced inconclusive results. OBJECTIVE: To assess the efficacy and safety of metformin as an adjunct to insulin in treating overweight adolescents with type 1 diabetes. DESIGN, SETTING, AND PARTICIPANTS: Multicenter (26 pediatric endocrinology clinics), double-blind, placebo-controlled randomized clinical trial involving 140 adolescents aged 12.1 to 19.6 years (mean [SD] 15.3 [1.7] years) with mean type 1 diabetes duration 7.0 (3.3) years, mean body mass index (BMI) 94th (4) percentile, mean total daily insulin 1.1 (0.2) U/kg, and mean HbA1c 8.8% (0.7%). INTERVENTIONS: Randomization to receive metformin (n = 71) (≤2000 mg/d) or placebo (n = 69). MAIN OUTCOMES AND MEASURES: Primary outcome was change in HbA1c from baseline to 26 weeks adjusted for baseline HbA1c. Secondary outcomes included change in blinded continuous glucose monitor indices, total daily insulin, BMI, waist circumference, body composition, blood pressure, and lipids. RESULTS: Between October 2013 and February 2014, 140 participants were enrolled. Baseline HbA1c was 8.8% in each group. At 13-week follow-up, reduction in HbA1c was greater with metformin (-0.2%) than placebo (0.1%; mean difference, -0.3% [95% CI, -0.6% to 0.0%]; P = .02). However, this differential effect was not sustained at 26-week follow up when mean change in HbA1c from baseline was 0.2% in each group (mean difference, 0% [95% CI, -0.3% to 0.3%]; P = .92). At 26-week follow-up, total daily insulin per kg of body weight was reduced by at least 25% from baseline among 23% (16) of participants in the metformin group vs 1% (1) of participants in the placebo group (mean difference, 21% [95% CI, 11% to 32%]; P = .003), and 24% (17) of participants in the metformin group and 7% (5) of participants in the placebo group had a reduction in BMI z score of 10% or greater from baseline to 26 weeks (mean difference, 17% [95% CI, 5% to 29%]; P = .01). Gastrointestinal adverse events were reported by more participants in the metformin group than in the placebo group (mean difference, 36% [95% CI, 19% to 51%]; P < .001). CONCLUSIONS AND RELEVANCE: Among overweight adolescents with type 1 diabetes, the addition of metformin to insulin did not improve glycemic control after 6 months. Of multiple secondary end points, findings favored metformin only for insulin dose and measures of adiposity; conversely, use of metformin resulted in an increased risk for gastrointestinal adverse events. These results do not support prescribing metformin to overweight adolescents with type 1 diabetes to improve glycemic control. TRIAL REGISTRATION: clinicaltrials.org Identifier: NCT01881828.


Assuntos
Diabetes Mellitus Tipo 1/tratamento farmacológico , Hipoglicemiantes/administração & dosagem , Insulina/uso terapêutico , Metformina/administração & dosagem , Obesidade/complicações , Adolescente , Glicemia/análise , Índice de Massa Corporal , Peso Corporal , Criança , Diabetes Mellitus Tipo 1/complicações , Método Duplo-Cego , Quimioterapia Combinada , Feminino , Gastroenteropatias/induzido quimicamente , Hemoglobinas Glicadas/análise , Humanos , Hipoglicemiantes/efeitos adversos , Masculino , Metformina/efeitos adversos , Resultado do Tratamento , Adulto Jovem
5.
Endocr Rev ; 43(5): 794-823, 2022 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-34962573

RESUMO

Endocrine disorders in survivors of childhood, adolescent, and young adult (CAYA) cancers are associated with substantial adverse physical and psychosocial effects. To improve appropriate and timely endocrine screening and referral to a specialist, the International Late Effects of Childhood Cancer Guideline Harmonization Group (IGHG) aims to develop evidence and expert consensus-based guidelines for healthcare providers that harmonize recommendations for surveillance of endocrine disorders in CAYA cancer survivors. Existing IGHG surveillance recommendations for premature ovarian insufficiency, gonadotoxicity in males, fertility preservation, and thyroid cancer are summarized. For hypothalamic-pituitary (HP) dysfunction, new surveillance recommendations were formulated by a guideline panel consisting of 42 interdisciplinary international experts. A systematic literature search was performed in MEDLINE (through PubMed) for clinically relevant questions concerning HP dysfunction. Literature was screened for eligibility. Recommendations were formulated by drawing conclusions from quality assessment of all evidence, considering the potential benefits of early detection and appropriate management. Healthcare providers should be aware that CAYA cancer survivors have an increased risk for endocrine disorders, including HP dysfunction. Regular surveillance with clinical history, anthropomorphic measures, physical examination, and laboratory measurements is recommended in at-risk survivors. When endocrine disorders are suspected, healthcare providers should proceed with timely referrals to specialized services. These international evidence-based recommendations for surveillance of endocrine disorders in CAYA cancer survivors inform healthcare providers and highlight the need for long-term endocrine follow-up care in subgroups of survivors and elucidate opportunities for further research.


Assuntos
Sobreviventes de Câncer , Doenças do Sistema Endócrino , Doenças Hipotalâmicas , Neoplasias , Doenças da Hipófise , Neoplasias da Glândula Tireoide , Adolescente , Criança , Doenças do Sistema Endócrino/diagnóstico , Doenças do Sistema Endócrino/epidemiologia , Feminino , Humanos , Masculino , Neoplasias/epidemiologia , Sobreviventes , Adulto Jovem
6.
J Cancer Surviv ; 14(5): 660-665, 2020 10.
Artigo em Inglês | MEDLINE | ID: mdl-32394044

RESUMO

PURPOSE: To create a community of learning involving primary care providers and subspecialist to enhance providers' knowledge regarding care of adult childhood cancer survivors (CCS). METHODS: A stepwise approach was used to develop educational opportunities for providers. This process started with a local/regional in-person conference, which informed a webinar series, and resulted in the development of enduring material using a dynamic learning management system. RESULTS: Participants in all three learning platforms had an increase in knowledge from baseline regarding care for adult CCS. Majority of participants at the in-person conference and webinar series were oncology or other specialty providers. The enduring dynamic learning management system successfully reached a variety of providers and other allied health providers across the country. There was a slightly higher rate of participation on this platform by primary care providers of 12.5%. CONCLUSIONS: Care providers' knowledge of survivorship needs of adult CCS can be increased by multiple forms of instruction. However, the dynamic learning management system was most successful at reaching a broad audience. Advertisement through local and national organizations was not as successful as anticipated. Additional strategies are needed to successfully engage providers, specifically primary care providers (PCPs). IMPLICATIONS FOR CANCER SURVIVORS: The professional development needs of primary care providers regarding care of adult CCS is well recognized. A dynamic learning management system may represent the most convenient and accessible way to provide education, but new strategies for increasing providers' awareness and engagement are required. The goal of improving care of adult CCS requires increased providers knowledge.


Assuntos
Sobreviventes de Câncer/estatística & dados numéricos , Pessoal de Saúde/educação , Implementação de Plano de Saúde , Oncologia/educação , Neoplasias/terapia , Atenção Primária à Saúde/normas , Especialização/normas , Criança , Escolaridade , Feminino , Humanos , Aprendizagem , Masculino , Padrões de Prática Médica/normas , Sobrevivência
7.
AJP Rep ; 7(3): e181-e184, 2017 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-28948062

RESUMO

Neonatal Graves' disease presenting as conjugated hyperbilirubinemia is a diagnostic challenge because the differential includes a gamut of liver and systemic diseases. We present a unique case of neonatal Graves' disease in a premature infant with conjugated hyperbilirubinemia born to a mother with hypothyroidism during pregnancy and remote history of Graves' disease. Infant was treated with a combination of methimazole, propranolol, and potassium iodide for 4 weeks. Thyroid function improved after 8 weeks of treatment with full recovery of thyroid function, disappearance of thyroid-stimulating antibodies, and resolution of failure to thrive and conjugated hyperbilirubinemia. This case provides several clinical vignettes as it is a rare, severe, presentation of an uncommon neonatal disease, signs, symptoms, and clinical history presented a diagnostic challenge for neonatologists and endocrinologists, normal newborn screen was misleading, and yet timely treatment led to a full recovery.

8.
Diabetes Care ; 40(12): 1622-1630, 2017 12.
Artigo em Inglês | MEDLINE | ID: mdl-29162582

RESUMO

OBJECTIVE: To identify and define clinically meaningful type 1 diabetes outcomes beyond hemoglobin A1c (HbA1c) based upon a review of the evidence, consensus from clinical experts, and input from researchers, people with type 1 diabetes, and industry. Priority outcomes include hypoglycemia, hyperglycemia, time in range, diabetic ketoacidosis (DKA), and patient-reported outcomes (PROs). While priority outcomes for type 1 and type 2 diabetes may overlap, type 1 diabetes was the focus of this work. RESEARCH AND METHODS: A Steering Committee-comprising representatives from the American Association of Clinical Endocrinologists, the American Association of Diabetes Educators, the American Diabetes Association, the Endocrine Society, JDRF International, The Leona M. and Harry B. Helmsley Charitable Trust, the Pediatric Endocrine Society, and the T1D Exchange-was the decision-making body for the Type 1 Diabetes Outcomes Program. Their work was informed by input from researchers, industry, and people with diabetes through Advisory Committees representing each stakeholder group. Stakeholder surveys were used to identify priority outcomes. The outcomes prioritized in the surveys were hypoglycemia, hyperglycemia, time in range, DKA, and PROs. To develop consensus on the definitions of these outcomes, the Steering Committee relied on published evidence, their clinical expertise, and feedback from the Advisory Committees. RESULTS: The Steering Committee developed definitions for hypoglycemia, hyperglycemia, time in range, and DKA in type 1 diabetes. The definitions reflect their assessment of the outcome's short- and long-term clinical impact on people with type 1 diabetes. Knowledge gaps to be addressed by future research were identified. The Steering Committee discussed PROs and concluded that further type 1 diabetes-specific development is needed. CONCLUSIONS: The Steering Committee recommends use of the defined clinically meaningful outcomes beyond HbA1c in the research, development, and evaluation of type 1 diabetes therapies.


Assuntos
Diabetes Mellitus Tipo 1/sangue , Endocrinologistas/normas , Endocrinologia/normas , Hemoglobinas Glicadas/normas , Avaliação de Resultados em Cuidados de Saúde/normas , Diabetes Mellitus Tipo 1/diagnóstico , Diabetes Mellitus Tipo 2/sangue , Diabetes Mellitus Tipo 2/diagnóstico , Cetoacidose Diabética/sangue , Cetoacidose Diabética/diagnóstico , Endocrinologistas/educação , Endocrinologia/educação , Humanos , Hiperglicemia/sangue , Hiperglicemia/diagnóstico , Hipoglicemia/sangue , Hipoglicemia/diagnóstico , Sociedades Médicas , Estados Unidos
9.
J Clin Endocrinol Metab ; 100(6): 2192-203, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25839904

RESUMO

CONTEXT: GH and IGF-1 have been shown to affect tumor growth in vitro and in some animal models. This report summarizes the available evidence on whether GH therapy in childhood is associated with an increased risk of neoplasia during treatment or after treatment is completed. EVIDENCE ACQUISITION: A PubMed search conducted through February 2014 retrieved original articles written in English addressing GH therapy and neoplasia risk. Subsequent searches were done to include additional relevant publications. EVIDENCE SYNTHESIS: In children without prior cancer or known risk factors for developing cancer, the clinical evidence does not affirm an association between GH therapy during childhood and neoplasia. GH therapy has not been reported to increase the risk for neoplasia in this population, although most of these data are derived from postmarketing surveillance studies lacking rigorous controls. In patients who are at higher risk for developing cancer, current evidence is insufficient to conclude whether or not GH further increases cancer risk. GH treatment of pediatric cancer survivors does not appear to increase the risk of recurrence but may increase their risk for subsequent primary neoplasms. CONCLUSIONS: In children without known risk factors for malignancy, GH therapy can be safely administered without concerns about an increased risk for neoplasia. GH use in children with medical diagnoses predisposing them to the development of malignancies should be critically analyzed on an individual basis, and if chosen, appropriate surveillance for malignancies should be undertaken. GH can be used to treat GH-deficient childhood cancer survivors who are in remission with the understanding that GH therapy may increase their risk for second neoplasms.


Assuntos
Transtornos do Crescimento/tratamento farmacológico , Transtornos do Crescimento/epidemiologia , Hormônio do Crescimento Humano/uso terapêutico , Neoplasias/epidemiologia , Neoplasias/etiologia , Criança , Predisposição Genética para Doença/epidemiologia , Transtornos do Crescimento/genética , Terapia de Reposição Hormonal/estatística & dados numéricos , Humanos , Neoplasias/genética , Fatores de Risco , Sobreviventes/estatística & dados numéricos , Síndrome
10.
BMJ Open Diabetes Res Care ; 2(1): e000039, 2014.
Artigo em Inglês | MEDLINE | ID: mdl-25452876

RESUMO

BACKGROUND: Poor glycemic control early in the course of type 1 diabetes mellitus (T1DM) increases the risk for microvascular complications. However, predictors of deteriorating control after diagnosis have not been described, making it difficult to identify high-risk patients and proactively provide aggressive interventions. OBJECTIVE: We examined whether diagnostic age, gender, and race were associated with deteriorating glycemic control during the first 5 years after diagnosis. PARTICIPANTS: 2218 pediatric patients with T1DM. METHODS: We conducted a longitudinal cohort study of pediatric patients with T1DM from the Midwest USA, 1993-2009, evaluating within-patient glycated hemoglobin (HbA1c) trajectories constructed from all available HbA1c values within 5 years of diagnosis. RESULTS: 52.6% of patients were male; 86.1% were non-Hispanic Caucasian. The mean diagnostic age was 9.0±4.1 years. The mean number of HbA1c values/year/participant was 2.4±0.9. HbA1c trajectories differed markedly across age groups, with older patients experiencing greater deterioration than their younger counterparts (p<0.001). HbA1c trajectories, stratified by age, varied markedly by race (p for race×diagnostic age <0.001). Non-Hispanic African-American patients experienced higher initial HbA1c (8.7% vs 7.6% (71.6 vs 59.6 mmol/mol); p<0.001), and greater deterioration in HbA1c than non-Hispanic Caucasian patients across diagnostic ages (rise of 2.04% vs 0.99% per year (22.3 vs 10.8 mmol/mol/year); p<0.0001). CONCLUSIONS: Older diagnostic age and black race are major risk factors for deterioration in glycemic control early in the course of T1DM. These findings can inform efforts to explore the reasons behind these differences and develop preventive interventions for high-risk patients.

11.
Curr Hematol Malig Rep ; 6(3): 195-205, 2011 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-21695425

RESUMO

As survival rates for children treated for childhood cancers become significantly better, the focus is increasingly on determining the late effects of treatments and the best ways to monitor for them and prevent their occurrence. This review focuses on recent literature discussing the late effects of treatment in patients treated for acute myeloid leukemia and acute lymphoblastic leukemia during childhood. The late effects of therapy for childhood leukemia include secondary malignancy, cardiotoxicity, obesity, endocrine abnormalities, reproductive changes, neurocognitive deficits, and psychosocial effects. As clinicians have become more aware of the late effects of therapy, treatment regimens have been changed to decrease late effects, but patients still require long-term follow-up for their prevention and treatment.


Assuntos
Leucemia Mieloide Aguda/tratamento farmacológico , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Antineoplásicos/efeitos adversos , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Neoplasias do Sistema Nervoso Central/secundário , Criança , Doenças do Sistema Endócrino/induzido quimicamente , Doenças do Sistema Endócrino/etiologia , Fertilidade/efeitos dos fármacos , Transtornos do Crescimento/induzido quimicamente , Transtornos do Crescimento/etiologia , Cardiopatias/induzido quimicamente , Cardiopatias/etiologia , Humanos , Leucemia Mieloide Aguda/patologia , Obesidade/induzido quimicamente , Obesidade/etiologia , Leucemia-Linfoma Linfoblástico de Células Precursoras/patologia , Estresse Psicológico
12.
Am J Physiol Regul Integr Comp Physiol ; 293(1): R30-6, 2007 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-17255213

RESUMO

One of the prominent markers of end-stage heart failure at the molecular level is a decrease in function and/or expression of the sarcoplasmic reticulum ATPase protein [sarco(endo)plasmic reticulum calcium-ATPase, SERCA]. It has been often postulated that a decrease in SERCA pump activity can contribute in a major way to decreased cardiac function. To establish a functional relationship, we assessed how alterations in SERCA activity level affect basic contractile function in healthy myocardium devoid of other significant molecular changes. We investigated baseline contractile function, frequency-dependent activation, and beta-adrenergic response in ultrathin trabeculae isolated from hearts of mice overexpressing SERCA (transgenic, TG), underexpressing SERCA2a (heterozygous knockout, Het), and their respective wild-type (WT) littermates. At physiological temperature and frequency, compared with their respective WT littermates, SERCA1a mice displayed increased developed force at frequencies of 4-8 Hz ( approximately 90% increase at 4 Hz) and force equal to WT mice at 10-14 Hz. Force development at 4 Hz in presence of 1 muM isoproterenol was similar in TG and WT mice. In Het mice, developed force was nearly identical at the lower end of the frequency range (4-8 Hz) but slightly depressed at higher frequency (P < 0.05 at 14 Hz). In presence of 1 muM isoproterenol, developed force at 4 Hz was equal to that in WT mice. Compared with normal levels, increased SERCA activity enhanced force development only at subphysiological frequencies. A reduction in SERCA activity only showed a depression of force at the higher frequency range. Thus generalizations regarding the correlation between SERCA activity and contractility can be highly ambiguous, because this relationship is critically dependent on other factors including stimulation frequency.


Assuntos
Contração Miocárdica/genética , Contração Miocárdica/fisiologia , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/biossíntese , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/fisiologia , Retículo Sarcoplasmático/enzimologia , Retículo Sarcoplasmático/fisiologia , Agonistas Adrenérgicos beta/farmacologia , Animais , Interpretação Estatística de Dados , Contração Isométrica/fisiologia , Isoproterenol/farmacologia , Camundongos , Camundongos Transgênicos , Fenótipo , Retículo Sarcoplasmático/genética , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático/genética , Malha Trabecular/enzimologia
13.
Pflugers Arch ; 451(5): 625-30, 2006 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-16082545

RESUMO

Multicellular cardiac muscles are widely used to study cardiac (patho-)physiology in vitro. One of the potential pitfalls of such experiments is that muscles with a large diameter have a larger diffusion barrier for transport of oxygen and waste products and can thus potentially form a hypoxic core. Although a sufficiently small muscle size is critical for obtaining unambiguous data, the relationship between muscle diameter and contractile performance specifically under near-physiological conditions remains unknown. Small uniform trabeculae of various diameters isolated from LBNF1 rats were stimulated at different temperatures (27.5-37.5 degrees C) and frequencies (1-8 Hz). Twitch contractions and rapid cooling contractures were used to assess contractile performance and SR Ca2+ load, respectively. We observed that at physiological frequencies and temperatures, contractile performance was clearly diminished in muscles with diameter >150 microm, likely due to the decreased rates of oxygen supply and waste removal. At room temperature slower contractions allow sufficient time for oxygen diffusion into the muscle core, and as a result the difference in contractile performance between the thin and thick muscles was less. Thus, in order to exclude adverse effects on contractile performance in multicellular myocardium under physiological conditions, it is essential that the preparations are of sufficient small diameter (<0.15 mm).


Assuntos
Coração/fisiologia , Contração Miocárdica/fisiologia , Miocárdio , Animais , Coração/anatomia & histologia , Técnicas In Vitro , Masculino , Ratos
14.
Am J Physiol Heart Circ Physiol ; 290(5): H2092-7, 2006 May.
Artigo em Inglês | MEDLINE | ID: mdl-16603708

RESUMO

Cardiac contraction-relaxation coupling is determined by both the free intracellular calcium concentration ([Ca2+]i) and myofilament properties. We set out to develop a technique where we could assess these parameters (twitch and steady-state force [Ca2+]i) under near physiological conditions. Bis-fura-2 was iontophorically introduced into ultrathin rat trabeculae preparations to monitor the [Ca2+]i, and steady-state contractures were achieved by using a modified Krebs-Henseleit solution containing high K+. During K+ contractures, the very slow changes in [Ca2+]i and force development were in equilibrium and allowed for the construction of a steady-state, force-[Ca2+]i relationship. Twitch contractions before and after this myofilament calcium sensitivity assessment were unaltered, and this protocol could be repeated several times. For the first time, this novel protocol allows us to measure myofilament calcium sensitivity under physiological temperature. Not only do the data so obtained allow us to assess myofilament calcium sensitivity, the data also will allow us, in the same preparation under nearly identical conditions, to compare the dynamic to the steady-state, force-calcium relationship. To test whether the steady-state relationship between force and calcium in our novel protocol reproduces expected changes, we determined this relationship in the presence of isoproterenol and under acidosis and alkalosis. As expected, beta-adrenergic stimulation resulted in an increase of calcium amplitude and twitch force and a desensitization of the myofilaments as indicated by a rightward shift of the obtained steady-state, force-calcium relationship. An increase in pH shifted the curve leftward, whereas a decrease in pH resulted in the expected rightward shift.


Assuntos
Citoesqueleto de Actina/fisiologia , Sinalização do Cálcio/fisiologia , Cálcio/metabolismo , Contração Muscular/fisiologia , Receptores Adrenérgicos beta/metabolismo , Animais , Células Cultivadas , Masculino , Ratos , Temperatura
15.
J Biol Chem ; 281(7): 3972-9, 2006 Feb 17.
Artigo em Inglês | MEDLINE | ID: mdl-16365042

RESUMO

The role of sarcolipin (SLN) in cardiac physiology was critically evaluated by generating a transgenic (TG) mouse model in which the SLN to sarco(endoplasmic)reticulum (SR) Ca(2+) ATPase (SERCA) ratio was increased in the ventricle. Overexpression of SLN decreases SR calcium transport function and results in decreased calcium transient amplitude and rate of relaxation. SLN TG hearts exhibit a significant decrease in rates of contraction and relaxation when assessed by ex vivo work-performing heart preparations. Similar results were also observed with muscle preparations and myocytes from SLN TG ventricles. Interestingly, the inhibitory effect of SLN was partially relieved upon high dose of isoproterenol treatment and stimulation at high frequency. Biochemical analyses show that an increase in SLN level does not affect PLB levels, monomer to pentamer ratio, or its phosphorylation status. No compensatory changes were seen in the expression of other calcium-handling proteins. These studies suggest that the SLN effect on SERCA pump is direct and is not mediated through increased monomerization of PLB or by a change in PLB phosphorylation status. We conclude that SLN is a novel regulator of SERCA pump activity, and its inhibitory effect can be reversed by beta-adrenergic agonists.


Assuntos
ATPases Transportadoras de Cálcio/fisiologia , Cálcio/metabolismo , Proteínas Musculares/fisiologia , Contração Miocárdica , Miocárdio/metabolismo , Proteolipídeos/fisiologia , Retículo Sarcoplasmático/metabolismo , Animais , Transporte Biológico , Proteínas de Ligação ao Cálcio/metabolismo , Isoproterenol/farmacologia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Transgênicos , Fosforilação , ATPases Transportadoras de Cálcio do Retículo Sarcoplasmático
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