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J Robbins

Publications and source records attributed to J Robbins.

At least 145 records · Page 8Linked to original sources
PubMed1995

An in vivo analysis of transcriptional elements in the mouse alpha-myosin heavy chain gene promoter.

During development in the murine ventricle, there is a switch in myosin heavy chain gene (MyHC) transcription. The beta-MyHC is expressed in the ventricles during foetal development, but is shut down at or around birth, at which time alpha-MyHC transcription is activated. This antithetical switch is thought to be mediated by circulating levels of thyroid hormone (TH) and both low and high affinity thyroid response elements (TREs) have been identified in the proximal promoter region of the murine alpha-MyHC. Myosin gene expression in the atria is relatively unaffected by the TH status. Previously, we used site-directed mutagenesis of the promoter in a transgenic analysis to define those elements responsible for high levels of transcription in vivo. These analyses focused on the role(s) of two cis elements, TRE1 and TRE2 that are located at -129 to -149 and -102 to -120, respectively, on the alpha-MyHC promoter. Although the elements' ablation had differential effects on transgene expression, neither single mutation abolished transgene expression completely. Here, we show that mutating both elements results in a complete inactivation of the transgene in both ventricles and atria under euthyroid conditions. However, expression still can be detected in the hyperthyroid state, implying that, although the TRE1 and TRE2 elements are critical elements for high levels of alpha-MyHC transcription in vivo, other promoter sites can mediate at least some degree of transcriptional activation.

Animals↗
PubMed1995

Methods of assessing prevalent cardiovascular disease in the Cardiovascular Health Study.

The objective of this article is to describe the methods of assessing cardiovascular conditions among older adults recruited to the Cardiovascular Health Study (CHS), a cohort study of risk factors for coronary disease and stroke. Medicare eligibility lists from four US communities were used to obtain a representative sample of 5201 community-dwelling elderly, who answered standardized questionnaires and underwent an extensive clinic examination at baseline. For each cardiovascular condition, self-reports were confirmed by components of the baseline examination or, if necessary, by a validation protocol that included either the review of medical records or surveys of treating physicians. Potential underreporting of a condition was detected either by the review of medical records at baseline for other self-reported conditions or, during prospective follow-up, by the investigation of potential incident events. For myocardial infarction, 75.5% of the self-reports in men and 60.6% in women were confirmed. Self-reported congestive heart failure was confirmed in 73.3% of men and 76.6% of women; stroke, in 59.6% of men and 53.8% of women; and transient ischemic attack, in 41.5% of men and 37.0% of women. Underreporting was also common. During prospective follow-up of an average of about 3 years per person, approximately 50% of men and 38% of women were hospitalized or investigated for at least one potential incident event; for each cardiovascular condition, about 1 to 4% of those investigated during prospective follow-up were found to have had the cardiovascular condition prior to entry into the cohort.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

The effect of sodium bicarbonate ingestion on 1500-m racing time.

Twelve athletes, all of whom regularly participated in middle- or long-distance running races at club to national standard, competed in simulated 1500-m races under three conditions: following ingestion of 300 mg sodium bicarbonate per kg of body mass (B); following ingestion of a placebo (100 mg sodium chloride per kg of body mass and 200 mg calcium carbonate per kg of body mass) (P); and following ingestion of neither (C). A double-blind protocol was used between the B and P trials. Each condition was replicated so that the athletes competed in six races. Ten of the athletes completed all the races. The athletes' average times for trials B, P and C were 253.9, 256.8 and 258.0 s, respectively. The data were analysed using a two-way ANOVA with replicates and Tukey tests. This revealed a difference between trial B and trials P and C (P < 0.05), but no difference between trials P and C. These findings, therefore, indicate that sodium bicarbonate can have an ergogenic effect upon 1500-m running.

Administration, Oral↗
PubMed1995

Age effects on lingual pressure generation as a risk factor for dysphagia.

BACKGROUND: Tongue activity plays a crucial role in both oral and pharyngeal phases of swallowing. In this study, maximum lingual isometric and swallowing pressures were quantified in two groups of healthy men to investigate possible age effects on performance. Magnetic resonance images of the brain were also obtained to examine the relationship between age-related anatomical changes and swallowing function. METHODS: Pressures were recorded at three lingual sites (tip, blade, and dorsum) during a maximal isometric task and during saliva swallows. Task order was randomized, and subjects performed three trails per placement site. Additionally, t2-weighted MRIs were obtained on 9 of the 10 young subjects (mean age = 25 years) and all 15 older subjects (mean age = 75 years). RESULTS: Maximal isometric pressures were significantly greater for younger subjects at the tongue blade site (p = .002), whereas peak swallowing pressures remained similar across both age groups. Within-subject comparisons of maximum isometric to swallowing pressures, a measure of reserve capacity, revealed reduced difference scores at the tongue blade in the older group (p = .02). Older subjects exhibited significantly more cerebral atrophy (p = .001) and greater incidence of periventricular white matter lesions (p = .0001) than did younger subjects. CONCLUSIONS: While swallowing pressures remain similar across the life span, overall pressure reserve declines with age. The implications are: (a) older people may be working harder to produce adequate swallowing pressures, and (b) age-related illness may put geriatric patients at higher risk for dysphagia, thus further complicating recovery.

Adult↗
PubMed1995

Hematological and biochemical laboratory values in older Cardiovascular Health Study participants.

OBJECTIVE: To define reference hematologic and biochemical lab values in older individuals. DESIGN: Randomly selected, age- and gender-stratified participants. SETTING: Visits by participants to four research clinics. PATIENTS: A total of 5201 participants in the Cardiovascular Health Study, an observational study of older Medicare-eligible individuals living at home. MEASUREMENT: Information about health status, previous illness, and medication use was obtained from participants and/or their MDs. This information was used to define a healthy subset of the population. Blood samples were obtained for Cholesterol, HDL and LDL cholesterol, fasting and 2-hour postload glucose and insulin, fibrinogen, factors VII and VIII, potassium, creatinine, albumin, uric acid, white blood count, hematocrit, hemoglobin, and platelet count. RESULTS: Significant differences were found for age group and/or gender for all mean values. Many tests were significantly different from the generally accepted reference ranges used in clinical laboratories. CONCLUSIONS: In some situations accepted laboratory norms for the general population can not be extrapolated to older adults. There are implications for both research and clinical practice.

Age Factors↗
PubMed1995

Iodine-131 therapy for thyroid cancer patients with elevated thyroglobulin and negative diagnostic scan.

Seventeen patients with papillary thyroid cancer whose serum thyroglobulin (Tg) levels were elevated when hypothyroid, but whose diagnostic whole body scans were negative, were treated with 150-300 mCi 131I. All patients had total thyroidectomy and 131I ablation for thyroid remnants. Before the study, 9 patients had 131I therapy for tumor recurrence and/or metastases, and 5 patients had excisions of nonfunctioning metastasis. Radiological studies did not reveal evidence of metastases. In the initial evaluation, Tg levels ranged from 8-480 ng/mL (24 pmol/L to 1.5 nmol/L), and posttherapy whole body scans (RxWBS) revealed undiagnosed local recurrence and/or metastases in 16 of 17 patients. Follow-up from 6 months to 5 yr is available in 16 patients. RxWBS after a second treatment was positive in 8 of 13 patients, and after a third treatment in 5 of 5 patients, although in 3 cases, uptake in distant metastasis had disappeared. In 8 patients, Tg fell to 5 ng/mL or less. In 1 patient, RxWBS became negative, but Tg remained elevated; subsequent treatment revealed local and mediastinal uptake, but previous lung uptake had disappeared. In 8 patients, RxWBS remains positive, and elevated Tg persists. A total of 35 RxWBS were performed; 29 were positive. Follow-up Tg concentrations decreased in 81% of patients after the first treatment, in 90% after the second treatment, and in 100% of the patients after the third treatment. Tg (mean +/- SE) decreased from 74 +/- 33 ng/mL in the first evaluation to 62 +/- 32 ng/mL in the second study and 32 +/- 20 ng/mL in the third study. The therapeutic effectiveness of 131I treatment in patients with elevated Tg and negative diagnostic whole body scans is indicated by the conversion to negative RxWBS, the statistically significant decrease in the mean Tg level, and the reduction of serum Tg to 5 ng/mL or less in 50% of patients. Further experience with this therapeutic approach is required to evaluate its effectiveness in improving prognosis and survival.

Adult↗
PubMed1995

Putative M-type potassium channels in neuroblastoma-glioma hybrid cells: inhibition by muscarine and bradykinin.

Putative M-type K(+)-channels ('M-channels') were recorded in differentiated NG108-15 neuroblastoma x glioma hybrid cells transformed to express m1 muscarinic acetylcholine receptors using cell-attached patch-electrodes. Channels showed multiple conductances, with peaks at 6-9 and 12-15 pS. Averaged currents showed time-dependent activation during 1 s depolarization steps to around -30 mV. Steady-state Po increased in a voltage-dependent manner when the membrane was depolarized between 10 and 60 mV, with a limiting slope of 5.5 mV/e-fold change in Po. Steady-state kinetics were fit by two open and three shut times: depolarization shortened shut times and lengthened open times. Application of muscarine (10 microM) or bradykinin (10 microM) to the membrane outside the patch reversibly reduced steady-state in-patch channel activity to 38.4 +/- 11.7 and 28.8 +/- 6.1% of control values, respectively. Inhibition was accompanied by a lengthening of channel shut times without significant change in open times or distribution of conductance levels. No effect of muscarine or bradykinin on whole-cell or membrane patch delayed rectifier currents was detected. It is concluded that M-channels in NG108-15 cells are qualitatively similar to, but sparser than, those previously reported in rat sympathetic neurones. Their inhibition by extra-patch acetylcholine and bradykinin suggests that a mobile messenger is involved in the transduction process leading from receptor activation to channel closure.

Animals↗
PubMed1995

Remodeling the mammalian heart using transgenesis.

Our objective was to test the hypothesis that, via transgenesis, one can modify the contractile protein complement of the mouse heart. Using a promoter derived from the mouse myosin heavy chain gene (alpha-MyHC), we attempted to remodel the mouse myocardium by ectopically expressing a ventricular form of the myosin light chain 2 (MLC2v) in the atrium. The ability of the heart to maintain contractile isoform stoichiometry was tested by overexpressing the cDNA in both the atria and ventricle. The promoter drove high levels of transgene expression in both cardiac compartments and was controlled in an appropriate manner during development. The data show that ectopic overexpression of a contractile protein isoform can lead to compartment specific replacement. However, if the transgene encodes the isoform that is normally present (e.g., MLC2v expressed in the ventricle), the protein levels remain unaffected, although the transgenic transcript accumulates to very high levels. The basic function and the physiologic or pathophysiologic significance of differential MLC2 isoform content was examined. Using the whole working heart preparation, we show that an MLC2a --> MLC2v shift in the atrium severely affects contractile function and performance.

Amino Acid Sequence↗
PubMed1994

In vivo regulation of the mouse beta myosin heavy chain gene.

The interactions of trans-acting factors with their respective cis-acting elements in the 5' upstream region of the beta myosin heavy chain gene (MyHC) regulate its tissue- and developmental stage-specific expression. The role of three conserved elements, an MCAT or TEF-1 binding site, a C-rich region, and a beta e3 region, in muscle-specific gene expression was analyzed in vivo. Each cis-acting site was ablated in the context of the beta MyHC promoter, fused to the chloramphenicol acetyltransferase reporter gene, and used to generate transgenic mice. In contrast to results obtained in vitro, the data demonstrate that mutating any one of these cis-acting elements does not affect the level or tissue specificity of transgene expression. Sequences upstream of -600 can functionally substitute for any one of these regulatory cassettes and are important both for high levels of expression as well as for controlled muscle specificity. Mutation of any two of the cis-acting elements also does not affect transgene expression. However, simultaneous mutation of the three sites significantly reduces expression, indicating that these conserved sequences do play an important role and that combinatorial interactions underlie the beta MyHC's regulation.

Animals↗
PubMed1994

Prevalence of subclinical atherosclerosis and cardiovascular disease and association with risk factors in the Cardiovascular Health Study.

The prevalence of subclinical atherosclerosis and cardiovascular disease was evaluated among the 5,201 adults aged > or = 65 years in four communities participating in the Cardiovascular Health Study from June 1989 through May 1990. A combined index based on electrocardiogram and echocardiogram abnormalities, carotid artery wall thickness and stenosis based on carotid ultrasound, decreased ankle-brachial blood pressure, and positive response to a Rose Questionnaire for angina or intermittent claudication defined subclinical disease. The prevalence of subclinical disease was 36% in women and 38.7% in men and increased with age. Among women, low-density lipoprotein cholesterol, systolic blood pressure, blood glucose, and cigarette smoking were positively associated, and high-density lipoprotein cholesterol negatively associated, with subclinical disease. In men, systolic blood pressure, blood glucose, and cigarette smoking were independent risk factors in multiple logistic regression analyses. The risk factors for subclinical disease are, therefore, similar to those for clinical disease at younger ages, especially among women. It is possible that older individuals with subclinical disease are at very high risk of developing clinical disease and that more aggressive interventions to prevent clinical disease should be oriented to individuals with subclinical disease.

Aged↗
PubMed1994

Unprocessed myogenin transcripts accumulate during mouse embryogenesis.

The gene myogenin encodes a helix-loop-helix protein whose function is critical to the integrity of the mammalian myogenic cascade. In vitro, the expression of this gene immediately precedes terminal differentiation, as measured by the synthesis of those proteins that make up the contractile apparatus. However, during mammalian development, expression of myogenin and the appearance of sarcomeres are separated by at least 1 week. The observation that early embryos (10.5 days post coitum) do not possess myogenin protein despite the fact that transcripts are detected (Cusella-De Angelis et al. (1992) J. Cell Biol. 116, 1243-1255), suggests the possibility of post-transcriptional regulation. Using polymerase chain reaction and in situ analyses, we report here that the mouse embryo accumulates a significant pool of unprocessed myogenin RNA in the developing somites (10.5 days post coitum). These results indicate that post-transcriptional regulation of myogenin may occur at the RNA processing level.

Animals↗
PubMed1994

Murine pulmonary myocardium: developmental analysis of cardiac gene expression.

Long-standing observations that cardiac muscle exists in the walls of the pulmonary and caval veins have recently been confirmed at the molecular level (Lyons et al. [1990] J. Cell Biol. 111:2427-2436; Springall et al. [1988] Thorax 43:44-52; Subramaniam et al. [1991] J. Biol. Chem. 266:24613-24620). Using ventricle- and atrial-specific riboprobes, we determined that the pulmonary myocardium exhibits an atrial pattern of cardiac-specific gene expression. Additionally, the developmental pattern of expression was studied using a riboprobe specific to the alpha-cardiac myosin heavy chain (alpha-MHC) gene transcript. We find that alpha-MHC gene expression is first detectable in the lung between 13.9-14.3 days post-coitum. Extension of the alpha-MHC specific hybridization signal into the pulmonary venous bed progresses through the neonatal period. The data are consistent with the hypothesis that the extension of alpha-MHC gene expression into the lung occurs via the migration of atrial myoblasts into the vein during atrial septation and remodeling of the sinus venosus and pulmonary venous trunk.

Animals↗
PubMed1994

Activation of nucleotide receptors inhibits M-type K current [IK(M)] in neuroblastoma x glioma hybrid cells.

A phospholipase-C-linked nucleotide receptor, sensitive to both uridine and adenosine triphosphate (UTP and ATP) has been cloned from NG108-15 neuroblastoma x glioma hybrid cells. We have tested whether activation of this receptor could inhibit the voltage-dependent K+ current [IK(M) or "M-current"] in NG108-15 cells recorded using whole-cell patch-clamp methods. Both UTP and ATP inhibited IK(M) by 44% and 42%, respectively, at 100 microM. Mean IC50 values were: UTP, 0.77 +/- 0.27 microM; ATP, 1.81 +/- 0.82 microM. The order of nucleotide and nucleoside activity at 100 microM was: UTP = ATP > ATP [gamma S] = ITP > 2-MeSATP > ADP = GTP >> AMP-CPP, adenosine, where ATP[gamma S] is adenosine 5'-O-(3-thiotriphosphate), ITP is inosine 5'-triphosphate, 2-MeSATP is 2-methylthio ATP and AMP-CPP is alpha, beta methylene ATP. This rank order accords with their activities at the cloned P2U receptor. Effects were not inhibited by suramin (up to 500 microM) or by pre-incubation for 12 h in 500 ng.ml-1 Pertussis toxin. Inhibition of IK(M) was frequently preceded by a transient outward current, probably a Ca(2+)-activated K+ current, responding to Ca2+ mobilization. No effect on the delayed rectifier K+ current was observed. These observations match those expected from stimulating other phospholipase-C-linked receptors in NG108-15 cells.

Adenosine Triphosphate↗
PubMed1994

Quinapril hydrochloride effects on renal function in patients with renal dysfunction and hypertension: a drug-withdrawal study.

Patients with mild to moderate hypertension (diastolic blood pressure > or = 95 and < or = 115 mmHg) and renal dysfunction entered one of two studies to assess the safety of efficacious daily doses of quinapril on renal function and blood pressure. Twenty-four patients with moderate renal impairment (MRI) (creatinine clearance > 30 and < or = 60 ml/min) entered 24 weeks of open-label quinapril treatment; 31 patients with chronic renal failure (CRF) (creatinine clearance < 30 ml/min) entered 16 weeks of open-label quinapril treatment. Patients with MRI initially received quinapril 5 mg once daily (qd) followed by titration to a maximum dosage of 40 mg/day (furosemide optional at 40 mg only). Patients with CRF initially received quinapril 2.5 mg qd and were titrated up to 20 mg/day (furosemide optional). Open-label quinapril treatment resulted in significant decreases in mean systolic (SBP) and diastolic (DBP) blood pressure. The 20 patients with MRI and the 28 with CRF who completed the open-label phase were then randomly assigned to continue active drug or to receive placebo in a 4-week, double-blind, drug-withdrawal phase. During the double-blind withdrawal phase, placebo-treated patients had significant increases in mean SBP and DBP from the end of open label. Creatinine clearance was essentially unchanged following open-label quinapril treatment or quinapril withdrawal. In conclusion, in patients with mild to moderate hypertension and renal dysfunction, quinapril in dosages of 5-40 mg qd for patients with MRI and 2.5 to 20 mg qd for patients with CRF significantly reduces blood pressure without adversely affecting renal function.

Adult↗
PubMed1994

Thyroid hormone binding to isolated human apolipoproteins A-II, C-I, C-II, and C-III: homology in thyroxine binding sites.

Thyroid hormone binding to lipid-free apolipoprotein (apo) A-II, C-I, C-II, and C-III isolated from human plasma was investigated by photoaffinity labeling with [125I]T4 and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Both the monomeric and polymeric forms were specifically labeled. Inhibition by 10 microM unlabeled L-T4 was > or = 50%, suggesting affinity constants in the nM to microM range; the least inhibition was seen with apoA-II. Unlabeled D-T4 and reverse T3 (rT3) gave the same inhibition as unlabeled L-T4. Inhibitors of thyroid hormone binding to plasma proteins showed a different inhibitor potency with each apolipoprotein and a pattern different from that seen with T4 binding globulin (TBG) and transthyretin (TTR). Also in contrast to TBG, where only unsaturated nonesterified fatty acids (NEFA) are effective inhibitors, both unsaturated and saturated NEFA as well as other lipids inhibited T4 labeling. The flavonoid EMD 21388 was ineffective, confirming that it is a selective inhibitor of T4 binding to TTR. T4 binding to the apoCs was confirmed by the quenching of tryptophan fluorescence by unlabeled L-T4. (ApoA-II was not studied since it lacks tryptophan). Since the self-association of apolipoproteins involves interaction between amphipathic alpha-helices, and since the polymeric forms show specific T4 binding properties as in the parent monomer, the T4-binding domain appears to be outside the alpha-helical domain, as previously seen with apoA-I.(ABSTRACT TRUNCATED AT 250 WORDS)

Affinity Labels↗