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Biomedical subjects

R Boxer

Publications and source records attributed to R Boxer.

11 recordsLinked to original sources
PubMed2006

Femoral bone mineral density in patients with heart failure.

INTRODUCTION: Heart failure and osteoporosis are common conditions in older, frail individuals. It is important to investigate interactions of the common problems in the aging population to devise relevant interventions. METHODS: Sixty individuals (43 men, mean age 77+/-9 years, and 17 women, mean age 78+/-12 years) with heart failure (HF) and 23 age- and gender-matched non-HF controls (15 men, eight women; mean age 77+/-9 years) underwent hip and bone mineral density (BMD) assessments; frailty assessment; physical performance assessment including 6-min walk, grip strength, and self-reported physical activity; and biochemical assessment including calcium, parathyroid hormone (PTH), 25-hydroxy vitamin D (25-OHD), estradiol, creatinine (Cr), and blood urea nitrogen levels (BUN). RESULTS: Significant differences between HF and control groups were found for BMD Z-scores of the femoral neck, total femur, and trochanteric region at the femur (p<.05). Further differences between groups included frailty score (p=.02), 6-min walking distance (p<.001), and self-reported physical activity (p=.001). In addition, several differences between groups were present for calcium (p=.054), PTH (p<.001), 25-OHD (p=.01), Cr (p=.04), and BUN (p=.01). In regression analysis, HF (defined as case, by ejection fraction, or by New York Heart Association class), frailty status, and vitamin D were significant predictors of lower bone mass at the femur. CONCLUSIONS: Individuals with HF have lower BMD, in part related to lower vitamin D status and higher frailty rates. Interventions to optimize vitamin D and physical activity should be explored to prevent bone loss in individuals with heart failure.

Aged↗
PubMed1999

Usefulness of triiodothyronine (T3) treatment after surgery for complex congenital heart disease in infants and children.

This is a study of the use of T3 infusion in the postoperative period in 6 pediatric patients who underwent complex cardiac surgical procedures under cardiopulmonary bypass. Normalization of serum T3 levels was reflected in a marked decrease in requirement of inotropic support, conversion to normal sinus rhythm, and progressively improving clinical course.

Child, Preschool↗
PubMed1998

Differential responses of brain, liver, and muscle glycogen to opiates and surgical stress.

We examined the effects of intracerebroventricular (ICV) cannula implantation followed by the administration of morphine sulfate (MOR) and its metabolite, morphine-6-glucuronide (M6G), on the glycogen content of the brain, liver, and muscle. ICV cannulation resulted in nearly a 30% reduction in brain glycogen, and ICV MOR resulted in a 36% reduction in liver glycogen content compared to time-matched controls, but it had no additional effect on either the brain or muscle glycogen content. ICV M6G showed a more significant reduction, to 50% of liver glycogen, but it had no effect on either brain or muscle glycogen. Neither IV MOR nor M6G produced any significant alteration in tissue glycogen content. These results indicate that the stress response associated with neurosurgery, especially the placement of the ICV cannula, is associated with a decrement in brain glycogen. The activation of opioid receptors in the brain results in enhanced hepatic glycogenolysis but has no additional effect on the brain glycogen content.

Analgesics, Opioid↗
PubMed1997

An avian sodium-hydrogen exchanger.

Intestinal sodium transporters, such as the Na+/H+ exchanger (NHE) are important for Na+ conservation in land birds. In mammals, at least five isoforms of the exchanger, NHEs 1-5, have been cloned, with NHE-1 occurring in epithelial basolateral and nonepithelial cell membranes and NHE-3 being restricted to epithelial apical/brush border membranes. We had demonstrated earlier that chicken intestinal brush border membranes possess NHE activity that functionally resembles mammalian NHE-3. In this study, we used mammalian NHE-1 and NHE-3 probes to examine if chicken enterocytes possess these transporters. Antisera against rat NHE-3 recognized a 97 kDa protein in chicken intestinal brush border membrane, while a NHE-3 cDNA probe failed to recognize any transcript. A NHE-1 antibody failed to recognize any protein in brush border or basolateral membrane, while a NHE-1 cDNA probe recognized a 3.9 kb transcript. Thus, there is more than one NHE isoform in chicken intestine, and our results suggest a novel avian NHE family.

Animals↗
PubMed1995

Modulation of endogenous opiate production: effect of fasting.

The endogenous opiate alkaloid content in tissues from fed, 24 h and 48 h fasted rats was determined. Plasma morphine and codeine concentrations did not change in response to fasting. Morphine levels in the spleen increased 3-fold after 24 h of fasting and were lower than fed rats by 48 h of fasting; no change was detected in spleen codeine levels. Brain morphine levels were elevated 5-fold after 24 h of fasting and were two-fold higher than those of fed rats after 48 h of fasting. Brain codeine levels did not change with fasting. These results indicate that opiate alkaloids are endogenously produced in rodent tissues, particularly in the spleen, liver, and adrenals. The synthesis of morphine, in the spleen and brain, is maximally stimulated after 24 h of fasting, without alterations in tissue codeine synthesis. These suggest differential regulation of the endogenous synthetic pathways of morphine and codeine in response to the stress of fasting.

Adrenal Glands↗
PubMed1991

Bronchial hyperreactivity in children with Marfan syndrome.

Marfan syndrome is known to have pulmonary manifestations such as pneumothorax. There have been few previous studies of pulmonary function tests and none of bronchial hyperreactivity. Therefore, pulmonary function tests were performed in 11 children with Marfan syndrome and 11 normal children. Bronchial responsiveness was tested in ten of the Marfan patients by methacholine challenge test and response to bronchodilator. Because of disproportionate length of legs in Marfan patients, an "ideal" standing height was calculated from sitting height. Pulmonary function tests, as absolute values or as percent predicted based on "ideal" height, were not different in Marfan patients and normals, although a few individual patients had abnormal function (mostly airway obstruction and hyperinflation). Response to methacholine challenge was positive on forced expiratory volume in 1 second (FEV1), forced expiratory flow between 25 and 75% VC (FEF25-75%), and FEF50%, in 37.5%, 60%, and 70% of tests respectively. A significant response to bronchodilators was obtained in 40% of patients as measured by FEV1, in 90% by FEF25-75% and in 100% by FEF50%. Pulmonary function tests after bronchodilator were significantly higher when compared with values before the bronchodilator as well as with the baseline before methacholine. Therefore, most if not all patients with Marfan syndrome had hyperreactive airways in this relatively small group of patients. Even though only one patient had a diagnosis of asthma, six more had subtle symptoms. It is concluded that tests for bronchial hyperreactivity could be part of the routine investigation in Marfan syndrome. Further studies on larger numbers of patients are still needed.

Adolescent↗
PubMed1979

Abnormal septal motion in patients with postoperative right bundle branch block pattern.

Echocardiograms were performed on 25 patients with postoperative right bundle branch block pattern 3 to 93 months after surgery to assess the possible effects of abnormal cardiac excitation on septal motion. Each of the 25 patients demonstrated a unique pattern of septal motion characterized by the presence of an early systolic anterior septal notch, brief in duration and unrelated to subsequent systolic septal motion, right ventricular size, or surgical procedure. Beginning approximately 70 to 80 msec. after the initial QRS deflection, the septum abruptly moved anteriorly 2 to 7 mm. and then returned to a baseline position. The total duration of this abnormal septal motion lasted 78 to 155 msec. This echocardiographic pattern was not seen in any of 30 patients in two control groups. Twenty had a normal QRS pattern and ten demonstrated right ventricular hypertrophy. In addition, patients who underwent open heart surgery and had normal right ventricular conduction postoperatively did not show this echocardiographic pattern with either normal or paradoxical septal motion. This previously undescribed echocardiographic pattern demonstrates that septal motion is uniquely affected in patients with postoperative right bundle branch block pattern.

Adolescent↗
PubMed1978

Electrograms from the canine sinoatrial pacemaker recorded in vitro and in situ.

We have identified extracell potential changes associated with the electrical activity of the canine sinoatrial pacemaker. Small nonpolarizable electrodes and low frequency high gain amplification were used to record unipolar electrograms from both the epicardial and the endocardial surfaces of the canine sinus node. Initially in vitro studies were performed so that transmembrane action potential changes could be recorded simultaneously with the extracell potentials. The sinus nodal electrogram showed two characteristic potentials when the electrode was in immediate proximity to pacemaking cells: (1) During phase 4 there was a steady slope of about -30 to -100 muv/sec, and (2) during the transition from phase 4 to phase 0 of the transmembrane action potential the slope of the electrogram increased smoothly to approximately -400 to -1,000 muv/sec. These potentials were followed by high frequency deflections as cells in the surrounding atrium depolarized. Tetrodotoxin (5 mg/liter) rendered the atrial muscle inexcitable and delayed and then abolished the high frequency activity in the sinus electrogram, which then appeared as a continuous smooth tracing similar to the sinus pacemaker action potential but reversed in polarity. We then recorded these small localized potentials from the in situ canine heart. Sinus nodal electrograms could be obtained from beating hearts with hand held probes on the epicardial surface and with conventional recording catheters on the endocardial surface. The results demonstrate that the canine sinus node gives rise to detectable and characteristic changes in extracell potential and suggest that similar potentials can be recorded from man to evaluate sinus nodal function.

Action Potentials↗