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Biomedical subjects

B Baron

Publications and source records attributed to B Baron.

At least 73 records · Page 4Linked to original sources
PubMed1988

The development of a role charter for nursing unit administrators.

Issues of decentralization and changes in the structure of the traditional Head Nurse role were motivating factors for the proactive stance taken by the Medical-Surgical Head Nurse Group at The Wellesley Hospital. Increasing frustration with the conventional role and the need for a reflective performance appraisal tool provided further impetus for the development of a revised job description. The three departments of nursing each submitted their perception of the role. A task force was established whose mandate was to review and revise the three separate submissions and combine them into a composite document. This article describes the process from the initial motivating factors to the development of a cohesive Total Head Nurse Group and finally a 'Role Charter for Nursing Unit Administrators.'

Humans↗
PubMed1987

Acute hemodynamic effects of intravenous nicardipine in patients treated chronically with propranolol for coronary artery disease.

Intravenous nicardipine, 5 mg, was infused over 5 minutes in 2 comparable groups of 8 patients with chronic coronary artery disease but no clinical signs of heart failure. Eight patients had received no previous treatment and served as a control group; 8 other patients had received long-term treatment with large doses of propranolol. The hemodynamic responses to nifedipine were similar in the 2 groups, but was greater in patients taking propranolol. At 10 minutes, systemic vascular resistance decreased by 47% in patients taking propranolol and by 39% in the control group; mean aortic pressures decreased by 25% and 10%; heart rate increased by 23% and 19%; and cardiac index increased by 45% in both groups. At 20 minutes, left ventricular end-systolic volume index decreased by 20% in patients taking propranolol and 15% in the control patients; angiographic stroke index increased by 19% and 8%; left ventricular ejection fraction increased by 22% and 11%; and mean circumferential fiber velocity increased by 46% and 32%. Intravenous nicardipine infusion (5 mg) did not induce negative inotropic effects in patients with chronic coronary heart disease, and no evidence of congestive heart failure was seen, even in patients receiving large doses of propranolol. Nicardipine counteracted the potential deleterious effects of propranolol; increased peripheral vascular resistance and left ventricular stroke work and decreased cardiac output.

Adult↗
PubMed1987

Could inspiratory apnea disturb left ventricular volume assessment by contrast angiography?

To assess the influence of postinspiratory apnea on the measurement of the left ventricular volumes, contrast ventriculography was performed on 19 patients during spontaneous breathing and then in postinspiratory apnea. Data obtained were similar for end diastolic volumes (81 +/- 29 ml/m2 vs. 83 +/- 25; NS), end systolic volumes (35 +/- 20 ml/m2 vs. 34 +/- 19; NS), systolic index (46 +/- 13 ml/m2 vs. 49 +/- 12; NS), and ejection fraction (0.57 +/- 0.11 vs. 0.59 +/- 0.12; NS). Postinspiratory apnea suppressed the overlapping of the left ventricle with abdominal viscera in 15 of 17 patients. Diaphragmatic immobility permitted the assessment of regional left ventricular function in all 19 patients. However, pressures recorded in inspiratory apnea can no longer be compared to a transmural pressure, and, to assess ventricular compliance, intrapleural pressure must be measured simultaneously. We conclude that left ventricular volume assessment by contrast ventriculography is not disturbed by inspiratory apnea. This maneuver improves the quality of the images and allows a better evaluation of left ventricular segmental function. Spontaneous breathing can be recommended to simplify left ventricular compliance study.

Adult↗
PubMed1986

Cloning of DNA libraries from mouse Y chromosomes purified by flow cytometry.

To purify mouse Y chromosomes by flow cytometry, a male cell line containing the Robertsonian translocation Rb(9.19)163H has been established by SV40 transformation. Flow karyotypes obtained from these cells exhibit a well-isolated peak of fluorescence corresponding to the single Y chromosome, clearly distinct from that of chromosome 19. From this peak, 650,000 chromosomes were sorted, and two restriction fragment libraries were constructed from the DNA of the sorted chromosomes. The characterization of several Y-specific fragments has shown that the Y DNA was enriched at least 36-fold. Furthermore, given that there are likely homologies between the X and Y chromosomes, we can assume that this calculated value of the purification factor is an underestimation and that the Y DNA was more highly purified by flow sorting.

Animals↗
PubMed1986

Hemodynamic effects of intravenous diltiazem in patients treated chronically with propranolol.

In the search for any deleterious hemodynamic effects of the acute administration of intravenous diltiazem (0.25 mg/kg), in patients on beta blockers, studies were performed in two comparable groups of eight patients with chronic coronary heart disease without clinical signs of heart failure. In the first group, with no previous treatment, the only significant variations observed were a decrease in systemic vascular resistance (p less than 0.01) and an increase in cardiac index (p less than 0.01), which were noted only at 5 minutes. In the second group, receiving long-term oral doses of 120 to 240 mg/day of propranolol, at 5 minutes, despite a slight decrease in peak positive first derivative of left ventricular pressure (p less than 0.05), cardiac index and systolic index increased (p less than 0.05 and p less than 0.01) with decreases in systemic vascular resistance (p less than 0.01) and mean blood pressure (p less than 0.05); at 15 minutes, systemic vascular resistance was still decreased (p less than 0.05) and cardiac index and systolic index were still increased (p less than 0.05). In conclusion, intravenous administration of diltiazem (0.25 mg/kg) to patients with chronic coronary heart disease and no evidence of congestive heart failure, who were receiving propranolol, was safe and prevented, in these patients, the potential deleterious effects of beta blockers, that is, increased peripheral vascular resistance and decreased cardiac output.

Adult↗
PubMed1985

Arteriovenous shunt measured by bolus dye dilution: reproducibility and comparison between two injection sites.

Twenty-eight brachial arteriovenous fistulae (AVF) flows were assessed by the Stewart and Hamilton method by bolus dye injection. These measurements were divided in two groups: a first group with dye injection into the AVF artery and a second group with dye injection into the efferent vessel of the AVF in close proximity. The increase and the decrease of dye concentration were regular and the circulation occurred very late in both groups. Reproducibility was assessed by the usual index: the mean of the differences between two successive measurements of each series related to the first of these two and expressed as a percentage, m(Qn - Qn - 1)/Qn%. In the two groups, the reproducibility index was at 10.1%, similar to the index applied to Grimby's results, measuring successive cardiac output by dye bolus injection at 9.8%. Theoretical criteria of validity of the Stewart and Hamilton method were checked for all measurements. Even when the duration of the measurement was very short, arteriovenous flow fulfilled the criteria of validity in the same way as cardiac output. Two AVF flows were measured successively at both injection sites with no difference between the obtained values. The same reproducibility of the efferent vessel injection site group suggests that an arterial puncture is not necessary for a correct assessment of AFV flow.

Adult↗
PubMed1985

Heterogeneity of solubilized muscarinic cholinergic receptors: binding and hydrodynamic properties.

Previous studies have described the conversion, after detergent solubilization, of the multiple populations of membrane-bound muscarinic agonist binding sites to a population of uniform affinity. This paper describes the solubilization of at least two receptor species, distinct in their agonist binding characteristics, which are capable of interconversion by transition metal ions. This finding enabled a more detailed examination of the molecular properties and regional differences of brain muscarinic receptors than was previously possible. Muscarinic receptors (mAChR) obtained from the rat cerebral cortex or medulla pons were solubilized using digitonin or the zwitterion detergent, 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonate (Chaps). The equilibrium binding of the antagonist [3H]-4-N-methylpiperidyl benzilate ([3H]4NMPB) to detergent-solubilized receptors resembled binding to neural membranes and exhibited subnanomolar affinity, saturability, and simple mass action kinetics. Agonist binding to soluble preparations was measured by competition of [3H]4NMPB binding sites. Saturation isotherms for agonist binding to digitonin- and Chaps-solubilized mAChR obtained from various brain regions appear flattened and have Hill coefficients in the range 0.52-0.78. Computerized modelling techniques indicate that the best fit to the experimental data is provided by a model specifying two soluble muscarinic agonist binding sites with differing dissociation constants, KH and KL, respectively. Solubilization of cerebral cortex membranes with Chaps or digitonin resulted in a population with a composition of high- and low-affinity sites similar to that found in the membrane-bound state. In contrast, solubilization of the medulla pons resulted in an approximately 40% loss of high-affinity sites. Solubilized receptors retained the sensitivity to transition metals ions, but were insensitive to guanine nucleotides. Density gradient centrifugation indicated that Chaps-solubilized mAChR are composed of two molecular forms with S20,W equal to 9.9 S and 14.9 S. The 14.9 S species comprises approximately 30% of the total binding activity in the cortex and approximately 40% in the medulla. We identify the 14.9 S species as being associated with a guanylnucleotide binding protein because treatment of medulla membranes with guanylylimidodiphosphate prior to solubilization results in disappearance of 14.9 S with 9.9 S unchanged. Sedimentation of cortical mAChR in the presence of Cu+2 leads to an increase in 14.9 S to almost 50% of the total binding activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Linearization of human growth curves affords new classification of dwarfism.

We describe here a new technique for analyzing human growth curves using a first order kinetic representation. Plotting in ([h infinity-ht)/h infinity] vs time (where h infinity and ht represent the final and instantaneous heights) transforms growth curves into 3 linear phases and 2 interphases. These growth parameters can be quantitatively compared between normal individuals of the same gender, between different sexes, and between individuals of normal and aberrant growth. This analysis provides a new classification of dwarfism.

Anthropometry↗
PubMed1984

Solubilization and characterization of muscarinic receptors from bovine brain.

This study compared the capacity of different detergents to solubilize the muscarinic cholinergic receptor (mAChR) from bovine brain, evaluated various procedures for the measurement of [3H]-L-quinuclidinyl benzilate [( 3H]-L-QNB) binding to solubilized receptors, and examined some physical and chemical characteristics of the soluble material. An active form of the mAChR was solubilized using digitonin (1%), Triton X-100 (0.5%), and a digitonin-cholate mixture (1%, 0.1%). Values of maximal binding (Bmax) were 2.01, 0.47, and 0.68 pmoles/mg protein, respectively. Comparison of equilibrium dialysis, charcoal adsorption, and polyethylene glycol precipitation indicated that these methods differ in their estimation of Bmax. A decrease in [3H]-L-QNB binding to digitonin solubilized receptors occurred upon dilution or incubation at 37 degrees. The half-life at 37 degrees C was 25 min., but was increased by glycerol. Antagonist binding to digitonin solubilized receptors was saturable and of high affinity. Agonist binding had Hill coefficients less than 1 and was increased by micromolar concentrations of cupric ions.

Animals↗
PubMed1984

Fatty acid incorporation increases the affinity of muscarinic cholinergic receptors for agonists.

Incorporation of unsaturated fatty acids into membrane fragments from rat brain cortex and medulla pons selectively increased the affinity of the muscarinic agonist, carbamylcholine. The affinity and number of binding sites for the labeled antagonist, N-[3H]methyl-4-piperidyl benzilate was unchanged. The effect on agonist binding was most prominent in the cortex, in which carbamylcholine IC50 values were decreased up to 5-fold. Selectivity of the effect was observed with fatty acids of chain length 18-20 carbons, unsaturation in position 11-12, and a cis conformation of the double bond being most effective. The effects of fatty acids on agonist binding were due primarily to alterations in the affinity constants for the binding reaction, with minor increases in the proportion of high-affinity sites. Transition metals selectively increased the percentage of high-affinity sites in the cortex, but in cis-vaccenic-acid-treated membranes more than additive effects of the metal were observed; both were reversed by GTP. GTP also reversed binding parameters in cis-vaccenic-acid-treated medulla membranes to control level. We conclude that the primary effect of the active fatty acids is to alter the thermodynamic properties of muscarinic agonist binding without markedly inducing interconversion.

Animals↗
PubMed1984

Copper ions and diamide induce a high affinity guanine-nucleotide-insensitive state for muscarinic agonists.

The binding capacity of [3H]-acetylcholine for muscarinic receptors of rat cerebral cortex membranes is increased in the presence of Cu2+ ions from 690 to 1320 fmol/mg protein with no significant change in affinity. Membranes treated with 50 microM Cu2+ and washed retain the increased binding capacity. Agonist binding in copper-treated membranes is insensitive to guanylylimidodiphosphate even at high concentrations (greater than 200 microM). Similar results were obtained when the sulfhydryl oxidizing agent, diamide (2 mM) was substituted for Cu2+ in the treatment of membranes. These data suggest the involvement of inter- or intra-molecular SH/S-S transitions in the interaction between the muscarinic receptor and a guanine nucleotide binding regulatory protein.

Animals↗
PubMed1984

Flow cytometry isolation and improved visualization of sorted mouse chromosomes. Purification of chromosomes X and ISO-1 from cell lines with Robertsonian translocations.

While analysis and sorting of human chromosomes by flow cytometry has been widely used, isolation of a pure mouse chromosome remains very difficult, since most murine chromosomes are quite similar in size. To overcome this problem, we have analysed mouse cell lines having either Robertsonian translocations or isochromosomes. The resulting metacentric chromosomes are very different in size and in morphology from normal mouse acrocentric chromosomes. These characteristics have been analysed by computer-monitored flow cytometry, facilitated by improvements in the chromosome extraction procedure. Signals characteristic of the iso-lq chromosome in cell line PCC4 azaR1, and of the normal X chromosome in the mouse strain 22CD have thus been obtained. These chromosomes have been sorted and can be easily recognized by fluorescence microscopy when collected onto serum-albumin-coated microscope slides. The technical modifications made, coupled with the existence of a great diversity of metacentric chromosomes resulting from Robertsonian translocations, should allow the purification of a number of different mouse chromosomes.

Animals↗
PubMed1984

Differences between somatic growth curves of males and females are a secondary sex characteristic.

There are differences in male and female height throughout the growth period. Utilising reference standard height charts we calculated the difference in male and female height as a function of age. A triphasic relationship was observed with statistically significant peaks (males greater than females) at 8 months and 18 years and (females greater than males) at 11.5 years of age. Data for sex hormone concentrations during this period were collected from the literature. Computing a difference measure (males minus females) for androgen levels a similar triphasic curve was obtained. Positive peaks occurred at 3 months and 18 years and a negative peak around 10 years. All three peak differences were found to be statistically significant. Peak differences in estrogen levels were observed at similar ages. Whereas peak differences in androgens were positively correlated with those for height, a negative correlation was found for estrogen. This implies that somatic growth is a secondary sex characteristic facilitated by androgens and inhibited by estrogens.

Adolescent↗
PubMed1981

[Left ventricular performance in chronic hemodialysis patients studied during intense exercise and during a dextran infusion test (author's transl)].

In 14 chronic hemodialysis patients with recent circulatory pulmonary congestion or pulmonary edema, left ventricular failure was suspected. Left ventricular function was studied by a sitting exercise test and a dextran infusion test. According to the left ventricular function curves the left ventricular function was not altered in chronic hemodialysis patients compared to normal subjects. It is possible that on average the left ventricular performances is higher in chronic hemodialysis patients than in normal subjects. These results indicate that circulatory pulmonary congestion and pulmonary edema are not reliable signs of left ventricular failure in chronic hemodialysis patients.

Adult↗
PubMed1981

Hemodynamic effects of arteriovenous fistulae in chronic hemodialysis patients at rest and during exercise.

The effects of arteriovenous fistulae (AVF) on cardiac output (CO) and cardiac filling pressures were studied at rest and during exercise in 16 chronic hemodialysis patients. After the occlusion of the AVF, average CO fell but cardiac filling pressures remained unchanged, seven patients had a drop in CO greater than or equal to 1.0 l/min (group A) and nine patients had a drop in CO less than or equal to 0.9 l/min (group B). At rest, average CO was higher in group A than in group B, but cardiac filling pressures were the same in group A and in group B. During maximal exercise, average CO and cardiac filling pressures were the same in both groups.

Adult↗