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Biomedical subjects

J A Bauer

Publications and source records attributed to J A Bauer.

At least 73 records · Page 4Linked to original sources
PubMed1992

Complications of chest thump for termination of supraventricular tachycardia in children.

We report on two cases of mechanical termination of supraventricular tachycardia by chest thump which were followed by serious complications. In a 3-year-old boy with an otherwise normal heart, incessant supraventricular tachycardia was converted to sinus rhythm by a single precordial thump. This, however was followed by thrombo-embolic infarction of the left-sided middle cerebral artery. In another case of a 9-year-old girl, recurrent episodes of supraventricular tachycardia were associated with Ebstein anomaly of the tricuspid valve. Chest thump was successful in terminating supraventricular tachycardia but induced a short run of ventricular tachycardia which terminated itself and was then followed by sinus rhythm. It is concluded that even a slight precordial thump implies undetermined risks in the acute management of supraventricular tachycardia in children and should therefore be abandoned in favour of other methods.

Cerebral Infarction↗
PubMed1992

Synaptic contacts established by primary sensory fibers innervating the teeth of rats: an ultrastructural study of the pars interpolaris of the spinal trigeminal nucleus.

Transganglionic degeneration was used in an electron microscopic study of afferent synaptic contacts in the dorsomedial region of the pars interpolaris of rats. In one experiment, the left inferior alveolar nerve was transected and in the other, partial pulpectomy of the first and second left lower molars was performed. Well defined degenerating terminals, almost completely occupied by round synaptic vesicle profiles were found in both ipsi and contralateral sides. In both experiments, approximately 70% of these terminals formed single asymmetric contacts with intermediate or distal dendritic segments. Fewer contacts were observed with proximal dendritic segments, dendritic spines, perikarya and other terminals. In addition, double and multiple synaptic contacts (synaptic glomeruli), accounting for 10% of the total, were also observed. Quantitative data regarding ultrastructural synaptic elements suggest that there is no preference for post-synaptic sites of fibers related to different sensory modalities such as pain, conveyed by dental fibers or other modalities, conveyed by the inferior alveolar nerve fibers.

Afferent Pathways↗
PubMed1991

Chemical stabilization of a vasoactive S-nitrosothiol with cyclodextrins without loss of pharmacologic activity.

S-Nitrosothiols have been proposed as the endogenous chemical representing the vasoactive endothelium-derived relaxing factor, as well as the active cellular intermediates responsible for the therapeutic action of organic nitrates. The relatively stable analogue S-nitroso N-acetyl penicillamine (SNAP) is a potent vasodilator producing less pharmacologic tolerance than nitroglycerin upon prolonged administration. The therapeutic potential of this new class of vasodilators, however, may be limited by their chemical instability in solution (t1/2 of SNAP is 26 hr in 5% dextrose). We examined the usefulness of several cyclodextrins (CD) to stabilize this polar compound in solution. At cyclodextrin concentrations of 12 mM, hydroxypropyl-beta CD was most effective at stabilizing SNAP (t1/2 = 77 hr) when compared to alpha CD (41 hr), beta CD (69 hr), gamma CD (36 hr), and beta CD-tetradecasulfate (38 hr). Stability constants for the complexation of SNAP with the various cyclodextrins were determined by the classical solubility technique and were found to range from 26 to 435 M-1. Increased complexation brought about better SNAP stability. Complexation of SNAP with cyclodextrins, however, did not decrease the relaxation potency of SNAP as determined in an in vitro blood vessel preparation. Cyclodextrin complexation may be a useful approach to stabilize labile and polar compounds, such as S-nitrosothiols, without loss of pharmacologic activity.

Animals↗
PubMed1991

Regulation of K+ and Ca2+ channels in experimental cardiac failure.

To examine the status of ATP-sensitive K+ (K+ATP) channels and 1,4-dihydropyridine-sensitive Ca2+ (Ca2+DHP) channels during experimental cardiac failure, we have measured the radioligand binding properties of [3H]glyburide and [3H]PN 200 110, respectively, in tissue homogenates from the rat cardiac left ventricle, right ventricle, and brain 4 wk after myocardial infarction induced by left coronary artery ligation. The maximal values (Bmax) for [3H]glyburide and [3H]PN 200 110 binding were reduced by 39 and 40%, respectively, in the left ventricle, and these reductions showed a good correlation with the right ventricle-to-body weight ratio in heart-failure rats. The ligand binding affinities were not altered. In the hypertrophied right ventricle, Bmax values for both the ligands were not significantly different when data were normalized to DNA content or right ventricle weights but showed an apparent reduction when normalized to unit protein or tissue weight. Moderate reductions in channel densities were observed also in whole brain homogenates from heart failure rats. Assessment of muscarinic receptors, beta-adrenoceptors and alpha 1-adrenoceptors by [3H]quinuclidinyl benzilate, [3H]dihydroalprenolol, and [3H]prazosin showed reductions in left ventricular muscarinic and beta-adrenoceptor densities but not in alpha 1-adrenoceptor densities, consistent with earlier observations. It is suggested that these changes may in part contribute to the pathology of cardiac failure.

Animals↗
PubMed1991

Concurrent hydralazine administration prevents nitroglycerin-induced hemodynamic tolerance in experimental heart failure.

BACKGROUND: Organic nitrates such as nitroglycerin and isosorbide dinitrate are useful in the treatment of congestive heart failure (CHF), but tolerance develops rapidly during continuous administration. Because combination therapy of nitrate and hydralazine has been shown to provide both short- and long-term benefit but nitrate alone produces hemodynamic tolerance, we questioned whether hydralazine can preserve the favorable preload effects of nitroglycerin. METHODS AND RESULTS: Using an in vivo model of nitroglycerin tolerance in the CHF rat, we examined the effects of hydralazine bolus dosing during continuous nitroglycerin infusion. Continuous infusion of nitroglycerin alone (10 micrograms/min) produced initial reductions in left ventricular end-diastolic pressure of 40-50%, which returned to baseline by 8 hours (tolerance development). Coadministration of hydralazine (2 x 0.1 mg) maintained the effects of nitroglycerin infusion on left ventricular end-diastolic pressure (45% reduction at 10 hours). This hydralazine dose alone reduced left ventricular peak systolic pressure by approximately 12 +/- 3% but had no effect on left ventricular end-diastolic pressure. Hydralazine dosing did not affect steady-state plasma concentrations of nitroglycerin or metabolites, and hydralazine was unable to prevent nitroglycerin tolerance induced in vitro. CONCLUSIONS: The beneficial interaction of hydralazine on the preload effects of nitroglycerin may explain the long-term clinical efficacy of hydralazine/nitrate combination in CHF. Our results also suggest that the mechanism of in vivo nitrate tolerance in CHF may be systemic rather than vascular in origin.

Animals↗
PubMed1991

Differential hemodynamic effects and tolerance properties of nitroglycerin and an S-nitrosothiol in experimental heart failure.

S-nitrosothiols are potent in vitro vasodilators, but little is known about their in vivo action. In this study, we compared the effects of S-nitroso N-acetyl penicillamine (SNAP) and nitroglycerin (NTG) on left ventricular (LV) hemodynamics in congestive heart failure rats. By using a twoday crossover design, stepwise i.v. infusions of SNAP or NTG at 3, 5 and 8 micrograms/min were administered for 30 min each, followed by a dose of 10 micrograms/min over the next 10 h. LV end-diastolic and peak-systolic pressures (LVEDP and LVPSP, respectively) were measured at selected intervals. SNAP and NTG produced maximal LVEDP reductions of 46 and 44%, respectively, at the highest infusion rate. However, at the lower doses, greater reductions of LVEDP were seen with SNAP. NTG had a smaller effect on LVPSP (maximum 6% reduction) than SNAP (maximum reduction of 15%). During the 10-h infusion of NTG, LVEDP gradually returned to base-line values, indicating the development of tolerance, despite relatively constant plasma levels of NTG over the infusion period. Tolerance in LVEDP effects was not observed during the 10-h infusion of SNAP. In the presence of NTG tolerance, rats were still responsive to SNAP (mean reduction of LVEDP 24%), suggesting the absence of cross-tolerance between these two nitrovasodilators. These results suggest that SNAP is a more potent in vivo vasodilator than NTG, has more arterial action than NTG and is less prone to produce LV hemodynamic tolerance.

Animals↗
PubMed1991

Stereological analysis of the otic ganglia in adult rat: light microscopic study.

Quantifications in parasympathetic ganglia are not available in literature. The otic ganglia of 9 Wistar rats were studied (thick and semi-thin sections) in order to determine the following quantitative data: ganglionic volume (GV), neuronal volume density (Vv), neuronal cellular surface per cell volume (Sv), and neuronal numerical density (Nv). The results showed (mean +/- SD): GV = 0.31 +/- 0.05 mm3, Vv = 39.62 +/- 12.25%, Sv = 0.169 +/- 0.056 microns-1 and Nv = 3.84 x 10(-5) +/- 1.69 x 10(-5) microns-3. These determinations provide a basis for comparisons of parasympathetic with sympathetic ganglia.

Animals↗
PubMed1990

Effects of chronic glyceryl trinitrate on left ventricular haemodynamics in a rat model of congestive heart failure: demonstration of a simple animal model for the study of in vivo nitrate tolerance.

STUDY OBJECTIVE: The aim of the study was to investigate the problem of pharmacological tolerance to nitrate therapy in congestive heart failure, using an animal model. DESIGN: The effects of chronic glyceryl trinitrate infusions were studied in a rat model of congestive heart failure, induced by myocardial infarction, wherein surgical procedures have been developed to permit continuous monitoring of ventricular pressures in conscious animals for up to 4-5 d. SUBJECTS: male Sprague-Dawley rats were used, weight 300-325 g, n = 3-7 per experiment. MEASUREMENTS AND MAIN RESULTS: Glyceryl trinitrate infusion (18 micrograms.kg-1.min-1) in rats with congestive heart failure caused by a 28.5(SEM 3.5)% infarction induced a rapid fall in left ventricular end diastolic pressure from 12.0(0.8) mm Hg to a peak effect of 5.5(0.6) mm Hg within 30 min (n = 7), but rapid attenuation developed beginning about 4 h after the start of the infusion. Complete abolition of the haemodynamic effects of glyceryl trinitrate was observed after 8 h of infusion. After a 12 h wash out period, responsiveness to a new infusion of glyceryl trinitrate (same dose) was restored. Withdrawal of nitrovasodilator dose led to rapid return to baseline left ventricular end diastolic pressure values. Infusion of vehicle to control animals (infarct size not different from treatment group) caused no haemodynamic effects. CONCLUSIONS: The haemodynamic changes caused by glyceryl trinitrate resemble those seen in man and suggest a possible use for this animal model in examining the mechanisms of nitrate action and tolerance.

Animals↗
PubMed1990

Caring as the central focus in nursing curriculum development.

Nursing literature and conferences are advocating a return to the humanistic values and caring approach to people that has been a hallmark of nursing. A theory base for caring in nursing is emerging. Over the past 10 years several research studies in nursing have focused on the concept of caring. Most studies have dealt with defining and understanding the concept of caring and identifying attributes of caring from the perspective of the patient/client and from that of the nurse. New work on caring is looking at teaching of the concept in schools of nursing (Bauer, 1988), the economics of caring (Buerhaus, 1986), the relationship between caring and nurse burnout (Gustafson, 1984), issues of ethics and caring (Fry, 1988 & 1989), to name just a few. The concept of caring is being legitimized as an area appropriate for nurses to study. As nursing educators know, building a program on a strong philosophical base with faculty committed to implementation of the program philosophy is crucial for success of program outcome. Using a caring framework for teaching nursing exposes nursing students to more than an empirical basis for practice. An holistic approach to really understanding people as human beings of value, worth, and having needs becomes the focus of content. To effectively teach caring, faculty must role model the attributes of caring to nursing students. This involves accepting and treating students as having value, worth, and the potential for growth. Faculty must also feel good about themselves and their abilities as teachers. Faculty need to feel confident and comfortable in their role as educators, master their subject matter, and be willing to get involved with students. Faculty development programs, recruitment of faculty espousing a caring philosophy, and mentoring new faculty into their modeling role are important considerations for the effective teaching of caring. Promoting a caring framework for nursing and faculty modeling of caring behaviors and attitudes could affect student recruitment. In our highly technologic society, great emphasis is being placed on person-to-person relationships. Reaffirming the caring nature of nursing to the public and actively promoting these behaviors may make the nursing profession a more attractive and appealing career choice.

Curriculum↗
PubMed1989

A subset of human rosetted lymphocytes contains previously unidentified histamine.

By sequential solid-phase immunoadsorption (panning) steps, we have isolated a subset of lymphocytes (comprising 3-7% of rosetted cells) that contains high concentrations of histamine. We have used a radioenzymatic assay for the determination of histamine and have located 117 ng of histamine/1 x 10(6) cells in Leu-5+ (OKT-11), Leu-15+ cells. This subset did not contain basophils and was negative for Leu-4 (OKT-3), Leu-3 (OKT-4), Leu-2 (OKT-8), and 9.3 antigens. The function of this subset of rosetted cells has not been determined.

Antigens, Differentiation↗
PubMed1989

Cutaneous 10 MHz ultrasound B scan allows the quantitative assessment of burn depth.

Alterations in the epidermis and dermis after a scald burn (deep dermal wound) are sonographically displayed by different echo reflections. Histological slide preparations from various layers of healthy skin were studied to check the ultrasound analysis. Echo reflections of high and low density showed a close correlation to real anatomical structures in the histological slides. The 10-MHz B scan allows the differentiation of 0.1 mm. Heat causes an increase in dermal thickness of between 50 and 100 per cent for the period between 1 and 6 h after injury. Identifying the layers corresponding to the histological slides makes it is possible to measure the distance between the interfaces. This improves the quantitative assessment of both the depth and the area of thermal injury.

Animals↗
PubMed1989

New long-wavelength Nd:YAG laser at 1.44 micron: effect on brain.

A wavelength-shifted Nd:YAG laser, tuned to coincide with the infrared absorption peak of water at 1.44 microns, was used to make lesions in normal rabbit brain. A total of 48 lesions were made with power up to 20 W, with energy up to 40 joules, and with two different spot sizes. These lesions were compared to lesions made with 1.06 microns radiation from an Nd:YAG laser under identical operating conditions. Measurements of blood-brain barrier damage and width, depth, and volume of tissue affected were obtained 30 minutes after placement of the lesions. It was found that 1.44-microns lesions produced photoevaporative tissue loss at the highest intensities used. The layer of coagulated tissue remaining after photovaporization had a mean thickness of 0.6 mm irrespective of the volume of tissue removed. There was no photovaporization in the 1.06-microns lesions. In addition, the amount of peripheral edema per unit volume of tissue coagulated was approximately half at the 1.44-microns wavelength. These findings suggest that the 1.44-microns Nd:YAG laser may be a useful surgical instrument since it combines the photoevaporative effect of the CO2 laser while maintaining the advantages of the conventional Nd:YAG laser (quartz fiber delivery and effective hemostasis).

Animals↗
PubMed1989

Modulation of resynthesis of 1-alkyl-2-arachidonyl-glycero-3-phosphocholine and phosphatidylinositols for interception in vivo of free arachidonic acid, lyso-PAF, diacyl-glycerols, and phosphoinositides.

Thermal injury causes directly a liberation of inositolphosphates, diacylglycerols, free arachidonic acid, and lyso PAF from eukaryotic cells. From lyso PAF derivates PAF, from free arachidonic acid are derivating PG, LT, and TX. These "soluble mediators" are stimulating inflammatory cell populations in a feedback mechanism: the stimulus activates the inflammatory cells to produce the same soluble mediators (Fig.1). The arising soluble mediators are the take off for the inflammation cascade causing as later step the activation of kinin, clotting, and complement systems. The pure biochemical lesions at the onset results in the clinical manifestation of oedema, increased dermal temperature, and pains. The possibilities for prevention and allevation of early pain, due to the acute burn, lie in the inhibition of the spreading out of inflammatory mediators (Bauer 1987a) (Fig.2).

Animals↗
PubMed1988

Immediate rise in intracellular calcium and glycogen phosphorylase a activities upon acetaminophen covalent binding leading to hepatotoxicity in mice.

Drugs and chemicals that cause irreversible damage to cells may do so by producing specific defects in calcium regulation. The present studies examined glycogen phosphorylase as an index for assessing in vivo changes leading to excessive calcium ion activity, a putative pathogen, during the course of acetaminophen-induced liver injury. Administration of 500 mg/kg acetaminophen per os to mice depleted hepatic glutathione to a nadir by 1 h. Covalent binding to hepatocellular macromolecules commenced at this time and then rose out of the non-injurious background range at 1.5 h, coincident with a sharp rise in phosphorylase a activity. Phosphorylase activation preceded the leakage of alanine aminotransferase into plasma by several hours but appeared only after glutathione was depleted in excess of 80%. During the first 3 h, phosphorylase a activity rose in direct proportion to the amount of acetaminophen covalent binding. Glutathione depletion alone was not responsible for phosphorylase activation because the glutathione biosynthesis inhibitor, D,L-buthionine sulfoximine, produced comparable glutathione depletion but failed to stimulate phosphorylase activity or produce cell injury. Because phosphorylase a activity is thought to mirror changes in Ca2+ activity in vivo, these results support the hypothesis that acetaminophen-induced hepatocellular injury is related to the impairment of Ca2+ regulation.

Acetaminophen↗
PubMed1988

Fine structure and quantitative study in the otic ganglia of the rat.

Observations were concentrated on the ultrastructure of perikarya and satellite cells of the otic ganglion of the adult rat. Characteristics of both cell types were morphologically analysed as well as their relationship. Quantitative data concerning the volumetric density were calculated for the following elements of the ganglion: glial cells together (28.5%), unmyelinated fibres (13.4%), myelinated fibres (2.7%), connective tissue (13.6%). This electron microscopic study is a sequence of our previous light microscopic study which determined neuronal densities (COSTA, MANDARIM-DE-LACERDA and BAUER, in press).

Animals↗
PubMed1986

The location of the preganglionic neurons that innervate the submandibular gland of the cat. A horseradish peroxidase study.

Horseradish peroxidase was injected under pressure in the main excretory duct of the submandibular gland of cats, to locate the perikarya of the preganglionic parasympathetic salivatory neurons in the brainstem. Labeled multipolar neurons were found ipsilaterally in the lateral reticular formation, where they extended from the rostral plane that contains the genu of the facial nerve to the caudal plane that contains the rostral pole of the dorsal motor nucleus of the vagus nerve.

Animals↗