Showing papers by "Baylor College of Medicine published in 1976"

Left ventricular compliance: mechanisms and clinical implications.

Abstract: Left ventricular diastolic compliance is determined by the level of operating pressure and the diastolic pressure-volume relation. This relation is curvilinear and the slope of a tangent (operative chamber stiffness) to the pressure-volume curve increases as the chamber progressively fills. Such preload-dependent changes in compliance occur during any acute alteration in ventricular volume. At a given diastolic pressure, operative chamber stiffness (or its reciprocal, operative chamber compliance) is determined by the relative values for ventricular volume and muscle mass and by the stiffness of a unit of myocardium. Thus, there may be a leftward shift of the diastolic pressure-volume curve (increase in the modulus of chamber stiffness) as a consequence of ventricular hypertrophy or an increase in the stiffness of heart muscle itself (increase in modulus of muscle stiffness). To distinguish between hypertrophy and stiff muscle, it is useful to examine the modulus of chamber stiffness, derived from pressure-volume data, together with the volume/mass ratio of the ventricle. In this fashion, changes in the modulus of chamber stiffness that are inappropriate for a given volume/mass ratio may be attributed to changes in the material properties of the heart muscle. Examples of clinical and experimental pressure-volume studies are presented to illustrate the variety of mechanisms by which acute and chronic changes in ventricular chamber compliance evolve during the course of clinical heart disease. The pathophysiology of pulmonary congestion is best understood by considering the factors responsible for producing changes in chamber stiffness of the ventricle, whereas an examination of muscle stiffness is likely to provide more insight into the extent of irreversible functional and structural defects of the myocardium.

Influence of acute changes in preload, afterload, contractile state and heart rate on ejection and isovolumic indices of myocardial contractility in man.

Abstract: To determine the sensitivity of several isovolumic and ejection phase indices of myocardial contractility to loading, inotropic stimulation and heart rate in man, 14 patients (pts) were studied during cardiac catheterization with simultaneous recordings of left ventricular (LV) pressures and ultrasound dimensions. Measurements were made of instantaneous and mean circumferential fiber shortening velocity (VCF), maximal (max) rate of LV pressure rise (dP/dt), dPHdt divided by end-diastolic circumference [(dP/dt)/C], (DP/dt)/C divided by aortic valve opening pressure [(dP/dt/CP], PEAK CONTRACTILe element velocity (VCE) using total LV pressure, VCE extrapolated to zero total pressure (Vmax), VCE at a developed pressure of 10 mm Hg (VCEDP10) and dP/dt at a common isovolumic developed pressure of 40 mm Hg [(dP/dt)/DP40]. Resulta are expressed in per cent change of the mean for the group. Acute preload increase (8.6% increase in end-diastolic circumference) with volume expansion at constant heart rate in 7 pts produced insignificant changes in VSF, an 8.3% increase in max dP/dt, no change in (dP/dt)/C, a variable response in (dP/dt)/CP, 18% reduction in peak VCE, 16% reduction in Vmax, 14% increase in VCEDP10, and a 10% increase in (dP/dt)/DP40. An acute increase in afterload produced by angiotensin in 8 pts (44% increase in peak stress) led to a 38% decrease in VCF, a 2.5% increase in max dP/dt, no significant change in (dP/dt)/C, a 26% reduction in (dP/dt)/CP, variable responses in peak VCE and Vmax, an 11% increase in VCEDP10 and minor changes in (dP/dt)/DP40. All of the contractility indices were augmented significantly by isoproterenol and atrial pacing. In a given patient, max, dP/dt appears to be useful in the assessment of acute changes in inotropic state since the magnitude of its response to abrupt changes in preload is small and to afterload insignificant. Normalizing max dP/dt for end-diastolic circumference assures better stability during loading with good sensitivity to inotropic stimulation. VCF may be used whenever changes in afterload are minimal. The isovolumic measurements of VCE (regardless of whether total or developed pressure is used) lack sufficient stability during acute changes in loading conditions to warrant their use in the quantitative assessment of acute changes in inotropic state.

Effect of sediments on the survival of Escherichia coli in marine waters.

Abstract: Escherichia coli, a fecal coliform, was found to survive for longer periods of time in unsterile natural seawater when sediment material was present than in seawater alone, and at least on one occasion growth was observed to occur This enteric bacterium was found to increase rapidly in number in autoclaved natural seawater and autoclaved sediment taken from areas receiving domestic wastes, even when the seawater had salinities as high as 34 g/kg However, in autoclaved seawater, growth was always more gradual and never reached numbers as high as those observed when sediment was present It was found that nutrients were easily eluted from the sediment after autoclaving or upon addition to artificial seawater, but little elution occured during mixing of the sediments with unsterile natural seawater The longer survival of E coli in the sediment is attributed to the greater content of organic matter present in the sediment than the sweater These laboratory results, in part, could explain why on a volume basis larger numbers of coliforms and fecal coliforms and fecal coliforms were found in estuarine sediments than the overlaying water at field sites

Control of Uterine Estrogen Receptor Levels by Progesterone

Abstract: The mechanism by which progesterone antagonizes estrogenic stimulation of uterine growth was examined in the immature rat. Rats received daily injections of 2.5 µg estradiol (E) for 2 days and on day3 either 2.5 pig E or 2.5 µg E plus 2.5 mg of progesterone (P). The quantity of nuclear andcytoplasmic estrogen receptor was determined by [3]] estradiol exchange at various intervals after injection of E or E + P. In both groups, nuclear receptor-estrogen complex (RnE) increased dramatically one hour after injection and showed a gradual decline from 4 to 24 h after injection. The quantity of cytoplasmic receptor, Rc decreased to low levels by one hour and began a gradual increase from 4 to 8 h in both groups. However, between 8 and 24 h after injection, the level of Rc continued to increase in the E treatment group (2.39 ± 0.21 pmol⁄uterus at 24 h) but remained at the 8 h level in the E ± P group (1.09 ±0.04 pmol⁄uterus at 24 h). This observation suggests that two separate processes are involved in the replen...

Photoreceptor shedding is initiated by light in the frog retina.

Abstract: Frogs maintained on a diurnal light-dark cycle (14 hours light and 10 hours darkness) shed their rod photoreceptor outer segment tips shortly after the onset of light. Shedding is synchronous and occurs in about 25 percent of the rod photoreceptors each day. Prolonged exposure to total darkness decreases the amount of shedding, after which exposure to light results in a large burst of synchronous shedding. Thus in the frog retina, the synchronous shedding of rod outer segment tips is shown to be directly related to light stimulation.

Follicle-stimulating hormone, the Sertoli cell, and spermatogenesis.

Abstract: Publisher Summary This chapter reviews the current state of knowledge of the effects of follicle-stimulating hormone (FSH) on the testis and the elucidation of a specific target cell for this hormone. It also discusses the possibility that this hormone might play a role in the regulation of spermatogenesis in mammals. There is no doubt that FSH initiates a series of biochemical events in the testis of immature rats. These effects are confined to cells within the seminiferous epithelium. It is necessary to elucidate the target cell that is acted upon by this hormone to directly demonstrate a role of FSH. The chapter presents a diagram representing a temporal sequence of events that are initiated by FSH interacting with the testes of immature animals. This hormone first binds to specific receptors present on membranes of target cells with resultant stimulation of the adenylate cyclase system. This leads to an increase in intracellular concentration of cyclic adenosine monophosphate (cAMP), that in turn activates soluble protein kinase. The enhanced catalytic activity of this enzyme is responsible for increased phosphorylation of a variety of proteins. These proteins are postulated to play a role in underwriting the subsequent biochemical effects of this gonadotropin. The chapter also discusses elucidation of the sertoli cell as a primary target for FSH, androgen-binding protein as an end-point marker for assessing FSH action in sertoli cells, the sertoli cell as an androgen target cell, and isolation and translation of messenger RNA (mRNA) from sertoli cell-enriched testis.

Calcium release from skeletal muscle sarcoplasmic reticulum: site of action of dantrolene sodium

Abstract: The muscle relaxant dantrolene sodium acts directly and specifically on skeletal muscle, unlike other pharmacological agents which affect the central nervous system or act at the nueromuscular junction. Dantrolene sodium markedly suppresses the release of calcium previously sequestered by skeletal, but not cardiac, muscle sarcoplasmic reticulum. No effect in the total amount of calcium accumulated was found. In situ, the drug may reduce the amount of calcium necessary for muscle contraction.

Nuclear retention of receptor-oestrogen complex and nuclear acceptor sites

Abstract: Nuclear retention of receptor-estrogen complex and nuclear acceptor sites are discussed. Evidence that a limited number of receptor-estrogen complexes are bound in the nucleus of rat uterine cells and that these sites may be specific nuclear acceptor sites is presented. Salt extraction of uterine nuclei was used to test the hypothesis that long-term retention of the receptor-estrogen complex in the nucleus is due to the binding of these complexes to a limited number of nuclear acceptor sites and that retention at these acceptor sites for more than 4-6 hours is a requirement for true growth. The number of potassium chloride-resistant nuclear sites was identical to the number of sites required for maximal uterine growth therefore it is proposed that these binding sites in the nucleus represent specific acceptor sites.

Nuclear magnetic resonance patterns of intracellular water as a function of HeLa cell cycle.

Abstract: Nuclear magnetic resonance relaxation time (T1) of the intracellular water protons and water content were measured in synchronized HeLa cells. The T1 was maximum (1020 milliseconds) in mitotic and minimum (534 milliseconds) in S phase cells. The cyclic pattern of T1 values correlated well with the chromosome condensation cycle. By treating cells with spermine, it was possible to alter T1 without a significant change in the water content. The results of this study suggest that an additional variable, namely, the conformational state of macromolecules, should be incluced in any expression explaining the shortened relaxation times of water protons in biological systems.

Concentration of viruses from large volumes of tap water using pleated membrane filters.

Abstract: A method is described for the efficient concentration of viruses from large volumes of tap water in relatively short time periods Virus in acidified tap water in the presence of aluminum chloride is adsorbed to a 10-inch (ca 254 cm) fiberglass depth cartridge and a 10-inch pleated epoxy-fiberglass filter in series at flow rates of up to 378 liters/min (10 gallons/min) This filter series is capable of efficiently adsorbing virus from greater than 19,000 liters (5,000 gallons) of treated tap water Adsorbed viruses are eluted from the filters with glycine buffer (pH 105) and the eluate is reconcentrated using an aluminum flocculation process Viruses are eluted from the aluminum floc with glycine buffer (pH 115) Using this procedure, viruses in 1,900 liters (500 gallons) of tap water can be concentrated 100,000-fold in 3 h with an average recovery of 40 to 50%

Thymidine kinase, DNA synthesis and cancer

Abstract: A resume has been presented of some recent investigations which show that DNA synthesis can be initiated in many types of quiescent animal cells by external stimuli, by introducing a quiescent nucleus into the cytoplasm of a proliferating cell, or by a virus infection. The components of the DNA replication apparatus are described. It is shown that deoxyribonucleoside triphosphate pools increase substantially in animal cells at the time DNA synthesis is initiated due to the enhanced activities of enzymes functioning in nucleotide synthesis. Especially striking is the increase of thymidine kinase activity, indicating that this enzyme may be a useful marker of the shift from the quiescent to the replicative state. The thymidine kinase isozymes of vertebrate cells have been characterized. Thymidine kinase F, which is found principally in the cytosol, is the isozyme that increases when G1(Go) phase cells are stimulated or infected with oncogenic viruses. Chick cytosol thymidine kinase F can also be reactivated by introducing differentiated chick erythrocyte nuclei into the cytoplasm of enzyme-deficient LM(TK−) mouse cells. Furthermore, herpesviruses code for distinctive, virus-specific thymidine kinase isozymes, so that another way to transform thymidine kinase-deficient LM(TK−) cells to kinase-positive cells is by infecting them with UV-irradiated herpes simplex viruses. The experiments on the activation of DNA synthesis and thymidine kinase F activity have been discussed in the context of the proliferative activityin vivo and the immortalization in culture of neoplastic cells. These experiments suggest that genes determining cell cycle proteins are readily accessible to transcription and translation in essentially all nucleated cells. The tendency of transformed cells to become multinucleated after cytochaliasin B treatment also suggests that one important difference between malignant cells and most normal cells may be the ability of malignant cells to ‘stockpile’ the proteins (and/or their messenger RNAs) of the DNA replicative apparatus and to maintain the ‘stockpiles’ in progeny cells.

Energy dose for ventricular defibrillation of children.

Abstract: Transthoracic direct current shock is the recommended treatment for ventricular fibrillation in children as in adults. To determine the appropriate energy dose, data were collected from 71 defibrillation attempts in 27 children. Sixty-three of the 71 shocks (89%) were successful in terminating fibrillation. Fifty-seven shocks were within 10 watt-seconds (w-sec) above or below an energy dose of 2 w-sec/kg of body weight. Fifty-two (91%) of these were effective and five (9%) were ineffective. In every case, fibrillation was ultimately terminated by a shock of 4 w-sec/kg or less. The results of these studies suggest that an energy dose of 2 w-sec/kg (or approximately 1 w-sec/lb) is adequate to defibrillate most children weighing under 50 kg. We currently use 2 w-sec/kg and double the energy dose if the first defibrillation attempt is unsuccessful.

Left atrial enlargement. Echocardiographic assessment of electrocardiographic criteria.

Abstract: A comparison of electrocardiographic manifestations of left atrial enlargement (LAE) and left atrial size by echocardiography was made in 307 patients in sinus rhythm. Electrocardiographic criteria used were L:P wave duration in lead II equal to or greater than 0.12 sec; Va: the ratio of the duration of negative terminal P in V1 to the P-R segment equal to or greater than 1.0; Vb: a negative P terminal force in V1 less than -0.03 mm sec. The echocardiographic diagnosis of left atrial enlargement was based on 1) transverse dimension greater than 4.0 cm; or 2) a ratio of transverse atrial to transverse aortic root dimension greater than 1.17. In the presence of left atrial enlargement, a combination of criteria occurred more often than a single criterion. The overall predictive index of the electrocardiogram for left atrial enlargement was 63% (excluding criterion Vb raised probability to 80%); and that for absence of left atrial enlargement was 78%. The index of coarse versus fine fibrillary waves was unreliable in predicting left atrial enlargement. Changes in P wave morphology may be used as a reasonably specific but less sensitive indicator of left atrial enlargement.

Biochemical actions of follice-stimulating hormone in the sertoli cell of the rat testis.

Abstract: The sequence of biochemical events associated with the action of follicle-stimulating hormone (FSH) in the testis has been investigated using a Sertoli cell-enriched testis model system. The Sertoli cell-enriched testis, created by irradiation of male rats in utero, is devoid of germinal elements but contains a normal complement of supportive Sertoli cells. Comparison of the Sertoli cell-enriched testis with normal testis, demonstrates that the two types of testes contain equal numbers of FSH specific receptors, judged by the binding of labeled hormone. In addition, FSH over a concentration range from 6 × 10-11 to 6 × 10-9M will stimulate the production of adenosine 3′,5′monophosphate (cAMP) in the Sertoli cell-enriched testis in a manner indistinguishable from that of the normal testis. Incubation of Sertoli cell-enriched testis also results in the activation of soluble cAMPdependent protein kinase. This response to FSH is dependent upon the age of the animal and disappears at about 32 days of age. While...

Bone Concentrations of Antimicrobial Agents After Parenteral Administration

Abstract: Bone concentrations of seven antimicrobial agents were determined after parenteral administration. Antibiotics were administered in large doses at customary intervals for 12 to 20 h before total hip or knee replacement; anticipated levels of each drug were achieved in the serum. Methicillin, carbenicillin, and clindamycin were detected in bone with greatest frequency. Cefazolin and gentamicin were each detected in bone specimens from only one of four patients. Neither penicillin G nor cephalothin was present in bone in sufficient quantity to be measurable. These data suggest that a number of factors, in addition to serum concentration, affect concentration of antimicrobial agents in bone. The clinical significance of the relationship between bone concentrations of antibiotics and therapeutic outcome is not certain.

Regional cerebral blood flow in the diagnosis of vascular headache.

Abstract: SYNOPSIS Potential availability of a reliable non-invasive system for measuring regional cerebral blood flow (rCBF)prompted measurement of rCBF in patients with vascular headache in order to assess its diagnostic value. The rCBF in migraine varied with the clinical phase. During the prodrome phase the blood flow was reduced; whereas during the headache phase, a striking cortical hyperperfusion was noted. Patients who continued to have neurologic symptoms of the prodrome in the headache phase showed a mixed pattern of reduced and increased blood flow. The rCBF was found normal in the headache phase in patients with muscle contraction and psychogenic headache. In patients with headache as a prominent symptom of cerebrovascular insufficiency, rCBF was reduced but was not significantly different from rCBF in patients with cerebrovascular insufficiency without headache.

Pneumomediastinum in heroin and marijuana users

Abstract: During the past three years, more than 500 patients were seen with mediastinal or cervical emphysema or both the Ben Taub General Hospital Emergency Center. In all but 15 there was a history of recent trauma or antecedent respiratory conditions with repeated sustained intrabronchial pressure, such as asthma. These 15 patients had a common history of repeated sustained Valsalva's maneuvers during marijuana smoking or during intravenous injections of heroin. The results of esophagography, bronchoscopy, and esophagoscopy were normal in these 15 patients. Conservative management consisted of close observation and re-evaluation for possible causes of secondary pneumomediastinum. All recovered without sequelae with resolution of the pneumomediastinum within 2 to 5 days. Radiographic and physical findings in primary pneumomediastinum resulting from prolonged intraalveolar hyperpressure are similar to those seen in patients with trauma or spontaneous rupture of the esophagus.