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Biomedical subjects

C S Hall

Publications and source records attributed to C S Hall.

At least 37 records · Page 2Linked to original sources
PubMed1998

Nutrient requirements for dairy cattle of the National Research Council versus some commonly used ration software.

The first edition of the Nutrient Requirements of Dairy Cattle was published by the National Research Council (NRC) in 1945. The current document is the sixth revised edition, published in 1989, and it appears that we are a few years from another edition being in print. Software designed to evaluate and formulate rations for dairy cattle commonly determine nutrient requirements using the NRC as a standard. However, the generation of new knowledge in dairy nutrition occurs more rapidly than the release of the NRC publication, and the developers of the software often modify the requirements based on more recently published research, geographical peculiarities, or factors not explicitly considered by NRC. The first step in evaluating or formulating rations is the prediction of dry matter intake (DMI). The primary variables used by NRC to predict DMI are body weight (BW) and fat-corrected milk (FCM) yield; however, developers of software programs often use different equations based on personal preference, availability of research data with given equations, and incorporation of other factors in addition to BW and FCM yield. The additional factors are included to provide a more dynamic estimation of DMI and, therefore, reduce the difference between predicted and actual DMI. Nutrients required for maintenance, lactation, and growth must be consumed in adequate quantities (e.g., kilograms or calories), but the dietary concentration of nutrients for a given animal group may differ because of DMI. Even when nutrients are fed above the requirements, dietary concentrations of nutrients may be important in some situations to minimize the risk of underfeeding caused by variability in the nutrient composition of feedstuffs and to account for interactions of certain nutrients (e.g., minerals). New research discoveries need to be incorporated into ration formulation strategies promptly, and the strategies used for ration formulation need to be dynamic.

Animal Nutritional Physiological Phenomena↗
PubMed1997

Comparison of integrated backscatter values obtained with acoustic densitometry with values derived from spectral analysis of digitized signals from a clinical imaging system.

Time-domain-based integrated backscatter values obtained with the use of acoustic densitometry (AD) were compared with values determined from a spectral-based analysis of the radio-frequency (RF) signals with a modified Hewlett-Packard Sonos 1500 imaging system. Integrated backscatter images of five specimens of bovine tendon were acquired in the AD acquisition mode, and the corresponding signals related to the backscattered RF were digitized for each angle of insonification as the specimens were rotated in 10-degree increments. The integrated backscatter images were analyzed with the AD analysis package, and the corresponding values determined from the RF power spectra were obtained from the digitized ultrasonic signals. Good agreement was found between the two methods over the entire range of measured values. The mean anisotropy in the measured integrated backscatter (mean +/- standard error) was found to be 27 +/- 2 dB for time-domain-based analysis and 25 +/- 2 dB for RF spectral-based analysis.

Acoustics↗
PubMed1997

Angiotensin II receptor blockade in Syrian hamster (T0-2) cardiomyopathy does not affect microscopic cardiac material properties: implications for mechanisms of tissue remodeling.

This study delineates the role of angiotensin II type I (AT1) receptor in the remodeling of Syrian cardiomyopathic hamsters. Twelve cardiomyopathic (T0-2) hamsters received L-158,809 treatment and libitum in their drinking water (27 micrograms/ml) and 9 cardiomyopathic and 9 normal FL-B hamsters received tap water from 1 to 4 months of age. Although pharmacologically effective with regard to complete suppression of the blood pressure response to angiotensin II infusion, L-158,809 did not diminish the progression or severity of cardiomyopathy. Heart weight/100 g body weight and left ventricular wall thickness adjusted for body weight of both L-158,809 and cardiomyopathic control hamsters did not differ and exceeded those of F1-B controls (p < 0.05). Myocardial material properties (e.g., stiffness and density) of cardiomyopathic hamsters treated with L-158,809 were not affected. Thus, the progression of fibrosis, calcification, and necrosis in T0-2 cardiomyopathic hamsters was not sensitive to AT1 receptor blockade.

Angiotensin II↗
PubMed1997

Anisotropy of the apparent frequency dependence of backscatter in formalin fixed human myocardium.

Measurements of the frequency dependence of ultrasonic backscatter are presented for specific angles of insonification for regions of infarcted and noninfarcted human myocardium. A 5-MHz transducer was used to insonify cylindrical cores taken from 7 noninfarcted regions and 12 infarcted regions of the left ventricular free wall of 6 formalin-fixed human hearts explanted because of ischemic cardiomyopathy. The dependence of apparent (uncompensated for diffraction effects and attenuation) backscatter on frequency was approximated by a power-law dependence, magnitude of B(f)2 = afn. Under ideal conditions in a lossless medium, the effect of not compensating for the effects of diffraction and attenuation leads to the value of n to be 2.0 for Rayleigh scatterers while the frequency dependence of the fully compensated backscatter coefficient would be f4. The value of n was determined over the frequency range, 3-7 MHz. Both nonifarcted and infarcted myocardium exhibited anisotropy of the frequency dependence of backscatter, with maxima occurring at angles that were perpendicular to the predominant myofiber direction and minima when parallel to the fibers. Perpendicular insonification yielded results for n of 1.8 +/- 0.1 for noninfarcted myocardium and 1.2 +/- 0.1 for infarcted myocardium while parallel insonification yielded results of 0.4 +/- 0.1 for noninfarcted and 0.0 +/- 0.1 for infarcted myocardium. The functional form of the angle-dependent backscatter is similar for both noninfarcted and infarcted myocardium, although the frequency dependence is clearly different for both tissue states for all angles of insonification. The results of this study indicate that the anisotropy of the frequency dependence of backscatter may play a significant role in ultrasonic imaging and is an important consideration for ultrasonic tissue characterization in myocardium.

Anisotropy↗
PubMed1997

Inorganic phosphate as regulator of adenosine formation in isolated guinea pig hearts.

This study evaluated cytosolic P(i) as an independent regulator of cardiac adenosine formation by dissociating changes in P(i) from changes in AMP and ADP. Myocardial high-energy phosphates (HEP), measured by (31)P nuclear magnetic resonance spectroscopy, were depleted acutely by perfusing isolated guinea pig hearts with 2-deoxyglucose (2-DG), and the effects of 2-DG were compared with a norepinephrine infusion producing similar changes in HEP. 2-DG treatment resulted in lower adenosine release (R(ado)) (54 +/- 18 vs. 622 +/- 199 pmol x min(-1) x g(-1)) and P(i) concentration ([P(i)]) (0.5 +/- 0.1 vs. 6.0 +/- 0.9 mM) than norepinephrine despite similar AMP concentration ([AMP]). Chronic phosphocreatine depletion produced by beta-guanidinopropionic acid feeding also reduced R(ado) and P(i) during hypoxia. Replacement of perfusate glucose and pyruvate with acetate increased R(ado) (from 39 +/- 12 to 356 +/- 100 pmol x min(-1) x g(-1)) and [P(i)] (from 2.0 +/- 0.5 to 5.1 +/- 0.6 mM) with no change in cytosolic [AMP]. Adenosine kinase isolated from guinea pig hearts was inhibited by [P(i)] values seen during hypoxia or hypoperfusion. We conclude that cytosolic [P(i)] can be an important regulator of cardiac adenosine formation through inhibition of adenosine kinase.

Acetates↗
PubMed1997

Targeting of ultrasound contrast material. An in vitro feasibility study.

PURPOSE: It would be beneficial to design a targetable microbubble ultrasound contrast agent that would selectively bind to the areas of interest in the body and enhance the target organ in the ultrasound examination. MATERIAL AND METHODS: We have studied the feasibility of targeting in a model system. We used avidin and biotin as a model ligand-receptor pair. Avidin was adsorbed on the surface of polystyrene, and biotin derivative was attached to microbubble shells. After removal of unincorporated biotin from the microbubbles, they were allowed to come in contact with avidin-coated or albumin-coated plastic. Unbound bubbles were washed by a stream of water. RESULTS: Binding of microbubbles to the surface occurred selectively in the areas where avidin layer was deposited. Binding of microbubbles to avidin layer was dependent on the amount of biotin incorporated in the microbubble shell. Presence of free biotin blocked targeting completely. Acoustic studies were performed using a custom-built ultrasound measurement apparatus and an ultrasound medical imaging system. Microbubble-coated areas of the plastic dish were clearly visualized with ultrasound imaging. A strong backscattered signal was obtained for microbubble surface densities as low as 3%. CONCLUSION: Microbubbles have been selectively targeted via a ligand-receptor system in vitro. Firm binding of microbubbles to avidin-coated surface has been achieved. Microbubbles deposited on the target were visualized with ultrasound imaging systems.

Animals↗
PubMed1995

Ultrasonic tissue characterization of end-stage dilated cardiomyopathy.

The clinical use of angiotensin-converting enzyme (ACE) inhibitors now represents the standard of care for the treatment of chronic congestive heart failure. We utilized ultrasonic tissue characterization to define potentially salutary effects of treatment with ACE inhibitors on the material properties of the heart and its potential influence on cardiac remodeling at the cellular level. Ten 1-month-old cardiomyopathic (CM) Syrian hamsters were treated with captopril (2 g/L water ad libitum), and 10 CM and 5 normal hamsters were maintained untreated for 9 months. Hearts were excised, and backscattered radio-frequency data were acquired from 1200 independent sites from each specimen with a high-resolution 50-MHz acoustic microscope for calculation of integrated backscatter. Treatment with captopril elicited relative decreases in left ventricular (LV) wet weight, LV calcium concentration and integrated backscatter (IB) in treated as compared with untreated cardiomyopathic hearts without affecting LV collagen concentration. The IB from hearts of treated cardiomyopathic hamsters was significantly less in both grossly normal regions of myocardium (P < 0.02) and scar tissue regions (P = 0.0005) as compared with IB from hearts of untreated hamsters. The reduced integrated backscatter from hearts of treated cardiomyopathic hamsters indicates direct alterations in the material properties of cardiomyopathic hearts after captopril therapy. The lower IB from scar tissue in the treated animals was associated with decreased scar tissue calcification, which represents a novel therapeutic effect of captopril. This is the first report that delineates direct effects of ACE inhibitors on the material properties of both scar tissue and grossly normal myocardium at the cellular level in experimental dilated cardiomyopathy.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin-Converting Enzyme Inhibitors↗
PubMed1995

A proposed microscopic elastic wave theory for ultrasonic backscatter from myocardial tissue.

The physical structures responsible for ultrasonic scattering from myocardial tissue have not yet been conclusively defined. It is hypothesized in this paper that the backscatter from myocardium is primarily due to inhomogeneities approximately the size of the myocytes. In particular, it is proposed that the acoustic contrast responsible for the scattering is that between the extracellular collagen network that surrounds each myocyte (or myocyte bundle) and the rest of the tissue (the myocytes' intracellular contents). To test this hypothesis, a simple elastic wave scattering model for myocardium was developed. An elementary scatterer is modeled as an ellipsoidal shell, having the material properties of wet collagen, imbedded in a host medium having the average properties of myocardium. The first Born approximation to elastic scattering is used to calculate the frequency-dependent scattering from a single scatterer. To scale up from a single scatterer to a distribution of scatterers, it is assumed that the power received at the transducer is simply the sum of the power scattered in the direction of the transducer by each individual scatterer located in the active volume of the beam (an independent-scatterer approximation). Calculations are restricted to the backscattering direction (pulse-echo), although the theory can accommodate pitch-catch scattering at all angles. With the aid of a computer program, the acoustic backscatter coefficient is calculated using the Born formalism and then measurement effects (frequency-dependent beam width and attenuation correction factors) are incorporated to arrive at calculated integrated (frequency-averaged) backscatter. Both the backscatter coefficient and integrated backscatter are calculated for angles of incidence that range from parallel to the long axis of the scatterer to perpendicular to this fiber direction. For the low MHz frequencies typically used in clinical echocardiography, the calculated absolute magnitude of the acoustic backscatter coefficient lies within a range from 0.0001 to 0.001 cm-1 sr-1. For selected fiber geometries, the anisotropy in integrated backscatter as the angle of incidence is varied with respect to the fiber orientation is about 10 dB. The predicted frequency dependence of the acoustic backscatter coefficient is calculated to be about f3.9 in the low MHz frequency range. These calculated results are reasonably consistent with published experimental measurements and provide a successful preliminary test of the hypothesis.

Acoustics↗
PubMed1994

Cellular mechanisms of captopril-induced matrix remodeling in Syrian hamster cardiomyopathy.

BACKGROUND: Although angiotensin-converting enzyme (ACE) inhibitors have become a mainstay of treatment for chronic congestive heart failure (CHF), it is not known whether the cardiac remodeling effects are a secondary phenomenon, resulting from ACE inhibitors' hemodynamic actions of afterload reduction, or occur through an independent mechanism. METHODS AND RESULTS: We used ultrasonic tissue characterization to define potentially salutary effects of treatment with ACE inhibitors on the material properties of the heart and its potential influence on cardiac remodeling at the cellular level. Ten 1-month-old, cardiomyopathic (CM) Syrian hamsters and 6 normal (NL) hamsters were treated with captopril (2 g/L water ad libitum), and 10 CM hamsters and 10 NL hamsters were maintained untreated for 3 months. Hearts were excised, and backscattered radiofrequency data were acquired from 1200 independent sites from each specimen with a high-resolution 50-MHz acoustic microscope for calculation of integrated backscatter (IB). Treatment with captopril reduced left ventricular mass, calcium concentration, and IB in CM hearts without affecting myofiber size or collagen concentration. The IB from grossly normal regions of myocardium in NL hamsters, treated CM hamsters, and untreated CM hamsters was not significantly different. The IB from the microscopic regions of scar tissue in treated CM hamsters was significantly less (P = .0004) than that from scar tissue in untreated CM hamsters. CONCLUSIONS: The reduced IB from treated scar tissue components reflects specific alterations in the material properties (elastic stiffness, density) of fibrous regions in CM hearts induced by captopril. This is the first report that defines specific cellular effects of ACE inhibitors on the material properties of isolated components of cardiac tissue in experimental cardiomyopathy. These alterations in material properties of scar tissue components represent a potential mechanism for the salutary actions of ACE inhibitors in heart failure.

Animals↗
PubMed1984

"A ubiquitous sex difference in dreams" revisited.

Males dream more often of males than females do. This sex difference was found in 29 comparisons of male and female dreams. It holds for children, adolescents, college students, and adults in all parts of the world; and for dreams collected in the laboratory, as well as dreams reported under nonlaboratory conditions. Various explanations for this ubiquitous sex difference are discussed.

Adolescent↗
PubMed1981

The Narcissistic Personality Inventory: alternative form reliability and further evidence of construct validity.

The aim of this study was twofold: (a)to measure the alternate form reliability of the Narcissistic Personality Inventory, and (b)to determine its construct validity by correlating it with the four scales of the Eysenck Personality Questionnaire (EPQ). The alternate form reliability was .72. The Extraversion and Psychoticism scales of the EPQ were positively and significantly correlated with the narcissism measure, and the Lie scale showed a significant negative correlation. The Neuroticism scale showed a nonsignificant relationship with narcissism. In addition, the combined Extraversion and Psychoticism scales produced[ a Multiple R with the narcissism measure that accounted for significantly more of the variance in narcissism than did either measure alone.

Journal Article↗
PubMed1978

5alpha-reductase activity of genital and nongenital skin fibroblasts from patients with 5alpha-reductase deficiency, androgen insensitivity, or unknown forms of male pseudohermaphroditism.

Serially subcultured fibroblast strains from genital (foreskin, labium majus) skin, as a group, have considerably more steroid (testosterone) 5alpha-reductase activity than those form nongenital skin. Foreskin strains varied 40-fold and labial strains even more. Labial strains overlapped nongenital strains of either sex more frequently than did prepuce strains. The activity of foreskin strains from two siblings with proven 5alpha-reductase deficiency was clearly lower than that of any of 18 control stains. The comparative behavior of the various strain types indicates that labial and nongenital strains should not be used to support a clinical suspicion of male pseudohermaphroditism due to 5alpha-reductase deficiency. The activities of labial strains from patients with complete androgen insensitivity (testicular feminization) - five with the receptor-negative variety and two with the receptor-positive type - were as variable as those of control labial strains. The decreased 5alpha-reductase activity observed in fresh skin slices of some patients is probably and expression of their functional estrogen/androgen imbalance in vivo.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1978

Steroidogenic activity of hACTH and related peptides on the human neocortex and fetal adrenal cortex in organ culture.

Explants prepared from the neocortex and the fetal zone of the human fetal adrenal (gestational age 13 to 18weeks) were maintained under conditions of organ culture for 7 to 9 days during which time they were exposed to hACTH and various related peptides. Corticotrophic activity was monitored by the daily release of dehydroepiandrosterone sulfate (3beta-hydroxy-5-androsten-17-one, 3-sulfate; DHA-S) and cortisol as quantified by radioimmunoassay, hACTH (2.2 x 10(-9) - 2.2 x 10(-8)M) was the most active in sustaining steroidogenesis by both neocortical and fetocortical cells. alpha-MSH possessed similar properties but not at concentrations lower than 10(-6)M, whereas CLIP (4.4 x 10(-9) - 1.1 x 10(-7)M), the 18-39 C-terminal moiety of ACTH, was devoid of activity. Corticotrophic activity with respect to fetocortical explants appeared to be that of maintenance of function best illustrated by dehydroepiandrosterone sulfate biosynthesis, while enhancement of steroidogenesis was observed in the neocortex as manifested by cortisol release. Although not eliminating the possible existence of a specific fetal corticotrophin related to ACTH1-39, the data indicate that hACTH is capable of regulating steroidogenesis in the fetal zone which is primarily geared to the formation of dehydroepiandrosterone sulfate.

Adrenal Cortex↗
PubMed1977

Exploration of the human fetal pituitary adrenal axis: stimulation of cortisol and dehydroepiandrosterone sulfate biosynthesis by homologous pituitary in organ culture.

Adrenals obtained from human abortices at midpregnancy were kept under conditions of tissue culture and the production of cortisol and dehydroepiandrosterone sulfate (3beta-hydroxy-5-androsten-17-one, 3-sulfate; DHA-S) monitored by radioimmunoassays for up to 2 weeks. Basal production of dehydroepiandrosterone sulfate was considerably higher than that of cortisol. alpha1-24corticotrophin, alpha1-39corticotrophin, (a long acting porcine corticotrophin) at the concentration of 1 mU/ml of culture medium in both instances, and dibutyryl cyclic AMP (1mM) enhanced the production of both steroids some 3 to 30 times above control values. Medium harvested from homologous pituitary cultures had comparable corticotrophic activity. It is concluded that at midpregnancy the regulation of corticoidogenesis implies the existence of a corticotrophic factor either identical or closely related to ACTH.

Dehydroepiandrosterone↗