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Biomedical subjects

D A Hall

Publications and source records attributed to D A Hall.

At least 127 records · Page 7Linked to original sources
PubMed1979

Computed body tomography in chronic pancreatitis.

CT of the pancrease permitted correct positive diagnosis in 28/50 or 56% of patients with chronic pancreatitis proved by laparotomy or retrograde ductography. Diagnoses were based on CT identification of one or more specific hallmarks of chronic pancreatitis including calcifications (18/50 or 36%), parenchymal atrophy (7/50 or 14%) and pancreatic duct dilatation (2/50 or 4%), as well as the principal surgical complications, pseudocyst and abscess (15/50 or 30%). In 9 patients, CT disclosed pancreatic calcifications not visible on conventional radiographs. In 32 patients, ultrasound was less informative than CT giving a correct diagnosis in 8 pseudocycts (25%). In the patient with unexplained upper abdominal complaints, a positive CT diagnosis of chronic pancreatitis permits more confident patient management than a negative, or "no tumor" diagnosis rendered by other noninvasive examinations.

Chronic Disease↗
PubMed1979

Sonographic morphology of the normal menstrual cycle.

Sequential gray-scale sonograms were obtained during 20 menstrual cycles in 16 normal female volunteers. Hormonal and physical parameters of an ovulatory cycle were correlated with morphological changes in the ovaries, uterus, and cul-de-sac as seen on the sonogram. Ovarian cysts of two sizes were observed, corresponding chronologically and morphologically to Graafian follicles and corpora lutea. Small amounts of free pelvic fluid were demonstrated in many women at ovulation. A characteristic uterine appearance is seen prior to menstruation and is related to hormonal influences on the uterus. These findings emphasize the importance of recognizing normal physiological changes when interpreting gynecologic sonograms.

Douglas' Pouch↗
PubMed1978

Clinical application of a single compartment model to urea and creatinine kinetics in dialysis therapy.

A single compartment mathematical model has been shown to accurately described changing serum concentrations of low molecular weight solutes (urea and creatinine) during dialysis. Clinical application of the model permits prediction of serum concentrations in response to changes in prescription of dialysis therapy. The programs presented here can be used to predict the effect of changes in treatment time and dialyzer clearance on serum concentrations. Sequential pre- and end-dialysis solute concentrations are displayed on a programmable pocket calculator. Dialyzer clearance during any individual dialysis can be calculated. These programs permit an evaluation of the efficacy of prescribed dialysis treatment schedules in advance of therapeutic trials.

Computers↗
PubMed1978

Scanning techniques in computed body tomography.

Clinical examinations with the whole body CT scanner require considerable individualization of examination technique in relation to specific organs, anatomic areas, and clinical problems. Careful selection of radiographic factors, patient position, contrast agents, and pharmacologic adjuncts will optimize diagnostic results and patient throughput.

Contrast Media↗
PubMed1978

Sleep, mood, and fatigue during a 14-day He-O2 open-sea saturation dive to 850 fsw with excursions to 950 fsw.

To obtain information on sleep, mood, and performance of divers and surface support personnel during deep dives in the open sea, 12 divers and 12 surface support personnel were monitored during a 14-day open-sea saturation dive using the U.S. Navy Deep Diving System, Mark 2, Mod O. Divers lived in the deck decompression chambers at 850 fsw equivalent and made 5 days of excursion wet dives to approximately 950 fsw via the Personnel Transfer Capsule. Electroencephalographic and self-report measures of sleep, and measures of mood, anxiety, and 4-choice reaction time performance were obtained during a predive base-line period and throughout the dive and decompression. Results suggested that, unless personnel are rotated, there are limitations to the practical duration of very deep open-sea saturation dives caused by the accumulation of sleep debt, fatigue, and loss of psychological vigor.

Affect↗
PubMed1978

Diving experience and emotional factors related to the psychomotor effects of nitrogen narcosis.

Simple and complex psychomotor performance were tested among 21 Navy divers under normal conditions and during nitrogen narcosis in simulated dives to 170 ft of sea water. Complex psychomotor performance was impaired significantly during narcosis, while simple psychomotor performance remained essentially normal. Differences between baseline scores for complex psychomotor performance (pre- and post-dive combined) and scores obtained from the two combined testing sessions administered during narcosis were correlated with official Navy records of diving experience and self-reported moods. None of the diving experience measures was associated significantly with these difference scores. The moods of Fatigue and Happiness were, however, correlated significantly with impairment. These results indicate that, although previous experience with nitrogen narcosis and diving tasks do not mediate the performance effects of nitrogen narcosis, the complex psychomotor effects nitrogen narcosis are related to emotional traits.

Adult↗
PubMed1977

Cyclic AMP in action of antidiuretic hormone: effects of exogenous cyclic AMP and its new analogue.

Exogenous cyclic 3',5'-adenosine monophosphate (cAMP) stimulates the effect of the antidiuretic hormone, vasopressin (VP), only in pharmacologic quantities and results have often been inconsistent. The present study examined the ability of a new analogue, 8-[p-Cl-phenylthio]cyclic 3',5'-adenosine monophosphate (C1-PheS-cAMP) to mimic the effect of VP, both biochemically (protein kinase activation) and functionally (hydrosomatic response of perfused collecting tubules) in mammalian kidney tissue. C1PheS-cAMP was found to be about 100 times as effective as cAMP both biochemically and functionally. The increased effectiveness of C1PheS-cAMP is probably is probably due to a greater permeability across the cell membrane and to the resistance of C1PheS-cAMP to enzymatic degradation, Cyclic AMP phosphodiesterase inhibition was observed with C1PheS-cAMP, but its contribution to overall effect was minor. C1PheS-cAMP was found to be more effective than exogenous vasopressin, an effect probably due primarily to its resistance to catabolism. The results provide further new evidence that cAMP and protein kinase are involved in the cellular action of vasopressin. C1PheS-cAMP proved to be a useful tool in the study of hormone action, especially in steps subsequent to cAMP generation.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMed1977

Extension of pulmonary O2 tolerance in man at 2 ATA by intermittent O2 exposure.

To study extension of O2 tolerance by interruption of hyperoxic exposure, as compared to previous studies of continuous oxygen exposure, five healthy volunteers were exposed to oxygen at 2 ATA on an intermittent schedule of 20 min breathing O2, alternating with 5 min on a normoxic N2-O2 mixture. The cycle was repeated until symptoms or signs of O2 toxicity caused cessation of the experiment. Tracheal irritation and burning on inspiration occurred after 6-9 "oxygen hours" of exposure and progressed to severe tracheobronchial burning sensation, chest pain, and dyspnea after 11-15 h of O2. Average duration of exposure was 13.7 O2 h, inducing a mean vital capacity decrease of 10.3%. The decrease began soon after onset of symptoms. With intermittent O2 administration, nearly a doubling of the average duration of actual oxygen breathing was required to induce marked vital capacity change (greater than 10%) as compared to the previous studies of continuous O2 exposure. The increased duration of tolerable O2 exposure in man resembles the extension of O2 tolerance known to occur in animals exposed to intermittent hyperoxia.

Adult↗
PubMed1977

The breast as a mirror of systemic diseases.

This paper reemphasizes that xeromammographic changes in the skin, parenchyma, and vascular structures of the breast may be manifestations of a host of systemic diseases. Xeromammographic examples of such diseases as congestive heart failure, diabetes mellitus, collagen vascular diseases, and endocrine diseases are presented and discussed.

Adult↗
PubMed1976

The physical properties of elastic fibers and elastolysis.

The effects of two forms of elastase on the Young's Modulus of elastic tissue have been studied. The monomeric, calcium poor form of the enzyme lowers the value of the Young's Modulus before an appreciable amount of protein is taken into solution. The polymeric, calcium rich enzyme on the other hand degrades the protein before reduction in Young's Modulus occurs. On the basis of these observations, it is confirmed that the enzyme/substrate complex in elastolysis is formed by interaction through a co-ordinately bound calcium atom and that this atom can be derived either from the substrate, where it stabilises the molecule, or from the enzyme.

Animals↗