Biomedical subjects
Publications and source records attributed to W White.
A rotating disk method has been used to study the dissolution of bovine enamel. A diffusion model adequately describes the reaction for a wide range of conditions, and the rate is also hydrogen ion dependent. The solubility product of bovine enamel, 5.9 +/- 1.8 X 10(-59) moles9 1(-9) at 25 C is derived by a method that minimizes the possibility of phase changes.
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An automatic control system has been developed to balance and control the output of an artificial heart. The system consisted of 2 linked negative feedback loops. The left ventricle was controlled by a Servo-Stroke Optimizer, which insured complete filling and full stroke operation of the left pump with each beat and changed the beat rate in accord with changes in aortic pressure. The right ventricle was controlled by a Servo-Variable Systolic Duration unit, which changed the stroke of the right ventricle to maintain the left atrial pressure within a preset band. In the initial animal studies, control pressures (aortic and left atrial pressure) were obtained from implanted transducers. More recently, a method has been devised whereby the control pressures were obtained from specific points on the left air line pressure wave, obviating the need for implanted transducers. The control system has been evaluated in a mock circulatory loop and in 9 calves with implanted artificial hearts. The system has provided balance of the 2 implanted ventricles and changes in flow rate in response to changes in peripheral resistance. The need for an operator to make manual adjustment to the power units has been considerably reduced. Further studies are indicated to evaluate the function of the control system in animals performing moderate-to-maximal exercise. Furthermore, the ultimate benefits of full stroke operation vs fill limited mode operation remain to be delineated.
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Kilham rat virus (KRV) contains linear, single-stranded DNA in the virion. The fate of radioactive viral DNA was followed after infection of monolayer cells. Within 60 min after infection of cells, 28 to 42% of the parental viral DNA is converted to a new form. This new DNA form is believed to be double stranded and linear on the basis of its sedimentation in neutral and alkaline sucrose gradients, elution from hydroxyapatite columns, its buoyant density in equilibrium CsCl density gradients, and appearance in the electron microscope. The double-stranded linear KRV DNA may be analogous to the replicative form of certain bacteriophages, including phiX174, which contain single-stranded circular genomes.
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Plasma alpha 1-acid glycoprotein (AGP) levels were measured in 49 subjects with major depressive disorder, 15 subjects with anorexia nervosa and 18 subjects with bulimia nervosa, together with age- and sex-matched controls. AGP levels were elevated in depression and bulimia compared to controls. They were particularly elevated in depressed subjects who proved unresponsive to treatment with a standard course of antidepressants. In the depressed subjects, elevated AGP levels returned to control levels after treatment whether or not treatment was successful. There was a correlation between AGP and post-dexamethasone plasma cortisol levels in depression but not in bulimia and a correlation with age in depressed subjects only. There was no correlation between AGP values and tritiated imipramine binding parameters. Further studies are suggested to explore the issue of whether variations in AGP level are responsible for the abnormalities in platelet 5HT uptake and tritiated imipramine binding that have been reported in depression or for treatment non-response.
Large meals scheduled at greater-than-circadian periods (such as T = 31 h) tend to elicit enhanced activity approximately 24 h subsequent to receipt. These studies characterized the process responsible for this meal-engendered "circadian ensuing activity" (meal CEA). Female Sprague-Dawley rats were housed in stations containing a running wheel, pellet dispenser, and lights. Young, middle-aged, or suprachiasmatic-nucleus (SCN)-lesioned rats were given two 1-h meals every 31 or 34 h. Meals were separated by alternating short and long fasts. Most young intact rats engaged in enhanced activity approximately 24 h subsequent to the start of the two-meal series. This circadian ensuing activity underwent large, abrupt daily displacements in response to daily meal delays, was manifested to some degree at all times of day, had an amplitude that was modulated by circadian time of day, was attenuated in middle-aged rats, was evident in SCN-lesioned rats, and oscillated following termination of the feeding schedule. A single experience with food at a novel time of day can "reset" an SCN-independent oscillating process responsible for a circadian activity pattern. CEA has features not readily accommodated by present models of "food-anticipatory activity." The readiness with which the process can be reset implies a keen sensitivity to shifts in the time of food availability but could also produce aberrant behavioral patterns. A T >> 24-h feeding schedule appears to be an ideal procedure with which to study the specific food-related factors responsible for resetting circadian processes and producing a subsequent reallocation of daily activity.