Circadian rhythms in the Zucker obese rat: assessment and intervention

The proximate determinants of fertility framework, developed in its current form by Bongaarts, has been used extensively by researchers for the past 20 years. Since the initial framework was developed, a wealth of new survey data on the proximate determinants has become available. This article reviews the new data and past experiences and suggests modifications to the framework that would take advantage of this experience. The major modifications suggested are (1) the use of sexual activity rather than marriage to indicate exposure to pregnancy; (2) a revision of the sterility index to measure infecundity from all causes; (3) a revised index of contraception that accounts for the fact that users of sterilization may become infecund before age 49; and (4) a revised definition and estimate of total fecundity.     

Acute in vivo studies of the Pittsburgh intravenous membrane oxygenator

The efficacy of an innovative intravenous membrane oxygenator (IMO) was tested acutely (6-8 hrs) in seven calves. The IMO prototypes consisted of a central polyurethane balloon within a bundle of hollow fibers with a membrane surface area of 0.14 m2. The IMO devices were inserted through the external jugular vein into the inferior vena cava of anesthetized calves (68.9 +/- 2.3 kg). Rhythmic balloon pulsation (60-120 bpm) was controlled with an intra-aortic balloon pump console. Oxygen sweep gas was delivered through the device at 3.0 L/min. Gas concentrations were monitored continuously by mass spectroscopy. The principal results were as follows: 1) oxygen and carbon dioxide exchange ranged from 125 to 150 ml/min/m2 and 150 to 200 ml/min/m2, respectively; 2) there was at least a 30-50% augmentation of gas exchange with balloon pulsation; 3) maximum exchange occurred with 60-90 bpm balloon pulsations; and 4) hemodynamic parameters remained unchanged. There were no device related complications, and the feasibility of insertion of the device by a cervical cut-down was established. These acute in vivo experiments show that the Pittsburgh IMO device can exchange oxygen and carbon dioxide gases in vivo at levels consistent with this current prototype design, and that intravenous balloon pulsation significantly enhances gas exchange without causing any end-organ damage.     

AIDS-associated vacuolar myelopathy and tumor necrosis factor-alpha (TNF alpha)

The spinal cords from 15 patients with AIDS-associated vacuolar myelopathy (VM), 4 AIDS patients without VM, and 5 HIV-seronegative controls, were studied with immunocytochemistry for TNF alpha. CSF and blood from HIV-seropositive patients with VM (n = 16), non-vacuolar myelopathies (n = 8), CNS infection but no clinical myelopathy (n = 31), no clinical or radiological evidence of CNS disease (n = 9), and from 7 HIV-seronegative controls with motor neurone disease were assayed for TNF alpha using an ELISA technique. TNF alpha was present on immunostaining in all the 15 cords with VM studied. The stained cells were macrophages, microglia and endothelial cells. The amount of immunostaining was higher in cords with VM compared with cords from HIV-seropositive patients without VM (p = 0.001). The distribution of staining corresponded to the areas of pathology but did not correlate with the severity of the VM. Immunostaining was also higher in the HIV-seropositive group compared to the HIV-seronegative controls (p = 0.001). There was no significant difference in the levels of TNF alpha in the CSF of patients with VM compared to any of the other groups studied. Blood levels of TNF alpha were lower in the HIV-seropositive controls without CNS disease and in the HIV-seronegative MND controls, than in patients with VM, non-vacuolar myelopathies, and CNS disease. CSF TNF alpha levels did not appear to be a reliable indicator of intramedullary levels. The findings support the hypothesis that TNF alpha may be relevant in the pathogenesis of vacuolar change in VM.     

Electrical cardioversion of atrial fibrillation or flutter with conscious sedation in the age of cost containment

OBJECTIVE: To determine if there is a significant difference in the degree of pelvic organ prolapse assigned during examination in the standing position compared with the dorsal lithotomy position with the patient performing maximal Valsalva maneuver. METHODS: Fifty-one women with symptoms of pelvic organ prolapse were examined in both the dorsal lithotomy position, while performing maximal Valsalva, and in the standing position at the same visit by one of two examiners. Nine site-specific measures and summary stages were recorded, as outlined by the International Continence Society's classification system for pelvic organ prolapse. The data were analyzed by Wilcoxon signed-rank test and correlation coefficients. RESULTS: The mean age was 52 +/- 15 years. Excellent correlation was noted between all six points representing the vaginal prolapse. The R values for point Aa were 0.97, Ba 0.96, C 0.98, Ap 0.97, Bp 0.96, and D 0.97. The total vaginal length, perineal body, and genital hiatus measurements were performed in the dorsal lithotomy position with the patient at rest and were not repeated. The stages were identical in 48 of 51 patients. The average stage in the dorsal lithotomy position was 2.3 and in the standing position, 2.3. There was no statistically significant difference between the stage or any of the measured points in the dorsal lithotomy and standing examinations. CONCLUSION: The degree of pelvic organ prolapse can be assessed adequately in the dorsal lithotomy position with the patient performing maximal Valsalva. It is not necessary to routinely repeat the examination in the standing position.     

Regulatory feedback pathways in the thymus

The idea that thymocytopoiesis may be subject to feedback regulation by mature lymphocytes is proposed on the basis of recent data from in vitro experimental models. Analysis of the data using mathematical models, presented here by Ramit Mehr and colleagues, suggests possible feedback control mechanisms in T-cell development.     

Memory and learning abilities in everyday life of the elderly

Self-evaluations by adults (varying in age from 45-92 years) of their memory and learning abilities were investigated and related to performance on laboratory and ecological memory tasks. Hardly any association was found between subjective and objective measures. Self-evaluations were strongly influenced by (systematically varied) frames of reference: optimistic in comparisons with other people, pessimistic in comparisons with their own previous level of functioning. The most frequent problems were 'learning something new' and 'remembering names'. In contrast to external memory aids, cognitive strategies were rarely used spontaneously. Strategy training led to significant improvement of performance, that remained stable at follow-up. A further opportunity for improving performance was realized by ergonomic adaptations of computerized systems (teleshopping). Problems in learning to use such systems were strongly reduced by decreasing the load on working memory and by adapting the system to existing knowledge and skills of the users. A general observation in the different projects was that age-differences could explain only a small percentage of the variance in subjective and objective memory measures.