A micropuncture study of the renal response to haemorrhage in rats: assessment of the role of vasopressin

The acute effects of haemorrhage (15 ml (kg body wt)-1) on renal function at whole-kidney and single-nephron levels were studied in Inactin-anaesthetized rats. In order to assess the role of vasopressin in mediating the haemodynamic effects, responses in untreated Long-Evans rats were compared with those in Brattleboro rats (which lack circulating vasopressin) and in Long-Evans rats treated with a V1 receptor antagonist. In time-control animals, there were no significant changes in mean arterial pressure (MAP), excretion rates, glomerular filtration rate (GFR), superficial-nephron GFR (SNGFR) or fluid reabsorption in the superficial proximal tubules during the course of the experiment. Following haemorrhage, the immediate reduction in MAP was followed in each group by partial recovery for 30 min; thereafter, MAP was stable. In untreated Long-Evans rats, haemorrhage was followed by a 26% reduction in GFR (P < 0.001, measured 60-150 min post-haemorrhage) and a larger reduction (45%, P < 0.001) in SNGFR, so that the SNGFR/GFR ratio fell significantly ((27.9 +/- 1.9) x 10(-6), control period; (20.2 +/- 2.2) x 10(-6) post-haemorrhage, P < 0.01). Slightly greater reductions in GFR and SNGFR were seen in Brattleboro rats and V1 antagonist-treated Long-Evans rats, which corresponded to slightly greater haemorrhage-induced reductions in blood pressure in these groups; the falls in the SNGFR/GFR ratio were similar to that in untreated Long-Evans rats. In all three groups of bled rats, fractional reabsorption by the proximal convoluted tubule increased slightly 30-60 min after haemorrhage, but during the subsequent period (60-150 min) returned to values indistinguishable from those during the control period. The results suggest that the renal haemodynamic changes that follow moderate haemorrhage include a preferential reduction in the GFR of superficial nephrons. Vasopressin appears to play no role in this response. Increases in fractional reabsorption in the proximal tubules are seen only during the immediate post-haemorrhage period.     

An integrated modeling approach to solder joint formation

The attachment of electronic components to printed circuit boards using solder material is a complex process. This paper presents a novel modeling methodology, which integrates the governing physics taking place. Multiphysics modeling technology, imbedded into the simulation tool-PHYSICA is used to simulate fluid flow, heat transfer, solidification and stress evolution in an integrated manner. Results using this code are presented, detailing the mechanical response of two solder materials as they cool, solidify and then deform. The shape that a solder joint takes upon melting is predicted using the SURFACE EVOLVER code. Details are given on how these predictions can be used in the PHYSICA code to provide a modeling route by which the shape, solidification history, and resulting stress profiles can be predicted     

Linear and nonlinear optical properties of organic crystals: MBANP and its derivatives

In addition to possessing strong optical nonlinearity, the (−)-2-(α-methylbenzylamino)-5-nitropyridine (MBANP) crystal has been shown to have unusual linear optical properties. Two methyl derivatives of MBANP have now been synthesized and grown as large single crystals; their refractive indices have been measured as a function of frequency and second-harmonic generation, including the determination of the phase matching loci has been investigated. Data is also available on the racemic form of crystalline MBANP. The properties of this family of crystals have been reviewed and an attempt is made to relate the experimental responses of the crystals to their molecular structure and the calculated properties of the molecules.     

The necessities and luxuries of mate preferences: Testing the tradeoffs.

Social exchange and evolutionary models of mate selection incorporate economic assumptions but have not considered a key distinction between necessities and luxuries. This distinction can clarify an apparent paradox: Status and attractiveness, though emphasized by many researchers, are not typically rated highly by research participants. Three studies supported the hypothesis that women and men first ensure sufficient levels of necessities in potential mates before considering many other characteristics rated as more important in prior surveys. In Studies 1 and 2, participants designed ideal long-term mates, purchasing various characteristics with 3 different budgets. Study 3 used a mate-screening paradigm and showed that people inquire 1st about hypothesized necessities. Physical attractiveness was a necessity to men, status and resources were necessities to women, and kindness and intelligence were necessities to both. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Liver transplantation for decompensated cirrhosis after jejunoileal bypass: a strategy for management

BACKGROUND: Although jejunoileal bypass results in end-stage liver disease in up to 100% of patients, little is known about outcome after liver transplantation. METHODS: The clinical courses of six patients who underwent liver transplantation at UCLA for decompensated cirrhosis owing to a jejunoileal bypass were reviewed. Liver function, allograft pathology, renal function, and nutritional status were assessed. RESULTS: Of the four patients with an intact jejunoileal bypass, two of the three who were biopsied had recurrent steatotic liver disease. The two patients whose jejunoileal bypass was reversed at the time of liver transplantation had lower alkaline phosphatase, lower creatinine, higher albumin, and higher cholesterol, and were more obese than their counterparts with intact bypasses. CONCLUSIONS: Patients undergoing liver transplantation for jejunoileal bypass-associated liver disease should, if possible, have their bypass reversed at the time of transplantation; otherwise, they must be followed closely and be biopsied routinely. Recurrent liver disease should prompt reversal of the jejunoileal bypass.     

Effects of sleep deprivation and user interface on complex performance: a multilevel analysis of compensatory control

This study was carried out to test the compensatory control model, which predicts performance maintenance under stress at the expense of effort and increased selectivity. It examined the effects of sleep deprivation on performance in an automated process control task based on a simplified life support system with two types of operator control panel interface: machine centered (M-C), in which access to the system was scheduled by the computer, and human-centered (H-C), in which access was ad-lib. The task environment also permitted the analysis of changes in strategy and in subsidiary activities (alarm reaction time, prospective memory). In a 2 x 2 repeated-measures design, 16 participants carried out the task with each interface after both normal sleep and one night of sleep deprivation (SD). No effects of SD were observed on primary task performance. As predicted, SD effects were confined to strategy changes and subsidiary task impairment and occurred only under the (low control) M-C interface. Subjective effort was increased under SD, with greater increases of effort associated with high levels of performance protection. The findings provide strong evidence in favor of the compensatory control model and argue for the use of complex, multilevel tasks in the analysis of performance under stress. Actual or potential applications include the development of more sensitive performance-testing systems based on multilevel analysis of decrement, and the design of interfaces for shift work and other suboptimal work conditions.     

Ocular bubble formation as a method of assessing decompression stress

Human well-being depends on the entrainment of endogenous circadian rhythms of biological functions and the sleep-wake rhythm. Although the incidence of otherwise healthy subjects with chronically altered sleep-wake rhythms is rather low, the investigation of these patients provides new sights into circadian entrainment mechanisms. We therefore examined the circadian rhythm of circulating melatonin and the sleep-wake rhythm in five patients with chronic sleep-wake rhythm disorders and ten age-matched healthy controls. All patients showed altered circadian melatonin rhythm parameters in relation to their sleep-wake cycle compared to age-matched controls. These alterations were random, i.e., independent of the type, the duration, and the age of onset of the disorder. The melatonin onset to sleep onset interval varied between the patients and the melatonin acrophase to sleep offset interval was prolonged in four patients. These findings indicate individual phase relations between the circadian melatonin rhythm and the sleep-wake cycle in patients with chronic sleep-wake rhythm disorders. Since the prolonged melatonin acrophase to sleep offset interval was the most consistent finding independent of aetiological origins, this abnormality may be one possible maintaining factor in chronic sleep-wake rhythm disorders due to reduced phase-resetting properties of the circadian pacemaker. Furthermore, rather low circadian melatonin amplitudes and a subsensitivity to daylight may maintain the disorder in at least some patients.