Insulin depletion leads to adipose-specific cell death in obese but not lean mice

Mutation of the obese gene produces obesity, hyperinsulinemia, and compensatory "overexpression" of the defective gene. As insulin activates obese gene expression, it seemed possible that hyperinsulinemia might be responsible for overexpression of the gene. To address this question we rapidly neutralized circulating insulin by injection of an insulin antibody. Unexpectedly, insulin depletion in obese (ob/ob or db/db) mice caused massive adipose RNA degradation confirmed by histological analysis to result from adipocyte cell death by a largely necrotic mechanism. This effect was not observed in lean littermates and was completely corrected by coadministration of insulin. Comparison of multiple tissues demonstrated that the effect was restricted to adipose tissue. Insulin depletion in obese mice by administration of streptozotocin also led to cell death, but this death was less extensive and appeared to be apoptotic in mechanism. Thus insulin may promote the survival side of the physiological balance between adipocyte survival and death.     

Laparoscopic versus open appendectomy

BACKGROUND: Clinical manifestations and course of sickle-cell anemia are variable. Knowledge about the factors, possibly geographic, that influence prognosis are still scanty. POPULATION AND METHODS: Data of hospitalization and management of children with sickle-cell disease were studied during two years (1992-1993) in the Pediatric Unit of Libreville Hospital. They concerned 205 admissions of 171 children and 131 outpatients. RESULTS: The main causes of hospitalization were: acute anemia (36 cases before the age of 5 years); painful crisis whose frequency increased with age (23% before 5 years, 35% between 5 and 10, 42% after 10 years); infections, essentially pulmonary occurring early, and bone infections at any age. Eight children died (because a complication of their disease). Among the 131 outpatients, half were detected because pyrexia, anemia and/or more often "hand-foot syndrome". More than 60% had hepatomegaly, one third still had splenomegaly after five years of age and more than one third was icteric. More than half children older than ten years had growth disorders. Mean hemoglobin level was 7 g/dL. 21 of the 83 tested children for HBsAg were positive and only one out of 79 was positive for HIV. CONCLUSIONS: Clinical manifestations and course of sickle-cell anemia in our patients are similar to those reported in Congolese children. Genetic and environmental factors may be responsible for differences with children from other, in particular French, cohorts.     

Fasciola hepatica development in the experimentally infected black rat Rattus rattus

Coat colour changes in polar animals are related to seasonal variation in photic inputs. The present work was performed to study the photoresponses of hair follicular melanocytes in human skin. The melanocytes, being photosensitive cells, can function as UV biosensors, since dendrites extend towards the source of UV light. Fifty-one skin biopsies from the margin of vitiligo were subjected to whole skin organ cultures. These were exposed to a pulse of UV light to study hair bulb melanocytes in vitiligo. It is observed that the melanocytes are seen within the anagen matrix. These melanocytes are poorly dendritic in control and dark-incubated cultures. On UV exposure, they become highly dendritic, the dendrites extending towards the hair shaft in 93.5%. They show prominent catechol oxidase and noradrenaline positivity, all features of UV responsiveness. The melanocytes within the hair follicle are not directly exposed to UV light. The melanocyte dendricity and the alignment of dendrites towards the shaft on UV exposure indicate that the columns of the cells in the hair shaft act as an efficient fibre-optic system, transmitting UV light. Morphologically, the keratinocytes in the hair shaft are arranged in compressed linear columns which resemble the coaxial bundles of commercial fibre-optic strands as is observed in plants. Keratinocytes in the inner and outer sheaths do not show this arrangement. Thus the hair follicle functions as a specialised UV receptor in the skin responding to nuances of photic inputs in human skin. This is reflected in coat colour changes in animals exposed to large variations in day-night cycles.     

Estimation of reliability of stress-strength model with non-identical component strengths

An attempt has been made in this paper to estimate the reliability of an s-out-of-k system with non-identical component strengths when component strengths follow an exponential distribution. A further assumption is made that all the components are subjected to a common random stress which also follow an exponential distribution. Bayes and maximum likelihood estimators of such system reliability are considered. A Bayes estimate is obtained by using Lindley's approximation. Comparisons are made on the basis of efficiency and Pitman nearness probability through a Monte-Carlo study.     

A microprogramming animation

This paper describes a successful project using computer animation to teach the concepts of microprogramming to lower division computer science majors. The students write a simulator for the Mic-1 horizontal microcontroller described in the book Structured Computer Organization by Tanenbaum. The simulation is enhanced by the use of a graphical representation of the machine to animate the simulation. This creative use of computer animation enables the students to see the results of their simulation without having to write an extensive user interface. They can concentrate on implementing the instruction cycle, an activity that directly enhances their understanding of microprogramming and the conventional machine level. The XTango animation package is used, making the animation facility portable to any Unix system with an X display. The user interface and additional instructional material are available via the web     

Advances in Space Traveling-Wave Tubes for NASA Missions

Significant advances in the performance and reliability of traveling-wave tubes (TWTs) utilized in amplifying space communication signals for NASA missions have been achieved over the last three decades through collaborative efforts between NASA and primarily L-3 Communications Electron Technologies, Inc. (L-3 ETI). This paper summarizes some of the key milestones during this period and includes development of TWTs for the Communications Technology Satellite, Cassini, and Lunar Reconnaissance Orbiter missions. Technical advances in computer modeling, design techniques, materials, and fabrication have enabled power efficiency to increase by almost 40% and the output power/mass figure-of-merit to increase by an order of magnitude during this period.     

An effective back‐off selection technique for reliable beacon reception in VANETs

In safety‐critical scenarios, reliable reception of beacons transmitted by a subject vehicle is critical to avoid vehicle collision. According to the employed contention window sizes in IEEE 802.11p, beacons are transmitted with a small contention window size. As a result, multiple vehicles contend for the shared channel access by selecting the same back‐off slot. This is a perfect recipe for synchronous collisions wherein reliable beacon delivery cannot be guaranteed for any vehicle. We consider the problem of selecting the back‐off slots from the current contention window to provide reliable delivery of beacons transmitted by a subject vehicle to its neighbors. Given a safety scenario, we propose a Pseudo‐Random Number Generator (PRNG)‐inspired back‐off selection (PBS) technique. The proposed technique works on the hypothesis that synchronous collisions of beacons transmitted by a subject vehicle can be reduced if all its neighbors select different back‐off slots (ie, not the back‐off slot selected by the subject vehicle). The discrete‐event simulations demonstrate that PBS can increase the overall message reception from a subject vehicle, in comparison with the uniform random probability back‐off selection in IEEE 802.11p.     

The politics of conservative elites and the 'liberal media' argument

Recent evidence suggests that conservative elites' claims of a liberal media are having an impact upon public perceptions of news coverage. With this in mind, we examined two related questions in the context of the 1988, 1992, and 1996 presidential elections. First, what factors may be prompting conservative elites to make allegations of liberal media bias? Second, what factors may influence when news media report these criticisms during presidential campaigns? Findings suggest that these criticisms of news media are at least partly strategic and reflect a dynamic relationship between political elites and journalists during a presidential campaign.     

A Generalized System for Photo-Responsive Membrane Rupture in Polymersomes

Polymersomes are vesicles whose membranes are comprised of self-assembled block co-polymers. We recently showed that co-encapsulating conjugated multi-porphyrin dyes in a polymersome membrane with ferritin protein in the aqueous lumen confers photo-lability to the polymersome. In the present study, we illustrate that the photo-lability can be extended to vesicles containing dextran, an inert and inexpensive polysaccharide, as the luminal solute. Here we explore how structural features of the polymersome/porphyrin/dextran composite affect its photo-response. Increasing dextran molecular weight, decreasing block copolymer molecular weight, and altering fluorophore-membrane interactions results in increasing the photo-responsiveness of the polymersomes. Amphiphilic interactions of the luminal encapsulant with the membrane coupled with localized heat production in the hydrophobic bilayer likely cause differential thermal expansion in the membrane and the subsequent membrane rupture. This study suggests a general approach to impart photo-responsiveness to any biomimetic vesicle system without chemical modification, as well as a simple, bio-inert method for constructing photo-sensitive carriers for controlled release of encapsulants.