Radiation from an open waveguide with reactive walls

An exact solution is obtained for the problem of a radiating parallel plate waveguide when the inside walls are inductively loaded and the outside walls are capacitively loaded. Also, an impedance boundary condition is assumed along the center line of the configuration. The structure serves as a canonical model for two important types of antennas: an inductively loaded horn and a horn-type surface wave launcher. Exact closed-form expressions are computed for quantities of physical interest: the reflection coeffieient at the waveguide mouth, the radiation power pattern, and the power in the radiated surface wave. Various graphs show how the antenna pattern and the launching efficiency vary with the different parameters.     

Massive renal angiomyolipoma in tuberous sclerosis

Endoscopic surgery has been used as a new procedure to simplify different surgical processes. The goal of this study was to evaluate the benefits of endoscopic retroperitoneal surgery for lumbar sympathectomies. Between February 93 and November 95 we performed 35 lumbar sympathectomies using this technique. All patients were arteritic. The results were as follows: for 25% of the patients, conversion classical open technique was required; 6% complications (septic); 3% of the patients died. In comparing the various techniques of sympathectomy and sympatholysis, it would appear that the endoscopic technique produces fewer complications. However we believe that a learning period is necessary before this technique can be fully mastered.     

Effects of gastric mucosal blood flow (GMBF) on the role of adaptive cytoprotection of rat gastric mucosa

It has been reported that ingestion of an ammonium-containing diet produces hyperammonemia without encephalopathy, thus permitting the study of the specific effects of ammonia toxicity. The present study investigated the rat cerebral somatostatinergic system using this experimental model of hyperammonemia. Wistar rats were fed a high ammonia diet prepared by mixing a standard diet with ammonium acetate (20% w/w); in addition, 5 mM of ammonium acetate was added to their water supply. Control rats were fed with a standard diet. The animals were sacrificed at 3, 7 and 15 days of ammonia ingestion. Ammonia levels in blood had increased approximately 3-fold at 7 days of ammonia ingestion. These changes were associated with a significant decrease in the specific binding of somatostatin (SS) to putative receptors sites in the frontoparietal cortex and hippocampus at 7 and 15 days after starting the high ammonia diet. Scatchard analysis shows that the decrease in SS binding resulted from a decrease in the number of available SS receptors rather than a change in receptor affinity. No changes in the somatostatin-like immunoreactivity content (SSLI) were detected in either brain area at the three study times. These results suggest that hyperammonemia alone can affect the rat brain somatostatinergic system. However, the animal model of hyperammonemia used here is insufficient to produce encephalopathy despite the significant increase in serum ammonia.     

Retroviral transfer of antisense integrin alpha6 or alpha8 sequences results in laminar redistribution or clonal cell death in developing brain

To assess the roles of two integrin alpha subunits (alpha6 and alpha8) in the developing chicken optic tectum, progenitors were infected with retroviral vectors that contained the marker gene lacZ plus antisense sequences from either the alpha6 or alpha8 integrin subunit cDNAs. On embryonic day 3 (E3), the vector was injected into tectal ventricles of chicken embryos. On E6, E7.5, E9, or later, chicken embryos were killed, and optic tecta were dissected and processed for histochemical detection of lacZ-positive cells. The antisense-bearing cell clones (descendants of a single infected progenitor) were analyzed for proliferation and migration patterns and were compared with lacZ-only vector-infected control clones. At E6, both alpha6 and alpha8 integrin antisense-containing cell clones were similar to controls. At E7.5, integrin alpha8 antisense-containing clones exhibited a cell number reduction in upper laminae (intermediate zone and tectal plate), and at E9, they exhibited a reduction in the ventricular zone as well. Integrin alpha6 antisense-containing cell clones exhibited no difference in total cell number at E9 but had a net laminar redistribution of more cells in the ventricular zone and less cells in the tectal plate. Our data show that different integrins play different roles during brain development: alpha6 integrin is essential for migration of tectal cells into specific laminae, and alpha8 integrin is essential for the survival of optic tectum cells. Also alpha8 integrin-substrate interactions may suppress early programmed cell death in premigratory and migratory neuroblasts.     

A pregnancy-specific glycoprotein is expressed in the brain and serves as a receptor for mouse hepatitis virus

Mouse hepatitis virus (MHV), a murine coronavirus known to cause encephalitis and demyelination, uses murine homologues of carcinoembryonic antigens as receptors. However, the expression of these receptors is extremely low in the brain. By low-stringency screening of a mouse brain cDNA library, we have identified a member of the pregnancy-specific glycoprotein (PSG) subgroup of the carcinoembryonic antigen gene family. Unlike other PSG that are expressed in the placenta, it is expressed predominantly in the brain. Transfection of the cDNA into COS-7 cells, which lack a functional MHV receptor, conferred susceptibility to infection by some MHV strains, including A59, MHV-2, and MHV-3, but not JHM. Thus, this is a virus strain-specific receptor. The detection of multiple receptors for MHV suggests the flexibility of this virus in receptor utilization. The identification of this virus in receptor utilization. The identification of a PSG predominantly expressed in the brain also expands the potential functions of these molecules.     

mraY is an essential gene for cell growth in Escherichia coli

The synthesis of the murein precursor lipid I is performed by MraY. We have shown that mraY is an essential gene for cell growth. Cells depleted of MraY first swell and then lyse. The expression of mraY DNA in vitro produces a 40-kDa polypeptide detectable by sodium dodecyl sulfate-polyacrylamide gel electrophoresis.     

Refocusing the lens: epidemiologic transition theory, mortality differentials, and the AIDS pandemic

The epidemiologic transition theory presented first by Omran [Omram. A. R. (1971) The epidemiologic transition: a theory of the epidemiology of population change, Mildbank Quarterly 49(4), 509-538] was designed to explain global trends in the dynamic relationship between epidemiological phenomena and demographic change. This paper argues that universalizing this theory only partially serves to explain mortality declines over the last century and eclipses key epidemiologic differences between population subgroups based on socioeconomic status, race, and sex. This paper examines morbidity and mortality differentials between population subgroups and demonstrates important inconsistencies with the optimistic trends implied by the epidemiologic transition theory, an argument further developed using the HIV/AIDS pandemic as a case study. The paper argues that these differences should be brought from margins to center to present a more complex and comprehensive picture of how population subgroups experience epidemiologic transitions differently.