Influences of temperature change on the relaxation and amplitude inhibition by noradrenaline in the rabbit jejunum.

In the rabbit jejunum, the elevation of temperature within the range of 25-37 degrees C diminished the sensitivity to noradrenaline (NA) for both the relaxation and amplitude inhibition. The relaxation by NA was mainly mediated via adrenergic beta-receptors at 25, 30 or 37 degrees C. The amplitude inhibition was mediated via alpha-receptors at 37 degrees C, and both alpha- and beta-receptors at 30 or 25 degrees C.     

Retention of topical liposomal formulations on the cornea

The ability of liposomes composed of different kinds of phospholipid materials to adhere to the surface of the cornea was studied in the rabbit. The liposomes were labelled with tracer amounts of an I125-labelled phosphatidylethanolamine derivative and were instilled in 10 microliters drops onto the cornea. The retention of radioactivity was monitored. The results show that liposomes containing positively charged phospholipids are better retained than an albumin control. Thus, it may be possible to develop a drug delivery liposome system which would permit long-term sustained release of ophthalmic drugs onto the cornea.     

Mammalian pineal melatonin: a clock for all seasons

The central role of the pineal gland and its hormone melatonin (MEL) in mammalian photoperiodic responses is discussed in terms of: 1) evidence for the involvement of MEL in photoperiodism, 2) which feature of the MEL secretion profile might be most important for regulating photoperiodic responses, 3) evidence for the modulation of responses to changes in daylength based on previous photoperiod exposure (i.e., photoperiodic history) and 4) how the MEL signal might be processed at its target sites to elicit physiological responses.     

Comparison of retinal pigment epithelium cell preparations from the bovine eye

Summary Retinal pigment epithelium (RPE) cells were collected from, bovine eyes using a new method. The cells were harvested by vortexing the RPE and underlying choroid in 0.05 M citrate phosphate buffer, pH 5. RPE cells recovered by this method were compared to a standard method by microscopic examination of cell integrity, estimation of total protein, and assay of 11-cis and all-trans retinyl ester hydrolase (REH) activities. Results suggest that this method collects RPE cells of good integrity and with a significantly higher protein yield than the conventional method. Additionally, a much higher retinyl ester hydrolase activity was noted. Therefore we propose that this procedure offers a new and convenient method in the collection of RPE proteins for certain purposes such as enzyme purification.     

Development of venous occlusions in mice transgenic for the plasminogen activator inhibitor-1 gene

The fibrinolytic potential of the vasculature is modulated primarily by the availability and activity of plasminogen activators, which convert the zymogen plasminogen into the active fibrin-degrading enzyme plasmin. The activities of these key regulatory enzymes are directly neutralized by their primary endogenous inhibitor, plasminogen activator inhibitor-1 (PAI-1). Although some individuals with a tendency to develop thrombotic disorders exhibit elevated levels of PAI-1 in their plasma, the cause-and-effect relationship between increased PAI-1 and thrombosis is still unclear. Specifically, it is not known whether chronic depression of fibrinolytic activity results in the development of thrombosis. To address this question we developed transgenic mice in which the contribution of PAI-1 to thrombus formation could be evaluated. The results presented in this report indicate that elevated levels of PAI-1 contribute to the development of venous but not arterial occlusions.     

Effect of equal channel angular pressing on aging treatment of Al-7075 alloy

The effect of aging treatment on microstructure and mechanical properties of equal channel angular pressed Al-7075 alloy was examined.Commercial Al-7075 alloy in the solid solution heat-treated condition was processed by equal channel angular pressing through route BCat both the room temperature and 120 1C. Only three passes of equal channel angular pressing was possible due to the low ductility of the alloy at both temperatures. Followed by equal channel angular pressing, the specimens have been aged at 120 1C for different aging times. Mechanical properties were measured by Vickers microhardness and tensile tests and microstructural observations were undertaken using transmission electron microscopy, X-ray diffractometer as well as optical microscopy. Microstructural investigations showed that ultrafine-grained materials with grain size in the range of 200–350 nm and 300–500 nm could be obtained after three passes of equal channel angular pressing at room temperature and 120 1C, respectively. Equal channel angular pressing of solid solution heat-treated Al-7075 alloy accelerates precipitation rate and subsequently leads to a significant decrease in aging time to attain maximum mechanical properties. Furthermore, it is possible to achieve maximum mechanical properties during equal channel angular pressing at 120 1C as a result of dynamic aging and formation of small η′ phase.     

Adrenaline and the electrogenic sodium pump in Rana catesbeiana sympathetic ganglion cells.

The effect of adrenaline on the Na+-pump in bullfrog (Rana catesbeiana) sympathetic ganglion cells was studied by use of electrophysiological methods. The rate of removal of excess Na+ injected into a ganglion cell was increased by adrenaline. The K+-activated hyperpolarization of cell membrane, which might be produced by an electrogenic Na+-pump, was also increased by adrenaline. These results suggested that adrenaline was able to accelerate the Na+-pump, possibly the electrogenic Na+-pump.     

Selective agenesis of the dorsal pancreas in mice lacking homeobox gene Hlxb9.

The initial stages of pancreatic development occur early during mammalian embryogenesis, but the genes governing this process remain largely unknown. The homeodomain protein Pdx1 is expressed in the developing pancreatic anlagen from the approximately 10-somite stage, and mutations in the gene Pdx1 prevent the development of the pancreas. The initial stages of pancreatic development, however, still occur in Pdx1-deficient mice. Hlxb9 (encoding Hb9; ref. 6) is a homeobox gene that in humans has been linked to dominant inherited sacral agenesis and we show here that Hb9 is expressed at early stages of mouse pancreatic development and later in differentiated beta-cells. Hlxb9 has an essential function in the initial stages of pancreatic development. In absence of Hlxb9 expression, the dorsal region of the gut epithelium fails to initiate a pancreatic differentiation program. In contrast, the ventral pancreatic endoderm develops but exhibits a later and more subtle perturbation in beta-cell differentiation and in islet cell organization. Thus, dorsally Hlxb9 is required for specifying the gut epithelium to a pancreatic fate and ventrally for ensuring proper endocrine cell differentiation.