Sendai virus fusion activity as modulated by target membrane components

It is generally known that the anuran stomach begins to express pepsinogens (Pg) during metamorphosis. To clarify the mechanisms of differentiation of Pg-producing cells, we examined immunohistochemically the epithelial transformation from larval to adult form in Xenopus laevis stomach at the cellular level. At the beginning of metamorphic climax, concomitantly with the modification of the basement membrane, apoptotic cells labelled by TUNEL suddenly increased in number in the entire epithelium except for the primordia of adult epithelial cells in the basal region of larval glands. Subsequently, with the development of connective tissue, the adult epithelial cells actively proliferated and replaced the larval cells from the basal to the luminal region. Following the start of morphogenesis of adult glands, Pg-producing cells became differentiated in newly formed adult glands, but not in the adult surface epithelium. We then developed an organ culture system and examined effects of thyroid hormone (TH) on the differentiation of Pg-producing cells in X. laevis stomach in vitro. In the presence of TH, just as in spontaneous metamorphosis, Pg-producing cells differentiated from the adult epithelial primordia after the apoptosis of larval epithelial cells. In contrast, in the absence of TH, neither apoptotic larval cells no Pg-producing cells were detected. Therefore, we conclude that TH triggers organ-autonomously the entire process leading to the differentiation of Pg-producing cells in X. laevis stomach. In addition, the strict localization of Pg-producing cells in the adult glands both in vivo and in vitro suggests the correlation between the differentiation of Pg-producing cells and morphogenesis of the glands surrounded by the developed connective tissue.     

Intracellular glucose concentration in derepressed yeast cells consuming glucose is high enough to reduce the glucose transport rate by 50%

1. This study describes the in vitro characterization of two potent and selective 5-HT6 receptor antagonists at the rat and human recombinant 5-HT6 receptor. 2. In binding assays with [3H]-LSD, 4-amino-N-(2,6 bis-methylamino-pyrimidin-4-yl)-benzene sulphonamide (Ro 04-6790) and 4-amino-N-(2,6 bis-methylamino-pyridin-4-yl)-benzene sulphonamide (Ro 63-0563) had mean pKi values +/-s.e.mean at the rat 5-HT6 receptor of 7.35+/-0.04 and 7.83+/-0.01, respectively and pKi values at the human 5-HT6 receptor of 7.26+/-0.06 and 7.91+/-0.02, respectively. 3 .Both compounds were found to be over 100 fold selective for the 5-HT6 receptor compared to 23 (Ro 04-6790) and 69 (Ro 63-0563) other receptor binding sites. 4. In functional studies, neither compound had any significant effect on basal levels of cyclicAMP accumulation in Hela cells stably expressing the human 5-HT6 receptor, suggesting that the compounds are neither agonists nor inverse agonists at the 5-HT6 receptor. However, both Ro 04-6790 and Ro 63-0563 behaved as competitive antagonists with mean +/-s.e.mean pA2 values of 6.75+/-0.07 and 7.10+/-0.09, respectively. 5. In rats habituated to observation cages, Ro 04-6790 produced a behavioural syndrome similar to that seen following treatment with antisense oligonucleotides designed to reduce the expression of 5-HT6 receptors. This behavioural syndrome consisted of stretching, yawning and chewing. 6. Ro 04-6790 and Ro 63-0563 represent valuable pharmacological tools for the identification of 5-HT6 receptors in natural tissues and the study of their physiological function.     

Effect of duodenal glucose infusion on blood glucose concentration in endotoxin-treated calves

The effect of endotoxemia on the intestinal absorption of glucose was evaluated in nine experiments performed on seven 3- to 5-week-old calves fitted with a duodenal cannula. An intraduodenal glucose load trial (infusion of 2 g glucose/kg b.w. as a 10% aqueous solution through the cannula over 60 min) was conducted in a group of 5 calves three times during the 4-day period: 48 h before and at 2 and 24 h after i.v. injection of E. coli 0111:B4 endotoxin (LPS) at a dose of 0.1 microgram/kg b.w. Control calves were treated similarly but instead of glucose they were infused intraduodenally with deionised water at a volume of 20 ml/kg b.w. In trial with glucose load performed 48 h before LPS administration, blood glucose concentration increased during the absorptive phase from 4.32 +/- 0.32 mmol/l to 11.45 +/- 0.87 mmol/l at 60 min and then decreased to a minimum value of 3.16 +/- 0.51 mmol/l at 240 min. During the initial phase of endotoxemia, blood glucose concentration did not change from baseline values in both groups of calves. Glucose concentration in control calves started to decrease at 165 min reaching a minimum value of 1.39 +/- 0.17 mmol/l at 210 min and then increased to 2.44 +/- 0.11 mmol/l at 480 min after LPS administration. The intraduodenal infusion of glucose at 2 h after LPS administration resulted in an increase in blood glucose concentration during the absorptive phase only in one calf. Blood glucose concentration in this calf increased between 30 and 90 min reaching a maximum value of 7.19 mmol/l at 60 min, and then decreased to a minimal value of 0.94 mmol/l at 180 min after glucose load. In the remaining four calves in this group, blood glucose concentration ranged from 3.89 +/- 0.37 mmol/l to 4.48 +/- 0.45 mmol/l up to 120 min, and then steadily decreased to a minimal value of 2.41 +/- 0.41 mmol/l at 300 min. In trial with glucose load performed 24 h after LPS administration, the rate of entry of glucose into the circulation during the absorptive phase was similar to that observed in the trial performed 48 h before LPS administration. In conclusion, these results indicate that endotoxemia impairs the intestinal absorption of glucose in calves. The magnitude of the absorption disturbance may vary in individual calves, and the inhibitory effect of LPS on the intestinal glucose absorption lasts less than 24 h.     

The priming effect of glucose on insulin secretion from isolated islets of Langerhans

Biphasic insulin secretion from perifused rat islets of Langerhans was enhanced if islets had previously been stimulated with glucose 16.6 mmol/l. The priming effect of glucose was reduced if mannoheptulose (16.6 mmol/l), deuterium oxide (D2O; 98% v/v) or adrenaline 10 mumol/l) was included in the medium during the initial stimulation period, or if Calcium was omitted. Glyceraldehyde (16.6 mmol/l) but not theophylline (5 mmol/l) could substitute for glucose during the initial stimulation and make islets more responsive to subsequent stimulation. The results suggest that the priming effect of glucose on insulin secretion may be related to 1) glucose metabolism and 2) Ca fluxes in the B cell and the consequent activation of the microtubular system. Neither the generation of intracellular cyclic AMP nor the release of insulin per se appears to be involved in the priming process.     

Medullary respiratory neuronal activity modulated by stimulation of the fastigial nucleus of the cerebellum

The ability of the rostral fastigial nucleus (FNr) of the cerebellum to modulate medullary respiratory neuronal activity was examined in 17 anesthetized, paralyzed and ventilated cats. A bipolar stimulating electrode was positioned into the FNr and tungsten microelectrodes used to record units within the nucleus tractus solitarius (NTS), nucleus ambiguus (NA) and nucleus retroambigualis (NRA). Transient stimuli (< 150 microA, 5-200 Hz) were delivered during inspiration or expiration, and the effects noted on medullary neuronal activity and the phrenic neurogram. The results showed that FNr stimulation: (1) modulated inspiratory and expiratory neuronal (ramp-, early- and late-inspiratory and stage I and II expiratory) discharges recorded from the NTS, NA and NRA (n = 67, 14 and 28) when stimuli (> or = 20-50 Hz) were delivered during either the inspiratory or expiratory phases; (2) terminated the burst durations of inspiratory (77%) and expiratory (94%) neurons with stimulus-response latencies of 28.2 +/- 3.1 ms (inspiratory) and 29.4 +/- 3.6 ms (expiratory); (3) elicited changes in phrenic neurogram concomitant with the effects noted on medullary neuronal activities; (4) failed to change heart rate and arterial blood pressure; and (5) did not affect medullary neuronal and phrenic nerve activity following kainic acid injection into the FNr. We conclude that activation of the FNr (likely its cell bodies) can modulate the respiratory output via influences on medullary respiratory-related neurons. The primary cerebellar effect across all sub-types of respiratory neurons was early termination.     

NADPH diaphorase activity in mammalian retinas is modulated by the state of visual adaptation

NADPH diaphorase histochemistry is commonly used to identify cells containing nitric oxide synthase (NOS), the enzyme catalyzing the production of nitric oxide from L-arginine. NADPH diaphorase activity and NOS immunostaining was demonstrated in different cells of the vertebrate retina; photoreceptors, horizontal cells, amacrine cells, ganglion cells, and Müller cells. However, the physiological role of nitric oxide (NO) in the retina has yet to be elucidated. In this study, we tested the assumption that NADPH diaphorase activity in the retinas of rabbits and rats depended on the state of visual adaptation. In the rabbit, light adaptation enhanced NADPH diaphorase activity in amacrine cells and practically eliminated it in horizontal cells. Dark adaptation induced the opposite effects; the NADPH diaphorase activity was reduced in amacrine cells and enhanced in horizontal cells. Retinas from eyes that were injected intravitreally with L-glutamate exhibited a pattern of NADPH diaphorase activity that was similar to that seen in dark-adapted retinas. In rats, the NADPH diaphorase activity of amacrine and horizontal cells exhibited adaptation dependency similar to that of the rabbit retina. But, the most pronounced effect of dark adaptation in the rat's retina was an enhancement of NADPH diaphorase activity in Müller cells, especially of the endfoot region. Assuming that NADPH diaphorase activity is a marker for NOS, these findings suggest that NO production in the mammalian retina is modulated by the level of ambient illumination and support the notion that NO plays a physiological role in the retina.     

Plasma cholesteryl ester transfer activity is modulated by the phase transition of the lipoprotein core

Previous studies have shown that lipid transfer protein (LTP) activity is strongly temperature dependent, demonstrating a dramatic rise in activity near 37 degrees C. We have investigated the origin of this rapid rise in LTP activity. LTP-mediated transfers of radiolabeled cholesteryl ester (CE) from LDL to HDL, HDL to LDL, LDL to biotin-LDL, HDL to biotin-HDL, and between liposomes were determined as a function of assay temperature. Only assays containing LDL demonstrated this rapid rise in CE transfer activity. In contrast, TG transfer was almost linear with assay temperature. As human LDL CE undergoes a thermal phase transition near 37 degrees C, we investigated whether the rapid rise in CE transfer was dependent on this transition. Monkey LDL were isolated from animals consuming diets containing cholesterol and enriched in saturated, monounsaturated, or polyunsaturated fatty acids. With these LDL as substrate, the CE transfer between 21 degrees and 49 degrees C could be described by two straight lines, the intersection of which defined the inflection temperature. Among eight LDL samples, the inflection temperature was highly correlated with the CE phase transition determined by differential scanning calorimetry (r2 = 0.86). Both calorimetry and CE transfer activity inflection values were correlated with the saturated + monoene/polyene ratio of the LDL cholesteryl esters (r2 = 0.733 and 0.612, respectively). For LDL with inflection temperatures below 37 degrees C, CE transfer activity at 37 degrees C increased 10-14% for each 1 degree C decrease in the inflection temperature. We conclude that LTP activity is markedly affected by the physical state of the core CE. Diets rich in saturated fatty acids may result in LDL that are poor LTP substrates, which may hinder LTP's ability to promote normal lipoprotein remodeling.     

In vivo and in vitro regulation of hepatic glucagon receptor mRNA concentration by glucose metabolism

We have recently cloned the murine glucagon receptor (GR) gene and shown that it is expressed mainly in liver. In this organ, the glucagon-GR system is involved in the control of glucose metabolism as it initiates a cascade of events leading to release of glucose into the blood stream, which is a main feature in several physiological and pathological conditions. To better define the metabolic regulators of GR expression in liver we analyzed GR mRNA concentration in physiological conditions associating various glucose metabolic pathways in vivo and in vitro in the rat and in the mouse. First, we report that the concentration of the GR mRNA progressively increased from the first day of life to the adult stage. This effect was abolished when newborn rodents were fasted. Second, under conditions where intrahepatic glucose metabolism was active such as during fasting, diabetes, and hyperglycemic clamp, the concentration of GR mRNA increased independent of the origin of the pathway that generated the glucose flux. These effects were blunted when hyperglycemia was corrected by phlorizin treatment of diabetic rats or not sustained during euglycemic clamp. In accordance with these observations, we demonstrated that the glycolytic substrates glucose, mannose, and fructose, as well as the gluconeognic substrates glycerol and dihydroxyacetone, increased the concentration of GR mRNA in primary cultures of hepatocytes from fed rats. Glucagon blunted the effect of glucose without being dominant. The stimulatory effect of those substrates was not mimicked by the nonmetabolizable carbohydrate L-glucose or the glucokinase inhibitor glucosamine or when hepatocytes were isolated from starved rats. In addition, inhibitors of gluconeogenesis and lipolysis could decrease the concentration of GR mRNA from hepatocytes of starved rats. Combined, these data strongly suggest that glucose flux in the glycolytic and gluconeogenic pathways at the level of triose intermediates could control expression of GR mRNA and participate in controlling its own metabolism.     

Effect of decreased glucose concentration on cerebrovascular tone in vitro

A single Polymerase Chain Reaction (PCR) within the rpoV gene was developed to rapidly distinguish mycobacteria isolated from clinical specimens. The species identifications of Mycobacterium avium complex (MAC) and Mycobacterium tuberculosis were congruent with standard typing techniques. The analysis was targeted toward the identification of species-specific markers for the clinically relevant M. tuberculosis and M. avium. In addition, HaeIII digestion of the amplification products yielded isolates-specific bands.     

电催化氧化芬顿法处理高质量浓度含氰废水

电化学处理技术可应用于许多水处理领域,是一种基本对环境无污染的"绿色"水处理技术。该文采用电催化氧化-芬顿技术组合工艺对铅锌矿冶炼生产过程产生的难降解高质量浓度含氰废水处理进行试验研究,其结果表明:该处理技术是可行的,可以使铅锌矿含氰废水中的COD由11 810 mg/L降至60 mg/L以下、总去除率为99.5%,CN_T~-由2 350 mg/L降至0.5 mg/L以下、去除率近100%,达到了国家排放标准。该处理技术是在常温常压条件下进行的,电化学设备相对简单,工艺技术灵活,设备占地面积小,处理周期短、效率高,可控制性强,无二次污染。     

Sensing by intrahepatic muscarinic nerves of a portal-arterial glucose concentration gradient as a signal for insulin-dependent glucose uptake in the perfused rat liver

In vivo, insulin increases net hepatic glucose uptake efficiently only in the presence of a portal-arterial glucose gradient. In isolated perfused rat livers supplied with a glucose gradient (portal 10 mM/arterial 5 mM) insulin-induced glucose uptake was blocked by atropine; in livers not supplied with the gradient (portal = arterial 5 mM) insulin-dependent glucose uptake was elicited by acetylcholine. Apparently, the gradient was sensed and transformed into a metabolic signal by intrahepatic nerves, releasing acetylcholine to muscarinic receptors.     

Causes of wavelike variation in the cross section and breaking of fibers obtained by pendant drop melt extraction

The causes of emergence of wavelike variations in the cross section of metal fibers obtained by pendant drop melt extraction on a cold rotating wheel in vacuum are analyzed. The theoretical results are confirmed by experimental data for fibers made from aluminum and the VT1 titanium alloy. It is shown that the variation in the diameter and fiber breaking are caused by capillary waves (Rayleigh waves) on the surface of the melt drop, which are induced by rotation of the cold rotating wheel. The waves at the fiber surface apparently emerge under the effect of vibrations with frequencies higher by a factor of 3000–3500 compared with the rotation speed of the wheel or by the defects located on the fiber surface at a distance of ～0.2–0.3 mm from each other.     

Antioxidant pyrrolidine dithiocarbamate prevents defective bradykinin-stimulated calcium accumulation and nitric oxide activity following exposure of endothelial cells to elevated glucose concentration

Previous studies from our laboratory suggest that reactive oxygen contributes to diminished bradykinin-stimulated calcium accumulation in endothelial cells exposed to elevated glucose concentrations. In this study, we evaluated the efficacy of the antioxidant pyrrolidine dithiocarbamate (PDTC), in preventing defects in intracellular calcium signalling and nitric oxide (NO) activity in endothelial cells exposed to elevated glucose concentration. We show that PDTC prevented the elevated glucose-induced impairment in bradykinin-stimulated calcium accumulation without changing the normal calcium accumulation in response to ionomycin. Furthermore, the impaired cyclic GMP in RFL-6 detector cells (an index of NO activity) generated by bradykinin-stimulation of high glucose-exposed endothelial cells was restored to normal by pretreatment with PDTC. These studies support a role of reactive oxygen in elevated glucose-induced defects in calcium signalling and NO activity by endothelial cells and that antioxidants may be useful in preventing this defect.     

Use of a subcutaneous glucose sensor to detect decreases in glucose concentration prior to observation in blood

The development of a hypoglycemic alarm system using a subcutaneous glucose sensor implies that a decrease in blood glucose is rapidly followed by a decrease in the signal generated by the sensor. In a first set of experiments the linearity and the kinetics of the response of sensors implanted in the subcutaneous tissue of normal rats were investigated during a progressive increase in plasma glucose concentration: the sensitivities determined between 5 and 10 mM and between 10 and 15 mM were not significantly different, and a 5-10 min delay in the sensor's response was observed. In a second set of experiments, performed in diabetic rats, the kinetics of the decrease in subcutaneous glucose concentration following insulin administration was monitored during a decrease in plasma glucose level, from 15 to 3 mmol/L. During the 20 first min following insulin administration, the sensor monitored glucose concentration in subcutaneous tissue with no lag time. Subsequently, the decrease in the estimation of subcutaneous glucose concentration preceded that of plasma glucose. This phenomenon was not observed when the same sensors were investigated in vitro during a similar decrease in glucose concentration and may be due to a mechanism occurring in vivo, such as the effect of insulin on glucose transfer from the interstitial space to the cells surrounding the sensor. It reinforces the interest of the use of implantable glucose sensors as a part of a hypoglycemic alarm.     

The activity of topoisomerase I is modulated by large T antigen during unwinding of the SV40 origin

When simian virus 40 (SV40) large T antigen binds to the virus origin of replication, it forms a double hexamer that functions as a helicase to unwind the DNA bidirectionally. We demonstrate in this report that T antigen can unwind and release an origin DNA single strand of less than full length in the presence of purified human topoisomerase I. The sites nicked by topoisomerase I in the strands released by T antigen during DNA unwinding were localized primarily to the "late" side of the origin, and the template for lagging strand synthesis was preferred significantly over the one for leading strand synthesis. Importantly, these sites were, for the most part, different from the sites nicked by topoisomerase I in the absence of T antigen. These data indicate that T antigen activates topoisomerase I nicking at discrete sites and releases these nicked strands during unwinding. We hypothesize that a single molecule of topoisomerase I can form a functional complex with a double hexamer of T antigen to simultaneously relax and unwind double-stranded origin-containing DNA.