Stretch activated ion channels in ventricular myocytes

Patch-clamp recordings from ventricular myocytes of neonatal rats identified ionic channels that open in response to membrane stretch caused by negative pressures (1 to 6 cm Hg) in the electrode. The stretch response, consisting of markedly increased channel opening frequency, was maintained, with some variability, during long (>40 seconds) stretch applications. The channels have a conductance averaging 120 pS in isotonic KCl, have a mean reversal potential 31 mV depolarized from resting membrane potential, and do not require external Ca⁺⁺ for activation. The channels appear to be relatively non-selective for cations. Since they are gated by physiological levels of tension, stretch-activated channels may represent, a cellular control system wherein beat-to-beat tension and/or osmotic balance modulate a portion of membrane conductance.Abbreviations SACs stretch-activated channels - HEPES 4-(2-hydroxyethyl)-1-piperazine-ethanesulfonic acid     

The profile distribution of total and extractable boron in cacao-growing soils in southwestern Nigeria

The profile distribution of total and extractable B was determined in 16 Nigerian cacao-growing soil profiles formed from different parent materials. Total B for all soils ranged from 8 to 54μgg⁻¹ with a mean of 24μgg⁻¹. The soils formed from sandstones in the rainforest zone contained higher amounts of total B than soils derived from basement complex. Boron extractable in hot water, in 0.1% CaCl₂, and in 1N NH₄OAc varied from 0.13 to 1.38, 0.44 to 1.20 0.03 to 0.56μgg⁻¹ respectively. The corresponding means were 0.66, 0.75 and 0.27μgg⁻¹ B. Soils on metamorphic rocks gave the highest values. All extractable B values were related to organic matter while only CaCl₂-extractable B correlated with total B. Generally total and extractable B values were higher in the top soils than in the subsoils.     

On the mechanism of formation of N-acetyldopamine quinone methide in insect cuticle

The mechanism of formation of quinone methide from the sclerotizing precursor N-acetyldopamine (NADA) was studied using three different cuticular enzyme systems viz. Sarcophaga bullata larval cuticle, Manduca sexta pharate pupae, and Periplaneta americana presclerotized adult cuticle. All three cuticular samples readily oxidized NADA. During the enzyme-catalyzed oxidation, the majority of NADA oxidized became bound covalently to the cuticle through the side chain with the retention of o-diphenolic function, while a minor amount was recovered as N-acetylnorepinephrine (NANE). Cuticle treated with NADA readily released 2-hydroxy-3′,4′-dihydroxyacetophenone on mild acid hydrolysis confirming the operation of quinone methide sclerotization. Attempts to demonstrate the direct formation of NADA-quinone methide by trapping experiments with N-acetylcysteine surprisingly yielded NADA-quinone-N-acetylcysteine adduct rather than the expected NADA-quinone methide-N-acetylcysteine adduct. These results are indicative of NADA oxidation to NADA-quinone and its subsequent isomerization to NADA-quinone methide. Accordingly, all three cuticular samples exhibited the presence of an isomerase, which catalyzed the conversion of NADA-quinone to NADA-quinone methide as evidenced by the formation of NANE—the water adduct of quinone methide. Thus, in association with phenoloxidase, newly discovered quinone methide isomerase seems to generate quinone methides and provide them for quinone methide sclerotization.     

An electronic mechanism in the action of drugs, ATP, transmitters and other cardinal adsorbents. II. Effect of ouabain on the relative affinities for Li+, Na+, K+, and Rb+ of surface anionic sites that mediate the entry of Cs+ into frog ovarian eggs

Ouabain enhanced the inhibitory effects of Li+, Na+, and K+ on the rate of Cs+ permeation into frog ovarian eggs while it reduced the inhibiting effect of Rb+. The data agree with earlier demonstrated effects of ouabain on the rank order of selective accumulation of the five alkali-metals in frog muscles and on the relative effectiveness of glycine, Li+, Na+, K+, Rb+, and Cs+ in inhibiting the rate of entry of Cs+ into frog sartorius muscle. In all three cases, the ouabain behaved as an electron-donating cardinal adsorbent (EDC) causing a rise of the electron density (c-value) of the beta- and gamma-carboxyl groups in the cell cytoplasm (for selective accumulation) and on the cell surface (for selective ion permeation). Explanations based on the association-induction hypothesis were offered why an EDC like ouabain does not initiate cell activation (like veratridine does) and why Ca++ and tetradotoxin delays or inhibits physiological and artificial cell activation.     

新生儿巨细胞病毒感染的检测

建立了用ELISA检测巨细胞病毒(HCMV)IgA抗体的方法,並用于检测北京地区100对母婴的HCMV抗体,母血、脐带血、母乳中HCMV-IgG抗体的阳性率分别为83％,75％和38％,HCMV-IgA抗体的阳性率分别为19％,15％和58％,对其中的16名婴儿半年后追踪观察,5名出生时母、脐血全为阴性的,有2名抗体阳转。8名出生时母、脐血均阳性的,有1名IgA仍阳性並检查发现肝大肋下二指。另1名IgG持续阳性,其他6名婴儿抗体转阴。3名出生时母血HCMV-IgG阳性者中,1名婴儿IgA和‘gG转阳,此时母亲IgA也阳转。随访的16名婴儿中有3名可能是生后半年内受HCMV感染。     

银额果蝇的B染色体研究 2.昆明群体的生活力和B染色体的关系

本文分析了钮额果蝇的生活力和B染色体的关系。结果表明,银额果蝇的B染色体在其生长和发育过程中具双重性调节作用。一方面,B染色体以单一的形式存在于单雌系核型中,即1B或2Bs,可刺激生长、发育,增强生活力。另一方面,在单雌系的细胞中存在多条B染色体,并形成核型多态性,这似乎对生长和发育又有一定的抑制作用而减弱其生活力。     

Swimming response of goldfish,Carassius auratus,and the tetra,Hemigrammus caudovittatus,larvae to individual food items and patches

Synopsis Swimming speed and swimming path of goldfish and tetra larvae were studied in aquaria containing food patches composed of decapsulated cysts and immobilized nauplii of Artemia salina or sparsely distributed prey. The mean swimming speed of starved larvae in the medium without food was about four times higher than the speed of larvae feeding in a patch. Satiated larvae swam about 1.5 times slower than hungry fish. Consumption of single prey items by starved larvae caused the following sequence of swimming responses: handling pause (cessation of swimming), slow swimming in a restricted area, and fast swimming (approximately twice as fast as hungry larvae before encountering food) accompanied by a widening of the area searched (area increased searching). Mean swimming speed was constant over a broad range (10¹–10³ ind·1^–1 of food density, although at extreme (high or low) values of food density it depended on swimming responses of the predator. Frequency of visits to the different parts of the aquarium strongly depended on encounters of hungry fish with food particles or patches.     

Sensitization of low-dose-rate irradiation by nonlethal hyperthermia

To assess whether hyperthermia could radiosensitize cells irradiated at a low dose rate, Chinese hamster V79 cells were simultaneously heated and irradiated at 0.86 Gy/h. The data showed that heat treatments at 39 and 40 degrees C, which did not induce heat killing alone or high-dose-rate radiosensitization, resulted in enhanced cell killing with low-dose-rate irradiation. The dose-modification factor (ratio of the slopes of the curves for low dose rate and high dose rate) was reduced to 1.8 at 39 degrees C and 1.4 at 40 degrees C, compared to a value of 2.1 at 37 degrees C. These data indicate that nonlethal heat treatments can cause enhanced radiosensitization under low-dose-rate conditions. The implications of these results for interstitial thermoradiotherapy are discussed.     

Changes in pulmonary Cu−Zn contents in superior mesenteric artery occlusion shock of rabbit

Contents of Cu and Zn of into-pulmonary blood (IPB), out-pulmonary blood (OPB), Lung tissue, and supernatant and macrophages of Lung Lavage were determined in superior mesenteric artery occlusion (SMAO) shock of rabbits. Zn of pulmonary tissue was 11.42 +/- 0.60 and 14.52 +/- 1.78 (micrograms/g wet wt) in SMAO shock and control groups, respectively. Content of Zn was found to be lower, Cu was not changed, and Cu/Zn ratio increased in lung tissue in SMAO shock. Contents of Cu and Zn in other samples were not changed. The results suggest that lower Zn in lung tissue related to acute lung injury.