Catchlike property of rat diaphragm: subsequent train frequency effects in variable-train stimulation.

A high-frequency burst of pulses at the onset of a subtetanic train of stimulation allows skeletal muscle to hold force at a higher level than expected from the extra pulses alone because of the catchlike property of muscle. The present study tested the hypothesis that the presence and degree of force increase induced by a high-frequency burst are strongly modulated by the subsequent train frequency. Rat diaphragm muscle strips (studied in vitro at 37 degrees C) underwent two-, three-, or four-pulse bursts [interpulse interval (IPI) of 5 or 10 ms] at the onset of 10- to 50-Hz subtetanic trains. Force was quantified during the train with respect to its peak value (F(peak)), mean value (F(mean)), and force-time integral (F(area)), and it was compared with that produced during subtetanic trains of an equal number of pulses without preceding pulse bursts (Diff-F(peak), Diff-F(mean), Diff-F(area)). F(peak) and F(mean) increased with two-, three-, and four-pulse bursts, and Diff-F(peak) and Diff-F(mean) increased progressively with decreasing frequency of the subtetanic train. F(area), the best reflection of catchlike force augmentation, was increased mainly by the four-pulse bursts with an IPI of 10 ms, and Diff-F(area) was maximal at subsequent train frequencies of 15-25 Hz. The use of incorrect patterns of burst stimulation could also precipitate F(area) decreases, which were observed with the four-pulse, 5-ms IPI paradigm. The time required to reach 80% of maximal force (T(80%)) became shorter for each of the pulse burst stimulation patterns, with maximal reduction of Diff-T(80%) occurring at a subsequent train frequency of 20 Hz in all cases. These data indicate that extra-pulse burst stimulation paradigms need to incorporate the optimal combinations of extra-pulse number, IPI, and the frequency of the subsequent subtetanic train to take greatest advantage of the catchlike property of muscle.     

化学结构与生物活性:N-取代氨基甲酸乙酯的合成与驱蚊活性

用氯甲酸乙醇与不同的胺类反应,合成了一系列取代氨基甲酸乙酯类化合物。用埃及伊蚊(`Aedes aegypti`` L.)进行驱避活性测定,所得结果表明,N-一元取代化合物的效果,以K-1023较明显。在N,N-二元取代化合物中,以K-1065的效果最好。一些化合物的分配系数与驱避比值的对数值之间,大致有一条直线关系,分配系数低时,驱避比值大致要高一些。在所测化合物的红外强吸收峰波数与驱避比值,看不出有相关性。     

中国幽灵蛛属一新种（蜘蛛目：幽灵蛛科）

本文记述了中国幽灵蛛科Pholcidae幽灵蛛属Pholcus蜘蛛一新种;太白幽灵蛛,新种Pholcus taibaiensis sp. nov,采自陕西省太白山自然保护区。模式标本分别保存在西安师范学院生物系和河北教育学院生物系。     

土曲霉金色变种AT8951菊粉酶的纯化和性质的研究

土典霉金色变种AT8951菊粉酶粗酶液经硫酸铵分段沉淀、DEAE Cellulose DE32离子交换、超滤、Sephadex G-150凝胶过滤和FPLC,获得两个菊粉酶组分EⅠ和EⅡ,经分析型FPLG和PAGE鉴定为单一纯和分析纯。EⅠ分子量为66KD,最适作用温度和pH分别55℃和5.8;EⅡ分子量为56KD,最适作用温度为57℃,最适pH为6.0。EⅠ和EⅡ皆为糖蛋白,多糖含量分别为24.7％和22％,都属于内切酶。本文还对EⅠ和EⅡ的Km值和I/s值,温度、pH、离子对酶活作用的影响等进行了研究。     

昆虫病原细菌“010”的鉴定

1970年初,我们发现从蜜蜂幼虫中分离的芽孢杆菌“010”在生产性能和对昆虫的致病方面,均显示了良好的特性。该年我组曾与南苑公社化工厂共同对此菌的生产及毒效进行了初步摸索。继之,考察了它的营养要求及某些生产工艺条件,并对不同害虫进行了室内及大田的毒力测定。1971—1972年,通过培养基试验和上罐考察,选出两组综合利用较为理想的培养基。其中一组配比是:豆饼粉2.4％、玉米浆2％、麦芽粉4％、碳酸钙0.1％。菌数曾达48亿/毫升。“010”杀虫范     

Conversion of hydrogen sulphide by acidophilic bacteria

Conversion of hydrogen sulphide (H₂S) by the bacterium Thiobacillus thiooxidans to sulphur or sulphate was demonstrated in a continuous column contacter using a countercurrent flow of gas and liquid medium. The initial conversion to sulphur was much faster than subsequent oxidation to sulphate, allowing for removal of elemental sulphur. The rate of H₂S removal increased with available surface area in the column bed and with time. The number of bacteria in the column increased very slowly with time, placing great importance on the initial concentration of bacteria in the column. Correspondence to: H. M. Lizama     

Comparison of the collagenous products synthesized in culture by pig aortic endothelial and smooth-muscle cells. Variability in endothelial-cell cultures.

In contrast with smooth-muscle cells from the same tissue, endothelial cells from pig aorta were found to exhibit in culture considerable variability in the pattern of collagen synthesis between one isolation of cells and the next. Synthesis varied from largely collagen type I to virtually all type III in the absence of type I but with small amounts still of collagens types IV and V, to, in one instance, synthesis basically of only type V. Synthesis usually by these cells of collagen predominantly of the interstitial type (I and III) rather than, as might be expected, that from basement membrane (type IV) was not attributable to the influence of subculture. All four collagen types were deposited in the cell layer to an increased extent in primary compared with secondary cultures of either smooth muscle or endothelial origin. Endothelial cells appeared sometimes to synthesize a large-Mr collagenous entity that might conceivably be related to 'short-chain' collagen. In addition, small-Mr hydroxyproline-containing peptides were detected that might reflect rapid collagen(s) turnover in endothelial cultures.     

Analysis of the collagen types synthesized by bovine corneal endothelial cells in culture.

Bovine corneal endothelial cells synthesize in culture predominantly type III collagen, with lesser amounts of types I and V and apparently little if any type IV. This pattern of synthesis is observed in both dividing and post-confluent cultures and irrespective of whether cells are attached to plastic or collagen-coated surface.