Voltage-dependent depolarization of bacterial membranes and artificial lipid bilayers by the peptide antibiotic nisin

The peptide antibiotic nisin is shown to disrupt valinomycin-induced potassium diffusion potentials imposed on intact cells of Staphylococcus cohnii 22. Membrane depolarization occurred rapidly at high diffusion potentials while at low potentials nisin-induced depolarization was slower suggesting that nisin requires a membrane potential for activity. This assumption was proven in experiments with planar lipid bilayers (black lipid membranes). Macroscopic conductivity measurements indicated a voltage-dependent action of nisin. The potential must have a trans-negative orientation with respect to the addition of nisin (added to the cis-side) and a sufficient magnitude (ca. -100 mV). With intact cells the threshold potential was lower (-50 to -80 mV at pH 7.5 and below -50 mV at pH 5.5). Single channel recordings resolved transient multistate pores, strongly resembling those introduced by melittin into artificial bilayers. The pores had diameters in the range of 0.2–1 nm, and lifetimes of few to several hundred milliseconds. The results indicate that nisin has to be regarded as a membrane-depolarizing agent which acts in a voltage-dependent fashion.Abbreviations BLM Black lipid membranes - CCCP carbonyl cyanide m-chlorophenylhydrazone - DOPC dioleoyl phosphatidylcholine - PS phosphatidylserine - TPP⁺ tetraphenylphosphonium cation     

The pattern of organization of intermediate filaments and their asymmetrical association with dense bodies in smooth muscle of an ascidian Halocynthia roretzi

Summary An extensive network of intermediate filaments that interconnected cytoplasmic dense bodies and connected the dense bodies to the cell surface was revealed in double-fixed, tannic acid-stained preparations of ascidian smooth muscle. The filament network ran through spaces in the continuous network of myofibrils, connecting them longitudinally, obliquely and transversely to form an intimately associated, dual network. In their transverse passage, the intermediate filaments ran across myofibrils along I-zones exclusively, interconnecting successive dense bodies.The pattern of attachment of intermediate filaments to dense bodies was predominantly one-sided. The filaments, which themselves were not incorporated into the contractile apparatus, remained folded or unfolded between myofibrils and between sarcomere-like structures in synchrony with the contraction-relaxation cycles.These results suggest that the intermediate filaments mechanically maintain the organization and arrangement of myofibrils via an intimate association with the myofibrils in the regions of the dense bodies, in such a way that the filaments do not impede muscle function.Based on these observations, a new model for the network of intermediate filaments in smooth muscle cells is proposed.     

Electron-microscopic studies on the threshold value of calcium concentration for the release of storage granules and the acceleration of their degradation in the rat parathyroid gland

Summary To determine both a threshold value of calcium concentration (CC) for the release of storage granules and that for the acceleration of degradation of these granules, the rat parathyroid glands were perfused in situ with HEPES-Ringer solutions containing different concentration of Ca²⁺ for 10 min. With perfusates containing 0.83–1.21 mM Ca²⁺ (equivalent to 8–11 mg/dl serum calcium), the number of type-I storage granules (large core) [NSG-I] and that of type-II storage granules (small core) [NSG-II] remained unchanged. With perfusates containing 0.83 mM Ca²⁺ (7.5 mg/dl) or less, however, both NSG-I and NSG-II decreased remarkably and the former was larger than the latter. On the contrary, with perfusates containing 1.27 mM Ca²⁺ (11.5 mg/dl) or more, NSG-II increased and the ratio of NSG-I to NSG-II was changed reversely. We concluded that a thereshold value of CC required for the release of storage granules may be present between 0.88 and 0.83 mM Ca²⁺ (8 and 7.5 mg/dl) and that a threshold value of CC for accelerating the transformation of type-I granules into type-II, the degradation of storage granules, may be situated at about 1.27 mM Ca²⁺ (11.5 mg/dl). Additionally, it was suggested that both prosecretory and storage granules are not only formed at the innermost Golgi cisterna but also at the trans-Golgi network.     

带有隐含神经元的单层神经网络模型

提出了一种带有隐含神经元的单层神经网络模型。把网络的记忆容量区分为信息记忆容量和物理记忆容量。新模型能记忆相关图样,其信息容量α_i(最大记忆图样数/表达神经元数)首次超过了1。所作出的计算机模拟结果,表明了理论分析的正确性,证实了由5×5个显神经元组成的点阵能记住包含26个英文字母和4个任选图样的30个图样,因此该模型为神经网络的广泛应用提供了一条重要途径。     

一种复合神经元网络结构的并行动力学及快速学习算法

提出两种功能互相不同的神经细胞组成的复合神经元网络(CNN)模型;导出一种特殊结构的CNN的并行动力学;而且证明了它的稳定性。在这些结果基础上,得到快速的假逆矩阵学习算法。计算机仿真试验证实学习算法与动力学稳定性的正确性,并表现出良好的容错性能与存储容量。     

Diversity in the immune system: “Preconceived ideas” or ideas preconceived?

Two concepts of the evolution and regulation of expression of the combining site repertoire of the immune system, are compared. One view is based on the Associative Recognition Theory as formulated by the author and the other is based on the Idiotype Network Idea as conceived by Jerne. The two concepts are analyzed from the point of view of their logic, internal consistency and factual support.     

Voiceprint identification and its application to sociological studies of wild Japanese monkeys (Macaca fuscata yakui)

Japanese monkeys often exchange the particular vocal sound, “coo,” especially when they feed or move as a group. It was considered that the “coo” sound had no positive social meaning, perhaps because the “coo” sound network and its function were hidden behind other behavioral observations. For identification of the vocalizer only from hearing the “coo” sound, three phonetic values, i.e., the “fundamental,” “duration,” and “formants,” plus other characteristics were used as indices of voiceprints. The results indicated that these were effective for identifying the vocalizer in two-thirds of the adults in the study troop which was composed of 12 adults and 16 immature members. The “coo” sound exchange network among the troop members (adults) was drawn on the basis of the voiceprint identification. The network showed three characteristics as follows: (1) matriarchs of the kin-groups frequently exchanged “coo” sounds with each other; (2) the other females exchanged “coo” sounds mostly within their own kin-groups; and (3) males seldom participated in the “coo” sound exchange. This suggests that “coo” sound exchange plays a central role for the matriarch of kin-groups in binding each kin-group and, ultimately, in binding all members together into an organized troop.     

Diffusion of a lymph-carried antigen in the fiber network of the lymph node of the rat

Summary A lymph-carried antigen is retained preferentially in those areas of the subcapsular sinus of a lymph node overlying the extrafollicular zone of the peripheral cortex. There, it becomes associated with the reticular fibers crossing these particular sinus areas. We wondered whether the antigen thereafter diffuses along the extensions of these fibers which form a peculiar network in the cortical pathways of migration of circulating lymphocytes (CPMCL), leading to the different cell populations effecting the immune responses. Fluorescein isothiocyanate (FITC)-conjugated antigens were injected locally into rats sacrificed 0.5–24 h later. The antigens diffused along the fibers of the CPMCL. It is proposed that this diffusion constitutes one mechanism of stimulation of recruited circulating lymphocytes and of orientation of their migration towards the proper effector-cell population.This work was supported by the Medical Research Council of Canada     

Mode of antitumor action of recombinant human tumor necrosis factor on the sarcoma Meth A transplanted in the mouse

The mode of antitumor action of rHu-TNF was elucidated in BALB/c mice bearing Meth A fibrosarcoma 7 days after transplantation with respect to time course, dose-response relationships and selectivity of the effects. The maximal cytotoxic effect on tumor cells revealed by inhibition of DNA synthesis and maximal lesional effect on tumor vasculature revealed by change in blood pool-size in the tissue were detected at 30 min and I h after administration of rHu-TNF, respectively. The dose-response relationship between cytotoxic and tumoricidal effects of rHu-TNF was irrespective of administration route. ED₅₀s of these antitumor effects afteri.v. administration of rHu-TNF were about 50 times as high as ED₅₀s afteri.t. administration. ED₅₀ ofi.t. given rHu-TNF for vascular effect was about 20 times as high as that for cytotoxicity while ED₅₀ ofi.v. rHu-TNF for vascular effect was only 2–3 times as high as that for cytotoxicity. The whole body autoradiographies with [¹²⁵I] HSA giveni.v. to see the blood influx into tumor tissue and [¹⁴C]thymidine given i.v. to see DNA synthesis in the whole body after administration of rHu-TNF revealed that the distribution of radioactivity was markedly changed in the tumor alone without any detectable change in other whole body tissues.In conclusion, thein vivo antitumor effect of rHu-TNF giveni.t. ori.v., appears to be exerted through the direct action on Meth A sarcoma rather than indirectly on tumor vasculature. Under present conditions, the effect of rHu-TNF in the whole body tissues seems rather selective on cells and vasculature of the tumor.