Receptive field mechanisms of ganglion cells in the cat retina

On the basis of anatomical and physiological results of the vertebrate retina, a method is proposed for analysing the respective fields of ganglion cells in the cat retina. In the model, we assume the following: (a) Ganglion cells receive their input from bipolar and/or amacrine cells. (b) The nonlinearity of ganglion cell responses is due to the activities of transient type amacrine cells. The method has been proved to be effective. According to the results of this investigation, the receptive field properties of X type and Y type ganglion cells are heterogeneous. Thus, it may be considered that their receptive fields consist of center and surround mechanisms. The receptive field properties of X-cells are almost linear and the X-cells seem to receive most of their input from bipolar cells. On the other hand, the ones of Y-cells are highly nonlinear. Consequently, it is conceivable that the Y-cells receive their input mainly from transient type amacrine cells.     

Restriction fragment length polymorphism detected by human salivary amylase cDNA

Summary The plasmid clone which contains human salivary amylase cDNA was used to detect restriction fragment length polymorphisms (RFLPs). After double digestion with Pst 1 and Bam H1, a polymorphism with two alleles was observed. In Japanese, frequencies of these alleles, tentatively called 5.7kb and 6.5kb fragment alleles, are 0.55 and 0.45, respectively.     

Spider toxin (JSTX) on the glutamate synapse

A new neurotoxin (JSTX) was separated from spider (Nephila clavata, Joro spider) venom. JSTX irreversibly suppressed the excitatory postsynaptic potential (EPSP) and the glutamate potential in the lobster neuromuscular junction with high degree of specificity. The threshold concentration for suppressing EPSPs corresponds to a small fraction of the toxin in a venom gland, roughly estimated as low as 10(-10) M/l. 10(-10) M/l. In the giant synapse of squid stellate ganglion JSTX suppressed EPSPs without affecting the antidromic response. Glutamate-induced membrane depolarization was blocked by JSTX. In mammalian brain slice preparation, JSTX suppressed the orthodromic spike response but failed to affect on the antidromic spike in the hippocampal pyramidal neuron of CA1 and CA3 region. The above results strongly support the view that the squid giant synapse and synapses in the hippocampal pyramidal neuron are mediated by glutamate.     

Changes of aldolase A and B messenger RNA levels in rat liver during azo-dye-induced hepatocarcinogenesis

The expression of aldolase A and B mRNAs during azo-dye-induced carcinogenesis in rat liver was examined. After feeding the dye for 18 weeks, the level of aldolase A mRNA increased to about 11 times that in a normal liver, with the concomitant decrease of aldolase B mRNA level to about 25% of that in a normal liver. These changes did not occur progressively during the carcinogenesis, but occurred as an additional phase after 4 week-feeding of the azo-dye. At this stage, the levels of aldolase A and B mRNAs were about 7 times and 45% of that in a normal liver, respectively. This biphasic pattern in the aldolase isozyme expression in the azo-dye-fed rat liver is discussed together with the kinetic data of the enzyme activity.     

Respiration and avoidance reaction of a cyprinid fishPseudogobio esocinus under hypoxia

A cyprinid fish,Pseudogobio esocinus showed gradual bradycardia at oxygen saturation (%) of less than 29.7±4.6 (1.89±0.29 ml/l of oxygen concentration), surfacing at 14.7±1.3 (0.94±0.09ml/l), drastic decrease of oxygen consumption at less than 14.2±0.8 (0.91 ±0.06ml/l) and asphyxia at 9.7±1.4 (0.62±0.09ml/l). The fish avoided water having low oxygen saturation of less than 54.0± 5.4 (3.38±0.30ml/l), and markedly at less than 26.2±3.4 (1.62±0.16 ml/l).     

A new life table of leaves ofPhaseolus vulgris L. in relation to their position within the canopy and plant density

In order to demonstrate in detail the relationship between the longevity and productivity of leaves within a canopy, a new life table approach, the ‘bioeconomic life table’, was applied to the leaves of kidney bean plants (Phaseolus vulgaris L.) in relation to planting density and their position within the canopy. The net photosynthetic rate for upper leaves under full daylight tended to decline gradually due to leaf senescence from about 20 days after leaf emergence, and for the lower leaves the decrease was very rapid due to both shading and senescence about 10 days after emergence. Analysis of the survivorship curves and daily surplus production of leaves suggested that the lower and middle leaves, especially the latter, survived without surplus production of dry matter after they had reached mean longevity, and while the upper leaves at high density had a much shorter mean longevity, they had very large values of daily surplus production throughout the survival period. For the total foliage, the summed value of accumulated surplus production during the survival period was about five times as large as the summed value of the dry weight of the dead leaves, regardless of planting density. The daily rate of canopy leaf respiration was almost proportional to that of canopy gross photosynthesis for the various leaf area indices of the canopy, so that there was no optimum leaf area index that maximized canopy daily surplus production.     

Genotoxicity of quinone pigments from pathogenic fungi

The genotoxicity and mutagenicity of several kinds of quinone pigments from pathogenic fungi were examined by means of the hepatocyte primary culture (HPC)/DNA repair test and of Ames test with TA98 and TA100. Clear genotoxicity of the two quinone chemicals, xanthomegnin and luteosporin were observed in the HPC/DNA repair test, though definite mutagenicity was not detected in the Salmonella microsome test. These two pigments are thus suspected to be genotoxic carcinogens.     

Distinction of two subtypes of human leukocyte interferon (IFN-alpha) on B cell activation. B cell proliferation by two subtypes of IFN-alpha

We examined the effect of interferon (IFN), with particular emphasis on the effects of the two subtypes of IFN-alpha (IFN-alpha A and IFN-alpha B) on the B cell proliferation induced by Staphylococcus aureus Cowan I bacterium (SpA Col). An increase of SpA Col-induced proliferation was observed in the presence of 100 to 1000 U/ml of IFN-alpha, but a decrease of SpA Col-induced proliferation was observed in the presence of 1000 to 10,000 U/ml of IFN-beta. The two subtypes of IFN-alpha had different effects on cell proliferation; a significant enhancement was shown in the presence of 1000 to 10,000 U/ml of IFN-alpha A, but inhibition was shown in the presence of 1000 to 10,000 U/ml of IFN-alpha B. In the reconstitution test of the two subtypes of IFN-alpha, the boundary between enhancement and inhibition of SpA Col-induced proliferation was revealed when the proportion of IFN-alpha A and IFN-alpha B (IFN-alpha A:IFN-alpha B) ranged between 8:2 and 9:1. Toward the SpA Col-induced responses, the above IFN were all found to act on B cells directly, independent of the presence of T cells. Proliferative responses by IFN-alpha and IFN-alpha A, however, were shown to be slightly dependent on the presence of monocytes. The lymphocyte proliferation induced by other mitogens (phytohemagglutinin, concanavalin A, pokeweed mitogen, and protein A of S. aureus) were all inhibited by the above IFN.