Distribution and different activation of adenylate cyclase by NaF and of guanylate cyclase by NaN3 in neuronal and glial cells separated from rat cerebral cortex

Distribution of adenylate cyclase and guanylate cyclase activities in neuronal perikarya and glial cells separated from rat brain, and cellular differences in activation between of adenylate cyclase by NaF and of guanylate cyclase by NaN3 have been studied. Adenylate cyclase activity was higher in the glial cells than in the neuronal fraction, while guanylate cyclase activity was equally detected in both cell fractions. Adenylate cyclase was mainly derived from the particulate fraction of both brain cell homogenates, whereas the major portion of guanylate cyclase activity was found in their soluble rather than in the particulate fractions. Although bulk-separated neurons and glial cells almost failed to change intracellular cyclic nucleotide levels in response to some putative neurotransmitters, activation of adenylate cyclase by NaF was found to be greater in neuronal than in glial cell fractions, and was observed more clearly in the soluble than in the particulate fractions. Sodium azide greatly increased guanylate cyclase in the particulate fraction, but did not affect it considerably in the soluble one. Addition of catalase to the reaction mixture together with NaN3 further stimulated guanylate cyclase both int he soluble and the particulate fractions. These results suggest that adenylate cyclase and guanylate cyclase without intimate coupling to the transmitter-receptor system, but with activation by NaF or NaN3, may be distributed ubiquitously in the cells separated from rat cerebral cortex.

Task redundancy and an enhancement of the late positive components in human visual evoked potentials

VEPs to four or six repetitive letter and checkerboard stimuli were measured. These stimuli were presented in a first triplet and a single stimulus or in first and second triplets. Three stimuli in a triplet were identical. The subject's task was either naming the letter stimulus or pattern matching the checkerboard. A degree of task-redundancy of the stimuli at intratrial stimulus positions 2 and 3 was varied by means of stimulus duration and indication of the task stimulus prior to the triplet. The stimulus duration was 300 msec and the prior information of the task stimulus was delivered by a letter or checkerboard warning stimulus (WS) in session 1. The stimulus duration was shorter (10 msec in session 2, 20 microseconds in session 3) and the WS of random pattern did not deliver the information of the task stimulus in session 2 and 3. At stimulus positions 2 and 3, the P260 of the occipital VEP enhanced in amplitude for the letter and checkerboard stimuli in session 1, whereas the P260 decreased in amplitude for both stimuli at the same positions in session 3.

Reduction of ferricytochrome c by human red cells

Human red cells reduced extracellular ferricytochrome c to ferrocytochrome c under various conditions, suggesting that ferricytochrome c reducing systems are present at the outer surface of the red cell membrane.

[Non-surgical collection of uterine eggs in the rat (author's transl)]

The non-surgical collection of rat embryos were examined. The apparatus for uterine flushing (Fig. 1 and 2) were designed to have a two-way system. Egg collection were made 5 days after mating. Eggs were collected from anesthetized donors using a pair of glass pipettes inserted to the end of each uterine horn through the cervix uteri. By non-surgical technique, it was successful to collect the eggs at an average of 4.0 from all the animal. The recovery rate was 40.7% as estimated the number of corpora lutea counted after the slaughter of the donor. The recovery rat in non-surgical methods was considerably lower as compared with that of the uterine flushing after the slaughter.

Involvement of a macromolecular activating factor in activity of guanylate cyclase partially purified from supernatant of a pig lung extract

A guanylate cyclase preparation partially purified from supernatant of a pig lung extract was subjected to affinity chromatography on an Agarose-GTP column. The major portion of the cyclase activity was adsorbed on the column and then eluted with 50 mM EDTA and 0.5 M KCl, whereas the fractions non-adsorbed on the column contained a factor which enhanced the cyclase activity. Addition of the activating factor to a cyclase reaction mixture increase the enzyme activity without a time lag, and this enhancement by the factor was dose-dependent. With concomitant presence of cyclase and the factor in the reaction mixture the apparent Km value for GTP-Mn2+ of the enzyme was 56 microM, this value being the same as in absence of the factor, however, here the maximum velocity increased 4-fold. The factor was nondiffusable, heat-labile, partially sensitive to trypsin, and resistant to acid or alkali. As estimated by gel filtration, this factor had an apparent molecular weight of 85 000.

Visual evoked potentials associated with the verbal and non-verbal problem-solving processes

VEPs to six repetitive checkerboard and letter or number stimuli (presented in two triplets) were measured. The task solution process was separated into the store, retention, solve and post-solve stages. Three stimuli in intratrial stimulus positions 1, 2 and 3 were identical and another three in positions 4, 5 and 6 were also identical. The subject's task was either naming the letter-number or matching the checkerboard stimuli in two triplets. For both stimuli, the occipital P270 was almost the same in amplitude as positions 1 and 4. During the memory retention (at position 2) the P270 enhanced for the letter-number stimulus, but not for the checkerboard. During the post-solve stage (at positions 5 and 6) the P270 enhanced for both stimuli. The occipital P270 enhancement seems to correlate with the decrease in the degree of significance of the task relevant stimuli.

The cumulative inhibitory effect of repetitively flashed stimuli on the recovery process of the human visual evoked potential to a test stimulus

Cumulative inhibitory effects produced by visual response to flashed conditioning stimuli were measured by means of the amplitude reduction of the visual evoked potential (VEP) to a test stimulus. Four kinds of conditioning stimuli were used: a single conditioning stimulus and 3 repetitive conditioning stimuli with interstimulus intervals (ISIs) of 100, 200 and 400 msec, respectively. The VEP amplitude for the test stimulus was reduced most when the stimulus was paired with the single conditioning stimulus. It still remained small when the test stimulus was paired with the repetitive conditioning stimulus of 400 msec ISI, increased significantly when the ISI was shortened from 400 to 200 msec. Explanations of the VEP behaviors in terms of the stimulus relevance, task difficulty and the recovery rate of the cortical excitability were discussed.