Modulation of cerebral acetylcholine metabolism by the dorsal diencephalic conduction system in the rat

We investigated the effects of interruption of the impulse flow in the habenulopeduncular pathways by local infusion of tetrodotoxin on the acetylcholine and choline content in selected dopamine rich regions in the forebrain and midbrain in rats. The tetrodotoxin infusion caused a marked increase in acetylcholine content in the medial frontal cortex, striatum and ventral tegmental area+interpeduncular nucleus, but not in the limbic area or the substantia nigra, whereas choline content was reduced only in both the striatum and ventral tegmental area+interpeduncular nucleus. There was an increase in 3,4-dihydroxyphenylacetic acid content in the striatum after the manipulation. These findings suggest that the dorsal diencephalic conduction system may be involved in the integration of the activity of cholinergic neurons in the forebrain and midbrain regions and striatal dopanine neurons may play a role in the modulation of cholinergic neurons.     

Frequency domain studies of impedance characteristics of biological cells using micropipet technique. I. Erythrocyte.

This study aims at precise measurement of the membrane capacity and its frequency dependence of small biological cells using the micropipet technique. The use of AC fields as an input signal enables the magnitude and phase angle of membrane impedance to be measured at various frequencies. The micropipet technique was applied to human erythrocyte, and passive membrane capacity and conductivity were determined between 4 Hz and 10 KHz. Membrane capacity thus determined changed from 1.05 to 0.73 microF/cm2 between 4 Hz and 10 KHz. In addition to the micropipet technique, we used suspension method between 50 KHz and 10 MHz for the purpose of supplementing the new method with the one which has been in use for many years. We obtained a membrane capacity of 0.65-0.8 microF/cm2 using this technique. These values agree with the capacitance obtained with the micropipet method. Although this paper discusses only human erythrocytes, the study has been performed with lymphocytes and various forms of cancer cells. This paper is the first of the series of reports on frequency domain studies of the impedance characteristics of various biological cells.     

A new species ofScymnodalatias from the southern oceans,and comments on other squaliform sharks

Scymnodalatias albicauda sp. nov. is described from two specimens taken at high latitudes (45°S and 49°S). It is distinguished fromS. sherwoodi, only known species of the genus, by having white markings on the caudal fin, the second dorsal posterior tip almost reaching the upper caudal fin, shorter snout and head, smaller eye and larger fins. Relationships ofScymnodalatias to the generaScymnodon, Centroscymnus, andZameus are discussed, based chiefly on dermal denticle structure.Scymnodalatias andZameus uniquely share transverse ridges on their dermal denticles, and on this character they are treated as sister-groups. Comments on the above genera,Z. squamulosus and some species ofScymnodon are made to clarify their systematic status. As a result, it is proposed thatScymnodon includesichiharai, macracanthus, plunketi, andringens, thatCentroscymnus includescoelolepis, crepidater, crypt acanthus, andowstonii, and thatZameus includessquamulosus.     

Benzodiazepines and their metabolites: relationship between binding affinity to the benzodiazepine receptor and pharmacological activity

Experiments were carried out to study the relationship between binding affinity to the benzodiazepine receptor and pharmacological activity, especially anti-anxiety activity, of clinically useful benzodiazepines. In the in vitro experiments, fludiazepam showed the highest affinity to the benzodiazepine receptor with 4 times more potency than that of diazepam, which paralleled the in vivo activity. Diazepam and nimetazepam also bound with high affinities as expected from their in vivo activities. On the contrary, medazepam and cloxazolam showed extremely low affinities and oxazolam showed no affinity, although they showed moderate in vivo activity. However, their metabolites were found to have both high affinity and in vivo activities. These results strongly suggest that in the case of medazepam, cloxazolam and oxazolam, their metabolites may bind to receptor sites in the brain and then elicit pharmacological action. This conclusion was supported by the fact that a good correlation between the binding affinity and the anti-anxiety activity of the tested compounds was observed.     

Molecular cloning of the cls gene responsible for cardiolipin synthesis in Escherichia coli and phenotypic consequences of its amplification.

The cls gene responsible for cardiolipin synthesis in Escherichia coli K-12 was cloned in a 5-kilobase-pair DNA fragment inserted in a mini-F vector, pML31, and then subcloned into a 2.0-kilobase-pair fragment inserted in pBR322. The initial selection of the gene was accomplished in a cls pss-1 double mutant that had lesions in both cardiolipin and phosphatidylserine synthases and required either the cls or the pss gene product for normal growth at 42 degrees C in a broth medium, NBY, supplemented with 200 mM sucrose. The cloned gene was identified as the cls gene by the recovery and amplification of both cardiolipin and cardiolipin synthase in a cls mutant as well as by the integration of a pBR322 derivative into its genetic locus at 27 min on the chromosome of a polA1 mutant. The maxicell analysis indicated that a protein of molecular weight 46,000 is the gene product. The cls gene is thus most likely the structural gene coding for cardiolipin synthase. Hybrid plasmids of high copy numbers containing the cls gene were growth inhibitory to pss-I mutants under the above selective conditions, whereas they inhibited neither the growth of pss-I mutants at 30 degrees C nor that of pss+ strains at any temperature. Amplification of cardiolipin synthase activity was observed, but was not proportional to the probable gene dosage (the enzyme activity was at most 10 times that in wild-type cells), and cardiolipin synthesis in vivo was at the maximum 1.5 times that in wild-type strains, implying the presence in E. coli cells of a mechanism that avoids cardiolipin overproduction, which is possibly disadvantageous to proper membrane functions.     

On the specificity of cytochrome c synthetase in recognition of the amino acid sequence of apocytochrome c

Two forms of yeast cytochrome c synthetases with different specificities were resolved, one (synthetase I), solubilized from mitochondria or the cell debris with Triton X-100, recognizing not horse apocytochrome c but yeast apo-iso-1-cytochrome c as a substrate and the other (synthetase II) still bound with the particulate fraction from mitochondria after treatment with Triton, recognizing both horse and yeast apocytochromes c. The activity with labeled yeast apo-iso-1-cytochrome c as a substrate of cytochrome c synthetase I can be quantitatively inhibited by nonlabeled Candida krusei apocytochrome c and partially by nonlabeled tuna apocytochrome c but not by nonlabeled horse apocytochrome c indicating a specific amino acid sequence being recognized. However, an enzyme similarly solubilized from beef heart mitochondria recognized both horse apocytochrome c and yeast apo-iso-1-cytochrome c for attachment of heme. In view of the fact that the yeast synthetase II and the beef synthetase can both utilize either horse apocytochrome c or yeast apo-iso-1-cytochrome c as substrates, we suggest that these enzymes may also be involved in biosynthesis of cytochrome c1, that is, the ability to attach heme to apocytochrome c and apocytochrome c1 may have been conserved in eucaryotic cells, and that both synthetases may therefore be homologous.