Effects of acutely and chronically administered antidepressants on the brain regional 3-methoxy-4-hydroxyphenylethyleneglycol sulfate in the forced swimming rat

The reducing effect of desipramine (DMI) on the duration of immobility induced in rats by forced swimming was markedly potentiated after chronic injection of the lower dose, whereas the action of chronic amitriptyline (AMI) was similar to that of acute treatment. MHPG-SO₄ in most of the brain regions, particularly that in the septal area, was increased by the forced swimming. Unlike the effect in the normal rats, acutely administered AMI and DMI did not reduce MHPG-SO₄ in the brain regions other than the septal area in the forced swimming rats. Similar to the effect in the normal rats, chronic treatment with DMI increased MHPG-SO₄ in the cortex, hippocampus and the thalamus in the forced swimming rats. In these rats, MHPG-SO₄ in the septal area was still lowered by both drugs. These results indicate that 1) inhibitory effect of acutely administered AMI and DMI on the presynaptic noradrenergic neurons disappears in most of the brain regions after the forced swimming, 2) chronic treatment with DMI increases the noradrenergic activity in the cortex, hippocampus and thalamus and 3) both acute and chronic treatments with the drugs inhibit the forced swimming-induced increase in noradrenergic activity in the septal area. The relevance of these effects to the behavioral action of the drugs is discussed.     

Epitope study and cDNA screening of major surface glycoprotein of Pneumocystis carinii.

Use of monoclonal antibodies against the major glycoprotein of Pneumocystis carinii (P115) implicated the sugar moiety as being strongly antigenic. Furthermore, monoclonal antibodies directed against the peptide portion of P115 were generated by using synthetic oligopeptides after amino acid sequencing was done on P115 proteolytic fragments.     

A model for the mechanisms of sensitivity control in the submammalian vertebrate retina

A model is proposed for the mechanisms of sensitivity control at the outer and inner plexiform layers in the submammalian vertebrate retina on the basis of Werblin's results and other physiological results. The model is especially based on the following suggestions: The signal that acts to shift the bipolar curves is probably carried by horizontal cell processes extending from the surround to the center of the receptive field. Furthermore, amacrine cells carry a lateral antagonistic signal across the inner plexiform layer that affects the response properties of ganglion cells. The simulations of the model were made and the results of the ones considerably coincided with the experimental results of Werblin.     

Lipolysis induction in adipocytes by a protein from tumor cells

Extracts of thymic lymphoma that are obtained from AKR mice and are kept in the cold for at least several days can induce lipolytic activity in rat adipocyte suspensions. Freshly prepared extracts have low activity but contain a low molecular weight material of less than 10,000 daltons that aggregates on standing in the cold and becomes active. Treatment of aged extracts with trypsin causes a loss in activity indicating that the active material is a protein. It has been obtained in partially purified form, is relatively heat stable, and is not a lipase. Activity was also demonstrated in AKRXDBA/2 lymphoma (induced by AKR SL3-3 virus) and in transplanted lymphomas from a Friend-virus-induced erythroleukemia cell line in DBA/2 mice, but was not detected in normal thymus, spleen, liver, or other tissues. The partially purified material produced a massive fat mobilization when injected into normal mice.     

Tonoplast action potential inNitella in relation to vacuolar chloride concentration

Summary The action potential ofNitella internode was studied in relation to K⁺ and Cl^– concentrations in the vacuole. When the vacuole ofNitella pulchella was filled with an artificial solution with extremely low Cl^– concentration, a diphasic action potential (DAP) was observed. The first phase consists of a rapid depolarization followed by a relatively rapid repolarization, and the second one consists of a strong hyperpolarization followed by a gradual return to the resting potential.When the cell was stimulated immediately after the generation ofDAP, a monophasic action potential which resembles an action potential of the natural cell was observed, indicating that theDAP consists of two components with different refractory periods. The refractory period of the component responsible for the depolarizing phase is shorter than that of a component responsible for the hyperpolarizing phase. Measuring the plasmalemma potential and vacuolar potential separately, it was demonstrated that the hyperpolarizing component ofDAP originates from the tonoplast.The action potential of the tonoplast, in contrast with that of the plasmalemma, could be generated independently of concentration of K⁺ in the vacuole. Since the maximum amplitude of hyperpolarization decreased significantly by increasing Cl^– concentration of the vacuole, it is concluded that the tonoplast is very sensitive to Cl^– during excitation.     

Expression of human pituitary adenylate cyclase activating polypeptide (PACAP) cDNA in CHO cells and characterization of the products.

cDNA encoding human PACAP precursor was expressed in non-neuroendocrine Chinese hamster ovary cells, CHO-K1, The cells were transfected with expression vector (pTS705) containing the human PACAP cDNA by electroporation. A cell line which produced more than 80 ng/ml of immunoreactive PACAP (ir-PACAP) into the conditioned medium was established. RP-HPLC analysis of culture medium of this established cell line exhibited the presence of two types of PACAP, i.e. PACAP38 and PACAP27. At the same time, it was also revealed that immunoreactive PACAP-related peptide (ir-PRP) was secreted into the cultured medium. The ir-PACAPs were confirmed to ahve biological activities such as induction of cAMP and neurite outgrowth in rat pheochromocytoma PC12h cells.     

Solution conformation of endothelin determined by nuclear magnetic resonance and distance geometry

The solution conformation of endothelium-derived vasoconstrictor peptide, endothelin, has been determined by two-dimensional 1H-NMR spectroscopy and distance geometry. Conformation in the N-terminal core region (residues 1-15) is well-defined and a characteristic is the helix-like conformation in the segment from Lys9 to Cys15. Contrarily, the C-terminal tail region (residues 16-21) does not assume a defined conformation and there are no specific interactions between the core and the tail regions.