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R Schultz

Publications and source records attributed to R Schultz.

10 recordsLinked to original sources
PubMed1979

Mode of stimulation by injection of cyclic AMP and external acidification of the sodium efflux in barnacle muscle fibres.

1. A study has been made in single barnacle muscle fibres of the effect of micro-injected pure protein kinase inhibitor (PKI) on the response of the Na efflux to injection of cyclic AMP and external acidification. 2. (i) Injection into fibres of 1.6 x 10(-4) M-pure PKI is without effect on the resting Na efflux. (ii) Injection of 1.6 x 10(4) M-pure PKI before 0.03 M-cyclic AMP causes a marked reduction in the magnitude of the response of the Na efflux to the nucleotide. The same is true when 10(-4) M-cyclic AMP is injected after PKI. (iii) Injection of partially pure catalytic subunits causes a sustained stimulation of the ouabain-insensitive Na efflux, which is almost completely reversed by injecting PKI. (iv) Injection of 100 mM-EGTA before PKI fails to alter the lowered response of the ouabain-insensitive Na efflux to injection of 10(-4) M-cyclic AMP. (v) Ouabain (10(-4) M) when applied following the injection of 10(-4) M-cyclic AMP causes a drastic fall in the stimulated Na efflux. 3. (i) Injection of 1.6 x 10(-4) M-pure PKI before or after external acidification fails to abolish or reduce the stimulatory response to acidification. (ii) Injection of 1.6 x 10(-4) M-pure PKI before acidification practically abolishes the response of the ouabain-insensitive Na efflux to 0.03 M-cyclic AMP in the presence of acidification. (iii) Radioimmunoassay of total cyclic AMP and cyclic GMP content in single fibres before and after acidification shows no appreciable alteration in nucleotide content following acidificiation. (iv) Injection of 100 mM-EGTA before acidification enhances the stimulatory response to acidification. (v) External application of Dantrolene (10(-5) M) fails to alter the size of the stimulatory response to acidification. 4. (i) Prior external application of 5 x 10(-4) M-benzolamide results in a marked reduction in the magnitude of the response of the ouabain-insensitive Na efflux to the injection of 3 x 10(-4) M-cyclic AMP. (ii) Benzolamide totally abolishes the response of the ouabain-insensitive Na efflux to the injection of catalytic subunits. 5. The evidence brought forward is compatible with the view that (a) The mechanism by which cyclic AMP stimulates the Na efflux involves activation by cyclic AMP of the cyclic AMP-dependent protein kinase system, and hence release of the catalytic subunit, and (b) the mechanism by which external acidification leads to stimulation of the Na efflux involves activation of a benzolamide-sensitive system, possibly carbonic anhydrase, rather than the adenyl cyclase system. The actions of cyclic AMP and catalytic subunits on the Na efflux are closely linked to activation of the benzolamide sensitive system.

Animals↗
PubMed1978

Modification of UV-induced mutation frequencies in Chinese hamster cells by dose fractionation, cycloheximide and caffeine treatments.

Chinese hamster (V79) cells were irradiated with a fractionated regime of ultraviolet light (UV1 + UV2). The fractionation of a UV dose always increased the colony-forming ability but reduced (or it did not change) the mutation frequencies. Treatment with cycloheximide between the two UV irradiations resulted in two types of effects, depending on the protocols used. Long exposures to cycloheximide (i.e., greater than 6 h) for the entire period between UV1 and UV2 or partial treatment of cycloheximide (i.e., 3 h) long before UV2 always resulted in reduced colony-forming ability and enhanced or unchanged mutation frequencies. Exposure to cycloheximide for the entire period in the short fractionated regime (i.e., 4 h) between UV1 and UV2 or partial treatment of cycloheximide just prior to UV2 tended to give the opposite effects. Caffeine treatment before UV2, with or without UV1, significantly increased the mutation frequencies. These results suggest that an error-free postreplication repair system exists in Chinese hamster cells which is inhibitable by particular cycloheximide or caffeine treatments.

Caffeine↗
PubMed1977

Establishment and characterization of a cell line derived from a spontaneous murine lung carcinoma (M109).

The Madison lung (M109) tumor cell line, initiated from a "spontaneous", anaplastic murine lung carcinoma, has been propagated continuously in vitro for more than 300 cell generations. Cytogenetic analysis revealed a mouse karyotype with a mode of 78 chromosomes (2n = 40). Three distinct marker chromosomes were identified by trypsin-giemsa banding. The cells piled up in culture and had a short generation time and high plating efficiency. Electron microscopy revealed highly undifferentiated cells with little rough endoplasmic reticulum, an abundance of free polysomes, the presence of few and often odd-shaped mitochondria, lipid bodies and phagocytic vacuoles. Virus particles of the C-type were found frequently. The subcutaneous transplantation of M109 cultured cells at a relatively low cell inoculum produced highly metastatic tumors in syngeneic BALG/c mice.

Adenocarcinoma, Bronchiolo-Alveolar↗
PubMed1976

Dependence liability of enkephalin in the myenteric plexus of the guinea pig.

The endogenous ligands of opiate receptors, methionine-eukephalin and leucine-enkephalin, were tested for their ability to maintain or to reinduce dependence in myenteric plexus-longitudinal muscle strips taken from tolerant/dependent guinea pigs. Both peptides fully substituted for the function morphine exerts in this preparation. It is concluded that the enkephalins posses a high degree of dependence liability.

Animals↗
PubMed1976

Mode of stimulation by adenosine 3':5'-cyclic monophosphate of the sodium efflux in barnacle muscle fibres.

1. Giant fibres of the barnacle Balanus nubilus have been used as a preparation for studying the mode of action of cAMP on sodium transport. 2. It is shown that a concentration of cAMP as low as 10(-6)M, when micro-injected, causes a sharp rise in the radio-Na efflux. Ouabain fails to reverse the cAMP effect. 3. The magnitude of the response of the Na efflux to cAMP is markedly reduced by pre-injecting 100 or 500 mM-EGTA solutions or by omitting Ca2+ from the bathing medium. Both together fail to bring about a greater reduction in the response. 4. The response to cAMP is greatly reduced by pre-injecting the protein inhibitor of Walsh and practically abolished by pre-injecting 500 mM-EGTA and soaking in Ca-free artificial sea water, ASW. 5. The Ca2+-independent component of the Na efflux which is also stimulated by cAMP is shown to involve Na for H exchange. The magnitude of this exchange is governed by external pH. 6. The Na efflux into Ca2+-free, Li+-ASW is shown to be markedly stimulated by injecting cAMP, an effect which is enhanced by reducing external pH. 7. The Na efflux at 0 degrees C is stimulated by injecting cAMP. This is shown to be related to activation of the protein kinase by cAMP and to depend on the presence of external Ca2+. 8 (i) Ethacrynic acid when injected reduces the ouabain-insensitive Na efflux into HEPES-Ca2+-free ASW at pH 6-3. These same fibres show a marked response to cAMP. (II) The ouabain-insensitive Na efflux into HCO3-, Ca2+-free ASW from fibres pre-treated with ethacrynic acid fails to respond to external acidification. This is interpreted as indicating that ethacrynic acid inactivates the CO2-sensitive adenyl cyclase system. These same fibres when injected with cAMP show a marked response. (iii) Stimulation of the ouabain-insensitive Na efflux into HCO-3, Ca2+-free ASW by external acidification is reversed by injecting ethacrynic acid. These fibres when injected with cAMP show a reduced response. 9. It is concluded that: (i) stimulation of the Na efflux by injected cAMP is mainly due to activation of cAMP-dependent protein kinase; (ii) the underlying exchange mechanism consists of Na:Ca and Na:H exchange. Interaction of Ca2+ with a phosphorylated membrane, thereby modifying permeability remains as a real possibility; (iii) the site of action of CO2 and ethacrynic acid is the adenyl cyclase system. 10. The implications of activation of the adenyl cyclase system by CO2 and Na:H exchange are briefly touched upon.

Animals↗