Combined administration of human corticotropin-releasing factor and lysine vasopressin induces cortisol escape from dexamethasone suppression in healthy subjects

Inadequate suppression of plasma cortisol after 1-2 mg dexamethasone is frequently observed in depressive patients. To further investigate the pathophysiology underlying cortisol nonsuppression after dexamethasone we compared cortisol and corticotropin (ACTH) response to human corticotropin-releasing factor (h-CRF), lysine vasopressin (LVP), and a concurrent administration of both peptides after pretreatment with 1.5 mg dexamethasone in six male controls. Neither h-CRF nor LVP were able to produce a marked elevation of dexamethasone suppressed plasma cortisol and ACTH. If both peptides were administered in combination, a substantial escape of plasma cortisol from dexamethasone suppression was observed. ACTH responses changed in concordance with those of cortisol indicating that the LVP-CRF interaction takes place at the pituitary level. Our finding is consistent with a multihormonal control of pituitary-adrenal activity and bears several implications for interpretation of dexamethasone suppression test results in depressive illness.     

Regional assignment of the genes for TK1, GALK, ALDC, and ESD on chromosome 8 in the American mink by chromosome-mediated gene transfer

Summary A panel of clones of mink-Chinese hamster somatic cell hybrids was analysed to obtain data for assigning the genes for thymidine kinase-1 (TK1), galactokinase (GALK), subunit C of aldolase (ALDC), and esterase D (ESD) to specific mink chromosomes. The results demonstrate that the genes for TK1, GALK, ALDC and ESD are syntenic and located on mink chromosome 8. Prometaphase analysis of transformed mouse cells obtained by transfer of mink genes by means of metaphase chromosomes demonstrated the presence of mink chromosome 8 fragments of different sizes in some of the independent transformants. Segregation analysis of these fragments and mink TK1, GALK, ALDC and ESD allowed us to assign the genes for TK1 and GALK to 8p24, ALDC to pter-8p25, and ESD to 8q24-8qter.     

Study of 2'-phosphodiesterase activity in cultured NIH 3T3 cells during activation of cAMP-dependent phosphorylation

A rapid and transient decrease in 2'-phosphodiesterase activity in NIH 3T3 mouse cells was observed after adrenaline addition. The decrease of activity was accompanied by an elevation of intracellular cAMP level. The 2'-phosphodiesterase activity changed similarly when cells sink deeper into the resting state. In the latter case, the fall of the enzyme activity was correlated with elevation of the activity of cAMP-dependent proteinkinase and, moreover, a considerable increase of the intracellular level of 2',5'-oligoadenylate was observed. Phosphorylation of proteins by cAMP-dependent proteinkinase in the cell lysate also produced a pronounced drop of 2'-phosphodiesterase activity. Exogenous 2',5'-oligo (A) treatment of the cells resulted in the rise of 2'-phosphodiesterase activity; actinomycin D prevented this effect. The data presented suggest the involvement of two different mechanisms in regulation of 2'-phosphodiesterase activity: cAMP-dependent phosphorylation and induction of 2'-phosphodiesterase by 2',5'-oligoadenylate.     

Barley straw decomposition with varied levels of microbial grazing by Folsomia fimetaria (L.) (Collembola,Isotomidae)

Summary Folsomia fimetaria (L.) were added (0, 5, 10, 20 animals) to 0.100 g barley straw which had been inoculated 10 days (244 h) earlier with a natural soil microflora. Respiration (CO₂ evolution) was monitored continuously. Mass loss, fungal standing crop (total and FDA-active), bacterial and protozoan biomass were estimated 42 days (1,000 h) after microbial inoculation. The degree of surface cover by hyphae was surveyed at regular intervals. No significant differences (P>0.05) were found in respiration, mass loss or microbial biomass, but the density of surface hyphae were reduced by addition of Collembola. Fungal production was low, less than 5% of the estimated microbial production, and could not account for all collembolan growth during incubation. F. fimetaria appeared to consume mainly bacteria and protozoa, and had little impact on carbon mineralization.     

Interdependence of growth, water relations and abscisic acid level in Phaseolus vulgaris during waterlogging

The interdependence between changes in growth and water relations after waterlogging was investigated by recording simultaneously growth, transpiration, water potential, turgor, leaf diffusion resistance and abscisic acid content in Phaseolus vulgaris L. cv. bruine Noord-Hollandse. Growth was inhibited immediately after flooding, whereas transpiration decreased gradually to a low level in about three days. The first two days after flooding a small increase in abscisic acid content in the leaves was observed which was accompanied by an increase in diffusion resistance. The increase in abscisic acid content could result from an inhibited export from the leaves. After the first two days a decrease in water potential and turgor was accompanied by a drastic increase in both abscisic acid content and diffusion resistance. This large increase in abscisic acid content occurred before the turgor had reached its minimum value. The change in diffusion resistance kept showing a lag of about one day with the change in abscisic acid content. The possibility is discussed that besides abscisic acid also its metabolite phaseic acid is involved in stomatal closure. After the formation of adventitious roots on the hypocotyl, abscisic acid level, diffusion resistance, water potential and turgor returned to the control values. Transpiration showed a slow recovery from the sixth day after flooding, whereas growth was inhibited for at least nine days. A remarkable similarity exists between our observations on the responses of bean plants to flooding and the well known responses to drought.     

Physiological and isotopic aspects of photosynthesis in peperomia

Physiological and isotopic aspects of several Peperomia species were investigated. All but one species had C₃-like stomatal behavior, in that stomata were open during the day and closed during the night. In these species, most atmospheric CO₂ uptake occurred during the day. Concurrent with this stomatal behavior, there were Crassulacean acid metabolism-like acid fluctuations in most species. Carbon and hydrogen isotope ratios of cellulose nitrate from Peperomia reflect their physiological behavior. The δ¹³C values of cellulose nitrate from Peperomia species were similar to values observed in C₃ plants and consistent with the daytime uptake of exogeneous CO₂ via the C₃ photosynthetic pathway. The δD values of cellulose nitrate from Peperomia species approach those of Crassulacean acid metabolism plants. These elevated δD values are caused by fractionations occurring during biochemical reactions and not as a consequence of water relations.     

Effects of Acifluorfen on Endogenous Antioxidants and Protective Enzymes in Cucumber (Cucumis sativus L.) Cotyledons

The herbicide acifluorfen (2-chloro-4-(trifluoromethyl)phenoxy-2-nitrobenzoate) causes strong photooxidative destruction of pigments and lipids in sensitive plant species. Antioxidants and oxygen radical scavengers slow the bleaching action of the herbicide. The effect of acifluorfen on glutathione and ascorbate levels in cucumber (Cucumis sativus L.) cotyledon discs was investigated to assess the relationship between herbicide activity and endogenous antioxidants. Acifluorfen decreased the levels of glutathione and ascorbate over 50% in discs exposed to less than 1.5 hours of white light (450 microeinsteins per square meter per second). Coincident increases in dehydroascorbate and glutathione disulfide were not observed. Acifluorfen also caused the rapid depletion of ascorbate in far-red light grown plants which were photosynthetically incompetent.

Glutathione reductase, dehydroascorbate reductase, superoxide dismutase, ascorbate oxidase, ascorbate free radical reductase, peroxidase, and catalase activities rapidly decreased in acifluorfen-treated tissue exposed to white light. None of the enzymes were inhibited in vitro by the herbicide. Acifluorfen causes irreversible photooxidative destruction of plant tissue, in part, by depleting endogenous antioxidants and inhibiting the activities of protective enzymes.

     

Modulation of postinhibitory increase in plasma prolactin by domperidone in patients with prolactin secreting adenoma

To evaluate the PRL secretory mechanism in patients with PRL-secreting adenoma (PRL-oma), plasma PRL responses to dopamine (DA) were studied in these cases and in normal subjects. Plasma PRL values showed clear decreases during the infusion of DA (5 micrograms/kg/min for 90 min) in both 6 normal and 7 PRL-oma subjects (%decrease: 43.8 +/- 3.9% vs. 53.9 +/- 5.6%; NS) and postinhibitory increases after the termination. However, the postinhibitory increase occurred more promptly and markedly in PRL-oma patients than in normal subjects, i.e. the postinhibitory increase exceeded the basal level 45 min after the termination of DA infusion in PRL-oma patients, whereas the increase in normal subjects did not exceed the basal level even 90 min after the infusion. When domperidone was injected at the termination of DA infusion, the postinhibitory increases were significantly enhanced in either PRL-oma or normal subjects. The maximal increments in plasma PRL in the combination test of DA plus domperidone were significantly larger in PRL-oma patients, but were almost the same in normal controls, compared to the single domperidone test. In contrast, TRH did not modify the postinhibitory rises in 9 PRL-oma patients. These results indicate that the secretory properties and the sensitivities of lactotrophs to decreasing action of DA might be different between PRL-oma patients and normal controls. Further, the postinhibitory rebound phenomenon in PRL-oma patients is possibly determined by an overshoot of PRL storage concomitantly with a decreasing DA action.(ABSTRACT TRUNCATED AT 250 WORDS)     

Component X. An immunologically distinct polypeptide associated with mammalian pyruvate dehydrogenase multi-enzyme complex

The mammalian pyruvate dehydrogenase multi-enzyme complex contains a tightly-associated 50 000-Mr polypeptide of unknown function (component X) in addition to its three constituent enzymes, pyruvate dehydrogenase (E1), lipoate acetyltransferase (E2) and lipoamide dehydrogenase (E3) which are jointly responsible for production of CoASAc and NADH. The presence of component X is apparent on sodium dodecyl sulphate/polyacrylamide gel analysis of the complex, performed in Tris-glycine buffers although it co-migrates with the E3 subunit on standard phosphate gels run under denaturing conditions. Refined immunological techniques, employing subunit-specific antisera to individual components of the pyruvate dehydrogenase complex, have demonstrated that protein X is not a proteolytic fragment of E2 (or E3) as suggested previously. In addition, anti-X serum elicits no cross-reaction with either subunit of the intrinsic kinase of the pyruvate dehydrogenase complex. Immune-blotting analysis of SDS extracts of bovine, rat and pig cell lines and derived subcellular fractions have indicated that protein X is a normal cellular component with a specific mitochondrial location. It remains tightly-associated with the 'core' enzyme, E2, on dissociation of the complex at pH 9.5 or by treatment with 0.25 M MgCl2. This polypeptide is not released to any significant extent from E2 by p-hydroxymercuriphenyl sulphonate, a reagent which promotes dissociation of the specific kinase of the complex from the 'core' enzyme. Incubation of the complex with [2-14C]pyruvate in the absence of CoASH promotes the incorporation of radio-label, probably in the form of acetyl groups, into both E2 and component X.