Quantitative relationships between the measurable transport resistances of membrane carriers: theory and experiment

A theoretical analysis is made of the possible quantitative relationships between the transport resistances that characterise membrane carrier systems. It is shown that there exist only five possible patterns in which to rank the four transport resistances. Symbolising these as A, B, C and D, the five possible patterns are (i) A = B = C = D; (ii) A = B much greater than C, D; (iii) A = B much greater than C = D; (iv) A = B = 2C = 2D; (v) A = 2B = 2C much greater than D. A survey of the available experimental data shows that pattern (ii) is the most prevalent, pattern (v) is often found and pattern (iii) has been identified. None of the ten transport systems so far analysed experimentally failed to fit one of the predicted patterns.     

Hyperoxia causes increased albumin permeability of cultured endothelial monolayers

The effect of phasic eye movement activity on ventilation during rapid-eye-movement (REM) sleep was studied in seven healthy young adults by use of the respiratory inductive plethysmograph. Mean ventilation (VE) and ventilatory components during REM sleep were not significantly different from that seen in either stages 1-2 or 3-4 sleep. The percent of rib cage contribution to ventilation in REM sleep, 29.3 +/- 5.1%, was reduced compared with 54.4 +/- 5.8% in stage 1-2 and 52.2 +/- 4.3% in stage 3-4 sleep (P less than 0.005). When one separated breaths by the degree of associated phasic eye movement activity, it became apparent that breathing during REM sleep is very heterogeneous. Increasing eye movement activity was associated with inhibition of ventilation with a reduction in VE from 5.1 +/- 0.3 to 3.8 +/- 0.3 l/min. Tidal volume and frequency both fell, whereas inspiratory duration was unchanged. Compartmental ventilation was also affected, with the fall in the rib cage contribution from 37.8 +/- 6.4 to 15.3 +/- 5.6%. Chest wall and abdominal movement became more asynchronous as phasic-eye-movement activity increased and frank paradoxical breathing was seen.     

S-oxalylglutathione is a substrate for gamma-glutamyltransferase (GGT). Implications for the role of GGT in cell proliferation

With glycylglycine or water as acceptor, bovine kidney gamma-glutamyltransferase catalyzes reactions of the known mammalian metabolite, S-oxalylglutathione, at rates comparable to those of L-gamma-glutamyl-p-nitroanilide, a known good substrate. N-Oxalyl-cysteinylglycine is the eventual product of the former reaction. Since oxalyl thiolesters are implicated as important cell proliferation inhibitors, it is proposed that this reaction plays a major role in controlling cell proliferation.     

Electron paramagnetic resonance saturation studies of P-700+ reaction center chlorophyll in plant photosynthesis

Electron paramagnetic resonance (EPR) power saturation and saturation recovery methods have been used to determine the spin lattice, T1, and spin-spin, T2, relaxation times of P-700+ reaction-center chlorophyll in Photosystem I of plant chloroplasts for 10 K less than or equal to T less than or equal to 100 K. T1 was 200 mus at 100 K and increased to 900 mus at 10 K. T2 was 40 ns at 40 K and increased to 100 ns at 10 K. T1 for 40 K less than or equal to T less than or equal to 100 K is inversely proportional to temperature, which is evidence of a direct-lattice relaxation process. At T = 20 K, T1 deviates from the 1/T dependence, indicating a cross relaxation process with an unidentified paramagnetic species. The individual effects of ascorbate and ferricyanide on T1 of P-700+ were examined: T1 of P-700+ was not affected by adding 10 mM ascorbate to digitonin-treated chloroplast fragments (D144 fragments). The P-700+ relaxation time in broken chloroplasts treated with 10 mM ferricyanide was 4-times shorter than in the untreated control at 40 K. Ferricyanide appears to be relaxing the P-700+ indirectly to the lattice by a cross-relaxation process. The possibility of dipolar-spin broadening of P-700+ due to either the iron sulfur center A or plastocyanin was examined by determining the spin-packet linewidth for P-700+ when center A and plastocyanin were in either the reduced or oxidized states. Neither reduced center A nor oxidized plastocyanin was capable of broadening the spin-packet linewidth of P-700+ signal. The absence of dipolar broadening indicates that both center A and plastocyanin are located at a distance at least 3.0 nm from the P-700+ reaction center chlorophyll. This evidence supports previous hypotheses that the electron donor and acceptor to P-700 are situated on opposite sides of the chloroplast membrane. It is also shown that the ratio of photo-oxidized P-700 to photoreduced centers A and B at low temperature is 2 : 1 if P-700 is monitored at a nonsaturating microwave power.     

The phosphorylation of adrenal proteins in response to adrenocorticotropic hormone

The phosphorylation of rat adrenal protein components in response to adrenocorticotropin has been studied in adrenal quarters, isolated cells, and in vivo. In adrenal quarters, adrenocorticotropic hormone (ACTH)-stimulated phosphorylation or dephosphorylation of proteins was not affected by the presence of protein synthesis inhibitors despite a total inhibition of steroidogenesis. (The term dephosphorylation refers to an apparent decrease in the labeling of a particular protein with 32P at various times after the addition of ACTH. This may be due to enzymatic removal of phosphate or protein degradation or complexation of this protein with another cellular component.) Studies with isolated cell preparations identified several proteins that are phosphorylated or dephosphorylated in response to hormone. These changes in phosphorylation were also observed in adrenal quarters and correlated well with ACTH-stimulated steroidogenesis as determined by temporal analysis and dose-response studies of corticosterone production. In vivo injection of male hypophysectomized rats with [32P]phosphate and ACTH demonstrated changes in the labeling of six adrenal proteins. Many of the proteins phosphorylated in vivo were also demonstrated to be phosphorylated in both in vitro systems. Finally, the injection of a physiological dose of ACTH appeared to selectively activate the type I cAMP-dependent protein kinase within the microsomal fraction as determined by the binding of a photoaffinity-labeled reagent. These results suggest that alterations in phosphorylation of adrenal proteins in response to ACTH is proximal to or independent of the obligatory role of protein synthesis in acute steroidogenesis.     

A numerical taxonomic study of Actinobacillus, Pasteurella and Yersinia

A numerical taxonomic study of strains of Actinobacillus, Pasteurella and Yersinia, with some allied bacteria, showed 23 reasonably distinct groups. These fell into three major areas. Area A contained species of Actinobacillus and Pasteurella: A. suis, A. equuli, A. lignieresii, P. haemolytica biovar A, P. haemolytica biovar T, P. multocida, A. actinomycetemcomitans, 'P. bettii', 'A. seminis', P. ureae and P. aerogenes. Also included in A was a composite group of Pasteurella pneumotropica and P. gallinarum, together with unnamed groups referred to as 'BLG', 'Mair', 'Ross' and 'aer-2'. Area B contained species of Yersinia: Y. enterocolitica, Y. pseudotuberculosis, Y. pestis and a group 'ent-b' similar to Y. enterocolitica. Area C contained non-fermenting strains: Y. philomiragia, Moraxella anatipestifer and a miscellaneous group 'past-b'. There were also a small number of unnamed single strains.     

Acetylcholine responses of identified neurons in Helix pomatia--III. Ionic composition of the depolarizing currents induced by acetylcholine

The ionic composition of the currents underlying the acetylcholine (ACh) depolarizations in the identified neurons B1 and B3 of the buccal ganglia of Helix pomatia was analysed. The equilibrium potential of the ACh responses was -2.8 +/- 0.6 mV (N = 49) and -4.0 +/- 0.7 mV (N = 79; mean +/- SEM) in the neurons B1 and B3, respectively. Replacement of NaCl in the bath solution by sucrose shifted the ACh equilibrium potential into the negative direction. A similar but less pronounced shift occurred when Ca2+ was substituted for Na+. Substitution of Cl- in the bath solution by propionate or an increase of the intracellular Cl- concentration did not affect the ACh equilibrium potential. Changes of K+ concentration in the bath between 1 and 50 mmol/l left the ACh equilibrium potential nearly unaffected when the Na+ concentration was at the control level. With a simultaneous reduction of extracellular Na+ an increase of K+ concentration shifted the ACh equilibrium potential towards more positive potentials. The findings are compatible with calculated K+ permeabilities if a K+ redistribution across the cell membrane is considered. In the neurons B1 and B3, channels operated by ACh are permeable for K+, Na+ and Ca2+, with the relative permeabilities 1.6:1.0:0.1.     

Inhibitton of prolactin release by stimulation of presynaptic serotonin autoreceptors

The effects of 5-methoxy-N, N-dimethyltryptamine (5-MeODMT), a serotonin agonist with a preferential action on presynaptic autoreceptors, on prolactin release in male rats was determined. Basal serum prolactin levels were not altered after administration of 1.0, 2.0, 5.0, 10.0 or 20.0 mg/kg of 5-MeODMT.Pretreatment with 5-MeODMT reduced prolactin release by agents that depend on serotonergic neurotransmission for part of their prolactin release stimulation. Prolactin release in response to L-5-hydroxytryptophan (5-HTP) or morphine was significantly reduced by pretreatment of the rats with 5-MeODMT.The results of this experiment indicate that 5-MeODMT act as a presynaptic serotonin autoreceptor stimulant and not as a postsynaptic serotonin agonist on the neuronal systems that control prolactin release.