Brain hypoxia and control of breathing: neuromechanical control

The effects of graded brain hypoxia on respiratory cycle timing, the lung inflation reflex, and respiratory compensation for an inspiratory flow-resistive load were studied in unanesthetized goats. Two models, inhalation and CO and acute reduction of brain blood flow (BBF) were used to produce comparable levels of brain hypoxia. The lung inflation reflex was assessed as the ratio of inspiratory time of an occluded breath to that of the preceding spontaneous breath (TIoccl/TIspont). Compensation for flow-resistive loading was assessed as the effect of the load upon the airway occlusion pressure response to rebreathing CO2 (delta P 0.1/delta PCO2). Major findings were 1) severe brain hypoxia (HbCO of 60% or BBF of 42%) caused tachypnea due to a 50% or more reduction of expiratory time but only a 20% or less reduction of inspiratory time; 2) moderate carboxyhemoglobinemia (HbCO of 25-30%) enhanced TIoccl/TIspont from 1.5 +/- 0.1 at control to 2.1 +/- 0.1, while severe brain hypoxia (HbCO of 60% and BBF of 42%) reduced the ratio to 1.0 +/- 0.2; and 3) compensation for a flow-resistive load, manifested by increases of delta P 0.1/delta PCO2 of 75-300% in the control state, was abolished at HbCO of 45-50% and BBF of 60%. The data suggest that in unanesthetized animals brain hypoxia elicits tachypnea largely by an effect on the expiratory phase of the bulbopontine timing mechanism. The observed enhancement of the lung inflation reflex and abolition of flow-resistive load compensation are best explained by hypoxic depression of higher than brain stem neural function.     

Efficient protoplast isolation from fungi using commercial enzymes

Several commercial polysaccharases have been compared for their ability to liberate protoplasts from fungi. These enzymes were found to contain side activities capable of hydrolysing fungal cell walls. Protoplasts have been commonly isolated from fungi using enzyme systems prepared by workers in their own laboratories. However, these procedures are time consuming and considerable variation may be found between different batches of enzyme. The present study shows that high yields of protoplasts can be prepared from a variety of fungi using relatively cheap commercial enzymes. The yields obtained were normally as good as or better than those previously produced.     

NADH-cytochrome c reductase, succinate cytochrome c reductase and phospholipids.

Phospholipid peroxidation of isolated rat liver inner mitochondrial membranes induced by either ascorbate or cysteine was accompanied by a release of flavins and coenzyme Q. A straight correlation between this release and the alteration of molecular species of phosphatidylcholine and phosphatidylethanolamine containing one saturated and one unsaturated fatty acid has been found. Peroxidation induced on molecular species of phosphatidylcholine and phosphatidylethanolamine containing only unsaturated fatty acids were accompanied by losses in enzyme activities of NADH-cytochrome c reductase and succinate cytochrome c reductase.     

Aminoacid composition and hydrophobicity index of mitochondrial polypeptides

The aminoacid composition of protein stained bands in polyacrylamide gels, after electrophoresis of proteins from inner mitochondrial membranes, was investigated hydrolyzing directly the gel slices. The Hydrophobicity Index of 18 prominent polypeptide bands was calculated after their aminoacid analysis. The polypeptides less related to the membrane have low hydrophobicity as inferred from their Hydrophobicity Indexes.     

The differential effects of PGE on the immune response in normal and immunosuppressed mice

The effect of 16,16-dimethyl-PGE₂-methyl ester (di-M-PGE₂) on humoral and cellular immunoresponsiveness has been compared in normal mice and in mice immunosuppressed by splenectomy and thymectomy plus antithymocyte serum (ATS). Splenectomy resulted in immunosuppression manifested by augmentation of B-16 melanoma growth; this stimulatory effect was reversed by di-M-PGE₂. In animals immunosuppressed by thymectomy plus ATS, di-M-PGE₂ augmented the humoral and cellular immune responses; this was manifested by slowing of the growth of B-16 melanoma and by stimulating the number of plaque-forming cells, hemagglutinin titers, and delayed-hypersensitivity reactions to sheep erythrocytes. In contrast, in normal (nonthymectomized) mice, di-M-PGE₂ was mildly immunosuppressive. Finally, adriamycin-immunosuppressed normal mice and this suppression were reversed by the addition of di-M-PGE₂ to the treatment regimen.     

Inverse modification of antibody responsiveness to RGG in lines of mice selected for high or low responses to somatic antigen of Salmonella

High (H/s) and low (L/s) antibody responder lines of mice selected according to their response to the somatic (s) antigen of Salmonella (Selection IV) have unexpected inverse capacity for antibody production to rabbit gamma globulin (RGG): H/s mice are low or even nonresponders to this antigen, whereas L/s mice are high responders. It was shown that the phenotypic variability within each line is due to environmental factors. RGG was a selection antigen in Selection V; the high (H/p) and low (L/p) responder mice are therefore considered as homozygous for the RGG genes. Responsiveness to RGG was investigated in F₁ and F₂ hybrids obtained by crossing the phenotypically similar RGG responder or nonresponder mice of Selections IV and V. The results support the hypothesis that the same genes control the response to RGG in L/s and H/p lines as well as in H/s and L/p lines. This means that the genes specific for RGG responsiveness were independent from those regulating responses to the s antigen. Unaffected by the selective breeding in Selection IV, they have been fixed by chance in an inverse way in H/s and L/s lines.     

Ca2+o-Independent Veratridine-Evoked Acetylcholine Release from Striatal Slices Is Not Inhibited by Vesamicol (AH5183): Mobilization of Distinct Transmitter Pools

The effect of 2-(4-phenylpiperidino)cyclohexanol (AH5183 or vesamicol), a compound known to block the uptake of acetylcholine (ACh) into cholinergic synaptic vesicles, on the release of endogenous and [14C]ACh from slices of rat striatum was investigated. ACh release was evoked either by electrical stimulation or by veratridine. The effect of electrical stimulation was entirely dependent on external Ca2+. By contrast, veratridine (40 microM) also enhanced ACh release in the absence of Ca2+. Indeed, with veratridine two components were clearly distinguished: one dependent on external Ca2+ and the other not. Vesamicol inhibited [14C]ACh release evoked by both veratridine and electrical stimulation in the presence of external Ca2+, provided it was added to the tissue prior to loading with [14C]choline. With the same treatment vesamicol only slightly affected the release of endogenous ACh. Under the same conditions the Ca2(+)-independent [14C]ACh release evoked by veratridine was not prevented by vesamicol. The differential responsiveness to vesamicol suggests that ACh pools involved in Ca2+o-dependent ACh release are different from those mobilized during Ca2+o-independent ACh release.     

Endoglin is a component of the transforming growth factor-beta receptor system in human endothelial cells.

Endoglin, a dimeric membrane glycoprotein expressed at high levels on human vascular endothelial cells, shares regions of sequence identity with betaglycan, a major binding protein for transforming growth factor-beta (TGF-beta) that co-exists with TGF-beta receptors I and II in a variety of cell lines but is low or absent in endothelial cells. We have examined whether endoglin also binds TGF-beta and demonstrate here that the major TGF-beta 1-binding protein co-existing with TGF-beta receptors I and II on human umbilical vein endothelial cells is endoglin, as determined by specific immunoprecipitation of endoglin affinity-labeled with 125I-TGF-beta. Furthermore, endoglin ectopically expressed in COS cells binds TGF-beta 1. Competition affinity-labeling experiments showed that endoglin binds TGF-beta 1 (KD approximately 50 pM) and TGF-beta 3 with high affinity but fails to bind TGF-beta 2. This difference in affinity of endoglin for the TGF-beta isoforms is in contrast to beta-glycan which recognizes all three isoforms. TGF-beta however is binding with high affinity to only a small fraction of the available endoglin molecules, suggesting that some rate-limiting event is required to sustain TGF-beta binding to endoglin.