Adenosine receptor-mediated changes in cyclic AMP production and DNA synthesis in cultured arterial smooth muscle cells

The effects of adenosine and two analogs, L-phenylisopropyladenosine (L-PIA) and 5'-N-ethylcarboxamidoadenosine (NECA), on cAMP production and on platelet-derived growth factor (PDGF)-stimulated initiation of DNA synthesis in growth-arrested cultures of rat arterial smooth muscle cells (SMC) were studied. The intracellular cAMP concentration was dose-dependently enhanced by micromolar concentrations of adenosine and its analogs, with the potency order NECA greater than adenosine greater than L-PIA. The effect was antagonized, in a competitive manner, by the adenosine receptor antagonist 8-phenyltheophylline (8-PT). The stimulatory effect of adenosine was enhanced by 3 microM dipyridamole an adenosine-uptake blocker. DNA synthesis was inhibited in a parallel manner, showing the same potency order. The inhibition was antagonized by 8-PT. Forskolin, a diterpene with the ability to stimulate the catalytic unit of adenylate cyclase and thereby cAMP formation, potentiated the effects of micromolar concentrations of NECA and L-PIA. Forskolin, by itself, stimulated cAMP production and inhibited DNA synthesis. The forskolin-stimulated increase in cAMP was inhibited by L-PIA at nanomolar concentrations. L-PIA in the nanomolar concentration range also stimulated DNA synthesis when initiation was stimulated with suboptimal concentrations of PDGF. These findings suggest the presence of adenosine receptors of both the A1- and A2-subtype on SM-mediating bidirectional changes of cAMP and DNA synthesis.     

Nesting holes and food supply in relation to forest bird densities on islands and mainland

Summary Bird densities were estimated on 41 small islands and two mainland plots at a South Swedish lake both in 1976 and 1983. In the latter year, three additional plots were also censused. The ratio between combined densities of hole-nesting birds on the mainland and on islands was 3:1 both in plots without and with nest boxes. In plots with boxes combined densities of hole-nesting birds doubled compared with control plots. This increase was caused by a tenfold increase of pied flycatcher Ficedula hypoleuca. Territories of this species were on average established about a week later on the islands compared with the mainland. Furthermore, 50% of the males on the islands did not attract a female. Densities of great tit Parus major, marsh tit Parus palustris and nuthatch Sitta europaea were unaffected by increased nesthole availability. For P. major this result contrasts with those in other studies.The density of chaffinch Fringilla coelebs in habitats with similar height and vertical structure was two times higher on the islands compared to the mainland. On the islands the density was the same on islands with only one pair and on those with two or more pairs. In spring, there were no significant differences between islands and the mainland in the proportion of leaves with insect feeding traces. The proportion of Salix leaves with feeding traces increased with island size, but this was not so for Alnus and Betula leaves. In late summer, the proportion of leaves with feeding traces were halved inside a plot with nest boxes and hence increased bird densities compared to a nearby control plot. This result was the same along the lake shore and about 150 m away from the shore.The discussion centers on the effect of man on the food-and nest site-availability of hole-nesting birds, food limitation of insectivorous birds and density compensation on islands.     

Early stimulation of ATP turnover induced by growth factors : Synergistic effect of EGF and insulin and correlation with DNA synthesis

Addition of a mixture of EGF + insulin to quiescent cell cultures synergistically stimulates the cells to reinitiate DNA synthesis and cell division. We have previously demonstrated that this mixture rapidly increases ATP turnover in quiescent cells. The present work shows that each of the two growth factors, EGF and insulin, when added separately to quiescent cells was able to stimulate the phosphorylation of the organic acid-soluble compounds (Po) pool and ATP turnover. The stimulation of ATP turnover was closely correlated with the increase in phosphorylation of the Po pool which suggests that Po labelling reflects the ATP turnover. In many experiments, the synergy between the two growth factors on the early increase in phosphorylation of the Po pool was clearly shown. Doubling the concentration of EGF (12-24 ng/ml) or insulin (50-100 ng/ml) did not increase early stimulation of phosphorylation of the Po pool, whereas simultaneous addition of the two growth factors induced a greater stimulation than that of each growth factor separately added. The augmentation in Po labelling after addition of EGF or insulin alone was transient. The synergistic effect of the two growth factors was more significant when determined 150 or 300 min after growth-factor addition. In our experimental conditions, each of the two growth factors, EGF and insulin, was able to induce a stimulation of DNA synthesis. However, the best stimulatory effect was observed with the mixture of the two which synergistically increased DNA synthesis determined between 6 and 24 h after growth-factor addition. The comparison between DNA replication and Po labelling suggests a correlation between the increase in DNA replication and in the total ATP synthesized in the first 5 h after cell stimulation by growth factors added separately or in combination.     

Neuropeptides in the gastrointestinal canal of Necturus maculosus

Summary The presence and distribution of regulatory peptides in nerves and endocrine cells of the stomach, intestine and rectum of a urodele amphibian, the mudpuppy, Necturus maculosus, was studied immunohistochemically in sections or whole-mount preparations of the gut wall. The effect of the occurring peptides on gut motility was studied in isolated strip preparations of circular and longitudinal smooth muscle from different parts of the gut.Bombesin-, neurotensin-, substance P- and VIP-like immunoreactivity was present in abundant nerve fibres in the myenteric plexus of both stomach, intestine and rectum. Single fibres or bundles were present in the circular muscle layer and in a well-developed deep muscular plexus in the intestine and rectum. Immunoreactive nerve cells were found in the myenteric plexus of the stomach, intestine (neurotensin only) and rectum. Gastrin/CCK-like immunoreactivity was observed only in a few fibres in stomach and rectum.Endocrine cells containing bombesin-, met-enkephalin-, gastrin/CCK-, neurotensin-, somatostatin- or substance P- like immunoreactivity were present in the mucosa.The effect of bombesin was an inhibition of the rhythmic activity in circular muscle preparations and in longitudinal muscle from the rectum, while longitudinal muscle from the stomach usually responded with a weak increase in tonus. Neurotensin, like bombesin, was inhibitory on the spontaneous rhythmic activity of circular muscle throughout the gut, while the effect on longitudinal muscle was an increase in tonus. Met-enkephalin and substance P increased the tonus of all types of preparations, and often, in addition, initiated a rhythmic activity superimposed on this maintained tonus. VIP had a general inhibitory effect on the preparations, decreasing tonus and/or abolishing rhythmic activity.It is concluded that bombesin-, neurotensin-, substance P- and VIP-like peptides are present in nerves throughout the urodele gut and may have physiological functions in regulating the motility of the gut. The gastrin/CCK-like peptide present in nerves of the stomach and rectum may affect the function of these parts of the gut. The regulatory peptides present in endocrine cells may, perhaps with the exception of the somatostatin-like peptide, affect the motility humorally.     

Degradation of phenol by Pseudomonas putida ATCC 11172 in continuous culture at different ratios of biofilm surface to culture volume

Pseudomonas putida ATCC 11172 was grown in continuous culture with phenol as the only carbon and energy source; a culture practically without biofilm was compared with biofilm cultures of differing surface area/volume ratios. The biofilm did not significantly affect the maximal suspended cell concentration in the effluent, but it increased the maximal phenol reduction rate from 0.23 g/liter per h (without biofilm) to 0.72 g/liter per h at the highest biofilm level (5.5 cm2 of biofilm surface per ml of reactor volume). The increase in phenol reduction rate was linear up to the surface area/volume ratio of 1.4 cm2/ml. The continuous cultures with biofilms could tolerate a higher phenol concentration of the medium (3.0 g/liter) than the nonbiofilm system (2.5 g/liter). At higher dilution rates an intermediate product, 2-hydroxymuconic semialdehyde, accumulated in the culture. When the biomass of the effluent started to decrease, the concentration of 2-hydroxymuconic semialdehyde reached a peak value. We conclude that biofilms in continuous culture have the potential to enhance the aerobic degradation of aromatic compounds.     

Differences in species richness and site preference of the vascular plant flora of river shores in northern Sweden in relation to the degree of natural habitat disturbance

Samples from sixty-two geolittoral sites along two rivers in northern Sweden were analysed in order to quantify possible differences in the vascular plant flora related to differences in the type of natural disturbance of the habitat (more disturbed: rapids (water flow) and lakes (wave action); less disturbed: slow-flowing stretches). We found that the mean species richness was lower along the slow-flowing stretches, than along the rapids and lakes, which were quite similar. When the geolittoral was subdivided into the three vertical belts, the floras of both the upper and middle belts exhibited this same pattern, whereas the species richness of the lower geolittoral belt was also low along the stretches of rapids. Along both rivers, the steepest gradient in mean species richness was recorded on the shores bordering rapids. The highest numbers of 'constant' species (frequency (F) > 60%); and of those which showed a statistically significant (probability (p) > 0.05) preference for a certain type of stretch in at least one of the three geolittoral belts, or in the entire geolittoral, were found along the rapids, in comparison to the flora of the slow-flowing stretches. The flora of the lake shores also comprised a large number of specific species compared to that along the slow-flowing stretches. The predominant species along the above-mentioned stretches reflect both phytogeographical and habitat differences.     

D- and L-isoprenaline have different effects on adrenoceptors in the systemic vasculature of the cod, Gadus morhua

The effects of D- and L-isoprenaline on systemic vascular adrenoceptors of the cod was studied using blood pressure recording from conscious cod in vivo and isolated coeliac artery strip preparations in vitro. Experiments with isolated artery preparations demonstrated that the D-, but not the L-isomer of isoprenaline acts as an alpha-adrenoceptor antagonist. A dose-dependent reduction of ventral and dorsal aortic blood pressures together with a dose-dependent increase in the heart rate could be produced by injection of L-isoprenaline. D-Isoprenaline, on the other hand, had no effect on the blood pressures or heart rate except in the highest dose injected. The results show an alpha-adrenoceptor blocking capacity of D-isoprenaline in the cod. The effect of L-isoprenaline on the blood pressure supports the idea that the hypotensive effect of DL-isoprenaline seen in previous studies of the cod may be attributed to an effect of the L-isomer on beta-adrenoceptors mediating vasodilation of the cod systemic vasculature.     

Expression of the gene encoding protein A in Staphylococcus aureus and coagulase-negative staphylococci

Two shuttle vectors containing the gene for protein A (spa) from Staphylococcus aureus have been constructed to study expression of the gene in various strains of S. aureus and in the coagulase-negative species Staphylococcus epidermidis, Staphylococcus capitis, and Staphylococcus xylosus. One plasmid, pSPA15, contains the complete structural gene for protein A, which binds to the cell wall in various Staphylococcus species. The other plasmid, pSPA16, codes for a truncated protein A lacking the C-terminal part called region X. The latter is exclusively extracellular in all Staphylococcus species tested, which confirms the importance of region X for cell wall binding. The expression of the plasmid-coded protein A in various strains of S. aureus is strongly correlated to the expression of the chromosomal spa gene. The coagulase-negative species expressing plasmid-encoded protein A produce 12 to 30% of the amount coded by the chromosomal spa gene in S. aureus strains Cowan I and A676.     

Peptide synthesis in aqueous-organic solvent mixtures with alpha-chymotrypsin immobilized to tresyl chloride-activated agarose

alpha-Chymotrypsin was immobilized with a high coupling yield (up to 80%) to tresyl chloride activated Sepharose CL-4B.The immobilized enzyme was tested for its ability to synthesize soluble peptides from N-acetylated amino acid esters as acyl donors and amino acid amides as acceptor amines in water-water-miscible organic solvent mixtures. It was found that the yield of peptide increased with increasing concentration of organic cosolvent. Almost complete synthesis (97%) of Ac-Phe-Ala-NH(2) was obtained from Ac-Phe-OMe using a sixfold excess of Ala-NH(2). The rate of peptide formation in aqueous-organic solvent mixtures was good. Thus, 0.1M peptide was formed in less than 2 h in 50 vol% DMF with 0.1 mg immobilized chymotrypsin/mL reaction mixture. The immobilized enzyme distinguished between the L and D configurations of acceptor amino acid amides even in high concentration of nonaqueous component (90% 1,4-butanediol). The effect of temperature was studied. It was found that both the yield of peptide and the stability of immobilized enzyme increased when the temperature was lowered. Experiments could be performed at subzero temperatures in the aqueous-organic solvent mixtures resulting in very high yield of peptide. After three weeks continuous operation at 4 degrees C in 50% DMF, the immobilized enzyme retained 66%of its original synthetic activity. The activity of the immobilized enzyme was better conserved with a preparation made from agarose with a higher tresyl group content compared to a preparation made from a lower activated agarose, indicating that multiple point of attachment has a favorable effect on the stability of the enzyme in aqueous-organic solvent mixtures. The major advantage of using water-miscible instead of water-immiscible organic solvents to promote peptide syntheses appears to be the increased solubility of substrates and products, making continuous operation possible.     

Extracellular and intracellular acid-base status following strenuous activity in the sea raven (Hemitripterus americanus)

Summary Exhausting activity in the sea raven resulted in a pronounced extracellular acidosis, which consisted of a large, short-lived respiratory component and a small, longer-lived metabolic component. Thi disturbance had been corrected by 12 h. White muscle experienced a pronounced intracellular acidosis of chiefly metabolic origin, with pH_i dropping from a resting value of 7.51 to a low of 7.10 immediately post-activity. The recovery of pH_i was associated with a reduction in muscle lactate. Despite the large increase in , cardiac muscle pH_i remained constant postactivity, actually showing an alkalosis at 30 min into recovery. Maintenance of cardiac muscle pH_i was achieved by an accumulation of HCO ₃ ^– intracellularly.