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.     

Priming immunization against cholera toxin and E. coli heat-labile toxin by a cholera toxin short peptide-beta-galactosidase hybrid synthesized in E. coli.

A synthetic oligodeoxynucleotide encoding for a small peptide was employed for the expression of this peptide in a form suitable for immunization. The encoded peptide, namely, the region 50-64 of the B subunit of cholera toxin (CTP3), had previously been identified as a relevant epitope of cholera toxin. Thus, multiple immunizations with its conjugate to a protein carrier led to an efficient neutralizing response against native cholera toxin. Immunization with the resulting fusion protein of CTP3 and beta-galactosidase, followed by a booster injection of a sub-immunizing amount (1 microgram) of cholera toxin, led to a substantial level of neutralizing antibodies against both cholera toxin and the heat-labile toxin of Escherichia coli.     

Detection of a high frequency RsaI polymorphism in the human pro alpha 2(I) collagen gene which is linked to an autosomal dominant form of osteogenesis imperfecta.

Screening of the pro alpha 2(I) collagen genes of Southern African populations for restriction fragment length polymorphisms (RFLPs) has revealed a locus polymorphic for the restriction enzyme RsaI. The frequency of the RFLP was 0.38 in Afrikaners, but much lower in indigenous Southern African populations, which suggests that it is of European origin. The polymorphism was used to study 19 affected and non-affected individuals in a four generation family with the autosomal dominant disorder, osteogenesis imperfecta (OI) type I. Co-inheritance of the loss of the RsaI site and the OI phenotype was observed with a lod score of 3.91 at a recombination fraction (theta) of zero, indicating strong linkage. This suggests that the defect in this family is caused by a structural mutation within or close to the pro alpha 2(I) collagen gene. The use of this high frequency RFLP together with other recently described polymorphisms at this locus will facilitate the analysis of the role of this gene in OI and other inherited disorders of connective tissue.     

Laryngeal influences on breathing pattern and posterior cricoarytenoid muscle activity

Receptors responding to transmural pressure, airflow, and contraction of laryngeal muscles have been previously identified in the larynx. To assess the relative contribution of these three types of receptors to the reflex changes in breathing pattern and upper airway patency, we studied diaphragmatic (DIA) and posterior cricoarytenoid muscle (PCA) activity in anesthetized dogs during spontaneous breathing and occluded efforts with and without bypassing the larynx. Inspiratory duration (TI) was longer, mean inspiratory slope (peak DIA/TI) was lower, and PCA activity was greater with upper airway occlusion than with tracheal occlusion (larynx bypassed). Bilateral section of the superior laryngeal nerves eliminated these differences. When respiratory airflow was diverted from the tracheostomy to the upper airway the only change attributable to laryngeal afferents was an increase in PCA activity. These results confirm the importance of the superior laryngeal nerves in the regulation of breathing pattern and upper airway patency and suggest a prevalent role for laryngeal negative pressure receptors.     

Assessment of pharyngeal airway stability in normal and micrognathic infants

A current hypothesis for obstructive sleep apnea states that 1) negative airway pressure during inspiration can collapse the pharyngeal airway, and 2) neural control of pharyngeal airway-dilating muscles is important in preventing this collapse. To test this hypothesis we performed nasal mask occlusions to increase negative pharyngeal airway pressures during inspiration in eight normal and five micrognathic infants. Both groups developed midinspiratory pharyngeal obstruction, but obstruction was more frequent in micrognathic infants and varied in some infants with sleep state. The airway usually reopened with the subsequent expiration. The occasional failure to reopen was presumably due to pharyngeal wall adhesion. If airway obstruction occurred in sequential breaths during multiple-breath nasal mask occlusions in normal infants, there was a breath-by-breath change in the airway pressure associated with airway closure (airway closing pressure); the airway closing pressure became progressively more negative. Micrognathic infants showed less ability to improve the airway closing pressure, but this ability increased with age. These findings suggest that nasal mask occlusion can test the competence of the neuromuscular mechanisms that maintain pharyngeal airway patency in infants. Micrognathic infants had spontaneous midinspiratory pharyngeal airway obstructions during snoring. Their episodes of obstructive apnea began with midinspiratory pharyngeal obstruction similar to that seen during snoring and nasal mask occlusions. These findings imply a similar pathophysiology for snoring, spontaneous airway obstruction, and obstruction during snoring.     

In vitro selective effect of melphalan on human T-cell populations

Summary In vitro treatment with 2 g/2×10⁶ cells melphalan (l-PAM: l-phenylalanine mustard) significantly decreased the total number of T lymphocytes from peripheral blood (PBL) of healthy human donors and of the OKT₄ population (precursor suppressor/helper/inducer) T cells as defined by monoclonal antibodies OKT₃ and OKT₄, respectively. No changes in the OKT ₈ ⁺ lymphocyte population (cytotoxic/mature suppressor cells) were observed following the same treatment. Preincubation of PBL with l-PAM at concentrations that do not affect the rate of DNA synthesis in PHA-stimulated lymphocytes inhibited the generation of T suppressor lymphocytes by ConA, as shown by their effect on PHA stimulation. Treatment of allogeneic PBL with l-PAM had no effect on mature suppressor T cells already induced by Con A, as shown by incubation of PBL with l-PAM after incubation with ConA.     

Phosphorylation of purified glucocorticoid receptor from rat liver by an endogenous protein kinase

Glucocorticoid receptor was purified from rat liver cytosol using a dexamethasone affinity column. The receptor thus purified displayed a single protein band when subjected to SDS-polyacrylamide gel electrophoresis. It had a molecular weight of 90,000 which was consistent with the reported value for other glucocorticoid receptor preparations. Incubation of the purified preparation with [gamma 32P] ATP and Mg2+ resulted in transfer of [32P] to the receptor protein indicating the presence of an endogeneous protein kinase activity capable of phosphorylating the receptor molecule. Phosphorylation of the glucocorticoid receptor by the endogenous protein kinase might serve as a direct mechanism for the activation of the receptor.     

Growth and mortality of individual plants as a function of “available area”

Summary We looked at the relationship between available area, as defined by Thiessen polygons around individual plants, and plant size and mortality in even-aged green-house populations of Lapsana communis L. Polygon area was a good predictor of plant weight in these populations. After nine weeks growth, just prior to the onset of self-thinning, the dry weight of plants was directly proportional to the square root of polygon area. After the onset of selfthinning, plant weight appeared to be directly related to polygon area to the 3/2 power. Plants in small polygons were much more likely to die than those in larger areas. Thinning changed the frequency distribution of polygon sizes from highly skewed and unequal to normal and more equal, while inequality in surviving plant sizes did not appear to be affected by thinning.