Ecology and biogeography of plant communities associated with the post Plio-Pleistocene relict Rhododendron ponticum subsp. baeticum in southern Spain

Aims Rhododendron ponticum L. is reputed to be a post Plio‐Pleistocene relict plant species with a disjunct distribution that comprises the Iberian Peninsula to the west and the Euxinian region plus some restricted Mediterranean areas to the east. We analysed the ecological range (of subsp. baeticum) in the western area (Aljibe Mountains, north of the Strait of Gibraltar) to understand the factors determining the present area limitation. Location Sierra del Aljibe, north of the Strait of Gibraltar (Iberian Peninsula). Methods We selected 20 riparian sites where R. ponticum is common, and compiled data on the ecological diversity of associated woody species and ferns. We established a 500‐m main transect in each site, along the stream or river course, in which we placed five 20‐m‐long plots at regular intervals. We recorded physiographic habitat features, woody plants and fern abundance, and the number of R. ponticum individuals. Results Rhododendron ponticum in southern Spain is restricted to riparian forests in acidic soils (pH 4.0–6.4), and is mainly found on the banks of inclined and enclosed streams. In our inventory we recorded 59 woody taxa and 12 ferns, with R. ponticum being the dominant species of the understorey (mean abundance 78.6%). The communities are characterized by a high incidence of the humid warm temperate element, both in number of species (18.8 ± 3.7 per site) and abundance; meanwhile, the presence of the modern Mediterranean element (mean number of species 3.4 ± 3.8 per site) appears to be favoured by disturbance. These ecological–historical groups of taxa also show distinct patterns of typological habit, frequency of endemism, infrageneric diversity and geographical range. Populations of R. ponticum are characterized by a very variable density of seedlings in many sites, and the virtual lack of juveniles. Main conclusions Riparian forests of the Aljibe Mountains constitute a refuge for R. ponticum where the species persists, but populations appear to be in decline. The narrow ecological range of R. ponticum in the area strongly contrasts with its wide amplitude in the eastern natural area, mainly the Euxinian region, where R. ponticum probably finds better conditions due to the environmental heterogeneity of the region, and the lack of a hot dry season.     

Studies on the simultaneous production of single cell protein and polygalacturonase fromKluyveromyces fragilis

Summary Kluyveromyces fragilis produces polygalacturonase (PG) on a lactose medium. Although the enzyme is normally repressed at high aeration levels, significant amounts of PG can be produced under such conditions when pectin is added as inducer. The productivity and yield of cell mass were not significantly affected by the presence of inducer, suggesting potential applications to current single cell protein processes from whey.     

On the preservation of avian blood cells

The functional state of erythrocytes from hen during their conservation with a preserving solution for 24 days at 4 degrees C, has been estimated by studying some biochemical and hemorheological parameters. Results show an initial phase in the preservation period (4-5 days) in which red blood cells maintain their values at levels similar to those at the beginning of the experience, except for osmotic resistance. Furthermore a progressive erythrocyte deformability loss, linked to ATP depletion (with rise in inorganic phosphate levels) as well as a gradually higher rate of hemolysis, were detected.     

Action of mercury on sugar transport across rat small intestine, in vivo

Absorption of galactose from in vivo perfused rat jejunum was inhibited by 0.1-0.5 mM Hg2+. A few minutes' delay was required for maximal inhibition values. The effects remained after saline solution washing but were in part reversed by EDTA and in higher proportion by dithioerythritol. Absorption inhibition could be ascribed to impairment of the sugar-Na phlorizin-sensitive cotransport component: The passive apparently diffusional component that remains under 0.5 mM phlorizin and absorption of L-sorbose were unaffected by the metal. Hg action is explained as due to its binding to thiol and perhaps other chemical groups of proteins, at different depths in the membrane, which are directly or indirectly related to the sugar transport system.     

The action of adrenoceptor agonists and antagonists on the guinea pig and dog trachea

The action of beta- and alpha-adrenoceptor agonists (isoprenaline, orciprenaline, noradrenaline, phenylephrine and ephedrine) and antagonists (propranolol, metipranolol, exaprolol, BL 445 and phentolamine) on the resting tension and cAMP level of the guinea pig and the mechanical and electrical activities of the dog trachea were studied. By activating beta 2-adrenoceptors, isoprenaline and orciprenaline relaxed the smooth muscle, elevated the membrane potential and attenuated the excitatory effect of histamine on membrane potential and muscle tension. Noradrenaline and phenylephrine, acting on alpha 1-receptors, did not affect the membrane potential and increased the basal tension of the dog trachea only insignificantly. Ephedrine, in high concentrations, however, hyperpolarized the smooth muscle membrane and relaxed the dog trachea, while it did not alter the cAMP level in the guinea pig preparations. It is, therefore unlikely that alpha 1-adrenoceptors play a major role in the excitation of the dog trachea under resting conditions whereas the participation of alpha 2-receptors in the mechanisms of adrenergic relaxation could not be ruled out. All the beta-adrenoceptor antagonists studied enhanced the action of low isoprenaline concentrations and competitively antagonized it in high concentrations. The order of their antagonistic potency in the guinea pig trachea was as follows: metipranolol greater than propranolol = exaprolol greater than or equal to BL 445. It was suggested that metipranolol and exaprolol are nonselective beta-adrenoceptor antagonists, similarly as propranolol, whereas BL 445 shown some beta 1-selectivity. In contrast to their antagonistic effects on the membrane activities and muscle tension, both histamine and isoprenaline increased the level of cAMP in smooth muscle cells and, when present simultaneously, their effect was additive. The mechanism of histamine-induced cAMP level elevation and the possible involvement of different subcellular compartments in the action of isoprenaline and histamine in relation to the contraction-relaxation cycle is discussed.     

Changes in H1 complement in differentiating rat-brain cortical neurons

Neuronal nuclei have a low H1 content. A stoichiometry of 0.47 molecule/nucleosome, on average, is calculated for rat brain cortical neurons by comparing its H1 content with that of liver nuclei. The H1 fraction of rat cerebral cortex neurons has been resolved into five subtypes, H1a--e, that have the same mobility as the unphosphorylated H1 forms of other rat tissues. The subtypes H1a--d decay exponentially during postnatal development and are substituted to different extents by H1e. The higher replacement rate is shown by H1a with an apparent half-lifetime of about 5 days. The corresponding values for H1b, H1c and H1d are 11, 21 and 15 days. Several conclusions can be drawn from the observation of postnatal changes in H1 subtype proportions. The low H1 content of neuronal nuclei does not imply the presence of notable peculiarities in subtype composition or in subtype substitution pattern. There is turnover of H1 in differentiating neurons once cell proliferation and DNA replication have ceased. The relative rates of synthesis and/or degradation of the subtypes differ in germinal cells and in neurons. Comparison with previous results on H1 degrees accumulation also shows that in cortical neurons the regulation of the subtypes H1a--e differs from that of H1 degrees.     

Partial 1p monosomy in a physically and mentally retarded boy

An 8-year-old boy is reported with marked mental and physical retardation, microcephaly, hypertelorism, mongoloid palpebral fissures, hypoplasia of the maxillary portion of the face, and other discrete anomalies. Deletion of the distal portion of the short arm of the chromosome 1 and the karyotype 46,XY, del(1)(p33----pter) was detected.     

Long-term effects of low-level 239Pu contamination on murine bone-marrow stem cells and their progeny

The effects of long-term internal contamination with 13.3 kBq kg-1 239Pu injected intravenously were studied in 10-week-old ICR (SPF) female mice. Radiosensitivity of spleen colony-forming units (CFU-S) and 125IUdR incorporating into proliferating cells of vertebral bone marrow and spleens were determined in plutonium-treated and control animals one year after nuclide injection. The CFU-S in 239Pu-treated mice were more sensitive to X-rays (D0 = 0.52 +/- 0.01 Gy) than in controls (D0 = 0.84 +/- 0.02 Gy). 125IUdR incorporation into bone marrow and spleen cells was reduced after plutonium contamination. At one year following plutonium injection, the occurrence of chromosome aberrations was evaluated in metaphase figures of femoral bone marrow cells. The frequency of aberrations increased early after plutonium treatment, at later intervals it tended to decrease but not below the control level. While the relative numbers of vertebral marrow CFU-S decreased significantly, but only to 86 per cent of normal, cellularity of vertebral bone marrow, peripheral blood counts and survival of 239Pu-treated mice did not differ from the control data.     

Isolation from urine of two Serratia marcescens strains excreting a diffusible yellow pigment

Two bacterial strains excreting a yellow pigment were isolated from human urine and identified as Serratia marcescens. The pigment was produced in the late exponential and early stationary phases of growth. Minimal media supplemented with tyrosine, phenylalanine, 3,4-dihydroxyphenylacetate or tryptophan, as well as complex media, induced pigment production. UV-visible spectra of the extracted pigment had peaks characteristic of 2-hydroxy-5-carboxymethylmuconate semialdehyde, produced from meta-cleavage of 3,4-dihydroxyphenylacetate by the enzyme 3,4-dihydroxyphenylacetate 2,3-dioxygenase (EC 1.13.11.15). This enzyme was active when the bacteria were grown under conditions promoting pigment production. The kinetics and factors affecting pigment production are also reported.     

2,3-Bisphosphoglycerate protects mitochondrial and cytosolic proteins from proteolytic inactivation

2,3-bisphosphoglycerate at physiological concentration similar to that found in many tissues protects effectively ornithine transcarbamoylase (OTC) from proteolytic inactivation by broken lysosomes. 2,3-bisphosphoglycerate protects also many other mitochondrial and cytosolic proteins, such as glutamate dehydrogenase (GDH) an glyceraldehyde-3-phosphate dehydrogenase (GAPDH), from proteolysis by broken lysosomes and other proteases. It is, thus, suggested that 2,3-bisphosphoglycerate may play an important role in the control of the degradative rates of some proteins, which may explain its high concentration in certain cells.