EFFECTS OF COMPETITION AND DISTURBANCE ON THE RESPROUTING PERFORMANCE OF THE MEDITERRANEAN SHRUB ERICA MULTIFLORA L. (ERICACEAE)

Two field experiments were designed to evaluate the importance of competition, fire, repeated disturbance, and their interactions on the vegetative and reproductive performance of the Mediterranean shrub Erica multiflora over a 2.5-yr period. In a burn experiment, fire was applied to the ground-level stumps of previously clipped 13-yr-old plants with a propane torch and competition was diminished by removal of neighboring plants. Fire resulted in a reduction of sprout vigor and biomass of flowers; mature neighbors also reduced E. multiflora sprout vigor and flowering. The interaction between fire and competition was nonsignificant. In a stand burned by a wildfire we studied the effects of regenerating neighbors on target plants by removing all neighbors or only Quercus coccifera, the most dominant species in the burned stand. In this stand we also simulated herbivory by repeatedly clipping the sprouts of E. multiflora. Regenerating neighbors did not affect target plant sprout vigor after the wildfire, but did cause a decrease in the biomass of flowers per plant. Survival decreased after repeated clipping but was not affected by neighborhood treatment. The results suggest that the importance of competition on resprouting vigor was temporally variable. Variables related to plant size rather than species determined competitive superiority: resprouting neighbors did not affect resprouting performance of target plants, but mature neighbors did. In nature, fire may directly reduce vegetative and reproductive biomass by the heating effect. But it may have an indirect positive effect on biomass, by reducing competition among plants. Frequent disturbances that removed aboveground biomass of E. multiflora had a detrimental effect on target plant survival independent of neighborhood effect.     

De novo missense mutation Y174S in exon 1 of the adrenoleukodystrophy (ALD) gene

Adrenoleukodystrophy (ALD) is an X-linked disease, characterised by an alteration of the peroxisomal -oxidation of the very long chain fatty acids. The ALD gene has been identified and mutations have been detected in ALD patients. We report here a new missense mutation in the ALD gene of a male patient, predicting a tyrosine to serine substitution at codon 174 (mutation Y174S). The mother of the ALD patient does not have the Y174S mutation in her leukocyte DNA, indicating that Y174S arose de novo in the patient. Y174S is the first reported de novo mutation in the ALD gene.     

Circadian organization in the ruin lizard Podarcis sicula: the role of the suprachiasmatic nuclei of the hypothalamus

The effects of electrolytic lesions to the suprachiasmatic nuclei of the hypothalamus (SCN) on circadian rhythms of locomotor activity were examined in ruin lizards Podarcis sicula maintained in constant darkness and constant temperature (29°C). All lizards (N=15) in which the lesion damaged 80% or more of the SCN became behaviorally arrhythmic. On the contrary, locomotor rhythms persisted in all cases (N=11) when the SCN remained intact and lesions were confined to neighbouring regions of the preoptic area. Taken together with previous work which demonstrates that the pineal and the retinae are not essential for the persistence of circadian locomotor rhythmicity in Podarcis sicula and with recent evidence showing the homology between the SCN of lizards and those of mammals the present results strongly support the view that the SCN of Podarcis sicula contain the primary pacemaker(s) for locomotor rhythms.Abbreviations DD constant darkness - LL constant light - SCN suprachiasmatic nuclei of the hypothalamus - PH nucleus periventricularis hypothalami - OC optic chiasm - te length of circadian activity - freerunning circadian period     

Behavior of vitamin A, beta-carotene, retinol binding protein and prealbumin in the plasma of hypo- and hyperthyroid subjects

Plasma concentrations of beta-carotene and retinol, determined by HPLC, and of transport proteins, ascertained by immunodiffusion technique, in hypo and hyperthyroid subjects are reported. In hypothyroid subject a considerable increase in carotene was noted. This was not the case for retinol. In hyperthyroids both beta-carotene and retinol levels were found to be normal. Transport protein (PA and RBP) levels were found to be lower only in cases of hyperthyroidism but unchanged for hypothyroids. According to the Authors the results show that the alteration in plasma carotene levels to be found in hypothyroid subjects is not the direct consequence of a lack of thyroid hormone in the metabolism of vitamin A but the indirect effect of thyroid disease.     

Regulatory properties of rabbit red blood cell hexokinase at conditions close to physiological

The true level of hexokinase in rabbit erythrocytes was determined by three different methods, including the spectrophotometric glucose-6-phosphate dehydrogenase coupled assay and a new radioisotopic assay. The value found at 37°C (pH 7.2) was 10.23±1.90 μmol/h per ml red blood cells, which is lower than previously reported values. More than 40 cellular components of the rabbit erythrocytes were tested for their effects on the enzyme. Their intracellular concentrations were also determined. Several of these compounds were found to be competitive inhibitors of the enzyme with respect to Mg·ATP^2?. Furthermore, reduced glutathione at a concentration of 1 mM was able to maintain hexokinase in the reduced state with full catalytic activity. The ability of orthophosphate to remove the inhibition of some phosphorylated compounds was examined under conditions similar to cellular (pH 7.2 and 50 μM of orthophosphate) and found to be of no practical interest. In contrast, the binding of ATP^4? and 2,3-diphosphoglycerate to the rabbit hemoglobin significantly modifies their intracellular concentrations and the formation of the respective Mg complexes. The pH-dependence of the reaction velocity and of the kinetic properties of the enzyme in different buffer systems were also considered. This information was computerized, and the rate of glucose phosphorylation in the presence of the mentioned compounds was determined. The value obtained, 1.94±0.02 μmol/h per ml red blood cells, is practically identical to the measured rate of glucose utilization by intact rabbit erythrocytes (1.92±0.3 μmol/h per ml red blood cells). These results provide further evidence for the central role of hexokinase in the regulation of red blood cell glycolysis.     

Rabbit red blood cell hexokinase

Summary Rabbit hexokinase (EC 2.7.1.1) has been shown to exist in reticulocytes as two distinct molecular forms, designated hexokinase Ia and Ib, but only one of these was consistently present in mature red cells. In vivo, hexokinase la and Ib show a decay rate of 3 and 8% a day, respectively, while in vitro they show a similar stability.The possibility that the proteolytic activities of the reticulocyte could be responsible for the fast decay of hexokinase was investigated. No differences were found in the decay rates of hexokinase la and Ib during in vitro reticulocyte maturation in presence or absence of proteolytic inhibitors. Contrariwise, many findings indicate the ATP-dependent proteolytic system of the reticulocyte as a possible mechanism. In fact, the decay of hexokinase and the degradation of 3H-globins are both stimulated by ATP and ubiquitin; they show similar kinetic properties and both disappear during reticulocyte maturation.The cellular localization of hexokinase la and Ib was shown to be responsible for the differences found between their decay rates.Abbreviations PMSF phenylmethylsulfonyl fluoride - TPCK 1-1-tosylamide-2-phenylethyl-chloromethyl ketone - TLCK N -p-tosyl-L-lysine chloromethyl ketone     

Cell-mediated immunity in human acute myeloblastic leukemia

Summary Lymphocyte stimulation tests with autologous myeloblasts were performed in 31 patients with nonlymphatic acute leukemia. Twenty-five patients were receiving chemotherapy combined with immunotherapy; six received chemotherapy only. Thirteen nonleukemic patients with various disorders and six healthy control patients were also studied.It was found that 4/15 patients in 9/38 tests had autologous lymphocytes stimulated by autologous circulating myeloblasts. Bone marrow cells also effected stimulation, significantly more often if the marrow was taken in relapse than when it was taken in remission.However, so-called immunotherapy with allogeneic leukemic myeloblasts and BCG could not be shown to increase these frequencies. Nor did it significantly increase the degree of stimulation measured as DNA synthesis in lymphocytes.Moreover, nonleukemic bone marrow cells from patients with other disorders also stimulated autologous lymphocytes in 1/13 patients. No recognition of autologous myeloblasts was observed when the responding lymphocytes were taken in incomplete remission or during the month preceding relapse.with the technical assistance of T. Lehtinen and A. M. SjögrenSupported by the Swedish Cancer Research Foundation Grant no. 699-B76-04XA     

Role of erythrocyte membrane lipids in the antagonism between vitamin A and D3

The "in vitro" lytic effect of retinol (35 microM) on various animal species erythrocytes is partially inhibited by cholecalcipherol. The inhibition observed is not related with reduction of retinol bound by erythrocytes membranes while it can be related with the amount of glycolipids not gangliosides of these cells. Instead, we have observed that the amount of retinol molecules bound to erythrocytes membranes and their haemolysis can be related with the gangliosides contents of red cells membranes.     

In vivo and in vitro activity of Streptococcus faecium extract on Herpes simplex virus

The effects of substance or substance extracted from Str. faecium SF 68 on HSV-1 are evaluated. The "in vivo" assay show that bacterial extract introduced i.p. in mice simultaneously with HSV-1 brought about 100% of survival, but bacterial extract after virus challenge brought about complete mortality of mice. "In vitro" assays show that bacterial extract reduce significantly PFU number. It seemed that Str. faecium extract affected the virus at the stage of adsorption on the host cells.