In vitro effects of thyroxine on the mechanical properties of erythrocytes

In vitro effects of thyroxine on erythrocyte deformability and mechanical fragility were observed. Deformability of erythrocytes was improved in a dose dependent manner by thyroxine. Mechanical hemolysis was found to be lower if thyroxine was included in erythrocyte suspensions at concentrations close to the physiological levels (10(-9)M). These changes might be related to the alterations of intracellular calcium concentration, as in the erythrocyte suspensions containing 10(-9)M thyroxine, intracellular calcium concentration was found to be 30 times lower than the control suspensions which did not contain thyroxine. Thyroxine also reduced the mechanical hemolysis ratio in calcium loaded cells. These observations suggest that thyroxine might play some role in the regulation of the mechanical properties of erythrocytes which might be mediated via the effects on calcium metabolism.     

A Direct Screening Procedure for Gravitropism Mutants in Arabidopsis thaliana (L.) Heynh.

In order to isolate gravitropism mutants of Arabidopsis thaliana (L.) Heynh. var Estland for the genetic dissection of the gravitropism pathway, a direct screening procedure has been developed in which mutants are selected on the basis of their gravitropic response. Variability in hypocotyl curvature was dependent on the germination time of each seed stock, resulting in the incorrect identification of several lines as gravitropism mutants when a standard protocol for the potentiation of germination was used. When the protocol was adjusted to allow for differences in germination time, these lines were eliminated from the collection. Out of the 60,000 M2 seedlings screened, 0.3 to 0.4% exhibited altered gravitropism. In approximately 40% of these mutant lines, only gravitropism by the root or the hypocotyl was altered, while the response of the other organ was unaffected. These data support the hypothesis that root and hypocotyl gravitropism are genetically separable.     

Evidence for a composite phylogenetic origin of the plastid genome of the brown alga Pylaiella littoralis (L.) Kjellm

The nucleotide sequence and the 5 flanking region of the rbcL gene coding for the large subunit of ribulose bisphosphate-1,5-carboxylase/oxygenase of Pylaiella littoralis, a brown alga, has been determined and the deduced amino-acid sequence has been compared to those of various photosynthetic and chemoautotrophic Eubacteria, of a red alga and of green plastids (Euglena gracilis, green algae and higher plants). Unlike the rbcL genes of green plastids which are more closely related to those of cyanobacteria the P. littoralis rbcL gene is more closely related to that of a -purple bacterium, as was found for the rbcS gene of another chromophytic alga [Boczar et al., Proc Natl Acad Sci USA 86: 4996–4999, 1989]. Matrix data of homology between the rbcL gene of P. littoralis and the same gene of other organisms are presented. Based on our previous report, the gene coding for the 16S rRNA from P. littoralis is closely related to that of E. gracilis (Markowicz et al., Curr Genet 14: 599–608, 1988). We suggest that the large plastid DNA molecule of P. littoralis is a phylogenetically composite genome which probably resulted from mixed endosymbiosis events, or from a horizontal transfer of DNA.     

Progress in botany

Book Review

Progress in botanyH.-D. Behnke, K. Esser, K. Kubitzki, M. Runge and H. Ziegler (Eds.), 50. Berlin: Springer-Verlag, 1989. XIX+386 pages. DM 258.00. ISBN 3-540-50289-0     

The effect of lidocain on the renal function

The evidence supporting a role for direct neurogenic control of renal function was investigated in twenty anaesthetized dogs. Unilateral renal sympathectomy was induced by 0.5 mg/kg/min of lidocain infusion into the left renal artery and the kidney function changes were compared to those observed in the right non infused kidney. The renal parameters were similar in the kidneys during the control periods. 0.5 mg/kg/min of lidocain infusion into the left renal artery resulted in significant reductions of the RBF, GFR, urine and sodium excretion in the left kidney. The intrarenal lidocain infusion induced a small decrease of the arterial blood pressure but this can not explain the changes observed in the left kidney. The modifications of the right kidney function during lidocain infusion were significantly less than those observed in the left kidney. Comparing the measured RBF and the renal blood flow calculated by the CPAH in the left kidney during the lidocain infusion, we have found a marked difference, when the decrease of the calculated RBF was greater. We believe that effects of pharmacological denervation can be best explained by the intrarenal hemodinamically mediated changes. The sympathectomy produces a considerable vasoconstriction in the renal cortical vascular bed, subsequently it decreases the RBF, GFR renal sodium and water excretion. But the lidocain blocks the sympathetic nerves influencing the renal medullary vessels and the renal medullary blood flow increases. These observations are not consistent with the notion that renal nerves are at least partially responsible for the natriuresis accompanying salt loading.     

Two-compartment model for rabbit skin organ culture

Summary A new method was developed for rabbit skin organ culture. In a two-compartment model, skin discs were cultured on a Millicell-HA insert unit with a microporous membrane which allows transport of culture medium via the dermis into the epidermis, whereas the epidermal side remains free of direct contact with culture medium. In this relatively simple two-compartment organ culture model, rabbit skin could be cultured for 7 d in RPMI 1640 medium supplemented with fetal bovine serum, or for 2 d in RPMI 1640 medium supplemented with cofactors. The histomorphology and ultrastructure of 7-d cultured rabbit skin discs was essentially similar to that of freshly isolated rabbit skin. Keratinocytes in the stratum basale continued to divide during organ culture. The terminal differentiation of the epidermis continued in vitro as was found by the presence of keratohyalin granules, the intact stratum corneum, and keratin expression. Furthermore, glucose consumption continued until culture Day 7, but thereafter it declined rapidly. Concomitantly, degenerative changes were found. At the end of the 7-d culture period the distance between single dermal collagen fibrils had increased as compared to noncultured skin. This model of skin organ cultures can be used to study biological processes, dermal toxicity, and penetration and metabolism of xenobiotics in intact skin. Furthermore, within certain limits, processes responsible for repair and regeneration of damaged skin can also be studied in this model because the rabbit skin can be cultured for 7 d. The present study was financially supported by grants of Duphar B. V. (Weesp, Netherlands), the European Community, and the Dutch animal welfare organizations Samenwerkingsverband van de Nederlandse Vereniging tot Bescherming van Dieren en de Nederlandse Bond tot Bestrijding van de Vivisectie, Anti-Vivisectie Stichting en Stichting Schoonheid Zonder Wreedheid.     

Preference for plants damaged by conspecific larvae in ovipositing cabbage root flies: influence of stimuli from leaf surface and roots

In laboratory dual-choice assays females of the cabbage root fly, Delia radicum, prefer for oviposition plants with roots damaged by conspecific larvae to undamaged controls. Cauliflower and kale plants were inoculated with root fly eggs (25 per plant) and the hatching larvae were allowed to feed on the roots for various periods of time (1–17 days). After 4 (cauliflower) or 5 (kale) days of larval feeding the oviposition preference was most pronounced and flies laid between 64% and 68% of their eggs near plants with damaged roots. Later, with increasing damage but fewer surviving, and thus actively feeding, larvae, the magnitude of the preference declined. The preference for plants already damaged by conspecific larvae may contribute to the previously observed aggregated distribution of D. radicum eggs in Brassica crop fields.Further experiments revealed that the sensory cues inducing this oviposition preference originate from the complex consisting of the damaged roots, the surrounding substrate (soil) and associated microbes, rather than from the aerial plant parts. In choice assays using the root-substrate complex of damaged and control plants (aerial parts removed), the observed preference for damaged roots was similar to that found for the entire plant but was more pronounced. The damaged roots alone, compared to control roots, received up to 72% (cauliflower) and 75% (kale) of the eggs. By contrast, surrogate leaves sprayed with methanolic leaf surface extracts from the most preferred plants which had been damaged were not discriminated from surrogate leaved sprayed with extracts of the respective control plants. Analysis of glucosinolate levels in methanolic leaf surface extracts revealed that root damage resulted in enhanced concentrations of indole-glucosinolates on the leaf surface in kale but not in cauliflower. Although indole-glucosinolates are oviposition stimulants for the cabbage root fly, the induced changes were apparently too small to influence oviposition behaviour.     

Continuity,Collapse or Metamorphosis? Demographic anthropology and the study of change within human populations.Foreword

this first paper introduces the topic of the volume, outcomes of a symposium organised at the 13th ICAES held in Mexico in August 1993. It briefly reminds of the convergence between anthropology and demography up to date and stresses on the need of real transdisciplinary work in this challenging domain. The aim of the symposium was to make a contribution on the central theme chosen by the congress — the cultural and biological dimensions of global change — while examining the place of demographic anthropology in the study of change. The papers presented at the symposium have been organised in three parts which form the present volume: the composition of population, the choice of spouse and mobility, the reproduction and dynamics of populations. The basic mechanisms of change are considered through examples at the level of local populations. This also leads to question the definitions of human groups and to make a “declaration” stressing on the importance of individual heterogeneity and the arbitrariness and reductive nature of any grouping of individuals, stating therefore the misapprehension of the most recent scientific work inherent to the rationale of programs of “ethnic cleasing”. Translated from the french by prof. Derek F. Roberts     

Transformation of haploid, microspore-derived cell suspension protoplasts of rice (Oryza sativa L.)

We compared the transient activity of three cereal gene-derived promoter-gus fusions and the efficiency of selection mediated by three different selectable genes in a polyethylene glycol transformation system with haploid cell suspension protoplasts of rice. The maize ubiquitin promoter was found to be the most active in transformed protoplasts, and selection on ammonium glufosinate mediated by the bar gene was the most efficient for producing resistant calluses. Cotransformation of protoplasts with two separate plasmids carrying the gus and the bar genes, at either a 21 or 11 ratio, led to 0.8 × 10^–5 and 1.6 × 10^–5 resistant callus recovery frequencies and 59.7 and 37.9 cotransformation efficiencies respectively. No escapes were detected in dot blot analyses of 100 resistant calluses with a probe consisting of the bar coding region. Cotransformation efficiency, based on resistance to basta and -glucuronidase staining of the leaf tissue of 115 regenerated plants, was 47%. Resistance tests and Southern analysis of seed progenies of three diploid transgenic plants demonstrated homozygous integration of multiple copies of the transgene at one locus at least in the first plant, heterozygous integration at one locus in the second plant and heterozygous integration at two loci in the third plant.Abbreviations PEG polyethylene glycol - T₀ regenerated transgenic plant - GUS -glucuronidase - CaMV cauliflower mosaic virus - ARE anaerobic responsive element - OCS octopine synthase - T₁ first generation progeny of transgenic plants