Photosynthesis of plant régénérants. Specificity ofin vitro conditions and plantlet response

Regenerants from tobacco(Nicotiana tabacum L. cv. White Burley) leaf segments cultivatedin vitro in vessels with solid agar medium under usual conditions (plantlets) grew under very low irradiance (I = 40 μxmol m?2 s?1), very high relative humidity (more than 90%) and decreased CO₂ concentration (c_a) during light period. In comparison with seedlings of a similar number of leaves and similar total leaf area grown in sand and nutrient solution, the plantlets had lower dry mass of shoots and roots per plant and thinner leaves almost without trichomes and epicuticular waxes. Due to a low transpiration rate under high relative humidity the water potential of plantlet leaves was higher than that of seedling leaves and the difference in water potential between leaves and medium was lowei. The rate of water loss from leaves detached from plantlets was considerably faster than that from seedlings under the same conditions (I = 110 μrnol m^?2; s^?1, temperature 30 °C, relative humidity 50 %). Net photosynthetie rates (P_n) of leaves of plantlets and seedlings measured under saturating I, natural ca and the leaf temperature 20 °C were similar, nevertheless the shape of curves relating Pn to c» indicated some differences in photosynthetie parameters(e.g. saturation of Pn under lower ca> higher CO2 compensation concentration in plantlets than in seedlings). Similarly compensation and saturating I were lower in plantlets than in seedlings. The shape of transpiration curves as well as the expressive linear phases of P_N(ca) and P_N(I) curves of plantlet leaves indicated ineffective stomatal control of gas exchance. These results were confirmed by microscopic observations of stomatal movementsin situ     

Padé-Laplace method for analysis of fluorescence intensity decay.

This novel approach to the analysis of multiexponential functions is based on the combined use of the Laplace transform and Padé approximants (Yeramian, E., and P. Claverie. 1987. Nature (Lond.). 326:169-174). It is similar in principle to the well-known Isenberg method of moments (Isenberg, I. 1983. Biophys. J. 43:141-148) traditionally applied to the analysis of fluorescence decay. The advantage of the Padé-Laplace method lies in its ability to detect the number of components in a multiexponential function as well as their parameters. In this paper we modified the original method so that it can be applied to the analysis of multifrequency phase/modulation measurements of fluorescence decay. The method was tested first on simulated data. It afforded recovery up to four distinct lifetime components (and their fractional contributions). In the case of simulated data corresponding to continuous lifetime distributions (nonexponential decay), the results of the analysis by the Padé-Laplace method indicated the absence of discrete exponential components. The method was also applied to real phase/modulation data gathered on known fluorophores and their mixtures and on tryptophan fluorescence in phospholipase A2. The lifetime and fraction recoveries were consistent with those obtained from standard methods involving nonlinear least-square fitting.     

The distribution of microtubules in differentiating cells of Micrasterias denticulata bréb.

Summary As an extension of earlier cytophysiological and morphological studies on differentiating cells of Micrasterias denticulata, a fine structural investigation of glutaraldehyde-osmium tetroxide fixed material has been made. Special emphasis has been placed on the distribution of cytoplasmic microtubules and on their possible role in the processes of growth and differentiation. Four distinct systems of microtubules were found: (a) a band in the cortical protoplasm of the isthmus region which surrounds the nucleus; (b) several bands in the cortical protoplasm of the old half cells, with rod-like cross bridges between individual microtubules and between the microtubules and the plasmalemma; (c) clusters of microtubules near the posttelophase nucleus, some separated by intertubular structures possibly fibrils; and (d) microtubules in the internal and cortical protoplasm of differentiating half cells.This work was supported by a National Science Foundation Senior Foreign Scientist Fellowship to Dr. Oswald Kiermayer,and by funds of Training Grant 5-T1-GM-707-06 to Dr. Keith R. Porter.     

Epidémie de dysentérie bacillaire.

An outbreak of bacillary dysentery in 1978 affecting 928 persons, most of whom were living in the village of St-Jacques, PQ, is described. An epidemiologic study suggested the water supply as the source of the infection, and it was established that the water carried by the municipal aqueduct was contaminated by feces containing the causal agent, Shigella sonnei. This epidemic, the largest mentioned in he Canadian medical literature, demonstrates how contagious this infection is.     

On the origin and characteristics of noise-induced Lévy walks of E. coli

Lévy walks as a random search strategy have recently attracted a lot of attention, and have been described in many animal species. However, very little is known about one of the most important issues, namely how Lévy walks are generated by biological organisms. We study a model of the chemotaxis signaling pathway of E. coli, and demonstrate that stochastic fluctuations and the specific design of the signaling pathway in concert enable the generation of Lévy walks. We show that Lévy walks result from the superposition of an ensemble of exponential distributions, which occurs due to the shifts in the internal enzyme concentrations following the stochastic fluctuations. With our approach we derive the power-law analytically from a model of the chemotaxis signaling pathway, and obtain a power-law exponent μ ≈ 2.2, which coincides with experimental results. This work provides a means to confirm Lévy walks as natural phenomenon by providing understanding on the process through which they emerge. Furthermore, our results give novel insights into the design aspects of biological systems that are capable of translating additive noise on the microscopic scale into beneficial macroscopic behavior.     

Fluorescence studies of ATP-diphosphohydrolase from Solanum tuberosum var. Desirée

Chemical modification of potato apyrase suggests that tryptophan residues are close to the nucleotide binding site. Kd values (+/- Ca2+) for the complexes of apyrase with the non-hydrolysable phosphonate adenine nucleotide analogues, adenosine 5'-(beta,gamma-methylene) triphosphate and adenosine 5'-(alpha,beta-methylene) diphosphate, were obtained from quenching of the intrinsic enzyme fluorescence. Other fluorescent nucleotide analogues (2'(3')-O-(2,4,6-trinitrophenyl) adenosine 5'-triphosphate, 2'(3')-O-(2,4,6-trinitrophenyl) adenosine 5'-diphosphate. 1,N6-ethenoadenosine triphosphate and 1,N6-ethenoadenosine diphosphate) were hydrolysed by apyrase in the presence of Ca2+, indicating binding to the active site. The dissociation constants for the binding of these analogues were calculated from both the decrease of the protein (tryptophan) fluorescence and enhancement of the nucleotide fluorescence. Using the sensitised acceptor (nucleotide analogue) fluorescence method, energy transfer was observed between enzyme tryptophans and ethene-derivatives. These results support the view that tryptophan residues are present in the nucleotide-binding region of the protein, appropriately oriented to allow the energy transfer process to occur.     

Prévalence d'Aeromonas spp. dans les gastro-entérites de l'enfant.

A selective medium and biochemical tests were used to search for Aeromonas spp. in the stools of 536 children, more than 90% of whom had "gastroenteritis", seen at Sainte-Justine Hospital, Montreal, in June or July 1986. The organism was found in seven children, six of whom had bloody diarrhea. One of the six, a 6 1/2-year-old boy, required intravenous alimentation and later manifested ulcerative colitis; the other five recovered. The remaining child, a 14-year-old boy, had synovitis of the knee and spondylarthritis. Two of the seven carried other enteric pathogens. The authors discuss the pathogenicity of Aeromonas spp., which is not very marked in temperate climates, in human summer diarrhea and its possible role in the development of ulcerative colitis.     

Instability of anthocyanin accumulation inVitis vinifera L. var. Gamay Fréaux suspension cultures

The inherent instability of metabolite production in plant cell culture-based bioprocessing is a major problem hindering its commercialization. To understand the extent and causes of this instability, this study was aimed at understanding the variability of anthocyanin accumulation during long-term subcultures, as well as within subculture batches, inVitis vinifera cell cultures. Therefore, four cell line suspensions ofVitis vinifera L. var. Gamay Fréaux, A, B, C and D, originated from the same callus by cell-aggregate cloning, were established with starting anthocyanin contents of 2.73±0.15, 1.45±0.04, 0.77±0.024 and 0.27±0.04 CV (Color Value)/g-FCW (fresh cell weight), respectively. During weekly subculturing of 33 batches over 8 months, the anthocyanin biosynthetic capacity was gradually lost at various rates, for all four cell lines, regardless of the significant difference in the starting anthocyanin content. Contrary to this general trend, a significant fluctuation in the anthocyanin content was observed, but with an irregular cyclic pattern. The variabilities in the anthocyanin content between the subcultures for the 33 batches, as represented by the variation coefficient (VC), were 58, 57, 54, and 84% forV. vinifera cell lines A, B, C and D, respectively. Within one subculture, the VCs from 12 replicate flasks for each of 12 independent subcultures were averaged, and found to be 9.7%, ranging from 4 to 17%. High- and low-producing cell lines, VV05 and VV06, with 1.8-fold differences in their basal anthocyanin contents, exhibited different inducibilities tol-phenylalanine feeding, methyl jasmonate and light irradiation. The low-producing cell line showed greater potential in enhanced the anthocyanin production.     

Epididymite,M. S. T. et Fertilité

Before the antibiotic’s era, the clinicians have shown the relation between epididymitis and Infertility. At the moment, venerial diseases are the principal cause of Epididymitis by the young man. The early diagnosis of the urethral infection (acute or not) associated with a suitable antibiotherapy will allow to protect the fertility.     

Hypoglycémie spontanée et insuffisance rénale chronique.

Although glucose intolerance occurs as a consequence of chronic renal failure, improvement of a diabetic state by deterioration of renal function is a well known phenomenon. Recently occasional cases of spontaneous hypoglycemia in patients with chronic renal failure have been reported; two such cases and the results of metabolic studies are described in this paper. Pituitary, thyroid and adrenal function appeared to be normal. The results of an oral glucose tolerance test were normal; an appropriate insulin response was demonstrated in one patient, and a slightly elevated basal insulin value with a delayed insulin response to oral administration of glucose was demonstrated in the other. An insulin tolerance test did not support the hypothesis of increased insulin sensitivity as a factor, and the growth hormone response to hypoglycemia was normal. An intravenous glucagon test caused a subnormal increase in plasma glucose concentration, and the intravenous administration of tolbutamide produced hypoglycemia without an increase insulin sensitivity as a factor, and the growth hormone response to hypoglycemia was normal. An intravenous glucagon test caused a subnormal increase in plasma glucose concnetration, and the intravenous administration of tolbutamide produced hypoglycemia without an increase in insulin values. The plasma alanine concentration was low and the proinsulin/insulin ratio was increased. The origin of this hypoglycemia is not clear but is probably multifactorial. However, low hepatic glycogen stores and inadequate gluconeogenesis due to substrate deficiency seem to be involved.     

L'éléphantiasis péno-scrotal. A propos d'un cas

Massive scrotal lymphoedema with gross genital deformation is called penoscrotal elephantiasis. It is a rare syndrome outside of filariasis endemic regions. It is usually idiopathic and rarely congenital or secondary. It is both physically disabling and emotionally distressing for the patient. Surgical treatment is often necessary. The authors report a case of a patient with penoscrotal elephantiasis in whom no aetiology could be found. Complete surgical resection of the diseased tissue and scrotum and penile reconstruction were performed with good cosmetic and functional results.