Karyological variation in the group ofMyosotis alpestris (boraginacea)

A total of 6 population samples ofMyosotis stenophylla Knaf, a rare species showing great ecological disjunction in its distribution, were examined to clarify the present status of its karyological variation. In order to elucidate relationships between lowland tetraploid populations ofM. stenophylla and diploid and tetraploid montane populations ofM. alpestris F.W. Schmidt, four population samples ofM. alpestris were also examined. The karyotypes of all populations ofM. alpestris s.l. studied were highly asymmetrical and heterogeneous, being composed of metacentric, submetacentric, subtelocentric and satellited acrocentric chromosomes. The karyotype formula for haploid chromosome set was established: n=x=12=6m+2sm+3st+1t^SAT. Multivariate analysis based on chromosome length and shape showed significant differences between diploid and tetraploid forms ofM. alpestris s.l. Four numerical parameters, used to characterize the karyotype ofM. stenophylla, revealed significant differences between populations on serpentine and on non-serpentine substrates. In addition, the noticeable affinity of the karyotype of non-serpentine populations to that ofM. alpestris tetraploids has been shown by means of discriminant analysis. These data suggest that the unique features of serpentine play an important role in the origin of karyotypic differentiation within populations ofM. stenophylla.     

Temperature and dissolved oxygen concentration as parameters of Azotobacter chroococcum cultivation for use in biofertilizers

Summary Azotobacter chroococcum was grown in continuous culture at two temperatures (30 °C and 20 °C) and different dissolved oxygen tensions (DOT) (30 % to 40 % and 70 % to 80 % of air saturation), respectively. At the temperature of 30 °C and low DOT a relatively high volumetric productivity and efficiency of nitrogen fixation were obtained. After lowering the temperature to 20 °C, an intensive formation of cysts was observed associated with a drastic decrease of the bacterial growth. Bacteria in the form of cysts kept their physiological activity for a long period of time depending on temperature and preparation.     

Drug resistance inYarrowia lipolytica

Six strains ofYarrowia lipolytica tested here were resistant to 10–20 g erythromycin or chloramphenicol per L glycerol-agar medium. Cells tolerating 4 g chloramphenicol per L were very rare and reverted rapidly to the highest resistance. In analogy with Ery^R mutants ofKluyveromyces lactis, our strains did not grow at 36°C but did not lose their viability at that temperature. Two levels of resistance were found with oligomycin and antimycin A,i.e. 10 and 3 mg/L in the former and 10 and 2 mg/L in the latter. The higher resistance levels segregated mitotically and were, therefore, controlled extrachromosomally. The lower resistance levels showed very frequent changes from sensitivity to resistance that prevented the genetic analysis of this resistance. An almost continuous range of tolerance to <5–400 μg mucidin per L was found in populations of the strains analyzed. Newly formed Muc^R cells were established only in the presence of the antibiotic. Pure cultures of Muc^R cells showed an extremely high instability caused by their lower viability and very low growth rate in the absence of mucidin. No loss of resistance to antimycin A was found, although Ant^R cells revealed similar negative selection. Mutability Muc^S»Muc^R and Muc^R»Muc^S was higher in Ant^R cells than in Ant^S ones.     

Transcapillary escape rate of albumin in humans during exercise-induced hypervolemia

Haskell, Andrew, Ethan R. Nadel, Nina S. Stachenfeld, KeiNagashima, and Gary W. Mack. Transcapillary escape rate of albuminin humans during exercise-induced hypervolemia. J. Appl. Physiol. 83(2): 407-413, 1997.To test thehypotheses that plasma volume (PV) expansion 24 h after intenseexercise is associated with reduced transcapillary escape rate ofalbumin (TER_alb) and that localchanges in transcapillary forces in the previously active tissues favorretention of protein in the vascular space, we measured PV,TER_alb, plasma colloid osmoticpressure (COP_p), interstitialfluid hydrostatic pressure (Pi), and colloid osmotic pressure in legmuscle and skin and capillary filtration coefficient (CFC) in the armand leg in seven men and women before and 24 h after intense uprightcycle ergometer exercise. Exercise expanded PV by 6.4% at 24 h (43.9 ± 0.8 to 46.8 ± 1.2 ml/kg, P < 0.05) and decreased total protein concentration (6.5 ± 0.1 to6.3 ± 0.1 g/dl, P < 0.05) andCOP_p (26.1 ± 0.8 to 24.3 ± 0.9 mmHg, P < 0.05), although plasmaalbumin concentration was unchanged. TER_alb tended to decline (8.4 ± 0.5 to 6.5 ± 0.7%/h, P = 0.11) and was correlated with the increase in PV(r = 0.69,P < 0.05). CFC increased in the leg(3.2 ± 0.2 to 4.3 ± 0.5 µl · 100 g¹ · min¹ · mmHg¹,P < 0.05), and Pi showed a trend toincrease in the leg muscle (2.8 ± 0.7 to 3.8 ± 0.3 mmHg, P = 0.08). These datademonstrate that TER_alb isassociated with PV regulation and that local transcapillary forcesin the leg muscle may favor retention of albumin in the vascular spaceafter exercise.

     

Mutations in the SLC3A1 Transporter Gene in Cystinuria

Cystinuria is an autosomal recessive disease characterized by the development of kidney stones. Guided by the identification of the SLC3A1 amino acid–transport gene on chromosome 2, we recently established genetic linkage of cystinuria to chromosome 2p in 17 families, without evidence for locus heterogeneity. Other authors have independently identified missense mutations in SLC3A1 in cystinuria patients. In this report we describe four additional cystinuria-associated mutations in this gene: a frameshift, a deletion, a transversion inducing a critical amino acid change, and a nonsense mutation. The latter stop codon was found in all of eight Ashkenazi Jewish carrier chromosomes examined. This report brings the number of disease-associated mutations in this gene to 10. We also assess the frequency of these mutations in our 17 cystinuria families.     

Apoptosis and nutrition: Involvement of amino acid transport system in repression of hybridoma cell death

Mouse hybridoma cells cultured on the verge of starvation-induced apoptosis, i.e. in a medium diluted with saline, proved to serve as a sensitive screening system for apoptosis-suppressing activity of nutrient medium components. Conventional amino acid mixtures were found to suppress the starvation-induced apoptosis, whereas a vitamin mixture was ineffective. (Frank F (1995) Biotechnol. Bioeng. 45: 86–90). Recent experiments showed that suppression of apoptosis, and concurrent resumption of growth, could be achieved by addition of single substances at millimolar concentrations. The set of active substances included certain coded L-amino acids (glycine, alanine, serine, threonine, proline, asparagine, glutamine, histidine), non-coded amino acids (-alanine, taurine, 4-aminobutyric acid), and a non-metabolizable analogue (2-aminoisobutyric acid). This finding shows that some amino acids do not act solely as nutrients, but also as specific signal molecules. The specificity of the effect points to the involvement of adaptively regulated amino acid transport systems A and N in maintaining the balance between triggering and suppression of starvation-induced apoptosis.     

Effect of growth supplements and whey pretreatment on butyric acid production by Clostridium butyricum

Improved production of butyrate (up to 19 g/l) from whey by Clostridium butyricum was achieved by adding either yeast extract (5 g/l) or biotin (50 g/l). Hydrolysed lactose and proteolysed whey were less effective even with added biotin.The authors are with the Department of Biochemical Technology, Faculty of Chemical Technology, Slovak Technical University, Radlinského 9, Bratislava 812 37, Slovakia     

Increased α1 receptor density in brown adipose tissue of cafeteria-fed rats

A possible general corollary between ₁-receptor density in brown adipose tissue and the degree of activation of the tissue was investigated. For this purpose, the effect of cafeteria feeding on ₁-adrenergic receptors in brown adipose tissue of seven-week-old female rats was studied by the use of the ₁-antagonist (³H)prazosin. In cafeteria-fed rats, the K_D of the ₁-receptor for (³H)prazosin was unchanged (about 0.35 nM), but the receptor density was doubled (up to 40 fmol per mg of membrane protein). This was also observed when the results were expressed per unit of a plasma-membrane marker (5-nucleotidase). It was concluded that an increased ₁-receptor density is seen not only in cold-acclimated rats, but also in other conditions where brown fat is activated, and a possible general physiological significance of ₁-adrenergic pathways in brown adipose tissue is discussed.     

The biology ofChlamydomyxa montana: Ultrastructure of the cyst

Summary Cells ofChlamydomyxa montana Lankester photosynthesize within a cyst under bright light and ingest diatoms in an excysted amoeboid form during periods of low light intensity. Cyst cell walls are partially comprised of cellulose and vary in thickness. The cells are multinucleate and intracellular bacteria are closely associated with the nuclei. A pair of centrioles is also present adjacent to individual nuclei. Chloroplasts are numerous and thylakoids are generally organized into bands of three. No endoplasmic reticulum was found surrounding the plastids, nor was a complete girdling lamella ever observed within.C. montana chloroplasts appear to be its own but this protist does not precisely fit into an algal class.