Cell adhesion molecule in the hexactinellid Aphrocallistes vastus

Abstract. The Hexactinellida sponge Aphrocallistes vastus contains a soluble aggregation factor (AF) whose purification has been described in this communication. It is characterized by a S°_20.w value of 37 and a buoyant density of 1.45 g/cm³. The AF is a glycoporteinaceous particle composed of three major protein species; no core structure could be visualized. In the presence of Ca²⁺, the AF causes secondary aggregation of single cells. The aggregation process is temperature, pH, and ionic strength independent within a broad range. Evidence is presented indicating that two (or more) AF molecules are required for the establishment of a stable cell: cell interaction. In contrast to the AFs from demosponges, the hexactinellid AF functions species-unspecifically.     

Dsi-1, a region with frequent proviral insertions in Moloney murine leukemia virus-induced rat thymomas.

Dsi-1 is a region of chromosomal DNA that underwent proviral insertion in 3 of 24 Moloney murine leukemia virus-induced rat thymomas. In one of these tumors, a provirus is also integrated adjacent to the proto-oncogene c-myc. The proviruses in Dsi-1 have been characterized and appear to be complete. The proviruses were located within a 2-kilobase region that contained four prominent DNase I-hypersensitive sites. These hypersensitive sites were observed in Moloney murine leukemia virus-induced thymomas but not in NRK cells. The region of Dsi-1 immediately 3' to the insertions cross-hybridized with human and chicken DNA, indicating that it contains highly conserved sequences. No evidence could be found for the expression of this highly conserved region. Dsi-1 was mapped to mouse chromosome 4. This location demonstrates that Dsi-1 is different from 16 of the known proto-oncogenes (c-abl, c-erbA c-erbB, c-ets-1, c-ets-2, c-fes, c-fos, c-myb, c-myc, c-raf, A-raf, c-Ha-ras, c-Ki-ras, N-ras, c-sis, and c-src) and 12 cellular regions of tumor-associated integrations in retrovirus-induced tumors (c-erbB, Fis-1, int-1, int-2, Mis-1/pvt-1, Mlvi-1, Mlvi-2, c-mos, c-myb, c-myc, Pim-1, and c-Ha-ras). Hybridization experiments indicated that Dsi-1 is probably different from five additional proto-oncogenes (c-fgr, c-fms, c-mos, neu, and c-yes) and from two additional frequent integration regions (lck and Mlvi-3).     

Characterization of microcarrier cultures of neurons and astrocytes from cerebral cortex and cerebellum

In the present investigation a method is described for culturing cerebellar granule cells (glutamatergic neurons), cerebral cortical neurons (GABAergic neurons) and cortical astrocytes on Cytodex 3 microcarriers. It was possible to obtain a high yield of attached neurons and astrocytes on the microcarriers and the cell specific characteristics such as the ability to release neurotransmitter (neurons) and a high activity of glutamine synthetase (astrocytes) were preserved. This system, allowing mixtures of neurons and astrocytes at any given ratio to be produced, may constitute an attractive model system by which the interaction between neurons and astrocytes with regard to exchange of neurotransmitter precursors as well as other compounds may be studied.     

Plasma volume changes in middle-aged male and female subjects during marathon running

Circulatory fluid shifts were studied in middle-aged runners (6 males and 5 females, ages 32-58 yr) during a 42.2-km marathon race run in mild weather (dry-bulb temperature = 17.5-20.4 degrees C). Running times for the subjects were 3:12-4:40 (mean values were 3:34 for males and 4:10 for females). Venous blood samples were taken without stasis in all subjects seated at rest before the start of the race and within 3 min of finishing; eight of the subjects also paused for samples at 6 and 27 km during the race. At 6 km, body weight loss averaged less than 1%, whereas plasma volume (PV) had decreased by 6.5% in male subjects and 8.6% in female subjects. By the end of the race, hypohydration had reached 3.2% in male subjects and 2.9% in female subjects, but PV in both groups remained stable. Sweat rates during the race averaged 545 and 429 g X m-2 X h-1 for male and female subjects, respectively, with ad lib. water intake replacing 21-72% of fluid loss. Increases in plasma protein concentration throughout the race reflected the observed initial decrease in PV. The interpretation of PV responses to exercise and/or hypohydration is critically dependent on selection of base-line conditions; we were able to control for posture-exercise effects by treating the early exercise (6 km) sample as the base line for examining the effects of later fluid loss. Under these conditions, the vascular compartment resisted volume depletion. The ability to maintain stable PV can be explained in part by relationships among oncotic and hydrostatic pressures in the intra- and extravascular fluid compartments.     

Shoot regeneration of mesophyll protoplasts transformed by Agrobacterium tumefaciens,not achievable with untransformed protoplasts

Summary Alternative methods for shoot regeneration in protoplast derived cultures were developed in Nicotiana paniculata and Physalis minima. In both species protoplast derived callus is not regeneratable to shoots by conventional methods, e.g. hormone treatment. Leaf discs and stem segments of N. paniculata and P. minima were incubated with Agrobacterium tumefaciens shooter strains harbouring pGV 2215 or pGV 2298 or wildtype strain B6S3. After 36 h of co-incubation protoplasts were prepared. (Leaf disc and stem segment cloning). Co-cultivation experiments were also undertaken with protoplasts of both species. Transformed clones, characterized by their hormone independent growth and octopine production, could be isolated after about two months. Transformation frequencies of leaf disc and stem segment cloning and co-cultivation experiments varied from 5×10^–3 to 5×10^–5. After about one year of cultivation on hormone-free culture medium, shoots could be recovered from colonies of N. paniculata, transformed by the strain harbouring pGV 2298. In protoplast derived colonies of P. minima, shoot induction was obtained only after transformation by bacteria carrying pGV 2215. This demonstrates the importance of the particular shooter mutant, as well as the response of the host plant. Transformed shoots of P. minima produced octopine, whereas octopine production in transformed shoots and callus of N. paniculata was undetectable after one year of cultivation, though T-DNA was still present in the plant genome. Transformed shoots of N. paniculata and P. minima do not produce any roots. Shoots of N. paniculata have an especially tumerous phenotype. Shoots of both species were successfully grafted to normal donor plants of N. tabacum.Abbreviations B5-h Gamborg medium without hormones (Gamborg 1968) - V47 protoplast medium (Binding 1974) - D2a protoplast medium (Li et al. 1980) - MS-h Murashige and Skoog medium without hormones (Murashige and Skoog 1962) Dedicated to Professor Dr. G. Melchers in occasion of his 80th birthday     

Diurnal variations in abscisic acid content and stomatal response to applied abscisic acid in leaves of irrigated and non-irrigated Arbutus unedo plants under naturally fluctuating environmental conditions

Summary Endogenous abscisic acid content (ABA) of Arbutus unedo leaves growing under natural conditions in a macchia near Sobreda, Portugal, was very high (0.25 to 2.3 g g¹ fresh weight). Highest concentrations were found during the very early morning hours and at midday. During the late morning hours and in the late afternoon ABA concentrations decreased to between one-third and one-fourth of peak values. The samples for ABA content were obtained from both irrigated ( between-10 and-25 bar) and non-irrigated plants experiencing natural water stress during the dry season ( of-50 bar). During the course of the measurement day, stomatal conductance was relatively constant and conductance of watered plants was 50 to 100% greater than that of unwatered plants. No clear correlations between ABA content and stomatal conductance and/or xylem water potential were observed. Despite large differences in water potential and differences in degree of stomatal opening, absolute concentrations of ABA were not found to differ.Small quantities (8–14 pmoles cm² leaf area) of ABA were applied to leaves of irrigated and non-irrigated Arbutus unedo plants by injection into the petiole. These extremely small ABA doses resulted in transient reductions in stomatal conductance. The effectiveness with which injected ABA closed stomata was highest during the morning and decreased substantially at midday. Increased sensitivity to injected ABA may again occur in the late afternoon but recent measurements suggest that this may depend on long-term drought experience of the plants. The characteristics of the response to injected ABA were similar in irrigated and non-irrigated plants although irrigated plants responded in general more strongly.