In vitro synthesis and stability of RNA in isolated nuclei from bovine lymphocytes

Nuclei from Concanavalin A-stimulated lymphocytes (30 hr after Con A addition) incorporate up to 5 times more (3-H)UTP into RNA than nuclei from resting lymphocytes. The incorporation kinetics is linear for almost 60 min. 14–20% of the $\text{in vitro}$ labeled RNA is polyadenylated. Poly(A) (?)RNA from both types of nuclei sediments from 4–5S up to more than 30S on sucrose gradients. Nuclei from stimulated cells synthesize about double the amount of RNA larger than 18S than nuclei from resting cells. The same holds for poly(A) (+)RNA. Poly(A) (?) RNA labeled during 10 min in both types of nuclei is stable during a 30 min chase. Under the same conditions poly(A) (+)RNA in nuclei from resting cells is degraded to about 50% during the chase whereas it is stable in nuclei from stimulated cells.     

Immunochemical and biochemical investigation of hexosaminidase S.

Hexosaminidase S (HEX S), the residual isozyme found in tissues and body fluids of children with the O variant of GM2 gangliosidosis, was purified from tissues of variant individuals and biochemically and immunochemically characterized. This enzyme has an apparent molecular weight of 103,000 with an isoelectric point of 4.2, is heat labile to the same extent as HEX A, and loses most of its activity following heating for 30 min at 50 degrees C. HEX S reacts immunologically with the antisera against either HEX A or B, but the reaction is considerably stronger with the anti-A serum or with antibody preparations which react exclusively with the A isozyme. Results obtained by a radioimmunoassay using the various antisera indicated that there is no antigenically cross reacting material which lacks enzymatic activity in the variant tissues. These findings are in accord with a suggested molecular structure of two subunits, each composed of two alpha chains (alpha2 alpha2) for HEX S; it also implies that alpha and beta chains have some structural similarity which is manifested in antigenic cross-reactivity.     

Hormone-dependent terminal differentiation in vitro of chicken erythroleukemia cells transformed by ts mutants of avian erythroblastosis virus

Chicken erythroblast cell strains and a cell line transformed by ts mutants of avian erythroblastosis virus (AEV) terminally differentiate when shifted to the nonpermissive temperature (42°C). The differentiated cells resemble mature erythrocytes with respect to morphology and ultrastructure, expression of differentiation-specific cell-surface antigens, pattern of protein synthesis and hemoglobin content. Terminal differentiation is dependent on conditions favoring the differentiation of normal erythroid progenitor cells, including an erythropoietin-like factor. Colonies of ts AEV cells grown at 42°C in semisolid medium resemble erythrocyte colonies derived from normal erythroid progenitor cells. The colonies obtained were comparable in size or slightly larger than the late erythroid precursor (CFU-E) colonies. These results suggest that AEV-transformed cells are blocked at a stage of differentiation that is more advanced than that of the uninfected target cells. ts AEV cells are irreversibly committed to terminal differentiation within 20 to 30 hr after shift to 42°C.     

Anti-microtubular herbicides and fungicides affect Ca2+ transport in plant mitochondria

The herbicides amiprophosmethyl (APM) trifluralin, and oryzalin as well as the fungicides methylbenzimidazolyl carbamate (MBC), O-isopropyl N-phenyl carbamate (IPC), and chlorisopropyl N-phenyl carbamate (CIPC), which are known to cause the destruction of microtubules in vivo but do not interfere with tubulin polymerization in vitro, have been examined with respect to their ability to affect Ca²⁺ transport in isolated cell organelles. In contrast to colchicine which has no effect on Ca²⁺ transport in isolated mitochondrial and microsomal fractions, all of the substances investigated caused considerable reduction of ca²⁺ net uptake into mitochondrial but not into microsomal fractions. This reduction has been shown to be due to an increase in passive Ca²⁺ efflux. These results have been extrapolated to in vivo situations where they are postulated to act by raising cytoplasmic Ca²⁺ levels.Abbreviations APM amiprophosmethyl - CIPC chlorisopropyl N-phenyl carbamate - IPC O-isopropyl N-phenyl carbamate - MBC methylbenzimidazolyl carbamate - Mops 3-(N-Morpholino) propanesulfonic acid - DMSO dimethylsulfoxide     

Specificity of the spermidine requirement for the replication of phi X174 DNA be cell-free extracts of Escherichia coli

A new experimental approach for assessing the biological significance of spermidine interactions in isolated systems is applied to the stimulation by spermidine of the conversion of phi X174 virion DNA to its replicative form by cell-free extracts of Escherichia coli. At 2.5 mM Mg2+, spermidine activated the reaction 20-fold. Varying the spermidine concentration affected both the rate and extent of this DNA synthetic reaction without altering the nature of the reaction products. We evaluated the biological significance of the spermidine requirement by measuring reaction rates in the presence of a homologous series of spermidine analogs of known activity in vivo. There was a lack of specificity, in that all of these analogs were capable of efficiently substituting for spermidine in stimulating the reaction rate. The relevance of this in vitro spermidine stimulation to Escherichia coli chromosome replication in vivo is discussed in light of the results obtained with the spermidine analogs.     

Intercellular junctions in the uterine epithelium of Salamandra salamandra (L.) (Amphibia,Urodela)

Summary Intercellular junctions in the uterine epithelium of the ovoviviparous urodele Salamandra salamandra were studied in pregnant and non-pregnant females by freeze-fracture technique. Junctional complexes consist of zonulae occludentes (tight junctions) and numerous maculae adhaerentes (desmosomes); z. adhaerentes and nexuses (gap junctions) could not be identified. Tight junctions are of the flexible type exhibiting loosely interconnected fibrils. The fibrillary network appears stretched more often in pregnant females possibly due to the mechanical stress of pregnancy. The structure and occurrence of the junctions identified, especially that of the tight junctions, is discussed with regard to the functions of the uterus during pregnancy.Zusammenfassung Mit Hilfe der Gefrierbruchtechnik wurden im Uterus-epithel trächtiger und nichtträchtiger Feuersalamanderweibchen (Salamandra salamandra) Zonulae occludentes und Maculae adhaerentes, jedoch keine Z. adhaerentes sowie Nexus identifiziert. Die Z. occludentes sind flexibel. Ihr fibrilläres Netzwerk ist bei trächtigen Weibchen öfter gestreckt; das ist möglicherweise auf die stärkere Ausdehnung des Uterusgewebes während der Trächtigkeit zurückzuführen. Das Vorkommen der verschiedenen Kontakt-strukturen, namentlich das der Z. occludentes, wird im Hinblick auf die Funktionen des Uterus während der Trächtigkeit diskutiert.We are indebted to Mrs. K. Ott for excellent technical assistance and to Miss Dr. U. Beigel for linguistic help     

Asymptotic oscillations in the tracking behaviour of the fly Musca domestica

From recent theoretical work (Poggio and Reichardt, 1981), high frequency oscillations are expected in the angular trajectory of houseflies tracking a moving target if the target's retinal position controls the flight torque by means of a stronger optomotor response to progressive than to regressive motion. Experiments designed to test this conjecture have shown that (a) asymptotic non-decaying oscillations are found in the torque of female houseflies tracking targets moving at constant angular velocity; (b) the magnitude of the oscillations grows monotonically with mean retinal excentricity of the target; (c) the period of the oscillation is around 180–200 ms. The experimental findings are consistent with the hypothesis that a progressive-regressive mechanism plays a significant role in the tracking behaviour of female houseflies. From this phenomenological point of view a flicker mechanism that is active only for nonzero motion is equivalent to a progressive-regressive system. The relatively long period of the oscillation requires more complex reaction dynamics than a pure single dead-time delay. As a specific example we show that a model where the reaction to progressive motion is sticky, holding for a longish time after the ending of the stimulus, is consistent with the experimental data.     

Determination of 2,4-diamino-5-benzylpyrimidines in combination with sulphadiazine in biological fluids using high-performance liquid chromatography

High-performance liquid chromatographic methods for the simultaneous analysis of tetroxoprim (TXP)/sulphadiazine (SDZ) and metioprim (MTP)/SDZ in serum and prostatic secretion (PS) are described. The detection limits in serum and PS were 50 ng TXP per ml and 100 ng SDZ per ml, and 40 ng MTP per ml and 100 ng SDZ per ml, respectively. The intra-assay coefficients of variation were in the range of 2.7–2.19%. Some preliminary data from a pharmacokinetic study in geriatric patients and a distribution study in dogs are presented. These methods enable the investigator to process a large number of TXP/SDZ and MTP/SDZ samples in one working day.     

On head and body movements of flying flies

Head and body movements of flies (Musca domestica and Calliphora erythrocephala) have been studied during sustained flight. Two main points emerge from the analysis: a) Changes in body direction and head direction occur simultaneously in almost all cases. b) During visually guided flight active neck movements are initiated together and in the same direction of body movements. This does not hold in absence of a visual pattern (search). Implications of these findings with respect to the organization of the control system underlying head-body coordination in flies are briefly discussed.     

Ecophysiological investigations on lichens of the Negev desert

Summary Previous publications have reported on investigations of CO₂ exchange in the desert lichenRamalina maciformis both in its natural habitat in the Negev and in the laboratory. Utilizing laboratory data, net photosynthesis and dark respiration were expressed as mathematical functions of the most important environmental factors. Based on these relationships, a model is developed that allows one to predict CO₂ exchange of the plant. Input data are light intensity, temperature, and water content of the thallus, together with a measure of the rate of the seasonal change of photosynthetic and respiratory activity. The validity of the model is tested by comparing simulated daily courses of CO₂ uptake and release of the lichen with independent results of CO₂ exchange measurements conducted in the field during and after the condensation of dew. The sensitivity of the model is shown by simulating changes in the input data of temperature and water content of the lichen.This paper is dedicated to Dr. h.c. Oscar Klement on the occasion of his 80th birthday