Preparation of raf-oncogene-specific antiserum with raf protein produced in E. coli

In this report we describe the expression of v-raf protein in E. coli using a tryptophan-promoter-driven expression vector and its immunological characterization by anti-peptide sera. The purified recombinant protein was used to produce raf-specific antibodies which are suitable for studying v-raf and c-raf proteins in vitro and in vivo in a variety of species ranging from mouse to man.     

The Evolution of Restricted Recombination and the Accumulation of Repeated DNA Sequences

We suggest hypotheses to account for two major features of chromosomal organization in higher eukaryotes. The first of these is the general restriction of crossing over in the neighborhood of centromeres and telomeres. We propose that this is a consequence of selection for reduced rates of unequal exchange between repeated DNA sequences for which the copy number is subject to stabilizing selection: microtubule binding sites, in the case of centromeres, and the short repeated sequences needed for terminal replication of a linear DNA molecule, in the case of telomeres. An association between proximal crossing over and nondisjunction would also favor the restriction of crossing over near the centromere. The second feature is the association between highly repeated DNA sequences of no obvious functional significance and regions of restricted crossing over. We show that highly repeated sequences are likely to persist longest (over evolutionary time) when crossing over is infrequent. This is because unequal exchange among repeated sequences generates single copy sequences, and a population that becomes fixed for a single copy sequence by drift remains in this state indefinitely (in the absence of gene amplification processes). Increased rates of exchange thus speed up the process of stochastic loss of repeated sequences.     

Identification of the major endogenous leukotriene metabolite in the bile of rats as N-acetyl leukotrience E4

Mercapturic acid formation, an established pathway in the detoxication of xenobiotics, is demonstrated for cysteinyl leukotrienes generated in rats after endotoxin treatment. The mercapturate N-acetyl-leukotriene E₄ (N-acetyl-LTE₄) represented a major metabolite eliminated into bile after injection of [³H]LTC₄ as shown by cochromatography with synthetic N-acetyl-LTE₄ in four different HPLC solvent systems. The identity of endogenoud N-acetyl-LTE₄ elicited by endotoxin was additionally verified by enzymatic deacetylation followed by chemical N-acetylation. The deacetylation was catalyzed by penicillin amidase. Endogenous cysteinyl leukotrienes were quantified by radioimmunoassay after HPLC separation. A N-acetyl-LTE₄ concentration of 80 nmol/l was determined in bile collected between 30 and 60 min after endotoxin injection. Under this condition, other cysteinyl leukotrienes detected in bile by radioimmunoassay amounted to less than 5% of N-acetyl-LTE₄. The mercapturic acid pathway, leading from the glutathione conjugate LTC₄ to N-acetyl-LTE₄, thus plays an important role in the deactivation and elimination of these potent endogenous mediators.     

Communication and control in reproduction: the ubiquity of periodic phenomena

Two statements will be presented and defended in this paper. First, it is claimed that oscillations are common in all biological systems. From the subcellular to the organismic levels of organization, oscillations are the normal operational mode for many biochemical and physiological control networks. Second, it will be demonstrated that periodic control offers several functional advantages over steady-state control.     

Volume comparisons in the cerebellar complex of primates. II. Cerebellar nuclei

Volumes of medial, interposed, and lateral cerebellar nuclei (MCN, ICN, and LCN) were measured in Insectivora, Scandentia, and Primates, including man. The relative size of the nuclei was expressed in size indices. Insectivora had by far the smallest cerebellar nuclei. The simians, in general, had larger cerebellar nuclei than the prosimians, but there was considerable overlap. From Insectivora to man, the MCN was the least progressive and the LCN the most progressive. The indices are expected to reflect the relative size of the three longitudinal zones of the cerebellum (vermis/MCN, pars intermedius/ICN, hemisphere/LCN). They, together with those of the ventral pons and cerebellum (part I), are discussed in relation to the predominant locomotor pattern of a species, and with reference to evolutionary trends in primate phylogeny.     

Determination of the hydraulic conductivity of Lamprothamnium by use of the pressure clamp

By use of the pressure-clamp technique, the hydraulic conductivity of the brackish-water alga Lamprothamnium was found to be 5·10^-6 cm s^-1 bar^-1. The dimensions of the internodes are so small that it is possible, for the first time, to measure a complete volume relaxation upon clamping the turgor pressure to a preset value by a feedback control of the pressure probe. As theoretically predicted, the values of the hydraulic conductivity obtained from the initial slope of the volume relaxation induced by the pressure clamp are in agreement (within experimental error) with those obtained from the half-time of the relaxation process. The cell volume also obtained from the analysis of the volume relaxation is the osmotically effective cell volume and is therefore slightly smaller than the value obtained by taking the dimensions of the cell including the cell wall.Abbreviations and symbols Lp hydraulic conductivity - P turgor pressure - S_v initial slope of volume relaxion - T_1/2 half-time of volume relaxation Dedicated to Professor Dr. H. Ziegler on the occasion of his 60th birthday     

The role of insulin, glucagon and growth hormone in the regulation of plasma glucose and free fatty acid levels in anorexia nervosa

It is well established that glucagon plays an important role in the regulation of fuel supplies as its plasma level increases during the first days of a complete fast. However, it is not certain that glucagon is involved in the adaptation to chronic starvation. In the present study, this problem was investigated by the determination of the changes in the plasma glucagon level elicited by an i.v. glucose tolerance test followed by an i.v. arginine perfusion in 26 self starved patients suffering from anorexia nervosa (AN) and 14 control patients having only minor neurotic disorders. The basal plasma glucagon level tended to be higher in the AN patients than in the controls; but the difference was not statistically significant. Glucagon responses to glucose and arginine observed in the AN patients were not significantly different from those seen in the control patients. In the AN patients, the insulin response to both loads was reduced and the plasma GH level increased paradoxically after the glucose load, whereas it rose normally after the arginine load. It may be concluded that in chronic starvation by AN the regulation of fuel supplies depends mainly on decreased insulin and increased growth hormone secretion. The role of glucagon seems to be of minor importance in this condition.     

Cellulose degradation and monitoring of viscosity decrease in cultures of Cellulomonas uda grown on printed newspaper

The rheological behavior of cultures of Cellulomonas uda with shredded printed newspaper as the carbon source was studied. The initial substrate concentrations ranged from 23 to 60 g/L. The changes in apparent viscosity were followed on-line by applying a commercially available process viscometer and discretely using a rotational viscometer with an anchor impeller. During the time of highest cellulose degradation, the broths exhibited a pseudoplastic behavior which could be explained satisfactorily by the power-law model. At the end of cultivation when cellulose degradation slowed down, the broths became Newtonian in behavior. Endo-1,4-beta-glucanase, 1,4-beta-xylanase, beta-glucosidase, and beta-xylosidase activities were also determined during cultivation as well as cellulose degradation and cell mass production. The beginning of endoglucanase formation and the start of the final viscosity decrease of the bacterial paper pulp suspensions could be correlated.     

Electrorotation of lymphocytes—The influence of membrane events and nucleus

Electrorotation—the spin of cells in rotating high frequency electric fields—has been used to investigate properties of human peripheral blood lymphocytes. The rotation spectra of lymphocytes deviate from those of single shell spheres. The deviations are caused by the electrical properties of the nucleus in the cell interior.Electrorotation allows the distinction between successfully stimulated lymphocytes and unstimulated cells after application of concanavalin A. Notwithstanding the fact that only a proportion of the cells will be mitogenically stimulated we detected an enhanced cell membrane conductivity for the whole cell population immediately after the addition of mitogen.