Differential expression of the c-myb proto-oncogene marks the pre-B cell/B cell junction in murine B lymphoid tumors

A series of murine B lymphoid tumor cell lines which are representative of the pre-B cell, immature and mature B cell, and plasma cell stages of B cell development have been examined for expression of c-myb proto-oncogene mRNA. The pre-B cell lymphoma cell lines express equivalent high steady state levels of c-myb mRNA. In contrast, the B cell lymphoma and plasmacytoma cell lines express steady state c-myb mRNA at levels which are 0.005 to 0.1 times that of the pre-B cell lymphoma lines. These results correlate high levels of c-myb mRNA expression with the pre-B cell stage of development. Subclones of the 1881 pre-B cell lymphoma which express K light chain and are surface IgM-positive as well as two types of hybrid B lymphoid cell lines have been used to demonstrate that surface immunoglobulin expression is not sufficient to result in the down-regulation of c-myb mRNA levels or changes in the expression N-myc mRNA, lambda 5 mRNA, or the BP-1 surface antigen which are markers of the pre-B cell stage of development. Thus, changes in the expression of genes which are independent of immunoglobulin expression are associated with transition from the pre-B cell to the immature B cell stage of development.     

Characterization of a meta-Fluorotyrosine-Tolerant Cell Culture of Eschscholtzia californica Cham

A cell line of Eschscholtzia californica selected for meta-fluorotyrosine (MFT) tolerance was found to have 10-fold increased levels of phenylalanine and tyrosine compared to the parent line, while most other amino acids were only increased 2-fold. Tracer experiments with shikimic acid in the presence of MFT showed that the biosynthesis of the aromatic amino acids was not impaired in the tolerant line. Feeding experiments with phenylalanine, tyrosine, or shikimic acid also revealed a reduced turnover of the pools of the aromatic amino acids in the variant. Thus undisturbed de novo biosynthesis of the aromatic amino acids and dilution of toxic effects of MFT by the enlarged pool sizes seemed to be the main reason for the acquired tolerance. Despite the enlarged availability of the precursor tyrosine, formation of the benzophenanthridine alkaloids was enhanced neither in the growth nor in the production medium.     

Autoradiographic localization of vasoactive intestinal polypeptide receptors in the rat mesenteric vascular tree

By the use of combined in vitro radioreceptor binding and autoradiographic techniques, we analyzed the pharmacological properties and the anatomical localization of the vasoactive intestinal polypeptide (VIP) receptor in rat superior mesenteric artery and in medium and small mesenteric artery branches. 125I-VIP was bound by sections of rat superior mesenteric artery in a manner consistent with the labeling of specific VIP receptors, with Kd and Bmax values of 0.23 nM and 0.71 pmol/mg protein respectively. Inhibition of 125I-VIP binding with VIP and related peptides gives the following rank order of potency: VIP greater than peptide histidine methionine greater than secretin. Light microscope autoradiography reveals specific VIP binding sites within the medial layer of superior mesenteric artery and its branches. Medium and small sized vessels are richer in 125I-VIP binding sites than the larger ones.     

Structure and activity of proteins from pathogenic fungi Phytophthora eliciting necrosis and acquired resistance in tobacco

The phytopathogenic fungi Phytophthora cryptogea and Phytophthora capsici cause systemic leaf necrosis on their non-host tobacco; in culture they release proteins, called cryptogein and capsicein, which elicit similar necrosis. In addition, both proteins protect tobacco against invasion by the pathogen Phytophthora nicotianac, the agent of the tobacco black shank, that is unable to produce such an elicitor. Cryptogein causes visible leaf necrosis starting at about 1 microgram/plant, whereas 50-fold as much capsicein is required for the same reaction. Capsicein induces protection even in near absence of leaf necrosis. The activities of both elicitors are eliminated upon pronase digestion. They are proteins of similar Mr (respectively 10,323 and 10,155) and their complete amino acid sequences were determined. They consist of 98 residues, with some internal repetitions of hexapeptides and heptapeptides. 85% identity was observed between both sequences: only two short terminal regions are heterologous, while the central core is entirely conserved. Secondary structure predictions, hydropathy and flexibility profiles differ only around position 15 and at the C-terminus; these modifications could play a role in the modulation of their biological activities. After a search of the sequence data bases, they appear to be novel proteins.     

Dehydroquinate synthase: the role of divalent metal cations and of nicotinamide adenine dinucleotide in catalysis

The cofactor requirements of dehydroquinate synthase from Escherichia coli have been characterized. The homogeneous enzyme, purified from the overproducing strain RB791 (pJB14), is a monomeric metalloenzyme of Mr = 39,000 that contains 1 mol of tightly bound Co(II) according to atomic absorption analysis. The holoenzyme rapidly loses activity upon incubation with EDTA, giving rise to a stable but catalytically inactive apoenzyme. Activity is fully restored by reconstitution with Co(II) and partially restored with other divalent cations. Reconstitution of the apoenzyme with Zn(II) (which is probably the functioning metal in vivo) restores activity to 53% of the level observed with the Co(II)-holoenzyme. The presence of the substrate 3-deoxy-D-arabino-heptulosonate 7-phosphate (1) blocks the inactivation by EDTA. Dehydroquinate synthase also binds 1 mol of NAD+, the presence of which is essential for catalytic activity. The rate constant for the dissociation of NAD+ from the Co(II)-holoenzyme was found to be 0.024 min-1. Under turnover conditions with saturating levels of substrate, the dissociation rate of NAD+ increases by a factor of 40, to 1 min-1. Under these conditions (pH 7.5, 20 degrees C), the Km for NAD+ was determined to be 80 nM.     

Linkage between the variegate porphyria (VP) and the alpha-1-antitrypsin (PI) genes on human chromosome 14

Summary We describe a new rare allele for esterase D (EsD) occurring in a Portuguese family with retinoblastoma in two generations.     

Chromosomal aberrations and sister-chromatid exchanges in lymphocytes from coke oven workers

To test whether coke oven workers, an occupational group known to be at increased cancer risk, manifest increased peripheral blood chromosomal aberration frequencies, we obtained samples from a group of 30 steelworker volunteers, who had worked several years at coke oven jobs. Exposure estimates were made using measurements of work place atmospheric coal tar pitch volatiles and work histories. No statistically significant positive regression of chromosomal aberrations on exposure estimates was found. The data from the coke oven workers were also compared with the obtained concurrently and employing precisely the same laboratory protocol from a group of male Brookhaven National Laboratory employees. The coke oven workers as a group were found to have statistically significantly elevated frequencies of chromatid aberrations and of sister-chromatid exchanges.     

Evidence for involvement of the astrocytic benzodiazepine receptor in the mechanism of action of convulsant and anticonvulsant drugs

The anticonvulsant drugs carbamazepine, phenobarbital, trimethadione, valproic acid and ethosuximide at pharmacologically relevant concentrations inhibit [3H]diazepam binding to astrocytes in primary cultures but have much less effect on a corresponding preparation of neurons. Phenytoin as well as pentobarbital (which is not used chronically as an anticonvulsant) are equipotent in the two cell types. The convulsants picrotoxinin and pentylenetetrazol, the convulsant benzodiazepine RO 5-3663 and the two convulsant barbiturates DMBB and CHEB similarly inhibit diazepam binding to astrocytes but have little effect on neurons. On the basis of these findings it is suggested that these convulsants and anticonvulsants owe at least part of their effect to an interaction with the astrocytic benzodiazepine receptor, perhaps by interference with a calcium channel.     

A comparison of net and gross rates of oxygen production as a function of light intensity in some natural plankton populations and in a Synechococcus culture

In vitrorates of gross and net oxygen production were measuredas a function of light intensity in some plankton communitiescollected from Bedford Basin, Nova Scotia, and in a monoclonalculture of Synechococcus. The rate of gross oxygen productionwas measured by a technique in which the stable oxygen isotope,¹⁸O, serves as a photosynthetic tracer Net oxygen productionwas measured by automated Winkler technique. The rate of communityrespiration in the light was then determined by the differencebetween gross and net rates of oxygen production. In the naturalpopulations examined, neither gross nor net oxygen productionrates were significantly inhibited at the highest light intensitymeasured (500–800 µE m^–2 s^–1) In a samplein which the dark respiration rate was small relative to themaximal rate of production [P_max;sensu Platt et al (1980) JMar. Res., 38, 687–701] the rates of ‘light’respiration were 3 times greater. In two other communities,with high rates of dark respiration relative to P_maxthe ratesof ‘light’ respiration were closer to rates of darkrespiration. In the Synechococcus clone, both gross and netoxygen production rates were inhibited at high light intensities.Rates of ‘light’ respiration were found to varyas a function of light intensity. The greatest rates of respirationwere measured in samples incubated at light intensities thatwere just saturating (100 µE m^–2 s^–1). Therates of ¹⁴C production were also measured as a function oflight intensity The photosynthetic quotients, based on ¹⁴C productionrates and gross oxygen production rates, average 1 9     

Ten different Polycomb group genes are required for spatial control of the abdA and AbdB homeotic products.

Mutations in genes of the Polycomb (Pc) group cause abnormal segmental development due to ectopic expression of the homeotic products of the Antennapedia and bithorax complexes. Here the requirements for Pc group genes in controlling the abdA and AbdB products of the bithorax complex are described. Embryos containing mutations in the genes Polycomb (Pc), extra sex combs (esc), Enhancer of zeste [E(z)], polyhomeotic (ph), Sex comb on midleg (Scm), Polycomb-like (Pcl), Sex comb extra (Sce), Additional sex combs (Asx), Posterior sex combs (Psc) and pleiohomeotic (pho) were examined. In every case, both abdA and AbdB are expressed outside of their normal domains along the anterior-posterior (A-P) axis, consistent with these Pc group products acting in a single pathway or molecular complex. The earliest detectable ectopic expression is highest in the parasegments immediately adjacent to the normal expression boundary. Surprisingly, in the most severe Pc group mutants, the earliest ectopic AbdB is distributed in a pair-rule pattern. At all stages, ectopic abdA in the epidermis is highest along the anterior edges of the parasegments, in a pattern that mimics the normal abdA cell-specific pattern. These examples of highly patterned mis-expression show that Pc group mutations do not cause indiscriminate activation of homeotic products. We suggest that the ectopic expression patterns result from factors that normally activate abdA and AbdB only in certain parasegments, but that in Pc group mutants these factors gain access to regulatory DNA in all parasegments.