Relaxant effect of dopamine on isolated rabbit pulmonary artery

In rabbit pulmonary artery, dopamine (10(-11)-10(-5) M) produced a concentration-dependent relaxation of the arterial strips contracted with prostaglandin F2 alpha (PGF2 alpha) in the presence of prazosin (10(-6) M), yohimbine (10(-6) M), propranolol (10(-6) M), and methysergide (10(-6) M). SKF38393, an agonist for D1 or DA1 dopamine receptor, mimicked partially the concentration-response curve for dopamine, whereas LY171555 and apomorphine did not. The order of potency of dopamine antagonists on the inhibitory effect was: cis-flupenthixol greater than bulbo-capnine greater than metoclopramide greater than haloperidol. Sulpiride was inactive. Cis-flupenthixol did not block the relaxation induced by acetylcholine, adenosine, and papaverine. In the arterial strips of the rabbits pretreated with 6-hydroxydopamine, the concentration-response curve for dopamine was similar to that in non-treated rabbits. Thus it is concluded that a specific dopamine receptor is located on the postsynaptic muscle membrane of the rabbit pulmonary artery.     

The presence of the 30 nm filament structure of chromatins in intact chicken erythrocytes observed by 31P NMR

A 31P NMR spectrum of chicken erythrocyte chromatins in vivo was obtained. The spectrum was characterized by examining the spectra of isolated nuclei and nondigested chromatins under various conditions. The results have shown that most chromatins in chicken erythrocyte nuclei assume the 30 nm filament structure as a second step of condensation of DNA in vivo.     

Purification of human placental glucocerebrosidase using a two-step high-performance hydrophobic and gel permeation column chromatography method

Glucocerebrosidase was purified from human placenta approximately 10,600-fold to apparent homogeneity with an overall yield of 37% using cholate extraction, ammonium sulfate fractionation, butanol delipidation, and a two-step high-performance hydrophobic and gel permeation column chromatography method. A Phenyl-5PW (21.5 X 150 mm) column was used in the first step. Approximately one litre of delipidated and dialysed extract containing 3.7 X 10(6) units of enzyme activity from 1 kg of placental tissue was processed by the column at a flow rate of 5 ml/min. Glucocerebrosidase was eluted using a linear cholate gradient (2-3%). There was a 50-fold purification and 89% recovery. The run was completed in about 7 h. In the second step, the concentrated enzyme preparation from the phenyl column was run through two Bio-Sil TSK 250 gel permeation columns (21.5 X 600 mm) connected in series at a flow rate of 1.5 ml/min. A symmetrical peak of glucocerebrosidase activity (Ve = 253 ml) which had constant specific activity (47,000 units/h/mg protein) was noted. There was a 17-fold purification and 80% recovery in this run which was completed in 4 h. Sodium dodecylsulfate-polyacrylamide gel electrophoresis and protein staining with silver compounds of the purified preparation revealed the presence of one band of Mr 68,000.     

Purification and characterization of erythroid differentiation factor (EDF) isolated from human leukemia cell line THP-1

We isolated a protein, from a cell line of human origin, which exhibits extensive differentiation inducing activity toward Friend leukemia cells. The protein, called Erythroid Differentiation Factor (EDF), was found in a 4 day culture of THP-1 cells performed in the presence of 4 beta-phorbol 12-myristate 13-acetate(PMA). EDF is a homodimer of a molecular weight of 25,000, with an NH2-terminal sequence identical to that of the beta A-chain of porcine Inhibin. It was suggested that a single protein species is responsible for the activities of both EDF and FRP, a FSH releasing protein isolated from porcine ovarian follicular fluid.     

Methyl iodide, a potent inducer of the adaptive response without appreciable mutagenicity in E. coli

Methyl iodide (MeI), a very weak mutagen, induced the adaptive response in E. coli to a similar extent to those induced by potently mutagenic methylating agents. MeI potentiated the mutagenicity of a methylating mutagen, N-methyl-N-nitrosourea, by its co-treatment. These results might give indication that MeI directly methylates O6-methylguanine-DNA methyltransferase resulting in induction of the adaptive response and depletion of the repair capacity of enzyme.     

Induction of cell surface insulin antigenicity in fibroblasts transfected with islet genomic DNA

Intact platelets were stimulated with thrombin and the amount of GTP-binding protein (G-protein) oligomers was assessed by measuring ADP ribosylation of 40-41 kDa protein by pertussis toxin in isolated membranes. The toxin substrate fell by 57-62% in 10-60 s, but then returned towards normal over 5 min. Recovery was greatly enhanced by removal of thrombin from receptors with hirudin. Phorbol myristate acetate increased ADP-ribosylatable protein, but only back to initial levels prior to PMA. In contrast prostaglandin D2 plus theophylline (which increase cyclic AMP) did not increase ADP ribosylation, but could completely block the fall of the toxin substrate caused by thrombin. These results indicate that activation of thrombin receptors promotes the dissociation of G-protein oligomers to release free alpha-subunits, and this effect can be modulated by protein kinase C and cyclic AMP-dependent protein kinase. The possible relationships of these findings to the regulation of stimulus-response coupling in platelets is discussed.     

Characterization of the androgen-dependent 22Kdalton glycoprotein from rat ventral prostate

Oxidation by molecular oxygen converted the 22Kdalton glycoprotein from rat ventral prostate into a 34K species and this reaction could be reversed by thiol reducing reagent. Measurement of the level of the 22Kdalton glycoprotein in prostatic cytosol by the radial immunodiffusion technique showed that changes in the 22Kdalton glycoprotein concentration in response to androgen withdrawal and replacement were slow in comparison to androgen regulated levels of mRNA coding for the protein. (3) Charcoal absorption steroid binding assays of the 22Kdalton glycoprotein revealed that the protein did not bind testosterone, estradiol, progesterone or corticosterone. These results indicate that the 22Kdalton glycoprotein is metabolically stable, not steroid-binding, and exists as an oligomer through disulfide crosslinking.     

Phosphorylated proteins from anuran intestinal microvilli membranes--I. Relations with alkaline phosphatase

The degree of phosphorylation of intestinal microvilli membrane proteins in an adult amphibian, Rana esculenta, was investigated under various experimental conditions. The microvilli protein phosphorylation rate rapidly increases during the first 4 min of incubation in a medium containing [gamma-32P]ATP. This increase is slower afterwards. Cyclic nucleotides (cyclic AMP, cyclic GMP) and sorbitol do not modify the microvilli protein phosphorylation rate. On the contrary, this phosphorylation rate significantly decreases in the presence of L-lysine, when its concentration in the incubation medium is greater than 25 mM. The time course of phosphorylation confirms the inhibitory effects of L-lysine (100 mM). The microvilli membrane proteins were distinguished by polyacrylamide gel electrophoresis. In heated samples, electrophoresis followed by an radioautograph systematically reveals the existence of a very phosphorylated protein with a mol. wt of 86 kDa. The phosphorylation of this protein is partially inhibited by L-lysine (100 mM). The very phosphorylated protein could be the monomer of alkaline phosphatase. The dimer (170 kDa) is visualized on electrophoretograms by its catalytic activity. In mammals, several authors have established a correlation between phosphorylation of the microvilli membrane proteins and the intensity of intestinal calcium absorption. Such a control is presently being investigated in adult Rana esculenta.     

Expression of c-myc oncogene during differentiation of human burst-forming unit, erythroid (BFU-E)

We investigated the serial expression of c-myc oncogene during differentiation of normal human burst-forming unit, erythroid (BFU-E), in vitro, together with the replating efficiency and the expression of transferrin receptors. We found that the c-myc oncogene was expressed in the early progeny of BFU-E and that this expression decreased during erythroid differentiation. This change of the c-myc expression was well correlated to changes in the replating efficiency and the expression of transferrin receptors. These observations indicate that the c-myc oncogene probably has a physiological role in normal human hematopoiesis as well as leukemic hematopoiesis.