Reduction of nitrite by NADH catalyzed by Pseudomonas aeruginosa nitrite reductase is inhibited by a high concentration of nitric oxide NO. Contrary to what is currently admitted, we find that the nitrite reduction proceeds to the nitrogen monoxide N2O stage. EPR spectra show that, during the catalytic cycle, the enzyme forms specific Fe2+-NO heminic complexes.
It is shown that in living cells, some liposoluble collisional quenchers like n-iodo hexane and iodo benzene can be used to selectively quench the benzo(a)pyrene fluorescence, leving the diol-epoxide benzo(a)pyrene metabolite emission. The preferential solubilities of these compounds, fluorophors and quenchers, explain the results and the fluorophor location.
Cellular esterases of 14 strains of Klebsiella pneumoniae, 14 strains of K. oxytoca, 16 strains of Enterobacter aerogenes and 16 strains of E. gergoviae were analysed by polyacrylamide-agarose gel and polyacrylamide gradient gel electrophoresis. Four principal esterase bands and nine minor bands, differing in their activity towards synthetic substrates and in their sensitivity to heat and to di-isofluoropropyl phosphate (DEP) were defined. The comparative distribution of bands showed that the four species analysed were characterized by distinct electrophoretic patterns of their esterases.
In the anaesthetized Rat, the entire population of dorsal horn convergent neurones is differentially affected by a noxious stimulus: while exciting the segmental pool, it strongly inhibits the remaining population. The inhibitory effects, which involve supraspinal mechanisms, are reduced to a great extent in parachlorophenylalanine pretreated animals. The role of raphé-spinal serotonergic pathways in nociception is discussed.
Local hyperthermia--insufflation in the upper respiratory paths of humidified air at 43 degrees C, three 30 min sessions at 2-3 hrs. interval--cures a high percentage of infective Coryza and exerts a prolonged beneficial effect on an important fraction of persistent allergic rhinitis.
The inhibiting effect of Cytembena on HeLa cell kinetics has been demonstrated and analyzed. The percentage of cycling cells decreases, according to the concentration, between 7.5 and 2.5 x 10(-5) M. Estimation of DNA by cell flow cytophotometry shows an important shift in the distribution of cycling cells with a relative decrease of G1 cells and a very important accumulation of G2 cells. According to our experimental conditions, the blocking up in G2 is irreversible only at 7.5 x 10(-5) M.
Casein is submitted to a severe alkaline treatment (NaOH 0,2 or 0,5 N, 1 hr., 80 degrees C). The hydrolysis by pancreatic enzymes (trypsin or chymotrypsin) is reduced in vitro and, in the case of the more severe treatment, stopped. After an extended (24 hrs.) trypsin and pronase hydrolysis, it is shown, by affinity chromatography, that peptides, which are not hydrolysable, can bind to trypsin and inactivate this enzyme in vitro.
Fluid obtained from Rat uteri during the uterine state of non-receptivity refractory for nidation, contains a substance of about 700 dalton (blastocidin) which exerts a lethal effect on Rat blastocysts in vitro.
We present a model for the secondary structure of 16S ribosomal RNA from E. coli. This model has been deduced by restricting the total number of theoretical base pairings using the following criteria: (1) susceptibility of residues towards enzymatic probes that are specific for either paired or single stranded regions; (2) reactivity of certain residues to chemical modification; (3) evidence for medium and long range interactions; (4) comparative analysis of ribosomal RNA sequences from other organisms.
The presence of a CSF activity in long term bone marrow cultures in Mice was not described until now. Using a double layer agar technique directly on the adherent layers of the cultures, a strong CSF activity is detected in these adherent layers, before recharging the cultures at the third week, or when the cultures are not recharged. The role of this activity in long term myelopoiesis maintenance in vitro is discussed.
Extracts of the corpuscules of Stannius enhance Eel gill calcium efflux and increase bone resorption in the Rat. Thus the hormone is hypocalcaemic in the Eel although hypercalcaemic in the Rat. We show here that a 15 min. pulse perfusion of a synthetic fragment of human PTH 1-34 had a similar effect on gill calcium fluxes to that of CS extract. Further, we found that Eel plasma contains a substance reacting with five different antibodies against bovine PTH. The concentration of this plasma material is enhanced seven-fold by parenteral calcium and rendered extremely low or absent by CS removal. A convenient name for this major calcium-regulating hormone is parathyrine of the corpuscles of Stannius (PCS) since this reflects both its glandular source and chemical structure.
A frozen strain of Plasmodium yoelii nigeriensis is inoculated at 4 pm, midnight and 9 am onto inbred Mice. In all instances young gametocytes (type 0) appear in the blood only between 10 am and 6 pm. Although the erythrocytic schizogony occurs regularly during the whole circadian period, the latency increases progressively when the infective subinoculations are made at midnight, 4 pm and 9 am. Possibly, the infective merozoite can only enter the red blood cell around midnight.
OEnanthotoxin applied locally onto the Cat cortex produced a long-lasting epileptic focus. The basic cortical level of extracellular calcium concentration ([Ca2+]e) was decreased before the actual onset of paroxysmal discharges. In the active focus the [Ca2+]e decrease induced by a cortical or a thalamic stimulation was larger than in normal cortex. Maximal decreases were found at a depth of 300 micrometer below cortical surface. It is suggested that at this cortical level calcium conductances are increased by oenanthotoxin. This increase may be one of the mechanisms of onset of epileptic seizures.
A "fraction P" analogue possessing immunosuppressive properties during pregnancy in the Salamandra, can be induced by treating males and females with oestradiol. Both fractions possess the same physiochemical characteristics, and equally react against a Rabbit immune serum anti "fraction P" of pregnant Salamandra. But the proteic fraction induced by hormonal treatment does immunosuppressive properties.
By a laser beam, enamel and dentin are changed into an identical crystalline structure observed in reflected light and described as recrystallisation after fusion. The Vickers pyramidal numbers of these areas are the same as the mature enamel surface (590 VPN). The theoretical calculation proved that after irradiation in enamel there is an elevation of temperature about 2,5 degrees C through 3 mm. These observations suggest that new operative techniques might be possible.
In the Baboon, two regions could be distinguished within the dentate nucleus according to the complexity of motor effects induced through localised electrical stimulation. (a) A rostromedial region, from which synergistic effects were elicited. This part mainly controls proximal muscles. (b) A caudolateral region from which simple movements were induced. A separate area for hand control could be identified within this part of the nucleus.
Some newborns infants (screened for congenital hypothyroïdism) and their mothers were found to present an apparent isolated hyperthyrotropinemia. A large molecular size material (150 000 dalton) was found to carry the apparent immunoreactivity and was characterized as immunoglobulins, capable of binding TSH as well as Rabbit IgG. These maternal immunoglobulins are passively transferred to the newborn infants and interfere in various radioimmunoassays.
Intraperitoneal injection of Rat Prolactin to cyclic female Rats results in preovulatory changes which depend on the strain of animals. Specifically, preovulatory surges of luteinizing hormone and follicle stimulating hormone were suppressed in Sprague-Dawley Rats while delayed but enhanced preovulatory surges of both gonadotropins were observed in Wistar strain.
Supernatants from mouse spleen leukocytes stimulated by concanavalin A or from a secondary MLC between donor and recipient of a skin allograft can induce in bone marrow cells an exponential growth of mononuclear cells with cytoplasmic basophilic granules. These cells can be maintained in liquid suspension culture for up to 6 months. They lack the properties of T or b lymphocytes, monocytes or macrophages. They have the morphological features of mast cells or basophils; the cytoplasmic granules are metachromatic for toluidine blue, alcian blue-positive at pH 0.3 and contain histamine. In addition, these cells bind monoclonal mouse IgE. They may be considered as cells of the basophil-mast cell lineage.
In this communication, we present the effect of two parameters, temperature and daylight-at high ionic strength-on the stability of H-flavocytochrome b2 solutions prepared using [H-flavocytochrome b2 (S) or not [H-flavocytochrome b2 (n) n-butanol during extraction. These two enzyme preparations presented the same behaviour towards these two parameters: in the dark, temperature was critical; in daylight, an opposite effect was observed for this parameter: the stability of samples was smaller at 0 degrees C. However, the evolution of life of the classical kinetic parameters (Km and Vm) of the enzymatic reaction is presented for three samples of H-flavocytochrome b2 (n) or (s) exposed to daylight at 20 +/- 0,1 degrees C.
