PubMed Health⌕ Search

Biomedical subjects

F Ungar

Publications and source records attributed to F Ungar.

At least 37 records · Page 2Linked to original sources
PubMed1982

Hypothalamic and pituitary periodicity demonstrated by isolated rat adrenal cells.

Rats were maintained under standardized conditions of food and water ad libitum and a lighting schedule of 12 h light/we h dark for seven days. Animals were sacrificed at 0500 and 1700 h and tissues were removed and washed. Isolated intact adrenal and pituitary cells were prepared by collagenase treatment. Using a sequential incubation procedure, the release of pituitary ACTH by hypothalamic acid extracts (CRF) was assayed by stimulation of corticosteroid secretion from isolated adrenal cells. Maximum stimulation of adrenal steroids was achieved with hypothalamic extracts and pituitary cells from rats sacrificed at 1700 h, and minimum values were obtained at 0500 h. Intermediate levels were obtained when hypothalamic extracts at one time point were incubated with pituitary cells at the other. The results substantiate the late afternoon peak level of hypothalamic and pituitary secretion occurring prior to the peak activity pattern of the rat.

Adrenal Cortex Hormones↗
PubMed1982

Formation and isolation of delta 5-3-ketosteroids using a purified rat liver alcohol dehydrogenase.

3 beta-Hydroxy-5-androsten-17-one is converted to 5-androstene-3, 17-dione by rat liver alcohol dehydrogenase (ADH). We have reported on the purity of the enzyme which is eluted with pyrazole as a single homogeneous protein using an AMP-agarose affinity column. Rat liver ADH can oxidize hydroxyl groups not only at 3 beta-, but also at 3 alpha-, and 17 beta-positions to a lesser extent; thus it is a pure mammalian enzyme with multifunctional activity for steroids. Since it does not contain delta 5-isomerase activity, the reaction of the dehydrogenase to form the delta 5-ketosteroid intermediate can be observed at pH 7.0, 25 degrees C. Similarly, intermediary product, 5-pregnene-3,20-dione, can be isolated in the conversion of pregnenolone by ADH to progesterone. With buffer alone in a cuvette, a non-enzymatic isomerization of the delta 5-3-ketone occurs at a slow rate (t 1/2 = 6 hrs) but occurs rapidly during isolation procedures. The delta 5-3-ketosteroid intermediates were identified by their behavior on TLC plates with UV light and by their characteristic spectra in the NMR.

Alcohol Dehydrogenase↗
PubMed1981

Calcium accumulation in intracellular compartments of frog retinal rod photoreceptors.

The accumulation of calcium in the rod cells of isolated frog retinas was studied by methods involving the pretreatment of tissue with saponin, which reduces the permeability barrier posed by the plasma membrane, and the inclusion of a Ca2+ trapping agent, oxalate, in incubation media. X-ray microanalysis using an analytical transmission electron microscope was employed to verify the presence of calcium in the deposits produced by these methods. Ca2+ was found to accumulate in the rough endoplasmic reticulum (ER) and the agranular reticulum of the myoid region and in the presynaptic terminals of the rods. At least one aspect of this accumulation appears to depend upon the presence of ATP.

Animals↗
PubMed1980

Histogenesis of the goldfish retina.

The order of production of retinal cells was studied in embryos of the goldfish, Carassius auratus, using 3H-thymidine autoradiography. Cell division ceases first in the neuroepithelium at the fundus of the eye between embryonic stages 19 and 20 and gradually becomes restricted to the retinal margin by stage 24. In the fundus the cells whose nuclei will reside in the inner layer of the retina stop dividing earlier than the cells whose nuclei will reside in the outer retinal layers. Thus the ganglion cells in the fundus of the retina are produced first and the receptors and horizontal cells last.

Animals↗
PubMed1979

Growth hormone effects on creatine uptake by muscle in the hypophysectomized rat.

Specific radioactive enzyme assays were developed to measure the effect of growth hormone on kidney transamidinase and liver methyltransferase in the hypophysectomized rat. In contrast to minimal changes (20%) in liver methyltransferase, kidney transamidinase was decreased threefold in the hypophysectomized rat. Enzyme activities were equal to normal values in those rats receiving growth hormone for three days. The formation of creatine from radioactive precursors and the uptake of 14C-creatine in muscle was examined under these conditions. After injection of 14C-arginine in the hypophysectomized rat, the 14C-creatine content of muscle was greatly decreased compared to sham operated controls and the 14C-creatine content was normal after growth hormone administration. After injection of 14C-guanidoacetate and of 14-creatine, the 14C-creatine content of muscle was decreased in the hypophysectomized rat, but was equal to sham control values in rats receiving growth hormone. These studies indicate that the uptake of newly synthesized creatine by muscle is impaired in the hypophysectomized rat and that growth hormone can have a role in controlling the rate of creatine uptake by muscle in addition to its effect on kidney transamidinase and to other factors involved in creatine metabolism.

Amidinotransferases↗
PubMed1979

Non-enzymic interactions of nicotinamide adenine dinucleotide, of some of its synthetic analogues and other compounds with orthophosphate.

Changes in the ultraviolet (UV) absorption spectra of nicotinamide adenine dinucleotide (NAD), of its synthetic analogues, and of adenosine and its derivatives in the presence of high concentrations of orthophosphate were studied. The role of the carboxamide group of the nicotinamide moiety of NAD on these spectral changes was investigated by replacing that group with an acetyl or aldehyde group. The effect of the 6-amino group of the purine was investigated by studying the interaction of deamino-NAD and various adenosine derivatives with orthophosphate. 2,4-Dinitrophenol was also found to give a charge transfer complex with phosphate. Molar extinction coefficients (E) and association constants (K) of these charge transfer reactions were determined.

Adenine Nucleotides↗
PubMed1978

Preliminary studies of the sodium borohydride stabilizable binding of phenylethylamine and tyramine to brain preparations.

The borohydride stabilizable binding of 2-phenylethylamine and p-tyramine to mouse brain homogenates was compared to that of tryptamine and of serotonin. The highest binding was found to be that of tryptamine, followed by that of serotonin, tyramine, and phenylethylamine. The stabilizable binding of phenylethylamine to calf midbrain (including corpus striatum) homogenates and synaptic membranes was decreased by dopamine; this amine and D-amphetamine also decreased the stabilizable binding of tyramine to rat brain homogenates. The subsynaptosomal distribution of the binding of phenylethylamine to synaptic calf midbrain fractions was also investigated. The highest binding capacity was found in the 0.8 M fraction, rich in myelin.

Animals↗
PubMed1977

Studies on membrane receptor sites for serotonin in the brain.

The competitive effect of 5,6-dihydroxytryptamine, morphine and chlorpromazine on the binding of serotonin (5-HT) to rat brain slices was investigated. Ths busynaptosomal localization of the binding of morphine in bovine midbrain preparations was compared to that of 5-HT and found to be considerably higher. The condensation of 5-HT and tryptamine receptor carbonyl groups in brain with phenylisopropylhydrazine was shown in vitro and vivo. Membrane particles labeled with [14C] tryptamine or 5-HT in presence or absence of sodium borohydride (NaBH4) were extracted with chloroform-methanol (C-M) 2:1. The labeled proteolipid precipitated by ether from these extracts showed on electropherograms one single radioautographic spot which was more intense with samples treated with sodium borohydride. In column chromatography, the bound radioactivity peak eluted with the gel void volume, was associated with a protein peak. The eluted, lyophilized material of this fraction was extracted by chloroform methanol (2:1) thus suggesting its proteo-lipid nature.

5,6-Dihydroxytryptamine↗
PubMed1977

Tyramine-binding by synaptosomes from rat brain: effect of centrally active drugs.

Incubation of p-tyramine (TRM) with rat midbrain plus corpus striatum (MB+ CS) crude synaptosomal preparations, under conditions which reduce to a minimum amine uptake, results in appreciable binding of this amine by synaptosomes. This process is inhibited by preincubation with a number of drugs active in the CNS, e.g., chlorpromazine, desipramine, d-amphetamine, and diphenhydramine. Morphine, however, does not affect this binding. The Ki for each one of these compounds, as well as the K association constant and concentration of the binding sites of TRM, were determined. These results suggest a role for TRM in synaptic transmission mechanisms occurring in the nigrostriatal system, a function which could be regulated by a number of substances representing some of the major chemical classes of centrally active drugs (CD).

Animals↗
PubMed1977

Effects of monoamine oxidase inhibitors on the borohydride stabilizable binding of serotonin and tryptamine in brain.

The in vivo and in vitro effects of various monoamine oxidase inhibitors (MAOI) on the borohydride stabilizable finding of serotonin (5-HT) or tryptamine in brain was investigated. A significant correlation between the extent of Mao inhibition and the amount of stabilized binding of the indolealkylamines was demonstrated. All hydrazine-type MAOI and harmine, a reversible nonhydrazine-type MAOI, employed in vitro, were shown to decrease the binding. beta-Phenylisopropylhydrazine apparently blocks the receptor carbonyl groups in the brain in vitro as well as in vivo.

Animals↗
PubMed1976

Drug antagonism and reversibility of the binding of indoleamines in brain.

The specificity of the binding of serotonin to brain preparations was investigated with various competitive agents. A probable relationship between their structure and their capability of displacement was suggested. Bufotenine and morphine displaced serotonin (0.5 X 10(-5) M) binding to synaptic membranes 87 and 49% respectively. Dissociation constants of the binding of 5-HT and tryptamine to synaptic membranes, and displacement constants of certain drugs were determined. The binding of 5-HT and tryptamine to calf brain preparations was also investigated by equilibrium dialysis, in order to determine affinity constants and reversibility of the binding. Differences were noted in the specificity of binding sites for serotonin and tryptamine, suggesting a different binding site for tryptamine. Extrapolations of Scatchard plots were used for determination of the constants. A characteristic low dissociation constant was found for 5-HT in synaptic membranes (K approximately X 10(-6) M). Probably, the binding macromolecule (receptor?) is a proteolipid.

Animals↗