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Biomedical subjects

E Richelson

Publications and source records attributed to E Richelson.

At least 217 records · Page 12Linked to original sources
PubMed1978

Histamine H1 receptor-mediated guanosine 3',5'-monophosphate formation by cultured mouse neuroblastoma cells.

Incubation of cultured mouse neuroblastoma cells with histamine caused a rapid and marked increase in the formation of guanosine 3',5'-monophosphate (cyclic GMP) by these cells. Receptor agonists for H1, but not H2, caused this effect which was reduced by H1 but not by H2 or muscarinic acetylcholine receptor antagonists. These results indicate that activation of H1 receptors in these cultured nerve cells stimulated cyclic GMP formation.

Animals↗
PubMed1977

Biochemical differentiation of aggregating cell cultures of different fetal rat brain regions.

Rotation-mediated aggregating cell cultures of mechanically dissociated fetal rat brains divided into three (telencephalon, mesencephalon-diencephalon and rhombencephalon), or two (telencephalon and mesencephalon-diencephalon plus rhombencephalon) parts were examined for their biochemical differentiation by measuring the specific activities of choline acetyltransferase, acetylcholinesterase, glutamic acid decarboxylase, tyrosine 3-monooxygenase, aromatic L-amino acid decarboxylase, catechol methyltransferase and monoamine oxidase. The results showed that such parts yielded cultures that were relatively enriched for acetylcholine-synthesizing (telencephalon) or catecholamine-synthesizing (mesencephalon-diencephalon and mesencephalon-diencephalon plus rhombencephalon) enzymes. For cultures which were derived from two brain divisions, the sum of the total activity for each enzyme in the parts after 30 days equalled that in whole brain cultures derived from the same group of embryos, suggesting that development of these enzymes was unaffected by division of the brain in two. In experiments to determine the effects of culture conditions on this development, chronic administration of certain drugs was found to selectively influence the specific activity of certain neurotransmitter metabolizing enzymes. Thus, in cultures of whole brain, ascorbic acid (0.2 mM) decreased tyrosine 3-monooxygenase and aromatic L-amino acid decarboxylase while other enzymes were slightly increased; and in cultures of telencephalon and mesencephalon-diencephalon plus rhombencephalon, N6, O2'-dibutyryladenosine 3',5'-cyclic phosphate (0.2 mM) decreased the specific activities of choline acetyltransferase acetylcholinesterase, glutamic acid decarboxylase and monoamine oxidase. These results demonstrate the feasibility of growing these cultures for pharmacological studies in developmental neurobiology.

Acetylcholinesterase↗
PubMed1977

Lithium ion entry through the sodium channel of cultured mouse neuroblastoma cells: a biochemical study.

Lithium ion entry at low concentrations (1 to 5 mM) into an electrically active adrenergic clone of mouse neuroblastoma cells was stimulated by veratridine; and this stimulation was blocked by tetrodotoxin, These data provide biochemical evidence that lithium ions enter by way of the sodium channel which may be a major pathway for entry of this ion into electrically active cells.

Action Potentials↗
PubMed1977

Blockade by psychotropic drugs of the muscarinic acetylcholine receptor in cultured nerve cells.

The ability of antimuscarinics, tricyclic antidepressants, and antipsychotics to block the muscarinic acetylcholine receptor was determined using an assay for this receptor in cultured nerve cells. The technique involved the assay of receptor-mediated formation of guanosine 3',5'-cyclic phosphate (cyclic GMP) from radioactively labeled guanosine 5'-triphosphate in living mouse neuroblastoma cells (clone N1E-115). This cyclic GMP formation occurred rapidly (peak at 30 sec) and was dependent on the concentration of agonist. The psychotropic drugs tested blocked the muscarinic receptor and equilibrium dissociation constants (KB) were calculated from the parallel displacement of dose-response curves. The most potent compound was the antimuscarinic dexetimide (KB= 5 X 10(-11) M); while the least potent was the antipsychotic prochlorperzine (KB=4X10(-5) M). All tricyclic antidepressants with tertiary amine side chains were more potent (2-20 times) than those with secondary amine side chains; whereas phenothiazine potency correlated with the side chain structure as follows: piperadine greater than alkylamine greater than or equal to piperazine. These data for psychotherapeutic drugs may have direct clinical application.

Acetylcholine↗
PubMed1976

Biochemical differentiation of mechanically dissociated mammalian brain in aggregating cell culture.

Mouse and rat brain cells were dissociated by a simple mechanical sieving technique and studied in culture for the formation of aggregates and the activities of choline acetyltransferase, acetylcholinesterase, glutamic acid decarboxylase, tyrosine 3-monooxygenase, aromatic L-amino acid decarboxylase, catechol methyltransferase, and monoamine oxidase. Cells from fetal and neonatal tissue formed aggregates but not cells from tissue older than two days after birth. The pattern of development of enzyme activities in these aggregates varied with the age of starting tissue. The highest levels of specific activity for the neuron-specific enzymes were found after 3-4 weeks in culture for aggregates of cells derived from relatively undeveloped brains.

Acetylcholinesterase↗
PubMed1976

Properties of tyrosine hydroxylation in living mouse neuroblastoma clone N1E-115.

Tyrosine hydroxylation was studied in intact cells of mouse neuroblastoma clone N1E-115 which have high levels of tyrosine 3-monooxygenase (EC 1.14.16.2) and which have been fully characterized for tyrosine transport. Measurement of [3H]OH formed from L-[3,5(-3)H]tyrosine in the medium was the method of assay and [3H]OH formed was stoichiometric with the formation of L-[3H]3,4-dihydroxyphenylalanine. Tyrosine hydroxylation was dependent on time of incubation, cell number, and the concentration of [3H]tyrosine in the medium. From velocity vs. [3H]tyrosine concentration experiments, two apparent Km values were obtained: Km1 = 10 +/- 2 microM; Km2 = 140 +/- 10 microM. Substrate inhibition occurred with tyrosine concentrations between 20 and 50 microM. The reaction was twice as fast at pH 5.5 as at pH 7.4. alpha,alpha'-Dipyridyl (1 mM) caused major inhibition (75%) when [3H]tyrosine concentration was 10 microM. L-3-Iodotyrosine was a competitive inhibitor with Ki = 0.3 microM. Dopamine was a non-competitive inhibitor with Ki = 500 microM. 1-Norepinephrine had no effect. These results show that the hydroxylation of tyrosine by living N1E-115 cells has many of the properties of the reaction catalyzed by purified tyrosine 3-monooxygenase from normal tissue.

Animals↗
PubMed1975

Ionic excitation of a clone of mouse neuroblastoma.

The electrical properties and the possible regulation of these properties were studied by means of intracellular microelectrode recordings in cells of mouse neuroblastoma clone N1E-115. This clone has high levels of tyrosine hydroxylase and regulates this enzyme. Cells treated for 24 h with 4 muM aminopterin followed by at least 5 days in culture developed rhythmic discharge of action potentials when superfused with phosphate-buffered saline containing less than 0.2 mM calcium or less than 0.2 mM calcium and zero potassium. This ionic excitation occurred in no cells at less than 5 days after treatment with aminopterin but at 5 days or more after treatment, 20% of cells responded to low calcium while 52% responded to low calcium and zero potassium. Concomitant with the development of a susceptibility to ionic excitation was an increase in the average resting membrane potential and morphologic maturation. This ionic excitation of cultured mouse neuroblastoma cells may be useful for studying biochemical events associated with repetitive discharge of action potentials.

Action Potentials↗