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A C Towle

Publications and source records attributed to A C Towle.

51 records · Page 3Linked to original sources
PubMed1985

pp60c-src in the developing cerebellum.

pp60c-src was localized in the cerebellum of developing chicken embryos by immunoperoxidase staining with antisera raised against bacterially expressed pp60v-src. Immunoreactivity (IR) appeared in the cerebellum of the chicken embryos at the time of neuronal differentiation. pp60c-src IR was detected in regions of the developing cerebellum where processes of developing neurons and glia are located. In the early embryo (stage 17), pp60c-src IR was localized in the marginal zone of the cerebellar plate. By stage 40, pp60c-src IR was localized in the process-rich molecular layer of the cerebellum and between the cells of the developing internal granular layer. Cell bodies of cerebellar neurons did not show pp60c-src IR at any stage of development. Mitotically active neuroepithelial cells of the metencephalon did not express pp60c-src before the onset of differentiation in the early embryo, nor did proliferating cells of the external granular layer express pp60c-src at later stages. Although it is not possible to ascertain whether pp60c-src is localized in developing neurons or glia at the light microscope level, the time of its appearance and pattern of distribution in the molecular layer is suggestive of a localization within the developing neuronal processes which compose the bulk of this layer. Biochemical analyses of pp60c-src in the developing cerebellum by the immune complex protein kinase activity and sensitivity of the kinase to inhibition by P1,P4-di(adenosine-5')tetraphosphate confirmed that the expression of pp60c-src coincided with the time of neuronal differentiation. We conclude from these results that in the central nervous systems, pp60c-src may be more important in an aspect of cell differentiation or a mature neuronal function than in the proliferation of neuronal or glial precursors.

Animals↗
PubMed1984

Early postnatal administration of 5,7-DHT: effects on serotonergic neurons and terminals.

Serotonergic neurons throughout the brain were destroyed by early postnatal treatment of rats with an intracisternal injection of 5,7-dihydroxytryptamine (5,7-DHT), as demonstrated with biochemical measurements of serotonin and immunocytochemical localization of serotonin-containing neurons. Using these methods, it was shown that approximately 75-98% of serotonergic neurons underwent cell death in rats which were treated on day 3. In contrast, intracisternal administration of 5,7-DHT in adult rats led to the loss of distal serotonergic terminals without apparent loss of the cell bodies. Desipramine pretreatment prevented significant effects of 5,7-DHT on noradrenergic neurons.

5,7-Dihydroxytryptamine↗
PubMed1984

Supersensitivity to the respiratory stimulatory effect of TRH in 5,7-dihydroxytryptamine-treated rats.

Rats treated neonatally with pargyline and 5,7-dihydroxytryptamine (5,7-DHT) have an elevated paCO2 and reduced minute ventilation when given 0.7% halothane in oxygen as adults. Serotonin content in the spinal cord of 5,7-DHT treated rats was undetectable and TRH content was reduced by 35%. The 5,7-DHT treated rats were supersensitive to the increase in minute ventilation and CO2 sensitivity produced by intraventricular TRH. It is possible that the supersensitivity to exogenous TRH after neonatal 5,7-DHT treatment may be secondary to decreased availability of TRH in the CNS.

5,7-Dihydroxytryptamine↗
PubMed1984

Optimization of tyrosine hydroxylase immunocytochemistry in paraffin sections using pretreatment with proteolytic enzymes.

Immunocytochemical localization of tyrosine hydroxylase (TH) was performed on paraffin sections pretreated with various proteolytic enzymes. It was found that pretreatment with trypsin (1.2 mg/ml) for 5 min resulted in a dramatic increase in the number of TH-positive terminals throughout the brain, especially in the cerebellum, which contains fine preterminal and terminal axons that are difficult to stain. This pretreatment also led to a significant reduction in background staining and allowed for the use of the TH antiserum at high working dilutions. Several other proteolytic enzymes were tested and only chymotrypsin was nearly as effective as trypsin with respect to TH staining.

Animals↗
PubMed1984

Ethanol-induced locomotor stimulation in rats after thyrotropin-releasing hormone.

Ethanol-induced sedation in Sprague-Dawley rats was antagonized by intracisternally administered thyrotropin releasing hormone (TRH) at a dose as low as 1 microgram. Furthermore, when a dose of 25 micrograms or greater of TRH was combined with ethanol doses above 2 g/kg, the locomotor activity was significantly greater than observed for TRH alone. A dose-related increase in activity was observed when varying doses of ethanol were administered with a constant dose of TRH (100 micrograms). This increase in locomotion induced by the TRH-ethanol combination could not be attributed to a change in TRH concentration, ethanol distribution or to a pituitary action of TRH. Inasmuch as tert-butanol in combination with TRH produced the same effects as ethanol, the hyperactivity does not appear to be associated with acetaldehyde formation. TRH acid and His-Pro-diketopiperazine, metabolites of TRH, did not produce hyperactivity when administered with ethanol, whereas MK-771, a TRH analog, produced a significant increase in locomotion in ethanol-treated rats greater than that for MK-771 alone. Three lines of evidence suggested that the hyperactivity induced by the TRH-ethanol combination could not be attributed to an influence of ethanol on the stimulant effects of TRH. First, pentobarbital- and chlordiazepoxide-induced depression of locomotion was antagonized by TRH (100 micrograms) but, unlike ethanol, locomotor stimulation greater than that for TRH was not observed. Second, behavioral observations did not reveal ethanol altering any effects of TRH that would compete with locomotion.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Codepletion of serotonin and TRH induces apparent supersensitivity of spinal TRH receptors.

Thyrotropin-releasing hormone (TRH), substance P (SP) and serotonin (5-HT) coexist in raphe efferents to the spinal cord. Lesions of these serotonergic projections by intracisternal injection of 5,7-dihydroxytryptamine (50 micrograms) in rat pups resulted in 93% and 65% decreases in 5-HT and TRH content of adult rat spinal cords, respectively. This codepletion induced a 30-40% increase in binding of [3H][3-Me-His2]TRH [( 3H]MeTRH) to TRH receptors. The affinity and pharmacological specificity of [3H]MeTRH binding to control and DHT-lesioned cords appeared closely similar.

5,7-Dihydroxytryptamine↗
PubMed1983

Inactivation by Na+,K+-ATPase of cytosol glucocorticoid receptors from rat brain and liver.

We have examined the effect of Na+,K+-ATPase on 3H-triamcinolone acetonide binding capacity of cytosol glucocorticoid receptors from rat brain and liver. Preincubation of the brain or liver cytosol with Na+,K+-ATPase (10 units/ml) at 30 degrees C resulted in a rapid loss of specific 3H-triamcinolone acetonide binding, with a half-life of approximately 7 min. The ATPase effect could be prevented by the addition of 10(-5) M ouabain, or substantially reduced by the omission of Na+,K+ or Mg+2. The cytosol receptor bound with 3H-triamcinolone acetonide was totally resistant to the inactivation by the ATPase. Since there is some evidence that ATP may bind to glucocorticoid receptor, our findings indicate that an ATP-receptor complex may be essential for steroid binding. The effects of the ATPase in the inactivation of the receptor are very similar to those of alkaline phosphatase reported by others. This raises doubts about the proposal based on the phosphatase inactivation that the cytosol glucocorticoid receptor may be phosphorylated.

Adenosine Triphosphate↗
PubMed1983

Steroid binding to synaptic plasma membrane: differential binding of glucocorticoids and gonadal steroids.

The specific binding of [3H]-corticosterone, [3H]-17 beta-estradiol, [3H]-testosterone, and [3H]-progesterone to synaptic plasma membrane (SPM) prepared from rat brain has been characterized. The dissociation constant is estimated as on the order of 1 x 10(-7) M for corticosterone and 1 x 10(-8) M for the other three steroids. In a competition experiment, none of the 3H-steroids was displaced by the other steroids at 500-fold excess, indicating the presence of specific binding sites on the membrane for each type of steroid. Moreover, pre-incubation of the SPM with phospholipase A2 or phospholipase C totally destroys the membrane binding of corticosterone and testosterone, but the binding of estradiol and progesterone remains intact. Since the SPM prepared from brain tissue is derived from many different neuronal cell types, it is possible that the membrane binding sites for glucocorticoids and for gonadal steroids are present in different neurons.

Adrenalectomy↗
PubMed1983

Increased uptake of [3H]choline by rat superior cervical ganglion: an effect of dexamethasone.

The high affinity uptake of [3H]choline by the superior cervical ganglion, isolated from the rat, was found to be increased by dexamethasone. Maximal increase (60-65% above control values) occurred at the steroid concentration of 5 X 10(-5) M. Other glucocorticoids (triamcinolone, corticosterone and hydrocortisone) were without an effect on the [3H]choline uptake. Following administration of dexamethasone (25 mg/kg, i.p.), there was a marked increase in the level of choline in the ganglion. The increase was 3-fold at 1 hr and 10-fold at 6 hr, and by 24 hr the choline levels still remained higher in the steroid-treated animals than in the controls. Levels of acetylcholine in the ganglion were also increased, beginning at 1 hr after the injection of steroid. The increase was 85% by 3 hr and 60% by 6 hr. Triamcinolone, a glucocorticoid that was without an effect on [3H]choline uptake in vitro, was also ineffective in altering the levels of choline and acetylcholine in vivo. It seems probable that the increase of choline uptake in the ganglion induced by dexamethasone may, at least in part, occur in the preganglionic cholinergic terminals, leading to increased synthesis of acetylcholine. Such an effect of dexamethasone provides another case of a selective steroid acting directly on nerve terminals by altering a transport mechanism.

Acetylcholine↗
PubMed1982

[3H] Corticosterone binding in rat superior cervical ganglion.

Binding of [3H]corticosterone was examined in the soluble fraction (100,000 g) from superior cervical ganglia dissected from adrenalectomized and perfused rats. A large binding capacity (2100 fmol/mg protein) was found. However, no binding for [3H]-dexamethasone and [3H]triamcinolone was detected. The binding protein present in the ganglion preparation was characterized by DEAE-cellulose and DNA-cellulose chromatography and by isoelectric focusing. The corticosterone binding protein from the ganglia was found to be different from the cytoplasmic glucocorticoid receptor, but similar to plasma transcortin. A large portion (approximately 75%) of the transcortin-like [3H]corticosterone binding protein was located in the interstitial space between the sheath and the ganglionic cells. However, 25% of the binding protein was retained in the desheathed ganglion even after extensive washing with saline. Our findings indicate that cytoplasmic glucocorticoid receptors are not present in the superior cervical ganglion. It is possible that the transcortin-like protein associated with the desheathed ganglion may be intracellular, as other investigators have suggested similar intracellular presence of a transcortin-like protein in the liver, uterus, and pituitary.

Animals↗
PubMed1982

Cytosol glucocorticoid binding in monoaminergic cell groups.

The following nuclei containing monoaminergic neurons were punched out from frozen sections of rat brain: locus coeruleus, dorsal raphe nucleus, medial raphe nucleus, and substantia nigra zona compacta. Cytosol preparations from the dissected tissues were examined for 3H-corticosterone binding. Only the locus coeruleus showed a substantial level of 3H-corticosterone binding. No binding capacity was found in cytosols from the raphe nuclei and the substantia nigra. The cytosol steroid binding of the locus coeruleus was determined developmentally. The binding capacity was found to remain virtually unchanged from postnatal day 5 (the earliest period examined) to adulthood. It is possible that a cytoplasmic glucocorticoid receptor may be present in the noradrenergic neurons of the locus coeruleus. Since 3H-corticosterone binding is absent in the raphe nuclei and substantia nigra, biochemical mechanisms involving a glucocorticoid-receptor interaction directly in these serotonergic and dopaminergic neurons may be ruled out.

Animals↗
PubMed1982

Glucocorticoid influence on tyrosine hydroxylase activity in mouse locus coeruleus during postnatal development.

Administration of corticosterone (10 mg/kg, ip, twice daily for 3 days) to mice during the second week of postnatal development led to an increase of tyrosine hydroxylase (TH) activity in the locus coeruleus, but not in the substantia nigra. The corticosterone effect was observed only transiently during this developmental period. Tritiated corticosterone can bind to a cytosol fraction prepared from mouse locus coeruleus, with a specific binding capacity of 110 fmol/mg protein. There is a correlation between the ability of various steroids to increase TH activity and their binding to the cytosol glucocorticoid receptor. Cortexolone and progesterone, two antiglucocorticoids that can bind to the cytosol receptor, were found to abolish the effect of corticosterone in increasing TH activity. It appears that the noradrenergic neurons in the locus coeruleus may be target cells for glucocorticoids, and that the glucocorticoid effect on TH may be a receptor-mediated mechanism.

Animals↗