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Query: UMLS:C0040822 (tremor)
 18,428 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The characteristics of the steroidogenic response of reaggregated rat interstitial cells were examined in a perifusion system. Interstitial cells were isolated from 19-day-old rat testes by digestion with collagenase. The cells were cultured for 3 days as monolayers and were resuspended by brief treatment with trypsin. Constant gyratory shaking of the dispersed cells resulted in the formation of round and compact aggregates of 70-140 microns. The functional characteristics of these aggregates were examined by studying the output of cAMP, C19 steroids (testosterone and androstenedione), and C21 steroids (progesterone, 17 alpha-hydroxyprogesterone, 20 alpha-hydroxypregn-4-en-3-one) in a perfusion system. It is demonstrated that reaggregated interstitial cells maintain their responsiveness to LH, LHRH, and Leydig cell stimulatory factor(s) produced by Sertoli cells for at least 12 days. When exposed to low concentrations of LH (1 ng/ml), either in a continuous or in a pulsatile fashion, perifused aggregates maintain a constant output of steroids for more than 20 h. Under these conditions, LH-dependent differentiation of the steroidogenic machinery can be observed in vitro. In fact, although the sum of the measured steroids remains constant, C21 steroids progressively decrease whereas C19 steroid output increases during perifusion. When perifused with high concentrations of LH (10 ng/ml), desensitization becomes the predominant phenomenon. It is demonstrated that the steroid output of reaggregated interstitial cells considerably exceeds that of similarly treated cells maintained as monolayers. Moreover, perifusion of aggregates results in a 6-fold increase in steroid output as compared to static incubation and in a selective increase in androgen output. It is concluded that prepubertal interstitial cells allowed to reaggregate in suspension culture form functional multicellular structures. Perifusion of these aggregates is a useful tool in the study of the dynamics of the regulation of steroidogenesis.
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PMID:The dynamics of steroid and adenosine 3',5'-cyclic monophosphate output in perifused interstitial cell aggregates derived from prepubertal rat testes. 301 35

Extracellular adenosine 3',5'-cyclic monophosphate (cAMP) is required for cell-type-specific gene expression in developing Dictyostelium discoideum. We have developed a microassay for the expression of these genes, using antibodies directed against their protein products. To characterize the transduction mechanism, we have used in this assay cAMP analogues that preferentially activate either the cell-surface cAMP receptor or the internal cAMP-dependent protein kinase. N6-(aminohexyl) cAMP activates the Dictyostelium cAMP-dependent protein kinase but does not bind to the cell-surface cAMP receptor and does not cause cell-type-specific gene expression. 2'-Deoxy-cAMP does not activate the cAMP-dependent protein kinase but binds to the receptor and causes cell-type-specific gene expression. Cyclic AMP-induced accumulation of prestalk mRNA in shaking cultures still occurs in the presence of caffeine, which blocks the receptor-coupled activation of adenyl cyclase. This suggests that the extracellular cAMP induction of cell-type-specific gene expression in developing Dictyostelium cells is mediated by the cell-surface cAMP receptor and that activating adenyl cyclase by this receptor is not essential. Using the N6-(aminohexyl) cAMP to competitively inhibit phosphodiesterase, we show that 30 nM cAMP is sufficient to induce prestalk or prespore gene expression.
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PMID:cAMP induction of prespore and prestalk gene expression in Dictyostelium is mediated by the cell-surface cAMP receptor. 302 99

A group of 10 patients with chronic asthmatic bronchitis was titrated with slow-release theophylline (Theolin Retard) to a steady state plasma theophylline level of 10 mg/l. After one week of this treatment a single s.c. dose of 0.5 mg terbutaline (Bricanyl) at 10:30 a.m was administered. Lung function at 8:15 a.m. on this day was better than on the reference day without any medication, but the differences were not statistically significant. At 11:00 p.m., 30 min after s.c. administration of terbutaline all lung function parameters (VC, FEV1, MMEF and sGaw) were significantly raised compared to the values of 8:15 p.m. cAMP levels and tremor were significantly higher after the combined medication (30, as well as 150 min after s.c. administration of terbutaline) than on the reference day. This observation implies that we have to be careful with the administration of terbutaline s.c. to patients on theophylline treatment in the daily practice of the lung function laboratory.
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PMID:Pharmacodynamics (lung function tests, tremor measurements and cAMP determinations) of a single dose of 0.5 mg terbutaline subcutaneously during sustained-release theophylline medication in patients with asthmatic bronchitis. 302 43

Constructs were made in which approximately equal to 500 base pairs of the 5' flanking region of the ras gene of Dictyostelium discoideum and variable amounts of the coding region were linked to a ras cDNA in a transformation vector. These constructs then were used to transform Dictyostelium cells and their regulation was examined. In Dictyostelium transformants, transcripts from the ras gene constructs were found at high levels in cells in fast-shaking cultures containing cAMP, whereas transcripts were either not detectable or present at very low levels in cultures lacking exogenous cAMP. In slow-shaking culture, a significantly lower level of ras RNA was detected. When normal developing aggregates were dissociated, RNA from the ras constructs decreased rapidly but then reaccumulated in the presence of cAMP. These results show that the sequences necessary for the response to external cAMP are present within an approximately equal to 650-base-pair region upstream from the ATG start codon and/or within portions of the protein-coding region. Moreover, the proper regulation of ras gene expression in high-copy-number transformants suggests that trans-acting factors which may control transcription are not limiting. Vector constructs were also examined in which the cDNA was present in the opposite orientation compared to the gene fragment (antisense orientation). When these were transfected into cells, no transformants were obtained, suggesting that expression of the ras gene is essential for vegetative growth.
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PMID:Regulated expression of ras gene constructs in Dictyostelium transformants. 386 37

The efficacy of the selective adenosine cyclic 3',5'-monophosphate (cAMP) phosphodiesterase (PDE) inhibitor (+/-)-rolipram and its optical isomers (0.006 to 25 mg kg-1) in inducing characteristic behavioural changes like hypothermia, hypoactivity, forepaw shaking, grooming and head twitches in rats has been examined. (+)-Rolipram was found some 15 times less potent than the racemate suggesting a stereoselective interaction with a rat brain cAMP phosphodiesterase isoenzyme. Following their intracerebral administration, the stereoisomers also demonstrated their unusual potency ratio. These findings suggested that (+)-rolipram is a less potent neurotropic PDE inhibitor in-vivo than its (-)-enantiomer.
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PMID:Neurotropic effects of the optical isomers of the selective adenosine cyclic 3',5'-monophosphate phosphodiesterase inhibitor rolipram in rats in-vivo. 613 85

The effect of the phosphodiesterase (PDE) inhibitors rolipram, Ro 20-1724 and isobutylmethylxanthine (IBMX) on motor behaviour and rectal temperature was studied in mice, rats and guinea pigs following intraperitoneal administration (0.39 to 25 mg/kg). The selective adenosine cyclic 3',5'-monophosphate (cAMP) PDE inhibitors rolipram and Ro 20-1724 in each species caused a dissimilar pattern of neurotropic effects: Hypothermia and hypokinesia in mice, hypothermia, hypokinesia and head twitches in rats, hypothermia, hyperkinesia and head twitches in guinea pigs. The head twitches were associated with forepaw shaking and increased grooming. Rolipram was the most potent compound in the three species. In guinea pigs it was less active than in rats or mice. Ro 20-1724 was approx. 15 to 30 times less potent in inducing the characteristic alterations in the various species. The alkylxanthine PDE inhibitor IBMX, 0.39 to 6.25 mg/kg, slightly stimulated the locomotor activity of mice and rats, most probably due to antagonism of central adenosine actions. IBMX, 6.25 to 25 mg/kg, caused a pattern of neurotropic effects identical to that produced by the selective cAMP PDE inhibitors, indicating the prevalence of the cAMP PDE inhibitory action over the adenosine antagonistic action at higher dosages. IBMX was approx. as potent as Ro 20-1724 in this respect. The species differences in the neurotropic responses to cAMP PDE inhibition in vivo presumably reflect similar differences in the extent of cAMP accumulation in brain tissue of the three species in vitro. Enhanced availability of brain cAMP in vivo in the various rodent species seems to be correlated with diverse patterns of more or less complex motor behavioural symptoms.
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PMID:Species differences in behavioural effects of rolipram and other adenosine cyclic 3H, 5H-monophosphate phosphodiesterase inhibitors. 619 Sep 91

A novel method has been developed for the preparation of nearly pure separate cultures of astrocytes and oligodendrocytes. The method is based on (a) the absence of viable neurons in cultures prepared from postnatal rat cerebra, (b) the stratification of astrocytes and oligodendrocytes in culture, and (c) the selective detachment of the overlying oligodendrocytes when exposed to sheer forces generated by shaking the cultures on an orbital shaker for 15--18 h at 37 degrees C. Preparations appear greater than 98% pure and contain approximately 1-2 x 10(7) viable cells (20--40 mg of cell protein). Three methods were used to characterize these two culture t ypes. First, electron microscopic examination was used to identify the cells in each preparation (mixed and separated cultures of astrocytes and oligodendrocytes) and to assess the purity of each preparation. Second, two oligodendroglial cell markers, 2',3'-cyclic nucleotide 3'-phosphohydrolase (EC 3.1.4.37) and glycerol phosphate dehydrogenase (EC 1.1.1.8) were monitored. Third, the regulation of cyclic AMP accumulation in each culture type was examined. In addition to these studies, we examined the influence of brain extract and dibutyryl cAMP on the gross morphology and ultrastructure of each preparation. These agents induced astroglial process formation without any apparent morphological effect on oligodendrocytes. Collectively, the results indicate that essentially pure cultures of astrocytes and of oligodendrocytes can be prepared and maintained. These preparations should significantly aid in efforts to examine the biochemistry, physiology, and pharmacology of these two major classes of central nervous system cells.
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PMID:Preparation of separate astroglial and oligodendroglial cell cultures from rat cerebral tissue. 624 68

Repeated finger tremor measurements have been performed in six normal and eight asthmatic subjects after subcutaneous and oral administration of terbutaline. Prior to the investigations the patients had not used bronchodilators for 10-14 days. The finger tremor pattern showed a striking parallelism with the terbutaline serum concentrations and with the cAMP plasma levels. After subcutaneous administration the increase in tremor values in asthmatic subjects was significantly less than in normals. This suggests a beta-blockade in skeletal muscle of asthmatics. The difference after oral administration was not statistically significant.
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PMID:Tremor measurement in asthma. II. Changes after terbutaline administration suggesting beta-adrenergic blockade. 629 71

We have identified genes that are expressed preferentially in either prestalk or prespore cells in Dictyostelium. The prestalk mRNAs are detectable at 7.5 hr prior to the completion of cell aggregation, while the prespore mRNAs are not detectable until approximately 15 hr of development. Exogenous cAMP in the absence of sustained cell contact is sufficient to induce prestalk-specific gene expression, while multicellularity is required for the induction of prespore-specific genes. A gene expressed equally in both cell types, which has the same developmental kinetics as the prestalk genes, is induced in shaking culture in the absence of either cAMP or stable cell associations. Dissociation of aggregates results in the rapid loss of prespore- and prestalk-specific mRNAs, and these can be induced to reaccumulate with the addition of cAMP. We conclude that there are substantial differences in the timing and requirements for tissue-specific gene expression in Dictyostelium.
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PMID:Induction and modulation of cell-type-specific gene expression in Dictyostelium. 629 75

Single B-cells have been previously shown to respond poorly to glucose, in contrast to B-cells lodged in intact islets or in small groups of structurally coupled B-cells, isolated as such from islets. To analyze the role of cell coupling in glucose-induced insulin release, single B-cells were reaggregated in vitro and then tested for their secretory capability. Glucose as well as (Bu)2cAMP stimulated the degree of reaggregation during short shaking incubations (up to 180 min); onset of this process was most rapidly observed with (Bu)2cAMP (within 20 min), but after 180 min a comparable extent was measured with either 20 mM glucose or 0.5 mM (Bu)2cAMP. Calcium was an absolute prerequisite for reaggregation of B-cells. Glucose-induced insulin release from reaggregated B-cells was 4-fold higher than from single B-cells; this difference was not caused by some metabolic priming effect of glucose or (Bu)2cAMP, but appeared primarily mediated by the aggregated state of the cells. It is concluded that the secretory response of pancreatic B-cells is highly dependent on their aggregation with other B-cells. Both glucose and cAMP promote the adhesion of B-cells, and this may contribute to their well known insulinotropic effects.
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PMID:Effects of glucose and 3',5'-cyclic adenosine monophosphate upon reaggregation of single pancreatic B-cells. 632 39


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