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J Segal

Publications and source records attributed to J Segal.

At least 109 records · Page 6Linked to original sources
PubMed1980

Direct and synergistic interactions of 3,5,3'-triiodothyronine and the adrenergic system in stimulating sugar transport by rat thymocytes.

Isolated rat thymocytes were preincubated with various catecholamines, alone and together with 3,5,3'-triiodothyronine (T(3)), and the accumulation of the glucose analogues, 2-deoxy-d-glucose (2-DG) and 3-O-methylglucose (3-O-MG), was then measured. Epinephrine induced a time- and dose-dependent increase in the 15-min accumulation of 2-DG; at a concentration of 100 muM epinephrine, the effect was evident after a preincubation period of only 5 min. The lowest concentration of epinephrine at which a significant effect was evident was 1 muM. Epinephrine also produced a dose-dependent increase in the accumulation of 3-O-MG, and the lowest concentration at which a significant effect was evident was again 1 muM. Isoproterenol, a beta-adrenergic agonist, like epinephrine, increased the accumulation of 2-DG, whereas the alpha-agonist, phenylephrine, had no effect. The response to epinephrine was inhibited by the beta-antagonist, alprenolol, but the alpha-antagonist, phentolamine, had no effect. As previously demonstrated, T(3) increased 2-DG accumulation, and like epinephrine, its effect was blocked by alprenolol. Neither T(3) (0.1 nM) nor epinephrine (0.1 muM) had any effect when acting alone, but when added together at these concentrations, they significantly increased the accumulation of both 2-DG and 3-O-MG. Neither T(3) with isoproterenol nor T(3) with phenylephrine produced a comparable synergistic effect. But T(3) (0.1 nM) acting with isoproterenol (0.1 muM) and phenylephrine (0.1 muM) together, synergistically increased 2-DG accumulation. In addition, the alpha-antagonist, phentolamine, which alone had no effect, inhibited the synergistic effect induced by T(3) and epinephrine. The effects of epinephrine and T(3) alone, as well as their combined synergistic effect on 2-DG accumulation, were not blocked by the inhibitor of protein synthesis, puromycin. FROM THESE RESULTS WE CONCLUDE THE FOLLOWING: (a) the stimulatory effect of the catecholamines on the accumulation of 2-DG and 3-O-MG reflects an action at the beta-receptor; (b) the synergistic interaction between T(3) and epinephrine requires the participation of both beta- and alpha-adrenergic components; (c) T(3) and epinephrine act on 2-DG and 3-O-MG accumulation through a common mechanism or inter-related mechanisms, probably mediated at the beta-adrenergic site; and (d) these effects of T(3) and epinephrine, alone and together, are independent of new protein synthesis. These results suggest that, with respect to the response we are describing, T(3) and epinephrine do not act on nuclear mechanisms, but may act instead at the level of the plasma membrane.

Alprenolol↗
PubMed1980

Triage: overcoming organizational and financial barriers to care for the elderly.

Triage is a model designed to overcome organizational and financial problems inhibiting the provision of appropriate care to the elderly. The model is being evaluated by the functioning status of the elderly, use of services, and health care costs of a group of elderly people served by Triage and one served by the conventional system. Preliminary results show, for the Triage group, improved mental functioning, less use of institutional services, and lower spending on conventional Medicare services.

Aged↗
PubMed1979

Stimulation by triiodothyronine of the in vitro uptake of sugars by rat thymocytes.

Studies were conducted to ascertain the in vitro effect of 3,5,3'-triiodothyronine (T(3)) on the accumulation of the glucose analogue, 2-deoxyglucose (2-DG), by thymocytes freshly isolated from weanling rats. At a concentration of 1 muM, T(3) stimulated the 15-min uptake of (3)H-2-DG after cells had been exposed to T(3) for only 30 min. Significant stimulation of 2-DG accumulation was produced by 1 nM T(3), with increasing stimulation at doses ranging up to 10 muM. T(3) did not alter the fraction of accumulated 2-DG that was phosphorylated, and kinetic studies indicated that its effect was associated with a significant increase in the apparent V(max) of 2-DG accumulation, but not the apparent K(m). T(3) also enhanced the accumulation by thymocytes of the nonmetabolized glucose analogue, 3-O-methylglucose (3-O-MG), an effect that was evidently the result of an increase in 3-O-MG transport into the cell, because it was seen in cells incubated with (3)H-3-O-MG for only 30 s. The proportionate increase in 2-DG accumulation produced by T(3) was not altered by preincubating cells with concentrations of puromycin or cycloheximide sufficient to reduce [(3)H]-leucine incorporation by 95%, and T(3) over a period of >2 h had no effect on [(3)H]leucine incorporation itself. These results indicate that T(3) stimulates the uptake of sugars in rat thymocytes in vitro by an effect on their inward transport. The promptness of the effect and its failure to be inhibited during profound inhibition of protein synthesis further indicate that this effect of T(3) is not mediated through a nuclear-dependent mechanism. Rather, the properties of this response, and of the increases in amino acid and 2-DG accumulation produced by T(3) in other tissue preparations, strongly suggest that these effects of T(3) are mediated at the level of cell membrane.

Animals↗
PubMed1979

Beta-adrenergic potentiation of the increased in vitro accumulation of cycloleucine by rat thymocytes induced by triiodothyronine.

We have previously demonstrated that 3,5,3'-triiodothyronine (T(3)), whether administered in vivo or added to suspending media in vitro, promptly stimulates the in vitro accumulation of the nonmetabolized amino acids, alpha-aminoisobutyric acid, and cycloleucine (CLE) by thymocytes isolated from weanling rats. In these studies, we have examined the in vitro interaction between catecholamines and T(3) with respect to this effect. The previously reported enhancement of CLE accumulation in thymocytes by T(3) in vitro (1 muM) was confirmed. When added alone in concentrations ranging between 10 nM and 0.1 mM, the adrenergic agonists, epinephrine and norepinephrine, had no effect on CLE accumulation. At a concentration of 1 muM, isoproterenol, terbutaline, and phenylephrine were also without effect. However, the effect of T(3) was clearly potentiated by the concomitant addition of epinephrine, norepinephrine, and possibly isoproterenol, whereas terbutaline and phenylephrine were without effect. Neither basal nor T(3)-enhanced CLE accumulation was affected by the addition alone of the adrenergic blocking agents, propranolol (0.1 mM), phentolamine (10 muM), or practolol (0.1 mM). Nevertheless, the beta(1)- and beta(2)-antagonist, propranol, and the beta(1)-antagonist, practolol, blocked the increment in CLE accumulation produced by epinephrine; the alpha-antagonist, phentolamine, was without effect. The enhancement of CLE accumulation that occurred in the presence of T(3), with or without epinephrine, was seen to be a result of an inhibition of CLE efflux, because T(3) alone inhibited CLE efflux, and this effect was increased when epinephrine was also present. On the other hand, neither T(3) alone nor T(3) plus epinephrine appreciably altered the rate of inward transport of CLE. As judged from studies of the ability of thymocytes to exclude trypan blue, neither T(3) alone nor T(3) plus epinephrine either enhanced or impaired viability of cells during 3-h periods of incubation. Cell water content, measured with [(3)H]urea, was unaffected by T(3), either alone or in the presence of epinephrine. In confirmation of previous results, the stimulatory effect of T(3) on CLE accumulation was unaffected by concentrations of puromycin sufficient to inhibit protein synthesis by at least 95%, and the potentiating action of epinephrine on the response to T(3) was similarly unaffected. From these findings, it is concluded that the effect of T(3) to increase CLE accumulation by thymocytes in vitro, though itself independent of adrenergic mediation, is potentiated by beta(1)-adrenergic stimulation. This interaction appears distinctly different from other thyroid hormone-catecholamine interactions, in which thyroid hormones enhance physiological responses to catecholamines. Its mechanism remains unclear, but the properties of the T(3) effect, and possibly the interaction itself, suggest that T(3) enhances CLE accumulation by an action at the level of the cell membrane.

Adrenergic beta-Agonists↗
PubMed1977

The effect of triiodothyronine on 2-deoxy-D-(1-3H)glucose uptake in cultured chick embryo heart cells.

The uptake of 2-deoxy-D-[1-3H]glucose ([1-3H]DOG)by cultured chick embryo heart cells was stimulated by exposure to triiodothyronine (T3). The concentration of free T3 for half maximal stimulation of [1-3H]DOG uptake was 8.7 x 10(-10)M. Nuclear binding studies revealed that the Kd for T3 was 4.2 x 10(-10)M. The molar potencies of other thyroactive compounds in stimulating [1-3H]DOG uptake, relative to L-T3, were: 500% for 3'-isopropyl-3,5-diiodo-L-thyronine, 20% for L-thyroxine (T4), 17% for D-T3, 2.2% for D-T4, 0.6% for 3,5-diiodo-L-thyronine and less than 0.1% for 3',5',3-triiodo-L-thyronine and L-thyronine. These data suggest that cultured chick embryo heart cells may serve in the study of the mode of action of thyroid hormones.

Animals↗
PubMed1977

The effects of actinomycin D, puromycin, cycloheximide and hydroxyurea on 3',5,3-triiodo-L-thyronine stimulated 2-deoxy-D-glucose uptake in chick embryo heart cells in vitro.

The uptake of 2-deoxy-D-[1-3H]glucose ([1-3H]DOG) by cultured chick embryo heart cells was stimulated by L-triiodothyronine (T3). This stimulation began with the exposure to T3, rose linearly for about 8 h and reached a plateau around 24h. Actinomycin D, puromycin and cyclohexmide had no effect on the stimulated sugar uptake during the first 6h. These agents prevented the further increase in the rate of [1-3H]DOG uptake in T3-treated cultures that occurred between 6 and 24h. In the presence of hydroxyurea the uptake of [1-3H]DOG in both control and T3-treated cells was unchanged. These results suggest that some of the effects of T3 may not require new synthesis of either RNA, proteins or DNA.

Animals↗
PubMed1977

The effect 3,5,3'-triiodo-L-thyronine on the kinetic parameters of sugar transport in cultured chick embryo heart cells.

The effect of 3,5,3'-triiodo-L-thyronine (T3; 10(-8)M) on sugar transport was studied in cultured chick embryo heart cells. T3 did not increase the uptake of L-glucose, a sugar which enters the cell by simple diffusion. The effect of T3 on the kinetic parameters of the uptake of both 3-0-methyl-D-glucose (3-OMET) and 2-deoxy-D-glucose (2-DOG) was studied after 6 and 24 h exposure to T3. T3 had no effect on the Km for either sugar. T3 increased the Vmax for the first 6 h or exposure for 3-OMET, a sugar which is only transported, and increased the Vmax after 6 and 24 h for 2-DOG, a sugar both transported and phosphorylated. T3 also increased the relative phosphorylation of 2-DOG within the cells in the period between 6 and 24 h. The data show a biphasic effect of T3 on sugar accumulation, an early effect on transport along and a later effect on phosphorylation as well.

Animals↗
PubMed1977

[Schwannoma of the trachea: discussion of a case and review of the literature].

The authors report the case of a 71 years old woman admitted for severe asthmatic condition of recent origin. The chest X ray showed the opaque image of a tumour against the clearness of the trachea. Its benignity was confirmed by endoscopy. A complete surgical exerese is impossible because of the friable nature of the tumour but was attempted to relieve a worsening respiratory distress. A new intervention was necessary because of a mediastinitis; the patient died of renal insufficiency. Only one observation of schwannoma and 3 cases of tracheo-bronchial schwannoma were found in the literature. The nosological place of these tumours was debated particularly in their relation with Recklinghausen disease. Diagnosis was usually done only a few years after an endoscopic exploration. Some symptoms could nevertheless make up a "tracheal syndrome". Endoscopic exeresis of the tumour successfully tried on some cases should be attempted on a first step.

Adult↗
PubMed1976

Lymphedema tarda.

The clinical recognition and evaluation of congenital lymphedema of the lower extremities with abrupt onset in a 51-year-old man are reviewed. A rational, systematic approach is outlined and exemplifies the use of an interdisciplinary effort to achieve accurate diagnosis through readily available diagnostic procedures.

Age Factors↗