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T Lin

Publications and source records attributed to T Lin.

At least 55 records · Page 3Linked to original sources
PubMed1987

Transforming growth factor-beta inhibits Leydig cell steroidogenesis in primary culture.

The effects of transforming growth factor (TGF) on Leydig cell steroidogenesis in primary culture were investigated. Basal testosterone levels were 3.7 +/- 0.54 ng/ml (mean +/- SE, N = 7). In the presence of hCG (10 ng/ml), testosterone levels increased to 22.77 +/- 3.05 ng/ml. TGF-beta caused a dose dependent inhibition of hCG-stimulated testosterone formation but without effects on basal levels. TGF-beta also inhibited 8-bromo cyclic AMP-induced testosterone formation and hCG-stimulated cyclic AMP formation. In contrast, TGF-alpha had no effect on either basal or hCG-stimulated testosterone formation and did not modify the inhibitory effect of TGF-beta. Present study indicates that TGF-beta can modulate Leydig cell steroidogenesis.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1987

Frequency-dependent ultrasonic differentiation of normal and diffusely diseased liver.

The attenuation coefficient in 38 pathologically graded in vitro liver specimens was measured over a frequency range from 1.25-8 MHz and fitted to the power law model. The attenuation in the normal group (n = 17) exhibited a frequency dependence of the form 0.399f1.139; in the mild disease group (n = 13), it exhibited a dependence of the form 0.395f1.212; and in the moderate/severe disease group (n = 8), it exhibited a dependence of the form 0.391f1.325. Using a Student's t test, it is shown that, due to these differences in the frequency dependence, the statistical significance level at which the null hypothesis regarding the difference between the mean attenuation slopes of any two of these categories is rejected, is a strong function of frequency in the range of 1-4 MHz. The significance level relating to the difference between the normal and moderate/severe disease group is more than one order of magnitude better than the other categories. In all cases, no substantial improvement occurs beyond 4 MHz. It is also shown that attenuation slope values at 3 MHz confirm in vivo literature results obtained via different techniques.

Fatty Liver↗
PubMed1987

Suppression of the delayed-type hypersensitivity and cell-mediated immune responses to Listeria monocytogenes induced by Pseudomonas aeruginosa.

Pseudomonas aeruginosa-mediated suppression of the immune response to Listeria monocytogenes was investigated in mice. Because delayed-type hypersensitivity (DTH) footpad swelling to L. monocytogenes was suppressed equally in lipopolysaccharide-responsive and -hyporesponsive mouse strains, the lipopolysaccharide component of P. aeruginosa could not have been the suppressive agent. Mucoid P. aeruginosa cells were no more suppressive than their nonmucoid revertants; therefore, mucoid coating was not an additional immunosuppressive element. Interleukin-1 and macrophage inhibitory factor production to L. monocytogenes and clearance of L. monocytogenes from mouse spleens were all decreased by prior Pseudomonas infection, indicating that cell-mediated immunity, as well as DTH, was decreased to a sublethal Listeria dose. The timing of Pseudomonas exposure relative to Listeria sensitization was varied. P. aeruginosa injected 24 or 6 h before or at the same time as L. monocytogenes depressed DTH to Listeria challenge 7 days later. Animals treated in this way could not respond to reinfection with L. monocytogenes at 13 days. P. aeruginosa administered to L. monocytogenes-sensitized mice at the time of footpad challenge was suppressive, but these mice responded normally upon reinfection. It appears that P. aeruginosa induced two types of suppression to L. monocytogenes: a transient suppression, affecting DTH challenge but not resensitization, and a longer lasting suppression that did not permit mice exposed to P. aeruginosa at the time of Listeria sensitization to respond to subsequent Listeria exposure.

Animals↗
PubMed1987

Correlations of sound speed with tissue constituents in normal and diffuse liver disease.

The speed of sound in normal and diffusely-diseased liver specimens was measured. There were four experimental groups, consisting of normal (n = 21), fatty (n = 7), fibrotic (n = 7) and mixed fatty and fibrotic (n = 9). These classifications were based on histological grading. We found that the results corroborate and extend most of the results of Bamber and coworkers. Specifically, no significant correlation was found between speed of sound and fibrosis score; a moderate correlation was found between speed of sound and tissue water content; and a relatively good correlation (r = -0.670, p less than 0.1%) was found between the speed of sound and the histological fat score, which increased to r = -0.819 (p less than 0.1%) when a correction for variations in water content was used.

Fatty Liver↗
PubMed1986

Characterization of insulin and insulin-like growth factor I receptors of purified Leydig cells and their role in steroidogenesis in primary culture: a comparative study.

Characterization of insulin and type I insulin-like growth factor (IGF-I) receptors and the effects of insulin and IGF-I on steroidogenesis were evaluated by using purified adult Leydig cells from Sprague-Dawley rats. Purified Leydig cells were found to contain both high and low affinity binding sites for insulin, with Ka values of 1.08 X 10(9) and 1.1 X 10(7) M-1, respectively. Using affinity cross-linking of [125I]iodoinsulin to plasma membrane insulin receptor, several bands were identified by autoradiography under nonreduced conditions with mol wt of 230,000, 280,000, and 300,000. After reduction with 50 mM dithiothreitol, only one band was identified with a mol wt of 130,000, consistent with the alpha-subunit of insulin receptor. Purified Leydig cells also contain specific type I IGF receptors with estimated binding affinity of 0.6 X 10(9) M-1. Multiple high mol wt bands (greater than 250,000) were identified under nonreduced conditions by affinity cross-linking. Under reduced conditions, one band with an approximate mol wt of 135,000 was identified. Purified Leydig cells (10(5) cells/ml) were cultured in Dulbecco's Modified Eagle's Medium-Ham's F-12 Nutrient Mixture (1:1) containing 0.1% fetal calf serum at 37 C in a humidified atmosphere of 5% CO2-95% air. Insulin and IGF-I stimulated testosterone formation as early as 3 h after administration, and their effects were completely blocked by the addition of a protein synthesis inhibitor, cycloheximide (1 microgram/ml). Insulin and IGF-I also significantly potentiated hCG-and 8-bromo-cAMP-induced testosterone formation. Furthermore, insulin and IGF-I potentiated hCG-stimulated cAMP formation. This suggests that insulin and IGF-I have effects at both the LH receptor sites and the steps beyond adenylate cyclase. The ED50 values of insulin and IGF-I-stimulated testosterone formation were comparable (25 ng/ml). In conclusion, we found that Leydig cells contain specific insulin and type I IGF receptors, and both insulin and IGF-I are capable of modulating Leydig cell steroidogenesis.

Animals↗
PubMed1985

The effects of homogeneous human prealbumin on in vitro and in vivo immune responses in the mouse.

A highly purified preparation of human prealbumin was shown to potentiate the sensitivity of rosette spleen forming cells of adult thymectomized mice to azathioprine in vitro and in vivo and to induce the appearance of the Thy 1, 2 antigen in vitro on spleen cells of adult thymectomized mice. Prealbumin also enhanced IgM antibody synthesis to sheep red blood cells (SRBC) in vitro in 12 week old mice and in vivo in aged (45 - 58 week old) and nude (nu/nu) mice. In vivo administration, to mice that had been pre-treated with hydrocortisone, resulted in a decrease in the specific activity of thymocyte terminal deoxynucleotidyl transferase. The data indicate that the prealbumin molecule possesses immunopotentiating properties in a number of in vitro and in vivo immunocompromised murine models and that the immuno-enhancing properties of the partially purified preparation previously described were in fact due to the prealbumin component and not to other contaminating proteins.

Adjuvants, Immunologic↗
PubMed1985

The role of calcium/phospholipid-dependent protein kinase in Leydig cell steroidogenesis.

Purified rat Leydig cell cytosol was found to contain a protein kinase which was dependent on the presence of both calcium and phospholipids (phosphatidylserine and diolein), i.e. calcium/phospholipid-dependent protein kinase. The peak of Ca/phospholipid-dependent protein kinase was separated from type I and type II cAMP-dependent protein kinase by DE-52 chromatography. 4 beta-Phorbol-12-myristate-13-acetate (PMA), a tumor-promoting agent, could substitute for diolein in activation of Ca/phospholipid-dependent protein kinase. PMA caused dose-dependent increments of testosterone formation by Leydig cells, whereas inactive phorbol esters had no significant effects. PMA-induced testosterone formation was dependent on extracellular calcium and could be blocked by the addition of the calcium channel-blocking agent nifedipine. Since PMA can directly activate Ca/phospholipid-dependent protein kinase and increase testosterone formation, these results suggest that Ca/phospholipid-dependent protein kinase may be involved in modulating Leydig cell steroidogenesis in addition to the classical cAMP-dependent protein kinase pathway.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1979

In vitro studies of the testis: the effect of LH on cyclic nucleotides.

This study evaluated the relationship between LH, cyclic AMP, cyclic GMP, and testosterone using in vitro incubation of decapsulated rat testes and sampling incubation medium. With added LH (1.0, 5.0, 100, and 500 mIU/ml) there were statistically significant increases in cyclic AMP at 5 mIU/ml or more LH, and progressively greater titers of this nucleotide were produced as LH was increased. For cyclic GMP all levels of added LH caused significant increments in titers of nucleotide; however, peak cyclic GMP concentrations occurred with 5 mIU/ml of LH. The addition of 10(-3) and 10-(4)M 8-bromo-cyclic AMP caused significant increases in testosterone production, while no changes in production of this androgen were found with 10(-3), 10(-4), or 10(-5)M 8-bromo-cyclic GMP. Neither cyclic AMP nor cyclic GMP titers were altered by the addition of 1 to 50 micrograms/ml of testosterone to medium bathing the rat testes. The dose response curves of cyclic AMP and cyclic GMP to LH are different. Progressive increments in added LH cause parallel increases of cyclic AMP and a biphasic change of cyclic GMP, 8-bromo-cyclic GMP does not cause testosterone generation, suggesting that cyclic GMP does not result in androgen synthesis. However, cyclic GMP may be involved in other Leydig cell functions.

Animals↗
PubMed1979

Plasma cyclic nucleotide levels in hyperthyroidism.

Plasma cyclic AMP and cyclic GMP levels were studied in a group of normal subjects and 10 subjects with hyperthyroidism. In the control group, mean plasma cyclic AMP levels were 15.3 +/- 1.3 nmol/l (SEM), and plasma cyclic GMP levels were 9.4 +/- 0.58 nmol/l (SEM). In untreated hyperthyroid subjects, both plasma cyclic AMP and cyclic GMP levels were significantly elevated above normal with mean values of 35.0 +/- 2.4 nmol/l (SEM) (P less than 0.001) and 14.7 +/- 0.2 nmol/l (SEM), (P less than 0.001), respectively. Six of the hyperthyroid subjects were re-studied when they became euthyroid; plasma cyclic nucleotide concentrations all fell within the normal range. To evaluate the relative contribution of triiodothyronine and thyroxine to elevated plasma cyclic nucleotide levels, two hyperthyroid subjects were treated with propylthiouracil and iodide. Plasma cyclic nucleotide levels were normalized when plasma triiodothyronine levels declined to normal range, at the time when plasma thyroxine levels were still elevated. These preliminary data suggest that increased triiodothyronine production is responsible for the increased cyclic nucleotide levels in hyperthyroidism.

Adult↗
PubMed1978

Effect of treadmill exercise on plasma and urinary cyclic adenosine 3'5'-monophosphate.

The effect of treadmill exercise on plasma and urinary cyclic adenosine 3'5' monophosphate levels (cyclic AMP) was studied in twelve healthy subjects. Plasma cyclic AMP levels were found to be markedly elevated without significant changes in urinary cyclic AMP or cyclic AMP/creatine ratio. Most likely altered plasma glucagon and catecholamine levels were responsible for these changes.

Adult↗
PubMed1977

Circadian rhythms in the urinary excretion of cyclic 3',5'-adenosine monophosphate (cyclic AMP) and cyclic 3',5'-guanosine monophosphate (cyclic GMP) in human subjects.

Significant circadian rhythns in urinary excretion of cyclic AMP, cyclic GMP, creatinine, 17-hydroxycorticosteroids and inorganic phosphorus were demonstrated in three normal subjects (two males and one post-menopausal female) who collected serial 4-h specimens for periods of 33, 22, and 14 days, respectively. Peak excretion of the above substances occurred, respectively, at approximately 1500-1700, 2300-0200, 1700-1800, 1100-1300, and 1800-2200 h. The estimated amplitudes of the rhythms expressed as a percentage of the mean 4-h excretion rate were 12-13%, 9-13%, 9-15%, 30-78% and 22-26%, respectively. With the possible exception of cyclic GMP, all of the observed rhythms appeared to be sinusoidal, with normal periods of 24 h. The rhythms in both cyclic AMP and creatinine excretion, but not in the remaining substances may be explained largely in terms of the known rhythm in glomerular filtration rate. The factors responsible for the rhythm in cyclic GMP excretion are unknown.

17-Hydroxycorticosteroids↗
PubMed1977

Construction of outcome scales measuring addicts' community functioning.

The current status of research in chemical abuse has depended heavily on unreliable cure rate as a criterion measure. This study was designed to construct reliable and valid quantitative outcome scales. One hundred and eighteen true-false items, all indicating changeable criterion behaviors, were written and administered to 154 hospitalized chemical abusers and 93 staff members. Clinical and factorial manipulation were employed to delete unwanted items. Tentatively, three scales of 41 items were derived, namely, Personal/Economic Independence, Chemical Use, and Job Satisfaction.

Economics↗