Biomedical subjects
Publications and source records attributed to T Lin.
Experiments were performed in vivo in a mouse model of acute toxoplasmosis to evaluate the effectiveness of the combination azithromycin/sulfadiazine. Azithromycin alone or sulfadiazine alone, at doses that did not provide any protection against death due to toxoplasmosis, were remarkably and significantly synergistic against murine toxoplasmosis when administered in combination.
B-1 (CD5+ B) cells appear early in ontogeny, produce mainly unmutated polyreactive antibodies, and are capable of self-renewal. B-1 cells clonally expand with age and are the malignant cell in chronic lymphocytic leukemia. In this report immunological analysis of B-1 malignancies in NZB mice, a murine model of chronic lymphocytic leukemia, is related to current information on B-1 cells. B-1 clones from NZB mice produce high levels of interleukin-10, detected at the RNA level by semi-quantitative polymerase chain reaction. In addition, the B-1 malignant clones in NZB mice and their hybrids, are negative for B220/6B2 expression, the B-specific antigenic form of CD45 which is a membrane-associated phosphatase involved in lymphocyte activation. Both the autocrine production by B-1 cells of interleukin-10 and altered CD45 expression may be responsible for the clonal expansion of these cells, as well as the accompanying T cell expansion. We report the establishment of an in vitro cytotoxic CD8+ T cell line derived from an NZB with a B-1 malignancy. The effect of B-1 cell-derived interleukin-10 on subsets of T lymphocytes may account for the immunoregulatory properties of B-1 cells. In addition, the NZB malignancies were also characterized for immunoglobulin variable region sequence and antigen specificity. The B-1 malignancies produced immunoglobulin derived from unmutated germline sequences with no N base substitutions. It appears that both the immunoglobulin and interleukin-10 produced by the B-1 malignant cell in NZB mice may have immunoregulatory properties. A study of B-1 malignancies may shed light on the immunoregulatory properties of non-clonally expanded normal B-1 cells.
The activity of the macrolide antibiotic clarithromycin was examined alone or in combination with other drugs for the treatment of acute or chronic infections with Toxoplasma gondii in mice. A dose of 300 mg of clarithromycin per kg per day administered alone for 10 days, beginning 24 hours after infection, protected 10 to 30% of mice infected with lethal inocula of tachyzoites or tissue cysts of different strains of T. gondii, including some strains isolated from patients with both AIDS and toxoplasmosis. Although clarithromycin was protective, a wide variation in its activity against different strains was observed. Survival of infected mice was increased significantly by treatment with clarithromycin in combination with pyrimethamine or with sulfadiazine. Treatment of chronically infected mice with clarithromycin at 300 mg/kg/day administered alone for 8 weeks resulted in significant reduction in the numbers of T. gondii cysts in their brains. The combination of clarithromycin and minocycline resulted in an activity against T. gondii cysts that was significantly greater than the activity of clarithromycin or minocycline administered alone. These results indicate a role for clarithromycin in the treatment of human toxoplasmosis, particularly when this antibiotic is used in combination with other drugs with activity against T. gondii.
We have reported previously that insulin-like growth factor-I (IGF-I) messenger RNA (mRNA) is expressed in Leydig cells and that IGF-I can enhance androgen production, whereas interleukin-1 (IL-1) is a potent inhibitor of Leydig cell steroidogenesis. Molecular cloning studies have confirmed the existence of at least two species of IL-1: IL-1 alpha and IL-1 beta. Both IL-1 alpha and beta bind to the same receptors and have the same spectrum of biological activities. The purpose of the present study was to elucidate the molecular mechanisms of the interaction between IGF-I and IL-1 both in vivo and in vitro. Adult Sprague-Dawley rats (55-65 days old) were treated with three injections of human recombinant IL-1 beta (1 microgram/rat ip) at 12-h intervals. Rats were killed 2 h after the last injection of IL-1 beta. Purified Leydig cells were isolated and RNA extracted for Northern blot analyses. For in vitro studies, highly purified Leydig cells were cultured in Dulbecco's modified Eagle's medium/F-12 supplemented with 0.1% fetal calf serum with or without IL-1 beta (1-100 ng/ml) for 24 h. RNA was then extracted from these cells. For time course studies, purified Leydig cells were initially cultured for 24 h. Fresh medium was then added with or without IL-1 beta (10 ng/ml), and the cultures were continued for an additional 2, 4, or 6 h. In vivo administration of IL-1 beta inhibited IGF-I mRNA expression in Leydig cells (a 40% reduction, P less than 0.05). IL-1 beta also suppressed IGF-I mRNA expression in Leydig cells in vitro in a time- and dose-dependent fashion. Inhibitory effects of IL-1 beta (10 ng/ml) could be demonstrated as early as 2 h and reached a nadir at 6 h (a 60% reduction, P less than 0.05). IL-1 beta (100 ng/ml) inhibited IGF-I mRNA expression to about 10% of the controls (P less than 0.01). Moreover, the inhibitory effect of IL-1 beta could be reversed by the addition of IL-1 receptor antagonist. In conclusion, IL-1 beta could directly inhibit the mRNA expression in Leydig cells for IGF-I, an important autocrine modulator of Leydig cell function. This suggests that the effect of IL-1 beta on Leydig cell function is, at least in part, achieved by down-regulation of IGF-I mRNA levels.
We studied relative changes of serum cholesterol in obese patients during and after weight loss to determine if they depend on initial cholesterol levels as classified by the National Cholesterol Education Program. Three groups of obese free-living outpatients with desirable (normal) (less than 5.17 mmol/l, n = 26), borderline-high (5.17-6.18 mmol/l, n = 29), and high (greater than 6.21 mmol/l, n = 32) initial total cholesterol completed a 26-week program employing a very low calorie diet. The program involved 12 weeks of supplemented fasting, followed by 6 weeks of refeeding and then 7 weeks consumption of step 1 diet that maintained the new reduced weight. The groups were similar in initial clinical characteristics and they also lost comparable percentages of initial weights. Relative reduction in total cholesterol throughout the study was significantly larger in both borderline-high and high cholesterol groups compared to normal. In patients of borderline-high and high cholesterol groups favourable and significant reduction of total cholesterol, LDL cholesterol, total cholesterol/HDL cholesterol, and LDL cholesterol/HDL cholesterol ratios were maintained at the end of the study. The percent decrease in total serum cholesterol at the end of the study positively correlated with the percent of weight loss in patients of the high cholesterol group. We conclude that obese hypercholesterolemic patients have favorable changes in cholesterol profile following weight loss, and that relative reduction of cholesterol levels depend on initial levels. However, specific roles of weight loss, change in diet and/or increased physical activity in observed changes in lipid profiles cannot be determined by this study.
We describe an adult patient who developed persistent hypercalcemia while bedridden for more than three months with pancreatitis and sepsis. On the basis of hypercalciuria, suppressed serum intact PTH, suppressed serum 1,25-dihydroxy vitamin D3 and no clinical evidence of malignancy, the diagnosis of immobilization hypercalcemia was established His hypercalcemia improved during treatment with saline, calcitonin and/or etidronate. With active mobilization and weight-bearing exercises, serum calcium finally normalized. We discuss clinical and laboratory features as well as current modalities of treatment of this rare form of hypercalcemia in adults.
Schisanhenol (SAL) had been shown to have potent antioxidant activities. The protective effects of SAL against oxygen radical induced mitochondrial injuries of rat heart and liver were investigated in the present study. The ferrous-cysteine induced mitochondrial lipid peroxidation was significantly inhibited by SAL, while the loss of ATPase activity induced by the lipid peroxidation was prevented. The rigidification of mitochondrial membrane, as well as swelling, lysis and disintegration of the mitochondria induced by ferrous-cysteine were all significantly inhibited by SAL. These results further confirm that SAL possesses antioxidant activity.
Recent work has implicated the activated ras oncogene, whose gene product is a G-protein located in the plasma membrane, as well as the activated raf oncogene, whose gene product is a membrane-associated protein kinase, in contributing to radioresistance. Another transforming oncogene whose gene product is localized to the plasma membrane is v-src. We have examined a rat fibroblast line (RAT-1) infected with an avian sarcoma virus carrying a temperature-sensitive mutation in the v-src tyrosine kinase domain (LA-24). At 40 degrees C, LA-24 cells have a flat morphology and grow as a contact-inhibited monolayer, while at 35 degrees C, LA-24 cells have a transformed morphology, lose contact inhibition, grow in soft agar, and exhibit 3.5-fold higher tyrosine kinase activity. The parental RAT-1 line, not infected by the virus, grows at both temperatures as a contact-inhibited monolayer. This well-characterized system represents a good model for examining the effect of v-src transformation on radiosensitivity. RAT-1 and LA-24 cells grown at 35 and 40 degrees C were irradiated with graded doses of radiation, and clonogenic survival was assayed. For LA-24 cells grown at 35 and 40 degrees C, and for RAT-1 cells grown at 35 and 40 degrees C, calculated D0, n, alpha, and beta values did not differ significantly. To determine whether there might be differences in radiation damage repair capacity too subtle to detect by comparing radiation survival curves, sublethal damage repair capacity was assessed. There was no difference in sublethal damage repair capacity for LA-24 cells grown at 35 or 40 degrees C. Other studies have associated multidrug resistance with radioresistance. We have examined the radiation sensitivity of two colchicine-resistant LA-24 clones with four- to fivefold amplification of the P-glycoprotein gene, which are four-to fivefold more resistant to colchicine than the parental LA-24 line. In these multidrug-resistant clones, v-src activation does appear to increase radiation resistance. This did not appear to be due to alteration in cell cycle kinetics. We conclude that oncogene activation, or even protein kinase activity per se, does not necessarily lead to radiation resistance. Rather, radiation resistance following oncogene activation depends upon the oncogene and cell line studied, and perhaps upon specific protein phosphorylation.
Explore the source record for details and available documents.
Previously we have reported that interleukin-1 (IL-1) is a potent inhibitor of Leydig cell function. Most recently, IL-1 receptor antagonist (IL-1ra) has been purified, sequenced and cloned. In the present study, we evaluated the recombinant monocyte-derived IL-1ra on the inhibitory effects of IL-1. The addition of recombinant human IL-1ra up to 1000 ng/ml has no discernible effects on human chorionic gonadotropin (hCG)-stimulated testosterone formation in primary cultures of rat Leydig cells. Similar to that reported previously, IL-1 beta caused a dose-dependent inhibition of hCG-induced testosterone. The inhibitory effect of IL-1 beta could be reversed by the concomitant addition of IL-1ra. The amounts of IL-1ra required to reverse the effect of IL-1 were 25-fold higher. Our results suggest that IL-1 is important in modulating Leydig cell function and its effect most likely is mediated by specific IL-1 receptors.
Interleukin-1 (IL-1) is a potent inhibitor of Leydig cell function. We have reported that IL-1 inhibited hCG-induced cAMP and testosterone formation. In the present study we evaluated the effect of IL-1 on Leydig cell cholesterol side-chain cleavage cytochrome P450 (P450scc) mRNA levels. P450scc is the rate-limiting enzyme for Leydig cell steroidogenesis. Highly purified Leydig cells were prepared from adult Sprague-Dawley male rats (55-65 day-old) using the combination of elutriation and Percoll gradient. Purified Leydig cells were then cultured with or without IL-1 beta (1-100 ng/ml) and recombinant human monocyte-derived IL-1 receptor antagonist (250 ng/ml) for 24 h. hCG (10 ng/ml), 8-bromo-cAMP (0.1 mM), or 4 beta-phorbol 12 beta-myristate 13 alpha-acetate was then added, and cultures were continued for an additional 6 h. P450scc mRNA levels of Leydig cells were very low to undetectable after 24 h in culture and could be stimulated by the addition of either hCG (10 ng/ml) or 8-bromo-cAMP (0.1 mM), but the addition of 4 beta-phorbol 12 beta-myristate 13 alpha-acetate had no effect. P450scc mRNA levels increased as early as 2 h after the addition of hCG. Furthermore, cycloheximide (1 microgram/ml) markedly blocked hCG-induced P450scc mRNA expression. This indicates that synthesis of a labile new protein(s) is required for the induction of P450scc mRNA by hCG. IL-1 beta inhibited hCG-stimulated testosterone formation and P450scc mRNA expression in a dose-dependent manner. The inhibitory effects of IL-1 beta could be reversed by the concomitant addition of IL-1 receptor antagonist. Our results suggest that P450scc mRNA levels of Leydig cells are modulated by IL-1. This may be one mechanism that could explain the inhibitory effects of IL-1 on Leydig cell steroidogenesis.
The effects of hCG, 8-bromo-cAMP, 4 beta-phorbol 12 beta-myristate 13 alpha-acetate, and forskolin on insulin-like growth factor-I (IGF-I) receptor gene expression of Leydig cells were studied. The treatment of purified Leydig cells with hCG caused a dose-dependent increase in [125I]IGF-I binding to Leydig cells without changes in binding affinity, indicating that the increased binding was due to increased receptor numbers and not to increased affinity. The minimal time required for hCG to induce IGF-I binding was 6 h, and it had reached a plateau at 16 h. 8-Bromo-cAMP (1 mM) increased IGF-I binding about 2-fold, and forskolin (10 microM) increased binding about 51%. Using the ribonuclease protection assay, we found that hCG and 8-bromo-cAMP could increase IGF-I receptor mRNA expression as early as 2 h before the increase in IGF-I binding. The induction by hCG was over 3.5-fold at 4 h and decreased to about 2-fold at 6 h. 4 beta-Phorbol 12 beta-myristate 13 alpha-acetate had a very small effect on IGF-I receptor mRNA levels (1.5-fold increase at 2 h and no changes at 4 and 6 h). In conclusion, IGF-I receptors can be up-regulated by hCG, 8-bromo-cAMP, and forskolin. The up-regulation of IGF-I receptor number is associated with transient increases in IGF-I receptor mRNA levels. This could be a mechanism by which hCG and IGF-I interact to enhance Leydig cell steroidogenesis.
Previously, we have reported that interleukin-1 (IL-1) can modulate Leydig cell steroidogenesis. Recently, IL-1-like material has been shown to be present in the testis; however, the cellular source of this material remains unclear. In the present study we found that human recombinant IL-1 beta (1-100 ng/ml) caused dose-dependent increases in IL-1 alpha mRNA expression in Leydig cells. Similar to that reported in other tissues, IL-1 alpha mRNA from Leydig cells is mainly 2.2 kilobases. IL-1 alpha mRNA expression in Leydig cells was detectable as early as 2 h after the addition of IL-1 beta (10 ng/ml) and persisted for up to 24 h. Lipopolysaccharide also stimulated IL-1 alpha mRNA expression in these cells, but phorbol ester had no effect. Our results indicate that Leydig cells are a potential source of IL-1, which has both autocrine and paracrine effects.
In the present study, we evaluated insulin-like growth factor-I (IGF-I) messenger RNA expression in the rat testis. Crude interstitial cells were separated into three distinct bands on 15-60% Percoll density gradients. IGF-I mRNA was mainly localized in the Leydig cell-enriched fraction (band 3), while band 1 and band 2 cells did not contain significant amounts of IGF-I mRNA. Leydig cell IGF-I mRNA consisted of multiple species varying from 0.8 to 7.5 kb and was present in rat Leydig cells all ages examined, from 25 to 55 days old. To further document that IGF-I mRNAs are present in Leydig cells, the method of Klinefelter et al. (Biol. Reprod. (1987) 36, 769-783) was used to isolate highly purified (greater than 98% pure) Leydig cells. Most of the IGF-I mRNA was localized in these Leydig cells, while there was no detectable IGF-I mRNA in the whole testis or other interstitial cells. Furthermore, IGF-I mRNA in Leydig cells was increased more than 2-fold by growth hormone (GH) administration in vivo. This suggests that IGF-I mRNA in Leydig cells is also GH dependent. Interstitial IGF-I produced in Leydig cells may have both autocrine and paracrine effects in the testis.
Previously we have reported that human chorionic gonadotropin(hCG)-stimulated testosterone biosynthesis was markedly inhibited by purified natural human interleukin-1 (IL-1). In the present study we evaluated the effects of human and murine recombinant IL-1 (rIL-1) on Leydig cell steroidogenesis in primary culture. Human rIL-1 beta caused a dose-dependent inhibition of hCG-, 8-bromo cyclic AMP-, and forskolin-induced testosterone formation. In contrast, human rIL-1 alpha was considerably less potent. When the effects of the cytokines were corrected for their biological potencies, human rIL-1 beta and murine rIL-1 alpha were still more effective than human rIL-1 alpha in inhibiting testosterone production (at least 100-fold more potent). Thus, even though IL-1 alpha and IL-1 beta bind to the same receptors on T cells, Leydig cells exhibit differential sensitivity in response to rIL-1 alpha and rIL-1 beta which is partly species dependent.
Human recombinant tumor necrosis factor-alpha (rTNF alpha) alone (up to 1000 units/ml) did not alter either basal or human chorionic gonadotropin (hCG)-induced testosterone formation in primary culture of rat Leydig cells. However, concomitant addition of rTNF alpha with human recombinant interleukin-1 beta (rIL-1 beta) enhanced the inhibitory effects of rIL-1 beta. The rIL-1 beta dose response curve was shifted to the left (IC50 changed from 1 ng/ml to 0.3 ng/ml). Even though rTNF alpha had no effect on testosterone formation, hCG-stimulated cyclic AMP formation was inhibited by rTNF alpha in a dose dependent manner. In the presence of both rTNF alpha and rIL-1 beta, hCG-induced cyclic AMP formation and binding of [125I]-hCG to Leydig cells were further inhibited. Testicular macrophages represent about 20% of the interstitial cells. TNF alpha and IL-1 may be produced locally by interstitial macrophages and have paracrine effects on Leydig cell function.
A vision-dependent feedback mechanism contributes to the regulation of postnatal eye growth and refraction; this mechanism is located at least in part in the retina. In chicks and rhesus monkeys, visual deprivation leads to ocular enlargement and a myopic refractive error, and it also reduces the retinal concentration of dopamine. In neonatal chicks, local application of the dopamine agonist apomorphine limits the excessive axial elongation that is associated with visual deprivation. Both D1 and D2 dopamine receptor mechanisms may participate. Remarkably, apomorphine is geometrically selective, not limiting the exaggerated equatorial growth that occurs during visual deprivation. Preliminary results in neonatal rhesus monkeys indicate that apomorphine eye drops also suppress exaggerated axial growth and myopic refractive error during visual deprivation; equatorial diameters were not measured. Our observations are consistent with a retinal hypothesis for emmetropization and suggest that retinal dopamine participates in a mechanism linking ocular growth control to vision. In addition, we conclude that axial and equatorial dimensions are independently regulated in the chick.
Two cases of germ cell tumors (GCTs) of the basal ganglia are presented and 40 previously reported cases are reviewed. The incidence of GCTs of the basal ganglia and thalamus was estimated as less than 14% of all intracranial GCTs. All patients except for two (95%) were male, aged 7-19 years. The clinical course was usually slow. The major symptoms were hemiparesis, mental deterioration such as dementia or character change, precocious puberty, diabetes insipidus, oculomotor palsy, speech disturbance, and hemianopsia. Signs of intracranial hypertension did not occur until the late stages of the disease. The plain CT finding was characterized by an irregularly defined, slightly high-density area frequently accompanied by central low-density areas without significant mass effect. The tumors showed mild to moderate and nonhomogeneous contrast enhancement. An ipsilateral cerebral hemiatrophy was often found. MR images demonstrated the corresponding findings. GCTs of the basal ganglia had a high possibility of containing components other than germinoma such as choriocarcinoma, endodermal sinus tumor, and embryonal carcinoma. Thus, tumor markers in the serum, CSF, or cyst fluid were frequently positive. With recent refinement of microsurgical techniques as well as immunohistochemical study and measurements of tumor markers of serum, CSF, and cyst fluid, major resections of tumor, accurate pretreatment histologic diagnosis, and early determination of the specific types of this tumor appear to be readily possible. This is essential for effective treatment of patients not only with radiosensitive germinoma, but also those with radioinsensitive nongerminoma variants and a combination of them located in this region.