Biomedical subjects

M Goh

Publications and source records attributed to M Goh.

24 records · Page 2Linked to original sources

PubMed1986

The dopaminergic regulation of plasma growth hormone secretion in normal subjects.

The role of endogenous dopamine (DA) on plasma GH secretion was studied using domperidone (DA receptor blocker which does not cross blood brain barrier) in 16 normal subjects. After a bolus injection of domperidone (10 mg, i.v.), plasma PRL in 11 cases rose quickly and markedly from the basal level of 9.5 +/- 1.2 ng/ml (Mean +/- S.E.) to a maximum of 76.3 +/- 10.6 ng/ml at 30 min. In contrast, plasma GH in these cases showed a delayed and slight increases to domperidone injection where the values at 90 min and 120 min (3.5 +/- 0.8 ng/ml and 3.7 +/- 1.0 ng/ml) were significantly higher than those in control study (1.2 +/- 0.2 ng/ml and 1.0 +/- 0.1 ng/ml; p less than 0.05; n = 8). Domperidone infusion (0.22 mg/min/3 hr) was performed in the remaining 5 subjects. The plasma PRL responses were similar to those in the bolus injection of domperidone. These PRL responses were not modified when L-dopa was administered 30 min after the start of iv infusion of domperidone. Plasma GH showed slight but significant increases 135 min after the infusion compared to control study (4.3 +/- 1.2 ng/ml vs. 1.0 +/- 0.1 ng/ml; p less than 0.05). By the prior infusion of domperidone plasma GH responses to L-dopa was delayed and blunted, i.e., the occurrence of elevation and peak value of GH delayed by 15 min.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

Modulation of postinhibitory increase in plasma prolactin by domperidone in patients with prolactin secreting adenoma.

To evaluate the PRL secretory mechanism in patients with PRL-secreting adenoma (PRL-oma), plasma PRL responses to dopamine (DA) were studied in these cases and in normal subjects. Plasma PRL values showed clear decreases during the infusion of DA (5 micrograms/kg/min for 90 min) in both 6 normal and 7 PRL-oma subjects (%decrease: 43.8 +/- 3.9% vs. 53.9 +/- 5.6%; NS) and postinhibitory increases after the termination. However, the postinhibitory increase occurred more promptly and markedly in PRL-oma patients than in normal subjects, i.e. the postinhibitory increase exceeded the basal level 45 min after the termination of DA infusion in PRL-oma patients, whereas the increase in normal subjects did not exceed the basal level even 90 min after the infusion. When domperidone was injected at the termination of DA infusion, the postinhibitory increases were significantly enhanced in either PRL-oma or normal subjects. The maximal increments in plasma PRL in the combination test of DA plus domperidone were significantly larger in PRL-oma patients, but were almost the same in normal controls, compared to the single domperidone test. In contrast, TRH did not modify the postinhibitory rises in 9 PRL-oma patients. These results indicate that the secretory properties and the sensitivities of lactotrophs to decreasing action of DA might be different between PRL-oma patients and normal controls. Further, the postinhibitory rebound phenomenon in PRL-oma patients is possibly determined by an overshoot of PRL storage concomitantly with a decreasing DA action.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenoma↗

PubMed1985

GHRF test in acromegalic patients for the evaluation of therapeutic results.

We studied here the clinical significance of GHRF test in evaluating therapeutic results in patients with acromegaly. Three cases of acromegaly were studied at pre- and posttreatment. Case 1 is a 42 year old woman, and her plasma GH showed slight increases responding to TRH and arginine administration before therapy. Eleven years after the pituitary irradiation, basal plasma GH decreased to low normal ranges and showed no response to the above two agents. Only an insufficient increase in plasma GH was observed after GHRF injection. This case would have pituitary lesions not only in the tumor somatotrophs but also in the normal somatotrophs. Case 2 is a 38 year old man. His plasma GH showed a marked increase after TRH injection. To GHRF administration, however, no clear response was observed. After transsphenoidal adenomectomy, the aberrant responses to TRH was still observed despite the marked GH decrease to the near normal ranges. Interestingly, plasma GH became responsive to GHRF after the operation. It seems that the adenomectomy was inadequate in this case and the normal somatotrophs recovered the responsiveness to GHRF. Case 3 is a 53 year old woman, and she showed aberrant GH responses to TRH and to L-dopa. Her plasma GH clearly increased after GHRF injection. Postoperatively, the abnormal responses of plasma GH disappeared completely, while a normal GH response was observed following GHRF injection.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗

PubMed1984

Modulation of postinhibitory rebound rise in plasma GH by hypothalamic hormones in patients with acromegaly.

To evaluate the GH regulating mechanism in acromegalic patients, post-inhibitory rebound rise in GH secretion induced by somatostatin was studied in these cases and normal subjects, and was compared with the rebound GH rise induced by dopamine. After somatostatin infusion (500 micrograms/75 min) both 5 normal and 9 acromegalic subjects showed prompt GH decreases during the infusion (% decrease: 69.1 +/- 10.4 vs 74.4 +/- 5.1) and showed rebound rises after its termination. However, the rebound rises occurred more promptly and markedly in normal controls than in acromegalic patients, i.e. the rebound peak appeared at 45 min in normal controls and at 75 min in acromegalic patients after the cessation of somatostatin infusion. Dopamine (DA) infusion (5 micrograms/kg/min for 90 min) also induced similar inhibition and postinhibitory rebound rises in GH secretion in 7 patients with acromegaly. Although the maximum inhibition (65.6 +/- 6.4% vs 74.4 +/- 5.1%) and the inhibitory area (4338.0 +/- 481.5% X min vs 3682.5 +/- 295.5% X min) during the DA or somatostatin infusion were not different, the rebound at 15 min was significantly greater after DA than after somatostatin (p less than 0.02). When TRH was injected at the termination of somatostatin infusion, the rebound increase was significantly enhanced and the rebound peak appeared 45 min earlier than after a single somatostatin administration. Similarly, hp GRF (1-44)-NH2 enhanced the postinhibitory rebound rises in 4 patients studied.(ABSTRACT TRUNCATED AT 250 WORDS)

Acromegaly↗

PubMedDate not supplied

Phenylbutyrate attenuates the expression of Bcl-X(L), DNA-PK, caveolin-1, and VEGF in prostate cancer cells.

Phenylbutyrate (PB) is a histone deacetylase inhibitor that has been shown to induce differentiation and apoptosis in various cancer cell lines. Although these effects are most likely due to modulation of gene expression, the specific genes and gene products responsible for the effects of PB are not well characterized. In this study, we used cDNA expression arrays and Western blot to assess the effect that PB has on the expression of various cancer and apoptosis-regulatory gene products. We show that PB attenuates the expression of the apoptosis antagonist Bcl-X(L), the double-strand break repair protein DNA-dependent protein kinase, the prostate progression marker caveolin-1, and the pro-angiogenic vascular endothelial growth factor. Furthermore, PB was found to act in synergy with ionizing radiation to induce apoptosis in prostate cancer cells. Taken together, our results point to the possibility that PB may be an effective anti-prostate cancer agent when used in combination with radiation or chemotherapy and for the inhibition of cancer progression.

Apoptosis↗

PubMedDate not supplied

Effect of food-simulating liquids on the flexural strength of composite and polyacid-modified composite restoratives.

This study investigates the effects of food-simulating liquids on composite and polyacid-modified composite restoratives. Three composite (Z100, Spectrum TPH, and Tetric Ceram) and three polyacid-modified composite (F2000, Dyract AP, and Compoglass) restoratives from the same manufacturers were selected for the study. Flexural strength specimens (25 x 2 x 2 mm) based on ISO 4049 specifications were fabricated according to the manufacturers recommendations. After light polymerization, the specimens were removed from their molds and conditioned for one week at 37 degrees C in the following mediums: (1) deionized water, (2) 0.02 M citric acid, (3) heptane, and (4) 50% ethanol-water solution. Specimens stored in air were used as controls. The sample size was five for each material-medium combination. After conditioning, the specimens were blotted dry, measured, and subjected to flexural strength testing using an Instron Universal Testing Machine with a crosshead speed of 0.05 mm/minute. With the exception of Compoglass, flexural strength of all restoratives after conditioning in heptane was significantly greater than that after conditioning in all other mediums and the control. Although no significant difference in flexural strength values was observed between the different restoratives when the materials were conditioned in heptane or air (control), significant differences were observed between the different restoratives after conditioning in aqueous solutions (water, citric acid, and ethanol-water solution). The flexural strengths of the composites were generally significantly higher than their polyacid-modified counterparts after conditioning in the various aqueous solutions. The detrimental effects of aqueous solutions on flexural strength appeared to be greater with polyacid-modified composite resins than with composite restoratives.

Air↗