Melatonin inhibits naloxone-induced luteinizing hormone release in ovariectomized estrogen-primed rats

The present study aimed to examine the effect of melatonin on naloxone-induced luteinizing hormone (LH) secretion in ovariectomized estrogen-primed rats. A single intracerebroventricular (i.c.v.) injection of naloxone (mu opioid receptor blocker, 15 micrograms) or an intravenous (i.v.) injection of LH-releasing hormone (LHRH, 50 ng/kg) elicited a transient and significant increase in the serum LH concentration within 10 min. While an i.c.v. injection of 100 ng melatonin by itself did not change the basal LH release, it almost completely inhibited the naloxone-induced LH release. Melatonin (10 ng) also significantly reduced the effect of naloxone. However, an i.c.v. injection of 100 ng melatonin did not affect the LHRH-induced LH release. In separate experiments, the effect of melatonin on naloxone-induced pulsatile LH secretion was studied in estrogen-treated rats. A continuous i.v. infusion of naloxone (20 mg/kg/h) induced LH pulses in rats treated i.c.v. with saline. An i.c.v. administration of 100 ng melatonin, which by itself did not affect basal LH secretion, significantly reduced the frequency, but not the amplitude, of LH pulses induced by the naloxone infusion. These results show that melatonin has a suprapituitary site of action to inhibit naloxone-induced LH release, and suggest that melatonin has an effect in inhibiting the activity of the hypothalamic LHRH pulse generator, either directly or indirectly, in female rats.     

Monomer recycling for vulcanized silicone rubbers in the form of cyclosiloxane monomers. Role of acid buffers

The KOH-catalyzed depolymerization of vulcanized silicone rubbers to reproduce cyclosiloxane monomers was studied. First, the depolymerization was carried out in toluene with varying amounts of KOH to find that the yield of monomers first increased and then decreased with the increment of KOH, the highest yield was 65% at the molar ratio KOH/(Si–O) UNITS=0.08. At the molar ratio 0.13 in the absence of solvent, the monomers yield was 46%. However, when an acid buffer such as KH₂PO₄ and KCOOC₆H₄COOH was added after the KOH-catalyzed depolymerization was over, the product yield was increased remarkably to more than 80%.     

Molecular analysis of p21 and p27 genes in human pituitary adenomas

OBJECTIVES: To determine the prevalence of thyroid dysfunction in institutionalised elderly people in Cape Town and to assess the usefulness of an abnormal thyroid-stimulating hormone (TSH) concentration as a screening test in this group. DESIGN: Cross-sectional survey. SETTING: Four old-age homes in Cape Town. SUBJECTS: Old-age home residents aged 60 years and over. OUTCOME MEASURES: Serum concentrations of TSH, free thyroxine and free tri-iodothyronine. RESULTS: Serum TSH estimations were performed on 658 participants, and were abnormal in 103 (15.6%)-41 (6.2%) being elevated (> 5.0 microU/ml) and 62 (9.4%) being low (> 0.4 microU/ml). There were 3 newly diagnosed cases of hyperthyroidism and 7 of hypothyroidism. Subclinical disease was diagnosed in 40 subjects. The overall prevalence of thyroid dysfunction in this population was 11.2%. In 22 (3.4%) this had previously been recognised, while in 50 (7.8%) the dysfunction was newly diagnosed by the current survey. The positive predictive value of a TSH concentration > 20 microU/ml in predicting hypothyroidism is 67%, while it will predict 100% of cases of subclinical hypothyroidism. A TSH concentration < 0.1 microU/ml will predict 23% of cases of hyperthyroidism, but 81% of cases of subclinical disease. CONCLUSIONS: The prevalence of thyroid dysfunction in institutionalised elderly people in Cape Town is similar to that reported for elderly people in other centres. Thyroid dysfunction had not previously been recognised in approximately two-thirds of the subjects in this study. The serum TSH concentration is a reliable screening test for thyroid dysfunction in the elderly, but is less useful if used to identify biochemical thyroid disease. An elevated TSH concentration is a better predictor of thyroid dysfunction in the elderly than a depressed TSH concentration.     

TDMA based adaptive modulation with dynamic channel assignment(AMDCA) for large capacity voice transmission in microcellular systems

The authors propose an adaptive modulation with dynamic channel assignment (AMDCA) to achieve high capacity voice transmission in microcellular systems. The proposed system measures the received carrier-to-noise plus interference power ratio (C/(N+I)) of each time division multiple access (TDMA) slot to search for available slots and to discover the optimum modulation parameters for each slot, thereby effectively combining the buffeting effect of spatially distributed electric field strength by slow adaptive modulation, and that of spatially and temporally distributed traffic by dynamic channel assignment (DCA). Computer simulation confirms that the proposed AMDCA system can achieve ~7.5 times higher system capacity than the conventional QPSR with a fixed channel assignment (FCA)     

Transiliac catheterization of the inferior vena cava for long-term venous access in children

In infants and children requiring prolonged, multiple central venous (CV) catheterizations, the superior (SVC) and inferior vena cava may become thrombosed or stenotic, making CV access a difficult problem. Use of the iliac vein may be an acceptable alternative. We report a patient with thrombosis of the SVC in whom the external iliac vein was accessed through a retroperitoneal approach for placement of an implantable port. This technique is easy to perform, and there are no special materials or patient positioning required.     

Myositis caused by hydroxyurea in a patient with chronic myelogenous leukemia

A 59-year-old man with chronic myelogenous leukemia (CML) had a white-blood-cell (WBC) count of 55,400/microliter when admitted in July 1997, and was placed on oral hydroxyurea (HU) of 1,500 mg/day. Treatment with 600 MU/day of interferon alpha (IFN alpha) was started on August 5. HU was discontinued when the patient's WBC count dropped to 8,100/microliter on August 18. However, HU was resumed about a month later, after his WBC count increased to 10,100/microliter, but discontinued when the patient started to complain of chills, high fever, and bilateral femoral pain. HU treatment was initiated again one week later, after the patient's WBC count had begun rising but ceased again after he experienced chills, high fever, and bilateral femoral pain. The patient's myogenetic enzymes were found to be increasing the following day, and a lymphocyte stimulation test (LST) with HU showed a high stimulation index of 41.7%. The elevation of myogenetic enzymes and the results of the LST suggested that myositis due to HU was the cause of the patient's clinical manifestations. His myositis spontaneously disappeared after HU was discontinued. Although the patient is no longer receiving HU, IFN alpha has brought his CML under control. To our knowledge, this is the first reported case of myositis caused by HU.     

Appraisal of a manual blunt dissection for an intraoperative diagnosis of extrahepatic cancer invasion

BACKGROUND/AIMS: Liver cancer extension to the adjacent organs does not necessarily indicate tumor invasion. It is very hard to diagnose extrahepatic cancer invasion to the adjacent organs using preoperative imaging. This study was undertaken, therefore, to determine the real cancer invasion using a manual dissection. METHODOLOGY: Of the 51 consecutive patients with liver cancer, 6 cases with extrahepatically growing tumors were suspected to have cancer invasion both preoperatively and intraoperatively. Thus, we diagnosed whether or not any real extrahepatic cancer invasion was present by either removing the tumour by hand or by performing a blunt gauze dissection. RESULTS: Three hepatocellular carcinomas and one metastatic cancer were stripped off from the adjacent organ using a manual blunt dissection. However, the other two tumors could not be removed in the same manner and therefore a combined resection of the invaded portion had to be performed along with the hepatectomy. A postoperative detailed pathological examination revealed no cancer cells on the surface of the adjacent organ in the former 4 tumors. Cancer invasion was recognized, however, on the outside of the liver in the latter 2 combined resected tumors. CONCLUSIONS: An accurate intraoperative diagnosis of extrahepatic cancer invasion can be made using manual blunt dissection.     

On the method-independent lower bound (MILB) to the variance of attenuation estimation in random reflection

Based on the Cramer-Rao inequality, the MILB is calculated for the problem of estimating the frequency slope of the attenuation coefficient of tissue from random reflections of ultrasonic waves. Under typical signal conditions, this bound for a 1-cm x 1-cm region was found to be about 0.08 db/(MHz-cm), rather close to the clinical requirement of 0.1 dB/(MHz-cm). Comparison to existing methods (including an autoregressive deconvolution method) shows room for further improvement.