Beta thalassemia in Melanesia: association with malaria and characterization of a common variant (IVS-1 nt 5 G----C)

Data on the distribution of beta thalassemia among over 6,000 Melanesians reveals a major difference in the carrier rates between populations in the malarious coastal regions of New Guinea and those living in the historically malaria-free Highlands. The island of Maewo in Vanuatu has a particularly high incidence of beta + thalassemia associated with a single restriction enzyme haplotype. Direct cloning into a plasmid vector and sequence analysis demonstrate that the mutation is a G to C transversion at position 5 of intron 1 of the beta- globin gene. Oligonucleotide probe surveys indicate that this variant accounted for all cases of beta thalassemia studied from Maewo. It is also common in coastal Papua New Guinea where haplotype and oligonucleotide probe data suggest that the molecular basis of beta thalassmia is more heterogeneous.     

Expression of growth hormone-releasing hormone (GHRH) messenger ribonucleic acid and the presence of biologically active GHRH in human breast, endometrial, and ovarian cancers

GHRH is produced in a variety of extrahypothalamic tissues, including some neoplasms. We have previously reported that GHRH antagonists can inhibit the growth of various human cancers xenografted into nude mice. These observations suggest that locally produced GHRH might directly affect tumor cell proliferation. To investigate this possibility, we have examined the local production of GHRH in human endometrial, ovarian, and breast cancers obtained after surgery or grown in nude mice as xenografts. We have also examined whether the GHRH produced in these tumors is biologically active. RT-PCR and Southern blotting showed expression of messenger ribonucleic acid for GHRH in 17 of 22 endometrial and 17 of 22 ovarian cancer specimens and in all of the human endometrial, ovarian, and breast cancer xenografts studied. Acid extracts of endometrial cancer specimens and breast cancer xenografts that expressed the GHRH gene contained immunoreactive GHRH peptide, as assessed by RIA for GHRH. The level of immunoreactive GHRH detected was equivalent to 2.7-6.4 ng GHRH-(1-29)/g tissue. Purified extract from one of these tumor samples induced a powerful stimulation of GH release from rat pituitary cells. The presence of biologically and immunologically active GHRH and messenger ribonucleic acid for GHRH in human breast, endometrial, and ovarian cancers supports the hypothesis that locally produced GHRH may play a role in the proliferation of these tumors.     

Luteolytic effect of D-Trp6-luteinizing hormone-releasing hormone in the rhesus monkey (Macaca mulatta)

A potent agonist of luteinizing hormone, D-Trp6-LRH, was administered at different stages during the luteal phase of rhesus monkeys (Macaca mulatta). Luteolysis, evidenced by short luteal phases and decreased serum progesterone concentrations, was consistently induced when the analog was injected on days 3 or 5 post ovulation; however, no effect was observed when it was given on day 7 post ovulation. Increasing doses of hCG administered from days 6-10 post ovulation prevented the luteolytic effect of D-Trp6-LRH. The possible mechanisms of action and the potential uses of LRH analogs as contraceptive agents are discussed.     

Use of the mouse vas deferens assay to evaluate the action of somatostatin peptides on gastric acid secretion

Six closely related analogues of somatostatin were tested for their ability to inhibit electrically induced contractions of the mouse vas deferens. Their inhibiting activities tended to parallel their reported effects on gastric acid secretion in vivo, while no correlation to their in vitro growth hormone release-inhibiting activities was observed. It is suggested that information derived from the vas deferens assay may provide a relatively rapid and inexpensive assessment of the effects of somatostatin analogues on gastric acid secretion. The vas deferens assay was also used to test several somatostatin analogues for antagonistic activity, which was not found.     

Correlation between the effects of bombesin antagonists on cell proliferation and intracellular calcium concentration in Swiss 3T3 and HT-29 cell lines.

Bombesin (BN) acts as an autocrine mitogen in various human cancers. Several pseudononapeptide BN-(6-14) analogs with a reduced peptide bond between positions 13 and 14 have been shown to suppress the mitogenic activity of BN or gastrin-releasing peptide (GRP) when assessed by radioreceptor or proliferation assays and may have significant clinical applications. The search for potent and safe BN antagonists requires the evaluation of a large series of analogs in radioreceptor and proliferation assays. In this paper, we report that the ability of BN analogs to inhibit BN-induced calcium transients in Swiss 3T3 cells shows a high correlation with their inhibitory potency as evaluated by classical proliferation tests. The assay of calcium transients allows a rapid characterization of new BN analogs (in terms of minutes rather than days) and can be adapted as a labor and cost-effective screening step in the selection of potentially relevant BN antagonists for further characterization in cell proliferation systems. We also observed that results from the assay of calcium transients in Swiss 3T3 cells can be correlated with the results of the proliferative response in HT-29 cells, a cell line that does not seem to use the same early transmembrane ionic signal system. This result suggests that the calcium pathway is not mandatory for triggering cell division by the BN receptor.     

Inhibition of growth hormone and thyrotropin release by growth hormone-release inhibiting hormone

Addition of increasing doses of synthetic growth hormone-release inhibiting hormone (GH-RIH) leads to a progressive decrease of the basal and N⁶monobutyryl cyclic AMP-,theophylline- and prostaglandin E₂-induced release of immunoreactive growth hormone (GH) and thyrotropin (TSH) release from rat anterior pituitary cells in monolayer culture. A halfmaximal effect is measured at 3 × 10^?9 M GH-RIH while a maximal inhibition to 10–20% of the control level is found at 1 × 10^?7 M. Using rat hemipituitaries and measurement of GH release by both polyacrylamide gel electrophoresis and radioimmunoassay, a maximal effect of GH-RIH was found in the first 5 min of incubation. The inhibitory effect of GH-RIH on GH release remained constant for at least 3 h. GH-RIH does not affect the basal or induced release of prolactin and luteinizing hormone nor the high K ⁺-induced release of GH and TSH.