Pituitary somatostatin receptor (sst)1-5 expression during rat development: age-dependent expression of sst2.

The capacity of the pituitary to suppress hormone secretion in response to somatostatin (SRIF) is markedly age dependent. Immature pituitaries are relatively resistant to SRIF effects, and increasing sensitivity to SRIF with advancing age is believed to cause characteristic developmental changes in pituitary hormone secretion in mammals. However, the cellular mechanism(s) underlying this developmental pattern of response to SRIF are not understood. Because somatostatin receptors (ssts) are critical mediators of SRIF's actions on target tissues, we investigated the expression of sst1, sst2, sst3, sst4, and sst5 messenger RNA (mRNA) in pituitaries of developing and mature rats. Animals were studied at embryonic day 19.5, and at postnatal days 2, 12, 30, 45, 70, and 1 yr; these ages correspond to major changes in circulating GH levels and pituitary responsiveness to SRIF. Pituitary levels of sst2 mRNA increased strikingly and progressively with advancing age after birth (F = 30.92, P < 0.0001). Compared with 2-day-old pituitaries, sst2 mRNA abundance rose 3.25-fold by 12 days of age and 6-fold by 70 days of age. Moreover, Western blot analysis indicated a marked increase in pituitary expression of sst2A protein with advancing age. By contrast, pituitary abundance of sst1, sst3, sst4, and sst5 mRNAs did not differ with age. To assess the role of endogenous SRIF in regulating perinatal sst2 gene expression, we also administered a well-characterized SRIF antiserum (or NSS as controls; 10 microl/10 g) sc daily from postnatal days 2 to 12 of life. Treatment with SRIF antiserum raised GH levels but did not alter pituitary sst2 mRNA abundance, compared with controls. Taken together, these data indicate that 1) the perinatal rat pituitary expresses the same complement of ssts as the adult pituitary; 2) expression of ssts is developmentally regulated in a highly subtype-specific manner; 3) pituitary sst2 mRNA and sst2A protein increase markedly and progressively with advancing age after birth; and 4) the perinatal rise in sst2 mRNA levels is unlikely to be regulated by endogenous SRIF. The finding of subtype-specific, developmentally determined sst expression indicates a novel and potentially fundamental mechanism of sst regulation, and suggests a molecular mechanism underlying developmental maturation in the capacity of the pituitary to respond to SRIF.

Immortalization of equine trophoblast cell lines of chorionic girdle cell lineage by simian virus-40 large T antigen.

Immortalized cell lines have many potential experimental applications including the analysis of molecular mechanisms underlying cell-specific gene expression. We have utilized a recombinant retrovirus encoding the simian virus-40 (SV-40) large T antigen to construct several immortalized cell lines of equine chorionic girdle cell lineage - the progenitor cells that differentiate into the equine chorionic gonadotropin (eCG) producing endometrial cups. Morphologically, the immortalized cell lines appear similar to normal chorionic girdle cells. Derivation of the immortalized cell lines from a chorionic girdle cell lineage was verified by immunological detection of cell-surface antigens specific to equine invasive trophoblasts. The cell lines differed, however, from mature chorionic girdle cells or endometrial cup cells in that they did not produce eCG and did express MHC class I molecules. Thus, these cell lines appear to have been arrested at a stage of development prior to final differentiation into endometrial cup cells. It was also determined that some of these cell lines as well as endometrial cups express the estrogen receptor-related receptor beta gene, but not the glial cell missing gene (GCMa) both of which are expressed in the murine and human placenta. Among these cell lines, three (eCG 50.5, 100.6 and 500.1) express eCG alpha mRNA. Since regulation of eCG alpha subunit gene is largely unknown, we investigated the signal transduction pathways regulating the eCG alpha subunit gene. Both activators of protein kinase A (PKA) and protein kinase C (PKC) induced the expression of eCG alpha subunit expression 3.2 (P<0.05)- and 1.9 (P<0.05)-fold respectively, in the eCG 500.1 cell line. However, activation of these pathways failed to induce eCG beta subunit expression. In conclusion, lines of equine trophoblast cells have been immortalized that display markers characteristic of those with the equine chorionic girdle and endometrial cup cell lineage. A subset of these cells expresses the eCG alpha subunit gene which is responsive to activators of the PKA and PKC signal transduction pathways.

Extractives of seeds of the meliaceae: Effects onSpodoptera frugiperda (J.E. Smith),Acalymma vittatum (F.), andArtemia salina Leach.

Hexane and ethanol extracts of seeds from 22 species of plants of the family Meliaceae from a number of countries were prepared. The extracts were submitted to antifeedant and toxicity bioassays utilizing fall armyworm [Spodoptera frugiperda (J.E. Smith)] (Lepidoptera: Noctuidae) larvae and striped cucumber beetle [Acalymma vittatum (F.)] (Coleoptera: Chrysomelidae) adults. Toxicity tests were also performed with brine shrimp,Anemia salina Leach. Feeding inhibition and mortality produced by some of these extracts were comparable to and, in certain cases, slightly greater than the effects produced by comparable neem (Azadiracta indica A. Juss.) seed preparations. Brine shrimp toxicity data do not extrapolate to insect activity, and vice versa.

Residues in the alpha subunit of human choriotropin that are important for interaction with the lutropin receptor.

Synthetic peptides were used to probe the structure-function relationships between human choriotropin (hCG) and the lutropin (LH) receptor. Previously, a peptide region of the alpha subunit of hCG, residues 26-46, had been shown to inhibit binding of 125I-hCG to the LH receptor in rat ovarian membranes (Charlesworth, M.C., McCormick, D.J., Madden, B., and Ryan, R.J. (1987) J. Biol. Chem. 262, 13409-13416). To determine which residues are important for this inhibitory activity, peptides were truncated from either the amino or carboxyl terminus, or individual residues were substituted with alanine. The amino-terminal boundary was determined to be Gly-30 and the carboxyl-terminal boundary, Lys-44. This core peptide contained all the residues needed for full activity of the parent peptide 26-46. Arg-35 and Phe-33 were particularly important residues; when they were substituted with alanine, the peptide inhibitory potencies were decreased. Ser-43, Arg-42, Cys-32, and Cys-31 were also important but to a lesser degree. These results are consistent with predictions based on chemical and enzymatic modification studies and provide insight into which residues are important for interaction between hCG and the LH receptor.

Ovipositional behavior of lesser peachtree borer in presence of host-plant volatiles.

Reactions of lesser peachtree borer [Synanthedon pictipes (G&R)] to volatiles of peach wood, either natural or chemically fractionated, were observed. Mated females were stimulated by and responsive to such materials and deposited significantly more eggs on substrates, including unnatural hosts, that had been treated with aqueous mixtures of bark-canker materials. Stimulation to oviposit occurred even when the female was blinded, indicating the presence of chemical cues. Natural canker-bark extracts immediately stimulated ovipostion and for a few hours significantly increased the number of eggs laid. However, average fecundity was not increased. Antennectomy did not significantly decrease response to volatiles by gravid females, and alternate sites of such chemoreception were not located. Complex mixtures derived by solvent extraction, steam distillation, and volatiles trapping from bark, canker, and gum all had activity. Observations of insect behavior in outdoor cages and also in the laboratory indicated that visual, chemosensory, and mechanosensory receptors are involved in host finding and oviposition.

Degradation of the Alzheimer's amyloid beta peptide by endothelin-converting enzyme.

Deposition of beta-amyloid (Abeta) peptides in the brain is an early and invariant feature of all forms of Alzheimer's disease. As with any secreted protein, the extracellular concentration of Abeta is determined not only by its production but also by its catabolism. A major focus of Alzheimer's research has been the elucidation of the mechanisms responsible for the generation of Abeta. Much less, however, is known about the mechanisms responsible for Abeta removal in the brain. In this report, we describe the identification of endothelin-converting enzyme-1 (ECE-1) as a novel Abeta-degrading enzyme. We show that treatment of endogenous ECE-expressing cell lines with the metalloprotease inhibitor phosphoramidon causes a 2-3-fold elevation in extracellular Abeta concentration that appears to be due to inhibition of intracellular Abeta degradation. Furthermore, we show that overexpression of ECE-1 in Chinese hamster ovary cells, which lack endogenous ECE activity, reduces extracellular Abeta concentration by up to 90% and that this effect is completely reversed by treatment of the cells with phosphoramidon. Finally, we show that recombinant soluble ECE-1 is capable of hydrolyzing synthetic Abeta40 and Abeta42 in vitro at multiple sites.

Variability of ciliary ultrastructure in normal dogs.

The incidence of abnormal tracheal cilia from each of seven normal healthy dogs was estimated using samples prepared for TEM and SEM from the dorsal, lateral, and ventral aspects of the 3rd, 12th, and 24th tracheal rings. Some samples were demembranated with Triton X-100 and stained with tannic acid to visualize microtubular protofilaments. From each region of each ring of each dog on which TEM was done, 500 transversely sectioned cilia were observed, 27,000 cilia overall. Abnormal numbers of central microtubules and abnormal numbers of peripheral microtubules occurred in all samples in about 2% of all cilia. Compound cilia were consistently observed in samples from the 3rd ring and were not observed in any samples from the 24th ring. Therefore, before abnormal ciliary ultrastructure may be associated with disease, the rate of occurrence must exceed that in appropriate control individuals. Additionally, compound cilia, which have previously been associated with a variety of diseases, obviously occur in normal individuals; however, their observation may be a function of biopsy site selection.

Analysis of peach bark volatiles and their electroantennogram activity with lesser peachtree borer,Synanthedon pictipes (Grote and Robinson).

Bark volatiles from two peach cultivars (Bisco and Redskin) were obtained by vacuum steam distillation and fractionated by preparative gas chromatography. The fractions were then assayed with the electroantenno- gram (EAG) method on antennae of female lesser peachtree borer [Synanthedon pictipes (Grote and Robinson)]. With both cultivars, two fractions elicited the largest responses. Analysis of this material by GC-MS revealed a complex mixture made up of aromatic alcohols, esters, ketones, and acids, as well as phenols, aliphatic aldehydes, and aliphatic acids. EAG responses to pure samples of all identified components were recorded, and many of these compounds were found to be quite active. Among the most stimulatory were guaiacol, methyl benzoate, and l-phenyl-1,2-propanedione. Also tested were six-carbon aliphatic aldehydes and alcohols which are components of the foliar tissue of most plants. Of these, 1-hexanol showed moderate activity, while the aldehydes and unsaturated alcohols were only weakly active.

Biological activities ofTrewia nudiflora extracts against certain economically important insect pests.

An ethanol extract ofTrewia nudiflora (Euphorbiaceae) seed was tested as an agent for controlling several economically important insects. Results suggest that this plant extract acts as an antifeedant for the spotted cucumber beetle (Diabrotica undecimpunctata howardi Barber) and the European corn borer [Ostrinia nubilalis (Hübner)] but not for the other insects tested. Also indicated were morphogenic effects on the codlingmoth [Laspeyresia pomonella (L.)], disruption of the normal life cycle of the redbanded leafroller [Argyrotaenia velutinana (Walker)], and reduction in the progeny of the plum curculio [Conotrachelus nenuphar (Herbst)]. In addition, the extract was toxic to the striped cucumber beetle [Acalymma vittatum (F.)] and gave 100% control of the chicken body louse [Menacanthus stramineus (Nitzsch)] from 5 to 28 days. Fractionation of the extract was monitored by a bioassay usingO. nubilalis. This fractionation yielded six pure compounds, the most abundant of which was trewiasine. Its LD50 was 7.4 ppm when incorporated into the diet ofO. nubilalis. Dose-mortality relationships for the other compounds withO. nubilalis are presented.

An analysis of the relationship between the cellular distribution and the rate of turnover for the separate classes of unoccupied, noncovalently occupied, and covalently occupied insulin receptor.

To further investigate insulin's role in regulating the turnover of insulin receptor during down-regulation in 3T3-L1 adipocytes, the relationship between the cellular distribution and turnover of unoccupied, noncovalently occupied, and covalently occupied receptor was examined. At steady-state 12% of the unoccupied receptors and 46% of covalently occupied receptors are intracellular. The apparent first-order rate constant (Kapp) for turnover of the total pool of covalently occupied receptors (0.16 h-1) is 3.8-fold higher than that for unoccupied receptors (0.042 h-1). When unlabeled insulin is added, identical values for both Kapp (0.10 h-1) and distribution (26% internal) are measured for noncovalently and covalently occupied receptors. The rate constant (Kdeg), describing the relative sensitivity of internalized receptor to degradation, is identical (0.36-0.41 h-1) for unoccupied, noncovalently occupied, and permanently occupied pools of internal receptor. Mechanisms for down-regulation postulating: (a) an occupancy-dependent alteration in the conformation of internal receptor increasing receptor sensitivity to internal proteases, (b) a preferential sorting of internal occupied receptor to degradative pathways, or (c) induction of intracellular proteases by insulin, would all reflect a substantial change in Kdeg for occupied receptor and thus are unlikely mechanisms by which insulin increases the rate of receptor turnover. The turnover of insulin receptor in 3T3-L1 adipocytes is regulated primarily by its intracellular concentration and not by the state of occupancy of internalized receptor.

Elevation of the number of cell-surface insulin receptors and the rate of 2-deoxyglucose uptake by exposure of 3T3-L1 adipocytes to tolbutamide.

Sulfonylurea compounds are hypoglycemic agents which by unknown mechanisms alter the amount of insulin receptor and the rate of glucose utilization in tissues exposed to the drugs. In this study the effects on insulin binding and uptake of 2-deoxyglucose by 3T3-L1 adipocytes were assessed after maintaining cell monolayers for 1-3 days in medium containing different concentrations of the sulfonylurea, tolbutamide. The amount of 125I-insulin bound by treated monolayers gradually increased to values 150-250% of those of control monolayers after 2-3 days of exposure to 1.5 mM tolbutamide. Such increases in insulin binding capacity arose primarily from an increase in receptor number and not from an alteration in the affinity of the receptor for insulin. Concomitant with the changes observed for the insulin receptor, tolbutamide-treated monolayers expressed 1.5-2-fold higher rates of uptake of 2-deoxyglucose relative to control monolayers at concentrations of insulin between 0 and 10(-10) M. This study thus demonstrates the responsiveness of adipocytes to tolbutamide and also establishes the usefulness of 3T3-L1 cells as a model system in which to study the mechanism of tolbutamide action, both as it relates to the use of sulfonylurea compounds in clinical applications and as possible probes for perturbing and studying relatively uncharacterized regulatory pathways controlling receptor level and biological responses to insulin.

Further characterization of the receptor-binding region of the thyroid-stimulating hormone alpha subunit: a comprehensive synthetic peptide study of the alpha-subunit 26-46 sequence.

Previously, using a synthetic peptide strategy, we determined that the region of the common glycoprotein hormone alpha subunit between residues 26 and 46 is a site of interaction of the hormone with the thyroid membrane-bound receptor for thyroid-stimulating hormone (TSH). We have undertaken to identify further the specific residues within this 21-amino acid span that are critical in hormone receptor binding. We synthesized three nested sets of peptide, two in which we systematically truncated the amino-terminal region of the sequence and another in which we truncated the carboxyl-terminal region, and we synthesized a fourth nested set in which we systematically substituted alanine for the native residues from the region of highest activity. Each peptide was tested in a TSH radioreceptor assay for its ability to inhibit binding of 125I-labeled bovine TSH to porcine thyroid membranes. Removal either by truncation or alanine substitution, of several specific residues resulted in a significant reduction in the ability of the sequence to interact with receptor; these residues included Cys31, Cys32, Phe33, Arg35, Arg42, Lys44, and Lys45, suggesting that they are crucial for binding activity. Loss of activity also occurred with substitution for Gly30 and Ser34, but the reduction was less pronounced. Amino-terminal truncation of the sequence through Arg35 (leaving the alpha-subunit peptide 36-46) resulted in greater than 98% loss of activity of the sequence. We conclude that two distinct receptor binding regions lie within the alpha-subunit 26-46 sequence. The first lies between residues Gly30 and Arg35 and includes Cys31, Cys32, and Phe33 as important constituents, and the second region lies between residues Arg42 and Lys45 and includes Lys44 as an important residue and Ser43 as a less important component.

Olfactory responses of the parasitoidDiaeretiella rapae (Hymenoptera: Aphidiidae) to odor of plants, aphids, and plant-aphid complexes.

Diaeretiella rapae (M'Intosh) (Hymenoptera: Aphidiidae) is a parasitoid of several aphid species, including the Russian wheat aphid (RWA),Diuraphis noxia (Mordvilko), and the cabbage aphid (CA).Brevicoryne brassicae (L.). The response of matedD. rapae females to odors from wheat, cabbage, and plant-host complexes was investigated using a four-choice olfactometer. Experienced parasitoids, but not inexperienced females, responded positively to odors of the wheat-RWA complex in a no-choice test. In choice tests, experienced parasitoids did not respond to odors of uninfested cabbage and wheat leaves, but did respond positively to aphid-infested plants and to aphids alone. The response ofD. rapae to the cabbage-CA complex and to CA alone was significantly greater than to the wheat-RWA complex and RWA alone, suggesting an innate odor preference for crucifer-feeding aphids.

Pre- and intraoperative localization of small bowel arteriovenous malformation.

Patients with chronic gastrointestinal bleeding with no source found after standard radiographic and endoscopic procedures are diagnostic challenges. Since angiodysplasia is a frequent cause of such bleeding, selective angiography has become an essential diagnostic tool in identifying arteriovenous malformations (AVM) of the large and small bowel. In addition to preoperative identification, some method of intraoperative localization is essential to assure removal of the involved segment. In a patient with a 7-year history of gastrointestinal bleeding from an AVM of the small bowel, a technique of preoperative angiographic catheter placement with intraoperative confirmation of catheter position proved a useful way to find such small bowel lesions and insured adequate but not excessive resection.