An antibody against secretogranin I (chromogranin B) is packaged into secretory granules

We have investigated the sorting and packaging of secretory proteins into secretory granules by an immunological approach. An mAb against secretogranin I (chromogranin B), a secretory protein costored with various peptide hormones and neuropeptides in secretory granules of many endocrine cells and neurons, was expressed by microinjection of its mRNA into the secretogranin I-producing cell line PC12. An mAb against the G protein of vesicular stomatitis virus--i.e., against an antigen not present in PC12 cells--was expressed as a control. The intracellular localization and the secretion of the antibodies was studied by double-labeling immunofluorescence using the conventional and the confocal microscope, as well as by pulse-chase experiments. The secretogranin I antibody, like the control antibody, was transported along the secretory pathway to the Golgi complex. However, in contrast to the control antibody, which was secreted via the constitutive pathway, the secretogranin I antibody formed an immunocomplex with secretogranin I, was packaged into secretory granules, and was released by regulated exocytosis. Our results show that a constitutive secretory protein, unaltered by genetic engineering, can be diverted to the regulated pathway of secretion by its protein-protein interaction with a regulated secretory protein. The data also provide the basis for immunologically studying the role of luminally exposed protein domains in the biogenesis and function of regulated secretory vesicles.     

Studies of sibling Drosophila species from Laguna Verde, Veracruz, Mexico: I. Species frequencies, viability, desiccation resistance, and vagility

The sibling species Drosophila melanogaster and D. simulans were collected at Laguna Verde, Veracruz, Mexico. D. melanogaster was found in significantly greater frequency than was D. simulans. Ten isofemale lines of each species were tested for egg to adult viability, desiccation resistance, and vagility. D. melanogaster surpassed D. simulans in all three characteristics. The findings are discussed with reference to the climatic conditions at Laguna Verde and the expected effect of such an environment on the relative frequencies of these species. The dichotomous results in regard to desiccation resistance and vagility that were observed between recently collected D. melanogaster and the Oregon-R laboratory stock of that species are also discussed.     

Arg74 in HLA-DRBI and DRB3 controls a DR3-related epitope

TR81 is a specificity closely related to or identical with DR3. In Caucasoids two amino acids, Tyr at position 26 and Arg at position 74 of HLA class II DR chains, have been found to be associated with the presence of TR81. Recently, a variant of DRBI *03 identified in American Blacks has been shown to possess Arg at position 74 but Phe at position 26. This codon combination is found to be present in four other cell lines where it still specifies the TR81 determinant. This suggests that the TR81 specificity is uniquely dependent on the presence of Arg at position 74.     

Origin heterogeneity of Hb Lepore-Boston gene in Italy

Forty-three hybrid delta-beta-globin genes were characterized by DNA sequence analysis and associated RFLP haplotypes in 40 families from Abruzzo and Campania, which are on the east and west coast of Italy, respectively. All the genes had the delta-globin sequence up to the exon 2 codon 87 and had the beta-globin sequence from IVS-2-8; between these two ends, they had 58 bp in common with the delta- and beta-globin genes. Thus, they were all of the Lepore-Boston type. A chromosomal background heterogeneity was present among the mutant genes. In fact, they were all associated with (+ - - - -) 5' subhaplotype, but 23/31 from Campania were associated with (+ +) 3' subhaplotype, whereas 12/12 genes from Abruzzo and 8/31 from Campania were associated with (+ -). DNA sequencing of homozygous subjects showed that (+ +) 3' subhaplotype was associated, at IVS-2-74, with G, while (+ -) was associated with T; that is they were associated with the beta-globin gene sequence of frameworks 1 and 2, respectively. The molecular characteristics of this heterogeneity, as well as its geographical patterns in the eastern and western regions of Italy, represent strong evidence for the recurrent and multicentric origins of the mutation.     

Substance P affects the GABAergic system in the hypothalamo-pituitary axis

In the present work we examined the effect of the neutralization of endogenous substance P by the administration of an anti-substance P serum (ASPS) on GABA concentration in the anterior pituitary in hyperprolactinemic conditions induced by 5-hydroxytryptophan or by grafting anterior pituitaries. ASPS reduced the increase in the anterior pituitary GABA concentration induced by hyperprolactinemia. In vitro experiments showed that substance P inhibited K⁺-evoked GABA efflux from hypothalamic fragments and decreased GABA concentration in the anterior pituitary but ASPS increased it. Our results demonstrate that substance P modifies hypothalamic GABA release and anterior pituitary GABA concentration and suggest that an interaction exists between substance P and GABA.     

Fruit infesting tephritids [Dipt.: Tephritidae] and associated parasitoids in Chiapas,Mexico

A total of 1,302 parasitoids representing 8 species and 4 families were recovered from 9,818 fruit fly host fruits sampled. The most common parasitoid species wasDiachasmimorpha longicaudata (Ashmead). Average percent parasitism ranged between 0.44 and 29.23%. Parasitoid emergence data indicate thatAnastrepha ludens (Loew),A. obliqua (Sein),A. serpentina (Wiedeman),A. striata (Schiner) andToxotrypana curvicauda (Gerstaecker) were subject to parasitism. We provide information on the population fluctuation ofAnastrepha ludens, A. obliqua, A. serpentina, A. distincta (Greene),A. striata, A. fraterculus (Wiedeman),A. chiclayae (Greene),A. montei (Costa Lima),A. leptozona (Hendel) andA. tripunctata (Wulp).Anastrepha ludens andA. obliqua were the most common species, representing 95.3% of all fruit fly species caught in McPhail traps.      

Protein polymorphism inEligmodontia typus. Genetic divergence with other phyllotine cricetids

By means of gel electrophoresis of tissue extracts we have studied protein polymorphism inEligmodontia typus. The analysis was performed on specimens from five population samples collected at different sites in Patagonia (Argentina). Mean heterozygosity (\-h) and proportion of polymorphic loci (P) were determined on the basis of 19 loci. Considering all individuals as one sample, \-h gave a value of 0.16 and P was 70%. Although these values are much higher than those reported for most rodent species, they are very similar to those obtained by us for four species of the genusCalomys and forGraomys griseoflavus. There is a striking genetic identity (I_N=0.99) among populations from regions with different environmental conditions, indicating that the species possesses a common genic pool. Genetic distance with other species of the Phyllotini was estimated. D_N was lower betweenE. typus andCalomys (mean D_N=0.88) than betweenE. typus andGraomys griseoflavus (D_N=1.01). The high morphological similarity between these last two species, especially regarding those characters related to desert life adaptation, could be assigned, at least in part, to convergent evolution.     

Bacterial expression of an active class Ib chitinase from Castanea sativa cotyledons

Ch3, an endochitinase of 32 kDa present in Castanea sativa cotyledons, showed in vitro antifungal properties when assayed against Trichoderma viride. The characterization of a cDNA clone corresponding to this protein indicated that Ch3 is a class Ib endochitinase that is synthesized as a preprotein with a signal sequence preceding the mature polypeptide. Bacterial expression of mature Ch3 fused to the leader peptide of the periplasmic protein ompT resulted in active Ch3 enzyme. A plate assay was adapted for semi-quantitative determination of chitinase activity secreted from cultured bacteria, which should facilitate the identification of mutants with altered capacity to hydrolyse chitin.