Brain CCK receptors are structurally distinct from pancreas CCK receptors

Brain and pancreas cholecystokinin (CCK) receptors differ markedly in their selectivity for CCK analogs. To determine the size and subunit structure of the brain CCK receptor and compare it to that of the pancreas, 125I-CCK33 was covalently cross-linked with ultraviolet light to its receptor on mouse brain particles and purified pancreatic plasma membranes. When CCK was crosslinked to brain membranes, a single consistent major labeled protein band of Mr = 55,000 was observed in both the presence and the absence of DTT. These data with brain receptors contrast to results with pancreatic receptors where two bands of Mr = 120,000 and 80,000 are labeled in the absence and presence of DTT, respectively. These studies indicate, therefore, that the brain and pancreas CCK receptors are structurally and functionally distinct.     

Serum indole-3-acetic acid in control subjects and newly abstinent alcoholics after an oral loading with L-tryptophan: a preliminary study using liquid chromatography with amperometric detection

Described in this paper is a rapid, isocratic assay for serum indole-3-acetic acid (IAA). The sample preparation involves only protein precipitation using sulfosalicylic acid, and the sensitivity of amperometric detection is in the picogram range. The chromatographic analysis time is approximately 4 min. The devised method was used for a longitudinal study of IAA levels in serum samples from control subjects and newly abstinent alcoholics. Dietary variations were eliminated by administering a 2.0-g loading dose of L-Trp to all subjects investigated. The results are presented in the form of cumulative frequency polygons. Preliminary data indicate no differences in IAA levels between newly abstinent alcoholics and control subjects.     

Binding of simple carbohydrates and some N-acetyllactosamine-containing oligosaccharides to Erythrina cristagalli agglutinin as followed with a fluorescent indicator ligand

Erythrina cristagalli agglutinin, a dimeric lectin [J. L. Iglesias, et al. (1982) Eur. J. Biochem.123, 247–252] was shown by equilibrium dialysis to be bivalent for 4-methylumbelliferyl-β-d-galactoside. Upon binding to the lectin, this ligand showed a difference absorption spectrum with two maxima (at 322 and 336 nm) of equal intensity (Δ? = 1.2 × 10³m^?1 cm^?1). A similar spectrum with a comparable value of Δ? was obtained with 4-methylumbelliferyl-N-acetyl-β-d-galactosaminide. Binding of methyl-α-d-galactoside, lactose, and N-acetyllactosamine all produced small but equally intense protein difference spectra with a maximum (Δ? = 2.8 × 10² M^?1 cm^?1) at 291.6 nm. Upon binding of N-dansyl-d-galactosamine to the lectin, there was a fivefold increase in fluorescence intensity of this ligand. The association constant for N-dansyl-d-galactosamine was caused by a very favorable ΔS° of the dansyl group without affecting the strictly carbohydrate-specific character of binding. N-Dansyl-d-galactosamine was employed as a fluorescent indicator ligand in substitution titrations. This involved the use of simple carbohydrates, N-acetyllactosamine, and oligosaccharides which occur in the carbohydrate units of N-glycoproteins; the latter were Gal(β → 4)GlcNAc(β1 → 2)Man, Gal(β1 → 4)GlcNAc(β1 → 6)Man, and Gal(β1 → 4)GlcNAc(β1 → 6)[Gal(β1 → 4)GlcNAc(β1 → 2)]Man. The titrations were performed at two temperatures to determine the thermodynamic parameters. In the series N-acetyl-d-galactosamine, methyl-α-d-galactoside, and lactose, ?ΔH° increased from 24 to 41 kJ mol^?1; it increased further for N-acetyllactosamine and then remained unchanged for the N-acetyllactosamine-containing oligosaccharides (55 ± 1 kJ mol^?1). This indicated that the site specifically accommodated the disaccharide structure with an important contribution of the 2-acetamido group in the penultimate sugar. Beyond this, no additional contacts seemed to be formed. This conclusion also followed from considerations of ΔS° values which became more unfavorable in the above series (?23 to ?101 ± 4 J mol^?1 K^?1); the most negative value of ΔS° was observed with N-acetyllactosamine and the three N-acetyllactosamine-containing oligosaccharides.     

Vitamin K-dependent carboxylase: Evidence for a semiquinone radical intermediate

Nanosecond laser flash photolysis has been used to produce and identify the vitamin K semiquinone (radical) from vitamin K dihydroquinone and to observe its formation and decay in the presence of vitamin K-dependent carboxylase (epoxidase). The activity of vitamin K-dependent carboxylase is not decreased by exposure to the laser. Absorbance of the semiquinone is proportional to enzyme concentration and is stimulated by a synthetic substrate, PheLeuGluGluIle. Stabilization of the semiquinone is observed in the presence of the enzyme. The semiquinone is rapidly destroyed in the presence of inhibitors of vitamin K-dependent carboxylase and vitamin K epoxidase.     

Transport of mercury compounds across bimolecular lipid membranes: effect of lipid composition, pH and chloride concentration

The use of bimolecular lipid membranes (BLM) as model membrane allows the analysis of the transport of mercury compounds across the lipidic barriers of biological membranes. The results of flux measurements show that two mercury compounds--HgCl2 and CH3HgCl--cross the BLM but the overall permeabilities are dependent on the pH of the aqueous media, and are not apparently influenced by the different phospholipid constituents of the bilayers. On the other hand, electrical measurements show that, function of the chemical speciation, the transport of this metal is done essentially in the neutral form.     

Medfly eradication in California:

The impact of malathion-bait sprays (directed against medfly, Ceratitis capitata [Wiedemann]) on an endemic gall midge (Rhopalomyia californica Felt) and its parasitoids was investigated during 1982–83 in the south San Francisco Bay area of northern California. In a heavily sprayed area (Woodside), a population explosion of the midge was detected following 24 applications of malathion bait. The midge population reached levels ca. 90x greater than those observed in an adjacent unsprayed area (Jasper Ridge). In a moderately sprayed area (Portola Valley), the midge population increased as much as 5x that observed in the adjacent unsprayed area (Jasper Ridge), following 12 applications of malathion bait. In laboratory tests, the malathion bait was toxic to both the midge and its parasitoids. The major parasitoids were Torymus koebelei (Huber), Zatropis capitis Burks, Platygaster californica (Ashmead) and Mesopolobus sp. Population increases of the midge following malathion-bait sprays were attributed to destruction of parasitoids and other natural enemies of the midge. If the environmental impact of malathion-bait sprays is related to the number of applications (as suggested in this study), then it would be worthwhile to determine the appropriate bait-spray strategy for a given situation, so as to minimize adverse effects on nontarget species, yet insure suppression or eradication of medfly.

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Résumé L'impact des pièges tratiés au malathion (destinés à Ceratitis capitata Wiedem) sur Rhopalomyia californica Felt et ses parasitoïdes a été examiné en 1982–1983 dans le sud de la zone de la baie de San Francisco en Californie. Dans une zone fortement traitée (Woodside), une explosion de population a été décelée après 24 traitements. La population de R. californica a atteint des niveaux 90 fois supérieurs à ceux observés dans une zone contiguë non traitée (Jasper Ridge). Dans une zone modérément traitée (Portola Valley), avec 12 traitement, la population de R. californica a atteint jusqu'a 5 fois celle de Jasper Ridge. Au laboratoire, le piège à malathion a été toxique tant pour R. californica que pour ses parasitoïdes, dont les principaux étaient: Torymus koebelei (Huber), Zatropis capitis Burks, Platygaster californica(Ashmead) et Mesopolobus sp. L'accroissement de la population de C. capitata après traitement a été attribué à la destruction de parasitoïdes et d'autres ennemis naturels. Si l'effet su l'environnement du traitement est lié au nombre d'interventions (comme le suggère cette étude), alors cela vaudrait la peine de définir une stratégie de traitement appropriée à une situation donnée, de façon à minimiser les effets négatifs sur des espèces non visées, tout en assurant la suppression ou l'éradication de C. capitata.

     

A diphenylmethane derivative specific for the antiestrogen binding site found in rat liver microsomes

A new para-diphenylmethyl derivative, N,N-diethyl-2-[(4-phenylmethyl)-phenoxy]-ethanamine·HCl (N,N-DPPE) has been synthesized which binds with high affinity to the anti-estrogen binding site found in male rat liver microsomes. However, no evidence of significant interaction with the estrogen receptor can be observed at or below 10 μM in rat uterine cytosols; 10 nM N,N-DPPE fails to significantly induce progesterone receptor in MCF-7 cells. Tamoxifen also binds to anti-estrogen binding site but, unlike N,N-DPPE, binds significantly to estrogen receptor at much loeer concentrations and induces MCF-7 progesterone receptor. This property of high affinity for anti-estrogen binding site but not for estrogen receptor may make N,N-DPPE an important probe for the study of anti-estrogen binding site and its biological relevance.     

Association of leukotriene B4 with the cytoskeleton of rabbit neutrophils. Effect of chemotactic factor and phorbol esters

Following its addition to a suspension of rabbit neutrophils, leukotriene B4 is rapidly (less than 1 min) recovered from the cytoskeletal fraction (Triton X-100 insoluble pellet) of these cells. The association of leukotriene B4 with the cytoskeleton can be competed with by leukotriene B4 itself and by 20-OH leukotriene B4 but not by 20-COOH leukotriene B4. In addition, the preincubation of the cells with fMet-Leu-Phe or with phorbol 12-myristate 13-acetate, but not with 4 alpha-phorbol 12,13-didecanoate, results in a greatly decreased association of leukotriene B4 with the cytoskeleton. These results suggest that a specific association between the leukotriene B4 receptors and the cytoskeleton may be involved in signal transduction in the leukotriene B4 stimulated neutrophils.     

Ca2+-dependent K+ permeability of heart sarcolemmal vesicles. Modulation by cAMP-dependent protein kinase activity and by calmodulin

The Ca2+-dependent K+ permeability of heart sarcolemma vesicles was measured by following the transmembrane movement of the charge compensating tetraphenylborate anion. The increase in vesicles permeability induced by Ca2+ is lost when membrane proteins are dephosphorylated by an endogenous protein phosphatase and is restored by a phosphorylation process catalysed by a cAMP-dependent protein kinase. The calmodulin antagonist R 24571 lowers the Ca2+-dependent K+ permeability by decreasing the Ca2+ affinity of the K+ transporting system.     

Distribution of repeated DNA families in the human genome

By means of restriction enzymes analysis and molecular hybridization, the distribution of repeated DNA families has been studied in the different DNA components into which the human genome can be fractionated by density gradient techniques. Three classes of DNA molecules have been analyzed: i) an homogeneous DNA component (satellite-like sequences; Q = 1.696 g/cm3, 3% of total DNA, AT repeated), ii) AT rich (Q = 1.698 g/cm3, 30% of total DNA, AT main-band) and GC rich (Q = 1.708 g/cm3, 6% of total DNA, GC main-band) DNA components. By this approach we have observed that Sau3A digestion of GC main-band gives rise to two bands of 75bp and 150bp, absent or under-represented in both AT rich DNA components. A preliminary characterization of these DNA fragments suggests that they contain one or more families of repeated sequences which fail to hybridize to EcoRI, HindIII and AluI families of repeats. In addition, we have observed that EcoRI sequences (alpha-RI DNA) are under-represented in GC main-band and show the same clustered organization in both AT rich DNA components.