Immunohistochemical localization of bioactive peptides and amines associated with the chromaffin tissue of five species of fish

Biogenic peptides and amines associated with the chromaffin tissue in Atlantic cod (Gadus morhua), rainbow trout (Oncorhynchus mykiss), European eel (Anguilla anguilla), spiny dogfish (Squalus acanthias) and Atlantic hagfish (Myxine glutinosa) were identified utilizing immunohistochemical techniques. Within the posterior cardinal vein (PCV) in cod, trout and eel, a subpopulation of chromaffin cells displayed immunoreactivity to tyrosine hydroxylase (TH) and dopamine--hydroxylase (DH) but not to phenylethanolamine-N-methyltransferase (PNMT). TH-like immunorectivity was observed within cells in hagfish hearts. Nerve fibres displaying vasoactive intestinal peptide (VIP) immunoreactivity and pituitary adenylyl cyclase activating peptide (PACAP) immunoreactivity innervated cod, trout and ell chromaffin cells. In eel, neuropeptide Y (NPY)-like and peptide YY (PYY)-like immunoreactivity was located within cells in the PCV, including chromaffin cells. Serotonin-like immunoreactivity was observed within eel and cod chromaffin cells and in hagfish hearts. In the dogfish axillary bodies, nerves displaying TH-like, VIP-like, PACAP-like, substance P-like and galanin-like immunoreactivity were observed. These results are compared with those of other vertebrates, and potential roles for these substances in the control of catecholamine release are suggested.     

Behavioral and neurochemical changes in the dopaminergic system after repeated cocaine administration

In order to determine whether repeated cocaine administration produced persistent changes in dopamine (DA) receptor binding and release consistent with behavioral sensitization, rats were treated with either cocaine (25 mg/kg ip) or saline twice daily for 14 consecutive days followed by a 3-d withdrawal period. The DA transporter site was assayed using [³H]GBR 12935, whereas D₁ and D₂ sites were assayed using [³H]SCH 23390 and [³H]spiperone, respectively. The density (B _max) of the DA transporter binding sites in the ST of the cocaine-treated group increased significantly (p<0.05) over controls 3 d after the last injection, whereas the density of striatal D₁ and D₂ binding sites remained unchanged. The DA transporter in the nucleus accumbens (NA) was also studied with [³H]GBR 12935 and was unchanged following drug treatment. D₁ and D₂ binding parameters for the NA were not determined in this study. Furthermore, cocaine administration did not affect the affinities (K _d ) of the radioligands used to label the transporter, D₁, or D₂ sites in any of the studies performed. In addition, striatal DA release was measured using in vivo microdialysis in anesthetized rats. Linear regression analysis on maximal decreases in DA release after apomorphine (0.02, 0.2, and 2.0 mg/kg sc) injection showed no difference in the functional capacity of the ST to modulate DA transmission between control and treated groups. Moreover, animals pretreated with cocaine showed a significant (p<0.01) decrease in locomotor activity (LA) after a presynaptic, autoregulating dose of apomorphine (0.03 mg/kg sc) was given. These results suggest that the effects seen after repeated exposure to cocaine may be regulated, in part, by changes in striatal DA transporter binding site densities and not necessarily by DA-releasing mechanisms or D₁ and D₂ receptor modification.     

Ecological distinctions between sympatric species of Saguinus and Sciurus

Tamarins are small New World monkeys that have been described as "squirrellike." Squirrels, along with bats and birds, are the taxa most likely to utilize resources similar to those used by primates in the tropical forest canopy. In this paper we compare differences in ecology, diet, locomotion, and habitat utilization between sympatric populations of tamarins (Saguinus oedipus) and tree squirrels (Sciurus granatensis) in Panama. Data presented indicate that although there is some degree of resource overlap, patterns of habitat utilization differ significantly. Rather than being "squirrellike," the Panamanian tamarin exhibits a pattern of locomotor and feeding behavior consistent with that found in other arboreal primates.     

Modulation of the cAMP relay in Dictyostelium discoideum by ammonia and other metabolites: possible morphogenetic consequences

Using a perfusion technique (P.N. Devreotes, P.L. Derstine, and T.L. Steck, 1979, J. Cell Biol. 80, 291-299), it has been shown that cAMP secretion by aggregation-competent cells in response to an exogenous cAMP signal is significantly reduced by exposure to NH4Cl or any of a set of carboxylic acids that includes propionate, succinate, pyruvate, and acetate. The effects of NH4Cl and any of the carboxylic acids are additive and the combinations restrict cAMP secretion to barely detectable or insignificant levels. The inhibitions are rapidly expressed, and are reversible. The activity of NH4Cl is marked at pH 7.2 and undetectable at pH 6.2. Hence, NH3 is presumably the active molecular species. Propionate activity is significantly greater at pH 6.2 than 7.2, indicating that the un-ionized acid is the active species. The data presented herein indicate that these effects are exerted via two separate and independent routes. During exposure of cAMP-stimulated cells to NH4Cl, the decrease in intracellular cAMP accumulation was even greater than the decrease in extracellular accumulation. Hence, NH3 appears to act as a cAMP accumulation inhibitor (CAI). In contrast, exposure to carboxylic acid concentrations that drastically reduce extracellular cAMP accumulation can actually enhance or, at worst, only slightly reduce intracellular accumulation. Hence, the carboxylic acids appear to act as cAMP release inhibitors (CRI). Stationary phase cells incubated on solid substratum in the presence of NH4Cl plus succinate (or propionate) for 18 hr failed to exhibit even the earliest signs of aggregation. If then harvested and redeposited in the absence of the metabolites, they proceeded through the morphogenetic sequence with approximately normal kinetics, suggesting that no significant morphogenetic competence had been achieved during their previous tenure. The morphogenetic implications of cAMP relay modulation are discussed.     

Reversible inhibition of aggregation-related cohesivity in Dictyostelium discoideum by diffusible metabolites

Evidence presented elsewhere (G.B. Williams, E.M. Elder, and M. Sussman 1984, Dev. Biol. 105, 377-388) indicates that NH3 and certain carboxylic acids including propionate, succinate, and acetate modulate the cAMP relay in Dictyostelium discoideum. The former appears to act as a cAMP accumulation inhibitor, the latter as cAMP release inhibitors. The cohesive properties of aggregation competent cells have been assayed quantitatively in the presence of these modulators. The following results were obtained: (1) At pH 7.5, EDTA-resistant cohesivity was greatly inhibited by NH4C within the concentration range tested (30-3.8 mM). Even at the higher concentrations the effect was not immediate but required ca. 10 min for full expression. At the lower concentrations, the inhibitory level was only slightly reduced but the time for full expression progressively increased. At pH 6.5, the level of inhibition was marginal, indicating that NH3 is the active molecular species. By themselves, neither ambient pH nor ionic strength appeared to affect cohesive performance within the ranges employed. The inhibition was immediately and completely reversed upon removal of NH4Cl or a shift of ambient pH from 7.5 to 6.5. The presence of cycloheximide did not affect the recovery of cohesivity after NH4Cl removal. (2) The presence of 15 mM succinate, propionate, or acetate also reduced cell cohesivity. The timing and extent of the inhibition were identical at pH 7.5 and 6.5. The inhibition was expressed immediately and was reversible. Each of the acids acted synergistically with NH4Cl. The relative potencies of these metabolites acting singly or in combination as inhibitors of cohesivity corresponded roughly to their potencies as modulators of the cAMP relay (Williams et al., 1984). (3) The sensitivity to the metabolites was stage specific, being maximal during and shortly after aggregation and disappearing abruptly at 11-12 hr. This corresponds to the time at which this cohesive system, responsible for the end-to-end cell associations evident during aggregation (H. Beug, G. Gerisch, S. Kempff, V. Riedel, and G. Cremer, 1970, Exp. Cell. Res. 63, 147-158) is supplanted by a newly arisen, serologically and genetically distinct system which thereafter maintains the integrity of the aggregate (C. Steinemann and R.W. Parish, 1980, Nature (London) 286, 721-724; D.K. Wilcox and M. Sussman, 1981, Dev. Biol. 82, 102-112, and Proc. Natl. Acad. Sci. USA 78, 358-362; C.L. Saxe III and M. Sussman, 1982, Cell 29, 755-759). The activities of the metabolites, detailed above, are discussed in relation to their previously demonstrated activities as morphogens.     

Decrease in ribosomal proteins 1, 2/3, L4, and L7 in Drosophila melanogaster in the absence of X rDNA

Summary The rRNA genes (rDNA) in Drosophila melanogaster are found in two clusters, one on the X and one on the Y chromosome. We have compared the ribosomal protein composition of wild-type Oregon-R flies containing both X-linked and Y-linked rDNA with that of flies containing only the Y-linked rDNA by two-dimensional polyacrylamide gel electrophoresis. Four basic proteins (1, 2/3, L4, and L7) normally present in wild-type flies were either electrophoretically not detectable (1, 2/3, and L4) or marginally detectable (L7) in flies with only Y-linked rDNA. No additional proteins were observed in these flies. However, immunodiffusion assays using specific antibodies raised against purified protein L4 confirmed that L4 was present but in relatively lower amounts in these Y-linked rDNA flies. An investigation was carried out to determine whether these electrophoretically undetectable proteins were more readily lost during ribosome preparation and hence were not readily detectable in the 80S particles by gel electrophoresis or whether they had been modified. Thus the proteins in the post-ribosomal cell supernatant and the high salt sucrose gradient were analyzed by two-dimensional gel electrophoresis and immunochemical assays with antibodies raised against protein L4 and total 80S ribosomal proteins. The experimental evidence indicates that there is a small amount of protein L4 and probably proteins 1, 2/3, and L7 in flies with only Y-linked rDNA but significantly less of these proteins than in wild-type flies.     

Induction of stage-specific cell cohesion in D. discoideum by a plasma-membrane-associated moiety reactive with wheat germ agglutinin

Dictyostelium discoideum strain JC-5 is a temperature-sensitive, cohesion-defective mutant. At the restrictive temperature, aggregates are formed and develop normally to a specific late stage, but then disperse to a lawn of noncohesive cells. The defect stems from the inability of the mutant at the restrictive temperature to accumulate or retain an adequate level of a newly arisen, plasma-membrane-associated cohesive moiety during the later stages of morphogenesis. We now report that the noncohesive mutant cells can be induced to cohere at a level of greater than 99% by addition of a fraction reactive with wheat germ agglutinin and isolated from the plasma membranes of late-stage, cohesive mutant or wild-type cells. Furthermore, the cohesivities of late-stage, cohesive mutant or wild-type cells can be significantly enhanced by the same preparations but early-stage cohesive cells remain unaffected. The cohesion-inducing activity can be recovered from two regions of a one-dimensional polyacrylamide gel electropherogram following elution and renaturation. The first is associated with a single silver-staining band (apparent molecular weight 95,000). It appears de novo at a postaggregative stage, and accumulates in a thermostable fashion in the wild-type and in a thermosensitive fashion in the mutants, concurrent with the loss of cohesivity. The second is associated with a complex of silver-staining bands (apparent molecular weights 40,000-50,000). The activity of the eluate reactive with wheat germ agglutinate is destroyed within 5 min at 100 degrees C.     

The biological activity of catfish pancreatic somatostatin

Catfish pancreatic somatostatin, which contains eight additional amino acids on the amino terminus of a tetradecapeptide with considerable homology to tetradecapeptide somatostatin (SRIF), is a naturally occurring homology of the hypothalamic peptide. The purpose of these studies was to determibe the biological activity of this somatostatin homolog. Inhibition of ¹²⁵I-labelled tyr¹-SRIF binding to bovine pituitart plasma membranes by catfish pancreatic somatostatin was approximately 33% that of SRIF. Pancreatic somatostatin has full biological activity measured by inhibition of growth hormone release from isolated rat pituitary cells, but 0.01–0.1% the potency of SRIF. Pancreatic somatostatin at 100 ng/ml produced a 50–60% inhibition of insulin and glucagon secretion from perfused rat pancreas, while SRIF produced comparable inhibition at 10 ng/ml. This report demonstrates that a larger molecular form and natural homolog of SRIF, isolated from fish pancreas, has the same (but reduced) biological activities in rat assay systems as somatostatin originally isolated from sheep hypothalamus.     

Presence of an actin-like protein in mycelium of Neurospora crassa.

Addition of ATP, CaCl2, and KCl to supernatants prepared from mycelia of Snowflake (strain 507), a morphological mutant of Neurospora crassa, results in the formation of filaments 70 nm in diameter. The "decorated" appearance of these filaments after incubation with heavy meromyosin from rabbits suggests they are actin-like.