Lipid composition and food quality of some freshwater phytoplankton for cladoceran zooplankters

The nutritional value of several planktonic algae was testedby means of feeding trials with three cladoceran zooplankters.The algae were monocultures and included two blue-greens, fourgreens and four flagellates with a size range of 5–48µm. The specific growth rates of the zooplankters werechosen as the measure of the nutritional value of the algae.The three cladocerans showed large differences in growth ratein the different algae, but the two cryptomonads were withoutdoubt best suited as food for all. The fatty acid compositionfor the cryptomonads were different from the other algae. Theycontained high percentages of the polyunsaturated fatty acids20:5æ3 (EPA) and 22:6æ3 (DHA), which also are commonin fish. It is suggested that the lipid composition is a probablefactor determining the nutritional quality of the algae.     

The social development of free-ranging infantLemur catta at Berenty reserve,Madagascar

The social development of 11 free-ranging infantLemur catta was examined over the first 16 weeks of the infants' lives. By 16 weeks, infants still occasionally suckled and were carried dorsally, but on the whole, they were independent of their mothers. Sex or mother's rank was not found to affect frequency or type of play behavior. Mother's rank had no effect on frequency of maternal rejections, from the nipple or from riding, but female infants were rejected slightly more frequently than males were. Mothers tended to reject infants more severely and more frequently from dorsal riding than from the nipple. Sex and rank differences were not found with respect to behaviors determined as measures of independence; however, lower-ranking infants engaged in significantly more dependent behaviors than higher-ranking young did. It may be necessary for the infant of a low-ranking mother to maintain closer proximity to its mother for a longer period of time during infancy because such infants may be subject to abuse by higher-ranking group members and, furthermore, may not be as readily rescued in a stressful or dangerous situation as a higher-ranking infant. Sex was not found to be a factor in terms of measures of dependence. The lack of sex differences in developmental behaviors in this species may be related to female dominance, as well as to the fact that, as adults, both sexes engage in aggressive territorial behavirs.     

N-α-biotinylated-neuropeptide Y analogs: Syntheses, cardiovascular properties, and application to cardiac NPY receptor visualization

Two monobiotinylated analogs of neuropeptide Y (NPY) were synthesized by coupling the N-hydroxysuccinimidyl esters of biotin and (6-biotinylamido)-hexanoic acid, respectively, to the free alpha-NH2 group of the side chain protected NPY peptide resin. Crude peptides obtained by HF cleavage were purified by RPLC and their integrities were confirmed by amino acid and mass spectral analysis. As with NPY, both biotinylated analogs inhibited 125I-NPY binding and adenylate cyclase activity of rat cardiac ventricular membranes in a dose-dependent manner. N-alpha-[(6-biotinylamido)-hexanoyl]-NPY exhibited potencies comparable to that of NPY whereas N-alpha-biotinyl-NPY was slightly less potent. In the in vivo experiments, however, both the biotinylated analogs exhibited responses comparable to NPY in increasing arterial blood pressure and decreasing heart rate in anesthetized rats. The responses of the biotinyl analogs were longer lasting than those of NPY. Histochemical studies revealed that N-alpha-[(6-biotinylamido)-hexanoyl]-NPY could label the NPY receptors in rat cardiac ventricular tissues. This labeling was specific since intact NPY inhibited the staining. These studies show that biotinyl-NPY analogs exhibit biological potencies comparable to intact NPY and can therefore be used to further probe the NPY-receptor interaction.     

Activation of Protein Kinase C Augments Peptide Release from Rat Sensory Neurons

Abstract: To determine whether protein kinase C (PKC) mediates release of peptides from sensory neurons, we examined the effects of altering PKC activity on resting and evoked release of substance P (SP) and calcitonin gene-related peptide (CGRP). Exposing rat sensory neurons in culture to 10 or 50 n M phorbol 12,13-dibutyrate (PDBu) significantly increased SP and CGRP release at least 10-fold above resting levels, whereas the inactive 4α-PDBu analogue at 100 n M had no effect on release. Furthermore, 100 n M bradykinin increased peptide release approximately fivefold. Down-regulation of PKC significantly attenuated the release of peptides evoked by either PDBu or bradykinin. PDBu at 1 n M or 1-oleoyl-2-acetyl- sn -glycerol at 50 µ M did not alter resting release of peptides, but augmented potassium- and capsaicin-stimulated release of both SP and CGRP approximately twofold. This sensitizing action of PKC activators on peptide release was significantly reduced by PKC down-regulation or by pretreating cultures with 10 n M staurosporine. These results establish that activation of PKC is important in the regulation of peptide release from sensory neurons. The PKC-induced enhancement of peptide release may be a mechanism underlying the neuronal sensitization that produces hyperalgesia.     

Comparing the spectroscopic and electrochemical properties of ruthenium and osmium complexes of the tridentate polyazine ligands 2,2′:6′,2″-terpyridine and 2,3,5,6-tetrakis(2-pyridyl)pyrazine

A number of osmium and ruthenium complexes of the tridentate ligands 2,2′:6′,2″-terpyridine (tpy) and 2,3,5,6-tetrakis(2-pyridyl)pyrazine (tpp) have been prepared and characterized by our laboratory. All these complexes possess metal based oxidations and ligand based reductions localized on each polyazine ligand. Polymetallic complexes bridged by the tpp ligand exhibit two sequential tpp based reductions prior to the reduction of other polyazine ligands in these complexes. The spectroscopy of these complexes is dominated by ligand based π-π^* transitions in the ultraviolet and MLCT (metal-to-ligand charge transfer) bands terminating on each polyzine ligand in the visible. For the complexes reported herein the lowest lying optical transitionis a M → BL CT band. For most of the complexes reported, occupation of this excited state gives rise to an observable emission at room temperature. For ruthenium complexes of these tridentate ligands, the presence of a low-lying LF state shortens the excited state lifetimes of these chromophores. This gives rise to ruthenium complexes that display shorter excited state lifetimes than the analogous osmium based systems. Incorporation of tpp based chromophores into polymetallic frameworks leads to the production of bimetallic species with long-lived excited states, 100 ns at room temperature. This makes these chromophores good candidates for the development of stereochemically defined supramolecular complexes. It is possible to measure an electrochemical HOMO-LUMO energy gap and a correlation between this electrochemically measured energy gap and the spectroscopic energy associated with this HOMO→LUMO transition are reported herein (HOMO== highest occupied molecular orbital, LUMO = lowest unoccupied molecular orbital).     

Rapid Stimulation of EAAC1-Mediated Na+-Dependent l-Glutamate Transport Activity in C6 Glioma Cells by Phorbol Ester

Abstract: C6 glioma cells were used as a model system to study the regulation of EAAC1-mediated Na⁺-dependent l -[³H]glutamate transport. Although a 30-min preincubation with forskolin had no effect on transport activity, preincubation with phorbol 12-myristate 13-acetate (PMA) increased transport activity two- to threefold. PMA caused a time-dependent and concentration-dependent increase in EAAC1-mediated l -[³H]glutamate transport activity. A 2-min preincubation with PMA was sufficient to cause more than a twofold increase in transport activity and the protein synthesis inhibitor cycloheximide had no effect on the increase. These data suggest that this increase is independent of protein synthesis. The EC₅₀ value of PMA for stimulation of transport activity was 80 nM. Kinetic analyses demonstrated that the increase in transport activity was due to a 2.5-fold increase in V_max with no change in K_m. PMA also increased the transport of the nonmetabolizable analogue, d -[³H]aspartate to the same extent. In parallel assays, PMA did not, however, increase Na⁺-dependent glycine transport activity in C6 glioma. The inactive phorbol ester 4α-phorbol 12,13-didecanoate, did not stimulate l -[³H]glutamate transport activity, and the protein kinase C inhibitor chelerythrine blocked the stimulation caused by PMA. Okadaic acid and cyclosporin A, which are phosphatase inhibitors, had no effect on the stimulation of transport activity caused by PMA. The Ca²⁺ ionophore A23187 did not act synergistically to increase PMA stimulation. In previous studies, PMA caused a rapid increase in amiloride-sensitive Na⁺/H⁺ transport activity in C6 glioma. In the present study, pre- and coincubation with amiloride had no effect on the stimulation of transport activity caused by PMA. These studies suggest that activation of protein kinase C causes a rapid increase in EAAC1-mediated transport activity. This rapid increase in Na⁺-dependent l -[³H]-glutamate transport activity may provide a novel mechanism for protection against acute insults to the CNS.     

Duplication of the PMP22 gene in 17p partial trisomy patients with Charcot-Marie-Tooth type-1A neuropathy

Autosomal dominant Charcot-Marie-Tooth type-1A neuropathy (CMT1A) is a demyelinating peripheral nerve disorder that is commonly associated with a submicroscopic tandem DNA duplication of a 1.5-Mb region of 17p11.2p12 that contains the peripheral myelin gene PMP22. Clinical features of CMT1A include progressive distal muscle atrophy and weakness, foot and hand deformities, gait abnormalities, absent reflexes, and the completely penetrant electrophysiologic phenotype of symmetric reductions in motor nerve conduction velocities (NCVs). Molecular and fluorescence in situ hybridization (FISH) analyses were performed to determine the duplication status of the PMP22 gene in four patients with rare cytogenetic duplications of 17p. Neuropathologic features of CMT1A were seen in two of these four patients, in addition to the complex phenotype associated with 17p partial trisomy. Our findings show that the CMT1A phenotype of reduced NCV is specifically associated with PMP22 gene duplication, thus providing further support for the PMP22 gene dosage mechanism for CMT1A. Received: 3 May 1995 / Revised: 1 August 1995     

Vigilance behavior during the birth and lactation season in naturally occurring ring-tailed lemurs (Lemur catta) at the Beza-Mahafaly Reserve,Madagascar

I examined the vigilance behavior of adult males and females in two groups of ring-tailed lemurs(Lemur catta)during the birth and lactation season at the Beza-Mahafaly Reserve, southwestern Madagascar. I found no sex difference with respect to the rates of overall vigilance, rates of vigilance toward a potential predator or unfamiliar sound, or rates of vigilance toward conspecifics from other social groups, nor were there sex differences in the percentage of time spent vigilant in any of the above categories. Higher-ranking females were vigilant significantly more often toward predators or potential predators than lower-ranking females were. I detected no relationship between vigilance behavior and dominance rank among adult males. The alpha female in each group exhibited significantly more vigilance behavior than all other members of her group. It was predicted that males should exhibit more vigilance behavior than females do, particularly during the birth and lactation season, when predator pressure is high, if they are benefiting females in this respect. I discuss the results in the context of this prediction and in terms of how ring-tailed lemur males benefit females, and why they may be tolerated in social groups.     

A pathogenic bacterium triggers epithelial signals to form a functional bacterial receptor that mediates actin pseudopod formation.

Enteropathogenic E. coli (EPEC) belongs to a group of bacterial pathogens that induce actin accumulation beneath adherent bacteria. We found that EPEC adherence to epithelial cells mediates the formation of fingerlike pseudopods (up to 10 microm) beneath bacteria. These actin-rich structures also contain tyrosine phosphorylated host proteins concentrated at the pseudopod tip beneath adherent EPEC. Intimate bacterial adherence (and pseudopod formation) occurred only after prior bacterial induction of tyrosine phosphorylation of an epithelial membrane protein, Hp90, which then associates directly with an EPEC adhesin, intimin. These interactions lead to cytoskeletal nucleation and pseudopod formation. This is the first example of a bacterial pathogen that triggers signals in epithelial cells which activates receptor binding activity to a specific bacterial ligand and subsequent cytoskeletal rearrangement.