Control of a teleost social signal

Territorial male Haplochromis burtoni (Teleostei; Cichlidae) have a dark facial stripe, the 'eyebar', which can appear and disappear within seconds, independently of other coloration patterns. It is used to signal territory ownership and aggressive intent. Some males, called 'barless', have functional melanophores in the eyebar region but never display this pattern, because melanin in eyebar pigment cells is never dispersed. The eyebar melanophores are controlled by a specialized branch of the maxillary nerve. Lesioning the 'eyebar nerve' resulted in immediate melanin dispersion and consequent darkening of the eyebar pattern, and it abolished the normal paling response in all behavioral situations. Nerve lesion produced similar results in both barred and barless males, except that the coloration of the denervated eyebar in barless males was more similar to camouflage markings than to the conspicuous black eyebar used as a social signal. Electrical stimulation of the maxillary nerve produced melanin aggregation. Photoelectric recordings of this paling response revealed no differences between barred and barless males, or between the eyebar and other facial chromatophores that do not function as visual displays. Thus, the difference in the physiological state of eyebar melanophores in intact barred and barless males cannot be explained by differences in peripheral nerve anatomy or physiology.     

Neurochemical evidence for two types of presynaptic alpha2-adrenoceptors

Neurochemical and pharmacological evidence has been obtained that noradrenergic varicosities (in mouse and rat vas deferens) and cholinergic varicosities (in the Auerbach's plexus) contain heterogenous alpha₂-adrenoceptors through which the release of [³H]noradrenaline and [³H]acetylcholine can be modulated. The quantitative data also support the hypothesis that different noradrenaline and xylazine sensitive alpha₂-adrenoceptors are present prejunctionally in the vas deferens and Auerbach's plexus preparations. Prazosin, although it has a presynaptic inhibitory effect on alpha₂-adrenoceptors of noradrenergic axon terminals, has no effect on cholinergic axon terminals. These data suggest that there are two different types of alpha₂-adrenoceptors at the presynaptic axon terminals.Special Issue Dedicated to Dr. Abel Lajtha     

Functional and structural analyses of mouse genomic regions screened by the morphological specific-locus test

Genetic analyses of certain classes of mutations recovered in the mouse specific-locus test (SLT) have characterized arrays of deletions, overlapping at the marked loci. Complementation maps, generated for several of the regions, have identified a number of functional units surrounding each marked locus and have ordered the mutations into complementation groups. Molecular entry to all but one of the marked regions has been achieved by (1) identifying proviral integrations in, or close to, the specific loci (d, se, a, c); (2) mapping random anonymous clones from appropriately enriched libraries to the longest deleted segments, then submapping to more limited segments on the basis of complementation and deletion-breakpoint maps (c, p); (3) similarly mapping known clones thought to be located in pertinent chromosomal regions (p, c, d); and (4) cloning specific genes that reside in regions corresponding to the deletions (b, c, p). The molecular analyses have confirmed that genetically-inferred deletions are structural deletions of DNA. The emerging physical maps are concordant with the complementation maps, and in several cases have discriminated among members of a complementation group with respect to breakpoint positions. Deletion-breakpoint-fusion fragments have prove to be highly useful for making large chromosomal jumps to facilitate physical mapping. The recent advances toward correlating physical and functional maps of specific regions of the mouse genome owe much to the existence of arrays of mutations involving loci marked in the SLT. In turn, the characterizations of these regions have made it possible to demonstrate qualitative differences among mutations resulting from different treatments. This new capability for qualitative analysis, which will increase as the molecular studies proceed, further enhances the value of the SLT, which has been extensively used for quantitative studies in germ-cell mutagenesis.     

Ecological analyses of nesting success in evening grosbeaks

Summary We studied the nesting success of Evening Grosbeaks (Coccothraustes vespertinus) inhabiting two areas of the Front Range of the Rocky Mountains of Colorado from 1983–1987. Sixty-four nests were followed during building, incubating, brooding, and fledging; 54.7% were successful (young fledged). The largest number of nests failed during incubation. Nests started later were more successful than nests begun earlier in the season. Failure was most likely due to severe weather, abandonment during building, or predation. Specific habitat characteristics of grosbeak nesting sites and where nests were placed in trees were consistently associated with nesting success. Successful nests, when compared with nests that failed, were: (1) built in more open areas characterized by dispersed vegetation and a higher minimum canopy, (2) oriented in more southerly directions, (3) built closer to the main trunk of the nest tree, and (4) built in larger trees. Current ideas about whether or not birds actually select nest-sites are briefly discussed. We conclude that some grosbeaks optimally select nest sites where the likelihood of producing fledglings is higher than in other areas.     

V-Y advancement flaps for closure of nasal defects

The nose is a difficult anatomic region in which to close defects resulting from resection of cutaneous malignancies. The V-Y flap is a technique for advancing adjacent tissue, thereby achieving wound closure while minimizing tension. A total of 120 V-Y flaps were used to close 114 nasal defects. The average defect size was 13.5 x 11 mm. Partial flap loss occurred in five patients, with total flap loss in one. One wound infection and two hematomas occurred.     

Ultrastructure of vegetative organization and cell division in the freshwater red algaCompsopogon

Summary Uniseriate filaments of the freshwater red algaCompsopogon coeruleus were examined by transmission electron microscopy for details of vegetative organization and cell division with the goal of providing useful taxonomic characters. Each cell's single, complex chloroplast contains a peripheral encircling thylakoid, and unlike the vast majority of red algae, the cis-regions of dictyosomes are not consistently juxtaposed with mitochondria. These subcellular features, which are present in all examined genera in theCompsopogonales, Erythropeltidales, andRhodochaetales, along with certain unique reproductive characteristics, unify these three orders. During mitosis in uncorticated axial cells, a small, ring-shaped nucleus associated organelle (NAO) is located at each division pole, an intranuclear spindle comes to a moderately acute focus at the flattened, fenestrated metaphase-anaphase division poles and perinuclear ER partially encloses dividing nuclei, including a well-developed interzonal midpiece. The cleavage furrow penetrates the large, central vacuolar region to separate daughter nuclei. These cell division features most closely resemble the pattern described for the orderCeramiales. Our observations of vegetative and dividing cells ofC. coeruleus supplement the growing volume of evidence in favour of uniting all red algae into a single class without subclass designations.Abbreviations ER endoplasmic reticulum - IZM interzonal midpiece - MT microtubule - MTOC microtubule organizing center - NAO nucleus associated organelle - NE nuclear envelope - PER perinuclear endoplasmic reticulum     

Cytoskeletal involvement in spermiation and sperm transport

The process of spermiation and sperm transport was studied using specific inhibitors of cytoskeletal elements. Within 12-24 hr after the intratesticular injection of taxol, a compound that acts to stabilize microtubules and inhibit microtubule-related processes, an unusually large number of microtubules was seen within the body of the Sertoli cell. At the same time, transport of elements within the seminiferous epithelium was affected. At the end of stage VI of the cycle, step 19 spermatids were maintained in the deep recesses of the Sertoli cell and not transported to the rim of the seminiferous tubule lumen. At stage VIII, residual bodies remained at, or near, the rim of the tubule and were not transported to the base of the tubule. They underwent only partial degradation at this site, indicating that there may have been two phases involved in their dissolution--one autophagic and one phagocytic, but the latter did not occur since the residual bodies were not transported to Sertoli lysosomes at the base of the tubule. The observations suggest that microtubules are involved in transport processes within the seminiferous epithelium. Within 1-12 hr after the intratesticular injection of 500 microM cytochalasin D, a compound which interferes with actin-related processes, normal appearing tubulobulbar complexes were not present. The tubular portion (distal tube) of the complex did not initiate development. It was assumed that filaments (which were identified as such using NBD-phallacidin and the S-1 fragment of myosin) played an important role in the development of this portion of the complex. Cells did not eliminate cytoplasm normally, as evidenced by an enlarged cytoplasmic droplet, further emphasizing the published role for tubulobulbar complexes in cytoplasmic elimination. Although sperm were released normally from stage VIII tubules, many remained within the tubular lumen and did not traverse the duct system. Cytochalasin did not inhibit fluid secretion by the Sertoli cell, as demonstrated by efferent duct ligation, but did alter myoid cell actin cytoskeletal organization, suggesting that myoid cell contractility is primarily responsible for transport of sperm. Overall, the observations suggest that cytoskeletal activity of the Sertoli cell is important for several aspects of the spermiation process as well as sperm transport.     

More monensin-sensitive, ammonia-producing bacteria from the rumen

Two monensin-sensitive bacteria which utilized carbohydrates poorly and grew rapidly on amino acids were isolated from the bovine rumen. The short rods (strain SR) fermented arginine, serine, lysine, glutamine, and threonine rapidly (greater than 158 nmol/mg of protein per h) and grew faster on casein digest containing short peptides than on free amino acids ().34 versus 0.29 h(-1)). Gelatin hydrolysate, an amino acid source containing an abundance of long peptides, was unable to support growth or ammonia production, but there was a large increase in ammonia production if strain SR was cocultured with peptidase-producing ruminal bacteria (Bacteroides ruminicola or Streptococcus bovis). Cocultures showed no synergism with short peptides. Strain SR washed out of continuous culture ().1 h(-1)) at pH 5.9. The irregularly shaped organisms (strain F) deaminated glutamine, histidine, glutamate, and serine rapidly (greater than 137 nmol/mg of protein per min) and grew faster on free amino acids than on short peptides ().43 versus 0.21 h(-1)). When strain F was provided with casein or gelatin hydrolysate and cocultured with peptidase-producing bacteria, there was a more than additive increase in ammonia production. Strain F grew in continuous culture (0.1 h(-1)) when the pH was as low as 5.3. The irregularly shaped cells and short rods were present at less than 10(9)/ml in vivo, but they ahd very high specific activities of ammonia production (greater than 310 nmol of ammonia/mg of protein per min) and could play an important role in ruminal amino acid fermentation.     

Dietary fat influences electric membrane properties of neurons in cell culture

1. SJL/J mice were maintained on semipurified diets which differed in the ratio of polyunsaturated/saturated fatty acid content (P/S). Exposure was from conception and was maintained for periods ranging from 6 to 34 weeks. 2. Neural cell cultures were prepared from dorsal root ganglia (DRG). After 6 and 20 days of culture, neuronal electric membrane properties were determined quantitatively by intracellular recording. 3. A number of significant differences were observed for the two dietary conditions. DRG from mice on the low-P/s diet had an increase in the rate of fall of both phases of repolarization which, in conjunction with the reduced action potential overshoot, led to a reduced action potential duration. This shift to shorter-duration action potentials was accompanied by a shift to more monophasic falling phases. The low-P/S neurons also exhibited a decreased afterhyperpolarization, decreased specific membrane resistance, and decreased membrane electrical time constant compared to high-P/S neurons. 4. It was concluded that the P/S ratio in the diet can have a significant effect on the electric properties of neurons. The high-P/S neurons tended to have action potentials with biphasic repolarizations and longer durations. In contrast, the low-P/S neurons tended to have action potentials with monophasic repolarizations and shorter durations. Moreover, the known ionic dependence of these two types of action potentials suggested that the low-P/S diet resulted in action potentials with a more exclusive Na dependence, while the high-P/S diet resulted in action potentials with both Na and Ca dependence.