Territoriality and changes in resource use by sunbirds at Leonotis leonurus (Labiatae)

Summary Leonotis leonurus was studied with the aim of characterising nectar quality and quantity, and of monitoring the sunbirds' response to the resource. The flowers produced high quality nectar in low quantities. Nectar quality remained constant during the day and averaged 23.4% sucrose equivalents (an energy content of 3.8j/l). Nectar production was highest during the morning when flow rates reached a peak of 3.3 l/h. L. leonurus was visited by four species of sunbirds. In 1977 there were 7.8 visits/h to the flowers. The clump was defended by a single Olive Sunbird (Nectarinia olivacea) who defended the flowers intra- and interspecifically. On one day the territorial bird obtained approximately 57.1 kJ from the Leonotis flowers and expended 5.4 kJ on defence and 13.6 kJ overall while on the territory. Territorial behaviour and intruder pressure was a function of resource availability. When Leonotis nectar levels were high intruder pressure was intense and the territorial bird employed long chases as a defence behaviour. When nectar levels desreased intruder pressure was lower, the territorial bird chased less and employed vocalisations as a relatively inexpensive form of territorial behaviour.In 1978 there was an abundance of nectar sources in the study area due to the late onset of the dry season. Sunbirds were not territorial at Leonotis and visiting rates were lower than in 1977, averaging only 1.7 visits per hour. Instead the sunbirds concentrated on contemporaneously flowering plant species, particularly Halleria lucida.     

Patients with myotonic dystrophy,a possible segmental progeroid syndrome,and duchenne muscular dystrophy have fibroblasts with normal limits for in vitro lifespan and growth characteristics

Myotonic dystrophy (MyD) has been suggested to be a segmental progeroid syndrome in man, as this syndrome has some clinical manifestations of premature aging. Fibroblasts from patients with other progeroid syndromes have been shown to have diminished in vitro lifespans or growth characteristics; therefore, it was of interest to study cellular senescence in fibroblasts from patients with MyD. Fibroblast cultures from patients with Duchenne muscular dystrophy (DMD) were used as additional controls, as premature aging is not associated with this genetic disorder. Primary skin fibroblast cultures obtained from patients with MyD or DMD and from age-sex matched controls were grown in DMEM plus 10% FBS. The in vitro lifespan was determined by either a 1:4 split ratio or with a constant initial inoculum of 1 × 10⁴ cells/cm², followed by determination of the final density at weekly intervals. Our results demonstrate that there is no difference in the limits of the in vitro lifespan for either the MyD or DMD fibroblast strains compared to the controls. Likewise, no difference could be detected in the growth characteristics of these cells. The only observable difference was that the pooled age-matched controls and MyD cultures had a shorter in vitro lifespan than the DMD group and their pooled controls, a finding expected because of the age of the patients in each group. Unlike the other progeroid syndromes, MyD fibroblasts have normal limits for in vitro lifespan. MyD is probably not closely related to the other premature aging syndromes, although there is an increasing phenotypic expression as a function of age.     

Comparative Biochemical Studies on F and EDP208 Conjugative Pili

EDP208 pili are encoded by a derepressed derivative of a naturally occurring lac plasmid, F(0)lac (incompatibility group FV), originally isolated from Salmonella typhi. EDP208 pili are serologically unrelated to F pili and do not promote infection by F-specific ribonucleic acid bacteriophages. However, they do confer sensitivity to the F-specific filamentous deoxyribonucleic acid phages. EDP208-containing cells are multi-piliated and contain approximately 20 pili per cell. These pili contain a single polypeptide subunit of 11,500 daltons. EDP208-specific RNA phages were readily isolated from local sewage. These phages were somewhat smaller in diameter than the F-specific ribonucleic acid phages and absorbed relatively weakly to EDP208 pili. Comparing EDP208 pilin to F, it was found that both contain the equivalent of two to three hexose units per subunit as well as blocked N-termini. EDP208 pilin contains one covalently linked phosphate residue per subunit, whereas the F pilin subunit contains two such residues. Although notable differences were found in the case of three or four amino acids, the overall amino acid compositions of F and EDP208 were very similar. Moreover, the tryptic peptide maps of the two proteins contained seven peptides with similar mobilities, suggesting considerable homology in their amino acid sequences. Substantial similarities were also noted in the secondary structures of F and EDP208 pilin on the basis of circular dichroism studies. The alpha-helix content of both proteins was calculated to be 65 to 70%. X-ray fiber diffraction studies have indicated that the arrangements of subunits in F and EDP208 pili are also similar. It was concluded that F and EDP208 pili are closely related structures.     

Stimulation of human peripheral blood lymphocytes by a sodium periodate (NaIO4) induced growth factor

Sodium periodate treated lymphocytes engage in cell to cell interaction and also yield a soluble growth factor that stimulates DNA synthesis when added to naive autologous cells. Adherent cells enhance the factor mediated activity. Sodium periodate stimulated lymphocytes, treated with mitomycin C, produced no growth factor activity. Partial characterization of the factor indicates that it is non-dialyzable, resistant to ribonuclease, and sensitive to heat, trypsin, and papain.     

Arterio-venous heat exchange systems in the Jackass penguin Spheniscus demersus

Extensive arterio-venous associations occur in the head, axillae and legs of the Jackass penguin Spheniscus demersus. These vascular arrangements appear to facilitate counter-current heat exchange. The major heat exchange system in the head is the post orbital rete mirabile formed by the superior orbital artery. Blood from this rete supplies the eye, nasal passages and superficial jaw muscles. Other blood vessels supplying the superficial areas of the head and mouth associate closely with their corresponding veins.
In the axilla the brachial artery divides to form a humeral plexus of parallel running arteries each associating with up to three interlinking veins. Only the marginal vein does not associate with an artery. It appears that a shunt mechanism, which bypasses the veins in the humeral plexus, functions to permit heat loss when required; for instance in a heat-stressed bird breeding or moulting on land.
In both the upper and lower leg all the major arteries and their branches associate closely with corresponding veins.
The development of these arterio-venous associations indicates that Spheniscus demersus is adapted to a cool aquatic environment in which heat retention is of prime importance.     

Volumetric growth in gammaridean Amphipoda

A non-destructive, direct volumetric method is described for measuring absolute growth rates throughout embryonic and postembryonic life of gammaridean Amphipoda. The method is demonstrated by following embryonic and early postembryonic growth of individuals from a population of Platorchestia platensis Krøyer 1844 living on a fixed shingle shore in the Bay of Fundy, Canada.     

Characterization of the oriT region of the IncFV plasmid pED208

DNA sequence analysis of a 2.2kb EcoRI-HindIII fragment from pED208, the derepressed form of the IncFV plasmid Folac, revealed sequences highly homologous to the oriT region, traM, and traJ genes of other IncF plasmids. The TraM protein was purified and immunoblots of fractionated cells containing pED208 or Folac showed that TraM was predominantly in the cytoplasm. Using DNA retardation assays and the DNase I footprinting technique, the TraM protein was found to bind to three large motifs in the oriT region: (I) an inverted repeat, (II) two direct repeats, and (III) the traM promoter region. These three footprint regions contained a Hinfl-like sequence (GANTC) that appeared 16 times, spaced 11-12 bp (or multiples thereof) apart, suggesting that TraM protein binds in a complex manner over this entire region.     

KILLER WHALES, ORCINUS ORCA, IN THE SOUTHEASTERN BERING SEA: RECENT SIGHTINGS andPREDATION ON OTHER MARINE MAMMALS

An unusual number of killer whales appeared in inshore waters of the southeastern Bering Sea in summer 1989 and 1990. Multiple sightings occurred in Bristol and Kuskokwim bays where killer whales had been seen only rarely in previous years. Three animals became stranded on mud flats in Kuskokwim Bay but were able to free themselves on a high tide. Killer whales were observed interacting with salmon, harbor seals, Steller sea lions, walruses, and beluga whales. Detailed observations were made of killer whales attacking belugas in the Naknek River. Local conditions and behavioral adaptations may reduce the susceptibility of belugas to killer whale predation. Continued killer whale activity in this area would be unlikely to affect fish resources, but might have some influence on beluga whales.     

Structure and function of conjugative pili: monoclonal antibodies as probes for structural variants of F pili.

The lac-tra operon fusion plasmid pTG801 contains the known F plasmid DNA transfer (tra) genes required by Escherichia coli to elaborate functional F pili (T. Grossman and P. M. Silverman, J. Bacteriol. 171:650-656, 1989). Here, we show that these pili are actually structural variants of normal F pili and that the F plasmid must contain additional genes that affect pilus structure and function. We confirmed a previous report that two monoclonal antibodies that recognize epitopes at and near the amino terminus of F pilin do not decorate the sides of normal F pili, as determined by immunogold electron microscopy. However, both antibodies laterally decorated pTG801 pili. The epitope for one of the antibodies has been shown to include the amino-terminal acetyl group of F pilin, which must therefore also be present on pTG801 pilin. Normal antibody staining was restored to pTG801 pili when cells contained, in addition to pTG801, the compatible plasmid pRS31, which must therefore include at least one gene affecting F-pilus structure. One candidate, traD, was excluded as the sole such gene, since traD+ derivatives of a pTG801 strain still elaborated pili that could be laterally decorated with antibody. Moreover, although traD alone restored RNA bacteriophage R17 infectivity to pTG801 cells, as expected, it did not mimic pRS31 in restoring to pTG801 pili other characteristics of normal F pili. We conclude that pRS31 contains as yet uncharacterized genes required for elaboration of structurally normal F pili. Finally, we identified vesicular material, especially abundant in cultures of pTG801 transformants, that stained heavily with the anti-F-pilin monoclonal antibodies. This material may reflect the inner membrane pool of F pilin.