The influence of prey consumption and demographic stochasticity on population growth rate of Isle Royale wolves Canis lupus

The relationship between the rates of prey capture and predator population growth is a fundamental aspect of predation, yet it is rarely measured for vertebrate predators. For the isolated wolf population on Isle Royale, annual variation in kill rate explains 22% of the variation in wolf population growth rate. From the slope of this relationship, we estimate that the production efficiency (ratio of production to respiration) of wolves is between 0.5% and 1.5%. More generally, we assess the relative extent to which wolf population growth rate is affected by density dependence, prey availability (moose, Alces alces ), winter weather, and demographic stochasticity. Prey availability explains the most variation in wolf growth rate (42%), but this is only recognized after accounting for the influence of a disease-induced population crash and age structure of the prey population (i.e. number of vulnerable moose, >9 years of age). Demographic stochasticity accounts for approximately 30% of the variation in wolf growth rate. This recognition is important, but not surprising, given that the average population size of Isle Royale wolves is 22. Previous work indicates that the effect of winter climate, as mediated through prey vulnerability and kill rates, is substantial. This work indicates that the direct effect of winter climate is weak, and explains only about 4% of the variation in wolf growth rate (P=0.10).     

Biosynthetic uniform 13C,15N-labelling of zervamicin IIB. Complete 13C and 15N NMR assignment.

Zervamicin IIB is a member of the alpha-aminoisobutyric acid containing peptaibol antibiotics. A new procedure for the biosynthetic preparation of the uniformly 13C- and 15N-enriched peptaibol is described This compound was isolated from the biomass of the fungus-producer Emericellopsis salmosynnemata strain 336 IMI 58330 obtained upon cultivation in the totally 13C, 15N-labelled complete medium. To prepare such a medium the autolysed biomass and the exopolysaccharides of the obligate methylotrophic bacterium Methylobacillus flagellatus KT were used. This microorganism was grown in totally 13C, 15N-labelled minimal medium containing 13C-methanol and 15N-ammonium chloride as the only carbon and nitrogen sources. Preliminary NMR spectroscopic analysis indicated a high extent of isotope incorporation (> 90%) and led to the complete 13C- and 15N-NMR assignment including the stereospecific assignment of Aib residues methyl groups. The observed pattern of the structurally important secondary chemical shifts of 1H(alpha), 13C=O and 13C(alpha) agrees well with the previously determined structure of zervamicin IIB in methanol solution.     

A-Factor as a selective agent for isolation of the soil Gram-negative bacterium strain--the producent of an antibacterial antibiotic]

It was shown the stimulating role of A-factor on soil prokaryotes growth. Soil sample culturing on agar medium, containing A-factor, resulted in the colony forming units (CFU) increasing in comparison with culturing on the medium without this regulator. Gram-negative bacteria were the reason of CFU increasing; previously the effect of A-factor on bacteria of this group was not shown. Gram-negative rod bacterial strain No. 35 was isolated and shown that CFU number was approximately twice increased at A-factor concentration in agar medium 2 and 7 mcg/ml; high A-factor concentration up to 28 mcg/ml was not effective. Isolated strain No. 35 is the producer of antibiotic, effective against gram-positive bacteria.     

Variations in the sulfide regime and the distribution of macrofauna in an intertidal flat in the North Sea

Sulfide concentrations were measured in the inner and outer Königshafen (Sylt, Wadden Sea) from November 1990 to December 1991 to assess the fluctuations of sulfide levels in natural tidal habitats. Three different areas were compared: (1) muddy sediment (2) fine-medium sand, and (3) a mussel bed. Other abiotic factors such as Eh, pH, temperature, grain size and organic content were measured. After assessment of the macrofaunal distribution, an attempt was made to relate the distribution to the sulfide concentrations in the benthic habitat. Sulfide concentrations varied between sites throughout the year with considerable differences ranging from below 5 μM (limit of detection) to about 1 mM (Oct. 1991). The faunal composition (Table 2) at the different sites hardly varied; it was always dominated by annelids: The cirratulidTharyx marioni was the most abundant species in the upper layers of all sites, where it occurred at low sulfide concentrations (<50 μM).Heteromastus filiformis was commonly found in the deeper sediment layers of the muddy site where it was regularly exposed to sulfide levels around 75 μM and peak concentrations in autumn up to 1 mM.Capitella capitata, Tubificoides pseudogaster andTubificoides benedii were very common in the upper sediment layers where sulfide levels were about 150 μM in autumn. These species also occurred, however, in the deeper layers with higher sulfide concentrations. These results document not only the wide annual range of sulfide concentrations at different depths in a tidal flat, they also emphasize that under natural conditions tidal flat annelids are exposed to considerable concentrations of hydrogen sulfide.     

A Sperm Midpiece Defect in a Hereford Bull with Variable Semen Quality and Freezability

A midpiece sperm defect with a frequency of 25-35% in ejaculates obtained from a Hereford bull with a 60 d non-retum rate of 76.4% after careful pre- and postfreeze semen selection was studied in light microscope and by transmission electron microscopy. The defect consisted in a folding and coiling of the distal midpiece characterized by disorganization and irregularity of mitochondria surrounding the axial fiber bundle, combined with retraction of doublet fibers and dislocation and fracturing of these elements and the corresponding dense fibers. Based on examination of the sper- matogenic epithelium it was concluded that the alterations in the axial fiber bundle were secondary to those in the mitochondrial sheath. The abnormality appeared to be related to the “Dag-like” defect earlier observed in different breeds.     

Serum high density lipoprotein cholesterol,alcohol, and coronary mortality in male smokers.

OBJECTIVE--To determine whether the increase in mortality from coronary heart disease with high concentration (> 1.75 mmol/l) of high density lipoprotein cholesterol could be due to alcohol intake. DESIGN--Cohort study. SETTING--Placebo group of the alpha tocopherol, beta carotene cancer prevention (ATBC) study of south western population in Finland. PARTICIPANTS--7052 male smokers aged 50-69 years enrolled to the ATBC study in the 1980s. MAIN OUTCOME MEASURES--The relative and absolute rates adjusted for risk factors for clinically or pathologically verified deaths from coronary heart disease for different concentrations of high density lipoprotein cholesterol with and without stratification for alcohol intake. Similar rates were also calculated for different alcohol consumption groups. RESULTS--During the average follow up period of 6.7 years 258 men died from verified coronary heart disease. Coronary death rate steadily decreased with increasing concentration of high density lipoprotein cholesterol until a high concentration. An increase in the rate was observed above 1.75 mmol/l. This increase occurred among those who reported alcohol intake. Mortality was associated with alcohol intake in a J shaped dose response, and those who reported consuming more than five drinks a day (heavy drinkers) had the highest death rate. Mortality was higher in heavy drinkers than in non-drinkers or light or moderate drinkers in all high density lipoprotein categories from 0.91 mmol/l upward. CONCLUSIONS--Mortality from coronary heart disease increases at concentrations of high density lipoprotein cholesterol over 1.75 mmol/l. The mortality was highest among heavy drinkers, but an increase was found among light drinkers also.     

Structural and immunochemical studies on the lipopolysaccharide of the ‘T-antigen’-containing mutant Proteus mirabilis R14/1959

Abstract In DOC-PAGE, lipopolysaccharide (LPS) of Proteus mirabilis R14/1959 (Rb-type) mutant showed a ladder-like migration pattern indicating the presence of a high molecular weight polysaccharide chain. The isolated polysaccharide, called T-antigen because of similarity with the T1 chain of Salmonella friedenau LPS, contained d -glucose, d -galacturonic acid ( d -GalA), and d -GlcNAc in molar ratios 2:1:1 and was structurally different from the O-antigen of the parental S-strain P. mirabilis S1959 but identical to the O-antigen of another S-strain Proteus penneri 42. The importance of a d -GalA( l -Lys)-containing epitope, most likely present in the core region of LPS, and of GalA present in the T-antigen chain in manifesting the serological specificity of P. mirabilis R14/1959 were revealed using rabbit polyclonal homologous and heterologous R- and O-specific antisera and the appropriate antigens, including synthetic antigens which represent partial structures of various Proteus LPS.