Estimating survival of the shortfin mako Isurus oxyrinchus (Rafinesque) in the north-west Atlantic from tag-recapture data

Survival was estimated for shortfin mako Isurus oxyrinchus in the north-west Atlantic from tag-recapture data. The data used in this study were collected by the National Marine Fisheries Service Cooperative Shark Tagging Programme from 1962 to 2003. In total, 6309 shortfin mako sharks were tagged, of which 730 were recaptured. The high recapture rate of 11·6% for this species provided adequate recapture data to carry out survival analyses. Estimates of survival were generated with the computer software MARK, which provided a means for estimating parameters from tagged animals when they were recaptured. The results of several models are presented with various combinations of constant and time-specific survival and recovery rates. A parametric bootstrap and the median variance inflation factor ( ) approach were used to test the fit of the general model to the data. The estimated indicated a very good model fit. The models with time invariant survival rate had the most support from the data and no group or time period effects were found. Recovery rate ( f ) appeared to increase from 0·043 in the early years to 0·056 in the later years. The nominal survival rate of 0·59 year⁻¹ was adjusted with an estimated tag-shedding rate of 0·26 year⁻¹ to generate a final corrected annual survival estimate of 0·79 with a 95% CI of 0·71–0·87.     

5'-Methylbenzimidazolyl-cobamides are the corrinoids from some sulfate-reducing and sulfur-metabolizing bacteria

The sulfate-reducing bacteria Desulfobacterium autotrophicum, Desulfobulbus propionicus and Archaeoglobus fulgidus (VC-16) and the sulfur-metabolizing archaebacteria Desulfurolobus ambivalens and Thermoplasma acidophilum were found to contain considerable amounts of corrinoids, that were isolated and crystallized in their Co beta-cyano form. In three other sulfur-metabolizing archaebacteria, Thermoproteus neutrophilus, Pyrodictium occultum and Staphylothermus marinus significant amounts of corrinoids were not detected under the isolation methods used. The samples from the three sulfate-reducers were identified with Co alpha-[alpha-(5'-methylbenzimidazolyl)]-Co beta-cyanocobamide. This corrinoid was also obtained from a 5-methylbenzimidazole-supplemented Propionibacterium fermentation and was structurally characterized by ultraviolet/visible, CD, fast-atom-bombardment MS, 1H-and 13C-NMR spectroscopy. Also the major corrinoid from T. acidophilum was (tentatively) analyzed as a 5'-methylbenzimidazolyl-cobamide, whereas the main corrinoid from D. ambivalens was indicated to be vitamin B12 (a 5',6'-dimethylbenzimidazolyl-cobamide). The 5'-methylbenzimidazolylcobamides are found here as the common corrins of some sulfate-reducing and sulfur-metabolizing bacteria. The structural diversity due to the differing nucleotide bases of the corrins examined here and in methanogenic and acetogenic bacteria appears not to correlate to the biological function(s) of the corrins, but rather to be determined by biosynthetic properties of these organisms under natural growth conditions.     

Regulation of clones responding to dextran B1355S. III. The thymic-independent and thymic-dependent antibody responses

The primary antibody response of different mouse strains challenged with two antigenic forms of alpha (1-3) dextran, dextran B1355S and dextran-hemocyanin, was examined. Only BALB/c mice responded with both kappa and lambda antibodies. The kappa to lambda ratio was affected by factors such as the antigenic form of dextran, the time at which the serum was analyzed, and the priming regimen. Surprisingly, priming with hemocyanin in adjuvant increased the kappa portion of the response not only to dextran-hemocyanin but also to dextran B1355S. Other strains of mice responded with only lambda antibodies. These results extend our previous results on the analysis of dextran-specific B cell precursors.     

On the role of Ca2+-calmodulin-dependent and cAMP-dependent protein phosphorylation in the circadian rhythm ofNeurospora crassa

Summary Pulses of some Ca²⁺ channel blockers (dantrolene, Co²⁺, nifedipine) and calmodulin inhibitors (chlorpromazine) lead to medium (maximally 5–9 h) phase shifts of the circadian conidiation rhythm ofNeurospora crassa. Pulses of high Ca²⁺, or of low Ca²⁺, a Ca²⁺ ionophore (A23187) together with Ca²⁺, and other Ca²⁺ channel blockers (La³⁺, diltiazem), however, caused only minor phase shifts. The effect of these substances (A 23187) and of different temperatures on the Ca²⁺ release from isolated vacuoles was analyzed by using the fluorescent dye Fura-2. A 23187 and higher temperatures increased the release drastically, whereas dantrolene decreased the permeation of Ca²⁺ (Cornelius et al., 1989).Pulses of 8-PCTP-cAMP, IBMX and of the cAMP antagonist RP-cAMPS, also caused medium (maximally 6–9 h) phase shifts of the conidiation rhythm. The phase response curve of the agonist was almost 180° out of phase with the antagonist PRC. In spite of some variability in the PRCs of these series of experiments all showed maximal shifts during ct 0–12. The variability of the response may be due to circadian changes in the activity of phosphodiesterases: After adding cAMP to mycelial extracts HPLC analysis of cAMP metabolites showed significant differences during a circadian period with a maximum at ct 0.Protein phosphorylation was tested mainly in an in vitro phosphorylation system (with³⁵S-thio -ATP). The results showed circadian rhythmic changes predominantly in proteins of 47/48 kDa. Substances and treatments causing phase-shifts of the conidiation rhythm also caused changes in the phosphorylation of these proteins: an increase was observed when Ca²⁺ or cAMP were added, whereas a decrease occurred upon addition of a calmodulin inhibitor (TFP) or pretreatment of the mycelia with higher (42° C) temperatures.Altogether, the results indicate that Ca²⁺-calmodulin-dependent and cAMP-dependent processes play an important, but perhaps not essential, role in the clock mechanism ofNeurospora. Ca²⁺ calmodulin and the phosphorylation state of the 47/48-kDa proteins may have controlling or essential functions for this mechanism.     

31P nuclear magnetic resonance spectroscopy study of the anaerobic threshold in humans

The relationships among the lactate threshold (LT), ventilatory threshold (VT), and intracellular biochemical events in exercising muscle have not been well defined. Therefore 14 normal subjects performed incremental plantar flexion to exhaustion on 2 study days, the first for determination of LT and VT and the second for continuous 31P nuclear magnetic resonance spectroscopy of calf muscle. Exercising calf muscle pH fell precipitously at 66.4 +/- 3.4% (SE) of the maximum O2 uptake (VO2max) and was termed the intramuscular pH threshold. This did not occur at a significantly different metabolic rate from that at the LT (78.6 +/- 5.9% VO2max) or at the VT (75.0 +/- 4.1% VO2max, P = 0.15 by analysis of variance). Four subjects showed an intramuscular pH threshold and VT without a perceptible rise in forearm venous blood lactate. It is concluded that traditional markers of the "anaerobic threshold," the LT and VT, occur as intramuscular pH becomes acid for a group of normal subjects undergoing incremental exercise to exhaustion. It is speculated that neuronal pathways linking intramuscular biochemical events to the ventilatory control center may explain the intact VT in those subjects without an "intermediary" LT.     

Complete microbial degradation of both enantiomers of the chiral herbicide mecoprop [(RS)-2-(4-chloro-2-methylphenoxy)propionic acid] in an enantioselective manner by Sphingomonas herbicidovorans sp. nov.

Sphingomonas herbicidovorans MH (previously designated Flavobacterium sp. strain MH) was able to utilize the chiral herbicide (RS)-2-(4-chloro-2-methylphenoxy)propionic acid (mecoprop) as the sole carbon and energy source. When strain MH was offered racemic mecoprop as the growth substrate, it could degrade both the (R) and the (S) enantiomer to completion, as shown by biomass formation, substrate consumption, and stoichiometric chloride release. However, the (S) enantiomer disappeared much faster from the culture medium than the (R) enantiomer. These results suggest the involvement of specific enzymes for the degradation of each enantiomer. This view was substantiated by the fact that resting cells of strain MH grown on (S)-mecoprop were able to degrade the (S) but not the (R) enantiomer of mecoprop. Accordingly, resting cells of strain MH grown on (R)-mecoprop preferentially metabolized the (R) enantiomer. Nevertheless, such cells could transform (S)-mecoprop at low rates. Oxygen uptake rates with resting cells confirmed the above view, as oxygen consumption was strongly dependent on the growth substrate. Cells grown on (R)-mecoprop showed oxygen uptake rates more than two times higher upon incubation with the (R) than upon incubation with the (S) enantiomer and vice versa.     

Vascular morphology of the bovine spermatic cord and testis

Summary The highly coiled testicular artery within the bovine spermatic cord has a constant luminal diameter but a continuously decreasing mural thickness. The pampini form plexus is composed of three interconnected venous networks differing in mesh sizes and calibres. The large veins of the first network display pouches and permanent constrictions, which may serve as throttle devices. The constitutents of the third network are venules or venous capillaries with diameters between 10 and 20 m; they favor a periarterial position or even occupy the media-adventitia border of the testicular artery. All plexus veins are devoid of valves. The existence of true arteriovenous anastomoses between smaller branches of the testicular artery and plexus veins was established by serial sections. The vascular morphology of the spermatic cord is discussed with special attention to a postulated venous-arterial steroid transfer in this region.Supported by the Deutsche Forschungsgemeinschaft and the Stiftung zur Förderung der wissenschaftlichen Forschung an der Universität Bern     

Orientation and dynamics of phospholipid head groups in bilayers and membranes determined from 31P nuclear magnetic resonance chemical shielding tensors

31P nuclear magnetic resonance (NMR) powder spectra have been used to determine the principal values of the chemical shielding tensors of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, and phosphatidic acid. The shielding tensors in all cases were clearly nonaxial. The principal values for the monoester phosphatidic acid shielding tensor are -40, -4, and 48 ppm relative to 85% H3PO4. By contrast the diesters have values of -87, -25, and 119 ppm for phosphatidylcholine, -81, -20, and 105 ppm for phosphatidylethanolamine, and -80, -20, and 112 ppm for phosphatidylserine. This difference reflects the sensitivity of the 31P shielding tensor to chemical environment. Anisotropic motion of the molecules in lamellar dispersions of phospholipids caused an incomplete averaging of the shielding tensors resulting in partially narrowed spectra. Spectra of various phospholipid dispersions were recorded as a function of temperature and transitions observed at the gel-liquid crystalline phase transition temperatures. Using a reasonable set of initial conditions, it was shown that a simple model of molecular motion could successfully predict the observed spectra and their temperature dependences. The model includes rotations about the P-O(glycerol) bond and the molecular z axis and a wobble of the molecule about the bilayer normal. As the temperature increases, the wobble amplitude increases and the spectra narrow. A preliminary 31 P NMR spectrum of chick embryo fibroblasts is included. The similarities between this spectrum and those of the lamellar dispersions indicate that some of the predominant features are due to the phospholipid resonances.