Spring migration of Atlantic mackerel,Scomber scombrus,in relation to water temperature through Cabot Strait (Gulf of St. Lawrence)

Synopsis Sea surface temperatures across Cabot Strait (Gulf of St. Lawrence) ranged from 6 to 9°C on June 3, 1989, but only from 3 to 5°C on June 2, 1990. Periods of peak commercial landings of mackerel in eastern Cape Breton Island extended from May 22 to June 3 in 1989, and from May 28 to June 2 in 1990. In late May 1990, Atlantic mackerel were captured with a purse-seiner during exploratory fishing in Cabot Strait; commercial quantities were caught in water as cold as 2.8°C. The presence of mackerel in water a full 4°C colder than its reported lower tolerance limit indicates that the development of the 7°C isotherm is not a requirement for the vernal appearing of mackerel. The overlap of the periods of peak commercial landings between 1989 and 1990, despite: marked differences in warming chronology, suggests that the movements of mackerel are not as closely linked to water temperature as previously reported. The fish's thermal preferences could be subordinate to their reproductive requirements at this stage of their spawning migration.     

On the compatibility of carbon uptake rates calculated from stable and radioactive isotope data: implications for the design of experimental protocols in aquatic primary productivity

Basic differences between the ¹³C and the ¹⁴C techniques ofmeasuring carbon uptake by phytoplankton exist at the levelof the isotopic analysis. With the first method, a ratio ofisotopic abundances is measured on the sample, whereas an absoluteamount of isotope is estimated with the second method. If acarbon source other than the labeled one is utilized by thephytoplankton during incubation, the stable isotope method maybe biased. Specific uptake values will be underestimated bythis effect. It is, however, possible to obtain unbiased estimatesof the ¹³C-labeled carbon uptake by using an equation containinga term describing the final particulate carbon concentration.Only under this condition will carbon uptake rates derived from¹³C isotope data be always compatible with the ¹³C method ofmeasuring primary production ^*This paper is the result of a study made at the Group for AquaticPrimary Productivity (GAP), Second International Workshop heldat the National Oceanographic Institute, Haifa, Israel in April–May1984.     

A proton-deuterium exchange study of three types ofDesulfovibrio hydrogenases

Summary Hydrogenases are among the main enzymes involved in bacterial anaerobic corrosion of metals. The study of their mode of action is important for a full comprehension of this phenomenon. The three types ofDesulfovibrio hydrogenases [(Fe), (NiFe), (NiFeSe)] present different patterns in the pH dependence of their activity. The periplasmic enzyme fromDesulfovibrio salexigens and the cytoplasmic enzyme fromDesulfovibrio baculatus both have pH optima at 7.5 for H₂ uptake and 4.0 for H₂ evolution and H⁺–D₂ exchange reaction (measured by membrane-inlet mass-spectrometry). The H₂ to HD ratio at pH above 5.0 is higher than 1.0. The periplasmic hydrogenase fromD. gigas presents the same pH optimum (8.0) for the H⁺–D₂ exchange as for H₂ consumption. In contrast, the enzyme fromD. vulgaris has the highest activity in H₂ production and in the exchange at pH 5.0. Both hydrogenases have a H₂-to-HD ratio below 1.0.     

The relationship between hydrogen metabolism,sulfate reduction and nitrogen fixation in sulfate reducers

Summary Hydrogenase and nitrogenase activities of sulfate-reducing bacteria allow their adaptation to different nutritional habits even under adverse conditions. These exceptional capabilities of adaptation are important factors in the understanding of their predominant role in problems related to anaerobic metal corrosion. Although the D₂–H⁺ exchange reaction indicated thatDesulfovibrio desulfuricans strain Berre-Sol andDesulfovibrio gigas hydrogenases were reversible, the predominant activity in vivo was hydrogen uptake. Hydrogen production was restricted to some particular conditions such as sulfate or nitrogen starvation. Under diazotrophic conditions, a transient hydrogen evolution was followed by uptake when dinitrogen was effectively fixed. In contrast, hydrogen evolution proceeded when acetylene was substituted as the nitrogenase substrate. Hydrogen can thus serve as an electron donor in sulfate reduction and nitrogen metabolism.     

Criteria for Internal Mammary Artery Implantation Based on Cine Coronary Arteriography

Preoperative coronary arteriograms were correlated, in a group of 50 patients, with left internal mammary angiograms obtained from 11 to 32 months, with a mean of 17 months, after mammary artery implantation. In all patients in whom the internal mammary artery was patent and considered functional with good angiographic opacification of the anterior descending coronary artery, the preoperative coronary angiogram showed total or subtotal obstruction of the latter vessel, with indirect evidence of decreased flow and pressure distal to the obstruction. This evidence was provided by the presence of a collateral circulation or, in a few cases of subtotal obstruction, delayed opacification of the vessel distal to the obstruction.In patients in whom the internal mammary artery was patent but showed no anastomotic connection with the anterior descending coronary artery or only opacification of small coronary branches, the degree of coronary obstruction was, in most cases, less than 90% of the lumen of the coronary artery in the absence of any collateral circulation or delayed opacification of the vessel distal to the obstruction.Occlusion of the internal mammary artery was seen as often in the presence of total or subtotal obstructions as with lesser degrees of anterior descending coronary artery obstruction, and is believed unrelated to the degree of pre-existing coronary artery disease.Successful internal mammary artery implantation can be related to specific coronary angiographic patterns recognizable before operation; these may serve as reliable criteria for the selection of patients.     

Considérations sur la nature,l'origine,et le comportement des elaioplastes chez les Monocotylédones

Résumé L'étude en microscopie photonique et électronique, chez quatre espèces de Monocotylédones, a permis de mettre en évidence en plus de certains caractères concernant leur morphologie et leur répartition, le comportement des élaïoplastes au cours de la mitose et l'origine intracytoplasmique de ces organites sous forme d'amas de vésicules en relation probable avec reticulum endoplasmique. Enfin des rapprochements ont été faits avec les corps centraux des quelques bryophytes et certaines formations particulières aux Desmidiées.

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Summary The study in photonic and electronic microscopy of four species of monocotyledons allowed us to make obvious, in addition to several characteristcs concerning their morphology and repartition, the behaviour of the elaïoplasts during mitosis, and the intracytoplasmic origin of these organelles in the shape of vesicle gatherings probably related to the endoplasmic reticulum. Besides some comparisons have been made with the central bodies of Bryophyts and several formations peculiar to Desmids.

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Zusammenfassung Die licht- und elektronenmikroskopische Untersuchung von vier Monokotyledonenarten ermöglichte uns, zusammen mit bestimmten Kennzeichen ihrer Morphologie und ihrer Verteilung, das Verhalten der Elaioplasten im Laufe der Mitose und die Bildung der Bläschenhaufen, die mit dem endoplasmatischen Reticulum wahrscheinlich in Verbindung stehen, klarzustellen. Schließlich sind Vergleiche mit den Zentralkörpern der Bryophyten und mit gewissen Bildungen, die den Desmidiaceen eigentümlich sind, angestellt worden.

     

Time-resolved spectroscopy of the blue fluorescence of spinach leaves

When excited by ultraviolet radiation, leaves of a great number of species of higher plants exhibit emission of blue fluorescence, comparable in intensity to the red emission of chlorophyll. The fluorescence decay of the blue emission of spinach leaves recorded by single photon counting techniques is decomposed into exponential components and it is shown that at least three different components are present. The lifetime of the three components does not show significant variations with the excitation or emission wavelengths. The excitation and emission spectra of each component were determined. The nature of the chemical compounds which cause this emission is discussed in relation to these spectra.     

A serum-free system for culturing human placental trophoblasts

Summary We have compared hormone production by early gestation and term human placental trophoblasts cultured in Ham's F10 medium containing 10% fetal bovine serum with that by cells cultured in serum-free HB102 medium. Mean daily production of progesterone on Days 3 to 7 was approximately 25% less by both early gestation and term cells cultured in HB102 as compared to Ham's F10, but production was maintained at a stable level for at least 7 d longer than the cells in Ham's. Estradiol production from 10⁻⁶ M dehydroepiandrosterone by both early gestation and term cells was comparable in both media. Human placental lactogen production on Days 3 to 7 was 40% less by cells cultured in HB102. Human chorionic gonadotropin (hCG) output by early gestation cells was also 50% less in HB102 but term cells in HB102 produced twice as much hCG as those in Ham's F10. 3B-Hydroxysteroid dehydrogenase (3BHSD) activity in early gestation and term cells and 11B-hydroxysteroid dehydrogenase (11BHSD) activity of early gestation cultures was comparable in the two media. 11BHSD activity was decreased in the term cultures, and this decrease was more marked in Ham's than in HB102. Sulfatase and aromatase activities in the early gestation cultures were comparable in both media; sulfatase activity was comparable and aromatase activity only 20% less in the term cells cultured in HB102. These results indicate that serum-free HB102 supports differential function of human trophoblast cells and is useful for studies of placental activity for as long as 14 d in culture.