Age-related changes of the somatotrophs of the domestic fowl Gallus gallus

Summary The ultrastructure of the somatotrophs of the caudal pituitary of the domestic fowl was studied quantitatively. Two age groups of male chickens were compared: 4–6 weeks and 24–30 weeks post-hatching. With age, somatotrophs decreased from about 40% to about 30% of the pituitary cell population. Their volume density decreased similarly. Mean volume of a somatotroph was the same in young and adult animals. Because the granule volume density of the somatotrophs was unchanged, but the somatotroph volume density of the gland declined, the granule volume density of the caudal pituitary gland dropped in parallel with that of the somatotrophs. Thus the volume of the gland comprised of somatotroph granules fell about 32%: from 6.57% to 4.45%. This lowered pool of stored hormone may be linked to the lowered circulating levels of growth hormone found in older animals by other investigators.The granule volume density of the somatotrophs was unchanged but the numerical density approximately doubled; thus the mean granule size decreased by 47% with age. The relationship of the size reduction of the granules to the lowered plasma growth hormone levels is not understood at present.Supported in part by Hatch and State funds from the New Jersey State Agricultural Experimental Station and NSF grants PCM 8,0227,27 and PCM 8,302197.     

Midbody sealing after cytokinesis in embryos of the sea urchin Arabacia punctulata

Summary Cytokinesis consists of a contractile phase followed by sealing of the connecting midbody to form two separated cells. To determine how soon the midbody sealed after cleavage furrow contraction, the fluorescent dye Lucifer Yellow CH(457.3 M.W.) was microinjected into cells at various intervals after cleavage had begun. Mitotic PtK₂ cells were recorded with video-microscopy so that daughter cells in the epithelial sheet could be identified for several hours after cell division. One daughter cell of each pair followed was microinjected to determine whether the dye diffused into the other daughter cell. For intervals up to four hours after the beginning of cytokinesis, diffusion took place between daughter cells. After this time the dye did not spread between daughter cells. In sea urchin blastomeres of the first, second and third divisions, Lucifer Yellow passed between daughter blastomeres only during the first 15 min after cytokinesis. If one cell of a two-cell, four-cell or eight-cell embryo was microinjected more than 15 min after the last cleavage, the dye remained in the injected cell and was distributed to all progeny of that cell, resulting in blastulae that were either one-half, one-quarter or one-eighth fluorescent, respectively. Thus, although cleavage furrow contraction takes approximately the same amount of time in sea urchin blastomeres and PtK₂ cells, the time of midbody sealing differs dramatically in the two cell types. Our results also indicate the importance of knowing the mitotic history of cells when injecting dyes into interphase cells for the purpose of detecting gap junctions.     

Effect of initial developmental stage on morphology of transplanted embryonic chick pancreas

Summary It has been reported that only certain types of pancreatic parenchymal cells survive transplantation. This study examines whether the extent of differentiation of the pancreas at the time of transplantation affects the resulting morphology or viability of its components. Segments of chick pancreas or its primordia from stages preceding formation of dorsal bud (60 h) through hatching (day 21) were implanted in the abdominal region of three-day chick embryos. After various periods of growth, grafts were examined by light- and electron microscopy. In all transplants, individual endocrine cells (A, B, D, PP) and islet structure were identical to those of normal embryos of comparable age. The exocrine portion also appeared normal in implants from embryos younger than seven days. In grafts from older donors, however, normal acini and ducts were replaced by dilated, irregularly shaped tubules from which new islets appeared to develop. These results suggest that transplantation causes structural modification of exocrine tissue, which may reflect its initial functional capabilities. These observations are compared with similar structural alterations that occur following experimental obstruction of ducts and in human pancreatic pathology.     

Circadian Rhythms in Competitive Sabre Fencers: Internal Desynchronization and Performance

During a 7-10 day span, circadian rhythms of sleep-wake, self-rated fatigue and mood, oral temperature, eye-hand skill and right and left hand grip strength were investigated in eight subjects: five males (21-28 years of age), members of the French sabre fencing team selected for the 1984 Olympic Games in Los Angeles, and three females (19-26 years of age) practicing fleuret (foil) fencing as a sports activity. On the average six measurements/day/variable/subject were performed. The single cosinor method showed that a circadian rhythm was detectable for only 26 out of the 56 time series (46.4%). Power spectrum analysis gave almost the same figure (19 out of 48: 39.5%) with regard to rhythms with τ=24hr indicating that with one exception (subject JFL) rhythms were internally desynchronized including differences τ between right and left hand grip strength rhythms for three subjects. Results suggest: (a) a physiologic synchronization of circadian rhythms may be a predictor of good performance; (b) however, internal desynchronization as shown previously may be a trivial phenomenon and thus does not imply in itself alterations of either health or performance; (c) chronobiologic methods should be recommended for a better understanding of changes in performance by those participating in competitive and other sports.     

Whole-cell antigens of members of the sulfate-reducing genus Desulfovibrio

Antisera have been developed against the wholecell antigens of Desulfovibrio africanus Benghazi and Walvis Bay, D. vulgaris Hildenborough, D. salexigens British Guiana, D. gigas, and D. desulfuricans Essex 6. An enzymelinked immunoadsorption assay (ELISA) was developed to measure the reaction of these antisera with the homologous and heterologous antigens. The ELISA method demonstrated a reaction between pre-immune sera and cells of D. africanus, D. gigas and D. desulfuricans, suggesting the presence of a lectin-like substance on these cell surfaces. Extensive cross-reactions were seen between the antisera and heterologous cells, suggesting the sharing of a number of surface antigens amongst the Desulfovibrio. However, the pattern of these cross-reactions was different from that observed for an ELISA reaction developed for the cytochrome c₃ from various Desulfovibrio.Abbreviation ELISA enzyme-linked immunoadsorption assay     

Cellobiose metabolism in Erwinia: genetic study

Summary The study of mutants of Erwinia specifically unable to ferment cellobiose indicates that the mutations are clustered between arg and ile on the chromosome of this organism. In vivo cloning of the genes responsible for cellobiose utilization lead to a plasmid, pBEC2, which complements all Erwinia Clb^- specific mutants. When introduced into wild-type E. coli it allows this organism to use cellobiose, arbutin and salicin; it also complements bglB and bglC mutants of Escherichia coli indicating that arbutin and salicin utilization is due to the products of the pBEC2 cloned genes. From the characterization of mutants pleiotropically affected in the utilization of various carbon sources, including cellobiose, arbutin and salicin, it is proposed that the three--glucosides are substrates of the phosphoenolpyruvate-dependent phosphotransferase system (PTS).     

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.     

An interpretation of Fujita's frequency diagrams in phyllotaxis

Fujita's diagrams in phyllotaxis, showing the frequencies of divergence angles as a function of these angles for low phyllotactic patterns such as (2, 1) and (3, 2), which are approximately normal curves centered at the limitdivergence angle of 137.51°, are shown to be puzzling when compared to results and observations in the field. An analysis of these diagrams is proposed, in the context of Fujita's methodology, of data from other sources, of a mathematical theorem on lattices, and of the contact pressure theory of phyllotaxis.