X-ray absorption spectroscopy of selenium-containing amino acids

Received: 2 April 1999 / Accepted: 17 September 1999     

Alternative routes for the establishment of surface polarity during compaction of the mouse embryo

During the process of compaction, mouse 8-cell blastomeres flatten upon each other and polarize along an axis perpendicular to cell contacts. If the process of flattening is prevented, polarization can still occur, but does so in a lower proportion of cells than for control populations, and without the normal contact-directed orientation. We compared contact-directed and noncontact-directed processes to see if they involve common mechanisms. In nonflattened cells, surface polarization was favored in cells with nuclei located close to the cell surface, and the positions of surface poles and of nuclei tended to coincide. We present evidence that microtubules are involved in the development of microvillous poles associated with nuclei. In contrast it is known that polarization of microvilli occurs in the absence of microtubules if blastomeres are allowed to flatten. We conclude that surface polarization of mouse blastomeres can be accomplished by at least two alternative routes. One requires flattening but is independent of microtubules, and another can occur without flattening but involves a microtubule-mediated interaction between the nucleus and the cell cortex. It seems that both these pathways operate in the undisturbed embryo.     

The cytoskeleton, endocytosis and cell polarity in the mouse preimplantation embryo

The process of cell polarization in mouse 8-cell embryos includes the formation of a polar cluster of cytoplasmic endocytotic organelles (endosomes) subjacent to an apical surface pole of microvilli. A similar polar morphology, supplemented by basally localized secondary lysosomes, is evident following division to the 16-cell stage in outside blastomeres, precursors of the trophectodermal lineage. The roles of microfilaments and microtubules in generating and stabilizing endocytotic and surface features of polarity (visualized by horseradish peroxidase incubation and indirect immunofluorescence labeling, respectively) have been evaluated by exposure of 8- and 16-cell embryos and 8-cell couplets to drugs (cytochalasin D, colcemid, nocodazole) that disrupt the cytoskeleton. The generation of endocytotic polarity is dependent upon intact microtubules and microfilaments, but the newly established endocytotic pole in blastomeres from compacted 8-cell embryos appears to be stabilized exclusively by microtubules. Polarized endocytotic organelles at the 16-cell stage are more resistant to drug treatment than at the 8-cell stage (probably due to microfilament interactions) indicating a maturation phase in the polar cell lineage. Microtubules are also responsible for the orientation of endocytotic clusters along the cell's axis of polarity. In contrast, the generation and stability of polarity at the cell surface appears relatively independent of cytoskeletal integrity. The results are discussed in relation to the mechanisms that may control the development and stabilization of polarization during cleavage.     

Comparison of health problems related to work and environmental measurements in two office buildings with different ventilation systems.

A cross sectional survey investigating "building sickness" was carried out in two buildings with similar populations of office workers but differing ventilation systems, one being fully air conditioned with humidification and the other naturally ventilated. The prevalence of symptoms related to work was assessed by a questionnaire administered by a doctor. A stratified, randomly selected sample of workers was seen (84% response). Building sickness includes several distinct syndromes related to work, most of which were significantly more common in the air conditioned building than the naturally ventilated building--namely, rhinitis (28% v 5%), nasal blockage and dry throat (35% v 9%), lethargy (36% v 13%), and headache (31% v 15%). The prevalence of work related asthma and humidifier fever was low and did not differ significantly between the two buildings. An environmental assessment of the offices was performed to attempt to identify possible factors responsible for the differences in the prevalence of disease. Globe temperature, dry bulb temperature, relative humidity, moisture content, air velocity, positive and negative ions, and carbon monoxide, ozone, and formaldehyde concentrations were all measured. None of these factors differed between the buildings, suggesting that building sickness is caused by other factors.     

Effects of endurance training on the cardiovascular system and water compartments in elderly subjects

Pickering, Gisèle P., Nicole Fellmann, BéatriceMorio, Patrick Ritz, Aimé Amonchot, Michel Vermorel, and JeanCoudert. Effects of endurance training on the cardiovascularsystem and water compartments in elderly subjects. J. Appl. Physiol. 83(4): 1300-1306, 1997.Theeffects of endurance training on the water compartments and thecardiovascular system were determined in 10 elderly subjects [age62 ± 2 yr, pretraining maximal oxygen consumption(O_{2 max})/kg = 25 ± 2 ml · min¹ · kg¹body wt]. They trained on a cycloergometer 3 times/wk for 16 wk(50-80%O_{2 max},then 80-85%O_{2 max}). They werechecked at 8 wk, 16 wk, and 4 mo after detraining. Training improvedO_{2 max} (+16%) andinduced plasma volume expansion (+11%). No change in total body water,extracellular fluid, interstitial and intracellular fluid volumes,fat-free mass, and body weight was detected in this small sample withtraining. Body fat mass decreased (2.1 ± 2.2 kg).Echocardiography at rest showed increased fractional shortening andejection fraction and decreased left ventricular end-systolic dimension(P < 0.05). Blood volume expansioncorrelates with cardiac contractility and has an impact on cardiacfunction. These improvements are precarious, however, and arecompletely lost after 4 mo of detraining, when elderly subjects losethe constraints and the social stimulation of the imposed protocol.

     

The sick building syndrome: prevalence studies.

Random samples or the entire workforce in nine offices in which similar clerical work was being performed were studied using a doctor administered questionnaire that inquired into symptoms that have been linked with the "sick building syndrome." Five of the offices were fully air conditioned, one had recirculation of air and mechanical ventilation, and three were naturally ventilated. Workers in three air conditioned and three naturally ventilated buildings were interviewed blind. Seven of the buildings were studied at our request in the absence of any known problem. Comparison of prevalences of symptoms between the naturally ventilated and the other buildings showed a repeated pattern of nasal, eye, and mucous membrane symptoms with lethargy, dry skin, and headaches. There were highly significant excesses of these six symptoms in the air conditioned buildings when compared by chi 2 tests with the naturally ventilated buildings. It is suggested that these six symptoms represent the sick building syndrome and that the size of the problem is probably greater than is currently recognised. Possible causes are discussed.     

Monosomic and double monosomic substitutions of Hordeum bulbosum L. chromosomes into H. vulgare L.

Summary One of the aims of the interspecific crossing programme between Hordeum vulgare L. and H. bulbosum L. has been to introgress desirable genes into barley from the wild species. However, despite their close taxonomic relationship there have been few reports of achieving this objective using amphidiploid hybrids. In order to broaden the range of available hybrids, partially fertile triploids between H. vulgare (2n = 2x = 14) and H. bulbosum (2n = 4x = 28) were developed and crossed with H. vulgare as female parent. From 580 progeny which were screened, eight putative single monosomic chromosome substitution lines and one double monosomic substitution were identified by cytological analysis. These involved the substitution of H. vulgare chromosome 1 (two lines), 6 (four lines), 6L (one line), 7 (one line) and 1 + 4 (one line) by their respective H. bulbosum homoeologues. The H. bulbosum chromosome was frequently eliminated during plant development, but it was observed regularly in pollen mother cells of two lines. However, pairing between the H. bulbosum chromosome and its H. vulgare homoeologue was low. Several of the lines were more resistant than their H. vulgare parents to powdery mildew (Erysiphe graminis DC. f.sp. hordei Em. Marchai), net blotch (Drechslera teres Sacc.) and scald (Rhynchosporium secalis (Oudem.) Davis). Apart from their use in studying genome relationships, their value to plant breeders will depend on the ease of inducing translocations between the parental chromosomes.     

Pathogenic fungal dynamics in a fall population of the blackmargined aphid (Monellia caryella)

A fall population of the blackmargined aphid, Monellia caryella (Fitch) (Homoptera: Aphididae), was monitored daily for mortality caused by fungi and parasitoids. Three species of Entomophthorales fungi were found. Fungal-induced mortality was found to be correlated with minimum temperature. During the period when the minimum temperature was consistently above 8°C, fungal-induced mortality was positively correlated with the sum of hours of leaf-wetness on days 5, 6, and 7 before sampling. Parasitoid wasps killed fewer hosts than fungi and were not affected by environmental factors.

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Résumé La mortalité quotidienne provoquée par des parasitoïdes et des champignons sur une population automnale de M. caryella Fitch (Homopt. Aphididae) a été suivie à Byron (Géorgie, USA), avec enregistrement de la température, de la pluie et de l'humidité des feuilles. 3 espèces de champignons entomophthorales ont été trouvées: Neozygites sp., Entomophthora planchoniana et Erynia sp. 54% des pucerons morts étaient contaminés par Neozygites et 46% par E. planchoniana. Seuls 2 pucerons avaient été tués par Erynia sp. Les taux de mortalité quotidienne par champignons s'élevaient après les périodes pluvieuses et d'humidité des feuilles. La mortalité due au parasitisme était inférieure à la mortalité due aux champignons et ne semblait pas liée aux conditions écologiques. La discussion porte sur l'importance de la mortalité provoquée par les champignons sur la dynamique de la population de pucerons.

     

Precursors in the biosynthesis of vasopressin and oxytocin in the rat. Characteristics of all the components in high-performance liquid chromatography.

A reverse-phase high performance liquid-chromatography (h.p.l.c.) protocol has been developed, whereby all the major known posterior-pituitary components that are derived from the processing of pro-oxytocin and pro-vasopressin can be separated one from another. Thus, in a single chromatographic step, it has been possible to separate vasopressin (VP), oxytocin (OT), oxytocin-neurophysin (rOT-Np), vasopressin-neurophysin (rVP-Np) and vasopressin-glycopeptide (rVP-GP) from acid extracts of the neurointermediate lobes of rat pituitary glands. All these peptides except rVP-GP were labelled in the neural lobe by 24h after a hypothalamic injection of [35S]cysteine, whereas all except VP were labelled by 24h after a similar injection of [3H]leucine. Three major labelled proteins were isolated from 20 min [35S]cysteine-injected rats when extracts of the supraoptic nucleus were subjected to Sephadex G-75 chromatography, h.p.l.c. and sodium dodecyl sulphate/polyacrylamide-gel electrophoresis. Immunoprecipitation with antisera raised against rat neurophysins, VP and OT revealed 21000- and 19000-mol.wt. common precursors to VP and rVP-Np and a 15000-mol.wt. common precursor to OT and rOT-Np. Some immunoreactive rVP-Np could occasionally be detected in the Vo of Sephadex G-75 chromatograms of Wistar rat supraoptic-nucleus extracts, but no evidence of [35S]neurophysin in this fraction was obtained from h.p.l.c. fingerprinting of its S-carboxymethylated tryptic digests. Radioimmunoassay for rVP-Np and rOT-Np revealed that about 70-80% of the total recovered immunoreactive neurophysin (IR-Np) in the supraoptic nucleus eluted from Sephadex G-75 and h.p.l.c. in the positions of rVP-Np and rOT-Np. Evidence is presented for an approx. 20000-mol.wt. rOT-Np in both Wistar and Brattleboro rats and for an approx. 20000-mol.wt. component in the Brattleboro rat that is recognized by vasopressin-neurophysin antisera.     

Sexual differences in the incidence and severity of ectoparasitic infestation of the brown trout, Salmo trutta L.

Hatchery-reared and wild brown trout, Salmo trutta L., were examined for skin ectoparasites during their spawning period in 1977 and 1978. A total of eight genera of parasites, comprising five ciliates, one flagellate, one monogenean and one parasitic fungus, were identified with as many as five different genera occurring on a single fish. Sexually mature male fish were more frequently or more severely infested by species of Ichthyophthirius, Scyphidia, Gyrodactylus and Saprolegnia than were immature fish of either sex or mature female fish. The differences in ectoparasitic loading could not be correlated with known, seasonal changes in the mucus-producing potential of the epidermis. These findings are discussed in relation to the defence mechanisms of teleost fish and to some of the endocrinological changes that occur in salmonid fish during the spawning season.