Ultrastructural evaluation of 8–16 cell human embryos cultured in vitro

The fine structure of eight human embryos cleaving in culture are described. Preovulatory human oocytes aspirated at diagnostic laparoscopies were fertilized and developed in vitro by methods which produced normal pregnancies. Three 8-cell and five 10–16 cell embryos showing delayed cleavage were fixed, serially sectioned and examined to determine whether the embryos were developing normally or otherwise.The organization of two 8-cell embryos was apparently normal while the other embryos showed varying aspects of abnormal development. Most blastomeres contained organelles normally present in human ova and their fine structure closely resembled those of comparable mammalian embryos. Nearly all the cellular components encountered in early mammalian embryos were observed. Certain morphogenetic changes were also noted during early cleavage involving nuclei, smooth endoplasmic reticulum and mitochondria.Both normal and abnormal features of the embryos are reported. Multi-nucleated blastomeres and partial fragmentation were commonly seen in abnormal embryos. The importance of ultrastructural evaluation of embryos in an in vitro programme is revealed in this investigation.     

Fine-scale spatio-temporal patterns in a mountain grassland: do species replace each other in a regular fashion?

Abstract. Long-term ‘high spatial resolution’ permanent plot data were used to determine whether fine-scale species replacements in space occur more often than expected on the basis of random processes, and to test whether these replacements are species-specific. Monte Carlo tests were used. There was no indication of significance in associated positive change (species A increased when B increased); the overall number of significant results was not higher than expected on a random basis. For associated negative change, or replacements (species A increased when B decreased) the overall number of significant results was significantly higher than expected. Significant reciprocal replacements between Deschampsia flexuosa, Festuca rubra and Nardus stricta were frequent; changes in Anthoxanthum alpinum and Polygonum bistorta were uncorrelated with changes of the former three. The first three species thus use the ‘same’ space. Both the latter species often reproduce by seeds and their turnover is much higher. The prevalence of negative correlations of changes (i.e. correlation of increase with decrease) supports the concept of an internal structuring within the grassland community.     

Agonistic behavior in wild male Magellanic penguins: when and how do they interact?

Game-theory models predict that the frequency and type of agonistic interactions should vary with the value of the resource being contested. We describe bill duels and overt fighting in male Magellanic penguins (Spheniscus magellanicus) at a breeding colony and determine whether these behaviors change with the value of the nests over which they interact. Bill duels represent low levels of aggression while overt fighting high levels of aggression. Consistent with predictions, overt fighting was more common before egg laying when nests have the highest potential value while bill duels were more common at failed nests later in the season when nests are less valuable as they could not be used for reproduction until the next season. Contrary to expectations, overt fights were shorter and resulted in fewer cuts before egg laying than after egg laying. Large size asymmetries between opponents before egg laying may enable losers to quickly assess their opponents and leave before they are hurt. As predicted, the duration and damage occurring during overt fights were positively correlated with nest cover, which is correlated with higher reproductive success. We conclude that male Magellanic penguins have rules of engagement that in the most cases follow game-theory predictions on when and how to interact.     

Interview with the retinoblastoma family members: Do they help each other?

The ultimate destiny of a cell to undergo division, differentiation, survival, and death results from an intricate balance between multiple regulators including oncogenes, tumor suppressor genes, and cell cycle associated proteins. Deregulation of the cell cycle machinery switches the phenotype from a normal cell to a cancerous cell. Fundamental alterations of tumor suppressor genes may result in an unregulated cell cycle with the accumulation of mutations and eventual neoplastic transformation. As such, one may define cancer as a genetic disease of the cell cycle. In this review, we will emphasize our current understanding of how the cell cycle machinery maintains cellular homeostasis by studying the consequences of its deregulation.     

Gluttony and sex in female ixodid ticks: how do they compare to other blood-sucking arthropods?

The central issue dealt with here is the role of copulation in the control of feeding behaviour in ticks and some haematophagous insects. Female ticks of the family Ixodidae normally engorge to approximately 100 x their unfed body weight, and then drop from the host, produce and lay eggs, and die. Virgins, on the other hand, normally do not exceed 5-40% (depending on species) of the normal engorged body weight. But instead of detaching voluntarily at that point most virgins remain fixed to the host for extended periods, waiting for males to find them so they can complete engorgement. Virgin haematophagous insects, and virgin ticks of the family Argasidae display little, if any, reduction in blood meal size compared to mated females, at least not during the first ovarian cycle. During subsequent ovarian cycles, meal size in some virgin insects may be somewhat reduced depending on how many eggs are retained in the reproductive tract, but the reduction is not nearly to the same extent as that observed for virgin ixodid females. The stimulatory effect of copulation on engorgement in the latter is caused by a pair of proteins (voraxin alpha and beta) produced in the testis and transferred to the female with the spermatophore. Here, I propose why it might be adaptive for an ixodid female to remain small until mated. The hypothesis is suggested from the facts that ixodid ticks remain attached to the host for days (rather than minutes), and that virgin ticks, above a certain critical weight, lose all opportunity for producing viable offspring should they be groomed off the host prematurely, or should the host die while ticks are still attached.     

Cancer metabolism and tumor microenvironment: fostering each other?

Science China Life Sciences - The changes associated with malignancy are not only in cancer cells but also in environment in which cancer cells live. Metabolic reprogramming supports tumor cell...     

Biofeedback in medicine: who,when, why and how?

Biofeedback is a mind-body technique in which individuals learn how to modify their physiology for the purpose of improving physical, mental, emotional and spiritual health. Much like physical therapy, biofeedback training requires active participation on the part of patients and often regular practice between training sessions. Clinical biofeedback may be used to manage disease symptoms as well as to improve overall health and wellness through stress management training. Research has shown that biofeedback interventions are efficacious in treating a variety of medical conditions, and many Americans are turning to biofeedback and other less traditional therapies for their routine healthcare.Clinical biofeedback training is growing increasingly popular in the USA, as many people are seeking out relatively new approaches to healthcare. This article provides an overview of clinical biofeedback training, outlines two models of training, details research which has established how effective biofeedback is in patients with a given disease, and describes who should be referred for biofeedback training.     

Biofilms in vitro and in vivo: do singular mechanisms imply cross-resistance?

Microbial biofilm has become inexorably linked with man's failure to control them by antibiotic and biocide regimes that are effective against suspended bacteria. This failure relates to a localized concentration of biofilm bacteria, and their extracellular products (exopolymers and extracellular enzymes), that moderates the access of the treatment agent and starves the more deeply placed cells. Biofilms, therefore, typically present gradients of physiology and concentration for the imposed treatment agent, which enables the less susceptible clones to survive. Such clones might include efflux mutants in addition to genotypes with modifications in single gene products. Clonal expansion following subeffective treatment would, in the case of many antibiotics, lead to the emergence of a resistant population. This tends not to occur for biocidal treatments where the active agent exhibits multiple pharmacological activity towards a number of specific cellular targets. Whilst resistance development towards biocidal agents is highly unlikely, subeffective exposure will lead to the selection of less susceptible clones, modified either in efflux or in their most susceptible target. The latter might also confer resistance to antibiotics where the target is shared. Thus, recent reports have demonstrated that sublethal concentrations of the antibacterial and antifungal agent triclosan can select for resistant mutants in Escherichia coli and that this agent specifically targets the enzyme enoyl reductase that is involved in lipid biosynthesis. Triclosan may, therefore, select for mutants in a target that is shared with the anti-E. coli diazaborine compounds and the antituberculosis drug isoniazid. Although triclosan may be a uniquely specific biocide, sublethal concentrations of less specific antimicrobial agents may also select for mutations within their most sensitive targets, some of which might be common to therapeutic agents. Sublethal treatment with chemical antimicrobial agents has also been demonstrated to induce the expression of multidrug efflux pumps and efflux mutants. Whilst efflux does not confer protection against use concentrations of biocidal products it is sufficient to confer protection against therapeutic doses of many antibiotics. It has, therefore, been widely speculated that biocide misuse may have an insidious effect, contributing to the evolution and persistence of drug resistance within microbial communities. Whilst such notions are supported by laboratory studies that utilize pure cultures, recent evidence has strongly refuted such linkage within the general environment where complex, multispecies biofilms predominate and where biocidal products are routinely deployed. In such situations the competition, for nutrients and space, between community members of disparate sensitivities far outweighs any potential benefits bestowed by the changes in an individual's antimicrobial susceptibility.     

The timing of hibernation in Tasmanian echidnas: why do they do it when they do?

We investigated the patterns of hibernation and arousals in seven free-ranging echidnas Tachyglossus aculeatus setosus (two male, five female) in Tasmania using implanted temperature data loggers. All echidnas showed a ‘classical’ pattern of mammalian hibernation, with bouts of deep torpor interrupted by periodic arousals to euthermia (mean duration 1.04±0.05 (n=146). Torpor bout length increased as body temperature fell during the hibernation season, and became more variable as temperature rose again. Hibernation started in late summer (February 28±5 days, n=6) and males aroused just before the winter solstice (June 15±3 days, n=3), females that subsequently produced young aroused 40 days later (July 25±3, n=4) while females that did not produce young hibernated for a further two months (arousal Sept 27±5, n=7). We suggest that hibernation in Tasmanian echidnas can be divided into two phases, the first phase, marked by declining minimum body temperatures as ambient temperature falls, appears to be obligatory for all animals, while the second phase is ‘optional’ and is utilised to varying amounts by females. We suggest that early arousal and breeding is the favoured option for females in good condition, and that the ability to completely omit breeding in some years, and hibernate through to spring is an adaptation to an uncertain climate.     

How do avian embryos breathe? Oxygen transport in the blood of early chick embryos

1. Chick embryos with primary circulation, up to about 3 days of development, show no hemoglobin-mediated transport of oxygen. 2. In embryos with secondary circulation, between 3 and 6 days of incubation, the vascular area acts as the respiratory organ. Its efficiency in the oxygen uptake is less than that of the chorioallantois of later embryos. On the contrary, oxygen release to the tissues is highly efficient. 3. A full efficient hematic uptake of oxygen is reached at about the 6th incubation day, when chorioallantois acts as the embryonic respiratory organ. 4. The different respiratory mechanisms of developing chick embryo are closely related to the functional properties of the various hemoglobins which are produced during the embryonic life.     

Interaction of α-thalassemia genes with each other and with HbC in an American black family

The relative rates of in vitro synthesis of hemoglobin chains have been studied in an American black family in which the mother is doubly heterozygous for alpha-thalassemia and HbC and the father is heterozygous for alpha-thalassemia. The alpha/non-alpha synthetic ratio was equally unbalanced in both the bone marrow and the peripheral blood of the mother. Although HbC comprised 35% of her hemoglobin (compared to 42.2 +/- 2.2 in individuals with HbC trait and balanced globin synthesis), synthetic data showed that the newly synthesized beta C chain was 44% of the total newly synthesized beta chains. Isolated membranes contained more newly synthesized beta C than beta A chains. Three of the offspring were within the normal range, and the remaining three had alpha-thalassemia. There were two spontaneous abortions during the second trimester of pregnancy. Hydrops fetalis did not occur, and none of the children had HbH disease or HbC trait.