Histone acetylation: A possible mechanism for the inheritance of cell memory at mitosis

Immunofluorescent labelling demonstrates that human metaphase chromosomes contain hyperacetylated histone H4. With the exception of the inactive X chromosome in female cells, where the bulk of histone H4 is under-acetylated, H4 hyperacetylation is non-uniformly distributed along the chromosomes and clustered in cytologically resolvable chromatin domains that correspond, in general, with the R-bands of conventional staining. The strongest immunolabelling is often found in T-bands, the subset of intense R-bands having the highest GC content. The majority of mapped genes also occurs in R-band regions, with the highest gene density in T-bands. These observations are consistent with a model in which hyperacetylation of histone H4 marks the position of potentially active gene sequences on metaphase chromosomes. Since acetylation is maintained during mitosis, progeny cells receive an imprint of the histone H4 acetylation pattern that was present on the parental chromosomes before cell division. Histone acetylation could provide a mechanism for propagating cell memory, defined as the maintenance of committed states of gene expression through cell lineages.     

The severe phenotype of females with tiny ring X chromosomes is associated with inability of these chromosomes to undergo X inactivation.

Molecular typing of HLA class II loci has been performed on a sample of 196 patients with Hodgkin lymphoma. Division of patients into two histological categories--nodular sclerosing Hodgkin disease versus all other types--shows significant overall association of the nodular sclerosing group with the HLA class II region. Haplotypes and alleles defined for the four loci typed--DRB1, DQA1, DQB1, and DPB1--were present in both excess and deficit in the nodular sclerosing sample. Some of the effects are attributable to particular DRB1 and DQB1 alleles, while other effects are best explained by haplotypes marking the entire class II region. The latter effects might be due to variation in additional, as-yet-unexamined loci in the class II region or to particular combinations of alleles from two or more loci. These data also explain why earlier studies showed HLA linkage but not association, and they substantiate the specific involvement of the immune system in certain neoplastic diseases.     

Shelter availability reduces the effects of the invasive Red Swamp Crayfish (Procambarus clarkii) on eelgrass-dominated clear-water lakes: a mesocosm approach

Hydrobiologia - Shelter availability is one of the key features governing crayfish habitat quality. It can directly influence crayfish’s individual survival of by lowering the risk of...     

Higher Serum Concentrations of N-Terminal Pro-B-Type Natriuretic Peptide Associate with Prevalent Hypertension whereas Lower Associate with Incident Hypertension

BackgroundThe role of the natriuretic peptides (NPs) in hypertension is complex. Thus, a higher blood NP concentration is a robust marker of pressure-induced cardiac damage in patients with hypertension, whereas genetically elevated NP concentrations are associated with a reduced risk of hypertension and overweight individuals presumably at high risk of hypertension have lower NP concentrations.ObjectiveTo investigate the associations between serum N-terminal pro-B-type natriuretic peptide (NT-proBNP), used as a surrogate marker for active BNP, and prevalent as well as 5-year incident hypertension in a Danish general population sample.MethodsCross-sectional and prospective population-based study.ResultsAt baseline, among 5,307 participants (51.3% women, mean age 46.0±7.9 years) with a complete set of data, we recorded 1,979 cases with prevalent hypertension (PHT). Among 2,389 normotensive participants at baseline with a complete set of data, we recorded 324 cases with incident hypertension (IHT) on follow-up 5 years later. In models adjusted for age, sex, lifestyle, social, dietary, anthropometric, pulmonic, lipid, metabolic and renal risk factors, as well as heart rate and baseline blood pressure (only incident model), one standard deviation increase in baseline log-transformed NT-proBNP concentrations was on one side associated with a 21% higher risk of PHT (odds ratio [OR]: 1.21 [95% confidence interval (CI): 1.13-1.30], P<0.001), and on the other side with a 14% lower risk of IHT (OR: 0.86 [95%CI:0.76-0.98], P = 0.020).ConclusionsHigher serum concentrations of NT-proBNP associate with PHT whereas lower concentrations associate with IHT. This suggests that a lower amount of circulating BNP, resulting in diminished vasodilation and natriuresis, could be involved in the pathogenesis of hypertension in its early stages.     

Progressive infertility in female lethal yellow mice (Ay/a; strain C57BL/6J)

Obese Ay/a females of 120 days or older, when compared to age-matched a/a controls (strain C57BL/6J), exhibited abnormal oestrous cyclicity characterized by reduced frequencies of true oestrous-stage smears, decreased mating success to proven a/a males, lowered uterine weights, and depressed ovulation rates. Exogenous gonadotrophins (PMSG/hCG) partly restored ovulation in obese Ay/a females to near control levels, demonstrating the sensitivity of Ay/a ovarian tissues to FSH and LH, at least at superovulatory levels. Concentrations of endogenous gonadotrophins and/or sensitivity of ovarian target cells to gonadotrophins may therefore be impaired in obese Ay/a females. Aberrant copulatory behaviour, reduced uterine weights, and depressed conception rates strongly suggest ovarian steroid deficiencies, perhaps secondary effects of reduced endogenous gonadotrophin activity. As in other obese rodent syndromes e.g. ob/ob, db/db, and fa/fa), a possible fundamental Ay-induced hypothalamic lesion is consistent with our data.     

The role of cladocerans in tracking long-term change in shallow lake trophic status

Shallow lakes have been affected by a variety of human activities profoundly altering their ecological structure and function. Cladocerans have been used to track change resulting from a variety of drivers at a number of time scales. Aquatic macrophytes are well recognised as reflecting the ecological condition of a lake. Here, we compare the plant macrofossils with the sub-fossil cladoceran assemblages from 20 dated sediment cores. Co-correspondence analysis was used to determine the degree of commonality of change in community composition of the two biological groups through time. This analysis revealed very high levels of agreement in the nature and timing of change at all the sites examined with very high correlation coefficients between the axis 1 scores for macrofossils and cladocerans. Furthermore, at all sites a high proportion of the variance (min 20%, max 54%) in the macrofossil data was explained by the change in the cladoceran assemblage. Sub-fossil macrofossil and cladoceran assemblages, from at least from 1700 AD onwards, were examined in more detail at three sites: Ormesby Great Broad, Felbrigg Lake and Lake Søbygaard. There was very good accord in the main shifts of the cladoceran and macrofossil assemblages at all three sites. This may reflect the long-term shift in the principal focus of primary production from the benthic to the pelagic habitat. We suggest that the combination of their central position in the food-web and the presence of both pelagic and benthic taxa make cladocerans a strong candidate as the single best indicator of (palaeo) ecological condition related to changing trophic status and alteration in food-web structure in shallow lakes.     

Effects of Submerged Vegetation on Water Clarity Across Climates

A positive feedback between submerged vegetation and water clarity forms the backbone of the alternative state theory in shallow lakes. The water clearing effect of aquatic vegetation may be caused by different physical, chemical, and biological mechanisms and has been studied mainly in temperate lakes. Recent work suggests differences in biotic interactions between (sub)tropical and cooler lakes might result in a less pronounced clearing effect in the (sub)tropics. To assess whether the effect of submerged vegetation changes with climate, we sampled 83 lakes over a gradient ranging from the tundra to the tropics in South America. Judged from a comparison of water clarity inside and outside vegetation beds, the vegetation appeared to have a similar positive effect on the water clarity across all climatic regions studied. However, the local clearing effect of vegetation decreased steeply with the contribution of humic substances to the underwater light attenuation. Looking at turbidity on a whole-lake scale, results were more difficult to interpret. Although lakes with abundant vegetation (>30%) were generally clear, sparsely vegetated lakes differed widely in clarity. Overall, the effect of vegetation on water clarity in our lakes appears to be smaller than that found in various Northern hemisphere studies. This might be explained by differences in fish communities and their relation to vegetation. For instance, unlike in Northern hemisphere studies, we find no clear relation between vegetation coverage and fish abundance or their diet preference. High densities of omnivorous fish and coinciding low grazing pressures on phytoplankton in the (sub)tropics may, furthermore, weaken the effect of vegetation on water clarity.     

Consumer-driven nutrient release to the water by a small omnivorous fish enhanced ramet production but reduced the growth rate of the submerged macrophyte Vallisneria denseserrulata (Makino) Makino

Small fish are highly associated with submerged macrophytes but may potentially hamper their growth due to nutrient excretion that stimulate growth of phytoplankton and periphyton growth. We conducted a mesocosm experiment to elucidate the effects of the small omnivore Chinese bitterling Acheilognathus macropterus on the growth of phytoplankton, periphyton and the submerged macrophyte Vallisneria denseserrulata. The treatments were fishless as well as low (LF) and high (HF) fish density. We found that the concentrations of nutrients and the phytoplankton biomass increased substantially in both fish treatments, leading to a significantly higher light attenuation compared with the control. Moreover, bitterling substantially enhanced the biomass of periphyton on plant leaves. Consequently, the relative growth rate (RGR) of V. denseserrulata was significantly suppressed in HF, while RGR in the LF treatment did not differ significantly from the controls. However, the bitterling also stimulated the ramet production of V. denseserrulata, significantly. Our results indicate that Chinese bitterling reduce the RGR of V. denseserrulata under high fish density condition. Therefore, the density of Chinese bitterling should be kept low in order to reduce the negative effects of the fish on the RGR of submerged macrophytes (e.g. V. denseserrulata), when restoring lakes by plant transplantation.

     

The effect of age at introduction and number of milk-portions on the behaviour of group housed dairy calves fed by a computer controlled milk feeder

This study is an investigation of the effect of age at introduction (6 days versus 14 days) and number of milk-portions (four milk-portions a day versus eight milk-portions a day) on integration into a large dynamic group of calves, fed by a computer controlled milk feeder. Forty calves (Jerseys, Danish Reds and Holstein-Friesians) were allocated equally to the two age conditions (A6 and A14) and the two milk-portion conditions (M4 and M8) in a 2 × 2 factorial design, according to sex and breed, and introduced into the group in pairs (one A6 and one A14). The behaviour of each pair was video-recorded for 8 h from 8 a.m. to 4 p.m. and 1 h from 1 to 2 a.m. on days 1, 8 and 15 after introduction.

The A6 calves performed less licking and sniffing, changed posture more often and tended to spend less time standing than the A14 calves. In the course of time A14 calves lay closer to other calves than the A6 calves.

The M8 calves, which were offered the same daily milk allowance as the M4 calves stood for a longer time in the milk feeding station and the M8 calves also sucked the empty teat more frequently than the M4 calves. Finally, the M8 calves initiated more social play behaviour than the M4 calves. On the first day after introduction the M8 calves lay closer to other calves than the M4 calves.

The results suggest that calves integrate better into a group when introduced at the age of 14 days than at the age of 6 days. Distributing the milk into eight daily milk-portions, rather than four milk-portions in the first period after introduction, increased milk feeder occupancy, which may facilitate learning to use the milk feeder. Surprisingly, more milk-portions also stimulated play behaviour, which is suggested to be due to M8 calves encountering more calves in the milk feeder area.