Carbon Dioxide Production by Dry Grain of Zea mays

Use of the gas chromatograph and a mercury-to-glass sealed respirometer adapted for gas syringe sampling, allowed the rapid, accurate characterization of CO₂ evolution rates from live and from dead-sterile Zea mays L. grain dried to moisture levels of 12.6 to 1.4%. The live grain at the lowest moisture level showed an elevated rate inconsistent with the exponential increase in rate of CO₂ evolution with increasing moisture found for maize with moisture contents from 4 to 12.6%. At the lowest moisture level, rates of CO₂ evolution from dead-sterile grain were greater than for live grain. Moisture had no effect on CO₂ evolution from dead-sterile grain. Increasing temperature and increasing levels of O₂ in the storage atmosphere resulted in increased rates of CO₂ evolution from both live and dead-sterile maize. CO₂ production rates from live and from dead-sterile grain decreased with increasing storage time, even though respirometer CO₂ concentrations were less than 1% at the end of the experiment. Our results indicate that CO₂ production is not a dependable measure of respiration in dry seeds. Other experiments indicate that oxygen absorption also is not reliable in maize grain.     

Small tropical forest trees have a greater capacity to adjust carbon metabolism to long-term drought than large canopy trees

The response of small understory trees to long-term drought is vital in determining the future composition, carbon stocks and dynamics of tropical forests. Long-term drought is, however, also likely to expose understory trees to increased light availability driven by drought-induced mortality. Relatively little is known about the potential for understory trees to adjust their physiology to both decreasing water and increasing light availability. We analysed data on maximum photosynthetic capacity (J_max, V_cmax), leaf respiration (R_leaf), leaf mass per area (LMA), leaf thickness and leaf nitrogen and phosphorus concentrations from 66 small trees across 12 common genera at the world's longest running tropical rainfall exclusion experiment and compared responses to those from 61 surviving canopy trees. Small trees increased J_max, V_cmax, R_leaf and LMA (71, 29, 32, 15% respectively) in response to the drought treatment, but leaf thickness and leaf nutrient concentrations did not change. Small trees were significantly more responsive than large canopy trees to the drought treatment, suggesting greater phenotypic plasticity and resilience to prolonged drought, although differences among taxa were observed. Our results highlight that small tropical trees have greater capacity to respond to ecosystem level changes and have the potential to regenerate resilient forests following future droughts.     

Isolation and NH2-terminal sequence of a highly conserved human and porcine pituitary protein belonging to a new superfamily: Immunocytochemical localization in pars distalis and pars nervosa of the pituitary and in the supraoptic nucleus of the hypothalamus

The isolation and purification of a 21,000-Da (pI 4.9) novel protein from porcine anterior pituitary and whole human pituitary is described. Comparison of the NH₂-terminal sequence of the first 77 and 81 residues of the human and porcine homologs shows only one conservative substitution at residue 12, namely an Ala for a Thr between these two species. Such high sequence homology is also reflected in their amino acid composition. A computer data-bank search using a mutation data matrix and comparison with 338,327 segments of proteins revealed that this substance should be classified as belonging to a new protein superfamily. Immunocytochemical staining, using an antibody produced against a synthetic fragment, revealed the presence of immunostainable material in the anterior and posterior lobe of the pituitary and in the supraoptic nucleus of the hypothalamus. No staining was observed in the intermediate lobe of the pituitary. Furthermore, purified neurointermediate lobe secretory granule preparations were also shown to contain this novel polypeptide.     

Circadian rhythms in hot flashes in natural and surgically-induced menopause

The aim of this study was to investigate circadian and ultradian variations in menopausal hot flash. The number of hot flashes per 2-hr period was collected from 25 diurnally-active, perimenopausal women for 1 week in January or February of each year for 3 consecutive years. Fourteen women were experiencing natural menopause (NM) (mean age 51.9 years) and 11 were experiencing surgically-induced menopause (SIM) (mean age 52.0 years). The difference in the number of hot flashes between the two types of menopause at each clock time was not statistically significant; neither was the mean number of hot flashes per 24 hr different between the two groups (Student's t-test). Data when normalized for each woman and placed end-to-end revealed by cosinor analysis circadian rhythmicity in the SIM group (P = 0.02) but not in the NM group. A 12-hr periodicity was detected in both groups (P less than 0.001 for both). An 8-hr rhythm was detected only for the NM group (P = 0.04). Both groups combined exhibited statistically significant rhythmicities with periods of 24 hr (P = 0.003), 12 hr (P less than 0.001) and 8 hr (P = 0.005). Regardless of the type of menopause, the women could be separated into two groups based on the temporal pattern of hot flashes during the day. One group was defined by the occurrence of peak frequency of flashes during the morning (0400-0959), while the second group was defined by the occurrence of the peak in the evening (1600-2159).(ABSTRACT TRUNCATED AT 250 WORDS)     

Caveolin‐1 down‐regulation is required for Wnt5a‐Frizzled 2 signalling in Ha‐RasV12‐induced cell transformation

Caveolin‐1 (Cav1) is down‐regulated during MK4 (MDCK cells harbouring inducible Ha‐Ras^V12 gene) transformation by Ha‐Ras^V12. Cav1 overexpression abrogates the Ha‐Ras^V12‐driven transformation of MK4 cells; however, the targeted down‐regulation of Cav1 is not sufficient to mimic this transformation. Cav1‐silenced cells, including MK4/shCav1 cells and MDCK/shCav1 cells, showed an increased cell area and discontinuous junction‐related proteins staining. Cellular and mechanical transformations were completed when MDCK/shCav1 cells were treated with medium conditioned by MK4 cells treated with IPTG (MK4+I‐CM) but not with medium conditioned by MK4 cells. Nanoparticle tracking analysis showed that Ha‐Ras^V12‐inducing MK4 cells increased exosome‐like microvesicles release compared with their normal counterparts. The cellular and mechanical transformation activities of MK4+I‐CM were abolished after heat treatment and exosome depletion and were copied by exosomes derived from MK4+I‐CM (MK4+I‐EXs). Wnt5a, a downstream product of Ha‐Ras^V12, was markedly secreted by MK4+I‐CM and MK4+I‐EXs. Suppression of Wnt5a expression and secretion using the porcupine inhibitor C59 or Wnt5a siRNA inhibited the Ha‐Ras^V12‐ and MK4+I‐CM‐induced transformation of MK4 cells and MDCK/shCav1 cells, respectively. Cav1 down‐regulation, either by Ha‐Ras^V12 or targeted shRNA, increased frizzled‐2 (Fzd2) protein levels without affecting its mRNA levels, suggesting a novel role of Cav1 in negatively regulating Fzd2 expression. Additionally, silencing Cav1 facilitated the internalization of MK4+I‐EXs in MDCK cells. These data suggest that Cav1‐dependent repression of Fzd2 and exosome uptake is potentially relevant to its antitransformation activity, which hinders the activation of Ha‐Ras^V12‐Wnt5a‐Stat3 pathway. Altogether, these results suggest that both decreasing Cav1 and increasing exosomal Wnt5a must be implemented during Ha‐Ras^V12‐driven cell transformation.     

Chromatin remodeling by ISW2 and SWI/SNF requires DNA translocation inside the nucleosome

Chromatin-remodeling complexes regulate access to nucleosomal DNA by mobilizing nucleosomes in an ATP-dependent manner. In this study, we find that chromatin remodeling by SWI/SNF and ISW2 involves DNA translocation inside nucleosomes two helical turns from the dyad axis at superhelical location-2. DNA translocation at this internal position does not require the propagation of a DNA twist from the site of translocation to the entry/exit sites for nucleosome movement. Nucleosomes are moved in 9- to 11- or approximately 50-base-pair increments by ISW2 or SWI/SNF, respectively, presumably through the formation of DNA loops on the nucleosome surface. Remodeling by ISW2 but not SWI/SNF requires DNA torsional strain near the site of translocation, which may work in conjunction with conformational changes of ISW2 to promote nucleosome movement on DNA. The difference in step size of nucleosome movement by SWI/SNF and ISW2 demonstrates how SWI/SNF may be more disruptive to nucleosome structure than ISW2.