We studied the perennial vine Passiflora incarnata Linnaeus (Passifloraceae) in Alachua County, Florida, from May to August 1983 to determine the breeding system and investigate seasonal changes in phenotypic gender of individual plants. Passiflora incarnata is an obligate outcrosser, incapable of self-fertilization. The major pollinators were carpenter bees (Xylocopa sp.). The proportion of flowers setting fruit was not limited by pollinator service, but the weight of individual fruits and number of seeds/fruit was increased over naturally pollinated flowers by manually performing cross-pollination. Morphological differences in style position among flowers caused some flowers to function primarily as males and others to function as hermaphrodites. Although some of the flowers that functioned as males set fruit when manually cross-pollinated, the proportion of these male flowers capable of setting fruit was lower than the proportion of hermaphroditic flowers setting fruit when manually cross-pollinated. Further, some male flowers had atrophied ovary and styles and were completely incapable of setting fruit. Passiflora incarnata is thus functionally andromonoecious. The relative production of male versus hermaphroditic flowers varied among individuals and over the course of the flowering season. Unmanipulated plants in the population became increasingly male-biased in floral sex ratios as the reproductive season progressed. We attempted to modify phenotypic gender in experimental plants by limiting the ability of plants in some treatment groups to set fruit. Treatment groups significantly affected production of hermaphroditic flowers, but production of male flowers was not affected by treatment. Treatment did not significantly affect fruit weight, number of seeds per fruit or the percentage of hermaphroditic flowers that successfully matured fruit. These results suggest that andromonoecy in P. incarnata is a mechanism for adjusting allocation of reproductive effort to male and female function, and that maternal investment in this species is regulated primarily by varying production of hermaphroditic flowers. 相似文献
BACKGROUND: Benzo(a)pyrene (BaP), anthracene (ANTH) and chrysene (CHRY) are polynuclear aromatic hydrocarbons (PAHs) implicated in renal toxicity and carcinogenesis. These PAHs elicit cell type-specific effects that help predict toxicity outcomes in vitro and in vivo. While BaP and ANTH selectively injure glomerular mesangial cells, and CHRY targets cortico-tubular epithelial cells, binary or ternary mixtures of these hydrocarbons markedly reduce the overall cytotoxic potential of individual hydrocarbons. METHODS: To study the biochemical basis of these antagonistic interactions, renal glomerular mesangial cells were challenged with BaP alone (0.03 - 30 microM) or in the presence of ANTH (3 microM) or CHRY (3 microM) for 24 hr. Total RNA and protein will be harvested for Northern analysis and measurements of aryl hydrocarbon hydroxylase (AHH) and ethoxyresorufin-O-deethylase (EROD) activity, respectively, to evaluate cytochrome P450 mRNA and protein inducibility. Cellular hydrocarbon uptake and metabolic profiles of PAHs were analyzed by high performance liquid chromatography (HPLC). RESULTS: Combined hydrocarbon treatments did not influence the cellular uptake of individual hydrocarbons. ANTH or CHRY strongly repressed BaP-inducible cytochrome P450 mRNA and protein expression, and markedly inhibited oxidative BaP metabolism. CONCLUSION: These findings indicate that antagonistic interactions among nephrocarcinogenic PAHs involve altered expression of cytochrome P450s that modulate bioactivation profiles and nephrotoxic/ nephrocarcinogenic potential. 相似文献
A series of experiments have been carried out to determine whether follicles secrete factors able to affect the growth and development of other, like-sized follicles. Late preantral mouse ovarian follicles were either cocultured or cultured in media conditioned by previously cultured follicles. In particular, the experiments examined whether follicles do secrete such factors, whether the level of FSH in the culture media can affect that process, and what the nature of such secretory factor(s) might be. First, pairs of follicles were cocultured across a polycarbonate membrane containing pores. This showed that communication between the follicles resulted in the stimulation of growth and that the stimulation was due, at least in part, to the production of secretory factor(s). In subsequent experiments, follicles were cultured in media that had been preconditioned by previously cultured follicles. The concentration of FSH in the cultures determined the effect of the conditioned media: conditioned media was stimulatory to follicle growth when levels of FSH remained high throughout the culture, but inhibitory when FSH levels were dropped midway through the cultures. Heat inactivation removed this inhibitory effect, showing that the factor was likely to be a protein; addition of follistatin to the conditioned media did not alter its effect, indicating that the factor was unlikely to be activin. We have shown through a series of culture experiments that mouse follicles secrete factor(s) that can affect the development of other like-sized follicles when cultured from the late preantral to Graafian stages. Furthermore, we have shown that the effect (or production) of such factors is dependent on the FSH environment of the follicles. 相似文献
Estrogen receptor-alpha (ERalpha) knockout (ERalphaKO) female mice are infertile. Initially, they exhibit normal follicular development, but by 4-5 wk of age, they begin to develop hemorrhagic ovarian cysts. Follicles in adult ERalphaKO female mice progress to the graafian stage, but there are no corpora lutea (CL). To test whether ERalpha is required for ovarian folliculogenesis, ovulation, and CL formation, eCG and hCG were used to ovulate 3- to 5-wk-old ERalphaKO and wild-type (WT) sibling mice. Gonadotropin administration resulted in ovulation in both ERalphaKO and WT mice. Gonadotropin-treated ERalphaKO females that ovulated produced 7.09 +/- 0.77 oocytes per mouse, whereas gonadotropin-treated WT female mice had 16.17 +/- 0.84 oocytes. Surprisingly, ruptured ERalphaKO ovarian follicles developed into CL that had normal morphology. Gonadotropin-treated ERalphaKO mice had 3-fold higher concentrations of serum progesterone than did control ERalphaKO mice that had been administered saline rather than gonadotropins. Thus, the CL in gonadotropin-treated ERalphaKO mice appeared to be steroidogenically functional. On the basis of these findings, ovarian folliculogenesis, ovulation, and CL formation can occur in the absence of ERalpha, although to a lesser extent than in WT mice. 相似文献
High solubility of certain trace minerals (TM) in the rumen can alter nutrient digestibility and fermentation. The objectives of the present studies were to determine the effects of TM source on 1) nutrient digestibility and ruminal fermentation, 2) concentrations of soluble Cu, Zn, and Mn in the rumen following a pulse dose of TM, and 3) Cu, Zn, and Mn binding strength on ruminal digesta using dialysis against a chelating agent in steers fed a diet formulated to meet the requirements of a high producing dairy cow. Twelve Angus steers fitted with ruminal cannulae were adapted to a diet balanced with nutrient concentrations similar to a diet for a high producing lactating dairy cow for 21 d. Steers were then randomly assigned to dietary treatments consisting of 10 mg Cu, 40 mg Mn, and 60 mg Zn/kg DM from either sulfate (STM), hydroxychloride (HTM) or complexed trace minerals (CTM). The experimental design did not include a negative control (no supplemental Cu, Mn, or Zn) because the basal diet did not meet the National Research Council requirement for Cu and Zn. Copper, Mn, and Zn are also generally supplemented to lactating dairy cow diets at concentrations approximating those supplied in the present study. Following a 14-d adaptation period, total fecal output was collected for 5-d. Following the fecal collection period, rumen fluid was collected for Volatile fatty acid (VFA) parameters. On the following day, the same diet was provided for 14 d, without supplemental Cu, Zn, and Mn. This period served as a wash-out period. A pulse dose of 100, 400, and 600 mg of Cu, Zn, Mn, respectively, from either STM, HTM, or CTM, was administered via ruminal cannulae to the steers on day 15. Over a 24-h period ruminal samples were obtained every 2-h. Following centrifugation, the supernatant was analyzed for Cu, Mn, and Zn. Ruminal solid digesta samples from times 0, 12, and 24 h after bolus dosing were exposed to dialysis against Tris-EDTA. Digestibility of NDF and ADF were lesser in STM vs. HTM and vs. CTM supplemented steers. Steers receiving HTM and CTM had greater total VFA concentrations than STM, and molar proportions of individual VFA were not affected by treatment. Ruminal soluble Cu and Zn concentrations were greater post dosing in STM and CTM supplemented steers at 2, 4, and 6 h for Cu and 4, 6, 8, 10 and 12 h for Zn when compared to HTM supplemented steers. The release of Cu and Zn from ruminal solid digesta following dialysis against Tris-EDTA at 12 and 24 h postdosing was greater for steers receiving HTM compared to those receiving STM or CTM. Results indicate trace mineral source impacts: 1) how tightly bound Cu and Zn are to ruminal solid digesta; 2) fiber digestion; 3) and ruminal total VFA concentrations. 相似文献
Sediment and water column phosphorus fractions were recorded monthly for one year (April 2004–April 2005) in a shallow lake
recovering from nutrient pollution (Loch Leven, Scotland). Equilibrium phosphate concentration (EPC0) and gross sediment phosphorus
(P) release rates were estimated from laboratory experiments. Pore water and organic P pools were lowest during warm water
periods whereas bottom water P was lowest during cold water periods. Reductant-soluble, organic, metal oxide-adsorbed, residual
and sediment total phosphorus pools all varied significantly with overlying water depth. Short-term, high magnitude, redox
initiated P release events occurred in late summer and winter as a result of anoxic sediment conditions. Lower magnitude long-term
release conditions were maintained for most of the year, most likely as a result of organic P cycling and maintenance of high
concentration gradients between the pore and bottom water P pools. Estimates of summer P uptake/release rates, across an intact
sediment-water interface, suggested that maximum gross internal release was ~12 mg SRP m−2 lake surface area d−1 with EPC0 values ranging between 180 and 270 μg P L−1. This study highlights the biological mediation of internal loading in shallow eutrophic lakes, and in particular, the role
of sediment algae in decreasing, and sediment bacteria in enhancing, sediment P release. 相似文献
Phospholamban cardiomyopathy is an inherited cardiomyopathy, characterised by a defect in regulation of the sarcoplasmic reticulum Ca2+ pump, often presenting with malignant arrhythmias and progressive cardiac dysfunction occurring at a young age.
Methods
Phospholamban R14del mutation carriers and family members were identified from inherited arrhythmia clinics at 13 sites across Canada. Cardiac investigations, including electrocardiograms, Holter monitoring (premature ventricular complexes, PVCs), and imaging results were summarised.
Results
Fifty patients (10 families) were identified (median age 30 years, range 3–71, 46% female). Mutation carriers were more likely to be older, have low-voltage QRS, T‑wave inversion, frequent PVCs, and cardiac dysfunction, compared to unaffected relatives. Increasing age, low-voltage QRS, T‑wave inversion, late potentials, and frequent PVCs were predictors of cardiac dysfunction (p < 0.05 for all). Older carriers (age ≥45 years) were more likely to have disease manifestations than were their younger counterparts, with disease onset occurring at an older age in Canadian patients and their Dutch counterparts.
Discussion
Among Canadian patients with phospholamban cardiomyopathy, clinical manifestations resembled those of their Dutch counterparts, with increasing age a major predictor of disease manifestation. Older mutation carriers were more likely to have electrical and structural abnormalities, and may represent variable expressivity, age-dependent penetrance, or genetic heterogeneity among Canadian patients.
ERRATUM: Macho GA and Spears IR. 1999. Effects of Loading on the Biomechanical Behavior of Molars of Homo, Pan, and Pongo. Am J Phys Anthropol 109:211–227. The correct title of the article is given above. The word “biochemical” should be read as “biomechanical.” 相似文献
A central issue in stem cell biology is the determination of function and activity of differentiated stem cells, features
that define the true phenotype of mature cell types. Commonly, physiological mechanisms are used to determine the functionality
of mature cell types, including those of the nervous system. Calcium imaging provides an indirect method of determining the
physiological activities of a mature cell. Camgaroos are variants of yellow fluorescent protein that act as intracellular
calcium sensors in transfected cells. We expressed one version of the camgaroos, Camgaroo-2, in mouse embryonic stem (ES)
cells under the control of the CAG promoter system. Under the control of this promoter, Camgaroo-2 fluorescence was ubiquitously
expressed in all cell types derived from the ES cells that were tested. In response to pharmacological stimulation, the fluorescence
levels in transfected cells correlated with cellular depolarization and hyperpolarization. These changes were observed in
both undifferentiated ES cells as well as ES cells that had been neurally induced, including putative neurons that were differentiated
from transfected ES cells. The results presented here indicate that Camgaroo-2 may be used like traditional fluorescent proteins
to track cells as well as to study the functionality of stem cells and their progeny. 相似文献