Chromosomal diversity in two synchronopatric species of Hoffmannseggella (Orchidaceae)

Hoffmannseggella viridiflora Verola & Semir (Laeliinae, Orchidaceae) is a recently discovered species in the campos rupestres vegetation of the Espinhaço Range, MG, Brazil, in synchronopatry with H. bradei (Pabst) V. P. Castro & Chiron. Both morphological and phenological studies indicate that these species are closely related. To substantiate the differentiation of these two species we examined their chromosome numbers and morphologies. The two species had different chromosome numbers, with H. bradei having 2n = 40 and H. viridiflora having 2n = 44 chromosomes, an aneuploid number not previously documented in the genus. Meiotic behavioral studies undertaken with H. bradei revealed many abnormalities related to bivalent numbers and chromosome migration, suggesting that meiotic abnormalities could generate aneuploid gametes and perhaps aneuploid zygotes. Karyotype formulas and chromosome morphologies are quite different between the species, so H. viridiflora was not directly derived from H. bradei through simple chromosome additions. Complementary analyses are necessary to understand the process and species involved in the origin of H. viridiflora.     

Lack of adequate seed supply is a major bottleneck for effective ecosystem restoration in Chile: friendly amendment to Bannister et al. (2018)

We argue that the need for a quality seed supply chain is a major bottleneck for the restoration of Chile's native ecosystems, thus supplementing the list of bottlenecks proposed by Bannister et al. in 2018. Specifically, there is a need for defining seed transfer zones, developing standards and capacities for properly collecting and storing seeds, reducing information gaps on seed physiology and longevity, and implementing an efficient seed supply chain with certification of seed origin and quality. Without such capacities, countries are unlikely to meet their restoration commitments. Although we focus on bottlenecks in Chile, the issues we raise are relevant to other countries and thus the global agenda for ecological restoration.     

EFFECTS OF LIGHT ON PHOTOSYNTHESIS,GRAZING, AND POPULATION DYNAMICS OF THE HETEROTROPHIC DINOFLAGELLATE PFIESTERIA PISCICIDA (DINOPHYCEAE)1

In studying how environmental factors control the population dynamics of Pfiesteria piscicida Steidinger et Burkholder, we examined the influence of light regime on kleptoplastidic photosynthesis, growth, and grazing. Prey (Rhodomonas sp.)‐saturated growth rate of P. piscicida increased (0.67 ± 0.03 d^?1 to 0.91 ± 0.11 d^?1) with light intensity varying from 0 to 200 μmol photons·m^?2·s^?1. No significant effect was observed on grazing, excluding the possibility that light enhanced P. piscicida growth through stimulating grazing. Light‐grown P. piscicida exhibited a higher gross growth efficiency (0.78 ± 0.10) than P. piscicida incubated in the dark (0.32 ± 0.16), and photosynthetic inhibitors significantly decreased growth of recently fed populations. These results demonstrate a role of kleptoplastidic photosynthesis in enhancing growth in P. piscicida. However, when the prey alga R. sp. was depleted, light's stimulating effect on P. piscicida growth diminished quickly, coinciding with rapid disappearance of Rhodomonas‐derived pigments and RUBISCO from P. piscicida cells. Furthermore, the effect of light on growth was reversed after extended starvation, and starved light‐grown P. piscicida declined at a rate significantly greater than dark‐incubated cultures. The observed difference in rates of decline appeared to be attributable to light‐dependent cannibalism. Using a 5‐chloromethylfluorescein diacetate staining technique, cannibalistic grazing was observed after 7 days of starvation, at a rate four times greater under illumination than in the dark. The results from this study suggest that kleptoplastidy enhances growth of P. piscicida only in the presence of algal prey. When prey is absent, P. piscicida populations may become vulnerable to light‐stimulated cannibalism.     

Induction of globin mRNA expression by interleukin-3 in a stem cell factor-dependent SV-40 T-antigen-immortalized multipotent hematopoietic cell line

Erythropoiesis requires the stepwise action on immature progenitors of several growth factors, including stem cell factor (SCF), interleukin 3 (IL-3), and erythropoietin (Epo). Epo is required to sustain proliferation and survival of committed progenitors and might further modulate the level of expression of several erythroid genes, including globin genes. Here we report a new SCF-dependent immortalized mouse progenitor cell line (GATA-1 ts SCF) that can also grow in either Epo or IL-3 as the sole growth factor. When grown in SCF, these cells show an "open" chromatin structure of the beta-globin LCR, but do not significantly express globin. However, Epo or IL-3 induce globin expression and are required for its maintainance. This effect of IL-3 is unexpected as IL-3 was previously reported either to be unable to induce hemoglobinization, or even to antagonize it. This suggests that GATA-1 ts SCF cells may have progressed to a stage in which globin genes are already poised for expression and only require signal(s) that can be elicited by either Epo or IL-3. Through the use of inhibitors, we suggest that p38 may be one of the molecules modulating induction and maintenance of globin expression.     

Acute colitis induced by dextran sulfate sodium progresses to chronicity in C57BL/6 but not in BALB/c mice: correlation between symptoms and inflammation

Exposure to dextran sulfate sodium (DSS) induces acute colitis, which is normally resolved after DSS removal. To study chronicity, mice are typically subjected to three to five cycles of weekly DSS exposures, each followed by a 1- to 2-wk rest period. Here, we describe a novel and convenient way of inducing chronic, progressive colitis by a single exposure to DSS. C57BL/6 mice exposed to DSS for 5 days developed acute colitis that progressed to severe chronic inflammation. The plasma haptoglobin levels remained high during the chronic phase, showing that the inflammation was active. Surprisingly, the mice regained their original weight along with the progression of colitis, and the only apparent symptom was loose feces. Histopathological changes 4 wk after DSS removal were dense infiltrates of mononuclear cells, irregular epithelial structure, and persistent deposits of collagen. A progressive production of the cytokines IL-1beta, IL-12 p70, and IL-17 correlated with the extensive cellular infiltration, whereas high IFN-gamma production was mainly found late in the chronic phase. Similar to C57BL/6 mice, BALB/c mice exposed to 5 days of DSS developed acute colitis as previously described. The acute colitis was accompanied by elevated plasma levels of haptoglobin and increased colonic levels of IL-1alpha/beta, IL-6, IL-18, and granulocyte colony-stimulating factor. However, soon after DSS removal, BALB/c mice recovered and were symptom free within 2 wk and completely recovered 4 wk after DSS removal in terms of histopathology, haptoglobin levels, and local cytokine production. In summary, these data stress the effect of genetic background on the outcome of DSS provocation. We believe that the present protocol to induce chronic colitis in C57BL/6 mice offers a robust model for validating future therapies for treatment of inflammatory bowel disease.     

An improved histochemical method for measuring nitric oxide synthase activity

The previous quantitative histochemical method for measuring nitric oxide synthase (NOS) activity in tissue sections involved the loss of about 15 per cent of the NOS, presumably from the section into the reaction medium. Two changes are now described. The first is concerned with the preparation in the laboratory of the active reagent, lead ammonium citrate/acetate (LACA). The second change involves an improvement of the procedure for measuring NOS activity. The new method appears to retain all the measurable NOS activity inside the section. Copyright © 1999 John Wiley & Sons, Ltd.