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121.
In a comparative study the requirement of several strains of autotrophic hydrogen-oxidizing bacteria for nickel was examined. Autotrophic growth was studied both in liquid media, previously freed from trace metals; and on solidified media, using a plate diffusion assay. The latter assay was based on the observation that EDTA causes complete inhibition of autotrophic growth on agar medium as a result of nickel deficiency. Nickel was shown to be required as a trace element in five strains of Alcaligenes eutrophus, in two strains of Xanthobacter autotrophicus, in Pseudomonas flava, in Arthrobacter spec. 11X and in strain 12X. In these bacteria nickel was not replaceable by cobalt, copper, manganese or zinc ions. No significant nickel requirement was detected by these methods, however, for Paracoccus denitrificans and Nocardia opaca 1b. 相似文献
122.
Mildred S. Seelig 《Biological trace element research》1979,1(4):273-297
Except for a few experimental models of magnesium (Mg)-deficiency-induced neoplasms, less attention has been paid in the past
quarter century in the Western world to this macromineral than to the trace elements; e.g., selenium (Se) and zinc (Zn), and
to vitamins, deficiencies of which are each considered probable factors in oncogenesis. Although early epidemiologic studies
showed an inverse correlation between the amount of Mg in soil and water and the incidence of (gastric) cancer, and several
animal studies supported the premise that Mg has a prophylactic effect against induction of cancer, other studies showed that
Mg supplementation increased the growth of established experimental tumors. Thus, enthusiasm for this approach subsided. The
early epidemiologic findings have since been confirmed, and there have been studies demonstrating the importance of Mg in
maintaining immunocompetence, and others indicating that immunodeficiencies increase susceptibility to the development of
cancer. Evidence has now accrued that indicates that Mg deficiency increases susceptibility to chemical oncogens. The abnormal
metabolism of tryptophan (yielding a carcinogenic metabolite) that indicates functional or absolute pyridoxine deficiency
is an indirect clue to Mg deficiency. Vitamin B6-activated enzymes require Mg as a cofactor. However, the early warnings against the use of Mg as part of an antineoplastic
program against established cancer were justified, since rapidly metabolizing cells (such as cancers) are dependent on Mg.
There are similarities between experiences with Mg and with Se and Zn. All three are required for normal metabolism; Se also
protects against free radicals in the environment. Mg and Zn have increased established tumor growth, and their depletion
has been applied to antineoplastic programs, with risks comparable to those of using antimetabolic agents. 相似文献
123.
Growth of Methanobacterium thermoautotrophicum on H2 and CO2 as sole energy and carbon sources was found to be dependent on Ni, Co, and Mo. At low concentrations of Ni (<100 nM), Co (<10 nM) and Mo (<10 nM) the amount of cells formed was roughly proportional to the amount of transition metal added to the medium; for the formation of 1 g cells (dry weight) approximately 150 nmol NiCl2, 20 nmol CoCl2 and 20 nmol Na2MoO4 were required. A dependence of growth on Cu, Mn, Zn, Ca, Al, and B could not be demonstrated. Conditions are described under which the bacterium grew exponentially with a doubling time of 1.8 h up to a cell density of 2 g cells (dry weight)/1. 相似文献
124.
125.
Prof. Dr. A. L. Polenov Dr. M. A. Belenky M.Sc. P. E. Garlov M. S. Konstantinova 《Cell and tissue research》1976,170(1):113-128
Summary The proximal neurosecretory contact region (PCR) of Acipenseridae, a homologue of the tetrapod median eminence, has been studied by light, fluorescence and electron microscopy. It occupies the rostral and chiefly the ventral surfaces of the hypothalamic tuber cinereum. PAF-positive fibres occur in the zone of the preoptico-hypophysial tract but their terminal enlargements are concentrated mainly in the external zone. They make contact with the primary portal capillaries situated in the pia mater. Monoaminergic fibres and terminals with an intense green fluorescence are localized in the same regions. The fibres of some bipolar monoaminergic neurons of the PCR make contact both with the third ventricle and the primary portal capillaries.Three types of granule-containing neurosecretory fibres and terminals have been recognized in the PCR. Fibres of types A1 (d=120–300 nm) and A2 (d=100–170 nm) are peptidergic PAF-positive, although some fibres, including some of type A1; belong possibly to PAF-negative type. Monoaminergic type B fibres have granules 80–100 nm in diameter. Neurosecretory terminals and vascular endfeet of tanycytes make contact with the 70 nm thick outer basement membrane of the primary portal capillaries. Several laminae of thin horizontally oriented tanycyte processes form a boundary between the external zone and the preoptico-hypophysial tract. Few neuroglial cells with pale cytoplasm, numerous lysosomes and lipofuscin granules are seen in this region. It is hypothesized that, as in other vertebrates, both peptide hypophysiotropic neurohormones and monoamines are discharged from the PCR into the portal circulation and affect the activity of the glandular cells of the pars distalis.Dedicated to Prof. Dr. Drs. h.c. W. Bargmann on the occasion of his 70th birthday 相似文献
126.
Cribra orbitalia (CO), or porotic hyperostosis (PH) of the orbital roof, is one of the most common pathological conditions found in archaeological subadult skeletal remains. Reaching frequencies higher than 50% in many prehistoric samples, CO has been generally attributed to a variety of factors including malnutrition (e.g., megaloblastic anemia) and parasitism. In this study, we tested the relationship between CO, trace element concentrations, and stable isotope values (δ13C, δ15N, δ18O) in subadult skeletons from a 17th to 18th century cemetery in the historic town of JĿkabpils, Latvia. A total of 28 subadults were examined, seven of which (25%) showed evidence of CO. Bioarchaeological evidence indicated high mortality for children in this cemetery: half of the burials were subadults under the age of 14, while a third were under the age of four. Life expectancy at birth was estimated to have been only 21.6 years. Trace element concentrations measured by Inductively Coupled Plasma Mass Spectrometry (ICP-MS) showed no relationship between presence or absence of CO and levels of manganese, zinc, strontium, barium, copper, cadmium, or lead in the bones (p > 0.05). However, a significant correlation (p < 0.05) was found between the presence of CO and decreased levels of iron. The correlations between CO and decreased levels of copper and lead approached significance (p = 0.056 for both elements). Individuals with CO furthermore displayed significantly lower δ15N isotope values, suggesting greater consumption of lower trophic level food resources than those unaffected by CO; δ13C and δ18O values, in contrast, showed no significant differences. These results suggest that the prevalence of CO may be related to dietary deficiencies. In this case, low iron levels may also signify a diet low in other key vitamins (e.g., B9 and B12), which are known to cause megaloblastic anemia. 相似文献
127.
Splicing and alternative splicing in rice and humans 总被引:1,自引:0,他引:1
Rice is a monocot gramineous crop, and one of the most important staple foods. Rice is considered a model species for most gramineous crops. Extensive research on rice has provided critical guidance for other crops, such as maize and wheat. In recent years, climate change and exacerbated soil degradation have resulted in a variety of abiotic stresses, such as greenhouse effects, lower temperatures, drought, floods, soil salinization and heavy metal pollution. As such, there is an extremely high demand for additional research, in order to address these negative factors. Studies have shown that the alternative splicing of many genes in rice is affected by stress conditions, suggesting that manipulation of the alternative splicing of specific genes may be an effective approach for rice to adapt to abiotic stress. With the advancement of microarrays, and more recently, next generation sequencing technology, several studies have shown that more than half of the genes in the rice genome undergo alternative splicing. This mini-review summarizes the latest progress in the research of splicing and alternative splicing in rice, compared to splicing in humans. Furthermore, we discuss how additional studies may change the landscape of investigation of rice functional genomics and genetically improved rice. [BMB Reports 2013; 46(9): 439-447] 相似文献
128.
Cristiano Nogueira Síria Ribeiro Gabriel C. Costa Guarino R. Colli 《Journal of Biogeography》2011,38(10):1907-1922
Aim To test predictions of the vicariance model, to define basic biogeographical units for Cerrado squamates, and to discuss previous biogeographical hypotheses. Location Cerrado; South American savannas south of the Amazon, extending across central Brazil, with marginal areas in Bolivia and Paraguay and isolated relictual enclaves in adjacent regions. Methods We compiled species occurrence records via field sampling and revision of museum specimens and taxonomic literature. All species were mapped according to georeferenced locality records, and classified as (1) endemic or non‐endemic, (2) typical of plateaus or depressions, and (3) typical of open or forested habitats. We tested predictions of the vicariance model using biotic element analysis, searching for non‐random clusters of species ranges. Spatial congruence of biotic elements was compared with putative areas of endemism revealed by sympatric restricted‐range species. Effects of topographical and vegetational mosaics on distribution patterns were studied according to species composition in biotic elements and areas of endemism. Results We recorded 267 Cerrado squamates, of which 103 (39%) are endemics, including 20 amphisbaenians (61% endemism), 32 lizards (42%) and 51 snakes (32%). Distribution patterns corroborated predictions of the vicariance model, revealing groups of species with significantly clustered ranges. An analysis of endemic species recovered seven biotic elements, corroborating results including non‐endemics. Sympatric restricted‐range taxa delimited 10 putative areas of endemism, largely coincident with core areas of biotic elements detected with endemic taxa. Distribution patterns were associated with major topographical and vegetational divisions of the Cerrado. Endemism prevailed in open, elevated plateaus, whereas faunal interchange, mostly associated with forest habitats, was more common in peripheral depressions. Main conclusions Our results indicate that vicariant speciation has strongly shaped Cerrado squamate diversity, in contrast to earlier studies emphasizing faunal interchange and low endemism in the Cerrado vertebrate fauna. Levels of squamate endemism are higher than in any other Cerrado vertebrate group. The high number of recovered endemics revealed previously undetected areas of evolutionary relevance, indicating that biogeographical patterns in the Cerrado were poorly represented in previous analyses. Although still largely undocumented, effects of vicariant speciation may be prevalent in a large fraction of Cerrado and Neotropical biodiversity. 相似文献
129.
Autism spectrum disorder (ASD) is a common childhood neurodevelopmental disorder that may be related to trace elements. However, reports on the relationship between them are still inconsistent. In this article, we conducted a meta-analysis on this issue. We searched the PubMed, EMBASE, and Cochrane databases as of November 15, 2019. A random-effects model was used, and subgroups of studies were analyzed using samples of different measurements. Twenty-two original articles were identified (18 trace elements, including a total of 1014 children with ASD and 999 healthy controls). In autistic children, the overall levels of barium (Ba), mercury (Hg), lithium (Li), and lead (Pb) were higher. There were significant differences in the levels of copper (Cu) in the hair and serum between autistic children and the control group. The levels of Hg, Li, Pb and selenium (Se) in the hair of autistic children were higher than those of healthy children, while the levels of zinc (Zn) in the blood were lower. Excessive exposure to toxic heavy metals and inadequate intake of essential metal elements may be associated with ASD. Preventing excessive exposure to toxic metals and correcting poor dietary behaviors may be beneficial for the prevention and treatment of the disease. 相似文献
130.
Cancer is the second leading cause of death worldwide. Research on the relationships between trace elements (TE) and the development of cancer or its prevention is a field that is gaining increasing relevance. This review provides an evaluation of the effects of TE (As, Al, B, Cd, Cr, Cu, F, I, Pb, Li, Mn, Hg, Mo, Ni, Se, Si, Sn, V and Zn) intake and supplementation in cancer risk and prevention, as well as their interactions with oncology treatments. Advancements in the knowledge of TE, their dietary interactions and their main food sources can provide patients with choices that will help them to improve their quality of life and therapy outcomes. This approach could open new opportunities for treatments based on the integration of conventional therapies (chemotherapy, radiotherapy, and immunotherapy) and dietary interventions that provide advanced personalized treatments. 相似文献