Natural Occurrence (natural + occurrence)

Distribution by Scientific Domains

Selected Abstracts

Natural occurrence of ,Candidatus Phytoplasma ziziphi' isolates in two species of jujube trees (Ziziphus spp.) in India

M. S. Khan
No abstract is available for this article. [source]

PCR-based identification of Bacillus thuringiensis pesticidal crystal genes

Manuel Porcar
Abstract The polymerase chain reaction (PCR) is a molecular tool widely used to characterize the insecticidal bacterium Bacillus thuringiensis. This technique can be used to amplify specific DNA fragments and thus to determine the presence or absence of a target gene. The identification of B. thuringiensis toxin genes by PCR can partially predict the insecticidal activity of a given strain. PCR has proven to be a rapid and reliable method and it has largely substituted bioassays in preliminary classification of B. thuringiensis collections. In this work, we compare the largest B. thuringiensis PCR-based screenings, and we review the natural occurrence of cry genes among native strains. We also discuss the use of PCR for the identification of novel cry genes, as well as the potential of novel technologies for the characterization of B. thuringiensis strains. [source]

Assessment of aflatoxin M1 levels in selected dairy products in north-western Iran

The purpose of this survey was to evaluate the natural occurrence and content of aflatoxin M1, AFM1, in dairy products marketed in Urmia. During September 2007, 40 samples of pasteurised milk, 40 samples of ultra high temperature-treated (UHT) milk, 40 samples of creamy cheese and 40 samples of Iranian Feta cheese were collected from different supermarkets in Urmia city. AFM1 contents were determined by the competitive enzyme-linked imunosorbent assay (ELISA) technique. All milk samples analysed showed a mean of AFM1 concentrations lower than the permissible level of 50 ng/kg in Iran (23.22 and 19.53 ng/kg in pasteurised milk and UHT milk respectively). The mean levels of AFM1 contamination were 43.31 ng/kg in Feta cheeses and 21.96 ng/kg in creamy cheeses. The potential risk of human exposure to aflatoxin M1 via consumption of milk and milk products is well known. Dairy products must therefore be evaluated for aflatoxin and kept free from fungal contamination as much as possible. [source]

Seasonal, sexual and developmental differences in hoopoe Upupa epops preen gland morphology and secretions: evidence for a role of bacteria

Manuel Martín-Vivaldi
The uropygial glands of birds serve multiple functions, and there is great interspecific variability in the composition and properties of their secretions. A special case is the secretion in the hoopoes Upupa epops, and green woodhoopoes Phoeniculus purpureus, which, contrary to the commonly white and odourless secretions, are dark with pungent odour. Recently, bacteria have been isolated from glands of both woodhoopoes and hoopoes and here we test the hypothesis that bacteria are responsible of some of the special properties of glands and secretions of this group of birds. We explore natural seasonal changes and intersexual differences in the properties of hoopoe glands and secretions, check the natural occurrence of bacteria within secretions, and analyse the effect of experimental injection of antibiotics on uropygial gland properties. Male glands underwent no seasonal changes, and their secretions were invariably white and odourless, very similar to female glands outside the breeding season. However, in comparison to the uropygial gland of non-breeding females, those of incubating females showed a marked increase in size and volume of secretion produced, which became dark and pungent. All these parameters increased until the hatching date and returned to values similar to those in the prelaying phase towards the end of the nestling period. Nestling glands produced secretions similar to those of females in colour and odour. Gland size of both females and nestlings predicted the amount of secretion produced. Microscopic techniques confirmed the presence of bacteria at high density and in active division in all dark secretions examined. The antibiotic treatment significantly reduced the load of enterococci in nestling glands, did not affect size of glands, but diminished the volume of secretion, which was lighter in colour than that of control nestlings. In nesting females, the experimental injection of antibiotic affected some measurements of gland size and secretion colour. Because the experiment did not affect general health estimates (immunocompetence, body condition or growing) of nestlings, our results suggest that some of the special properties of hoopoe glands are mediated by the presence of symbiotic bacteria. [source]

Delta sleep-inducing peptide (DSIP): a still unresolved riddle

Vladimir M. Kovalzon
Abstract Delta sleep-inducing peptide (DSIP) was isolated from rabbit cerebral venous blood by Schoenenberger-Monnier group from Basel in 1977 and initially regarded as a candidate sleep-promoting factor. However, the link between DSIP and sleep has never been further characterized, in part because of the lack of isolation of the DSIP gene, protein and possible related receptor. Thus the hypothesis regarding DSIP as a sleep factor is extremely poorly documented and still weak. Although DSIP itself presented a focus of study for a number of researchers, its natural occurrence and biological activity still remains obscure. DSIP structure is different from any other known representative of the various peptide families. In this mini-review we hypothesize the existence of a DSIP-like peptide(s) that is responsible (at least partly) for DSIP-like immunoreactivity and DSIP biological activity. This assumption is based on: (i) a highly specific distribution of DSIP-like immunoreactivity in the neurosecretory hypothalamic nuclei of various vertebrate species that are not particularly relevant for sleep regulation, as revealed by the histochemical studies of the Geneva group (Charnay et al.); (ii) a large spectrum of DSIP biological activity revealed by biochemical and physiological studies in vitro; (iii) significant slow-wave sleep (SWS) promoting activity of certain artificial DSIP structural analogues (but not DSIP itself!) in rabbits and rats revealed by our early studies; and (iv) significant SWS-promoting activity of a naturally occurring dermorphin-decapeptide that is structurally similar to DSIP (in five of the nine positions) and the sleep-suppressing effect of its optical isomer, as revealed in rabbits. Potential future studies are outlined, including natural synthesis and release of this DSIP-like peptide and its role in neuroendocrine regulation. [source]

Occurrence and Distribution of Microdochium and Fusarium Species Isolated from Durum Wheat in Northern Tunisia and Detection of Mycotoxins in Naturally Infested Grain

Lobna Gargouri Kammoun
Abstract An outbreak of Fusarium Head Blight of durum wheat occurred in 2004 being localized in sub-humid and higher semi-arid region of Northern Tunisia. A mycological survey carried out throughout these regions, revealed that 78% of the prospected fields were infested. Results of the morphological and molecular identification, showed that the most common species isolated from diseased wheat spikes was Microdochium nivale var. nivale (63.5%), followed by Fusarium culmorum (26%), F. pseudograminearum (9%) and F. avenaceum (1.5%). To evaluate mycotoxin content of naturally infected grain, the amounts of trichothecene mycotoxin deoxynivalenol (DON) in harvested grain from 45 fields were quantified by RIDASCREEN DON Enzyme Immunoassay Kit (ELISA). This study showed that the infection levels in freshly harvested grain were very low and the maximum deoxynivalenol (DON) level of the positive samples was 53 ppb. This is the first report on the natural occurrence of DON in naturally infected wheat grain sampled from Northern Tunisia. [source]

The Presence of Phytoplasma in Black Currant Infected with the Blackcurrant Reversion Disease


Abstract A plant of black currant cv. Karl,tejnský dlouhohrozen showing symptoms of the severe Russian (R) form of the blackcurrant reversion disease (BCRD) was shown to contain phytoplasma bodies measuring 530,750 nm. Phytoplasma infection was confirmed by polymerase chain reaction (PCR) with the universal primer pair R16F1/R16R0, followed by PCR with the primer pair fU5/rU3. A comparison of the sequence of an amplification product of approximately 880 bp with sequences available in the GenBank confirmed the classification of the phytoplasma in the 16SrI (Aster yellows group). This is the first evidence of the natural occurrence of phytoplasma infection in black currant. Blackcurrant reversion virus (BRV), the cause of BCRD, was confirmed in the plant by RT-PCR. A 481 nt cDNA fragment of BRV was sequenced and compared with sequences in GenBank. Rhabdovirus-like particles were also observed in the plant by electron microscopy. [source]

Occurrence of Bremia lactucae in Natural Populations of Lactuca serriola

I. Petr, elová
Abstract In the period 1996,2001 the natural occurrence of Bremia lactucae (lettuce downy mildew) on Asteraceae plants was studied in the Czech Republic. Lactuca serriola (prickly lettuce) is the most common naturally growing host species of B. lactucae. Infection of plants was recorded during the whole vegetation season with the first occurrence in April and last in November. Bremia lactucae was found on host plants in all developmental stages. High percentages of naturally infected populations of L. serriola were recorded. Host plants exhibited broad variation in phenotypic expression of disease symptoms and degree of infection, however, the intensity of infection was rather low in the majority of populations. Geographic distribution of B. lactucae was studied in the two main parts of Czech Republic, central and southern Moravia, and eastern, northern and central Bohemia. Bremia lactucae was recorded in all these areas. Nevertheless, in the warmest parts of the Czech Republic (southern Moravia) only sporadic occurrence of the pathogen was recorded. Bremia lactucae infection on L. serriola and disease severity was judged also in relation to the type of habitat, and the size and density of host plant populations. However, no substantial differences among various habitats were found; only host plants growing in urban areas were frequently free of infection and the degree of infection was very low. Nevertheless, these plants were commonly infected with powdery mildew (Golovinomyces cichoracearum), which is most aggressive pathogen of this type of habitat. [source]

Piperidone derivative from Dalbergia sympathetica

N. Shanmugam Nagarajan
Abstract An alcoholic extract of Dalbergia sympathetica, on column chromatography, yielded a compound which analyzed for C6H11NO3 (M+ 145). The IR spectrum of the compound showed the presence of carbonyl and hydroxyl groups. PMR, 13C and DEPT NMR spectral studies of the compound showed the presence of one N -methyl, two methine and two methylene groups. A quaternary carbon signal at , 172.88 ppm was assigned to C-2 carbonyl of the compound. From all the above observations and also from the HMQC 2D NMR spectrum, the compound was identified as 3, 6-dihydroxy- N -methyl-2-piperidone. This is the first report of the natural occurrence of this compound from plant sources. Copyright © 2004 John Wiley & Sons, Ltd. [source]

Three stones for three seeds: natural occurrence of selective tool use by capuchins (Cebus libidinosus) based on an analysis of the weight of stones found at nutting sites

Renata G. Ferreira
Abstract Capuchins (Cebus libidinosus) occupy areas of Caatinga in northeast Brazil. They consume the nuts of several species of difficult-to-open fruits (two species of Palmae and one species of Euphorbiacea) and are reported to use stones as hammers to crack open the nuts. This article describes the weight of hammers found on anvils and presumably used for nut-cracking by individuals in two groups of wild unprovisioned capuchin monkeys. Hammer weights ranged from less than 200 to over 3,kg. Based on a correlation between the type of broken nuts found at a site and the stones present on anvils, there was evidence that hammer weight differed according to nut size. These findings are consistent with experimental data recently published by Visalberghi et al. [Current Biology 19, 2009, DOI: 10.1016/j.cub.2008.11.064] and indicate that capuchins are capable of choosing stones of appropriate weight to effectively use pounding tools in natural environments without interference from humans. Am. J. Primatol. 72:270,275, 2010. © 2009 Wiley-Liss, Inc. [source]

The challenge of follow-up in narrowband ultraviolet B phototherapy

B.L. Diffey
Summary Background, The use of narrowband ultraviolet (UV) B phototherapy to treat psoriasis and other disorders has increased markedly since the TL-01 lamps were introduced in the 1980s. While broadband UVB phototherapy has generally been considered to be a relatively safe treatment, some concern has been raised about the potential increased skin cancer risk with narrowband UVB. Objectives, The likelihood of a patient who is free of nonmelanoma skin cancer (NMSC) at the start of phototherapy developing a malignancy after a certain follow-up period will be dependent not only on the carcinogenic potential of the treatment but also on the age-conditional probability of natural occurrence. We were interested to explore the potential difficulty of designing studies to separate these two events. Methods, Mathematical models were developed that combined age-conditional probabilities of developing NMSC due to natural causes with the risk of inducing these cancers from narrowband UVB phototherapy in order to estimate the excess number of cancers resulting from this therapeutic intervention in a cohort of patients. Results, Within-department studies will be most unlikely to demonstrate that the number of NMSCs observed in follow-up studies is significantly different from that expected in an untreated population, even for a follow-up period of 20 years. Conclusions, Determination of the carcinogenic potential associated with narrowband UVB will require large multicentre studies typically involving several thousand new patients per year and followed up for 10 years or more. [source]

Severe acute respiratory syndrome, tourism and the media

Peter Mason
Abstract There has been an assumption, based on trends from the last two decades of the twentieth century, that global tourism will continue to grow. A number of events in the early twenty first century, however, have called this into question. Some of these have been natural occurrences, others anthropogenic, such as the terrorist attacks in New York in 2001, which indirectly affected global tourism, and that in Bali in 2002, where tourists were the major target. The outbreak of the disease severe acute respiratory syndrome (SARS) in early 2003 had direct and significant impacts on global tourism. This article provides an overview of the SARS outbreak and its impact on global tourism, and focuses on the role of the media in relation to the disease outbreak. Eighteen months on from the height of the outbreak, SARS appeared to have been checked, but there have a number of subsequent cases and of particular concern, it has been predicted that the disease will return on a large scale, and therefore a future research agenda is also presented. Copyright © 2005 John Wiley & Sons, Ltd. [source]