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101.
102.
M.J.B.M. Weijtens J. van der Plas P.G.H. Bijker H.A.P. Urlings D. Koster J.G. van Logtestijn & J.H.J. Huis in't Veld 《Journal of applied microbiology》1997,83(6):693-698
The campylobacter infection of 10 sows and their piglets was monitored. These pigs werekept on two multiplier farms. Rectal faeces samples were taken from the sows shortly beforelittering and at different intervals after littering. Swab samples of rectal content were taken fromsix piglets per sow at different intervals after birth. Nine sows were shown to be infected withcampylobacter before litter and all sows after litter, with an average colony count of 4·1in log N g–1 of faeces. Half of the piglets became infected withcampylobacter during the first week of life and 85%, after four weeks. Two genetic subtypingmethods (ERIC-PCR and RFLP) were used to study the relationships between campylobacterisolates from sows and piglets. A large diversity of campylobacter subtypes was found.Nevertheless, piglets and their mothers often harboured campylobacter isolates with identicalgenetic subtyping profiles, suggesting that piglets become infected via their mothers. However,observed similarities in genetic subtyping profiles between campylobacters isolated on differentfarms made this difficult to prove. 相似文献
103.
The history of allergic disease goes back to 1819, when Bostock described his own 'periodical affection of the eyes and chest', which he called 'summer catarrh'. Since they thought it was produced by the effluvium of new hay, this condition was also called hay fever. Later, in 1873, Blackley established that pollen played an important role in the causation of hay fever. Nowadays, the definition of allergy is 'An untoward physiologic event mediated by a variety of different immunologic reactions'. In this review, the term allergy will be restricted to the IgE-dependent reactions. The most important clinical manifestations of IgE-dependent reactions are allergic conjunctivitis, allergic rhinitis, allergic asthma and atopic dermatitis. However, this review will be restricted to allergic rhinitis. The histopathological features of allergic inflammation involve an increase in blood flow and vascular permeability, leading to plasma exudation and the formation of oedema. In addition, a cascade of events occurs which involves a variety of inflammatory cells. These inflammatory cells migrate under the influence of chemotactic agents to the site of injury and induce the process of repair. Several types of inflammatory cells have been implicated in the pathogenesis of allergic rhinitis. After specific or nonspecific stimuli, inflammatory mediators are generated from cells normally found in the nose, such as mast cells, antigen-presenting cells and epithelial cells (primary effector cells) and from cells recruited into the nose, such as basophils, eosinophils, lymphocytes, platelets and neutrophils (secondary effector cells). This review describes the identification of each of the inflammatory cells and their mediators which play a role in the perennial allergic processes in the nose of rhinitis patients. 相似文献
104.
Lack of geographic variation in anonymous nuclear polymorphisms in the American oyster, Crassostrea virginica 总被引:1,自引:0,他引:1
Comparing geographic variation of noncoding nuclear DNA polymorphisms,
which presumably are neutral to natural selection, with geographic
variation of allozymes is potentially a good way to detect the effects of
selection on allozyme polymorphisms. A previous study of four anonymous
nuclear markers in the American oyster, Crassostrea virginica, found
dramatic differences in allele frequency between the Gulf of Mexico and the
Atlantic Ocean. In contrast, 14 allozyme polymorphisms were fairly uniform
in frequency between the two areas. This led to the conclusion that all of
the allozyme polymorphisms were kept uniform in frequency by balancing
selection. To test the robustness of this pattern, six additional anonymous
nuclear DNA polymorphisms were surveyed in oysters from Panacea, Fla, and
Charleston, S.C. on the Gulf and Atlantic coasts, respectively. Unlike the
previously studied DNA markers, the six DNA polymorphisms examined here
show geographic variation that is not significantly greater than that of
allozymes. The reason for the discrepancy between the two sets of DNA
polymorphisms is unclear.
相似文献
105.
The diurnal pattern of parasitization and eclosion of the trichogrammatidUscana lariophaga Steffan, egg parasitoid of the cowpea bruchidCallosobruchus maculatus (Fabricius) was studied for L12:D12 photoperiods. The wasp parasitized eggs throughout each 24-h period with about 70% of
the parasitization taking place during the first 12 h regardless whether it was the photophase or the scotophase. More female
progeny was produced when the first 12-h period was photophase instead of scotophase. Eclosion of wasps took place over a
period of 4 days and occurred during the second half of the scotophase and the first half of the photophase. The number of
wasps eclosed during the photophase was similar to that eclosed during the scotophase. Average development time was 8.9 days
at 30°C. Male development was completed 6 to 8 h before the females, hence a higher percentage of females emerged in the later
eclosion peaks. During scotophases more females eclosed than during photophases. Although the results indicate that the wasp
is able to perform under dark storage conditions the effect of permanent low light intensity remains to be studied. 相似文献
106.
Modelling Bacterial Growth of Lactobacillus curvatus as a Function of Acidity and Temperature 总被引:2,自引:1,他引:1 下载免费PDF全文
T. Wijtzes J. C. de Wit in Huis Ri van't M. H. Zwietering 《Applied microbiology》1995,61(7):2533-2539
Models that describe the effect of acidity, temperature, and the combined effect of these variables on the growth parameters of Lactobacillus curvatus are developed and validated. Growth parameters (lag time, specific growth rate, and maximum population density) were calculated from growth data at different temperature-acidity combinations. Experiments were set up to assess the quantitative effects of temperature and acidity on the growth parameters rather than for parameter estimation solely. The effect of acidity is monitored at several constant temperature values. Models are set up and fitted to the data. The same procedure is used at constant acidity values to model the effect of temperature. For lag time, specific growth rate, and maximum population density, the effect of temperature could be multiplied with the effect of acidity to obtain combinatory models that describe the effect of both controlling factors on the growth parameters. Lag time measurements showed large deviations, and therefore the lag time models developed can only be used to estimate the order of magnitude of lag time. 相似文献
107.
Birgit Janning P.H. in't Veld S. Notermans J. Krämer 《Journal of applied microbiology》1994,77(3):319-324
The Viability of 18 bacterial strains desiccated on anhydrous silica gel and stored at a temperature of 22°C for at least 3 months was determined. According to their stability in the dried state, these strains could be classified into three typical groups. Group 1, containing Gram-positive strains and Salmonella serotypes, was marked by a very slow decrease of the concentration of culturable cells from day 14 on (respectively day 21 for Salmonella thompson . The rate of decrease expressed as regression coefficient (b) ranged from —0.000389 to —0.00521 log (cfp ml-1 ) per d. The Group 2 strains Enterobacter cloacae and Escherichia coli did not reach a comparable slow decrease in the dry material within the indicated time period. Regression coefficients were respectively —0.04406 and —0.03412 log (cfp ml-1 ) per d. The reciprocal values —(1/b) were respectively 23 d per log (cfp ml-1 ) and 29 d per log (cfp ml-1 ), indicating the time periods in which a reduction of 1 log unit of culturable cells occurred. Group 3 strains Pseudomonas aeruginosa, Aeromonas hydrophila and Aer. sobria were marked by a significant susceptibility to cell damage caused during desiccation and reconstitution. A high initial decrease (ID) of the concentration of culturable organisms seems to be a characteristic property of these bacterial strains: culturable organisms could not be detected after storage for 1 d ( Aer. hydrophila, Aer. sobria ) or 7 d ( Ps. aeruginosa ). The wide range of resistance of the different bacterial strains tested indicated that the silica gel model system is a suitable tool for microbiological challenge tests to investigate the survival of micro-organisms exposed to desiccation and their stability in dry materials. 相似文献
108.
P. Van Netten J.H.J. Huis in t Veld D.A.A. Mossel 《Journal of applied microbiology》1994,77(5):490-496
P. VAN NETTEN, J.H.J. HUIS IN'T VELD AND D.A.A. MOSSEL. 1994. The kinetics of the bactericidal effect of lactic acid decontamination (LAD) on meat-borne pathogens ( Salmonella spp., Campylobacter jejuni and Listeria monocytogenes ) was studied in an in-vitro model. The bactericidal effect was greatest on organisms in the lactic acid film that replaced the natural fluid on the meat surface during LAD. A stepwise increase in pH from 2.6 to 3.5 and 4.0 progressively reduced the bactericidal effect of decontamination. For treatment with 2% lactic acid for 30–90 s at 21C, the immediate death of Salmonella spp. decreased from about 0.5–2 log10 cfu at pH 2.6 to an insignificant level at pH 4.0. The immediate death for Camp. jejuni decreased from 2.6 to >5.3 at pH 2.6 to 0.3–1.0 at pH 4.0. The decrease in bactericidal effect with increasing pH could, however, be countered by an increase in the temperature from 21C to 37C. It is suggested that 2% LAD at 37C for 30–90 s is suitable for elimination of salmonellas on meat but not for L. monocytogenes. Decontamination with 1% lactic acid at pH 3.0 and 21C for at least 30 s was effective for Camp. jejuni. Mesophilic Enterobacteriaceae were reliable indicators of the LAD-induced bactericidal effect on Salmonella spp. and Camp. jejuni. 相似文献
109.
Natural selection and the molecular clock 总被引:13,自引:1,他引:12
110.
Labeled leucine, serine, galactose, glucosamine and sulphate were administered to rat stomachs in a perfusion system. Sections of the gastric fundus were studied by light microscopic autoradiography. Five categories of mucous cells were distinguished and their glycoprotein synthetic activity was measured in autoradiographs by counting silver grains over each category. During their differentiation, while migrating from the isthmus of the fundic glands to the free luminal surface, the surface mucous cells (SMC) showed an increase in incorporation of all precursors used. Differences between the incorporation patterns of the various precursors, in cells of different ages, suggest that structural development runs ahead of functional activity, and that the latter continues up to the very moment the cell is shed from the surface. Sulphate was incorporated at a considerably lower rate by the SMC of the free surface than by the foveolar SMC, in which by cytochemical staining strongly acidic glycoproteins were shown. Since the mucous neck cells incorporated all precursors at a low rate, these cells apparently do not play an important role in gastric mucus synthesis. They did not incorporate sulphate, which is consistent with histochemical observations. 相似文献