Showing papers on "Incubation published in 2009"

Does Incubation Enhance Problem Solving? A Meta-Analytic Review

Abstract: A meta-analytic review of empirical studies that have investigated incubation effects on problem solving is reported. Although some researchers have reported increased solution rates after an incubation period (i.e., a period of time in which a problem is set aside prior to further attempts to solve), others have failed to find effects. The analysis examined the contributions of moderators such as problem type, presence of solution-relevant or misleading cues, and lengths of preparation and incubation periods to incubation effect sizes. The authors identified a positive incubation effect, with divergent thinking tasks benefiting more than linguistic and visual insight tasks from incubation. Longer preparation periods gave a greater incubation effect, whereas filling an incubation period with high cognitive demand tasks gave a smaller incubation effect. Surprisingly, low cognitive demand tasks yielded a stronger incubation effect than did rest during an incubation period when solving linguistic insight problems. The existence of multiple types of incubation effect provides evidence for differential invocation of knowledge-based vs. strategic solution processes across different classes of problem, and it suggests that the conditions under which incubation can be used as a practical technique for enhancing problem solving must be designed with care.

Physicochemical properties of ferumoxytol, a new intravenous iron preparation

Abstract: Background Intravenous iron is a critical component of anaemia management. However, currently available preparations have been associated with the release of free iron, a promoter of bacterial growth and oxidative stress. Materials and methods We determined the molecular weight, dialysability and capacity for free iron release of ferumoxytol, a semi-synthetic carbohydrate-coated superparamagnetic iron oxide nanoparticle. Ferumoxytol was compared with three intravenous iron preparations in clinical use: iron dextran (low molecular weight), sodium ferric gluconate and iron sucrose. Intravenous iron preparations were also incubated in rat, and pooled human sera (at concentrations of 600 μM and 42 μg mL−1 respectively) from healthy subjects. Results The molecular weight of ferumoxytol was 731 kDa. The relative order of molecular weight was as follows: ferumoxytol > iron dextran > iron sucrose > sodium ferric gluconate. The least ultrafilterable iron was observed with ferumoxytol and the most with ferric gluconate. The least dialysable free iron was observed with ferumoxytol and the most with ferric gluconate. Incubation of intravenous iron preparations in rat or pooled human sera demonstrated minimal free iron release with ferumoxytol. The order of catalytic iron release as detected by the bleomycin detectable iron assay was as follows: ferumoxytol < iron dextran < iron sucrose < ferric gluconate. A similar trend was observed for the in vivo serum concentration of free iron in rats. Conclusions In vitro observations from these experiments suggest that ferumoxytol has a favourable profile in terms of tendency to release free iron, in comparison with currently available intravenous iron preparations.

Temperature and life history: experimental heating leads female tree swallows to modulate egg temperature and incubation behaviour

Abstract: Summary 1. Life-history decisions are strongly affected by environmental conditions. In birds, incubation is energetically expensive and affected significantly by ambient temperature. We reduced energetic constraints for female tree swallows ( Tachycineta bicolor ) by experimentally heating nests during incubation by an average of 6·9 ° C to test for changes in incubation behaviour. 2. Females in heated boxes (hereafter ‘heated females’) increased time spent incubating and maintained higher on-bout and off-bout egg temperatures. This indicates that female energetic constraints, not maximizing developmental conditions of offspring, determine incubation investment. Furthermore, this result suggests that embryonic developmental conditions in unmanipulated nests are suboptimal. 3. We found individual variation in how females responded to experimental heating. Early-laying (i.e. higher phenotypic quality) females with heated nests increased egg temperatures and maintained incubation constancy, while later-laying (lower quality) heated females increased incubation constancy. Changes in egg temperature were due to changes in female behaviour and not due directly to increases in internal nest-box temperatures. 4. Behaviour during the incubation period affected hatching asynchrony. Decreased variation in egg temperature led to lower levels of hatching asynchrony, which was also generally lower in heated nests. 5. Our study finds strong support for the prediction that intermittent incubators set their incubation investment at levels dictated by energetic constraints. Furthermore, females incubating in heated boxes allocated conserved energy primarily to increased egg temperature and increased incubation attentiveness. These results indicate that studies investigating the role of energetics in driving reproductive investment in intermittent incubators should consider egg temperature and individual variation more explicitly.

Improved culturability of SAR11 strains in dilution‐to‐extinction culturing from the East Sea, West Pacific Ocean

Abstract: Although the SAR11 clade of the Alphaproteobacteria represents the most abundant and ubiquitous bacterioplankton in the ocean, very few laboratories have successfully cultured SAR11 cells. All of the SAR11 strains isolated thus far have been retrieved from the Oregon coast and the Sargasso Sea. In this study, a modified dilution-to-extinction culturing with prolonged incubation at low temperature was applied in an effort to cultivate major bacterioplankton lineages in the East Sea, Western Pacific Ocean. Five to 10 cells were inoculated into each well of 48-well plates, followed by the incubation of the plates at 10 degrees C for 4, 8, 20, and 24 weeks. Among a total of 35 isolated strains, 18 strains assigned to the SAR11 clade were isolated after 8, 20, and 24 weeks of incubation, whereas no SAR11 cells were detected in the samples after 4 weeks of incubation. The SAR11 isolates, noticeably, comprised 64-82% of the total isolates from the plates incubated for 20 and 24 weeks. Extinction cultures belonging to the Roseobacter, OM43, and SAR92 clades were also cultivated. The results of this study suggest that long-term incubation at low temperatures might prove an alternative for the efficient cultivation of new variants of the members of the SAR11 clade.

Avian incubation inhibits growth and diversification of bacterial assemblages on eggs.

Abstract: Microbial infection is a critical source of mortality for early life stages of oviparous vertebrates, but parental defenses against infection are less well known. Avian incubation has been hypothesized to reduce the risk of trans-shell infection by limiting microbial growth of pathogenic bacteria on eggshells, while enhancing growth of commensal or beneficial bacteria that inhibit or competitively exclude pathogens. We tested this hypothesis by comparing bacterial assemblages on naturally incubated and experimentally unincubated eggs at laying and late incubation using a universal 16S rRNA microarray containing probes for over 8000 bacterial taxa. Before treatment, bacterial assemblages on individual eggs from both treatment groups were dissimilar to one another, as measured by clustering in non-metric dimensional scaling (NMDS) ordination space. After treatment, assemblages of unincubated eggs were similar to one another, but those of incubated eggs were not. Furthermore, assemblages of unincubated eggs were characterized by high abundance of six indicator species while incubated eggs had no indicator species. Bacterial taxon richness remained static on incubated eggs, but increased significantly on unincubated eggs, especially in several families of Gram-negative bacteria. The relative abundance of individual bacterial taxa did not change on incubated eggs, but that of 82 bacterial taxa, including some known to infect the interior of eggs, increased on unincubated eggs. Thus, incubation inhibits all of the relatively few bacteria that grow on eggshells, and does not appear to promote growth of any bacteria.

Influence of temperature stimulation during the last 4 days of incubation on secondary sex ratio and later performance in male and female broiler chicks

Abstract: 1. In 6 incubation trials a total of 9883 eggs (Ross 308) were incubated from d 1 to 17 under normal incubation conditions (37.2-37.4 degrees C) and then sorted into three hatch incubators (control: 37.2-37.4 degrees C; chronic warm incubation: 38.2-38.4 degrees C, 24 h daily; short-term warm stimulation: 38.2-38.4 degrees C, 2 h daily) in incubation trials 1 and 2 or two hatch incubators (control and short-term warm stimulation) in trials 3-6. 2. The one-day-old chicks were selected by sex and chick quality was analysed in random samples using the Pasgar score. A total of 120 male and 120 female one-day-old chickens from each incubator were used for a 35-d fattening period. 3. Neither chronic nor short-term increase in incubation temperature had a negative effect on hatchability and chick quality. Short-term warm stimulation improved hatchability by more than 1.5% and was associated with a significantly higher proportion of hatched male chicks. 4. In the subsequent broiler growth trial, the mean daily weight gain of the short-term warm stimulated male broiler chicks was significant higher than for the control group, which results in a body weight increase of 2.9%. 5. Feed conversion (feed:gain ratio) of the short-term warm stimulated male and female broilers was significantly lower than in the males and females of the control and chronic warm incubated groups. 6. In conclusion, an incubation temperature profile which includes short-term temperature variation can be important in improving poultry performance (European patent pending since March 2008).

Determinants of incubation period: do reptilian embryos hatch after a fixed total number of heart beats?

Abstract: SUMMARY The eggs of birds typically hatch after a fixed (but lineage-specific) cumulative number of heart beats since the initiation of incubation. Is the same true for non-avian reptiles, despite wide intraspecific variation in incubation period generated by variable nest temperatures? Non-invasive monitoring of embryo heart beat rates in one turtle species ( Pelodiscus sinensis ) and two lizards ( Bassiana duperreyi and Takydromus septentrionalis ) show that the total number of heart beats during embryogenesis is relatively constant over a wide range of warm incubation conditions. However, incubation at low temperatures increases the total number of heart beats required to complete embryogenesis, because the embryo spends much of its time at temperatures that require maintenance functions but that do not allow embryonic growth or differentiation. Thus, cool-incubated embryos allocate additional metabolic effort to maintenance costs. Under warm conditions, total number of heart beats thus predicts incubation period in non-avian reptiles as well as in birds (the total number of heart beats are also similar); however, under the colder nest conditions often experienced by non-avian reptiles, maintenance costs add significantly to total embryonic metabolic expenditure.

The relationship of oocyte diameter and incubation temperature to incubation time in temperate freshwater fish species.

Abstract: Based on the analysis of six egg variables and incubation temperature of 65 temperate freshwater fish species, the possible relationships between oocyte diameter, incubation time and incubation temperature were reassessed and compared to the results obtained from marine fishes. Most freshwater species have eggs (mean +/-s.d. 2.19 +/- 1.52 mm) larger than marine species, that are chiefly demersal and develop stuck to various substrata, such as plants or rocks. A strong negative relationship was found between incubation time (t, days) and incubation temperature (T, degrees C): t = 186.23e(-0.197T) (r(2)= 0.87). A strong dependence of incubation time on oocyte diameter (O, mm) and incubation temperature was also found and was defined as: log(10)t= 3.002 + 0.599 log(10)O - 1.91 log(10) (T + 2), which explained 92% of the variance of the data set. Five major groups of species were defined based on the principal component analysis (PCA) of four quantitative variables. There were two distinct groups of salmonids, displaying demersal and non-adhesive eggs with a long incubation time at low temperature, the eggs of which required a high number of degree-days. There was a large group of species possessing small, mostly demersal and adhesive eggs developing at high temperature during a short period of time, and requiring a low number of degree-days. Between these two extremes, there was a fourth group displaying intermediate values and a fifth group including three species with large, adhesive and demersal eggs incubating at high temperatures during a short period of time. The burbot Lota lota displayed an unusual combination of variables compared to the remaining species in the data set.

Changes in mineral and mineralizable N of soil incubated at varying salinity, moisture and temperature regimes.

Abstract: A laboratory incubation experiment was conducted to study the effect of factors like moisture, salinity and temperature on the release of N in plant-available forms (NH4 and NO3+NO2-N) and potentially mineralizable N in soil over a period of 8 weeks following amendment with leguminous plant residues. In this experiment, soil samples salinized to ECe 7, 9, and 18 dS m -1 (original ECe was 5.0 dS m -1 ) were amended with 0.5% plant material of Sesbania aculeata and incubated at three moisture levels of 15, 30 and 45%, w/w and three temperature regimes of 20, 30 and 40 o C for 8 weeks. Soil samples were sacrificed at 2, 4 and 8 weeks for the determination of NH4-N, NO3+NO2-N and mineralizable N. Ammonification of organic N as determined by the accumulation of NH4-N in soil was found to increase with time as salinity, moisture and temperature increased. However, the increase was more pronounced at higher moisture levels. While temperature had a positive effect on nitrification, increased salinity and moisture depressed the process. Net mineralization of N increased with time in all the treatments; the process being enhanced at higher incubation temperature with a maximum at 40 o C. Salinity and high moisture had a depressing effect on the mineralization of N. The content of mineralizable N determined by NH4-N accumulation following 2 weeks of incubation under submerged conditions in soil remained higher under high moisture conditions, while high salinity and temperature had a variable and negative effect. Apparently, high moisture content conserved organic N due to reduced mineralization, while high temperature had an opposite effect. A complete loss of NO3-N was observed during incubation of soil samples for the determination of mineralizable N. This was attributable to denitrification as sufficient amount of easily oxidizable C was still present in the soil after 8 weeks of incubation under relatively aerobic conditions.

Contrasting Effects of Heat Treatment and Incubation Temperature on Germination and Outgrowth of Individual Spores of Nonproteolytic Clostridium botulinum Bacteria

Abstract: In this study, we determined the effects of incubation temperature and prior heat treatment on the lag-phase kinetics of individual spores of nonproteolytic Clostridium botulinum Eklund 17B. The times to germination (tgerm), one mature cell (tC1), and two mature cells (tC2) were measured for individual unheated spores incubated at 8, 10, 15, or 22°C and used to calculate the tgerm, the outgrowth time (tC1 − tgerm), and the first doubling time (tC2 − tC1). Measurements were also made at 22°C of spores that had previously been heated at 80°C for 20 s. For unheated spores, outgrowth made a greater contribution to the duration and variability of the lag phase than germination. Decreasing incubation temperature affected germination less than outgrowth; thus, the proportion of lag associated with germination was less at lower incubation temperatures. Heat treatment at 80°C for 20 s increased the median germination time of surviving spores 16-fold and greatly increased the variability of spore germination times. The shape of the lag-time (tC1) and outgrowth (tC1 − tgerm) distributions were the same for unheated spores, but heat treatment altered the shape of the lag-time distribution, so it was no longer homogeneous with the outgrowth distribution. Although heat treatment mainly extended germination, there is also evidence of damage to systems required for outgrowth. However, this damage was quickly repaired and was not evident by the time the cells started to double. The results presented here combined with previous findings show that the stage of lag most affected, and the extent of any effect in terms of duration or variability, differs with both historical treatment and the growth conditions.

Proliferation of antibiotic-producing bacteria and concomitant antibiotic production as the basis for the antibiotic activity of Jordan’s Red Soils.

Abstract: Anecdotes, both historical and recent, recount the curing of skin infections, including diaper rash, by using red soils from the Hashemite Kingdom of Jordan. Following inoculation of red soils isolated from geographically separate areas of Jordan, Micrococcus luteus and Staphylococcus aureus were rapidly killed. Over the 3-week incubation period, the number of specific types of antibiotic-producing bacteria increased, and high antimicrobial activity (MIC, approximately 10 microg/ml) was observed in methanol extracts of the inoculated red soils. Antibiotic-producing microorganisms whose numbers increased during incubation included actinomycetes, Lysobacter spp., and Bacillus spp. The actinomycetes produced actinomycin C(2) and actinomycin C(3). No myxobacteria or lytic bacteriophages with activity against either M. luteus or S. aureus were detected in either soil before or after inoculation and incubation. Although protozoa and amoebae were detected in the soils, the numbers were low and did not increase over the incubation period. These results suggest that the antibiotic activity of Jordan's red soils is due to the proliferation of antibiotic-producing bacteria.

Incubation conditions affect leg health in large, high-yield broilers

Abstract: SUMMARY Leg problems are observed in every flock of broilers, and they occur more frequently in heavy, fast-growing broilers. Factors such as genetics, growth rate, stressors, nutrition, and lighting programs can contribute to and change the prevalence of these problems in broiler production. Our previous research has shown that elevated incubation temperatures and oxygen concentrations below 21% during the last days of embryo development can negatively affect thyroid hormones, relative asymmetry and normal development of leg bones, and development of other tissues and organs that influence leg health and locomotion in broilers. This project evaluated the effects of incubation profiles on leg health of high-yielding broilers at 8 wk of age under commercial conditions. Eggs from the same breeder flocks were incubated in either single-stage or multistage machines. Hatchlings were placed in paired houses on the same farms, and at 56 d of age, leg health was evaluated. There was variability among farms and hatches: leg problems such as footpad dermatitis were more closely related to farm conditions, whereas valgus and especially hock burns were influenced by incubation conditions within each farm. However, this fieldwork demonstrated that proper incubation conditions improve broiler performance, especially in females (1.2%); may reduce leg health problems such as crooked toes; and may even improve locomotion.

HUMAN CORNEAL ENDOTHELIUM IN ORGAN CULTURE: The Influence of Temperature and Medium of Incubation

Abstract: Forty-four human corneas from patients between 21 and 86 years were incubated in Eagle's minimum essential medium with Earle's salts 10--46 h post mortem The influence of incubation temperature and composition of the medium on endothelial survival was evaluated Whole corneas were stained by alizarine red Recent cell loss was indicated by morphological alterations in the endothelial pattern After 20--28 h of incubation minimum cell loss was found at 31 degrees C when 8% Dextrane-250 and 20% serum or 8% Dextrane-500 and 10% serum was added to the medium

Early morphological changes in organ cultured human corneal endothelium.

Abstract: Nineteen human cadaver corneas with few damaged endothelial cells were incubated under tissue culture conditions for time periods ranging from five min to 48 h. Morphological alterations of the endothelial cells were studied in whole wet mounts stained by alizarine red-alkohol-trypane blue and by scanning electron microscopy. Joint meetings of three cells are characteristic for normal corneal endothelium. After 15--60 min of incubation, damaged cells were expelled from the coherent cell sheet by expanding neighbouring cells. Joint meetings of 5--8 expanding cells were formed. After 24 h of incubation, joint meetings of four cells were the dominating morphological abnormality. Morphological changes during reduction of the numbers of cells in joint meetings are described.

Algoriphagus aquatilis sp. nov., isolated from a freshwater lake

Abstract: A Gram-negative, non-spore-forming, non-motile bacterium, strain A8-7T, was isolated from fresh water of a slightly alkaline lake, Longhu Lake, in Daqing, north-east China, and its taxonomic position was studied by using a polyphasic approach. Strain A8-7T was aerobic, heterotrophic and positive for catalase and oxidase. It grew at 20–37 °C (optimum 30 °C) and pH 5.5–10.5 (optimum pH 7.5) and in the presence of 0–3 % (w/v) NaCl. It formed pink-pigmented, smooth and circular colonies, 1–2 mm in diameter, on R3A-V agar plates after incubation at 30 °C for 3 days. Cells of strain A8-7T were rods, 0.2–0.4 μm wide and 1.6–4.0 μm long. The major fatty acids (>10 %) were iso-C15 : 0 (40.3 %) and summed feature 3 (C16 : 1 ω7c and/or iso-C15 : 0 2-OH; 12.1 %). The menaquinone was MK-7. The DNA G+C content was 43 mol% (T m). Phylogenetic analyses based on 16S rRNA gene sequences revealed that strain A8-7T was phylogenetically related to members of the genus Algoriphagus, with sequence similarities of 92.6–95.2 %, the highest sequence similarity being to the sequence from Algoriphagus mannitolivorans IMSNU 14012T. On the basis of phenotypic, chemotaxonomic and phylogenetic data, strain A8-7T was considered to represent a novel species of the genus Algoriphagus, for which the name Algoriphagus aquatilis sp. nov. is proposed. The type strain is A8-7T (=CGMCC 1.7030T =NBRC 104237T).

Effects of hydrogen peroxide (H2O2) on fresh and cryopreserved buffalo sperm functions during incubation at 37 degrees C in vitro.

Abstract: The magnitude of damage to buffalo spermatozoa during incubation with different levels of H2O2 was assessed. A total number of 24 ejaculates from four Murrah buffalo bulls were analysed in the study. Each ejaculate was split into two parts (part I and II). Part I was extended in Tris-egg yolk-citrate extender (20% egg yolk:7% glycerol), equilibrated (4 h at 5 degrees C) and cryopreserved in 0.5-ml French straws and stored in liquid nitrogen. The other part was utilized for fresh semen studies. The sperm in fresh, equilibrated and frozen-thawed semen was separated by centrifugation (1500 g; 15 min) and were washed with sperm TALP. The sperm cells were re-suspended in incubation TALP at the rate of 10(8) sperm cells per millilitre and incubated with 0, 10, 25, and 50 microm H2O2 per ml at 37 degrees C. Sperm motility, viability and intact acrosome percentages were assessed at 15-min intervals up to 60 min of incubation. Lipid peroxidation levels of sperm were assessed at 0 and 60 min of incubation. The results of the experiment revealed that sperm motility decreased drastically during incubation with H2O2. Among the different levels of H2O2, the 50-microm H2O2-incorporated group had significantly (p<0.05) higher malonaldehyde (MDA) level than the other groups. In the 50-microm H2O2-incorporated group, the MDA levels in fresh, equilibrated and frozen-thawed semen after incubation for 60 min were 961.6+/-12.7, 991.8+/-10.3 and 1234.9+/-9.6 nm per 10(9) spermatozoa respectively. An inverse relationship was observed between sperm motility, viability, intact acrosome percentages and concentration of H2O2 and duration of incubation. The decrease in sperm functions with duration of incubation and concentration of H2O2 was significantly (p<0.05) higher in frozen-thawed than fresh and equilibrated spermatozoa.

Investigations on the use of C-21-steroids as precursors for placental oestrogen synthesis in the cow

Abstract: Cotyledonary homogenates from 220 and 270 day pregnant and term cows were incubated (NADPH- and NAD(+)-regenerating system) with 3H-pregnenolone and 3H-progesterone, respectively. Identification of metabolites was based on separation on HPLC and the respective retention times. On days 220/270 the major metabolite formed after incubation with 3H-pregnenolone was progesterone, followed by 17 alpha-hydroxyprogesterone and dehydroepiandrosterone/17 alpha-hydroxypregnenolone; the formation of estrone was low (up to 6%), while it was the major metabolite after incubation of pregnenolone with term placenta. At all stages of pregnancy investigated, the only metabolite found after incubation with 3H-progesterone was 17 alpha-hydroxyprogesterone. These data provide evidence that 17 alpha-hydroxyprogesterone is the endpoint of steroid biosynthesis in the bovine placenta along the delta 4-route and that oestrogen synthesis follows the delta 5-pathway. Based on the high activity of 3 beta-hydroxysteroiddehydrogenase/delta 5/4-isomerase also found on days 220/270, the key enzyme allowing for placental oestrogen synthesis in the cow seems to be cytochrome P450c17 alpha. Thus the situation in the cow is similar to that in the sheep and the increased turnover of pregnenolone into estrone may explain the decrease of placental progesterone production in the cow towards the end of gestation.

Effect of incubation temperatures and chick transportation conditions on bone development and leg health.

Abstract: SUMMARY Bone development can be adversely affected by stressful environmental conditions early in life. One experiment was conducted to evaluate the effects of low temperature during early incubation, high temperature during late incubation, and transportation conditions from hatchery to the farm on the long bone development and leg health of broilers. Bone development was evaluated at hatch before transportation. Gait scores and leg health disorders were recorded at 41 d of age. Although incubation conditions did not affect chick BW, hot temperatures during late incubation reduced the relative weight of femurs and shanks. At 41 d, males had more leg problems than females. Late high temperature and transportation stress increased the incidence of crooked toes and the percentage of chickens with a gait score of 2. Transportation stress, including elevated temperature, caused a greater incidence of twisted legs. We concluded that low early incubation temperature, high late incubation temperature, and transportation stress can increase the incidence of leg problems in commercial broilers.

A comparative study of topical 5-aminolevulinic acid incubation times in photodynamic therapy with intense pulsed light for the treatment of inflammatory acne.

Abstract: BACKGROUND Photodynamic therapy (PDT) with topical 5-aminolevulinic acid (ALA) is used for effective treatment of facial acne vulgaris. OBJECTIVES To determine which of two different incubation times (30 minutes and 3 hours) is more effective in PDT with intense pulsed light (IPL) for acne vulgaris. METHODS & MATERIALS Twenty Korean subjects with moderate to severe acne were enrolled for a randomized, half-facial treatment study. Three sessions with short incubation with ALA plus IPL (30 minutes, n=9) or long incubation with ALA plus IPL (3 hours, n=11) on one side of the face and IPL alone on the other side were performed at 1-month intervals. RESULTS All subjects showed improvement in inflammatory acne lesions after three sessions of ALA-PDT or IPL alone (p<.001 in all groups). The degree of improvement in inflammatory acne lesions was greater in the long incubation time group than the short incubation time group or the IPL-alone group, although the mean reduction of inflammatory acne lesions was statistically different only between the long incubation group and the IPL-only group (p=.01). There were no statistical differences between the short incubation group and IPL-alone group. All three groups had decreased sebum secretion after three sessions (p<.001 in all groups), but the differences between groups were not statistically significant. Only transient erythema and mild edema were reported for all treatment groups. CONCLUSION PDT with a long ALA incubation time might be more adequate for a pronounced outcome with inflammatory acne.

Cross-reactivity between heat labile enterotoxins of Vibrio cholerae and Escherichia coli in neutralization tests in rabbit ileum and skin.

Abstract: Crude enterotoxin preparations of porcine-enteropathogenic Escherichia coli were found to be active both in the ileal loop model and in the intradermal test in rabbits, as was crude and isolated exo-enterotoxin of Vibrio cholerae. The skin activity of the E. coli enterotoxic preparations was destroyed by incubation at 65° C for 10 minutes. Neutralization studies in the ileal loop and the intradermal tests indicated that the heat-labile enterotoxins produced by E. coli of different O groups shared antigenic determinants to a varying extent, and also showed some immunological cross-reactivity with the cholera exo-enterotoxin.