Viability of Cryptosporidium parvum oocysts: correlation of in vitro excystation with inclusion or exclusion of fluorogenic vital dyes

A viability assay for oocysts of Cryptosporidium parvum based on the inclusion or exclusion of two fluorogenic vital dyes, 4',6-diamidino-2-phenylindole (DAPI) and propidium iodide, was developed by using several different isolates of oocysts. Correlation of this assay with viability measured by in vitro excystation was highly statistically significant, with a calculated correlation coefficient of 0.997. In this research, two similar excystation protocols were utilized, and no significant difference between excystation protocols was detected. Percent excystation of oocyst suspensions could be increased or reduced by inclusion of a preincubation treatment in either excystation protocol, and this alteration was also demonstrated in the viability assay. Oocysts which excluded both dyes would not excyst in vitro unless a further trigger was provided and were more resistant to acid or alkali treatment. The results of this research provide a reproducible, user-friendly assay which is applicable to individual oocysts and also provides a useful adjunct for identification of oocysts in water and environmental samples.

Survival of Cryptosporidium parvum oocysts under various environmental pressures

The survival of various isolates of Cryptosporidium parvum oocysts under a range of environmental pressures including freezing, desiccation, and water treatment processes and in physical environments commonly associated with oocysts such as feces and various water types was monitored. Oocyst viability was assessed by in vitro excystation and by a viability assay based on the exclusion or inclusion of two fluorogenic vital dyes. Although desiccation was found to be lethal, a small proportion of oocysts were able to withstand exposure to temperatures as low as -22 degrees C. The water treatment processes investigated did not affect the survival of oocysts when pH was corrected. However, contact with lime, ferric sulfate, or alum had a significant impact on oocyst survival if the pH was not corrected. Oocysts demonstrated longevity in all water types investigated, including seawater, and when in contact with feces were considered to develop an enhanced impermeability to small molecules which might increase the robustness of the oocysts when exposed to environmental pressures.

Characterization of IgE antibody binding profiles of sera from patients with atopic dermatitis to allergens of the domestic mites Dermatophagoides pteronyssinus and Euroglyphus maynei, using enhanced chemiluminescent immunoblotting

A rapid, sensitive, chemiluminescent immunoblotting method was used to identify IgE-binding components of Dermatophagoides pteronyssinus and Euroglyphus maynei that were recognized by sera of 16 D. pteronyssinus-sensitive patients with atopic dermatitis. Some 28 components (14-200 kD) were found in the D. pteronyssinus extract, and sera bound between 1 and 13 of them (mean 6.0). At least one of four components (97, 28, 24 and 14 kD) were bound by 14/16 sera. E. maynei had 25 components (14-227 kD), 13 in common with those of D. pteronyssinus by molecular size. Sera bound between 1 and 11 of them (mean 5.2) and 14/16 sera bound 1 of 38 kD (unique to E. maynei) and/or 1 of 175 kD. There were positive correlations between the number of D. pteronyssinus and E. maynei components bound and anti-D. pteronyssinus and E. maynei serum IgE values (p less than 0.001 in both cases) and between the number of D. pteronyssinus and E. maynei components bound and total serum IgE values (p less than 0.01 in both cases). These results demonstrate a very considerable diversity of IgE antibody responses to domestic mite allergens amongst patients with atopic dermatitis.

Cryptosporidium infection in cats: prevalence of infection in domestic and feral cats in the Glasgow area

A clinical and post mortem survey of domestic and feral cats in the Glasgow area revealed that 19 of 235 (8.1 per cent) were infected with Cryptosporidium species. More kittens than adults were infected (P less than 0.01), and of 51 of the cats which had diarrhoea, four also had cryptosporidium infection. Of seven domestic cats with cryptosporidium infection, two were also positive for feline immunodeficiency virus. There was no significant difference between the prevalence of cryptosporidium infection in domestic and feral cats. Cryptosporidium oocysts were detected in faecal and mucosal impression smears stained with auramine-phenol and modified Ziehl-Nielsen techniques. Endogenous developmental stages of cryptosporidium were found in the microvillus region of enterocytes of eight of 19 positive cats in sections stained with haematoxylin and eosin. The results suggest that cryptosporidium infection is common among young and newborn kittens, and that the disease is usually asymptomatic.

A Lyme borreliosis human serosurvey of asymptomatic adults in Ireland

Blood samples were obtained through the Blood Transfusion Service in Ireland in order to obtain information on the prevalence of asymptomatic B. burgdorferi infections and in an attempt to identify the type of habitat that presents the most risk of infection. Areas in the country were rated as low, medium or high risk based on the availability of suitable tick habitat, access to the public and the distribution of deer, the latter parameter being related to both the occurrence of rodent reservoir hosts and woodland recreational areas. Approximately 100 plasma samples from each of four areas were analysed for IgG anti-Borrelia antibodies by indirect immuno-fluorescence with a titre of 1 :80 indicating a positive reaction in asymptomatic individuals. Prevalence figures of 15, 11, 8 and 5% were obtained for high, high/medium, medium/low and low risk areas respectively. No positive samples were detected in blood from an Icelandic population which is not exposed to I. ricinus bites. The overall subclinical prevalence (9.75%) is surprisingly high in view of the apparent rarity of clinical cases in Ireland, though under-diagnosis probably occurs. These results seem to indicate that farmland is less important than woodland as Lyme borreliosis habitat. If this is so, it is probably due to the presence in woodland of Apodemus sylvaticus, a putative reservoir host, and also to the use of such areas for recreation at certain times of the year.

The surface lipid of parasitic nematodes: organization, and modifications during transition to the mammalian host environment

The biophysical properties of the surface lipid of a range of nematode species and their developmental stages were examined, using fluorescent lipid probes and fluorescence recovery after photobleaching (FRAP). These methods can be applied to living, intact parasites, and the analysis confined to lipid on the outermost surface. In all cases, surface lipid was unusual in its selectivity for the insertion of the lipid probes. In addition, a polar lipid probe was generally not free to diffuse in the plane of the surface, in contrast to a non-polar lipid probe which was free to diffuse. This is evidence that the surface lipid layer is heterogeneous, and possibly comprises lipid domains. The infective larvae of Acanthocheilonema viteae, Nippostrongylus brasiliensis, Trichinella spiralis and Ostertagia ostertagi were found to exhibit a rapid change in lipophilicity upon exposure to conditions simulating entry into a mammalian host environment. Parasitic nematodes, therefore, present their hosts not only with a highly unusual biological surface, but also one which can be rapidly re-organised upon a change of environment.

Waterborne cryptosporidiosis

Awareness of the importance of Cryptosporidium as a gastrointestinal parasite of developed countries not only stems from its prevalence in AIDS patients but also from its recent recognition as a possible contaminant of drinking water supplies. The importance of Cryptosporidium to public health has recently been revealed by a series of major epidemics of diarrhoeal disease in the USA and UK. In this review, Huw Smith and Joan Rose document what is known of the causes of some of these outbreaks and explain why this parasite can escape the battery of treatment processes normally used for drinking water supplies in these countries.

An outbreak of waterborne cryptosporidiosis caused by post-treatment contamination

An outbreak of waterborne cryptosporidiosis affecting 27 persons, diagnosed stool positive, occurred in Ayrshire in April 1988. Twenty-one in 27 confirmed cases required some form of fluid replacement therapy. Local general practitioners indicated a two- to fivefold increase in diarrhoeal disease during the outbreak, and following enquiries made by Environmental Health Officers it became apparent that many hundreds of people had suffered a diarrhoeal illness at that time. Cryptosporidium spp. oocysts were detected in the treated chlorinated water supply system, in the absence of faecal bacterial indicators. Oocyst contamination of a break-pressure tank containing final water for distribution was the cause of this waterborne outbreak. An irregular seepage of oocyst-containing water, which increased during heavy rains, was the cause of the break-pressure tank contamination, rather than a failure of the water-treatment processes. The waterborne route should be considered when clusters of cryptosporidiosis-associated with potable water occur. Waterborne cryptosporidiosis can occur in the absence of other faecal indicators of contamination.

An analysis of staining methods for the detection of Cryptosporidium spp. oocysts in water-related samples

The ability of five staining techniques, originally developed for the rapid identification of Cryptosporidium spp. oocysts in faecal samples, to detect oocysts in water and water-related samples was assessed. All the stains used (modified Ziehl Neelsen, auramine-phenol (Lempert), Wright-Giemsa, safranin-methylene blue and FITC-labelled monoclonal antibody) stained oocysts after storage in water for 2 months at 4 degrees C (71-89% of control values). Storage of oocysts below 0 degrees C greatly reduced the staining ability of auramine-phenol. With the exception of oocysts stored in raw and final waters, the histochemical stains proved less useful in detecting oocysts than the monoclonal antibody. Organisms of similar size and shape took up these stains, causing confusion in interpretation. Cold Ziehl Neelsen and the FITC-labelled monoclonal antibody were best at identifying oocysts from a waterborne outbreak. Screening with a fluorescent antibody, followed by confirmation with cold Ziehl Neelsen, where possible, are the currently recommended procedures for the detection of oocysts in water-related samples.

A comparison of fluorescein diacetate and propidium iodide staining and in vitro excystation for determining Giardia intestinalis cyst viability

The viability of 4 human isolates of Giardia intestinalis cysts using either the fluorogenic vital dyes fluorescein diacetate (FDA) and propidium iodide (PI) or in vitro excystation was assessed. Whereas viable cysts, as defined by in vitro excystation were present in each of the 4 isolates, cysts from only 3 of the 4 isolates took up the vital dyes. FDA consistently over-estimated cyst viability whilst PI under-estimated non-viable cysts when compared with in vitro excystation. Following in vitro excystation, both FDA and PI stained a proportion of unexcysted cysts indicating that FDA stained cysts which were incapable of excystation, whereas PI did not stain all cysts which were incapable of excystation. One human cyst isolate, which underwent in vitro excystation, could not be stained with either FDA or PI. In the absence of currently more specific fluorescent indicators of viability, PI alone could be used to determine the lower limit of nonviability in positive water-related samples, where small numbers of cysts are to be expected.

Antigenic relationships between the surface-exposed, secreted and somatic materials of the nematode parasites Ascaris lumbricoides, Ascaris suum, and Toxocara canis

The cosmopolitan nematode parasites Ascaris lumbricoides, Ascaris suum, and Toxocara canis are closely related phylogenetically, and are all pathogenic to man. In the case of the latter, the antigens released by the tissue-invasive parasitic larvae in vitro ('excretory/secretory' or 'ES' antigens) are routinely used for serodiagnostic purposes. Here we have found, using radioimmunoprecipitation with defined rabbit antiserum, and SDS-PAGE, that there is a significant antigenic similarity between the secreted and somatic antigens of the three nematodes, and have characterized cross-reactive components. Among these is a 14 kD internal protein which has a homologue in all three parasites. This molecule is the subject of an IgG antibody response in Ascaris infection, but there is no measurable response to it in toxocariasis. Lastly, using quantitative immunofluorescence, the antigens exposed on the surface of intact, living, larvae were found to be cross-reactive or specific depending on the developmental stage of the parasites. This means that the surface of tissue-invasive Ascaris larvae bears stage-specific epitopes.

Shared carbohydrate epitopes on distinct surface and secreted antigens of the parasitic nematode Toxocara canis

The nematode parasite Toxocara canis is found in all dog populations and poses a poorly defined health hazard to humans. We have studied excretory-secretory antigen (ES) and surface antigens of the infective larval stage which is tissue-invasive in mammalian hosts. Antigens were probed with a panel of eight monoclonal antibodies raised in mice to whole ES. Six of eight antibodies reacted with periodate-sensitive carbohydrate epitopes on ES molecules, and the remaining two (Tcn-3 and Tcn-6) recognized either peptide or periodate-resistant sugar determinants. By immunoprecipitation and immunoblotting, the anti-carbohydrate monoclonals each reacted with several distinct ES molecules, known from previously published work to possess contrasting biochemical properties. Tcn-3 and -6 were directed predominantly against 32,000 and 120,000 m.w. molecules, respectively. Iodinated surface antigens of similar m.w. were precipitated by each antibody after detergent solubilization, but only two clones (Tcn-2 and -8) were able to bind exposed sites on the epicuticle of intact Toxocara larvae. Significantly, these antibodies do not bind to newly hatched larvae, and their target antigens are poorly expressed until the second day of in vitro cultivation. The specificities of the monoclonals were further studied by cold antibody inhibition of radiolabeled monoclonal binding, and by a matrix of two-site binding assays. These data show that Tcn-2, -4, -5, and -8 recognize a related group of repetitive carbohydrate epitopes, whereas Tcn-1, -6, and -7 bind discrete determinants on the same molecules. These studies are being continued to define further the structure of antigenic Toxocara carbohydrates and to compare the diagnostic utility of carbohydrate and peptide antigens.

Species-specific and common epitopes on the secreted and surface antigens of Toxocara cati and Toxocara canis infective larvae

It is widely accepted that the major cause of visceral larva migrans (VLM) in man is Toxocara canis infection. This has been largely based on the detection of antibodies to this species. We have compared the antigens of T. canis and Toxocara cati in order to establish whether assay for the former might be compromised by infection with the latter. Comparisons were made by radioiodination of the surface and excretory/secretory (ES) glycoproteins of the infective larvae of both species, immunoprecipitation with poly- and monoclonal reagents, and SDS-PAGE. The SDS-PAGE profiles of surface antigens of the two species showed few similarities, whereas that of the ES material indicated considerable homology. Serum from infected animals and a human VLM patient exhibited complete cross reactivity, although there was evidence in the mouse of a specific response to one of the components of T. cati ES. Testing of ES against a panel of monoclonal antibodies (MoAbs) confirmed the similarity; all but one of the MoAbs recognized several of the components of both sources of ES. The only exception was MoAb Tcn-2, which did not react with T. cati surface, somatic or ES antigens. This antibody is known to recognize a carbohydrate determinant which is widespread on T. canis glycoproteins. This species-specific determinant, therefore, represents a reversal of the consensus that peptide determinants tend to be the more specific. Finally, the MoAbs were used to examine the exposure of shared epitopes on the surface of intact larvae of T. cati. Again, fine differences in binding by anti-carbohydrate monoclonals were observed when the two species of Toxocara were compared, reflecting a distinction in exposure or orientation of surface molecules on these nematodes. Moreover, these epitopes were absent or variably present on the surface of freshly hatched larvae, and full exposure did not occur until about 24 h post-hatching. This delay in the presentation of epitopes might have implications for the process of infection in sensitized hosts. In conclusion, it is probable that the serological response in man to T. canis is, by current serological methods, indistinguishable in specificity from that induced by T. cati infection, and that the MoAb which we describe could be used to permit discrimination.

Shared carbohydrate epitopes on distinct surface and secreted antigens of the parasitic nematode Toxocara canis

The nematode parasite Toxocara canis is found in all dog populations and poses a poorly defined health hazard to humans. We have studied excretory-secretory antigen (ES) and surface antigens of the infective larval stage which is tissue-invasive in mammalian hosts. Antigens were probed with a panel of eight monoclonal antibodies raised in mice to whole ES. Six of eight antibodies reacted with periodate-sensitive carbohydrate epitopes on ES molecules, and the remaining two (Tcn-3 and Tcn-6) recognized either peptide or periodate-resistant sugar determinants. By immunoprecipitation and immunoblotting, the anti-carbohydrate monoclonals each reacted with several distinct ES molecules, known from previously published work to possess contrasting biochemical properties. Tcn-3 and -6 were directed predominantly against 32,000 and 120,000 m.w. molecules, respectively. Iodinated surface antigens of similar m.w. were precipitated by each antibody after detergent solubilization, but only two clones (Tcn-2 and -8) were able to bind exposed sites on the epicuticle of intact Toxocara larvae. Significantly, these antibodies do not bind to newly hatched larvae, and their target antigens are poorly expressed until the second day of in vitro cultivation. The specificities of the monoclonals were further studied by cold antibody inhibition of radiolabeled monoclonal binding, and by a matrix of two-site binding assays. These data show that Tcn-2, -4, -5, and -8 recognize a related group of repetitive carbohydrate epitopes, whereas Tcn-1, -6, and -7 bind discrete determinants on the same molecules. These studies are being continued to define further the structure of antigenic Toxocara carbohydrates and to compare the diagnostic utility of carbohydrate and peptide antigens.

Cerebral lateralization and handedness and their effects on verbal and spatial reasoning

Consistent and inconsistent left- and right-handed male subjects completed four tests each of verbal and spatial reasoning. They also participated in tachistoscopic measures of verbal and spatial lateralization--consonant-vowel-consonant recognition and dot enumeration, respectively. The consistent handedness groups displayed significantly more lateralized patterns of cerebral organization that the inconsistent handedness groups. Increased lateralization was associated with superior performance on measures of spatial reasoning, but not on measures of verbal reasoning. Results are interpreted in terms of a competition hypothesis. No differences were found between the handedness groups on either the verbal or spatial reasoning tests.

Effects of rate and distance of procurement wheel-running on saccharin-and-sucrose solution drinking by non-deprived rats

Four non-deprived rats received daily sessions of 20 min access to a saccharin-and-sucrose solution following various prior activities, in an attempt to disentangle the normally confounded roles of time spent, amount and rate of procurement responding in causing an increase in consumption once access is gained. After the normal rate of running (approx 35 m/min) was established, six conditions were run in random order, involving waiting zero and 2.5 min in an immobilised running-wheel, and running, with the wheel rotated by a motor, in four conditions formed by combining two speeds (12 and 30 m/min) with two distances (12 and 30 m), prior to access to the solution. Drinking increased with the speed of prior running, and to a lesser extent with the distance run, but was not related systematically to the time spent running. It is suggested that information from the animal's own behavior in gaining access to a commodity, particularly the rate of energy expenditure, may influence its utilisation of the commodity by affecting the rate of subsequent consummatory responding.

Effect of procurement cost on the drinking of a saccharin-sucrose solution by non-deprived rats

Four non-deprived female rats were required to run in a wheel to obtain 20 min unconstrained access to a saccharin and sucrose solution. Each was run in a series of conditions in which the requirement was a proportion (0.25, 0.5, 1.0, 1.25 and 1.5) of the amount of running performed in a condition in which the wheel alone was available. A condition in which no running was required to gain access to the solution and one in which the subject was locked in the stationary wheel for the time taken to complete the highest requirement before being allowed access to the solution were also included. The results showed that as the requirement increased the amount of solution consumed also increased, and this relationship did not depend on the time taken to perform the requirement.

Effect of procurement wheel running on the rate of drinking in rats

Four rats, 22.5 hr deprived of water, were tested in 3 conditions, in which they were required to run zero, 5 or 300 one-sixth revolutions in a wheel to gain 30 min access to water in a drinking tube. The number of licks performed in the 30 min increased monotonically with the procurement cost, and was 20% greater following the larger cost than when there was no cost. However, examination of the rates of drinking throughout the 30 min revealed that differences occurred between the conditions only at the beginning of the period. In the first 3 min there was a monotonic relationship between the proportion of time spent drinking and the procurement cost, but no effect of the cost on the rate could be detected after the first 6 min. The results are consistent with the hypothesis that the effect is mediated by a transient elevation of the subject's arousal level.

Soluble antigens and antibodies in the sera of mice infected with Trichinella spiralis, detected by a modified double counterimmunoelectrophoresis technique

Double counterimmunoelectrophoresis, with a novel well format, was used as a sensitive technique for the rapid detection of circulating antigen and antibody in mice infected with Trichinella spiralis. In a primary infection, soluble antigen was initially detected in day 13, followed by a second wave on day 41. Circulating antibody was first apparent on day 34, increasing in intensity and number of precipitation bands until day 102. The first peak of circulating antigen is indicative of non-complexed antigen released from the developing larvae in striated muscle cells, whereas the presence of antigen late in infection is indicative of electrophoresis-labile immune complexes. On reinfection (day 35 of primary) circulating antigen was present which could be attributed to products of resident primary infection muscle larvae.

Experimental ocular toxocariasis: a mouse model

Male mice, strain C57 black, were infected with Toxocara canis by a single intragastric dose of 1500 infective eggs. The eyes were studied at sequential time periods after infection (6 to 63 days) by conventional microscopic techniques, and the histological characteristics of the inflammatory response were recorded. In the majority of animals the disease was unilateral. Twenty-six larvae were found in the retina, in the retinal vessels, and in the subretinal space in 20 eyes, while in 29 eyes there were inflammatory changes which were not related to the presence of intact or fragmented larval forms. The inflammatory reaction began as a polymorphonuclear response but after day 13 became a granulomatous reaction. This suggests that the inflammatory phenomenon may be propagated by the secreted surface antigens in the absence of the living or dead larvae.

The production of human A and B blood group like substances by in vitro maintained second stage Toxocara canis larvae: their presence on the outer larval surfaces and in their excretions/secretions

In vitro maintained second stage Toxocara canis larvae do not bind polyclonal anti-human A or B blood group antibodies onto their outer surface at 37 degrees C as detected by indirect fluorescence. When larvae are incubated at 2 degrees C under the same experimental conditions, intense fluorescence over the whole outer surface is observed. Re-incubation of such larvae at 37 degrees C results in a gradual loss of surface fluorescence. This loss is complete after 3 h. The excretions/secretions (ES) of in vitro maintained larvae can neutralize the reactivity of polyclonal anti-human A and B typing antisera against their respective erythrocytic antigens. Rabbits infected with T. canis infective eggs or immunized with ES produce elevated isohaemagglutinin titres against A and B erythrocyte antigens. The presence of epitopes, on the outer surfaces of T. canis larvae and in ES, which cross-react with human ABO blood group antibodies must be borne in mind when larvae or their products are used for the serodiagnosis of human toxocaral larva migrans.

Effects of procurement cost on food consumption in rats

Rats deprived of food for 23 hr were given unconstrained access to food for 1 hr following the completion of a lever-press requirement. Four experimental subjects were each tested for 7 sessions in each of a series of lever-press requirement conditions (1, 5, 10, 20, 50, 100, 150, 200) with a free access condition before and after this series, and with a final return to the 100 lever-press condition. To each experimental subject was yoked an equally deprived control subject which received access to food independently of its own responding, at the same time as its experimental partner. The food consumption of the experimental subjects, but not that of the controls, increased systematically as the lever-press requirement increased. It is argued that the results suggest that the way the procurement cost of food is related to both the frequency and size of meals is due to a direct but independent effect of the cost on both meal size and latency to initiate eating.

Laboratory evaluation of a living attenuated vaccine against bluetongue type 20 virus

Living attenuated bluetongue Type 20 virus vaccine was tested in 9 to 12 month-old Australian Merino sheep, held in air conditioned, insect-free accommodation. The vaccine appeared avirulent and immunogenic and protected against infection with a second dose of homologous vaccine virus. No enhancement of virulence or significant change in immunogenicity was observed when the vaccine was passaged 3 times through sheep without antibody to bluetongue virus.

Development of the serological response in rabbits infected with Toxocara canis and Toxascaris leonina

The indirect fluorescent antibody test using frozen sections of infective Toxocara canis and Toxascaris leonina eggs, and the enzyme linked immunosorbent assay using homogenized Toxocara canis embryonated egg extract and T canis excretory-secretory products as adsorbed antigens were used to determine the specificity and development of circulating antibodies in rabbits. Frozen sections were subdivided into four morphologically distinct compartments for analysis of the development of the circulating antibody response. The fluid surrounding the larva was the most reactive up to 21 days after infection, and this material was found to be predominantly excretory-secretory in nature. As the infection progressed antibodies directed against 'somatic' tissue materials increased. Cross reactions between sera from rabbits infected with T. canis eggs and Toxascaris leonina frozen sections, and rabbits infected with T. leonina eggs and Toxocara canis frozen sections occurred between both the excretory-secretory fluid and somatic components of the infective eggs. These results were substantiated using the enzyme linked immunosorbent assay. When T. canis excretory-secretory antigen was used, an earlier response (peak day 21) was detected than when using T. canis embryonated egg extract (peak day 35). However, cross reactions between T. canis excretory-secretory antigen and sera from rabbits infected with Toxascaris leonina occurred, indicating that the serodiagnosis of visceral larva migrans using Toxocara canis excretory-secretory antigen may still prove unsatisfactory when considering the role of Toxascaris as a possible causative agent.

The effect of temperature and antimetabolites on antibody binding to the outer surface of second stage Toxocara canis larvae

In vitro maintained second stage Toxocara canis larvae do not bind antiserum raised to their excretions and secretions (ES) at 37 degrees C as detected by indirect fluorescence. However, when these larvae were incubated at 2 degrees C under the same conditions intense fluorescence on the whole outer surface was observed. This fluorescence remained as long as the larvae were maintained at 2 degrees C. When these larvae were reincubated at 37 degrees C a gradual loss of fluorescence along their outer surfaces occurred. This loss was complete after 3 h. Larvae which were preincubated in antimetabolites at 37 degrees C exhibited intense fluorescence on their outer surfaces as did those incubated at 2 degrees C with antimetabolites. It is concluded that antigens present in ES occur along the whole length of the larval outer surface and turn over at 37 degrees C. This turnover occurs along the whole outer surface and is metabolically dependent. Should this occur in vivo it could afford the parasite with a mechanism for evasion of the immune response.

The use of topical thrombin to reduce wound haematoma in patients receiving low-dose heparin

The efficacy of topical thrombin in prevention of wound haematoma in patients receiving subcutaneous low-dose heparin was studied in a randomized, controlled trial. One hundred and two patients undergoing elective abdominal surgery were included in the trial. Haematological studies were carried out in the last 42 patients to determine whether introduction of thrombin into the wound resulted in any systemic effect via the coagulation pathways. The frequency of post-operative wound haematoma was significantly lower in the thrombin-treated group as compared to the control group and its action appeared to be independent of any change in coagulation parameters.

Studies on the incidence of Toxocara and Toxascaris spp. ova in the environment. 1. A comparison of flotation procedures for recovering Toxocara spp. ova from soil

Seven different flotation fluids were assessed for their efficiency in recovering Toxocara canis ova from artificially seeded soil samples. Using the most efficient (a saturated solution of magnesium sulphate plus 5% potassium iodide) 25 g amounts of 234 environmental soil samples were examined for the presence of Toxocara spp. and Toxascaris ova. Twenty-six samples (11.1%) yielded ova of one or other species. There was no discernible pattern of distribution of positives with relation to the source of the samples. The maximum number of ova recovered in any one sample was 19. All the ova recovered from the environment were considered viable and potentially infective.

A paper radioimmunosorbent test (PRIST) for the detection of larva-specific antibodies to Toxocara canis in human sera

A paper radioimmunosorbent test (PRIST) was shown to be sensitive and reproducible when used with excretory/secretory antigen of Toxocara canis second stage larvae. Whatman No. 50 filter paper (5 mm discs) gave the most consistent and clear results with antigen at a concentration of 100 micrograms/ml, and could be stored for up to 3 weeks in vacuo at -70 degrees C. Antigen coated discs were incubated with test sera at 1:10 dilution for 3 h at room temperature (21 degrees C), reacted with [125I]anti-human IgG for 1 h and counts determined in a gamma counter. Sera from patients with fascioliasis, taeniasis, schistosomiasis, oxyuriasis, trichinellosis and ancyclostomiasis gave counts similar to cord serum controls. Sera from patients with ascariasis gave counts of up to twice as great as controls, but sera from patients with toxicariasis produced counts of 7,000-13,000, a 4-6-fold increase.

The immune response of pigs to infection with the stomach worm Hyostrongylus rubidus (Hassall and Stiles, 1892). III. Effect of a primary infection on immunoglobulin-positive cell numbers

An immunofluorescent study has been made of IgG, IgM and IgA in the stomach of uninfected minimal disease pigs and pigs infected with a single dose of 100,000 third stage infective Hyostrongylus rubidus larvae. Immunoglobulin-positive cells were present in both uninfected and infected animals. In infected animals both IgM and IgA immunocytes increased in numbers following infection and the numbers remained raised during the histotropic phase of worm development. No increase in IgG immunocyte numbers was noticed throughout the course of infection (100 days).

The acquisition of antigens in the intercellular substance of mouse skin by schistosomula of Schistosoma mansoni

Serum from patients suffering from the autoimmune skin disease pemphigus vulgaris has been used to demonstrate the presence of intercellular substance (ICS) on the surface of these chistosomula of Schistosoma mansoni which has penetrated mouse skin in vitro or during a percutaneous infection. ICS was absent from mechanically transformed schistosomula or those formed in the peritoneal cavity of mice. Schistosomula which penetrated mouse skin rapidly in vitro acquired very little of the ICS. It was found during a percutaneous infection that schistosomula recovered from the skin after 10 min had no detectable ICS, while those recovered after 2 hr and 24 hr gained increasing quantities of the material. It is concluded that schistosomula which are delayed in their exit from the skin acquire more ICS. However, this material must be shed during subsequent migration since schistosomula from lung and liver, and 7-week-old worms do not posses it. The implications of the findings are discussed.

Antigens of Hyostrongylus rubidus, the red stomach worm of pigs. Analyses by means of passive haemagglutination and immediate hypersensitivity tests

Antigens were prepared from different stages of worm development and adult worm antigens were fractionated by ion exchange and exclusion chromatography. The antigens, or fractions of them, were assessed for their activity in passive haemagglutination reactions or intradermal tests. The results of the passive haemagglutination reactions indicated that circulating agglutinins were more readily detected when adult stage specific antigens were used. Antigen prepared from worms isolated when the population was declining was less sensitive. Fractions of adult worm antigen did not confer greater sensitivity than the whole worm extract.

Immunofluorescent patterns in the skin in Besnier's prurigo. The eczema asthma syndrome

The immunofluorescent patterns in the skin of eighteen patients with Besnier's prurigo were studied at different stages of eczematous lesions. The presence, distribution pattern, and numbers of immunoglobulin and complement-positive lymphocytes in twenty-nine biopsies are reported. In all cases IgE-positive lymphocytes were present in both clinically uninvolved and involved skin. IgG, IgM and IgE-positive lymphocytes showed a characteristic distribution pattern in the dermis. In the acute stages IgM deposition was prominent in the basement membrane zone and it is suggested that damage to the basement membrane results in diffusion of immunoglobulin and complement into the epidermis. These features were not present in a control group of normal skin and of other dermatoses.

The passive transfer of humoral immunity from sows infected with Hyostrongylus rubidus (Hassal and Stiles, 1892), the red stomach worm, to their offspring and its significance in the conferring of protective immunity

Sows repeatedly infected with large single doses of third stage infective Hyostrongylus rubidus larvae show an anamnestic circulating agglutinin response to the parasite as detected by the passive haemagglutination reaction. At farrowing the circulating antibody level dropped, whereas the colostral agglutinating antibody level increased for a period of a few hours. The predominant class of immunoglobulin which had agglutinating activity against H. rubidus was IgG. Offspring which had suckled the infected mothers had a demonstrable agglutinin titre 4 days after birth, whereas offspring which suckled non-infected mothers had no demonstable agglutinins. On infection of the offspring, those which suckled infected mothers showed a more rapid and pronounced increase and duration of circulating agglutinins than those which had suckled noninfected mothers. The parasitic burden, as determined by the duration of egg laying and total egg output, was considerably lower for the group reared on the infected mothers. These experiments show that passively transferred agglutinating antibodies, mainly of the IgG class, were associated with protection.

Coin value and perceived size: a longitudinal study

Decimalization of the Irish currency presented an opportunity to study the perceived size of coins as they were introduced or withdrawn and to examine the accentuation of differences between coins. Estimates were obtained of the sizes of 4 coins from 478 subjects in 3 groups tested at different times: just after decimalization, 2, or 3 yr. later. A newly introduced coin was significantly underestimated in size at first but came to be significantly overestimated later, while all familiar coins were always significantly overestimated. The amount of overestimation of a coin depended on its value, not its size, leading to an accentuation of the difference between any two coins if the larger coin was also the more valuable but sometimes to the opposite if the smaller coin were of higher value than the larger member of the pair.