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H V Smith

Publications and source records attributed to H V Smith.

At least 91 records · Page 5Linked to original sources
PubMed1987

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.

Animals↗
PubMed1986

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.

Adolescent↗
PubMed1986

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.

Animals↗
PubMed1984

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.

Animals↗
PubMed1984

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.

Animals↗
PubMed1984

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.

Animals↗
PubMed1984

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.

Animals↗
PubMed1983

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.

Analysis of Variance↗
PubMed1983

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.

ABO Blood-Group System↗
PubMed1982

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.

Animals↗
PubMed1982

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.

Animals↗
PubMed1981

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.

2,4-Dinitrophenol↗
PubMed1981

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.

Abdomen↗
PubMed1980

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.

Animals↗