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Biomedical subjects

L J Harrison

Publications and source records attributed to L J Harrison.

At least 19 recordsLinked to original sources
PubMed2000

Xanthones and triterpenoids from the bark of Garcinia vilersiana.

The hexane extract of the bark of Garcinia vilersiana from Vietnam contained four triterpenoids (olean-12-ene-3beta,11alpha-diol, lupeol, beta-amyrin and oleanolic acid), and six xanthones (globuxanthone, subelliptenone H, subelliptenone B, 12b-hydroxy-des-D-garcigerrin A, 1-O-methylglobuxanthone and symphoxanthone). The structure of 1-O-methylglobuxanthone, the only novel compound, was determined using 1D and 2D NMR techniques and by correlation with globuxanthone.

Magnetic Resonance Spectroscopy↗
PubMed2000

Four new clerodane diterpenoids from Callicarpa pentandra.

Leaf extracts of Callicarpa pentandra provided four new clerodane-type diterpenoids (1-4), of which 1, 2, and 4 have ring-A-contracted structures. Their structures and stereochemistry were established by spectral data interpretation, and for 3 also by single-crystal X-ray diffraction.

Chromatography, Liquid↗
PubMed2000

Differential diagnosis of Taenia saginata and Taenia solium infection by PCR.

We have designed species-specific oligonucleotides which permit the differential detection of two species of cestodes, Taenia saginata and Taenia solium. The oligonucleotides contain sequences established for two previously reported, noncoding DNA fragments cloned from a genomic library of T. saginata. The first, which is T. saginata specific (fragment HDP1), is a repetitive sequence with a 53-bp monomeric unit repeated 24 times in direct tandem along the 1, 272-bp fragment. From this sequence the two oligonucleotides that were selected (oligonucleotides PTs4F1 and PTs4R1) specifically amplified genomic DNA (gDNA) from T. saginata but not T. solium or other related cestodes and had a sensitivity down to 10 pg of T. saginata gDNA. The second DNA fragment (fragment HDP2; 3,954 bp) hybridized to both T. saginata and T. solium DNAs and was not a repetitive sequence. Three oligonucleotides (oligonucleotides PTs7S35F1, PTs7S35F2, and PTs7S35R1) designed from the sequence of HDP2 allowed the differential amplification of gDNAs from T. saginata, T. solium, and Echinococcus granulosus in a multiplex PCR, which exhibits a sensitivity of 10 pg.

Animals↗
PubMed2000

The intensity and duration of primary Heligmosomoides polygyrusinfection in TO mice modify acquired immunity to secondary challenge.

The effect of dose and duration of immunizing infections of Heligmosomoides polygyrus on protection against homologous challenge was studied in female TO mice. Primary infections were terminated at various levels with pyrantel embonate (adult infections) or ivermectin (larval infections) and mice were then challenged with 500 infective larvae (L3). The level of protection to secondary challenge positively correlated with the intensity of the primary immunizing infection but truncation of larval infection produced significantly better protection than termination of the adult nematode infection. The duration of the primary larval infection (1-6 days) positively correlated with the level of protection to secondary challenge, antibody responses and the proportion of circulating eosinophils. Histological changes in the gastrointestinal tract, peripheral leucocytic changes and antibody responses of the mice to H. polygyrus adult somatic antigens indicate both a cellular and humoral basis of host immunity to secondary challenge. Although the TO mice are slow responders in that they harbour chronic infections, immunization by intramucosal killing of the larval stage produced strong protection against secondary challenge infection. The presence of dead immunogenic larval stages within the intestinal wall may well be an important factor, since it exposes the host to stage specific antigens at an appropriate location. The implications of the findings for the control of gastrointestinal nematode infections are also discussed.

Analysis of Variance↗
PubMed1999

Heligmosomoides polygyrus and Trypanosoma congolense infections in mice: effect of immunisation by abbreviated larval infection.

Concurrent African trypanosome and gastrointestinal helminth infections are prevalent in sub-humid savannah where they are endemic. However, acquired resistance in animals varies with their responder status and exposure. As a guide to study in the definitive hosts, the effects of Trypanosoma congolense infection on the development and maintenance of homologous Heligmosomoides polygyrus resistance were investigated in outbred TO mice. These mice were immunised by abbreviation of larval infection. Immune or naive mice were either infected with 500 infective larvae (L3) of H. polygyrus and/or 10(4) bloodstream forms of T. congolense or were not infected. The outcome of infection was monitored by routine parasitological and immunological techniques for 30 days after the day of the T. congolense infection. Significantly more immune mice concurrently infected with both parasites survived than did immune mice in which H. polygyrus was superimposed on a 10-day-old T. congolense infection. Although all the mice in this latter group died before the end of the experiment, larval immunisation prolonged their survival, relative to similarly treated naive mice. The antibody titres to H. polygyrus in the sera of immune mice challenged with H. polygyrus alone were significantly higher than those of immune mice concurrently infected with both parasites but the levels of protection obtained were comparable. It is concluded that T. congolense may not completely block the strong acquired resistance induced by abbreviated H. polygyrus larval infection in TO mice but is capable of interfering with protective responses, especially if the trypanosome infection occurs prior to H. polygyrus challenge infection.

Administration, Oral↗
PubMed1998

Limitations of current diagnostic procedures for the diagnosis of Taenia solium cysticercosis in rural pigs.

The aim of the present study was to evaluate diagnostic procedures for porcine cysticercosis. Sera were obtained from 32 pigs reared in commercial farms, 47 pigs before and after experimental infection, 42 carefully necropsied rural pigs and 191 slaughtered pigs from rural communities in which the presence of the Taenia solium metacestode was assessed by tongue dissection. Sera were analyzed by ELISA to detect antibodies against T. solium antigens and to detect parasite antigens. Most sera from the necropsied rural pigs were also evaluated by the Western blot method. Antigen and antibody ELISA detection assays showed high sensitivity and specificity when applied to sera from pigs reared in commercial farms. In contrast, all methods (Ag-ELISA, Ab-ELISA assays, EITB and tongue inspection) showed lower sensitivity and specificity when applied to the generally lightly infected rurally reared pigs. The probability distribution of cysts in carcasses were also determined. These results emphasize the difficulties in detecting cysticercosis in rural pigs with low levels of cyst burdens.

Animals↗
PubMed1998

Sequence and preliminary characterisation of a Taenia saginata oncosphere gene homologue of the small heat-shock protein family.

During antibody screening of a Taenia saginata oncosphere cDNA library a clone (R-Tso2) sharing a high degree of homology at both the DNA and amino acid levels with the small heat-shock protein (shsp) family was identified. The R-Tso2 clone was a full-length sequence (1162 bp) with an open reading frame of 945 bp and 314 amino acids, corresponding to a deduced molecular mass of 35.6 kDa and isoelectric point of 5.6. R-Tso2 had the highest degree of homology with the Schistosoma mansoni major egg antigens, showing the characteristic shsp 100 amino-acid sequence motif duplicated. The R-Tso2 expression product was not immuno-precipitated by any serum from a panel of serum samples obtained from bovine, porcine and human hosts suffering from either T. saginata or T. solium cysticercosis.

Amino Acid Sequence↗
PubMed1998

Sequence and immunogenicity of the Taenia saginata homologue of the major surface antigen of Echinococcus spp.

A clone (R-Tso18) was isolated from a Taenia saginata oncosphere cDNA library by screening with sera from rabbits immunised with oncosphere extract. It contained a full-length cDNA sequence of 1893 bp with an open reading frame of 1680 bp, corresponding to 559 amino acids with a deduced molecular mass of 65.173 kDa and an isoelectric point of 6.08. The R-Tso18 protein showed 80-84% nucleotide identity with the major protoscolex surface antigens of Echinococcus multilocularis (EM10) and E. granulosus (EG10). Preliminary immunogenicity studies employing the radiolabeled R-Tso18 protein in immune co-precipitation assays indicated sero-positivity for T. saginata-infected calf sera (6/13), T. solium cysticercosis human (7/22) and pig (2/2) sera and E. multilocularis (6/10)- and E. granulosus (1/12)-infected human sera, whereas other helminth-infection sera were negative. As immuno-precipitation is a relatively insensitive assay, it was concluded that further studies on the diagnostic potential of the purified recombinant R-Tso18 antigen, or its peptides, are merited.

Amino Acid Sequence↗
PubMed1998

Comparison of production losses caused by chronic Fasciola gigantica infection in yearling Friesian and Boran cattle.

Yearling Friesian and Boran cattle were given a standard dose of Fasciola gigantica metacercariae designed to produce chronic infection. Their liveweights were then monitored for 23 weeks post-infection. Following standard meat inspection procedures, all the livers from the infected cattle were condemned. At 22 kg per animal, the mean reduction in liveweight gain in infected Borans was significantly greater than in infected Friesians. Compared to the control cattle and based on current sale prices in Kenya, the production losses from the combination of liver condemnations and reduction in liveweight gain constituted a loss in value of US$$12.11 (4.92%) and US$23.41 (10.34%) for Friesians and Borans respectively. These data indicate that productivity losses and the economic consequencies of fasciolosis in yearling Boran cattle are much more severe than in Friesians. These findings have implications for assessing the likely benefits of control measures against this parasite.

Animals↗
PubMed1997

Expression of acquired immunity to Heligmosomoides polygyrus in mice concurrently infected with Trypanosoma congolense.

The effects of concurrent Heligmosomoides polygyrus and Trypanosoma congolense infection on the expression of acquired resistance to homologous nematode challenge were studied in female outbred TO mice. Mice were infected with 500 infective larvae (L3) of H. polygyrus and the infection was terminated by anthelminthic treatment on Day 12, when the worms were adults. Eight days later sub-groups of these pre-exposed mice, and of similar mice which had not experienced the previous infection with H. polygyrus, were either simultaneously infected with 500 L3 of H. polygyrus and 10(4) bloodstream forms of T. congolense, or with only one of these parasites, or were not infected. The experiment was monitored by routine parasitological and immunological techniques, including quantitative assessment of worm burden, trypanosome parasitaemia, growth of nematodes and measurement of the parameters reflecting pathological and antibody responses for 30 days after immunization. Concurrent H. polygyrus and T. congolense infection resulted in abrogation of the partial immunity against challenge infection with H. polygyrus in the pre-exposed mice, and in depressed humoral antibody responses following infection. Mortality was greatly reduced in pre-exposed mice infected with T. congolense alone compared to naive mice. The growth of male H. polygyrus worms was not affected by either the immune or infection status of their host. Although the increased size of the female worms from pre-exposed and then concurrently infected mice compared to similar mice infected only with H. polygyrus was significant, the egg production per worm was not affected.

Animals↗
PubMed1996

Seroepidemiological survey of Taenia saginata cysticercosis in Kenya.

A sero-epidemiological study of Taenia saginata cysticercosis was carried out to determine the prevalence and distribution of the infection in three provinces of Kenya. Serum samples and meat inspection records were collected from cattle at slaughter at export and district abattoirs. Cattle origin and the presence of T. saginata cysticerci were noted as was the prevalence of other helminths such as Echinococcus granulosus and Fasciola gigantica. Serum samples were screened for circulating parasite antigen using a monoclonal antibody-based enzyme-linked immunosorbent assay (Ag-ELISA) and for ante-parasite antibody by indirect ELISA (Ab-ELISA). Eighty per cent of the sera were collected from cattle from the Rift Valley Province of Kenya. The prevalence of T. saginata cysticercosis and the other helminth infections varied between districts and was particularly high in Narok. Animal husbandry practices in arid areas such as Narok may be particularly conducive to transmission. The potential value of the Ag-ELISA for use in sero-epidemiological studies was verified by this study. It detected at least twice as many cases as T. saginata cysticercosis as meat inspection and, of the three methods investigated, was considered the most valuable.

Abattoirs↗
PubMed1996

Studies on helminthosis at the Centre for Tropical Veterinary Medicine (CTVM).

The research work relating to helminths, which has been conducted within the Helminthology Section of the CTVM, often in collaboration with colleagues from the tropics is reviewed and placed into a historical perspective. The research has, in the main, concentrated on the trematodes Fasciola hepatica and Fasciola gigantica and the cestodes Taenia saginata and Taenia solium, but work on other parasites including gastro-intestinal nematodes is also considered. All of these parasites are of obvious veterinary/economic importance particularly in the tropics and subtropics. While the zoonotic importance of T. saginata and T. solium has been recognised for many years, it is only more recently that the zoonotic impact of Fasciola spp. has been generally acknowledged.

Animals↗
PubMed1996

Diagnosis of Taenia saginata cysticercosis in Kenyan cattle by antibody and antigen ELISA.

Sera from calves, either experimentally or naturally infected with Taenia saginata, were screened for an antibody response to T. saginata, and for parasite antigen, by enzyme-linked immunosorbent assays (ELISAs). An antibody response was detected by 3 weeks post infection (p.i.), rose to a peak at 10-12 weeks p.i., and was still in evidence 1 year p.i. Parasite antigen was first detected 4-7 weeks p.i. and persisted until the end of the experiment, over 1 year p.i. In the experimentally infected animals, cattle with 14 or more live cysticerci had detectable levels of parasite antigen in their sera at slaughter, while animals with live cyst burdens ranging from 0 to 4 were negative. Furthermore, levels of circulating antigen were positively correlated with live cysticercus burden in the experimental animals. In naturally infected cattle, 83% (5/6) of those with 30 or more live cysts, and 22% (5/23) of those with 1-29 live cysts, could be detected by the ELISA for parasite antigen, although no significant correlation between antigen level and live cyst burden could be detected. Antibody levels were not found to be associated with cyst burdens in either experimentally or naturally infected cattle. In slaughterhouse cattle, the antigen assay was almost three times as sensitive as meat inspection. However, there was no agreement between cattle found positive at meat inspection and those found positive by the antigen detection ELISA. One possible reason is that the ELISA only detects live cysts, while lesions left by dead cysts are more noticeable at meat inspection. The mouse monoclonal antibody-based antigen detection ELISA is of value for the diagnosis of naturally occurring, viable, T. saginata cysticercosis in live cattle and has an immediate application for field based epidemiological studies designed to determine prevalence.

Abattoirs↗
PubMed1995

A ferulic acid ester of sucrose and other constituents of Bhesa paniculata.

A novel derivative of sucrose, beta-(3,6-di-O-feruloyl)-fructofuranosyl-alpha-(2,3,4,6-tetra-O-ac etyl)- glucopyranoside, was isolated from the wood of Bhesa paniculata. Its structure was determined by a combination of 2D 1H-1H and 1H-13C correlation NMR spectroscopy. The known compounds, glycerol 1-9',12'-octadecadienoate, beta-sitosterol, (+/-)-pinoresinol, methyl 3,4-dihydroxybenzoate, 4-hydroxy-3-methoxybenzoic acid, anofinic acid and 2-(1'-methylethenyl)-benzofuran-5-carboxylic acid were also isolated.

Carbohydrate Conformation↗
PubMed1994

Humane destruction of horses with a mixture of quinalbarbitone and cinchocaine.

One hundred and-two horses requiring to be euthanased for a variety of reasons were killed by the intravenous injection of a mixture of quinalbarbitone sodium (400 mg/ml) and cinchocaine hydrochloride (25 mg/ml). The dose rates used were 1 ml/10, 15, 20 and 30 kg bodyweight, and the time of injection was varied between 5 and 25 seconds. The average time to collapse from the start of the injection was 34 seconds and the average time to clinical death was 230 seconds. Slow injection (particularly of the low dose rates) and premedication with detomidine resulted in a longer time to collapse (median 46 seconds). Premedication with xylazine and low dose rates of the mixture resulted in an unacceptable degree of muscular activity and agonal gasping and death was delayed. Premedication with romifidine and butorphanol resulted in an apparent (but insignificant) reduction in the time to collapse and death but was also accompanied by significant agonal gasping. Without premedication quinalbarbitone and cinchocaine resulted in a smooth and quiet collapse with the cessation of cardiac and respiratory functions within three minutes in all cases, but the palpebral reflex of the horses was prolonged significantly beyond the time when all other reflex activity was lost. Occasional gasping and muscular tremors, particularly of the upper forelimb, occurred particularly when lower dose rates and either very slow or very fast rates of injection were used. One horse which was premedicated with xylazine and received a very low dose at a slow rate showed unacceptably violent muscular activity. At no other time was the procedure regarded as violent or unacceptable.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Welfare↗