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Biomedical subjects

K Pfister

Publications and source records attributed to K Pfister.

At least 19 recordsLinked to original sources
PubMed1992

The interaction of Trypanosoma congolense and Haemonchus contortus infections in trypanotolerant N'Dama cattle.

The interactions between Trypanosoma congolense and Haemonchus contortus infections were studied in N'Dama calves. A total of 38 N'Dama bulls was divided into four groups and each group infected either with H. contortus 1 week after infection with T. congolense or with T. congolense 4 weeks after infection with H. contortus, or with either infection singly. Parasitological (faecal egg counts, parasitaemia), haematological (packed cell volume, white blood cell counts, albumin) and clinical parameters (body weight change, mortality rate) were compared among the various groups. The results showed a reduced prepatent period and a markedly increased pathogenicity of H. contortus infections in animals with a concurrent T. congolense infection. The most harmful combination was a H. contortus infection 1 week after the T. congolense infection which resulted in a progressive and severe anaemia, accompanied by hypoalbuminaemia, increased weight loss and high mortality. The anaemia induced by dual infections showed a low responsiveness to chemotherapy and in several cases supportive treatment did not help recovery. The results also showed that animals with a concurrent T. congolense and H. contortus infection ran a higher risk of succumbing during the infection, and also during 10 weeks following treatment. Although infections with T. congolense alone produced no clinical signs, they were found to significantly reduce the ability of infected animals to mount a normal response to a subsequent H. contortus infection. It was concluded that the increased H. contortus egg excretion observed in animals infected with both parasites might significantly increase the risk of nematode infections and that the reduced prepatent period might necessitate more frequent anthelmintic treatments. These interactions should, therefore, be considered wherever attempts are made to control these two diseases.

Animals↗
PubMed1991

Cellular reactions in the small intestine of rats after infection with Fasciola hepatica.

Groups of five rats each were infected with metacercariae of Fasciola hepatica according to two experimental procedures. In the first experiment, they received 20 metacercariae 0, 1, 2 or 3 times at intervals of 4 weeks. In the second, both the inoculation dose and the interval between doses were varied. After the animals had been killed, the small intestine was prepared for histology and tissue sections were stained for the detection and quantification of mucosal mast cells (MMCs), eosinophils and goblet cells. The density of eosinophils and MMCs increased significantly with each reinfection in the first experiment; in the second, the MMC reaction reached a peak at 4 weeks post-infection (p.i.), whereas the eosinophils peaked at 4 and 17 weeks p.i. In addition, the reaction of these cells depended on the infectious dose. In both experiments, goblet cells reacted only weakly. These findings thus clearly reflect a considerable intestinal response against migrating juvenile F. hepatica. The pattern of these defence reactions in the small intestine suggests some similarities with the mechanisms of antibody-dependent cell-mediated cytotoxicity that have been shown to take place during Schistosoma mansoni reinfection.

Animals↗
PubMed1991

[The epidemiology of gasterophilosis of horses in Switzerland].

Between March 1988 and December 1989, 198 gastrointestinal tracts from slaughtered horses from different areas of Switzerland have been analysed for the presence and the frequency of Gasterophilus spp. During the same period--always between July and November--200 horses from selected areas of Western Switzerland have been checked for the presence of eggs and their subsequent developmental stages in order to investigate further clinical and biological aspects of this infection. The evaluation has been performed according to origin, age, sex, colour of the horse and seasonal pattern of the cases and the various larval stages, respectively. The prevalence of Gasterophilus spp. amounts to 64.6%, showing a marked seasonal distribution. Only Gasterophilus intestinalis has been detected and the Western part of Switzerland appears to be considerably more contaminated than the other areas of the country. The reasons are discussed. It is possible that an intensive horse-traffic at the border is partly responsible. Horses with a dark coat are more often parasitized whereas no difference occurs with regard to age and sex. The observed high prevalence of this parasite infection in the Swiss horse population confirms that gasterophilosis has to be taken into serious consideration and prophylactic measures might be indicated.

Animals↗
PubMed1991

[Intestinal cellular reaction of cattle after infection by Fasciola hepatica].

Defence reactions of cattle against Fasciola hepatica take place not only in the liver but also on a prehepatic level. The aim of the present experiments is to identify and quantify the cellular response in the small intestine. Five groups of two bulls (Simmental x Red Holstein, 6 months old) were infected by oesophageal probe with metacercariae of F. hepatica (MC) according to two experimental procedures. Two groups of bulls served as controls. In the first experiment both infected groups received 1000 MC once or twice at an interval of five weeks. The intestinal tissue was taken before infection and 5, 10 and 19 weeks p.i., respectively 5 and 14 weeks p. reinf. (p.ri.). In the second experiment, three infected groups received 400, 2 x 400 MC (at an interval of five weeks) and 800 MC respectively. Biopsies were taken one week ante infectionem, 6, 11 and 19 weeks p.i., respectively 1, 6 and 14 weeks post reinfectionem (p. ri.). The biopsies of the small intestine were prepared for histology and the tissue sections stained as follows: Astra blue for mucosal mast cells (MMC), Lendrum for eosinophils (EOS) and Periodic Acid Schiff (PAS) for goblet cells (GC). The density of the three cell populations in the mucosa was determined microscopically and quantified. In both experiments the density of the MMC and EOS increased with each reinfection and depended on the infectious dose. There was no significant variation of the GC-numbers. The described intestinal cellular reactions suggest a participation of the small intestinal wall in the immunity against the common liver fluke.

Animals↗
PubMed1990

The seasonal epidemiology of gastrointestinal nematodes in N'Dama cattle in The Gambia.

From June 1987 to June 1988, a total of 180 N'Dama cattle were necropsied to identify and enumerate parasites present, including 39 sick calves and 25 dead calves from local village herds, and 116 adult cattle from a local abattoir. Of 175 animals infected with one or more helminths (97%), Haemonchus contortus was found in 67% of all necropsied animals, Cooperia punctata in 75%, Cooperia pectinata in 55%, Oesophagostomum radiatum in 71% and Bunostomum phlebotomum in 21%. There was a wide range of worm burdens (0-22 925) and a pronounced seasonal pattern occurred. Eighty-two percent of the total adult Haemonchus burden occurred during the rainy season (June-October). By the end of the rainy season, almost 100% of the Haemonchus burden was present as inhibited larvae. By contrast, a different survival strategy appeared to occur in Cooperia spp.; Oesophagostomum spp. and Bunostomum spp., which were found as adults throughout the year. Results indicated that, apart from malnutrition during the dry season, gastrointestinal nematode infections, especially haemonchosis, represent a major constraint on the health and productivity of N'Dama cattle under West African savanna conditions.

Abomasum↗
PubMed1990

Serodiagnosis of fasciolosis in ruminants.

Various serological techniques including immunoprecipitation, indirect haemagglutination and the indirect fluorescence antibody test have been successfully applied for the detection of fasciolosis, mainly in experimental infections. Recently, the most frequently used assay is the ELISA technique with somatic or excretory-secretory antigens obtained from adult flukes. Further purification of such antigens has considerably increased both the sensitivity and specificity of the system. However, most data indicate that serodiagnosis is reliable in groups of naturally-infected cattle and sheep but cannot yet be applied for the detection of individually infected animals.

Animals↗
PubMed1989

Molecular and biophysical analysis of herbicide-resistant mutants of Chlamydomonas reinhardtii: structure-function relationship of the photosystem II D1 polypeptide.

Plants and green algae can develop resistance to herbicides that block photosynthesis by competing with quinones in binding to the chloroplast photosystem II (PSII) D1 polypeptide. Because numerous herbicide-resistant mutants of Chlamydomonas reinhardtii with different patterns of resistance to such herbicides are readily isolated, this system provides a powerful tool for examining the interactions of herbicides and endogenous quinones with the photosynthetic membrane, and for studying the structure-function relationship of the D1 protein with respect to PSII electron transfer. Here we report the results of DNA sequence analysis of the D1 gene from four mutants not previously characterized at the molecular level, the correlation of changes in specific amino acid residues of the D1 protein with levels of resistance to the herbicides atrizine, diuron, and bromacil, and the kinetics of fluorescence decay for each mutant, which show that changes at two different amino acid residues dramatically slow PSII electron transfer. Our analyses, which identify a region of 57 amino acids of the D1 polypeptide involved in herbicide binding and which define a D1 binding niche for the second quinone acceptor, QB of PSII, provide a strong basis of support for structural and functional models of the PSII reaction center.

Amino Acid Sequence↗
PubMed1989

[The effectiveness of the new morantel sustained-release trilaminate bolus against gastrointestinal nematode infections in cattle in their first grazing period].

The efficacy of a recently developed Morantel-Sustained-Release-Trilaminate-Bolus (Paratect Flex Bolus [PFB]-Pfizer Inc.) against gastrointestinal nematode infections in cattle was assessed by monitoring faecal egg counts (EpG), herbage larval counts, serum pepsinogen levels and liveweight gains in first season calves. In two field trials (1987 and 1988), a PFB-Bolus was administered to two different groups of animals (1987: 15 calves; 1988:13 calves) at turnout (29 May 1987; 26 May 1988), control groups were included. In 1988, 13 calves received for comparison an Oxfendazole-Release-Bolus (Systamex Intervall Bolus [OXF]-Coopers Inc.). All groups were grazed on adjacent but separately fenced pastures throughout the season, until housing (27 October 1987; 15 October 1988). When compared with controls, the PFB-groups showed significantly lower EpG values and consequently, lower herbage larval counts throughout the season in both trials. From day 30 after turnout, the PFB-group had significantly lower serum pepsinogen levels, which reflects the low degree of abomasal damage in these animals. When compared to controls, the PFB-treated animals showed significantly higher weight performances. The mean weight-gain benefit of PFB-treated animals was +12.5 kg (p less than 0.05) and +21.1 kg (p less than 0.005) in 1987 and 1988, resp. No difference occurred between PFB-treated and OXF-treated calves, the latter outperformed the control animals by +21.6 kg (p less than 0.005).

Animals↗
PubMed1988

Egasyn affects the processing of beta-glucuronidase in mouse liver.

Three differently modified forms of beta-glucuronidase are known to exist: a microsomal enzyme form (M) existing in tissues where egasyn, a second microsomal protein, is present; and an acidic (La; complex-type oligosaccharide) and a basic (Lb; non-complex type oligosaccharide) lysosomal form which occur in all mouse tissues. Lb predominates in tissues containing microsomal beta-glucuronidase, La in those lacking it. In pulse-labelling experiments using mouse strain C57BL/6 liver containing egasyn (Eg+/Eg+) and microsomal enzyme, about half of the newly synthesized beta-glucuronidase was processed to the microsomal enzyme form, which was evidently further processed to Lb, and about half directly to La. In contrast, in liver of the congenic line C57BL/6.YBR Es-1b Eg0 that lacks egasyn (Eg0/Eg0) and microsomal enzyme, most of the labelled beta-glucuronidase was processed to La, and only a minor portion to Lb. Newly synthesized enzyme appeared first in microsomal, then in light and heavy lysosomal fractions of Eg+/Eg+ liver. In Eg0/Eg0 liver, no labelled enzyme was measurable in the microsomes, but it appeared rapidly in both types of lysosomes. Taken together these findings indicate that the microsomal enzyme form serves as a precursor of Lb, and that La is synthesized independently. The apparent half-life of La is only two-thirds that of Lb; this fact accounts for the reduced beta-glucuronidase activity in Eg0/Eg0 liver, which contains La as the predominant form.

Animals↗
PubMed1986

The egasyn gene affects the processing of oligosaccharides of lysosomal beta-glucuronidase in liver.

The accumulation of the relatively large amounts of beta-glucuronidase in microsomal fractions of normal mice depends on formation of complexes with the protein egasyn. Unexpectedly, it was found that the egasyn gene also affects the processing of beta-glucuronidase, which is segregated to lysosomes. In egasyn-positive mice lysosomal beta-glucuronidase from liver has a mean pI of 5.9 with a minor proportion at pI 5.4, whereas in egasyn-negative mice the proportion of the two lysosomal forms is reversed. Combined experiments measuring susceptibility to neuraminidase and to endoglycosidase H and specific binding to Ricinus communis lectin-agarose columns showed that the alterations in isoelectric point were associated with a decrease in complex oligosaccharides of lysosomal beta-glucuronidase in egasyn-positive mice. Since this alteration occurs not only in a congenic strain carrying the Eg0 gene but also in several other inbred strains that are homozygous for this gene, it is considered to be a genuine effect of the Eg gene rather than other genes that might regulate oligosaccharide processing. Also, the alteration is likely to be a result of direct physical interaction of the egasyn protein and lysosomal beta-glucuronidase, since a second lysosomal enzyme, beta-galactosidase, which does not form complexes with egasyn, is unaffected. The results suggest a model in which egasyn not only causes accumulation of beta-glucuronidase in the microsomal compartment but also acts upon the precursor to lysosomal beta-glucuronidase to alter its interaction with trans-Golgi-apparatus processing enzymes.

Acetylglucosaminidase↗
PubMed1986

Comparison of spindle elongation in vivo and in vitro in Stephanopyxis turris.

The spindle in dividing cells of the diatom Stephanopyxis turris contains three distinct classes of microtubules: central spindle microtubules, which slide over each other and grow during anaphase spindle elongation; kinetochore-attached microtubules, which are located on the outer surface of the central spindle; and peripheral microtubules, which fan out from the spindle poles in astral-like arrays. The poles are multilayered structures, which remain attached to the spindle after isolation. In vitro, after addition of ATP, central spindles elongate and the two half-spindles slide completely apart with a concurrent decrease in the extent and magnitude of the zone of microtubule overlap. Spindle elongation takes place in spindles whose chromatin has been removed by enzymic digestion and the extent of elongation in vitro is increased by the addition of neurotubulin. After ATP addition the arrays of interdigitating microtubules in the zone of overlap become disordered and selectively depolymerize from the overlap zone polewards. In some reactivated spindles an unusual structure, a striated fibre, can be seen running from the pole plates part of the way towards the spindle midzone. The fibre has no precedent in mitotic ultrastructure and its function is unclear. These results demonstrate that we can duplicate the essential elements of anaphase B in vitro and that this system will be useful for further studies of the molecular basis of spindle elongation.

Anaphase↗
PubMed1985

Genetic variation for enzyme structure and systemic regulation in two new haplotypes of the beta-glucuronidase gene of Mus musculus castaneus.

Two new haplotypes of the [Gus] gene complex have been characterized following their transfer from Mus musculus castaneus, where they were found, to a C57BL/6J genetic background. The [GUS]CS haplotype carries a new structural allele, Gus-scs, coding for enzyme with decreased thermolability and lacking an antigenic site present in other beta-glucuronidase allozymes. The [Gus]CL haplotype carries another new structural allele, Gus-scl, that codes for enzyme with increased thermolability and possessing the antigenic site. Both CS and CL beta-glucuronidase have the same catalytic activity/molecule as the standard B allozyme from C57BL/6J mice. Mice carrying either the [Gus]CS or [Gus]CL haplotype have reduced enzyme activity in all tissues examined at all stages of development. The reduced enzyme activity is partially accounted for by reduced rates of enzyme synthesis, and the remainder probably results from increased rates of enzyme turnover. beta-Glucuronidase mRNA levels in these mice were not reduced suggesting that the observed reduction in enzyme synthesis is due to a decreased efficiency of translation for CS and CL mRNA.

Alleles↗