Biomedical subjects

K Pfister

Publications and source records attributed to K Pfister.

At least 37 records · Page 2Linked to original sources

PubMed1999

The periplasmic domain of the histidine autokinase CitA functions as a highly specific citrate receptor.

The two-component regulatory system CitA/CitB is essential for induction of the citrate fermentation genes in Klebsiella pneumoniae. CitA represents a membrane-bound sensor kinase consisting of a periplasmic domain flanked by two transmembrane helices, a linker domain and the conserved kinase or transmitter domain. A fusion protein (MalE-CitAC) composed of the maltose-binding protein and the CitA kinase domain (amino acids 327-547) showed constitutive autokinase activity and transferred the gamma-phosphate group of ATP to its cognate response regulator CitB. The autokinase activity of CitA was abolished by an H350L exchange, and phosphorylation of CitB was inhibited by a D56N exchange, indicating that H-350 and D-56 represent the phosphorylation sites of CitA and CitB respectively. In the presence of ATP, CitB-D56N formed a stable complex with MalE-CitAC. To analyse the sensory properties of CitA, the periplasmic domain (amino acids 45-176) was overproduced as a soluble, cytoplasmic protein with a C-terminally attached histidine tag (CitAPHis). Purified CitAPHis bound citrate, but none of the other tri- and dicarboxylates tested, with high affinity (KD approximately 5 microM at pH 7) in a 1:1 stoichiometry. As shown by isothermal titration calorimetry, the binding reaction was driven by the enthalpy change (DeltaH = -76.3 kJ mol-1), whereas the entropy change was opposed (-TDeltaS = + 46.3 kJ mol-1). The pH dependency of the binding reaction indicated that the dianionic form H-citrate2- is the citrate species recognized by CitAPHis. In the presence of Mg2+ ions, the dissociation constant increased significantly, suggesting that the Mg-citrate complex is not bound by CitAPHis. This work defines the periplasmic domain of CitA as a highly specific citrate receptor and elucidates the binding characteristics of CitAPHis.

Bacterial Proteins↗

PubMed1998

Biannual anthelmintic treatments in village Djallonke sheep in The Gambia: effects on productivity and profitability.

An on-farm deworming trial was conducted between 1991 and 1995 on traditionally managed Djallonke sheep in The Gambia to assess the impact on productivity and profitability of prophylactic biannual anthelmintic treatments- Fifteen private flocks with an average of 25 animals per flock participated in the experiment. Half of each flock was dewormed twice a year while the other half served as the control group. The two productivity traits that were significantly improved by the treatment scheme tested were the number of lambs per lambing which increased from 1.11 +/- 0.31 (Mean +/- S.D.) to 1.19 +/- 0.39 and the number of lambings per year which improved from 1.04 +/- 0.53 to 1.22 +/- 0.47. The mortality and weight at 12 months were not significantly affected by the treatment. Monitoring of sheep sales in the flocks and on surrounding markets allowed the calculation of a rate of return to the treatment scheme tested of 246%. Despite large variations in returns. The scheme studied is recommended as over 90% of the adopting farmers would yield positive returns to their investment.

Animal Husbandry↗

PubMed1998

Multiparasitism, Production and Economics in Domestic Animals in sub-Saharan West Africa.

Over the past ten years, an informal West African animal helminthosis network has developed (), with the aims of both improving livestock productivity through parasite control and, ultimately, increasing rural income. The network places a strong emphasis on building up local research capacity through scientific partnership. This article highlights recent findings from projects of the network.

Journal Article↗

PubMed1998

Reply.

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Journal Article↗

PubMed1998

[Swiss veterinary research and development project in the Gambia: the point of view of the breeder concerning control of helminthiasis in livestock].

The epidemiology of nematodes in livestock in The Gambia was assessed. A prophylactic biannual treatment was then tested on cattle and sheep. This treatment resulted in a significant improvement in the reproductive performances (sheep: lambings/year increasing from 1.04 to 1.22 and lambs/lambing increasing from 1.11 to 1.19; cattle: age at first calving decreasing from 58 to 50 months) and, in cattle, a significant improvement of the weight (varying between 8% and 17% in 1 to 4 year old animals). A socioeconomic study conducted in parallel showed that the treatment in cattle is on average profitable (benefit/cost ratio of 1.14) but remains a risky investment which should not be generalised (benefit/cost ratio would have been below 1 in more than half of the participating herds). In sheep, the benefit/cost ratio is high (2.47) with a low risk of losses (< 10%). The obstacles to the adoption by farmers of such a treatment and the usefulness of a pluridisciplinary approach in similar studies are then discussed.

Animals↗

PubMed1997

Effect of strategic gastrointestinal nematode control on fertility and mortality of N'Dama cattle in The Gambia.

A large-scale longitudinal study was undertaken to investigate the effects of a strategic treatment of gastrointestinal nematodes on the mortality and fertility of N'Dama cattle under village conditions. Initially, 1046 animals from 26 private N'Dama cattle herds, were monitored from October 1989 to December 1994. Each herd was stratified by age and the animals were randomly allocated to two groups with a similar average age. One group received a single anthelmintic treatment of fenbendazole (Panacur, 7.5 mg/kg BW, Hoechst Veterinä AG) in October 1989, whereas the other group remained untreated. In July 1990, the herds were subdivided into two different treatment schemes. In the herds of scheme 1, the treated animals (Treatment group I) were treated once (in August), whereas in the herds of scheme 2, the treated animals (Treatment group II) were treated twice (in July and September). The same treatment schedule was used in the subsequent rainy seasons until December 1994. One group in every herd of both schemes served as control (Treatment group 0) and received no anthelmintic treatment throughout the study. The average annual cumulative incidence mortality between 0-1 year was more than two times higher in treated animals compared to their controls (21% against 7.5%). No differences were found in older age categories. Survival analysis confirmed differences in mortality from 0-1 year, but were not significant in proportional hazard models. The 25% quantiles of age at first calving was used to quantify differences between twice treated animals (50.2 months) and its controls (58.3 months) which represents a decrease of 8 months in twice treated animals. Annual calving rates of twice treated animals were 52.2% compared to 43.6% in the control group (P < 0.001), which is an increase of 8.6% to the control rate. Possible causes of increased mortality in 0-1 year old treated calves are discussed. We can conclude that in the present epidemiological situation and the given parasite spectrum, gastro-intestinal nematodes mainly affect host fertility. Strategic control of gastro-intestinal nematodes is thus recommended for young heifers up to their age of first calving provided the overall financial analysis of the intervention is beneficial.

Abortion, Veterinary↗

PubMed1997

Methylmalonyl-CoA decarboxylase from Propionigenium modestum--cloning and sequencing of the structural genes and purification of the enzyme complex.

Methylmalonyl-CoA decarboxylase catalyses the only energy-conserving step during succinate fermentation by Propionigenium modestum: the decarboxylation of (S)-methylmalonyl-CoA to propionyl-CoA is coupled to the vectorial transport of Na+ across the cytoplasmic membrane, thereby creating a sodium ion motive force that is used for ATP synthesis. By taking advantage of the sequence similarity between the beta-subunits of other Na+-transport decarboxylases, a portion of the P. modestum beta-subunit gene was amplified by PCR with degenerated primers. The cloned PCR product then served as homologous probe for cloning suitable fragments from genomic DNA. Sequence analysis of a 3.7-kb region identified four genes which probably form a transcriptional unit, mmdADCB. Remarkably, a mmdE gene which is present in the homologous mmdADECB cluster from Veillonella parvula and encodes the 6-kDa epsilon-subunit, is missing in P. modestum. By sequence comparisons, the following functions could be assigned to the P. modestum proteins: MmdA (56.1 kDa; alpha-subunit), carboxyltransferase; MmdB (41.2 kDa; beta-subunit), carboxybiotin-carrier-protein decarboxylase; MmdC (13.1 kDa; gamma-subunit), biotin carrier protein. MmdD (14.2 kDa; delta-subunit) presumably is essential for the assembly of the complex, as shown for the corresponding V. parvula protein. Methylmalonyl-CoA decarboxylase was solubilized from membranes of P. modestum with n-dodecylmaltoside and enriched 15-fold by affinity chromatography on monomeric avidin resin. The purified protein was composed of four subunits, three of which were identified by N-terminal sequence analysis as MmdA, MmdD, and MmdC. The purified enzyme exhibited a specific activity of up to 25 U/mg protein and an apparent Km value for (S)-methylmalonyl-CoA of approximately 12 microM. Compared to the five-subunit complex of V. parvula, the four-subunit enzyme of P. modestum appeared to be more labile, presumably a consequence of the lack of the epsilon-subunit.

Amino Acid Sequence↗

PubMed1997

Returns from strategic anthelmintic treatments in village cattle in the Gambia.

A large-scale study was undertaken to investigate the effects of two systematic anthelmintic treatments on village cattle productivity in the Gambia. Treated animals had significantly higher performance in terms of live weights and age at first calving, but the mortality rate of 0- to 1-yr-old cattle appeared to be negatively affected. These results and financial data on treatment costs were used in a herd simulation model to assess the profitability of the intervention. Treatment was profitable on average, but the risks of losing money were large and average returns were sensitive to various hypotheses examined. The treatment regimen studied can only be recommended in certain herds and further research is needed to identify the factors determining the negative response in other herds.

Aging↗

PubMed1997

Effect of strategic gastrointestinal nematode control on growth of N'Dama cattle in Gambia.

From October 1989 to December 1994, a longitudinal study on the control of gastrointestinal nematodes was done on 1000 N'Dama cattle in 20 private herds in Gambia. Each herd was divided into two groups with an even distribution of age and sex. One group received a single anthelmintic treatment of Fenbendazole, Panacur Hoechst Veterinär GmbH, 7.5 mg kg-1 BW in October 1989, whereas the other group served as an untreated control. In July 1990, the herds were subdivided into two different treatment schemes. In the herds of the first scheme the treated animals (Treatment group I) were treated once (in August), whereas in the herds of the second scheme the treated animals (Treatment group II) were treated twice (in July and September). The same treatment schedule was used in the subsequent rainy seasons until December 1994. One group in every herd served as control (Treatment group 0) and received no anthelmintic treatment throughout the study. One annual fenbendazole treatment had no significant effect on liveweights, whereas two annual treatments significantly increased liveweights of the age group 12-24 and 24-36 months by 9.4%, and 17.5%, respectively. Animals less than 12 months old had 6.3% higher liveweights after two treatments, the difference was statistically not significant (P < 0.06). Average weights of 3- and 4-year-old, twice-treated animals were 13.1% and 8.2%, respectively, higher compared with their controls. No effect of anthelminthic treatment on liveweights was found in 5-year-old and older animals. Herd structure analysis demonstrated that overall male offtake rates ranged from 12 to 28% in the 3-, 4- and 5-year-old age categories. The age categories within which deworming improves liveweights thus coincides with the age at which males are mainly sold. These results suggest that biannual metaphylactic treatments (end of July and beginning of September) of all animals from birth to an age of 4 years should be recommended, provided that the financial analysis demonstrates the profitability of this intervention.

Animals↗

PubMed1997

Is ADHD a risk factor for psychoactive substance use disorders? Findings from a four-year prospective follow-up study.

OBJECTIVE: To evaluate whether attention-deficit hyperactivity disorder (ADHD) is a risk factor for psychoactive substance use disorders (PSUD), attending to issues of psychiatric comorbidity, family history, and adversity. METHOD: Using assessments from multiple domains, the authors examined 140 ADHD and 120 normal control subjects at baseline and 4 years later. Drug and alcohol abuse and dependence were operationally defined. RESULTS: No differences were detected in the rates of alcohol or drug abuse or dependence or in the rates of abuse of individual substances between the groups; both ADHD and control probands had a 15% rate of PSUD. Conduct and bipolar disorders predicted PSUD, independently of ADHD status. Family history of substance dependence and antisocial disorders was associated with PSUD in controls but less clearly so in ADHD probands. Family history of ADHD was not associated with risk for PSUD. ADHD probands had a significantly shorter time period between the onsets of abuse and dependence compared with controls (1.2 years versus 3 years, p < .01). CONCLUSIONS: Adolescents with and without ADHD had a similar risk for PSUD that was mediated by conduct and bipolar disorder. Since the risk for PSUD has been shown to be elevated in adults with ADHD when compared with controls, a sharp increase in PSUD is to be expected in grown-up ADHD children during the transition from adolescence to adulthood.

Adolescent↗

PubMed1997

[Recent data on the treatment of bovine hypodermyiasis using metrifonate (Neguvon) and ivermectin (Ivomec) in microdoses].

Large scale preventive treatments against bovine hypodermosis have been performed in the Canton of Grisons and in different Jura areas. Either Metrifonate (Neguvon 10% spot-on, Bayer AG) or Ivermectin "microdoses" (i.e. 0.1 ml Ivomec ad. inj-MSD AGVET-per animal) have been applied. The treatment of dairy cows with Neguvon at the then recommended dose (24 ml/animal) showed a low efficacy of 80%, without any correlation to the date of treatment. An increase of the dose to 36 ml/animal revealed an efficacy of 93%, while a weight-dependent dose of 6 ml/100 kg body weight reduced the warble infestation by 97.3% without any drug-related side-effects. The few observed side-effects-salivation and mild meteorism--are likely to be due to the destruction of Hypoderma lineatum larvae in the gullet of treated cows. No case of abortion was reported. The Ivomec--"microdose" applied to young animals or dry cows showed an efficacy > 99.8%. The available drugs would thus allow a quick and efficacious control of bovine hypodermosis, provided they would be used systematically and at an appropriate dose in endemic areas.

Animals↗

PubMed1996

[Histopathological analysis of bovine livers infested by Dicrocoelium dendriticum].

The object of this study was to determine the evolution of the lesions provoked by dicrocoeliasis in hepatic tissue, as a function of the quantity of parasites. Of the 274 bovine livers taken from the slaughterhouse and autopsied for Dicrocoelium dendriticum infection, 191 demonstrated hepatic lesions that revealed a proliferation of bile ducts, modifications of the bile ducts and hepatic fibrosis lesions. The modifications of the surfaces of the bile ducts and the hepatic fibrosis lesions increased with the level of infestation from 0 to 300 D dendriticum. Above these values, 301 to 600 flukes, a decrease was observed.

Animals↗

PubMed1996

[Cryptosporidiosis of calves as a serious farm problem].

Repeated outbreaks of cryptosporidiosis in three to fourteen days old calves on a dairy farm gave rise to a detailed description of the induced therapeutic, epidemiological and prophylactic measures. In farms with ongoing problems of diarrhea in calves, its etiology should be cleared. For cryptosporidiosis, which can not be cured by a conventional symptomatic treatment, only Lasalocid-Na is available. In Switzerland the ionophoric polyether antibiotic Lasalocid-Na is available as a food additive (Bovatec, 15% Lasalocid-Na, Hoffmann-La Roche AG). After the establishment of a diagnosis it must be administered as follows: 2 x 6 mg/kg BW, i.e. 2 x 40 mg Bovatec/kg BW, daily for three days. The recommended dose has to be respected because of a very high risk of intoxication. Moreover, on contaminated farms strict measures of hygiene, disinfection and cleaning have to be respected. Calving cows have to be kept separated during the calving period and the newborn calves must be separated from the adult cattle unit.

Animals↗

PubMed1995

Bovine cysticercosis: demonstration in experimentally infected calves of serum IgG antibodies reactive with neutral glycolipids of Taenia saginata and T. crassiceps metacestodes.

The immunoreactivity of Taenia saginata and T. crassiceps metacestode neutral glyco(sphingo)lipids towards IgG antibodies derived from the sera of calves with experimental cysticercosis has been established. The glyco(sphingo)lipids are separable by normal-phase HPTLC (high-performance thin-layer chromatography) into groups of increasing sugar-chain length (lipid/ceramide mono-, di-, tri-, tetra- and > tetrasaccharides), with those corresponding to three and four hexoses being the main immunoreactive components (HPTLC immunostaining). In ELISA (enzyme-linked immunosorbent assay), reverse-phase HPTLC-isolated T. crassiceps metacestode glyco(sphingo)lipids equivalent to tri- and tetrahexoside allowed a discrimination between non-infected and infected calves (at least 80 metacestodes recovered). The formation of IgG antibodies was correlated with the infection, not with other non-specific inducing factors, as seen by the differential humoral response detected in experimentally infected (T. saginata) calves before and after Praziquantel treatment (HPTLC immunostaining and ELISA).

Animals↗

PubMed1995

Effect of a single dry season anthelmintic treatment of N'Dama cattle on communal pastures in The Gambia.

The effect of a single anthelmintic treatment of cattle during the early dry season was studied. One hundred and sixty-six N'Dama cattle, 1-3 years old, were selected from five herds. There were 65 males and 101 females divided into two groups of 83 animals each. One group was treated with fenbendazole at 7.5 mg/kg body weight by mouth in November 1992; the other group remained as the untreated control. At monthly intervals from November 1992 to April 1993, each animal was weighed and the number of eggs/g of faeces (epg) was determined. The infective larvae (L3) were examined following culture of pooled samples from each group of animals. In April 1993, 6 animals (3 treated and 3 controls) from the herds under study were necropsied. The difference in the weight gains (4.6 kg) of the two groups was highly significant (p < 0.0001). The difference in the weight gains and the epg between the treated and control groups was influenced by the age of the animals. Of the treated animals, one contained no nematodes, one contained only 25 Oesophagostomum radiatum, and the third contained 25 Cooperia L4. The three untreated animals were all infected. It was concluded that the treatment in early dry season, with an anthelmintic effective against both adults and larvae, led to a significant reduction in egg counts, to elimination of adults and hypobiotic larvae and, consequently, to an increase in the body weight gain by the treated animals.

Animals↗

PubMed1995

Effect of herd management on the contamination of night holding areas (correos) and infections with gastrointestinal nematodes of N'Dama cattle in The Gambia.

The densities of infective nematode larvae (L3/m2) in the night holding places (locally called "correos") of 2 traditionally kept N'Dama herds were estimated at weekly intervals throughout an entire rainy season. Herd 1 moved correos every 3 weeks whereas herd 2 remained in the same area for most of the rainy season. Removal to a new correo was invariably accompanied by a drastic drop of L3/m2. Conversely, L3/m2 increased rapidly up to values of more than 1,000 when the herds used the same night holding place for more than 3 weeks. Calves kept in herds with frequent changes of the correo showed significantly lower nematode egg counts and higher growth rates during the rainy season, combined with a reduced weight loss during the following dry season. The results of this study indicate that a regular frequent change of the correo is an effective method of reducing nematode infection risk and increasing calf growth and that this might be a sustainable part of an integrated strategic programme to control gastrointestinal nematode infections wherever correos are used.

Animal Husbandry↗

PubMed1995

Somatic antigens of adult Dicrocoelium dendriticum recognised by bile antibodies of naturally infected cattle.

Bile samples, from slaughtered cattle harbouring between 120 and 280 adult lancet flukes, were used to investigate the range of somatic proteins inducing local antibody responses in naturally infected animals. Lancet fluke infections induced local (bile) antibody responses against Tris-buffered saline (TBS) soluble, sodium dodecyl sulphate (SDS) soluble and 2-mercaptoethanol (2-Me) soluble somatic proteins of adult Dicrocoelium dendriticum. IgA antibody isotypes predominated in the response against buffer-soluble somatic antigens, whereas SDS-soluble and 2-Me-soluble proteins induced similar level of both IgA and IgG1 antibodies. Analysis of the antigens recognised by particular isotype-specific bile antibodies suggests that different antigens preferentially induce isotype restricted antibody responses. The bile antibody response was highly species specific, only one antigen from somatic protein extracts of Fasciola hepatica being precipitated by bile samples showing the highest reactivity against D. dendriticum.

Animals↗

PubMed1995

Helminth parasites and hypobiosis of nematodes in N'Dama cattle during the dry season in The Gambia.

Three series of necropsies of cattle were performed, corresponding to early dry season, approximately 1 month after the last rains (November, n = 6), mid dry season (February, n = 6) and end dry season (April, n = 3). Eggs per gram of faeces (epg) were determined just before necropsy. Three trematodes (Fasciola gigantica, Schistosoma spp. and Paramphistomatids) and 11 nematodes were identified from cattle, with the prevalence rate varying from 6.7% to 100%. Haemonchus contortus was the most abundant nematode species, constituting from 81% (February) to 34.8% (April) of the total nematode burden. The proportion of L4 (indicating hypobiosis) of H. contortus was 85-99%. During the dry season, 44-67% of Oesophagostomum radiatum and 8-34% of Cooperia spp. population occurred as L4. There was no correlation between the number of worms found at necropsy and the epg. H. contortus survives almost exclusively as larvae in the abomasal mucosae, whereas Cooperia spp. and O. radiatum survive partly as larvae in the lumen, and also in nodules in the case of O. radiatum, and partly as hypometabolic adults with highly reduced fecundity. Trichostrongylus axei, T. colubriformis, Bunostomum phlebotomum, Strongyloides papillosus, Nematodirus spp. and Setaria labiatopapillosa occurred in small numbers.

Animals↗