Biomedical subjects

S van Dijk

Publications and source records attributed to S van Dijk.

At least 19 recordsLinked to original sources

PubMed2005

Hereditary melanoma and predictive genetic testing: why not?

BACKGROUND: Since p16-Leiden presymptomatic testing for hereditary melanoma has become available in the Netherlands, the benefits and risks of offering such testing are evaluated. The current paper investigated why the non-participants were reluctant to participate in genetic testing. METHODS: Sixty six eligible individuals, who were knowledgeable about the test but had not participated in genetic testing by January 2003, completed a self-report questionnaire assessing motivation, anxiety, family dynamics, risk knowledge and causal attributions. RESULTS: Non-participants reported anxiety levels below clinical significance. A principal components analysis on reasons for non-participation distinguished two underlying motives: emotional and rational motivation. Rational motivation for non-participation was associated with more accurate risk knowledge, the inclination to preselect mutation carriers within the family and lower scores on anxiety. Emotional motivation for non-participation was associated with disease misperceptions, hesitation to communicate unfavourable test results within the family and higher scores on anxiety. CONCLUSION: Rational and emotional motivation for non-participation in the genetic test for hereditary melanoma was found. Emotionally motivated individuals may be reluctant to disseminate genetic risk information. Rationally motivated individuals were better informed than emotionally motivated individuals. It is suggested that a leaflet is added to the invitation letter to enhance informed decision-making about genetic testing.

Adult↗

PubMed2003

Genetic counselling and the intention to undergo prophylactic mastectomy: effects of a breast cancer risk assessment.

Scientific reports suggest that women at risk for familial breast cancer may benefit from prophylactic mastectomy. However, few data are available about how women decide upon this clinical option, and in particular, what role an objective risk assessment plays in this. The purpose of the present study is to assess whether this objective risk information provided in genetic counselling affects the intention for prophylactic mastectomy. Additionally, the (mediating) effects of breast cancer worry and perceived risk are investigated. A total of 241 women completed a questionnaire before and after receiving information about their familial lifetime breast cancer risk in a genetic counselling session. Path analysis showed that the objective risk information had a corrective effect on perceived risk (beta=0.38; P=0.0001), whereas the amount of breast cancer worry was not influenced by the counselling session. The objective risk information did not directly affect the intention for prophylactic mastectomy. The intention was influenced by perceived risk after counselling (beta=0.23; P=0.002), and by the precounselling levels of perceived risk (beta=0.27; P=0.00025) and breast cancer worry (beta=0.32; P=0.0001), that is, higher levels of perceived risk and breast cancer worry imply a stronger intention for prophylactic mastectomy. A personal history of breast cancer did not directly influence the intention for prophylactic mastectomy, but affected women who had undergone a mastectomy as surgical treatment were more positively inclined to have a prophylactic mastectomy than women who had had breast-conserving therapy. The impact of objective risk information on the intention for prophylactic mastectomy is limited and is mediated by perceived risk. Important determinants of the intention for prophylactic mastectomy were precounselling levels of breast cancer worry and perceived risk, suggesting that genetic counselling is only one event in the entire process of decision making. Therefore, interventions aimed at improving decision making on prophylactic mastectomy should explicitly address precounselling factors, such as personal beliefs and the psychological impact of the family medical history.

Adult↗

PubMed2000

Ability of deproteinized cancellous bovine bone to induce new bone formation.

BACKGROUND: Preclinical and clinical studies indicate that deproteinized cancellous bovine bone is osteoconductive and may be osteopromotive. Previous studies using commercial preparations failed to demonstrate the presence of protein, implicating bone-mineral composition and 3-dimensional structure as reasons for clinical success; however, these studies did not examine whether osteoinductive factors might be present in close association with the mineral phase. METHODS: Deproteinized cancellous bovine bone was decalcified and any protein present released by chaotropic solvents using the protocol described for purification of bone morphogenetic proteins (BMPs). Three extracts were obtained and tested for their ability to support osteoinduction in the calf muscle of nude mice. RESULTS: Protein content averaged 11 microg/g based on absorbance at 280 nm using bovine serum albumin as a standard. All extracts contained material that stained positively with silver stain after sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). Western blots of these gels indicated the presence of transforming growth factor-beta (TGF-beta) and BMP-2. All 3 extracts were osteoinductive in the nude mouse model when combined with inactive DFDBA, and bone formation was comparable to that induced by active DFDBA. Deproteinized cancellous bovine bone by itself was not osteoinductive in the nude mouse, but in a clinical case, exhibited osteoclastic resorption with adjacent new bone formation. CONCLUSIONS: The results suggest that small amounts of protein are present in deproteinized cancellous bovine bone in close association with the mineral phase. Some of the extracted material has osteoinductive potential and may contain growth factors. This may explain the osteopromotive ability of deproteinized cancellous bovine bone clinically.

Adult↗

PubMed1998

Purification, amino acid sequence, and cDNA sequence of a novel calcium-precipitating proteolipid involved in calcification of corynebacterium matruchotii.

Corynebacterium matruchotii is a microbial inhabitant of the oral cavity associated with dental calculus formation. It produces membrane-associated proteolipid capable of inducing hydroxyapatite formation in vitro. This proteolipid was purified from chloroform:methanol extracts by chromatography on Sephadex LH-20 and migrated on SDS-polyacrylamide gel electrophoresis at 6-9 kDa. Removal of covalently attached acyl moieties by methanolic KOH decreased its molecular mass to approximately 5.5 kDa. The amino acid sequence of the apoproteolipid indicated a peptide of 50 amino acids, a calculated molecular weight of 5354 Da, and an isoelectric point of 4.28. Sequence analysis revealed an 8 amino acid sequence with homology to human phosphoprotein phosphatase 2A as well as several potential acylation sites and one phosphorylation site. The purified proteolipid induced calcium precipitation in vitro. Deacylation of the proteolipid by hydroxylamine treatment resulted in >50% loss of calcium-precipitating activity, suggesting that covalently attached lipids are required. Degenerate oligonucleotide primers, based on the amino acid sequence, were used to amplify the gene for the 5.5 kDa proteolipid from total chromosomal DNA of C. matruchotii by PCR. A 166 bp cDNA was isolated and sequenced, confirming the amino acid sequence of the proteolipid. Thus, we have sequenced a unique bacterial proteolipid that is involved in the formation of dental calculus by precipitating Ca2+ and possibly in transport of inorganic phosphate, necessary for hydroxyapatite formation.

Amino Acid Sequence↗

PubMed1995

Inhibition of pseudocholinesterase activity in a 20-year-old gelding.

A 20-year-old Arab crossbred gelding was examined because it had apparently suffered an overstimulation of the parasympathetic nervous system for three hours. The clinical signs consisted of hypersalivation, profuse sweating, maximal miosis, fasciculation of the muscles and lateral recumbency in combination with continuous convulsions without diarrhoea. The horse's plasma pseudocholinesterase activity was approximately 10 per cent of normal. It responded well to 10 mg atropine and 50 mg diazepam administered intravenously.

Animals↗

PubMed1994

[Neurodegenerative disorders of the central nervous system in horses].

The most important neurodegenerative diseases of the horse are reviewed. In addition to the literature, neurodegenerative diseases occurring in patients (horses, Mongolian Przewalski-horses, and two zebras) referred to the Utrecht Veterinary Faculty are mentioned. Neurodegenerative diseases described are: I. ataxia associated with: A/ static stenosis, B/ dynamic stenosis, C/ lesions at various locations in the central nervous system, D/ equine herpesvirus infections, E/ equine degenerative myelo-encephalopathy, or F/ cerebellar abiotrophy; II. equine motor neuron disease; III. grass sickness or equine dysautonomia; IV. postanaesthetic myelomalacia; and V. equine leuko-encephalomalacia. The patient descriptions show, that mixed forms of some of the differentiated diseases can be diagnosed. Little is known with certainty about the aetiology of the neurodegenerative lesions found. In some patients vitamin E may play a role, possibly in combination with other factors. A mycotoxin known to interfere with myelin metabolism is involved in leuko-encephalomalacia.

Animals↗

PubMed1993

Evidence that a non-RGD domain in rat osteopontin is involved in cell attachment.

The bone sialoprotein osteopontin (OPN) promotes cell attachment and spreading through its RGD (Arg-Gly-Asp) sequence. To study additional regions of OPN involved in cell attachment, peptides of rat OPN were evaluated for their capacity to mediate cell binding to wells in vitro. Human gingival fibroblasts were incubated on microtiter plates coated with either OPN or OPN peptides. A peptide of M(r) 28 kD, obtained after digestion with endoproteinase Arg-C and isolated by reversed-phase HPLC, enhanced cell attachment to a similar degree as OPN. Sequence analysis showed that the amino terminus of the 28 kD peptide starts at Ser142 and therefore does not contain the RGD cell attachment sequence (residues 128-130). Cell attachment mediated through both OPN and the 28 kD peptide was blocked by the addition of GRGDSPA peptides or LM-609, a monoclonal antibody to the integrin alpha V beta 3, a receptor for vitronectin. A variant peptide, GRG-ESPA, did not alter cell attachment. Based on these observations, we conclude that (1) binding of OPN and the 28 kD peptide to fibroblasts involves binding to alpha V beta 3, (2) a site other than the RGD sequence on OPN is also involved in binding to integrins, and (3) the binding of this second site to alpha V beta 3 is inhibited by RGD-containing peptides.

Amino Acid Sequence↗

PubMed1993

Dentin sialoprotein: biosynthesis and developmental appearance in rat tooth germs in comparison with amelogenins, osteocalcin and collagen type-I.

A non-collagenous protein, extracted from rat incisor dentin, is a dentin sialoprotein (DSP). We examined immunohistochemically the developmental appearance and tissue distribution of DSP in 1 to 3-day-old rat molar and incisor tooth germs. The earliest staining for DSP was observed in newly differentiated odontoblasts. In more advanced stages, immunostaining for DSP gradually increased in pre-dentin, odontoblasts and dentin, and appeared in many cells of the dental papilla. In early stages of development before the breakdown of the dental basement membrane, pre-ameloblasts were also positive for DSP. This staining disappeared from the ameloblast cell body soon after deposition of the first layer of mineralized dentin. Radiolabelling of tooth matrix proteins with 14C-serine in vitro followed by immunoprecipitation and fluorography confirmed that DSP was synthesized by tooth-forming cells. The immunolocalization for DSP was different from that of either collagen type-I, osteocalcin or the amelogenins. Whereas collagen type-I and osteocalcin were restricted to the mesenchymal dental tissues, the amelogenins were detectable in both epithelial and mesenchymal dental cells and tissues at the epithelio-mesenchymal interface at early stages of development, prior to the onset of dentin mineralization. We conclude that DSP is expressed in and secreted by odontoblasts and some dental papilla cells from early stages of dentinogenesis onwards, i.e. later than type-I collagen, but before deposition of the first layer of mineralized dentin. In pre-mineralizing stages, some of the matrix proteins may be endocytosed from the pre-dentin by both cell types involved in the epithelio-mesenchymal interaction.

Amelogenin↗

PubMed1993

Chemical cross-linking of porcine luteinizing hormone: location of the cross-link and consequences for stability and biological activity.

To study the interaction between the subunits of LH and determine which amino acid residues are involved in this interaction, porcine and ovine LH (pLH and oLH) were cross-linked with 0.02 M 1-ethyl-(3-(3-dimethylaminopropyl)carbodiimide to generate one specific intersubunit cross-link. The cross-linked hormone was separated from the noncross-linked dissociated subunits by gel filtration on a Sephadex G-75 column. The position of the cross-link in cross-linked pLH (X-pLH) was determined by sequencing peptide fragments that were generated by digestion with endoproteinase Arg-C. In accordance with previous data for bovine LH, the position of the cross-link was between alpha-Lys49 and beta-Asp111, indicating that these residues are at the subunit-subunit interface. The biological activity of cross-linked hormone was tested by radioreceptor binding assay. The receptor-binding activity of X-pLH was slightly reduced to 84%, suggesting that the conformational stability of X-pLH is similar to that of pLH as a result of the introduction of the covalent cross-link. The receptor-binding activity of X-oLH was decreased by approximately 30%, which we attribute to the formation of multiple cross-links within the ovine molecule, making the molecule more rigid, and to oligomeric forms, resulting from multiple intermolecular cross-links, that are not able to bind to the testicular LH receptor. This observation implies that the oLH has more amino-carboxyl functional groups that are sterically susceptible to carbodiimide cross-linking than does pLH under the reaction conditions used.

Amino Acid Sequence↗

PubMed1992

Hepatic lipidosis in pregnant cows on a dairy farm.

A syndrome very similar to hepatic lipidosis is described in dairy cows during the dry period. After being sent to pasture the animals did not eat well for undetermined reasons. The disease phenomena were mainly observed in animals carrying twins. At post mortem examination severe falty infiltration was found in the 3 animals made available for post mortem examination. Increase of the energy supply to the dry cows by addition of maize silage to the ration prevented new cases.

Animals↗

PubMed1992

Heterogeneity in porcine pituitary luteinizing hormone: amino acid and carbohydrate analysis.

Pituitary LH from porcine pituitary glands was purified by a buffered ethanol extraction procedure, ion exchange on DEAE- and carboxymethyl-cellulose, and molecular exclusion on Sephacryl S-200. Purity was assessed by amino acid composition, N-terminal sequence, and polyacrylamide gel electrophoresis. Subunits were isolated by countercurrent distribution and reverse phase HPLC. Four major forms of the alpha-subunit were detected: 1-96 (50%), 3-96 (23%), 4-96 (16%), and 7-96 (11%). [The original sequence report described only the 7-96 form, but we have detected the other forms in our studies of porcine FSH and in this and other species of LH.] Comparable N-terminal heterogeneity was not observed for the beta-subunit. Additional heterogeneity was observed for both subunits, attributable to heterogeneity in the N-linked oligosaccharide moieties. The isolated subunits were submitted to detailed compositional carbohydrate analysis, using pulsed amperometric detection of the HPLC-resolved sugar monomers after trifluoroacetic acid hydrolysis. Sialic acid and sulfate esters were estimated on separate hydrolyzates. The compositional data suggest that the two alpha-subunit N-linked moieties are hybrid complex biantennary structures with sulfated N-acetylgalactosamine (40-50%). Sixty to 70% of the alpha-subunit oligosaccharides are fucosylated. The beta-subunit of porcine LH has a single glycosylation site, which contains a mixture of biantennary oligosaccharide chains (80-90%) ending in N-acetylgalactosamine, half of which are sulfated. The balance (10-20%) are hybrid chains ending in sialylated galactose. The majority of the oligosaccharide on the beta-subunit is fucosylated.

Amino Acid Sequence↗

PubMed1989

Effect of clenbuterol on the incidence of abomasal ulcers in veal calves.

The effect of clenbuterol on the incidence of abomasal lesions in veal calves was studied in two fattening units. Some of the calves in each unit were treated with 1.6 micrograms clenbuterol/kg bodyweight/day from the seventh until the 23rd week of the fattening period. In one unit the calves were fed milk replacer only and 176 of the 236 calves were treated with clenbuterol. In the other unit the calves were fed roughage pellets in addition to milk replacer and 92 of the 194 calves were treated with clenbuterol. Only in the second unit did the calves treated with clenbuterol have significantly fewer abomasal lesions.

Abomasum↗

PubMed1989

Comparison of the lipoprotein pattern of the horse, the pony and the lactating and non-lactating cow obtained by a combination of an ultracentrifugation and a precipitation technique.

1. The serum lipoprotein pattern was studied in four horses, four ponies and in three high producing lactating and three non-lactating cows. The lipoprotein pattern was estimated with a combination of the preparative ultracentrifugation and the heparin-manganese precipitation technique. 2. The lipid composition of the lipoproteins of horse, pony, lactating cow and non-lactating cow was determined. 3. In all three species more than 50% of serum total lipids was found in the HDL fraction. 4. The mean chylomicron fraction in horse and pony was 3.1%. In the cow it varied from 1.5 to 2.5%. 5. Between the lactating cow and the non-lactating cow there were substantial differences in the concentration of LDL and HDL. 6. The cholesterylester concentration in VLDL, LDL and HDL was clearly higher in the lactating cow than in the non-lactating cow.

Animals↗

PubMed1987

Effects of two glucocorticoids on milk yield and biochemical measurements in healthy and ketotic cows.

The effects of two glucocorticoid compounds (Dexamedium; Intervet. Voreen; Boehringer Ingelheim) were tested in 20 healthy and 28 ketotic dairy cows. Both compounds induced an increased blood glucose concentration and a temporary decrease in the milk yield of healthy dairy cows. Dexamedium reduced the milk yield only of cows producing 25 or more kg milk daily. Of 28 ketotic cows 22 were treated with one of the two glucocorticoid compounds, while the remaining six were treated orally with propylene glycol. After treatment all but one of the cows improved clinically within one week. Biochemical analysis of blood samples revealed that after treatment with any of the three therapeutic compounds some animals responded inadequately to therapy or relapsed after initial recovery.

Acidosis↗

PubMed1986

The effect of feeding pellets of different types of roughage on the incidence of lesions in the abomasum of veal calves.

Pellets of three types of roughage were fed to veal calves, to determine their effect on the frequency of lesions (erosions or ulcers) of the abomasal mucosa. The number was increased in the calves fed roughage. Pellets produced from corn silage caused a greater number of lesions than pellets produced from barley straw or lucerne hay. It is concluded that the nature of the roughage plays a role in the pathogenesis of abomasal lesions.

Abomasum↗

PubMed1986

Sexual dimorphism in immunoneutralization of bioactivity of rat and ovine inhibin.

Inhibin was partially purified from bovine follicular fluid using chromatography on immobilized Procion Red 3B and anion-exchange chromatography. Ovariectomized Texel ewes were immunized against the inhibin-containing fraction from the Procion Red 3B column and the immune response was subsequently boosted with similar fractions or with the preparation obtained from the anion-exchange column. The potencies of the resulting antisera were evaluated in an in-vitro bioassay system for estimating inhibin activity, using dispersed rat pituitary cells. The antisera were found to inhibit the bioactivity of inhibin preparations from ovarian follicular fluid of bovine, porcine, ovine or human origin, as well as inhibin activity in ovine testicular lymph and rete testis fluid, in culture media from rat granulosa and rat Sertoli cells and in homogenates of rat ovaries and testes. These results indicate that the inhibin molecules from several species contain a common bioactive moiety. The results also showed that the antiserum was more effective in neutralizing inhibin activity from ovarian than from testicular sources in both sheep and rat, indicating a sex-related difference in the inhibin molecules within a species.

Animals↗

PubMed1985

Effects of trenbolone acetate and propylene glycol on pregnancy toxaemia in ewes.

Eleven ewes with pregnancy toxaemia were monitored clinically and biochemically after daily treatment with trenbolone acetate (30 mg) and propylene glycol (twice daily 100 ml), for at least one week. The clinical signs of pregnancy toxaemia at first examination were less severe than those described in ewes in other countries. After the first treatment, the appetite improved in nine ewes, blood glucose levels increased in 10 ewes and blood ketone body concentrations decreased in nine animals. A statistically significant decrease in mean ketone body levels was found between the day of first examination and the second day thereafter. Four animals recovered before lambing (group 1). One animal lambed one day after the first treatment and recovered. In the remaining ewes clinical and biochemical improvement did not last long. Three of these animals did not recover until after lambing (group 2) and three animals died (group 3). In three animals of group 2 and two animals of group 3 an increase of serum activities of lactate dehydrogenase, sorbitol dehydrogenase, gamma glutamyl transferase and alkaline phosphatase was found. In two necropsied animals of group 3 a severe fatty degeneration of the liver was found. Treatment of pregnancy toxaemia with trenbolone acetate and propylene glycol appeared to have some positive effect in mild cases. In more advanced cases the time of parturition is the crucial factor leading to recovery.

Animals↗

PubMed1985

Comparison between inhibin from human and bovine ovarian follicular fluid using fast protein liquid chromatography.

Inhibin from human and bovine ovarian follicular fluid was purified 700-900-fold using affinity chromatography on immobilized Procion Red 3B, desalting on Sephadex G-25, ion-exchange chromatography on the fast protein liquid chromatography (FPLC) columns Mono Q and Mono P and chromatography on immobilized lectins. Isoelectric points for inhibin from human and bovine origin were between 5.1-5.7 and 4.75-5.25, respectively. Inhibin from both sources was retained by immobilized lectins, indicating its association with a glycoprotein. Overall recoveries of inhibin activity after these chromatographic procedures were approximately 1%.

Animals↗