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Biomedical subjects

G Linden

Publications and source records attributed to G Linden.

At least 19 recordsLinked to original sources
PubMed2000

Bovine beta-lactoglobulin receptors on transformed mammalian cells (hybridomas MARK-3): characterization by flow cytometry.

Flow cytometry was used to demonstrate the presence of beta-lactoglobulin (betaLG) receptors on living murine hybridoma MARK-3 cells using a fluorescein isothiocyanate-betaLG conjugate (FITC-betaLG: molar ratio of 5:1). A site occupation curve was produced using a shift in the mean channel fluorescence at various concentrations of FITC-betaLG. The binding of labelled ligand was concentration dependent and was inhibited by unlabelled betaLG. The on-rate constant was 3.2x10(2) M(-1) min(-1) and the off-rate constant was 0.002 min(-1). Scatchard plot analysis gave a dissociation constant (K(d)) of 44+/-21x10(-7) and 39+/-24x10(-5) M (n=3). Flow cytometry indicated that at least 15% of the FITC-betaLG were internalized for 5 min and that internalization was temperature- and time-dependent. The internalization was confirmed by 3-D fluorescence microscopy (CELLScan system).

Animals↗
PubMed1998

DNA sequence and muscle-specific expression of human sarcosin transcripts.

We have characterized two abundant human cDNAs which, through Northern hybridization analysis, are selectively expressed in human sarcomeric muscle. DNA sequencing was performed and the two cDNAs were found to share sequence identity, with the exception of a 3' UTR extension present on the longer transcript. Our data suggest that the two transcripts are generated through alternative use of two poly(A) addition signals. The cDNAs encode a large open reading frame encompassing at least 435 codons. Through sequence comparisons, both at the DNA and predicted amino acid sequence level, we have been unable to find significant sequence similarity to any other characterized sequence. Consequently, we have termed this novel human sequence sarcosin. Although novel, Southern hybridization analysis demonstrated that the sarcosin sequence has been conserved in several mammalian species.

Amino Acid Sequence↗
PubMed1998

Structure of the O-glycopeptides isolated from bovine milk component PP3.

The heat-stable acid-soluble phosphoglycoprotein component PP3 was isolated from the bovine milk proteose peptone fraction by concanavalin A affinity chromatography. Glycopeptides from the ConA-bound fraction corresponding to the component PP3 were obtained by Pronase digestion and were separated by gel filtration into high and low-molecular-mass glycopeptides. In a previous work, we have investigated the structure of the N-glycans from the high-molecular-mass glycopeptides [Girardet et al. (1995) Eur J Biochem 234: 939-46]. Here, we describe the structure of the O-glycans from the low-molecular-mass glycopeptides. By combining methylation analysis, mass spectrometry, 400 MHz 1H-NMR spectroscopy and peptide sequence analysis, we show that the low-molecular-mass fraction contains several neutral glycopeptides. A mixture of the following three glycan structures linked to the Thr86 has been identified: GalNac alpha1-O-Thr, Gal(beta1-3)GalNAc alpha1-O-Thr and Gal(beta1-4)GlcNAc(beta1-6)[Gal(beta1-3)]GalNAc alpha1-O-Thr.

Amino Acid Sequence↗
PubMed1998

Conformational studies of a synthetic peptide from the putative lipid-binding domain of bovine milk component PP3.

In bovine milk, a glycosylated phosphoprotein, component PP3, is known for its remarkable emulsifying properties and its capability to inhibit lipolytic activities. The determination of its primary structure is not sufficient to explain these properties. Secondary structure predictions of component PP3 and of its homologous proteins were achieved using a combination of multiple predictive methods. Based on this study, the f 119-135 region of component PP3 was proposed to be likely to adopt an amphipathic helical conformation, which is a lipid-binding motif. The conformation of the synthetic peptide corresponding to the C-terminal f 119-135 part of bovine component PP3 was analyzed by circular dichroism experiments using various media. The circular dichroism data indicated that the peptide was able to form an amphipathic alpha-helix structure in trifluoroethanol as well as in the presence of sodium dodecyl sulfate or acidic and neutral lipids, but not in water. Moreover, the conformation of this peptide is solvent dependent because it was found to adopt a beta-sheet structure for low concentrations of sodium dodecyl sulfate or a low molar ratio of acidic lipid to peptide. Tensiometric measurements showed that the amphipathic C-terminal region of component PP3 is highly tensioactive and, thus, must be responsible for the particular behavior of the protein in emulsions.

Amino Acid Sequence↗
PubMed1997

Two-dimensional 1H-NMR and CD structural analysis in a micellar medium of a bovine alphaS1-casein fragment having benzodiazepine-like properties.

The conformation of the benzodiazepine-like decapeptide, YLGYLEQLLR, corresponding to residues 91-100 of bovine alphaS1-casein, has been examined in SDS micelles using CD, two-dimensional 1H-NMR and restrained molecular-dynamics simulation. Evidence is presented that the decapeptide adopts a rigid structure in water/SDS micellar medium, but not in water or dimethylsulfoxide. The three-dimensional structure, consistent with the proton-proton distances obtained from the quantitative analysis of the two-dimensional NOEs, was generated by restrained energy minimization and molecular-dynamics simulation. In water/SDS micellar medium, YLGYLEQLLR adopts an amphipathic helicoid structure with distinct hydrophobic and hydrophilic faces. The relative disposition of the tyrosine aromatic rings was compared with that of the aromatic rings in the benzodiazepines.

Animals↗
PubMed1997

Role of the O-phosphoserine clusters in the interaction of the bovine milk alpha s1-, beta-, kappa-caseins and the PP3 component with immobilized iron (III) ions.

alpha s1- and beta-Caseins have a sequence cluster -Ser(P)-Ser(P)-Ser(P)-Glu-Glu- which is not present in kappa-casein and the whey PP3 component. The affinity of these phosphoproteins for the iron(III)-iminodiacetic acid (IDA) complex immobilized on Sepharose was studied as a function of pH, urea concentration, calcium ion concentration, enzymatic dephosphorylation and temperature. The affinity of the three polyphosphorylated proteins (alpha s1- and beta-caseins, PP3) was similar. The sequence cluster was not a specific recognition pattern of the iron(III) ion. These three proteins presented a site of high affinity and a site of weak affinity. kappa-Casein, which had only one Ser(P) residue, presented only the site of weak affinity. Their primary site which was absent after dephosphorylation or calcium ion addition required the presence of at least two Ser(P) residues close in space. Their secondary site was sensitive to the presence of urea. It was sensitive to pH variation for PP3 and kappa-casein. The study of the affinity of a few free amino acids towards iron(III)-IDA showed that the secondary site involved tryptophan and tyrosine residues for alpha s1- and beta-caseins, histidine residues for PP3 and cysteine residues for kappa-casein.

Adsorption↗
PubMed1997

Biologically active factors in bovine milk and dairy byproducts: influence on cell culture.

Substantial progress has been made in our knowledge of the biological properties of mammal milks. Many nutritional, biochemical, immunological, or other biological properties have been studied in mature or industrially processed bovine milk as well as in human milk and colostrum. This article is a critical review of selected publications covering (1) the use of bovine milk or dairy byproducts (processed acid and enzymatic whey fractions) as a serum substitute for cell cultures, (2) specific factors in bovine milk and industrially processed milk the affect cell proliferation, and (3) the known functional and biological roles of two whey proteins: beta-lactoglobulin and the PP3 component.

Animals↗
PubMed1995

Structure of glycopeptides isolated from bovine milk component PP3.

The heat-stable acid-soluble phosphoglycoprotein component PP3 was isolated from the bovine milk proteose peptone fraction by concanavalin A affinity chromatography. Glycopeptides were released by pronase digestion of the milk component PP3 and were subsequently separated by high-pH anion-exchange chromatography on CarboPac PA-1. The primary structures of the glycan and peptide moieties of eight N-glycopeptides have been established by combining methylation analysis, mass spectrometry, 400-MHz 1H-NMR spectroscopy, and peptide sequence analysis. All the analyzed fractions contained biantennary N-acetyllactosamine-type carbohydrate chains, some of them with a GalNAc(beta 1-4)GlcNAc or a NeuAc(alpha 2-6)GalNAc(beta 1-4)GlcNAc group. This particular sequence did or did not replace the Gal(beta 1-4)GlcNAc group usually found in most N-linked glycans. Moreover, the sialylated Gal and GalNAc residues were only found on the Man(alpha 1-3) antenna.

Amino Acid Sequence↗
PubMed1995

Rapid determination of the ratios of three aromatic residues in peptides by reversed-phase high-performance liquid chromatography with a high-resolution photodiode-array detector.

A method for the simultaneous determination of the ratios of three aromatic residues in peptides by derivative UV spectrophotometry on a spectrophotometer with a resolution of 0.1 nm can be used for the RP-HPLC analysis of peptides because of the recent development of high-resolution photodiode-array detectors (1.2 nm). The difference between the theoretical and experimental ratios of aromatic residues of peptides determined in real time is less than 5%. This method could become a powerful tool for the study of peptides and hydrolysates: A variety of possible applications are discussed.

Amino Acid Sequence↗
PubMed1995

Determination of the ratios of the aromatic amino acid residues by first- or second-derivative UV spectrometry for a simple characterization of peptides.

A method for the simultaneous determination of the ratios of the three aromatic amino-acid residues in peptides was set up in acidic conditions. Binary and ternary mixtures of these amino acids were prepared, and first- and second-derivative spectra then calculated from their 0.1 nm resolution spectra between 240 and 320 nm. Certain spectral bands were chosen to differentiate tyrosine from tryptophan on the first-derivative spectra, and phenylalanine from tyrosine and tryptophan on the second-derivative spectra. Variation of the amplitude of the chosen bands was shown to be a linear function of the ratio of the aromatic amino acids in the mixture. This technique was validated with peptides whose sequence was known. The difference between theoretical and experimentally determined ratios was lower than 10%. Since the results are obtained as ratios, neither the concentration nor the nature of the peptide has to be known. The feasibility of application using a photodiode array detector with high resolution in reversed-phase high-performance liquid chromatography is discussed.

Amino Acid Sequence↗
PubMed1995

Proteolysis in samples of quarter milk with varying somatic cell counts. 2. Component PP3 and beta-casein-1P (f29-105 and f29-107) of the proteose-peptone fraction.

The proteose-peptone fraction was studied to measure proteolysis in 86 samples of quarter milk from 31 cows with subclinical mastitis. The relative content of component PP3 decreased significantly in the total of proteose-peptone as plasmin activity increased, but the content of this component in milk was not correctly correlated with the plasmin activity (r = .52). Electrophoresis, amino acid composition, and sequence analysis showed that the component beta-CN-1P (f29-105/7) of the proteose-peptone fraction was a terminal product of plasmin-like activity and was located correctly electrophoretically. Correlation factors between the plasmin activity and content in milk of component beta-CN-1P (f29-105/7) was very high (r = .87). This component could be used as indicator of the endogenous proteolysis in milk from cows with subclinical mastitis.

Amino Acid Sequence↗
PubMed1995

Health directed and health related dimensions of oral health behaviours of periodontal referrals.

The aim of this study was to investigate attitudes and oral health behaviours of people referred to a specialist periodontal clinic. The method of Ajzen and Fishbein was used to construct a questionnaire to examine the attitudes and the influence of 'important others' associated with the oral health of a consecutive group of 214 first time attenders at a hospital periodontal clinic. The mean age of those investigated was 38.8 (SD 11.2) years. They were predominantly female (66 per cent) and from a higher socioeconomic status group (66 per cent). Significantly more of those in a high oral health behaviour group scored higher for the dental health attitudes--'clean teeth' and 'fresh breath'--and for the 'important other', the dentist. This suggested that two sets of attitudes existed--health related and health directed--and that the dentist was the most salient referent. Principle components analysis demonstrated the dual nature of attitude and suggested that family and friends were also influential 'important others'. This suggested a clash exists between lay and professional dental health perspectives. Clinicians should be aware that patients who are referred for consultations to their clinics arrive with their own strongly held attitudes and beliefs, appearing to value the advice of family as well as that of the dental health professional.

Adult↗
PubMed1994

Quantitative characterization of bovine plasminogen binding to caseins.

The binding of bovine plasminogen to whole casein, alpha s-casein, beta-casein, and kappa-casein is responsible for the progressive proteolysis of milk and dairy products. A sensitive and accurate microparticle-enhanced nephelometric immunoassay was developed to measure free plasminogen after interaction between bovine plasminogen and caseins and the quantitative parameters of plasminogen/casein binding were established. Two classes of binding sites for plasminogen were found in this study on each of the investigated caseins. Their dissociation constants (Kd) were determined by varying the plasminogen concentration at pH 6.6 and performing Scatchard analysis. The two binding sites appeared to be one of high affinity (Kd = 32 nM) and the other of lower affinity (Kd > 370 nM). The number of both binding sites per casein monomer was low (0.04 to 0.53). The great propensity of casein monomers to self-associate in homopolymers where plasminogen binding sites could be hidden and in copolymers present in bovine milk in the form of whole casein micelles accounts for calculated binding sites < 1 per monomer.

Animals↗
PubMed1994

Localized prepubertal periodontitis in a 5-year-old child: investigations and clinical observations over a 3-year period.

A 5-year-old boy presented with persistent generalized gingival inflammation. Clinical and radiographic examination supplemented by immunological and microbiological investigation led to a diagnosis of localized prepubertal periodontitis. The child was subsequently monitored for 3 years and despite treatment there was continued bone loss related to his primary teeth. This case highlights the need for liaison between specialists in paediatric dentistry, periodontology, immunology and microbiology in order to diagnose prepubertal periodontitis and to establish a rational basis for treatment to prevent progression to juvenile periodontitis.

Aggressive Periodontitis↗