Biomedical subjects

C Seidel

Publications and source records attributed to C Seidel.

At least 55 records · Page 3Linked to original sources

PubMed1997

Concentration measurement of unpurified proteins using biosensor technology under conditions of partial mass transport limitation.

Using biosensor technology, it is possible to measure protein concentration when the binding of the protein to an appropriate ligand immobilized on the sensor surface is totally limited by diffusion and mass transport, a condition difficult to achieve in practice. In such a case, the observed binding rate does not reflect the intrinsic binding capacity of the molecular partners, but is simply proportional to the concentration of the protein analyte that is introduced in a continuous flow over the ligand. We describe here a more general biosensor method for measuring protein concentration which is applicable to conditions where mass transport is not totally but only partially rate limiting. The proposed method, which is based on measurements at different flow rates, does not require a standard of known protein concentration and can be used with unpurified proteins. The method is applicable to ligand-analyte pairs with an association rate constant as low as 10(3) M-1 s-1 and requires only knowledge of the molecular weight and diffusion coefficient of the analyte. The method was used successfully to measure the concentration of monoclonal antibodies, monoclonal antibody fragments (Fab) obtained by papain cleavage, and recombinant Fab fragments of widely different affinities in crude Escherichia coli extracts.

Amino Acid Sequence↗

PubMed1997

Body growth in primary de Toni-Debré-Fanconi syndrome.

Body growth in nine children with primary de Toni-Debré-Fanconi syndrome was followed from birth to adolescence or adult life. At the time of diagnosis, corresponding to the start of treatment, the median age was 2.3 (range 0.4-13.9) years and height standard deviation score (SDS) was always decreased (median -3.5, range -6.8 to -2.1). Despite continuous electrolyte and bicarbonate supplementation only four patients showed a slight improvement in growth. At the time of the last observation at the age of 17.2 (4.5-20.1) years median height was -4.7 (-5.9 to -1.8) SDS. The median difference between height at last observation and target height was -4.5 SDS. Final height (n = 5) ranged between -1.8 and -5.5 (median -4.3) SDS. The pubertal growth spurt was absent in two children. Metabolic acidosis was identified as a significant growth-retarding factor. Mean serial blood bicarbonate levels and height SDS at the last observation were correlated (r = -0.87, P < 0.01). No correlation was observed between last height SDS and the degree of hypokalemia, hypophosphatemia, or hypercalciuria. In conclusion, patients with primary de Toni-Debré-Fanconi-syndrome present severe growth failure at the time of diagnosis which persists into adult life. Supportive therapy is frequently unable to prevent further loss of relative height.

Adolescent↗

PubMed1996

Hepatocyte growth factor and its receptor c-met in multiple myeloma.

We have examined whether the hepatocyte growth factor (HGF)/c-met receptor-ligand pair is expressed in freshly isolated and highly purified myeloma cells and whether HGF can be found in the sera of myeloma patients. Myeloma cells were purified with an immunomagnetic method using the syndecan 1-specific antibody B-B4. HGF and c-met mRNA in these cells were examined by reverse transcriptase-polymerase chain reaction (RT-PCR). HGF and c-met proteins were detected by enzyme-linked immunosorbent assay (ELISA) and Western blot, respectively. Serum from 13 myeloma patients was obtained at diagnosis and the levels of HGF were determined by ELISA. HGF and c-met mRNA were expressed in all examined samples (n = 7). HGF was detected in the supernatants of 17 of 20 primary cultures of myeloma cells, whereas bone marrow mononuclear cells from normal controls did not produce detectable amounts of HGF (n = 3). The mean HGF level in serum of myeloma patients at diagnosis was more than fourfold higher than the mean level in normal controls. Possible implications of HGF/c-met expression for the pathophysiology of multiple myeloma are discussed.

Bone Marrow↗

PubMed1996

Plant glyoxysomal but not mitochondrial malate dehydrogenase can fold without chaperone assistance.

Glyoxysomal (gMDH) and mitochondrial malate dehydrogenase (mMDH) from watermelon are synthesized as higher molecular weight precursor proteins. By overexpressing the precursor forms as well as the mature subunits with a histidine arm at the carboxy-terminus, it has been possible to purify relatively large amounts especially of the glyoxysomal precursor protein for studies of their refolding capacities after denaturation with guanidinium hydrochloride, heat or low pH. Glyoxysomal MDH and its precursor is capable of its spontaneous folding over a wide range of temperature conditions. Refolding can be enhanced by inclusion of BSA and ATP as stabilisers in the folding buffer. The N-terminal transit peptide of gMDH facilitates folding, but does not function as an intramolecular chaperon. Chemically denatured mitochondrial MDH requires chaperones for refolding. GroEL/GroES/ATP increase the yield and rate of watermelon mMDH folding dramatically while GroEL and Mg-ATP alone are not sufficient to provide folding assistance similar to the results with hydrophobic mammalian mMDH. The watermelon glyoxysomal MDH interacts with GroEL-like hydrophilic mammalian cytoplasmic MDH, a binding which has to be released by Mg-ATP before spontaneous folding can ensue. Interestingly, watermelon mMDH exhibited a much higher heat stability than gMDH or mammalian mMDH in the presence of BSA/ATP as well as GroEL/GroES/ATP. The differences between glyoxysomal and chaperone-assisted mitochondrial folding patterns are discussed.

Adenosine Triphosphate↗

PubMed1996

Differentiated vascular myocytes: are they involved in neointimal formation?

The role of differentiated vascular myocytes are neointimal formation in canine carotid artery was investigated. Using antibodies and cDNA probes, cells were characterized in situ and after isolation. In situ characterization indicated the majority of medial cells expressed both smooth muscle myosin and alpha actin but many cells were negative to these markers. All adventitial cells were negative for these proteins. The muscle protein-positive cells were designated differentiated, vascular myocytes (VSMC). The others were designated type 2 cells. Sequential enzyme digestion from lumenal surface yielded VSMC ( > 90%) while digestions from the adventitial surface yielded type 2 cells ( > 90%). VSMC were viable in culture but did not spread, proliferate, or alter expression of muscle proteins. Type 2 cells proliferated and increased their expression of muscle actin but did not express muscle myosin. Characterization of neointimal cells from injured carotid arteries indicated they were morphologically and immunologically identical to cultured type 2 cells. We concluded that: (a) canine carotid artery media consists of a heterogeneous cell population: (b) serum does not stimulate isolated VSMC to undergo phenotypic modulation or proliferate: and (c) type 2 cells may be responsible for neointimal formation because they proliferate and acquire a phenotype identical to in situ neointimal cells.

Actins↗

PubMed1996

Human thyroglobulin reference material (CRM 457). 1st Part: Assessment of homogeneity, stability and immunoreactivity.

This paper describes the assessment of the homogeneity and stability of a purified and lyophilized human thyroglobulin (Tg), and characterizes its immunoreactivity. The purified and lyophilized Tg is intended to be used as a primary reference material to establish calibration of working serum based reference material. The programme involved the participation of 15 European laboratories and one laboratory from the United States. The homogeneity of the content of the ampoules was considered acceptable (< 9%). The stability was tested by accelerated temperature degradation showing predicted annual relative losses of 0.01% at -70 degrees C and 1.04% at -20 degrees C. The immunoreactivity of the Tg material as measured in different laboratories varied mostly according to the method used rather than the laboratory. The interlaboratory variability showed that the two commercial methods used in several laboratories (kit 1 and 2) had an interlaboratory variation (CV) of 15.9% (N = 5) and 7.1% (N = 3), respectively, whereas the total interlaboratory CV was 64.3% (N = 18). The immunoreactive Tg had dilution curves parallel with other Tg calibrators (those of the methods). Dilution curves of the Tg material after storage at various temperatures and time were parallel in both RIA and IRMA. In conclusion, we have prepared a Tg reference material which in extensive studies in several participating laboratories has demonstrated a sufficient homogeneity and stability as well as dilution curves parallel to the calibrators of all the immunoassays tested in the study. This reference material is considered the first step towards decreasing the interlaboratory variability between Tg immunoassays.

Drug Stability↗

PubMed1996

Human thyroglobulin reference material (CRM 457). 2nd Part: Physicochemical characterization and certification.

This report describes the characterization of a purified human thyroglobulin (Tg) reference material, and details the procedures used in its certification. The purified Tg is intended to be used as a primary reference material to establish calibration of working serum based reference material for immunoassay procedures. The programme involved the participation of 15 European laboratories and one laboratory from the United States. The physicochemical characterization showed by polyacrylamide gel electrophoresis and immunoblotting that the purified Tg had for the major part the expected molecular size of 660 kDa with traces of lower molecular forms. The amino acid composition was close to that demonstrated for the cDNA and the content of iodine was in keeping with a moderately to highly iodinated Tg. The mass concentration in reference material RM 457 is certified to be (0.324 +/- 0.018) g/L on the basis of protein determined by the Lowry method and supported by nitrogen determination, absorbance measurement, and amino acid analysis. This reference material is considered the first step towards decreasing the interlaboratory variability between Tg methods of measurement.

Amino Acids↗

PubMed1995

Pre-pubertal growth in the hyperprostaglandin E syndrome.

Pre-pubertal body growth was followed in eight children with the hyperprostaglandin E syndrome (neonatal Bartter syndrome) treated with indomethacin over a period of 5-12 years. When corrected for prematurity, the general growth pattern was normal, with the exception of a child with delayed therapy. From the first observation (usually at birth) to the start of indomethacin, the mean height standard deviation score (SDS) corrected for prematurity changed from -0.2 to -2.8. During the first 2 years of therapy rapid catch-up growth occurred, followed by a slow adaptation of the growth pattern to that of healthy children born at term. At last observation the mean corrected height SDS was -0.5 (range -1.9 to +0.9) and the mean target height -0.9 SDS (range -1.8 to +0.1). Weight, body mass index and bone maturation also reached the normal range. No correlation was found between height SDS per year and serum potassium levels or calcium excretion. We conclude that under indomethacin treatment long-term skeletal growth of children with the hyperprostaglandin E syndrome is similar to that of other preterm children.

Bartter Syndrome↗

PubMed1995

[Disordered cutaneous microcirculation in diabetic neuropathic foot ulcer. Is modification by retrograde transvenous perfusion therapy possible?].

Due to the high risk of amputation they involve, diabetic neuropathic plantar ulcers (DNPU) must be regarded as a late manifestation/complication of diabetes mellitus. The suspected cause of these ulcers--disturbed cutaneous microcirculation--was studied by simultaneously measuring laser-Doppler flux (LDF) and cutaneous oxygen tension (pCUO2) in 14 patients with DNPU at three differently affected sites (dorsal forefoot, ulcer edge, lower leg). Dynamic tests (arterial occlusion, local hyperthermia) as a measure of vascular reactivity showed significantly reduced pCUO2 parameters coinciding with elevated LDF values. This reflects a shift of blood flow from the nutritive capillaries towards deeper vessels. Abolition of normal vasoconstriction in the arteriovenous shunt vessels by diabetic polyneuropathy is the assumed cause of increased AV perfusion, with a consequent rise in LDF values. In a subgroup of the above patients (n = 7) undergoing daily intravenous retrograde perfusion therapy (RVP) over 10 days several basic and dynamic microcirculatory functions were studied before and after this treatment. This subgroup showed on the forefoot and the lower leg a remarkable improvement of the microcirculatory parameters investigated, suggesting a better oxygen supply to the tissues after RVP therapy.

Adult↗

PubMed1995

Isolation of atypical mycobacteria from tap water in hospitals and homes: is this a possible source of disseminated MAC infection in AIDS patients?

Infections caused by mycobacteria other than tuberculosis (MOTT), especially Mycobacterium avium complex (MAC), are common in AIDS patients, but rare in immunocompetent persons. The route of transmission is unknown, but tap water could provide a possible source of infection: MAC was isolated from tap water in the U.S.A. but this has not been reported in Germany. We therefore investigated tap water in Berlin for the presence of mycobacteria and compared radiometric (Bactec) and standard plate culture methods processing large volumes of water samples. The Bactec method yielded equal results compared to standard methods but had the advantage of easy handling. Mycobacteria were isolated from 50/118 (42.4%) samples and from 21/30 (70%) sites. The most frequently isolated species was Mycobacterium gordonae (from 28% samples and from 53.3% sites); MAC was isolated from two samples only (1.7%).

AIDS-Related Opportunistic Infections↗

PubMed1995

Kringle 4 of human apolipoprotein[a] shares a linear antigenic site with human catalase.

Monoclonal antibody (mab) 1A2, directed against human apolipoprotein[a] (apo[a]), revealed a strong reaction with peroxisomes as shown by immuno-gold labeled cryosections of human liver biopsies. This reactivity was not due to the presence of apo[a] in peroxisomes but to a cross-reactivity of mab 1A2. Immunoblot analysis of peroxisomal fractions and purified human catalase demonstrated that mab 1A2 reacts with catalase. Conversely, an anti-catalase antibody also recognized apo[a]. By sequence comparison we identified a 4-amino acid motif (Y-Y-P-N) that is shared between the highly repetitive kringle 4 motif of apo[a] and the carboxy-terminal third of the peroxisomal marker enzyme catalase. No other identical sequences were identified in these proteins. Results from the following experiments indicated that 1A2 recognizes this short linear epitope. i) Mab 1A2 reacted only with the 4 amino acid peptide sequence in a pin-ELISA using immobilized overlapping peptides. ii) A synthetic peptide including this sequence completely inhibited the 1A2 immunoreactivity to apo[a] and catalase. iii) A recombinant fusion protein tagged with the putative epitope was recognized by mab 1A2. Our findings demonstrate that unknown linear epitopes in native proteins can be identified by sequence comparison between known proteins. The practical implication is that antibodies against apo[a] must be controlled for this cross-reactivity before using them for immunohistochemical studies of intracellular apo[a] in tissues or cells.

Amino Acid Sequence↗

PubMed1995

Influx of antibiotics into diabetic legs with plantar ulcerations: regional and systemic Netilmycin levels compared after retrograde-venous and systemic-venous application.

Retrograde venous perfusions (RVP) of antibiotics were proven to be therapeutically more effective than systemic venous infusions (SVI) in patients with infected diabetic neuropathic plantar ulcers (DNPU: no additional macronagiopathy of leg arteries). In order to study some pharmakokinetic features of RVP application paratibial tissue levels of Netilmycin (NL; from suction blister fluid) and cubital venous NL were compared under each SVI and RVP therapy in 8 patients with DNPU. Tissue (11.6 +/- 6.4 micrograms/l) were significantly higher (p < 0.001) an within the therapeutic range after RVP (SVI: 4.31 +/- 1.68). In ulcer transsudate (RVP only; n = 4) NL mounted to 36.4 +/- 11.6 microgram/ml. Peak and base NL in cubital blood were within the normal range for both SVI and RVP (no significant difference). The date indicate that RVP is superior to SVI application of Netilmycin (and probably other antibiotics) as surmounting the damaged microcirculation in DNPU to achieve effective drug levels in the target tissue.

Aged↗

PubMed1994

[Therapeutic superiority of regional retrograde venous antibiotic pressure infusion versus systemic venous infusions in diabetic patients with infected neuropathic plantar ulcers].

Since systemic treatment of neuropathic plantar ulcers in diabetics (DNPU) has so far been rather ineffective, recent reports of successful management of DNPU by short-term retrograde transvenous leg perfusion (RVP) by South American angiologists encouraged us to apply this treatment method in diabetics suffering from chronic DNPU. Hence, in a prospective comparative clinical trial started in 1989 we have treated 45 male diabetics suffering from DNPU with the same daily doses of netilmycin, administered either in systemic venous infusions (SVI: n = 21, three times/day) or in RVP (n = 24, once/day). After 10 consecutive days of treatment, ulcers had closed in 8 of the 24 patients treated with RVP, as against 3 of the 21 treated with SVI. Diminution of the ulcer area by > 30% including full debridement was achieved in 10/24 of the RVP cases (SVI: 4/21). During 6 months of follow-up, amputation of toes or forefoot was necessary in only 1 patient in the RVP group, but in 4 in the SVI group. Partial restitution of osteolytic damage was observed in some cases after RVP. Our results show that regional netilmycin therapy given by the RVP procedure is clearly superior to equal netilmycin doses administered by SVI for the treatment of DNPU. RVP can be recommended in DNPU, particularly when the ulcers are complicated by infections.

Adult↗

PubMed1994

Disturbances of cutaneous microcirculation in patients with diabetic legs: additional parameters for a new therapeutic concept?

To study disturbed microcirculation involved in the pathogenesis of diabetic neuropathic plantar ulcers (DNPU), we recorded dynamic changes in laser-Doppler flux (LDF) and cutaneous oxygen tension (pcuO2) caused by short-time arterial occlusion and local heating at three different sites (forefoot, ulcer edge, lower leg) in patients (n = 14) with DNPU and healthy controls (n = 18). Significantly reduced dynamic pcuO2 parameters coincided with a significant increase of flux in the patient group. This post-stimulatory "hypoxic hyperemia" indicates a shifting of blood flux, reducing circulation of the nutritive capillaries comparable to an internal "steal effect". This may predispose to the development of DNPU when additional stresses influence the initial borderline balance, characterized by similar pcuO2 and increased flux values compared to controls. Abolishment of normal vasoconstriction in the shunt vessels by diabetic polyneuropathy is the assumed cause of increased arteriovenous perfusion and therefore raised flux values. Non-invasive testing of microcirculatory functions demonstrates characteristic disturbances in DNPU patients and could be used as additional parameters for new therapeutic concepts as the intravenous retrograde perfusion (RVP). After RVP therapy, applied to a subgroup (n = 7) of the patients, some dynamic microcirculatory parameters improved, allowing a preliminary quantitative evaluation of a therapeutic regimen.

Adult↗

PubMed1993

Pharmacokinetics of recombinant human erythropoietin applied subcutaneously to children with chronic renal failure.

The single-dose pharmacokinetics of recombinant human erythropoietin (rHuEPO) given SC was investigated in 20 patients aged 7-20 years at different stages of chronic renal failure. In a pilot study we confirmed the lower bioavailability of the drug in 2 children when given SC compared with the IV route (24% and 43%, respectively). Following administration of 4,000 units/m2, rHuEPO SC effective serum erythropoietin concentrations increased from a mean baseline level (+/- SD) of 23 +/- 13 units/l to a mean peak concentration of 265 +/- 123 units/l, which was reached after 14.3 +/- 9.4 h, followed by a slow decline until baseline values were attained at 72 h. Mean residence time was 30 +/- 9 h and mean elimination half-time 14.3 +/- 7 h. The single-dose kinetics of SC rHuEPO in children with different degrees of renal failure are comparable to those in adult patients. Possibly, the higher efficacy of SC rHuEPO in patients with renal anaemia compared with IV rHuEPO is related to its prolonged action.

Adolescent↗

PubMed1993

Body growth in urinary tract malformations.

Body height and height velocity were analysed in 54 children with obstructive urinary tract malformations over a mean period of 8.7 years, using new auxological methods. At the time of diagnosis, 9% of patients had a height of more than 2 standard deviations below the normal mean. Mean relative height changed significantly from the first to the last observation, the standard deviation score (SDS) increasing from -0.16 to +0.36 in patients with hydronephrosis compared with normal children (P < 0.05) and from -0.63 to +0.02 SDS in those without hydronephrosis (P < 0.005). The pathogenesis of the described growth disturbance is not clear. Stepwise multiple regression analysis pointed to a possible link between the duration of antibiotic treatment and the recovery of growth capacity, but improved growth could not clearly be attributed to any medical or surgical treatment. The synchronized average growth velocity curve was similar to that of healthy children and showed a normal pubertal spurt. Final height and target height calculated from parents' height differed only slightly from that of the normal population.

Adolescent↗

PubMed1993

Electronic effects on the fluorescence of tyrosine in small peptides.

It is shown for a series of tyrosine-derivatives and tyrosine-containing peptides that the amide group in combination with electron-withdrawing substituents quenches the fluorescence of the phenol moiety. The ammonium group has the strongest electron-withdrawing effect and thus the largest influence on the quenching rate. The peptide group itself does not quench the fluorescence. In a series of peptides with an increasing number of alanines the decreasing quenching efficiency of the peptide group due to the greater distance of the ammonium group is demonstrated. In tyrosine-containing di- and tripeptides a linear correlation between the 13C-NMR chemical shift delta of the C alpha atom of various aliphatic amino acids and the fluorescence-quenching constant confirms the hypothesis that electron-withdrawing and -donating groups are modulating the fluorescence-quenching efficiency of the peptide group. In small peptides the fluorescence lifetime of tyrosine is characteristic for the neighboring amino acids. Using model substances the redox properties of a peptide group and the phenol ring were studied electrochemically. The highest occupied molecular orbital of the tyrosine (1.4 V vs saturated calomel electrode [SCE]) and the lowest unoccupied molecular orbital of the peptide group (-3.12 V vs SCE) have appropriate energies for a photoinduced electron transfer reaction. For solute-quenching experiments quencher molecules can be systematically selected.

Amino Acid Sequence↗

PubMed1993

[Systemic infusion therapy versus retrograde intravenous perfusion: comparative results in patients with diabetic neuropathic plantar ulcer].

Concerning the resistance of diabetic neuropathic plantar ulcers (DNPU) against systemically applied drugs, the "Retrograde Venous Perfusion" (RVP) was introduced as a therapeutic alternative by C. P. Ferreira in 1988. An isotonic saline solution containing gentamycin, buflomedil, dexamethasone, heparin and lignocain is injected into a dorsal foot vein under arterial occlusion of the lower leg. In the present study RVP treatment was done in 20 patients with DNPU and the results were compared to a group treated with systemic intravenous infusions (SVI; n = 20). After 10 days of treatment, 8 out of 20 ulcers were closed (SVI: 4). In 9 ulcers (SVI: 4) size had diminuted by > 30%. Non responders were not observed under RVP in contrast to SVI (7/20 cases). In 4 of 5 patients with osteolytic bone lesions (SVI: 0/7), partial restoration was observed. Rate of toe amputation dropped to 0% (SVI: 20%). Considering the striking differences between either regimen, RVP can be recommended for treatment of DNPU especially when complicated by osteomyelitis.

Adult↗