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Biomedical subjects

M Lehmann

Publications and source records attributed to M Lehmann.

At least 181 records · Page 10Linked to original sources
PubMed1994

A novel multispecific competitor fragment for quantitative PCR analysis of cytokine gene expression in rats.

Competitive polymerase chain reaction (PCR) is a sensitive method for quantification of cytokine mRNA expression. Co-amplification of an internal standard serves as control for comparing the efficiency of PCR in different samples. We have developed a novel control fragment for multiple analyses of rat cytokine gene expression containing primers for IL-1 beta, IL-2, IL-4, IL-5, IL-6, IL-10, TNF-alpha, TGF-beta 1, IFN-gamma and MIP-2. Additional primers were incorporated to analyse the content of T cells (CD3), activated T cells (CD25) and housekeeping genes (beta-actin and HPRT). As an example we demonstrate analysis of IL-2 mRNA expression in small pieces of kidney tissue obtained from rats after kidney allotransplantation. The IL-2 expression decreased tenfold during treatment with an anti-rat CD4 monoclonal antibody as compared to untreated animals.

Animals↗
PubMed1994

Co-mutagenic effect of tannic acid on ring-X chromosome loss induced by mitomycin C in sperm cells of Drosophila melanogaster.

To investigate the effects of tannic acid (TA) on ring-X chromosome loss, Drosophila melanogaster females exposed to different TA concentrations were crossed with untreated, methyl methanesulfonate (MMS)- or mitomycin C (MMC)-treated males which carried a ring-X chromosome. Progeny were analyzed for loss of the ring-X. The results of this in vivo study showed that TA had no suppressing effect on chromosome loss occurring spontaneously or after induction by MMS in mature spermatozoa. In contrast, TA caused a significant increase in the frequency of MMC-induced ring-X loss. The increase caused by this co-mutagenic effect reached values of 34, 33 and 40% at TA concentrations of 10, 25 and 50 mM, respectively. These increments may reflect the action of TA on a uvrABC-type enzyme which, by increasing the double-strand breaks (DSBs), somehow interferes with the post-replicational repair responsible for the final DSB correction.

Animals↗
PubMed1994

A monoclonal antibody inhibits adhesion to fibronectin and vitronectin of a colon carcinoma cell line and recognizes the integrins alpha v beta 3, alpha v beta 5, and alpha v beta 6.

Using whole viable human colon carcinoma HT29 cells as immunogen, we produced a monoclonal antibody (mAb) termed 69-6-5. The antibody was functionally selected on its anti-cell-spreading activity. By immunoprecipitation of surface radiolabeled cell lysates from HT29-D4 cells (an HT29 cell clone), mAb 69-6-5 recognized a molecular complex resembling integrin heterodimers. Sequential immunodepletions with mAb to the integrin alpha v subunit demonstrated that this complex was composed of alpha v-containing integrins. Accordingly, mAb 69-6-5 reacted with integrin alpha v beta 3 immunopurified from melanoma cells and integrins alpha v beta 5 and alpha v beta 6 immunopurified from pancreatic carcinoma cells. In cell adhesion assays, the 69-6-5 mAb was able to inhibit strongly in a dose-dependent manner arginine-glycine-aspartic acid-mediated adhesion of HT29-D4 cells to vitronectin, fibronectin, or ProNectin F but not to laminin or collagen. Immunoprecipitations with beta chain-specific antisera indicated that these cells express integrins alpha v beta 5 (receptor for vitronectin) and alpha v beta 6 (receptor for fibronectin) but neither alpha v beta 1 nor alpha v beta 3. In summary, these results indicated that mAb 69-6-5 reacts with several alpha v integrins and that it can effectively interfere with the adhesive functions of at least alpha v beta 5 and alpha v beta 6, which represent the major receptors on HT29-D4 cells responsible for their adhesion on vitronectin and fibronectin.

Amino Acid Sequence↗
PubMed1994

Purification and characterization of isoquinoline 1-oxidoreductase from Pseudomonas diminuta 7, a novel molybdenum-containing hydroxylase.

Isoquinoline 1-oxidoreductase, which catalyzes the hydroxylation of isoquinoline to 1-oxo-1,2-dihydroisoquinoline with concomitant reduction of a suitable electron acceptor, was purified from the isoquinoline degrading bacterium Pseudomonas diminuta 7 to apparent homogeneity. The native enzyme was a heterodimer with a molecular mass of 95 kDa consisting of a 16- and a 80-kDa subunit. It contained 0.85 g atom molybdenum, 3.95 g atom iron, 3.9 g atom acid-labile sulfur, 2.1 mol of phosphate, and 1 mol of CMP/mol of enzyme. CMP and phosphate are suggested to originate from molybdopterin cytosine dinucleotide of the pterin molybdenum cofactor. It is assumed that the iron and the acid-labile sulfur are arranged in two (2Fe-2S) clusters. The isoelectric point of the isoquinoline 1-oxidoreductase was within the range of pH 6.2 to 6.8. Cytochrome c, ferricyanide, and several non-physiological electron acceptors served as oxidizing substrates, whereas O2 and NAD were not used. Isoquinoline 1-oxidoreductase revealed a high specificity toward the reducing substrates isoquinoline, 5-hydroxyisoquinoline, quinazoline, and phthalazine. Isoquinoline 1-oxidoreductase was inactivated by methanol, arsenite, p-hydroxymercuribenzoate, 1,10-phenanthroline, and cyanide. Additionally, the enzyme was inactivated upon incubation with its substrates isoquinoline, which slowly inhibited the enzyme in the absence of an electron acceptor, and 5-hydroxy-isoquinoline, which rapidly and very effectively inactivated the enzyme in the presence as well as in the absence of the electron acceptors iodonitrotetrazolium chloride, phenazine methosulfate, or ferricyanide.

Chromatography, Gel↗
PubMed1994

Clinical evaluation of serum tissue polypeptide-specific antigen (TPS) in non-small cell lung cancer.

M3 is an epitope of the tissue polypeptide antigen detectable in the serum by immunoradiometric assay. This epitope is referred to as tissue polypeptide-specific antigen (TPS). We examined the pretreatment TPS level of 160 non-small cell lung cancer (NSCLC) patients and 71 patients who suffered from non-malignant pulmonary diseases. The upper limit of normal values was 140 U/l. Using this cutoff, the sensitivity and specificity were 36 and 90%, respectively. The TPS was significantly higher in NSCLC patients with an advanced stage, a mediastinal lymph node involvement or a poor performance status. This level was significantly higher in the group of patients for whom the disease proved to progress during chemotherapy. In univariate analysis, patients with a high TPS level proved to have a shorter survival than patients with a TPS < or = 140 U/l. In Cox's model analysis, performance status, stage of the disease and serum TPS were the only significant prognostic variables. The low sensitivity of TPS precludes its use for diagnosis. However, the pretreatment TPS level adds information to the management of NSCLC inasmuch as it predicts a low sensitivity to chemotherapy and a poor prognosis.

Adult↗
PubMed1994

Surface distribution of the EGF receptor during differentiation of the human colon carcinoma cell line HT29-D4.

The clone HT29-D4 can be induced to differentiate into enterocyte-like cells, by simply removing glucose from culture medium. In this report, we used the HT29-D4 model to study the membrane segregation of the EGF receptor on epithelial intestinal cells. Differentiated and undifferentiated cells displayed a single class of EGF binding sites with similar dissociation constants. However, differentiation of HT29-D4 led to a 3-fold decrease in the total number of EGF binding sites, while the number of IGF-I binding sites was unchanged. Fifteen percent of EGF receptors present on differentiated HT29-D4 cells were localized in the apical surface, whereas 98% of IGF-I receptors were segregated to the basolateral domain. By covalent cross-linking experiments using 125I-EGF and by immunoprecipitation with an anti-EGF receptor antibody, we have characterized the HT29-D4 EGF receptor as a Mr = 165,000 protein in both differentiated and undifferentiated cells. Apical EGF receptors were functional, as evidenced by their ability to be internalized in response to EGF binding. Thus, intact and functional EGF receptors are present at the apical surface of differentiated HT29-D4 cells, suggesting the presence of EGF receptors on the apical domain of enterocytes.

Adenocarcinoma↗
PubMed1993

Weak magnetic fields change extinction of a conditioned reaction and daytime melatonin levels in the rat.

Altogether 100 albino rats were conditioned to flee after an acoustic stimulus (1000 Hz). During the following retention period (extinction of the reaction), half of the animals (test group) were exposed to a vertically directed, weak and extremely low-frequency magnetic field (10 Hz, 10(-4) T). Under the field's influence, the animals showed an increased retention of conditioned reactions and had an elevated level of serum melatonin compared with the animals of the control group. These effects disappeared when the investigation was performed in the dark.

Acoustic Stimulation↗
PubMed1993

Clinical evaluation of serum tumour marker CA 242 in non-small cell lung cancer.

CA 242, a novel tumour carbohydrate antigen present in serum (upper limit of normal values: 20.0 U ml-1), has been measured in a group of 102 pathologically confirmed non-small cell lung cancer patients. The aim of the present prospective study was to identify any relationship between pre-treatment serum CA 242 level and different features of lung cancer including prognosis. Serum CA 242 was measured using the delayed europium lanthanide fluoroimmunometric assay. Sensitivity and specificity were 28.5% and 95.6% respectively. Its level was significantly lower in squamous cell carcinoma in comparison with non-squamous histologies (adenocarcinoma and large cell carcinoma). The CA 242 level was higher in metastatic disease (median: 15.3 U ml-1) in comparison with non-metastatic (median: 7.9 U ml-1; Mann Whitney U test; P < 0.003), and increased significantly from stage I to stage IV. In 50 patients who underwent chemotherapy, the serum CA 242 level was higher in non-responder patients when compared with responders (median: 16.8 U ml-1 and 9.5 U ml-1 respectively; Mann Whitney; P < 0.02). Univariate analysis of the entire population showed serum CA 242 levels were not related to survival. However, patients with unresectable non-small cell lung cancer and elevated CA 242 level proved to have a significantly shorter survival than those with a CA 242 < 20 U ml-1. In Cox's model analysis, stage of the disease and performance status were the only significant determinants of survival. We conclude that a high level of serum CA 242 (1) is significantly related to the stage of disease, (2) predictive of no response to chemotherapy but seems to add weak prognostic information to stage of disease and performance status, the main prognostic determinants of non-small cell lung cancer.

Adult↗
PubMed1993

Distribution and conservation of sequences homologous to the 1731 retrotransposon in Drosophila.

The distribution of 1731 retrotransposon-hybridizing sequences in the family Drosophilidae has been studied using a 1731 probe from Drosophila melanogaster. Squash blot and Southern blot analyses of 42 species reveal that the 1731 sequences are widespread within both the Sophophora and Drosophila subgenera and are also present in the genera Scaptomyza and Zaprionus. Hence the 1731 retrotransposon family appears to have a long evolutionary history in the Drosophilidae genome. Differences of hybridization signal intensity suggested that the 1731 sequence is well conserved only in the three species most closely related to D. melanogaster (D. simulans, D. mauritiana, and D. sechellia). A survey of insertion sites in numerous different populations of the previous four species by in situ hybridization to polytene chromosomes has shown in all cases both chromocentric hybridizations and a low number of sites (0-5) on the chromosomal arms. This number of sites is among the lowest observed in D. melanogaster and D. simulans when 1731 is compared with other retrotransposon families. In addition, we have observed species-specific patterns of the chromocentric hybridization signal, suggesting rapid modifications of the beta-heterochromatin components since the radiation of the melanogaster subgroup.

Animals↗
PubMed1993

Influence of 6-week, 6 days per week, training on pituitary function in recreational athletes.

The influence on pituitary function of 6 weeks of training on 6 days a week was examined in six recreational athletes. Endurance training on a bicycle ergometer for 31-33 min was performed on 4 days each week at 90-96% (weeks 1-3) and 89-92% (weeks 4-6) of the 4 mmol lactate thresholds determined on day 0 and day 21, respectively, with interval training of 3-5 x 3-5 min in addition on 2 days a week at 117-127% and 115-110%, respectively. Determination of the serum hormone levels and a combined pituitary function test (200 micrograms thyrotropin releasing hormone (TRH), 100 micrograms gonadotrophin-releasing hormone (GnRH), 100 micrograms corticotrophin releasing hormone (CRH), 50 micrograms growth hormone releasing hormone (GHRH)) were made before training, after 6 weeks of training and after another 3 weeks of recovery. Training increased performance at 2 mmol lactate by 25%, at 4 mmol by 12%, and maximum performance by approximately 12%. The releasing hormone-stimulable prolactin, thyroid stimulating hormone (TSH) and somatotrophic hormone (STH) synthesis-secretion capacity remained unchanged, the adrenocorticotrophic hormone (ACTH) was increased after training. Cortisol release was reduced, follicle-stimulating hormone (FSH)-synthesis-secretion capacity was increased after training, and the luteinizing hormone (LH)-synthesis-secretion capacity reduced. This had no influence on base or exercise-induced serum hormone levels (cortisol, aldosterone, insulin, prolactin, FSH, LH, TSH, ACTH, ADH and STH), which showed no dependence on training, except for free testosterone which showed a decreasing trend (P < 0.10) of 19-25% and post-exercise ACTH which showed an increasing trend of 33% (P < 0.10). Conditioning (cortisol sensitivity and ACTH response) or adaptation (FSH and LH responses) to changed testosterone serum levels and altered spermatogenesis is discussed.

Adrenocorticotropic Hormone↗