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W Becker

Publications and source records attributed to W Becker.

At least 127 records · Page 7Linked to original sources
PubMed1996

Bifunctional NHS-BAT ester for antibody conjugation and stable technetium-99m labeling: conjugation chemistry, immunoreactivity and kit formulation.

UNLABELLED: Conjugation chemistry and kit formulated binding of the NHS ester of 6-(4'-(4"-carboxyphenoxy)butyl)-2, 10-dimercapto-2,10-dimethyl-4,8-diazaundecane (NHS-BAT ester) to monoclonal antibodies (MAbs) was investigated. The functionalities of the resulting BAT conjugated and 99mTc-labeled MAbs BW 431/26, MAb 425 and bispecific MDX210 (fragment construct) were tested by immunoreactivity and immunoscintigraphy. METHODS: The kinetics and chemistry of the conjugation reaction were monitored by high-performance liquid chromatography, size-exclusion chromatography and positive fast-atom-bombardment mass spectra (FAB-MS). The 99mTc BAT-MAbs were tested with various immunoreactivity assays. The biodistribution of 99mTc-BAT-BW 431/26 in rats was compared with directly labeled BW 431/26. RESULTS: At pH 8.5 and 25 degrees C, the reactivity of the NHS-BAT ester was high with 90% completion after 30 min. The conjugation yield of 19 microM MAb and 228 microM NHS-BAT ester amounted to 30%. Higher NHS-BAT ester concentrations afforded higher BAT-to-MAb ratios. According to FAB-MS, the conjugation competing hydrolysis surprisingly occurred at the NHS ring. Almost quantitative 99mTc labeling was achieved after 5 min at 25 degrees C. Immunoreactivity of the 99mTc-BAT antibodies showed > 90% recovery and proved to be insensitive to BAT-to-MAb ratios of up to 10. The 99mTc-BAT-BW 431/26 showed similar organ distribution but revealed less urinary excretion compared with the directly labeled BW 431/26. Immunoscintigraphy with 99mTc-labeled and BAT-BW 431/26 and BAT-MAb 425 showed the respective biological function in vivo. CONCLUSION: According to straightforward conjugation chemistry, the ease of 99mTc labeling and the application of a simple ultrafiltration technique, the NHS-BAT ester represents a nondestructive, universally applicable biofunctional ligand to introduce stable 99mTc protein binding sites. Kit formulated conjugation/labeling can be performed with little time requirements and laboratory experience.

Animals↗
PubMed1996

[Detection of antibodies against Neospora caninum in cows on Hessian farms with abortion and fertility problems].

To address the question whether N. caninum-infections occur in German cattle, 388 sera from dairy farms with abortions and fecundity problems in North Hesse were tested for antibodies to N. caninum and seropositive farms epidemiologically analyzed. 16 sera (4.1%) with titres of > or= 1:400 from a total of 10 farms (45.5% of the farms) were considered Neospora-positive. There was a conspicuous clustering of seropositive and indifferent animals in three farms. A history of abortion could not be established for all seropositive cows, a finding which may indicate that some animals mount an immune response that can protect against abortions. The validity of the indirect immunofluorescent assay for the diagnosis of the Neospora caninum-infection of cattle is discussed.

Abortion, Veterinary↗
PubMed1995

Cloning of a novel family of mammalian GTP-binding proteins (RagA, RagBs, RagB1) with remote similarity to the Ras-related GTPases.

cDNA clones of two novel Ras-related GTP-binding proteins (RagA and RagB) were isolated from rat and human cDNA libraries. Their deduced amino acid sequences comprise four of the six known conserved GTP-binding motifs (PM1, -2, -3, G1), the remaining two (G2, G3) being strikingly different from those of the Ras family, and an unusually large C-terminal domain (100 amino acids) presumably unrelated to GTP binding. RagA and RagB differ by seven conservative amino acid substitutions (98% identity), and by 33 additional residues at the N terminus of RagB. In addition, two isoforms of RagB (RagBs and RagB1) were found that differed only by an insertion of 28 codons between the GTP-binding motifs PM2 and PM3, apparently generated by alternative mRNA splicing. Polymerase chain reaction amplification with specific primers indicated that both long and short form of RagB transcripts were present in adrenal gland, thymus, spleen, and kidney, whereas in brain, only the long form RagB1 was detected. A long splicing variant of RagA was not detected. Recombinant glutathione S-transferase (GST) fusion proteins of RagA and RagBs bound large amounts of radiolabeled GTP gamma S in a specific and saturable manner. In contrast, GTP gamma S binding of GST-RagB1 hardly exceeded that of recombinant GST. GTP gamma S bound to recombinant RagA, and RagBs was rapidly exchangeable for GTP, whereas no intrinsic GTPase activity was detected. A multiple sequence alignment indicated that RagA and RagB cannot be assigned to any of the known subfamilies of Ras-related GTPases but exhibit a 52% identity with a yeast protein (Gtr1) presumably involved in phosphate transport and/or cell growth. It is suggested that RagA and RagB are the mammalian homologues of Gtr1 and that they represent a novel subfamily of Ras-homologous GTP binding proteins.

Amino Acid Sequence↗
PubMed1995

Targeting of liver metastases of colorectal cancer with IgG, F(ab')2, and Fab' anti-carcinoembryonic antigen antibodies labeled with 99mTc: the role of metabolism and kinetics.

The aim of this study was to investigate targeting of the liver metastases by directly 99mTc-labeled complete (IgG) and fragmented antibodies [F(ab')2 and Fab'] in relation to their kinetics and metabolic fate. A total of 127 patients with metastatic colorectal cancer were examined [IgG1, BW 431/26 (Behringwerke, Marburg, Germany) n = 50; F(ab')2, F023C5 (Sorin Biomedica, Saluggia, Italy) n = 58; Fab', IMMU-4 (Immunomedics, Morris Plains, NJ) n = 19]. Native monoclonal antibodies (MAbs), serum samples from 10 min to 24 h postinjection (p.i.), and urine were analyzed by gel filtration chromatography. Kinetic data were deduced from whole-body and single-photon emission computed tomographic scans, performed 10 min to 24 h p.i. (region-of-interest technique). In BW 431/26, 96% of injected activity was labeled IgG1; in F023C5, 29% was F(ab')2, and 71% was Fab'; and in IMMU-4, 92% was Fab', and 8% was F(ab')2. Serum half-lives were: IgG1, 36 h (liver uptake predominant); F(ab')2, 16 h; and Fab', 4 h (renal uptake predominant). All MAbs were metabolized, fragments more rapidly than IgG, to low-molecular-weight products and excreted into the urine (e.g., Tc-cystine). In targeting liver metastases, sensitivities were found to be higher for fragments (44.1, 72.5, and 80% for BW 431/26, F023C5, and IMMU-4, respectively) but at significantly lower tumor:background ratios than with IgG (1.78 +/- 0.29 versus 1.29 +/- 0.11 and 1.43 +/- 0.53; P < 0.01). With IgG, there was a continuous tumor uptake over 24 h, whereas with fragments, the maximal uptake occurred mostly within 1 h, with subsequent clearance being slower for antigen-bound activity than for nonspecific background. Hence, diagnosis was possible mostly after 4 h with fragments but often not before 24 h with IgG. These results show that the higher sensitivity of fragments in liver lesion targeting at earlier p.i. times does not rely on an increased antibody uptake but on a more rapid clearance of nonspecific background activity due to faster metabolism and excretion. Intact MAbs show a slow, continuous uptake, leading to higher tumor:background ratios at later p.i. times, often beyond the imaging possibilities of 99mTc.

Carcinoembryonic Antigen↗
PubMed1995

Mutation of two conserved arginine residues in the glucose transporter GLUT4 supresses transport activity, but not glucose-inhibitable binding of inhibitory ligands.

Two arginine residues (RR333/334) in the conserved GRR motif located in the endofacial loop between helix 8 and 9 of the glucose transporter GLUT4 were substituted for leucine and alanine, respectively. Reconstituted glucose transport activity of the construct (GLUT4-RR333/4LA) expressed in COS-7 or LM(TK-) cells was less than 10% of that of the wild-type GLUT4. In contrast, binding of the inhibitory ligand cytochalasin B and glucose-inhibitable photolabeling with IAPS-forskolin were not significantly affected. Exchange of a histidine residue (H337Q) previously believed to be involved in the binding of inhibitory ligands failed to affect any of the investigated parameters. These data suggest that positive charges in the GRR motif at the cytoplasmic surface of the transporter participate in the conformational changes of the carrier protein during the process of facilitated diffusion.

Animals↗
PubMed1995

The contribution of nuclear medicine to the patient with infection.

Nuclear medicine imaging of infection has two major indications: (a) the localization of a focus of infection in patients with fever of unknown origin; in this context the radio-pharmaceutical should be highly sensitive whereas specificity is not so important because subsequent biopsy or morphologically based imaging can be performed; (b) the diagnosis of an infection in patients with localized symptoms, for example after surgery, when normal anatomy is absent or when metal implants prevent computed tomography or magnetic resonance imaging. In these latter cases high sensitivity and to an even greater extent high specificity are mandatory to guide further clinical management (conservative or surgical). All radiopharmaceuticals available to date, such as technetium-99m nanocolloids, gallium-67 citrate, indium-111- and 99mTc-labelled white blood cells, 99mTc-antigranulocyte antibodies, and 99mTc-or 111In-labelled unspecific human immunoglobulin, have different biodistributions and different physical characteristics. The absence of physiological uptake in an organ and the radiation exposure of a patient are reasons to use different radiopharmaceuticals in different clinical situations, adapted to the individual circumstances of the patient.

Citrates↗
PubMed1995

Replacement of maxillary and mandibular molars with single endosseous implant restorations: a retrospective study.

This retrospective report presents findings on 22 patients with 24 implants replacing single molars with implant-supported restorations. Patients with known bruxism habits were not considered for single-molar implant replacement. The patients underwent follow-up for an average of 24 months. The cumulative success rate was 95%, which reflects the loss of one 5 x 6 mm wide implant. Eleven implants were placed in edentulous ridges, and 13 were placed in extraction sockets. Most of the implants were placed in type B and C bone quantity and type 2 and 3 bone quality. All implants were restored on abutments with nonrotating gold cylinders. The occlusion for all restorations was developed to minimize centric contacts and lateral interferences. The frequency of gold retaining-screw loosening was obtained for 21 patients. The gold retaining screws loosened in eight implants between one and three times (38%). No incidence of crown or implant fracture occurred. Within the limits of this study, replacement of single-tooth molars by implant-supported restorations was predictable; however, a high incidence of gold screw loosening was seen.

Aged↗
PubMed1995

G-CSF-stimulated PMN in immunotherapy of breast cancer with a bispecific antibody to Fc gamma RI and to HER-2/neu (MDX-210).

Myeloid cells can mediate tumor cell cytotoxicity via certain receptors for immunoglobulins. Among the different Fc receptors, the high-affinity IgG receptor (Fc gamma RI, CD64) is a promising trigger molecule because it is selectively expressed on effector cells, including monocytes/macrophages and granulocyte colony-stimulating factor (G-CSF)-primed neutrophils. In vitro, a bispecific antibody (BsAb) (MDX-210, constructed by chemically cross-linking F(ab') fragments of monoclonal antibody (mAb) 520C9 to HER-2/neu and F(ab') fragments of mAb 22 to Fc gamma RI) mediated effective lysis of HER-2/neu overexpressing breast cancer cell lines. HER-2/neu (c-erbB2) is overexpressed in approximately 30% of breast and ovarian carcinomas and is a target for immunotherapy in clinical trials. In vitro assays showed Fc gamma RI-positive neutrophils to constitute a major effector cell population during G-CSF therapy. Based on these preclinical data and a preceding study at Dartmouth (New Hampshire) with a single dose of MDX-210 alone, a combination of G-CSF and MDX-210 is tested in a phase I study in breast cancer patients. In this study, patients receiving G-CSF are treated with escalating single doses of MDX-210. This therapy was generally well tolerated by the treated patients, some of whom reacted with fever and short periods of chills, which were temporally related to elevated plasma levels of IL-6 and TNF-alpha. After MDX-210 application, a transient decrease in the total white blood count and absolute neutrophil count (ANC) was observed. During G-CSF application, isolated neutrophils were highly cytotoxic in the presence of MDX-210 in vitro. These data indicate a potential role for G-CSF and BsAb in immunotherapy.

Antibodies, Bispecific↗
PubMed1995

Is there still a need for Tc-99m DMSA renal imaging?

Scintigraphy with Tc-99m MAG3 is, to date, the most commonly used technique for evaluating separate renal function (SRF). In this study, the performance of this technique is compared to Tc-99m DMSA. A total of 37 patients with various kidney disorders (12 children and 25 adults) underwent both Tc-99m DMSA and Tc-99m MAG 3 scintigraphy. In children and adults of normal weight the correlation coefficient between the two methods was 0.99 (P < 0.001), whereas in individuals who were more than 10% overweight according to Broca, or who had abnormal anatomical positions of the kidneys, the correlation coefficient was 0.82 (P < 0.05). Scintigraphy with Tc-99m DMSA was more accurate in renal parenchyma lesions. These results indicate that Tc-99m DMSA scintigraphy is preferable for the evaluation of SRF in patients who are more than 10% overweight, or have abnormal positions of the kidneys.

Adolescent↗
PubMed1995

Comparative assessment of saccadic eye movements, psychomotor and cognitive performance in schizophrenics, their first-degree relatives and control subjects.

This study is aimed at detecting biological markers for schizophrenia. For this purpose, a total of 70 subjects (21 schizophrenic patients, 27 first-degree relatives and 22 controls) performed a series of tests assessing various attentional, psychomotor and cognitive functions and saccadic eye movements. The schizophrenics performed significantly poorer than both high-risk and control subjects in most of the tests demanding attention, concentration and psychomotor speed (d2 concentration test, reaction times and Stroop test of perceptual interference) as well as cognition (Wechsler intelligence scales). On the other hand, these tests did not differentiate between the high-risk and control subjects. This distinction, however, could be made by two other parameters: hypometria score of saccadic eye movements and ratio of verbal to performance intelligence scores. Both parameters were significantly increased in both the schizophrenic and the high-risk group, distinguishing both from the control group. The relevance of these findings in indicating a schizophrenic disposition is discussed.

Adult↗
PubMed1995

Uptake and interconversion of plasma unesterified n-3 polyunsaturated fatty acids by the GI tract of rats.

The origin of the linoleic [18:2(n-6)], arachidonic [20:4(n-6)], and docosahexaenoic acid [22:6(n-3)] of the mucosal phospholipids in the gastrointestinal (GI) tract is not known. This study examines whether stomach, small intestine, and colon take up and desaturate-elongate unesterified polyunsaturated fatty acids (PUFA) from blood. Albumin-bound unesterified alpha-[14C]linolenate [18:3(n-3)] and [3H]eicosapentaenoate [20:5(n-3)] were injected intravenously. After 10 min, 1 h, and 18 h, radioactivity of tissue lipids and the degree of interconversion of the 3H-labeled and 14C-labeled fatty acids were determined. After 10 min, the lipids of the gastrointestinal tract contained 3.6% of the 14C (0.5% in stomach, 2.7% in small intestine, and 0.4% in colon) and 4.9% of the 3H (0.6% in stomach, 3.6% in small intestine, and 0.7% in colon). Both fatty acids were acylated mainly into phospholipids, both in liver and gastrointestinal tract. Although the proportions of radioactivity found in desaturation-elongation products increased with time, 15% of the 14C in the liver, 6% in the stomach, 8% in the small intestine, and 11% in the colon were in 20:5 already after 10 min. A rapid interconversion of 18:3 thus occurred both in the liver and in the gastrointestinal tract. In all tissues examined, interconversion of [3H]20:5 to [3H]22:5 also occurred. Interconversion of unesterified PUFA taken up from blood may be an important source of eicosanoid precursors in the gastrointestinal tract.

Animals↗
PubMed1995

Human demineralized freeze-dried bone: inadequate induced bone formation in athymic mice. A preliminary report.

The purpose of this study was to test the osteoinductive properties of demineralized freeze-dried bone (DFDBA) randomly purchased from four commercial bone banks. Twenty-five (25) milligrams of bone from each of the banks was implanted into the hindquarter muscles of athymic mice. Two samples from each of the banks were compared with samples from the other banks. A total of 16 implants were grafted into 8 mice. Two additional mice served as controls. One mouse received an implantation of deactived human cortical bone matrix (DBM) (negative control). The other mouse received an implant of human bone morphogenetic protein/non-collagenous proteins (hBMP/NCP) infused to surface demineralized human cortical bone (positive control). At 21 days the mice were killed, the hindquarters were photographed, and the tissues were prepared for histologic evaluation. Of the 16 commercial DFDBA implants, 12 were available for histologic evaluation. There was no radiographic evidence of bone formation for the DFDBA implanted mice or the DBM implants. Small bone ossicles were scarcely visible in the hindquarters of the mouse which received the hBMP/NCP infused bone. Histomorphometric analysis was used to determine the percentage of new and dead bone. The bone was measured in pixels. The predominant histologic feature of the DFDBA implants was non-vital bone chips with minimal amounts of new bone. The average amount of non-vital bone ranged from 78.4% to 92.5%. There was no evidence of bone formation for the DBM implants. The average amount of bone for the mouse which received hBMP/NCP was 96%. The results of this pilot study indicate that commercially-available DFDBA induced clinically insignificant amounts of bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗