Stable one-step technetium-99m labeling of His-tagged recombinant proteins with a novel Tc(I)-carbonyl complex.

We have developed a technetium labeling technology based on a new organometallic chemistry, which involves simple mixing of the novel reagent, a 99m Tc(I)-carbonyl compound, with a His-tagged recombinant protein. This method obviates the labeling of unpaired engineered cysteines, which frequently create problems in large-scale expression and storage of disulfide-containing proteins. In this study, we labeled antibody single-chain Fv fragments to high specific activities (90 mCi/mg), and the label was very stable to serum and all other challenges tested. The pharmacokinetic characteristics were indistinguishable from iodinated scFv fragments, and thus scFV fragments labeled by the new method will be suitable for biodistribution studies. This novel labeling method should be applicable not only to diagnostic imaging with 99mTc, but also to radioimmunotherapy approaches with 186/188 Re, and its use can be easily extended to almost any recombinant protein or synthetic peptide.

Characterization of an epithelial and a tumor-associated human small cell lung carcinoma glycoprotein antigen.

The small cell carcinoma (SCC) antigens recognized by LAM2 and LAM8 antibody were characterized by comparison of their tissue expression and analysis of their biochemical composition. LAM2, but not LAM8 antigen could be demonstrated in lipid extracts of SCC cells. By immunohistochemical staining the SCC antigen LAM2 was shown to be an epithelial type membrane antigen. Immunoblotting experiments and competition solid phase radioimmunoassays showed LAM2 antigen to be a native conformation of a glycoprotein with major bands at Mr 100,000-120,000 and a minor band at Mr 210,000. L-Fucose was a dominant part of the epitope which appeared to be closely related to the carbohydrate epitope of the blood group antigen H(O). The tumor-associated membrane antigen LAM8 was shown to be a glycoprotein with major bands at Mr 90,000-135,000 and a minor band at Mr 200,000. Neuraminic acid was the predominant part of the carbohydrate epitope. LAM8 antibody recognized a structure in the saliva of Lea positive probands, but untreated and neuraminidase-treated SCC extracts were unreactive with anti-Lea antibody. Anti CA 19-9 (sialo-Lea antigen) and LAM2 antibodies did not compete for LAM8 binding in direct radioimmunoassays. The sialo-GP90-135 antigen recognized by LAM8 antibody therefore is likely to represent a novel tumor antigen.

Tumor-associated membrane sialoglycoprotein on human small cell lung carcinoma identified by the IgG2a monoclonal antibody SWA20.

A mouse IgG2a monoclonal antibody, SWA20, defining a tumor-associated cell surface antigen on small cell carcinoma of the lung (SCC) was generated. The reactivity of the antibody with cell lines was examined by indirect immunofluorescence staining and solid phase radioimmunoassay and the reactivity with tissues by immunoperoxidase staining. The antibody reacts with a proportion of small cell carcinoma cell lines (4 of 8) and tissues (7 of 12), but not with other pulmonary or extrapulmonary cell lines (0 of 30) or tumor tissues (0 of 78). The antibody was unreactive with primary cultures of normal bronchial epithelial cells, RBC, and WBC. Immunoperoxidase staining of normal tissues showed rare antigen-positive cells in suprabasal layers of bronchial epithelium and less than 10% of positive cells in colon epithelium. Immunoblots of SCC extracts demonstrated antibody reactivity with a doublet band at Mr 40,000, a broader band at Mr 100,000, and a band at Mr 180,000. The antigen was not present in crude lipid extracts of SCC cells. Solid phase radioimmunoassays and immunoblots showed binding competition with the lectin Triticum vulgaris, sensitivity of the antigen to neuraminidase, and a partial sensitivity to treatment with periodate. The antigen was coexpressed on SCC cell lines with the antigen sGP90-135 defined first by antibody LAM8 (R. Waibel, C. J. O'Hara, and R. A. Stahel. Cancer Res., 47:3766-3770, 1987) but differed from it by lack of reactivity with Lea-positive saliva and partial resistance to periodate treatment. There was no binding competition between radiolabeled antibodies SWA20 and LAM8 to SCC target cells. The IgG2a antibody SWA20 identifies a previously undescribed tumor-associated surface membrane antigen, sGP100, expressed selectively on a proportion of SCC.

Imaging and therapy of small cell carcinoma xenografts using 131I-labeled monoclonal antibody SWA11.

The IgG2a monoclonal antibody SWA11 has been evaluated as a radioimmunotherapeutic agent for use in the treatment of small cell cancer of the lung. This antibody was initially selected for in vivo localization studies in a nude mouse model system because of its high affinity for the SW2 small cell cancer cell line in vitro. Following i.v. injection of 125I labeled antibody into nude mice bearing SW2 xenografts good selective accumulation was observed with 10.5% of injected material/g of tumor. The level remained constant from day 2 to day 4 following injection. At day 4 the tumor:blood ratio was 7:1 and tumor:liver, tumor:kidney, and tumor:lung ratios were 17:1, 24:1, and 12:1, respectively. Initial radioimmunotherapeutic studies performed on established small cell cancer of the lung xenografts have shown reduction in tumor burden following a single injection of 300 microCi of 131I labeled SWA11 with no evidence of regrowth up to day 34 postinjection. Histological evaluation of treated tumors revealed large areas of necrosis and extensive fibrosis. A few residual cells of tumor origin could be observed and these displayed atypical morphology. The clonogenic potential of such cells remains to be determined by long term observation.

CD24, a signal-transducing molecule expressed on human B cells, is a major surface antigen on small cell lung carcinomas.

Cell lines derived from human small cell carcinoma of the lung express high levels of a surface polypeptide termed the cluster-w4 antigen, which was previously identified as a potential target for toxin-based immunotherapy of lung cancer. We have cloned a complementary DNA encoding the cluster-w4 antigen from COS-1 fibroblasts transfected with a SW2 small cell carcinoma library, by panning with a mixture of the cluster-w4-specific monoclonal antibodies SWA11, SWA21, and SWA22. The sequence of the cluster-w4 complementary DNA encodes an unusually short (80-amino acid) protein identical to that recently reported for the leukocyte activation molecule CD24 except for a single valine-alanine substitution due to a single-base polymorphism within the region of the gene coding for the extracellular domain. Biochemical analyses of the cloned cluster-w4 antigen confirmed both the presence of the phosphatidylinositol tail and the extensive glycosylation reported for the CD24 molecule. Furthermore, the cloned cluster-w4 antigen expressed on COS cells was shown to react with a comprehensive panel of CD24-specific monoclonal antibodies, as assessed by indirect immunofluorescence staining. Northern blot hybridization indicated the presence of several transcript sizes for the cluster-w4 antigen that were greatly overexpressed in small cell carcinoma cell lines, compared with normal hemopoietic cells and CD24-positive cell lines. Southern blot hybridization of restriction digests of genomic DNA identified a complex pattern of bands consistent with either a complex gene structure containing many exons or the presence of a family of closely related genes.

High thermal stability is essential for tumor targeting of antibody fragments: engineering of a humanized anti-epithelial glycoprotein-2 (epithelial cell adhesion molecule) single-chain Fv fragment.

The epithelial glycoprotein-2 is abundantly expressed on many solid tumors and is a suitable target for antibody-based therapy. In the present study, an antiepithelial glycoprotein-2 single-chain Fv (scFv) was derived from the hybridoma MOC31 by phage display. Despite its high affinity (KD = 3.9 x 10(-9) M), however, this antibody fragment failed to significantly enrich at lung tumor xenografts in mice, mostly because of its insufficient thermal stability. To overcome this limitation, the antigen-binding residues of the MOC31 scFv fragment were grafted onto the framework of the highly stable and well-folding anti-c-erbB2 scFv 4D5. Further modification of the resulting 4D5 MOC-A, which was performed by transferring eight additional residues of the heavy chain variable domain core of the parent MOC31 antibody, produced 4D5 MOC-B, resulting in increased serum stability at 37 degrees C and also significantly improved expression behavior while retaining the antigen specificity and affinity of the parent MOC31 scFv. In mice, the scFv 4D5 MOC-B, which was radiolabeled with 99mtechnetium using a new histidine-tag specific labeling method (Waibel et al., Nature Biotechnol., 17: 897-901, 1999), showed favorable blood clearance and efficient enriches at lung tumor xenografts, with a tumor:blood ratio of 5.25 and a total dose of 1.47% injected dose per gram after 24 h. Biophysical properties such as high thermal stability are thus decisive for whether these molecules are useful in vivo, and our approach may provide a general strategy to solve this problem. This is also the first report of using a humanized anti-EGP-2 scFv in vivo for targeting solid tumors, which is a promising targeting moiety for the diagnostics and therapy of EGP-2-positive tumors in patients.

Monoclonal antibody SEN7 recognizes a new epitope on the neural cell adhesion molecule present on small cell lung cancer but not on lymphocytes.

In our continuing attempt to select monoclonal antibodies for immunotargeting of small cell lung carcinoma (SCLC) we have developed the IgG1 murine antibody SEN7 which by immunofluorescence stained all SCLC cell lines tested. On frozen tumor section six of seven SCLCs were positively stained. The reactivity of this antibody in a series of lung tumors and on normal tissues has some similarities with cluster 1 antibodies and cluster w4 antibodies, as defined by the First and Second International Workshop on Lung Cancer Antigens [P.C.L. Beverley, Y. Olabrian, J.A. Ledermann, L.G. Bobrow, and R.L. Souhami, Br. J. Cancer, 63 (Suppl): 10-19, 1991], particularly with regard to staining of neuroendocrine tissues. The similarities in staining of neuroendocrine tissues between antibody SEN7 and cluster 1 and cluster w4 antibodies prompted us to examine the binding of SEN7 with transfectants expressing the respective antigens. On the murine lymphoma cells B-9, stably transfected with a complementary DNA clone coding for an M(r) 140,000 isoform of human SCLC neural cell adhesion molecule (NCAM), antibody SEN7 reacted positively whereas the cluster w4 antibody was negative. The reaction of antibody SEN7 with the NCAM transfected murine lymphoma cells was unexpected in view of its lack of binding to peripheral blood mononuclear cells which regularly stain positive with NCAM antibodies. Western blotting of a renatured SCLC extract revealed a strong band around M(r) 180,000 in contrast to other cluster 1 antibodies which recognized a broad polydisperse band with a molecular weight of 140,000 to 210,000. Antibody binding was sensitive to tunicamycin treatment, suggesting the epitope to reside on an N-linked carbohydrate structure. No significant competition for SEN7 binding on SCLC cells was seen with other NCAM antibodies against the three distinct epitopes described on SCLC. This finding together with the lack of staining of peripheral blood mononuclear cells and the selected reactivity with the M(r) 180,000 band of NCAM indicate the antibody SEN7 recognizes an epitope on NCAM which has not been described previously. Biodistribution studies with radiolabeled SEN7 in nude mice bearing s.c. SCLC xenografts demonstrated the selective localization of more than 30% of the total injected dose per g tissue at day 4 following i.v. injection. The homogeneous binding to SCLC, the lack of binding to peripheral blood mononuclear cells, and the favorable tumor localization in a xenograft model indicates that SEN7 is a good antibody for immunotargeting of SCLC.

Cytotoxic murine monoclonal antibody LAM8 with specificity for human small cell carcinoma of the lung.

The reactivity of the murine immunoglobulin monoclonal antibody LAM8 directed against a membrane antigen of human small cell carcinoma (SCC) of the lung was investigated on human cell lines and tissues. Indirect immunofluorescence staining, radioimmunoassays, and cytotoxicity assays showed LAM8 antibody to selectively react with SCC but not with non-SCC lung cancer cell lines and extrapulmonary tumor cell lines. Unlike other SCC antibodies, including those we have previously described, highly preferential reactivity with SCC tissues was also demonstrated by immunoperoxidase staining of deparaffinized formalin-fixed tissue sections. Membrane and cytoplasmic staining was seen in of 9 of 12 SCC tissues. No significant staining was seen in non-SCC lung cancer and a wide range of other tumors, including mesothelioma and bronchial carcinoids. Significant LAM8 reactivity was also absent in normal tissues of all major organs. Few tumors and epithelial tissues, including bronchial epithelium had rare LAM8 positive cells which were always less than 2% of the entire cell population. In vitro treatment with antibody and human complement was highly cytotoxic to SCC cells, but had not effect on bone marrow progenitor cells. Immunoblotting of membrane extracts separated on sodium dodecyl sulfate-polyacrylamide gels showed the LAM8 antigen to have a band of an approximate molecular weight of 135,000 and a cluster of bands with approximate molecular weights of 90,000. This reactivity was lost after incubation of the extracts with periodate. LAM8 antibody shows a highly preferential reactivity with SCC cell lines and formalin-fixed paraffin-embedded SCC tissues and is selectively cytotoxic to cells expressing LAM8 antigen.

Pharmacokinetics of morphine and its glucuronides after intravenous infusion of morphine and morphine-6-glucuronide in healthy volunteers.

Steady-state pharmacokinetics of morphine and morphine-6-glucuronide (M-6-G) after intravenous administration of either morphine or M-6-G were determined in healthy volunteers. With a dosing regimen calculated on the basis of data obtained in a first series of experiments in four subjects (morphine: intravenous loading dose of 0.24 mg/kg for 5 minutes and an intravenous infusion of 0.069 mg.kg-1.hr-1 for 4 hours; M-6-G: loading dose of 0.011 mg/kg for 5 minutes and an infusion of 0.006 mg.kg-1.hr-1 for 4 hours), it was possible to yield plasma concentrations of morphine and M-6-G in another four subjects close to predefined targeted levels (35 and 45.5 ng/ml morphine and M-6-G, respectively). This dosing regimen may be used in further pharmacodynamic studies to compare the analgesic effects of morphine and M-6-G. In addition, metabolite kinetics of M-6-G were calculated as a function of time with use of a linear systems approach to the estimation of rate and fraction of morphine glucuronidation to M-6-G.

Cytochemical detection of hyaluronidase activity in single human and mouse sperm by an improved substrate-film technique.

A substrate-film method is described that allows the detection of hyaluronidase activity in nearly 100% of single human and mouse sperm. The level of hyaluronidase activity as determined by halo diameters was greater in mouse than in human sperm. This simple method may have use as a screening method for identifying compounds that cause developmental or genetic defects in male germ cells, or for the diagnosis of infertility due to decreased hyaluronidase activity.

Organometallic 99mTc-aquaion labels peptide to an unprecedented high specific activity.

UNLABELLED: A new peptide labeling method that uses the organometallic aquaion [99mTc(H2O)3(CO)3]+ has been developed. METHODS: A selection of amino acids was labeled at different concentrations with the organometallic aquaion, and the labeling yield was determined by high-performance liquid chromatography. This investigation has shown histidine to be a very potent ligand, with specific activities of up to 6 TBq/micromol (160 Ci/micromol) ligand. Histidine derivatives have been coupled to neurotensin(8-13) (NT[8-13]) and have been labeled with the aquaion, resulting in high specific activities with (N(alpha)-histidinyl)acetic acid-NT(8-13) similar to those with histidine. RESULTS: Histidine derivatives of NT(8-13) labeled using this approach fully retained their receptor affinity, showing KD values of all investigated NT analogs below 1 nmol/L on colon carcinoma HT29 cells. Biodistrbution experiments in BALB/c mice showed complete clearance of (N(alpha)-histidinyl)acetic acid-NT(8-13) from the blood after 24 h and no unwanted accumulation in any tissue. CONCLUSION: The novel labeling method using the organometallic 99mTc-aquaion combines the advantage of highest specific activities with minimal functionalization of proteins and peptides under retention of biologic affinity.

Is the formation of R-ibuprofenyl-adenylate the first stereoselective step of chiral inversion?

Coenzyme A thioester formation is reported to be the first step of chiral inversion of R-ibuprofen. In order to investigate the mechanism of this reaction adenylate derivatives of the ibuprofen enantiomers were synthesized chemically. R- and S-ibuprofenyl-adenylates as well as free acids were incubated with rat liver mitochondria in the presence of coenzyme A, MgCl2 with or without ATP. The optical antipodes formed by inversion and the coenzyme A thioester derivatives of both enantiomers were found after incubation of both R- or S-ibuprofenyl-adenylate and R-ibuprofen. By contrast, after incubation with S-ibuprofen neither R-enantiomer nor coenzyme A thioesters were detected. These experiments suggest that the formation of R-ibuprofenyl-adenylate may be the first stereoselective step of chiral inversion.

Isolation and characterization of rat liver microsomal R-ibuprofenoyl-CoA synthetase.

Microsomal long-chain acyl-CoA synthetase (EC 6.1.2.3.) has been suggested to be involved in the stereoselective formation of the CoA thioester of ibuprofen. In this study, we demonstrated that the microsomal enzyme from rat liver responsible for palmitoyl-CoA synthesis also catalyzes the formation of R-ibuprofenoyl-CoA in a Mg(2+)- and ATP-dependent process. Long-chain acyl-CoA synthetase from rat liver microsomes was purified to homogeneity as evidenced by SDS-gel electrophoresis. Simultaneous measurements of palmitoyl-CoA and R-ibuprofenoyl-CoA formation with HPLC in various fractions and purification steps during protein isolation revealed a high correlation between both activities. The purification procedure included solubilization of the microsomes obtained from rat livers with Triton X-100 and subsequent chromatography of the 100,000 x g supernatant on blue-sepharose, hydroxyapatite, and phosphocellulose. The purified enzyme exhibited an apparent molecular weight of 72 kDa as estimated by SDS gel electrophoresis, with specific activities of 71 nmol.min-1.mg-1 protein and 901 nmol.min-1.mg-1 protein for formation of R-ibuprofenoyl-CoA and palmitoyl-CoA, respectively. Palmitoyl-CoA formation catalyzed by the purified enzyme exhibited biphasic kinetics indicative of two isoforms, a high-affinity (KM 0.13 +/- 0.11 microM), low-capacity form and a low-affinity (KM 81 +/- 11.5 microM), high-capacity form. In contrast, measurement of R-ibuprofenoyl-CoA synthesis over a concentration range from 5 to 3000 microM showed the participation of a single CoA ligase with a KM of 184 +/- 19 microM, corresponding to the low-affinity isoform of palmitoyl-CoA synthesis with a marked enantioselectivity towards the R-form of ibuprofen. R-ibuprofenoyl-CoA formation of the enzyme preparation was inhibited by palmitic acid (KI 13.5 +/- 0.5 microM) and S-ibuprofen (KI 405 +/- 10 microM). In summary, these data give strong evidence for the identity of R-ibuprofenoyl-CoA and long-chain acyl-CoA synthetase.

Aporphinoid alkaloids and other constituents from Lettowianthus stellatus.

Two new aporphinoid alkaloids, f1ttowianthine and 11-methoxylettowianthine were isolated from the root bark of Lettowianthus stellatus, together with the new sesquiterpene 11-hydroxyguaia-4,6-diene and the known compounds liriodenine, (Z)-7-octadecen-9-ynoic acid, methyl (2E,6E,10R)-10,11-epoxy-3,7,11-trimethyl-2,6-dodecadienoate, methyl (2E,6E,10R)-10,11-dihydroxy-3,7,11-trimethyl-2,6-dodecadienoate , and 3,4,5-trimethoxyphenol. The structure elucidation was achieved by spectroscopic methods.

Radiation studies on B cell differentiation marker CD24/SCLC Cluster-4 antigen expressing and non-expressing lung cancer cell lines and mouse fibroblasts.

A correlation between CD24 expression and higher intrinsic radiation sensitivity has been described in B-lineage acute lymphoblastic leukaemia (B-ALL). We recently identified the SCLC surface antigen Cluster-4 (CL-4) to be identical to the B cell differentiation marker CD24, except for one amino acid residue. The CD24/CL-4 antigen is highly expressed on SCLC, but rarely on NSCLC cells. In order to investigate the influence of the expression of CD24/CL-4 on the radiation sensitivity in a non-leukaemic cell system, sublines of the human SCLC H249 cell line transfected with mutated ras oncogene, and differing in their CD24/CL-4 expression, were studied. In addition, we stably transfected the NSCLC A125 cell line and the mouse fibroblast NIH3T3 cell line with the CL-4 cDNA. The differential expression of CD24/CL-4 on the cells had no influence on morphology, proliferation and cloning efficiency. Radiation studies were done with cells in exponential growth phase. In the highly resistant NSCLC A125 cells no difference in radioresponsiveness was observed between CD24/CL-4 expressing and non-expressing cells. In the rather radiosensitive cells, similar responses to radiation were observed between CD24/CL-4 expressing and non-expressing SCLC H249-ras cells, whereas the CL-4 transfected NIH3T3 mouse fibroblasts showed a substantially higher radioresistance than the CD24/CL-4 non-expressing control cells. In conclusion, the correlation between CD24/CL-4 expression and radiation sensitivity is controversial and depends on the cell type.

Biokinetics of a F(ab')3 iodine-131 labeled antigen binding construct (Mab 35) directed against CEA in patients with colorectal carcinoma.

UNLABELLED: An 131I labeled trivalent antigen binding construct, formed from 3 Fab' fragments of murine anti-CEA monoclonal antibody (Mab) 35, has shown favorable biokinetics in animal studies. OBJECTIVES: The aim of this study was to evaluate biodistribution and tumor uptake of 131I-F(ab')3 in patients and its potential utility for radioimmunotherapy of CEA expressing tumors. PATIENTS AND METHODS: Six patients (5 M, 1 F; age 62 +/- 13 y) with liver metastases of colorectal cancer, scheduled for hepatic surgery were studied by 2-3 whole body scans immediately post infusion of 111-137 MBq of 131I labeled Mab 35 F(ab')3 and up to 72 h. Circulating CEA ranged from 1.2 to 1930 ng/ml. We evaluated plasma and whole body clearance, activity accumulation by post-surgical ex-vivo tissue measurement in primary tumor (T) and metastases (M), and calculated M to blood (M/B) and M to liver (M/L) ratios. RESULTS: All known tumor sites were detected by immunoscintigraphy and confirmed at surgery. Whole body effective T1/2 calculated in two patients was 51.5 h and 55.6 h respectively. Effective serum T1/2 was mono-exponential in 3 patients (short observation interval) with 20.9 +/- 7 h and bi-exponential in three with alpha T1/2 of 6.3 +/- 1 h and beta T1/2 of 38.6 +/- 5 h. In a patient with concomitant colic and hepatic lesions uptake of primary tumor was 0.0071% injected dose per gram of tissue (%ID/g) and mean metastases activity was 0.0275 %ID/g at 48 h. In the 3 patients who had surgery at 48 h, mean uptake in metastases and normal liver was 0.0182 %ID/g and 0.0021 %ID/g, respectively (M/L 8.67). In the single subject followed until 7 days post infusion, residual activity in liver metastases was 10 times higher than in normal parenchyma. CONCLUSIONS: Tumor uptake and tumor to blood ratio, as well as serum clearance of the triconstruct are similar to those observed with intact iodinated anti-CEA antibodies. In the patient studied for 7 days the tumor residence time was favorable. Further improvements, however, need to be obtained before considering this approach for radioimmunotherapy.

Immunological identification of sperm antigens that participate in fertilization.

Using monoclonal antibodies (mAbs) as probes for specific components of the spermatozoon, we have initiated an investigation aimed at identifying those sperm components that participate in the events of gamete interaction. We intend to exploit these mAbs not only for identifying functional sperm components, but also for defining the constituents of discrete domains that comprise the structure of this highly differentiated cell. Among the large group of anti-sperm mAbs that we have generated, we have focused to date upon two categories. The first category consists of mAbs that localize to the acrosomal crescent, a restricted region of plasma membrane overlying the acrosome. Within this category, the mAbs share many similarities with regard to subclass, species and tissue cross-reactivity, and antigen solubility, in addition to cellular distribution. Nevertheless, despite these similarities, some mAbs in this category (e.g., M42) inhibit fertilization, whereas others (e.g., M41) are non-inhibitory. The block to fertilization observed in the presence of M42 is dependent upon the zona pellucida surrounding the egg. The specific event prevented by M42 appears to be the induction of the acrosome reaction at its physiological site, the surface of the zona pellucida. The sperm components recognized specifically by M42 are a cluster of high molecular weight moieties, ranging from approximately 220,000 to 240,000. The mAbs described in the second category display common localization at the equatorial segment of the sperm head. The pair of mAbs discussed from this category, M2 and M29, again bear considerable similarity to each other, yet differ significantly in their ability to inhibit fertilization. M2 does not inhibit, whereas M29 causes a marked inhibition of fertilization. With M29, however, the block to fertilization is independent of the zona pellucida. The M29 mAb interferes with sperm interaction with the egg plasma membrane subsequent to sperm attachment; since M29 does not prevent sperm binding to the egg plasma membrane, the specific event affacted, in all likelihood, is gamete membrane fusion. M29 recognizes a single sperm component, with subunit molecular weight of approx. 40,000. A variety of experiments are underway currently, both to characterize the antigens recognized by these mAbs further as well as to identify additional sperm components that participate in the fertilization process.

[High voltage power station to study the influence of the DC-field with superimposed AC-field on humans (author's transl)]. / Hochspannungsanlage zur Untersuchung des Einflusses eines Gleichfeldes mit überlagertem Wechselfeld auf den Menschen.

Due to the great progress in electrical engineering man is exposed to electric fields in a high degree. However, the effect of the electric field has not been definitely cleared up till now. The following parameters are of decisive importance: Field intensity- Frequency-Shape of curve-Boundary conditions. As scientific investigations can only be reproduced and accepted when the experimental conditions are clearly defined, a station meeting these requirements has been developed. It consists of Testing room: Electric screen damping higher than 80 dB-Magnetic screen damping higher than 45 dB-large, cased ceiling electrode. Control room: Same as testing room, but no screening. High voltage generator: a) DC-Voltage 0-20 kV ripple & noise less than 0.01%; b) Alternating voltage 0-300 Vss frequency 5 Hz-50 kHz; c) combination of a) and b).