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Biomedical subjects

G Bernhardt

Publications and source records attributed to G Bernhardt.

At least 19 recordsLinked to original sources

Efficacy of BCNU and paclitaxel loaded subcutaneous implants in the interstitial chemotherapy of U-87 MG human glioblastoma xenografts.

Nude mice were challenged with human U-87 MG glioblastoma tumors to assess the efficacy of different cytostatics and different application protocols. While the intraperitoneal application of BCNU solutions (3 times 20 mg BCNU/kg) had no effect on tumor growth, the application of polymer matrices made of a physical mixture of poly(1,3-bis[carboxyphenoxpropane]-co-sebacic acid) 20:80 with poly(D,L-lactic-co-glycolic acid) loaded with 0.25 mg BCNU, slowed down the growth of tumors significantly. When the animals were treated with implants carrying 0.25 mg BCNU they responded to the treatment whether the tumor had been inoculated recently (9 days ago) or whether it was fully established (after 20 days). After its sensitivity was proven, the xenograft model was used to further investigate the efficacy of anticancer drugs and some treatment regimens using polymer implants. Thus the tumor model allowed to discriminate between the efficacy of different doses of BCNU. Only implants loaded with 0.75 or 1 mg of BCNU led to a substantial suppression of tumor growth over approximately 2 months. While BCNU was only able to suppress the growth of the tumor, the combination of BCNU with paclitaxel led to a complete remission in some animals. These preliminary results suggest that combinations of cytostatics might improve local chemotherapy of malignant glioma substantially. Based on our data it will be worthwhile to investigate implants that release drugs such as BCNU and paclitaxel closer. Amongst other factors we will try to elucidate the effect of repetitive doses of drugs using programmable implants.

Animals↗

The poliovirus receptor CD155 mediates cell-to-matrix contacts by specifically binding to vitronectin.

The human receptor for poliovirus (CD155) is an immunoglobulin-like molecule with unknown normal function(s). Here we provide evidence that CD155 binds specifically to vitronectin with a dissociation constant (K(d)) of 72 nM as determined by surface plasmon resonance. Based on sequence homology to the CD155 gene, three poliovirus receptor-related genes (PRR1, PRR2, and PRR3) were cloned recently. PRR proteins were reported by others to mediate homophilic cell adhesion. Neither PRR1 nor PRR2 binds poliovirus and it is assumed that their physiological functions differ from that of CD155. Indeed, mPRR2 was found to bind to vitronectin only weakly, while its self-adhesion activity is characterized by a K(d) of 310 nM. Moreover, there is no evidence for CD155 self-adhesion. Both CD155 and vitronectin colocalize to follicular dendritic cells and B cells inside the germinal centers of secondary lymphoid tissue (tonsils)-an observation suggesting that the CD155/vitronectin interaction is required for the establishment of a proper immune response in this particular context.

Animals↗

Programmable biodegradable implants.

Pulsatile release implants were developed that release substances up to 58 days post implantation. With a cylindrical size of 2 mm diameter and 1.8 mm height the matrices can carry as much as 1 mg of drug and allow even for intracranial implantation into a rodent model. The matrices are made of materials that have been used for parenteral applications in humans before such as surface eroding polyanhydrides and bulk eroding poly(D,L-lactic acid) or poly(D,L-lactic acid-co-glycolic acid). The onset of drug release is controlled by the degradation of bulk eroding polymers which are known to exhibit a certain stability over a defined period of time and which start eroding after they reach a critical degree of degradation. The time of drug release onset was found to depend on the molecular weight and the chemical state of the carboxylic acid end of the polymer chain. For testing the onset of release in vivo a nude mouse model was developed where the release of Evan's blue could be observed visually after subcutaneous application. By combining individual matrices with different release onset, a therapeutic system can be composed that releases drugs after implantation at predetermined time points in a preprogrammed way. Potential applications for such matrices is vaccination and local tumor therapy.

Absorbable Implants↗

1-(2,6-dichloro-4-hydroxyphenyl)-2-phenylethanes--new biological response modifiers for the therapy of breast cancer. Synthesis and evaluation of estrogenic/antiestrogenic properties.

[meso-1,2-Bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine]platinum(II) complexes (meso-1-PtLL'; L,L' = Cl or L = H2O and L' = OSO3) are highly effective towards hormone-sensitive, rodent breast cancers due to their significant estrogenic potencies. Their antitumor activities are caused by modification of the immune response. The pharmacophor of these compounds, the 1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethane (23H), was used as the lead structure in a structure-activity study with the goal of finding new biological response modifiers for the therapy of breast cancer. As intermediates for the synthesis of the 23H derivatives, the CH3O-substituted stilbenes 12E/12Z-16E/16Z were prepared by reaction of the related benzyltriphenylphosphonium halides with 2,6-dichloro-4-methoxybenzaldehyde by the method of Wittig/Campbell and Donald, respectively. Separation of the E/Z-mixtures was performed by fractional crystallization and/or column chromatography. The E-1,2-bis(2,6-dichloro-4-methoxyphenyl)ethene (17E) was obtained by reductive coupling of 2,6-dichloro-4-methoxybenzaldehyde with TiCl4/Zn according to the method of Mukaiyama. Illumination of the solution of 17E in benzene with UV light resulted in an E/Z-isomerization. Compound 17Z could be isolated from this mixture. The CH3O-substituted stilbenes were transformed into their 1,2-diphenylethanes (12H-17H) by catalytic hydrogenation of the C1=C2 double bond. Ether cleavage of the compounds was performed with BBr3. In the estrogen receptor binding assay all OH-substituted 1,2-diphenylethanes showed affinity to the estrogen receptor, which was about two orders of magnitude lower than that of 17 beta-estradiol. In the uterus weight test on the immature mouse 1,2-diphenylethanes with 4-substituted OH groups proved to be "true" estrogens (19H: 2-F/4-OH; 20H: 2-Cl/4-OH; 23H: 2,6-Cl2/4-OH), while those with a 3-substituted OH group in the 2-phenyl ring showed the properties of a "partial" estrogen (18H: 3-OH) or of an "impeded" estrogen (21H: 2-Cl/3-OH; 22H: 2-Cl/5-OH). The latter also showed significant additional antiestrogenic activity. The related E-stilbenes mostly exhibit similar hormonal activities. As a rule, the replacement of the OH groups by the CH3O groups and the change from the E- to the Z-configuration led to a reduction of the estrogenic potencies. Several of the 1-(2,6-dichloro-4-methoxyphenyl)-2-phenylethenes (12E: 3-OCH3; 12Z: 3-OCH3; 15E: 2-Cl/3-OCH3; 15Z: 2-Cl/3-OCH3; 16E: 2-Cl/5-OCH3) produced antiestrogenic effects in the uterus weight test. It is supposed that those new 1-(2,6-dichloro-4-hydroxyphenyl)-2-phenylethanes endowed with marked estrogenic properties are also active as biological response modifiers in animals bearing hormone-sensitive breast cancer. The antiestrogenic derivatives presumably inhibit the breast cancer development by competing with tumor growth stimulating endogenous estrogens for the binding to the receptor. This is to be confirmed in a further study.

Animals↗

Does [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine] dichloroplatinum(II) act as an immune response modifier? IV. Inhibition of the proliferation-increasing effect of progressively growing MXT-M-3,2 breast cancer on phagocytes by the title compound.

In female B6D2F1 mice bearing an MXT-M-3,2 breast cancer graft the level of the phagocytic cells (e.g. of granulocytes and macrophages in the spleen and of granulocytes and monocytes in the blood) is significantly elevated. The positive correlation between the number of the phagocytic cells and the weight of the tumor indicates that the MXT-M-3,2 breast cancer promotes myelopoiesis, presumably by secretion of hematopoietic growth factors like GM-CSF. This process can be described for each phagocyte type by a regression equation. Due to its hormonal potency [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine] dichloroplatinum(II) (meso-1-PtCl2) can reduce the excessive numbers of the granulocytes and macrophages, which seem to be responsible for the progressive growth of the MXT-M-3,2 breast cancer. This process leads to an interruption of the vicious circle of mutual growth stimulation of breast cancer cells and these phagocytes. The target of meso-1-PtCl2 is the estrogen receptor (ER) of the breast cancer cell. The interaction between meso-1-PtCl2 and the ER presumably results in a diminished secretion of hematopoietic growth factors and hence in a decline of the number of phagocytic cells. Meso-1-PtCl2 does not inhibit the proliferation of tumor cells by direct interaction with their DNA, as is described for platinum complexes like cDDP. In its mode of action the equipotent, breast cancer inhibiting drug cDDP differs from meso-1-PtCl2. This is obvious from the fact that in cDDP--but not in meso-1-PtCl2-treated, tumor bearing mice the number of granulocytes and macrophages does not markedly deviate from that in untreated control mice with tumors of the same weight. The drug cDDP probably does not interfere with the mechanism of the secretion of hematopoietic growth factors. The reduction of the number of tumor cells by cDDP leads to a decline of the number of phagocytic cells in accordance with the respective regression equations. In contrast to meso-1-PtCl2 and cDDP, ovariectomy causes elevated phagocyte numbers, probably due to the strongly reduced estrogen level. The studies described in this publication indicate that the anti-breast cancer activity of meso-1-PtCl2 is caused by a decimation of phagocytes and with this by an abolition of the tumor promoting effect. Furthermore, a restoration of the natural immunosurveillance seems to be of importance.

Adjuvants, Immunologic↗

Chiral separation of pheniramine-like 3-phenyl-3-heteroarylpropylamines by CE and HPLC methods.

Analytical CE and HPLC methods were developed for the chiral separation of halogen-substituted 3-phenyl-3-(2-pyridyl)propylamines 1-4 (1: 3-(4-fluorophenyl) approximately, 2: 3-(3,4-difluorophenyl) approximately, 3: 3-(4-chlorophenyl) approximately, 4: 3-(3,4-dichlorophenyl) approximately ), 3-(4-fluorophenyl)-3-(2-thiazolyl)propylamine (5), and 3-(4-fluorophenyl)-3-(1-benzylimidazol-2-yl)propylamine (6), which are building blocks for the preparation of very potent arpromidine-type histamine H(2) receptor agonists. All amines were enantioseparated by CE with resolutions of at least 1.8 using alpha-, beta-, or gamma-cyclodextrin (CD) as chiral selectors. With heparin as buffer additive for CE the optical antipodes of 1-4 and 6 were separated with resolutions > or = 1.8. On RP-18 columns the separation of the (+)-(S)-acetylmandelic acid amides of racemic 2 (R = 0.9, alpha = 1.07) and the thioureas prepared by addition of 6 to 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate (R = 2.0, alpha = 1.20) was successful, whereas the diastereomeric ureas prepared from 3 and (+)-(S)-1-(1-naphthyl)ethyl isocyanate could not be resolved. Separation of the diastereomeric isoindoles prepared from 1-5, o-phthaldialdehyde and 2,3,4,6-tetra-O-acetyl-1-thio-beta-D-glucopyranoside was achieved on a RP-18 phase (R > or = 0.4, a > or = 1.02). Direct separation of the enantiomers of 3 and 4 was achieved on a Cyclobond I column (R > or = 0.9, alpha > or = 1.07). alpha- and beta-CD were also useful as mobile phase additives for HPLC (3 and 4: RP-18 column, beta-CD, R > or = 0.4, alpha > or = 1.03; 3: RP-18 column, alpha-CD: R = 0.5, alpha = 1.04).

Chromatography, High Pressure Liquid↗

Structure-activity relationships of neuropeptide Y Y1 receptor antagonists related to BIBP 3226.

Analogues of BIBP 3226, (R)-N(alpha)-diphenylacetyl-N-(4-hydroxybenzyl)argininamide, were synthesized and investigated for Y1 antagonism (Ca2+-assay, HEL cells) and binding on Y1, Y2 and Y5 receptors. Replacing the benzylamino by a tetrahydrobenzazepinyl group preserves most of the Y1 activity. Combination with a N(G)-phenylpropyl arginine and a N(alpha)-p-biphenylylacetyl moiety shifted the NPY receptor selectivity towards Y5.

Animals↗

Identification of a nuclear respiratory factor-1 binding site within the core promoter of the human polio virus receptor/CD155 gene.

In this report we describe a cis-acting element within the core promoter of the CD155 gene specifying the polio virus receptor that is bound by the nuclear respiratory factor-1 (NRF-1) transcription factor. DNase I footprint analysis identified a nuclear protein binding site from -282 to -264 nucleotides upstream of the translation initiation codon of the CD155 gene, which we have called foot print IV (FPIV). Linker scanning mutagenesis revealed that a tandem repeat motif, GCGCAGGCGCAG, located within FPIV was essential for the basal activity of the CD155 core promoter. The results of the electrophoretic mobility shift assay experiments suggested that identical FPIV binding activities were present in a variety of nuclear extracts and that the tandem repeat was essential for binding. A one-hybrid screen was then carried out using FPIV as bait to clone the cDNA of the FPIV binding factor. The sequences of the cDNAs that were cloned from the screen were identical to NRF-1, a result that was confirmed by further electrophoretic mobility shift assay experiments. Overexpression of full-length NRF-1 and a dominant-negative form of NRF-1 modulated reporter gene expression driven by the core promoter. Remarkably, CD155 is the first gene shown to be regulated by NRF-1 that possesses an expression profile during embryogenesis correlating with this factor's proposed role in the development of the vertebrate optic system. We propose that NRF-1, which has been shown by others to be expressed during embryogenesis in animal systems, may be involved in regulating the expression of CD155 at specific stages of central nervous system development.

Animals↗

Sphingosine-1-phosphate is a ligand for the G protein-coupled receptor EDG-6.

EDG-6 is a recently cloned member of the endothelial differentiation gene (EDG) G protein-coupled receptor family that is expressed in lymphoid and hematopoietic tissue and in the lung. Homology of EDG-6 to the known sphingosine-1-phosphate (SPP) receptors EDG-1, EDG-3, and EDG-5 and lysophosphatidic acid (LPA) receptors EDG-2 and EDG-4 suggested that its ligand may be a lysophospholipid or lysosphingolipid. We examined the binding of [(32)P]SPP to HEK293 cells, transiently transfected with cDNA encoding EDG-6. Binding of [(32)P]SPP was saturable, demonstrating high affinity (K(D) = 63 nmol/L). Binding was also specific for SPP, as only unlabeled SPP and sphinganine-1-phosphate, which lacks the trans double bond at the 4 position, potently displaced radiolabeled SPP. LPA did not compete for binding of SPP at any concentration tested, whereas sphingosylphosphorylcholine competed for binding to EDG-6, but only at very high concentrations. In addition, SPP activated extracellular signal-regulated kinase (Erk) in EDG-6 transfected cells in a pertussis toxin-sensitive manner. These results indicate that EDG-6 is a high affinity receptor for SPP, which couples to a G(i/o) protein, resulting in the activation of growth-related signaling pathways. (Blood. 2000;95:2624-2629)

Animals↗

Does [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine]- dichloroplatinum(II) act on the hormone-sensitive, murine breast cancer as a biological response modifier? Part 1: The MXT-M-3.2 breast cancer stimulates the growth of an identical second graft; [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine]dichloroplat inum (II) inhibits this process.

The MXT-M-3.2 breast cancer implanted into female B6D2F1 mice accelerates the growth of an identical second tumor. This process is inhibited by [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl) ethylenediamine]dichloroplatinum(II). The possible modes of action of this compound as a biological response modifier are discussed.

Animals↗

Does [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine]- dichloroplatinum(II) act on the hormone-sensitive, murine breast cancer as a biological response modifier? Part II. Studies on the influence of [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine] dichloroplatinum(II) on the specific immune defense in MXT-M-3,2 breast cancer bearing mice.

The anti-tumor activity of [meso-1,2-bis(2,6-dichloro-4- hydroxyphenyl)ethylenediamine]dichloroplatinum(II) on the MXT-M-3,2 breast cancer implanted into B6D2F1 mice was not significantly reduced by splenectomy or co-administration of cyclosporine A. Neither did the use of T-lymphocyte-deficient NMRI (nu/nu) mice as hosts substantially influence its anti-tumor effect. Obviously, [meso-1,2-bis(2,6-dichloro-4- hydroxyphenyl)ethylenediamine]dichloroplatinum(II) does not act by an enhancement of the specific immune defense.

Animals↗

Does [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine]- dichloro-platinum(II) act as an immune response modifier? Part III: Progressively growing MXT-M-3,2 breast cancer stimulates the proliferation of phagocytes in B6D2F1 mice.

MXT-M-3,2 breast cancer implanted into female B6D2F1 mice accelerates the growth of an identical second tumor. This process is accompanied by a significant increase of the granulocyte and monocyte numbers in the blood and of the granulocyte and macrophage numbers in the spleen. A significant positive correlation of strong intensity was found between the tumor weight on the one hand and the number of the granulocytes and macrophages on the other hand. The tumor-dependent promotion of the myelopoiesis is explained with a secretion of hematopoietic growth factors, e.g. of the granulocyte-macrophage-stimulating growth factor (GM-CSF), by the breast cancer cells.

Animals↗

Cloning and functional expression of the hNPY Y5 receptor in human endometrial cancer (HEC-1B) cells.

Aiming to develop a functional assay for the human NPY Y5 receptor based on adenylyl cyclase activity, HEC-1B cells, in which cAMP synthesis can be efficiently stimulated with forskolin, were selected for the transfection with the pcDNA3-Y5-FLAG and the pcDEF3-Y5 vectors. After optimization of the transfection procedure, the binding of [3H]propionyl-NPY to transiently and stably expressed Y5 receptors was determined. The affinities of NPY, NPY derivatives, and rPP (pNPY > or = p(Leu31Pro34)NPY = p(2-36)NPY > or = p(D-Trp32)NPY > p(13-36)NPY > rPP) were in accordance with the NPY Y5 receptor subtype. For [3H]propionyl-pNPY approximately 1.7 x 10(5) and 1 x 10(6) binding sites per transiently and stably transfected cell, respectively, were determined. The KD values were 2.4 +/- 0.4 and 1.7 +/-0.2 nM, respectively. Due to the high expression of the receptor protein, both stably and transiently transfected cells can be conveniently used in routine radioligand binding studies. By contrast, functional assays were only feasible with HEC-1B cells stably expressing the Y5 receptor. In these cells, 10 nM pNPY inhibited the forskolin-stimulated cAMP synthesis by 75%. This effect was partially antagonized by the Y5 antagonist N-¿trans-[4-(2-naphthylmethylamino)-methyl]cyclohexylmethyl) naphthalene-2-sulfonamide. Although the genetic variability of cancer cells is in principle incompatible with a stable phenotype, both ligand binding characteristics and functionality of the Y5 receptor remained unchanged for more than 30 passages.

Cloning, Molecular↗

Identification and characterization of the cis-acting elements of the human CD155 gene core promoter.

The CD155 protein is the founding member of a new group of related molecules within the immunoglobulin superfamily sharing a V-C2-C2 domain structure and significant amino acid identity. We have recently isolated the promoter of the CD155 gene so that we may determine the transcription factors that regulate its expression and possibly gain insight into the cell biology of this gene. Here we report the mapping of three cis-elements within the CD155 core promoter, designated FPI, II, and III. The results of linker scanning mutagenesis suggest that all three of these cis-elements are required in varying degrees for the promoter activity of the core promoter fragment. The relative contribution of each region ranked in the following order: III > II > I. Interestingly, footprint and electrophoretic mobility shift assays show that FPIII binding activity is much reduced in a human cell line that does not express CD155. Additionally, protein binding to FPI and FPII was also investigated. DNase I footprinting using recombinant hAP-2alpha indicated that this transcription factor bound to both the FPI and FPII regions of the CD155 core promoter fragment. Electrophoretic mobility shift assays and supershift analysis confirmed the binding of AP-2 from crude nuclear extracts to FPI and to FPII. Lastly, cotransfection of the CD155 promoter with an AP-2alpha expression vector indicates that overexpression of AP-2alpha modulated the promoter activity of a CD155 promoter construct.

Base Sequence↗

[meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl) ethylenediamine]dichloroplatinum(II), a compound with a specific activity on hormone-sensitive breast cancers--evidence for a diethylstilbestrol-like mode of action.

[meso-1,2-Bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine]- dichloroplatinum(II) (meso-1-PtCl2), an estrogenic and cytotoxic platinum complex, shows activity against ER+ but not against ER- breast cancers in vivo (ER: estrogen receptor; ER+ and ER- indicate the presence or absence of the ER). To clarify whether its estrogenic or its cytotoxic potency or both properties are the cause of this specific inhibitory effect, we tested meso-1-PtCl2 comparatively in vivo on an ER+ and an ER- murine breast cancer (MXT-M-3.2 MC and MXT-M-3.2(ovex) MC, respectively), and in vitro on two cell lines derived from the former in vivo models (MXT+ and MXT-, respectively). The estrogens diethylstilbestrol (DES) and the ligand of meso-1-PtCl2 (meso-1), responsible for the hormonal effect of meso-1-PtCl2, and the cytotoxic drug cisplatin (cDDP) were used as comparative substances. Meso-1-PtCl2. DES and cDDP showed a strong and comparable activity on the ER+ MXT-M-3.2 MC in vivo, meso-1 being somewhat less inhibitory. In experiments on the murine, ER- MXT-M-3.2(ovex) MC only cDDP caused a marked inhibitory effect. The other compounds were inactive or only marginally active. In accordance with the in vivo results cDDP was also very active on the MXT+ and MXT- breast cancer cell line. In contrast to this meso-1-PtCl2, meso-1, and DES proved to be only weakly active or inactive on both cell lines. From these results it can be concluded that there is only little if any contribution of the cytotoxic PtCl2 moiety of meso-1-PtCl2 to the anti-breast cancer activity in vivo. On the ER+ MXT-M-3.2 MC transplanted into ovariectomized mice meso-1-PtCl2 yielded a biphasic dose activity curve, i.e. an increase of the tumor growth at low doses followed by a decrease at high doses, identical with those of the estrogens DES and meso-1. These results indicate that meso-1-PtCl2 inhibits ER+ breast cancers by its estrogenicity in the same manner as meso-1 and DES. The complex mechanism of anti-breast cancer active estrogens involves presumably the endocrine and/or the immune system. Its investigation is the subject of further studies.

Animals↗

[meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine] sulfatoplatinum(II)--pharmacokinetic studies.

The maximally attainable level of the non-plasma protein bound fraction of a single 10.0 mumol/kg i.p. dose of [meso-1,2-bis(2,6-dichloro-4-hydroxyphenyl)ethylenediamine] sulfatoplatinum(II), a drug active on the murine, hormone-sensitive MXT-M-3.2 breast cancer, lies markedly below the concentration causing a significant cytotoxic effect on a cell line derived from this tumor. This result confirms our opinion that the strong in vivo activity of this drug on hormone-sensitive breast cancers is mediated by its estrogenic potency by analogy with high dosed steroidal and non-steroidal estrogens. A specific cytotoxic effect utilizing the estrogen receptor as carrier, as formerly postulated, is unlikely.

Animals↗

Antispasmodic activity of Thymus vulgaris extract on the isolated guinea-pig trachea: discrimination between drug and ethanol effects.

The effect of an extract of Thymus vulgaris on induced spasms was investigated on guinea-pig trachea preparations. By the experimental setup used, effects of ethanol as the vehicle could be differentiated from the activity of the herbal constituents. The extract reversibly and concentration-dependently antagonized the contraction of the Musculus transversus tracheae, provoked by four different spasmogens (BaCl2, carbachol, histamine, prostaglandin F2 alpha). The degree of the antispasmodic activity was dependent on the individual spasmogen with prostaglandin F2 alpha being most efficiently antagonized.

Animals↗