Biomedical subjects

J Buck

Publications and source records attributed to J Buck.

At least 19 recordsLinked to original sources

PubMed1992

Retinoids are important cofactors in T cell activation.

Murine thymic T cells depleted of antigen-presenting cells proliferate poorly in response to crosslinking anti-CD3 monoclonal antibodies or concanavalin A when cultured in conventional fetal calf serum-containing serum. However, in a serum-free medium formulated to contain, in addition to basic ingredients, insulin, transferrin, albumin, linoleic acid (ITLB), and retinol, proliferation is vigorous. The presence of retinol is critical, because when omitted, cells do not become activated. The subsets of T cells proliferating with the assistance of retinol cofactor are both CD4+ and CD8+ thymic T cells, and CD4+ peripheral T cells. Mature CD8+ T cells of lymph nodes can also be activated in ITLB medium plus retinol, provided that interleukin 2 (IL-2) is added. Retinol needs to be present at the time when T cell receptor triggering is initiated, suggesting that early activation events (G0 to G1 transition) are dependent on retinol. It is currently less clear whether or not subsequent events associated with G1 to S phase transition also require the presence of retinol. 14-hydroxy-retroretinol (14HRR) is a metabolic product of retinol in lymphocytes, and this retinoid effectively supports T cell activation in conjunction with a mitogen in lieu of retinol. Thus, while retinol and its intracellular product, 14HRR, are unable to activate T cells on their own, they are important cofactors. The requirement for retinol in CD3-mediated T cell activation cannot be satisfied by retinoic acid or ILs-1, 2, 4, and 6, and tumor necrosis factor-alpha whereas interferon gamma can substitute for retinol. Our experiments are compatible with the idea that retinol, in the course of cellular activation, is converted to 14HRR, which is needed as intracellular messenger. If substantiated by molecular studies now underway, our data should lead to the description of a new signal pathway distinct from the retinoic acid signal pathway observed in nonlymphoid cells, but perhaps functioning by a similar mechanism, i.e., ligand-assisted transcriptional regulation.

Animals↗

PubMed1992

Differential expression and processing of two cell associated forms of the kit-ligand: KL-1 and KL-2.

The c-kit ligand, KL, and its receptor, the proto-oncogene c-kit are encoded, respectively, at the steel (Sl) and white spotting (W) loci of the mouse. Both Sl and W mutations affect cellular targets in melanogenesis, gametogenesis, and hematopoiesis during development and in adult life. Although identified as a soluble protein, the predicted amino acid sequence of KL indicates that it is an integral transmembrane protein. We have investigated the relationship between the soluble and the cell associated forms of KL and the regulation of their expression. We show that the soluble form of KL is generated by efficient proteolytic cleavage from a transmembrane precursor, KL-1. An alternatively spliced version of KL-1, KL-2, in which the major proteolytic cleavage site is removed by splicing, is shown to produce a soluble biologically active form of KL as well, although with somewhat diminished efficiency. The protein kinase C inducer phorbol 12-myristate 13-acetate and the calcium ionophore A23187 were shown to induce the cleavage of both KL-1 and KL-2 at similar rates, suggesting that this process can be regulated differentially. Furthermore, proteolytic processing of both the KL-1 and KL-2 transmembrane protein products was shown to occur on the cell surface. The relative abundance of KL-1 and KL-2 is controlled in a tissue-specific manner. Sld, a viable steel allele, is shown to encode a biologically active secreted mutant KL protein. These results indicate an important function for both the soluble and the cell associate form of KL. The respective roles of the soluble and cell associated forms of KL in the proliferative and migratory functions of c-kit are discussed.

Alleles↗

PubMed1991

Intracellular signaling by 14-hydroxy-4,14-retro-retinol.

In mammals, retinol is the precursor for retinoids, which affect various aspects of morphogenesis and development. However, B lymphocytes, although retinol-dependent, do not use retinoic acid as mediator. Retinol is metabolized by B lymphocytes and other cell lines to optically active 14-hydroxy-4,14-retro-retinol; it is this compound that mediates the growth control. Thus another second messenger molecule, in addition to retinoic acid and retinal, is derived from retinol.

Animals↗

PubMed1991

Differences in the action and metabolism between retinol and retinoic acid in B lymphocytes.

We have previously reported on the dependency of activated B lymphocytes for retinol. Here we confirm and extend these findings that cells deprived of retinol perish in cell culture within days, displaying neither signs of apoptosis nor of cell cycle arrest. Cell death can be prevented by physiological concentrations of retinol and retinal, but not by retinoic acid or three synthetic retinoic acid analogues. To exclude the possibility that retinoic acid is so rapidly degraded as to escape detection, we have tested its stability in intra- and extracellular compartments. Contrary to expectation, we find that retinoic acid persists for longer (t 1/2 3 d) in cultures than retinol (t 1/2 1 d). Furthermore, despite the use of sensitive trace-labeling techniques, we cannot detect retinoic acid or 3,4-didehydroretinoic acid among retinol metabolites. However, retinol is converted into several new retinoids, one of which has the ability to sustain B cell growth in the absence of an external source of retinol, supporting the notion of a second retinol pathway. We have also determined which of the known retinoid-binding proteins are expressed in B lymphoblastoid cells. According to results obtained with polymerase chain reaction-assisted mRNA detection, they transcribe the genes for cellular retinol- and cellular retinoic acid-binding proteins, for the nuclear retinoic acid receptors, RAR-alpha, -gamma, and RXR-alpha, but not RAR-beta. Our findings that B cells do not synthesize retinoic acid or respond to exogenous retinoic acid on the one hand, but on the other hand convert retinol to a novel bioactive form of retinol, suggest the existence of a second retinoid pathway, distinct from that of retinoic acids.

B-Lymphocytes↗

PubMed1990

The hematopoietic growth factor KL is encoded by the Sl locus and is the ligand of the c-kit receptor, the gene product of the W locus.

Mutations at the steel locus (Sl) of the mouse affect the same cellular targets as mutations at the white spotting locus (W), which is allelic with the c-kit proto-oncogene. We show that KL, a hematopoietic growth factor obtained from conditioned medium of BALB/c 3T3 fibroblasts that stimulates the proliferation of mast cells and early erythroid progenitors, specifically binds to the c-kit receptor. The predicted amino acid sequence of isolated KL-specific cDNA clones suggests that KL is synthesized as an integral transmembrane protein. Linkage analysis maps the KL gene to the Sl locus on mouse chromosome 10, and KL sequences are deleted in the genome of the Sl mouse. These results indicate that the Sl locus encodes the ligand of the c-kit receptor, KL.

Amino Acid Sequence↗

PubMed1990

Retinol is essential for growth of activated human B cells.

When EBV-transformed human B cells are removed from conventional cell cultures, washed, and seeded at a low cell density in serum-free medium, their growth potential is greatly diminished. Fresh serum restores the growth of low density B cell cultures. We have traced this restorative effect to an essential factor present in the lipid fraction of serum and have identified it as all-trans retinol. The identification is based on the close similarities of the factor isolated from serum with authentic all-trans retinol as revealed by mass spectrometry, HPLC chromatography, and the ability to stimulate the growth of lymphoblastoid cells in the bioassay. Retinol is active at concentrations equal to its concentration in serum. Retinol is also a requirement for growth in suspension cultures at cell densities of 3 x 10(5)/ml. Cells removed at any time from such exponentially growing cultures and transferred to retinol-free medium cease to grow and consequently die, whereas in the continued presence of retinol, cell growth is unabated. All-trans retinal can substitute for retinol, but retinoic acid fails to stimulate the growth of lymphoblastoid cells at physiological concentrations. Normal human B lymphocytes also require retinol as a costimulator of proliferation after activation by anti-mu antibody or Staphylococcus aureus (Cowan strain) bacteria. In serum, retinol is bound to retinol-binding protein, which in turn forms a complex with prealbumin. Accordingly, we find that B cells respond to retinol bound to its physiological serum carrier, retinol-binding protein. In conclusion, human B cells are critically dependent for optimal growth in cell culture on an external supply of retinol.

B-Lymphocytes↗

PubMed1990

Candidate ligand for the c-kit transmembrane kinase receptor: KL, a fibroblast derived growth factor stimulates mast cells and erythroid progenitors.

The c-kit proto-oncogene encodes a transmembrane tyrosine kinase receptor for an unidentified ligand and is allelic with the murine white-spotting locus (W). W mutations affect melanogenesis, gametogenesis and hematopoiesis during development and in adult life. Cellular targets of W mutations in hematopoiesis include distinct cell populations in the erythroid and mast cell lineages as well as stem cells. In the absence of interleukin-3 (IL-3) mast cells derived from normal mice but not from W mutant mice can be maintained by co-culture with 3T3 fibroblasts. Based on the defective proliferative response of W mast cells in the 3T3 fibroblast co-culture system it had been proposed that fibroblasts produce the c-kit ligand. We have used a mast cell proliferation assay to purify a 30 kd protein, designated KL, from conditioned medium of Balb/3T3 fibroblasts to apparent homogeneity. KL stimulates the proliferation of normal bone marrow derived mast cells but not mast cells from W mice, although both normal and mutant mast cells respond similarly to IL-3. Connective tissue-type mast cells derived from the peritoneal cavity of normal mice were found to express a high level of c-kit protein on their surface and to proliferate in response to KL. The effect of KL on erythroid progenitor cells was investigated as well. In combination with erythropoietin, KL was found to stimulate early erythroid progenitors (BFU-E) from fetal liver and spleen cells but not from bone marrow cells of adult mice and from fetal liver cells of W/W mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Alleles↗

PubMed1990

A novel autoregulatory cytokine is required for the regulation of autoaggressive responses.

Limiting dilution studies indicate that cells with the potential to lyse autologous target cells exist in the peripheral blood of all normal individuals. In contrast to allocytotoxic cells, autocytolytic cells are down-regulated by a second less frequent cell population. When recombinant interleukin 2 is substituted for crude lymphocyte conditioned medium in these limiting dilution experiments, autocytotoxicity develops normally. Under these conditions, however, the autocytotoxic response is not down-regulated. Mixing crude lymphocyte-conditioned medium together with recombinant interleukin 2 restores the regulation of autocytotoxicity normally seen at high responder cell dose. These findings indicate that a second soluble factor present in the conditioned medium is necessary either for the activation, growth, or differentiation of the regulatory cell population or alternatively, to render the cytotoxic population responsive to the activity of regulatory cells. Gel filtration studies indicate that the molecular weight of this factor is between 60 and 80 kd. This factor appears to be distinct from known immunologically active cytokines. It is conceivable that deficiencies of this cytokine may be relevant to the pathogenesis of autoimmune diseases or graft-versus-host reactions.

Biological Factors↗

PubMed1988

Cytotoxic effects of m-[131I]- and m-[125I]iodobenzylguanidine on the human neuroblastoma cell lines SK-N-SH and SK-N-LO.

As we have reported recently, the human neuroblastoma cell line SK-N-SH is able to take up and store m-iodobenzylguanidine (mIBG). This is in contrast to several other neuroblastoma cell lines, among which are SK-N-LO cells. Both cell lines were used in cell killing experiments with unlabeled and radioactive-labeled mIBG. Using 1-200 microCi m-[131I]IBG (1 h incubation time), only SK-N-SH cells could to a large extent be destroyed in a dose-dependent manner. This effect is completely caused by the radioactive labeling of the molecule, because unlabeled mIBG proved not to be toxic in the concentration range used in experiments with radiolabeled mIBG (30 nM-3 microM). The killing effect was strongly reduced when m-[131I]IBG with low specific activity (0.2-0.3 mCi/mg) was used instead of 20-30 mCi/mg. Similar effects in both cell lines were obtained using m-[131I]-and m-[125I]IBG. SK-N-SH cells that survived a first treatment with m-[131I]IBG were less sensitive to a second treatment. SK-N-LO cells were more sensitive against m-[131I]- and m-[125I]IBG than SK-N-SH cells if both cell lines are exposed to these radioactive compounds over a long period of time (24 h). The reason that only SK-N-SH cells could be destroyed in short-term incubation experiments is that mIBG is stored for approximately 7 days in these cells only. SK-N-LO cells could only be destroyed to a significant degree if m-[131I]IBG was permanently present in the test system. Bone marrow stem cells (CFU-c) also proved to be sensitive against m-[131I]IBG, although the effects were less pronounced than on SK-N-SH cells.

3-Iodobenzylguanidine↗

PubMed1988

Synchronous rhythmic flashing of fireflies. II.

Synchronized flashing by males of some firefly species involves a capacity for visually coordinated, rhythmically coincident, inter-individual behavior that is apparently unique in the animal kingdom except for a few other arthropods and for man. This paper reviews (1) diverse communicative interactions that have evolved from elementary photic signals, (2) physiological mechanisms of synchronism, and (3) theories about its biological meaning. Work of the past 20 years shows that flash synchrony is widespread geographically and taxonomically, appears in an astonishing range of spectacular display types, utilizes several neural flash-control mechanisms and is pervasively but enigmatically involved in courtship. No proposed function for synchrony has been fully established but theory and physiology concur in indicating that synchrony aids male orientation toward the female, female recognition of male flashing, or both. Increased mate choice for the female is one likely ultimate benefit.

Animals↗

PubMed1987

Purification and biochemical characterization of a human autocrine growth factor produced by Epstein-Barr virus-transformed B cells.

Autocrine growth factor for Epstein-Barr virus-transformed human B cells (aBGF), a protein that is constitutively produced by the human EBV-transformed B cell line 5/2, has been purified from serum-free conditioned medium. The purification involved sequential ammonium sulfate precipitation, ion exchange chromatography, gel filtration, and reversed-phase high performance liquid chromatography. The purified protein has a m.w. of 16,000 in NaDodSO4/polyacrylamide gel electrophoresis and an isoelectric point between 7.0 and 8.0. The relative molecular mass 16,000 form exists in equilibrium with dimeric and tetrameric forms. aBGF supports the growth of EBV-transformed B cells, which have been deprived of their own conditioned medium. The purified aBGF is fully effective at 0.5 ng/ml and has no interleukin 1 activity in the lymphocyte activation factor assay. Because several randomly selected lines of EBV-transformed cells and one EBV-negative lymphoma cell line both produce aBGF activity and show growth dependency on aBGF and because stimulation of normal B cells with anti-immunoglobulin M is increased by aBGF, we propose that aBGF has general significance for growth control of human B cells.

B-Lymphocytes↗

PubMed1986

[Persistent varicocele following high ligation of the internal spermatic vein. Phlebography and vaso-occlusion with ethibloc].

The importance of phlebography and vaso-occlusion using ethibloc in diagnosis and treatment of the persistent varicocele following ligation ("Bernardis' technique") is demonstrated. We performed 280 surgical ligations of the internal spermatic vein. In 30 patients persistence of the varicocele was found. In 9 patients following phlebography embolisation of a long segment including smaller collaterals was performed using ethibloc. The other 21 patients were treated surgically because of unusual draining of the collaterals into renal capsular veins, into the hemiazygos vein and into renal segmental veins. In all cases following embolisation complete resolution of the varicocele was observed within 3 months.

Diatrizoate↗

PubMed1986

Clinical experiences in the treatment of neuroblastoma with 131I-metaiodobenzylguanidine.

Treatment of neuroblastoma is an unsolved problem of pediatric oncology. In spite of highly intensified chemotherapy, the long-term survival rate of children with a metastatic neuroblastoma is below 10%. We therefore used 131I-metaiodobenzylguanidine (MIBG) for the first time to treat children with a neuroblastoma in relapse or primary unresponsiveness to chemotherapy. We had previously demonstrated that MIBG is useful for the scintigraphic imaging of neuroblastoma lesions and had investigated the cytotoxicity and uptake of MIBG in various neuroblastoma cell lines. We treated 6 children with neuroblastoma in a total of 19 courses. Three of the children suffered from a relapse of neuroblastoma; 3 had never gained a remission. Four of the 6 children lost their bone pain and fever during the first 3 days. In 5 of the 6 children the solid tumor as well as the bone marrow infiltration responded to MIBG treatment, with responses ranging from transitory decrease of the tumor mass to complete disappearance of abdominal tumors. We also witnessed a stabilization of osteolytic lesions, a decrease in elevated serum catecholamines, and a decrease in bone marrow infiltration. Five of the 6 children died of tumor progression 55-249 days after the first MIBG treatment.

3-Iodobenzylguanidine↗

PubMed1986

[Diagnostic problems of alveolar cell carcinoma].

The clinical and radiological symptoms and differential diagnosis of four out of seven cases of alveolar cell carcinomas of the lung, which were observed during the last years, have been compared. Some characteristics are shown, which make the differentiation possible between tuberculosis, sarcoidosis, chronic carcinogenic pneumonia and interstitial lung diseases. Early diagnosis by histological investigation of cells from sputum or from bronchial secretion and by needle biopsy seems possible. During the earliest stage alveolar cell carcinoma can be cured by surgery.

Adenocarcinoma, Bronchiolo-Alveolar↗

PubMed1986

[Lung complications in AIDS].

A short description of epidemiologic and clinical facts correlated with the acquired immunodeficiency syndrome (AIDS) is followed by a report on the manifestation of pulmonary infections mostly effected by Pneumocystis carinii. Two examples out of four cases will demonstrate the radiographic appearance of the Pneumocystis carinii pneumonia and clinical data. Only in rare cases does it seem possible to reduce the fatal outcome by early diagnosis.

Acquired Immunodeficiency Syndrome↗

PubMed1986

[Angiocinedensitometry with ECG-controlled injections in patients with healthy kidneys and kidney tumors].

According to the method, the necessary equipment and actual attainment of measurements, the results of cinedensitometric evaluations are discussed. The results are based on angiographic examinations of 80 patients (41 hypernephroma and 39 normal kidneys) who have been studied using X-ray cinedensitometry. It could be proven that with the ECG-triggered injection of contrast-medium, measurements of the pulsatile flow in the renal artery during the various periods of heart-motions could be performed with a high degree of accuracy. Curves of the velocity of the bloodflow are therefore attainable. The average velocities of bloodflow show normal values of 8.5 ml/s in normal kidneys, which means 570 ml/min. In hypernephromas, there were increased velocities of bloodflow measuring up to 1400 ml/min, that is a maximal flow of 760 ml/min. Depending upon the pulsatile flow the curves of the bloodflow velocity are very distinctive. The examples of values of bloodflow velocity in hypertrophic kidneys or in hypervascularized renal tumors support these findings. The lower the measured flow velocity is, the more uniform the pattern of the flow profile will be.

Absorptiometry, Photon↗

PubMed1985

The role of reactive oxygen compounds derived from 6-hydroxydopamine for bone marrow purging from neuroblastoma cells.

6-Hydroxydopamine(6-OHDA), a specific neurotoxin against sympathetic nerve cells, is a drug already used for purging of bone marrow from neuroblastoma cells before autologous bone marrow transplantation. However, we could not detect significant differences in the toxicity of 6-OHDA against neuroblastoma and other tumor cells under the purging conditions clinically used. In contrast, bone marrow stem cells were much more resistant. The unspecific toxic effect of 6-OHDA is caused by H2O2 or H2O2-derived products which are generated by auto-oxidation in the incubation medium before a significant amount of 6-OHDA is taken up by the cells. Withdrawal of oxygen during the incubation period and subsequent incubation with an oxygen containing medium led to a more specific destruction of neuroblastoma cells which can take up 6-OHDA selectively.

Ascorbic Acid↗

PubMed1985

Distribution and oxidation of malondialdehyde in mice.

The in vivo metabolism of malondialdehyde (MDA) by male and female Swiss mice was investigated. Distribution of an i.p. dose of MDA is rapid and uniform throughout the body. Conversion of 14C-labeled MDA to CO2 is complete 4 hours after an i.p. dose of 5 mumol to 200 mumol with no signs of short term toxicity. The yields of CO2 from [1-14C]-beta-alanine, [3-14C]-beta-alanine, [1-14C]-sodium acetate, and [2-14C]-sodium acetate were also determined. Comparison of the yields of CO2 from this series of compounds suggests the intermediacy of malonic semialdehyde in the metabolism of MDA. High doses (600 mumol) of beta-alanine or acetate given prior to 14C-MDA reduced the yield of 14CO2. Ethanol and disulfiram were both inhibitors of MDA metabolism, indicating the involvement of aldehyde dehydrogenase in the oxidation of MDA. These data demonstrate the ability of animal tissues to rapidly remove exogenously administered MDA. They also have implications with respect to the possible pathological consequences of in vivo MDA generation.

Acetates↗