Search PubMed⌕ Search

Biomedical subjects

C Huber

Publications and source records attributed to C Huber.

At least 91 records · Page 5Linked to original sources
PubMed1998

Immunologic findings in workers formerly exposed to 2,3,7,8-tetrachlorodibenzo-p-dioxin and its congeners.

One hundred ninety-two workers in a German pesticide factory who were exposed to polychlorinated dibenzodioxins and -furans (PCDD/PCDF) were investigated for former and present diseases and laboratory changes of the immune system. Moreover, in a subgroup of 29 highly exposed and 28 control persons, proliferation studies were performed. In addition to assays such as blood count, immunoglobulins, serum electrophoresis, monoclonal bands, surface markers, autoantibodies, and lymphocyte proliferation, two new methods, the rise of tetanus antibody concentration after vaccination and the in vitro resistance of lymphocytes to chromate, were used to diagnose the morphologic and functional state of the immune system. There was no stringent correlation of actual PCDD/PCDF concentrations with the occurrence of infections or with one of the immune parameters. In addition, outcomes of the tetanus vaccination and the chromate resistance test were not correlated with PCDD/PCDF. However, the chromate resistance of lymphocytes stimulated by phytohemagglutinin of highly exposed persons was significantly lower than that for the control group. These findings indicate that the function of lymphocytes can be stressed and possibly impaired by high exposure to PCDD/PCDF.

Adult↗
PubMed1998

Induction of macrophage-inflammatory protein 1alpha (MIP-1alpha) by interferon-alpha.

The biological functions of macrophage-inflammatory protein 1alpha (MIP-1alpha) include the regulation of inflammatory processes and the inhibition of early hematopoiesis. We investigated the regulation of MIP-1alpha in various cell types in response to IFN-alpha and IL-4 by mRNA analysis and examination of MIP-1alpha protein levels in culture supernatants. In peripheral blood mononuclear cells (PBMNCs) and purified monocytes, IFN-alpha induced MIP-1alpha mRNA expression and stimulated MIP-1alpha secretion in LPS-activated monocytes to almost twice the value observed with LPS alone, whereas IL-4 caused a reduction by 80-95%. The stimulatory effect of IFN-alpha on MIP-1alpha production appeared to be dominant over its inhibition by IL-4. This effect was most pronounced after prolonged incubation periods. In fibroblasts obtained from human foreskin, IFN-alpha in combination with IL-1 stimulated MIP-1alpha secretion to more than three times the level obtained with IL-1. Stimulation of MIP-1alpha expression by IFN-alpha may indirectly influence inflammatory processes and the regulation of early hematopoiesis.

Cells, Cultured↗
PubMed1998

Pharmacokinetics of meloxicam in animals and the relevance to humans.

The pharmacokinetic profile of the new nonsteroidal anti-inflammatory drug meloxicam was investigated in a number of animal species, including mice, rats, dogs, mini-pigs, and baboons, after administration of [14C]meloxicam. The plasma concentration-time profiles for meloxicam in rats and dogs were comparable to that in humans, whereas there were marked differences between humans and mice, mini-pigs, and baboons. The highest tissue concentrations of meloxicam in rats and mini-pigs were seen in the liver and kidneys. In contrast, low concentrations of meloxicam were found in the central nervous system, compared with those in plasma. The excretion balance in mini-pigs resembled that in humans, with almost equal concentrations being eliminated in the urine and the feces. As in humans, meloxicam circulated mainly in the form of the parent compound in the plasma of mice, rats, dogs, mini-pigs, and baboons. The main metabolites in rats, mini-pigs, and humans were a 5'-hydroxymethyl derivative (AF-UH 1 SE) and a 5'-carboxy metabolite (UH-AC 110 SE). The percentage of meloxicam binding to protein was higher in rats and humans (>99%) than in other species. The pharmacokinetic profile of meloxicam in rats most closely resembles that in humans; therefore, reliable clinical predictions can be made from studies in this rodent species.

Animals↗
PubMed1997

Loss of heterozygosity studies and deletion mapping identify two putative chromosome 14q tumor suppressor loci in renal oncocytomas.

Renal oncocytoma is considered to be a benign tumor that shares some phenotypic features with chromophobe renal cell carcinoma (RCC). Recently, we described high frequencies of allelic loss at 1p, 2p, 6p, 10p, 13q, 14q, 17p, and 21q, which correlate significantly with the chromophobe subtype of RCC. To investigate the genetic relationship between these two entities, we examined 12 oncocytomas for loss of heterozygosity (LOH) at these regions. In addition, we included markers for 3p, 5q, 7q, 11p, and 22q. The only chromosomal region showing similarly high frequencies of allelic loss for both subtypes was 14q. Therefore, a genetic relationship between renal oncocytoma and chromophobe RCC seems questionable. Eight of 12 oncocytomas (67%) showed LOH at 14q, a frequency that was significantly higher (P < 0.001, chi(2) test) than the frequencies of LOH in all other regions. To define regions potentially harboring novel tumor suppressor genes, we performed multifluorescence microsatellite analysis with 13 markers spanning 14q. Interstitial deletions at different regions of 14q were detected, with the highest frequencies at D14S258 (14q23-24.3) and D14S292 (14q32.1-32.2). 14q LOH might be associated with advanced-stage RCCs or other tumors, but it does not seem to indicate progression in oncocytomas. Its role in pathogenesis of renal oncocytomas remains to be clarified. Here, we provide evidence for two distinct tumor suppressor gene loci at 14q in renal oncocytoma, which will be useful for further fine-mapping studies of these critical regions.

Adenoma, Oxyphilic↗
PubMed1997

Isoalloxazine derivatives promote photocleavage of natural RNAs at G.U base pairs embedded within helices.

We have recently shown that isoalloxazine derivatives are able to photocleave RNA specifically at G.U base pairs embedded within a helical stack. The reaction involves the selective molecular recognition of G.U base pairs by the isoalloxazine ring and the removal of one nucleoside downstream of the uracil residue. Divalent metal ions are absolutely required for cleavage. Here we extend our studies to complex natural RNA molecules with known secondary and tertiary structures, such as tRNAs and a group I intron (td). G.U pairs were cleaved in accordance with the phylogenetically and experimentally derived secondary and tertiary structures. Tandem G.U pairs or certain G.U pairs located at a helix extremity were not affected. These new cleavage data, together with the RNA crystal structure, allowed us to perform molecular dynamics simulations to provide a structural basis for the observed specificity. We present a stable structural model for the ternary complex of the G. U-containing helical stack, the isoalloxazine molecule and a metal ion. This model provides significant new insight into several aspects of the cleavage phenomenon, mechanism and specificity for G. U pairs. Our study shows that in large natural RNAs a secondary structure motif made of an unusual base pair can be recognized and cleaved with high specificity by a low molecular weight molecule. This photocleavage reaction thus opens up the possibility of probing the accessibility of G.U base pairs, which are endowed with specific structural and functional roles in numerous structured and catalytic RNAs and interactions of RNA with proteins, in folded RNAs.

Base Composition↗
PubMed1997

Activated acetic acid by carbon fixation on (Fe,Ni)S under primordial conditions.

In experiments modeling the reactions of the reductive acetyl-coenzyme A pathway at hydrothermal temperatures, it was found that an aqueous slurry of coprecipitated NiS and FeS converted CO and CH3SH into the activated thioester CH3-CO-SCH3, which hydrolyzed to acetic acid. In the presence of aniline, acetanilide was formed. When NiS-FeS was modified with catalytic amounts of selenium, acetic acid and CH3SH were formed from CO and H2S alone. The reaction can be considered as the primordial initiation reaction for a chemoautotrophic origin of life.

Acetic Acid↗
PubMed1997

Involvement of the chromosomal region 11q13 in renal oncocytoma: case report and literature review.

Renal oncocytomas comprise a cytogenetically heterogeneous group of tumors consisting potentially of cytogenetic distinguishable subgroups. Review of the literature revealed loss of chromosome 1 and Y as a possible anomaly for at least one subset oncocytomas. The frequent finding of rearrangements involving chromosome 11 band q13 characterizes another subset of oncocytomas. We report the cytogenetic and pathological features of a renal oncocytoma diagnosed in a 72-year-old woman and found a t(9;11)(p23;q13) as a consistent abnormality. This supports the idea that translocations involving 11q13 define a further subset of oncocytoma.

Adenoma, Oxyphilic↗
PubMed1997

Three-dimensional representations of corneal deformations from keratotopography data.

PURPOSE: To improve the perception of corneal shape from the data measured by a corneal topography system. METHODS: A computer program to illustrate the deformation of the cornea measured by corneal topography is described. The deviations from a regular corneal curvature are presented in a three-dimensional (3-D) map. Elimination of the basic curvature in the individual cornea allows the small deformations of the cornea to be seen as shapes and not as power maps. CONCLUSION: The images obtained with the 3-D maps are different from the keratotopographic images. The latter show the deformation of the cornea on a micro-metric scale and are understandable in terms of shape or surgical planning. Using our inborn 3-D perception mechanism provides a better understanding of corneal shape. A shape reconstruction from the keratotopographic image alone is nearly impossible.

Cornea↗
PubMed1997

Infectious complications during neutropenia subsequent to peripheral blood stem cell transplantation.

Type, severity and incidence of infection during the neutropenic period after peripheral blood stem cell transplantation (PBSCT) for treatment of malignant disease were studied in 66 patients treated at a single institution. Data of 34 female and 32 male patients with a median age of 43 years suffering from leukemia (12), lymphoma (35), multiple myeloma (six) or solid tumors (13) were retrospectively analyzed. All patients had received at least 2.5 x 10(6) CD34-positive cells for stem cell rescue after high-dose chemotherapy. Ninety-four percent of the patients experienced at least one febrile episode during their post-transplant course. The patients recovered quickly and defervesced after a median of 4 days. The incidence of bacteremia was 39% and gram-positive cocci were the predominant pathogens. In contrast, severe organ infections were rare. Only 5% of the patients suffered from lung infiltrates. No invasive fungal infections were observed. No transplant-related deaths occurred in the 66 patients studied. We conclude that the severe, but shortlasting neutropenia after peripheral blood stem cell transplantation is associated with a high incidence of bacterial infection. The severity of the majority of these infections is moderate. With appropriate anti-infective therapies these infections can be managed and life-threatening infectious complications, in particular fungal infections, are rare. Empirical anti-infective regimens specifically designed for this clinical situation should be explored.

Adolescent↗
PubMed1997

Peripheral blood stem cell (PBSC) mobilization with chemotherapy followed by sequential IL-3 and G-CSF administration in extensively pretreated patients.

Extensive pretreatment has been identified as a significant risk factor for failure of sufficient PBSC mobilization. From published data and our own experience we defined pretreatment variables which render patients at risk for not collecting at least 2.5 x 10(6) CD34-positive cells per kg bodyweight (BW). These variables were previous unsuccessful PBSC mobilization trial, previous large field radiotherapy, four or more cycles of myelosuppressive chemotherapy regimens, and combinations of extended field radiotherapy plus chemotherapy. Based on these inclusion criteria we treated 19 patients with disease-specific conventional-dose chemotherapy followed by sequential subcutaneous administration of IL-3 (5 microg/kg BW) for 5 consecutive days and G-CSF (10 microg/kg) until PBSC collection or neutrophil recovery. Patients were 10 males and nine females with a median age of 43 years. Diagnoses were non-Hodgkin's lymphoma n = 5, Hodgkin's disease n = 2, multiple myeloma n = 2, CML n = 4, AML n = 4 and testicular cancer n = 2. Twelve patients had prior unsuccessful trial of PBSC mobilization with chemotherapy followed by G-CSF. Except for mobilization chemotherapy-related neutropenic fever, no major toxicities (WHO grade > or = 2) were observed. Growth factors were well tolerated. Collection of at least 2.5 x 10(6) CD34-positive cells per kg BW was possible in 11 out of 19 patients (58%). In five out of 12 patients with a previous unsuccessful trial of PBSC mobilization, the study regimen mobilized sufficient CD34-positive cells. Nine patients went on to high-dose chemotherapy followed by autologous PBSC transplantation. Prompt hematologic recovery was seen in all of them. In conclusion, the sequential administration of IL-3 followed by G-CSF after conventional-dose chemotherapy allows successful PBSC collection in the majority of extensively pretreated patients.

Adult↗
PubMed1997

A comparative study of the in vitro immunomodulatory activity of human intact immunoglobulin (7S IVIG), F(ab')2 fragments (5S IVIG) and Fc fragments. Evidence for post-transcriptional IL-2 modulation.

During the past few decades intravenous immunoglobulin (IVIG) has been used successfully in the treatment of various immunoregulatory disorders. Treatment results have been attributed to immunomodulation mainly via Fc receptors or by anti-idiotypic antibodies to disease-causing autoantibodies. From the present study it is clearly evident that 7S IVIG (intact immunoglobulin) as well as 5S IVIG [F(ab')2 fragments] and Fc fragments have a potent immunomodulatory capacity. We demonstrate that mainly 7S IVIG inhibits alloantigen-induced T-cell proliferation and generation of cytotoxic T lymphocytes. Reduced interleukin-2 (IL-2) protein levels in culture supernatants of IVIG-supplemented mixed lymphocyte reactions (MLR) but unchanged IL-2 mRNA levels strongly argue in favour of a post-transcriptional interference of IVIG with cytokines and/or cytokine production. Interferon-gamma (IFN-gamma), soluble IL-2 receptor (sIL-2R) and monokines such as IL-1 beta, IL-6, IFN-alpha and tumour necrosis factor (TNF-alpha) were not affected by IVIG supplementation to MLR. Fc fragments were superior to F(ab')2-containing IVIG (5S and 7S IVIG) in inhibiting lectin stimulation of peripheral blood mononuclear cells (PBMC), whereas natural killer (NK) cytotoxicity was primarily inhibited by Fc-bearing IVIG (7S IVIG and Fc fragments), suggesting multiple mechanisms of IVIG immunomodulatory activity.

Antigen Presentation↗
PubMed1997

Analysis of the MHC class I antigen presentation machinery in human embryonal carcinomas: evidence for deficiencies in TAP, LMP and MHC class I expression and their upregulation by IFN-gamma.

The expression of the major histocompatibility complex (MHC) class I antigens is suppressed in early post-implantation embryonic cells as well as in embryonal carcinoma (EC) cells, but could be upregulated by treatment with interferon (IFN)-gamma or retinoic acid. In a number of human and murine tumours, defects in the expression of the different components of the MHC class I antigen processing machinery, such as the proteasomal subunits LMP-2 and LMP-7 and the peptide transporters TAP-1 and TAP-2, account for impaired MHC class I surface expression. Here, we analysed the constitutive and IFN-gamma regulated mRNA and protein expression of the LMP, TAP and MHC class I molecules in the human EC line 577LM. In comparison to lymphoblastoid control cells, poor constitutive mRNA and protein expression of LMP-7, TAP-1, HLA class I, and beta 2-microglobulin, but not of TAP-2 and LMP-2, was detected in 577LM cells. The lack of MHC class I surface expression on 577LM cells could not be enhanced either by culturing cells at low temperature or by their incubation with exogenous MHC class I specific binding peptides: thus, the defective MHC class I surface expression was not only caused by impaired generation and processing of antigenic peptides. IFN-gamma treatment of 577LM resulted in a significant increase of MHC class I surface expression which was preceded by an upregulation of TAP, LMP and MHC class I transcripts as well as of TAP-1 and TAP-2, but not of LMP-2 and LMP-7, protein expression. These data suggest that human EC cell lines show a stable expression of a MHC class I low/deficient phenotype. The deficiencies associated with this phenotype involve different levels of the MHC class I restricted antigen presentation machinery and could be modified by treatment with IFN-gamma.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

A heterotrimeric G protein-phospholipase A2 signaling cascade is involved in the regulation of peroxisomal motility in CHO cells.

Peroxisomal motility was studied in vivo in CHO cells following transfection with a green fluorescent protein construct containing the C-terminal peroxisomal targeting signal 1 (GFP-PTS1). Time-lapse imaging and evaluation of difference images revealed that peroxisomes attach to microtubules in a Ca2+ requiring step and are transported in an ATP-dependent manner. Following microinjection of guanosine-5'-O-(3-thiotri-phosphate) (GTP(gamma)S), peroxisomal movements were arrested, indicating regulation by GTP-binding proteins. The effect of GTP(gamma)S was mimicked by AlF4- and mastoparan, two drugs which are known to activate heterotrimeric G proteins. Pertussis toxin which prevents Gi/Go protein activation completely abolished the effect of GTP(gamma)S and mastoparan on peroxisomal motility suggesting that the G protein belongs to the Gi/Go class. At least one effector of the G protein is phospholipase A2 as demonstrated by the observation that the phospholipase A2 activating protein peptide efficiently blocks peroxisomal motility, and that the effect of mastoparan and AlF4- is largely abolished by various phospholipase A2 inhibitors. In summary, these data provide evidence for a new type of regulation of organelle motility mediated by a Gi/Go-phospholipase A2 signaling pathway. This type of regulation has not been observed so far with other cell organelles such as mitochondria, the endoplasmic reticulum or axonal vesicles. Thus, motility is regulated individually for each cell organelle by distinct mechanisms enabling the cell to fulfill its vital functions.

Animals↗
PubMed1997

Expression and function of the peptide transporters in escape variants of human renal cell carcinomas.

The transporter associated with antigen processing (TAP) complex is a heterodimeric transmembrane pump consisting of the TAP-1 and TAP-2 subunits; these subunits translocate peptides from the cytoplasm into the lumen of the endoplasmic reticulum, where they bind nascent major histocompatibility complex (MHC) class I molecules. Loss or reduced expression of the TAP genes results in the synthesis of unstable peptide free MHC class I molecules that are only weakly expressed on the cell surface. In a number of human tumor cell lines, downregulation of MHC class I expression has been found to be associated with reduced or absent TAP expression. To investigate whether alterations in MHC class I expression occur during transformation and subsequent progression and whether MHC class I suppression is caused by impaired TAP function, we analyzed the protein expression of MHC class I heavy and light chain and TAP-1 in three renal cell carcinoma (RCC) cell lines and short-term cultures from corresponding normal kidney tissue. In one case a cell line established from a metastatic lesion was also available. Compared with normal epithelial cells, suppression of TAP-1 and MHC class I molecules was detected in all three primary RCC cells and was even more pronounced in the metastatic cell line. In contrast to normal epithelial cells, MHC class I membrane expression of two RCC lines was enhanced by culture in the presence of MHC class I binding peptides or at low temperature (26 degrees C) instead of 37 degrees C. Unstable MHC class I surface expression is caused by dissociation of the MHC class I heavy and light chain molecules as a result of functional defects in the antigen processing machinery, e.g., impaired peptide transport. Attempts to counteract the reduced immunogenicity by transferring the TAP genes into these cells demonstrated that TAP-1-modified RCC cells expressed higher levels of MHC class I molecules. These data indicate that downregulation and instability of MHC class I surface expression in RCC cells is at least partially caused by deficient loading with endogenous peptides and can be restored by TAP gene transfer.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1997

Spontaneous and interleukin-2-modulated cytokine release by bronchoalveolar cells in pulmonary malignancy.

In a recent phase I study of inhalative, human natural interleukin-2 (hnIL-2) treatment of pulmonary metastases from previously resected solid tumors (mainly renal carcinoma), we have reported that this treatment resulted in an increased accessory function of alveolar macrophages (AM) [1]. Encouraged by these data, we investigated the influence of hnIL-2 inhalation on proinflammatory cytokines spontaneously released by AM. Bronchoalveolar lavage was performed in four groups, each of four patients, before and after 2 weeks of daily inhalation of 0, 200,000, 600,000 and 1,200,000 IU of hnIL-2, respectively. Bronchoalveolar cells were cultured without stimulation to allow spontaneous release over a period of 24 h, into the supernatant. Concentrations of tumor necrosis factor-alpha (TNF-alpha), IL-6, IL-8 and macrophage inflammatory protein-1alpha (MIP-1alpha) were determined by the ELISA technique. Before hnIL-2 inhalation, we measured the following spontaneous cytokine release: TNF-alpha: 1,115.4 +/- 469.1 pg/ml, IL-6: 267.5 +/- 67.7 pg/ml cells, IL-8: 137.8 +/- 40.5 ng/ml, MIP-1alpha: 9.5 +/- 6.8 ng/ml. Inhalation of hnIL-2 did not result in any significant changes in these cytokines. Comparing TNF-alpha release in healthy controls (250.6 +/- 46.7 pg/ml) with that of tumor patients (1,115.4 +/- 469.1 pg/ml), we observed significantly (p < 0.05) elevated TNF-alpha levels in the patient group, which did not change significantly in response to IL-2 inhalation. Our data demonstrate that the activation of AM previously observed after hnIL-2 inhalation is not directly related to a hnIL-2-induced cytokine release by bronchoalveolar cells.

Adult↗
PubMed1997

IFN-gamma-mediated coordinated transcriptional regulation of the human TAP-1 and LMP-2 genes in human renal cell carcinoma.

Some human tumor cells exhibit deficient expression of the peptide transporters TAP1 and TAP2 and of the proteasome subunits low molecular weight protein (LMP)-2 and LMP-7, which could be partially restored by cytokine treatment. Here, we show that IFN-gamma stimulation of human renal cell carcinoma lines increased the MHC class I, transporter associated with antigen processing (TAP), and LMP transcript and protein levels, but TAP and LMP expression are more rapidly induced by IFN-gamma than MHC class I molecules. No correlation between the level of induction of the MHC class I antigen presentation genes and IFN sensitivity/resistance was detected. The IFN-gamma-mediated increase of MHC class I, TAP-1, and LMP-2 expression was independent of de novo protein synthesis. Analysis of the dual TAP-1/LMP-2 promoter activity revealed that TAP-1 and LMP-2 expression are controlled by IFN-gamma at the transcriptional level. Site-specific mutations in the IFN-gamma-responsive element of the TAP-1/LMP-2 promoter blocked induction by IFN-gamma. Thus, the IFN-gamma-mediated coordinated transcriptional up-regulation of TAP-1 and LMP-2 expression occurs through the use of a common regulatory element, which might result in enhanced recognition of renal cell carcinoma cells by the immune system.

ATP Binding Cassette Transporter, Subfamily B, Mem↗