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Biomedical subjects

C Hofmann

Publications and source records attributed to C Hofmann.

At least 55 records · Page 3Linked to original sources
PubMed1997

The monocyte chemotactic protein-4 induces oxygen radical production, actin reorganization, and CD11b up-regulation via a pertussis toxin-sensitive G-protein in human eosinophils.

The novel human CC-chemokine monocyte chemotactic protein-4 (MCP-4) is a chemotaxin for eosinophils. Here, the biological activities and the activation profile of MCP-4 was further characterized in eosinophils and compared to other activators such as platelet activating factor (PAF), Eotaxin and RANTES. As demonstrated by lucigenin-dependent chemiluminescence and superoxide dismutase-inhibitable cytochrome C reduction MCP-4 stimulated the production of reactive oxygen metabolites. Furthermore, MCP-4 induced up-regulation of the integrin CD11b. Flow cytometric studies revealed rapid and transient actin polymerization upon stimulation with MCP-4. At optimal concentrations the changes induced by MCP-4 were weaker than the effects after stimulation with PAF and comparable to those obtained by RANTES and Eotaxin. Cell responses elicited by MCP-4 were inhibited by pertussis toxin indicating involvement of Gi-proteins in this signal pathway. These findings point to a role of MCP-4 in the pathogenesis of eosinophilic inflammation as chemotaxin as well as activator of pro-inflammatory effector functions.

Actins↗
PubMed1997

Evidence for the involvement of phosphatidylinositol 4,5-bisphosphate 3-kinase in CD18-mediated adhesion of human neutrophils to fibrinogen.

The CD18 integrin mediates chemotaxin-induced adhesion of neutrophils to fibrinogen. In neutrophils chemotaxins activate different intracellular pathways, which metabolize phosphatidylinositol 4,5-bisphosphate. To analyse the functional role of phosphatidylinositol 4,5-bisphosphate 3-kinase in the adhesion response, studies with the fungal metabolite wortmannin and the chemically unrelated compound LY 294002 were performed. These compounds inhibited with similar concentration dependency chemotaxin-induced formation of [32P]phosphatidylinositol 3,4,5-trisphosphate and CD18-mediated adhesion of neutrophils to fibrinogen, but did not influence expression of CD18 molecules at the cell surface. These data suggest involvement of phosphatidylinositol 4,5-bisphosphate 3-kinase in chemokine-induced avidity changes of CD18 integrins.

Androstadienes↗
PubMed1997

Down-regulation of tissue specific tumor necrosis factor-alpha in the liver and lung after burn injury and endotoxemia.

Burn injury and endotoxin lead to the development of a systemic inflammatory response. Because tumor necrosis factor-alpha (TNF-alpha) is a component of the proinflammatory response, we have determined the effect of burn injury and endotoxin in a murine model of thermal on tissue specific TNF-alpha levels in the liver and lung. Male mice were divided into four groups and injected with endotoxin (ETX) (2.5 mg/kg intraperitoneally) or saline (CNTL) or subjected to a 16% full-thickness scald burn (B), or ETX administration 72 hours after burn injury (B+ETX). Animals were killed at 0 to 24 hours after ETX or CNTL, 0 to 72 hours after B, and 72 to 96 hours after B+ETX (ETX administration 72 hours after B). TNF-alpha mRNA by Northern blot and protein analysis by enzyme-linked immunosorbent assay were determined and protein expressed as nanogram per gram of tissue. Statistical analysis was performed using analysis of variance with significance at p < 0.05. Burn injury did not result in detectable levels of liver or lung TNF protein or mRNA. Endotoxin administration resulted in a near six-fold rise in liver TNF protein compared with controls at 1, 2, and 6 hours after ETX (p < 0.05 to p < 0.001). Liver mRNA remained elevated from 20 minutes to 24 hours after ETX versus CNTL (p < 0.05). Endotoxin injection produced a persistent lung TNF protein elevation reaching significance at 1 and 2 hours (p < 0.001) and a rise in mRNA at 40 minutes to 6 hours (p < 0.05) versus CNTL. The liver showed a trend of reduced mRNA after B+ETX versus ETX (p = NS), whereas protein levels were reduced by 50 to 60% at 1 and 2 hours (p < 0.01). Lung mRNA values after B+ETX were only 40% compared with ETX at nearly all time points (p < 0.001) but were 15 times above CNTL values at 2 hours (p < 0.05). Based on these results, we conclude that burn injury did not cause an increase in liver or lung tissue specific TNF-alpha. However, the presence of a preexisting burn injury dramatically altered the response to endotoxin and the primary point of regulation appears to be at the posttranscriptional level.

Animals↗
PubMed1997

Augmentation of deglutitive upper esophageal sphincter opening in the elderly by exercise.

Earlier studies have shown that the cross-sectional area of the deglutitive upper esophageal sphincter (UES) opening in healthy asymptomatic elderly individuals is reduced compared with healthy young volunteers. The aim of this study was to determine the effect of a head-raising exercise on swallow-induced UES opening and hypopharyngeal intrabolus pressure in the elderly. We studied a total of 31 asymptomatic healthy elderly subjects by videofluoroscopy and manometry before and after real (19 subjects) and sham (12 subjects) exercises. A significant increase was found in the magnitude of the anterior excursion of the larynx, the maximum anteroposterior diameter, and the cross-sectional area of the UES opening after the real exercise (P < 0.05). These changes were associated with a significant decrease in the hypopharyngeal intrabolus pressure studied in 12 (real-exercise) and 6 (sham-exercise) subjects (P < 0.05). A similar effect was not found in the sham-exercise group. In normal elderly subjects, deglutitive UES opening is amenable to augmentation by exercise aimed at strengthening the UES opening muscles. This augmentation is accompanied by a significant decrease in hypopharyngeal intrabolus pressure, indicating a decrease in pharyngeal outflow resistance. This approach may be helpful in some patients with dysphagia due to disorders of deglutitive UES opening.

Aged↗
PubMed1996

Gene transfer into hepatocytes and human liver tissue by baculovirus vectors.

Gene therapy of liver diseases requires the development of efficient vectors for gene transfer in vivo. Retroviral and adenoviral vectors have been shown to deliver genes efficiently into hepatocytes in vitro and in vivo. However, these vectors do not allow for exclusive infection of the liver which would be highly advantageous for in vivo gene therapy strategies. We have recently demonstrated that genetically modified baculoviruses (Autographa californica nuclear polyhedrosis virus) efficiently deliver genes into cultured cells and have a strong preference for hepatocytes of different origin. Baculoviral gene transduction efficiency into human hepatocytes was determined to approach 100% and expression levels are high, provided that gene expression is controlled by mammalian promoters. In this report, we present further properties of baculoviruses regarding their use for hepatocyte gene transfer. Baculovirus-mediated gene expression declines rapidly in the hepatocellular carcinoma cell line Huh7 and more slowly in primary cultures of mouse hepatocytes. Direct application of baculoviruses for gene delivery to the liver in vivo is hampered by serum components, presumably by complement. However, we demonstrate here that baculoviral gene transfer is feasible in ex vivo perfused human liver tissue. This result suggests the development of a strategy using baculoviral vectors for liver-directed gene therapy.

Animals↗
PubMed1996

BMP 7 is required for nephrogenesis, eye development, and skeletal patterning.

In summary, the generation of BMP-7-deficient mice has provided additional evidence that this family of growth factors regulate many morphogenetic processes including but not limited to skeletal development. In particular our experiments demonstrate that BMP 7 acts as an early inducer of glomeruli formation, and that it is required for skeletal patterning and lens formation. Our results not only demonstrate that BMP 7 is involved in the differentiation of several organs during development, but also raise the hypothesis that mutations in the Bmp 7 gene itself or in the genetic pathway could be responsible for several human genetic diseases in which glomerulus formation is impaired.

Animals↗
PubMed1996

Analysis of limb patterning in BMP-7-deficient mice.

Bone morphogenetic proteins (BMPs) are polypeptide signaling molecules, belonging to the TGF-beta superfamily. They were originally identified by their ability to induce ectopic bone formation, but their expression patterns in embryos suggest multiple functions. BMP-7-deficient mice show among other mesodermal and skeletal patterning defects, polydactyly in the hindlimbs [Luo G, Hofmann C, Bronckers ALJJ, Sohocki M, Bradley A, Karsenty G (1995): Genes Dev 9:2808-2820; Dudley AT, Lyons KM, Robertson EJ (1995): Genes Dev 9:2795-2807]. Here we report a more detailed analysis of the limb phenotype in BMP-7-deficient mice using in situ hybridization to monitor expression of molecules implicated in patterning processes of the developing vertebrate limb. In previous studies we showed that Sonic hedgehog (Shh) was expressed normally, but Hoxd-13 expression in limb mesenchyme was lower in BMP-7 mutant limbs. Here we show that Hoxd-11 expression domains are also contracted and decreased in intensity in mutant limbs, suggesting that 5' genes of the Hoxd cluster are coordinately downregulated, while another Bmp, Bmp-2, which can be activated by Shh, is similarly expressed. The mutant limb buds are broader than normal buds, and fibroblast growth factor Fgf-8 is expressed throughout the extended ridge. However, expression of the homeobox gene Msx-1, which has been shown to be involved in epithelial-mesenchymal interactions during limb development, was decreased in the mesenchyme of BMP-7 mutant limbs. Taken together, our data suggest that BMP-7 is involved in regulating proliferation and/or epithelial-mesenchymal interactions in the developing limb.

Animals↗
PubMed1996

Inhibition of progressing primary esophageal peristalsis by pharyngeal water stimulation in humans.

BACKGROUND & AIMS: Sensory impulses initiated from the pharynx exert differing effects on the deglutitive apparatus. They have an inhibitory effect on the lower esophageal sphincter but an excitatory effect on the upper esophageal sphincter. The aim of this study was to systematically investigate the effect of pharyngeal sensory impulses evoked by water stimulation on the progressing esophageal peristalsis. METHODS: Sixteen healthy young volunteers were studied in the supine position. The presence of normal peristalsis was verified. Esophageal peristalsis was recorded 3, 6, 9, 12, 15, and 18 cm above the lower esophageal sphincter. Pharyngeal stimulation was performed by injecting a predetermined threshold volume into the pharynx 2 cm above the upper esophageal sphincter, directed posteriorly. The injections were timed to coincide with the arrival of the peristaltic wave induced by dry swallows at respective recording sites. RESULTS: Injection of the threshold volume (0.5 +/- 0.1 mL) stopped the progression of peristalsis at both the striated and smooth muscle esophagus. Topical pharyngeal anesthesia blocked this inhibitory effect (P < 0.01). CONCLUSIONS: Sensory impulses initiated from the pharynx evoked by water injection inhibit the progression of primary esophageal peristalsis. Although the clinical significance of these findings is not determined, they may explain the mechanism of some of the failed esophageal peristalsis.

Adult↗
PubMed1996

Insulin-like growth factor-1 induces rapid tyrosine phosphorylation of the vav proto-oncogene product.

The vav proto-oncogene product (p95(vav)) is specifically expressed in cells of hematopoietic origin and has one src homology 2 (SH2) domain, two SH3 domains, and motifs typical of guanine exchange factors. Insulin-like growth factor-1 (IGF-1) receptors are expressed on a variety of hematopoietic cells and, upon ligand binding, mediate signals regulating hematopoietic cell proliferation. We studied the phosphorylation status of p95(var) in the U-255 human myeloma cell line, in response to IGF-1 stimulation. Immunoblotting experiments with an antiphosphotyrosine monoclonal antibody disclosed that p95(vav) is phosphorylated on tyrosine in an IGF-1-dependent manner. The tyrosine phosphorylation of 95(vav was rapid, appearing within 5 minutes of IGF-1 treatment, amd transient, diminishing by 90 minutes. Similar results were obtained when the mouse plasmacytoma J558L cell line was studied. IGF-1-dependent tyrosine phosphorylation of p95(vav) was also seen in the 32D mouse myeloid cell line that lacks expression of insulin receptor substrate (IRS) proteins, suggesting that it is not regulated by activation of the IRS-signaling system. Taken together, these data suggest that the vav proto-oncogene is a substrate for the IGF-1 receptor tyrosine++ kinase and may be involved in the signal transduction of IGF-1 in cells of hematopoietic origin.

Animals↗
PubMed1996

Gene therapy: prospects for treatment of liver disease.

Gene therapy in the liver for treatment of metabolic diseases is a great challenge. The development of vectors for gene transfer to hepatocytes in vitro and to the liver in vivo has advanced very rapidly within the last few years. However, none of the existing vectors would allow for expression of therapeutic levels of a gene product for a longer period of time. Our laboratory is developing alternative strategies for gene transfer to the liver in vivo which are based on composite vectors consisting of envelopes and promoters derived from hepatitis B virus, an EBV-derived replicon, and the chromosomal protein HMG1. Hepatocyte specificity of both, binding of the particles and expression of foreign genes, was demonstrated.

Arteriosclerosis↗
PubMed1996

[Bone bank management using a thermal disinfection system (Lobator SD-1). A critical analysis].

In the study presented on 380 allogenic bone donations from living and organ donors, we analyzed the safety of allograft handling bone-band documentation, logistics and costs. For transplant treatment we routinely used a thermal disinfection system (Lobator SD-1). From 380 allograft donors, 400 bone transplants were gained. The rejection rate was 12.2%. After thermal disinfection for 1 h at 80 degrees C, the grafts were cryopreserved at -80 degrees C and released from the bone bank for potential transplantation after 14-16 days. Five of 730 microbiological specimens showed bacterial contamination after thermal graft decontamination. The bacterial species found on the allografts normally have an inactivation temperature under 80 degrees C. Therefore, only secondary contamination can explain the positive bacteriological test results. With reform of the health care system the economical aspects of bone banking have triggered more interest. The cost for one bone transplant released from the bone bank was 424.75 DM: the overall cost for the bone bank in one year was 75,076 DM. Laboratory (58.2%) and material costs (22.5%) were the major factors. Personnel costs and apparatus costs were relatively low (< 20%). With introduction of the thermal disinfection system (Lobator SD-1) into the bone bank, the safety of allogenic bone transplants was greatly improved. Clinical and serological donor screening must be performed according to international bone bank directives. Considering the low rejection rate and the short turnover rate, the economical costs could be reduced. Using an appropriate disinfection system (thermal disinfection at 80 degrees C), laboratory tests covering venereal diseases, malaria and cytomegalia are no longer required. Also, secondary HIV testing of living donors can be omitted without reducing the safety of the transplant.

Bone Banks↗
PubMed1995

BMP-7 is an inducer of nephrogenesis, and is also required for eye development and skeletal patterning.

Bone morphogenetic proteins (BMPs) are multifunctional growth factors originally identified by their ability to induce ectopic bone formation. To investigate the function of one of the BMPs, BMP-7, we have generated BMP-7-deficient mice using embryonic stem cell technology. BMP-7-deficient mice die shortly after birth because of poor kidney development. Histological analysis of mutant embryos at several stages of development revealed that metanephric mesenchymal cells fail to differentiate, resulting in a virtual absence of glomerulus in newborn kidneys. In situ hybridization analysis showed that the absence of BMP-7 affects the expression of molecular markers of nephrogenesis, such as Pax-2 and Wnt-4 between 12.5 and 14.5 days postcoitum (dpc). This identifies BMP-7 as an inducer of nephrogenesis. In addition, BMP-7-deficient mice have eye defects that appear to originate during lens induction. Finally, BMP-7-deficient mice also have skeletal patterning defects restricted to the rib cage, the skull, and the hindlimbs.

Animals↗
PubMed1995

Efficient gene transfer into human hepatocytes by baculovirus vectors.

Viral vectors are the most efficient tools for gene delivery, and the search for tissue-specific infecting viruses is important for the development of in vivo gene therapy strategies. The baculovirus Autographa californica nuclear polyhedrosis virus is widely used as a vector for expression of foreign genes in insect cells, and its host specificity is supposed to be restricted to arthropods. Here we demonstrate that recombinant A. californica nuclear polyhedrosis virus is efficiently taken up by human hepatocytes via an endosomal pathway. High-level reporter gene expression from heterologous promoters was observed in human and rabbit hepatocytes in vitro. Mouse hepatocytes and some other epithelial cell types are targeted at a considerably lower rate. The efficiency of gene transfer by baculovirus considerably exceeds that obtained by calcium phosphate or lipid transfection. These properties of baculovirus suggest a use for it as a vector for liver-directed gene transfer but highlight a potential risk in handling certain recombinant baculoviruses.

Animals↗
PubMed1995

Altered expression of insulin signaling components in streptozotocin-treated rats.

Insulin signaling is known to proceed through the insulin receptor to the insulin receptor substrate-1 (IRS-1). Tyrosine-phosphorylation of IRS-1 causes it to associate with the src-homology-2 (SH2) domains of at least four other proteins: phosphatidylinositol 3'-kinase (PI3K), growth factor receptor-bound protein-2 (GRB2), Nck, and Syp. In order to understand the cellular derangements associated with type I diabetes, the levels of these four SH2-containing proteins was determined in streptozotocin-induced diabetic rats. In liver tissue of diabetic rats, the levels of Nck and Syp were significantly decreased to 71 +/- 6% and 61 +/- 4% control, respectively, while in fat tissue only the Syp levels were significantly reduced to 72 +/- 9% control. PI3K levels were higher in livers of diabetic rats than controls, but unchanged in fat. The insulin-deficient diabetic condition was thus associated with altered levels of insulin signaling components.

1-Phosphatidylinositol 4-Kinase↗
PubMed1995

Insulin sensitization in diabetic rat liver by an antihyperglycemic agent.

This study aimed to demonstrate directly that the thiazolidinedione pioglitazone acts as an insulin sensitizer. We tested the hypothesis that pioglitazone treatment of diabetic rats alters liver function such that responsiveness of selected genes to subsequent insulin regulation is enhanced. Although flux through gluconeogenic/glycolytic pathways involves regulation of many enzymes, we presently report the effects of insulin on expression of two key enzymes in these metabolic pathways, ie, phosphoenolpyruvate carboxykinase (PEPCK) and glucokinase (GK). Rats were either studied as nondiabetic controls or injected with streptozotocin as a model for insulin-deficient diabetes. Diabetic animals were treated without or with pioglitazone and subsequently examined for acute responses to insulin. Pioglitazone treatment of diabetic animals significantly enhanced the effects of insulin to reverse elevated blood glucose. Although the mean level of liver mRNA transcripts encoding PEPCK was increased to nearly 300% in diabetic animals as compared with nondiabetic controls (100%), it was significantly lower in pioglitazone-treated diabetic rats (119% of control) than in diabetic rats without pioglitazone (223% of control) after insulin treatment. By contrast, mRNA transcripts encoding GK were not detectable in diabetic animals, but were increased markedly by insulin treatment in all animal groups. Insulin-enhanced expression of GK was significantly greater in liver from animals that were treated earlier with pioglitazone (291% of control) than in liver from those that were untreated (214% of control). An amplified acute response of liver to insulin thus established pioglitazone as an insulin sensitizer. Our findings further showed that such sensitization can be developed even in the insulin-deficient state.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

Compensatory alterations for insulin signal transduction and glucose transport in insulin-resistant diabetes.

Insulin binding activates the receptor tyrosine kinase toward the insulin receptor substrate-1 (IRS-1). Phosphorylated IRS-1 then interacts with the p85 alpha subunit of phosphatidylinositol 3-kinase (PI3K), Nck, growth factor receptor-bound protein 2 (GRB2), and Syp, thus branching insulin's signal for both mitogenic and metabolic responses. To determine whether the expression of these proteins is altered in insulin resistance, the levels of these proteins were compared in adipose and liver tissues of nondiabetic mice and obese insulin-resistant diabetic KKAy mice. IR and PI3K p85 alpha protein levels were significantly lower in KKAy mice than in control nondiabetic mice, whereas IRS-1 protein levels were not altered. In contrast, the protein levels of GRB2, Nck, Syp, and GLUT-1 were dramatically elevated in KKAy fat, with less striking changes in liver. Treatment of diabetic animals with pioglitazone, an insulin-sensitizing antihyperglycemic agent, partially corrected the expression of some of these proteins. Taken together, these findings suggest that the insulin-resistant diabetic condition is characterized by changes in expression of insulin signal transduction components that may be associated with altered glucose metabolism.

Adaptation, Physiological↗