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Theo Hafmans

Publications and source records attributed to Theo Hafmans.

6 recordsLinked to original sources
PubMed2005

Titin and diaphragm dysfunction in chronic obstructive pulmonary disease.

RATIONALE: Recently, we have shown that Ca2+-activated force generation in diaphragm single fibers is impaired in patients with mild to moderate chronic obstructive pulmonary disease (COPD). For optimal active-force generation, the passive elasticity provided by titin is indispensable. OBJECTIVES: In the present study, we determined the passive-tension-length relations of single fibers of patients with mild to moderate COPD, hypothesizing that passive-elastic properties of diaphragm fibers are compromised. METHODS: Passive-tension-length relations were determined in diaphragm fibers from patients with and without COPD (predicted mean FEV1, 76 and 102%, respectively). In diaphragm homogenates titin expression was studied at the protein level by gel electrophoresis and at the transcript level by using a novel titin exon microarray. RESULTS: Diaphragm fibers from patients with COPD generate less passive tension on stretch. Titin content in the diaphragm did not differ between patients with and without COPD. However, titin exon transcript studies revealed up-regulation of seven exons, which code for spring elements in the elastic segment rich in proline, glutamate, valine, and lysine. Immunofluorescence analysis indicated elevated protein expression of the up-regulated splice variant in the COPD diaphragm. Simulation studies on titin molecules including the amino acids encoded by the seven up-regulated exons predicted reduced passive-tension generation on molecule stretch. CONCLUSIONS: Passive-tension generation of diaphragm single fibers is reduced in patients with COPD. Our results suggest that alternative splicing of the titin gene, resulting in increased length of the elastic segment rich in proline, glutamate, valine, and lysine, is involved. Interestingly, these changes occur already in patients with mild to moderate COPD.

Adult↗
PubMed2005

Localization and functional characterization of glycosaminoglycan domains in the normal human kidney as revealed by phage display-derived single chain antibodies.

Glycosaminoglycans (GAG) play an important role in renal homeostasis. They are strongly negatively charged polysaccharides that bind and modulate a myriad of proteins, including growth factors, cytokines, and enzymes. With the aid of specific phage display-derived antibodies, the distribution of heparan sulfate (HS) and chondroitin sulfate (CS) domains in the normal human kidney was studied. HS domains were specifically located in basement membranes and/or surfaces of renal cells and displayed a characteristic distribution over the nephron. A characteristic location in specific parts of the tubular system was also observed. CS showed mainly an interstitial location. Immunoelectron microscopy indicated specific ultrastructural location of domains. Only partial overlap with any of seven different proteoglycan core proteins was observed. Two HS domains, one highly sulfated (defined by antibody HS4C3) and one low sulfated (defined by antibody RB4Ea12), were studied for their cell biologic relevance with respect to the proliferative effect of FGF-2 on human mesangial cells in vitro. Fibroblast growth factor 2 (FGF-2) binding was HS dependent. Addition of purified HS4C3 antibody but not of the RB4Ea12 antibody counteracted the binding and the proliferative effect of FGF-2, indicating that the HS4C3 domain is involved in FGF-2 handling by mesangial cells. In conclusion, specific GAG domains are differentially distributed in the normal human kidney and are likely involved in binding of effector molecules such as FGF-2. The availability of tools to identify and study relevant GAG structures allows the development of glycomimetica to halt, for instance, mesangial proliferation and matrix production as seen in diabetic nephropathy.

Adult↗
PubMed2004

Use of physicochemical calculation of pKa and CLogP to predict phospholipidosis-inducing potential: a case study with structurally related piperazines.

Several cationic amphiphilic compounds are known to induce phospholipidosis, a condition primarily characterized by excessive accumulation of phospholipids in different cell types, giving the affected cells a finely foamy appearance. Excessive storage of lamellar membranous intralysosomal inclusion bodies is the hallmark for phospholipidosis on the electron microscopic level. In case of alveolar phospholipidosis, foamy macrophages accumulate within the alveolar spaces of the lung. Based on such findings in a one-year toxicity study with gepirone in rats, we studied the molecular properties of this compound and compounds suspected of being phospholipidosis inducers by means of physicochemical calculations. Physicochemical molecular calculations of molecular weight, ClogP (partition coefficient octanol/water), logD at pH 7.4, and pKa were performed, for the cationic amphiphilic compounds chlorpromazine, amiodarone, imipramine, propranolol and fluoxetine, and for the structurally related compounds 1-phenylpiperazine (1-PHP), gepirone (and its major metabolites, 3-OH-gepirone and 1-pyrimidinylpiperazine [1-PP]), and buspirone. ClogP and calculated pKa cluster differently for the amphiphilic drugs compared to the chemical series of piperazines. In line with this analysis, lamellar inclusion bodies were found in an in vitro validation experiment in the human monoblastoid cell line U-937, incubated for 96 h at 10 microg/mL with cationic amphiphilic drugs (amiodarone, imipramine, or propranolol). No such lamellar inclusion bodies were seen for any of the compounds from the chemical series of piperazines including gepirone and its metabolites. The data presented support the use of simple physicochemical calculations of ClogP and pKa to discriminate rapidly between compounds suspected of being phospholipidosis inducers. Finally, the discriminative power of these physicochemical ClogP and pKa calculations to predict phospholipidosis-inducing potential was further validated by extension of the set of compounds.

Administration, Oral↗
PubMed2003

Differential expression of heparan sulfate domains in rat spleen.

The microarchitecture of the spleen is composed of a meshwork of reticulum cells and their matrix. Heparan sulfates (HS) are important components of this meshwork and are involved in processes such as cell adhesion, cell migration, and cytokine/growth factor binding. The expression of HS epitopes was analyzed using anti-HS antibodies. Four different staining patterns were observed, as exemplified by antibodies RB4EA12, HS4E4, AO4B08, and HS4C3. These antibodies recognize different chemical modifications in HS. In adult spleen, RB4EA12 stained only the reticular meshwork and blood vessels in the red pulp and marginal zone. HS4E4 stained blood vessel-associated basal lamina. AO4B08 and HS4C3 stained the reticular meshwork and blood vessels throughout the spleen, but only AO4B08 strongly stained smooth muscle cells and ring fibers. Interleukin-2 localized in the red pulp and marginal zone and was bound to HS. AO4B08, HS4C3, and RB4EA12 but not HS4E4 co-localized with interleukin-2. In 10-day-old spleen, HS4E4 recognized reticular fibers, which were not stained in the adult stage. Immunoelectron microscopy revealed that HS was restricted to basal laminae and reticular fibers. Taken together, data show that HS epitopes are differentially expressed in the spleen and that this may create specific extracellular environments for immunological processes.

Animals↗
PubMed2002

Spatiotemporal distribution of heparan sulfate epitopes during myogenesis and synaptogenesis: a study in developing mouse intercostal muscle.

Formation of a basal lamina (BL) ensheathing developing skeletal muscle cells is one of the earliest events in mammalian skeletal muscle myogenesis. BL-resident heparan sulfate proteoglycans have been implicated in various processes during myogenesis, including synaptic differentiation. However, attention has focused on the proteoglycan protein core, ignoring the glycosaminoglycan moiety mainly because of a lack of appropriate tools. Recently, we selected a panel of anti-heparan sulfate antibodies applied here to study the spatiotemporal distribution of specific heparan sulfate (HS) epitopes during myogenesis. In mouse intercostal muscle at embryonic day (E14), formation of acetylcholine receptor clusters at synaptic sites coincides with HS deposition. Although some HS epitopes show a general appearance throughout the BL, one epitope preferably clusters at synaptic sites but does so only from E16 onward. During elongation and maturation of primary myotubes, a process preceding secondary myotube development, significant changes in the HS epitope constitution of both synaptic and extrasynaptic BL were observed. As a whole, the data presented here strengthen previous observations on developmental regulation by BL components, and add to the putative roles of specific HS epitopes in myogenesis and synaptogenesis.

Animals↗