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D Scholz

Publications and source records attributed to D Scholz.

At least 37 records · Page 2Linked to original sources
PubMed1998

Vascular remodeling and altered protein expression during growth of coronary collateral arteries.

The cellular mechanism of growth of coronary collateral vessels (adaptive arteriogenesis) is still poorly understood. To define a possible role of an altered expression pattern of cellular and matrix proteins in this process we implanted a constricting device around the left circumflex artery in 25 canine hearts and sacrificed the animals at the time of initiation (3 weeks), high activity (6 weeks) and discontinuation (8 weeks) of vessel growth. Methods were electron microscopy, labeling with Ki-67, the TUNEL method and immunofluorescence with confocal laser microscopy. As described earlier, the collateral vessels increased in wall thickness by the formation of a neointima without luminal narrowing. We report here for the first time that extensive vascular remodeling including migration, proliferation and apoptosis in all cell types takes place during the growth phase but not in more mature vessels. The most obvious difference with normal vessels is the reiteration of an embryonal expression pattern in smooth muscle cells of the neointima which includes a significant reduction of desmin and alpha-smooth muscle actin, calponin and vinculin. Fibronectin as a promoter of migration and adhesion was abundant, its antagonist tenascin and chondroitin sulfate showed patchy localization. A completely new finding in arteriogenesis is the involvement of mast cells releasing histamine and serotonin and probably cytokines. Vascular protein expression returned to almost normal at 8 weeks indicating cessation of remodeling. We conclude that in collateral vessel development an altered cellular and matrix protein expression is involved in a drastic case of positive vascular remodeling finally resulting in mature vessels 20-fold increased in size which are capable of maintaining the functional and structural integrity of the myocardium at risk.

Actins↗
PubMed1998

Stimulation of human immunodeficiency virus expression in permanent monocytic cells by Sarcocystis gigantea extract.

As recently reported, a strong stimulation of noninfected CD4+ H9- cells by Sarcocystis gigantea (syn. S. ovifelis) extract (SGE) was observed using the lymphocyte proliferation assay. After SGE prestimulation, human immunodeficiency virus (HIV)-infected H9+ cells showed an exacerbation of viral replication. In the present study we investigated the reactivity of HIV-infected human monocytes using SGE. The highly sensitive p24 core-profile enzyme-linked immunosorbent assay (ELISA) was used to examine directly the amount of HIV produced. Experiments were performed using U937 permanent monocytic cells. Permanent incubation as well as preincubation with SGE before virus infection stimulated HIV expression in all the cells. In U937 cells the viral release per cell was 64 times higher on permanent stimulation with 320 microg SGE relative to controls and 9 times higher following prestimulation.

Animals↗
PubMed1998

The internal and external protein scaffold of the T-tubular system in cardiomyocytes.

The transverse tubule system of the cardiomyocyte remains undeformed despite the extreme forces it undergoes during the contraction-relaxation cycle, but the morphological basis for its stability remains unclear. Therefore, we have investigated the architecture and subcellular protein scaffold of the cardiac T-tubules and compared it with that of the costameres and of the free sarcolemma. Tissue samples from normal rat and monkey hearts, and left ventricular tissue from normal and cardiomyopathic human hearts obtained at transplantation surgery were investigated using immunocytochemistry and confocal microscopy and by electron microscopy. In addition, we used a re-differentiation model of isolated, cultured adult rat cardiomyocytes. The cell membrane of the cardiac T-tubules was found to contain the cell-matrix focal adhesion molecules (FAMs) vinculin, talin, the alpha5beta1 integrin and the membrane-associated proteins (MAPs) dystrophin and spectrin. FAMs and MAPs were localized in the T-tubular membrane in a similar pattern: in longitudinally oriented myocytes as transverse punctate lines at the Z-level; in transversally cut myocytes a radial tubular network was found to extend throughout the interior of the cell. Immunolabeling for basement membrane components including collagen IV, fibronectin and laminin showed a colocalization with FAMs and MAPs parallel to the transverse T-tubules. The costameres of the sarcolemma showed a protein composition resembling that of the T-tubules but the intervening segments of free sarcolemma showed absence of FAMs and presence of MAPs. For the first time, we demonstrate the existence and protein composition of the T-tubular scaffold in the human heart. Furthermore, we show that cardiomyocytes from human failing hearts have less abundant but more dilated T-tubules than do experimental animals. These results indicate that the cardiac T-tubular system contains a subcellular scaffold closely resembling that of the costameres. It consists of FAMs, MAPs and basal lamina proteins that confer structural integrity to the cardiac T-tubular membrane during contraction/relaxation cycles.

Animals↗
PubMed1997

Platelet/endothelial cell adhesion molecule-1 (PECAM-1) is localized over the entire plasma membrane of endothelial cells.

The subcellular localization of PECAM-1 in endothelial cells was examined by using advanced morphological techniques, such as confocal scanning microscopy and immunolabeling procedures for electron microscopy. The localization of PECAM-1 was studied immunohistochemically with five specific monoclonal antibodies and one polyclonal antibody (all anti-human) in human and rabbit myocardium and in isolated endothelial cells. In vivo, PECAM-1 was localized uniformly on the plasma membrane of all vascular endothelial cells, predominantly on the luminal side of vessels. No specific increase in labeling was found at sites of cell-to-cell contact. In vitro, primary isolated cells (human umbilical vein endothelial cells) showed continuous labeling of the entire cell membrane. Cells of higher passages were labeled in a manner similar to freshly isolated cells. Our findings refute the commonly accepted hypothesis that PECAM-1 is localized only at cell-to-cell contacts. Further, we have not been able to confirm the hypothesis regarding the important mechanical role of PECAM-1 in stabilizing the endothelial monolayer. Since PECAM-1 is also expressed on platelets and is known to bind to itself, the way in which PECAM-1-positive endothelial cells are protected against binding of PECAM-1-positive platelets remains unclear. In view of these findings, the role of PECAM-1 in the leukocyte migration cascade needs to be re-evaluated.

Animals↗
PubMed1997

Upregulation of cell adhesion molecules and the presence of low grade inflammation in human chronic heart failure.

BACKGROUND: In the present study, the hypothesis was tested that cell adhesion molecules are expressed in failing human hearts and that a chronic inflammatory process contributes to chronic degeneration known to occur in cardiac incompetence. The cell adhesion molecules: ICAM-1, VCAM-1, PECAM-1, and E-selectin were studied, in addition to cellular markers of inflammation. METHODS AND RESULTS: Tissue was obtained at transplantation from patients with either myocarditis, chronic ischaemic heart disease, or dilated cardiomyopathy. Controls were taken from patients with normal ventricles. Cell adhesion molecules were qualitatively evaluated and counted using specific antibodies and confocal microscopy. Additionally, semiquantitative evaluation of the presence of the CD3 antigen (T-lymphocytes), CD68 (macrophages), CD11a/CD18 (ICAM-1 receptor) and human tumour necrosis factor-a were used as indicators of chronic inflammation. PECAM-1 stained all endothelial cells but ICAM-1 was only present in 80% of all capillaries in control tissue. The ratio ICAM-1/PECAM-1 was significantly enhanced in all groups of diseased hearts. Myocytes in myocarditic hearts expressed ICAM-ICAM. CD3 positive lymphocytes, CD68 positive macrophages and CD11a/CD18 positive cells were more abundantly present than in control. Macrophages expressing tumour necrosis factor-a were found in failing myocardium but not in control tissue. CONCLUSION: Independent of the cause of heart failure, chronic low grade inflammation is present in failing human myocardium. This may significantly contribute to the structural deterioration that is the basis of reduced cardiac function in congestive heart failure.

Adult↗
PubMed1997

Elevated levels of testosterone receptors in keloid tissue: an experimental investigation.

Testosterone-binding receptor protein analyses were performed in keloids of 24 patients. According to their clinical appearance (hyperemia, pain, rapid growth, etc.), the lesions were subdivided into regions of minor and major clinical keloid activity. Biopsies were taken from active and inactive parts of the keloids, respectively, as well as from normal adjacent skin. The mean receptor amount in femtomoles per milligrams of tissue was 0.046 for active (SD = 0.037), 0.038 for inactive keloidal lesions (SD = 0.032), and 0.012 for normal skin. The corresponding receptor amount per microgram of DNA was 3.356 fmol (SD = 2.171) for active, 2.077 fmol (SD = 1.427) for inactive keloidal, and 1.010 fmol (SD = 1.190) for normal tissue. Statistical evaluation was performed using a two-way analysis of variance, with the two factors being individual subject and type of tissue. When differences were found, then Tukey's comparison was done to assess where those differences were. Comparisons of the receptor amount per milligram of tissue significant at the 0.05 level revealed significant differences between active keloid tissue and normal skin tissue and inactive and normal tissue (p < 0.01) respectively, while different receptor amount per microgram of DNA was significant between active and inactive and active and normal tissue (p < 0.01). These data suggest that elevated androgen receptor levels exist in clinical active keloid tissue and that possible therapeutic means might include topical antiandrogen therapy.

Adolescent↗
PubMed1997

Angiogenesis but not collateral growth is associated with ischemia after femoral artery occlusion.

It remains unclear whether capillary sprouting (angiogenesis) and in situ growth of muscular collateral arteries share the same or different molecular mechanisms. To study the role of ischemia in these two forms of vascular proliferation, we measured tissue flows and maximum collateral conductances in hindlimbs of 22 rabbits previously subjected to either acute, 7-day, 21-day, or no femoral artery occlusion. After 1 wk of femoral artery occlusion, corkscrew collaterals were observed radiographically in the thigh. These collaterals showed histochemical evidence for active proliferation of endothelial and smooth muscle cells. Maximum collateral conductance increased sixfold in the 1st wk. Perfusion deficits, however, were only observed in the distal adductor muscles (region of collateral reentry). In the lower leg, which suffered from a profound perfusion deficit, conductance increased in the absence of any visible collateral arteries but with evidence for capillary proliferation. This study therefore demonstrates that upon femoral artery occlusion angiogenesis occurs in regions of profound ischemia, whereas no direct correlation can be drawn between ischemia and collateral artery development.

Angiography↗
PubMed1997

Endothelium-derived hyperpolarizing factor, but not nitric oxide, is reversibly inhibited by brefeldin A.

The subcellular localization of the enzymes synthesizing endothelium-derived vasodilator autacoids has been proposed to play a role in determining the ability of endothelial cells to enhance autacoid production in response to stimulation. We therefore investigated the effects of brefeldin A-induced disruption of the Golgi apparatus and Golgi-plasma membrane trafficking on the production of nitric oxide (NO), prostacyclin, and the endothelium-derived hyperpolarizing factor (EDHF) by native and cultured endothelial cells. In porcine coronary artery segments, brefeldin A (35 micromol/L, 90 minutes) did not affect relaxations to sodium nitroprusside or the K+ channel opener cromakalim but elicited a rightward shift in the concentration-response curve to bradykinin without altering the maximum vasodilator response (Rmax). Brefeldin A failed to attenuate the bradykinin-induced, NO-mediated relaxation under depolarizing conditions but inhibited the bradykinin response under conditions of combined cyclooxygenase/NO synthase blockade, suggesting that this agent selectively interferes with the production of EDHF. Indeed, incubation of porcine coronary arteries with brefeldin A, which did not affect the bradykinin-induced accumulation of either cyclic GMP or 6-keto-prostaglandin F1alpha, markedly and reversibly attenuated the EDHF-mediated hyperpolarization of detector smooth muscle cells in a patch-clamp bioassay system. The microtubule destabilizer nocodazole also affected both the EC50 and Rmax to bradykinin in porcine coronary arteries. Since EDHF is thought to be a cytochrome P450-derived metabolite of arachidonic acid and both brefeldin A and nocodazole are known to interfere with the targeting of cytochrome P450 from the Golgi apparatus to the plasma membrane, it is conceivable that brefeldin A inhibits EDHF formation by preventing the targeting of the EDHF-synthesizing enzymes to the plasma membrane.

6-Ketoprostaglandin F1 alpha↗
PubMed1997

Monocyte chemotactic protein-1 increases collateral and peripheral conductance after femoral artery occlusion.

Monocytes are activated during collateral artery growth in vivo, and monocyte chemotactic protein-1 (MCP-1) has been shown to be upregulated by shear stress in vitro. In order to investigate whether MCP-1 enhances collateral growth after femoral artery occlusion, 12 rabbits were randomly assigned to receive either MCP-1, PBS, or no local infusion via osmotic minipump. Seven days after occlusion, isolated hindlimbs were perfused with autologous blood at different pressures, measuring flows at maximal vasodilation via flow probe and radioactive microspheres, as well as peripheral pressures. This allowed the calculation of collateral (thigh) and peripheral (lower limb) conductances from pressure-flow tracings (slope of the curve). Collateral growth on postmortem angiograms was restricted to the thigh and was markedly enhanced with MCP-1 treatment. Both collateral and peripheral conductances were significantly elevated in animals with MCP-1 treatment compared with the control group, reaching values of nonoccluded hindlimbs after only 1 week of occlusion (collateral conductance, 70.6 +/- 19.23 versus 25.1 +/- 2.59 mL/min per 100 mm Hg; P < .01; peripheral conductance, 119.3 +/- 22.37 versus 45.4 +/- 6.80 mL/min per 100 mm Hg; P < .05). These results suggest that activation of monocytes plays an important role in collateral growth as well as in capillary sprouting.

Angiography↗
PubMed1996

Inhibitors of human immunodeficiency virus type 1 protease containing 2-aminobenzyl-substituted 4-amino-3-hydroxy-5-phenylpentanoic acid: synthesis, activity, and oral bioavailability.

Systematic modifications of HIV protease inhibitor (2R,3S,4S)-4-[[(benzyloxycarbonyl)-L-valyl]-amino]-3-hydroxy-2-[(4- methoxybenzyl)amino]-5-phenylpentanoyl)-L-valine 2-(aminomethyl)- benzimidazole amide led to a novel series of inhibitors with shortened, modified carboxy terminus. Their synthesis, in vitro enzyme inhibitory data, and antiviral activities are reported. Of particular interest are derivatives featuring the (1S,2R)-1-amino-2-hydroxyindan moiety at the P2'-position since some of them exhibit substantial oral bioavailability in mice. The influence of aqueous solubility and structural parameters on the oral resorption of the inhibitors is discussed. Optimum enhancement of oral bioavailability was observed with L-tert-leucine in P2-position, resulting in the discovery of (2R,3S,4S)-4-[[(benzyloxycarbonyl)-L-tert-leucyl]- amino]-3-hydroxy-2-[(4-methoxybenzyl)amino]-5-phenylpentanoic acid (1S,2R)-1-amino-2-hydroxyindan amide which combines high antiviral activity (IC50 = 250 nM) with a good pharmacokinetic profile (AUC = 82.5 microM.h at a dose of 125 mg/kg po in mice).

Administration, Oral↗
PubMed1996

Expression of adhesion molecules is specific and time-dependent in cytokine-stimulated endothelial cells in culture.

The time course of expression of the adhesion molecules E-selectin, VCAM-1, ICAM-1 and PECAM-1 was studied in interleukin-1 beta-stimulated human umbilical vein cells (HUVEC) and the subcellular sites of synthesis were determined by means of fluorescence immunohistochemistry. The maximal number of cells labelled for E-selectin was observed at 2-4 h, for VCAM-1 at 4-8 h and ICAM-1 at 6-72 h. At 8 h, E-selectin and VCAM-1 started to disappear, but ICAM-1-positive cells persisted. PECAM-1 was constitutively expressed. De novo synthesis for E-selectin started at 1 h and for both, VCAM-1 and ICAM-1 at 1.5-2 h. Maximal synthetic activity was observed at 2.5-4 h for E-selectin and at 4-6 h for VCAM-1 and ICAM-1; thereafter, synthesis slowly decreased. Transport granules occurred at 1.5 h for E-selectin and 4 h for VCAM-1; they were absent for ICAM-1. Diffuse cellular and membrane labelling indicative of the functional activity of the adhesion molecules began at 2-4 h for E-selectin, and 4 h for VCAM, but was constitutively present for ICAM-1. In conclusion, each adhesion molecule shows a specific time-dependent course of appearance and disappearance in interleukin-1 beta-stimulated HUVECs in accordance with their physiological role in vivo. These morphological results confirm data obtained by flow cytometry and Western blotting, but they provide new information about the behaviour of individual cells with regard to the sites of synthesis and cellular localization of the adhesion molecules.

Antigens, Differentiation, Myelomonocytic↗
PubMed1996

Importance of simultaneous active cytomegalovirus and Epstein-Barr virus infection in renal transplantation.

BACKGROUND: Although being the most common infective complication after transplantation, cytomegalovirus (CMV) infection does not always produce disease symptoms in immunosuppressed patients. Development of CMV disease may depend on different factors such as virulence of particular CMV strains and impairment of CMV-specific immune reactions. OBJECTIVE: Demonstration of the importance of simultaneous Epstein-Barr virus (EBV) activation for development of symptomatic CMV infections. STUDY DESIGN: 208 renal transplantation patients were monitored for 3 years with respect to (i) CMV and EBV replications, and (ii) clinical symptoms associated with combined and single infections, respectively. RESULTS: CMV and EBV replications were observed in 22% and 19% of the patients, respectively. Many of these active virus infections were found to overlap in time (59% and 74% of all active CMV and EBV infections, respectively). The increased detection of combined CMV and EBV infections probably does not result from higher initial immunosuppression in these patients, since the percentage of patients receiving OKT3 or ATG was almost identical in the groups of single and combined infections. In 18 cases of combined infections, CMV replication preceeded EBV replication, while EBV replication prior to CMV replication was observed in one case only, indicating that activation of latent EBV infection may be induced during active CMV infection. CONCLUSIONS: Simultaneous replication of both viruses seems to be clinically important, since severe clinical symptoms were observed only in the group of combined CMV and EBV infections. Symptoms were similar to the clinical pictures of CMV disease. Thus, simultaneous EBV replication may be an important co-factor for the development of CMV disease, possibly by further decreasing the number of functional CD4 T cells or enhancing the CD8-positive cytolytic/suppressor T-cell subset as reflected by the comparatively stronger decrease of CD4/CD8 ratio during simultaneous CMV and EBV replication, particularly in the case of symptomatic infections.

Journal Article↗
PubMed1996

[Effect of Sarcocystis gigantea extract (SGE) on the replication of human immunodeficiency virus (HIV)].

Basis of this study were the previous findings regarding isolation and characterization of a Sarcocystis gigantea lectin (SGL) especially the activation of human mononuclear cells (CD3+, CD4+, CD8+, Mø, B-lymphocytes). HIV-susceptible, immortaliced cell lines (H9-, MT-4) should be investigated to examine their reactivity against SGE which contains this strong mitogen. Using lymphocyte proliferation assay a strong stimulation of noninfected CD(4+)-positive H9-cell by SGE was observed. HIV-infected H(9+)-cells showed after SGE stimulation (20-160 micrograms) an exacerbation with an optimum at day 4. The virus replication in the H(9+)-hostcells was 13 times stronger. This result could also be detected indirectly because of the higher cytotoxicity in the MT-4 cell system. Cytopathogeny was measured by MTT cellvitality assay. In parallel, the high sensitive p24 core Profile-ELISA was used to directly examine the amount of produced HIV. In case of the H(9+)-cells the virus release per cell was 5 times higher after SGE stimulation compared with control.

Animals↗
PubMed1995

SDZ PRI 053, an orally bioavailable human immunodeficiency virus type 1 proteinase inhibitor containing the 2-aminobenzylstatine moiety.

A series of inhibitors of human immunodeficiency virus type 1 (HIV-1) proteinase containing the 2-aralkyl-amino-substituted statine moiety as a novel transition-state analog was synthesized, with the aim to obtain compounds which combine anti-HIV potency with oral bioavailability. The reduced-size 2-aminobenzylstatine derivative SDZ PRI 053, which contains 2-(S)-amino-3-(R)-hydroxyindane in place of an amino acid amide, is a potent and orally bioavailable inhibitor of HIV-1 replication. The antiviral activity of SDZ PRI 053 was demonstrated in various cell lines, in primary lymphocytes, and in primary monocytes, against laboratory strains as well as clinical HIV-1 isolates (50% effective dose = 0.028 to 0.15 microM). Cell proliferation was impaired only at 100- to 300-fold-higher concentrations. The mechanism of antiviral action of the proteinase inhibitor SDZ PRI 0.53 was demonstrated to be inhibition of gag precursor protein processing. The finding that the inhibitory potency of SDZ PRI 053 in chronic virus infection, determined by p24 release, was considerably lower than that in de novo infection may be explained by the fact that the virus particles produced in the presence of SDZ PRI 053 are about 50-fold less infectious than those from untreated cultures. Upon intravenous administration, half-lives in blood of 100 and 32 min in mice and rats, respectively, were measured. Oral bioavailability of SDZ PRI 053 in rodents was 20 to 60%, depending on the dose. In mice, rats, and dogs, the inhibitor levels after oral administration remained far above the concentrations needed to efficiently block HIV replication in vitro for a prolonged period. This compound is thus a promising candidate for clinical use in HIV disease.

Administration, Oral↗
PubMed1995

[Interactions between cardiomyocytes and extracellular matrix in the failing human heart].

Numerous morphological changes can be observed in human myocardium failing because of dilated cardiomyopathy. These can be observed by electron microscopy and by immunofluorescence microscopy using monoclonal antibodies. These changes include: 1) the occurrence of hypertrophied and atrophied myocytes as well as cells of normal size, 2) degenerative changes in myocytes; these consist of nuclei of varying size and shape, lack of contractile material, disorganization of the cytoskeleton, and sequestration of cellular particles into the extracellular space and 3) an enlarged extracellular space, that is, fibrosis, which contains increased amounts of the different matrix proteins such as fibronectin and laminin, the various collagens, and chondroitin sulfate, in addition to cellular debris and numerous macrophages and fibroblasts. On the basis of these findings it is hypothetized that there exists an interaction between myocytes and the extracellular matrix. The cells of the latter may be stimulated to higher rates of proteins synthesis by the presence of cellular debris. This process, in turn, may be harmful for the structural integrity of myocytes which consequently sequester more cellular particles. In this manner, a vicious circle may be started that leads to further structural and functional deterioration of the myocardium, finally resulting in failure.

Cardiomyopathy, Dilated↗
PubMed1994

Inhibitors of HIV-1 proteinase containing 2-heterosubstituted 4-amino-3-hydroxy-5-phenylpentanoic acid: synthesis, enzyme inhibition, and antiviral activity.

A convenient procedure for the synthesis of 2-heterosubstituted statine derivatives as novel building blocks in HIV-protease inhibitors has been developed. The synthesis starts with protected L-phenylalaninols, which were converted to gamma-amino alpha, beta-unsaturated esters in a one-pot procedure. A highly diastereoselective epoxidation of the N-protected (E)-enoates, followed by regioselective ring opening of the corresponding 2,3-epoxy esters with a variety of heteronucleophiles, resulted in 2-heterosubstituted statine derivatives. The overall stereo-chemical outcome of the transformations meets the required configuration of HIV-protease inhibitors. The short, synthetically flexible, and highly diastereoselective synthesis of 2-heterosubstituted statines has enabled a broad derivation, covering the S3, S2, and S1'-S3' sites of the enzyme. In a series of 46 derivatives, several potent inhibitors were obtained with Ki values as low as 3.4 nM and antiviral activity in the lower nanomolar-range. The structural parameters of the compounds which determine the potency of inhibition and selectivity for the viral enzyme are discussed.

Amino Acid Sequence↗