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Biomedical subjects

F Blumenstock

Publications and source records attributed to F Blumenstock.

9 recordsLinked to original sources
PubMed2000

Transglutaminase-mediated fibronectin multimerization in lung endothelial matrix in response to TNF-alpha.

Exposure of lung endothelial monolayers to tumor necrosis factor (TNF)-alpha causes a rearrangement of the fibrillar fibronectin (FN) extracellular matrix and an increase in protein permeability. Using calf pulmonary artery endothelial cell layers, we determined whether these changes were mediated by FN multimerization due to enhanced transglutaminase activity after TNF-alpha (200 U/ml) for 18 h. Western blot analysis indicated that TNF-alpha decreased the amount of monomeric FN detected under reducing conditions. Analysis of (125)I-FN incorporation into the extracellular matrix confirmed a twofold increase in high molecular mass (HMW) FN multimers stable under reducing conditions (P < 0.05). Enhanced formation of such HMW FN multimers was associated with increased cell surface transglutaminase activity (P < 0.05). Calf pulmonary artery endothelial cells pretreated with TNF-alpha also formed nonreducible HMW multimers of FN when layered on surfaces precoated with FN. Inhibitors of transglutaminase blocked the TNF-alpha-induced formation of nonreducible HMW multimers of FN but did not prevent either disruption of the FN matrix or the increase in monolayer permeability. Thus increased cell surface transglutaminase after TNF-alpha exposure initiates the enhanced formation of nonreducible HMW FN multimers but did not cause either the disruption of the FN matrix or the increase in endothelial monolayer permeability.

Animals↗
PubMed1998

Cloning of the cDNA and nucleotide sequence of a skeletal muscle protease from myopathic hamsters.

A neutral protease with an estimated Mr of about 26 kD and responsible for cleavage ofmyosin LC2 was isolated from hamster skeletal muscle. Complementary DNAs were generated by RT-PCR using total hamster muscle RNA and degenerate oligonucleotide primers based on the sequences of two internal peptides. The nucleotide sequences of the resultant cDNAs were subsequently determined and the complete amino acid sequence of the protease deduced. Although the hamster protein shared 63-85% identity in nucleotide and amino acid sequences with rat and mouse mast cell proteases, it had a higher degree of specificity for myosin LC2 than mast cell proteases which also digested myosin LC1 and myosin heavy chains. As a result, the hamster protease was designated mekratin because of its unique enzymatic specificities to distinguish it from other mast cell proteases. A polyclonal antibody was raised specific to the hamster muscle and human cardiac muscle mekratins without apparent cross-reaction with rat mast cell proteases. We have earlier demonstrated the presence in excess of a neutral protease that specifically cleaves LC2 in human hearts obtained at end stage idiopathic dilated cardiomyopathy (IDC). Western analyses revealed that heart tissue from patients with IDC contained 5-10 fold more mekratin than control samples. Furthermore, the level of the protease in human IDC tissues was similar to that seen in myopathic hamster skeletal muscle. No bands were recognized by the antibody when IDC myofibrils were probed due to the removal of soluble proteins during sample preparation. Thus, these results strongly suggest that the anti-mekratin antibody will provide positive identification of IDC in many cases and diagnosis by exclusion may be replaced.

Amino Acid Sequence↗
PubMed1992

Collagen-induced rat platelet reactivity is enhanced in whole blood in both the presence and absence of dense granule secretion.

Collagen induced aggregation, ATP secretion and thromboxane (TxB2) generation of storage pool deficient platelets were compared to normal platelets of closely related rat strains. Platelet function was monitored in citrated-platelet-rich-plasma (PRP) and citrated whole blood. Wistar (W) and fawn-hooded (FH) rat strains and their F2 hybrids were utilized. The W strain, which is ancestral to the FH strain, is not storage pool deficient while the FH strain is. This was manifested by the total lack of collagen induced ATP secretion from platelets of the FH strain while the platelets of the W strain secreted normally. Utilizing platelets from the F2 generation of WxFH matings, the absence of dense granule secretion (ATP) from the FH platelets, as well as other platelet defects of FH rats, were shown to be associated with homozygosity for the red-eyed dilution gene [r]. The non-secreting FH platelets were utilized to determine the effects of secreted dense granule constituents upon collagen induced aggregation and TxB2 generation. The non-secreting storage pool deficient platelets did aggregate and did generate TxB2 upon stimulation with collagen; however, the storage pool deficient FH platelets demonstrated less TxB2 generation and did not aggregate as effectively as the normally secreting platelets of the W strain. When evaluating collagen induced platelet function in whole blood as compared to PRP, the storage pool deficient platelets remained less reactive than normally secreting platelets, but both platelet types demonstrated enhanced aggregation and increased TxB2 generation in whole blood.

Adenosine Triphosphate↗
PubMed1991

Serum albumin decreases transendothelial permeability to macromolecules.

We examined the effects of serum albumin and other serum proteins on the fluxes of tracer 125I-albumin (MW 69 kDa) and 125I-haptoglobin (MW 100 kDa) across the pulmonary artery endothelial monolayer in vitro to test the role of serum proteins in modulating the endothelial barrier function. Replacement of control complete culture medium (20% fetal calf serum in DMEM) with DMEM alone increased the transendothelial 125I-albumin clearance rate (a measure of 125I-albumin permeability) by 83% of the control value. Repletion with 50% calf serum or with 2.0 g% albumin (i.e., the albumin concentration in 50% serum) decreased 125I-albumin permeability to the control value. This effect of serum or albumin was concentration-dependent since neither 12.5% serum nor 0.5 g% albumin (i.e., albumin concentration in 12.5% serum) altered 125I-albumin permeability from control values. The ammonium sulfate-precipitated serum protein fraction rich in albumin decreased 125I-albumin permeability from the control DMEM value, whereas serum fractions containing predominantly gamma-globulin or depleted of protein did not significantly alter 125I-albumin permeability. Other serum proteins that have been proposed to reduce endothelial permeability, alpha 1-acid glycoprotein (0.035-0.14 g/100 ml) and fibronectin (5 mg/100 ml), did not decrease 125I-albumin permeability from DMEM values. The endothelial permeability of 125I-haptoglobin of 4.63 +/- 0.53 x 10(-6) cm/sec in the presence of DMEM was 30% of the 125I-albumin permeability value. The addition of 2.0 g% albumin or 50% serum decreased 125I-haptoglobin permeability to 57 and 31%, respectively, of the DMEM value. These results indicate the critical role of serum albumin in regulating the restrictiveness of the endothelial barrier to macromolecules.

Animals↗
PubMed1981

Environmental chemical-induced macrophage dysfunction.

Immunomodulation by environmental chemical contaminants and the role immune parameters play in toxicity and risk assessment studies is of increasing concern. Although considerable evidence has indicated that various xenobiotics may be immunosuppressive, little attention has been directed toward ascertaining a specific cellular locus which could be responsible for the impaired immune responsiveness. Since previous studies had suggested a macrophage defect in xenobiotic-induced immunosuppression and since macrophages are integral components of an immune response, an in-depth evaluation of macrophage function was conducted in xenobiotic-exposed mice. Macrophages isolated from mice receiving PCB, HCB, and dieldrin had no alteration in their in vitro O2 consumption while at rest or during phagocytosis. In addition, no alteration in in vitro phagocytic activity, phagocytic capacity or microbicidal activity was demonstrated. However, a significant impairment in the in vivo phagocytic clearance of a labelled antigen and an altered tissue distribution of the antigen was observed and was, perhaps, related, in part, to a significant decrease in serum fibronectin, an opsonic alpha 2 surface-binding glycoprotein. Furthermore, animals exposed to HCB and dieldrin, but not to PCB, had a profound decrease in their resistance to a challenge tumor cell implant which was related to a select alteration in tumor cell killing. The adherent spleen cells from HCB-treated mice had a profound suppression in their tumoricidal activity which was in contrast to dieldrin-treated mice, where the target cell type appeared to be the nonadherent cells. However, although dieldrin-exposed adherent cells (macrophages ?) did nt appear to have an altered tumoricidal capacity, all four macrophage types isolated from dieldrin-treated mice had a significantly impaired ability to process a cellular antigen. Splenic and alveolar macrophages appeared to be the most sensitive cell types to dieldrin. The present studies suggest that macrophage dysfunction may be an integral part of xenobiotic-induced immunosuppression and that the effector but not affector component of macrophage function may be the site of alteration.

Animals↗
PubMed1977

Electroimmunoassay of alpha-2-opsonic protein during reticuloendothelial blockade.

Physiological regulation of reticuloendothelial (RE) phagocytic activity by a plasma opsonic factor has been documented. In the recent study, serum levels of this alpha-2-opsonic protein in rats during colloid-induced RE blockade were measured utilizing an electroimmunoassay (Rocket immunoelectrophoresis) with monospecific antiserum to the purified alpha-2-glycoprotein. RE blockade was produced by the intravenous injection of the gelatinized "RE-test-lipid emulsion" at a dose of 50 mg/100 g body wt. The opsonic activity of serum at various intervals during colloid-induced RE blockade as measured by tissue slice bioassay manifested a high correlation (r = 0.98) with the serum opsonic protein concentration as measured by the electroimmunoassay. During RE blockade (30 min), there was a rapid depletion of the opsonic alpha-2-glycoprotein to 20% of the initial preinjection levels. Serum concentration of this glycoprotein remained low for at least 2-3 h after which time its concentration progressively increased with approximation of normal values by 6 h postblockade. Opsonic protein concentration at 24 h postinjection were significantly (P less than 0.05) elevated above controls. Thus, colloid-induced RE blockade is associated with the removal of this glycoprotein from the serum and recovery from RE blockade is accompanied by a restoration of opsonin levels. The electroimmunoassay can provide a sensitive technique to monitor this humoral factor known to exert a physiological control on the RE system.

Alpha-Globulins↗