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Biomedical subjects

M Herrmann

Publications and source records attributed to M Herrmann.

At least 19 recordsLinked to original sources
PubMed1992

The effect of corrosive environment on the porcelain-to-metal bond--a fracture mechanics investigation.

Microcracks, flaws, and voids inside a metal-porcelain restoration may cause the restoration to fracture in service. Such cracks result in the concentration of stresses. The dynamic nature of the stresses due to mastication promotes crack growth. In addition, corrosive components of the oral environment enhance the growth rate. In the present investigation, fracture mechanics has been used to analyze the in vitro resistance to fracture of the porcelain-fused-to-metal restoration. The risk of a clinical failure of porcelain-fused-to-metal decreases with enlarged crack resistance (increasing work of fracture). The work of fracture represents an average of the energy for initiation and propagation of a crack through the interface separating porcelain and metal. This work also indicates a material's ability to stop a crack once it is moving. This study utilized the three-point bending test for the crack resistance measurement, and investigated one palladium and five base metal alloys. Corrosive components of the oral environment and the details of firing were of crucial importance for long-term bond stability.

Corrosion↗
PubMed1992

Antibodies against p24 of HIV-1 in patients with systemic lupus erythematosus?

The involvement of retroviruses in the etiopathogenesis of autoimmunity is discussed. Recently antibodies against p24 of HIV-1 were described in patients from Texas with SLE. Therefore we investigated the presence of these antibodies in our SLE collective (German caucasians and blacks from Michigan) employing ELISA and Western blot. No anti-p24 reactivity was observed in our SLE patients in Western blots, suggesting that there may be ethnological or regional differences between our patients those from Texas.

AIDS-Related Complex↗
PubMed1992

[Definitive surgery in complicated gastroduodenal ulcers].

Indications for surgical therapy in uncomplicated peptic ulcer disease have decreased considerably since the introduction of H2-receptor blocking drugs and more recently omeprazole. On the other side, the number of acute complications such as perforation or hemorrhage has remained nearly constant. The recent literature seems to indicate that the pattern of patients presenting with complications has changed and that the number of acute ulcers has increased. In a review of 283 patients, we found 150 perforated ulcers (PU) and 133 bleeding ulcers (BU). Almost all the patients with PU and 70% of the patients with BU have been treated operatively. The mortality is 14.3% and 12.5%, respectively. The vast majority of our patients have chronic ulcers, and only 7% have acute or subacute lesions confirmed by histologic examination. Based on our experience and the literature, we propose a therapeutic algorythm for these two conditions.

Aged↗
PubMed1992

[Case reports of arteriovenous fistulas of coronary vessels in adulthood].

It is reported on the diagnosis and therapy of arteriovenous fistulae of coronary arteries. With the help of 5 casuistic instances external fistulae could be demonstrated by invasive diagnostic procedures. In three cases the fistulae drained from the left coronary into the pulmonary artery, at the second instance from the right coronary artery into the right ventricle, in the fifth instance from the right coronary artery into the right atrium. In addition to this there were coronary stenoses which needed a bypass. In all cases the tentative diagnoses were confirmed intraoperatively. The indication to operative ligatures of the congenital fistulae is discussed and supported depending upon the picture of the complaint.

Adult↗
PubMed1992

[Surgery of varicose veins and varicose complications in a tropical country. A personal experience].

Venous pathology and its complications reach much more important dimensions in tropical countries due to temperatures, working conditions and fault of hygiene. These conditions require adaptation of the surgical treatment for varicose complication. Unfortunately, venous surgery is mostly uncommon in regions where the pathology originate an important morbidity. A personal experience is presented.

Adult↗
PubMed1991

Pathogenesis of SLE: immunopathology in man.

Antibodies against native DNA are not only a disease-specific marker for systemic lupus erythematosus (SLE); in addition, there is good direct evidence that these antibodies also play a major part in pathogenic mechanisms leading to systemic and organ-specific disease manifestations. The origin of anti-dsDNA antibodies is still poorly understood, especially as dsDNA per se is not immunogenic. As recently shown, evidence is now accumulating that anti-dsDNA antibodies are not germline-encoded but antigen-driven, as demonstrated by the establishment of human anti-dsDNA antibody clones from SLE patients and sequence analysis. In sera of SLE patients there is an elevated level of nucleic acids, which indicates that defective clearance mechanisms for nucleic acids are present. The question as to whether these nucleic acids could serve as an antigen has been recently addressed by studies of plasma nucleic acids isolated from circulating immune complexes from SLE patients. These studies indicate that plasma nucleic acids in SLE patients have structures of amino acid sequences which have a striking homology with the gag-pol overlap region of HIV-1. Whether these nucleic acids play a role in the pathogenesis of SLE, indicating the involvement of a retrovirus in the pathogenesis, or whether they rather reflect an amino acid homology with an endogenous human retrovirus family is not yet known.

Antibodies, Antinuclear↗
PubMed1991

The innervation of the trapezius muscle in connection with radical neck-dissection. An anatomical study.

The accessory nerve, the cervical plexus, the sternocleidomastoid and trapezius muscles and neighbouring structures were examined in 47 corpses. Considerable inter- as well as intra-individual differences could be found both in the course and shape of the accessory nerve and in the participation of the cervical plexus in the innervation of the trapezius muscle. The great variation in the manifestation of the shoulder-arm-syndrome in patients after radical neck-dissection can thus be explained. Finally a new method of restoring the innervation of the trapezius muscle is proposed.

Accessory Nerve↗
PubMed1991

Morphological and hormonal changes following vasectomy in rats, suggesting a functional role for Leydig-cell associated macrophages.

The effects of bilateral vasectomy on hormone serum levels as well as Leydig cell and associated macrophage structure were analysed in parallel in rats 36 weeks following the operation. Serum testosterone was decreased in vasectomized rats (1.96 +/- 0.11 ng/ml) compared with control animals (3.44 +/- 0.22 ng/ml, p less than 0.05). Vasectomy also resulted in an increase in serum luteinizing hormone (LH) to 0.299 +/- 0.02 ng/ml compared to the control group (0.175 +/- 0.01 ng/ml, p less than 0.05). Also serum follicle-stimulating hormone (FSH) was increased following vasectomy (350.88 +/- 15.5 ng/ml) compared to 132.0 +/- 4.8 ng/ml in control animals (p less than 0.01). Morphometric analysis of Leydig cells showed hypertrophy with a 19% increase of total cell area, p less than 0.01 (cytoplasm 28%, nucleus 8% increase). On the ultrastructural level, leydig cells demonstrated massively dilated smooth endoplasmic reticulum characteristic for stimulated cells. There was also a significant hypertrophy of the Leydig cell-associated macrophages. The macrophage cell area was enlarged by 22%, p less than 0.01 (cytoplasm 25%, nucleus 18%). Vasectomy also led to remarkable ultrastructural changes of macrophages with a marked dilated and extended rough endoplasmic reticulum. Macrophages were found in apposition to Leydig cells with close cellular contact zones, and they frequently formed cell extensions on Leydig cells. Our data obtained following vasectomy indicate that, by their close contacts to Leydig cells, as well as the known influence on Leydig-cell steroidogenesis, macrophages may form the basis of a local immunoendocrine regulation of the pituitary-gonadal axis.

Animals↗
PubMed1991

Successful therapy of experimental chronic foreign-body infection due to methicillin-resistant Staphylococcus aureus by antimicrobial combinations.

We compared the efficacy of a long-duration (3-week) therapy of vancomycin, fleroxacin, fleroxacin plus rifampin, and vancomycin plus fleroxacin and rifampin in a recently developed rat model of chronic staphylococcal foreign-body infection. Subcutaneous tissue cages containing polymethylmethacrylate coverslips were infected with 1 x 10(5) to 5 x 10(5) CFU of methicillin-resistant Staphylococcus aureus. Three weeks later, a quantitative culturing of the fluid that had accumulated in the cages was done (mean, 6.72 log10 CFU/ml; n = 110) and treatment was initiated after randomization. The CFUs in the cage fluid were counted on days 11 and 22 and 1 week after the termination of treatment; in addition, a final culture of coverslips (surface-bound microorganisms) was performed. The three-drug therapy was significantly superior to the other treatments on day 11 (a 5.16 log10 decrease of bacterial counts versus a 2.12 log10 to 2.94 log10 decrease for vancomycin, fleroxacin, and fleroxacin plus rifampin; P less than 0.01). On day 22, count decreases were 4.16 log10 for vancomycin, 4.91 log10 for fleroxacin (vancomycin versus fleroxacin, not significant), 6.14 log10 for two-drug therapy, and 6.34 log10 for three-drug therapy (vancomycin-fleroxacin-rifampin versus fleroxacin-rifampin, not significant; fleroxacin-rifampin versus monotherapies, P less than 0.01); the numbers of CFU in most cage fluids were under the detection limit (20 CFU/ml) in combination groups. One week after the end of treatment, 92% of fluids and coverslips (detection limit, 1 CFU) were culture negative with tritherapy, 88% of fluids and 41% of coverslips were negative with bitherapy, and less than 12% of fluids and coverslips were negative with single drugs (for coverslips, P was <0.01 for vancomycin-fleroxacin-rifampin versus fleroxacin-rifampin and P was <0.001 for fleroxacin-rifampin versus the monotherapies). No mutants resistant to rifampin or fleroxacin were detected. In conclusion, antimicrobial combinations were highly effective and superior to single drugs in treating a chronic staphylococcal foreign-body infection for 3 weeks. The three-drug therapy decreased bacterial counts more rapidly than the two-drug therapy under study and appeared to be curative in most cases.

Animals↗
PubMed1991

Thrombospondin binds to Staphylococcus aureus and promotes staphylococcal adherence to surfaces.

Bacterial adherence to surfaces is the determining first step in staphylococcal infections. Activated platelets mediate adherence of staphylococci to tissues during inflammation or infection; however, the molecular mechanisms of this interaction are not clearly understood. Thrombospondin, a large multifunctional glycoprotein, is the principal platelet-stored glycoprotein. It is secreted upon platelet activation and either bound to receptors on the platelet surface or released and incorporated into blood clots and extracellular matrices. To characterize thrombospondin binding to staphylococci, we incubated [125I]thrombospondin with Staphylococcus aureus Cowan 1 in the presence of albumin and separated bound and free thrombospondin by centrifugation. We found that binding was (i) specific, since it was up to 76% inhibitable and up to 60% reversible in the presence of a 100-fold excess of unlabeled thrombospondin, (ii) saturable, with an apparent dissociation constant (Kd) of 5.6 x 10(-9) M and a maximal number of 2,600 binding sites per microorganism, and (iii) Ca2+ dependent, since omission of this ion from the medium decreased significantly the binding capacity. The binding reaction was insensitive to previous trypsin treatment of bacteria, but it was strongly inhibited in the presence of heparin. Protein A-negative and -positive strains had similar binding characteristics. To determine the promotion of staphylococcal adherence to surfaces by solid-phase thrombospondin, we incubated 3H-labeled S. aureus Cowan 1 and 26 pathogenic staphylococcal isolates with thrombospondin-coated polymethylmethacrylate disks and found that adherence was significantly promoted as a function of adsorbed thrombospondin. These results indicate a role for thrombospondin as an important mediator of staphylococcal adherence to activated platelets, to blood clots, or to extracellular matrices in pyogenic infections.

Bacterial Adhesion↗
PubMed1991

Resistance of Staphylococcus aureus recovered from infected foreign body in vivo to killing by antimicrobials.

Because persistence of infections associated with prosthetic material despite the use of appropriate antibiotics is a major clinical problem, the antimicrobial susceptibility of bacteria responsible for a chronic subcutaneous tissue cage infection in rat was investigated ex vivo. Three to 6 weeks after the initiation of infection, suspensions of two strains of Staphylococcus aureus recovered from the foreign body surface and surrounding fluid were exposed to either oxacillin, vancomycin, fleroxacin, gentamicin, or rifampin. The MBCs of these bacteria were markedly elevated, in most cases 128 to greater than 256 times higher than the MBC of batch culture S. aureus in either logarithmic or stationary phase. Kinetic studies showed the bacteria did not grow when incubated for 2 h in Mueller-Hinton broth, possibly reflecting dormancy. Their killing was slow and incomplete by all antibiotics at greater than 8 times their MIC. These data provide direct evidence of a decreased susceptibility of S. aureus to the killing effect of antimicrobials during chronic foreign body infections in vivo.

Animals↗
PubMed1990

Circulating immune complexes in HIV-infected persons.

Circulating immune complexes are part of normal immune defense mechanisms and, therefore, present in various infectious--bacterial and viral--diseases. On the other hand, they are obviously involved in pathogenic mechanisms, e.g., autoimmune diseases or different forms of malignancies. Both autoimmune and infectious features are recorded in the acquired immunodeficiency syndrome. Thus, elevated levels of antigen-antibody complexes in HIV-infected persons had to be expected, and they were in fact demonstrated by several authors. In a cohort study, it was additionally shown that circulating immune complexes are of prognostic relevance. After an introduction concerning the physiological and pathophysiological role of circulating immune complexes in general, their involvement in the course of HIV infections is presented and discussed. In addition, there is a critical review of the most commonly applied assay systems for the detection and quantification of circulating immune complexes.

Antigen-Antibody Complex↗
PubMed1990

Monoclonal antibodies directed against the rev protein of human immunodeficiency virus type 1.

The rev (art/trs) protein of human immunodeficiency virus type 1 (HIV-1), a phosphoprotein of 20 K apparent molecular weight, is essential to target the mRNA for virion polypeptides into the cytoplasm. The rev protein was expressed in Escherichia coli as a beta-galactosidase fusion protein with a cleavage site for proteinase factor Xa. The rev-specific fragment was isolated to immunize mice. Five stable hybridoma cell lines were obtained producing monoclonal antibodies that reacted with rev protein in Western blot and ELISA. Using the monoclonal antibodies in indirect immunofluorescence, the rev protein could be localized in the nucleus, mostly in the nucleoli, of Hela cells that were transfected with a eukaryotic rev expression plasmid.

Animals↗
PubMed1990

Treatment of experimental foreign body infection caused by methicillin-resistant Staphylococcus aureus.

A novel model of experimental foreign body infection was developed in rats: four perforated Teflon tissue cages per animal were implanted subcutaneously and 3 to 4 weeks later were infected with 0.5 x 10(5) to 2 x 10(5) CFU of methicillin-resistant Staphylococcus aureus. After 2 weeks, the number of CFU in the cage fluid was determined [day 1 mean, (7.25 +/- 0.79) log10 CFU/ml], and treatment with vancomycin (50 mg/kg twice a day [BID]), fleroxacin (50 mg/kg BID), or fifampin (25 mg/kg BID), alone and in combination, was initiated for a duration of 6 days. Concentrations of antibiotics in cage fluids were in the range of those encountered in clinical conditions. Eighteen hours after the last injection (day 7), the number of CFU in the cage fluid was determined and the difference between day 1 and day 7 values was calculated. Rifampin, alone and in combination with fleroxacin or vancomycin, was the most effective regimen in reducing the bacterial counts in the tissue cage fluids [(1.87 +/- 1.44, 2.18 +/- 1.02, and 2.55 +/- 1.09 log10) CFU/ml, P less than 0.001, respectively]. After treatment, cage fluids and cages were analyzed for resistant bacteria. Resistance to rifampin occurred in 15 of 19 cages in animals treated with rifampin alone and in 4 of 25 in animals treated with rifampin plus vancomycin. We detected no development of resistance to rifampin in animals treated with rifampin plus fleroxacin or to fleroxacin in animals treated with this antimicrobial agent. In conclusion, regimens including rifampin alone or in combination with vancomycin or fleroxacin were an effective treatment of foreign body infection due to methicillin-resistant S. aureus in reducing bacteria counts, but rifampin monotherapy was compromised by significant emergence of resistance. The combined therapy of fleroxacin with rifampin prevent development of resistance to rifampin.

Animals↗