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Biomedical subjects

M W Meyer

Publications and source records attributed to M W Meyer.

At least 19 recordsLinked to original sources
PubMed2006

[Intermittent ciliary block as a result of haemodialysis].

We report the case of a patient who experienced recurrent elevations of intraocular pressure during haemodialysis. We measured a rise in intraocular pressure of 10-12 mmHg after dialysis. The lens showed intumescence, and a ciliary block was detected by means of Orbscan II. Within 6 h findings had normalized. Changes in serum osmolarity due to haemodialysis may result in fluid shifts between different compartments. Decrease of serum osmolarity during dialysis may lead to lens swelling and thus cause a ciliary block. This may end with regression of the lens swelling.

Aged↗
PubMed2006

[Intraocular pressure measurements with the Proview self-tonometer in comparison of Goldmann applanation tonometry in healthy and glaucomatous eyes].

BACKGROUND: The aim of this study was to compare the results of intraocular pressure (IOP) measurements obtained using the pressure phosphene tonometer Proview with those from Goldmann applanation tonometer (GAT) in normal and glaucomatous eyes. PATIENTS AND METHODS: The IOP in 150 eyes of 62 healthy volunteers and 88 patients with glaucoma or ocular hypertension was measured prospectively in a sitting position. After being trained to use the Proview device, Goldmann applanation tonometry was performed first. Then the patient took a reading with the Proview self-tonometer. RESULTS: For all investigated eyes the measurements with the Proview were on average 5.5 mmHg higher than those by GAT. Only 34 % of the readings from the two devices were within a difference range of +/- 3 mmHg. On comparing the group of glaucomatous patients with slight visual field defects with the group of healthy subjects and patients with ocular hypertension without visual field defects we determined almost the same mean difference between the Proview and GAT (mean difference in the group with visual field defects = 4.7 +/- 4.1 mmHg; without defects = 4.8 +/- 2.9 mmHg). CONCLUSIONS: The tonometer Proview did not show a close agreement to GAT. Therefore, the PPT does not offer an alternative method for measuring IOP. We do not recommend the Proview for self-tonometry at home or for clinical management of patients with glaucoma. Slight visual field defects seem to have no influence on intraocular pressure measurement with the self-tonometer.

Adolescent↗
PubMed2001

Anti-fibrin antibody binding in valvular vegetations and kidney lesions during experimental endocarditis.

In Streptococcus sanguinis (sanguis) induced experimental endocarditis, we sought evidence that the development of aortic valvular vegetation depends on the availability of fibrin. Endocarditis was induced in New Zealand white rabbits by catheter placement into the left ventricle and inoculation of the bacteria. Fibrin was localized in the developing vegetation with 99mTechnetium (Tc)-labeled anti-fibrin antibody one or three days later. When rabbit anti-fibrin antibody was given intravenously on day 1, the mass of aortic valvular vegetation was significantly reduced at day 3; infusion of non-specific rabbit IgG showed no effect. The 99mTc-labeled anti-fibrin antibody also labeled kidneys that showed macroscopic subcapsular hemorrhage. To learn if the deposition of fibrin in the kidneys was a consequence of endocarditis required a comparison of farm-bred and specific pathogen-free rabbits before and after the induction of endocarditis. Before induction, the kidneys of farm-bred rabbits were labeled, but specific pathogen-free rabbits were free of labeling and signs of macroscopic hemorrhage. After 3 days of endocarditis, kidneys of 10 of 14 specific pathogen-free rabbits labeled with 99mTc-labeled anti-fibrin antibody and showed hemorrhage. Kidney lesions were suggested to be a frequent sequellae of S. sanguinis infective endocarditis. For the first time, fibrin was shown to be required for the continued development of aortic valvular vegetations.

Animals↗
PubMed1999

Streptococcal reporter gene-fusion vector for identification of in vivo expressed genes.

To study streptococcal genes that are specifically induced in the host during endocarditis, we have developed a novel plasmid for use in in vivo expression technology (IVET). This IVET uses an integration plasmid, pAK36, that carries dual (amy-cat) reporter genes. A gene-fusion strain library was constructed with the plasmid randomly inserted into the chromosome of Streptococcus gordonii V288 by insertion-duplication. The library was inoculated intravenously into a rabbit that had been prepared for experimental endocarditis. Beginning 6 h after the inoculation, the rabbit was given chloramphenicol (Cm) intravenously twice a day to a final serum level of 5 microg/ml and was euthanized 3 days later. The aortic valve vegetations containing Cm(R) S. gordonii clones were cultured. Colonies were screened in vitro for negative amylase activity and sensitivity to Cm. Forty-eight such colonies showed 13 different insertion patterns when Southern hybridization blots were probed with labeled pAK36. For each of the 13 isolates, the gene fragment proximal to the insertion of the reporter amy-cat was cloned, and its nucleotide sequence was determined. Functions of these genes were inferred by their homology to known genes. Therefore, this novel IVET vector can be useful for identification of in vivo induced genes in S. gordonii and other streptococcal species.

Animals↗
PubMed1998

Streptococcus sanguis-induced platelet clotting in rabbits and hemodynamic and cardiopulmonary consequences.

By mimicking hemostatic structural domains of collagen, Streptococcus sanguis (aggregation-positive phenotype; Agg+) induces platelets to aggregate in vitro. To test the hypothesis that aggregation occurs in vivo, S. sanguis (Agg+ or Agg- suspension) was infused intravenously into rabbits. The extent of hemodynamic and cardiopulmonary changes and the fate of circulating platelets were Agg+ strain dose dependent. Within 45 to 50 s of the start of infusion, 40 x 10(8) CFU of the Agg+ strain caused increased blood pressure. Thirty seconds after infusion, other changes occurred. Intermittent electrocardiographic abnormalities (13 of 15 rabbits), ST-segment depression (10 of 15 rabbits), and preventricular contractions (7 of 15 rabbits) manifested at 3 to 7 min, with frequencies dose dependent. Respiratory rate and cardiac contractility increased during this phase. Blood catecholamine concentration, thrombocytopenia, accumulation of 111Indium-labeled platelets in the lungs, and ventricular axis deviation also showed dose dependency. Rabbits were unaffected by inoculation of an Agg- strain. Therefore, Agg+ S. sanguis induced platelet aggregation in vitro. Platelet clots caused hemodynamic changes, acute pulmonary hypertension, and cardiac abnormalities, including ischemia.

Animals↗
PubMed1997

Gender stereotypes: a bias against men.

In a class on the psychology of male roles, 38 undergraduates (18 men, 20 women) participated in an activity designed to assess gender stereotypes. A chi-square analysis revealed that participants produced significantly more negative stereotypes for men than for women. These results, consistent with crosscultural findings, are discussed in terms of methodological issues and the differential socialization of men and women.

California↗
PubMed1997

Host-pathogen interactions in bacterial endocarditis: streptococcal virulence in the host.

To identify streptococcal genes that are expressed during experimental endocarditis, we developed a promoter-less dual reporter gene-fusion (amy, cat) plasmid, pAK36. Chromosomal DNA from S. gordonii V288 was digested with Sau3A1. The resulting fragments were ligated into pAK36. Following transformation into S. gordonii, the library of random gene fusion clones was inoculated into a rabbit to induce experimental endocarditis. Chloramphenicol treatment effected positive selection. Upon euthanization of the rabbits, the valvular vegetations were excised in a sterile field. Surviving clones were isolated and screened in vitro for chloramphenicol sensitivity and negative amylase activity. From the 48 randomly picked, double-negative clones, DNA was isolated and analyzed by Southern hybridization with labeled pAK36 probe. Different insertion patterns were identified, suggesting that no fewer than 13 S. gordonii genes were induced. Therefore, S. gordonii genes are induced during experimental endocarditis, which may contribute to virulence.

Animals↗
PubMed1996

Residues of organochlorines in mallards and blue-winged teal collected in Colombia and Wisconsin, 1984-1989.

We compared the seasonal concentrations of 12 organochlorine (OC) compounds in samples of breast muscle, associated skin, and subcutaneous fat of blue-winged teal (Anas discors) collected in Ciénaga Grande de Santa Marta, Colombia (1987-1988), and of mallards (Anas platyrhynchos) and blue-winged teal collected in Wisconsin (1984-1989). Although these species have similar feeding habits and overlapping breeding distributions, their winter ranges differ markedly. Most blue-winged teal winter in the Neotropics, whereas most mallards remain in the temperate regions of North America. A seasonal comparison of OC exposure in these species may help determine the geographic origins of contamination. All examined OCs were found to be below concentrations known to affect reproduction in waterfowl. DDE was most often detected in blue-winged teal and PCBs, in mallards. DDE exposure may have predominantly occurred outside of Wisconsin. The DDE concentration in blue-winged teal samples collected in Wisconsin in the spring (GM=0.406 microg/g) were greater (P<0.001) than in the fall (GM=0. 033 microg/g) and greater than the concentrations in mallard samples from the spring (GM=0.058 microg/g; P<0.001). Ciénaga Grande, however, was not a source of DDE contamination. The DDE concentrations in blue-winged teal samples from Ciénaga Grande did not differ between the spring (GM=0.037 microg/g) and the fall (GM=0. 039 microg/g) and were lower (P<0.001) than the concentration in blue-winged teal samples from Wisconsin in the spring. In contrast, PCB contamination seemed to have occurred in Wisconsin and affected mostly mallards. PCBs were not detected in the samples from Colombia and were detected in only five (8.3%) of the blue-winged teal samples from Wisconsin (GM=0.025 microg/g), however, those compounds were detected in 47% of the mallard samples collected in Wisconsin (GM=0.272 microg/g). DDE and PCB concentrations were greater (P=0.0) in mallard samples collected from wetlands adjacent to Lake Michigan than in samples from inland wetlands.

Adipose Tissue↗
PubMed1996

Effects of oral flora on platelets: possible consequences in cardiovascular disease.

During episodes of dental bacteremia, viridans group streptococci encounter platelets. Among these microorganisms, certain Streptococcus sanguis induce human and rabbit platelets to aggregate in vitro. In experimental rabbits, circulating streptococci induced platelets to aggregate, triggering the accumulation of platelets and fibrin into the heart valve vegetations of endocarditis. At necropsy, affected rabbit hearts showed ischemic areas. We therefore hypothesized that circulating S. sanguis might cause coronary thrombosis and signs of myocardial infarction (MI). Signs of MI were monitored in rabbits after infusion with platelet-aggregating doses of 4 to 40 x 10(9) cells of S. sanguis 133-79. Infusion resulted in dose-dependent changes in electrocardiograms, blood pressure, heart rate, and cardiac contractility. These changes were consistent with the occurrence of MI. Platelets isolated from hyperlipidemic rabbits showed an accelerated in vitro aggregation response to strain 133-79. Cultured from immunosuppressed children with septic shock and signs of disseminated intravascular coagulation, more than 60% of isolates of viridans streptococci induced platelet aggregation when tested in vitro. The data are consistent with a thrombogenic role for S. sanguis in human disease, contributing to the development of the vegetative lesion in infective endocarditis and a thrombotic mechanism to explain the additional contributed risk of periodontitis to MI.

Animals↗
PubMed1995

Therapeutic advantage of recombinant human plasminogen activator in endocarditis: evidence from experiments in rabbits.

In infective endocarditis vegetations are stabilized by fibrin. To learn if fibrin digestion would be therapeutic, experimental endocarditis was induced in rabbits by inoculation with a platelet-aggregating strain (Agg+) of Streptococcus sanguis and treated with recombinant tissue plasminogen activator (rt-PA), rt-PA with penicillin, or penicillin alone. Control rabbits were inoculated with saline. All treatments of Agg+ endocarditis reduced the mass of valvular vegetations and clinical signs of endocarditis, including the frequency of left axis deviation and heart ischemia. rt-PA with penicillin was more effective than penicillin or rt-PA alone, reducing the mass of vegetations and clinical signs to that of saline controls. Within 50 min, rt-PA cleared 5-fold more 111Indium-labelled platelets from the heart than untreated rabbits and 1.4-fold more after 3 days. Combined with penicillin, thrombolytic therapy for human endocarditis should be reconsidered.

Animals↗
PubMed1993

Orf virus infection in pregnancy.

Orf virus infection is endemic among sheep and goats, and can occur in humans who handle these animals. Orf virus infection in humans causes a characteristic skin lesion, and systemic symptoms can occur. Very little is known about Orf virus infection in human pregnancy. A case of Orf virus infection, with onset at 33 weeks gestation, is presented. There were no pathological findings in the infant born at term, or in the placenta.

Adult↗
PubMed1992

The platelet interactivity phenotype of Streptococcus sanguis influences the course of experimental endocarditis.

A strain of Streptococcus sanguis that induced rabbit platelets to aggregate in vitro (Agg+ phenotype) was hypothesized to be a more virulent pathogen than an Agg- strain in experimental endocarditis in rabbits. A left ventricular catheter was implanted, and then an Agg+ or Agg- strain was inoculated intravenously. Vegetations formed on the aortic semilunar valves but were unaffected by the duration of implantation of the catheter. Vegetations enlarged by accumulating platelets and their mass increased directly with the duration of endocarditis. Inoculation of the Agg+ strain consistently caused endocarditis with significantly larger vegetations, a more severe clinical course (including febrile episodes, hematological changes, and signs of myocardial ischemia), more gross lesions in major organs, and greater mortality than inoculation with the Agg- strain, saline, or the Agg+ strain pretreated with monospecific rabbit immunoglobulin G or Fab fragments against its platelet aggregation-associated protein (PAAP; class II). In experimental endocarditis, PAAP expressed by Agg+ S. sanguis appeared to be an important virulence factor.

Animals↗
PubMed1992

[Functional structures of the aorta as a predilection area of the earliest atherosclerotic changes].

Marked lipid deposits selectively localized in the grooves of so-called aortic functional structures were found in a 5-month-old infant who died of rapidly progressing crescentic glomerulonephritis. A prominent nephrotic syndrome comprising hypercholesterolemia and triglyceridemia was present and led to extensive lipid infiltration of the aortic intima. Development of the intimal lesions was probably enhanced by hypertension found in final phase of the illness. Spontaneously enhanced permeability of the intima in the "grooves" and a special constellation of haemodynamic forces along the functional structures were probably responsible for the peculiarly selective localization of lipid deposits that has so far not been described in the literature.

Aorta, Abdominal↗
PubMed1991

The kinetics of diastereomeric amino acids with o-phthaldialdehyde.

The kinetics of the reaction of the amino acid epimers L-isoleucine, D-allo-isoleucine, L-threonine, and D-allo-threonine with o-phthaldialdehyde and mercaptoethanol were determined at 25 degrees C. L-Isoleucine reacts faster than its D-epimer whereas L-threonine reacts slightly slower than its D-epimer. In the case of isoleucine, the consequence can be an allo/iso ratio which in the worst case is 25% too low if these amino acids are quantified by liquid chromatography and o-phthaldialdehyde fluorescence detection. The effect on dating of fossils by amino acid racemization is discussed.

Amino Acids↗
PubMed1986

Umbilical blood pressures and utero-placental blood flow in spontaneously hypertensive rats.

Some substrains of spontaneously hypertensive rats (SHR) are hypertensive at birth, suggesting the possibility of pre-natal hypertension. Fetal haemodynamics are sensitive to utero-placental blood flow changes. Thus, we used micropuncture to measure umbilical vein blood pressure (BP) in SHR and Wistar-Kyoto rats (WKY) at 18 and 20 days post-conception. We determined utero-placental blood flow (UPBF) at 17 and 20 days post-conception by the microsphere method. Results showed that SHR fetuses were hypertensive only at 20 days. Fetal heart:body weight ratio was higher in SHR, decreased with age and was not associated with BP or heart rate. Utero-placental weight was not affected by either age or strain. However, utero-placental blood flow was low in SHR at 20 days. Thus, in SHR pre-natal hypertension occurs between 18 and 20 days post-conception; pre-natal hypertension is associated with low utero-placental blood flow.

Animals↗
PubMed1984

Mechanisms of recovery from aphasia: evidence from serial xenon 133 cerebral blood flow studies.

In 21 patients who suffered aphasia resulting from left hemisphere ischemic infarction, the xenon 133 inhalation cerebral blood flow technique was used to measure cerebral blood flow within 3 months and 5 to 12 months after stroke. In addition to baseline measurements, cerebral blood flow measurements were also carried out while the patients were performing purposeful listening. In patients with incomplete recovery of comprehension and left posterior temporal-inferior parietal lesions, greater cerebral blood flow occurred with listening in the right inferior frontal region in the late studies than in the early studies. In patients with nearly complete recovery of comprehension and without left posterior temporal-inferior parietal lesions, early listening studies showed diffuse right hemisphere increases in cerebral blood flow. Later listening studies in this latter patient group showed greater cerebral blood flow in the left posterior temporal-inferior parietal region. The study provides evidence for participation of the right hemisphere in language comprehension in recovering aphasics, and for later return of function in left hemisphere regions that may have been functionally impaired early during recovery.

Adult↗
PubMed1983

Flap design and the LeFort III osteotomy: blood flow investigation.

The effect on local blood flow of flap design in a LeFort III osteotomy was examined in this study. The radioactive microsphere technique was used to make serial flow determinations in two groups of macaque monkeys. The use of seven skin and mucosal incisions was compared with a coronal flap procedure. Significant blood flow reductions to the midface segment where measured when a coronal incision was the sole access in performance of the osteotomies. The findings indicate that the multiple incision approach is more biologically sound than the coronal incision approach in the LeFort III osteotomy. Important information about the surgical techniques can be determined from the data and applied to a more successful performance of the LeFort III osteotomy.

Animals↗