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Biomedical subjects

J A Schmidt

Publications and source records attributed to J A Schmidt.

At least 55 records · Page 3Linked to original sources
PubMed1994

[Iodine-induced hyperthyroidism in metastatic thyroid carcinoma].

A 75-year-old man with nodular goitre (for the preceding 2 years treated with 75 micrograms/dl L-thyroxine) complained of pain over the left hip: on auscultation an arterial flow murmur was audible over the hip. The radiograph demonstrated extensive osteolysis in the flat part of the ilium. Search for the primary tumour, including two pelvic angiographs, was unsuccessful. Examination of a biopsy from the right ilium revealed a metastasis from a highly differentiated follicular thyroid carcinoma, which could not be demonstrated scintigraphically because of a reduced 99mTc-pertechnetate and 123I-iodine uptake, the result of the L-thyroxine administration. A thyrotoxic crisis occurred 2 days after the second angiography (free thyroxine 3.17 ng/dl, triiodothyronine 219 ng/dl, thyroglobulin > 250 ng/ml). Treatment with thiamazole (40 mg/d) and perchlorate (1 g/d) reduced the concentration of peripheral thyroid hormone, but the patient's general condition improved only slowly. As a result, radioiodine treatment could not be started until 9 months later. He died a further 9 months later from septicaemia originating from the metastasis.

Adenocarcinoma, Follicular↗
PubMed1993

On the use of primary reference grade polydimethylsiloxane.

There has been an increase in the use of primary reference material as a standard for identifying the cellular response to biomaterials. One such material is NHLBI-DTB polydimethylsiloxane (PDMS). The PDMS was developed for blood contacting studies and is composed of PDMS backed on one side with mylar. The results of implantation studies of two different publications are discussed in light of the different materials and different surface topographies of each of the materials. The appropriateness of in vivo studies using this reference material is questioned.

Dimethylpolysiloxanes↗
PubMed1993

Periodic hemodynamics (flow motion) in peripheral arterial occlusive disease.

PURPOSE: The occurrence of periodic blood flow variations (flow motion) in health and disease is controversially discussed. This is partly due to not reporting the incidence and to performing the analysis solely visually. We have therefore studied flow motion with computerized methods. METHODS: We used a computerized Prony spectral line estimator program to analyze the frequencies of resting skin blood flow variations, as determined by laser Doppler flowmetry on the thumb and great toe, in 50 male control subjects (group a), in 50 patients with mild peripheral arterial occlusive disease (PAOD stages I and II; group b), and in 25 patients with severe PAOD (stages III and IV; group c). RESULTS: The median ankle/arm pressure ratio was 1.10 in the control group, 0.72 in the mild PAOD group, and 0.66 in the severe PAOD group. Slow wave flow motion was detected in 19% of all thumbs from groups a and b (systolic arm pressures > 100 mm Hg) and in 12% of the toes in the control group. Patients with mild PAOD exhibited slow wave flow motion in 46% of the toes. Patients with severe PAOD showed slow waves in 77% of the toes. The median flow motion frequencies were about 1.6 cycles/min for groups a and b, when present. The median frequency in group c was significantly higher at 4.0 cycles/min, though still in the range of slow waves. The median peak-to-through amplitude was between 17% and 20% of mean flow for all groups. CONCLUSIONS: We conclude that evaluation of flow motion requires computerized frequency analysis and that slow wave flow motion is a perfusion pattern characteristic of PAOD rather than of normal perfusion states. This finding has potential implications for diagnostic and therapeutic approaches in arterial occlusive disease.

Arterial Occlusive Diseases↗
PubMed1993

Neurogenic modulation of periodic hemodynamics in rabbit skeletal muscle.

We characterized the effect of various forms of neural blockade and vasopressin infusion on regular slow-wave flux oscillation (RSWFO). RSWFO, measured with laser-Doppler flowmetry (LDF), was induced by local reduction of arterial pressure in the gastrocnemius muscle of 30 New Zealand White rabbits. At normal median femoral arterial mean pressure, LDF only showed irregular variations. With an intact innervation, RSWFO was maximal at a median femoral mean pressure of 30 mmHg (range 25-53), the median frequency was 1.7 cycles/min (range 1.0-3.0), and the maximum amplitude was 50% (range 19-119). Application of lidocaine to the sciatic nerve, or cutting of this nerve, when arterial pressure was reduced, resulted in disappearance of slow waves in all cases. Intravenous application of guanethidine resulted in a significant reduction of the flux oscillation amplitude from 47 to 10% (P < 0.001). In an additional nine animals with sciatic denervation and local blood pressure reduction, RSWFO could be induced by intravenous vasopressin infusion. These results offer a new pathophysiological concept of periodic hemodynamics as a locally controlled and, with intact innervation, a neurally modulated mechanism for blood flow redistribution in cases of reduced blood pressure and flow.

Animals↗
PubMed1993

The vascular origin of slow wave flowmotion in skeletal muscle during local hypotension.

Intravital microscopy (IVM) and laser-Doppler-flowmetry- or fluxmetry (LDF) were used to simultaneously assess periodic hemodynamics (vaso/flowmotion) in the tenuissimus muscle of eleven New Zealand White (NZW)-rabbits during local reduction of arterial pressure. Diameter changes of transverse arterioles (TR) were monitored with the microscope, and in six animals also blood cell velocity measurements were performed with a cross-correlation technique. One LDF was positioned at the tenuissimus muscle as close to the objective as possible without causing optical interference. A second LDF was positioned at the underlying gastrocnemius muscle. Slow wave vaso/flowmotion was not present at control arterial pressure (x = 73 mmHg, range-r: 60-87) but was induced as local femoral pressure was reduced, being minimal at 35 mmHg (r: 20-50). The vaso/flowmotion frequencies of the IVM, tenuissimus-LDF, and the gastrocnemius-LDF signals were in the order of 1.5 cpm. LDF-flowmotion frequencies in the two muscles showed no correlation (R = +0.06, P = 0.4). The IVM flow-frequencies in the TR, however, correlated well with the oscillations recorded with the tenuissimus-LDF placed nearby (R = +0.89, p +0.01). Regular diameter variations were recorded only in the eleven cases where the microscope focused on the proximal portion of the TR; these oscillation frequencies were correlated with corresponding LDF-tenuissimus recordings (R = +0.97, p < 0.01). We conclude that slow wave vasomotion in rabbit skeletal muscle is not present during control conditions, but is induced on a regular basis by local blood pressure reduction and that it originates in the proximal part of the TR as reflected by slow wave flowmotion in LDF.

Animals↗
PubMed1992

Surface characterization of microtextured silicone.

A set of microtextured silicone surfaces was manufactured using the technique of photolithography. The textures consist of a uniform array that imparts anisotropy to the surfaces. Processing the material required multiple steps which may have altered the surface characteristics. This project aimed to determine if a surface texture on implant grade silicone would affect the material characteristics. ESCA and contact angle studies revealed no measurable alteration of the surface chemistry or surface energy due to the texturing procedure or the presence of the texture. Both analytical techniques confirmed the material was silicone. The actual dimensions of the surface textures, size, spacing, depth and orientation of the textures were found to be close to the design values, using SEM and quantitative two- and three-dimensional profilometry. Standard 2D profilometry was not sufficient to characterize the surfaces, as a direct result of the uniformity of the arrays. A method of characterizing regular surface periodic structures is presented.

Chemistry, Physical↗
PubMed1992

Macrophage response to microtextured silicone.

Seven different silicone surface textures were tested for effect on macrophage spreading and metabolic activity in vitro. Variables of the textured arrays that could modify spreading were determined to be the size, spacing between, depth, density, and orientation of the individual surface events and the roughness of the surfaces. Cells were influenced by the size of the events and the roughness of the surfaces more than any other variables. Cell morphology data, surface area and perimeter, could be divided into discrete regions that correlated well with the size of the events. Cell dimensions on 5 microns textures were smallest while those on smooth silicone and glass surfaces were the largest. Surface texture events may be modifying contact guidance of the cells or interacting with specific transmembrane proteins to alter cell shape and function. The mitochondrial activity of cells attached to the textured silicones was determined by measuring the amount of reduced MTT directly through live cells. Cells on polystyrene (PS), 5VP and 8VP textures were metabolically more active than cells on the other textures. PMA was used to stimulate cells on the various textures. PMA-stimulated cells, on the smaller textures, 2VP, 5VP and 5CP, were less active than test cells that were not stimulated. The inability of PMA to stimulate these cells may be due to a structural alteration of protein kinase C. An hypothesis is introduced that includes a possible mechanism of how a micrometre-sized surface texture could modify cell function.

Animals↗
PubMed1992

Determination of three-dimensional morphometry of adherent cells by surface profilometry.

A three-dimensional, non-contacting surface profiler was used to analyse cells that had been previously prepared for scanning electron microscopy. The height of ten attached and spread cells was measured in both two- and three-dimensions (2-D and 3-D). The 2-D scan is a typical, linear profilometer output, while a 3-D image is produced with a 3-D detector. The 3-D contour plots of each cell were then compared with scanning electron microscopy micrographs by digitizing four morphological parameters: perimeter, surface area, long axis and short axis of each cell. A paired Student's t test showed that the two imaging techniques are not equivalent. Non-equivalence was attributed to a difference in the method of calibration. However, when combined with scanning electron microscopy, the profiler allowed complete three-dimensional quantitative analysis of cellular morphology.

Animals↗
PubMed1992

Periodic hemodynamics in skeletal muscle during local arterial pressure reduction.

The time-dependent features of red blood cell flow were evaluated with laser-Doppler flowmetry (LDF) in the left gastrocnemius muscle of 31 anesthetized New Zealand White rabbits during stepwise arterial occlusion. During the control period with a median femoral pressure of 72 mmHg, 29 animals showed minor irregular fluctuations in LDF blood flow, and only two animals displayed periodic variations of blood flow. Lowering femoral arterial pressure induced maximal periodic blood flow variations at a median pressure of 35 mmHg in all animals with a median frequency of 1.5 cycles/min (termed "slow-wave flow motion"). The median amplitude was 48% of the corresponding average flow. These slow waves disappeared at a median femoral pressure of 20 mmHg. The median LDF flow value was 4.00 arbitrary units (AU) at control pressure and 2.05 AU at maximum slow-wave flow motion. When slow-wave flow motion was seen at several pressure levels, their frequency was identical, which supports the local pacemaker concept. This study promotes a novel concept for the role and physiological significance of periodic hemodynamics in that it is a condition not characteristic for normal control situations but is activated below a specific local arterial blood pressure and flow threshold, which is known to be the lower end of autoregulation in the microcirculation of rabbit skeletal muscle. This also suggests that slow-wave flow motion is primarily under local control mechanisms.

Animals↗
PubMed1992

[Transcutaneous oxygen pressure in the foot in treadmill stress before and after percutaneous atherectomy].

Transcutaneous oxygen pressure (tcPO2) on the dorsum of the foot and Doppler ankle/arm pressure ratio (AAR) were measured in nine patients with peripheral arterial occlusive disease (PAOD)-stage IIb-III during treadmill exercise before and after (two days and one month) atherectomy. These parameters were compared with nine normal controls and nine PAOD I-IIa patients without atherectomy. All patients with atherectomy showed an increase in their pain free walking distance, and, both two days and one month after the intervention, a significant (p less than 0.05) increase in their exercise/rest tcPO2 ratio (pre-atherectomy: 25% (12-81), two days after: 78% (49-92), one month after: 85% (81-92). AAR displays a significant increase only between pre- and two days after atherectomy, without further significant improvement after one month. We conclude that tcPO2 measurement is an adequate measurement for follow-up studies in patients with PAOD after invasive therapeutic interventions. Furthermore, these data suggest that, while the maximum improvement for the macrocirculation (AAR) occurs shortly after atherectomy, improvement of the microcirculation (tcPO2) is delayed for a prolonged period after revascularization of major arteries, possibly due to reperfusion injury.

Adult↗
PubMed1992

Slow-wave flowmotion in rabbit skeletal muscle after acute fixed-volume hemorrhage.

Laser Doppler flux (LDF) was used to detect flowmotion (regular cyclic alterations in red blood cell flux) in the left gastrocnemius muscle of 14 rabbits that were bled 30% of their blood volume and let to recover spontaneously for 30 min. Only rabbits that met stated inclusion criteria during control conditions were used in the study. During control conditions when femoral artery pressure averaged 68 mm Hg (range 60-80), no animal displayed regular flowmotion. After the end of the acute hemorrhage, arterial pressure was 35 mm Hg (20-51) and slow wave flowmotion appeared instantaneously in 13 of the 14 animals. The maximum relative amplitude of the induced flowmotion was 31% (7-100) and the frequency was 1.8 cycles per minute (cpm) (1.4-4.0). Flowmotion persisted throughout the 30 min observation period in 11 animals, during which time arterial pressure recovered to 46 mm Hg (42-50). Fast-wave flowmotion was not detected in the present study. These results suggest that slow-wave flowmotion as measured with LDF is not a phenomenon characteristic of normal regulation of blood flow in skeletal muscle. After a 30% fixed-volume hemorrhage, slow-wave flowmotion is induced as arterial pressure drops below a certain threshold.

Acute Disease↗
PubMed1991

Texturing of polymer surfaces at the cellular level.

A technique to surface-texture polymer sheets with any conceivable surface morphology is described. It uses technology developed for semiconductor device fabrication. It allows the definition and control of implant surface texture at subcellular levels, down to 2 micron dimensions, and the cellular response to those textures to be studied in vitro and in vivo. The results of a pilot study are presented and the biological significance of a microscopic surface texture is discussed.

Animals↗
PubMed1991

The processing of interleukin-1 beta studied with antibodies raised against synthetic peptides from the precursor N-terminal region.

The exact sequence of events during processing of human interleukin-1 beta (IL-1 beta) and the fate of the N-terminal region are unknown. We have used anti-peptide sera specific for the precursor and mature regions of IL-1 beta to study biosynthesis. These were raised against peptides corresponding to amino acids 1-15, 17-32, and 43-54 of the precursor and a peptide corresponding to the C-terminal 33 amino acids of mature human IL-1 beta. Antiserum to the mature region peptide immunoprecipitated the 35-kD precursor from cell lysates and 17-kD mature IL-1 beta and a 31-kD protein from the culture supernatants from radiolabeled human peripheral blood monocytes stimulated with lipopolysaccharide (LPS). Antisera to peptides from the precursor region also immunoprecipitated the 35-kD IL-1 beta precursor but not the 31-kD or 17-kD forms. Of the precursor-specific sera, only antiserum to amino acids 1-15 specifically recognized any other proteins; a peptide of 18 kD and a low molecular weight peptide, both of which accumulated in the medium. The 18-kD protein was not recognized by any of the other antisera and is unlikely to be the N-terminal region of the precursor removed during processing. Pulse-chase experiments indicated that the 31-kD protein could be a processing intermediate and also that it was itself an end product along with full-length precursor. Only 17-kD mature IL-1 beta had biological activity.

Antibodies↗