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Biomedical subjects

W Krebs

Publications and source records attributed to W Krebs.

At least 55 records · Page 3Linked to original sources
PubMed1988

Epibulbar fibroma of the conjunctival substantia propria.

A 39-year-old black woman had a 12-year history of slowly progressive left temporal juxtalimbal conjunctival swelling. The lesion was freely movable over the surface of the globe and was believed to be situated within the substantia propria. Histopathologic evaluation of the excised tissue disclosed that it was a collagenous mass of lamellar architecture, with a hypocellular dispersion of mesenchymal cells and a scattering of capillaries in the absence of inflammation. Electron microscopic examination revealed that the lamellar arrangement had regular lobular subdivisions composed of collagen fibers approximately 50 nm in diameter. Compressed fibroblasts occupied the peripheries of the lobules; the former exhibited abundant rough-surfaced endoplasmic reticulum and failed to elaborate basement membrane material. Delicate processes of the fibroblasts extended into the centers of the collagenous aggregates. To our knowledge, this is the first convincingly documented case of an acquired fibroma of the substantia propria of the epibulbar conjunctiva. The differential diagnosis in this case included related fibroblastic and simulating nonfibroblastic lesions.

Adult↗
PubMed1988

Papillary oncocytoma of the eyelid. A previously undescribed tumor of apocrine gland origin.

Oncocytomas are uncommon tumors arising within the ductular cell lining of glandular structures. The oncocytic cells are characteristically large and rich in eosinophilic cytoplasm. Electron microscopic studies show densely packed mitochondria with irregular, whorled, or fragmented cristae. Ocular adnexal oncocytomas have been reported to arise in the caruncle, lacrimal gland, and lacrimal sac. The authors recently encountered an oncocytic tumor occurring in a most unusual location, the skin of the medial lid margin and commissure. Microscopically, the lesion was papillary and cystic in architecture, and arose from an adjacent apocrine gland of the eyelid margin (gland of Moll). Electron microscopic studies showed that the tumor cells were packed with malformed mitochondria to the exclusion of other organelles. This is the first report documenting an oncocytic lesion arising in the skin from an adnexal gland.

Adenoma, Acidophil↗
PubMed1988

Infantile subconjunctival and anterior orbital fibrous histiocytoma. Ultrastructural and immunohistochemical studies.

A fleshy, polypoidal and partially lobulated lesion that protruded between the eyelids from the medial caruncular region and that infiltrated the contiguous anterior orbital tissues developed over 1 month in a 9-month-old infant. The microscopic features of the tumor included a plump spindle cell population, more polygonal cells, early xanthoma cell transformation, infiltrating lymphocytes and eosinophils, and multinucleated giant cells, the last not exhibiting classic Touton characteristics. The histopathologic differential diagnosis ranged among fibrous histiocytoma, juvenile xanthogranuloma, and eosinophilic granuloma (histiocytosis-X). Results of electron microscopy disclosed abundant rough-surfaced endoplasmic reticulum, a paucity of lysosomes, and no Langerhans' (Birbeck) granules. Immunohistochemistry corroborated the fibrohistiocytic nature of the tumor, because histochemical stains for the enzymes alpha-1-antichymotrypsin and lysozyme, and monoclonal or polyclonal antibodies against common leukocytic antigen and S-100 protein, were negative--whereas they would have been expected to be positive in various combinations in the different histiocytic proliferations. Vimentin was identified in the tumor cells; this is an intermediate cytoplasmic filament almost always present in mesenchymal proliferations. The distinctions between fibrous histiocytomas of stromal cell origin and true histiocytic proliferations of bone marrow cell provenance are explored.

Conjunctival Neoplasms↗
PubMed1988

Benign mixed tumor of the palpebral lobe of the lacrimal gland. Clinical diagnosis and appropriate surgical management.

The treatment of suspected benign mixed tumor (pleomorphic adenoma) of the lacrimal gland consists of wide local surgical excision of the tumor and its capsule in their entirety. The tumor should be approached routinely via a lateral orbitotomy to provide maximal exposure and allow complete removal of the lesion. However, if clinical and radiographic evidence indicates a far anterior location implying an origin in the more superficial palpebral lobe, an anterior transcutaneous approach is advantageous and preferred. The authors report an adult case of an anteriorly located benign mixed tumor of the palpebral lobe of the lacrimal gland. The authors reviewed the characteristic clinical, echographic, and computed tomographic (CT) features, offered a differential diagnosis, and described surgical removal using a cryoprobe via an anterior lid approach. An awareness of the distinctive clinical and diagnostic features of benign mixed tumor of the palpebral lobe should help to avoid the complications that ensue from an incisional biopsy or piecemeal resection through the lid, and also to avoid the need for more extensive surgery for removal of residual or recurrent tumor.

Adenoma↗
PubMed1988

The effect of accelerated argon ions on the retina.

It has been postulated that high energy heavy ions cause a unique form of damage in living tissue, which results from the high linear energy transfer of accelerated single particles. We have searched for these single-particle effects, so-called "microlesions," in composite electron micrographs of retinas of rats which had been irradiated with a dose of 1 Gy of 570 MeV/amu argon ions. The calculated rate of energy deposition of the radiation in the retina was about 100 keV/micron and the influence was four particles per 100 micron 2. Different areas of the irradiated retinas which combined would have been expected to be traversed by approximately 2400 particles were examined. We were unable to detect ultrastructural changes in the irradiated retinas distinct from those of controls. The spatial cellular densities of pigment epithelial and photoreceptor cells remained within the normal range when examined at 24 h and at 6 months after irradiation. These findings suggest that the retina is relatively resistant to heavy-ion irradiation and that under the experimental conditions the passage of high energy argon ions does not cause retinal microlesions that can be detected by ultrastructural analysis.

Animals↗
PubMed1987

Quantitative morphology of the primate peripheral retina (Macaca irus).

By using electron microscopy to study the quantitative morphology of the retina, it was possible to determine the spatial density of all principal retinal cells at a defined retinal location. In two retinas of cynomolgus monkeys at a position of 30 degrees nasal of the fovea centralis, the following cell densities were determined from composite electron micrographs: retinal pigment epithelium: 3,400 cell/mm2; rod cells: 115,000 and 168,000 cells/mm2; cone cells: 8,200/mm2; horizontal cells: 7,000/mm2; bipolar cells: 50,000/mm2; amacrine cells: 11,500/mm2; Müller cells: 16,000/mm2; and ganglion cells: 5,350 and 6,750/mm2.

Animals↗
PubMed1987

Metastatic colloid carcinoma versus primary carcinoma of the ciliary epithelium.

Ocular metastases developed from breast carcinomas in two women 7 and 19 years after their mastectomies. They were both ciliary body metastases that had eroded through the root of the iris to present as unifocal globular, gelatinous (colloid) masses in the anterior chamber, and were amenable to local surgery. Histopathologically, small cellular clusters were widely separated in a sea of mucin; the tumor cells failed to display marked pleomorphism or mitotic activity. In each case, the distinction from a primary mucinous ciliary epithelial neoplasm had to be made both clinically and pathologically. For comparison, the authors also report a unique primary ciliary carcinoma that caused intractable glaucoma by spreading diffusely throughout the iris, ciliary body, and anterior chamber angle, and that necessitated enucleation. The tumor cells failed to produce hyaluronic acid but elaborated a mucosubstance which was histochemically indistinguishable from that of the metastatic carcinomas. This primary neoplasm, however, exhibited the following histologic differences from the metastases: more architectural variability, including garlands and festoons of cells not forming lumens that were suspended in a mucinous matrix; much more abundant intracellular mucin; foci of sheet-like and pleomorphic cellular proliferations with mitotic activity; and partial replacement of the ciliary processes by a comparatively benign-appearing mucinous columnar epithelium.

Adenocarcinoma, Mucinous↗
PubMed1986

Right ventricular volume determination in isolated human hearts.

For right ventricular volume determination a new method was developed that took into account right ventricular imaging by apical two-dimensional echocardiography in the four- and two-chamber views. Right ventricular volume was calculated by subtraction of the partial volume of the left ventricle and interventricular septum from the total heart volume of the right and left ventricles including the interventricular septum. Accuracy of the subtraction method was evaluated in isolated human hearts by two-dimensional echocardiography and radiography. Regression analysis indicated that for both the echocardiographic and radiologic procedures, the subtraction method gave the best correlation with the right ventricular filling volume. The correlation coefficients obtained using the echocardiographic procedure were 0.964, 0.848, and 0.851 for the subtraction method, pyramid method, and Simpson's rule method, respectively. For the radiographic procedure, these values were 0.946, 0.860, and 0.872. Percentage difference calculations indicated that the subtraction method systematically underestimated (-7.4%) the filling volume in the echocardiographic procedure, but this was not seen with the radiologic procedures. The random error associated with the subtraction method was only half (10.5%, 13.9%) of that seen with the other two methods in both the echocardiographic and radiological procedures. These results indicate that right ventricular volume determination by the subtraction method seems to be suitable for apical two-dimensional echocardiography and is more accurate than the pyramid method and Simpson's rule method.

Echocardiography↗
PubMed1986

Light and electron microscopic findings with permanent eyeliner.

Pathologic studies were performed on two specimens of eyelid that had been treated with permanent eyeliner (tattooing with ferrous oxide), one specimen excised four days after injection of the pigment, and the other obtained 12 months later. Each patient had undergone an ectropion repair of the lower eyelid that provided the specimen. The specimen studied four days after injection revealed by light microscopy scattered pigment granules within the epidermis and fine granules and small aggregates dispersed within the dermis. No acute or chronic inflammatory cells were observed in relationship to the deposits. The specimen obtained 12 months after eyeliner injection was studied by both light and electron microscopy. No pigment particles were observed within the epidermis, but rather there were coarse clumps of granular material in the dermis. Apart from scattered mast cells, which occasionally contained fine granules, and apart from the macrophages which appeared to have ingested the pigment granules, no other acute and chronic inflammatory cells were found. Electron microscopy demonstrated that while most of the granular material had been phagocytosed by macrophages, occasional granules were found in small dispersions within the cytoplasm of mast cells and fibroblasts of the dermis. Minimal migration of pigment within macrophages occurred to locations around lymphatic channels and within the superficial orbicularis muscle connective tissue.

Aged↗
PubMed1986

A new laser for collagen wounding in corneal and strabismus surgery: a preliminary report.

It has been shown that using a small spot size 2 to 5 mu, a dye modified excimer laser emitting at 595 nm can produce laser ablation of tissue in corneal stroma without compromising anterior and posterior limiting membranes. The surface of extraocular muscle tendon sheath has been similarly laser modified. An instrument, under prototype construction, designed for clinical application of this laser energy is described as well as clinical implications of such surgical interventions in corneal and extraocular muscle surgery.

Collagen↗
PubMed1986

[A new echocardiographic procedure for calculation of the accurate volume of the right atrium].

The right atrial (RA) volume can be determined angiographically from two perpendicular projections. Up to now volume calculations by means of two-dimensional echocardiography (2-DE) have only been attempted in a single plane, the apical four-chamber view. Our study reports a new method for RA volume calculation using two intersecting cross-sectional echocardiographic views. For this purpose silicone rubber casts of 20 human necropsy hearts were obtained and thin walled natural rubber moulds of the RA casts were prepared. Totally filled with and immersed in water, the mouls could be visualized in the apical four-chamber view and an additional echocardiographic plane, the latter corresponding to the subcostal view in vivo. In this view the vertical extension of RA could be estimated. Areas and length of RA were determined in the respective planes and RA volume was calculated by applying the formula: - Area X Length - to two intersecting planes. Finally, the latex moulds were filled with diluted contrast agent and the volume was determined angiographically using a biplane disc method. Real volume of RA was 112 +/- 23 ml (mean +/- 1 SD). Angiographically, an overestimation resulted: the calculated volume amounted to 119 +/- 24 ml, the mean difference was 7 +/- 2 ml (p less than 0.001). The regression equation was y = 1.04 X + 2.34, r = 0.995, SEE = 2.3 ml. Volume determination from the apical four-chamber view using a monoplane disc method resulted in a mean volume of 62 +/- 17 ml. The mean difference to the real RA volume was 50 +/- 17 ml, p less than 0.001.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Sensitivity of cross-sectional echocardiography in detection of impaired global and regional left ventricular function: prospective study.

In order to establish the sensitivity and specificity of cross-sectional echocardiography for detection of global and regional left ventricular function a prospective study was performed in 80 patients suspected of having coronary artery disease. Twenty four hours before heart catheterization, cross-sectional echocardiograms were recorded in the apical RAO-equivalent view and high quality echocardiograms were obtained in 71/80 patients (89%). M-mode echocardiograms of the left ventricle could be performed in 56/71 patients (79%). Based on normal values sensitivity and specificity of cross-sectional echocardiography were calculated in comparison to cineventriculography. For fractional shortening (normal value greater than 25%) sensitivity measured 46% and specificity 93%, and when the E-point septal separation was measured (normal value less than 7 mm), sensitivity increased to 73% and specificity was 84%. For detection of increased end-diastolic volume (less than 155 ml) sensitivity reached 84% and specificity 98% and for increased end-systolic (less than 70 ml) volume it was 86 and 97%, respectively. A depressed left ventricular ejection fraction (greater than 49%) was found with a sensitivity of 93% and specificity of 100%. Regional left ventricular wall motion, analyzed by an area method, revealed for anterior wall motion a sensitivity of 68% and a specificity of 94%, whereas for posterior wall motion sensitivity reached 80% and specificity 96%. Regression equation between the number of pathological segments and left ventricular ejection fraction for cineventriculography was given by Y = -4.06 X + 73.4, r = 0.93 and for cross-sectional echocardiography by Y = -3.69 X + 62.6, r = 0.85. We conclude that cross-sectional echocardiography can be used as a screening method to detect impaired left ventricular function. It is superior to M-mode echocardiography. Reduced regional function of the posterior wall can be found with high sensitivity, but depressed motion of the anterior wall may be overlooked.

Adult↗
PubMed1985

[Analysis of right atrium function in patients with chronic pressure overload of the right ventricle].

Right atrial function was evaluated in 16 patients with and without chronic right ventricular pressure overload. A simultaneous right atrial pressure recording using a catheter-tip-micromanometer and right atrial volume determination using cross-sectional echocardiography were performed. The pressure-volume curve of the right atrium was composed of an a-loop and a v-loop. The ratio of active atrial emptying to right ventricular stroke volume in patients with right ventricular pressure overload was significantly larger than in the control group (36 +/- 6% vs. 23 +/- 5%, p less than 0.04). The right atrial work was also significantly greater in patients with right ventricular pressure overload (6.2 +/- 2.0 mWs) than in normal subjects (4.2 +/- 2.0 mWs, p less than 0.04). The ratio of active atrial emptying to ventricular stroke volume and right atrial work were significantly related in both control group and patients with right ventricular pressure overload (r = 0.83). Right atrial work also showed a significant linear correlation with right atrial work before active atrial emptying (r = 0.92). We conclude that in patients with right ventricular pressure overload the right atrium shows more pronounced active emptying and contributes to better diastolic filling of the right ventricle.

Angina Pectoris, Variant↗
PubMed1985

[Pathophysiology of tricuspid insufficiency: analysis of the motion of the tricuspid valve annulus using 2-dimensional echocardiography].

We investigated tricuspid annular motion in patients with pulmonary hypertension and in normal controls to determine the greatest minimal diameter and percentage shortening of the tricuspid annulus required for functional tricuspid regurgitation. 73 patients were studied by 2-dimensional echocardiography: a control group of 30 patients (group I); 43 patients had pulmonary hypertension, 9 of whom were still in sinus rhythm (group II), the other 34 patients had atrial fibrillation. 19 of these showed competent tricuspid valve with contrast echocardiography (group III), whereas the 15 remaining patients had functional tricuspid regurgitation (group IV). An analysis of shape and position changes of tricuspid annulus during the heart cycle was performed. The maximal diameter (mm/m2) in the apical 4 chamber view was in group I 17.5 +/- 1.4, in group II 20.7 +/- 3.2 (vs. group I p less than 0.05), in group III 19.0 +/- 3.4 (vs. group II NS) and in group IV 25.7 +/- 6.0 (vs. group III p less than 0.001). The values for the minimal annular diameter (mm/m2) were in group I 13.7 +/- 1.2, in group II 17.4 +/- 3.5 (vs. group I p less than 0.01), in group III 16.6 +/- 3.3 (vs. group II NS) and in group IV 23.6 +/- 5.7 (vs. group p less than 0.001). The percent decrease (%) in group I was 21.5 +/- 3.3, in group II 17.0 +/- 6.9 (vs. group I p less than 0.05), in group III 12.8 +/- 4.7 (vs. group II p less than 0.05) and in group IV 7.9 +/- 3.4 (vs. group III p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Echocardiography↗
PubMed1984

Effects of heart rate changes on left ventricular volume and ejection fraction: a 2-dimensional echocardiographic study.

The influence of heart rate on left ventricular (LV) volumes and ejection fraction (EF) using 2-dimensional (2-D) echocardiography during atrial pacing was analyzed. The study was performed in 13 normal control subjects, 23 patients with coronary heart disease and 8 patients with dilated cardiomyopathy. An electronic sector scanner (2.25 MHz, 84 degrees) was used. Under constant scanning of the left ventricle, heart rate was increased, in steps of 20 beats/min, from 80 to 140 beats/min. The 2-D echocardiograms were stored on videotape and analyzed off-line. The end-diastolic and end-systolic volumes (EDV and ESV) were determined using a disc method. Stroke volume (SV) and EF were calculated. Constant LV scanning was possible during atrial stimulation, as shown by the analysis of simultaneously recorded 2-D echocardiograms and cineventriculograms at different heart rates, revealing a constant position of the echocardiographic transducer. Simultaneous recordings of cineventriculography and 2-D echocardiography at 80 and 120 beats/min showed that despite differences in absolute values, percent changes of LV volumes and EF determined with both methods were similar. Thus, changes of LV function can be analyzed by 2-D echocardiography. In normal control subjects, an increase in heart rate of 10 beats/min reduced EDV by 4 ml, ESV by 2 ml, SV by 2 ml and EF by 1%, corresponding to percent reductions of 4, 2, 5 and -2%, respectively. In contrast, the absolute decreases in the patients were 6 ml, 1 ml, 5 ml and 2% and the percent changes 2%, 1%, 8% and 5%.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗