Biomedical subjects
Publications and source records attributed to W Krebs.
The authors had interviewed 134 former students of the Thuringian low vision school, of Weimar, concerning the course and outcomes of their vocational training as well as their current occupational situation at the study time, i.e. May/June 1990. The findings show a picture of largely successful vocational rehabilitation within the then-existing societal conditions.
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UNLABELLED: The beginning of this century saw the establishment of the first special school for people with poor vision; nowadays, in contrast, there is a trend to integrate such people into mainstream education. In the former GDR (now the new federal länder), however, the traditional special school system survived until 1990, which provides a unique opportunity of assessing the positive value of this type of education with a view to obtaining insights that will help in the future integration of people who have poor vision or are blind. Probands: A total of 134 former pupils (older than 18) of the former special school in Weimar were traced and asked about their development between leaving school and the present. RESULTS: We analysed factors of medical, occupational and cultural rehabilitation, of rehabilitation in their families (e.g. 10th class exams = 84.3%; completed vocational training = 84.3%; marriage/permanent relationship = 47.8%; own flat = 67.2%) but also such problems as contrasts between hoped for occupation and training, later changes of job, availability of aids to vision at places of work. CONCLUSIONS: Advantages of special schools should be taken into account. Vocational training, applications of aids to vision and after-care are all capable of improvement.
DESIGN AND METHODS: Local elastic properties of the descending aorta at different levels were evaluated by means of intravascular ultrasound images and pressure measurements. For this purpose, 30 normotensive patients and 30 age-matched medically treated patients with essential hypertension, all undergoing diagnostic cardiac catheterization, were studied. RESULTS: Hypertension was well controlled in the essential hypertensives (137.1 +/- 6.79/74.5 +/- 2.65 mmHg). Systolic but not diastolic blood pressure in the hypertensive patients was significantly different from that of the normotensives (118.8 +/- 4.38/69.7 +/- 1.65 mmHg). The continuous loss of volume compliance with increasing distance from the heart was significantly higher in the hypertensives than in the normotensive patients [normotensives (1.45 +/- 0.19) x 10(-10) m5/N at the thoracic aorta, (0.08 +/- 0.05) x 10(-10) m5/N at the external iliac artery; hypertensives (0.81 +/- 0.09) x 10(-10) and (0.05 +/- 0.01) x 10(-10) m5/N at the corresponding sites]. Similarly, the hypertensives had an elevated elastic modulus proximal to the aortic bifurcation compared with the normotensives (244.47 +/- 44.06 versus 108.10 +/- 17.76 m/s, respectively). The decrease in buffering function of the vessel at this site is presumably caused by a turbulent flow pattern. Compared with the normotensives, the treated hypertensives had a significantly higher elastic modulus at each site where this was measured, whereas volume compliance and sectional compliance were lower. CONCLUSION: The differences in elastic modulus and compliance between hypertensive and normotensive patients seem disproportionate to the difference in systolic blood pressure (within the normal range in both the treated hypertensives and the normotensives). Therefore, normalization of high blood pressure by long-term antihypertensive treatment may not fully reverse changes, caused by arterial hypertension, in the viscoelastic properties of the arterial wall.
The prototype of a multiplanar transesophageal echocardiographic transducer was evaluated clinically. This 5 MHz, phased array, 64-element transducer allows to continuously rotate the imaging plane from the transverse (0 degree) position to a maximal 180 degrees position, thus encompassing transverse, longitudinal, and every intermediate position. The transducer is incorporated in the echoscope tip measuring 16 by 11 by 40 mm. The shaft of the instrument is 110-cm long and has a 9-mm diameter. The instrument has pulsed wave, continuous wave, and color Doppler capabilities. 176 clinical patients were examined with the multiplane transducer. No complications occurred. Advantages of this transducer included: 1) comprehensive scanning of the whole mitral circumference and mitral valve; 2) quick and precise alignment of aortic valve long and short axis views, including long axis views of the ascending aorta, with a mean visualized length of 6 cm; 3) improved imaging and evaluation of transvalvular and paravalvular regurgitant jets in mitral and aortic valve prostheses; 4) complete evaluation of all left ventricular segments using multiple planes from transgastric and transesophageal transducer positions. An important potential application is three-dimensional reconstruction of cardiac structures and color Doppler jets.
A 4 1/2 year old female was treated for embryonal rhabdomyosarcoma of the left orbit in 1975 with radiation (59.5 Gy in 5 weeks), followed by chemotherapy. An electroretinogram (ERG) in March, 1988 revealed cone responses 3% of normal and no rod responses in the left eye, and normal responses in the right eye. The eye was enucleated in April 1988. In the fovea no choroidocapillaris was seen at the intact Bruch's membrane, and the pigment epithelium was preserved only in small patches. No photoreceptor cells were seen in the areas devoid of pigment epithelial cells. The parafoveal and peripheral (30 degrees eccentricity) retina was better preserved. The thickness of the layer of rods and cones and of Henle's fiber layer was reduced. Very few outer segments were present. Macrophages had invaded the retinal tissue in moderate numbers. The retinal vessels were ensheathed by several layers of collagen fibrils. The spatial densities of pigment epithelial, cone, rod, and bipolar cells had been reduced. The optic nerve contained a total number of 1,022,000 nerve fibers.
Primary adenocarcinomas of the lacrimal gland rarely display sebaceous differentiation. An anaplastic lacrimal gland neoplasm manifesting this feature was excised from a 64-year-old man who initially appeared with recurrent painless subconjunctival hemorrhages. Globe displacement and tumor-induced hyperopia were later findings. Electron microscopic studies performed on the widely excised tumor documented prominent lipid vacuoles, desmosomes, scattered cytoplasmic filaments, and linear segments of basement membrane material. The patient refused radical surgery and instead opted for 6,000 rads of adjuvant radiotherapy. Eleven months postoperatively liver and bone metastases developed, but he was free of local orbital recurrence. Twenty-two months postoperatively he died from complications of his metastatic disease. This most unusual lacrimal neoplasm is discussed in terms of its initial signs and symptoms and its histopathology. When the current case is analyzed in combination with three earlier reports, there is evidence that primary lacrimal gland sebaceous carcinoma is probably among the most malignant orbital tumors due to its uniform early fatality.
We report the unusual case of a 43-year-old woman who presented with Romberg's progressive facial hemiatrophy and spontaneous scleral perforation in the ipsilateral eye, for which scleral grafting was performed. Histologic and ultrastructural examination of the scleral specimen revealed a noninflammatory lytic process. The location of the scleral loss, exactly on the line of the "en coup de sabre" atrophy, as well as the light microscopy and ultrastructural histopathologic findings suggest that the scleral destruction was a late manifestation of Romberg's disease.
Isolated rods enzymatically removed from normal adult rat retina have been transplanted to the subretinal space of adult rats with a retinal dystrophy which has destroyed almost all the photoreceptors. These transplanted rods survive for months after transplantation during which time they form synapses with other retinal cells. Rod spherules with large amounts of synaptic vesicles and synaptic ribbons are found forming discreet contacts with pre- and post-synaptic densities in arrangements closely resembling those seen in the normal retina.
In the central choroid of three cynomolgus monkeys (Macaca irus) and a baboon (Papio anubis) the shape of the choroidocapillary sinus is determined by a system of interstitial collagen fibers, the "fiber system of the choroidocapillaris". The inner leaflet of this system is Bruch's membrane. The outer leaflet consists of interwoven collagen bundles, covering the roof of the capillary sinus. Straight bundles of collagen fibers passing through connective tissue columns in the choroidocapillary sinus connect both leaflets. Forces created by changes in the arterial tone in the vascular stroma may be transmitted by the choroidocapillary fiber system to the elastic layer of Bruch's membrane.
The eyes of rats were exposed to doses of 0.1 and 2.5 Gy of 450-MeV/amu 56Fe particles (LET approximately 195 keV/microns). The beam axes were oriented perpendicular to the central retina of the animals. Retinas were harvested immediately (less than 10 min), 24 h, 15 days, 136 days, and 186 days after the experiment. The retinas of animals of equivalent ages were sampled at the same intervals. By Day 15, the spatial densities of the pigment epithelial, photoreceptor, and bipolar cells in retinas irradiated with 2.5 Gy were 15 to 20% lower than those of the controls. The cellular density of the pigment epithelium returned to the control level by Day 186 while photoreceptor and bipolar cell numbers remained depressed. One and fifteen days after irradiation, the choroidal vessels showed signs of radiation damage. Exposure to 0.1 Gy did not affect the cellular density within the retina at the interval examined (186 days). None of the retinas showed evidence of track-specific injury that could be interpreted as microlesions or tunnel lesions.
Electron micrograph composites of tangenital sections of the fovea centralis of three cynomolgus monkeys (Macaca irus) and one baboon (Papio anubis) were used to determine the spatial density of the principal retinal cells. In the center of the foveola, the density of cones ranged from 113,000 to 230,000/mm2, and pigment epithelial cells from 4,900 to 7,000/mm2. At a distance of 500 microns from the foveolar center the density of the cone cell pedicles ranged from 29,000 to 36,300/mm2, and the density of horizontal cells ranged from 19,000 to 25,100/mm2. Densities of bipolar, Müller, and amacrine cells were determined in only two monkeys and in the baboon. The fact that the cone cell pedicles have a larger diameter than the foveolar cones explains the geometry of the fovea. The morphology of the junction between foveolar cone outer segments and the pigment epithelium reflects the complex metabolism of this functional unit. The comparison with the peripheral primate retina suggests that the densities of horizontal and bipolar cells, but not of amacrine and Müller cells, are correlated with the density of cone cell pedicles.
Until now, right atrial (RA) volume calculation by means of two-dimensional echocardiography (2-DE) has 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 2-DE views. For this purpose, silicone rubber casts of 19 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 moulds could be visualized in the apical four-chamber view and an additional 2-DE plane, the latter corresponding to the subcostal view in vivo. In this view the vertical extension of RA could be estimated. Areas and lengths 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, volume of the silicone casts was determined angiocardiographically (Angio) using a biplane method (30 degrees RAO, 40 degrees LAO-40 degrees hepatoclavicular). The true RA volume was 106 +/- 23 ml (mean +/- 1 SD) as determined by water displacement. Using Angio an excellent correlation was found: the calculated volume amounted to 106 +/- 23 ml; the difference was 5.5 +/- 4.8 ml (n.s.); Angio vol = 0.93 true vol + 7.77; r = 0.95; SEE = 7.4 ml. Volume determination from the apical four-chamber view of 2-DE using a monoplane disk method resulted in a mean volume of 62 +/- 17 ml. The mean difference to the true RA volume was 44 +/- 16 ml (p less than 0.001). When volume calculations were made using the biplane method, a value of 105 +/- 22 ml resulted. The mean difference to true volumes was 7.4 +/- 4.8 ml: y = 0.84x + 15.88; r = 0.91; SEE = 9.4 ml. In an in vivo study endsystolic RA volumes were calculated in a normal adult population (n = 40) from the same intersecting planes as in vitro. A normal value of 38 +/- 6 ml/m2 was found. In vivo validation using Angio showed a slightly higher normal value of 43 = 7 ml/m2. Thus, 2-DE is highly accurate in determining RA volume. In the in vitro as well as in the in vivo study the results of monoplane calculations are clearly inferior to a method which also takes account of the vertical extension of RA.
Efforts to assess radiation risk in space have been complicated by the considerable unknowns regarding the biological effects of the heavy ion component (HZE particles) of the cosmic rays. The attention has focused primarily on the assignation of a quality factor (Q) which would take into account the greater effectiveness of heavy ions vis-a-vis other forms of ionizing radiation. If however, as the so-called "Microlesion Theory" allows, the passage of HZE particles through living tissue produces unique biological damage, the traditional use of Q becomes meaningless. Therefore, it is critical to determine if microlesions, in fact, do exist. While the concept does not necessarily require detectable morphological damage, "tunnel-lesions" or holes in ocular tissues have been cited as evidence of microlesions. These data, however, are open to reinterpretation. On-going light, scanning and transmission electron microscopic studies of the corneas, lenses and retinas of rat eyes exposed to 450 MeV/amu 56Fe ions thus far have not revealed tunnel-lesion damage. The morphological effects of the heavy ions have been found to be qualitatively similar to the changes following other kinds of ionizing radiation.
In the center of the fovea centralis of retinas of three cynomolgus monkeys, one baboon and one male human, the external limiting membrane contains circumscribed areas in which zonulae adherentes are lacking between cone inner segments and apices of Müller cells. These discontinuities of the external limiting membrane begin about 300 microns from the foveolar center, involving only a few cones. Towards the center of the fovea the discontinuities become larger.
For 15 years, a 48-year-old woman had been aware of a pinkish translucent inferior epibulbar mass toward the fornix that was stationary in size. Light microscopic evaluation of the excised specimen showed that it was a gland-forming benign tumor. It originated from the surface epithelium by the downward invagination of tubular formations that underwent secondary and tertiary ramifications. The surface epithelium overlying the mass was not normal conjunctival squamous epithelium, but it was a modification in the form of a superficial layer of columnar to cuboidal cells surmounting several nuclei similar to the cells lining the subepithelial lumen-forming units. Electron microscopy showed that both the surface and tumor epithelium contained apical lacrimal-type zymogen granules and basilar whorls of rough-surfaced endoplasmic reticulum. Scattered myoepithelial cells were associated with the acinar-type epithelium of the tumor, and there were goblet cells intermixed. Neither light nor electron microscopy disclosed the presence of true ducts. The authors conclude that the lesion was a benign proliferation of lacrimal secretory-type cells and suggest the term "dacryoadenoma" for this previously undescribed entity.
The present paper deals with the efficiency of vitamin E in the prevention of progress of ROP. 80 premature infants with oxygen therapy and vitamin E all from the year 1986 are compared with 80 premature infants with oxygen therapy without vitamin E from the years 1984 and 1985. The group with protection by vitamin E shows a smaller rate of the higher stages of ROP. The stages II-V could be prevented in the studied group. The two groups of infants are too inhomogenous for an exact statistical analysis because some other factors are meaningful.