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Biomedical subjects

B Lorenz

Publications and source records attributed to B Lorenz.

At least 19 recordsLinked to original sources
PubMed1992

Leber's hereditary optic neuroretinopathy and the X-chromosomal susceptibility factor: no linkage to DXs7.

Leber's hereditary optic neuroretinopathy (LHON) was the first human disease for which mitochondrial inheritance was demonstrated. Analysis of genealogies, however, suggests the existence of an interacting X-linked factor, and linkage to DXS7 was recently described. We tested this location in four LHON families, with DXS7 and two flanking markers, OTC and DXS426. We found recombinations with DXS7 in two families and with DXS426 in one. The two point lod scores to DXS7 were negative with all the allele frequencies for the X-linked factor tested (q = 0.5; 0.35; 0.05).

Female↗
PubMed1992

Effect of mental task load on fronto-central theta activity in a deep saturation dive to 450 msw.

The increase of theta activity (4-7 Hz) in the electroencephalogram (EEG) during deep diving is commonly attributed to pathophysiologic mechanisms underlying the high pressure neurologic syndrome. The aim of this study was to clarify whether more precise cognitive aspects of the condition may be described in which theta activity occurs during a deep dive. Among 4 divers who were repeatedly examined during the GUSI 14 dive to 450 msw, 3 divers exhibited a pronounced correlation between short-term memory load, as varied by the memory set size of Sternberg's memory search task (MST), and the size of a distinct peak in the theta band of the EEG-power spectrum. The power of this peak was greatest in the fronto-central electrode position (Fz), increased dramatically during MST-performance at pressure, and failed to subside fully 1 day before surfacing. Despite the close dependency of observed theta activity on cognitive demands, no consistent correlation with performance measures (mean reaction time and errors) was found. In one diver, theta waves of similar morphology appeared in the resting EEG and increased significantly during the dive. We suggest two alternative explanations for the positive interaction of memory load and hyperbaric exposure on Fz-theta: a) Both factors induce a state of increased mental effort or selectivity of attention, known to be accompanied by frontal theta activity from normobaric studies. b) Pressure abnormally facilitates or patterns rhythmical excitations underlying theta activity that would occur naturally to a lesser extent during certain mental activities, learning, or repetitive short-term memory operations.

Adult↗
PubMed1991

Visual results in congenital cataract with the use of contact lenses.

The results obtained in 29 infants with congenital bilateral cataract and 24 with congenital unilateral cataract who underwent surgery at the Munich University Eye Hospital between April 1985 and August 1988 are reported. Postoperatively, the majority of patients were fitted with extended-wear contact lenses. Detailed functional results are reported on nine children with unilateral aphakia and nine with bilateral aphakia who were fitted with contact lenses within the 1st year of life. Whereas the functional results in bilateral aphakia were very satisfactory in the absence of neuroophthalmogical problems, the limited visual prognosis in unilateral aphakia continues to be a problem despite an intensive occlusion regimen. The functional results are compared with those of other authors who have used similar treatment modalities. These are discussed in terms of alternative correction modalities, i.e. intraocular lens implants and epikeratophakia.

Aphakia, Postcataract↗
PubMed1991

[Normal and disordered visual development with preferential looking].

Normal and disturbed development of grating acuity in preverbal infants has been studied using the Teller acuity card procedure. The results of 195 normal and 34 premature children are in good accordance with those reported in the literature. In more than 86% no interocular differences of grating acuity could be detected in these groups. On the other hand the incidence of interocular acuity differences reached 30% in 37 cases showing monolateral convergent squint. This is much higher than has been reported in current literature and may indicate that grating and Snellen acuity correlate better than expected in infants' squint amblyopia. As to the problem of monitoring early amblyopia therapy by PL, four longitudinal cases are presented.

Amblyopia↗
PubMed1991

Retrobulbar cysts in Aicardi's syndrome.

Case report of a four-year-old girl with Aicardi's syndrome diagnosed from the triad: absence of the corpus callosum, focal seizures, and chorioretinal lacunae. In addition, MR scans and orbital ultrasonography detected retrobulbar cysts behind the right microphthalmic eye not described so far. Analyzing the histological data from two previous reports, it becomes likely that the cysts have formed from abnormal migration of neuroretinal tissue through the border of the optic disc coloboma that was also present. This pathomechanism is also known in isolated colobomatous microphthalmos in which cysts may occur.

Agenesis of Corpus Callosum↗
PubMed1990

[Congenital fibrosis syndrome. Considerations on etiology, genetics and surgical therapy].

Fibrosis syndrome has been a well-known clinical entity for more than a century. Nevertheless, there are still some unresolved questions concerning its etiology, chronological course, and optimal timing of surgery. On the basis of their experience in 12 cases (2 unilateral, 10 bilateral, 7 with eye muscles and/or lid surgery), the authors attempt to help answer these questions.

Adolescent↗
PubMed1990

[Normal and defective development of visual stimulus processing: psychophysical and electrophysiologic test results].

Two methods were developed for the assessment of normal and disturbed visual development in infancy and early childhood: the preferential looking procedure (PL) as a psychophysical method and measurement of visual evoked potentials (VEP) as an electrophysiological principle. Both methods test visual functions, but on different levels of the visual system. Proper interpretation of the methods requires direct comparison. This was accomplished over a 12-months period in infants and young children with normal and disturbed visual development in the first year of life. For normal infants older than 4 weeks we found accurately configurated VEP responses and rapidly increasing visual accuity, ranging from 0.4 cpd (age 2.5 weeks) to 10 cpd (36 weeks) and better. There was a close agreement between the VEP and PL results, possibly due to our conservative interpretation of VEP acuity, which was not extrapolated from the VEP amplitude versus spatial frequency function, but defined by the relationship to the simultaneously registered noise level of the responses. The last response that could be differentiated from this noise level was defined as VEP acuity in analogy to the acuity definition of the Teller acuity cards. In visually impaired children there was a delay in visual development. Visual deficits in congenital cataract were much more marked than in congenital squint. Infants with congenital cataract showed a nearly newborn stage when tested shortly after lensectomy. With our preliminary results is was not possible to determine any statistical relationship among the psychophysical, electrophysiological and clinical findings.(ABSTRACT TRUNCATED AT 250 WORDS)

Attention↗
PubMed1989

Immunological comparison of subunits isolated from various hydrogenases of aerobic hydrogen bacteria.

Polyclonal, monospecific antibodies were produced against the two subunits (Mr 62,000, and Mr 31,000), isolated from the membrane-bound hydrogenase of Alcaligenes eutrophus H16. The antibodies (IgG fractions) were purified from crude sera by Protein A-Sepharose CL-4B chromatography. By double immunodiffusion assays and tandem-crossed immunoelectrophoresis the large and the small subunit were demonstrated not to be immunologically related. Immunological comparison of these subunits with the four non-identical subunits (Mr 63,000, 56,000, 30,000 and 26,000) of the NAD-linked, soluble hydrogenase from A. eutrophus H16 showed that the subunits of the membrane-bound hydrogenase did not cross-react with any of the antibodies raised against the four subunits of the NAD-linked enzyme and that, vice versa, none of these four subunits cross-reacted with antibodies raised against the two subunits of the membrane-bound hydrogenase. This means that A. eutrophus H16 contains altogether six non-identical immunologically unrelated hydrogenase polypeptides. The membrane-bound hydrogenases were isolated and purified from various aerobic H2-oxidizing bacteria: A. eutrophus H16, A. eutrophus type strain, A. eutrophus CH34, A. eutrophus Z1, A. hydrogenophilus, Paracoccus denitrificans and strain Cd2/01. All these proteins resembled each other and each consisted of two non-identical polypeptides. A complete separation of these subunits was achieved at high-yield by preparative FPLC gel filtration on three Superose 12 columns connected in series, using SDS and DTT-containing sodium phosphate buffer (pH 7.0). The small subunits of these enzymes turned out to be immunologically closely related to each other; they were either identical or almost identical. The large subunits were also related, but less pronounced. Only the large subunits from Z1 and type strain reacted fully identical with the H16 subunit. Of the two isolated, homogeneous subunits of the membrane-bound hydrogenase from A. eutrophus H16, the amino acid compositions and the NH2-terminal sequences have been determined. The results confirmed the diversity of the large and the small subunit. Furthermore, for comparison also the NH2-terminal sequences of the two subunits from the hydrogenase of A. eutrophus CH34 have been analysed.

Alcaligenes↗
PubMed1989

Linkage of X-linked retinitis pigmentosa to the hypervariable DNA marker M27 beta (DXS255).

A hypervariable DNA marker is closely linked to one of the most severe forms of night blindness, X-linked retinitis pigmentosa (RP). Affected individuals with X-linked RP, obligate carriers, and ophthalmologically identifiable carriers of the disease were included in a linkage study. The diagnosis was established in five sibships by funduscopic and electrophysiological investigations. When the X-linked probe M27 beta was used, 2 recombinants out of 29 informative meioses were detected (theta = 0.07 at a maximum lod of 4.75). The hypervariable probe detected two different alleles in 38 of 39 females tested. M27 beta is therefore a potentially very useful probe for carrier detection and prenatal diagnosis, as well as for addressing the question of heterogeneity of X-linked RP.

Female↗
PubMed1989

Clinical observations of six cases of laser injury to the eye.

During the last decade, five patients with laser injuries were examined at the University of Munich Eye Clinic, in addition to one laser-injury patient at the University of Erlangen Eye Clinic. From a review of these cases, it is possible to gain an insight into factors that led to the eye injuries and to predict the clinical sequelae of laser retinal injury. A possible means of treatment, using an ophthalmic Q-switched Nd:YAG laser, is suggested for some types of retinal injury involving vitreal hemorrhage.

Accidents, Occupational↗
PubMed1989

[Physician praise in the province. Comments on 2 ancient epitaphs from Trikka (Thessalia)].

With respect to the meaning of a physician for life and health of men, the Iliad says about the physician pi omicron lambda lambda omega nu alpha nu tau alpha xi iota omicron sigma alpha lambda lambda omega nu and reports upon two famous physicians: Machaon and Podaleirios from Thessaly, sons of Asclepios. Like these the qualified physician proves to be a man of knowledge and a man of arts-not only in antiquity--, for he has one passion: science as incorporated in the tau epsilon chi nu eta of medicine. Very often inscriptions--above all grave epigrams--with their great tradition from various times and localities provide many good examples of daily life including valuable references to the practice, ethics and social situation of physicians. As examples of the social status and of the praise of physicians, two grave poems from ancient Trikka in Thessaly are discussed here: one from the first century B. C., the other from the third century A. D. These two poems are documents of the medical history of Thessaly; a region important because of the tradition of the cult of Asclepios and the life and work of late Hippocrates.

Funeral Rites↗
PubMed1989

[Quantification of the wavelength dependence of laser-induced choroid coagulation].

The penetration depth of laser light into the fundus is dependent on the wavelength. Thereby, the profile of damage depends on the absorption and on the temperature profile. It has been demonstrated earlier that wavelength-dependent differences in penetration depth are hard to detect ophthalmoscopically or histologically in severe lesions in Chinchilla gray rabbits. Therefore in this study, the wavelength-dependent exposure powers necessary for (1) similar retinal effects and (2) similar choroidal effects were compared. The resulting wavelength-dependent differences were smaller than expected-due to at least three reasons: (1) predominance of the temperature profile over the absorption profile for clinically useful exposure times; (2) light scatter in the retina in relationship to the exposure time (and wavelength?): (3) changes in the choroidal geometry in relationship to the exposure time and wavelength. Nevertheless, it appears to be possible to spare the retina somewhat by using longer wavelengths. In order to evaluate the clinical situation experimentally despite the fact that the human choroid is about three times thicker than the rabbit choroid, a geometrical model has been developed. The results indicate that the retina is less damaged using Nd:YAG lasers than using argon lasers when similar choroidal effects are produced.

Animals↗
PubMed1988

Immunocytochemical studies on the pituitary gland and spontaneous pituitary tumors of Sprague-Dawley rats.

The review of our studies indicates a predictive value of the pituitary gland and spontaneous pituitary tumors of Sprague-Dawley rats for detecting and evaluating the effects and interactions of estrogens and dopamine agonists on the pathogenesis, functional morphology and therapy of human pituitary tumors, such as prolactinomas, gonadotroph adenomas and null cell adenomas. The functional classification of spontaneous pituitary tumors in old female Sprague-Dawley rats reveals a diversity of hormone content and morphologic appearance. They seem to be useful models of the human disease.

Animals↗
PubMed1988

[Blue cone monochromasia: diagnosis, genetic counseling and optical aids].

Cone and rod functions of three blue cone monochromats (age 13-20, male) from three different families were investigated. In contrast to rod monochromats, they lack prominent nystagmus. Color matches as determined using the Nagel anomaloscope came close to those of rod monochromats but the green primary appeared slightly brighter to them. In color discrimination tests (Farnsworth-Munsell 100-hue and Panel D-15 desaturated), maximum confusion followed protan rather than scotopic axes. Measurements of spectral sensitivity revealed action spectra exclusively of blue sensitive cones, even under conditions that should isolate green- or red-sensitive cones. After 20 minutes of dark adaptation, rods determined the spectral sensitivity function. Transient tritanopia, which in normals results from the interaction between cones sensitive to short and long wavelengths, was completely absent in blue cone monochromats. Visual acuity (Snellen charts and contrast gratings) revealed values between 20/200 and 20/60. Recognition of high-spatial low-contrast gratings was improved by blue cut-off filters (Schott BG 28) and considerably worsened by yellow cut-off filters (Schott OG 510). Since alteration of visual acuity induced by cut-off filters was not found in rod monochromats, this two-filter test is a means of differentiating quickly between rod achromats and blue cone monochromats. As the mode of inheritance is autosomal recessive in rod achromats and x-linked recessive in blue cone monochromats, differential diagnosis is important for correct genetic counseling.

Adult↗
PubMed1988

Reduction of beta-adrenoceptor density and evaluation of positive inotropic responses in isolated, diseased human myocardium.

Cardiac beta-adrenoceptors and the positive inotropic effects of adenylate cyclase-dependent (dobutamine, histamine, forskolin) and adenylate cyclase-independent agents (isobutylmethylxanthine (IBMX), dibutyryl-cAMP (db-cAMP), digoxin, digitoxin and calcium were measured in papillary muscle strips from severely failing (NYHA IV), moderately failing (NYHA II-III) and non-failing (NYHA I) human hearts. The density of beta-adrenoceptors in three NYHA I patients were 40.0, 42.0 and 42.9 fmol mg-1 protein. The density of cardiac beta-adrenoceptors was significantly reduced in NYHA II-III to 18.0 +/- 1.1 fmol mg-1 protein (n = 16) and further reduced in NYHA IV to 9.5 +/- 1.6 fmol mg-1 protein (n = 7). The KD values did not differ between the groups. Correspondingly, the positive inotropic effect of dobutamine was significantly reduced in NYHA II-III and almost lost in NYHA IV. The positive inotropic effect of histamine was similar in non-failing and moderately failing myocardium but reduced in preparations from severely failing hearts (NYHA IV). The positive inotropic effect of IBMX was diminished in moderately and severely failing myocardium depending on the functional class of heart failure. In contrast, the effects of forskolin, db-cAMP, digoxin and digitoxin were not impaired in NYHA IV when compared with the maximal positive inotropic effect of calcium. It is concluded that in the failing human heart (a) the number of cardiac beta-adrenoceptors is reduced proportional to the severity of heart failure; (b) the receptor coupling of H2-receptors to adenylate cyclase may be impaired, but only in severe heart failure; (c) the basal cAMP formation may be diminished; and that (d) the catalytic subunit of the adenylate cyclase and the cAMP-dependent protein kinases may be promising targets for drugs to restore force of contraction in human heart failure.

1-Methyl-3-isobutylxanthine↗