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Biomedical subjects

R Lehmann

Publications and source records attributed to R Lehmann.

At least 235 records · Page 13Linked to original sources
PubMed1986

A gap gene, hunchback, regulates the spatial expression of Ultrabithorax.

We have examined the distribution of Ultrabithorax (Ubx) proteins in embryos mutant for the zygotic gap class of segmentation genes. Members of this class include hunchback (hb), knirps (kni), and Krüppel (Kr). All three mutations disrupt segmentation in specific regions of the embryo. Mutations in kni and Kr produce complex alterations in the Ubx expression pattern. In hb mutants Ubx is ectopically expressed both anterior and posterior to its wild-type boundaries. Thus, the hb gene may play an important role in the specification of the boundaries of Ubx expression. Using the Ubx protein distribution as a marker for metameric organization and using Hoechst dye to monitor cell death, we could follow early events that lead to the final gap-segmentation phenotype in the larval cuticle.

Animals↗
PubMed1986

Abdominal segmentation, pole cell formation, and embryonic polarity require the localized activity of oskar, a maternal gene in Drosophila.

Embryos derived from oskar females lack pole cells and the specialized pole plasm including polar granules. In addition, the abdominal region remains unsegmented and eventually dies. Transplantation of cytoplasm from normal embryos into mutant embryos reveals that osk-dependent activity is strictly localized at the posterior pole and has three distinct functions. In mutant embryos the activity will normalize pole cell formation when transplanted into the posterior pole and abdominal segmentation after transplantation to a more anterior, the prospective abdominal, region. Furthermore, osk activity can provoke the formation of a second "posterior center" at the anterior. The participation of the osk product in the establishment of a source of morphogenetic activity in the posterior pole plasm is discussed.

Abdomen↗
PubMed1986

The collective dose equivalent due to the naturally occurring radionuclides in building materials in the German Democratic Republic. Part 1: External exposure.

The 226Ra, 232Th and 40K concentrations of building materials have been investigated by gamma spectrometry. The results demonstrate that 90% of bricks and concrete have 226Ra concentrations less than 85 mBq g-1 or less than 50 mBq g-1, respectively. In some waste products of mining and industry especially, the 226Ra concentrations are high compared to those of common building materials. Based on the results, the mean gamma dose equivalent to individuals and the collective dose equivalent have been calculated using the computer code ZYLIA-3. The mean indoor gamma dose equivalent to individuals is 510 mu Sv y-1 and the collective dose equivalent 8.5 X 10(3) man-Sv y-1. The outdoor values range from 60 to 81 mu Sv y-1 and 1.0 X 10(3) to 1.4 X 10(3) man-Sv y-1, respectively.

Construction Materials↗
PubMed1986

[The effect of the cell separation procedure on neutrophilic granulocyte function. I. Research on the morphology and phagocytosis behavior of isolated granulocytes].

The investigations were aimed at detecting the impact of various cell separating techniques on the morphology and function of neutrophilic granulocytes. Methodically simple cell separating techniques were used, such as spontaneous sedimentation of ACD-AG blood and mechanically defibrinated blood and a flotation technique which makes use of cell isolation by means of a separating solution and centrifugation. Granulocytes which were isolated by the cell separator Haemonetics M 30 for therapeutic purposes and which, according to data in literature, are not damaged by cell separating techniques were used as reference cells. The electronic-optical evaluation of granulocyte morphology and the in vitro investigation of the phagocytic capacity for rice starch (ingestion rate) of differently isolated granulocytes were made after cell separation.

Cell Separation↗
PubMed1986

[The effect of the cell separation procedure on neutrophilic granulocyte function. II. Research on the bactericidal capacity and the NBT reduction ability of isolated granulocytes].

The investigations were aimed at examining the impact of methodically simple separating and enriching techniques for gaining granulocytes on the bactericidal capacity and NBT reduction in isolated granulocytes. For this purpose, granulocytes were gained by the technique of sedimentation and flotation. Granulocytes isolated by the cell separator Haemonetics model 30 were used as reference material. The findings of the investigations together with those of previous studies revealed no indication of the granulocyte function and morphology being damaged by the separating techniques used.

Blood Bactericidal Activity↗
PubMed1986

[The function of granulocytes stored in whole blood in relation to the storage time].

Whereas numerous investigations and extensive experiences have been available for some years on problems of storing erythrocytes and thrombocytes, it was only recently that the storage of granulocytes with the aim at maintaining their function for a longer period has been given proper regard as a problem, which, however, could not be brought to a satisfactory solution. Primarily, attention is focused on specific cell physiology. At the same time it is necessary to have at hand a number of approaches covering as many partial aspects of the granulocyte function as possible to identify the functional damages or the extent of cell damage in connection with storage. In the present paper the behaviour of granulocytes under conditions commonly used in transfusion medicine for storing blood are investigated for a period of 4 days by controlling the total leukocyte and granulocyte values, pH value, osmolality, vitality test in the colour excluding test as well as by function tests such as behaviour of phagocytosis and NBT capability of reduction. A report is presented on the results of quantitative and qualitative changes in the investigated parameters.

Blood Physiological Phenomena↗
PubMed1985

[Cervical hemangioendothelioma in childhood].

A report is given on the course of the disease in a 6.2-year-old girl with a cervical, histologically verified malignant haemangioendothelioma, who died two years after the appearance of the first symptoms. In connection with this case, the scarce information in the literature about this kind of tumour is analysed and differential diagnostic discussions of vascular tumours, such as the benign haemangioendothelioma, benign and malignant haemangiopericytoma, haemangioblastoma and angioblastic meningioma are presented.

Cervical Vertebrae↗
PubMed1985

[Irreversible cerebral function loss (so-called brain death). Further experiences in diagnostic procedures].

Analyzing international 15 years experiences the authors characterize the present situation of knowledges and practical possibilities concerning brain death diagnostics. It must be differentiated between generally accepted obliging criterions and the remaining space of responcibility of the neurologist, who is acting as a member of a brain death commission. In this frame procedures have to be chosen, which allow to diagnosticate without any doubt and as early as possible. Further developmental possibilities are shown.

Brain Death↗
PubMed1985

[Computer tomography studies in irreversible cerebral function loss (brain death)].

12 patients, whose neurological findings had induced the procedure of brain death determination, and further 4 young children were examined correspondently by special CT methods. In conclusion cranial computerized tomography as a non-invasive method seems to be useful alternatively beside cerebral angiography for the documentation of cerebral circulation arrest.

Adolescent↗
PubMed1984

[Value of computer tomography in the diagnosis of impression fractures of the cranial vault].

There are only few statements about the validity of computed tomography for the identification of impression fractures of the skull cap. The diagnostic information of roentgenograms without contrast medium and computed tomograms of a total of 15 patients were evaluated and compared. It was found that computed tomography was slightly superior to conventional X-ray examinations with respect to the diagnostic accuracy. Exact localisation, size, shape, and position of the bony impressions can be better appraised by the assessment in several axial CT section planes. The simultaneous consideration of the sequelae of the intracranial traumata by computed tomography enables a complete assessment of the craniocerebral trauma. The appropriate combination of conventional X-ray diagnosis with computed tomography should lead to an optimum diagnostic information also for these clinical pictures.

Adolescent↗
PubMed1984

[Diagnostic problems of spinal tumors in childhood and adolescence].

In evaluation of the clinical-neurological symptoms of 59 children and juveniles with spinal space occupations, 43 of whom were operated on, the differential-diagnostic particularities especially with respect to the early symptoms are discussed. On the basis of representations of individual cases, the importance of metrizamide myelography and spinal computer tomography for the pre-operative diagnosis is pointed out.

Adolescent↗
PubMed1984

Identification of inner and outer cell proliferation centers during fetal tooth morphogenesis.

Patterns of cell division have been examined in the proliferative cervical loop tissues of fetal rabbit incisor tooth organs. Evaluation of the distribution patterns of silver grains, resulting from the incorporation of [3H]-thymidine into newly synthesized DNA within tooth organs in vitro, resulted in identification of two proliferation centers: (1) an inner center consisting of inner enamel epithelial cells (i.e., preameloblasts) and predontoblasts ; and (2) an outer center consisting of outer enamel epithelium and adjacent mesenchyme. In contrast to the classically held description of epithelial cell differentiation during tooth morphogenesis, our data suggest that outer enamel epithelial cells do not migrate around the cervical loop and do not provide progenitor cells for subsequent ameloblast cytodifferentiation. During tooth development, epithelial and mesenchymal cells, which arise from either an inner or outer proliferative center, migrate in distal directions relative to the proliferative sites. Therefore, the progenitor cells for ameloblasts and odontoblasts were found to be localized in the inner proliferation zone. The implications of these findings regarding the development of continuously erupting rabbit and rodent incisor tooth organs are discussed in the context of a model.

Animals↗
PubMed1983

Action of gamma-hydroxybutyrate and GABA on neurones of cultured rat central nervous system.

gamma-Hydroxybutyrate (GHB) and GABA caused a hyperpolarization of cultured spinal, brainstem and cerebellar neurones. When KCl electrodes were used, the hyperpolarizations were reversed to depolarizations, suggesting that the actions of GHB and GABA are associated with an increase in conductance for chloride ions. Both the hyperpolarizations and depolarizations by these compounds were accompanied by an increase in membrane conductance and were reversibly blocked by the GABA antagonist bicuculline. It is suggested that GHB might either exert its effects by mimicking the action of GABA, or act as neurotransmitter or neuromodulator in the mammalian CNS.

Animals↗
PubMed1983

Effects of the glutamate analogue AMPA and its interaction with antagonists on cultured rat spinal and brain stem neurones.

Glutamate and the glutamate analogue AMPA ((RS)-alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid) caused depolarizations of cultured rat spinal and brainstem neurones which were reversibly antagonized by the glutamate antagonist glutamic acid diethylester (GDEE) but not by 2-amino-5-phosphonovalerate (APV), an N-methyl-D-aspartate (NMDA) antagonist. In contrast, depolarizations by NMDA were blocked by APV but not by GDEE. These results suggest that the depolarization by AMPA is caused by the activation of glutamate/quisqualate-preferring receptors.

2-Amino-5-phosphonovalerate↗