Search PubMed⌕ Search

Biomedical subjects

R Lehmann

Publications and source records attributed to R Lehmann.

At least 217 records · Page 12Linked to original sources
PubMed1989

Segmental polarity and identity in the abdomen of Drosophila is controlled by the relative position of gap gene expression.

The establishment of the segmental pattern in the Drosophila embryo is directed by three sets of maternal genes: the anterior, the terminal and the posterior group of genes. Embryos derived from females mutant for one of the posterior group genes lack abdominal segmentation. This phenotype can be rescued by transplantation of posterior pole plasm into the abdominal region of mutant embryos. We transplanted posterior pole plasma into the middle of embryos mutant either for the posterior, the anterior and posterior, or all three maternal systems and monitored the segmentation pattern as well as the expression of the zygotic gap gene Krüppel in control and injected embryos. We conclude that polarity and identity of the abdominal segments do not depend on the relative concentration of posterior activity but rather on the position of gap gene expression. By changing the pattern of gap gene expression, the orientation of the abdomen can be reversed. These experiments suggest that maternal gene products act in a strictly hierarchical manner. The function of the maternal gene products becomes dispensable once the position of the zygotically expressed gap genes is determined. Subsequently the gap genes will control the pattern of the pair-rule and segment polarity genes.

Abdomen↗
PubMed1989

[Neuroradiologic diagnosis of elongated spinal tumors].

Elongated spinal space-occupying lesions are infrequent but not rare. They are found at all ages, most frequently in the thoracic spinal canal and are primarily of gliomatous origin. A survey of our cases from the last 25 years shows the enormous progress in the diagnosis of such processes. This applies to technical quality as well as improved diagnostic information of modern methods and significantly less discomfort to the patient. In the case of suspected space-occupying lesions, a consecutive diagnostic program is recommended, that implies first conventional radiographs of the structure of the spine (including tomography if necessary) followed by myelography with modern positive contrast media. Myelography should be combined with CT. Plain CT-scans can demonstrate hypodense or calcified tumours. MRT provides essential additional information by three dimensional imaging and the corresponding signal processing techniques. With increasing MRT-capacities and improving image quality medullary tumours will primarily investigated with this method. The relations between multiple intramedullary cavities can be explored by endomyelography before drainage.

Adolescent↗
PubMed1989

[A completely thrombosed giant aneurysm in an infant].

In a 16-month-old boy completely thrombosed aneurysm in the midline region (Regio pinealis) was successfully extirpated. The clinical symptoms were reduced by a pressure hydrocephalus, which was caused by an occlusion of the passage of the cerebrospinal fluid at the level of the aquaeductus. In the histological picture the inner third of the wall of the aneurysm was imposing as a necrosis with a membrane-like layer of elastin-like proteins on the outward side and adjacent loose connective tissue.

Arteries↗
PubMed1989

[Bone regeneration after filling of extensive cysts by means of bone collagen type 1].

It could be demonstrated by experimental studies on dogs that demineralized bone and bone products have a good osteogenetic potential which gives them a superior rating over artificial materials as replacement of autogenous bone transplants. The results of a prospective clinical study on 52 patients with 56 large mandibular or maxillary cysts are presented showing that bone collagen matrix type I is a good product for the filling of bone defects. Full reossification of a cyst was reaches as early as 8 months postoperatively in 20 cases. 32 defects had become substantially smaller. These results are discussed and compared to other methods mentioned in the literature.

Bone Regeneration↗
PubMed1989

[Filling cysts with type 1 bone collagen].

The good properties of bovine bone collagen type 1 for filling of bony defects was demonstrated in 56 cysts of the alveolar bone in 52 patients. 49 cysts (approx. 87%) healed without irritation. 8 months postop. complete reossification of the defects had been achieved in 20 (approx. 36%) of the cysts. Further 32 defects (approx. 57%) were markedly reduced. The discussion will compare the advantages of bone collagen and other materials.

Adolescent↗
PubMed1989

[The value of spinal CT in the planning of spinal surgery].

The diagnostic information gained by spinal CT for the planning of surgery of spinal disease is discussed under clinical aspects. For discogenic disease CT has replaced myelography in significance and as primary investigation, except for unclear complaints, that cannot be attributed to a specific segment. Here myelography still is the prime investigation. With CT degenerative peripheral appendages turned out to be significant for secondary stenosis syndromes of the spinal canal. In future it seems advisable, to differentiate between the facultatively pathogenetic important dorsal spondylosis and ventro-lateral spondylosis, which is unimportant for the spinal complaints. If surgical correction of congenital spinal malformations is considered, apparent or silent dysraphia must be ruled out in order to prevent neurological complications. Here CT can improve diagnostic safety significantly. For the resection of tumourous or inflammatory destructions CT provides an excellent means for preoperative statements on the necessary resection area, the size of the graft and the strength of adjacent soft tissues for the graft, the required stabilisation instruments, possible effects on adjacent organs, lumen reduction of the spinal canal, and the appropriate surgical entrance. The exploration of traumatic conditions of the spinal column by CT is of value especially for a detailed preoperative investigation, since it facilitates a quantification of the destruction of the vertebral body and the arches, the condition of the posterior body surface and the stenosis of the spinal canal.

Humans↗
PubMed1989

[Local intravasal fibrinolysis in acute cerebrovascular occlusions].

The development of local intravasal fibrinolysis in acute cerebrovascular obturations is lined out and the precautions, indications and contraindications as well as our results from 10 patients are described. The requirements of dosage, procedure and of a close cooperation and combination with further clinical treatment are given. Furthermore close cooperation with hemostaseology is stressed.

Acute Disease↗
PubMed1989

[Manifestation of sarcoidosis of the optic nerve].

Under the suspicion of an optic nerve glioma a resection of the optic nerve tumour was carried out in a 58-year-old female patient with an amaurosis on the right side. The diagnosis of the sarcoidosis of the Nervus opticus was only established on the basis of the histological findings obtained in the resected optic nerve. Even after a period of observation of five years no further general pathologic signs of the sarcoidosis appeared, so that it could be assumed that this was the case of an isolated sarcoid affection of the optic nerve.

Cranial Nerve Neoplasms↗
PubMed1988

Drosophila nurse cells produce a posterior signal required for embryonic segmentation and polarity.

The segmental pattern of insect embryos depends on influences from morphogenetic centres near each of the egg poles. In Drosophila, maternal effect mutations are known that impair the normal function of each centre. Injection of wild-type cytoplasm into mutant eggs has revealed that morphogenetic signals localized at the anterior and posterior pole of eggs can be transplanted. We show here that these activities can also be detected during oogenesis. Posterior activity can be recovered at an early stage (stage 10, ref. 5) from the oocyte-nurse cell complex, but anterior activity can only be detected in the mature oocytes (stage 14). We conclude that the bicoid-dependent anterior signal, although produced by the nurse cells, does not become active before it is localized to the anterior egg pole, whereas posterior activity can be detected in the nurse cells before, and therefore independently of, its localization to the posterior egg pole.

Animals↗
PubMed1988

Access to care.

Explore the source record for details and available documents.

Acquired Immunodeficiency Syndrome↗
PubMed1988

[Meningitis as a complication of anterior-sacral meningocele].

A 19-year-old young man was admitted with a serious clinical picture of an infected anterior sacral meningocele. Escherichia coli was identified as the pathogenic organism in the spinal putrid fluid. A catheter percutaneously introduced in the hernial sac served as an external drainage of the fluid. At the same time a systemic antibiotic treatment was carried out. After the sanation, the opening of the meningocele was surgically closed in the interval transdurally from the dorsal direction. For this fibrinous adhesive was used in addition to the suture. After six months the hernial sac closure could be demonstrated in the check-up myelo- and computer tomogram.

Adult↗
PubMed1987

Determination of anteroposterior polarity in Drosophila.

The principles of pattern formation in embryogenesis can be studied in Drosophila by means of a powerful combination of genetic and transplantation experiments. The segmented pattern of the Drosophila embryo is organized by two activities localized at the anterior and posterior egg poles. Both activities exert inducing and polarizing effects on the pattern when transplanted to other egg regions. A small set of maternal genes have been identified that are required for these activities. Mutants in these genes lack either the anterior or posterior part of the segmented pattern. The unsegmented terminal embryonic regions require a third class of genes and form independently of the anterior and posterior centers.

Animals↗
PubMed1987

hunchback, a gene required for segmentation of an anterior and posterior region of the Drosophila embryo.

The locus hunchback (hb) is a member of the gap class of segmentation genes of Drosophila. A number of X-ray-induced deletions locate the hb locus at the chromosomal site 85A3-B1, to the right of the pink locus, which maps in the same interval. A total of 14 EMS and 3 X-ray-induced hb alleles have been studied. Homozygous mutant embryos show deletions of segments in two separate regions. In the six strong alleles, the labium and all three thoracic segments are deleted anteriorly while posteriorly the 8th abdominal segment and adjacent parts of the 7th abdominal segment are lacking. The eight weak alleles show smaller deletions both in the thoracic and posterior abdominal region. In the weakest allele only part of the mesothorax is deleted. Three hb alleles produce a homoeotic transformation: superimposed on a strong or weak deletion phenotype, head or thoracic segments are transformed into abdominal segments, respectively. This suggests that hb might also be involved in the regulation of genes in the Bithorax complex (BX-C). Fate mapping of the normal-appearing segments in strong mutant embryos using the UV-laser beam ablation technique (Lohs-Schardin et al., 1979) shows that these segments arise from the normal blastoderm regions. The mutant phenotype can be recognized soon after the onset of gastrulation in a failure to fully extend the germ band. In 6-hr-old mutant embryos, two clusters of dead cells are observed in the thoracic and posterior abdominal region. These observations indicate region specific requirement of hb gene function. The analysis of germ line chimeras by transplantation of homozygous mutant pole cells shows that hb is already expressed during oogenesis. Homozygous mutant embryos derived from a homozygous mutant germ line have a novel phenotype. The anterior affected region is enlarged, including all three gnathal segments and the anterior three abdominal segments. In addition three abdominal segments with reversed polarity are formed between the remaining head structures and the posterior abdomen. Heterozygous mutant embryos derived from a homozygous mutant germ line develop normally, indicating that maternal gene expression is not required for normal development.

Abdomen↗