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R Lehmann

Publications and source records attributed to R Lehmann.

At least 199 records · Page 11Linked to original sources
PubMed1992

Pumilio is essential for function but not for distribution of the Drosophila abdominal determinant Nanos.

The Drosophila gene pumilio is expressed maternally, and its function is essential during early embryogenesis for the formation of abdominal segments. Our molecular analysis reveals that pumilio is a large gene that encodes a protein of 160 kD whose RNA is enriched at the posterior pole of the egg. As with pumilio, the maternal effect gene nanos is specifically required for abdomen formation. The Nanos protein is expressed in a posterior-to-anterior concentration gradient in the developing embryo. Previous experiments demonstrated a genetic interaction between pumilio and nanos, and led to the suggestion that pumilio is required for the proper spatial distribution of the Nanos protein. Here, we show that the expression and distribution of nanos RNA and protein in embryos derived from pumilio mutant females are indistinguishable from wild type. We conclude that abdomen formation depends both on Nanos activity, spreading from the localized posterior source, and on Pumilio activity, present throughout the embryo.

Abdomen↗
PubMed1992

The fat facets gene is required for Drosophila eye and embryo development.

In a screen for mutations affecting Drosophila eye development, we have identified a gene called fat facets (faf) which is required for cell interactions that prevent particular cells in the developing eye from becoming photoreceptors. Analysis of eyes mosaic for faf+ and faf- cells shows that faf is required in cells near to, but outside, normal developing photoreceptors and also outside of the ectopic photoreceptors in mutant facets. faf is also essential during oogenesis, and we show that a faf-lacZ hybrid protein is localized via the first 392 amino acids of faf to the posterior pole of oocytes. Posterior localization of faf-lacZ depends on oskar. oskar encodes a key organizer of the pole plasm, a specialized cytoplasm at the posterior pole of embryos. The pole plasm is required for germ cell formation and contains the determinant of posterior polarity, encoded by nanos. Although other pole plasm components are required for localization of nanos RNA or for nanos protein function, faf is not. We have cloned the faf gene, and have shown that it encodes two similar large (approximately 300 x 10(3) M(r)) proteins that are unique with respect to other known proteins.

Amino Acid Sequence↗
PubMed1992

[Reproducibility of bone density measurements of the distal radius using a high resolution special scanner for peripheral quantitative computed tomography (Single Energy PQCT)].

Reliable determination of bone loss in the skeletal system depends on the accuracy of bone mineral density (BMD) measurements. We investigated short-term and long-term accuracy in vitro and in vivo using a new, commercially available special-purpose computed tomography scanner (Single Energy Peripheral QCT: XCT 900, Stratec FRG) for BMD measurements. Using a phantom, the long-term accuracy (3 months) in vitro yielded a coefficient of variation (cv) of 0.18%. Repeated measurements in 37 patients showed excellent reproducibility, with a cv of 0.71%. The differentiation into groups of low, average and high trabecular bone density demonstrated values of 0.61%, 0.59% and 0.98%, respectively for cv. BMD determination with pQCT is a high-precision method. It seems to be suitable for detection of trabecular bone loss in the range of the annual decrease in bone mass, provided the forearm is positioned with maximum care.

Bone Density↗
PubMed1991

Vaccination of cats experimentally infected with feline immunodeficiency virus, using a recombinant feline leukemia virus vaccine.

A group of 15 cats experimentally infected with a Swiss isolate of feline immunodeficiency virus (FIV) and a group of 15 FIV-negative control cats were inoculated with an FeLV vaccine containing recombinant FeLV-envelope. High ELISA antibody titer developed after vaccination in FIV-positive and FIV-negative cats. Vaccinated and nonvaccinated controls were later challenge exposed by intraperitoneal administration of virulent FeLV subtype A (Glasgow). Although 12 of 12 nonvaccinated controls became infected with FeLV (10 persistently, 2 transiently), only 1 of 18 vaccinated (9 FIV positive, 9 FIV negative) cats had persistent and 2 of 18 had transient viremia. From these data and other observations, 2 conclusions were drawn: In the early phase of FIV infection, the immune system is not depressed appreciably, and therefore, cats may be successfully immunized; a recombinant FeLV vaccine was efficacious in protecting cats against intraperitoneal challenge exposure with FeLV.

Animals↗
PubMed1991

Nanos is the localized posterior determinant in Drosophila.

Segmental pattern in the Drosophila embryo is established by two maternal factors localized to the anterior and posterior poles of the egg cell. Here we provide molecular evidence that the localized posterior factor is the RNA of the nanos (nos) gene. nos RNA is localized to the posterior pole of early embryos, and nos protein acts at a distance to direct abdomen formation. Synthetic nos RNA has biological activity identical to that of the posterior pole plasm. Injection of nos RNA rescues the segmentation defect of embryos derived from females mutant for all nine known posterior group genes. Injection of nos RNA into the anterior is able to direct formation of ectopic posterior structures. Our results demonstrate that a localized source of nos RNA is sufficient to specify abdominal segmentation and imply that other posterior group genes are required for localization, stabilization, or distribution of the nos gene product.

Amino Acid Sequence↗
PubMed1991

Oskar organizes the germ plasm and directs localization of the posterior determinant nanos.

Oskar is one of seven Drosophila maternal-effect genes that are necessary for germline and abdomen formation. We have cloned oskar and show that oskar RNA is localized to the posterior pole of the oocyte when germ plasm forms. This polar distribution of oskar RNA is established during oogenesis in three phases: accumulation in the oocyte, transport toward the posterior, and finally maintenance at the posterior pole of the oocyte. The colocalization of oskar and nanos in wild-type and bicaudal embryos suggests that oskar directs localization of the posterior determinant nanos. We propose that the pole plasm is assembled stepwise and that continued interaction among its components is required for germ cell determination.

Alleles↗
PubMed1991

Changes of DNA-acridine orange binding in monocytes and endothelial cells of hypertensive arteries.

The interactions of monocytes and endothelial cells were examined employing acridine orange (AO) binding to chromatin as an electron microscopic probe for studying changes in nuclear activity. The number of AO labeled nuclei were determined in adherent and sub-endothelial monocytes, and endothelial cells either associated with or devoid of monocytes in mesenteric arteries of renal hypertensive and normotensive rats. No AO-positive cell nuceli were found in the few adherent monocytes in the normotensive rats while in hypertensive rats 63% of the adherent monocytes and 86% of the subendothelial monocytes were labeled by AO. The number of AO-positive cell nuclei increased in the endothelium from 2% in normotensive rats to 17% in hypertensive animals. Fifty-seven percent of these endothelial cells were associated with monocytes adhering to their surfaces. Thirty-nine (52%) of AO-positive and 24 (52%) of AO-negative cell pairs represented 84% of cell pairs with identical nuclear activity. These findings indicate a sequential interaction of monocytes and adjacent endothelial cells recognized at the nuclear level. According to other experimental work the binding capacity of chromatin for AO increases as cell nuclei are reactivated by stimulation of cell proliferation. In addition, AO labeling of chromatin visualized electron microscopically is confined to three of the four stages of the cell cycle. Therefore AO labeling in the present experiments might indicate the reentrance of monocytes and endothelial cells into the cell cycle.

Acridine Orange↗
PubMed1991

Light- and electron-microscopic study of the rat esophagus following intraluminal argon laser irradiation.

36 rat esophagi were irradiated by argon laser via an applicator with circumferential light distribution. They were perfused with glutaraldehyde and studied by light and transmission electron microscopy immediately, 2 days and 14 days after irradiation. Immediately after irradiation the laser center showed destruction of the keratinized stratified squamous epithelium. The collagenous fibers of the connective tissue were altered; fibrocytes and fibroblasts were severely damaged, and the microvascular lumina were occluded. The smooth muscle tissue and skeletal muscle tissue showed myofilament defects and initial karyonecrosis. There was decreasing damage of both fiber types up to 4 mm from the laser center. After 2 days the morphology of the laser center was not different from that seen immediately after irradiation. At a distance of 2 mm a partly differentiated new epithelium emerged below the necrotic epithelium. An inflammatory reaction was found in the connective tissue. After 14 days the esophageal wall was replaced and the lumen was occluded by young granulation tissue in the former laser center. Peripherally the esophageal wall appeared almost normal. As the rat esophagus serves as a model for esophagotracheal fistulae in newborn children, our findings indicate that the argon laser should be capable of occluding these fistulae likewise.

Animals↗
PubMed1991

The maternal gene nanos has a central role in posterior pattern formation of the Drosophila embryo.

A group of maternal genes, the posterior group, is required for the development of the abdominal region in the Drosophila embryo. We have used genetic as well as cytoplasmic transfer experiments to order seven of the posterior group genes (nanos, pumilio, oskar, valois, vasa, staufen and tudor) into a functional pathway. An activity present in the posterior pole plasm of wild-type embryos can restore normal abdominal development in posterior group mutants. This activity is synthesized during oogenesis and the gene nanos most likely encodes this activity. The other posterior group genes have distinct accessory functions: pumilio acts downstream of nanos and is required for the distribution or stability of the nanos-dependent activity in the embryo. Staufen, oskar, vasa, valois and tudor act upstream of nanos. Embryos from females mutant for these genes lack the specialized posterior pole plasm and consequently fail to form germ-cell precursors. We suggest that the products of these genes provide the physical structure necessary for the localization of nanos-dependent activity and of germ line determinants.

Abdomen↗
PubMed1991

Electron microscopic localization of acridine orange binding to euchromatin in human neuroblastoma cells.

The purpose of the present study was to examine the distribution pattern of acridine orange (AO) chromatin interaction products (AOCI) in human neuroblastoma IMR-32 cells and to test whether AO labeling is correlated with BrdU incorporation, and immunohistochemical localization of DNA polymerase alpha, and human N-myc-gene product. Effects of aphidicolin, alpha-amanitin, and actinomycin D on visualization of AO binding to euchromatin and on N-myc-gene expression were also examined. About 25% of the cell nuclei in logarithmic growth phase were immunohistochemically demonstrated to be labeled with BrdU after incubation at 37 degrees for 30 min, indicating cells in DNA synthesis. Most of the cell nuclei showed positive immunoreactivity to DNA polymerase alpha, while human N-myc gene product was found in about 60-80% of the cell nuclei. Electron microscopic studies revealed that about 25% of neuroblastoma cells showed characteristic AOCI within cell nuclei. In the presence of aphidicolin, alpha-amanitin, and actinomycin D, positive cells for N-myc gene product decreased markedly. Percentages of AO positive cells and numbers of AOCI per cell nucleus also showed a marked decrease. But northern blot analysis demonstrated that the expression level of N-myc gene was only repressed by the transcriptional inhibitors alpha-amanitin and actinomycin D. However, no repression was caused by aphidicolin. The present and previous studies of the authors suggest that the ultracytochemical AO method may be indicative for conformational changes of chromatin of cells confined to the cell cycle. Inhibitors of RNA and DNA synthesis then may change the conformational state of chromatin.(ABSTRACT TRUNCATED AT 250 WORDS)

Acridine Orange↗
PubMed1990

Electron microscopic localization of acridine orange chromatin interaction products in rat pheochromocytoma PC12 cells.

The purpose of the present study is to examine the distribution pattern of acridine orange (AO) binding to DNA in rat adrenal pheochromocytoma PC12 cells that respond to nerve growth factor (NGF). PC12 cells were incubated in a medium containing 100 ng/ml of NGF for 1-14 days for AO ultracytochemistry. Electron microscopic studies revealed that AO binds to DNA exclusively within the euchromatin portion of the cell nucleus. About 35% of the untreated PC12 cells showed characteristic electron-dense interaction products within the nuclei. The average numbers of AO chromatin interaction products per cell nucleus and per micron 2 nuclear area were 45 and 1.6, respectively. In the presence of NGF, cell proliferation was suppressed. The cells gradually extend neurite-like cell processes. Mean 3H-labeling index was 40.0 +/- 2.2% in untreated cells and 13.0 +/- 2.3% in PC12 cells with NGF for 6 days after incubation for 30 min. With increasing the cellular differentiation percentages of AO positive cells and average numbers of AO chromatin interaction products per cell nucleus and per micron 2 nuclear area showed a progressive decrease. The results of the present and previous studies suggest that AO chromatin interaction products may be indicative of cell proliferation and differentiation.

Acridine Orange↗
PubMed1990

Distribution pattern of acridine orange chromatin interaction products in rat glioma C6 cells at different phases of the cell cycle.

The purpose of the present study was to examine the distribution pattern of electron-dense acridine orange (AO) chromatin interaction products in rat glioma C6 cells at different phases of the cell cycle. For synchronization in the early S-phase the cells in logarithmic growth were treated with 3 micrograms/ml aphidicolin, a specific inhibitor of DNA polymerase alpha and then cultured in normal medium. For synchronization in the M-phase the cells cultured with aphidicolin and then returned to normal medium were treated with 0.05 micrograms/ml colcemid. Histoautoradiographic analysis of the C6 cells using the pulse chase method demonstrated approximately 16 h of cell cycle time and about 6.5 h of S-phase. Ultracytochemically, AO chromatin interaction products were found in all phases of the cell cycle except for the mitotic phase, namely in G1, S, and G2. The highest percentage of AO chromatin interaction products was observed in the early S-phase and the lowest in the G2 phase. The mean number of AO chromatin interaction products per nuclear area increased in the course of S-phase parallel with an increase of 3H-uridine uptake during the S-phase. The results show a characteristic distribution pattern of AO label specific for each of the four stages of the cell cycle, however, the significance of the coincident RNA synthetic activity remains to be elucidated.

Acridine Orange↗
PubMed1990

[Feline immunodeficiency virus in Switzerland: clinical aspects and epidemiology in comparison with feline leukemia virus and coronaviruses].

Serum samples from 1421 domestic cats (561 healthy, 860 sick) were tested for FIV-, FeLV- and coronavirus infection. The results were stored in a computer data base and compared with epidemiologic data and clinical findings. All 3 infections were significantly more prevalent in sick than healthy cats: FIV was found in 0.7% of healthy and 3.4% of sick cats. For FeLV the prevalence was 3.0% and 13.0% and for coronavirus 21% and 36.2%, respectively. FIV-infected cats were mostly male (73%); no sex predilection was observed in FeLV- and coronavirus infection. In sick cats FIV-infection was significantly more prevalent in cats greater than 2 years of age; no age-dependence was found in FeLV- and coronavirus infections. The prevalence of FIV-infection increased significantly with the number of animals per household. In contrast, the frequency of FeLV infection decreased with the number of animals per household. Prevalence of coronavirus infection did not vary with group size or living conditions. The following clinical symptoms were associated with infection: FIV: general depression, diseases of the urinary tract; FeLV: general depression, fever, rough hair coat, lymphadenopathy, impaired functions of heart and circulation and muscle atrophy; coronavirus: lymphadenopathy and alterations in the abdomen. It was concluded that based on the clinical symptoms alone FIV-infection could not be diagnosed nor differentiated from the other 2 infections.

Animals↗
PubMed1990

[The effect of endothelial interaction on the binding capacity of DNA acridine orange in hypertension].

Interaction of monocytes and endothelial cells were examined by acridine orange reaction in arteries of normotensive and hypertonic rats. The method is suitable for electron microscope study of DNA template activity. Activity of gen was compared in surface bound and subendothelial and in nonadhesive endothelial cells bound to monocyte. Acridine orange positivity, indicative of genic activity, was not found in few monocytes adhered in arteries of normotensive animals, while 62% of adhesive monocytes of hypertonic and 86% of ones accessed to endothelial space contained the products of acridine-orange-chromatin reaction in its nuclear, showing with it the gene derepression quickly ensuing in acute hypertensive vascular lesions. Only 2% of endothelial cells of pseudo-operated normotensive animals showed acridine orange positivity, while 17% of endothelial cells of hypertonic animals were positive. In the latter animals, 57% of endothelial cells showed acridine orange positivity, if monocytes adhered to their surface. In 84% of monocyte-endothelial pairs connected to each other, the nuclei have activity of same sign. Results show intensive activation of genes of monocytes in relation with adhesion and migration to vascular wall. Presumably, both hypertonia and monocyte adhesion have contributed to the increase of template activity of endothelial cells.

Acridine Orange↗
PubMed1989

[The disability concept in private accident insurance].

Last year the German personal accident insurers introduced a new set of General Conditions, the "AUB 88". These define permanent disability as the "permanent impairment of the insured's physical or mental faculties", whereas the former conditions defined it as the "permanent impairment of the ability to work". The new definition of permanent disability is something that the medical expert will also have to come to terms with when assessing a claim. Here he must first of all bear in mind that the consequences of an accident affecting limbs or sensory organs have to be assessed--as hitherto--on the basis of the "Gliedertaxe" or scale of disability benefits, which establishes degrees of disability for the loss of, or loss of the use or function of, limbs or sensory organs. If other parts of the body are affected, then, in accordance with Article 7 I. (2) AUB 88, "the degree to which, from a strictly medical point of view, normal physical or mental faculties are handicapped" shall be decisive. In such cases, therefore, it is no longer merely a question of whether and to what degree the insured is able to work. An assessment of permanent disability may not take non-medical circumstances into account.

Disability Evaluation↗
PubMed1989

The Drosophila posterior-group gene nanos functions by repressing hunchback activity.

The development of the body plan in the Drosophila embryo depends on the activity of maternal determinants localized at the anterior and posterior of the egg. These activities define both the polarity of the anterior-posterior (AP) axis and the spatial domains of expression of the zygotic gap genes, which in turn control the subsequent steps in segmentation. The nature and mode of action of one anterior determinant, the bicoid(bcd) gene product, has recently been defined, but the posterior determinants are less well characterized. At least seven maternally acting genes are required for posterior development. Mutations in these maternal posterior-group genes result in embryos lacking all abdominal segments. Cytoplasmic transplantation studies indicate that the maternally encoded product of the nanos(nos) gene may act as an abdominal determinant, whereas the other maternal posterior-group genes appear to be required for the appropriate localization and stabilization of this signal. Here we show that the lack of the nos gene product can be compensated for by eliminating the maternal activity of the gap gene hunchback (hb). Embryos lacking both of these maternally derived gene products are viable and can survive as fertile adults. These results suggest that the nos gene product functions by repressing the activity of the maternal hb products in the posterior of the egg.

Abdomen↗
PubMed1989

The function of PS integrins during Drosophila embryogenesis.

The Drosophila position-specific (PS) antigens are homologous to the vertebrate fibronectin receptor family, or integrins. A Drosophila gene required for embryonic morphogenesis, l(1)myospheroid, codes for a product homologous to the beta subunit of the vertebrate integrins. l(1)myospheroid mutants die during embryogenesis. We show here that they lack the beta subunit of the PS antigens. In the absence of the beta subunit in mutant embryos, the PS alpha subunits are not expressed on the cell surface. We conclude that the l(1)myospheroid phenotype represents the lack-of-function phenotype for these Drosophila integrins. In wild-type embryos, PS antigens are found at the interface between mesoderm and ectoderm, and later mainly at the attachment sites of muscles to the epidermis and gut. Together these results indicate that during embryogenesis, Drosophila integrins are used to attach mesoderm to ectoderm, and are required for the proper assembly of the extracellular matrix and for muscle attachment.

Animals↗