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Biomedical subjects

R Keller

Publications and source records attributed to R Keller.

At least 145 records · Page 8Linked to original sources
PubMed1994

[The occurrence of organic volatile compounds in a sample room of a new building in relation to the "natural" air exchange].

The occurrence of certain volatile organic compounds was to be investigated in a sample room of a new building to determine any health hazard arising from the employed materials. Approximately 60 volatile organic compounds, formaldehyde, polychlorinated biphenyls, inorganic fibrous particles and "natural" air-exchange were included in the investigation. The reasons for increased concentrations of formaldehyde and volatile organic compounds could be determined by material-emission-investigations. These investigations further revealed that medical-hygienic demands for sufficient "natural" air-exchange should possibly be given priority over warmth conservation regulations (Wärmeschutzverordnung) that require a high degree of insulation in windows and doors. If this is not taken into consideration then some of the staff may display a variety of symptoms known as "sick-building-syndrome".

Air Conditioning↗
PubMed1994

[Concentration of biocides in indoor rooms using pyrethroids as an example].

Pyrethroids are an analogous substance group to one of the oldest known, naturally occurring insecticides pyrethrum and have replaced a number of pesticides such as Lindane, DDT and PCP on the market. Biocides are more persistent indoors than in nature, which could lead to permanent health hazards for the people concerned. Within a few days after application pyrethroids are rarely detected in room air but can be traced for a long time on textiles, furniture and in dust particles (3, 8). The investigation results of approx. 100 analyses from dust and carpet samples show that approx. 1/3 of these samples are positive for at least one pyrethroid and contain a concentration of > 2 mg substance per kg sample. The evaluation of 35 air samples taken from rooms where substances containing pyrethroids had been used at least a month prior to the investigation (the samples were sampled on active charcoal or Chromosorb) showed that pyrethroids could no longer be traced above the detection limit of 0.05-0.1 micrograms/m3. We therefore think that when investigating a contamination of rooms by biocides it is more advisable to determine pyrethroid and its synergists in the suspended dust portion and corresponding dust sample rather than analysing air by adsorption to active charcoal, Chromosorb or other carrier materials. From the observed concentrations of biocides one could conclude that in an indoor setting secondary contamination by biocides plays a more significant role in the total-body-load than that of air contamination.

Air Pollution, Indoor↗
PubMed1994

Macrophage response to bacteria and bacterial products: modulation of Fc gamma receptors and secretory and cellular activities.

The ability of bacteria and bacterial products to modulate the expression of Fc gamma receptors and major histocompatibility complex (MHC) class II molecules in resting rat bone marrow-derived mononuclear phagocytes (BMM phi) was determined by means of flow cytometry (FCM). Binding of IgG via Fc gamma receptors was considerably enhanced by most microbial agents; bacterial lipopolysaccharide, lipoteichoic acid and some intact bacteria proved to be as active as interferon-gamma (IFN-gamma) and augmented binding of IgG via high- and low-affinity Fc gamma receptors. In contrast, expression of MHC class II molecules by BMM phi was only slightly affected by the microbial agents. Additional findings attest that resting unprimed rat BMM phi are able to respond directly to Gram-negative and Gram-positive bacteria and to some of their products with the expression of marked secretory [in particular tumour necrosis factor-alpha (TNF-alpha) and nitrite] and cellular activities (TNF-alpha-independent tumoricidal activity). This extensive, direct type of macrophage activation may substantially amplify the capability of these cells to cope with these infectious agents in first-line, non-specific host defence.

Animals↗
PubMed1994

[Yellow nail syndrome].

The yellow nail syndrome, first described in 1964 by Samman and White, consists of yellowish, dystrophic nails, lymphedema and pleural effusion. We present the clinical findings of a 53 years old woman who suffered of this very rare syndrome. The literature review reveals the different clinical features which were reported to be associated with the yellow nail syndrome. The pathogenesis of this autosomal-dominantly inherited syndrome consists of a dysfunction of the lymphatic drainage system, but details remain unknown. Up to now a causative treatment does not exist but topic tocopherol may improve the aspect of involved nails. A new study reports of good effects of oral zinc-application to nails and lymphedema.

Bronchiectasis↗
PubMed1993

Molecular cloning of crustacean putative molt-inhibiting hormone (MIH) precursor.

A cDNA encoding the complete precursor of the putative molt-inhibiting hormone (MIH) of the shore crab, Carcinus maenas, was isolated and sequenced. The precursor consists of a putative 35 amino acid signal peptide and the 78 amino acid mature MIH. The deduced MIH amino acid sequence is in complete agreement with the sequence previously determined by Edman degradation. In situ hybridization revealed MIH-expression in a subpopulation of large neurosecretory perikarya of the medulla terminalis X-organ in the eyestalk.

Amino Acid Sequence↗
PubMed1993

Molecular cloning of crustacean red pigment concentrating hormone precursor.

A cDNA encoding the precursor of the red pigment concentrating hormone (RPCH) of the shore crab, Carcinus maenas, was isolated and sequenced. The predicted preprohormone sequence consists of a putative 25 amino acid signal peptide, the eight amino acid RPCH sequence followed by a Gly as amide donor, a dibasic processing site and a 74 residue peptide of unknown function, referred to as RPCH-precursor-related peptide (RPRP). In in situ hybridisation experiments, the RPCH gene transcript could be localised in two clusters of neurons in the medulla terminalis of the eyestalk.

Amino Acid Sequence↗
PubMed1993

Structure and localization of mRNA encoding a pigment dispersing hormone (PDH) in the eyestalk of the crayfish Orconectes limosus.

The pigment-dispersing hormone (PDH) is produced in the eyestalks of Crustacea where it induces light-adapting movements of pigment in the compound eye and regulates the pigment dispersion in the chromatophores. To study this hormone at the mRNA level, we cloned and sequenced cDNA encoding PDH in the crayfish Orconectes limosus. The structure of the PDH preprohormone consists of a signal peptide, a PDH precursor-related peptide (PPRP) and the highly conserved PDH peptide at the carboxy-terminal end. In situ hybridization in combination with immunocytochemistry revealed four cell clusters expressing PDH in the optic ganglia of the eyestalk. Three clusters stained both with the PDH cRNA probe and the PDH antiserum, however, the perikarya in the lamina ganglionaris (LG) only stained with the PDH antiserum, suggesting the presence of a PDH-like peptide in the LG.

Amino Acid Sequence↗
PubMed1993

The homeobox gene goosecoid controls cell migration in Xenopus embryos.

Goosecoid (gsc), a homeobox gene expressed specifically in the dorsal blastopore lip of the Xenopus gastrula, is considered to play an important role in Spemann's organizer phenomenon. Lineage tracing and time-lapse microscopy were used to follow the fate of embryonic cells microinjected with gsc mRNA. Microinjected gsc has non-cell autonomous effects, recruiting neighboring uninjected cells into a twinned dorsal axis. Ectopic expression of gsc mRNA in ventral blastomeres as well as overexpression of gsc in dorsal blastomeres leads to cell movement toward the anterior of the embryo. The results suggest a function for gsc in the control of gastrulation movements in groups of cells, but not in dissociated cells, and demonstrate that a vertebrate homeobox gene can regulate region-specific cell migration.

Animals↗
PubMed1993

Induction of neuronal differentiation by planar signals in Xenopus embryos.

The induction of the central nervous system in amphibian embryos is mediated both by early planar signals produced by mesoderm at the dorsal lip and later vertical signals emanating from the dorsal mesoderm after involution. We have examined the role and spatial extent of planar signals in the induction of neuronal differentiation. Planar explants that included only the deep layer of the dorsal marginal zone, comprising both the dorsal mesoderm and the contiguous dorsal ectoderm, were isolated at the beginning of gastrulation. After removal of the epithelial layer, explants were maintained in modified Danilchik's medium until mid-neurula stages, when they were transferred to modified Danilchik's medium + 0.1% bovine serum albumin and cultured on laminin. Neurite outgrowth occurred in 90% of these planar explants. In contrast, little or no neuronal differentiation occurred in either ventral planar explants or explants of ectoderm alone. Video analysis of cell movements shows that large-scale cell mixing does not occur between mesoderm cells and ectoderm cells in planar explants. Retrograde labelling of neuronal cell bodies indicates that cells throughout the ectoderm undergo neuronal differentiation; neurons also differentiate in cultures of distal ectoderm isolated at early neurula stages from planar explants prepared at the beginning of gastrulation. These observations indicate that planar signals act over an extended range to induce neuronal differentiation. The inductive capacity of vertical signals was examined by recombining animal caps from ultra-violet (UV) irradiated embryos with involuted mesoderm from normal midgastrula embryos. Differentiation of either neurons or anterior neural structures occurred in 73% of vertical recombinates. Our results demonstrate that planar signals from the dorsal lip of the blastopore are capable of inducing neuronal differentiation over a considerable distance in the absence of epithelial confinement, convergence and extension, and mixing between the mesoderm and ectoderm.

Animals↗
PubMed1993

Characterization of a nuclear retention sequence within the 3' region of the HIV-2 envelope gene.

During the phenotypic analysis of mutations in the HIV-2 envelope protein (gp140), we have identified a mutant that expresses high levels of gp140 in the absence of the Rev protein. This mutant was obtained by deletion of a 190-base pair fragment at the end of the env coding region. Northern blot analysis of RNAs produced by transfected HeLa cells showed that this fragment inhibits the cytoplasmic transport of unspliced env-specific RNAs in the absence of Rev. The "inhibitory element" was only active in the sense orientation and appeared to be specific for unspliced HIV-2 env RNAs, suggesting that it may have an important regulatory role for HIV-2 expression.

Cell Compartmentation↗
PubMed1993

[Intraductal ultrasound of the pancreas--a procedure with diagnostic prospects? Initial preclinical experiences].

For the first time, human pancreas specimens (18 autopsy specimens, three resection specimens) were examined with high-resolution, flexible ultrasound catheters (20 MHz; 3.5 F, 4.8 F, 5.0 F and 6.0 F external diameters; mechanical and electronic systems). The ultrasound catheter was easily inserted into the pancreatic duct in all specimens. The sonographic tissue texture was correlated with its histological picture at defined positions. A high resolution was thus achieved in the sonomorphological differentiation of blood vessels, duct system elements, fibrotic tissue, fatty tissue and pancreas tissue with varying lipomatous composition. In a radius of an average of 5.5 mm, structures 0.1 mm large were recognised. Contrast media studies of the ductal system were carried out before and after ultrasound examination. No evidence of trauma due to catheterisation was found either with these studies or by histology. In one case, a 15 mm serous microcystic adenoma of the pancreatic head was found at intraductal examination of the resection specimen. Clinical examinations within the framework of endoscopic retrograde pancreaticography must clarify if the intraductal ultrasonography technique presented here can truly enlarge the diagnostic, repertoire used in the search of tiny focal pancreatic lesions.

Cystadenoma↗
PubMed1993

Ex vivo examination of the pancreas by intraductal ultrasonography (IDUS)

Pancreas specimens from humans (seven normal autopsy specimens, one surgical resection specimen containing a 15 mm microcystic adenoma in the pancreatic head) were examined by intraductal ultrasonography using flexible, high-resolution ultrasonic catheters (20 MHz, 4.8 and 6.0 French diameter). The catheters were easily inserted into the pancreatic duct in all specimens. The ultrasonographic tissue pattern could be correlated with the histological findings in tissue cross-sections at defined positions. A high degree of resolution was achieved in the differentiation of blood vessels, duct system elements, fibrotic tissue, fatty tissue and pancreatic tissue with a varying fat content. At an average distance of 5.5 mm, structures as small as 0.1 mm could be discriminated. No evidence of ductal trauma due to insertion of the catheters was found either on subsequent radiographic studies or on histologic examination. Clinical studies using this probe during ERCP are necessary to clarify whether intraductal ultrasonography could contribute to the diagnosis of small pancreatic lesions and to the differentiation of indeterminate ductal stenoses.

Adenoma↗
PubMed1993

[Morphology and rhinologic importance of intumescentia septi nasi anterior].

The intumescentia septi nasi anterior is a protuberance on each side of the anterior part of the nasal septum containing "cavernous" tissue. None of the previous studies devoted to the general aspects of endonasal "cavernous" tissue refer to the incidence and rhinological function of the intumescentia. This investigation revealed an incidence of more than 80% in 170 individuals without any rhinological symptoms. The external morphology observed in 7 cadavers indicated a close topographical correlation of the position of the middle turbinate, the depth of the lateral nasal wall and the extension of the intumescentia. Histological examination showed a glandular mass interspersed with a dense vascular network similar to the "cavernous" tissue found within the lateral turbinates. Various filling conditions of the intumescentia have no significant influence on rhinomanometrical parameters and the quantity of nasal airflow. However, visualization of the endonasal flow within a nasal model containing the septal protuberance indicated that the intumescentia considerably alters the quality and local velocities of the endonasal airstream. Considering the results of the study, the intumescentia must be regarded as a completely normal formation of particular rhinophysiological importance, which, up until now, has not been mentioned in rhinosurgery.

Adolescent↗
PubMed1993

Mononuclear phagocytes from human bone marrow progenitor cells; morphology, surface phenotype, and functional properties of resting and activated cells.

After 3-4 weeks culture of human bone marrow cells in medium supplemented with IL-3, macrophage- (M-CSF), and granulocyte-macrophage colony-stimulating factor (GM-CSF), the firmly adherent cells exhibited the morphologic features of mononuclear phagocytes and were strongly esterase-positive. Flow cytometric analysis revealed a rather homogeneous cell population with marked autofluorescence; the large majority of the cells expressed CD14, CD11a, b, and c, Fc receptors for IgG, Fc gamma RI, II, and III, and HLA class II molecules. Interferon-gamma (IFN-gamma), bacteria, and bacterial products modulated expression of some of the surface markers, induced and/or enhanced respiratory burst, phagocytic activity, secretion of tumour necrosis factor, and tumouricidal activity; in contrast, these cells were not able to generate reactive nitrogen intermediates.

Adult↗
PubMed1993

Amino acid changes in the fourth conserved region of human immunodeficiency virus type 2 strain HIV-2ROD envelope glycoprotein modulate fusion.

The fourth conserved region (C4) of human immunodeficiency virus type 1 (HIV-1) surface glycoprotein has been shown to participate in CD4 binding and to influence viral tropism (A. Cordonnier, L. Montagnier, and M. Emerman, Nature [London] 340:571-574, 1989). To define the role of the corresponding region of HIV-2, we introduce single amino acid changes into the C4 sequence of HIV-2ROD. The effects of these mutations on glycoprotein function and on virus infectivity have been examined. We have shown that the tryptophan residue at position 428 is necessary primarily for CD4 binding. The isoleucine residue at position 421 is necessary for the establishment of productive infection in the promonocytic cell line U937, while it is dispensable to some extent for infection of primary T lymphocytes or the lymphocytic cell line SUP-T1. This replication defect correlated with the failure of the Ile-421-to-Thr (Ile-421-->Thr) mutant glycoprotein to form syncytia in U937 cells. DNA analysis of revertant viruses revealed that a strong selective pressure was exerted on residue 421 of the surface glycoprotein to allow HIV-2 infection of U937 cells. These results demonstrate that this region of HIV-2 plays an important role in determining fusion efficiency in a cell-dependent manner and consequently can influence viral tropism.

Amino Acid Sequence↗
PubMed1993

A different type of amphibian mesoderm morphogenesis in Ceratophrys ornata.

Ceratophrys ornata, the Argentinean horned frog, has a significantly different pattern of early morphogenesis than does the most studied amphibian, Xenopus laevis. Time-lapse videomicroscopy, scanning electron microscopy, histological sections and lineage tracers have shown that, in C. ornata, some prospective notochord, somite and tailbud mesoderm cells leave the surface epithelium of the archenteron by ingression. After gastrulation, SEM reveals cells with constricted apices and a bottle shape in three zones on the archenteron roof and in a fourth zone around the blastopore. Prospective somitic tissue ingresses first from two lateral zones, followed by ingression of prospective notochord from the medial zone and tailbud mesoderm from the circumblastoporal zone. This is unlike X. laevis, in which no cells with constricted apices are present on the dorsal surface of the archenteron, nor do any cells ingress into the deep mesodermal layers from the surface layer.

Animals↗