PubMed Health⌕ Search

Biomedical subjects

H Hauser

Publications and source records attributed to H Hauser.

At least 145 records · Page 8Linked to original sources
PubMed1991

Expression and frameshifting but extremely inefficient proteolytic processing of the HIV-1 gag and pol gene products in stably transfected rodent cell lines.

Expression, ribosomal frameshifting, and proteolytic processing of HIV-1 GAG and POL proteins were investigated in heterologous mammalian cells in order to elucidate the influence of the cellular background on these events. DNA fragments encoded by the gag and pol region were expressed in two rodent cell lines, LTK- and BHK. Both stably transfected cell lines continuously produce recombinant proteins which react with HIV-specific antisera. The GAG precursor and a 39-kDa proteolytic fragment thereof were the major recombinant proteins detected. Expression of the gag-pol region leads to the production of the GAG-POL precursor. Ribosomal frameshifting at the HIV-1 shifty sequence to a typical extent could be positively demonstrated by an enzyme assay. Despite the presence of the viral protease within the GAG-POL precursors, proteolytic processing of the HIV-derived polyproteins was extremely inefficient. The efficiency could not be enhanced by overexpression of the HIV-1 protease encoding region.

Animals↗
PubMed1991

[Contribution of the CT scanner to the diagnosis of liposarcoma].

Analysis of the CT aspect and anatomopathologic correlation of 11 liposarcomas of the abdomen and chest enabled definition of CT criteria for diagnosis. Anatomo-radiologic correlation could be established both for well-defined and poorly-defined tumors. However, due to the uneasy localization and high recurrence rate of poorly defined tumors, the data provided by CT did not improve the prognostic rates.

Abdominal Neoplasms↗
PubMed1990

[Duodenal perforation as late complication following endoscopic retrograde bile duct prosthesis implantation. A case report with literature review].

Endoscopic drainage of the common bile duct by endoprosthesis has been advocated as an effective alternative to palliative surgery in the management of malignant occlusion icterus. Apart from other complications duodenal perforation may occur at the time of endoscopic insertion of the prosthesis. Perforation as a late sequel of endoscopic retrograde placement of such an endoprosthesis is rare. This paper presents the case of duodenal perforation eight days after implantation of a biliary endoprosthesis necessitating immediate surgical intervention.

Aged↗
PubMed1990

Test system for determination of HIV-1 frameshifting efficiency in animal cells.

We have developed a system in animal cells which allows the quantification of frameshifting determined by specific mRNA sequences. The method is based on the expression of an N-terminally extended firefly luciferase gene which requires frameshifting in order to be translated as a functional enzyme. The systems sensitivity is such that it allows the detection of even low efficiency of frameshifting. Our results show that the HIV-1 frameshift sequence including the 3' located stem-loop structure leads to ribosomal frameshifting at a lower level than that described for in vitro systems when tested in several fibroblastoid cell lines.

Amino Acid Sequence↗
PubMed1990

The uptake of phosphatidylcholine by small intestinal brush border membrane is protein-mediated.

Brush border membrane vesicles prepared from rabbit small intestine are essentially free of basolateral membranes and nuclear, mitochondrial, microsomal and cytosolic contaminants. The resulting brush border membrane is unstable due to intrinsic lipases and proteinases. The PC transfer between small unilamellar lipid vesicles or mixed lipid micelles as the donor and the brush border membrane vesicles as the acceptor is protein-mediated. After proteolytic treatment of brush border membrane with papain or proteinase K the PC transfer activity is lost and the kinetics of PC uptake are similar to those measured with erythrocytes under comparable conditions. Evidence is presented to show that the PC transfer activity resides in the apical membrane of the enterocyte and not in the basolateral part of the plasma membrane. Furthermore, the activity is localized on the external surface of the brush border membrane exposed to the aqueous medium with its active centre probably not in direct contact with the lipid bilayer of the membrane. Proteins released from brush border membrane by proteolytic treatment catalyze PC exchange between different populations of small unilamellar vesicles. Furthermore, these protein(s) bind(s) PC forming a PC-protein complex.

Animals↗
PubMed1990

Analysis of a soluble mutant des-methionine interleukin-2 receptor alpha chain (Tac protein) produced by transfected mammalian cells.

By using recombinant DNA technology the cytoplasmic and trans-membrane domain of the human interleukin-2 receptor alpha chain (IL-2R alpha, Tac) and of a mutant protein lacking methionine-residues 18, 25, 44, 88, 92, 126, 149, 167, 205, and 209 (des-Met IL-2R alpha) encoded by a chemically and enzymatically synthesized gene, were deleted. This leads to secretory expression of soluble wild-type and des-Met mutant Tac protein of 42-45 kDa after transfection of BHK-21 cells. Transfectants secreted up to 1.6 micrograms soluble wild-type IL-2R alpha protein/10(6) cells in 24 h into the culture medium. LTK- cell lines, expressing a large number of wild-type and des-Met mutant low-affinity IL-2R alpha of 50-55 kDa on their surface, shed a truncated form of the Tac protein of about 40 kDa into the culture medium. In contrast to wild-type IL-2R alpha, shedding of mutant Tac protein is strongly reduced. This phenomenon might be the result of higher protein stability of the mutant receptor which may also explain the about 10 times higher surface expression of des-Met IL-2R alpha in LTK- cells. There are no significant differences in the biosynthesis and post-translational modification of mutant or wild-type Tac proteins either in transfected LTK- or BHK-21 cells as analysed by pulse/chase labeling experiments.

Base Sequence↗
PubMed1990

Spontaneous formation of small unilamellar vesicles by pH jump: a pH gradient across the bilayer membrane as the driving force.

31P NMR and infrared spectroscopic methods have been used to study the formation of small unilamellar vesicles by the pH-jump method. It is shown that increasing the pH of different lamellar phospholipid dispersions (phosphatidic acids and phosphatidylserines) induces a pH gradient. This pH gradient is estimated to be 4 +/- 1 pH units, and its direction is such that the inner monolayer of the vesicles is at lower pH. There is spectroscopic evidence for tighter packing of the lipid hydrocarbon chains in the inner monolayer, probably due to the constraints imposed by the high curvature of the small vesicles formed. These results are discussed in terms of the driving force of the spontaneous vesiculation.

Animals↗
PubMed1990

Uptake of cholesterol by small intestinal brush border membrane is protein-mediated.

Absorption of cholesterol by small intestinal brush border membrane from either mixed micelles or small unilamellar vesicles is protein-mediated. It is a second-order reaction. The kinetic data are consistent with a mechanism involving collision-induced transfer of cholesterol. With micelles as the donor particle, there is net transfer of cholesterol while with small unilamellar vesicles as the donor, cholesterol is evenly distributed between the two lipid pools at equilibrium. The cholesterol absorption by brush border membrane from both mixed micelles and small unilamellar vesicles reveals saturation kinetics. Proteolytic treatment of brush border membrane with papain releases about 25% of the total membrane protein. As a result, the cholesterol uptake by brush border membrane changes from a second-order reaction to a first-order one. The reaction mechanism changes from collision-induced cholesterol uptake to a mechanism involving diffusion of monomeric cholesterol through the aqueous phase. The protein(s) released into the supernatant by papain treatment of brush border membrane exhibit(s) cholesterol exchange activity between two populations of small unilamellar vesicles. The supernate-protein(s) bind(s) the spin-labeled cholesterol analogue 3-doxyl-5 alpha-cholestane.

Animals↗
PubMed1990

Investigations concerning the potential for using 1H NMR relaxometry or high-resolution spectroscopy of plasma as a screening test for malignant lung disease.

In 158 plasma samples, obtained from patients with lung carcinoma, lung metastases, and infectious or inflammatory lung diseases and from healthy controls, the NMR relaxation times T1 and T2 of water protons were measured at a resonance frequency of 20 MHz by pulsed NMR techniques and adjusted to a standardized total plasma protein concentration. For one-third of these samples water-suppressed 500-MHz 1H NMR spectroscopy at 37 degrees C was used (a) to determine the widths of the composite lipid methyl and methylene signals, and (b) to quantitate individual lipid methylene signal components that could be detected in resolution-enhanced spectra. In addition, hematological parameters and the plasma levels of several acute phase proteins and apolipoprotein-A were monitored. No diagnostically significant differences between lung carcinoma patients and patients with nonmalignant lung disease could be found for any of the plasma NMR parameters, nor could T1 or lipid linewidth data distinguish between any patient group and healthy controls. However, the mean T2 was significantly shortened by about 15% for any kind of lung disease compared to healthy controls. Similar but less significant results were found for apolipoprotein-A levels. A linear discriminant function, calculated from the apolipoprotein-A and T2 data, did not improve the differentiation between malignant and nonmalignant lung disease but did improve the discrimination between tumor patients and healthy controls up to a sensitivity and specificity of 80 and 96.5%, respectively. T2 correlates inversely with plasma fibrinogen levels and the blood sedimentation rate and, therefore, appears to monitor a general inflammatory status of a tumor patient rather than the presence or absence of cancer. For all groups except healthy pregnant women, the lipid methylene composite signal linewidth correlates inversely with the fraction of mobile triglyceride present (mainly as VLDL), as estimated from resolution-enhanced spectra.

Blood Proteins↗
PubMed1990

Circadian rhythmicity and behavioral depression: I. Effects of stress.

Rats were exposed to repeated sessions of inescapable footshock, and behavioral depression was subsequently assessed by measuring escape performance during exposure to escapable shock in a different testing environment. Free-running circadian activity rhythms were assessed using running wheels for approximately three weeks before and after administration of inescapable shock. Several animals showed lengthening of free-running period and decreases in activity level following shock. Similar effects were also seen in rats that were removed from their running wheels, placed within the shock apparatus, and not given shock, but not in nonhandled control animals. Furthermore, period lengthening in shocked and handled rats was positively correlated with escape performance, suggesting that circadian rhythm alterations occurred in those animals that were best able to cope with shock or handling-related stressors. In contrast, individual differences in circadian period and activity level during baseline conditions were not predictive of either escape performance or circadian rhythm alterations. These results suggest that successful behavioral adaptation to stress may be associated with alterations of circadian rhythmicity.

Affect↗
PubMed1990

Maximal muscular power before and after exposure to chronic hypoxia.

The maximal muscular power (both instantaneous, w, and average, w-.) and the cross-sectional area of the left thigh (CSA) were measured on six subjects before (B) and after (A) prolonged exposure to high altitude (above 5000 m asl). w and w were determined during a standing high jump off both feet on a force platform, and CSA by computed tomography. It was observed that: (1) in B, body weight (BW) = 74.1 +/- 5.8 kg, w = 3330 +/- 460 W (44.8 +/- 3.4 W.kg-1). w-. = 1795 +/- 395 W (24.6 +/- 4.3 W.kg-1), and CSA = 184.5 +/- 23.1 cm2; 2) in A, BW = 70.4 +/- 6.6 kg, w = 3005 +/- 472 W (42.5 +/- 3.6 W.kg-1), w = 1531 +/- 267 W (21.9 +/- 3.1 W.kg-1), and CSA = 163.5 +/- 23.1 cm2. Thus, w and w-. were decreased both in absolute terms (-9.8% and -14.7%, respectively) and per unit BW (-5.1% and -11.0%). However, because of the concomitant decrease in CSA, when expressed per unit cross-sectional area of the muscle, w (9.04 +/- 0.71 and 9.20 +/- 0.72 W +/- cm2) and w (4.87 +/- 0.81 and 4.70 +/- 0.67 W/cm2) were unchanged. The intrinsic capacity of the muscle to generate explosive power is therefore preserved in A. It is concluded that the decrease in w and w after high-altitude exposure depends only on a net loss of muscle mass.

Acclimatization↗
PubMed1990

Physiological regulation of circadian and pulsatile thyrotropin secretion in normal man and woman.

The circadian and pulsatile TSH secretion profiles were investigated in 5 females at the time of menstruation and 21 healthy males by sampling blood every 10 min for 24 h. Computer-assisted analysis, i.e. the Cluster and Desade programs, revealed means of 9.9 +/- 1.7 (Cluster) and 11.4 +/- 3.9 (Desade) pulses/24 h. More than 50% of the TSH pulses were detected between 2000-0400 h. Male and female subjects showed no significant difference in the basal mean and pulsatile secretion of TSH or in the TSH response to TRH (200 micrograms). Repetition of the TSH secretion analysis in 4 healthy subjects after 1, 2, and 6 months (2 subjects) revealed a significantly better cross-correlation within than between individuals (P less than 0.0001). We modulate the circadian TSH secretion pattern by acute sleep withdrawal or prolonged sleep after a night of sleep withdrawal in six healthy male volunteers. Sleep withdrawal augmented the nightly TSH secretion (mean serum TSH, 2.1 +/- 1.3 mU/L; mean TSH in sleep, 1.3 +/- 0.5 mU/L; P less than 0.05), whereas sleep after sleep withdrawal almost completely suppressed the circadian variation (mean TSH, 1.1 +/- 0.7 mU/L; P less than 0.01). This modulation is due to a significant decrease in pulse amplitude, but not to an alteration in the frequency or temporal distribution of TSH pulses.

Adult↗
PubMed1990

Uptake of indium-111 in the liver of mice following administration of indium-111-DTPA-labeled monoclonal antibodies: influence of labeling parameters, physiologic parameters, and antibody dose.

Liver uptake of indium-111 (111In) in mice was investigated following administration of 111In-DTPA murine monoclonal antibodies (111In-DTPA-MAbs) labeled by the cyclic anhydride method. Biodistribution of HPLC-purified 111In-DTPA-MAb preparations was checked with a low (0.2 micrograms) and a high (8.0 micrograms) MAb dose. Using Bio Gel P-30 for desalting the MAb-conjugates, 111In uptake in the liver amounted to 8%-9% of the injected dose (ID) and was independent from the MAb dose, the DTPA-to-MAb molar ratio, tumor growth and biologic variability (different MAbs and different strains of mice). Using Sephadex G-25 for desalting, 0.2 micrograms doses from 7 out of 26 preparations showed increased liver accumulation of 111In in non-tumor mice ranging from 15%-25% of ID. Corresponding high doses led to a "normal" value of 8%-9%. Increased liver uptake of the low dose could not be reduced by coadministration of the unconjugated MAb, but was normal after reinjection of "in vivo filtered" material. An inverse intracellular distribution of 111In activity between sediment and supernatant of liver homogenates, following the administration of the low and the high MAb dose, indicated an artifact of the labeling procedure rather than an inherent biological property of labeled MAbs.

Animals↗
PubMed1989

Large-scale preparation of recombinant platelet-derived growth factor AA secreted from recombinant baby hamster kidney cells.

The short isoform of platelet-derived growth factor A (PDGF-A) was expressed in a mammalian host (BHK-21 cell). A cell line was obtained that secreted up to 0.3 micrograms/10(6) cells recombinant PDGF-A chain homodimer/day into the medium. For large-scale production of supernatant, cells were grown either in roller bottles or in 2.5-1 stirred tank fermenters. A simple two-step procedure was developed to purify recombinant PDGF-AA (rPDGF-AA). The first step was adsorption onto porous glass and the final step was reversed-phase high-performance liquid chromatography. The yield was 0.2 mg/l supernatant. A total amount of 20-30 mg pure rPDGF-AA may be obtained from a single fermenter run. Sequence analysis showed the correct amino terminus and no internal proteolytic cleavages. The specific activity was 5 ng/ml for mouse AKR-2B cells. [125I]rPDGF-AA had an affinity constant of approximately 0.5 nM to these cells and 25,000 binding sites were estimated/cell.

Animals↗
PubMed1989

Expression of human interleukin-2 in recombinant baby hamster kidney, Ltk-, and Chinese hamster ovary cells. Structure of O-linked carbohydrate chains and their location within the polypeptide.

The similarity or identity of O-glycosylation in glycoproteins from natural sources or produced in heterologous cell lines, a central problem for the development of many biotechnologically relevant production processes, was examined using interleukin-2 (IL-2) as a model. Human interleukin-2 was constitutively expressed in several mammalian cell lines in high amounts. The recombinant proteins were purified to homogeneity and their carbohydrate structures were analyzed. Only the NeuAc alpha 2-3Gal beta 1-3[NeuAc alpha 2-6]GalNAc oligosaccharide structure or the NeuAc alpha 2-3Gal beta 1-3GalNAc were found in all IL-2 preparations secreted from recombinant Ltk-, Chinese hamster ovary, and baby hamster kidney cell lines. The O-linked chains were exclusively linked to Thr in position 3 of the polypeptide chain which is the carbohydrate attachment site in natural human IL-2. The proportions of O-glycosylated versus nonglycosylated forms of the protein secreted by each recombinant cell line were independent of productivity or of cell culture conditions. Our results show that O-glycosylated human IL-2 can be produced by applying recombinant DNA technology in heterologous cell lines with the same type of post-translational modification that is observed for the protein secreted from natural T lymphocytes.

Animals↗
PubMed1989

Infrared and 31P-NMR studies of the interaction of Mg2+ with phosphatidylserines: effect of hydrocarbon chain unsaturation.

Infrared and 31P-NMR spectra of aqueous dispersions of 1,2-dimyristoyl-sn-glycero-3-phospho-L-serine (DMPS), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-L-serine (POPS), 1,2-dioleoyl-sn-glycero-3-phospho-L-serine (DOPS) and ox brain phosphatidylserine in the presence of excess Mg2+ have been recorded. A consistent picture emerges from the application of infrared and 31P-NMR spectroscopy to Mg2+-PS interactions. Mg2+ forms crystalline complexes with saturated phosphatidylserines, such as DMPS, and probably with POPS. In these crystalline PS-Mg2+ complexes the phosphate group loses its water of hydration but the serine carboxylate remains hydrated. Furthermore, there is formation of an additional hydrogen bond to one of the ester carbonyl groups of DMPS, and interchain interactions appear to be enhanced as reflected by a tighter packing of the fatty acyl chains. One main conclusion of this work is that Mg2+ binding to PS bilayers shows a gradation, the binding is in the order DMPS greater than POPS greater than ox brain PS greater than DOPS. The molecular area increases in the order DMPS less than ox brain PS less than POPS less than DOPS and is apparently an important parameter determining the affinity of PS for Mg2+. The general trend is that with increasing molecular area, and hence spacing of the ligands, the binding of Mg2+ decreases. While PS with two saturated fatty acyl chains forms tightly packed, crystalline Mg2+ complexes with an immobilized headgroup, the unsaturated PS molecules such as ox brain PS and DOPS interact only weakly with Mg2+. Their interaction seems to be restricted to electrostatic shielding, since no major changes in molecular conformation, chain packing and headgroup hydration are found. The interaction of POPS with Mg2+ is intermediate between that of saturated PS and that of DOPS. POPS exhibits a higher affinity for Mg2+ than ox brain PS, although their molecular areas (and the surface charge density) are approximately the same. This apparent anomaly is proposed to be due to a discreteness of charge effect. It is proposed that a lipid surface with regularly spaced polar groups has a higher affinity for binding Mg2+.

Calcium↗
PubMed1989

A new electron spin resonance assay for membrane asymmetry and entrapped volume of unilamellar lipid vesicles based on photoreduced flavin adenine dinucleotide.

A new ESR assay has been developed for the characterization of unilamellar lipid vesicles. It is based on the reduction by photogenerated FADH2 of amphiphilic spin-labels having the spin in the polar group. FADH2 is generated in situ under anaerobic conditions from its oxidized form (FAD) by photoreduction in the presence of excess EDTA as the reducing agent. Photoreduction is induced by exposing the FAD/EDTA mixture to white light of a commercial slide projector. FADH2 as an impermeable agent reduces spin-label molecules located on the outer layer of the bilayer that are readily accessible in a first fast reaction; spin-label located on the inner layer of the bilayer is reduced in a second slow reaction. The ESR assay is suitable for the routine characterization of unilamellar membrane vesicles: it allows the determination of the vesicle size, the entrapped volume, the bilayer asymmetry, the bilayer integrity, and the vesicle stability. The ESR assay developed is of general applicability: it can be used with charged and uncharged bilayers which may be labeled with either neutral or charged spin-labels. An assessment of the new ESR assay is given in comparison to the existing ascorbate method which uses sodium ascorbate as the reducing agent. Various other potential reducing agents for spin-labels have been tested and found unsuitable for the ESR assays discussed here.

Ascorbic Acid↗