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H Hauser

Publications and source records attributed to H Hauser.

At least 73 records · Page 4Linked to original sources
PubMed1997

The uptake of cholesterol at the small-intestinal brush border membrane is inhibited by apolipoproteins.

The uptake of free and esterified cholesterol at the brush border membrane is protein-mediated. Here we show that this sterol uptake is effectively inhibited by exchangeable serum apolipoproteins. Binding of the apolipoprotein to the brush border membrane mediates the inhibitory effect. Evidence is presented to show that the structural motif responsible for the inhibition is the amphipathic alpha-helix.

Amino Acid Sequence↗
PubMed1997

Comparison of cholesterol and sitosterol uptake in different brush border membrane models.

(I) There is little discrimination between cholesterol and the plant sterol sitosterol in the uptake at the brush border membrane (BBM). (II) This difference cannot account for the marked discrimination between cholesterol and sitosterol observed in the absorption of these two sterols by the small-intestinal epithelium. (III) This discrimination occurs during intracellular processing involving the esterification and incorporation into lipoprotein particles of the two sterols. This conclusion is based on a comparative study of sterol uptake by brush border membrane vesicles (BBMV) and sterol absorption by Caco-2 cells. (IV) The uptake of sitosterol by the BBM is energy-independent and facilitated in a manner analogous to cholesterol uptake [Thurnhofer, H., & Hauser, H. (1990a) Biochemistry 29, 2142-2148]. (V) The rate of cholesterol and sitosterol uptake by BBMV from both mixed bile salt micelles and small unilamellar vesicles (SUV) as the donor is directly proportional to the sterol content of the donor. (VI) The pseudo-first-order rate constants k1 for sterol uptake from SUV are independent of the sterol content up to 10-20 mol %. Above that, competition between the two sterols leads to a reduction of the k1 values.

Animals↗
PubMed1997

Phosphorylation events modulate the ability of interferon consensus sequence binding protein to interact with interferon regulatory factors and to bind DNA.

Two families of transcription factors mediate interferon (IFN) signaling. The first family, signal transducers and activators of transcription (STATs), is activated within minutes of IFN treatment. Specific phosphorylation events lead to their translocation to the nucleus, formation of transcriptional complexes, and the induction of the second family of transcription factors termed interferon regulatory factors (IRFs). Interferon consensus sequence binding protein (ICSBP) is a member of IRF family that is expressed only in cells of the immune system and acts as a transcriptional repressor. ICSBP binds DNA through the association with other transcription factors such as IRF-1 or IRF-2. In this communication, the domain that is involved in protein-protein interactions was mapped to the carboxyl terminus of ICSBP. This domain is also important for mediating ICSBP-repressing activity. In vitro studies demonstrated that direct binding of ICSBP to DNA is prevented by tyrosine (Tyr) phosphorylation. Yet, Tyr-phosphorylated ICSBP can bind target DNA only through the association with IRF-2 and IRF-1. This type of phosphorylation is essential for the formation of heterocomplexes. Tyr-phosphorylated ICSBP and IRF-2 are detected in expressing cells constitutively, and Tyr-phosphorylated IRF-1 is induced by IFN-gamma. These results strongly suggest that like the STATs, the IRFs are also modulated by Tyr phosphorylation that affects their biological activities.

Amino Acid Sequence↗
PubMed1997

Physical association between STAT1 and the interferon-inducible protein kinase PKR and implications for interferon and double-stranded RNA signaling pathways.

The interferon-inducible double-stranded RNA protein kinase PKR controls protein synthesis through the phosphorylation of eukaryotic translation initiation factor (eIF)-2. In addition to its demonstrated role in translational control, several reports have suggested a transcriptional role for PKR. Here we report that PKR is involved in IFN- and dsRNA-signaling pathways by modulating the function of the signal transducer and activator of transcription STAT1. We also show that PKR associates with STAT1 in mouse and human cells. The association is not a kinase-substrate interaction since STAT1 phosphorylation is not modified by PKR in vitro or in vivo. In addition, the formation of the PKR-STAT1 complex is not dependent upon the enzymatic activity of PKR but does require the dsRNA-binding domain of PKR. Moreover, there is a concomitant decrease in PKR-STAT1 interaction and increase in STAT1 DNA binding in response to IFNs or dsRNA. These findings suggest that PKR plays an important role in IFN and dsRNA-signaling pathways by modulating the transcriptional function of STAT1.

3T3 Cells↗
PubMed1997

Percutaneous endoscopic gastrostomy (PEG). 8 years of clinical experience in 232 patients.

BACKGROUND: Percutaneous endoscopic gastrostomy (PEG) is now a standard method for providing long-term enteral nutrition in patients who are unable to swallow. The aim of our study was to document clinical data that would allow prediction of a possible complicated clinical course. METHODS: The study was carried out retrospectively. Clinical data of patients having received a PEG tube by a single endoscopic technique were analyzed. RESULTS: Some 5. 17% of 232 patients showed complications requiring surgery including a mortality rate of 0.43%. Patients with complications had a significantly lower body mass index and there was a significantly higher complication rate in patients having obstructive malignancies compared with benign diseases. CONCLUSIONS: Low body mass index and advanced malignancies are predictors for complications after PEG application. Early installation should help prevent further nutritional deterioration and the related risk of complications.

Adolescent↗
PubMed1997

A sensitive method for the detection of murine C-type retroviruses.

A RT-PCR assay was developed for group-specific detection of murine C-type retroviruses using a nested set of degenerated primers. To distinguish exogenous viruses from related, but silent endogenous viruses, a DNAse I pretreatment of supernatants is applied. This is followed by a heat inactivation/denaturation step. The PCR method is ultrasensitive. which enables the detection of 100 attogram of MoMuLV proviral DNA or up to 1-10 infectious mouse C-type retroviruses in 10 microl supernatant of infected cells. The high specificity of the method allows the differentiation between mouse C-type retroviruses and related retroviruses of the A, B, and D type and C-type retroviruses found in other species. It serves as a valuable tool for the screening of animal cell cultures for contaminations with mouse retroviruses, e.g. hybridomas or recombinant cell lines producing foreign proteins.

3T3 Cells↗
PubMed1997

The transcriptional silencer protein NRF: a repressor of NF-kappa B enhancers.

NF-kappa B/rel proteins are present in most cell types. In concert with other transcriptional factors they regulate a variety of genes which contribute to a wide spectrum of physiological activities like inflammation and apoptosis. An excellent example of this combinatorial regulation takes place in the IFN-beta promoter. In this promoter the fundamental regulatory elements are assembled within less than 100 base pairs including a NF-kappa B/rel enhancer and a negative regulatory element, called NRE. NRE is a member of a new class of transcriptional repressor sequences with a silencing capacity targeted to the NF-kappa B/rel enhancer. NRF is a novel transcriptional factor that binds to NRE. NRF belongs to a major class of transcriptional repressors that interact with specific promoter elements and repress transcription by separable repression domains. Such molecules have been termed active repressors, because they act by inhibitory protein-protein interaction and not simply by steric hindrance.

Binding Sites↗
PubMed1997

Cystic retroperitoneal lymphangiomas in adults.

Lymphangioma (LA) is a rare benign tumour of the lymphatic tissue, most common in the neck and head, and clinically manifests itself mostly in childhood. Within this group, intra-abdominal and retroperitonal LA are the rarest tumours, especially when occurring in adults. We report four LAs localized in the retroperitoneum of patients aged between 28 and 72 years. One of these tumours infiltrated the transverse mesocolon and greater omentum, others were situated in the left retroperitoneum and retroperitoneally at the duodeno-jejunal flexure, and in the retrosplenal and retropancreatic area. Diagnosis was made by light microscopy supported by immunohistochemistry. In three cases the tumour could be removed by radical surgery and none of these patients had a recurrence (median follow-up time: 4 years). The tumour could not be removed completely from one patient with pre-operative chylascos. Six months after diagnosis of LA this patient died of cardiopulmonary failure due to progressive tumour chylascos. Isolation and ligation of the cystic LA's peduncle as well as ligation of lymph channels can prevent recurrences and chylascos.

Adult↗
PubMed1997

Experience with a high speed biopsy gun in breast cancer diagnosis.

Pre-operative determination of histology and receptor status is important in optimizing the management of breast cancer. The purpose of our study was to evaluate the high speed biopsy gun in 109 patients with palpable breast tumours. High speed biopsies were performed using the system BIP High Speed Multi 22 with 16-gauge-needles at a speed of 30 m/s. All biopsies could be used for frozen sections and for determination of receptor status. In 81 patients (74.3%) malignant breast tumours were diagnosed, and three patients (2.8%) had highly suspicious lesions. The oestrogen receptor status was negative in 32%, progesterone receptor status negative in 41%. In one patient (0.9%) a high grade non-Hodgkin's lymphoma of B-cell-type was diagnosed. In 21.1% benign tumours were found. In one patient a malignant tumour was missed at biopsy (0.9% false-negative). It was concluded that high speed biopsy is a reliable and simple method for preoperative sampling of breast lesions.

Biopsy, Needle↗
PubMed1997

Endocavitary Ir-192 radiation and laser treatment for palliation of obstructive rectal cancer.

Endoscopic laser therapy (ELT) either alone or combined with endocavitary Ir-192 radiation is performed for advanced, inoperable rectal cancer and when patients are ineligible for surgery due to severe concomitant medical illness. During the period from January 1984 to January 1997 we treated 81 patients (51 males, 30 females). Sixty-seven patients had ELT only using a ND-Yag Laser system. Twenty-five patients (average age: 80.5 years) were ineligible for surgery (Group I). Forty-two patients (74.1 years) had an advanced locally inoperable tumour (Group II). Fourteen patients (76.5 years) underwent a combined therapeutic regime with endocavitary Ir-192 afterloading following ELT (Group III). Adequate desobliteration was achieved in 100% (groups I and III) and 97% (group II) of the patients. The average interval to aftertreatment was 8.4 weeks in group I and 9.4 weeks in group II, compared to 11.5 weeks in group III. Serious complications (perianal abscess, rectovaginal fistula) occurred in 3.7%, minor complications (laser-induced bleedings, unclear fever) in 12.3%. All laser-induced bleedings could be dealt with using laser therapy. The frequency of treatment was governed by tumour mass and the patient's survival. The results suggest that additional endocavitary radiation significantly prolongs the maintenance of normal bowel function compared with laser therapy alone.

Aged↗
PubMed1996

Translational recoding induced by G-rich mRNA sequences that form unusual structures.

We investigated a herpesvirus mutant that contains a single base insertion in its thymidine kinase (tk) gene yet expresses low levels of TK via a net +1 translational recoding event. Within this mutant gene, we defined a G-rich signal that is sufficient to induce recoding. Unlike other translational recoding events, downstream RNA structures or termination codons did not stimulate recoding, and paused ribosomes were not detected. Mutational analysis indicated that specific tRNAs or codon-anticodon slippage were unlikely to account for recoding. Rather, recoding efficiency correlated with the G-richness of the signal and its ability to form unusual structures. These findings identify a mechanism of translational recoding with unique features and potential implications for clinical drug resistance and other biological systems.

Amino Acid Sequence↗
PubMed1996

Retroviral infection of Syrian hamster BHK cells depends on age and susceptibility toward sialidase.

Infection with recombinant retroviruses is a standard method to efficiently manipulate murine or human cells genetically. Due to differences in glycosylation of the hamster homologue to the murine ecotropic receptor and the absence of an amphotropic receptor, murine retroviruses are unable to infect hamster cells. Here we describe an isolated cell clone of the Baby Hamster Kidney cell line, BHK-21, that can be successfully infected with ecotropic murine retroviruses. This finding prompted us to investigate the possibility of changing the infectability of other cell strains by manipulating the receptors of these cell lines in vitro. We found that treatment of other BHK cell clones with sialidase from C. Perfringens makes these cell clones also permissive to murine ecotropic retroviruses. Long term cultivation of three tested cell clones increased this susceptibility. Although the resulting infectants show a higher rate of infectability, they still require the manipulation with sialidase for this superinfection to be efficient.

3T3 Cells↗
PubMed1996

On the use of double FLP recognition targets (FRTs) in the LTR of retroviruses for the construction of high producer cell lines.

A pilot experiment for the construction of a hamster derived, high producer cell line using site specific recombination is described. In the experiment chromosomal loci with intrinsic high expression characteristics were sought via infection with a retroviral construct, containing double FRT sites and subsequent screening for overproduction of an encoded markergene. These sites were then targeted with a second vector, that recombined via the FLP/FRT system from Saccharomyces cerevisiae yielding cells that had the second construct at exactly the same position as the first. By using retroviral vectors with double and single FRT sites, respectively, stable clones can be created that can no longer be excised with FLP.

Animals↗
PubMed1996

Vascular complications of lumbar disc surgery.

Over a period of seven years nine patients with vascular complications after lumber discectomy received medical care at the Clinic of Vascular Surgery, University of Graz Medical School. We report five acute bleeding complications occurring during the operation and four late manifestations of vascular lesions. Five patients presented with acute life-threatening iatrogenic haemorrhages from pelvic vessels. Three patients made a complete recovery, one patient died from acute haemorrhagic shock, one further patient died from sepsis due to an associated complication-an injury to the ureter. Over a period of two to ten years after primary surgery we corrected late complications such as 1 case of posttraumatic aneurysm of the aortic bifurcation found to have eroded the body of the fifth lumbar vertebra, and three cases of arteriovenous fistula between the common iliac artery and the common iliac vein. The four cases described below are an attempt to document the vascular surgical procedures involved and to provide typical findings. The risk of injuring the pelvic vessels intra-operatively can be explained by the close anatomical relation between the retroperitoneal vessels and the vertebral column and furthermore not only by the fact that pre-existent deficiencies but also injury to the anterior longitudinal ligament give access to the retroperitoneal space.

Adult↗
PubMed1996

Paragangliomas of the carotid bifurcation: oncological aspects of vascular surgery.

The present study reviews in concise form the past 12 years of our clinical experience with paragangliomas of the carotid body. Every aspect of the anatomical, histological and biological and biological behaviour of paragangliomas of the carotid body has been recorded in order to be able to define better surgical management and the clinical prognosis. In addition to the conventional histological methods of investigation we also applied immunohistochemistry and made use of electron microscopy. Eighteen tumours of the carotid body in 12 female and four male patients with a mean age of 54 years (34 to 70 years) were treated surgically. Angiography of the aortic arch and supra-aortic branches was undertaken diagnostically in every case. In three patients computer tomography and magnetic resonance imaging demonstrated spreading of the tumour up to the base of the skull and pre-operative embolization of the arteries supplying the tumour was performed to decrease tumour vascularity. In four cases (22%) resection of the internal carotid artery and its reconstruction by a saphenous vein graft was required in order to achieve the therapeutic aim of a complete extirpation of tumourous tissue and preserving the vascular system of the internal carotid artery. In three cases (16%) there was histological evidence of a metastasizing process to the local lymph nodes of the neck and, due to this criterion of malignancy, 50-60 Gy of radiation was applied to the site of the tumour after surgery. Four patients experienced a transient neurological deficit in the supply area of the hypoglossal and the recurrent nerves. In one case, the vagus nerve could not be retained. In an average follow-up of 102 months we recorded one case of local recurrence 13 months after the initial resection and radiation treatment applied to a malignant paraganglioma. All the other patients were doing well without evidence of recurrent disease.

Carotid Body Tumor↗
PubMed1996

Regulated ribosomal frameshifting by an RNA-protein interaction.

Ribosomal frameshifting is a translational mechanism used as an essential step in the replication cycle of retroviruses. Programmed frameshifting in retroviral translation involves two sequence elements: A heptanucleotide slippery sequence which induces a low basal level of frameshifting and a downstream RNA structure as an enhancer of the process. The precise mechanism of function of these downstream elements is still unclear, but their effect does not solely depend on their stability. Likewise, the possibility that frameshifting could be controlled by specific proteins that bind to these elements and enable or modulate their effects has yet not been substantiated. The RNA hairpin of the HIV-1 gag-pol frameshift cassette was replaced by the iron-responsive element (IRE) from ferritin mRNA, a stem-loop structure that binds iron regulatory proteins (IRPs) in dependence of the iron status of the cell. When a lacZ/luciferase reporter construct was expressed in transfected BHK-21 cells, the IRE or a point-mutated version that is unable to bind IRPs were found to functionally substitute for the HIV-1 hairpin. When cells were treated with the iron chelator desferrioxamine to stimulate IRP binding to the wild-type IRE, frameshift activity was specifically and strongly augmented by protein binding Our data establish that frameshifting can be regulated in a reversible fashion by mRNA-binding proteins.

Animals↗
PubMed1996

[Local vascular complications after iatrogenic femoral artery puncture].

Over a period of 5 years 81 vascular complications after 15,460 catheterizations of the femoral artery for diagnostic (n = 11,883) or therapeutic (n = 3577) procedures were registered. The following complications were observed in declining frequency: 1. False aneurysm (n = 65), 2. arterial occlusion (dissection, embolia, thrombosis) (n = 8), 3. vascular lesion causing profuse bleeding (n = 7), 4. AV-fistula (n = 1). The total complication rate was 0.52%. The complication rate was significantly higher in therapeutical procedures (1,03%) than in diagnostic investigations (0.37%). Pseudoaneurysms were complicated by thrombosis of the femoral vein (n = 3), lymphatic fistula (n = 3) and deep wound infection (n = 9); secondary complication rate 18.5%. Risk factors for local vascular complications are old age, female gender, high grade arteriosclerosis at the puncture site, overweight, manifest arterial hypertension and medication with cumarin, acetylsalicylic acid or heparin. Further complicating factors are connected with technical risks such as duration of the procedure. French size of the catheter, the catheter sheath and multiple punctures. Vascular repair was performed by simple angiography in most cases, but in 14.8% more extensive surgical procedures were required. In patients with signs of occlusive vascular disease the external iliac artery was replaced by a PTFE-vascular access graft in 4 cases and an arterioplasty of the deep femoral artery was performed in 2 patients. 36% of the operations were undertaken as emergencies. Reintervention was necessary for a postoperative bleeding complication in 1 case (surgical complication rate 1.2%). A female patient suffering from aortic valve stenosis died during emergency operation due to massive retroperitoneal hemorrhage after cardiac catheterization (mortality rate 1.2%). Over a median follow-up period of 37 months no late complications of the intervention were recorded, nor recurrences of peripheral arterial occlusive disease.

Aged↗