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Biomedical subjects

G Schuster

Publications and source records attributed to G Schuster.

At least 55 records · Page 3Linked to original sources
PubMed1996

Response of oral mucosal cells to glass ionomer cements.

Although glass ionomer cements are generally considered to be tissue-compatible, it has been suggested that unreacted components or setting reaction by-products can affect cell metabolism. The current study examined the effects of constituents leached out of three glass ionomer cements on growth and metabolism of oral epithelial cells. Aseptically prepared discs of Ketac-Cem Radiopaque (KCR), Ketac-Cem Maxicap (KCM) and Fuji I were incubated in Dulbecco's medium for 10 d, with daily medium changes. Cultures of hamster cheek pouch (HCP) cells, a line of hamster buccal pouch epithelial cells, were incubated in control or eluate-containing media for 24 h. Viable cell numbers were determined by the colorimetric MTS assay, and DNA and RNA syntheses were assessed using [3H]thymidine and [3H]uridine incorporation, respectively. Responses to materials were determined by comparison of cell numbers and radioisotope incorporation (counts per minute (cpm) per 1000 cells). Results were analysed by ANOVA and Duncan's multiple range test, then converted to percent control for comparison. The eluates of all three materials from the first 24 h of soaking inhibited HCP cell growth. The number of cells in cultures exposed to Fuji were 88% of control cultures, while those exposed to KCR and KCM were 58% and 59% of control, respectively. The difference between Fuji-exposed and control cultures was significant (P < 0.05). The two Ketac cements were different from Fuji-exposed and control cultures (P < 0.05) but not from each other. All of the materials caused significant increases in labelling of DNA compared to control cultures (P < 0.05) when calculated on a per cell basis, but the materials did not differ from each other. Both Ketac cements also significantly stimulated labelling of RNA per cell compared to control cultures (P < 0.05). All effects of the material decreased over time. Results suggest that leachable components of the materials may affect the rate of progression of HCP cells through the cell cycle, rather than overt toxicity that results in cell death.

Animals↗
PubMed1996

CSP41, a sequence-specific chloroplast mRNA binding protein, is an endoribonuclease.

Correct 3' processing of chloroplast precursor mRNAs (pre-mRNAs) requires a stem-loop structure within the 3' untranslated region. In spinach, a stable 3' stem-loop-protein complex has been shown to form in vitro between petD pre-mRNA, encoding subunit IV of the cytochrome b6/f complex, and chloroplast proteins. This complex contains three chloroplast stem-loop binding proteins (CSPs), namely, CSP29, CSP41, and CSP55. Here, we report the purification of CSP41 and cloning of the csp41 gene and show that CSP41 is encoded by a single nuclear gene. Characterization of bacterially expressed CSP41 demonstrates that this protein binds specifically to the 3' stem-loop structure and a downstream AU-rich element of petD pre-mRNA and that its binding affinity is enhanced by associating with CSP55. Our data also show that CSP41 has substantial nonspecific endoribonuclease activity. These data suggest that CSP41 could be involved in 3' processing of petD pre-mRNA and/or in RNA degradation. The fact that different reaction conditions favor RNA binding over ribonuclease activities suggests a possible mode of in vivo regulation.

Amino Acid Sequence↗
PubMed1995

[Interstitial pneumonia and sepsis due to a Pasteurella multocida infection].

HISTORY AND CLINICAL FINDINGS: A 65-year-old diabetic (requiring insulin during the last year) was admitted as an emergency because of a septic temperature rising to 40 degrees C with rigor, tachycardia (up to 120/min) and dyspnoea. On examination there was local reddening and swelling of the skin over the right thenar eminence and along the lower arm. Two days before admission a bad scratch had been inflicted on his right hand by a cat. He had first noticed the reddening and swelling 10 hours after the incident; 1 1/2 days after the scratch and 9-10 hours before hospitalization the first bouts of fever had occurred. EXAMINATIONS: The chest radiogram showed interstitial pneumonia. The clinical findings, the laboratory tests (white cell count 21 750/microliters, platelets 140,000/microliters, C-reactive protein 35 mg/l and positive blood cultures pointed to early septicaemia. The germ was identified as Pasteurella multocida two days after blood had been taken for culturing. HbA1c was 11.38%. TREATMENT AND COURSE: From the time of hospitalization the patient had been treated with ceftriaxon, 2 g daily intravenously, and also with erythromycin because atypical pneumonia had been the suspected diagnosis at first and acute chlamydia infection had at first not been excluded. The patient's general condition quickly improved and the fever started to go down a few hours after onset of treatment. Blood cultures became negative after the first administration of antibiotics. He was discharged in a good state on optimal insulin dosage. CONCLUSION: Pasteurella multocida is present in a high percentage of domestic animals and can be the cause of systemic infections in immunocompromised patients (e. g. poorly controlled diabetes mellitus).

Aged↗
PubMed1995

Phosphorylation of a chloroplast RNA-binding protein changes its affinity to RNA.

An RNA-binding protein of 28 kDa (28RNP) was previously isolated from spinach chloroplasts and found to be required for 3' end-processing of chloroplast mRNAs. The amino acid sequence of 28RNP revealed two approximately 80 amino-acid RNA-binding domains, as well as an acidic- and glycine-rich amino terminal domain. Upon analysis of the RNA-binding properties of the 'native' 28RNP in comparison to the recombinant bacterial expressed protein, differences were detected in the affinity to some chloroplastic 3' end RNAs. It was suggested that post-translational modification can modulate the affinity of the 28RNP in the chloroplast to different RNAs. In order to determine if phosphorylation accounts for this post-translational modification, we examined if the 28RNP is a phosphoprotein and if it can serve as a substrate for protein kinases. It was found that the 28RNP was phosphorylated when intact chloroplasts were metabolically labeled with [32P] orthophosphate, and that recombinant 28RNP served as an excellent substrate in vitro for protein kinase isolated from spinach chloroplasts or recombinant alpha subunit of maize casein kinase II. The 28RNP was apparently phosphorylated at one site located in the acidic domain at the N-terminus of the protein. Site-directed mutagenesis of the serines in that region revealed that the phosphorylation of the protein was eliminated when serine number 22 from the N-terminus was changed to tryptophan. RNA-binding analysis of the phosphorylated 28RNP revealed that the affinity of the phosphorylated protein was reduced approximately 3-4-fold in comparison to the non-phosphorylated protein. Therefore, phosphorylation of the 28RNP modulates its affinity to RNA and may play a significant role in its biological function in the chloroplast.

Amino Acid Sequence↗
PubMed1995

[Dolichoectatic intracranial arteries. Advances in images and therapeutics].

Dolichoectasia of intracranial arteries is an infrequent disease with an incidence less than 0.05% in general population. It represents 7% of all intracranial aneurysms. Commonly seen in middle age patients with severe atherosclerosis and hypertension, the affected arteries include the basilar artery, supraclinoid segment of the internal carotid artery, middle, anterior and posterior cerebral arteries; males are more frequently affected. The clinical features of these fusiform aneurysms are divided in three categories: ische-mic, cranial nerve compression and signs from mass effect. Hemorrhage may also occur. Nine patients with symptomatic cerebral blood vessel dolichoectasias are presented. Six of them were males with moderate or severe hypertension. Lesions were confined to the basilar artery in 3 cases, carotid arteries and the middle cerebral artery in 1 case, and both systems were affected in 4 patients. Middle cerebral arteries were affected in 5 cases and the anterior cerebral artery in one. An isolated fusiform aneurysm of the posterior cerebral artery is also presented (case 8) (Table 3). Motor or sensory deficits, ataxia, dementia, hemifacial spasm and parkinsonism were observed. One patient died from cerebro-meningeal hemorrhage (Table 2). All patients were studied with computerized axial tomography of the brain, 5 cases with four vessel cerebral angiography, 4 cases with magnetic resonance imaging (MRI) and case 5 with MRI angiography. Clinical symptoms depend on the affected vascular territory, size of the aneurysm and compression of adjacent structures. The histopathologic findings are atheromatous lesions, disruption of the internal elastic membrane and fibrosis of the muscular wall. The resultant is a diffuse deficiency of the muscular wall and the internal elastic membrane. Recent advances in neuroimaging such as better resolution of CT scan, magnetic resonance images (MRI) and MRI angiography increased the diagnosis of this pathology showing clearly the affected vessels. This avoids the use of conventional or digital subtraction angiography, reserved only for diagnosing suspected saccular aneurysm, evidence of subarachnoid hemorrhage or planning surgical treatment. The treatment of this entity may be medical or surgical. There is evidence suggesting a more favorable outcome with anticoagulation therapy, although antiaggregation is a reasonable alternative. In our experience no difference in clinical outcome was evident. Surgical treatment of this type of aneurysm includes intra- or extracranial occlusion of parent artery, clipping or aneurysm trapping, tourniquet occlusion, and circumferential wrapping with clip reinforcement. Endovascular occlusion has been accomplished with detachable balloon technique or coils. No surgical attempt was done in our cases. The prognosis is variable depending on the patients age, vessels involved and clinical complications.(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1994

RNA-binding activities of the different domains of a spinach chloroplast ribonucleoprotein.

An RNA-binding protein of 28 kD (28RNP) has been previously isolated from spinach chloroplasts and was found to be required for 3' end processing of chloroplast mRNAs. The amino acid sequence of 28RNP revealed two approximately 80 amino-acid RNA-binding domains, as well as an acidic and glycine-rich amino terminal domain. Each domain by itself, as well as in combination with other domains, was expressed in bacterial cells and the polypeptides were purified to homogeneity. We have investigated the RNA-binding properties of the different structural domains using UV-crosslinking, saturation binding and competition between the different domains on RNA-binding. It was found that the acidic domain does not bind RNA, but that each of the RNA-binding domains, expressed either individually or together, do bind RNA, although with differing affinities. When either the first or second RNA-binding domain was coupled to the acidic domain, the affinity for RNA was greatly reduced. However, the acidic domain has a positive effect on the binding of the full-length protein to RNA, because the mature protein binds RNA with a better affinity than the truncated protein which lacks the acidic domain. In addition, it was found that a stretch of two or three G residues is enough to mediate binding of the 28RNP, whereas four U residues were insufficient. The implications of the RNA-binding properties of 28RNP to its possible function in the processing of chloroplast RNA is discussed.

Base Sequence↗
PubMed1992

Accumulation of a light-harvesting chlorophyll a/b protein in the chloroplast grana lamellae. The lateral migration of the membrane protein precursor is independent of its processing.

The events that follow the import of pLHCPIIb, the apoprotein precursor of the major light-harvesting complex of photosystem II, were studied in intact pea chloroplasts. The distribution of the events of insertion into the membrane, and processing, to yield the mature form (LHCP) between stromal and granal lamellae regions of the thylakoids were followed. pLHCP was preferentially inserted into stromal lamellae (SL) from which it migrated to granal lamellae (GL). Migration occurred before or after processing, suggesting that migration and processing are independent of each other. When migration was slowed down, LHCP accumulated in SL. Prolonged inhibition of migration induced degradation of LHCP that had accumulated in SL, whereas inhibition of processing did not affect the migration of pLHCP into GL. A small difference in electrophoretic mobility was noted between LHCP in SL and in GL. The predominant mature form in SL migrated more slowly than LHCP from GL. When thylakoids were subjected to trypsin, all of the LHCP embedded in SL underwent cleavage, whereas up to 60% of the radioactive LHCP in GL was resistant to the enzyme. The possible implications of the differences in size and in the sensitivity to trypsin of LHCP are discussed.

Chloroplasts↗
PubMed1992

Effects of tung oil on salivary viscosity and extent and incidence of dental caries in rats.

Increased salivary viscosity may be associated with an increase in dental caries. In order to examine this relationship, the caries level in rats was monitored following gastric intubation with tung oil which has been shown to significantly increase salivary viscosity. Tung oil intubation over an 8-week period significantly increased the salivary viscosity in rats as compared with deoinized water and corn oil intubation. The total number of carious lesions was significantly increased (p less than 0.05) in the tung oil intubated rats as compared with the two other groups. This increase in carious lesions was primarily associated with the smooth surfaces of the teeth. There was also a significant increase (p less than 0.05) in the extent of enamel and dentin involvement of the tung oil intubated rats as compared with the other two groups. Histologic examination of the submandibular glands revealed an increase in the amount of glycoprotein material in the convoluted granular tubules of the tung oil intubated rats as compared with the deionized water and corn oil intubated animals. Collectively, these results suggest that tung oil intubation is correlated with both increased salivary viscosity and increased smooth-surface dental caries, suggesting that the viscosity may be related to dental caries progression.

Animals↗
PubMed1991

Heterologous regulation of the cardiac Ca2+ channel alpha 1 subunit by skeletal muscle beta and gamma subunits. Implications for the structure of cardiac L-type Ca2+ channels.

High threshold L-type Ca2+ channels of skeletal muscle are thought to consist of a complex of alpha 1, alpha 2 delta, beta, and gamma subunits. Expression of the cloned alpha 1 subunit from skeletal and cardiac muscle has established that this protein is the dihydropyridine-sensitive ion-conducting subunit. However, the kinetics of the skeletal muscle alpha 1 alone expressed in mouse L-cells were abnormally slow and were accelerated to within the normal range by coexpression with the skeletal muscle beta subunit. The kinetics of cardiac muscle alpha 1 were also slowed but to a lesser extent and were not altered by coexpression with skeletal muscle alpha 2. We show here that coexpression of the skeletal muscle beta subunit with the cardiac alpha 1 subunit in Xenopus laevis oocytes produced: 1) an increase in the peak voltage-sensitive current, 2) a shift of the peak current-voltage relationship to more hyperpolarized potentials, and 3) an increase in the rate of activation. Coexpression of the skeletal muscle gamma subunit did not have a significant effect on currents elicited by alpha 1. However, when gamma was coexpressed with beta and alpha 1, both peak currents and rates of activation at more negative potentials were increased. These results indicate that rather than simply amplifying expression of alpha 1, heterologous skeletal muscle beta and gamma subunits can modulate the biophysical properties of cardiac alpha 1.

3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethy↗
PubMed1991

Chloroplast mRNA 3' end processing requires a nuclear-encoded RNA-binding protein.

The protein coding regions of plastid mRNAs in higher plants are generally flanked by 3' inverted repeat sequences. In spinach chloroplast mRNAs, these inverted repeat sequences can fold into stem-loop structures and serve as signals for the correct processing of the mature mRNA 3' ends. The inverted repeat sequences are also required to stabilize 5' upstream mRNA segments, and interact with chloroplast protein in vitro. To dissect the molecular components involved in chloroplast mRNA 3' end processing and stability, a spinach chloroplast protein extract containing mRNA 3' end processing activity was fractionated by FPLC and RNA affinity chromatography. The purified fraction consisted of several proteins and was capable of processing the 3' ends of the psbA, rbcL, petD and rps14 mRNAs. This protein fraction was enriched for a 28 kd RNA-binding protein (28RNP) which interacts with both the precursor and mature 3' ends of the four mRNAs. Using specific antibodies to this protein, the poly(A) RNA-derived cDNA for the 28RNP was cloned and sequenced. The predicted amino acid sequence for the 28RNP reveals two conserved RNA-binding domains, including the consensus sequences RNP-CS1 and CS2, and a novel acidic and glycine-rich N-terminal domain. The accumulation of the nuclear-encoded 28RNP mRNA and protein are developmentally regulated in spinach cotyledons, leaves, root and stem, and are enhanced during light-dependent chloroplast development. The general correlation between accumulation of the 28RNP and plastid mRNA during development, together with the result that depletion of the 28RNP from the chloroplast protein extract interferes with the correct 3' end processing of several chloroplast mRNAs, suggests that the 28RNP is required for plastid mRNA 3' end processing and/or stability.

Amino Acid Sequence↗
PubMed1990

The P30 movement protein of tobacco mosaic virus is a single-strand nucleic acid binding protein.

The P30 protein of tobacco mosaic virus (TMV) is required for cell to cell movement of viral RNA, which presumably occurs through plant intercellular connections, the plasmodesmata. The mechanism by which P30 mediates transfer of TMV RNA molecules through plasmodesmata channels is unknown. We have identified P30 as an RNA and single-stranded (ss) DNA binding protein. Binding of purified P30 to ss nucleic acids is strong, highly cooperative, and sequence nonspecific with a minimal binding site of 4-7 nucleotides per P30 monomer. In-frame deletions across P30 were used to localize the ss nucleic acid binding domain to within amino acid residues 65-86 of the protein. We propose that binding of P30 to TMV RNA creates an unfolded protein-RNA complex that functions as an intermediate in virus cell to cell movement through plasmodesmata.

Chromosome Deletion↗
PubMed1990

The apoprotein precursor of the major light-harvesting complex of photosystem II (LHCIIb) is inserted primarily into stromal lamellae and subsequently migrates to the grana.

The formation of the lateral distribution of the major antenna complex of photosystem II (LHCIIb) between the granal and stromal lamellae was studied. Specifically, the localization of the insertion and the assembly of the precursor of the apoprotein of LHCIIb (pLHCP) were studied with isolated thylakoids. After insertion of pLHCP into isolated thylakoids, fractionation of the latter into granal and stromal lamellar was performed. At 25 degrees C most of the precursor was located in the granal lamellae, although both highly purified granal and stromal lamellar fractions demonstrated a similar capability to insert pLHCP. When the insertion reaction to the thylakoids was performed at 10 degrees C, followed by their separation into stromal and granal lamellae, the labelled pLHCP was localized in the stromal ones. To examine whether pLHCP inserts into both granal and stromal lamellae, or preferentially into stromal lamellae and subsequently migrating to granal lamellae, a chase experiment was performed. Insertion of pLHCP at 10 degrees C was followed by chase of the radioactive precursor with excess of non-radioactive pLHCP at 25 degrees C. From the results presented it is evident that the level of pLHCP in stromal lamellae was gradually reduced, while it gradually accumulated in the granal lamellae. Furthermore, the pLHCP in the stromal lamellae was found to be in a 'free' form, while after migrating to the granal lamellae it assembled into the pigmented LHCIIb.

Apoproteins↗
PubMed1990

Toxin and kinetic profile of rat brain type III sodium channels expressed in Xenopus oocytes.

Sodium (Na+) channels are members of a multigene family and are responsible for generation and propagation of the action potential in excitable cells. We have assembled, in a transcription-competent vector, a full-length cDNA clone encoding the rat brain type III Na+ channel. Xenopus oocytes microinjected with in vitro synthesized mRNA expressed functional rat brain Na+ channels from such 'cloned' RNA transcripts. We found that type III Na+ currents in whole cell microelectrode voltage clamp and in cell-attached patch recordings decayed much more slowly than any other reported Na+ current. In addition, we saw typical and additive effects of alpha- and beta-scorpion toxins, suggesting that the Na+ channel alpha-subunit itself contains functional and distinct toxin binding sites.

Amino Acid Sequence↗
PubMed1989

A novel potassium channel with delayed rectifier properties isolated from rat brain by expression cloning.

Voltage-activated potassium channels play an important part in the control of excitability in nerve and muscle. Different K+ channels are involved in establishing the resting potential, determining the duration of action potentials, modulation of transmitter release, and in rhythmic firing patterns and delayed excitation. Using in vitro transcripts made from a directional complementary DNA library we have isolated, by expression cloning in Xenopus oocytes, a novel K+-channel gene (drk1). Functionally, drk1 encodes channels that are K+ selective and belong to the delayed rectifier class of channels, rather than the A-type class encoded by the Shaker gene of Drosophila. The channels show sigmoidal voltage-dependent activation and do not inactivate within 500 ms. Structurally, drk1 encodes an amino-acid sequence which is more closely related to the Drosophila Shab gene than to the Shaker gene.

Amino Acid Sequence↗
PubMed1989

Mutagenicity of antiviral substances of nucleobase analogue type in Salmonella typhimurium employing metabolic activation by mouse liver homogenate or cell-free plant extracts.

Five nucleobase analogues with antiviral properties were tested for their mutagenic activity in his mutant strains TA 1535, TA 1537, TA 1538, TA98, and TA 100 of S. typhimurium by means of preincubation tests with and without metabolic activation by cell free fractions from mouse liver (S-9) and maize seedlings (S-14). In one bacterial strain 6-azathymine increased the revertant counts in the absence of metabolic activation systems. In the presence of S-9 mix, the same substance became mutagenic for another tester strain. Metabolic activation by S-14 resulted in weak mutagenicity of 5-azadihydrouracil in high concentrations. 6-Azauracil, 5-azauracil, and 5-azadihydro-1,3-diacetyluracil were without mutagenic activity in all Salmonella-strains used. Cyclophosphamide, like other standard promutagens, was shown to become mutagenic in the presence of S-14 plant fraction. Thus S-14 activation system besides the S-9 liver system can be employed in mutagenicity testing with microbial systems.

Animals↗