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Biomedical subjects

A Schmid

Publications and source records attributed to A Schmid.

At least 235 records · Page 13Linked to original sources
PubMed1988

Pore-forming activity of the Tsx protein from the outer membrane of Escherichia coli. Demonstration of a nucleoside-specific binding site.

The Tsx protein from the outer membrane of Escherichia coli is known to be involved in the permeation of nucleosides across the outer membrane under limiting substrate conditions. We purified Tsx from an E. coli strain that overproduces Tsx. The purified protein was still functional since it could neutralize the Tsx-specific bacteriophage T6 in vitro. When the purified Tsx was reconstituted into a lipid bilayer, there was a large increase of the membrane conductance, indicating pore-forming activity of Tsx in vitro. This increase could be strongly blocked with adenosine and to a much lesser extent with cytidine. Titration of the pore conductance with adenosine or cytidine suggested the presence of a binding site for nucleosides in the Tsx pore, with a Ks of 6 X 10(-4) and 2 X 10(-2) M for adenosine and cytidine, respectively. We propose that the Tsx protein functions in vivo as a pore that specifically facilitates the permeation of nucleosides across the outer membrane due to its binding site for nucleosides.

Adenosine↗
PubMed1988

Microvascular casting of the lung: effects of various fixation protocols.

Although techniques for preparing specimens for light and electron microscopy are well established, few studies have sought to establish methods for corrosion casting of the microscopic vessels of the lung. The effects of two concentrations of glutaraldehyde, formaldehyde, and no fixative (saline control) on the filling and structure of the microvascular casts of the lung were studied. All fixatives were infused 5 minutes before casting. Formaldehyde's fixation effects were intermediate between those of glutaraldehyde and no fixation. Leakage of casting material was increased in the animals that were fixed less. Digestion time was prolonged and more undigested tissue was found in the group receiving the concentrated glutaraldehyde, although the difference in neither of these features alone reached statistical significance. Circumferential bands occurred more frequently in the large vessel casts of the less fixed animals, which may account for the less filling microvasculature in these lungs. However, good quality casts were obtained with each method.

Animals↗
PubMed1988

Anion channels in giant liposomes made of endoplasmic reticulum vesicles from rat exocrine pancreas.

Using the method of dehydration and rehydration, rough endoplasmic reticulum (RER) vesicles, isolated by differential centrifugation, can be enlarged to giant liposomes with diameters ranging from 5 to 200 micron. Patch-clamp studies on these giant RER liposomes revealed the existence of a channel with a mean conductance of 260 +/- 7 pS (n = 23; 140 mmol/liter KCl on both sides). The channel is about four times more permeable for Cl- than for K+. Its activity is strongly voltage regulated. At low potentials (+/- 20 mV) the channel is predominantly in its open state with an open probability near 1.0, whereas it closes permanently at high positive and negative voltages (+/- 70 mV). The channel activity is not influenced by changing the free Ca2+ concentration from 1 mmol/liter to less than 10(-9) mol/liter on either side, and is also not affected by typical Cl- -channel blockers like diphenylamine-2-carboxylate (DPC, 1 mmol/liter) or 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic acid (SITS, 1 mmol/liter). Another chloride channel with a single-channel conductance of 79 +/- 6 pS (n = 4) was less frequently observed. In the potential range of -80 to +40 mV this channel displayed no voltage-dependent gating. We assume that these anion channels are involved in the maintenance of electroneutrality during Ca2+ uptake in the RER.

Animals↗
PubMed1988

Multiple viral mutations rather than host factors cause defective measles virus gene expression in a subacute sclerosing panencephalitis cell line.

A measles virus (MV) genome originally derived from brain cells of a subacute sclerosing panencephalitis patient expressed in IP-3-Ca cells an unstable MV matrix protein and was unable to produce virus particles. Transfection of this MV genome into other cell lines did not relieve these defects, showing that they are ultimately encoded by viral mutations. However, these defects were partially relieved in a weakly infectious virus which emerged from IP-3-Ca cells and which produced a matrix protein of intermediate stability. The sequences of several cDNAs related to the unstable and intermediately stable matrix proteins showed many differences in comparison with a stable matrix protein sequence and even appreciable heterogeneity among themselves. Nevertheless, partial restoration of matrix protein stability could be ascribed to a single additional amino acid change. From an examination of additional genes, we estimated that, on average, each MV genome in IP-3-Ca cells differs from the others in 30 to 40 of its 16,000 bases. The role of extreme variability of RNA virus genomes in persistent viral infections is discussed in the context of the pathogenesis of subacute sclerosing panencephalitis and of other human diseases of suspected viral etiology.

Animals↗
PubMed1988

[Use of arthrosonography in the diagnosis of Tossy injuries of the shoulder joint].

In a pilot study specificity and sensibility of ultrasonics on Tossy III lesions were tested, and that in 20 cases of guaranteed intact acromioclavicular joints and 22 cases of radiologically diagnosed Tossy III lesions with a following operative control. Additionally in these 22 cases the contralateral acromioclavicular joints were also examined by ultrasonics. All examinations were registered on video tape. With it in a single blind test the exact diagnosis was made in all cases. The diagnosis was based on ultrasonic findings as visible instability, unevenness of the joint line, haematoma formation with ligament stumps. Compared to radiologic diagnostics ultrasonics do not demand cooperative patients or special postures for the examination. A proved accuracy in the diagnosis and the capability of further extension of this technique are of clinical importance. A differentiation of various grades of Tossy lesions is possible.

Acromioclavicular Joint↗
PubMed1988

[Circumscribed changes in the cranium due to extracerebral fluid collection in the middle cranial fossa].

On the basis of 26 cases with extracerebral fluid accumulation in the middle cranial fossa the bony changes occurring in this connection are described and discussed in respect of their aetiology. If there are bony accompanying reactions, two entities can be observed in principle. One group shows thinning and protrusion of the temporal squama, raising of the lesser wing of the sphenoid bone and protrusion of the greater wing of the sphenoid bone. The second group is associated with thickening of the temporal squama and of the lesser and greater wing of the sphenoid bone without showing any change in volume of the middle cranial fossa. If we postulate in the first group a space-occupying property of the extracerebral fluid accumulation, the prominent reactions in the second group are those usually associated with absence of pressure exercised on the cranial vault by a space-occupying growth.

Adolescent↗
PubMed1988

Capillary structure in elastase-induced emphysema.

The essential component of pulmonary emphysema is destruction of alveoli. Because capillaries make up much of the alveolar wall, it has been a long-held opinion that capillary loss in this disease parallels the loss of other elements of the alveolar septum. Yet the nature of the damage to capillaries and the occurrence of microvascular remodeling are unknown. Scanning electron microscopy of vascular casts of lungs from rats given intratracheal elastase were studied for identifying capillary changes in this type of experimental emphysema. The pressure-volume curves showed a clear distinction between the elastase and saline control animals, and light microscopy showed alveolar enlargement consistent with mild emphysema. The casts of capillaries in the elastase lungs appeared to have larger alveolar baskets, and capillaries ended abruptly near areas of focally destroyed lung. The elastase animals had more nonconnecting capillary segments on the pleural surface where the emphysema was worse and folds in the capillaries were more pronounced, suggesting weakened alveolar walls. The capillary density was decreased on the pleural surface, although this decrease could have resulted from hyperinflation. No difference in capillary diameters or branching frequency occurred. It appears that in this model of emphysema, decreased elastic recoil occurs before diffuse loss of capillaries.

Animals↗
PubMed1988

[Clinical course, electrophysiologic monitoring and neuroradiologic findings in acute basilar artery thrombosis and local fibrinolytic therapy].

The development of new catheter materials and techniques has made it possible to perform local intraarterial fibrinolysis in the region of the basilar artery in case of thrombotic arterial occlusions. We present the case of a 27-year old patient suffering from thrombosis of the basilar artery in whom local fibrinolysis was performed. The clinical course is demonstrated in respect to imaging methods (angiography, CT and MRT) and electrophysiological monitoring.

Adult↗
PubMed1988

[Differential CT diagnosis of tumors of the cranial calotte with intracranial spread based on a case report].

A report on patient presenting in the cranial computer tomogram with changes in the cranium in the left temporal region typical of a meningioma, as well as with changes in the floor of the middle cranial fossa. Correct diagnosis was obtained only by the overall assessment comprising anamnesis, laboratory findings and state of the skeletal structure: namely, a plasmacytoma involving the calotte of the cranium.

Brain Neoplasms↗
PubMed1988

Pre- and postoperative changes in brain tissue surrounding a meningioma.

A retrospective study in 33 patients with intracranial meningioma demonstrates that two pathological mechanisms are involved in causing a hypodense area around the actual tumor: pressure-induced atrophy that persists after operation and true cerebral edema of unclear cause. The extent of the hypodense area is not related to tumor location or tumor size. A relationship between meningioma with a malignant tendency and the hemispheric spread of hypodensity can be observed.

Adult↗
PubMed1988

Microvascular casting of the lung: vascular lavage.

Corrosion casting is an important tool for the study of microvascular structure, but unlike tissue preparation for light and electron microscopy, few controlled studies of the methods for preparation of microvascular casts for scanning electron microscopy have been reported. Most vascular casting begins with rinsing cells from the lumen of the blood vessels, but the necessity of this has not been shown. Because of a report of successful casting without rinsing and light microscopic evidence of edema with complete rinsing prior to casting, this preparation procedure was examined. Casts of lung vasculature that were thoroughly rinsed were compared to those that were not. Of the six rats that were not lavaged, only one gave a completely filled cast, but of the six animals that were well rinsed, only one did not fill. Except for the filling and mild periarterial edema, no significant difference in cast quality or features was detected. Rinsing improves the frequency of obtaining completely filled casts. The edema does not greatly interfere with the capillary image and its location gives insight into this process in the lung.

Animals↗
PubMed1987

Photoaffinity labelling and phosphorylation of a 165 kilodalton peptide associated with dihydropyridine and phenylalkylamine-sensitive calcium channels.

Partially purified fractions of dihydropyridine and phenylalkylamine receptors associated with voltage-dependent calcium channels in rabbit skeletal muscle were found to contain two glycopeptides of similar molecular weight. A peptide of approximately 165 kDa was photoaffinity labelled with an arylazido-phenylalkylamine Ca channel inhibitor and also was phosphorylated with cAMP-dependent protein kinase. Another peptide of 170 kDa could be distinguished from the 165 kDa peptide by peptide mapping and differences in electrophoretic mobility. The results suggest that the 165 kDa peptide contains the sites responsible for regulation of calcium channel activity by calcium channel inhibitors as well as by neurotransmitters that regulate its activity in a cAMP-dependent manner.

Affinity Labels↗
PubMed1987

A procedure for selective full length cDNA cloning of specific RNA species.

A method allowing routine establishment of full length and functionally competent cDNA clones of particular mRNAs from small preparations of polyadenylated RNA is described. Pairs of synthetic primers are used for first and second strand synthesis. They include sequences complementary to the 3' terminal regions of the mRNAs and of the full length first cDNA strands, respectively and bear a few additional nucleotides at their 5' ends. After synthesis of both cDNA strands in one tube, they are precisely trimmed back with T4 DNA polymerase in presence of only two nucleoside triphosphates, to yield sticky ends fitting into a vector plasmid cleaved with two restriction endonucleases. The procedure was first applied to the simultaneous cloning of all five major measles virus (MV) mRNA species from a persistently infected cell line. Two thirds of all clones contained full length MV-specific cDNAs. Screening of less than 200 clones was sufficient to obtain several independent clones corresponding to each mRNA, except for gene F which was represented only once.

Cloning, Molecular↗
PubMed1987

The calcium channel antagonists receptor from rabbit skeletal muscle. Reconstitution after purification and subunit characterization.

The Ca2+ channel antagonists receptor from rabbit skeletal muscle was purified to homogeneity. Following reconstitution into phosphatidylcholine vesicles, binding experiments with (+)[3H]PN 200-110, (-)[3H]D888 and d-cis-[3H]diltiazem demonstrated that receptor sites for the three most common Ca2+ channel markers copurified with binding stoichiometries close to 1:1:1. Sodium dodecyl sulfate gel analysis of the purified receptor showed that it is composed of only one protein of Mr 170,000 under non-reducing conditions and of two polypeptides of Mr 140,000 and 32,000 under disulfide-reducing conditions. Iodination of the protein of Mr 170,000 and immunoblots experiments with antisera directed against the different components demonstrated that the Ca2+ channel antagonists receptor is a complex of Mr 170,000 composed of a polypeptide chain of Mr 140,000 associated to one polypeptide chain of Mr 32,000 by disulfide bridges. One of the problems concerning this subunit structure of the putative Ca2+ channel was the presence of smaller polypeptide chains of Mr 29,000 and 25,000. Peptide mapping of these polypeptide chains and analysis of their cross-reactivity with sera directed against the proteins of Mr 170,000 and 32,000 demonstrated that they were degradative products of the Mr 32,000 component. Both the large (140 kDa) and the small (32 kDa) component of the putative Ca2+ channel are heavily glycosylated. At least 20-22% of their mass were removed by enzymatic deglycosylation. Finally the possibility that both the 140-kDa and 32-kDa components originate from a single polypeptide chain of Mr 170,000 which is cleaved by proteolysis upon purification is discussed.

Animals↗