Search PubMed⌕ Search

Biomedical subjects

J Lang

Publications and source records attributed to J Lang.

At least 307 records · Page 17Linked to original sources
PubMed1989

Chlorophyll precursors in the plasma membrane of a cyanobacterium, Anacystis nidulans. Characterization of protochlorophyllide and chlorophyllide by spectrophotometry, spectrofluorimetry, solvent partition, and high performance liquid chromatography.

Plasma membranes were isolated and separated from thylakoid membranes by discontinuous sucrose density gradient centrifugation of crude membranes prepared by French pressure cell extrusion of lysozyme-treated Anacystis nidulans. Two distinct populations of chlorophyll-free plasma membrane vesicles were obtained exhibiting buoyant densities of 1.087 and 1.100 g/cm3 as opposed to a uniform density of 1.192 g/cm3 for thylakoid membranes. Plasma and thylakoid membranes were characteristically different also with respect to fatty acid and protein composition, cytochrome oxidase activity, and pigment content as analyzed by spectrophotometry, spectrofluorimetry, and high performance liquid chromatography. Apart from carotenoids, chlorophyll a was the only major photosynthetic pigment detected in thylakoid membranes while plasma membranes contained virtually no chlorophyll a but (besides large amounts of carotenoids) protochlorophyllide a and chlorophyllide a as revealed by solvent partition (between n-hexane and acetone or methanol), room and low temperature fluorescence emission and excitation spectra, and analytical separation and identification by high performance liquid chromatography and comparison with authentic standards. The protochlorophyllide in the plasma membrane could be transformed into chlorophyllide in the dark in vitro by incubating the membrane preparation with NADPH; NADP+ effected the reverse transition.

Cell Membrane↗
PubMed1989

Nucleotide sequence of the glyceraldehyde-3-phosphate dehydrogenase gene from the mesophilic methanogenic archaebacteria Methanobacterium bryantii and Methanobacterium formicicum. Comparison with the respective gene structure of the closely related extreme thermophile Methanothermus fervidus.

The genes for glyceraldehyde-3-phosphate dehydrogenase (gap genes) from the mesophilic methanogenic archaebacteria Methanobacterium formicicum and Methanobacterium bryantii were cloned and sequenced. The deduced amino acid sequences show 95% identity to each other and about 70% identity to the glyceraldehyde-3-phosphate dehydrogenase from the thermophilic methanogenic archaebacterium Methanothermus fervidus. Although the sequence similarity between the archaebacterial glyceraldehyde-3-phosphate dehydrogenase and the homologous enzyme of eubacteria and eukaryotes is low, an equivalent secondary-structural arrangement can be deduced from the profiles of the physical parameters hydropathy, chain flexibility and amphipathy. In order to find possible thermophile-specific structural features of the enzyme from M. fervidus, a comparative primary-sequence analysis was performed. Amino acid exchanges leading, to a stabilization of the main-chain conformation, could be found throughout the sequence of the thermophile enzyme. Striking features of the thermophile sequence are the preference for isoleucine, especially in beta-sheets, and a low arginine/lysine ratio of 0.54.

Amino Acids↗
PubMed1989

Direct modulation of voltage-dependent calcium channels by muscarinic activation of a pertussis toxin-sensitive G-protein in hippocampal neurons.

Acetylcholine (Ach) reversibly reduces the high voltage-activated (HVA) calcium (Ca) current in hippocampal neurons. Pretreatment of the cells with pertussis toxin (PTX) abolishes the Ach effect, suggesting that PTX-sensitive GTP-binding regulatory proteins (G-proteins) are involved in the signal transduction mechanism that links Ach receptor activation to inhibition of Ca channel activity. This effect is mimicked by intracellular application of the nonhydrolyzable GTP analog GTP gamma S. Intracellular application of purified G-proteins restored the response to Ach in PTX-treated cells. Furthermore, Ach inhibits the Ca current independently of the presence of cyclic AMP and of the protein kinase C inhibitor H-7 and neither does the Ach effect on the Ca current seem to be correlated to a transient increase in intracellular Ca. Our results suggest that activation of the alpha-subunit of the PTX-sensitive G-protein could directly modulate the HVA Ca channel without involving second messenger systems.

Acetylcholine↗
PubMed1989

A prospective randomized double-blind trial on efficacy of dexamethasone for endodontic interappointment pain in teeth with asymptomatic inflamed pulps.

To determine whether a relatively large dose of oral dexamethasone given for a short period of time would be effective in reducing endodontic interappointment pain, the current double-blind, placebo-controlled study was undertaken. After the visit for instrumentation, 40 patients with asymptomatic teeth having vital-inflamed pulps were randomly given either dexamethasone (3 tablets of 4 mg each) or a dextrose placebo identical in appearance (same dosage schedule). The outcome showed that the oral administration of dexamethasone resulted in a statistically significant reduction in endodontic interappointment pain at all three time periods evaluated, that is, at 8 hours, 24 hours, and 48 hours (p less than 0.01). It appears from the results of this study that this dosage schedule of oral dexamethasone is sufficient to significantly reduce endodontic interappointment pain for teeth with asymptomatic vital-inflamed pulps. Further studies are needed for teeth with other endodontic pulpal-periapical conditions and for symptomatic teeth.

Clinical Trials as Topic↗
PubMed1989

Chronic opiate receptor activation in vivo alters the level of G-protein subunits in guinea-pig myenteric plexus.

Studies with the longitudinal muscle-myenteric plexus preparation of the guinea-pig ileum were undertaken to investigate the relationship between guanine nucleotide-binding proteins (G-proteins) and chronic opioid receptor activation in vivo. Treatment with the narcotic agonist fentanyl, at doses which render the preparation tolerant and dependent, led to an increase of pertussis toxin-catalysed incorporation of ADP-ribose in a protein of approximately 40,000 mol. wt. Quantitative immunoblotting, using site-directed antisera, demonstrated an upregulation of G alpha i/G alpha o and, to an even greater degree, of G beta. However, the level of G alpha s was decreased by the same treatment. All alterations observed were abolished by the concomitant presence of the antagonist naloxone. The implications of this differential regulation of G-protein subunits for opiate-induced tolerance and dependence are discussed.

Adenosine Diphosphate Ribose↗
PubMed1989

Transplanted ossicles after two decades.

The authors now report on the histological appearance of two very long-term ossicles, an autologous incus removed from the middle ear at revision surgery 21 years after repositioning and a homologous incus removed from the middle ear after 20 years. Having been placed in formalin immediately after removal from the ear, both specimens were later decalcified by ethylene diamine tetra-acetic acid, embedded in paraffin wax, serially sectioned and stained with haematoxylin and eosin.

Bone Regeneration↗
PubMed1989

Pneumatization of the posteromedial air-cell tract.

Sixty consecutive temporal bone specimens were examined histologically by light microscopy to determine the incidence of a pneumatized posteromedial air-cell tract extending into the posterior wall of the internal auditory meatus. Thirteen were found to have this air-cell tract. The main potential surgical hazards of opening this air-cell tract are CSF otorhinorrhoea and meningitis.

Cerebrospinal Fluid Otorrhea↗
PubMed1989

Chronic exposure of NG 108-15 cells to opiate agonists does not alter the amount of the guanine nucleotide-binding proteins Gi and Go.

We have characterized the pertussis toxin substrate in NG 108-15 cell membranes using site-specific antisera and ADP-ribosylation. Cell membranes contain two pertussis toxin-sensitive guanine nucleotide-binding protein alpha-subunits (G alpha) whose Rf values in gel electrophoresis coincide with those of G alpha o and G alpha i2. The total quantity of Gi and Go immunoreactivity amounted to 24.3 +/- 2.8 pmol/mg, whereas only 1.5 +/- 0.2 pmol/mg are capable of undergoing ADP-ribosylation catalyzed by pertussis toxin. Pretreatment of cells with the agonist [D-Ala2,D-Leu2]-enkephalin (DADLE) for 24 h and DADLE or morphine for 72 h did not alter the incorporation of ADP-ribose or the immunoreactive amount of Gi and Go subunits. However, pretreatment for 72 h with naloxone increased the incorporation of ADP-ribose without an apparent change in affinity or in the immunochemically determined protein levels of Gi and Go. This indicates that the process of down-regulation and desensitization of the delta-opioid receptor neither requires quantitative alterations in the levels of Gi and Go nor changes in the degree of coupling among their subunits. In contrast, chronic exposure to antagonists seems to alter the degree of precoupling between alpha- and beta-subunits of Gi and/or Go.

Adenosine Diphosphate Ribose↗
PubMed1989

Effects of isoproterenol and propranolol on pharmacologically induced depression of intraventricular conduction.

The cardiac adrenergic system is known to have practically no influence on conduction velocity in the ventricles under normal conditions. The effects of isoproterenol and propranolol were investigated on depression of intraventricular conduction induced by a class IC antiarrhythmic drug, cibenzoline, in anaesthetized, closed-chest dogs. In addition to electrocardiogram for measurement of QRS duration in sinus rhythm, conduction time was measured in the ventricular contractile tissue between an electrode advanced to the apex and a pacing electrode near the base, at 400- and 200-ms pacing periods. Effective refractory period (ERP) was measured concurrently according to the extrastimulus method. After intraventricular conduction had been slowed down by cibenzoline IV administered (loading dose of 3 mg/kg plus infusion of 0.2 mg/kg/min over 15 min), isoproterenol was infused or propranolol injected by the intravenous route also (0.5 mn/micrograms/kg/min over 5 min and 0.4 mg/kg, respectively). When conduction time has been raised by 75/150% (depending on the pacing rate), isoproterenol appears to attenuate and propranolol to aggravate substantially the impairment of conduction, whereas the reduction undergone by ERP does not differ from usual. Thus, reentrant arrhythmias might be prevented by isoproterenol and triggered by propranolol. Intraventricular conduction, when depressed, therefore, is sensitive to adrenergic drugs, probably because of the enhanced influence of polarization of the fibres in the presence of a sodium conductance impairment.

Animals↗
PubMed1989

Sequence comparison of glyceraldehyde-3-phosphate dehydrogenases from the three urkingdoms: evolutionary implication.

The primary structure of the glyceraldehyde-3-phosphate dehydrogenase from the archaebacteria shows striking deviation from the known sequences of eubacterial and eukaryotic sequences, despite unequivocal homologies in functionally important regions. Thus, the structural similarity between the eubacterial and eukaryotic enzymes is significantly higher than that between the archaebacterial enzymes and the eubacterial and eukaryotic enzymes. This preferred similarity of eubacterial and eukaryotic glyceraldehyde-3-phosphate dehydrogenase structures does not correspond to the phylogenetic distances among the three urkingdoms as deduced from comparisons of ribosomal ribonucleic acid sequences. Indications will be presented that the closer relationship of the eubacterial and eukaryotic glyceraldehyde-3-phosphate dehydrogenase resulted from a gene transfer from eubacteria to eukaryotes after the segregation of the three urkingdoms.

Amino Acid Sequence↗
PubMed1989

Of cabbages and kings.

The experience in Florida with Amendment 10 highlighted the malpractice situation for the public, physicians, and the entire United States. It was hoped that a heightened awareness might help alleviate the situation.

Florida↗
PubMed1989

[X-ray studies of the cauda equina of dogs].

This article reviews the radiologic examination of the canine cauda equina. The radiographic technique and interpretation of survey radiographs, radiographs with the spine in flexion and extension, tomography and contrast procedures, the diagnostic value and limits of these methods are discussed. The diseases which may cause cauda equina compression and the radiographic findings are described and illustrated.

Animals↗
PubMed1989

[Celiotomy in tortoises: remedy of choice for dystocia (laying distress) and gastrointestinal foreign bodies].

The radiological findings regarding eggs (variation in form, size, shell thickness, degree of calcification) combined with the clinical symptoms (Ca-Gluconate and Oxytocin application as well as unsuccessful labour contractions and constipation) set up the diagnosis of dystocia in the tortoise. Celiotomy is the remedy for cesarean section, ovariosalpingotomy and gastrointestinal foreign body. A large, topographically well-placed Plastron incision, separation and reposition of the m. pectoralis and m. obliquus internus abdominis using cross-stitch sutures, as well as the careful manipulation of tissues, are of great importance. Gastrotomy is even feasible on terrapins through a partial detachment of the stomach from the liver, enabling a sufficient presentation of the stomach.

Animals↗
PubMed1989

[The superficial cerebral veins].

Estimated were the number, the course, and the width of the superficial cerebral veins. The veins on the superolateral surface of the brain are the prefrontal superficial lateral superior, the precentral superficial lateral superior, the central superficial lateral superior, the parietal superficial lateral superior, and the occipital superficial lateral superior veins which drain to the superior sagittal sinus, to bridging veins, and to the falx cerebri. The veins which drain the lateral surface of the brain downwards are the middle superficial cerebral veins, the temporal inferior, occipital inferior, and anastomotic veins. The diameters of these veins were measured at the perforation of the arachnoid membrane and the diameters of the anastomotic veins on their narrowest area. On the medial side of the hemispheres, we divided in precentral superficial superior medial, central superficial medial, parietal superficial medial, occipital superficial medial dorsal veins of the corpus callosum, and internal occipital veins. On the basal surface of the hemispheres, we studied and described the uncal veins and the inferior hemispheric veins. Studied and discussed are also the bridging veins in the course of the inferior cerebral veins, the paracavernous sinuses, and the last course of the veins and their connections with the dura mater or the course inside the dura. Given are besides the numbers of these veins, the area of perforation of the arachnoid membrane, and their width and medical importance.

Cerebral Veins↗
PubMed1989

[Electromyography and spinal evoked potentials in cauda equina syndrome of dogs].

In order to investigate usefulness of electrodiagnostic methods in Cauda Equina-Compression, 26 dogs with this disease were subjected to electromyography and spinal evoked potentials. 16 normal dogs served as controls. It was found that--after stimulation of the Nn.tibialis, peronaeus, pudendus and coccygeales and recording at the lumbosacral junction--latencies and nerve-conduction velocities were largely normal. However the amplitudes were decreased and--depending on the severity of the compression--the morphology of the potentials was altered although considerable standard deviations were obtained. Electromyographically, increased spontaneous activity with fibrillations and positive sharp waves were found in the myotomes of the lumbosacral nerves. Their number increased according to the severity of the cauda equina compression and they had a centrifugal distribution pattern. Based on these results it appears indicated to perform an electromyographic exam before applying myelography. The technique of spinal evoked potentials will need more refinement and standardisation before being useful in a clinical situation.

Animals↗