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Biomedical subjects

J Engel

Publications and source records attributed to J Engel.

At least 595 records · Page 33Linked to original sources
PubMed1980

Locomotor activity and catecholamine receptor binding in adult normotensive and spontaneously hypertensive rats.

The binding of 3H-WB 4101, an alpha 1-adrenoceptor antagonist, to membranes of the cerebral cortex, the hypothalamus, and the lower brainstem was examined in adult spontaneously hypertensive (SH) rats and in normotensive Wistar Kyoto (WK) controls. The specific binding of 3H-WB 4101 (0.33 nM) was significantly higher in homogenates from the cerebral cortex of SH rats as compared to WK rats. No differences were detected between SH and WK rats in the specific binding of 3H-spiroperidol (2.25 nM), a dopamine receptor antagonist, to membranes from the corpus striatum and the limbic forebrain. The locomotor activity was significantly higher in SH rats as compared to WK controls, in all probability due to a lack of habituation to environmental change. It is suggested that the high reactivity of SH rats in related to a dysfunction in the noradrenergic neurons in the central nervous system.

Adrenergic alpha-Antagonists↗
PubMed1980

Respiration-linked 'limbic spindles': vibration artifact recorded from nasopharyngeal and intracerebral electrodes.

Respiration-linked 20-40 c/sec spindles were recorded simultaneously from nasopharyngeal, sphenoidal and limbic depth electrodes in 10 patients under evaluation for temporal lobectomy. In addition, a piezo-electrode at the tip of one nasopharyngeal electrode recorded vibration from the nasopharynx in 3 patients. Results demonstrated that respiration-linked 20-40 c/sec spindles recorded from nasopharyngeal and sphenoidal electrodes are vibration artifact. In addition, similar vibration artifact also occurred in the limbic depth, indicating that at least some respiration-linked intracerebrally recorded limbic spindles also are not of neuronal origin.

Electroencephalography↗
PubMed1980

Sleep state and seizure foci related to depth spike activity in patients with temporal lobe epilepsy.

Depth spike activity was evaluated from medial temporal lobe sites using computer spike recognition techniques in all-night sleep records derived from 10 patients with medically refractory complex partial seizures. Sleep stages were classified into 1 of 4 groups: wakefulness, REM sleep, light sleep and deep sleep. Some disturbance in the periodicity of the sleep cycle was noted in most patients, but the relative proportions of REM sleep, light sleep and deep sleep were close to that reported for normals. Depth spike activity was observed to be most frequent in a majority of sites during deep sleep in 6 patients and during light sleep in 3 patients. In 1 patient equal numbers of sites showed maximal activation during light sleep and deep sleep. In 4 patients, certain sites in the more epileptogenic lobe demonstrated a maximal rate during waking or REM sleep. All patients reported in this study were considered to be suitable for temporal lobectomy. In contrast to the results obtained from a previous study, the side with the site demonstrating maximal mean spike rate did not necessarily correspond to the side chosen for lobectomy. Significant correspondence across patients between the more epileptogenic lobe and maximal spike rate was not found during waking and was further reduced during light sleep and deep sleep. The correspondence was, however, significant during REM sleep and for the side containing the site demonstrating the smallest activation in mean spike rate during light sleep or deep sleep relative to waking. These results indicate that an analysis of sleep induced changes in depth spike activity can be useful in improving predictions concerning epileptogenicity. Quantification of other aspects of the interictal EEG, such as background activity, may further improve such predictions.

Adolescent↗
PubMed1980

Evaluation of oxycodone and acetaminophen in treatment of postoperative dental pain.

Although both acetaminophen and oxycodone are commonly used analgesics, they were not available as a combination until recently. Since oxycodone is not available as a single entity, there is no archival or even anectodal information on the efficacy and safety of this combination. The purpose of this study was to evaluate the relative efficacy of various doses of the combination that could be used in dental situations. The single-dose efficacy and safety of acetaminophen 500 mg., oxycodone 5 mg., acetaminophen 500 mg. + oxycodone 5 mg., acetaminophen 1,000 mg. + oxycodone 5 mg., acetaminophen 1,000 mg. + oxycodone 10 mg., and placebo were compared in outpatients who experienced moderate to severe pain after surgical removal of inpacted third molars. Analgesic data were analyzed by analysis of variance and Duncan's multiple range test. All active treatments were superior to placebo, with the high-ratio combination being the most efficacious. This treatment also had the highest incidence of limiting side effects. A positive dose-effect relationship was evident for both acetaminophen 500 mg. and 1,000 mg. and for oxycodone 5 mg. and 10 mg.

Acetaminophen↗
PubMed1980

Kinetics of the cooperative association of T4 tail sheath protein P18 to polysheaths.

The polymerization of the monomeric sheath protein P18 to polysheath was followed by light scattering in 1 mM sodium phosphate buffer, pH 7 at a MgCl2 concentration of 5 mM. Sigmoidal kinetics were observed in the case of spontaneous nucleation. These were well fitted by a mechanism involving a slow nucleation step (rate constant kN = 10(-2) M-1 S-1) followed by propagation steps (k = 10(5) M-1 S-1) in which P18 protomers are added to the ends of the polysheath particles. When sonicated polysheaths or contracted sheaths were added as seeds exponential time courses were observed. From the pseudo first order rate constant and the concentration of seeds the above value for the rate constant of propagation was confirmed. The ability of contracted sheaths to nucleate polysheath formation lends support to the conclusion that polysheaths and contracted sheaths have identical structures and differ in their length distributions only. These were measured from electromicrographs and from the distribution of sedimentation coefficients. Poisson type, kinetically controlled size distributions were found after polymerization of polysheath. An extremely slow redistribution towards an exponential distribution was detected. The spontaneous slow formation of polysheaths is much slower than the formation of extended sheath are core baseplates. Extended sheath is a metastable assembly produce of P18 which either dissociates of contracts to form contracted sheath. Polysheaths and contracted sheaths are extremely stable products but their immediate formation is hindered by high nucleation difficulties.

Kinetics↗
PubMed1980

Assembly of subcomponents C1r and C1s of first component of complement: electron microscopic and ultracentrifugal studies.

Monomeric C1s (Mr, 85,000; s20,w, 4.3S), a subcomponent of first component of complement (C1), the dimer (Mr, 170,000; s20,w, 6.7 S) of C1r, another subcomponent, and the tetrameric complex (C1r,C1s)2 (Mr, 340,000; s20,w, 8.7 S) are elongated molecules. Hydrodynamic equivalents of cylindrical shape have a diameter of 3.3 nm and lengths of 20 nm for C1s, 36 nm for (C1r)2, and 64 nm for (C1r,C1s)2. In electron micrographs the C1r,C1s complex appears as a chain composed of six to eight globular domains with a contour length of 51 nm. A structure is proposed in which (C1r)2 forms a core to which C1s protomers are associated at both ends. The C1 complex (s20,w, 16.3 S) reconstituted from C1q, C1r, and C1s dissociates under the conditions used for electron microscopy. Some features of the C1 complex are revealed in the dissociation products.

Centrifugation, Density Gradient↗
PubMed1980

Choline acetyltransferase for differentiation between human motor and sensory nerve fibers.

A rapid and precise nerve fascicle identification method based on the enzymatic activity of choline acetyltransferase (choline acetylase, or ChAC) is described. Motor nerve facicles demonstrated significantly higher ChAC activity in comparison to sensory nerve facicles. Based on this difference in activity, matching of nerve fascicle cut ends is possible in cases of recent trauma.

Afferent Pathways↗
PubMed1980

Folding mechanism of the triple helix in type-III collagen and type-III pN-collagen. Role of disulfide bridges and peptide bond isomerization.

The kinetics of triple-helix formation in type III pN-collagen, type III collagen and a quarter fragment of type III collagen was followed by optical rotation and circular dichroism. Kinetic intermediates were detected by trypsin digestion and polyacrylamide gel electrophoresis. The end products of refolding at 25 degrees C were identical to the native molecules according to their melting profiles, molecular weights and sedimentation behavior. Only at low temperatures (4-15 degrees C) were mismatched structures of lower stability formed. At 25 degrees C helix formation started exclusively at the set of three disulfide bridges which link the three chains at the carboxy-terminal end. The growth of the triple helix proceeds from this single nucleus at a rather uniform rate in a zipper-like fashion. This gives rise to zero-order kinetics over a large fraction of the conversion. Consequently the time of half conversion is proportional to the length of the molecule. From the appearance and disappearance of intermediates the growth of the triple helix could be observed directly. The rate of helix propagation is determined by the rate of cis leads to trans isomerization of peptide bonds. A model mechanism was devloped which quantitatively described the overall kinetics as well as the time course of the intermediates with a single set of parameters: the rate constant of cis leads to trans isomerization k = 0.015 s-1 and an average number of 30 tripeptide units in uninterrupted stretches of residues with all peptide bonds in trans configuration.

Animals↗
PubMed1980

7-S collagen: characterization of an unusual basement membrane structure.

A new type of collageneous structure, tentatively named 7-S collagen, was isolated from a mouse tumor basement membrane, mouse and human placenta, bovine lens capsule and human kidney. The protein was solubilized from the tissues by limited digestion with pepsin or trypsin and could easily be separated from other collageneous protein because of its resistance towards further degradation by bacterial collagenase at 20 degrees C. 7-S collagen showed an amino acid composition typical of basement membrane collagen and contained 22% carbohydrate mainly as glucosyl-galactosyl bound to hydroxylysine but also some mannose and glucosamine. Ultracentrifugal analysis demonstrated that the proteins were homogeneous with a sedimentation coefficient of about 7.2 S and with a molecular weight of about 360,000 both in phosphate buffer pH 7 and 6 M guanidine. The peptide was triple helical as shown by circular dichroism and exhibited a biphasic melting profile indicating two conformationally distinct domains with tm = 48 degrees C and 70 degrees C. The more stable domain could be isolated as an homogeneous fragment (Mr = 225,000) after a second digestion with collagenase at 37 degrees C. This fragment contained all the disulfide bonds (42 Cys/1,000 residues) of the original molecule. Electron microscopy showed a rod-like structure in agreement with the hydrodynamic properties of 7-S collagen. The dimensions of these peptides were 3 X 95 nm (long form) and 2.4 X 40-50 nm (short form). Complete reduction of 7-S collagen under denaturing conditions produced several polypeptide chains in the molecular weight range of 27,000-153,000 which differ from each other by Mr increments 25,000-27,000. Separation of the chains on agarose did not reveal any simple stoichiometric relationship indicating that some chains are either cross-linked or represent fragments produced during proteolytic treatments. Complete reduction of 7-S collagen under non-denaturing conditions lowered the thermal transiton of the triple helix to 48 degrees C but did not change its molecular weight except when exposed to dissociating solvents. 7-S collagens were potent immunogens and could be characterized by radioimmunoassays. Antigenicity was slightly reduced by reduction and denaturation while collagenase at 37 degrees C produced a larger decrease. Proteins obtained from various sources showed distinct immunological relationships although interspecies differences in affinity exist. No or only little cross-reaction was observed with type IV and V collagens and some further fragments of basement membrane collagen. The data indicate that 7-S collagen is a unique component of basement membranes which shows a more compact and stable structure than other collageneous proteins.

Amino Acids↗
PubMed1980

Catecholamine concentration in the developing rat brain after gamma-hydroxybutyric acid.

The effect of the GABA receptor agonist gamma-hydroxybutyric acid (GHBA) on brain catecholamine concentration was investigated in 1 to 28 day old rats. The infant rats were given GHBA in various doses (375--1500 mg/kg) and the effects on whole brain or regional brain concentration of dopamine (DA) and noradrenaline (NA) were measured. Brain DA concentration increased in a dose-dependent way already from two days of postnatal age. In the regional brain study of the 14- and 28-day-old animals the increase in DA concentration was found to be almost exclusively located in the striatal region. Generally, no changes in NA concentration were found in the whole brain or various brain regions at any of the ages after GHBA. It is concluded that the inhibitory striatal-nigral neurons, utilizing GABA as a transmitter, are functionally developed during early postnatal age.

Aging↗
PubMed1980

Persistent dislocation of the shoulder in elderly patients.

Four elderly patients with longstanding unrecognized dislocation of the shoulder were treated by physiotherapy only. Good functional results, associated with a greatly increased range of pain-free motion, demonstrate the usefulness of conservative treatment in cases of persistent dislocation of the shoulder in the elderly.

Aged↗
PubMed1980

Anterior transposition of the ulnar nerve.

Twenty-four patients with 26 ulnar neuropathies in the elbow region were treated by anterior transposition of the ulnar nerve. The dominant arm was involved in 14 of these patients. Improvement of paresthesia was found in 17 out of 21 (75 per cent) in this series of patients; 10 out of 18 (55 per cent) had improvement of sensation; 7 out of 14 (50 per cent) had less pain; 10 out of 14 (71 per cent) showed an increase in motor power, but only 2 out of 12 patients (16 per cent) with long-standing muscle atrophy showed any improvement in their condition. Electromyographic studies (EMG) were carried out before and after operation. The postoperative studies revealed increased motor conduction velocity within the elbow segment of the ulnar nerve in 15 patients. Slowing in ulnar nerve conduction velocity was found in 3 patients, and in 8 the EMG remained unchanged. Our EMG series indicated that patients with a conduction velocity of less than 40 m/s will certainly benefit more from anterior transposition of the ulnar nerve than will patients whose measurements are within the normal range.

Adult↗