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Biomedical subjects

J Engel

Publications and source records attributed to J Engel.

At least 451 records · Page 25Linked to original sources
PubMed1986

Functional model of subcomponent C1 of human complement.

The domain organization of the zymogen subunits of the first component of human complement C1s, C1r2 and the complex C1s-C1r2-C1s was studied by electron microscopy. In the absence of Ca2+, monomeric C1s was visualized as a dumb-bell-shaped molecule consisting of two globular domains (center-to-center distance 11 nm) connected by a rod. One of the globular domains is assigned to the light chain (B-chain) of the activated molecule, which is homologous to trypsin and other serine proteases. The second globular domain and the rod are assigned to the heavy chain (A-chain) of CIs. The subunit C1r is a stable dimer in the presence or absence of Ca2+. This dimer C1r2 was visualized as composed of two dumb-bells of dimensions similar to those observed for C1s. These are connected near the junctions between the rod and one of the globular domains. This leads to the structure of an asymmetrical X with two inner closely spaced globules (center-to-center distance 7 nm) and two outer globules at a larger distance (14 nm). By comparison with fragment C1rII2, in which part of the A-chain is removed, the inner globular domains were assigned to the catalytic B-chains. This characteristic structure of C1r2 is readily recognized in the central portion of the thread-like 54 nm long C1s-C1r2-C1s complex formed in the presence of Ca2+. By affinity-labeling of C1s with biotin and visualization of avidin-ferritin conjugates in the reconstituted complex, it was demonstrated that C1s forms the outer portion of the complex. A detailed model of C1s-C1r2-C1s is proposed, according to which two C1s monomers bind to the outer globes of C1r2 by contacts between their heavy chains and those of C1r. According to this model the catalytic domains of C1r are located in the center and those of C1s at the very tips of the C1s-C1r2-C1s complex. On the basis of the structure of C1s-C1r2-C1s, we derived a detailed model of the C1 complex (composed of C1q and the tetrameric complex) and we discuss this model with a view to finding a possible activation mechanism of C1.(ABSTRACT TRUNCATED AT 400 WORDS)

Complement Activating Enzymes↗
PubMed1986

Purification and structural characterization of intact and fragmented nidogen obtained from a tumor basement membrane.

Extraction of a basement-membrane-producing mouse tumor with 6 M guanidine/HCl in the presence of protease inhibitors allowed the purification of the genuine form of the matrix protein nidogen (Mr = 150,000) and, in addition, two defined fragments (Mr = 130,000 and 100,000). Smaller fragments (Mr = 80,000 and 40,000) were obtained under conditions with less stringent control of endogenous proteolysis. Intact nidogen and the larger fragments were similar in amino acid and carbohydrate (about 5%) composition, the presence of a single polypeptide chain, conformational features as revealed by CD spectroscopy and all shared major epitopes located on the Mr = 80,000 fragment. Additional epitopes were found on intact nidogen and the Mr = 130,000 fragment. Nidogen and the various fragments possess different N-terminal amino acid sequences indicating a stepwise degradation from the N-terminal end of the molecule. Electron microscopical and hydrodynamic studies of the Mr = 80,000 fragment demonstrated a structure consisting of a globular head connected to a thin tail. Intact nidogen appears to contain a somewhat larger globule but the same tail, which is terminated at its opposite end by a second, smaller globular structure. The data suggest a multidomain structure for nidogen containing sites highly susceptible to proteolytic cleavage.

Amino Acids↗
PubMed1986

Structure and function of basement membrane proteoglycans.

Basement membranes contain at least three different proteoglycans. These are a large, low buoyant density heparan sulphate proteoglycan and two smaller, high density proteoglycans with either heparan sulphate or chondroitin sulphate side-chains. The large (Mr 400K-600K and small (Mr 130K) heparan sulphate proteoglycans were purified from the mouse EHS tumour. These proteoglycans are immunologically related by sharing some protein core antigenic determinants (epitopes) but do not cross-react with cell-surface heparan sulphate proteoglycans or with proteoglycans from interstitial connective tissue. This indicates that they belong to a distinct family of proteoglycans. Structural models were developed, based on electron microscopy and analytical ultracentrifugation, demonstrating that the small proteoglycan contains on average four heparan sulphate chains of about 30 nm in length, while the large proteoglycan consists of three long (about 90 nm) heparan sulphate chains connected to one end of a large core protein. Single heparan sulphate chains were isolated from the EHS tumour proteoglycans and from the corresponding proteoglycans from Reichert's membrane of the mouse embryo. The heparan sulphate from Reichert's membrane bound to antithrombin with high affinity and was found to contain the unique 3-O-sulphated glucosamine residue previously identified in the antithrombin-binding region of heparin. The EHS tumour heparan sulphate showed a higher N-/O-sulphate ratio and a lower affinity for antithrombin.

Animals↗
PubMed1986

Magnetic resonance imaging in intractable partial epilepsy: correlative studies.

A study was performed evaluating magnetic resonance imaging (MRI) in 35 patients with intractable complex partial seizures in whom computed tomographic (CT) scans showed no focal abnormalities. These results were correlated with positron emission tomography evaluation (PET), the electroencephalographic ictal onset, and findings during pathological examination. Seven patients had structural lesions that were epileptogenic, detected by MRI; the lesions were tuberous sclerosis, astrocytomas, or hamartomas. Three of these 7 patients underwent PET scanning, which was normal in all. Of 18 patients with mesial temporal sclerosis, 10 were shown by PET to have temporal lobe hypometabolism, though all 18 had normal MRI findings. The results indicate that MRI contributes information to that provided by CT and PET, by detecting nonsclerotic epileptogenic lesions of the temporal lobe.

Astrocytoma↗
PubMed1986

Prolactin in partial epilepsy: an indicator of limbic seizures.

A study was performed to evaluate changes in serum prolactin levels after simple and complex partial seizures, and to identify which specific anatomical structures must be involved in seizures for postictal elevation of prolactin levels to occur. Seventy-eight seizures were studied in patients with electrodes implanted bilaterally into amygdala, hippocampus, hippocampal gyrus, and frontal sites. All 38 complex partial seizures had bilateral limbic ictal discharges, and each was followed by a significant increase in prolactin concentration (mean peak, 50.8 ng/ml; range, 16.0 to 150.0 ng/ml). Eight of 10 simple partial seizures with unilateral high-frequency regional limbic discharges were followed by prolactin elevation (mean peak, 28.2 ng/ml; range, 13.4 to 44 ng/ml). Thirty simple partial seizures with other ictal limbic discharges or without limbic discharges were not followed by an elevated prolactin level. The data indicate that serum prolactin levels always rise after complex partial seizures involving the temporal lobes, and rise after certain simple partial seizures involving limbic structures. Thus, measurement of the prolactin level can help identify which simple partial seizures involve mesial temporal lobe structures. Limbic structures serve to trigger prolactin release, which may depend upon spread of the seizure to subcortical structures.

Electroencephalography↗
PubMed1986

Visual versus computer evaluation of thiopental-induced EEG changes in temporal lobe epilepsy.

Thiopental-induced EEG beta activity was analyzed both visually and by computer in 33 patients with complex partial epilepsy. Studies were done in 16 patients with depth electrodes in limbic structures and 17 patients with scalp and sphenoidal electrodes. The percentage of drug-induced change in beta activity was quantified by computer using spectral analysis. The statistical significance of asymmetries between homologous sites in the amount of change was determined. The spatial distribution of significant asymmetries was used for localization and compared with the results of independent visual analysis of the thiopental EEG. Concordance between computer and visual evaluation occurred in 10 of 17 scalp/sphenoidal and 10 of 16 depth electrode tests. The accuracy of visual and computer localization was determined by comparing them with locus of itcal EEG onset, interictal spikes, and positron emission tomography. In scalp/sphenoidal studies, computer analysis indicating asymmetry appeared more likely to correlate with independent clinical criteria than visual analysis. In depth studies the reverse appeared to be true. Scalp/sphenoidal tests yielded positive results in 25-30% of patients whereas depth electrode tests were positive in 50-70% of patients. The results indicate that computer analysis of surface thiopental tests is an accurate and useful supplement to visual evaluation of these tests.

Brain↗
PubMed1986

Mefenorex (Rondimen).

Mefenorex, N-(3-chloropropyl)-alpha-methylphenethylamine, (RONDIMEN), is included in the list of centrally acting stimulants and/or hallucinogens or related compounds to be considered by a World Health Organization (WHO) Expert Committee in 1985 for possible scheduling under the Convention on Psychotropic Substances, 1971. The therapeutic efficacy of mefenorex as an adjunctive support in the treatment of obesity for limited periods of time, as well as its ability to be well tolerated, has been amply demonstrated. There have been no reports of actual abuse. There have been no reports of illicit trafficking, falsification of packages or materials, or clandestine laboratories manufacturing the compound. Data from preclinical and clinical studies do not suggest a potential for abuse similar to that of amphetamine or related compounds. Moreover, the lack of pulmonary hypertension with mefenorex has been demonstrated in both preclinical and clinical studies. There have been no reports of any public health or social problems associated with mefenorex use. The compound is a well-tolerated anorectic agent with little central stimulant activity.

Adult↗
PubMed1986

Rupture of extensor digitorum communis after distal ulnar styloidectomy.

Attrition ruptures of tendons in the hand, other than those caused by rheumatoid arthritis, are rare. We report a case in which high styloidectomy of the distal ulna caused the rupture of the extensor digitorum communis tendon to the long finger. This complication can be avoided by resection of the smallest segment of the distal ulna that is compatible with relief of the problem. Soft tissue closure over the resected end of the ulna should also be carried out.

Adult↗
PubMed1986

An epidemiological study of lateral epicondylitis (tennis elbow) in amateur male players.

Our epidemiological study investigated lateral epicondylitis (tennis elbow) among 150 nonprofessional male tennis players (75% of the players approached consecutively) interviewed and examined physically at four local tennis clubs. The interview and examination covered over sixty possible risk factors, including demographic data, playing habits, anatomical measurements and racket characteristics. The "average" painfree player is 38 years old, has played tennis 11 years, and plays 5.5 hours a week, usually with a racket whose head area is 570 cm2. The "average" tennis elbow sufferer is a 45-year-old player who has been playing 16 years and has played 8 hours weekly before onset of pain with a racket whose head area is 613 cm2. Multivariate analysis indicated that number of playing years has no independent effect beyond its association with age. Playing hours per week, current age and age at pain onset have independent significant effects on number of pain episodes (0-7). Weekly number of playing hours is the best predictor of pain category (none, one or more currently or in the past).

Adult↗
PubMed1986

Peripheral nerve injection injury: an experimental pilot study of treatment modalities.

The accidental injection of various drugs into peripheral nerves has serious medical complications and medicolegal implications. The most neurotoxic substances of II agents tested in a previous study were penicillin G, diazepam, and chlorpromazine. The appropriate management of such an injury has not been well-established. In an attempt to define the proper treatment in accidental peripheral nerve injection, an experimental study was carried out, in which 70 sciatic nerves of rats were injected intrafascicularly with penicillin G and treated by neurolysis, neurolysis and Celestone irrigation (betamethasone, a synthetic glucocorticoid), and neurolysis and saline irrigation. The degree of damage was evaluated histologically after two weeks. Statistical analysis of the results showed that neurolysis performed at 24 hours after the injury lessened the damage to the peripheral nerve. No additional improvement was found when, in addition to neurolysis, the nerves were irrigated with Celestone or saline solutions.

Animals↗
PubMed1986

Neurobiology of behavior: anatomic and physiological implications related to epilepsy.

Controversy exists concerning whether epileptic seizures can produce enduring alterations in neuronal function that cause interictal behavioral disturbances. Although arguments favoring the occurrence of epilepsy-induced disorders of behavior must not be presented in a way that adds to the stigmata associated with epilepsy, it is not in the best interest of epileptic patients to deny this possible relationship and overlook an opportunity to prevent or treat a major cause of disability. There is evidence to suggest that psychosocial factors cannot account for all the behavioral problems suffered by patients with epilepsy. Behavioral disturbances ascribed to antiepileptic drugs and specific structural lesions may also be due, in part, to epileptogenic mechanisms. Some interictal behavioral disturbances may actually reflect unrecognized ictal events. Most importantly, data obtained from clinical research and animal investigations suggest testable hypotheses of how recurrent epileptic seizures can alter neuronal function in ways that would predispose to specific disruptive interictal behaviors, such as aggression, depression and schizophrenia.

Aggression↗
PubMed1986

Surgery for epilepsy: a review.

This year marks the centennial of the first surgical resection for epilepsy performed by Horsley. While epilepsy is generally considered a disease best treated with anticonvulsant medications, surgical therapy is of significant benefit to some patients in whom medical therapy has proved ineffective. Anterior temporal lobectomy has been the single most successful operation commonly performed today. In this paper we review current techniques of preoperative evaluation, the role of scalp and intracranial electrophysiologic monitoring, as well as the contribution of PET and MRI scanning to improving the selection of patients for surgical therapy. The role of focal cortical excisions, hemispherectomy, and corpus callosotomy in the surgical armamentarium is also outlined. A plea is made for establishment of additional regionalized centers for epilepsy surgery in which close collaboration among neurologists, neuropsychologists, neurosurgeons and neurophysiologists can enhance patient care and advance our knowledge of the partial epilepsies and human cerebral function.

Corpus Callosum↗
PubMed1986

Subclinical brachial plexopathy following median sternotomy.

In order to detect subclinical cases of brachial plexus injury following open heart surgery through median sternotomy, 15 patients were included in this prospective study. Physical and electrophysiologic examinations were performed preoperatively and postoperatively. The axillary F-loop latency was used to diagnose the brachial plexopathy. No clinical symptoms were found in this group postoperatively. Of the 15 patients, 13 (87%) were found to have a postoperative subclinical brachial plexopathy, at least on one side, and in eight of the patients, it was present on both sides.

Adult↗
PubMed1986

Intraoperative identification of peripheral nerve fascicle. Use of a new rapid biochemical assay technique.

An original nerve-identification technique based on the enzymatic activity of choline acetylase enables precise differentiation between motor nerve fascicles and sensory nerve fascicles. Within 70 to 80 minutes, an accurate matching of cut nerve ends is possible, both in recent and in late nerve injuries. Preliminary results of the clinical intraoperative application of this method are encouraging.

Choline O-Acetyltransferase↗