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Biomedical subjects

J Engel

Publications and source records attributed to J Engel.

At least 379 records · Page 21Linked to original sources
PubMed1990

Presurgical evaluation for partial epilepsy: relative contributions of chronic depth-electrode recordings versus FDG-PET and scalp-sphenoidal ictal EEG.

One hundred fifty-three patients with medically refractory partial epilepsy underwent chronic stereotactic depth-electrode EEG (SEEG) evaluations after being studied by positron emission tomography (PET) with 18F-fluorodeoxyglucose (FDG) and scalp-sphenoidal EEG telemetry. We carried out retrospective standardized reviews of local cerebral metabolism and scalp-sphenoidal ictal onsets to determine when SEEG recordings revealed additional useful information. FDG-PET localization was misleading in only 3 patients with temporal lobe SEEG ictal onsets for whom extratemporal or contralateral hypometabolism could be attributed to obvious nonepileptic structural defects. Two patients with predominantly temporal hypometabolism may have had frontal epileptogenic regions, but ultimate localization remains uncertain. Scalp-sphenoidal ictal onsets were misleading in 5 patients. For 37 patients with congruent focal scalp-sphenoidal ictal onsets and temporal hypometabolic zones, SEEG recordings never demonstrated extratemporal or contralateral epileptogenic regions; however, 3 of these patients had nondiagnostic SEEG evaluations. The results of subsequent subdural grid recordings indicated that at least 1 of these patients may have been denied beneficial surgery as a result of an equivocal SEEG evaluation. Weighing risks and benefits, it is concluded that anterior temporal lobectomy is justified without chronic intracranial recording when specific criteria for focal scalp-sphenoidal ictal EEG onsets are met, localized hypometabolism predominantly involves the same temporal lobe, and no other conflicting information has been obtained from additional tests of focal functional deficit, structural imaging, or seizure semiology.

Adolescent↗
PubMed1990

Stereotactic investigation of limbic epilepsy using a multimodal image analysis system. Technical note.

A methodology has been developed for stereotactic investigation of limbic epilepsy using an image-analysis system that simultaneously displays different structural and functional images of the brain. The validity and accuracy of this system were established with phantom studies. Surgical planning and electrode implantation are guided by stereotactic magnetic resonance imaging, digital subtraction angiography, and position emission tomography. This methodology provides the spatiotemporal relationship of cerebral structure and function necessary to identify seizure onset and propagation in human limbic system epilepsy.

Brain Mapping↗
PubMed1990

Nuclear magnetic resonance spectra and molecular structure of mesna.

Mesna (2-mercapto-ethane sulfonic acid sodium salt) is used as a reliably acting uroprotector in cancer chemotherapy with oxazaphosphorine cytostatics. 1H-, 13C[1H]- and C,H-COSY-NMR-spectra are analyzed. In solution state mesna exists predominantly in a trans-rotameric form. These findings are supported by hypothetical gas-phase-structures of mesna, simulated via the program system MOPAC.

Magnetic Resonance Spectroscopy↗
PubMed1990

[Epidemiology of basketball injuries].

The players of an elite basketball team were followed during the course of a season which included 71 games and 250 training sessions. All injuries were noted and were correlated with age, height and other physical parameters of the players, as well as with degree of fatigue during games and during training sessions. The lower extremity was the most common site of injury. Ligamentous injuries of the knee are more common in basketball than in soccer players, but they have fewer meniscal injuries than the latter. However, the upper extremity, especially the hand, is more frequently injured in basketball than in other sports. The age, height and personality of the player affect the injury pattern.

Arm Injuries↗
PubMed1990

Physiochemical features of monoclonal idiotype-anti-idiotype complexes: importance of inter-chain disulfides for size distribution patterns and molecular geometries.

Cyclic tetramers represent the preferentially formed complexes of a murine monoclonal idiotype-anti-idiotype (Id-anti-Id) system consisting of IgG antibodies or (Fab')2 fragments at micromolar concentrations. The cleavage of inter-chain disulfides of both Id and anti-Id caused the predominant generation of cyclic dimers at the expense of larger aggregates, suggesting with regard to already published data that the hinge located interheavy-chain disulfides are essential for the strain.

Antibodies, Anti-Idiotypic↗
PubMed1989

Dissection of laminin by cathepsin G into its long-arm and short-arm structures and localization of regions involved in calcium dependent stabilization and self-association.

Native laminin-nidogen complex isolated from mouse Engelbreth-Holm-Swarm tumor was treated with purified cathepsin G or leucocyte elastase, two neutral serine proteases which play a role in inflammatory processes accompanied by degradation of basement membranes. Both enzymes were found to be more active than porcine pancreatic elastase. In the absence of Ca2+, laminin fragments produced by leucocyte elastase resembled those formed by the pancreatic enzyme but at physiological concentrations of Ca2+ cleavage by cathepsin G was much more selective. Initially laminin (900 kDa) was cleaved at two major sites only with similar rates leading to three fragments. Fragment C1-4 (about 550 kDa) comprises the intact three short arms of the molecule and fragment C8-9 (about 350 kDa) contains the entire triple-coiled region by which its three chains are assembled and the major part of the terminal globular domain of the long arm. The remaining C-terminal region of this domain was recovered as fragment C3 of about 50 kDa. Stabilization against proteolytic attack was restricted to the region of fragment C1-4 and only this fragment exhibited strong Ca2+ dependent self-association similar to that of intact laminin or of its complex with nidogen. The associative properties of fragment C1-4 were dramatically diminished upon removal of the tip of one of the short arms comprising fragment 4. In addition, this provides a clear assignment of the important laminin function to a distinct domain in one of its short arms. The new fragment C8-9 may be employed for exploring the properties and possible functions of the upper long-arm region which so far has not been available as a fragment.

Animals↗
PubMed1989

Hyperosmotic relaxation lysis of chromaffin granules is caused by interactions between the granular membrane and intragranular vesicles.

Bovine chromaffin granules undergo irreversible structural changes during osmotic shrinkage in hypertonic sucrose and salt solutions, such that, on reexposure to isoosmotic conditions they do not regain their original morphology, but undergo lysis ('hyperosmotic relaxation lysis'). Irreversible alterations of granules were induced by hypertonic incubations lasting for as little as 1 min. Fluorescence and EPR membrane labelling experiments showed that hypertonicity did not induce membrane loss for instance by inwardly or outwardly directed pinching off of membrane material. The mean sizes of chromaffin granules as a function of increasing and subsequently decreasing osmotic pressure were measured by photon correlation spectroscopy; there was no significant difference in sizes of hyperosmotically pretreated granules as compared with controls. Freeze-fracture electron micrographs showed the formation of 'twins' and 'triplets' under hypertonic conditions. They also revealed intragranular vesicles of 50-200 nm in diameter in both hypertonically and isotonically suspended granules. 'Twin' and 'triplet' granules were formed by the attachment of intragranular vesicles to the granule membranes. We suggest that hyperosmotic relaxation lysis is caused by the fact that this adhesion partly prevents the granule membrane from reexpanding, thus, leading to its rupture.

Animals↗
PubMed1989

EGF-like domains in extracellular matrix proteins: localized signals for growth and differentiation?

Multidomain proteins of the extracellular matrix (ECM) play an important role in development and maintenance of cellular organization and in tissue repair. Several ECM proteins such as laminin, tenascin and thrombospondin contain domains with homology to epidermal growth factor (EGF) and exhibit growth promoting activity. The mitogenic activity of laminin is restricted to a fragment which consists of about 25 repeating domains with partial homology to EGF and comprises the rod-like inner regions of the three short arms of the four armed molecule. The mitogenic activity does not correlate with promotion of cell attachment and neurite outgrowth for which major functional sites have been found in other regions of the laminin molecule. It is suggested that EGF-like domains in laminin, in other ECM proteins and in the extracellular portions of some membrane proteins are signals for cellular growth and differentiation. Because they are integral parts of large molecules and often of supramolecular assemblies these domains are well suited to stimulate neighboring cells in a specific and vectorial way. This concept of localized growth or differentiation signals offers an attractive mechanism for the regulation of cellular development.

Amino Acid Sequence↗
PubMed1989

Domains of laminin with growth-factor activity.

Laminin and fragments (1, 1-4) containing the inner rod-like segments from its short arms, which consist of cysteine-rich, "EGF-like" repeats, stimulated thymidine incorporation in cultured cells possessing EGF receptors but had no effect on a cell line lacking this receptor. The response was comparable to that of EGF concerning effective concentrations, magnitude, time dependence, and synergistic enhancement by insulin. Other fragments (4 and 8) were inactive. Laminin and its active fragments could not compete with the binding of EGF to cells. There was no correlation between growth promotion and attachment of cells to a high affinity binding site present on laminin fragment 8. The data indicate that mitogenic effects induced by laminin and EGF proceed in some steps via related pathways and that different domains of laminin are involved in growth promotion and in adhesion and spreading of cells.

Amino Acid Sequence↗
PubMed1989

Memory following intracarotid amobarbital injection contralateral to hippocampal damage.

We examined the relationship between memory performance and hippocampal damage in temporal lobe epileptics undergoing the intracarotid amobarbital sodium procedure (IAP). Overall memory performance in the course of IAP was correlated with seizure lateralization. The hemisphere of seizure focus had impaired IAP memory in 63% (19/30) of the patients. The IAP memory performance following perfusion of the hemisphere contralateral to severe hippocampal lesions was impaired in five of six patients. These patients also exhibited hypometabolism of the impaired temporal lobe as determined independently by positron emission tomography. The single patient with a severely damaged hippocampus who did not demonstrate IAP memory impairment with contralateral hemisphere injection did not exhibit perfusion of the ipsilateral posterior cerebral artery with amobarbital. Memory performance following intracarotid amobarbital injection contralateral to a less severely damaged hippocampus was impaired in 14 of 24 patients and was not related to extent of hippocampal damage, temporal lobe hypometabolism of labeled glucose, perfusion of the ipsilateral posterior cerebral artery, hemispheric language dominance, or order of injection. These results indicate that impaired memory performance during IAP may reflect severe hippocampal damage and/or epileptogenic abnormality.

Adult↗
PubMed1989

Tumor inhibiting properties of stereoisomeric [1,2-bis(3-hydroxyphenyl)ethylenediamine]dichloroplatinum(II)-compl exe s, Part I: Synthesis.

The synthesis of the stereoisomeric 1,2-bis(3-hydroxyphenyl)ethylenediamines (1-4) from meso-1,2-bis(2-hydroxyphenyl)ethylenediamine and 3-methoxybenzaldehyde by a diaza-Cope-rearrangement and subsequent ether cleavage with BBr3 and their conversion into the [1,2-bis(3-hydroxyphenyl)ethylenediamine]dichloroplatinum(II)-complexes with K2PtCl4 (1-PtCl2 - 4-PtCl2) is described.

Antineoplastic Agents↗
PubMed1989

Tumor inhibiting properties of stereoisomeric [1,2-bis(3-hydroxyphenyl) ethylenediamine]dichloroplatinum(II)-complexes, Part II: Biological properties.

The activity of stereoisomeric [1,2-bis(3-hydroxyphenyl)ethylenediamine] dichloroplatinum(II)-complexes (1-PtCl2,R,S; 2-PtCl2, R,R/S,S; 3-PtCl2, R,R; 4-PtCl2, S,S) on several tumor models (MDA-MB 231 breast cancer cell line; P 388 leukemia, mouse; L 1210 leukemia, mouse; L 5222 leukemia, rat; Ehrlich ascites tumor, mouse--wildtype; cisplatin-, etoposide-, cyclophosphamide-, and daunomycin-resistant, resp.) is described. For comparison the analogous [1,2-bis(4-hydroxyphenyl)ethylendiamine]dichloroplatinum (II)-complexes (5-PtCl2, R, S; 6-PtCl2, R,R/S,S; 7-PtCl2, R,R; 8-PtCl2, S,S) and cisplatin are used. 1-PtCl2 to 4-PtCl2 (OH in 3,3'-positions) show their maximum antitumor effect at lower doses than 5-PtCl2 to 8-PtCl2 (OH in 4,4'-positions). 2-PtCl2 and 6-PtCl2 (R,R/S,S) are more active than 1-PtCl2 and 5-PtCl2 (R,S). 4-PtCl2 and 8-PtCl2 (S,S) are superior to 3-PtCl2 and 7-PtCl2 (R,R). On the L 5222 leukemia 2-PtCl2 (R,R/S,S), 4-PtCl2 (S,S) and 8-PtCl2 (S,S) markedly surpass cisplatin. Strong effects are produced by 2-PtCl2 to 4-PtCl2 on the Ehrlich ascites tumor (wildtype, cisplatin-, etoposide-, cyclophosphamide-, and daunomycin-resistant, resp.). The combination of 4-PtCl2 with cisplatin results in a weakly synergistic effect.

Animals↗
PubMed1989

Surgical treatment of epilepsy: opportunities for research into basic mechanisms of human brain function.

Numerous technological developments in neurology have increased the ability to localize structural and functional abnormalities within the human brain. Such techniques have contributed to a renewed interest in resective surgical treatment for medically refractory partial seizures. Enhanced capacity to carry out detailed in vivo and in vitro measurements of neuronal activity in patients, during the course of presurgical evaluation and following surgical resection, now offers unprecedented opportunities for invasive research into normal and abnormal human cerebral function. Electrophysiological, microanatomical, biochemical and behavioral studies can be carried out without presenting undue risk or discomfort to the patient. Such research in a clinical setting presents difficulties in experimental design for the basic neuroscientist. Problems are reduced in clinical programs where diagnostic and surgical procedures are carried out in a standardized fashion according to specific protocols. The UCLA clinical protocol for anterior temporal lobectomy, based on presurgical evaluation with stereotactically implanted depth electrodes, is particularly amenable to the integration of basic research projects. This protocol and related ongoing research projects are described.

Brain Mapping↗
PubMed1989

Ester derivatives of the mammary-tumor-inhibiting antiestrogen 2,3-bis(2-fluoro-4-hydroxyphenyl)-2,3-dimethylbutane.

The synthesis of the bisacetate (8), the bisdichloroacetate (9), the biscarbamate (10) and the bisphosphate (11) of the "partial" antiestrogen 2,3-bis(2-fluoro-4-hydroxyphenyl)-2,3-dimethylbutane (7) is described. In the case of 8-10 the introduction of ester functions slightly reduces the estrogen receptor affinity of 7. However, it was strongly diminished in 11. Compared with 7 the estrogenic potency of 8-11 is moderately increased. Compounds 8-11 cause a strong inhibition of the hormone-dependent MXT M3.2 mouse mammary tumor. Only 9 containing cytotoxic dichloroacetate groups shows a significantly better antitumor effect than 7.

Animals↗