Search PubMed⌕ Search

Biomedical subjects

J Engel

Publications and source records attributed to J Engel.

At least 487 records · Page 27Linked to original sources
PubMed1985

Different susceptibility of inter- and intra-chain disulfide bonds to reductive cleavage in native fibronectin and effect of their cleavage on conformation.

The two thread-like subunits (Mr approximately equal to 250 000) of the multidomain protein fibronectin are connected by a pair of inter-chain disulfide bridges in their C-terminal regions. In addition each chain contains 29 intra-chain disulfide bonds which are located in 12 type I and 2 type II structural domains in the N-terminal and C-terminal regions of the strands. The 15 to 17 type III domains in the central portion of the strands do not contain disulfide bonds. The susceptibility of inter-chain disulfide bonds to 10mM 1,4-dithiothreitol at pH 7.8 as quantitated by the rate of reductive cleavage of fibronectin into its subunits was found to be only 8-fold larger than that of the intra-chain bonds. Consequently at 90% completion of chain separation 30% of the intra-chain disulfides are also cleaved. The rate of inter-chain disulfide cleavage was found to be identical for fibronectin and a 140-kDa fragment comprising the C-terminal portions of the two subunits. This shows that the relatively high protection of the inter-chain disulfide bonds must originate from interactions between C-terminal domains which are probably also responsible for the V shaped arrangement of the two subunit strands. Changes of circular dichroism and thermal transition profiles for fibronectin and its C-terminal 140-kDa fragment indicated that already partial reduction of the intra-chain disulfide bonds alters the conformations of type I and II domains without affecting the type III domains.(ABSTRACT TRUNCATED AT 250 WORDS)

Circular Dichroism↗
PubMed1985

[Acetobacter methanolicus--a new organism for genetic studies].

A new bacterial strain is described belonging to Acetobacter methanolicus species. It is of industrial value as a producer of protein and methanol products. The strain is acidophile and this feature comprises a conspicuous technological advantage. The results of bacteriophage and cell interactions are reported. They might be potentially useful for elaboration of the transduction technique for the strain. The collection of mutants was obtained including those utilizing methanol, having auxotrophic markers as well as streptomycin and rifampicin resistances. The transfer of plasmids RSF1010 and R68 to Acetobacter methanolicus from other bacteria has been demonstrated.

Acetobacter↗
PubMed1985

Monitoring at the University of California, Los Angeles.

Long-term EEG monitoring with radio or cable telemetry and video recording can be performed efficiently as an organized team effort involving physicians, nurses, technologists and other ancillary personnel. We use telemetry primarily for screening patients for possible surgical treatment of partial epilepsy. The technique is also used occasionally to define better the patient's type(s) of seizures or to differentiate seizures from pseudoseizures. Important technical points include precise correlation of EEG with clinical events, choice of recording montage, use of a 1 Hz low filter, and use of sphenoidal electrodes. Patients may need to be stressed, exercised or have medications reduced to bring about a sufficient number of seizures during monitoring. Care is needed to avoid or to identify atypical seizures due to medication withdrawal.

California↗
PubMed1984

Domain structure of cartilage proteoglycans revealed by rotary shadowing of intact and fragmented molecules.

The rotary-shadowing technique for molecular electron microscopy was used to study cartilage proteoglycan structure. The high resolution of the method allowed demonstration of two distinct globular domains as well as a more strand-like portion in the core protein of large aggregating proteoglycans. Studies of proteoglycan aggregates and fragments showed that the globular domains represent the part of the proteoglycans that binds to the hyaluronic acid, i.e. the hyaluronic acid-binding region juxtapositioned to the keratan sulphate-attachment region. The strand-like portion represents the chondroitin sulphate-attachment region. Low-Mr proteoglycans from cartilage could be seen as a globule connected to one or two side-chain filaments of chondroitin sulphate.

Animals↗
PubMed1984

Structure and interactions of heparan sulfate proteoglycans from a mouse tumor basement membrane.

Various forms of heparan sulfate proteoglycan were solubilized from the mouse Engelbreth-Holm-Swarm (EHS) sarcoma by extraction with 0.5 M NaCl, collagenase digestion and extraction with 4 M guanidine. They could be separated into high (greater than or equal to 1.65 g/ml) and low (1.38 g/ml) buoyant density variants. The high-density form from the NaCl extract and collagenase digest had Mr = 130000 and So20,W = 4.5 S and contained 4-10% protein, indicating Mr = 5 000-12 000 for the protein core. This proteoglycan exhibited polydispersity as shown by rotary shadowing electron microscopy and ultracentrifugation. An average molecule consisted of four heparan sulfate chains (Mr = 29 000) each with a length of 32 +/- 10 nm. The low-density form (Mr about 400 000) could not be completely purified and contained about 50% protein. As shown by radioimmunoassay, the various proteoglycans shared similar protein cores. Labeling of the tumor in vivo or in vitro demonstrated preferential incorporation of radioactive sulfate in the high-density form. The high-density proteoglycan interacted in affinity chromatography by virtue of its heparan sulfate chains with laminin, fibronectin, the globular domain NC1 and the triple helix of collagen IV. These interactions were abolished at moderate concentrations of NaCl (0.1-0.2 M) and in the presence of heparin, chondroitin sulfate or dextran sulfate. Interactions with the globule NC1 could also be demonstrated by velocity band centrifugation in sucrose gradients and a binding constant of about 10(6) M-1 was derived.

Animals↗
PubMed1984

Subunit structure and assembly of the globular domain of basement-membrane collagen type IV.

The globular domain of collagen IV was solubilized by collagenase digestion from a mouse tumor, human placenta and bovine aorta and was purified by chromatographic methods. The materials show a unique, mainly non-collagenous amino acid composition and contain small amounts of glucosamine and galactosamine. The globular structures with Mr = 170 000 appear as a hexameric assembly originating from two collagen IV molecules. Subunits of this assembly are two different dimers Da and Db (Mr about 56 000) and monomers (Mr = 28 000). Their N-terminal amino acid sequences start with short triple-helical sequences, which overlap with the C-terminal triple helix of the alpha 1(IV) and alpha 2(IV) chain, demonstrating that the globule originates from the C terminus of collagen IV. Dimers arise from monomers by disulfide cross-linking (form Db) and/or formation of non-reducible cross-links (form Da). Reduction under non-denaturing conditions causes partial dissociation of the globule and of collagen IV dimers, indicating that reducible cross-links are formed between monomers of two different collagen IV molecules. Dissociation of the hexamer into the subunits can be achieved with 8 M urea, sodium dodecyl sulfate or in the pH range 2.5-4. The latter indicates that carboxyl groups are essential for association. Mixtures of the subunits (monomers and dimers) or purified dimers reassemble in neutral buffer into hexamers as shown by ultracentrifugation and electron microscopy. Reconstituted hexamers, however, dissociate in a much broader pH range than the native globules. Circular dichroic spectra indicate that the structure is more completely refolded from acid-treated than from urea-treated material. These data suggest that globules originating from monomers (as existing in single collagen IV molecules) are stabilized by the adjacent triple helix. Covalent cross-link formation stabilizes the globular structure and allows reconstitution in stoichiometric proportions.

Animals↗
PubMed1984

Evolutionary conservation in the untranslated regions of actin mRNAs: DNA sequence of a human beta-actin cDNA.

We report the complete nucleotide sequence of a human beta actin cDNA. Both the 5' and 3' untranslated regions of the sequence are similar (greater than 80%) to the analogous regions of the rat beta-actin gene reported by Nudel et al (1983). When a segment of the 3' untranslated region is used as a radiolabelled probe, strong hybridization to chick beta actin mRNA is seen. This conservation of sequences suggests that strong selective pressures operate on non-translated segments of beta actin mRNA.

Actins↗
PubMed1984

Localization of flexible sites in thread-like molecules from electron micrographs. Comparison of interstitial, basement membrane and intima collagens.

A computer method for detecting kinks and flexible sites in thread-like molecules was developed. The method is based on the determination of the local curvature along the digitized electron micrographs of the molecules. The root-mean-square curvature provided a measure for the local flexibility, which is related to the persistence length. The influence of various error sources was assessed using computer-simulated thread molecules. "Flexibility profiles" showing the variation of flexibility along molecules were calculated for interstitial, basement membrane and intima collagens. Approximately uniform stiffness corresponding to a persistence length of 60 nm was found for the triple helices of interstitial and monomeric intima collagen. A highly flexible site in interstitial collagen could be assigned to a non-triple helical segment in the sequence surrounding the linkage site of the N-terminal propeptide. A flexible site in the triple helix of collagen I corresponds to a segment of the sequence lacking proline residues. Flexibility varies strongly along the collagen IV molecule. This is consistent with the fact that a series of non-triple helical interruptions have already been found in the not yet completed amino acid sequence of basement membrane collagen. Most of the detected flexible sites allow random bending about the mean zero, but in one case, at the border of the 7S domain of polymeric collagen IV, a flexible site with a preferential angle of 40 degrees was found.

Animals↗
PubMed1984

Laminin, proteoglycan, nidogen and collagen IV: structural models and molecular interactions.

Major components of basement membranes, including collagen IV, laminin, heparan sulphate proteoglycan and nidogen, were isolated from the matrix of the EHS sarcoma. The purified components were analysed for their domain structure and for the participation of distinct domains in molecular interactions and cell binding. Collagen IV consists of four domains which have triple helical or non-collagenous structures. Self-assembly of the protein into a network-like organization occurs by specific interactions between N-terminal triple helical segments and between the C-terminal globules. Cell binding requires a central triple helical segment. Laminin has the shape of an asymmetrical cross; different globular domains within this structure mediate binding to proteoglycan and to cells. The proteoglycan consists of four heparan sulphate chains attached to a small protein core. These chains have the potential to bind laminin, fibronectin and collagen IV. Nidogen was isolated in several molecular forms which showed either self-aggregation or binding to laminin.

Animals↗
PubMed1984

Resumption of behavior following intracarotid sodium amobarbital injection.

Recovery rates of selected behaviors following intracarotid sodium amobarbital injection were examined in 17 patients with unilateral focal temporal lobe epilepsy. Left hemisphere injections resulted in more prolonged disruption of naming (p less than 0.00001), reading (p less than 0.0001), matching-to-sample behaviors (p less than 0.05), and short-term recognition memory for pictures (p less than 0.0001) and words (p less than 0.0003) than did right hemisphere injections. In addition, recovery of behaviors was prolonged if the injection was administered to the hemisphere contralateral to that with the primary seizure focus (p less than 0.005). A trend toward a similar pattern was seen in the postinjection electroencephalogram with the maximum slowing found in the injected hemisphere prolonged if the epileptic focus was in the contralateral hemisphere (p = 0.06). These findings suggest a negative effect of an epileptic lesion on the contralateral hemisphere.

Amobarbital↗
PubMed1984

Opioid-induced epileptogenic phenomena: anatomical, behavioral, and electroencephalographic features.

Recent animal studies have indicated a possible role of opioids in epilepsy. Intraventricular opioid administration induces a prolonged nonconvulsive stuporous state characterized by epileptiform electroencephalographic patterns, and reversed by naloxone. In high doses, naloxone itself causes generalized clonic convulsions. We compared opioid-induced and naloxone-induced epileptogenic phenomena using quantitative 2-deoxyglucose autoradiography in order to define the anatomical structures involved in these two different seizure types. When opioid-induced seizures occurred, limbic structures were preferentially activated, but when naloxone-induced clonic convulsions occurred, pyramidal and extrapyramidal motor areas and some limbic structures were activated. Based on the present experiments and currently available evidence, we speculate that opioid-mediated epileptogenic phenomena are similar to those occurring during the postictal state of a fully kindled seizure, whereas naloxone-induced epileptogenic phenomena are similar to the ictal state. Therefore, simple pharmacological manipulation of endogenous opioid systems may allow selective study of ictal and postictal phenomena.

Animals↗
PubMed1984

The use of positron emission tomographic scanning in epilepsy.

Positron emission tomography (PET) with fluorine-18-labeled fluorodeoxyglucose (18FDG) has demonstrated the epileptogenic lesion in partial epilepsy to be hypometabolic interictally . This finding is useful for localizing the area of resection when surgical therapy is contemplated. 18FDG scans during partial seizures show increased metabolism in areas of ictal onset and spread and in other regions of decreased metabolism that could reflect postictal effects. In the generalized epilepsies, petit mal absences and generalized convulsions induced by electroconvulsive shock therapy (ECT) are associated with global hypermetabolism, while global hypometabolism is seen in the postictal period following ECT. More information about the factors that influence the interictal hypometabolic zone in partial epilepsy should improve the diagnostic value of this finding for presurgical localization and perhaps also for the evaluation of other therapeutic regimens. New techniques for more dynamic PET studies with improved resolution, combined with computerized electroencephalographic analysis, should allow more accurate interpretation of ictal, as well as interictal, phenomena. Application of PET technology to other paroxysmal disorders may provide a basis for new diagnostic classifications that have therapeutic and prognostic value and may allow clearer differentiation among epileptic phenomena, myoclonus, and movement disorders. More clinical and animal research is needed, however, before we can delineate fundamental mechanisms of human epilepsy from PET data. To this end, it is now possible to use combined multidisciplinary parallel approaches in patients and animals to define specific aspects of epileptic disorders clinically, to intensively investigate them with experimental models in the animal laboratory, and to verify the relevance of these experimental results by returning to clinical studies.

Animals↗
PubMed1984

Chemical characterization of ASTA Z 7557 (INN mafosfamide, CIS-4-sulfoethylthio-cyclophosphamide), a stable derivative of 4-hydroxy-cyclophosphamide.

The primary metabolite of cyclophosphamide (CP, 1), i.e. 4-hydroxy-CP 2, has high pharmacological activity, but it is a very unstable compound. Chemical approaches to the stabilization involved in the substitution of the hydroxy group at the C 4-position, especially by a sulfoalkylthio-moiety. Within this new class of compounds ASTA Z 7557 (2-(bis-(2-chloroethyl]-amino-cis-4-[2-sulfoethyl)-thio)-tetrah ydr o-2H-1,3, 2-oxaza-phosphorine-r-2-oxide cyclohexylamine salt, i.e. cis-4-sulfoethylthio-CP, cis-13) was chosen for further evaluation. Cis-13 was synthesized by condensation of compound 2 and 2-mercapto-ethanesulfonic acid cyclohexylamine salt 14 in aqueous acetone yielding the cis-isomer with high stereoselectivity. It is a white crystalline powder, m.p. 126-134 degrees C, stable at room temperature, with a solubility of 16% in water. The stereochemistry was confirmed by NMR-data and X-ray diffraction. In 0.07 M phosphate buffer at pH 7 and 37 degrees C cis-13 isomerizes to the epimer trans-13, equilibrating at a cis-trans-ratio of 59 to 41 within less than 5 minutes. Simultaneously a rapid initial hydrolysis occurs to 2 and 14 followed by a time period with lower degradation due to the decomposition of 2. The rate of release of 2 increases with decreasing concentration and especially by addition of an oxidant. It could be retarded by addition of the corresponding thiol mesna, sodium 2-mercapto-ethanesulfonate 15, or of another thiol.(ABSTRACT TRUNCATED AT 250 WORDS)

Biotransformation↗
PubMed1984

The tumor-inhibiting effect of isomeric dichloro(diphenylethylenediamine)platinum(II) complexes.

Ring unsubstituted dichloro(diphenylethylenediamine)platinum(II) complexes show a dependence of their antitumor activity on the configuration and position of phenyl rings in ethylenediamine ligand. Dichloro(1,1-diphenylethylenediamine)platinum(II) (1d) and meso-dichloro(1,2-diphenylethylenediamine)-platinum(II) (meso-2d) have a weaker effect on the human breast-cancer cell line MDA-MB 231 and on rat leukemia L 5222 than (+/-)-dichloro(1,2-diphenylethylenediamine)platinum(II)((+)-2d) and its enantiomers (+)-2d and (-)-2d which cause marked and comparable inhibition of both tumors; (+/-)-2d is also active on ADJ/PC 6 plasmacytoma of the mouse and on cisplatin-, daunomycin-, and cisplatin/daunomycin-resistant Ehrlich ascites tumors of the mouse. The differences in activity of the diastereomers (+/-)-2d and meso-2d, for which distinct influences on the DNA secondary structure can be demonstrated CD spectroscopically may be explained by a steric hindrance of the drug-DNA interaction.

Animals↗
PubMed1984

Development of sexual behavior in prenatally ethanol-exposed rats.

Female rats were given 16% ethanol solution as the sole liquid during the entire period of gestation. At birth the offspring was removed and reared by foster dams consuming normal drinking water. When tested for feminine sexual behavior in adulthood, the males showed marked signs of feminization as evidenced by an increased amount of lordosis responses. No changes were seen in the masculine sexual behavior. No deviations were seen in the female estrous cycles or in onset of vaginal estrus, whereas the onset of behavioral estrus was delayed. It is suggested that prenatal ethanol exposure may lower the fetal testosterone production and thereby interfere with the normal course of sexual differentiation in the male.

Animals↗