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Biomedical subjects

J Engel

Publications and source records attributed to J Engel.

At least 649 records · Page 36Linked to original sources
PubMed1978

Anatomical correlates of electrical and behavioral events related to amygdaloid kindling.

Anatomical structures demonstrating increased glucose uptake during the various stages of amygdaloid kindling in rats were identified by the 14C-2-deoxyglucose (DG) autoradiographic technique. Partial (stages 1 and 2) seizures were correlated with increased DG uptake in the ipsilateral amygdala and its direct projection fields. The appearance of generalized motor (stages 3,4, and 5) seizures was accompanied by less limbic involvement and recruitment of a bilateral system including substantia nigra, specific and nonspecific thalamic nuclei, globus pallidus, and neocortex. Increased hippocampal DG uptake was correlated with prolonged amygdaloid after discharge duration but not with the behavioral seizure stage. This study does not reveal which of these structures are responsible for the observed behavioral and electrical events and which are activated by them. It does suggest, however, that three discrete anatomical systems underlie the generation of partial seizures, generalized motor seizures, and local after discharge.

Amygdala↗
PubMed1978

Noradrenaline receptor sensitivity after chronic ethanol administration.

The effects of the central noradrenaline receptor stimulating agent clonidine on blood pressure, heart rate, and flexor reflex activity were studied in intact rats and in rats chronically treated with ethanol. The clonidine-induced changes were similar in ethanol-treated animals and in animals never subjected to ethanol. The results suggest that the sensitivity of central noradrenaline receptors involved in the mediation of the circulatory changes and of the flexor reflex activity after clonidine is not altered by chronic administration of ethanol.

Animals↗
PubMed1978

'Limbic spindles': a re-appraisal.

Respiration-linked spindles are frequently recorded from nasopharyngeal electrodes and these have been reported to represent neuronally generated limbic activity. Evidence is presented from sphenoidal and nasopharyngeal recordings suggesting that these spindles are artifactual, due to unstable electrode contacts that record palatal vibration during partial airway obstruction.

Adult↗
PubMed1978

Kinetics of dimerization of the Bence-Jones protein Au.

The dimerization reactions of complete Bence-Jones protein Au (VC-Au) and of its variable fragment (V-Au) were compared in 0.2 M (ionic strength) sodium phosphate buffer, pH 6.8 at 20 degrees C. The dimerization constant for VC-Au (6.6 X 10(4) M-1) was slightly smaller than a previously published value for the fragment (1.1 X 10(5) M-1). The reaction enthalpies were positive for both processes. Temperature jump experiments exhibited two kinetic phases. The relaxation time of the fast phase as well as its concentration dependence and amplitude were almost identical for VC-Au and V-Au. Only small differences were observed in the slow phase. These close similarities between the reactions of the two proteins demonstrate that dimerization occurs mainly via interactions between the variable domains and that the constant domains interfere very little. From the observation of two relaxation times it follows that the dimerization mechanism for both VC-Au and A-Au must include at least three reacting species. Mechanisms with an isomerization between monomers in two conformational states and a single dimer species are excluded by the data. Alternative mechanisms with a single monomeric species but isomerization between dimers give a rather unsatisfactory fit. A good fit can be obtained if it is assumed that both monomers and dimers can exist in two states. Rate constants of the association and dissociation steps are of the order of 10(7) M-1 s-1 and 10(2) s-1. Isomerization rate constants are in the range of 10 s-1.

Bence Jones Protein↗
PubMed1978

Soft tissue stretching with magnets.

Various clinical conditions require soft tissue elongation that can later host a bone graft. The possibility of stretching the soft tissues by magnetic force was tested on the forearm of dogs. The results are encouraging, provided certain precautions are taken and the pull exerted is not too great.

Amputation Stumps↗
PubMed1978

Effect of hypoxia on monoamine synthesis in brains of developing rats. III. Various O2 levels.

1-, 4-, 14- and 28-day-old rats were exposed to a hypoxic environment of 5.9, 8.0 or 12.0% O2 during a period of 30 min. In the brain, tyrosine hydroxylase and tryptophan hydroxylase activity was studied in vivo by measuring the accumulation of dihydroxyphenylalanine (DOPA) and 5-hydroxytryptophan (5-HTP), respectively, after inhibition of L-aromatic amino acid decarboxylase with NSD 1015. Tyrosine and tryptophan levels in the brain were measured simultaneously. The brain tyrosine and tryptophan levels were generally not influenced either by age or hypoxic levels. Tyrosine and tryptophan hydroxylase activity decreased to about the same extent during the various hypoxic levels at all ages studied. It is concluded that the first, rate-limiting, step in the synthesis of the monoamine neurotransmittors dopamine (DA), noradrenaline (NA) and 5-hydroxy-tryptophan (5-HT) is affected during moderate as well as severe hypoxia at all stages of development.

5-Hydroxytryptophan↗
PubMed1978

Prolonged partial complex status epilepticus: EEG and behavioral observations.

Four prolonged episodes of partial complex status epilepticus were observed in a teenaged girl. During each there was an "ictal" phase, in which her mental state frequently fluctuated between mildly clouded consciousness and almost total unresponsiveness; once, she was also blind during this phase of impaired consciousness. With therapy, the periods of unresponsiveness became less frequent and less prolonged until a second, "postictal," phase occurred when she was alert, but with profound retrograde and anterograde amnesia that gradually resolved in several weeks. The "ictal" EEG pattern always consisted of lateral temporo-occipital fast and sharp waves continually alternating with slow activity. These cycled independently in the two hemispheres and correlated with the fluctuating behavioral state. During the "postictal" phase the EEG was diffusely slow with isolated bilaterally independent temporal spikes. The key to the diagnosis of partial complex status epilepticus may be the fluctuating mental state. Recognition and prompt treatment of this disorder are important since delay could result in prolonged or enduring memory impairment.

Adolescent↗
PubMed1978

Criterion-referenced testing in medical technology education: Professional Performance Situation Model.

In applying the Professional Performance Situation Model to the medical technology profession, situations describing actual laboratory performance are used as a basis for defining competence. As these definitions of competence are derived, appropriate criterion-referenced (domain-referenced) assessments are designed to measure the achievement of competence. This paper describes the process by which situations representing clinical practice are derived, the extrapolation of skill and knowledge statements reflecting expected performance, the generation of domains of competence, the design of criterion-referenced assessments, and some examples of prototype instruments used to assess attainment of the competence. The techniques include multiple choice items, checklists for use in the clinical component of the educational experience, and the adaptation of the written simulation for instruction and evaluation in medical laboratory sciences education. Validity of this approach is discussed, as well as possible implications for its use in developing assessments to measure continued competence in the profession beyond the baccalaureate education.

Clinical Laboratory Techniques↗
PubMed1977

The polymerization reaction of muscle actin.

Recent advances in the studies of the aggregation of G-actin monomers, containing one molecule of ATP, to long filaments of F-actin, with a concomitant hydrolysis of the nucleotide to ADP, are reviewed. With the aid of omega-ATP, the association and dissociation rate constant of the nucleotide could be determined. The binding of the nucleotide is enhanced by the binding of one Ca++ ion, probably at a different site. The delta G value of the Mg++ or Ca++ induced polymerization has been determined to --39 to--59 kJ/mole, the critical protein concentration for the ATP-G-actin to ADP-F-actin conversion is very strongly influenced by the concentration of bivalent cations. The rate constants of the protein monomers, and the rate and equilibrium constants for the propagation step show the process to be extremely cooperative. Actin shows the interesting phenomenon of translocational head-to-tail polymerization, which may be regulated by ATP. The contact sites between the monomers in F-actin have been labeled by chemical modification. Two tryosine residues, 53 and 69, are probably close to one of the two sites. The ATP binding sites has been labeled by an ATP analog, and there is evidence that it is close to the contact site.

Actins↗
PubMed1977

Kinetics of binding of oligosaccharides to a homogeneous pneumococcal antibody: dependence on antigen chain length suggests a labile intermediate complex.

Temperature-jump experiments were performed with di-, tetra-, and hexasaccharides derived from type III pneumococcal polysaccharide using a homogeneous corresponding antibody IgG 45-394. A decrease in stability of the oligosaccharide-antibody complexes with decreasing chain length was observed and entirely reflected in the decrease of the association rate constants which were 1.7 X 10(4) M-1 s-1 for the di-, 3.7 X 10(5) M-1 s-1 for the tetra-, and 1.1 X 10(6) M-1 s-1 for the hexasaccharide at 23 degrees C. The dissociation rate constants for all oligomers were about 12 s-1. This marked chain-length dependence of the association rate constants as well as their low values are unexpected for a single binding step. A mechanism is proposed which consists of a fast formation of a labile oligosaccharide-antibody precomplex followed by a slow isomerization step which is induced by the oligosaccharide ligands but which is chain-length independent.

Antibodies, Bacterial↗
PubMed1977

Purification and characterization of a peptide from the carboxy-terminal region of chick tendon procollagen type I.

A disulfide-bonded peptide with a molecular weight of about 100 000 was isolated from the medium of cultured chick embryo tendons. It was shown to be a trimer with two types of subunits in a 2:1 ratio, and tryptic fingerprinting and immunological evidence indicated that it was derived from the carboxy-terminal-precursor-specific region of procollagen. Amino acid analysis after reduction and alkylation indicated that the trimer contains about 30 residues of half-cystine involved in intrachain as well as interchain disulfide bonding. The interchain bonds could be reduced and alkylated under nondenaturing conditions. Carbohydrate analysis showed that each of the three peptide chains in the trimer contains about two residues of N-acetylglucosamine and about ten residues of mannose. This suggests the presence of one or two oligosaccharide units per chain.

Acetylglucosamine↗
PubMed1977

Antagonism of the analeptic activity of thyrotropin-releasing hormone (TRH) by agents which enhance GABA transmission.

Administration of 10 mg/kg TRH to mice was found to reduce the sleep and hypothermia induced by 4.7 g/kg ethanol. However, TRH did not reduce the sleep of mice that were given gamma-hydroxybutyric acid (GHBA), baclophen, or aminooxyacetic acid (AOAA) in combination with 3 g/kg/ ethanol. TRH also failed to reverse the hypothermia induced by the combination of ethanol and baclophen or GHBA, and the characteristic neurological effects of TRH e.g. tremor, increased muscle tone, and increased respiratory rate were reduced. In addition, TRH-induced locomotor stimulation was prevented by pretreatment with small doses of the GABA-ergic agents, and while 30 mg/kg TRH reduced the hypothermia produced by large doses of the GABA-ergic drugs, it did not antagonize the locomotor retardation produced by baclophen or GHBA. A hypothesis that the analeptic effects of TRH may be medicated via an inhibition of GABA systems is discussed.

Aminobutyrates↗