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Biomedical subjects

A Morel

Publications and source records attributed to A Morel.

At least 109 records · Page 6Linked to original sources
PubMed1984

Topographic and cytoarchitectonic organization of thalamic neurons related to their targets in low-, middle-, and high-frequency representations in cat auditory cortex.

We studied the topographic organization of thalamic projections upon different ranges of cortical frequency representation. Thalamic neurons were labeled by injecting horseradish peroxidase (HRP) or tritiated bovine serum albumin into auditory cortex. Injections in individual brains were confined to the same range of frequency representation, and distributed through three or four tonotopic cortical fields in order to label as much of the thalamic projection upon a limited range of frequency representation as practicable. Low, middle, and high ranges of the frequency representation were injected in different brains. The spatial organizations of arrays of labeled neurons are described, and each array is divided into a ventral division and lateral posterior complex (lateral part of the posterior thalamic group), both composed mainly of small cells; and a medial division, composed mainly of medium and large cells. The ventral and medial divisions (located laterally and medially within the medial geniculate body (MGB), respectively), both contact the lateral posterior complex which is located rostrally. The HRP cytoarchitecture of the three divisions is described, and the portions of the ventral division corresponding with the physiologically and cytoarchitectonically defined ventral nucleus are identified. Relatively few labeled neurons were found within other thalamic areas. The topographic organizations of the ventral division (and its tonotopic subdivision, the ventral nucleus), the lateral posterior complex (also tonotopically organized), and the medial division are described. There are planar and concentric components of the topographic organization in the ventral nucleus. Within the planar component, the low-frequency area is located laterally and the high-frequency area is located rostromedially. Within the concentric component, the low-frequency area is located centrally and the high-frequency area is located peripherally. Low-, middle-, and high-frequency areas course without interruption through the planar and concentric components. In the lateral posterior complex, the low-frequency area is located rostrally, and the high-frequency area is located caudally adjoining the high-frequency area in the ventral nucleus. The topographic organizations of the ventral nucleus and lateral posterior complex are consistent with tonotopic maps of these regions. The medium- and large-cell portion of the medial division is also topographically organized, although there may be more overlap among low-, middle-, and high-frequency arrays than in the ventral nucleus.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

Enzymes processing somatostatin precursors: an Arg-Lys esteropeptidase from the rat brain cortex converting somatostatin-28 into somatostatin-14.

The post-translational proteolytic conversion of somatostatin-14 precursors was studied to characterize the enzyme system responsible for the production of the tetradecapeptide either from its 15-kDa precursor protein or from its COOH-terminal fragment, somatostatin-28. A synthetic undecapeptide Pro-Arg-Glu-Arg-Lys-Ala-Gly-Ala-Lys-Asn-Tyr(NH2), homologous to the amino acid sequence of the octacosapeptide at the putative Arg-Lys cleavage locus, was used as substrate, after 125I labeling on the COOH-terminal tyrosine residue. A 90-kDa proteolytic activity was detected in rat brain cortex extracts after molecular sieve fractionation followed by ion exchange chromatography. The protease released the peptide 125I-Ala-Gly-Ala-Lys-Asn-Tyr(NH2) from the synthetic undecapeptide substrate and converted somatostatin-28 into somatostatin-14 under similar conditions (pH 7.0). Under these experimental conditions, the product tetradecapeptide was not further degraded by the enzyme. In contrast, the purified 15-kDa hypothalamic precursor remained unaffected when exposed to the proteolytic enzyme under identical conditions. It is concluded that this Arg-Lys esteropeptidase from the brain cortex may be involved in the in vivo processing of the somatostatin-28 fragment of prosomatostatin into somatostatin-14, the former species being an obligatory intermediate in a two-step proteolytic mechanism leading to somatostatin-14.

Animals↗
PubMed1984

Characterization of a somatostatin-28 containing the (Tyr-7, Gly-10) derivative of somatostatin-14: a terminal active product of prosomatostatin II processing in anglerfish pancreatic islets.

Anglerfish (Lophius piscatorius) Brockmann organs contain a form of somatostatin-14, identical to the hypothalamic tetradecapeptide, and two distinct forms of somatostatin-28, which can be separated by reversed-phase high-pressure liquid chromatography (HPLC). Analysis of the NH2-terminal amino acid sequence and comparison of the ability to incorporate 125I indicate that one of these forms corresponds to an octacosapeptide including in its sequence the (Tyr-7, Gly-10) derivative of somatostatin-14 (somatostatin II). Exposure of this somatostatin-28 species to an endopeptidase activity from the rat brain cortex generates a peptide immunologically related to somatostatin and undistinguishable from synthetic (Tyr-7, Gly-10) somatostatin-14 II by HPLC. This somatostatin-28 II exhibits a potent inhibitory effect on growth hormone release by rat anterior pituitary cells, comparable to the other somatostatin-28 form. Since (Tyr-7, Gly-10) somatostatin-14 II cannot be detected in anglerfish pancreatic islets, these results indicate that somatostatin-28 II represents the terminal active product of prosomatostatin II processing, whose structure was predicted from the cDNA nucleotide sequence corresponding to the second mRNA cloned from anglerfish Brockmann organs [Hobart, P., Crawford, R., Shen, L. P., Pictet, R. & Rutter, W. J. (1980) Nature (London) 288, 137-141].

Amino Acid Sequence↗
PubMed1984

[A new peptide alkaloid from Discaria febrifuga Mart].

On the basis of spectroscopic investigations (1H-NMR, 13C-NMR, UV, IR and MS spectroscopy), elemental analysis and degradation reactions the structure of a new alkaloid discarine G from the bark extract of Discaria febrifuga Mart. is elucidated.

Acetylation↗
PubMed1983

Evidence for a predominant form of Mr = 15,000 prosomatostatin in the mouse hypothalamus. Relationship with somatostatin-14 and -28.

This paper demonstrates the presence of a single predominant form of high molecular weight somatostatin (Mr congruent to 15,000) in mouse hypothalamus as judged by a combination of purification procedures including molecular sieve filtration, reverse phase high pressure liquid chromatography, isoelectric focusing, and gel electrophoresis under denaturing conditions. Furthermore, the conversion of the Mr = 15,000 somatostatin species by hypothalamic enzyme activities led to the formation of both somatostatin-14 and -28 which were identified by high pressure liquid chromatography. No evidence was found for the presence of molecular species containing the sequence of the (Tyr-7, Gly-10) derivative of somatostatin. These observations suggest that, in contrast to the situation encountered in the pancreas, a predominant form of prosomatostatin is synthesized in hypothalamic neurones. They indicate that, in the hypothalamus, both the tetradecapeptide and somatostatin-28 derive from a single prohormone.

Animals↗
PubMed1983

Regional distribution of the Mr 15,000 somatostatin precursor, somatostatin-28 and somatostatin-14 in the rat brain suggests a differential intracellular processing of the high molecular weight species.

Three different forms of immunoreactive somatostatin (Mr 15,000, 3,000 and 1,600) were immunologically detected in extracts made from six neural structures of the rat brain. The largest represents the proform, while the smaller were identified by high pressure liquid chromatography with bovine somatostatin-28 (S-28) and -14 (S-14) respectively. In each of the brain structures studied highly variable proportions of precursor, S-28 and S-14 were found. These observations provide suggestive evidence that the intracellular processing of the 15,000 Mr proform may occur differently in the various somatostatinergic pathways of the brain. They argue in favor of a biological role for the precursor in providing distinct relative proportions of S-14 and S-28 in specific rat brain regions.

Animals↗
PubMed1983

Intensity functions of single unit responses to tone in the medial geniculate body of cat.

Extracellular spike activity was recorded from single units in the medial geniculate body (MGB) of nitrous oxide anaesthetized cats. The responses of 291 units to tone bursts at the characteristic frequency (CF) were studied as a function of stimulus intensity, covering a range from 10 to 100 dB SPL. The proportion of MGB units characterized by a monotonic or a non-monotonic discharge rate--intensity function was 26% and 74%, respectively. In addition, changes of response latency as a function of tone levels were demonstrated to be either monotonic (38% of units) or non-monotonic (62% of units). One third Of MGB units showed a change of response pattern with increasing intensities, in similar proportion towards either prevailing excitatory or inhibitory components. The monotonic units tended to differ from non-monotonic ones in addition to their intensity function by showing shorter response latencies, a higher response probability to broad-band stimuli and simpler response patterns. The mean dynamic range of the monotonic unit population was 60 dB, with thresholds ranging from 10 to 90 dB SPL; most discharge rate--intensity functions did not saturate at sound levels of 100 dB SPL. In the population of non-monotonic units, the 'best' intensity, defined as th intensity giving the strongest response, ranged between 10 and 100 dB SPL. The present results suggest that the intensity could be signaled by the mean firing rate of a restricted population of monotonic units or place coded by the distribution of maximally activated non-monotonic units which are broadly tuned to different intensities.

Acoustic Stimulation↗
PubMed1983

[Peptide alkaloids from Discaria febrifuga Mart].

From the bark extract of Discaria febrifuga Mart. the known alkaloids frangufoline (I), adouétine (II), scutianine B (III), franganine (IV) and two new ones, discarine C (V) and D (VI), were isolated. Their structures are elucidated by degradation reactions and spectroscopic investigations.

Alkaloids↗
PubMed1982

Covariation of distributions of callosal cell bodies and callosal axon terminals in layer III of cat primary auditory cortex.

Primary auditory cortex in the cat is both the source and target of callosal fibers. Injection of horseradish peroxidase (HRP) in the high frequency representation of AI in one hemisphere retrogradely labels callosal cell bodies and anterogradely labels callosal axon terminals in AI of the opposite hemisphere. In tissue sections cut through layer III parallel to the cortical surface, elongated patches composed of dense aggregates of callosal cell bodies and callosal axon terminals alternate with regions containing lower concentrations of these elements. Labeling in AI is most dense in regions corresponding to the frequency representation of the injected site. In layer III of the densely labeled region, patches of high concentrations of labeled callosal axon terminals correspond with high concentrations of labeled callosal cell bodies. On the other hand, little correspondence is apparent between the distributions of the two elements in layer III in the surrounding area of lighter labeling. Layers V and VI contain relatively few labeled callosal axon terminals and cell bodies, and our data do not suggest whether the two distributions covary in these layers.

Afferent Pathways↗
PubMed1982

Identification of N- and C-terminal corticotropin peptides in the Mr 80000 form of neurophysin.

The 125I-labeled Mr 80000 form of neurophysin has been purified from bovine neurohypophysi. Tryptic digests of this species were analyzed, prior to or after treatment with carboxypeptidase B, by high-pressure liquid chromatography followed by isoelectric focusing and the fragments compared with those generated by a similar treatment of reference bovine 1-39 adrenocorticotropin. The ACTH peptides 22-39 and 1-8, as well as the 1-7 derivative of the latter were identified by those two independent criteria. This provides chemical evidence supporting the hypothesis [8] that high Mr neurophysin may contain the sequence of ACTH.

Adrenocorticotropic Hormone↗
PubMed1982

[Non typhoidal Salmonella infections: a clinical study of 491 cases (author's transl)].

491 cases of non typhoidal salmonella infections were studied in the Rouen Hospital University Centre. Affected patients are mainly children who usually present mild febrile gastroenteritis. Severe forms with septicemia, enteric fever, or focal manifestations, usually occur in adults. In nearly half the cases an underlying disease or another predisposing condition was found. In these cases, the mortality rate was increased. Antibiotic therapy prolonged post-convalescent excretion of salmonellae. Adequate diet and hygiene are sufficient in mild forms. Antibiotics should be used only in acute salmonella infections.

Adult↗
PubMed1979

[Localization of urinary infection by immunofluorescence of bacteria (author's transl)].

After having presented a method to detect antibody coated bacteria, the authors give reports about the first result they obtained with this technic. Among 41 patients they got a positive immunofluorescence in 18 of them, corresponding with a rate of 80% to the clinical and biological explorations. This research about antibody coated bacteria permits to state whether the kidney tissue is affected or not.

Antibodies, Bacterial↗
PubMed1979

[Use of electrosyneresis in the diagnosis of bacterial meningitis (author's transl)].

The authors present the interest of electrosyneresis for diagnosis of purulent meningitis. Test material is a study about 120 cerebrospinal fluids. Electrosyneresis sometimes permits to identify the germ when microscopic examination and culture are negative or when microscopy is positive and the culture negative. Application of electrosyneresis is still limited in France by the small immunogenicity of the specific polysaccharide of Neisseria meningitidis serotype B. principal etiologic agent of purulent meningitis, that do not allow, at present, to obtain suitable serums.

Counterimmunoelectrophoresis↗