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Biomedical subjects

F Morin

Publications and source records attributed to F Morin.

At least 37 records · Page 2Linked to original sources
PubMed1996

Membrane properties and synaptic currents evoked in CA1 interneuron subtypes in rat hippocampal slices.

1. Intrinsic membrane properties and pharmacologically isolated excitatory and inhibitory postsynaptic currents (EPSCs and IPSCs, respectively) were characterized with the use of whole cell current- and voltage-clamp recordings, in combination with biocytin labeling, in different subtypes of CA1 interneurons and pyramidal cells in rat hippocampal slices. 2. Three classes of interneurons were selected on the basis of their soma location in the CA1 region: 1) in stratum (str.) oriens near the alveus (O/A), 2) near str. pyramidale, and 3) near the border of str. radiatum and lacunosum-moleculare. Each class of biocytin-labeled cells demonstrated specific cellular morphology. The somata of all interneurons were nonpyramidal in shape and usually multipolar. However, the pattern of dendritic and axonal arborizations of labeled interneurons differed in each class. 3. In current-clamp recordings, all interneuron subtypes had shorter-duration and smaller-amplitude action potentials than pyramidal cells. Fast- and medium-duration afterhyperpolarizations were larger in amplitude in interneurons. Cell input resistance was greater and membrane time constant was faster in all interneuron subtypes than in pyramidal cells. 4. Depolarizing current pulses evoked regular firing in all classes of interneurons, whereas burst firing was observed in 50% of pyramidal cells. With hyperpolarizing current pulses, all nonpyramidal and pyramidal cell types displayed inward rectification followed by anodal break excitation. 5. Electrical stimulation of nearby afferents evoked excitatory postsynaptic potentials (EPSPs) in all cells. EPSPs were of short duration and usually followed by inhibitory postsynaptic potentials (IPSPs). EPSPs were mediated by glutamate, because they were blocked by non-N-methyl-D-aspartate (non-NMDA) and NMDA antagonists [6-cyano-7-nitroquinoxaline-2,3-dione (CNQX) and (+/-)-2-amino-5-phosphonopentanoic acid (AP5), respectively]. In the presence of these antagonists, IPSPs were evoked in isolation and reversed near -72 mV. 6. In voltage-clamp recordings, non-NMDA EPSCs were isolated pharmacologically in the presence of AP5 and the gamma-aminobutyric acid-A (GABAA) antagonist bicuculline (BIC). Their properties were similar in all interneuron subtypes and pyramidal cells. Current-voltage (I-V) relations were linear, and mean reversal potentials were near 5 mV. Non-NMDA EPSCs were reversibly antagonized by CNQX. 7. NMDA EPSCs were pharmacologically isolated during CNQX and BIC application and were observed in all cell types. I-V relations of NMDA EPSCs demonstrated a region of negative slope at membrane potentials between -80 and -20 mV and their reversal potential was near 7 mV. The rise time of NMDA EPSCs was significantly slower in O/A interneurons than in other cell types. NMDA EPSCs were reversibly antagonized by AP5. 8. GABAA IPSCs were pharmacologically isolated in AP5 and CNQX and their properties were similar in all cell types. I-V relations of GABAA IPSCs were linear with mean reversal potentials near -32 mV. GABAA IPSCs were reversibly blocked by BIC. 9. In conclusion, morphologically different subtypes of interneurons located in O/A, near str. pyramidale, and near the str. radiatum/lacunosum-moleculare border displayed intrinsic membrane properties that were distinct from pyramidal cells, but were similar among them. In contrast, the properties of non-NMDA, NMDA, and GABAA postsynaptic currents were similar between interneurons and pyramidal cells, except for NMDA EPSCs, which had slower rise times in O/A interneurons.

Animals↗
PubMed1995

Regulation of the sequence-specific DNA binding function of p53 by protein kinase C and protein phosphatases.

The p53 tumor suppressor protein is a transcription factor with sequence-specific DNA binding activity that is thought to be important for the growth-inhibitory function of p53. DNA binding appears to require activation of a cryptic form of p53 by allosteric mechanisms involving a negative regulatory domain at the carboxyl terminus of p53. The latent form of p53, reactive to the carboxyl-terminal antibody PAb421, is produced in a variety of eukaryotic cells, suggesting that activation of p53 is an important rate-limiting step in vivo. In this report we provide evidence that phosphorylation of serine 378 within the carboxyl-terminal negative regulatory domain of the human p53 protein by protein kinase C correlates with loss of PAb421 reactivity and a concomitant activation of sequence-specific DNA binding. These effects are reversed by subsequent dephosphorylation of the protein kinase C-reactive site by protein phosphatases 1 (PP1) and 2A (PP2A), which restore the reactivity of p53 to PAb421 and regenerate the latent form of p53 lacking significant DNA binding activity. Thus, p53 is subject to both positive and negative regulation by reversible enzymatic modifications affecting the latent or active state of the protein, suggesting a possible mechanism for the regulation of its tumor suppressor function.

Amino Acid Sequence↗
PubMed1995

Regional renal blood flow measurements using radioactive microspheres in a chronic porcine model with unilateral vesicoureteral reflux.

95Niobium labeled radioactive microspheres were used to determine regional renal blood flows in a porcine model of chronic sterile vesicoureteral reflux. Unilateral vesicoureteral reflux was surgically created in 5 mini-pigs and regional renal blood flows were determined by microsphere injection 6 months later. The contralateral nonrefluxing kidney acted as a control. There was a significant reduction of flow in the inner cortical regions of the middle (78% of control, p < or = 0.0437) and lower poles (69% of control, p < or = 0.0274), and the juxta-medullary cortical region of the lower pole (67% of control, p < or = 0.0124). There was no difference in flow in the other regions or when comparing whole kidneys. There were no differences between refluxing and nonrefluxing kidneys when comparing ratios of inner to outer cortical flow level by level. These observations are in contrast to those in acutely created vesicoureteral reflux in a porcine model, which had no significant differences in flow in any region using the microsphere technique. Decreases of blood flow in certain cortical regions may help explain some of the physiological changes in vesicoureteral reflux in children and experimental models of reflux.

Animals↗
PubMed1995

Farmer's lung and variables related to the decision to quit farming.

An exploratory strategy was used to investigate why 55% of patients with farmer's lung (FL) disease quit farming. Three groups were recruited: 47 patients with FL disease who quit farming because of the disease (FLq), 76 patients with FL disease who continued farming (FLc), and 123 control farmers without a history of FL disease. The severity of FL disease at diagnosis was similar in both groups of patients. For example, single-breath carbon monoxide diffusion capacity predicted for FLq and FLc was 64.4 +/- 28.2 and 63.9 +/- 22.0, respectively. Relying on a cognitive-behavior theory, numerous physiological, behavioral, cognitive, affective, and social variables were assessed. Results showed that the decision to quit farming was based on cognitive and behavioral motives rather than physiological factors. Subjects in the FLq group showed more negative beliefs toward FL and had more fears of FL disease. FLq subjects also reported that family members, friends, and family doctors were more inclined to consider that FL disease could stop them from farming. However, self-efficacy to continue farming despite having FL disease and perceived hindrance caused by FL disease played the most important roles in the decision to quit farming.

Agriculture↗
PubMed1994

Equivalent cell density in three areas of neonatal rat cerebral cortex.

Using the disector method, equivalent cell densities (number of cells per unit volume) were found in the frontal (motor), parietal (somatosensory) and occipital (visual) cortex of neonatal rat (1.2 x 10(6) cells/mm3). As determined with GABA post-embedding immunocytochemistry on semithin sections, at least 11% of these cells expressed GABA. Because neonate frontal cortex is thicker than the parietal or the occipital cortex, the number of cells under an unit area of pial surface was greater in this cortex. This clearly differed from the adult pattern, where the greatest number of cells beneath an unit pial area is that of the somatosensory versus the frontal and the occipital cortex. It suggests that the attainment of the adult number of cells in a cortical column is achieved through differential cell death in the different areas and that the amount of thalamic input could be a crucial determinant of the adult cytoarchitecture.

Animals↗
PubMed1994

Mutations in transcript isoforms of the neurofibromatosis 2 gene in multiple human tumour types.

The neurofibromatosis 2 gene (NF2) has recently been isolated and predicted to encode a novel protein related to the moesin-ezrin-radixin family of cytoskeleton-associated proteins. Here we describe a novel isoform of the NF2 transcript that shows differential tissue expression and encodes a modified C terminus of the predicted protein. Mutations affecting both isoforms of the NF2 transcript were detected in multiple tumour types including melanoma and breast carcinoma. These findings provide evidence that alterations in the NF2 transcript occur not only in the hereditary brain neoplasms typically associated with NF2, but also as somatic mutations in their sporadic counterparts and in seemingly unrelated tumour types. The NF2 gene may thus constitute a tumour suppressor gene of more general importance in tumorigenesis.

Alternative Splicing↗
PubMed1992

The difficulties in assessment of results of anterior acromioplasty.

A retrospective study of 59 decompressive anterior acromioplasties for chronic impingement of the shoulder in 54 patients compared the results of four different shoulder rating systems. The systems used by Neer, Hawkins, and Post include pain, range of motion, function, and strength, whereas the University of California at Los Angeles (UCLA) scale evaluates the same criteria but on a system of points. After a careful clinical evaluation, satisfactory results ranged from 37% to 80%, using the postoperative evaluation criteria chosen. The criteria defined by Neer, and based on patient satisfaction, minimal pain, full use of the shoulder, less than 20 degrees of limitation of overhead extension, and at least 75% of normal strength, provided the most accurate assessments for this series and resulted in a satisfactory outcome for 60% of the patients.

Acromion↗
PubMed1990

[Slip casting: design and processing].

With the "In-Ceram" system ceramic constructions are made without any metallic support. The cosmetic ceramic (Vitadur N) is reinforced by an aluminous oxide framework made with a bio-ceramic containing 85% aluminium. The nature of this bio-ceramic and its use provide the originality of this procedure. In order to make this framework, a replica in special porous plaster is made based on the working model. This replica is plunged into a "barbotine" (aluminous oxide grains in suspension in water) which is deposited on the surface. After modeling this paste with a brush, the totality is dehydrated and brought to 1, 100 degrees C for 2 h without. This still fragile calcination is infiltrated by coloured glass. This second thermal treatment is carried out, after dehydration, at 1,080 degrees for 2 to 4 h, still vacuum. The second heating allows the calcination to become coloured and fill in the porosities. The conventional feldspar ceramic is then placed onto this very resistant (more than 580 MPa flexural strength) and exceptionally well adapted framework. This procedure is remarkable regarding the marginal adaptation, the quality of the aesthetic result, its biocompatibility and its ease in positioning. Moreover, the minimal thickness of the aluminium coping is 4/10 mm on the lingual and 3/10 mm for other sides, which therefore do not require any more laboratory work than what is required for making a ceramo-metallic crown. Clinical follow-up over four years allows it to be stated that the mechanical and aesthetic qualities of the procedure permit the making of: single anterior and posterior units which can be made splinted; anterior maxillary small bridges (3 or 4 units) under normal occlusal conditions; posterior small bridges, under favourable occlusal conditions.

Aluminum Oxide↗
PubMed1988

[Perianal colloid adenocarcinoma. Apropos of a case].

A 50 year old man with a 5-year history of recurrent anal fistula was treated by abdominoperineal amputation of rectum for perianal colloid adenocarcinoma. Characters of this rare affection of debatable pathogenicity are described, based on a literature review of 82 similar cases. The findings illustrate the evocative nature of an induration or better still a mucoid discharge from a recurrent anal fistula, and the need for deep and repeated biopsies to establish diagnosis. Since the course remains for a long period at the local and regional levels the treatment of choice is abdomino-perineal amputation.

Adenocarcinoma, Mucinous↗