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Biomedical subjects

M Bernard

Publications and source records attributed to M Bernard.

At least 145 records · Page 8Linked to original sources

Neural and vascular complications of arthroscopic meniscal surgery.

Injuries to vessels and nerves are very rare complications of arthroscopic meniscal surgery. The clinical development and diagnosis of such complications are described and illustrated by cases described in the literature and by two of our own cases. Typical patterns of injury are simulated by dissection of cadaver knees. To avoid neural complications in suturing the menisci, on the medial side the joint capsule has to be prepared when using the inside-out or the outside-in technique. On the lateral side of the outside-in technique can be performed by small suture incisions in this area when the lateral knee structures can be palpated. When using the inside-out technique the peroneal nerve must be dissected free. When resecting the posterior horn of the medial meniscus forced external rotation of the knee should be avoided because in this position the popliteal artery and the medial inferior genicular artery lie close to the posterior horn.

Aneurysm, False↗

Regulation of hydroxyindole-O-methyltransferase gene expression in the pineal gland and retina.

Hydroxyindole-O-methyltransferase (HIOMT) catalyzes the final step of melatonin biosynthesis and appears to be specifically expressed in the pineal gland and in the retina. This review deals with the regulation of HIOMT by environmental light and with the developmental aspects of HIOMT expression in chicken and rat. Early studies based on HIOMT activity measurements and more recent studies involving cDNA hybridization to HIOMT mRNA are taken into consideration. Together, the data reveal that long term regulation of HIOMT by light would rely on a day/night rhythm of HIOMT gene transcription, coupled to a slow turnover of the protein. Rapid changes in HIOMT mRNA levels and early expression during embryonic development suggest that further studies on this gene may shed light on the molecular mechanisms involved in the differentiation of the melatoninergic function and in its regulation by light, both in the pineal gland and in the retina.

Acetylserotonin O-Methyltransferase↗

Characterization of melatonin binding sites in chicken and human intestines.

The radioligand 2-[125I]iodomelatonin was used to study melatonin binding sites in chicken and human intestines. In the chicken duodenum, 2-[125I]iodomelatonin binding sites were enriched in the musculosa layer (Bmax approximately 1 fmol/mg protein) as compared to the mucosa/submucosa layer (Bmax approximately 0.2 fmol/mg protein). 2-[125I]iodomelatonin bound with a Kd of 68 +/- 18 pM (mean +/- S.E.M., n = 13) and was displaced by melatonin with a Ki of 0.3 nM. The Kd value for 2-[125I]iodomelatonin was increased 2- to 4-fold by a GTP analog, suggesting that the binding sites might be coupled to a G-protein. The affinity order of nine melatonin analogs at the enteric binding sites was in agreement with the pharmacological profile of melatonin receptors described in other tissues. In the human jejunum, 2-[125I]iodomelatonin binding could be observed in the mucosa/submucosa layer (Kd = 150-200 pM, Bmax = 0.7 fmol/mg protein). The radioligand was efficiently displaced by melatonin (Ki = 0.6 nM) but only marginally by N-acetyltryptamine (Ki = 22 microM) and serotonin (Ki = 14 microM).

Animals↗

Transcriptional regulation of hydroxyindole O-methyltransferase in the chicken pineal gland: day/night changes and long-term effects of light and darkness.

The indolic hormone melatonin is produced by the pineal gland according to a daily rhythm. The terminal step of melatonin synthesis is catalysed by hydroxyindole O-methyltransferase (HIOMT, EC 2.1.1.4). Adaptation to constant light or darkness modifies HIOMT activity and concentration. Using a cDNA probe encoding HIOMT, we investigated the effect of environmental lighting on HIOMT gene expression in the chicken pineal gland. HIOMT mRNA levels increased by 100% in constant light as compared with constant darkness. In addition, the present study disclosed the existence of a day/night rhythm of HIOMT gene transcription, with 3-fold higher mRNA levels at midday than at midnight. This transcriptional rhythm was not accompanied by day/night changes in HIOMT concentration, probably due to a slow turnover of this protein. Unexpected darkness did not prevent the daytime rise in HIOMT mRNA levels, whereas unexpected light prevented the night-time fall in HIOMT mRNA levels. Together, the data would suggest that the day/night rhythm of HIOMT gene transcription in the chicken pineal gland involves both a response to light and the activity of a biological oscillator.

Acetylserotonin O-Methyltransferase↗

Cellular localization of hydroxyindole-O-methyltransferase mRNA in the chicken pineal gland.

Hydroxyindole-O-methyltransferase (HIOMT), is the last enzyme of the melatonin biosynthesis pathway. We have applied immunocytochemistry and in situ hybridization to localize HIOMT producing cells, in the chicken epithalamus including the pineal gland. The selectivity of the hybridization signal over melatoninergic cells was ascertained by comparison with the immunolabelling. HIOMT transcripts could be observed in the two cell layers of the pineal follicles and in the pineal stalk, but not in other epithalamic regions. These results indicate that pineal modified photoreceptors and parafollicular pinealocyte-like cells represent the two populations of melatonin-producing cells of the chicken epithalamus.

Acetylserotonin O-Methyltransferase↗

[Magnetic resonance tomography of new rupture of the anterior talofibular ligament].

Twenty acutely traumatised patients with a rupture of the anterior talofibular ligament were studied by MRI. The results of 3D-studies were correlated with conventional stress x-ray studies. The ruptured ligament was directly visualised in all cases as a thickened structure of high signal intensity. In case of complete ruptured ligaments free flowing ligamentous structures were seen in the signal intense exudation in the ankle joint. MRI can help to decide between surgery or conservative therapy.

Adolescent↗

[Surgical treatment of panaritium articulare with the external minifixator].

Septic interphalangeal arthritis can cause severe damage to the joint affected. Two patients treated by the appropriate operative procedure are presented. After interphalangeal distraction by external fixation two drains are placed in the joint and saline solution is infused regularly. The distraction improves the catheter irrigation and the prospects of success. At follow-up examination we saw no negative consequences of the joint distraction.

Adult↗

[Transcriptional regulation of an enzyme involved in the synthesis of melatonin].

The indolic hormone melatonin is produced by the pineal gland according to a daily rhythm. The terminal step of melatonin synthesis is catalyzed by hydroxyindole-O-methyltransferase (HIOMT, EC 2.1.1.4). Adaptation to constant light or darkness modifies HIOMT activity and concentration. Using a cDNA probe encoding HIOMT, we investigated the effect of environmental lighting on HIOMT gene expression in the chicken pineal gland. HIOMT mRNA levels increased by 100% in constant light as compared with constant darkness. In addition, the present study disclosed the existence of a day/night rhythm of HIOMT gene transcription, with 3-fold higher mRNA levels at midday than at midnight. Unexpected darkness did not prevent the daytime rise in HIOMT mRNA levels, whereas unexpected light prevented the night-time fall in HIOMT mRNA levels. Together, the data would suggest that the day/night rhythm of HIOMT gene transcription in the chicken pineal gland involves both a response to light and the activity of a biological oscillator.

Acetylserotonin O-Methyltransferase↗

[Gadolinium-DTPA enhanced MRT in the evaluation of the healing of autologous patellar ligament transplants for anterior cruciate ligament reconstruction].

Eighteen patients with autologous patellar tendon transplant for reconstruction of the anterior cruciate ligament were examined postoperatively. The time between operation and MR study was up to 3 weeks in ten patients, between 3 and 35 weeks in three patients and more than 35 weeks in five patients. In all patients, Gd-DTPA enhancement on the surface of the ligamentous transplant was visualized. This enhancement was between 1 and 10 mm thick. In all patients, complete stability of the knee joint was achieved, postoperatively. In 15 patients flexion and extension were normal at the postoperative investigation. Three patients had a limitation of knee movement. In these MR studies, significant hyperplasia of the synovial membrane of the entire joint was diagnosed, explaining the persisting problems. Gd-DTPA-enhanced MR of the knee joint allows non-invasive documentation of remodelling following a patellar ligament transplant and possible complications.

Adolescent↗

Patterns of alpha-L-fucosidase in acute myeloid leukemia cells. Comparison with promyelocytic HL-60 cell line.

Changes were observed in alpha-L-fucosidase forms in cells from acute myelocytic leukemias (AML). Total alpha-L-fucosidase activity was not significantly different for normal granulocytes and leukemic cells, but enzymic profiles obtained by chromatofocusing are quite different. In granulocyte profile, two main peaks are present (B and more acidic A) which were eluted at pH 5.2 with a shoulder at pH 4.6. In AMLs the B form is present but weakly expressed, whereas the more acidic forms are the major ones. This pattern may be related either to the malignancy character or to the stage at which the differentiation is stopped. Experiments on an HL-60 cell line (promyelocytic cells corresponding to the AML 3 type) showed that differentiation induced by dimethyl sulfoxide leads to the appearance of the B form present in normal mature cells. Thus the repartition of the enzyme forms seems to be related to the stage of differentiation of the myelocytic cells.

Acute Disease↗

Molecular cloning and nucleotide sequence of a cDNA encoding hydroxyindole O-methyltransferase from chicken pineal gland.

Hydroxyindole O-methyltransferase (EC 2.1.1.4) is the enzyme that catalyses the synthesis of melatonin in the pineal gland and in the retina. Polyadenylated RNA from chicken pineal glands was used to prepare a cDNA library in lambda gt11. The library was screened with an antiserum directed against chicken hydroxyindole O-methyltransferase, and one cDNA clone was isolated. The fusion protein expressed by phage lysogens was identified on Western blots as a 165 kDA immunoreactive protein (beta-galactosidase, 110 kDa; hydroxyindole O-methyltransferase, 38 kDa). The fusion protein exhibited hydroxyindole O-methyltransferase activity. Its Km values for N-acetyl-5-hydroxytryptamine and S-adenosylmethionine were 5 times those of the natural enzyme. The intrinsic activity of the fusion protein was approx. 0.25% that of the natural enzyme. The cDNA consisted of 1436 nucleotides, including a 1038-nucleotide sequence encoding a full-length 346-amino-acid hydroxyindole O-methyltransferase. Comparison with bovine hydroxyindole O-methyltransferase [Ishida, Obinata & Deguchi (1987) J. Biol. Chem. 262, 2895-2899] revealed 52% identity in nucleotide sequences and 44% identity in peptide sequences. Northern-blot analysis revealed the presence of hydroxyindole O-methyltransferase mRNA transcripts in chicken pineal gland and retina, but not in the telencephalon.

Acetylserotonin O-Methyltransferase↗

Dictyostelium discoideum as an expression host for the circumsporozoite protein of Plasmodium falciparum.

We have used the cellular slime mold, Dictyostelium discoideum (Dd), to express the Plasmodium falciparum circumsporozoite protein (CS), a potential component of a subunit vaccine against malaria. This was accomplished via an expression vector based on the discoidin I-encoding gene promoter, in which we linked a sequence coding for a Dd leader peptide to the almost complete CS coding region (pEDII-CS). CS production at both the mRNA and protein levels is induced by starving cells in a simple phosphate buffer. Variation in pH or cell density does not seem to influence CS synthesis. CS-producing cells can be grown either on their normal substrate, bacteria, or on a semi-synthetic media, without affecting CS accumulation level. The CS produced in Dd seems similar to the natural parasite protein as judged by its size and epitope recognition by a panel of monoclonal antibodies. We constructed a second expression vector in which the CS is under the control of a Dd ras promoter. CS accumulation can then be induced by external addition of cAMP. Such a tightly regulated promoter may allow expression of proteins potentially toxic to the cell. Thus, Dd could be a useful eukaryotic system to produce recombinant proteins, in particular from human or animal parasites like P. falciparum.

Amino Acid Sequence↗

Long-term effects of constant light or darkness on chicken pineal hydroxyindole-O-methyltransferase expression: biochemical and cellular aspects.

1. Chickens kept in constant light, as opposed to constant darkness, display a twofold increase in the activity of pineal hydroxyindole-O-methyltransferase (HIOMT), the last acting enzyme in the melatonin pathway. 2. Using an immunological approach, we presently show that this regulation of HIOMT activity reflects changes in the concentration of a single molecular form of the enzyme protein (a 38 kDa polypeptide). Immunohistofluorescence indicates that these concentration changes concurrently affect modified photoreceptors and pinealocyte-like cells in the chicken pineal organ. 3. Together, the present data support the hypothesis that environmental lighting might regulate the expression of the HIOMT gene.

Acetylserotonin O-Methyltransferase↗

Mammalian beta-D-mannosidase and beta-mannosidosis.

Lysosomal beta-D-mannosidase is the last exoglycosidase involved in the sequential degradation of the N-glycosylproteins glycans. Research on this enzyme was restricted before the discovery of its hereditary deficiency, first in goat (1981) and later in man (1986). We describe the biochemical aspects of these beta-mannosidosis and the properties of the beta-mannosidases of mammalian origin. Our own results concerning human enzyme (from kidney and urine, seminal plasma and blood cells) suggest that, apart from the case of the inherited disease, beta-mannosidase may become a useful tool in other pathologies.

Animals↗

[Volar plate osteosynthesis in typical and atypical distal radius fractures].

28 patients with a fracture of the distal end of the radius were treated by a T-plate osteosynthesis through the volar approach. There were 7 unstable distal metaphyseal fractures and 21 dislocated intra-articular fractures. 21 patients were investigated 6 months to 8 years after operation according to the scheme of Sarmiento. 17 patients had a good or excellent result, 4 patients a fair or poor result. 2 patients developed a Sudeck's dystrophy (Algodystrophy), one of them with a radial-ulnar bone bridge. The volar application of the plate is indicated for flexion and extension fractures. In cases with compression of the dorsal cortex a bone graft is indicated to improve a stable osteosynthesis. A conventional tomography on two views helps to diagnose exactly an intra-articular fracture and to decide whether to use a plate or pins and external fixation after open reduction. Remanipulation or an operation 2 weeks after trauma increases the risk of a Sudeck's dystrophy and leads to a poor result.

Adult↗

[Magnetic resonance tomographic diagnosis of internal lesions of the shoulder following luxation. A comparison with arthroscopic findings].

Fifteen patients with a recurrent dislocation of the glenohumeral joint were preoperatively investigated by MRI. We created a special protocol with axial T1-, T2-, proton-density- and sagittal T1-weighted images. MRI findings such as defects of the glenoid labrum and Hill-Sachs compression fractures proved to be correct during surgery. In the chosen protocol the diagnostic imaging of rotator cuff lesions was not specific. In 10 cases lesions were seen but in only 5 patients did these findings prove to be correct during surgery. However, MRI imaging of glenohumeral joints is a reliable non-invasive diagnostic method.

Adult↗