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Biomedical subjects

N Dourov

Publications and source records attributed to N Dourov.

At least 19 recordsLinked to original sources
PubMed1992

Induced and genetic mouse middle ear ossicular malformations: a model for human malformative ossicular diseases and a tool for clarifying their normal ontogenesis.

Oral administration of 13-cis retinoic acid (RA) to pregnant mice on the 9th gestation day provokes important malformations of the middle ear ossicles, associated with a general kind of craniofacial dysmorphogenesis evoking the human mandibulofacial dysostosis. The malleus, incus and stapes are affected. The malleus exhibits a handle separated from its head and keeping a persistant relationship with the tubotympanic recess. The stapes makes no contact with the otic capsule. The malformation pattern is visible early as shown by the appearance of an abnormally curved Meckel's cartilage at day 12, followed by the development of atypically shaped ossicular anlagen. The mouse "far" (first arch malformation) mutation is responsible for minor ossicular abnormalities which disrupts the normal relationships between the stapes, Reichert's cartilage and stapedial muscle. The administration of RA to pregnant mice and the comparison with a genetically induced malformation (the mutation far) provides some interesting information about the postulated mechanisms of human middle ear dysmorphogenesis, as well as precious data about the features of normal ossicular primordia formation. The comparison of these features with human middle ear abnormalities as revealed by medical imaging sheds light on human malformation patterns and provides a better understanding of normal and abnormal radiologic ossicular aspects.

Abnormalities, Drug-Induced↗
PubMed1992

Review and new case reports on scanning electron microscopy of pili annulati, Monilethrix and Trichothiodystrophy.

Pili annulati, Monilethrix and Trichothiodystrophy are uncommon conditions in which the hair shaft has a distinct appearance as seen by optical microscopy and scanning electron microscopy (SEM). We report several new cases and review the characteristic ultrastructural abnormalities investigated by SEM. Pili annulati: abnormal areas which show a longitudinal, "curtain-like" folding of the cuticular cells, alternating with normal areas. The latter present regularly non-systematized, superficial depressions. Hair specimens of the patient's mother show the same surface irregularities. Monilethrix: most hair shafts show variations in thickness giving a typical nodal appearance. In the isthmus area we noticed longitudinal ridging and cuticular scales that are extended lengthwise in a fish-scale-like pattern. In the nodus area a smooth surface due to a complete loss of cuticular cells, was observed. Trichothiodystrophy: the hair morphology observed by SEM is characterized by severe cuticular and secondary cortical degeneration along the entire length of the flattened hair shaft, with longitudinal ridging, cuticle loss, trichlorrhexis nodosa formation and trichoschisis. SEM observations show morphological abnormalities which are characteristic for each pathological condition described. This method may provide data that add some clarity in the surface changes of the different hair shaft anomalies.

Adult↗
PubMed1991

Nuclear ultrastructure of human parotid gland tumors with special focus on nuclear bodies.

The purpose of our study was to determine the morphology and the proportion of NB in 20 human parotid gland tumors. Types I and III NB were observed in benign as well as malignant tumors. Some atypical forms ("onion-like" NB and NB with lipidic inclusions) were found in benign tumors. The proportion of nuclear profiles containing one and more NB varied from 0 to 60% in the benign tumors, and from 4 to 50% in the malignant tumors. Nuclei containing 3 and more NB were observed as well in the benign as in the malignant tumors. The NB ratio cannot be taken for a malignancy criteria.

Adenocarcinoma↗
PubMed1991

Ultrastructural study on nuclear bodies of the rat parotid glands.

Nuclear bodies of types I, II, III and IV are constantly present in rat parotid glands. They become apparent on the 21st day and afterwards. Type IV nuclear bodies were chiefly found in the striated ducts. Nuclei containing 3 and more nuclear bodies were found as early as the 3rd month, although only in the striated ducts. Nuclear bodies are not related to glycogen or DNA replication but probably to rRNA metabolism. This study leads to a better understanding of nuclear bodies modifications which can be observed ultrastructurally in human salivary glands pathology. Their increased number in some nuclei may be the expression of an alteration of the cell metabolism.

Animals↗
PubMed1990

Anaemia and marrow blood flow in the rat.

An increase in bone marrow blood flow has been previously described in anaemic rabbits and dogs. We examined the effect of haemorrhage and haemolysis in female Sprague-Dawley rats, with the hypothesis that high blood flow was related to hyperplasia of bone marrow tissue and that the increase would affect bone as well. Blood flow was measured in tibia and femur by the microspheres trapping method. Chronic anaemia was accompanied at day 32 by a marked increase (factor of 1.7-1.9) in blood flow to bone marrow and to bone. On the other hand, no increase in blood flow was observed in chronic compensated anaemia, showing that anaemia per se and not stimulation of erythropoiesis was responsible for the increase. We then explored the effect on blood flow of two factors associated with anaemia. Erythropoietin 4 U/d for 4 d failed to induce any increase in bone and marrow blood flow. Systemic hypoxia (76 mmHg for 3 d) reduced the fraction of cardiac output conveyed to bone and marrow by 40-50%, but this decrease was more than compensated by an increase in cardiac output. We conclude that neither erythropoietin nor low tissue pO2 is the direct cause for the increase in bone and marrow blood flow observed in anaemia.

Anemia↗
PubMed1990

[Changes in the surface microrelief and the loss of dental enamel after the use of an abrasive spray of sodium bicarbonate].

Alterations of the surface dental microtopography and enamel loss due to the use of an air-abrasive system on polished and no-polished surfaces of extracted teeth, have been evaluated by scanning electron microscopy, and surface roughness and weight measurements. Results show irregular depressions and significant increased surface roughness on no-polished enamel surfaces while polished enamel surfaces are very lightly affected by the air-abrasive system. Enamel loss expressed in weight % attains 1%-5.3% after use of an air-abrasive system.

Bicarbonates↗
PubMed1990

Ultrastructure of the nuclear bodies in the human parotid gland.

The ultrastructure of 17 human parotid glands was studied in order to determine the features of the nuclear bodies and their possible relation to various pathological conditions. Types I and III nuclear bodies were frequently identified in acini and in striated ducts. Type IV nuclear bodies were seldom found. The percentage of nuclear sections containing nuclear bodies varied from 5.7 to 66.4 for the acini, and from 17.8 to 80% for the striated ducts. In 4 out of our 6 cases of chronic inflammation, numerous nuclear bodies were observed in the same nucleus. The increase in the number of nuclear bodies seemed to be related to an altered cell metabolism. In 3 cases, membranous type inclusions were found. This type of nuclear inclusion is quite different from the true nuclear bodies.

Actin Cytoskeleton↗
PubMed1989

Histopathology of the interactions between alveolar bone and impacted dental germs in osteopetrotic op/op rats.

Osteopetrosis, a general increase in bone density, is well-known as an autosomal recessive disease in several mammalian species. Compared with normal littermates, the osteopetrotic rats suffered from a complete failure of tooth eruption. Histologic and microradiographic studies show that the molars and the incisors developed a progressive ankylosis, the bone invades the germs and finally dissociates them. As early as the first days after birth, the incisors and the first molars are affected by the osteopetrotic process while the second and the third molars remain untouched. The periodontal membrane of the incisors is rapidly invaded by the osteopetrotic bone trabeculae. After the eleventh day, the process reached all molars. The germs were overlaid by an occlusal unresorbed bone. The formation of the gebernacular canal appeared to be independent of the prefunctional eruption.

Alveolar Process↗
PubMed1989

Effects of bone marrow transplantation on impacted dental germs in osteopetrotic op/op rats.

The osteopetrotic op/op rats suffered from a complete failure of tooth eruption in association with a reduced bone resorption. An unresorbed occlusal bone overlaid the germs which remained embedded in bone. The process of prefunctional eruption in limited growing teeth depends on the resorption of the alveolar bone covering the germs. The aim of this study was to investigate the effects of hematopoïetic grafts in newborn op/op rats on the process of prefunctional eruption. Fifteen op/op treated rats were used for radiographic, microradiographic and histologic examinations. After transfusion of bone marrow cells, we observed the restoration of bone resorption and a delayed eruption of the molars. The incisors never erupted. They developed odontome-like tumors near their apices. These results confirm the dependence of tooth eruption on bone resorption.

Animals↗
PubMed1989

Brushite in the pulp of primary molars.

This study was undertaken to investigate the mineral phase of spherulitic calcifications discovered in the pulpous mesenchyme of human primary molars by microradiography. Analytical scanning electron microscopy and x-ray diffraction disclosed that well-crystallized brushite is the major compound of the spherulites. The mechanism leading to the crystallization of brushite is far from well understood. Histologically, on decalcified sections, inflammatory cells and capillaries can be seen trapped in the spherulites. In the light of these findings, it could be suggested that metabolic conditions may promote the crystallization of brushite in the pulp of primary molars.

Adolescent↗
PubMed1989

[Ultrastructural bases for the synthesis of ribosomal RNA in the nuclei of the parotid gland. The role of intranuclear bodies].

Identification and numerations on electron microscopic samples of rat parotid glands revealed an unexpected high frequency of nuclear bodies in acini and in striated ducts. Three different morphological types of nuclear bodies were identified: type I corresponded to a circular outline of finely fibrillar or granular bodies. Type II exhibited an outer fibrillar cortex surrounding a central lucent core. Type III possessed a thick granular or fibrillar cortex surrounding dense granules. Type IV nuclear bodies appeared to be circumscribed by a thick lamellar cortex and contained dense and heavy stained granules. The biochemical content of the nuclear bodies mostly corresponds to proteins and it was possible to demonstrate slight quantities of RNA. Recent studies seem to confer to some of those nuclear bodies a possible role in RNA processing or transport. It is however peculiar to find nuclear bodies in striated ducts which are not involved in active protein synthesis as the acini.

Animals↗
PubMed1989

[Immunopathologic mechanisms associated with granulomas and odontogenic cysts: a general review].

The authors make a general survey of the immunopathological mechanisms involved in odontogenic cysts and granulomas. The dental pulp and the sound periapical tissues contain neither inflammatory nor immunoglobin-producing cells. Dental decay associated with bacterial aggression of the dental pulp and periapical tissues might induce a nonspecific inflammation which subsequently becomes more specific. Immunoglobulins are present in fluid aspirates from odontogenic cysts and granulomas. Several investigations have pointed out nonspecific inflammatory mediators (including the C3 complement components), T lymphocytes (helpers and suppressors), B lymphocytes, protein S-100 + cells (Langerhans cells). The presence of immunoglobulins, immunocompetent cells and C3 complement components confirms that all constituents of both humoral and cell-mediated immunological reactions might play an essential role in the pathogenesis of osteolysis.

Humans↗
PubMed1989

[The gold standard and optimalization of diagnostic choice: the pulmonary nodule and transthoracic pulmonary puncture-biopsy].

In this review of the literature, it is emphasized that the published results about the transthoracic pulmonary needle biopsy (TPNB) cannot be readily evaluated due to the inconsistency of the reference tests, the methods and the investigated subjects. Gold-standards for evaluation of lung tumors have been described and are recalled. The limits of the TPNB are pointed out in the diagnosis of solitary pulmonary nodules and benign lesions. In a bayesian approach, it is shown that the TPNB is only useful in confirming an a-priori diagnosis of cancer.

Bayes Theorem↗
PubMed1989

Concomitant osteitis fibrosa cystica and ameloblastoma of the mandible.

A patient with a multiloculated cystic lesion of the mandible, and clinical as well as biological features of hyperparathyroidism is presented. This association suggesting the diagnosis of brown tumor was actually due to an ameloblastoma of the mandible. Such a concomitant association of an ameloblastoma with symptomatic hyperparathyroidism has never been reported to our knowledge.

Adenoma↗
PubMed1989

Measurement of pulp temperature increase to externally applied heat (argon laser, hot water, drilling).

In order to weld cracks in tooth enamel, it is necessary to bring the surface of the tooth to the fusion temperature of the enamel (greater than 1,000 degrees C). The study investigated whether this increase in surface temperature can cause damage to the vitality of the tooth by recording, using a thermocouple, the temperature in the pulp chamber of teeth exposed to argon laser irradiation (power density after focusing: 4000 W/cm2; duration of continuous irradiation: 1-5 seconds). These pulp temperature increases were compared with those considered safe for the tooth, i.e., contact with a hot drink, drilling of cavities with air + water cooling. It was shown that punctual irradiations with an argon laser for periods of 2 or 4 seconds generated temperature increases in the pulp chamber which were less than inferior to those caused by contact with water at 54-55 degrees C for 1 or 2 seconds, and were of the same order as those caused by the drilling of class III or V cavities of 1 mm in depth and 1 mm in diameter. These results suggest that it is worth continuing research into applying the technique in the mouth.

Body Temperature↗
PubMed1989

[Ultrastructure of microcalcifications of the pulp mesenchyme of human deciduous teeth].

Scanning electron microscopic observations of pulp calcifications in deciduous molars were correlated with microradiographic findings. Numerous spherical calcifications were found in appearance similar to those in the permanent dentition. In a second type, mineralization took the form of diffuse deposits of calcium. The discrete diffuse foci coalesced into large islands of mineralized connective tissue. A third type of calcification was observed in which rhombic crystals were associated in a spherulitic pattern. The exact cause of the crystal formation is unknown. Moreover, as we are aware, the spherulitic calcifications have never been previously reported in this location. The preliminary results indicated that mineralization in the pulp of deciduous molars, takes a variety of forms, suggesting that calcium deposition can occur by different processes.

Dental Pulp↗