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Biomedical subjects

B Vidic

Publications and source records attributed to B Vidic.

At least 19 recordsLinked to original sources
PubMed1997

Targeted disruption of the peripheral-type benzodiazepine receptor gene inhibits steroidogenesis in the R2C Leydig tumor cell line.

To evaluate the role of the mitochondrial peripheral-type benzodiazepine receptor (PBR) in steroidogenesis, we developed a molecular approach based on the disruption of the PBR gene, by homologous recombination, in the constitutive steroid producing R2C rat Leydig tumor cell line. Inactivation of one allele of the PBR gene resulted in the suppression of PBR mRNA and ligand binding expression. Immunoblot and electron microscopic immunogold labeling analyses confirmed the absence of the 18-kDa PBR protein in the selected clone. Although mitochondria from the PBR-negative cells contained high levels of the constitutively expressed 30-kDa steroidogenic activity regulator protein, these cells produced minimal amounts of steroids compared with normal cells (5%). Moreover, mitochondria from PBR-negative cells failed to produce pregnenolone when supplied with exogenous cholesterol. Addition of the hydrosoluble cholesterol derivative, 22R-hydroxycholesterol, increased steroid production by the PBR-negative R2C cells, indicating that the cholesterol transport mechanism was impaired. Stable transfection of the PBR-negative R2C Leydig cells with a vector containing the PBR cDNA resulted in the recovery of the steroidogenic function of the cells. These data demonstrate that PBR is an indispensable element of the steroidogenic machinery, where it mediates the delivery of the substrate cholesterol to the inner mitochondrial side chain cleavage cytochrome P-450.

Animals↗
PubMed1997

Acute action of choriogonadotropin on Leydig tumor cells: qualitative and quantitative transformation of lipid moieties.

BACKGROUND: Testicular Leydig cells use either exogenous or de novo synthesized cholesterol as the substrate for the production of testosterone with hormone stimulation. Although the long-term effect of trophic hormones on Leydig cell cholesterol uptake, storage, and deesterification has been well documented, the early effects of the human choriogonadotropin (hCG) on cell cholesterol/lipid distribution are not yet known. METHODS: Sections of cells treated with hCG for 15 sec to 30 min were examined by electron microscopy (EM) for the surface density of lipid moieties in the cytoplasm. In addition, the time-dependent distribution of lipids within the cytoplasmic inclusions and the ultimate destination of this substrate were evaluated by EM. The results were analyzed with standard morphometric methods. RESULTS AND CONCLUSION: The surface density of cytoplasmic lipid pools increased significantly within the 15 sec following the exposure of cells to hCG, and it tapered off to the control level in the subsequent 30 min. Such a fluctuation in the amount of cytoplasmic lipids may be due to (1) the quantity of released substrate from the reticular compartment or (2) the rate of its transport across the outer mitochondrial membrane to the inner mitochondrial cytochrome P450 side-chain cleavage, where steroidogenesis begins with the conversion of cholesterol to pregnenolone. These two processes were not quantitatively coordinated in the stimulated cell during the initial 30 min, resulting in a surplus of cytoplasmic lipid pools. To compensate for such uneven metabolic balance, the cell apparently disposed of the excess substrate by a mechanism of molecular regrouping from a micellar configuration to a bilayer structure followed by exocytosis.

Animals↗
PubMed1997

Anatomical variant of the lateral pectoral nerve innervating the anterior portion of the deltoid muscle: a case report.

BACKGROUND: The deltoid muscle is innervated by the axillary nerve. There is no collateral nerve supply described for this muscle. Palsy of the axillary nerve is common in shoulder trauma due to its close relationship to the surgical neck of humerus. METHODS: A dissection of the pectoral and axillary regions of two female cadavers was performed bilaterally for a detailed analysis of the innervation of the deltoid muscle. RESULTS: A branch of the lateral pectoral nerve provided supplemental innervation to the anterior portion of the deltoid muscle bilaterally in both cadavers. CONCLUSION: A branch of the lateral pectoral nerve could provide collateral nerve supply to the deltoid muscle. The frequency of this anatomical variation requires further exploration.

Aged↗
PubMed1997

Atomic force microscope imaging of DNA and DNA repair proteins: applications in radiobiological research.

By using the atomic force microscope (AFM), three-dimensional structures of biological specimens may be imaged at nanometer resolution. Furthermore, samples can be imaged in air or in fluid environments. The tapping mode of AFM operation for imaging has offered a significant advance in visualizing soft biological structures, such as DNA, proteins, and membranes. Here, we review the principles underlying the application of this instrument to radiation biological investigations. We focus on examples of proteins involved in the processes of repair of damaged DNA, including poly(ADP-ribose) polymerase, Ku protein, and DNA protein kinase. Novel observations on the character of DNA damage and repair have been addressed by direct visualization of DNA and protein-DNA interactions, such as the observation that the Ku protein is capable of physically joining DNA fragments in vitro. The AFM offers a powerful tool for investigating biologically important molecular interactions that are relevant to DNA damage and repair processes.

Air↗
PubMed1997

Peripheral benzodiazepine receptor in cholesterol transport and steroidogenesis.

Steroidogenesis begins with the metabolism of cholesterol to pregnenolone by the inner mitochondrial membrane cytochrome P450 side-chain cleavage (P450scc) enzyme. The rate of steroid formation, however, depends on the rate of cholesterol transport from intracellular stores to the inner mitochondrial membrane and loading of P450scc with cholesterol. In previous in vitro studies, we demonstrated that a key element in the regulation of cholesterol transport is the mitochondrial peripheral-type benzodiazepine receptor (PBR). We also showed that the polypeptide diazepam binding inhibitor (DBI), an endogenous PBR ligand, stimulates cholesterol transport and promotes loading of cholesterol to P450scc in vitro, and that its presence is vital for hCG-induced steroidogenesis by Leydig cells. Based on these data and the observations that i) the mitochondrial PBR binding and topography are regulated by hormones; ii) the 18-kDa PBR protein is functionally coupled to the mitochondrial contact site voltage-dependent anion channel protein; iii) the 18-kDa PBR protein is a channel for cholesterol, as shown by molecular modeling and in vitro reconstitution studies; iv) targeted disruption of the PBR gene in steroidogenic cells dramatically reduces the ability of the cells to transport cholesterol in the mitochondria and produce steroids; v) endocrine disruptors, with known anisteroidogenic effect, inhibit PBR ligand binding; and vi) in vivo reduction of adrenal PBR expression results in reduced circulating glucocorticoid levels, we conclude that PBR is an indispensable element of the steroidogenic machinery.

Animals↗
PubMed1997

Regulation of rat testis gonocyte proliferation by platelet-derived growth factor and estradiol: identification of signaling mechanisms involved.

To determine what factors regulate gonocyte proliferation in newborn rats, we first examined the expression of several signal transduction molecules by immunocytochemistry in 3-day-old rat testis sections. We found that gonocytes specifically expressed the iota and zeta isoforms of protein kinase (PK) C (PKC) and the phosphatidylinositol 3-kinase (PI3-K). Because both the zeta PKC and PI 3-K have been shown to play a role in platelet-derived growth factor (PDGF)-induced cell proliferation, we examined the effects of PDGF on gonocytes. For this, we developed a method to obtain highly purified and viable gonocytes in culture. After enzymatic digestion, differential adhesion, and two successive gradient fractionations, the gonocyte suspension obtained was over 90% pure, as assessed by light microscopy. The viability of cultured gonocytes exceeded 90% after 48 h in the presence of 2.5% FBS used as a survival factor. Immunodetection studies showed that isolated gonocytes expressed zeta PKC, PI 3-K, and the PDGF receptor. Treatment with 10 ng/ml PDGF induced a 4-fold increase of bromodeoxyuridine incorporation into gonocytes (from 5% proliferative gonocytes under basal conditions to 20% in the presence of PDGF). Because neonatal Sertoli cells secrete high levels of the growth promoting steroid, 17 beta-estradiol, we also tested its effect and found that it induced gonocyte proliferation at a level comparable with that of PDGF and that this effect was blocked by the estrogen receptor antagonist, ICI 164384. The combination of PDGF and estradiol, however, was not additive, suggesting that their effects were mediated by common molecular target(s). These results demonstrate that PDGF and estradiol activate gonocyte proliferation in vitro, suggesting that they may act as the physiological regulators of gonocyte development in vivo.

Animals↗
PubMed1996

A morphometric and functional study of the toxicity of atmospheric ammonia in the extrathoracic airways in pigs.

The effects of atmospheric ammonia (NH3) on the nasal and tracheal mucosa of pigs were investigated by morphometric and functional methods. Pigs were exposed to four concentrations of NH3 [5 (control), 25, 50 and 100 ppm] for 6 days in a specially designed air-pollutant exposure chamber. Samples were taken from the turbinates and the trachea, and the respiratory mucosa was examined by light and scanning electron microscopy. Dose-response curves to carbachol and isoproterenol were constructed using isolated strips of tracheal smooth muscle, with or without epithelium. In pigs exposed to ammonia, considerable mucosal injuries were observed in the turbinates but not in the trachea. The number of neutrophils in the epithelial layer and in the lamina propria, and epithelial hyperplasia were closely and significantly correlated with the concentrations of ammonia (r = 0.894, p < 0.001; r = 0.727, P < 0.001; and r = 0.818, p < 0.001, respectively). Except for the lamina propria, all these changes were significant (p < 0.05) at ammonia concentrations as low as 25 ppm. The percentage of the surface of the turbinate mucosa that was ciliated tended to decrease with increasing ammonia concentration (r = 0.439, p < 0.082). Ammonia induced smooth-muscle hyperresponsiveness to carbachol with a close linear correlation between individual values of the carbachol-induced maximal effect and the NH3 concentrations (r = 0.526, p < 0.003). While mechanical destruction of the epithelium induced an increase in Emax in the control group, no difference was observed between the intact and denuded strips from animals exposed to ammonia. The response to isoproterenol was not influenced by ammonia. It was concluded that quantitative histological analysis of the inflammatory infiltration and epithelial hyperplasia in the turbinates is a useful tool for quantifying the effects of atmospheric pollutants in pigs; a 6-day exposure to ammonia induces nasal irritation and functional disturbances of the tracheal smooth-muscle contractions at concentrations as low as 25 ppm.

Adrenergic beta-Agonists↗
PubMed1996

Acute action of choriogonadotropin on Leydig tumor cells: changes in the topography of the mitochondrial peripheral-type benzodiazepine receptor.

We examined the topography of the MA-10 Leydig tumor cell mitochondrial peripheral-type benzodiazepine receptor (PBR). In previous studies, the 18 kDa PBR was found to be functionally associated with the voltage-dependent anion channel, located in the junctions between outer and inner membranes. Transmission electron (TEM) and atomic force microscopy (AFM) of immunogold labeled PBR on Leydig cell mitochondrial preparations showed that the 18 kDa PBR protein is organized in clusters of 4-6 molecules. Addition of hCG to Leydig cells induces a rapid, within 30 sec, increase in PBR ligand binding and morphological changes, namely redistribution of PBR molecules in large clusters (>7 particles). These hCG-induced changes were inhibited by a cAMP-dependent protein kinase inhibitor and by the benzodiazepine flunitrazepam. AFM further demonstrated the rapid reorganization of the mitochondrial membrane, where the formation of contacts between the outer and the inner mitochondrial membrane may facilitate cholesterol transfer.

Animals↗
PubMed1995

Atomic force microscopy of paired helical filaments isolated from the autopsied brains of patients with Alzheimer's disease and immunolabeled against microtubule-associated protein tau.

Atomic force microscopy was employed to study the structural features of paired helical filaments isolated from autopsied brains of Alzheimer's disease patients. The identity of paired helical filaments was confirmed following a specific immunogold labeling using antibodies directed against the microtubule-associated protein tau, which is the main constituent of paired helical filaments. Computer-assisted analysis of high resolution, three-dimensional images allowed us to study the longitudinal and cross-sectional profiles of individual filaments. Vertical dimensions of filaments were assessed along these sectional profiles. The smallest vertical diameter (6.66 +/- 0.78 nm) was obtained at the level of the greatest lateral profile (ie, "loop"), while the greatest vertical diameter was two times larger (13.68 +/- 1.46 nm) and was obtained at the level of the smallest lateral profile (ie, "crossover") of the filament. Based on the shapes of these sectional profiles and their vertical dimensions, paired helical filaments appeared to be composed of two identical integral subunits, each of a circular cross-sectional profile of approximately 7 nm in diameter, wound around one another in a left helical manner, with a 7-nm center-to-center separation. Half-period of this helix was estimated at 81.4 +/- 2.1 nm. Serial cross-sectional profiles of paired helical filaments were further utilized to construct a theoretical model of their internal organization. This model suggests that each structural subunit of the paired helical filament incorporates at least four identical protofilaments.

Alzheimer Disease↗
PubMed1994

Topography of the Leydig cell mitochondrial peripheral-type benzodiazepine receptor.

Native MA-10 mouse Leydig tumor cell mitochondrial preparations were examined by transmission electron (TEM) and atomic force (AFM) microscopic procedures in order to investigate the topography and organization of the peripheral-type benzodiazepine receptor (PBR). Mitochondria were immunolabeled with an anti-PBR antiserum coupled to gold-labeled secondary antibodies. Results obtained indicate that the 18,000 MW PBR protein is organized in clusters of 4-6 molecules. Moreover, on many occasions, the interrelationship among the PBR molecules was found to favor the formation of a single pore. Taking into account recent observations that the 18,000 MW PBR protein is functionally associated with the pore forming 34,000 MW voltage-dependent anion channel (VDAC) these results suggest that (i) the mitochondrial PBR complex could function as a pore, thus allowing the translocation of cholesterol and other molecules to the inner mitochondrial membrane, and (ii) the native receptor is a multimeric complex of an approximate 140,000 MW composed on an average of five 18,000 PBR subunits, one 34,000 VDAC subunit, and associated lipids.

Animals↗
PubMed1994

[Non-arteritic anterior ischemic optic neuropathy: long-term results after hemodilution therapy].

BACKGROUND: In patients with nonarteritic anterior ischemic optic neuropathy (AION) we investigated the long-term effect of hemodilution on functional results, recurrence rate in the affected and involvement of the second eye. PATIENTS AND METHODS: In a retrospective study we reviewed 24 patients ranging in age from 62 to 92 years (mean 77 years) with AION. The duration of follow-up was between 8-51 months (mean 24.8 months). All patients received iso- (Hct > 40%) or hypervolemic (Hct < or = 40%) hemodilution over 8-10 days with daily infusion of 10% hydroxyethyl-starch 200/0.5. The hematocrit decreased significant (p < 0.001) from 43.4 +/- 3.8% to 37.8 +/- 3.5% after this 10-day hemodilution treatment. RESULTS: After the longterm follow-up 29.1% of the patients had an improvement of the central vision by two or more lines, 16.7% had a deterioration, 54.2% remained unchanged. The resulting visual acuity was between 0.5-1.0 in 37.5%, between 0.4-0.1 in 41.7% and worse than 0.1 in 20.8%. Neither visual fields nor the VECP were significant changed by hemodilution. After the mean follow-up period of 24.8 months no recurrence occurred in the affected eye and the second eye as never involved. CONCLUSION: Hemodilution therapy has no significant longterm effect on visual acuity and visual fields, but it seems to have a beneficial influence on the recurrence rate in the affected and on the involvement of the second eye.

Aged↗
PubMed1991

[Optimizing target volume assessment in irradiation of intraocular melanomas with ruthenium applicators].

Radioactive applicators have been used for conservative therapy of melanomas in the vicinity of the nervus opticus and of melanomas of the ciliary body for a few years. The aim of optimal radiotherapy is to destroy all tumor cells and to protect the optic nerve and macula. Therefore, we calculated the dose distributions and isodoses for ruthenium applicators. Isodoses show underdosage or overdosage in the tumor area. We also present a calculation model with which it is possible to simulate selective shielding of activated parts of the applicator.

Brachytherapy↗
PubMed1990

Clinical significance of ultrastructural findings in the corpora cavernosa of normal and impotent men.

Corpora cavernosa of 5 normal and 11 impotent living men were studied by electron microscopy. Of the smooth muscle cells 42.3% from corporeal tissues of impotent men showed a pronounced thickening of the basal lamina, a paucity of dense bodies and contractile filaments, minimal or no glycogen and fewer vesicles on the cell surface, whereas only 5.4% of the smooth muscle cells from normal men showed similar alterations. These differences were statistically significant (p less than 0.003). The percentage of altered smooth muscle cells in corporeal tissues of impotent men was proportional to the severity of symptoms and clinical findings. Morphometric analysis revealed no significant differences in the relative proportions of the major components of corporeal tissue (smooth muscle cells, extracellular matrix, vascular lumina and endothelial cells). These findings suggest the need for early detection of corporeal tissue degeneration by preoperative biopsy to assist in better selection of candidates for a penile vascular operation. They also may contribute to the development of new therapeutic modalities for erectile dysfunction.

Adult↗
PubMed1990

Disk fragment migration.

This report analyzes the most frequently observed migration paths of disk fragments in 47 patients who had extruded or sequestered disks. Observations are based principally on magnetic resonance (MR) images. When disk fragments moved in a superior (42%) or inferior (40%) direction from the donor disk, the displaced disk components were most frequently (94%) dislodged into the right or left half of the anterior epidural space (AES) and rarely straddled the midline. To explain this phenomenon, the authors investigated the anatomy of the AES by dissecting four cadaver specimens and reviewing 300 MR images of the spine. They conclude that the migrating path of a disk fragment is determined by the anatomy of the AES, a fairly well-defined space delimited posteriorly by the posterior longitudinal ligament and by membranes laterally attached to it. It consists of two compartments separated by a sagitally aligned septum. During migration, sequestered disk fragments usually stay in these compartments.

Cervical Vertebrae↗
PubMed1990

[Long-term biometric results in glaucoma in children].

In a retrospective study 30 eyes of 18 patients suffering from developmental glaucoma (primary congenital glaucoma, Sturge Weber syndrome, juvenile glaucoma) were examined after surgery. The mean follow-up period was 13 years. Eyeball length and anterior chamber depth were measured by means of echooculometry. Biometric data (echooculometry, corneal diameter, cup to disk ratio) were compared with psychophysic data (visual acuity, visual field). Up to an axial length of 26 mm, myopia caused by elongation of the eyeball is compensated by the weak refractive power of the large cornea. In cases with an eyeball length of more than 27 mm, excessive myopia was found. There is a linear correlation between corneal diameter and axial length of the eyeball. In all cases with an axial length of more than 27 mm only low vision was achieved. From our results can be concluded that 27 mm is the "critical" eyeball length which carries a grave prognosis. Due to the late (minimum 4 years) onset of the disease, all the operated eyes with Sturge Weber syndrome and juvenile glaucoma were in normal size.

Adolescent↗
PubMed1989

[Diagnosis of ocular Chlamydia infections. Experiences with 2 test systems].

It is well known that both direct and indirect test systems are available for identifying chlamydial infections. In the author's laboratory two of these systems were compared by examining conjunctival scrapings, sera, and tears from more than 150 patients with chronic, therapy-resistant conjunctivitis. The principal criteria considered were the time and technical effort involved and the sensitivity and specificity of these tests in ophthalmology. According to the authors' findings, direct identification of the pathogens with FITC-labeled monoclonal antibodies is useful for diagnosing fresh infections. In cases of chronic disease, however, the indirect serologic test is of greater value, because it is usually impossible to isolate the viruses. This test shows specific IgA and IgG antibodies in serum and tears that do not occur before the tenth (IgA) or 30th (IgG) day after infection. The sensitivity and specificity of both tests seem to be on a par with the culture system, which is still the "gold standard" for diagnosis. For a secure diagnosis both test systems should be used, though of course always taking the clinical picture into consideration.

Adult↗