Biomedical subjects

O Collin

Publications and source records attributed to O Collin.

At least 19 recordsLinked to original sources

PubMed2006

Effects of haemorrhagic hypotension on the subcapsular artery and microvasculature of the rat testis.

Developing germ cells may be sensitive to even moderate reductions in blood flow. Surprisingly, however, experimental evidence suggests that the rat testis may be unable to maintain its blood flow during a decrease in systemic blood pressure. This study was therefore performed in order to answer the following questions: Is the testis able to maintain its blood flow during moderate to major reductions in blood pressure and, if so, at which level of the testicular vasculature (main artery or microcirculation) does this compensatory response take place? Moderate (-20%) and major (-40%) reductions in blood pressure were induced in anaesthetized rats by haemorrhage and the effects on testicular microvascular blood flow and subcapsular testicular artery diameter were examined by using laser Doppler flowmetry and in vivo video-microscopy respectively. Haemorrhagic hypotension led to decreased local testicular blood flow, but the relative reductions in flow were generally only half as large as the reductions in blood pressure. Hypotension also decreased the diameter of the main subcapsular testicular artery. During large reductions in blood pressure the subcapsular testicular artery constricts and testicular blood flow decreases. However, blood flow is reduced proportionally less than the mean arterial pressure, suggesting that local regulatory mechanisms are present in the testicular microvasculature, which may prevent blood flow from falling below a critical level.

Adaptation, Physiological↗

PubMed2005

Global analysis of endothelial cell line proliferation patterns based on nutrient-depletion models: implications for a standardization of cell proliferation assays.

It is known that cell populations growing in different environmental conditions may exhibit different proliferation patterns. However, it is not clear if, despite the diversity of the so-observed patterns, inherent cellular growth characteristics of the population can nevertheless be determined. This study quantifies the proliferative behaviour of the permanent endothelial human cell line, Eahy926, and establishes to which extent the estimation of the cell proliferation rate depends on variations of the experimental protocols. Cell proliferation curves were obtained for cells cultured over 16 days and the influences of cell seeding densities, foetal bovine serum content and frequency of culture medium changes were investigated. Quantitative dynamic modelling was conducted to evaluate the kinetic characteristics of this cell population. We proposed successive models and retained a nutrient-depletion toxicity dependant model, which takes into account the progressive depletion of nutrients, as well as the increase of toxicity in the cell culture medium. This model is shown to provide a very good and robust prediction of the experimental proliferation curves, whatever are the considered frequency of culture medium changes and serum concentrations. Thus, the model enables an intrinsic quantification of the parameters driving in vitro EAhy926 proliferation, including proliferation, nutrient consumption and toxicity increase rates, rather independently of the experiments design. We therefore propose that such models could provide a basis for a standardized quantification of intrinsic cell proliferation kinetics.

Cell Count↗

PubMed2001

Testicular damage by microcirculatory disruption and colonization of an immune-privileged site during Borrelia crocidurae infection.

The agent of African relapsing fever, Borrelia crocidurae, causes reversible multiple organ damage. We hypothesize that this damage is caused when the spirochete forms aggregate with erythrocytes in vivo, creating rosettes that plug the microcirculatory system. To test this hypothesis, we compared testicular microcirculation over an extended time period in two groups of rats: one experimentally inoculated with B. crocidurae, the other with the nonerythrocyte rosette-forming Borrelia hermsii. In the B. crocidurae group, erythrocyte rosettes formed during spiro-chetemia blocked precapillary blood vessels and reduced the normal pattern of microcirculatory blood flow. After spirochetemia, erythrocyte rosettes disappeared and flow was normalized. Decreased blood flow and focal vascular damage with increased permeability and interstitial bleeding adjacent to the erythrocyte microemboli induced cell death in seminiferous tubules. Interestingly, we found that B. crocidurae could penetrate the tubules and remain in the testis long after the end of spirochetemia, suggesting that the testis can serve as a reservoir for this bacteria in subsequent relapses. The group infected with B. hermsii displayed normal testicular blood flow and vasomotion at all selected time points, and suffered no testicular damage. These results confirmed our hypothesis that the erythrocyte rosettes produce vascular obstruction and are the main cause of histopathology seen in model animal and human infections.

Animals↗

PubMed2001

Effects of acute graded reductions in testicular blood flow on testicular morphology in the adult rat.

The effect of moderate reductions in testicular blood flow has not been studied systematically. The aim of this study was, therefore, to examine the effects of different degrees of blood flow reduction on testicular morphology and to determine how much flow can be reduced before damage occurs. The subcapsular testicular artery was partially ligated in the left testes of adult rats. Testicular blood flow was measured before, immediately after, and 5 h after the ligation using laser Doppler flowmetry. After 5 h of partial ligation, the testes were removed, and their morphology was examined and related to the degree of blood flow reduction. The number of in situ end-labeled- or TUNEL-positive (i.e., dying) germ cells and the volume density of intravascular polymorphonuclear (PMN) leukocytes were measured. When flow was reduced to approximately 70% or less of its pretreatment value, a dose-related increase in the number of dying spermatogonia and early spermatocytes was seen. The PMN leukocytes accumulated in testicular blood vessels after partial ligation, and the maximum number was observed in testes where flow was reduced by approximately 50% of the pretreatment value. In conclusion, early stages of spermatogenesis are sensitive to a moderate, acute reduction in blood flow. Discrete reductions in flow may, therefore, have a large impact on sperm production.

Animals↗

PubMed2000

Cigarette smoke and hypoxia induce acute changes in the testicular and cerebral microcirculation.

The acute effects of cigarette smoking and hypoxia on the cerebral and testicular microcirculation were studied in anestethised adult rats. Smoking for 2 min did not influence arterial pO2, pCO2 or pH but it induced an increase in cerebral blood flow by 34% and inhibited vasomotion in the testis for about 1 h. One hour after smoke exposure apnea induced a slight increase in arterial pCO2, a significant decrease in pO2, and an increase in cerebral blood flow (CBF) by 54%. In animals not previously exposed to cigarette smoke apnea increased CBF by 121%, demonstrating that a short-term exposure to tobacco smoke influences the cerebrovascular reactivity for more than one hour. In the testis, apnea resulted in a decreased blood flow by 39% and a complete depression of vasomotion. Breathing 10% O2/90% N2 resulted in moderate hypoxia, a total disappearance of the vasomotion in the testis, a 24% decrease in testicular blood flow, but a 23% increase in CBF.

Animals↗

PubMed2000

Testicular vasomotion in different mammals.

Vasomotion is a rhythmical variation in arterial blood flow present in many different organs among them the rat testis. Vasomotion is suggested to play an important role for the transvascular fluid exchange and the exchange of nutrients over the capillary wall as well as the formation of interstitial fluid. The present study was undertaken to elucidate whether vasomotion is present in the testes of different species independent of their anatomical vascular topography. Blood flow in the testes of mouse, brush-tailed possum, tammar wallaby, ram and human was investigated by using a laser Doppler flowmeter. Vasomotion was found in all the species investigated.

Animals↗

PubMed1998

A comparison of skin storage methods for oculoplastic surgery.

PURPOSE: To assess the level of contamination of full-thickness skin grafts stored with or without an antibiotic cover. METHODS: Full-thickness skin grafts were harvested from 40 bilateral upper lid blepharoplasties. Before surgery the face was sterilised, the head of the patient was packed with sterile, single-use surgical drapes and the whole face was left exposed. The harvested full-thickness skin grafts were conserved in sterile containers at 4 degrees C for 6 days, rolled in gauze moistened with either 4 ml of sterile saline solution (group I) or with 4 ml of gentamicin solution (2 mg/ml) (group II). The degree of contamination, expressed in colony forming units (CFU), was evaluated on days 2, 3, 4, 5 and 6. Identification of the microorganisms was done to species level following standard procedures and commercial methods. RESULTS: In group I 2 grafts (5%) were negative during the whole observation period while the other 38 grafts (95%) presented a degree of contamination ranging from 10(2) to 10(4) CFU. Microorganisms isolated were: Staphylococcus epidermidis (24 cases), Staphylococcus aureus (5 cases), Staphylococcus saprophyticus (2 cases), Pseudomonas aeruginosa (4 cases), Serratia liquefaciens (1 case) and Klebsiella oxytoca (2 cases). In group II, 26 grafts (65%) were negative during the whole observation time while in 14 cases (35%) a few colonies (3 to 6) of Candida albicans were isolated on day 2 and remained constant in number for the whole observation time. CONCLUSIONS: The storage of full-thickness skin graft with an antibiotic cover is more reliable than the storage of full-thickness skin graft without an antibiotic cover.

Anti-Bacterial Agents↗

PubMed1997

Atrial natriuretic peptide, brain natriuretic peptide and c-type natriuretic peptide: effects on testicular microcirculation and immunohistochemical localization.

The effect of local injection of atrial (ANP), brain (BNP) and C-type (CNP) natriuretic peptides and an ANP antagonist (HS-142-1) on testicular microcirculation and vasomotion was studied using laser Doppler flowmetry. The natriuretic peptides were also localized immunohistochemically within the testis. ANP, BNP-32, CNP-22 and CNP-53 all caused a dose-related increase in testicular blood flow. The effect of ANP was blocked by concomitant injection of the ANP antagonist. Immunoreactive (ir) CNP and ir BNP were found in Leydig cells whereas in ANP was observed in the seminiferous tubules. It is suggested that the natriuretic peptides could play a role in local regulation of the testicular microcirculation.

Animals↗

PubMed1997

Is nitric oxide involved in the regulation of the rat testicular vasculature?

Using immunohistochemistry, endothelial nitric oxide synthase (NOS), and neuronal NOS were localized in the endothelium of rat testicular arteries and in Leydig cells, respectively. NADPH-diaphorase activity, indicating NOS activity, however, was present only in endothelial cells. In order to examine the role of nitric oxide (NO) in the regulation of rat testicular vasculature, intact and hCG-pretreated (50-100 IU hCG given s.c. 6 h earlier) animals were given injections of the NOS inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME), 10 mg/kg i.v.). In all rats this resulted in a major increase in blood pressure. In intact, unstimulated animals, testicular vascular resistance was unaffected, and testicular blood flow consequently increased. In hCG-treated animals, in contrast, vascular resistance increased in an hCG dose-related way. L-NAME treatment also increased the hCG-induced accumulation of polymorphonuclear leukocytes in testicular venules. Treatment with N(G)-nitro-D-arginine methyl ester (D-NAME, 10 mg/kg i.v.), an inactive isomer of L-NAME, had no effect on the testicular vasculature. The study suggests that NO plays only a limited role in the regulation of testicular blood flow under basal conditions. After hCG treatment, however, NOS activity appears to be increased (increased endothelial NADPH-diaphorase staining), suggesting that NO in this situation is of importance to increase blood flow and to inhibit leukocyte accumulation.

Animals↗

PubMed1996

Leydig cells secrete factors which increase vascular permeability and endothelial cell proliferation.

Adult intact control rats, and animals treated with human chorionic gonadotrophin (hCG) or with ethane dimethane sulphonate (EDS) to deplete Leydig cells, were injected with bromodeoxyuridine (BrdU) to label proliferating cells. Apoptotic cells were visualized by in-situ end labelling (ISEL) of fragmented DNA. Three per cent of testicular endothelial cells were labelled with BrdU and few were apoptotic in intact testes. The BrdU endothelial cell labelling index was increased by hCG-treatment and decreased in Leydig cell-depleted testes. Immunohistochemical staining showed that Leydig cells and testicular macrophages contain immunoreactive vascular endothelial growth factor (irVEGF). The ability of testicular cells to stimulate angiogenesis was studied further by transplanting interstitial cells or seminiferous tubule segments under the kidney capsule. A prominent vascular network was observed around interstitial cell grafts, but not around tubule grafts. Treatment of transplanted rats with human chorionic gonadotrophin (hCG, 50 i.u.) resulted in an accumulation of PMN-leukocytes and an increase in vascular permeability in the remaining testis and in interstitial cell grafts. Interstitial cells from Leydig cell-depleted (EDS-treated) testes were also transplanted under the kidney capsule. This type of graft caused only a discrete stimulation of angiogenesis, and there was no increase in vascular permeability around the graft after hCG treatment. It is suggested that Leydig cells secrete angiogenic factors and that they are the source of the inflammation mediator(s) produced in the testis after hCG treatment. The high proliferation rate in endothelial cells suggests continuous remodelling of the testicular microvasculature, but the functional significance of this remains unknown.

Animals↗

PubMed1996

5-Hydroxytryptamine--a local regulator of testicular blood flow and vasomotion in rats.

The effects of 5-hydroxytryptamine (5-HT), 5-HT2 receptor antagonists (ritanserin and ketanserin), histamine and substance 48/80 on testicular blood flow and microcirculation were studied in adult rats. The substances were administered by topical application on the testicular surface and by intratesticular injections, and blood flow was measured by radioactive microspheres and with a laser Doppler flowmeter. Blood flow was decreased by 5-HT in a dose-dependent manner and vasomotion in the testis was inhibited, suggesting that it could be involved in the physiological regulation of the testicular vasculature. The 5-HT antagonists did not significantly influence flow or vasomotion in intact testes. Histamine did not cause any major effects on testicular blood flow. Substance 48/80 caused degranulation of testicular mast cells, and reduced testicular blood flow and vasomotion suggesting that testicular mast cells, possibly by releasing 5-HT, could be involved in the local control of the testicular vasculature.

Administration, Topical↗

PubMed1995

Arylsulphatase from Alteromonas carrageenovora.

Arylsulphatase activity was identified in cultures of the marine bacterium Alteromonas carrageenovora, using methylumbelliferyl sulphate as substrate. In contrast with most other microbial arylsulphatases, arylsulphatase production in A. carrageenovora was not repressed by sulphate. The structural gene of arylsulphatase (atsA) was cloned and sequenced. An ORF of 984 bp was found, specifying a primary translation product of 328 amino acids with a molecular mass of 35797 Da. Arylsulphatase was partially purified from cell extracts of both A. carrageenovora and recombinant Escherichia coli. Both the recombinant and native enzymes exhibited a pI of 5.5, a Michaelis constant for methylumbelliferyl sulphate of 68 microM, and a molecular mass of approximately 35,000 Da in SDS-PAGE analysis. Secondary structure comparisons using hydrophobic cluster analysis suggest functional analogies between the arylsulphatase of A. carrageenovora, that of Mycobacterium leprae and a 33.5 kDa protein from Porphyromonas gingivalis. It is speculated that these proteins are all glycosulphohydrolases, involved with desulphatation of sulphated polysaccharides.

Amino Acid Sequence↗

PubMed1995

Tobacco smoke disrupts testicular microcirculation in the rat.

Anaesthetized adult rats were exposed repeatedly to cigarette smoke for 2 s interspersed with exposure to fresh air for either 10, 15 or 30 s using a smoking apparatus. The acute effects of this treatment on testicular microcirculation were studied using laser Doppler flowmetry. Peripheral tissue O2 saturation was measured continuously in the foot during the experiment. Exposure to cigarette smoke caused a moderate acute increase in the testicular blood flow and it inhibited vasomotion. Blood flow and the pattern of vasomotion were normalized after termination of smoke exposure. The time between the last smoke exposure and flow normalization was dependent on the smoke/air dose. Peripheral tissue O2 saturation did not change during the experiments. The effects on testicular microcirculation of local injections of an aqueous extract of cigarette smoke and passive smoking were also studied. Local injection of smoke extract increased blood flow and inhibited vasomotion. Passive smoking caused a moderate decrease in the frequency of vasomotion and amplitude. The observation that cigarette smoke influences testicular microcirculation acutely is discussed in relation to possible adverse effects on spermatogenesis.

Animals↗

PubMed1993

Control of testicular vasomotion by testosterone and tubular factors in rats.

Testicular vasomotion (rhythmical variations in testicular blood flow) was studied in adult rats using laser Doppler flowmetry. Vasomotion was not present in testes in which the Leydig cells had been destroyed, but it could be induced by a low dose of testosterone. Transposition of a scrotal testis into the abdominal cavity inhibited vasomotion and this was apparently not caused by Leydig cell malfunction. Depletion of specific germ cells (by unilateral X-irradiation induced killing of spermatogonia and maturation depletion of germ cells) did not abolish vasomotion in the testis. It is suggested that testicular vasomotion is influenced by testosterone and by factors from Sertoli cells.

Animals↗

PubMed1990

Increased resolution of large DNA fragments by a two dimensional pulse field gel electrophoresis.

An electrophoretic method for separating well-defined large DNA fragments from higher and lower molecular weight molecules is described. It combines in a first dimension either a contour-clamped homogeneous electric field or an orthogonal field alternation gel electrophoresis technique followed by a perpendicular field inversion gel electrophoresis (FIGE) in a second dimension. A complex migration curve after the FIGE run is obtained depending on the applied pulse time, the forward/reverse ratio being kept constant at 3. However, a part of the curve appears as a straight line where the migration is inversely proportional to the molecular weight of the DNA fragments. In this zone, DNA molecules are particularly well separated from other fragments. When the forward pulse time increases, this part is displaced toward the higher molecular weights. Moreover a simple relationship between the middle part of the straight line and the forward pulse time has been established.

DNA↗

PubMed1988

Characterization of a ferritin isolated from the midgut epithelial cells of a homopteran insect, Philaenus spumarius L.

Crystalline accumulations of ferritin-like particles are present within the cytoplasma and the nucleus in midgut epithelial cells of the homopteran Philaenus spumarius. A structural study at the electron microscope level reveals that these particles have the morphological characteristics of the ferritin molecule: crystals have a face-centered cubic structure with a lattice parameter of 14 +/- 1 nm; negatively stained isolated particles have the appearance of ferritin; on rotary-shadowed particles 3 axes of symmetry are clearly seen; image processing performed on selected molecules demonstrates a 4-fold symmetry. A semiquantitative electron microprobe analysis effected on aggregates of microcrystals in thin sections reveals a high atomic ratio Fe/P. Analyzed by SDS-PAGE, the protein subunit has a molecular weight of 18,600. The amino acid composition of the protein bears the general characteristics of the ferritin molecule in terms of polar and nonpolar residues. But in terms of sequences, this protein displays a strong dissimilarity to rat liver ferritin as demonstrated with a common amino acid index test and with immunoelectrophoresis experiments.

Animals↗

PubMedDate not supplied

KID, a Kinase Inhibitor Database project.

The Kinase Inhibitor Database is a small specialized database dedicated to the gathering of information on protein kinase inhibitors. The database is accessible through the World Wide Web system and gives access to structural and bibliographic information on protein kinase inhibitors. The data in the database will be collected and submitted by researchers working in the kinase inhibitor field. The submitted data will be checked by the curator of the database before entry.

Databases as Topic↗

PubMedDate not supplied

Pituitary adenylate cyclase-activating polypeptide (PACAP): effects on blood flow in the testis and caput epididymidis of the rat.

Pituitary adenylate cyclase-activating polypeptide (PACAP) is synthesized in developing germ cells in the testis and may act as a paracrine modulator of spermatogenesis and/or participate in tubule-interstitial interactions. Despite the abundance of PACAP in the organ, its role in testicular function has not yet been studied in vivo. Using laser Doppler flowmetry, the effects of PACAP on blood flow in the testis and caput epididymidis were studied on anesthetized adult rats. When given intratesticularly as 5- and 50-ng doses, PACAP increased blood flow by 55+/-21% (mean +/- SEM, P < 0.05) and by 68+/-11% at 5 mm from the injection site, respectively. Whereas 5 ng PACAP did not influence blood flow 15 mm from the site of injection, flow was reduced (-7+/-3; P < 0.05) at this site following treatment with 50 ng. Injection of 50 ng PACAP into the caput epididymidis increased epididymal blood flow by 18+/-4% (P < 0.05) at 1 mm from the injection site. None of the treatments above significantly affected the mean arterial blood pressure. Using immunohistochemistry, PACAP was observed in elongated spermatids and in the acrosomes of round spermatids in some, but not all, seminiferous tubules. Also, distinct PACAP immunoreactivity was seen in epithelial cells, particularly in clear cells, of the caput epididymidis. In conclusion, PACAP can induce vasodilatation in both testicular and epididymal microvessels and may be involved in regulating blood flow in these organs. Whereas the vasodilatory effect of PACAP is strong in the testis, the epididymal response appears to be more moderate.

Animals↗