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Biomedical subjects

D Roy

Publications and source records attributed to D Roy.

At least 109 records · Page 6Linked to original sources
PubMed1999

Production of probiotic cheese (cheddar-like cheese) using enriched cream fermented by Bifidobacterium infantis.

Probiotic cheeses (Cheddar-like cheese) were produced with microfiltered milk standardized with cream enriched with native phosphocaseinate retentate and fermented by Bifidobacterium infantis. During the manufacture and storage of cheeses, viability of the bifidobacteria was determined. Biochemical changes such as proteolysis, sugar metabolism, and organic acids production were estimated. No bifidobacteria growth was observed during cheese-making steps. Bifidobacteria survived very well in cheeses packed in vacuum sealed bags kept at 4 degrees C for 84 d and remained above 3 x 10(6) cfu/g of cheese. No significant difference was observed between cheeses produced with or without bifidobacteria for fat, protein, moisture, salt, ash, or pH. After 12 wk of storage, more than 56% of the as1-CN was hydrolyzed in cheeses that were produced with bifidobacteria and inoculated at 10(8) cfu/g in the cream, and > 45% of hydrolysis was observed in the control cheese. However, no significant differences in the electrophoretic sodium dodecyl sulfate-PAGE patterns were observed in cheeses at any period of storage. At the first day after manufacture, lactose was completely hydrolyzed in cheeses made with bifidobacteria, which suggested high beta-galactosidase activity by B. infantis. Small quantities of acetic acid were detected in bifidus cheeses. The results indicated that B. infantis introduced into hard pressed cheese exhibited excellent viability during storage for 12 wk and could be metabolically active.

Bifidobacterium↗
PubMed1999

Transarterial embolization of aneurysms associated with spinal cord arteriovenous malformations. Report of four cases.

The authors sought to show the feasibility and discuss the rationale of embolization of aneurysms associated with spinal cord arteriovenous malformations (SCAVMs). The authors reviewed the clinical presentation, magnetic resonance (MR) images, spinal angiograms, and clinical evolution of four patients treated for aneurysms associated with an SCAVM. Aneurysms were located on branches of the anterior spinal artery in three patients and on radiculopial arteries in two patients; one patient harbored two lesions. Treatment consisted of superselective bucrylate embolization of the branches harboring the aneurysms, with preservation of the arterial axis. Follow-up angiograms were obtained at 3 to 6 months postembolization in all patients. All patients presented with hemorrhagic events. Hematomyelia was clearly related to a sulcocommissural or a vasa corona aneutrysm in two patients. Another sulcocommissural aneurysm and multiple radiculopial aneurysms were presumed to be the cause of subarachnoid hemorrhage in two other patients. One patient harbored aneurysms on a sulcocommissural artery and on a radiculopial artery. All aneurysms were permanently obliterated. In one patient with a single fistula, the SCAVM was cured. The SCAVM was only partially obliterated (95, 50, and 20% in apparent volume) in three other patients. There were no complications or rebleeding episodes during a follow-up period of 17 to 37 months. Aneurysms associated with SCAVMs can be eradicated by supraselective embolization, even on the anterior spinal artery territory. For patients presenting with hemorrhage and prohibitive risk of complete resection, embolization of aneurysms may decrease the risk of further rebleeding.

Adult↗
PubMed1999

Detection of mutation(s) or polymorphic loci in the genome of experimental animal and human cancer tissues by RAPD/AP-PCR depend on DNA polymerase.

Examination of mutations by random amplified polymorphic DNA (RAPD) (also called arbitrarily primed PCR = AP-PCR) in the breast and Wilm's human cancer tissues as well as in estrogen-induced hamster kidney cancer tissues revealed a gain or loss of amplified fragments sizes in breast and Wilm's tumors compared to their respective controls. We also observed changes in the intensity of amplified fragments in tumor DNA compared to control DNA. Most importantly, we found that detection of mutation in the genome of cancer tissue compared to normal tissue by RAPD/AP-PCR depends upon the type of DNA polymerases used. This is the first report showing that polymerase ability to extend a particular locus of the gene is influenced by mutation in the primer binding sites in the competitive environment where several genomic sequences flanked to a random primer are co-amplified by RAPD/AP-PCR. Findings of this study suggest that: i) instead of directly adopting published RAPD protocol it is essential to optimize RAPD reaction conditions by varying magnesium chloride and polymerase concentration with different amounts of DNA templates in order to observe reproducible fingerprints of randomly amplified polymorphic DNA fragments, ii) alterations in the genome as a loss, gain, or decrease and increase in amplification intensity of loci were observed in human tumors as well as in an experimental animal tumor, and iii) before concluding that a mutation is not present when using RAPD/AP-PCR, different polymerases should be used to amplify the genome of the same control or tumor tissues.

Animals↗
PubMed1999

Healing mechanisms in experimental aneurysms. I. Vascular smooth muscle cells and neointima formation.

PURPOSE: The purpose of this work is to better define healing phenomena in this model, in an effort to find strategies to improve long term results of endovascular treatment. METHODS: Lateral wall venous pouch aneurysms were constructed on both carotid arteries in 30 pigs. The aneurysms were packed with collagen sponges per-operatively in 25 animals. Angiography, serial histological studies and immuno-histochemistry tests were used to study healing phenomena and measure neointima formation at various time intervals from 1 day to 9 weeks after surgery. GDC embolization was performed in 5 other pigs for comparison with the collagen sponge model. Explants from the neointima at the neck of aneurysms as well as from the parent artery of 8 pigs were prepared in an attempt to grow and to characterize in vitro cells responsible for healing porcine aneurysms using immunocytochemistry and enzymatic assays. To confirm the hypothesis that an analogy exists between cells involved in aneurysmal healing and neointimal cells found in restenosis, explant outgrowths were scored and compared to explants from intact carotid arteries and carotid arteries subjected to angioplasty in 3 other animals. In addition, to test the value of neointima measurements in quantifying results, 6 dogs were analysed to correlate the thickness of the neointima formed at the neck of aneurysms with angiographic results in animals prone to recurrences. RESULTS: Histopathological findings with collagen sponge packing were similar to the ones following coil embolization. Porcine aneurysms had a strong tendency to heal with a thick neointima primarily composed of vascular smooth muscle cells (VSMCs). Aneurysms in dogs did not heal as well and the neointima at the neck of treated lesions was thin. Cells responsible for healing of experimental porcine aneurysms could be cultured in vitro, and are activated VSMCs. These cells, similar to those harvested following balloon injury, had a higher colony forming capacity and an accelerated explant outgrowth rate as compared to cells derived from the parent artery. CONCLUSION: Animals which heal poorly harbor a thin or deficient neointima at the neck of treated aneurysms. Favorable healing in porcine aneurysms involves VSMCs which form a thick neointima. These VSMCs can be cultured in vitro. They share similar outgrowth characteristics with VSMCs recovered after balloon angioplasty. The collagen sponge model may be useful to harvest cells for in vitro experimentation and in the in vivo evaluation of the local delivery of potential therapeutic molecules thought to improve healing following embolization of aneurysms.

Aneurysm↗
PubMed1999

Aorto-right ventricular fistula: a late complication of aortic valve replacement.

We report the case of a patient who was found to have an aorto-right ventricular fistula 17 years after receiving a Björk-Shiley prosthetic aortic valve. A pseudoaneurysm had formed at the aortotomy suture line, and it had extended into the interventricular septum and had eventually opened into the right ventricle. Using transesophageal echocardiography, we identified the defect in the ascending aorta, and a left-to-right shunt. Aortography was used to confirm these findings. The pseudoaneurysm was successfully resected and the ascending aorta was replaced with a Dacron graft. To the best of our knowledge, no similar late complication of aortic valve replacement has been reported in the medical literature.

Aged↗
PubMed1999

Healing of experimental aneurysms. II: Platelet extracts can increase the thickness of the neointima at the neck of treated aneurysms.

PURPOSE: To assess the effect of platelet extracts (PE) on neointima formation following gelfoam packing of experimental porcine aneurysms. A strategy involving the local delivery of platelet growth factors may potentially improve long term results of endovascular treatment of aneurysms. METHODS: Bilateral lateral wall common carotid aneurysms were constructed on 30 pigs. A collagen sponge containing a PE rich in growth factors was used to pack one aneurysm with the controlateral lesion being embolized with a sponge containing NaCl 0.9% (22 animals). In 8 animals, a control sponge was used on both sides. Animals were sacrificed at 1, 2, 3, 4 and 9 weeks and the thickness of the neointima covering the neck of PE-treated aneurysms was measured in 5 locations for each lesion at 2 and 3 weeks and compared with the control aneurysm of the same animal. Morphometric data was analysed using the paired Student's t-test. RESULTS: The thickness of the neointima was significantly increased in lesions treated with PE as compared to control lesions at 2 weeks (p = 0.008, n = 9). There was no significant difference at 3 weeks (p = 0.99, n = 9). There was no significant difference between lesions of control animals (p = 0.95, n = 8). CONCLUSION: PE rich in growth factors can increase the thickness of the neointima at the neck of treated experimental porcine aneurysms at 2 weeks, but had no effect at 3 weeks. This accelerated neointimal formation may have some value in improving healing following endovascular treatment. This hypothesis could not be supported with this experimental model which has a spontaneous tendency to heal. Further studies using an animal model which reproduces the clinical problem of recurrences may help to define the role of the local delivery of growth factors in combination with coils in a strategy designed to improve results of endovascular treatment.

Aneurysm↗
PubMed1998

Concentration dependence of prooxidant and antioxidant properties of catecholestrogens.

Estradiol is an established antioxidant in vitro and in vivo. In contrast, prooxidant effects such as 8-hydroxylation of guanine bases of DNA have been induced by various estrogens in hamsters and by 4-hydroxyestradiol or -estrone and a microsomal activating system in vitro. As part of an examination of these conflicting reports, we studied the enhancement or inhibition of lipid peroxidation (conjugated diene formation monitored at 240 nm) by catecholestrogens in human low-density lipoprotein (LDL) incubated with cupric sulfate in phosphate buffer. Addition of 2- or 4-hydroxyestradiol, 2- or 4-methoxyestradiol, or estradiol or estriol (0.5-50 microM) increased lag times for diene formation by 30 to <300% over control values in the absence of estrogens (lag time, 1.6 h). In contrast, low concentrations (5 pM-100 nM) of catecholestrogens decreased lag times by about 40-50%, demonstrating their prooxidant activities. The prooxidant capabilities of catecholestrogens were examined by assaying the reduction by estrogens of Cu(II) to Cu(I) and of Fe(III) to Fe(II). Both 2- and 4-hydroxyestradiol and 2- and 4-methoxyestradiol reduced Cu(II) and Fe(III) ions to their lower oxidation state. In conclusion, the reduction of Cu(II) to Cu(I) by catecholestrogens is proposed to initiate lipid peroxidation and thus oxidation of LDL. In contrast, at high concentrations of catecholestrogens, the scavenging of oxygen radicals may predominate over lipid peroxidation and free radical generation by analogy to the action of similar phenolic antioxidants. With estradiol, estriol, and the methoxyestrogen metabolites, only antioxidant effects were observed.

Animals↗
PubMed1998

Characterization of bifidobacteria by random DNA amplification.

RAPD conditions were optimized to generate reproducible banding patterns by testing primers, thermocyclers and overall reproducibility in repeat DNA analysis and separate DNA extractions. Five primers were chosen on the basis of band intensity and distribution (between 2 and 10 bands) which clearly distinguished among strains of Bifidobacterium adolescentis, B. animalis, B. bifidum, B. breve, B. infantis and B. longum. The use of five single-primer reactions under optimized conditions improved the resolution and accuracy of the RAPD method for the characterization of dairy-related bifidobacteria. The results indicated that this method was highly reproducible in repeated analysis. Similarity between bifidobacteria strains was evaluated based on their RAPD profiles. Using a set of five primers, it was demonstrated that it may be possible to distinguish three different species of Bifidobacterium (B. breve, B. bifidum and B. adolescentis), based on similarity of the RAPD profiles to known reference strains. Furthermore, application of the RAPD technique may also be useful and faster, than traditional systematics for placement of industrial strains into specific clusters (either B. longum/infantis or B. animalis/lactis).

Animals↗
PubMed1998

Is exposure to environmental or industrial endocrine disrupting estrogen-like chemicals able to cause genomic instability?

Human and wild life populations are continually exposed to a wide variety of environmental estrogen-like chemicals. Most research to date on environmental endocrine disrupting estrogen-like chemicals has focussed on screening of estrogenic activity of environmental or industrial chemicals, their bioaccumulative properties and toxicokinetics, and developing the structure-activity relationship between environmental or industrial chemicals and estrogen-receptor. Whether estrogen-like chemicals also possess the ability to alter the stability of the genome is not clear. It is very important to understand the effects of estrogen-like chemicals at the genome level. This article evaluates the current status of knowledge of the potential of producing genomic instability in response to the exposure of estrogen-like chemicals, which might help in understanding the mechanisms of some of the adverse effects. We and others have shown several structural, numerical, and functional changes at the cellular levels in response to DES exposure. Some other phenolic estrogen-like chemicals, such as, bisphenol A, phenylphenol and nonylphenol, also follow some of the pattern of effects similar to DES. These compounds also alter cell cycle kinetics, induce DNA damages, and produce telomeric associations and chromosomal aberrations. Whether weak or strong, the estrogenic response of a chemical, if not overcome, will add extra estrogenic burden to the system, and particularly those endocrine disrupting environmental and industrial estrogen-like chemicals capable of producing genomic instability will induce additional burden of genomic instability. Though, estrogenically some of these compounds may be weak, however, they may have different activities in generation of genomic instability. For example, nonylphenol is weak in estrogen-like action compared to DES, however, it is equal or more potent in producing telomeric associations in MCF-7 cells compared to DES. Additive or synergistic extra-burden of estrogenicity and genomic instability could produce detrimental effects compare to estrogenic action alone. Screening of endocrine disrupting environmental estrogen-like chemicals for their ability to produce genomic instability and analysis of molecular basis of some of the adverse human health outcomes as a result of exposure of these types of chemicals should lead to a better understanding of how these environmental estrogen-like chemicals may influence the development of some adverse effects in humans and wildlife.

Animals↗
PubMed1998

In vitro transformation of ampicillin to cephalexin by free and immobilized cells of Streptomyces sp.

In vitro transformation of ampicillin to cephalexin was studied using calcium alginate-immobilized and free Streptomyces sp. strain DRS-1 packed in glass columns. Tris-HCl buffer containing ampicillin was continuously circulated through the columns for four cycles, each cycle (with fresh ampicillin) being continued for 5 h. The pattern of product formation was identical in both cases, i.e. in each cycle, after reaching a certain concentration, its formation did not increase. Product formation was always higher with immobilized cells. Conversion of ampicillin to cephalexin by the strain was affected by cell and substrate concentration.

Alginates↗
PubMed1998

Legg-Perthes disease in three siblings, two heterozygous and one homozygous for the factor V Leiden mutation.

A family is described with three-generation transmission of factor V Leiden (a thrombophilic mutation that causes resistance to activated protein C). Legg-Perthes disease developed in three siblings in this family. The male proband and his sister were heterozygous for the mutation and had unilateral hip disease at age 2 years. The brother, who had bilateral hip disease, was homozygous. This novel family provides compelling evidence for the pathoetiologic role of familial thrombophilia in Legg-Perthes disease.

Adult↗
PubMed1998

A slipped replication intermediate model is stabilized by the syn orientation of N-2-aminofluorene- and N-2-(acetyl)aminofluorene-modified guanine at a mutational hotspot.

The Escherichia coli NarI restriction enzyme recognition site 5'G1G2C3G4C5C63' is a mutational hotspot for -2 deletions in E. coli plasmid pBR322, resulting in the sequence 5'GGCC3' when G4 is modified by the aromatic amine N-2-(acetyl)aminofluorene (AAF) [Burnouf, D., Koehl, P., and Fuchs, R. P. P. (1995) Proc. Natl. Acad. Sci. U.S.A. 86, 4147-4151] even though each G shows similar reactivity [Fuchs, R. P. P. (1984) J. Mol. Biol. 177, 173-180]. Modification at G4 by the related aromatic amine 2-aminofluorene (AF), which lacks the acetyl group of AAF, can also cause -2 deletions, but at a lower frequency [Bichara, M., and Fuchs, R. P. P. (1985) J. Mol. Biol. 183, 341-351]. A specific mechanism has been proposed to explain the double-base frameshifts in the NarI sequence in which the GC deletion results from a slipped mutagenic intermediate formed during replication [Schaaper, B. M., Koffel-Schwartz, N., and Fuchs, R. P. P. (1990) Carcinogenesis 11, 1087-1095]. We address the following key questions in this study. Why does AAF modification dramatically increase the mutagenicity at the NarI G4 position, and why does AAF enhance the mutagenicity more than AF? We studied two intermediates which model replication at one arm of a fork, using a fragment of DNA modified by AF or AAF at G4 in the NarI sequence: Intermediate I can be converted into intermediate II by misalignment. Elongation of intermediate I leads to error-free translesion synthesis, while elongation of intermediate II leads to a -2 frameshift mutation. Minimized potential energy calculations were carried out using the molecular mechanics program DUPLEX to investigate the conformations of the AF and AAF adducts at G4 in these two intermediates. We find that the slipped mutagenic intermediate is quite stable relative to its normally extended counterpart in the presence of AF and AAF in an abnormal syn orientation of the damaged base. An enhanced probability of elongation from a stable slipped structure rather than a properly aligned one would favor increased -2 frameshift mutations. Furthermore, AAF-modified DNA has a greater tendency to adopt the syn orientation than AF because of its greater bulk, which could explain its greater propensity to cause -2 deletions in the NarI sequence.

2-Acetylaminofluorene↗
PubMed1998

Feasibility of cardiac cryoablation using a transvenous steerable electrode catheter.

We investigated the feasibility of using cryogenic technology in an electrode catheter for percutaneous ablation of cardiac tissue. Despite its high success rate, radiofrequency catheter ablation has important limitations especially with regards to the treatment of ventricular arrhythmias associated with a chronic scar. Arrhythmia surgery experience has shown that freezing with a hand held probe can permanently ablate the arrhythmogenic substrate of ventricular tachycardia associated with an old scar. Moreover, cryosurgery also allows for reversible "ice mapping," in which the area likely responsible for the arrhythmia can be evaluated by suppressing its electrophysiologic properties prior to the creation of an irreversible state. A new steerable cryoablation catheter using Halocarbon 502 as a refrigerant was utilized in six dogs. Serial cryoapplications were performed in the right and left ventricles. In two dogs, we attempted reversible ice mapping of the AV node. Pathological evaluation of the lesions was done acutely in all the animals. Forty-two cryoapplications were delivered at a mean temperature of -45 +/- 9.8 degrees C. No lesion was found at pathological evaluation for 16 cryoapplications which did not achieve a temperature of less (colder) than -30 degrees C. The remaining applications resulted in 26 lesions which were hemorrhagic and sharply demarcated from normal myocardium. Histological evaluation revealed contraction band necrosis. Reversible ice mapping of the AV node was successfully achieved in two animals. Cryoablation is feasible using an electrode catheter with multiple electrodes. This technology has the potential to allow for reversible ice mapping to confirm a successful ablation target before definitive ablation.

Animals↗
PubMed1998

One-to-two atrioventricular conduction causing nonreentrant tachycardia: successful treatment with radiofrequency ablation.

The anatomical substrate for AV nodal reentrant tachycardia (AVNRT) is well known and is due to anterograde conduction through a slow conducting pathway and retrograde conduction using a fast conducting pathway. In this report, we describe a patient with AVNRT who also presented with frequent episodes of paroxysmal nonreentrant tachycardia due to the occurrence of two conducted ventricular beats for each sinus depolarization. Palpitations and arrhythmias were abolished after radiofrequency ablation of the slow pathway.

Adult↗
PubMed1998

Insulin stimulation of glucose uptake in skeletal muscles and adipose tissues in vivo is NO dependent.

The purpose of this study was to investigate whether in vivo nitric oxide synthase (NOS) inhibition influences insulin-mediated glucose disposal in rat peripheral tissues. The NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) or saline was infused constantly during a hyperinsulinemic-euglycemic clamp in normal rats. Glucose utilization rates of insulin-sensitive tissues (individual muscles, heart, and adipose tissues) were simultaneously determined using tracer infusion of 2-deoxy-D-[3H]glucose (2-[3H]DG). NOS blockade with L-NAME resulted in significant (P < 0.05) reduction in both whole body glucose disposal (-16%, P < 0.01) and plasma 2-[3H]DG disappearance rate (-30%, P < 0.05) during hyper-insulinemic-euglycemic clamp. L-NAME significantly decreased insulin-stimulated glucose uptake in heart (-62%, P = 0.01), soleus (-42%, P = 0.05), red (-53%, P < 0.001) and white (-62%, P < 0.001) gastrocnemius, tibialis (-57%, P < 0.01), and quadriceps (-33%, P < 0.05) muscles. The NOS inhibitor also decreased insulin action in brown interscapular (-47%, P < 0.01), retroperitoneal (-52%, P = 0.07), and gonadal (-66%, P = 0.06) adipose tissues. In contrast to in vivo NOS blockade, L-NAME failed to affect basal or insulin-stimulated 2-[3H]DG transport in isolated soleus or extensor digitorum longus muscles in vitro. These results support the hypothesis that the action of insulin to augment glucose uptake by skeletal muscles and other peripheral insulin-sensitive tissues in vivo is NO dependent.

Adipose Tissue↗
PubMed1998

Regulation of gonadotropin-releasing hormone (GnRH) gene expression by 5alpha-dihydrotestosterone in GnRH-secreting GT1-7 hypothalamic neurons.

Hypothalamic GnRH secretory neurons are precisely regulated by circulating gonadal steroids. However, the question of whether these cells are directly responsive to steroid hormones remains a central and controversial issue in reproductive science. In the present study, we demonstrate the expression of androgen receptor (AR) in a mouse hypothalamic GnRH-secreting cell line, GT1-7. AR messenger RNA was detected by Northern blot analysis of 10 microg total cellular RNA. Western blot analysis revealed a 110K AR immunoreactive band, and saturation binding analysis confirmed the presence of a high affinity low capacity androgen binding entity (Kd = 0.06 nM; Bmax = 12.4 fmol/mg protein). In addition, GT1-7 cells were found to express ARA70, an AR-specific coactivator that has been reported to enhance transactivational activity of the AR. GT1-7 cells transiently transfected with an androgen responsive MMTV-luciferase reporter construct displayed a 4.2-fold induction of luciferase reporter gene activity by 1 nM 5alpha-dihydrotestosterone (DHT), further demonstrating the presence of a functional AR. Treatment of GT1-7 cells with 1 or 10 nM DHT resulted in approximately 55% reduction in GnRH messenger RNA measured at 24 and 36 h after treatment. This repression was completely blocked by hydroxyflutamide, an AR antagonist. These results provide the first demonstration that androgen acts directly through an AR-mediated pathway to repress GnRH gene expression in hypothalamic GnRH-secreting neurons.

Animals↗