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Biomedical subjects

D Roy

Publications and source records attributed to D Roy.

At least 55 records · Page 3Linked to original sources
PubMed2000

Production of exopolysaccharide by Lactobacillus rhamnosus R and analysis of its enzymatic degradation during prolonged fermentation.

The potential of Lactobacillus rhamnosus R for producing exopolysaccharide (EPS) when grown on basal minimum medium supplemented with glucose or lactose was investigated. EPS production by L. rhamnosus R is partially growth associated and about 500 mg of EPS per liter was synthesized with both sugars. The product yield coefficient (Y(EPS/S)) was 3.15 (0.0315 g of EPS [g of lactose](-1)) and 2.88 (0.0288 g of EPS [g of glucose](-1)). It was clearly shown that the amount of EPS produced declined upon prolonged fermentation. Degradation of EPS in fermentation processes was also assessed by measuring its molecular weights and viscosities. As these reductions might have a negative effect on the yield and viscosifying properties of EPS, it was essential to examine possible causes related to this breakdown. The decrease in viscosities and molecular weights of EPS withdrawn at different cultivation times permitted us to suspect the presence of a depolymerizing enzyme in the fermentation medium. Our study on enzymatic production profiles showed a large spectrum of glycohydrolases (alpha-D-glucosidase, beta-D-glucosidase, alpha-D-galactosidase, beta-D-galactosidase, beta-D-glucuronidase, and some traces of alpha-L-rhamnosidase). These enzymes were localized, two of them (alpha-D-glucosidase and beta-D-glucuronidase) were partially purified and characterized. When incubated with EPS, these enzymes were capable of lowering the viscosity of the polymer as well as liberating some reducing sugars. Upon prolonged incubation (27 h), the loss of viscosity was increased up to 33%.

Biodegradation, Environmental↗
PubMed2000

Primary extracranial meningioma of the soft palate.

Extracranial meningiomas comprise two per cent of all meningiomas. Primary extracranial meningiomas are even less common. The authors report the first case of a primary extracranial meningiomas of the soft palate, which presented as an intraoral mass. This was treated by surgical excision and there was no evidence of tumour recurrence at four years of follow-up.

Adult↗
PubMed2000

P190-B, a Rho-GTPase-activating protein, is differentially expressed in terminal end buds and breast cancer.

Microdissection and differential display PCR were used to identify genes preferentially expressed in the highly proliferative terminal end buds (TEBs) in the mammary gland of 45-day-old virgin rats. One clone exhibited 87% homology to the human p190-B gene encoding a novel Rho-Gap. Using in situ hybridization, p190-B was detected in both the TEBs and the terminal ducts, with the highest expression observed in the outer layer of TEBs. During normal mammary gland development, p190-B mRNA expression was highest in the virgin mammary gland and decreased during late pregnancy and lactation. Interestingly, increased levels of p190-B mRNA relative to the normal mammary gland were seen in a subset of murine mammary tumors that appeared to be less well differentiated and potentially more aggressive. Transient transfection of a p190-B expression construct into MCF-10A human mammary epithelial cells resulted in disruption of the actin cytoskeleton, which suggests a role for p190-B in regulating the signaling pathways that influence cell migration and invasion. These results suggest that p190-B may be required for virgin mammary gland development, and its aberrant expression may occur in breast cancer.

Actins↗
PubMed1999

Estrogen, DNA damage and mutations.

Estrogen administration to rodents results in various types of DNA damage and ultimately leads to tumors in estrogen-responsive tissues. Yet these hormones have been classified as nonmutagenic, because they did not induce mutations in classical bacterial and mammalian mutation assays. In this review, we have discussed the induction by estrogens of DNA and chromosomal damage and of gene mutations, because the classical assays were designed to uncover mutations only at one specific locus and could not have detected other types of mutations or changes in other genes. Various types of estrogen-induced DNA damage include: (a) direct covalent binding of estrogen quinone metabolites to DNA; (b) enhancement of endogenous DNA adducts by chronic estrogen exposure of rodents; (c) free radical generation by metabolic redox cycling between quinone and hydroquinone forms of estrogens and free radical damage to DNA such as strand breakage, 8-hydroxylation of purine bases of DNA and lipid hydroperoxide-mediated DNA modification. Two different types of chromosomal damage have also been induced by estrogen in vivo and in cells in culture such as numerical chromosomal changes and also structural chromosomal aberrations. Gene mutations have been induced in several cell types in culture either by the parent estrogen or by reactive estrogen quinone metabolites. Furthermore, in estrogen-induced kidney tumors in hamsters, several mutations have been observed in the DNA polymerase beta gene mRNA. Estradiol also induces microsatellite instability in these kidney tumors and in premalignant kidney exposed to estradiol. Although this work is still ongoing, it can be concluded that estrogens are complete carcinogens capable of tumor initiation by mutation potentially in critical genes. The hormonal effects of estrogens may complete the development of tumors.

Animals↗
PubMed1999

Absence of correlation between amobarbital distribution as assessed with SPECT brain perfusion imaging and behavioral manifestations during the intracarotid amobarbital procedure (Wada test).

1. The IAP is used presurgically in patients with temporal lobe epilepsy to predict the effects on LTM and language of the planned temporal lobectomy. This prognosis presumes that a similar pattern of perfusion will result in anesthesia of the same cerebral regions in most patients. 2. Coinjection of Tc-99m HMPAO with the barbiturate during the IAP has been used to ascertain whether this actually is true, with variable results. Moreover, most studies document only unilateral IAPs and do not report on behavioral performance. 3. The authors coinjected Tc-99m HMPAO and amobarbital in 33 IAPs from 18 patients (15 injected bilaterally, 3 unilaterally) to clarify this and to evaluate the relationship of the perfusion pattern to behavioral performance; SPECT results were also compared to angiographic evaluation obtained at the time of catheter placement. 4. SPECT perfusion data was rated for presence/absence and intensity of perfusion to the ACA, MCA, PCA territories and to H, i or c to the injection site. V, STM and LTM were graded according to a standardized protocol. 5. MCAi was perfused in 100% of cases, ACAi in 91%, PCAi in 21% and Hi in only 6%. Cross-over flow was shown in 9 studies; 50% of the patients in whom both sides were injected (on different days) had crossover, involving the ACAc territory in 80% of cases. As expected, injection on the non-ES was associated with a significantly worse LTM performance than on the ES (p = 0.006). There was no relationship between the perfusion pattern and the V level of the patients (a potential confounding variable in memory/language evaluation) during IAP, nor between perfusion pattern and LTM. STM was significantly adversely affected by the presence of crossover perfusion. Angiography in general overestimated the extent of cerebral perfusion demonstrated by SPECT, most probably because of the markedly different injection conditions. 6. Despite the best efforts to standardize injections, the perfusion pattern has been mostly unpredictable in the patients. Moreover, it has little bearing on their behavioral performance, except for the prediction of poor STM performance (the clinical implications of this remaining dubious). Marked LTM alterations after non-ES injections confirm remote hippocampal effects in the presence of only rare direct perfusion of that region. Tc-99m HMPAO/Amobarbital coinjection was unhelpful from a clinical perspective, most probably because a large part of the effects of amobarbital arise from deafferentation of regions not directly perfused by the anesthetic agent.

Adult↗
PubMed1999

Endovascular treatment of hemifacial spasm associated with a cerebral arteriovenous malformation using transvenous embolization: case report.

OBJECTIVE AND IMPORTANCE: To illustrate that decompression of the facial nerve by transvenous endovascular treatment may relieve hemifacial spasm (HFS) caused by dilated veins. CLINICAL PRESENTATION: A 35-year-old man suffered severe chronic right HFS associated with a dilated right lateral mesencephalic vein lying in the vicinity of the facial nerve. This nonessential vein was recruited as a secondary collateral drainage from an inoperable left temporo-occipital arteriovenous malformation. INTERVENTION: The lateral mesencephalic vein was reached through the superior petrosal sinus using a transfemoral venous approach and was occluded with interlocking detachable coils (Target Therapeutics, Freemont, CA). There was complete remission of HFS without recurrence after 2.5 years of follow-up. CONCLUSION: This case report supports vascular compression in the pathogenesis of HFS and suggests that facial nerve injury is not essential for the therapeutic effect of surgical decompression.

Adult↗
PubMed1999

Transvenous catheter ice mapping and cryoablation of the atrioventricular node in dogs.

While radiofrequency catheter ablation is very effective, it does not allow for prediction of success prior to full delivery of the energy. We investigated the use of cryoablation using a new catheter on the AV node to determine (1) if a successful site might be identified prior to the ablation itself, and (2) the parameters of cryoablation of the AV node using a new cryocatheter. In eight dogs, the cryoablation catheter was advanced to the AV node to produce transient high degree AV block by lowering the temperature to a minimum of -40 degrees C (ice mapping). Transient high degree AV node block was obtained in seven of eight animals at a mean temperature of -39.9 +/- 11.6 degrees C. No significant pathological modification was found in all animals but one and, in all cases, electrophysiological parameters of the AV node measured before, 20 minutes, 60 minutes, and up to 56 days after cryoapplication were not significantly different. In the 12 other dogs, after ice mapping, cryoablation of the AV node was attempted with a single freeze-thaw cycle in 6 dogs (group I) and a double freeze-thaw cycle in the other 6 dogs (group II). Chronic complete AV block was obtained in only one animal in group I compared to all animals in group II. Ablation of the AV node is effective with a double freeze-thaw cycle using a percutaneous catheter cryoablation system. Ice mapping of the area allows for identification of the targeted site.

Animals↗
PubMed1999

Fibrinogen and vascular smooth muscle cell grafts promote healing of experimental aneurysms treated by embolization.

BACKGROUND AND PURPOSE: Residual necks and recurrences frequently occur after endovascular treatment of cerebral aneurysms. Addition of fibrinogen and vascular smooth muscle cells (VSMCs) to the embolic material may promote healing of embolized aneurysms by increasing neointima formation at the neck. METHODS: Bilateral carotid aneurysms were constructed with venous pouches in 31 dogs. Aneurysms were packed intraoperatively with bare Gelfoam sponges, sponges treated with fibrinogen, or fibrinogen sponges seeded with the animal's own VSMCs or peripheral blood mononuclear cells. Animals were killed after angiography at 3 weeks, and morphometric studies were performed to measure the thickness of the neointima at the neck of treated lesions. Angiographic results and mean thickness of neointimas were compared using ANOVA. In 8 animals, 1 aneurysm was embolized with sponge seeded with VSMCs transduced by adenoviral infection to express a fluorescent protein (green fluorescent protein), and gene expression was monitored for 4, 7, 14, and 21 days by fluorescent microscopy. RESULTS: Aneurysms treated with sponges seeded with VSMCs had significantly thicker neointimas and were more completely obliterated at 3 weeks than control aneurysms treated with fibrinogen sponges. Peripheral blood mononuclear cells could not reproduce these findings. Sponges treated with fibrinogen alone promoted formation of a thicker neointima than bare sponges. Transduced cells transplanted into in vivo aneurysms still expressed green fluorescent protein at 3 weeks. CONCLUSIONS: VMSC grafts can improve healing of experimental aneurysms treated by embolization. Transplantation of cells transduced to express a foreign gene opens the way for in situ gene therapy for cerebral aneurysms.

Adenoviridae↗
PubMed1999

Estrogen directly respresses gonadotropin-releasing hormone (GnRH) gene expression in estrogen receptor-alpha (ERalpha)- and ERbeta-expressing GT1-7 GnRH neurons.

Estrogen has wide-ranging and complex effects on the reproductive axis, which are often difficult to interpret from in vivo studies. Estrogen negatively regulates tonic GnRH synthesis and also plays a pivotal role in the positive regulation of GnRH necessary for the preovulatory surge. To dissect the mechanisms by which these divergent effects occur, we attempted to observe the direct action of estrogen on the regulation of GnRH messenger RNA (mRNA) levels using the well characterized, GnRH-secreting, hypothalamic cell line, GT1-7. Using RT-PCR, we first investigated estrogen receptor transcript expression in GT1-7 neurons. We found that the GT1-7 cells express both estrogen receptor-alpha (ERalpha) and the recently described ERbeta mRNAs. We also detected the presence of both receptor subtypes in the GT1-7 neurons by Western blot analysis using specific ER antibodies. By Northern blot analysis of total GT1-7 RNA, we found that 17beta-estradiol (1 nM) down-regulates GnRH mRNA levels to approximately 55% of basal levels over a 48-h time course. This effect appears to occur specifically through an ER-mediated mechanism, as ICI 182,780, a complete ER antagonist, blocks the repression of GnRH mRNA levels by estradiol. The recently reported ERalpha-specific agonist/ERbeta-specific antagonist 2,2-bis-(p-hydroxyphenyl-1,1,1-trichloroethane (HPTE), a methoxychlor metabolite, also down-regulated GnRH gene expression. The repression of GnRH mRNA levels appears to occur at the transcriptional level, as simian virus 40 T antigen mRNA expression, which is under the control of 2.3 kb of the rat GnRH 5'-regulatory region, mimics the down-regulation of GnRH after treatment with estradiol. As the rat GnRH regulatory region in GT1-7 neurons does not appear to harbor a classic estrogen response element, the mechanism involved in the repression of GnRH has yet to be determined. These results suggest that estradiol directly regulates GnRH gene expression at the level of the GnRH neuron and may exert its neuroendocrine control through direct interaction with specific receptors expressed in these cells.

Animals↗
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↗