Vikram Roy - Academia.edu (original) (raw)
Papers by Vikram Roy
Virology, 2002
We have cloned and characterized the Drosophila X virus (DXV) genome segment B and its encoded VP... more We have cloned and characterized the Drosophila X virus (DXV) genome segment B and its encoded VP1, the putative RNA-dependent RNA polymerase (RdRp) present in the virion. The 2991-bp open reading frame encodes the largest birnavirus VP1 at 977 aa, with a calculated M r of 112.8 kDa. As with the VP1 proteins of the type species of the other two genera in the family Birnaviridae, namely, infectious pancreatic necrosis virus (genus Aquabirnavirus) and infectious bursal disease virus (genus Avibirnavirus), the DXV (genus Entomobirnavirus) VP1 protein contains a consensus GTP-binding site and appears to possess self-guanylylation activity. All of the birnavirus VP1 proteins contain conserved RdRp motifs that reside in the catalytic "palm" domain of all classes of polymerases. However, the birnavirus RdRps lack the highly conserved Gly-Asp-Asp (GDD) sequence, a component of the proposed catalytic site of this enzyme family that exists in the conserved motif VI of the palm domain of other RdRps. All three birnavirus RdRps do contain downstream DD motifs that could function as part of the catalytic triad. These motifs are, however, located in spatially distinct regions of the various birnavirus VP1 proteins. These results suggest that the VP1 proteins of birnaviruses form a defined subgroup of polymerases that either are lacking the conserved RdRp motif VI or have repositioned this motif to different structural regions. © 2002 Elsevier Science (USA)
Journal of Vascular Surgery, 2006
The preferential use of endovascular techniques to treat complex aortoiliac disease has increased... more The preferential use of endovascular techniques to treat complex aortoiliac disease has increased in recent years. The purpose of this study was to review the outcomes and durability of recanalization, percutaneous transluminal angioplasty, and stenting for iliac occlusions based on the patient's TransAtlantic Inter-Society Consensus (TASC) stratification. Between 1998 and 2004, more than 628 patients with a clinical diagnosis of aortoiliac atherosclerotic disease underwent arteriography. The endovascular treatment of 89 consecutive patients (mean age, 66 years; 58% male) with symptomatic iliac occlusions (TASC-B, -C, and -D) was the basis for this study. Original angiographic imaging was evaluated for lesion grade and runoff. Electronic and hard copy medical records were reviewed for demographic data, clinical variables, and noninvasive vascular laboratory testing. Kaplan-Meier estimators were used to determine patency rates according to Society for Vascular Surgery criteria. Univariate and multivariate analyses were performed. P values of <.05 were considered significant. Recanalization and percutaneous transluminal angioplasty/stenting (total, 178 stents) of occluded iliac arteries was technically successful in 84 (91%) of 92 procedures. Patients in the TASC-C and -D groups often required multiple access sites (50%) and femoral artery endarterectomy/patch angioplasty for diffuse disease (24%). The mean ankle-brachial index increased from 0.45 to 0.83. Distal embolization led to major amputation and eventual death in one patient. Two other deaths occurred in the perioperative period secondary to cardiorespiratory causes. Three-year primary patency, secondary patency, and limb salvage rates were 76%, 90%, and 97%, respectively, and progression of infrainguinal disease led to late limb loss in two patients. Diabetes as a risk factor was significantly associated with decreased primary patency (57% vs 83%; P = .049). Critical ischemia at presentation was associated with decreased patency rates as well (P = .002), but TASC classification did not significantly alter patency rates. Complex long-segment and bilateral iliac occlusions can be safely treated via endovascular means with high rates of symptom resolution. Initial technical success, low morbidity, and mid-term durability are comparable to results with open reconstruction. A liberal posture to open femoral artery reconstruction extends the ability to treat diffuse TASC-C and -D lesions via endovascular means.
Journal of Endovascular Therapy, 2006
To examine the efficacy of a staged approach for the treatment of thoracoabdominal aneurysms, wit... more To examine the efficacy of a staged approach for the treatment of thoracoabdominal aneurysms, with open visceral revascularization followed by aortic endografting, in selected patients not considered candidates for conventional surgical repair. A retrospective review was conducted of 13 consecutive patients (8 women; mean age 64 years, range 33-77) who underwent visceral bypass followed by endovascular thoracoabdominal stent-graft implantation since 1999. Three patients presented with symptomatic aneurysms and 2 with rupture. Two patients had connective tissue disorders. All patients were deemed unfit for conventional thoracoabdominal repair due to comorbid conditions. The procedures were tailored to the pathology and specific patient anatomical situation: 5 aortic dissections with aneurysmal degeneration and 8 aneurysms (5 Crawford type II, 2 type III, and 1 type IV). The patients underwent retrograde visceral bypass (11 iliovisceral and 2 infrarenal aortic to visceral artery) followed by endovascular aortic relining with Zenith TX2 devices (n=7), homemade endografts (n=5), or a Talent thoracic endograft (n=1). Six patients required either a proximal or distal direct aortic repair (2 infrarenal reconstructions, 3 arch elephant trunk grafts, and 1 ascending aortic repair), while 3 patients also underwent left carotid-subclavian bypass grafting. Two patients developed paraplegia (1 following a ruptured aneurysm), and 2 patients had transient paraparetic events. Two patients had acute renal failure requiring short-term dialysis. Three patients died within 30 days; 2 late aneurysm-related deaths were noted. Three patients developed endoleaks during follow-up. Mean lengths of stay were 13 days (7-30) for the visceral bypass and 12 (3-25) for the endovascular stent-graft. In addition, remaining procedures in 8 patients required a mean of 7 days (0-14) in hospital. Staged endovascular and open procedures are feasible for thoracoabdominal aneurysms in patients at prohibitive risk for open thoracoabdominal reconstruction. However, this approach still carries a significant risk of perioperative mortality and morbidity. The potential for less invasive alternatives should be investigated.
American Journal of Surgery, 1985
We reviewed the records of 21 patients with recurrent head and neck cancer who were treated by re... more We reviewed the records of 21 patients with recurrent head and neck cancer who were treated by resection and intraoperative brachytherapy at our institution between 1979 and 1983. We excluded those patients who received
Gene Therapy, 2003
A strategy for inducing preferential proliferation of the engrafted hepatocytes over host liver c... more A strategy for inducing preferential proliferation of the engrafted hepatocytes over host liver cells should markedly increase the benefit of hepatocyte transplantation for the treatment of liver diseases and ex vivo gene therapy. We hypothesized that preparative hepatic irradiation (HIR) to inhibit host hepatocellular regeneration in combination with the mitotic stimulus of host hepatocellular apoptosis should permit repopulation of the liver by transplanted cells. To test this hypothesis, congeneic normal rat hepatocytes were transplanted into UDP-glucuronosyltransferase (UGT1A1)deficient jaundiced Gunn rats (a model of Crigler-Najjar syndrome type I), following HIR and adenovirus-mediated FasL gene transfer. Progressive repopulation of the liver by engrafted UGT1A1-proficient hepatocytes over 5 months was demonstrated by the appearance of UGT1A1 protein and enzyme activity in the liver, biliary bilirubin glucuronides secretion, and long-term normalization of serum bilirubin levels. This is the first demonstration of massive hepatic repopulation by transplanted cells by HIR and FasL-induced controlled apoptosis of host liver cells.
Hepatic tumors often recur in the liver after surgical resection. Postoperative radiotherapy (RT)... more Hepatic tumors often recur in the liver after surgical resection. Postoperative radiotherapy (RT) could improve survival, but curative RT may induce delayed life-threatening radiation-induced liver damage. Because RT inhibits liver regeneration, we hypothesized that unirradiated, transplanted hepatocytes would proliferate preferentially in a partially resected and irradiated liver, providing metabolic support. We subjected F344 rats to hepatic RT and partial hepatectomy with/without a single intrasplenic, syngeneic hepatocyte transplantation. Hepatocyte transplantation ameliorated radiation-induced liver damage and improved survival of rats receiving RT after partial hepatectomy. We further demonstrated that transplanted hepatocytes extensively repopulate and function in a heavily irradiated rat liver.
International Journal of Radiation Oncology Biology Physics, 1997
International Journal of Radiation Oncology Biology Physics, 1999
Applied Physics Letters, 1993
ABSTRACT
Neurology India, 2007
Discussion Cortical sinovenous thrombosis occurs in both males and females, but is more common in... more Discussion Cortical sinovenous thrombosis occurs in both males and females, but is more common in women in the postpartum period, especially in developing countries like India.[1] The common etiologies include prothrombotic states, infections, drugs and inflammatory ...
Virology, 2002
We have cloned and characterized the Drosophila X virus (DXV) genome segment B and its encoded VP... more We have cloned and characterized the Drosophila X virus (DXV) genome segment B and its encoded VP1, the putative RNA-dependent RNA polymerase (RdRp) present in the virion. The 2991-bp open reading frame encodes the largest birnavirus VP1 at 977 aa, with a calculated M r of 112.8 kDa. As with the VP1 proteins of the type species of the other two genera in the family Birnaviridae, namely, infectious pancreatic necrosis virus (genus Aquabirnavirus) and infectious bursal disease virus (genus Avibirnavirus), the DXV (genus Entomobirnavirus) VP1 protein contains a consensus GTP-binding site and appears to possess self-guanylylation activity. All of the birnavirus VP1 proteins contain conserved RdRp motifs that reside in the catalytic "palm" domain of all classes of polymerases. However, the birnavirus RdRps lack the highly conserved Gly-Asp-Asp (GDD) sequence, a component of the proposed catalytic site of this enzyme family that exists in the conserved motif VI of the palm domain of other RdRps. All three birnavirus RdRps do contain downstream DD motifs that could function as part of the catalytic triad. These motifs are, however, located in spatially distinct regions of the various birnavirus VP1 proteins. These results suggest that the VP1 proteins of birnaviruses form a defined subgroup of polymerases that either are lacking the conserved RdRp motif VI or have repositioned this motif to different structural regions. © 2002 Elsevier Science (USA)
Journal of Vascular Surgery, 2006
The preferential use of endovascular techniques to treat complex aortoiliac disease has increased... more The preferential use of endovascular techniques to treat complex aortoiliac disease has increased in recent years. The purpose of this study was to review the outcomes and durability of recanalization, percutaneous transluminal angioplasty, and stenting for iliac occlusions based on the patient's TransAtlantic Inter-Society Consensus (TASC) stratification. Between 1998 and 2004, more than 628 patients with a clinical diagnosis of aortoiliac atherosclerotic disease underwent arteriography. The endovascular treatment of 89 consecutive patients (mean age, 66 years; 58% male) with symptomatic iliac occlusions (TASC-B, -C, and -D) was the basis for this study. Original angiographic imaging was evaluated for lesion grade and runoff. Electronic and hard copy medical records were reviewed for demographic data, clinical variables, and noninvasive vascular laboratory testing. Kaplan-Meier estimators were used to determine patency rates according to Society for Vascular Surgery criteria. Univariate and multivariate analyses were performed. P values of <.05 were considered significant. Recanalization and percutaneous transluminal angioplasty/stenting (total, 178 stents) of occluded iliac arteries was technically successful in 84 (91%) of 92 procedures. Patients in the TASC-C and -D groups often required multiple access sites (50%) and femoral artery endarterectomy/patch angioplasty for diffuse disease (24%). The mean ankle-brachial index increased from 0.45 to 0.83. Distal embolization led to major amputation and eventual death in one patient. Two other deaths occurred in the perioperative period secondary to cardiorespiratory causes. Three-year primary patency, secondary patency, and limb salvage rates were 76%, 90%, and 97%, respectively, and progression of infrainguinal disease led to late limb loss in two patients. Diabetes as a risk factor was significantly associated with decreased primary patency (57% vs 83%; P = .049). Critical ischemia at presentation was associated with decreased patency rates as well (P = .002), but TASC classification did not significantly alter patency rates. Complex long-segment and bilateral iliac occlusions can be safely treated via endovascular means with high rates of symptom resolution. Initial technical success, low morbidity, and mid-term durability are comparable to results with open reconstruction. A liberal posture to open femoral artery reconstruction extends the ability to treat diffuse TASC-C and -D lesions via endovascular means.
Journal of Endovascular Therapy, 2006
To examine the efficacy of a staged approach for the treatment of thoracoabdominal aneurysms, wit... more To examine the efficacy of a staged approach for the treatment of thoracoabdominal aneurysms, with open visceral revascularization followed by aortic endografting, in selected patients not considered candidates for conventional surgical repair. A retrospective review was conducted of 13 consecutive patients (8 women; mean age 64 years, range 33-77) who underwent visceral bypass followed by endovascular thoracoabdominal stent-graft implantation since 1999. Three patients presented with symptomatic aneurysms and 2 with rupture. Two patients had connective tissue disorders. All patients were deemed unfit for conventional thoracoabdominal repair due to comorbid conditions. The procedures were tailored to the pathology and specific patient anatomical situation: 5 aortic dissections with aneurysmal degeneration and 8 aneurysms (5 Crawford type II, 2 type III, and 1 type IV). The patients underwent retrograde visceral bypass (11 iliovisceral and 2 infrarenal aortic to visceral artery) followed by endovascular aortic relining with Zenith TX2 devices (n=7), homemade endografts (n=5), or a Talent thoracic endograft (n=1). Six patients required either a proximal or distal direct aortic repair (2 infrarenal reconstructions, 3 arch elephant trunk grafts, and 1 ascending aortic repair), while 3 patients also underwent left carotid-subclavian bypass grafting. Two patients developed paraplegia (1 following a ruptured aneurysm), and 2 patients had transient paraparetic events. Two patients had acute renal failure requiring short-term dialysis. Three patients died within 30 days; 2 late aneurysm-related deaths were noted. Three patients developed endoleaks during follow-up. Mean lengths of stay were 13 days (7-30) for the visceral bypass and 12 (3-25) for the endovascular stent-graft. In addition, remaining procedures in 8 patients required a mean of 7 days (0-14) in hospital. Staged endovascular and open procedures are feasible for thoracoabdominal aneurysms in patients at prohibitive risk for open thoracoabdominal reconstruction. However, this approach still carries a significant risk of perioperative mortality and morbidity. The potential for less invasive alternatives should be investigated.
American Journal of Surgery, 1985
We reviewed the records of 21 patients with recurrent head and neck cancer who were treated by re... more We reviewed the records of 21 patients with recurrent head and neck cancer who were treated by resection and intraoperative brachytherapy at our institution between 1979 and 1983. We excluded those patients who received
Gene Therapy, 2003
A strategy for inducing preferential proliferation of the engrafted hepatocytes over host liver c... more A strategy for inducing preferential proliferation of the engrafted hepatocytes over host liver cells should markedly increase the benefit of hepatocyte transplantation for the treatment of liver diseases and ex vivo gene therapy. We hypothesized that preparative hepatic irradiation (HIR) to inhibit host hepatocellular regeneration in combination with the mitotic stimulus of host hepatocellular apoptosis should permit repopulation of the liver by transplanted cells. To test this hypothesis, congeneic normal rat hepatocytes were transplanted into UDP-glucuronosyltransferase (UGT1A1)deficient jaundiced Gunn rats (a model of Crigler-Najjar syndrome type I), following HIR and adenovirus-mediated FasL gene transfer. Progressive repopulation of the liver by engrafted UGT1A1-proficient hepatocytes over 5 months was demonstrated by the appearance of UGT1A1 protein and enzyme activity in the liver, biliary bilirubin glucuronides secretion, and long-term normalization of serum bilirubin levels. This is the first demonstration of massive hepatic repopulation by transplanted cells by HIR and FasL-induced controlled apoptosis of host liver cells.
Hepatic tumors often recur in the liver after surgical resection. Postoperative radiotherapy (RT)... more Hepatic tumors often recur in the liver after surgical resection. Postoperative radiotherapy (RT) could improve survival, but curative RT may induce delayed life-threatening radiation-induced liver damage. Because RT inhibits liver regeneration, we hypothesized that unirradiated, transplanted hepatocytes would proliferate preferentially in a partially resected and irradiated liver, providing metabolic support. We subjected F344 rats to hepatic RT and partial hepatectomy with/without a single intrasplenic, syngeneic hepatocyte transplantation. Hepatocyte transplantation ameliorated radiation-induced liver damage and improved survival of rats receiving RT after partial hepatectomy. We further demonstrated that transplanted hepatocytes extensively repopulate and function in a heavily irradiated rat liver.
International Journal of Radiation Oncology Biology Physics, 1997
International Journal of Radiation Oncology Biology Physics, 1999
Applied Physics Letters, 1993
ABSTRACT
Neurology India, 2007
Discussion Cortical sinovenous thrombosis occurs in both males and females, but is more common in... more Discussion Cortical sinovenous thrombosis occurs in both males and females, but is more common in women in the postpartum period, especially in developing countries like India.[1] The common etiologies include prothrombotic states, infections, drugs and inflammatory ...