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Dinesh Singh

Publications and source records attributed to Dinesh Singh.

17 recordsLinked to original sources
PubMed2006

Can gravity distinguish between Dirac and Majorana neutrinos?

We show that spin-gravity interaction can distinguish between Dirac and Majorana neutrino wave packets propagating in a Lense-Thirring background. Using time-independent perturbation theory and the gravitational phase to generate a perturbation Hamiltonian with spin-gravity coupling, we show that the associated matrix element for the Majorana neutrino differs significantly from its Dirac counterpart. This difference can be demonstrated through significant gravitational corrections to the neutrino oscillation length for a two-flavor system, as shown explicitly for SN 1987A.

Journal Article↗
PubMed2005

Optimizing cancer radiotherapy with 2-deoxy-d-glucose dose escalation studies in patients with glioblastoma multiforme.

BACKGROUND AND PURPOSE: Higher rates of glucose utilization and glycolysis generally correlate with poor prognosis in several types of malignant tumors. Own earlier studies on model systems demonstrated that the nonmetabolizable glucose analog 2-deoxy-D-glucose (2-DG) could enhance the efficacy of radiotherapy in a dose-dependent manner by selectively sensitizing cancer cells while protecting normal cells. Phase I/II clinical trials indicated that the combination of 2-DG, at an oral dose of 200 mg/kg body weight (BW), with large fractions of gamma-radiation was well tolerated in cerebral glioma patients. Since higher 2-DG doses are expected to improve the therapeutic gain, present studies were undertaken to examine the tolerance and safety of escalating 2-DG dose during combined treatment (2-DG + radiotherapy) in glioblastoma multiforme patients. PATIENTS AND METHODS: Untreated patients with histologically proven glioblastoma multiforme (WHO criteria) were included in the study. Seven weekly fractions of (60)Co gamma-rays (5 Gy/fraction) were delivered to the tumor volume (presurgical CT/MRI evaluation) plus 3 cm margin. Escalating 2-DG doses (200-250-300 mg/kg BW) were administered orally 30 min before irradiation after overnight fasting. Acute toxicity and tolerance were studied by monitoring the vital parameters and side effects. Late radiation damage and treatment responses were studied radiologically and clinically in surviving patients. RESULTS: Transient side effects similar to hypoglycemia were observed in most of the patients. Tolerance and patient compliance to the combined treatment were very good up to a 2-DG dose of 250 mg/kg BW. However, at the higher dose of 300 mg/kg BW, two out of six patients were very restless and could not complete treatment, though significant changes in the vital parameters were not observed even at this dose. No significant damage to the normal brain tissue was observed during follow-up in seven out of ten patients who received complete treatment and survived between 11 and 46 months after treatment. CONCLUSION: Oral administration of 2-DG combined with large fractions of radiation (5 Gy/fraction/week) is safe and could be tolerated in glioblastoma patients without any acute toxicity and late radiation damage to the normal brain. Further clinical studies to evaluate the efficacy of the combined treatment are warranted.

Administration, Oral↗
PubMed2005

Ureterocalicostomy: a contemporary experience.

OBJECTIVES: To report our contemporary experience with ureterocalicostomy to determine whether the indications or results have changed in modern practice. Ureterocalicostomy is a well-established treatment for patients with complicated ureteropelvic junction (UPJ) obstruction and other forms of proximal ureteral obstruction. Although both retrograde and antegrade endourologic interventions have become accepted forms of management, the success rates do not approach those of open or even laparoscopic interventions, potentially leading to a greater number of patients with treatment failure and the need for more complicated reconstruction. METHODS: Between July 1991 and February 2004, 11 patients (4 women and 7 men), aged 19 to 68 years (mean 38), underwent open surgical ureterocalicostomy. The indications for surgery were primary UPJ obstruction in 4, failed cutting balloon incision for UPJ obstruction in 3, proximal ureteral stricture after ureteroscopic stone removal in 2, and obliterated UPJ after percutaneous nephrolithotomy and failed antegrade endopyelotomy in 1 patient each. RESULTS: Hospitalization ranged from 4 to 7 days (mean 5.1). No patient experienced a significant perioperative complication. With follow-up ranging from 5 to 32 months (mean 10.1), relief of obstruction was evident in all patients as documented by intravenous urography or nuclear renography. Furthermore, differential function on the involved side improved from a mean of 54.6% preoperatively to 60.1% postoperatively (P <0.05). CONCLUSIONS: The spectrum of indications for ureterocalicostomy has changed, although excellent results can still be achieved. Although laparoscopic approaches are currently being evaluated, most patients currently undergoing this reconstructive procedure still require open operative intervention.

Adult↗
PubMed2005

Laparoscopic heminephrectomy for tumor.

OBJECTIVES: To present our experience with laparoscopic heminephrectomy. We defined heminephrectomy as excision of 30% or more of the renal parenchyma. Laparoscopic partial nephrectomy has typically been performed for smaller, exophytic tumors. With growing experience, we have performed more extensive resections for larger tumors, when indicated. METHODS: Since August 1999, we have performed laparoscopic partial nephrectomy in more than 300 patients. Of these, 41 patients were deemed to have undergone laparoscopic heminephrectomy (group 1). A contemporary group of 41 consecutive patients who underwent laparoscopic partial nephrectomy (less than 30% resection) were retrospectively identified for comparison (group 2). RESULTS: The preoperative patient demographics were similar, except for a greater body mass index (P = 0.02) in group 1. Group 1 had larger tumors (3.7 cm versus 2.3 cm, P <0.001) that were more commonly centrally located (41% versus 9.8%, P = 0.001) and more deeply infiltrating (P <0.001) compared with group 2. Group 1 underwent larger parenchymal resections (P <0.001) and routine pelvicaliceal suture repair (P = 0.002). The warm ischemia time was longer in group 1 (39 versus 33 minutes, P = 0.02); however, the amount of blood loss (150 versus 100 mL, P = 0.28) and total operative time (220 versus 190 minutes, P = 0.09) were comparable between the groups. The analgesic requirements, hospital stay, overall complications, and postoperative serum creatinine were comparable between the groups. Histopathologic examination showed that all 82 surgical margins were negative. CONCLUSIONS: Laparoscopic heminephrectomy is an advanced procedure that can be performed efficaciously with equivalent outcomes to those of less substantial resections. To our knowledge, experience with laparoscopic heminephrectomy has not been previously described.

Adult↗
PubMed2005

Lateral pedicle control during laparoscopic radical prostatectomy: refined technique.

OBJECTIVES: To report a technique of lateral pedicle control during laparoscopic radical prostatectomy that completely eliminates any form of electrocautery, ultrasonic thermal energy, clips, or bioadhesives. METHODS: The technique was used in 25 men undergoing nerve-sparing laparoscopic radical prostatectomy. Our antegrade technique involves transient control of the lateral prostate pedicles with an atraumatic vascular bulldog clamp. The pedicles were divided by precise cold cutting, and the neurovascular bundles (NVBs) were teased away with gentle blunt and sharp dissection. Hemostasis was secured with meticulous, superficial suturing of transected blood vessels with 4-0 Vicryl. Real-time transrectal ultrasound monitoring was performed preoperatively, during bulldog clamp application, and postoperatively. RESULTS: The mean bulldog clamp time for the right and left prostate pedicles was 11.1 and 11.2 minutes, respectively. Transrectal ultrasonography confirmed continued arterial blood flow within NVB during active bulldog clamping. Before clamping, during clamping, and after prostatectomy, the mean number of visible blood vessels within each NVB was 3.4, 2.2, and 2.1 (P <0.001 before versus during or after), and the mean resistive index of arterial blood flow was 0.86, 0.85, and 0.85, respectively. Positive surgical margins occurred in 1 patient (4%). Potency and continence data are awaited. CONCLUSIONS: We describe a technique of lateral pedicle ligation during laparoscopic radical prostatectomy using monitored cold cutting and delicate 4-0 hemostatic suturing that completely eliminates all electrocautery, ultrasound thermal energy, clips, and bioadhesives. Bulldog clamp placement on the lateral prostate pedicles did not interrupt blood flow within the NVB.

Hemostasis, Surgical↗
PubMed2005

Novel endourologic applications for holmium laser.

The holmium laser is used routinely during endoscopic procedures to treat stones, strictures, and tumors of the urinary tract. We report two successful novel endourologic applications of a holmium laser: division and removal of a synthetic urethral sling mesh in one patient and fragmentation of a tempered stainless steel surgical needle in another.

Adult↗
PubMed2005

Outpatient laparoscopic pyeloplasty.

OBJECTIVES: To assess the feasibility of ambulatory laparoscopic pyeloplasty. Laparoscopic pyeloplasty aims to reproduce the excellent functional outcomes of open pyeloplasty while diminishing procedural morbidity. METHODS: Six patients fulfilled specific inclusion criteria for outpatient laparoscopic pyeloplasty: informed consent, body mass index of 40 kg/m2 or less, primary ureteropelvic junction obstruction, uncomplicated laparoscopic surgery completed by 12:00 pm, and postoperative pain control by oral analgesics. All patients had a double-J ureteral stent placed cystoscopically before laparoscopic access. No drains were placed postoperatively. RESULTS: All 6 patients successfully underwent laparoscopic dismembered pyeloplasty (3 left, 3 right) using the retroperitoneal (n = 5) or transperitoneal (n = 1) approach. The average patient age was 22 years. The mean surgical time was 223 minutes (range 165 to 270), the mean blood loss was 82 mL (range 10 to 250), and the mean postoperative hospital stay was 359 minutes (range 226 to 424). Postoperative analgesia comprised a mean of 6 mg morphine sulfate and 32 mg of ketorolac. No complications or readmissions occurred postoperatively. Intravenous urography and Lasix technetium-99m mercaptoacetyltriglycine renal scans documented resolution of obstruction. With long-term follow-up (mean 38.4 months), no recurrences have developed. CONCLUSIONS: We report our initial series of ambulatory laparoscopic pyeloplasty. In this well-selected patient population, outpatient pyeloplasty was feasible and safe.

Adolescent↗
PubMed2005

Ureteropelvic junction obstruction after partial nephrectomy.

BACKGROUND AND PURPOSE: As the experience with partial nephrectomy continues to grow and the procedure increasingly becomes the standard of care for properly selected patients, it is critical to understand the potential complications and how these complications are best managed. Presented herein is the presentation, work-up, and treatment of ureteropelvic junction (UPJ) obstruction after partial nephrectomy. PATIENTS AND METHODS: From 1993 to 2004, 1154 partial nephrectomies have been performed at our institution by one surgeon. From the database of these patients, four (0.35%) were identified with postoperative UPJ obstruction. The charts of these patients were reviewed to identify preoperative and intraoperative characteristics as they relate to the development and risk of UPJ obstruction. Additionally, the presentation of UPJ obstruction, its management, and long-term follow-up are reported. RESULTS: Tumor location in the lower pole appears to be a risk factor for the development of UPJ obstruction, which is likely a result of ischemic or mechanical injury. This complication was managed successfully by endoscopic approaches in three of four cases. At a mean follow-up of 43 months, all patients remain free of obstruction according to both the absence of symptoms and radiographic evidence. CONCLUSION: Obstruction of the UPJ is an uncommon complication of partial nephrectomy. Endoscopic treatment of this complication yields a durable outcome, as all patients with a mean follow-up of more than 3 years show resolution of their obstruction.

Adult↗
PubMed2005

Laparoscopic partial nephrectomy.

In properly selected patients, partial nephrectomy yields oncologic efficacy similar to that of traditional radical nephrectomy. We have performed more than 415 laparoscopic radical nephrectomies over the 5-year period beginning in September 1999. All patients undergo a three-dimensional CT scan with 3-mm sections prior to the operation. We generally prefer the transperitoneal approach, although for posterior tumors, a retroperitoneal approach is preferred. The kidney is dissected using standard technique. Intraoperative hydration is given to maintain diuresis. Detailed real-time ultrasonographic delineation of the tumor is obtained to facilitate planning of the resection. We prefer en-bloc hilar clamping. The renal capsule is scored circumferentially with the "L" hook electrocautery. Parenchymal incision and tumor resection is performed using heavy reuseable scissors. The base of the resection defect is closed using a running 2-0 Vicryl on a CT-1 needle. The water-tightness of pelvicaliceal repair is tested by repeat gentle injection of indigo carmine through a ureteral catheter. Next, the parenchyma is closed with 1 Vicryl on a CTX needle placed over an oxidized cellulose bolster. The specimen is extracted within an entrapment bag. Initially, a surgeon should be highly selective, including patients with small, mostly exophytic, tumors. With increasing comfort and experience, the criteria can expand.

Hemostasis, Surgical↗
PubMed2005

Renal artery pseudoaneurysm following laparoscopic partial nephrectomy.

PURPOSE: We describe the presentation, evaluation and management of hemorrhage due to renal artery pseudoaneurysm following laparoscopic partial nephrectomy. MATERIALS AND METHODS: Of the 345 laparoscopic partial nephrectomies performed by us during a 5-year period 6 patients (1.7%) had postoperative hemorrhage from a renal artery pseudoaneurysm. Patient charts were reviewed to identify pertinent preoperative, intraoperative and postoperative data. RESULTS: Median tumor size was 3.5 cm (range 2.2 to 5), intraoperative blood loss was 175 cc (range 50 to 500), warm ischemia time was 32 minutes (range 30 to 45) and operative time was 3.8 hours (range 2.5 to 5). The mean percent of kidney excised was 31% and pelvicaliceal system entry was suture repaired in all 6 patients. No patient required blood transfusion perioperatively. Average hospital stay was 3.4 days (range 2.5 to 6). Delayed postoperative hemorrhage occurred at a median of 12 days (range 8 to 15). Angiography revealed a renal artery pseudoaneurysm most commonly at a third or fourth order branch (4 and 2 patients, respectively). Percutaneous embolization was successful in each patient. CONCLUSIONS: Renal artery pseudoaneurysm is an uncommon complication following laparoscopic partial nephrectomy. These patients often present in delayed fashion. Selective angiographic embolization is the initial treatment of choice.

Adult↗
PubMed2003

Evaluation of skin tumors by magnetic resonance imaging.

In vivo magnetic resonance imaging (MRI) is a powerful noninvasive technique in medical diagnosis; however, its application to analyze skin disorders is still at initial stages. To check whether MRI can be used as a noninvasive tool to analyze skin tumors, we carried out MRI of mice after treatment with benzo[a]pyrene (BP), a well known carcinogen. MRI was done on whole mice and was particularly focused on various layers and regions of interest of the skin: dermis, epidermis, and tumor. Initial MRIs of mice bearing skin tumors of 4, 8, 12, and 16 weeks after inducing BP clearly revealed the appearance of tumor. The MRIs of tumor-bearing mice with 20-week-old tumor development showed invasion to adjacent internal anatomic structures. The MRI data were in good agreement with the extent of cellular atypia and neoplastic changes that are typical of squamous cell carcinoma as noticed from the histopathologic findings. Therefore, MRI seems to have the potential to evaluate the tumor invasions equally well as that of histopathology or other clinical findings.

Animals↗
PubMed2002

Gene expression correlates of clinical prostate cancer behavior.

Prostate tumors are among the most heterogeneous of cancers, both histologically and clinically. Microarray expression analysis was used to determine whether global biological differences underlie common pathological features of prostate cancer and to identify genes that might anticipate the clinical behavior of this disease. While no expression correlates of age, serum prostate specific antigen (PSA), and measures of local invasion were found, a set of genes was identified that strongly correlated with the state of tumor differentiation as measured by Gleason score. Moreover, a model using gene expression data alone accurately predicted patient outcome following prostatectomy. These results support the notion that the clinical behavior of prostate cancer is linked to underlying gene expression differences that are detectable at the time of diagnosis.

Adult↗
PubMedDate not supplied

Acupressure and ondansetron for postoperative nausea and vomiting after laparoscopic cholecystectomy.

PURPOSE: To compare the efficacy of acupressure wrist bands and ondansetron for the prevention of postoperative nausea and vomiting (PONV). METHODS: One hundred and fifty ASA I-II, patients undergoing elective laparoscopic cholecystectomy were included in a randomized, prospective, double-blind and placebo-controlled study. Patients were divided into three groups of 50. Group I was the control; Group II received ondansetron 4 mg iv just prior to induction of anesthesia; in Group III acupressure wristbands were applied at the P6 points. Acupressure wrist bands were placed inappropriately in Groups I and II. The acupressure wrist bands were applied 30 min prior to induction of anesthesia and removed six hours following surgery. Anesthesia was standardized. PONV were evaluated separately as none, mild, moderate or severe within six hours of patients' arrival in the postanesthesia care unit and then at 24 hr after surgery by a blinded observer. If patients vomited more than once, they were given 4 mg ondansetron iv as the rescue antiemetic. Results were analyzed by Z test. A P value of < 0.05 was taken as significant. RESULTS: The incidence of PONV and the requirement of rescue medication were significantly lower in both the acupressure and ondansetron groups during the first six hours. CONCLUSION: Acupressure at P6 causes a significant reduction in the incidence of PONV and the requirement for rescue medication in the first six hours following laparoscopic cholecystectomy, similar to that of ondansetron 4 mg iv.

Acupressure↗
PubMedDate not supplied

Critique of laparoscopic lymphadenectomy in genitourinary oncology.

Regional lymphadenectomy is prognostic and selectively therapeutic in urologic oncology. The role of lymphadenectomy continues to be defined with the evolving multimodal management of genitourinary malignancies. Laparoscopy is playing a greater role in the management of genitourinary malignancies and thus, it is germane to critique the role of laparoscopic lymphadenectomy in the management of these tumors. Review of the literature suggests that laparoscopic pelvic lymphadenectomy is feasible with nodal yields commensurate to those in open published series. Although laparoscopic retroperitoneal lymph node dissection for nonseminomatous germ cell tumor is feasible, the technique and efficacy of this procedure require further investigation.

Humans↗