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Biomedical subjects

N Papanicolaou

Publications and source records attributed to N Papanicolaou.

At least 19 recordsLinked to original sources
PubMed2002

Vortex rings and lieb modes in a cylindrical Bose-Einstein condensate.

We present a calculation of a solitary wave propagating along a cylindrical Bose-Einstein trap. For sufficiently strong couplings of experimental interest, it is found to be a hybrid of a one-dimensional (1D) soliton and a three-dimensional vortex ring. The calculated energy-momentum dispersion exhibits characteristics similar to those of a mode proposed sometime ago by Lieb within a 1D model, as well as some rotonlike features.

Journal Article↗
PubMed2001

Gastric outlet obstruction caused by a giant gastroduodenal artery aneurysm: a case report.

Gastric outlet (GO) obstruction in an adult is usually caused by intrinsic gastric or duodenal lesions or pancreatic tumours. This study describes a case of a 77-year-old man who developed GO obstruction due to extrinsic compression from a large gastroduodenal artery aneurysm under rupture. This cause of GO obstruction has never previously been reported in the literature.

Aged↗
PubMed1999

Current concepts in imaging of adrenal masses.

Adrenal masses are a common entity. With the advent of improved cross-sectional imaging techniques the detection and characterization of adrenal masses has improved dramatically. We review the imaging features of benign and malignant adrenal masses and other entities that may cause mass-like enlargement of the adrenal glands.

Adrenal Gland Diseases↗
PubMed1998

Site-directed mutagenesis of conserved aspartates, glutamates and arginines in the active site region of Escherichia coli DNA topoisomerase I.

To catalyze relaxation of supercoiled DNA, DNA topoisomerases form a covalent enzyme-DNA intermediate via nucleophilic attack of a tyrosine hydroxyl group on the DNA phosphodiester backbone bond during the step of DNA cleavage. Strand passage then takes place to change the linking number. This is followed by DNA religation during which the displaced DNA hydroxyl group attacks the phosphotyrosine linkage to reform the DNA phosphodiester bond. Mg(II) is required for the relaxation activity of type IA and type II DNA topoisomerases. A number of conserved amino acids with acidic and basic side chains are present near Tyr-319 in the active site of the crystal structure of the 67-kDa N-terminal fragment of Escherichia coli DNA topoisomerase I. Their roles in enzyme catalysis were investigated by site-directed mutation to alanine. Mutation of Arg-136 abolished all the enzyme relaxation activity even though DNA cleavage activity was retained. The Glu-9, Asp-111, Asp-113, Glu-115, and Arg-321 mutants had partial loss of relaxation activity in vitro. All the mutants failed to complement chromosomal topA mutation in E. coli AS17 at 42 degreesC, possibly accounting for the conservation of these residues in evolution.

Amino Acid Sequence↗
PubMed1998

Pseudo-Meigs' syndrome caused by paraovarian fibroma.

Meigs' syndrome includes an ovarian tumor, usually fibroma, associated with hydrothorax and ascites. It is accepted that uterine tumors, like fibromas, can also be associated with ascites and hydrothorax, but this is extremely rare. The mechanism of formation of peritoneal and pleural effusion is not well documented. The most likely pathogenesis ascribes the fluid formation to the filtration of interstitial fluid in the peritoneal through the tumor capsule, and the diffusion to the pleural space through the diaphragm lymphatic vessels at the foramen of Bochdalek. Paraovarian fibromas are also extremely rare neoplasms, probably of paramesonephric origin. It has been hypothesised that they can develop by proliferation of connective tissue cells around the Wolfian remnants. In this article, probably for the first time, a case of paraovarian fibroma with ascites and hydrothorax is presented.

Ascites↗
PubMed1998

Congenital infection by human parvovirus B19 ascites-anaemia.

A case of intrauterine infection by human parvovirus B19 (HPV B19) manifested as ascites during pregnancy is presented. Ascites was diagnosed by ultrasound at 27 weeks' gestation. A caesarean section was performed at 37 weeks'. owing to affected mobility of the fetus. A pale, female infant with low haemoglobin and bradycardia was delivered. Polymerace Chain Reaction (PCR) lab tests revealed that the mother and the fetus were infected by HPV B19. The neonate was born with low haemoglobin (Hb = 10 g/dl) and with ascites; it was discharged in good general condition 50 days after delivery.

Anemia↗
PubMed1997

MR differentiation of phaeochromocytoma from other adrenal lesions based on qualitative analysis of T2 relaxation times.

AIM: To determine the diagnostic accuracy of MR imaging in differentiating phaeochromocytoma from other adrenal lesions. MATERIALS AND METHODS: Sixty-seven adrenal masses (65 patients) including 17 phaeochromocytomas were imaged using T2-weighted pulse sequences on 0.6 T and 1.5 T GE MR units. The adrenal lesions were qualitatively assessed by three observers and divided into three categories (benign adenomas, malignant lesions and phaeochromocytomas) based on lesion signal intensity relative to liver and cerebrospinal fluid. RESULTS: Eleven phaeochromocytomas (65%) were correctly identified while the remaining six (35%) were misclassified, five as malignant lesions and one as a benign adenoma, because of atypical low signal intensity on T2-weighted MR images. Conversely, six non-phaeochromocytomas (three benign adenomas, two adrenal carcinomas and one metastasis) were wrongly classified as phaeochromocytomas because of very high lesion signal intensity. The sensitivity of MR imaging for diagnosing phaeochromocytoma was 64.7%, specificity 88.0%, positive predictive value 64.7% and negative predictive value 88.0%. CONCLUSION: There is considerable overlap between the MR appearance of phaeochromocytoma and other adrenal lesions. A phaeochromocytoma cannot be excluded on the basis of a lack of high signal intensity on T2-weighted MR imaging.

Adenoma↗
PubMed1997

FDG PET characterization of renal masses: preliminary experience.

OBJECTIVE: This study was undertaken to evaluate the potential efficacy of fluorine-18 2-fluoro-2-deoxy-D-glucose positron emission tomography (FDG PET) to detect renal tumours and to characterize indeterminate renal cysts. SUBJECTS AND METHODS: Twenty-six PET scans were performed in 21 patients (14 PET scans in 10 patients with malignant renal tumours and 12 PET scans in 11 patients with Bosniak type 3 indeterminate renal cysts). Pathological proof was obtained in 18 of 21 patients (10 with solid neoplasms, eight with indeterminate cysts). Imaging was performed 1 h after injection of 5-10 mCi of FDG with IV administration of Lasix (10 mg) 20 mins after injection. Two consecutive 9.7-cm image segments were scanned to cover the entire renal areas. RESULTS: PET accurately depicted solid neoplasms as areas of increased uptake in nine of 10 patients. Bilateral renal cell carcinomas were missed in one diabetic patient. All but one indeterminate renal cysts were correctly classified as benign (photopenic areas), but an indeterminate cyst with a 4-mm papillary neoplasm was wrongly classified as benign. There were no false positive PET interpretations. The mean tumour-to-kidney ratio was 3.0 for malignant lesions. CONCLUSION: We conclude that FDG PET scanning shows promise in the evaluation of indeterminate renal cysts. A positive PET scan in the appropriate clinical setting obviates the need for cyst aspiration. A negative PET scan in conjunction with a negative cyst aspiration offers confirmatory evidence of benignity. Our preliminary results are encouraging and further work is ongoing.

Adult↗
PubMed1996

Gonadal vein recruitment in renal cell carcinoma: incidence, pathogenesis and clinical significance.

OBJECTIVE: Gonadal vein recruitment by collateral veins in patients with renal cell carcinoma is not routinely searched for during abdominal computed tomography. We performed a retrospective view to determine the incidence of gonadal vein recruitment for collateral venous drainage in patients with renal cell carcinoma and we discuss its potential importance. PATIENTS AND METHODS: Abdominal CT examinations were available for 58 of 95 patients with renal cell carcinoma identified during a 3-year-period. The presence of collateral veins and recruitment of the ipsilateral gonadal vein was recorded and correlated with the estimated blood loss at surgery. RESULTS: Eighteen of 58 tumours were small (less than 5 cm). Multiple (greater than three) collateral renal capsular veins were noted in 26 of 58 patients and few (less than three) were noted in 11. Recruitment of the gonadal vein (range 4-18 mm, mean 8 mm) was seen in 18 of 58 patients (31%) who all had multiple collaterals. Gonadal vein recruitment was only seen in patients with tumours greater than 5 cm. Mean estimated blood loss at surgery was significantly different (P < 0.01) in 18 of 58 patients (mean, 1078 ml) with gonadal vein recruitment compared to 40 of 58 patients (mean 304 ml) without distinct visualization of the gonadal vein and compared to 22 of 40 patients with large tumours (mean 368 ml). CONCLUSION: Gonadal vein recruitment signifies well-developed arteriovenous shunting and high flow collateral venous drainage pathways and may be used as an index of tumour vascularity. This finding may have clinical potential in triaging patients toward pre-operative renal embolization.

Adult↗
PubMed1996

Acute renal infections.

Most adults with uncomplicated acute pyelonephritis pose no diagnostic or therapeutic problems and recover fully. When imaging is requested in these cases, CT scan with and without contrast enhancement is preferable; however, depending on the condition of the patient and preference of the clinician an IVU, sonogram, or radionuclide scan may also provide adequate information. Patients at higher risk for complications, such as renal or perinephric abscesses with or without PHN and EPN, require aggressive and vigorous clinical and radiologic monitoring. CT scan is superior to other imaging modalities in the investigation of these complications. Interventional percutaneous procedures are established as safe and effective means of controlling or curing the infection in many patients and are often chosen over traditional surgical technique. The radiologist thus is an indispensable member of the management team and should be available for consultation and intervention.

Acute Disease↗
PubMed1995

Lymphoma of the kidney. A report of 11 cases.

We describe 11 patients first seen with symptoms or signs related to lymphoma predominantly or exclusively involving one or both kidneys. The patients were seven men and four women, aged 40-77 years (median, 67). Seven of them had one or more other prior (four), subsequent (two) or both simultaneous and subsequent (one) primary malignant or premalignant lesions. The presenting symptoms of the patients with lymphoma included local pain (five cases), loss of appetite or nausea (four cases), hematuria (two cases), weight loss (two cases) or malaise (two cases). One patient had renal failure at presentation. One lymphoma was an incidental finding at the time of aneurysm resection. Nine patients had unilateral disease; two patients had bilateral disease. Six unilateral cases were initially considered on clinical (five) or clinical and pathological (one) evaluation to be primary carcinomas of the kidney. Gross examination of nephrectomy specimens revealed fleshy or firm, yellow, tan, or gray tumors from 5.7 to 22 cm (median, 7.5) in greatest dimensions that frequently invaded perinephric fat and adjacent structures. The lymphomas were subclassified as diffuse large cell (seven cases), follicular and diffuse large cell (one case), small lymphocytic plasmacytoid (two cases), and small noncleaved cell lymphoma (non-Burkitt's type) (one case). Immunophenotyping in nine cases revealed that all were B-lineage tumors. Three patients had Ann Arbor stage I disease, three had stage II, and five had stage IV. On follow-up, ranging from 1 week to 169 months (median, 15 months), 5 patients were alive and free of lymphoma. Four patients died of progressive disease 1 week to 23 months after diagnosis. One patient is alive at 4 months but has not completed chemotherapy. One asymptomatic patient has not been treated. Renal lymphomas are predominantly large-cell lymphomas of B-lineage affecting middle-aged and older adults and often can be treated successfully. Both clinically and pathologically, they can be mistaken for carcinomas of the kidney. A high proportion of patients in this series had malignant tumors of other types.

Adult↗
PubMed1995

Imaging the effects of diabetes on the genitourinary system.

Diabetes mellitus is a common multisystemic disease with serious effects on the genitourinary system. In the radiology literature, little attention has been paid to developing an integral approach to imaging of the genitourinary tract in diabetes. The long-term effects of diabetes on the genitourinary system include diabetic nephropathy, papillary necrosis, renal artery stenosis, diabetic cystopathy, and vas deferens calcification. Diabetes-associated urinary tract infections include renal and perirenal abscesses, gas-forming infections such as emphysematous pyelonephritis and emphysematous cystitis, fungal infections, and xanthogranulomatous pyelonephritis. Diabetes-associated genital infections include Fournier gangrene and postmenopausal tubo-ovarian abscess. In a diabetic with fever of unknown origin or in the event of a persistent infection in a diabetic with clinical deterioration despite use of antibiotics, radiologic studies can demonstrate the presence of genitourinary complications. Finally, radiologists should be aware of the risk of contrast material-induced nephropathy in diabetics.

Abscess↗
PubMed1994

Percutaneous internal ureteral stent placement: review of technical issues and solutions in 50 consecutive cases.

Fifty consecutive percutaneous ureteral stent placements in 40 patients over 2 1/2 years were reviewed. Thirty-seven of 50 cases were performed following failed retrograde stenting. Antegrade stenting failed in 2/37 (5%) cases of malignant obstruction, and 4/13 (31%) cases of benign ureteral disease. Causes of failure and common technical problems included poor angulation of the percutaneous track, tortuous dilated ureters, tight obstructions, wedging of stent assembly components due to high resistance, and difficulty in positioning of the proximal pigtail. Helpful technical modifications included mid-pole rather than lower pole calyceal access, urinary decompression prior to stenting, and the routine use of a peel-away sheath (success rate 23/24 placements with sheath vs 21/26 without sheath). Stent patency rates were 95% at 3 months and 54% at 6 months. With attention to technique and appropriate modifications, success rate of percutaneous stenting remained high in this series despite the large number of cases referred after retrograde stenting had failed.

Adolescent↗