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Biomedical subjects

Peter L Choyke

Publications and source records attributed to Peter L Choyke.

At least 19 recordsLinked to original sources
PubMed2006

Simultaneous two-color spectral fluorescence lymphangiography with near infrared quantum dots to map two lymphatic flows from the breast and the upper extremity.

Due to their small size and poor access, the lymphatic function has been difficult to study in vivo. Especially difficult is the mapping of lymphatic drainage from two basins into the same node. Quantum dots can be used to perform multicolor images with high fluorescent intensity and are of a nano-size size suitable for lymphatic imaging via direct interstitial injection. Here we show simultaneous two-color in vivo wavelength-resolved spectral fluorescence lymphangiography using two near infrared quantum dots with different emission spectra, which allow non-invasive and simultaneous visualization of two separate lymphatic flows draining the breast and the upper extremity and variations in the drainage patterns and the water sheds within the axillary node. Two-color spectral fluorescence lymphangiography can provide insight into mechanisms of drainage from different lymphatic basins that may lead to sentinel lymph nodes detection of the breast cancer as well as prevention of complications such as lymphedema of the arm.

Animals↗
PubMed2006

Macromolecular MRI contrast agents for imaging tumor angiogenesis.

Angiogenesis has long been accepted as a vital process in the growth and metastasis of tumors. As a result it is the target of several novel anti-cancer medications. Consequently, there is an urgent clinical need to develop accurate, non-invasive imaging techniques to improve the characterization of tumor angiogenesis and the monitoring of the response to anti-angiogenic therapy. Macromolecular MR contrast media (MMCM) offer this diagnostic potential by preferentially exploiting the inherent hyperpermeable nature of new tumor vessels compared with normal vessels. Over the last 10-15 years many classes of MMCM have been developed. When evaluated with dynamic contrast enhanced (DCE) MRI, a number of MMCM have demonstrated in vivo imaging properties that correlate with ex vivo histological features of angiogenesis. The enhancement patterns with some MMCM have been reported to correlate with tumor grade, as well as show response to anti-angiogenic and anti-vascular drugs. Future applications of MMCM include targeted angiogenesis imaging and drug delivery of anti-cancer 'payloads'. Herein we discuss the best known MMCMs along with their advantages and disadvantages.

Contrast Media↗
PubMed2006

Targeted optical imaging of cancer cells using lectin-binding BODIPY conjugated avidin.

Lectins (asialo-receptor family) are expressed on a number of tumors that develop peritoneal metastases. To demonstrate that fluorescence imaging based on lectin binding is applicable for a variety of tumors, we conjugated BODIPY to avidin (avidin-BODIPY), and studied the efficacy of tumor targeting in 9 cancer cell lines in vitro and an ovarian cancer cell line in vivo using a murine peritoneal cancer model. All 9 cell lines showed specific intracellular accumulation with avidin-BODIPY on fluorescence microscopy and flow cytometry. In vivo spectral molecular imaging clearly visualized the peritoneal tumor foci with avidin-BODIPY, whereas, deglycosylated avidin-BODIPY (neutravidin-BODIPY) showed only minimal fluorescence from the tumor foci and was accompanied by higher background signals. These results suggest the lectin-targeted molecular imaging technique using a targeted green fluorescence probe is potentially useful in a wide variety of cancers with a proclivity for dissemination in the peritoneal space.

Animals↗
PubMed2006

Delivery of gadolinium-labeled nanoparticles to the sentinel lymph node: comparison of the sentinel node visualization and estimations of intra-nodal gadolinium concentration by the magnetic resonance imaging.

Sentinel node imaging is commonly performed prior to surgery for breast cancer and melanoma. While current methods are based on radio-lymphoscintigraphy, MR lymphangiography (MRL) offers the benefits of better spatial resolution without ionizing radiation. However, the optimal nanoparticle for imaging the sentinel nodes remains unclear. Gadolinium-labeled (Gd) contrast agents ranging in diameter from <1 to 12 nm were evaluated to determine which size provides the most rapid and most concentrated delivery of contrast agent to the lymph nodes in a mouse model of lymphatic metastases. Specifically, PAMAM-G2, -G4, -G6 and -G8, and DAB-G5 Gd-dendrimer agents, as well as Gadomer-17 and Gd-DTPA, were compared. Among these agents, the G6 Gd dendrimer depicted the lymphatics and lymph nodes with the highest peak concentrations and this occurred 24-36 min post-injection (p<0.01; all except G8). Based on ex vivo concentration phantoms, high accumulations of Gd(III) ions occurred within lymph nodes (1.7-4.4 mM Gd/270-680 ppm Gd) with high target to background ratios (>100). These concentrations are sufficient to contemplate the use of Gd-neutron capture therapy of regional lymph nodes. Thus, when injected interstitially, the PAMAM-G6 Gd dendrimer not only provides excellent opacification of sentinel lymph nodes, but also provides the potential for targeted therapy of sentinel lymph nodes.

Animals↗
PubMed2006

Dendrimer-based nanoprobe for dual modality magnetic resonance and fluorescence imaging.

A novel PAMAM dendrimer-based nanoprobe for dual magnetic resonance and fluorescence imaging modalities was synthesized. Fluorescence studies revealed that Gd(III) complexation to the probe has no effect on the quantum yield; however, increases in the dye content resulted in partial quenching. The potential of the new nanoprobe, G6-(Cy5.5)(1.25)(1B4M-Gd)(145), as a dual modality imaging agent was demonstrated in vivo by the efficient visualization of sentinel lymph nodes in mice by both MRI and fluorescence imaging modalities.

Animals↗
PubMed2006

Dynamic contrast-enhanced magnetic resonance imaging in the assessment of early response to tumor necrosis factor alpha in a colon carcinoma model.

OBJECTIVE: We describe the effects of tumor necrosis factor alpha (TNFalpha) on tumor microvasculature in a murine colon carcinoma model using serial dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI). MATERIAL AND METHODS: Mice with subcutaneous murine colon carcinomas (MC-38) were imaged at 4.7 T after administration of 0.2 mmol/kg gadolinium-DTPA. Both treated and control mice (each group, n = 4), were scanned at baseline and 2, 4, 6, and 96 hours. A 2-compartment pharmacokinetic model generated parameters such as K, kep, and initial area under the gadolinium concentration curve (IAUC). RESULTS: The treatment group revealed significant differences in K at all time points after TNFalpha. kep and IAUC were significantly reduced at 2, 6, and 96 hours. The coefficient of variation in control animals ranged from 0.13 for IAUC to 0.30 for K. Mild histologic changes were observed at 2 to 6 hours, but considerable central necrosis with a vascular tumor rim was seen at 96 hours. CONCLUSION: DCE MRI can be used to detect early effects of TNFalpha. Serial DCE MRI is a promising tool in assessing the early effects of antivascular therapies.

Animals↗
PubMed2006

In vivo spectral fluorescence imaging of submillimeter peritoneal cancer implants using a lectin-targeted optical agent.

Intraperitoneal metastases commonly recur after surgery because small tumor foci escape detection within the complex anatomy of the peritoneal cavity and mesentery. Accurate localization of peritoneal implants during surgery could improve the resection of ovarian cancer and other malignancies, but few practical techniques to enhance detectability are currently available. Here, we describe a targeted molecular imaging method that employs fluorescently labeled avidin to detect submillimeter peritoneal implants of ovarian cancer in mice. After binding to surface lectins on the tumor, fluorescein-conjugated avidin enabled the spectral fluorescence imaging of disseminated peritoneal implants. High spatial resolution and high tumor-to-background ratio allowed the visualization of implants as small as 0.3 mm (with 100% sensitivity and specificity; n = 150) and the identification of even smaller lesions ex vivo. These results suggest that targeted molecular imaging with a fluorescence-labeled lectin-ligand system is a promising technique for the detection of disseminated submillimeter foci of cancer.

Animals↗
PubMed2006

CT and MRI of hepatic abscess in patients with chronic granulomatous disease.

OBJECTIVE: We describe the spectrum of radiologic appearances of hepatic abscesses in patients with chronic granulomatous disease (CGD), a hereditary immunodeficiency presenting in childhood that occurs at a rate of 1 in 200,000-250,000 live births and predisposes patients to infection with catalase-positive organisms. CONCLUSION: Hepatic abscesses in patients with CGD show an atypical radiologic appearance compared with sporadic hepatic abscesses, and they are characterized by homogeneous enhancement and multiseptal enhancement. In the appropriate clinical setting, the appearance of an enhancing mass should suggest the possibility of a CGD-related hepatic abscess.

Adolescent↗
PubMed2005

Detection and localization of proteinuria by dynamic contrast-enhanced magnetic resonance imaging using MS325.

After renal transplantation, persistent glomerular disease affecting the native kidneys typically causes albuminuria, at least for a period of time, making it difficult to determine in a noninvasive fashion whether proteinuria originates in the native kidneys or the renal allograft. To address this problem, dynamic contrast-enhanced magnetic resonance imaging (MRI) using gadolinium (Gd)-based albumin-bound blood pool contrast agent (MS325) to localize proteinuria was investigated. Glomerular proteinuria was induced in Sprague-Dawley rats by intravenous injection of puromycin aminonucleoside (PAN), whereas control rats received physiologic saline vehicle. Both groups of animals underwent a 40-min dynamic contrast-enhanced MRI using radio frequency spoiled gradient echo imaging sequence after injection of Gd-labeled MS325. Contrast uptake and clearance curves for cortex and medulla were determined from acquired MR images. Compared with controls, proteinuric rats exhibited significantly lower elimination rate constants. The use of gadopentetate dimeglumine (Gd-DTPA) as a contrast agent showed smaller and less specific differences between proteinuric and control groups. In rats with one proteinuric kidney (PAN-treated) and one normal kidney (transplanted from a normal rat), MRI using MS325 was able to differentiate between the two kidneys. The results suggest that MRI with an albumin-bound blood pool contrast agent may be a useful noninvasive way to localize proteinuria. If this technique can be successfully applied in human patients, it may allow for the localization of proteinuria after kidney transplant and thereby provide a noninvasive way to detect disease affecting the renal allograft.

Animals↗
PubMed2005

Germline BHD-mutation spectrum and phenotype analysis of a large cohort of families with Birt-Hogg-Dubé syndrome.

Birt-Hogg-Dubé syndrome (BHD), a genodermatosis characterized by multiple hamartomas of the hair follicle (fibrofolliculoma), predisposes individuals to an increased risk of developing renal neoplasms and spontaneous pneumothorax. Previously, we localized the BHD locus (also known as FLCN) to chromosome 17p11.2 by linkage analysis and subsequently identified germline mutations in a novel gene in probands from eight of the nine families with BHD in our screening panel. Affected members of five of the families inherited an insertion/deletion of a cytosine in a C8 tract in exon 11. This mutation was also identified by exon 11 screening in probands from 22 of 52 additional families with BHD and therefore represents a hypermutable "hotspot" for mutation in BHD. Here, we screened the remaining 30 families from this large BHD cohort by direct sequence analysis and identified germline BHD mutations in 84% (51/61) of all families with BHD recruited to our study. Mutations were located along the entire length of the coding region, including 16 insertion/deletion, 3 nonsense, and 3 splice-site mutations. The majority of BHD mutations were predicted to truncate the BHD protein, folliculin. Among patients with a mutation in the exon 11 hotspot, significantly fewer renal tumors were observed in patients with the C-deletion than those with the C-insertion mutation. Coding-sequence mutations were not found, however, in probands from two large families with BHD whose affected members shared their family's BHD-affected haplotype. Of the 53 families with BHD whose members inherited either a germline mutation or the affected haplotype, 24 (45%) had at least one member with renal neoplasms. Three families classified with familial renal oncocytoma were identified with BHD mutations, which represents the first disease gene associated with this rare form of renal neoplasm. This study expands the BHD-mutation spectrum and evaluates genotype-phenotype correlations among families with BHD.

Adenoma, Oxyphilic↗
PubMed2005

Management of von Hippel-Lindau-associated kidney cancer.

Von Hippel-Lindau disease (VHL) is an autosomal-dominant inherited condition that predisposes patients to develop renal cysts and tumors, most commonly in the second to fourth decades of life. Renal cysts and tumors have historically been a major cause of disease-related morbidity and mortality, so urologists are often called on to manage patients with VHL. Knowledge of the extrarenal manifestations of VHL (hemangioblastomas of the central nervous system and retina, endolymphatic sac tumors, pancreatic cysts, epididymal and broad-ligament cysts, and pheochromocytomas) and integration of nonurologic specialties into management teams for VHL patients will help to achieve successful outcomes. Screening for renal manifestations of VHL, by regular imaging of the abdomen, begins late in the second decade of life. Because renal tumors in VHL can be multifocal and bilateral, management can be complex. Radical nephrectomy removes all tissue at risk for forming renal tumors; however, this necessitates renal replacement therapy. In an effort to control cancer effectively while preserving native renal function and minimizing intervention, some researchers have proposed an observational strategy. Patients are screened until the largest tumor reaches 3 cm in diameter, at which time operative intervention is recommended. Nephron-sparing surgery is undertaken, whenever technically feasible, with the goal of removing all tumors in that renal unit. The role of minimally invasive technologies is currently being evaluated in selected patients with VHL renal masses. Elucidation of molecular pathways associated with VHL renal tumors may facilitate development of effective medical treatments for these lesions in the future.

Humans↗
PubMed2005

Detection of lymph node involvement in hematologic malignancies using micromagnetic resonance lymphangiography with a gadolinum-labeled dendrimer nanoparticle.

Animal models of lymphoma should reflect their counterparts in humans; however, it can be difficult to ascertain whether an induced disease is intralymphatic or extralymphatic based on direct visualization. Current imaging methods are insufficient for identifying lymphatic and intralymphatic involvement. To differentiate intralymphatic from extralymphatic involvement, we have developed a magnetic resonance imaging-based lymphangiography method and tested it on two animal models of lymphoma. A gadolinium (Gd)-labeled dendrimer nanoparticle (generation-6; approximately 220 kDa/ approximately 10 nm) was injected interstitially into mice bearing hematologic malignancies to perform dynamic micromagnetic resonance lymphangiography (micro-MRL). Both a standard T1-weighted 3D fast spoiled gradient echo and a T2/T1-weighted 3D fast imaging employing steady-state acquisition (3D-FIESTA-C) were compared in an imaging study to differentiate intralymphatic from extralymphatic involvement of tumors. The lymphatics and lymph nodes were visualized with both methods in all cases. In addition, 3D-FIESTA-C depicted both the lymphatic system and the extralymphatic tumor. In an animal model, 3D-FIESTA-C demonstrated that the bulk of the tumor thought to be intralymphatic was actually extralymphatic. In conclusion, micro-MRL, using Gd-labeled dendrimer nanoparticles with the combined method, can define both the normal and abnormal lymphatics and can distinguish intralymphatic from extralymphatic diseases in mouse models of malignant lymphoma.

Animals↗
PubMed2004

Lymphatic drainage imaging of breast cancer in mice by micro-magnetic resonance lymphangiography using a nano-size paramagnetic contrast agent.

BACKGROUND: The presence of lymph node metastases is an important factor in breast cancer patient prognosis. Therefore, the precise identification of sentinel lymph nodes in these patients is critical. Improving current magnetic resonance (MR) imaging methods using a newly synthesized nano-size paramagnetic molecule, G6, as a contrast agent, provides an attractive means toward attaining this goal. METHODS: A four-dimensional method of micro-MR lymphangiography using G6 (9 nm/240 kd) was developed to visualize the lymphatic ducts and lymph nodes draining mouse mammary tumors over time. The ability of micro-MR lymphangiography with the G6 contrast agent to visualize lymphatic drainage of normal mouse mammary tissue was compared with that of the conventional MR contrast agent, Gd-[DTPA]-dimeglumine (<1 kd). Lymphatic drainage in spontaneous and xenografted breast tumor models was visualized using the G6 contrast agent. RESULTS: Draining lymphatic ducts and lymph nodes were clearly visualized in the mammary tissue of normal mice and in spontaneous and xenografted breast tumor models after a direct mammary gland or peritumoral injection of G6. Gd-[DTPA]-dime-glumine, by contrast, failed to depict lymphatic flow from the mammary tissue in normal mice using the same method. Micro-MR lymphangiography using the G6 contrast agent revealed the absence of filling in the metastatic foci of affected lymph nodes. CONCLUSIONS: The superior temporal and spatial resolution of micro-MR lymphangiography using the contrast agent G6 may facilitate the study of tumor lymphatic drainage and lymphatic metastasis in both experimental animals and clinical medicine. In addition, this may be a powerful new method for sentinel lymph node localization in human breast cancer.

Animals↗
PubMed2004

Congenital disorder of oxygen sensing: association of the homozygous Chuvash polycythemia VHL mutation with thrombosis and vascular abnormalities but not tumors.

Adaptation to hypoxia is critical for survival and regulates multiple processes, including erythropoiesis and vasculogenesis. Chuvash polycythemia is a hypoxia-sensing disorder characterized by homozygous mutation (598C>T) of von Hippel-Lindau gene (VHL), a negative regulator of hypoxia sensing. Although endemic to the Chuvash population of Russia, this mutation occurs worldwide and originates from a single ancient event. That VHL 598C>T homozygosity causes elevated normoxic levels of the transcription factor hypoxia inducible factor-1alpha (HIF-1alpha), serum erythropoietin and hemoglobin is known, but the disease phenotype has not been documented in a controlled manner. In this matched cohort study, VHL 598C>T homozygosity was associated with vertebral hemangiomas, varicose veins, lower blood pressures, and elevated serum vascular endothelial growth factor (VEGF) concentrations (P <.0005), as well as premature mortality related to cerebral vascular events and peripheral thrombosis. Spinocerebellar hemangioblastomas, renal carcinomas, and pheochromocytomas typical of classical VHL syndrome were not found, suggesting that overexpression of HIF-1alpha and VEGF is not sufficient for tumorigenesis. Although hemoglobin-adjusted serum erythropoietin concentrations were approximately 10-fold higher in VHL 598C>T homozygotes than in controls, erythropoietin response to hypoxia was identical. Thus, Chuvash polycythemia is a distinct VHL syndrome manifested by thrombosis, vascular abnormalities, and intact hypoxic regulation despite increased basal expression of hypoxia-regulated genes.

Adaptation, Physiological↗
PubMed2004

Polyamine dendrimer-based MRI contrast agents for functional kidney imaging to diagnose acute renal failure.

PURPOSE: To choose an efficacious renal functional MRI contrast agent to image early renal tubular damage. We synthesized and compared smaller polyamine dendrimer-based MRI contrast agents (<60 kD) that, unlike Gd-[DTPA], transiently accumulate in renal tubules and can be used to visualize renal structural and functional damage. MATERIALS AND METHODS: Six dendrimer-based MRI contrast agents smaller than 60 kD were studied by high resolution dynamic micro-MRI and compared to Gd-[DTPA]-dimeglumine and Gadomer-17. The best agent, DAB-G2, was further tested in a mouse ischemia/reperfusion model to validate its efficacy. RESULTS: Despite unequal renal clearance rates, all polyamine dendrimer agents visualized the renal functional anatomy of the mice better than Gd-[DTPA]-dimeglumine and Gadomer-17. DAB-G2 was excreted most rapidly, yet was able to visualize mild renal tubular injury very early after injury. CONCLUSION: DAB-G2 was found to be the best candidate for functional kidney imaging and enabled early diagnosis of acute renal injury.

Acute Kidney Injury↗