Immunocytochemical localization of kynurenine aminotransferase in the rat striatum: a light and electron microscopic study.

Kynurenine aminotransferase is the biosynthetic enzyme for kynurenic acid, an antagonist of excitatory amino acid receptors. Because of the possible role of kynurenic acid in basal ganglia diseases, the distribution of kynurenine aminotransferase immunoreactivity was examined in the adult rat striatum at the light and electron microscopic levels. Kynurenine aminotransferase immunoreactivity was detected in glial cells and in neurons. The preadsorption control vastly reduced or eliminated specific staining at both the light and electron microscopic levels. Kynurenine aminotransferase positive glial cells were abundant and contained a robust and homogeneous distribution of reaction product in both the nucleus and cytoplasm. The majority of neurons, both medium and large, were immunostained and exhibited granular kynurenine aminotransferase immunoreactivity in the cytoplasm of somata and proximal dendrites. At the ultrastructural level, kynurenine aminotransferase immunoreactive astrocytic processes were apparent throughout the neuropil where they often encircled capillaries and surrounded axospinous synapses. Reaction product was associated with the cytoplasmic matrix, filaments, rough endoplasmic reticulum, and the nucleus. In neurons, the majority of label occurred in round membrane-bound cytoplasmic organelles located adjacent to the Golgi apparatus, rough endoplasmic reticulum, and the cell or nuclear membranes. Cisternae and vesicles were identifiable in some of the labeled profiles. Polyribosomes and rough endoplasmic reticulum were also labeled. These data provide an anatomical basis for biochemical studies that have suggested the presence of striatal kynurenine aminotransferase in both astrocytes and neurons.

Recent advances in the design and synthesis of carbon-14 labelled pharmaceuticals from small molecule precursors.

Over the past decade, the increased chemical complexity of new drug candidates has resulted in a parallel need to develop innovative syntheses of carbon-14 labelled pharmaceuticals. Faced with short time-lines and a limited number of labelled precursors, radiochemists have addressed this challenge by developing new reagents and adapting existing technology to labelled syntheses. Selected examples from the recent radiochemical literature illustrate some of the creative strategies used to rapidly solve these synthetic challenges. Examples describing the handling and use of common small molecule reagents, such as carbon-14 labelled carbon dioxide, methyl iodide, cyanide, acetic acids, sulfur and phosphorous stabilized ylides for the synthesis of labelled steroids, prostanoids, nucleosides, pyridines, quinolines, benzazepines and other heterocycles are presented. Several general strategies for radiolabelling are also discussed including the degradation strategy for accessing necessary intermediates and precursors, the radiolabelling of aromatic substrates, transition metal mediated cross-couplings, and the use of chiral auxiliaries for the enantioselective syntheses of radiolabelled pharmaceuticals.

Right ventricular dysfunction and dilatation, similar to left ventricular changes, characterize the cardiac depression of septic shock in humans.

Septic shock in humans is usually characterized by a high cardiac output, a low systemic vascular resistance, reversible depression of left ventricular ejection fraction, and transient left ventricular dilatation. The relationship of left ventricular to right ventricular function in septic shock is poorly understood. To evaluate right ventricular vs left ventricular performance and to evaluate the relation of biventricular performance to survival, we performed serial hemodynamic and radionuclide angiographic studies in 39 patients with septic shock. Right ventricular ejection fraction was calculated using the two regions of interest method. There were 22 survivors and 17 nonsurvivors. Comparing initial with final (after recovery for survivors; within 24 hours of death for nonsurvivors) studies, each survivor's cardiovascular performance returned toward normal, with significant increases in mean arterial pressure, left and right ventricular ejection fraction, and right ventricular stroke work index. Their profiles also demonstrated significant decreases in central venous pressure, pulmonary artery wedge pressure, pulmonary artery mean pressure, and left and right ventricular end-diastolic volume indices. From initial to final study in the nonsurvivors, there was a statistically significant increase in heart rate but no change in any other cardiovascular parameter, indicating a persistence of the initial cardiovascular dysfunction until death. Comparing serial studies, the pattern of change in right vs left ventricular function was very similar (same direction in 82 percent of patients). Thus, myocardial depression in human septic shock affects both ventricles simultaneously with a similar pattern of dysfunction.

Gene-modified PA1-STK cells home to tumor sites in patients with malignant pleural mesothelioma.

BACKGROUND: Malignant mesothelioma is an uncommon but lethal cancer of increasing incidence, particularly among patients with a history of exposure to asbestos. Although numerous treatments have been employed, including chemotherapy, radiation therapy, surgical resection, and combinations of the above, no satisfactory treatment yet exists, and affected patients will die of this disease, usually within 12 months. Gene-based therapies constitute a new approach that offers hope of improved control of these tumors while being associated with less morbidity than conventional chemotherapeutic or surgical regimens. We demonstrated that PA1-STK cells home in vivo to mesothelioma deposits, a phenomenon that is required for optimal exertion of this therapeutic concept. METHODS: Gene-modified ovarian cancer cells expressing the thymidine-kinase gene (PA1-STK) were radiolabeled with 99Tc and infused into the pleural space of 4 patients with malignant pleural mesothelioma, then scanned to determine distribution of the cells. RESULTS: PA1-STK cells recognized and adhered preferentially to mesothelioma lining the chest wall. CONCLUSIONS: Cell-based "suicide gene" therapy utilizing the "bystander effect" with the gene-modified ovarian cancer cell line PA1-STK is feasible in human pleural mesothelioma. We have shown that this trafficking and homing of the therapeutic cells to the intrapleural tumor sites, a requirement for success with this novel therapeutic concept, is also valid in humans.

Immunocytochemical localization of the quinolinic acid synthesizing enzyme, 3-hydroxyanthranilic acid oxygenase, in the rat substantia nigra.

Quinolinic acid, an endogenous excitatory amino acid receptor agonist, may play a role in several brain diseases. In the present study, the immunocytochemical localization of 3-hydroxyanthranilic acid oxygenase (3HAO), the enzyme responsible for the synthesis of quinolinic acid, was examined in the adult rat substantia nigra at the light and electron microscopic levels. 3HAO-immunoreactivity was detected exclusively in astrocytes. Labeling was present in cell bodies and in fine glial processes, which frequently encircled capillaries and partially enveloped neuronal somata. Notably, 3HAO-labeled processes were in close contact with several types of synaptic profiles. Often, they partially engulfed asymmetric synapses, characteristic of excitatory neurotransmission. In addition, they were found in apposition to putative dopaminergic cell bodies. These data provide an anatomical basis for the idea that functional interactions may occur between glial processes which synthesize quinolinic acid, and synaptic profiles, many of which presumably utilize excitatory neurotransmitters.

Indium-111 leukocyte scintigraphic detection of subclinical osteomyelitis complicating delayed and nonunion long bone fractures: a prospective study.

Twenty patients were studied prospectively with indium-labeled leukocyte imaging to evaluate its effectiveness in differentiating noninfected delayed or nonunion from osteomyelitis complicating these entities. All patients underwent an open surgical procedure within 24 h of the scan. Bone specimens from the nonunion site were obtained for microbiological and histological analysis to confirm the presence or absence of osteomyelitis. In these twenty patients, the sensitivity of the indium scintigraphy was 100%, the specificity 100%, and the overall accuracy 100%. Indium-labeled leukocyte scintigraphy is significantly more accurate than 99mtechnetium and 67gallium imaging had been, when studied earlier, in detecting subclinical osteomyelitis complicating nonunion. Indium-labeled leukocyte scintigraphy should supplant sequential technetium and gallium studies in this patient population when the surgeon must determine whether subclinical osteomyelitis is complicating fracture management of delayed and nonunions.

Determination of losartan and its degradates in COZAAR tablets by reversed-phase high-performance thin-layer chromatography.

Losartan potassium is an angiotensin II receptor blocker. It has been formulated and marketed as a tablet dosage from (COZAAR). A reversed-phase high-performance thin-layer chromatography method has been validated and shown to be sensitive, efficient, and reliable, and can be used as an excellent alternative to the HPLC stability testing of losartan potassium in COZAAR tablets.

Is there scientific support for the use of juice to facilitate the nonstress test?

In this article, a review of the literature is presented regarding the practice of administering fruit juice to facilitate the nonstress test (NST). Seven studies were found that investigated the relationship between the administration of natural or artificial glucose and the NST. No support was found for the use of juice or glucose to facilitate the NST as commonly administered in practice or as noted in textbooks. Therefore, the practice and textbook references to it should be questioned. The use of rituals undermines the professionalism of nursing practice.

Diphosphonate intestinal activity seen on two bone images in neuroblastoma.

Neuroblastoma is well recognized as a cause of soft tissue uptake of Tc-99m MDP. Two cases of neuroblastoma arising in the midline from the celiac axis are reported. Bone imaging performed on two separate days showed not only typical soft tissue uptake, but also the appearance of the radiopharmaceutical in the bowel. At surgery, a midline upper abdominal neuroblastoma was found in both patients without evidence of involvement of the liver, kidneys, bowel, gallbladder or mesentery. It became apparent with delayed images in the second patient that this activity was in the bowel and moving around the abdomen in a typical large bowel pattern. Bowel activity was not seen in other patients having bone scans at this time. Follow-up bone imaging on the first patient after resection of the tumor did not demonstrate diphosphonate activity in the bowel. These authors have never seen or read of this finding previously in this condition, and report it in these two patients.

Experiences with high dose radiopeptide therapy: the health physics perspective.

One of the new, promising areas of nuclear medicine involves radiolabeled low-molecular-weight peptides for the diagnosis and management of cancer. Somatostatin analogous peptides bind to membrane receptors on tumors with high specificity. These analogues, when radiolabeled with 123I, 131I, 99mTc, or (111)In, allow for external scintigraphic imaging or radioguided surgical resection of tumors. Somatostatin analogues with high tumor binding affinity have also been used for high-dose radiotherapy at the Medical Center of Louisiana since 1994. Although we had extensive prior experience with relatively high-dose 131I administration for thyroid ablation, our personnel protection, contamination control, and other safety techniques required significant modification to ensure effective contamination and radiation exposure control. As therapy with radiolabeled peptides becomes more widely utilized, the controls developed at our institution may be implemented by others to maintain exposures ALARA.

[Dilated cardiomyopathy. Role of radioisotope technics]. / Cardiomiopatia dilatativa. Ruolo delle tecniche radioisotopiche.

Radionuclide techniques are easily obtainable, noninvasive examinations that provide useful information in the evaluation, diagnosis and management of patients with dilated cardiomyopathy. The gated blood pool scan allows the assessment of ventricular size, configuration, and wall and septal thickness. These data allow the functional class of the cardiomyopathy (congestive, restrictive or hypertrophic) to be defined. Often Thallium-201 myocardial perfusion imaging adds further information and is particularly useful in distinguishing congestive cardiomyopathy from severe coronary artery disease and in depicting septal abnormalities in hypertrophic cardiomyopathy. Useful as these techniques are, they are not substitutes for conventional approaches to diagnosis. Careful history taking and physical examination, as well as scrutiny of the electrocardiogram, chest X-ray and echocardiogram should be standard practice for the evaluation of patients with suspected cardiomyopathy. Judicious use of noninvasive techniques may obviate the need for cardiac catheterization in many patients.

In situ radiotherapy with 111In-pentetreotide. State of the art and perspectives.

111In-pentetreotide (Octreoscan) and other radiolabeled somatostatin analogs are useful in the management of well differentiated neuroendocrine malignancies such as carcinoid or islet cell neoplasms. These radiopeptides bind to membrane bound somatostatin receptors (sst 1-5) which are over-expressed in a wide variety of neoplasms, especially those arising from the neuroectoderm. Imaging advances allow for the noninvasive determination of the presence of sst receptors by combining radioactivity [111Indium with a somatostatin analog, DTPA-D-phe1-octreotide (pentetreotide)]. Radiolabeled somatostatin analogs bind to membrane receptors and internalization of the complex occurs. Auger emitting somatostatin analogs offer a novel and significantly less toxic approach to controlling neoplastic diseases by delivering targeted radiation specifically to receptor bearing cells while sparing receptor negative cells. Responses of 62-69% in 85 patients with metastatic neuroendocrine tumors treated with high dose (6-19.6 GBq) 111In-pentetreotide, specifically targeting tumor somatostatin receptors, have been reported. Objective responses observed included biochemical and radiographic responses with prolonged survival. This article will discuss and review the multi-center data available to date, the mechanisms of action of radiolabeled somatostatin analogs, dosimetry, clinical response parameters, and toxicity.

Pulmonary arterial hypertension: value of perfusion scintigraphy.

Records of 34 patients with established causes of pulmonary arterial hypertension were retrospectively reviewed. The ventilation-perfusion scans were blindly classified according to standardized criteria as normal or high, low, or intermediate probability of pulmonary embolism as the cause of pulmonary arterial hypertension. Twelve of 13 patients with primary pulmonary hypertension had normal or low-probability scans, but the perfusion pattern was not helpful in distinguishing between histologic subtypes. All eight patients with large-vessel thromboembolic hypertension had high-probability scans; however, three of 13 patients with nonembolic secondary pulmonary hypertension also had high-probability scans. While a normal or low-probability scan excluded proximal pulmonary emboli as a cause of pulmonary hypertension, a high-probability scan may be associated with a variety of other nonembolic causes of secondary pulmonary hypertension.

Radionuclide renography predicts functional changes in patients with renal artery involvement by Takayasu's arteritis.

Renovascular hypertension is a major complication of Takayasu's arteritis, which contributes to the high mortality associated with the disease. We studied 5 patients affected by different degrees of Takayasu's arteritis to assess the usefulness of radionuclide renography in evaluating renal perfusion and function, and to predict changes induced by the disease before and after therapeutic interventions. Computer-assisted dynamic renal imaging with Tc-99m diethylenetriaminepentaacetic acid (DPTA) and I-131 orthoiodohippurate (OIH), and renal arteriography were concurrently performed in all patients. Two patients with hemodynamically insignificant renal artery stenosis showed normal perfusion and function by renography. Three patients had significant renal artery stenosis and functional changes on renography. Subsequently, two of these patients had successful therapy (one had bilateral renal artery bypass grafts, and the other had renal artery angioplasty), and both showed functional improvement at renography. Our results demonstrate that radionuclide renography is valuable in the assessment of functional changes induced by Takayasu's arteritis as well as for determining the response to therapeutic interventions.

In situ radiotherapy with 111In-pentetreotide: initial observations and future directions.

PURPOSE: Somatostatin and its analogues, such as octreotide and lanreotide, are used to treat neuroendocrine malignancies. Somatostatin analogues bind to somatostatin receptors (sst 1-5), which are differentially expressed in a wide variety of neoplasms. Following ligand receptor binding, a fraction of these complexes internalize. Internalization of radiolabeled somatostatin analogues, especially those that emit Auger electrons, may allow treatment of somatostatin-receptor-positive tumors by delivering a radioactive isotope to the cancer cell in a targeted fashion. 111In-pentetreotide, an sst-2-preferring somatostatin analogue, has been used for scintigraphic evaluation and management of neuroendocrine cancer patients. We hypothesized that binding and internalization of 111In-pentetreotide, an Auger electron emitter, may induce receptor-specific cytotoxicity and could be a useful therapeutic agent in somatostatin-receptor-expressing malignancies. METHODS: To test this hypothesis, subjects who had failed conventional therapy and had somatostatin-receptor-positive malignancies, as determined by positive uptake on a 6.0 mCi 111In-pentetreotide scan, were treated with two monthly 180 mCi intravenous injections of 111In-pentetreotide. CT scans were obtained before therapy and within 30 days following the completion of the second 111In-pentetreotide dose. Toxicity was evaluated using standard criteria. RESULTS: Fourteen patients were studied from February 1997 to August 1997. Clinical benefit occurred in six of 10 gastroenteropancreatic tumor patients. Objective partial radiographic responses occurred in two of 14 patients, and significant tumor necrosis (defined by changes in Hounsfield units) developed in six of the 10 gastroenteropancreatic tumor patients. Possible treatment-related toxicity included two patients experiencing grade 3/4 myelosuppression, and two patients had no measurable toxicity. The most common toxicity was grade 1/2 hemoglobin (N = 6). CONCLUSION: One hundred eighty millicurie (180-mCi) doses of 111In-pentetreotide are well tolerated and are an effective therapy in some subjects with somatostatin receptor-expressing tumors. The maximal tolerated dose of 111In-pentetreotide and the optimal dosing schedules remain to be determined.

3-Hydroxyanthranilic acid oxygenase-containing astrocytic processes surround glutamate-containing axon terminals in the rat striatum.

Glutamate, the major transmitter of the corticostriatal pathway, is present in abundance in the striatum. 3-Hydroxyanthranilic acid oxygenase (3HAO) is the biosynthetic enzyme for quinolinic acid, an endogenous agonist of the NMDA glutamate receptor subtype and a potent neurotoxin. In order to explore the anatomical basis of possible functional interactions between glutamate and quinolinic acid in the rat striatum, pre- and postembedding immunocytochemical methods were used to localize 3HAO immunoreactivity (-i) and glutamate-i at the electron microscopic level. In accordance with previous light microscopic and biochemical studies, 3HAO-i was detected exclusively in astrocytes throughout the striatum. Notably, 3HAO-i was present in fine-caliber glial processes that often surrounded or abutted synaptic profiles, both asymmetric and symmetric. Glutamate-i was heavily deposited (3-13-fold higher gold particle density than tissue average) in axon terminals forming asymmetric synapses with spines and, occasionally, dendrites. In contrast, terminals forming symmetric synapses, dendrites, neuronal somata, and glial cells contained significantly less labeling than terminals forming asymmetric synapses. In double-labeled material, 3HAO-i was observed in glial processes that partially surrounded or were adjacent to glutamate-labeled terminals forming asymmetric synapses. 3HAO-labeled glial processes were also adjacent to unlabeled terminals forming symmetric synapses. Since quinolinic acid is known to enter the extracellular compartment readily, these results suggest that astrocytic quinolinic acid may participate in the regulation of glutamatergic neurotransmission in the rat striatum.