Antagonistic microtubule-sliding motors position mitotic centrosomes in Drosophila early embryos.

The positioning of centrosomes, or microtubule-organizing centres, within cells plays a critical part in animal development. Here we show that, in Drosophila embryos undergoing mitosis, the positioning of centrosomes within bipolar spindles and between daughter nuclei is determined by a balance of opposing forces generated by a bipolar kinesin motor, KLP61F, that is directed to microtubule plus ends, and a carboxy-terminal kinesin motor, Ncd, that is directed towards microtubule minus ends. This activity maintains the spacing between separated centrosomes during prometaphase and metaphase, and repositions centrosomes and daughter nuclei during late anaphase and telophase. Surprisingly, we do not observe a function for KLP61F in the initial separation of centrosomes during prophase. Our data indicate that KLP61F and Ncd may function by crosslinking and sliding antiparallel spindle microtubules in relation to one another, allowing KLP61F to push centrosomes apart and Ncd to pull them together.

Lava lamp, a novel peripheral golgi protein, is required for Drosophila melanogaster cellularization.

Drosophila cellularization and animal cell cytokinesis rely on the coordinated functions of the microfilament and microtubule cytoskeletal systems. To identify new proteins involved in cellularization and cytokinesis, we have conducted a biochemical screen for microfilament/microtubule-associated proteins (MMAPs). 17 MMAPs were identified; seven have been previously implicated in cellularization and/or cytokinesis, including KLP3A, Anillin, Septins, and Dynamin. We now show that a novel MMAP, Lava Lamp (Lva), is also required for cellularization. Lva is a coiled-coil protein and, unlike other proteins previously implicated in cellularization or cytokinesis, it is Golgi associated. Our functional analysis shows that cellularization is dramatically inhibited upon injecting anti-Lva antibodies (IgG and Fab) into embryos. In addition, we show that brefeldin A, a potent inhibitor of membrane trafficking, also inhibits cellularization. Biochemical analysis demonstrates that Lva physically interacts with the MMAPs Spectrin and CLIP190. We suggest that Lva and Spectrin may form a Golgi-based scaffold that mediates the interaction of Golgi bodies with microtubules and facilitates Golgi-derived membrane secretion required for the formation of furrows during cellularization. Our results are consistent with the idea that animal cell cytokinesis depends on both actomyosin-based contraction and Golgi-derived membrane secretion.

Sodium dependency of uptake of norepinephrine and m-iodobenzylguanidine into cultured human pheochromocytoma cells: evidence for uptake-one.

Radioiodinated m-iodobenzylguanidine (MIBG), a scintigraphic agent used in the detection of human pheochromocytomas, is thought to utilize the same uptake and retention mechanism(s) as norepinephrine (NE). Using primary cultures from 16 human pheochromocytomas, we compared the uptake of MIBG to that of NE. Two different uptake systems were identified. Both NE and MIBG were taken up by a sodium-dependent system that was characterized by: temperature dependency, high affinity, low capacity, saturability, ouabain sensitivity, and desmethylimipramine sensitivity. However, NE and MIBG were also taken up by a temperature-dependent, sodium-independent, apparently unsaturable system. The sodium-dependent uptake system fulfills many of the criteria for Uptake-one while the sodium-independent uptake system is most likely a passive diffusion process. Competitive inhibition studies demonstrated that NE and MIBG share a common uptake system; a concept consistent with the linear correlation between the rate of uptake of 1.0 microM NE and that of 1.0 microM MIBG (r = 0.942). At low concentrations, both NE and MIBG entered the tumor cells primarily by the sodium-dependent uptake system. Differential expression of the sodium-dependent and sodium-independent uptake systems, between different tumor cells, appears to be responsible for the variations of the kinetic parameters for both NE and MIBG. These studies provide the first direct characterization of a NE uptake mechanism in human pheochromocytoma cells.

The spectrum of pheochromocytoma in hypertensive patients with neurofibromatosis.

We have found an appreciable number of pheochromocytomas in patients with neurofibromatosis and concurrent hypertension (ten of 18 cases). At diagnosis, the patient age range was 15 to 62 years, the clinical appearance of the neurofibromatosis did not predict who would and who would not have pheochromocytomas, but the age at diagnosis was helpful in that our younger patients tended to have causes of hypertension other than pheochromocytoma. However, several causes of hypertension may coexist. The biochemical findings were highly diagnostic. The pheochromocytomas secreted epinephrine as well as norepinephrine and resided in or next to the adrenal gland. Where pheochromocytoma is the cause of hypertension, its resection generally results in a better control of hypertension than that obtained in patients whose BPs were elevated from other unknown causes.

Familial extra-adrenal pheochromocytoma. A new syndrome.

Pheochromocytomas in the same anatomic site, the right renal hilum, occurred in a family over three successive generations. For two patients in the latter two generations, scintigraphy with iodine 131-tagged metaiodobenzylguanidine (MIBG) showed tumors only in the region of the right renal hilum, thus indicating that they were primary lesions. At surgery, except for lymph node metastases noted microscopically in one patient, tumors were found only near the right renal hilum. The adrenal glands seemed normal on inspection, palpation, and computed tomography. In another family, a mother and son had primary pheochromocytomas arising from the urinary bladder. We suggest that primary extra-adrenal pheochromocytoma is a syndrome in which specific genetic abnormalities determine sites of tumor development.

QT interval prolongation and sudden cardiac death in diabetic autonomic neuropathy.

Alterations in cardiac sympathetic innervation may result in QT interval prolongation and predispose to sudden arrhythmias and death. Sudden cardiac death occurs in diabetic patients who have autonomic neuropathy, but the cause is uncertain. In 30 patients with insulin-dependent diabetes mellitus who had no evidence of ischemic heart disease, cardiac autonomic neuropathy, determined by clinical tests, was found in 17. The corrected QT interval (QTc), measured using Bazett's formula at rest and peak exercise, was prolonged (greater than 440 msec) in 12 of these patients at rest and in 15 at peak exercise. Prolonged QTc intervals were found only in patients who had definite cardiac autonomic neuropathy. As a group, the QTc interval (mean +/- SD) in the diabetic patients with cardiac autonomic neuropathy was prolonged compared to that in patients without cardiac autonomic neuropathy at rest (447 +/- 28 vs. 405 +/- 9 ms; P less than 0.0001) and peak exercise (468 +/- 23 vs. 402 +/- 23 ms; P less than 0.0001). There was a direct linear relationship between the extent of cardiac autonomic neuropathy and the QTc interval (r = 0.71; P less than 0.001). One of the patients with cardiac autonomic neuropathy and prolonged QTc intervals had a nonuniform loss of adrenergic neurons in his heart demonstrated by meta-iodobenzyl-guanidine scintigraphy, indicating sympathetic imbalance; he subsequently died unexpectedly. These data suggest that diabetic cardiac autonomic neuropathy may result in sympathetic imbalance and QTc interval prolongation, predisposing these patients to sudden arrhythmias and death.

Patterns of prolactin secretion in the syndrome of general resistance to thyroid hormones.

The dynamics of TSH and PRL secretion were studied in three patients with incomplete generalized resistance to thyroid hormones. Results in the first patient differed from those in the other two. The first patient had been treated previously with radioiodine but was clinically euthyroid when subsequently treated with supraphysiological quantities of T3 and T4. Increasing doses of T4 from 0.2-0.3 mg/day caused a decline in serum TSH levels and lesser increments in TSH to injected TRH in this patient. The other two patients had not been treated, but had basal TSH levels and TSH responses to TRH similar to those in the first patient. However, the TSH response to injected metoclopramide in the first patient was substantially higher than the responses in the other two patients. The basal levels of PRL in the first patient were elevated at both T4 doses; also, her PRL responses to TRH and metoclopramide were exaggerated and, compared to normal values, disproportionate to her TSH responses to these provocative agents. In contrast, the other two patients had normal basal PRL concentrations and normal or near-normal PRL responses to TRH and metoclopramide. We conclude that within the syndrome of resistance to thyroid hormones, there are heterogeneous patterns of PRL secretion. Dopaminergic tone on thyrotrophs and lactotrophs also differs among patients with the syndrome.

Uptake of 18-fluoro-2-deoxy-D-glucose by thyroid cancer: implications for diagnosis and therapy.

A patient developed a pulmonary metastasis from papillary thyroid carcinoma. This tumor concentrated relatively little 131I, but sufficient 18F-fluoro-2-deoxy-D-glucose (FDG) to be quantified and imaged by positron emission tomography. The uptake of FDG was lower on positron emission tomographic images after T4 therapy and when the serum TSH concentration was reduced to the low normal range. It may be possible to use decreases in FDG uptake by thyroid cancers, which represent declines in metabolism by the tumors, to indicate the optimum doses of T4 treatment for patients with these neoplasms. In addition, the ratio of tumor to background radioactivity was higher for FDG than for the flow agent 201Tl, so that studies with FDG may be a useful scintigraphic method for locating thyroid cancers when radioiodine imaging is unsatisfactory.

Pheochromocytoma, polycythemia, and venous thrombosis.

Polycythemia is rarely associated with pheochromocytoma. A patient with a 22-year history of malignant pheochromocytoma is presented in whom major complications developed as a result of long-standing polycythemia, apparently due to secretion of erythropoietin by the tumors. Despite attempts to reduce tumor burden by surgery, chemotherapy, and large doses of I-131-metaiodobenzylguanidine, polycythemia persisted. Extensive venous thrombosis developed requiring hospitalization and anticoagulation. Thus, polycythemia itself may be a cause of major morbidity in patients with pheochromocytoma, and prophylactic measures may be warranted. Review of the 130 patients with benign and malignant pheochromocytoma studied since the introduction of I-131-metaiodobenzylguanidine in 1980 revealed another six patients with hematocrits over 50 but only one had a hematocrit greater than 55 and required regular phlebotomy. In contrast, anemia (hematocrit less than 35) due to variety of causes was present in 18 cases.

Calculating radiation absorbed dose for pheochromocytoma tumors in 131-I MIBG therapy.

A protocol for calculating radiation absorbed dose to pheochromocytoma tumors during treatment with 131I-labeled metaiodobenzylguanidine (MIBG) is described. The technique calls for (a) obtaining tumor volumes from Computed Tomography and/or Magnetic Resonance Imaging, (b) computing energy absorbed by assuming complete beta-particle absorption and a standard shape for gamma-ray absorption and (c) scaling from tracer to therapy dose rate by the ratio of administered activities. Also a 131I time-activity curve is obtained from planar, Anger-camera, conjugate-view images of the tumor and a known-strength source, both over a series of days. In addition, to correct for any systematic errors in the calculated uptakes, a larger activity of 123I MIBG is administered separately and quantitative Single Photon Emission Computed Tomography (SPECT) is undertaken. A known-strength source also undergoes SPECT to calibrate the tomograms. Correction for Compton scattering is accomplished by the dual-energy-window technique. The subtraction fraction was found to be 0.7 for the 1/2" crystal camera and the mean reduction in tumor counts for seven tumors from Compton correction was 0.76. The normalization factor needed to bring the conjugate-view activities into agreement with the SPECT values ranged from 0.74 to 1.06. A test study on an anthropomorphic phantom indicated that the error in resultant activities might be estimated as +/- 13%. Application of the protocol led to the calculation of real, or potential (when decision was finally made to not administer therapy) radiation absorbed dose to seven tumors in three patients from an administration of about 8 GBq of MIBG. For two metastatic tumors in a 19-year old patient who did not have her primary cancer resected, the calculated radiation absorbed dose was 170 and 180 Gy. For the four metastatic deposits evaluated in two older patients, both of whom had their primary tumor surgically removed, the values ranged from 18 to 31 Gy.

Prognostic implications of the tall cell variant of papillary thyroid carcinoma.

The tall cell variant (TCV) of papillary thyroid carcinoma, characterized by a population of tall columnar cells with a height at least twice the width, was analyzed in 12 patients and compared to tumors from 12 patients with the usual type of papillary thyroid carcinoma (UPTC) matched for age, sex, and date of diagnosis to determine if tall cell histology had prognostic significance. Patients with TCV had significantly higher incidences of extrathyroidal disease, recurrent disease, and metastases compared to patients with UPTC. TCV patients also died of their tumors more frequently than UPTC patients (3/12 versus 0/12). There was no significant difference in tumor size or in the incidence of cervical lymph node involvement between the patient groups. These results show that TCV of papillary thyroid carcinoma has a more aggressive clinical course and a worse prognosis than UPTC in patient groups with similar age and sex distribution, length of follow-up, and tumor size.

Cardiac paragangliomas. A clinicopathologic and immunohistochemical study of four cases.

Cardiac paragangliomas are extremely rare neoplasms. Four surgically resected tumors were examined by immunohistochemistry and electron microscopy. The patients ranged in age from 18 to 36 years. All patients had hypertension and elevated urine catecholamine levels. Three tumors were located on the posterior left atrium, and one tumor was located in the interventricular groove at the aortic root. The tumors ranged in size from 5 to 7 cm, and they displayed a prominent Zellballen pattern without significant necrosis or mitosis. The tumors were mostly unencapsulated and infiltrated adjacent cardiac tissue in two cases. Immunoperoxidase staining showed that all tumors were positive for chromogranin and neuron-specific enolase. Three tumors were positive for methionine enkephalin. Positive staining for S-100 protein was seen in the sustentacular cells of all tumors but was negative in chromaffin cells. All tumors were negative for insulin, glucagon, gastrin, vasoactive intestinal polypeptide, somatostatin, adrenocorticotropic hormone, calcitonin, serotonin, pancreatic polypeptide, and rat atrial peptide. Ultrastructural studies of all four tumors showed moderate numbers of predominantly norepinephrine-type granules and a few epinephrine-type granules. These results show that cardiac paragangliomas are commonly found in close proximity to the left atrium and have immunohistochemical and ultrastructural features similar to other paragangliomas.

Medical treatment of benign and malignant thyroid tumors.

This article discusses the multiple types of benign and malignant thyroid tumors. Benign nodules are subclassified as hypofunctioning or functioning and hyperfunctioning, and the management and treatment of these nodules are outlined. The author also discusses in detail the morphologic types, distinctive prognoses, and responses to therapies of the various malignant tumors.

Thyrotoxicosis caused by thyroid cancer.

Well-differentiated follicular carcinoma causing thyrotoxicosis is a rare entity. The age and sex distribution is no different from that of other patients with follicular carcinoma, with 87% older than the age of 40 and a female:male ratio of 3:1. The clinical presentation is similar to that of Graves' patients except that evidence of metastatic disease is often present (soft tissue masses, bone pain). The metastases are in the usual locations (bone, lung, mediastinum) and are often bulky. Despite the poor efficiency of iodine uptake and thyroid hormone production, the large tumor mass is capable of producing excessive hormone. Laboratory data confirm the hyperthyroid state, but the occurrence of T3 elevations with normal T4 levels is common, and T3 toxicosis may be missed if only T4 levels are measured. The role of thyroid stimulating immunoglobulins is still evolving, but such stimulators may support the growth of metastatic thyroid carcinoma and promote the development of hyperthyroidism. The treatment of these patients varied. Most had thyroidectomy followed by 131I therapy. Dosimetry allows for the administration of the largest dose of 131I with acceptable side effects. A good response to radioiodine predicted a more favorable outcome. The survival of patients with metastatic thyroid carcinoma causing hyperthyroidism does not differ from euthyroid patients with metastatic follicular disease (10-year survival, 59%).

Familial partial peripheral and pituitary resistance to thyroid hormone: a frequently missed diagnosis?

The diagnosis of partial peripheral and pituitary resistance to thyroid hormone was ultimately made in two boys, 7 and 9 years of age, and a 10-year-old girl who had goiters and hyperthyroxinemia. The boys were treated with propythiouracil and/or thyroidectomy or iodine 131 for suspected thyrotoxicosis but had poorly suppressible serum thyroid-stimulating hormone (TSH) post treatment in spite of the usual L-thyroxine replacement. The girl had increasing goiter size while receiving propylthiouracil, 100 mg every eight hours. These findings led to reevaluation of thyroid hormone dynamics in these children and their families. Twelve additional family members, 3 to 38 years of age, compatible with an autosomal dominant inheritance, were also found to have peripheral and pituitary resistance to thyroid hormone. All affected individuals had elevated serum thyroxine and triiodothyronine levels, normal to slightly elevated triiodothyronine resin uptakes, and a nonsuppressed serum TSH. The five individuals who were given thyrotropin-releasing hormone showed exaggerated TSH responses, which normalized on L-thyroxine therapy. Misdiagnosis in six of 15 family members led to significant morbidity (hypothyroidism, delayed growth, and therapy risk). A nonsuppressed serum TSH in a patient with suspected thyrotoxicosis should lead to suspicion of this disorder. Appropriate management for this condition includes L-thyroxine therapy to decrease goiter size and normalize TSH responses to thyrotropin-releasing hormone.

What promise the preliminary tests of coronary artery disease?

For some patients with coronary artery disease (CAD), bypass operations prolong life. Angiograms, incurring some risk and considerable expense, are prerequisites to surgical therapy; they delineate the region and extent of disease. However, many people who complain of chest pain do not have disease that can be benefited by operation. Therefore, tests that will safely and economically select the appropriate individuals for angiography are most welcome. Yet, if the preliminary tests falsely declare affected people to be free of CAD, they will deny these patients angiography, and, consequently, surgical treatment that would prolong their lives. Decision analysis determines that a false-negative rate of less than 2% is necessary for tests preliminary to angiography if the average survival of patients is not to be shortened. No currently used procedure has attained this sensitivity. Radionuclide ventriculography approaches this precision, but its sensitivity must be sustained in more broadly based studies.

What causes uptake of technetium-99m methylene diphosphonate by tumors? A case where the tumor appeared to secrete a hypercalcemia-causing substance.

A patient exhibited an unusual constellation of findings: His extraosseous lymphoma sequestered [99mTc]MDP, a bone-seeking agent, while at the same time it appeared to produce a factor that caused hypercalcemia. The dispersed lymphoma cells took up more [99mTc]MDP in vitro than did cultured lymphoblasts suggesting that the in vivo sequestration may have been, at least in part, an active intracellular process.

Thyroid carcinoma with high levels of function: treatment with (131)I.

UNLABELLED: In some patients with well-differentiated thyroid carcinoma, dosimetry is necessary to avoid toxicity from therapy and to guide prescription of the administered activity of radioiodine. METHODS: The presentations and courses of 2 patients exemplify the points. In the second patient, the clues to the need for dosimetry were the large size of the tumor and high circulating levels of thyroxine in the absence of exogenous hormone. The other patient manifested hyperthyroidism from stimulation of the tumors by thyroid-stimulating immunoglobulin. Dosimetry was performed by published methods. RESULTS: Dosimetry of radioactivity in the body and blood warned of increased irradiation per gigabecquerel of administered (131)I. In each patient, the tumors sequestered a substantial amount of administered (131)I and secreted (131)I-labeled hormones that circulated for days. In 1 patient, the blood time--activity curve was complex, making a broad range of predictions for irradiation to blood and bone marrow. Still, dosimetry gave information that helped to avoid severe toxicity. At, respectively, 1.85 and 2.2 GBq (131)I, initial treatments were relatively low. There was a modest escalation in subsequent administered activities. Leukopenia with neutropenia developed in each patient, and one had moderate thrombocytopenia and anemia, but toxicity appeared to be transient. Each patient had a marked increase in well-being and evidence of reduced tumor function and volume. CONCLUSION: Two patients with advanced, well-differentiated thyroid carcinoma illustrate the need for dosimetry to help prevent toxicity to normal tissues from therapeutic radioiodine. Conversion of radioiodide to circulating radiothyroxine by functioning carcinomas increases the absorbed radiation in normal tissues. Yet, dosimetric data acquired for 4 d or more may be insufficient for accurate calculations of absorbed radiation in blood. Guidelines suggested for avoiding toxicity are based on the circulating thyroxine concentrations, the presence of thyroid stimulators, the amount of radioactivity retained in the body at 48 h, and the general status of the patient.

Iodine-131 MIBG scintigraphy of the extremities in metastatic pheochromocytoma and neuroblastoma.

Iodine-131 MIBG scintigraphy may be used to determine the presence or absence of metastases to the appendicular skeleton in malignant pheochromocytoma and neuroblastoma. Normal bones show no uptake of [131I]MIBG and the joints are seen as photon-deficient areas surrounded by background muscle activity. Discrete concentrations of radioactivity in bone are often seen in patients with malignant pheochromocytoma and neuroblastoma. Bone marrow involvement in neuroblastoma may be indicated by diffuse uptake of [131I]MIBG or focal accumulation at the metaphyses. Uncommonly, bone involvement may not be displayed by the [131I]MIBG images. Since conventional bone scanning agents may also fail to detect these tumors, skeletal scintigraphy with both [131I]MIBG and [99mTc]MDP is necessary to reliably stage malignant pheochromocytoma and neuroblastoma.

Effect of uptake-one inhibitors on the uptake of norepinephrine and metaiodobenzylguanidine.

The mechanisms underlying the uptake of the radiopharmaceutical metaiodobenzylguanidine (MIBG) and the catecholamine norepinephrine (NE) were studied using cultured bovine adrenomedullary cells as an in vitro model system. Sodium-dependent and sodium-independent uptake systems have been identified and characterized for both MIBG and NE. The sodium-dependent uptake of NE and MIBG was inhibited by the selective Uptake-one inhibitors, desmethylimipramine (DMI) and cocaine, whereas the sodium-independent uptake for NE and MIBG was much less sensitive to inhibition by these agents. The sodium-dependent uptake system fulfills the criteria for the neuronal Uptake-one system, and the sodium-independent uptake system fulfills the criteria for a passive diffusion mechanism. Both NE and MIBG were transported into cultured bovine adrenomedullary cells by both uptake systems; the relative role of each uptake system was dependent upon the concentration of NE and MIBG in the media. Arterial concentrations proximal to the dog adrenal were very small suggesting that the sodium-dependent (Uptake-one) system is predominant in vivo. Consistent with the in vitro observations, the in vivo uptake of MIBG and NE into dog adrenal medullae was effectively blocked by pretreatment with DMI or cocaine. Therefore, iodine-131 MIBG scintigraphy of the adrenal appears to reflect uptake by way of the Uptake-one system.