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PubMed1987

Reversible inhibition of microtubules and cell growth by the bicyclic colchicine analogue MTC.

2-methoxy-5-(2,3,4-trimethoxyphenyl) 2,4,6-cycloheptatrien-1-one (MTC) is a synthetic colchicine analogue, lacking the B ring of the alkaloid (Fitzgerald: Biochem. Pharmacol. 25:1381-1387, 1976). MTC has been shown to bind reversibly to the colchicine binding site of tubulin and to inhibit microtubule assembly in vitro (Andreu et al: Biochemistry 23:1742-1752, 1984; Bane et al: J. Biol. Chem. 259:7391-7398, 1984). Its action on different cultured cell lines (PtK2, Pk15, and SV-3T3) has now been studied. 0.2 X 10(-6) M MTC stopped Pk15 and SV-3T3 cell growth, inducing an accumulation of mitoses in a few hours. Removal of MTC from the culture medium rapidly restored normal mitotic index and growth rates. Partial depolymerization of the cytoplasmic microtubules of PtK2 cells was observed at concentrations ranging from 2 to 5 X 10(-7) M. Maximal microtubule network depolymerization was obtained after 4 h of treatment with 2 to 5 X 10(-6) M MTC or at a higher MTC concentration (2 X 10(-5) M) for less than 2 h. Removal of 2 X 10(-5) M MTC (the highest MTC concentration used) from the culture medium resulted in almost complete microtubule polymerization after 10 min of drug recovery and a normal microtubule network in 20-30 min. MTC constitutes an antimitotic drug directed to the colchicine site. It is water-soluble, shows a fast and reversible action, and may therefore be employed as a convenient tool to study cellular microtubule-dependent functions.

Animals↗

PubMed1990

Multiple signal transduction mechanisms leading to the secretion of 5-hydroxytryptamine by MTC cells, a neurectodermally derived cell line.

Parafollicular (PF) cells of the thyroid gland are neural crest derivatives. These cells remain plastic even in adult animals and can be induced to exhibit neural properties when exposed to NGF in vitro. A human cell line derived from PF cells, medullary thyroid carcinoma (MTC), has previously been shown to synthesize and store 5-HT, a serotonin-binding protein (SBP), and several neuropeptides; moreover, when grown in impoverished media, MTC cells display neural properties. The purpose of the current study was to utilize MTC cells as a neurally relevant model system to investigate factors involved in mediating 5-HT secretion. Electron microscopic immunocytochemistry revealed that secretory vesicles of MTC cells costore immunoreactive 5-HT with SBP and calcitonin. The cAMP derivative, N6-2'-O-dibutyryl-adenosine 3',5'-cyclic monophosphate (dibutyryl-cAMP; 1.0 mM) increased the concentration of 5-HT in MTC cells and almost doubled the rate of synthesis of 5-HT from L-tryptophan. Dibutyryl-cAMP also significantly increased the secretion of 5-HT. Cycloheximide (20 micrograms/ml) and anisomycin (20 microM) inhibited the dibutyryl-cAMP-induced increase of 5-HT release, suggesting that this action of dibutyryl-cAMP requires protein synthesis. Cholera toxin (1.0 microgram/ml) and forskolin (0.05 mM) in the presence of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (1.0 mM) both increased 5-HT biosynthesis and secretion. Attempts were made to identify a ligand that stimulates cAMP-mediated secretion of 5-HT. Both thyroid-stimulating hormone (TSH: 50 mU/ml) and elevated [Ca2+]e (7.0 mM), each of which acts as a secretogogue for PF cells, stimulated the secretion of 5-HT. The effect of TSH was Ca2(+)-dependent. Immunocytochemistry with monoclonal antibodies to the TSH receptor confirmed that these receptors are present on MTC cells. Neither TSH nor elevated [Ca2+]e elevated cAMP levels. Measurements of Fura-2 fluorescence, however, indicated that both TSH and elevated [Ca2+]e increased cytosolic calcium ([Ca2+]i), as did elevation of [K+]e. It is concluded that exocytosis can be triggered in MTC cells by multiple signal transduction mechanisms. Either cAMP or elevated [Ca2+]i can stimulate secretion; however, a secretogogue that increases cAMP has yet to be identified.

Animals↗

PubMed1990

Establishment and characterization of continuous cell line MTC-SK derived from a human medullary thyroid carcinoma.

Tumor cells of a human medullary thyroid carcinoma were isolated and propagated in tissue culture. Several cell lines with different morphology developed from the primary culture, among others a fibroblast-like growing cell line (MTC-F) and a cell line growing as a suspension of single cells and spherical cell clusters (MTC-SK). The MTC-SK cell line was serially propagated for 90 passages, over 3 years. When examined at different times throughout the in vitro period, MTC-SK exhibited properties characteristic of medullary thyroid carcinomas: the cells maintained their epithelioid morphology; endocrine granules were demonstrated in the cytoplasm by electron microscopy; in situ hybridization confirmed the production of calcitonin- and bombesin-mRNA (gastrin releasing peptide); the cells revealed positive immunoreactivity with antibodies to calcitonin, calcitonin gene-related peptide, and bombesin. The in vitro properties of the MTC-SK cells corresponded to the results obtained from the tissue of origin. Cytogenetic studies of the MTC-F cell line revealed a supernumerary metacentric chromosome (20?). In the MTC-SK cell line the predominant findings were terminal chromosomal rearrangements most frequently concerning chromosome 11p, i.e., the locus of the calcitonin and calcitonin gene-related peptide genes and the H-ras oncogene, and a characteristic instability of the centromeric region of chromosome 16 and somatic pairing of the homologous chromosomes 16.

Calcitonin↗

PubMed1987

Double-blind controlled trial of the antiemetic efficacy and toxicity of methylprednisolone (MP), metoclopramide (MTC) and domperidone (DMP) in breast cancer patients treated with i.v. CMF.

Sixty-two patients treated for the first time with i.v. CMF were included in a double-blind comparative study aimed at evaluating the efficacy of 3 different drugs (methylprednisolone (MP), metoclopramide (MTC), and domperidone (DMP) in preventing chemotherapy-induced nausea and vomiting. Complete protection from vomiting/nausea was obtained in 85%/80% in the group treated with MP; in 60%/65% in the group treated with MTC and in 38%/42% in the group treated with DMP. Average number of vomiting episodes was 2.4 with MP, and 1.7 with MTC and 6.2 with DMP. Older patients seem to be a prognostically unfavorable subgroup. Side-effects were mild and infrequent. We conclude that MP and MTC are probably equally efficacious antiemetic treatments in patients undergoing i.v. CMF chemotherapy, but due to the risk of extrapyramidal reactions with MTC, MP probably should be the treatment of choice in these patients.

Age Factors↗

PubMed1990

The mutation for medullary thyroid carcinoma with parathyroid tumors (MTC with PTs) is closely linked to the centromeric region of chromosome 10.

Two new morphs (F and G) detected by the centromeric alpha satellite probe p alpha 10RP8 and D10Z1 in HinfI digests are linked to the PstI polymorphisms of D10Z1, confirming their chromosome 10 location. The F and G morphs were in strong linkage disequilibrium with each other but were in weak linkage disequilibrium with the A and B morphs defined in PstI digests. Data for haplotypes formed by using the A and F morphs improved the lod score for linkage between the disease locus for multiple endocrine neoplasia type 2A (MEN2A) and D10Z1 (Z = 14.06 at theta = 0) in the six large families studied by Wu et al. Furthermore, the locus that codes for a distinct phenotype, medullary thyroid carcinoma (MTC) with parathyroid tumors (PTs) and no pheochromocytomas (PHEOs) (referred to as MTC with PTs), in one of the families was closely linked to two markers, D10Z1 and RBP3, with lodscores of 2.86 and 3.54, respectively, at theta = 0. A possible allelic association was noted between disease phenotypes and centromeric haplotypes. The phenotype MTC and PHEOs with and without PTs was associated with the same relatively common centromeric haplotype (A + B-F-G-) in the four families in which all four morphs could be determined, while the phenotype MTC with PTs was associated with the rare centromeric haplotype (A-B-F-G+) in one family.

Adrenal Gland Neoplasms↗

PubMed1991

Investigation of cerebral ischemia using magnetization transfer contrast (MTC) MR imaging.

The effects of cerebral ischemia in rat brain were monitored as a function of time using proton MR imaging. Spin-spin relaxation time (T2), proton density, and magnetization transfer contrast (MTC) were measured by MR imaging at various time intervals during a 1-week period following the induction of ischemic damage. Ischemic injury was characterized by a maximization of both T2 value and MTC appearance at 24 hr postischemic injury. These changes were accompanied by a gradual increase in MR observable water density over the first few days of ischemia. A reduction in the magnetization exchange rate between "free" and "bound" water protons as measured by MTC imaging is at least partially responsible for the elevation in T2 values observed during ischemia, and may accompany breakdown of cellular structure.

Animals↗

PubMedDate not supplied

Quantification of intracellular calcitonin gene transcripts in human medullary thyroid carcinoma (MTC) by in situ hybridization.

The human calcitonin gene generates 2 distinct mature mRNAs by alternative RNA processing, encoding calcitonin (CT) in thyroid C-cells or a neuropeptide (CGRP) in the brain. We evaluated quantitatively by in situ hybridization the expression of the CT gene in tissue section of 5 MTCs (2 sporadic and 3 familial forms). The primary tumor of one MTC was compared to a brain metastasis. In situ hybridization was carried out with tritiated cDNA probes coding for CT and CGRP mRNA. After autoradiography the number of silver grains was counted in 400 cells by computerized analysis of digitized images and expressed as the labelling level (L.L. = grain area/cell area per day of autoradiographic exposure). This was used to calculate the relative abundance per cell of the specific messengers studied, which depends on the autoradiographic efficiency and the specific activity of the probe used. The CT mRNA content was 3.25-6.55 10(-10) micrograms equivalents in the 3 familial forms of MTC and 4.95-9.25 10(-10) micrograms equivalents for the 2 sporadic forms. The levels of CT mRNA in the brain metastasis and in the primary tumor were identical (4.10 10(-10) micrograms equivalents). CGRP mRNA expression was weaker in the sporadic and in the familial thyroid tumors (0.60-1.65 10(-10) micrograms equivalents). The content of mRNA CGRP in the brain metastasis (0.60 10(-10) micrograms equivalents) was lower than that in the primary tumor (1.05 10(-10) micrograms equivalents).(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1992

Magnetization transfer contrast (MTC) imaging of skeletal muscle at 0.26 Tesla--changes in signal intensity following exercise.

Magnetization transfer contrast (MTC) imaging of skeletal muscle before and after exercise has been studied in normal volunteers at 0.26 Tesla. A saturation pulse was applied over a range of offset frequencies immediately before a gradient recall echo sequence. Substantial signal loss was observed in all muscles. After exercise, selective saturation resulted in a significant increase of contrast between active and less active muscle, a phenomenon attributable to an increase in extracellular water content. MTC imaging provides a more sensitive method to detect changes in water distribution in human skeletal muscle.

Adipose Tissue↗

PubMed1991

[A case of bilateral multiple pulmonary arteriovenous fistula treated by the right fistula plication and resection of the left lingual lobe with use of microwave tissue coagulator (MTC)].

A 53-year-old man with the history of brain abscess and multiple cerebral arterio-venous malformations underwent the staged operation for bilateral multiple pulmonary arterio-venous fistulas (PAVF). Right fistula plication and the resection of the left lingular lobe using MTC were performed through posterolateral thoracotomy. Postoperatively, the patient showed the right residual fistula, but, he has been doing well without PAVF complications such as polycythemia and hypoxemia. In conclusion, 1) PAVF with central nervous system complications should be treated aggressively either by surgery or by embolization. 2) MTC was useful for the resection of the lung because of no air leak and bleeding coming from the resected section.

Arteriovenous Fistula↗

PubMed1990

Long-term survival in sporadic and familial medullary thyroid carcinoma with special reference to clinical characteristics as prognostic factors. The Swedish MTC Study Group.

All the 249 patients with medullary thyroid carcinoma (MTC) diagnosed during a 23-year period in Sweden were followed up completely for 4-27 years. The overall relative survival was 79.9% at 5 years after diagnosis and 68.6% at 10 years. After 5 years of follow-up, the relative survival rate was 5 percentage points higher in females than in males; 30 percentage points higher in patients aged less than 40 than in those 60-69 years at diagnosis; 24 percentage points higher in patients with familial disease detected at screening than in those with sporadic MTC; 20, 26 and 48 percentage points lower in patients with stage II, III, and IV, respectively, than in those with stage I; and almost 30 percentage points lower in the group of patients with a large tumor (greater than 3 cm) than in the group with a small one (less than 1 cm). In multivariate proportional hazards analyses of all these important determinants of outcome, the prognostic information provided by age and stage was still significant when several morphologic characteristics were taken into account (nuclear DNA content, calcitonin immunoreactivity, amyloid content, argyrophil reaction and state of the tumor capsule).

Adolescent↗

PubMed1989

Right colonic hemangioma diagnosed by scintigraphy with 99-mTc sucralfate. A case report.

99-mTc-SF gastrointestinal scintigraphy used in recent years in the assessment of site and activity for ulcerative lesions, was shown to be very important for the diagnosis of a rare case of right colonic hemangioma. A young female patient suffering for some time from functional intestinal disorders, following negative radiologic and endoscopic findings, underwent 99-mTc-SF scintigraphy, which showed massive uptake of radioactivity in the ascending and right flexure of colon. A repeated colonoscopy with biopsy allowed the histologic diagnosis of capillary hemangioma.

Adult↗

PubMed1987

[Pulmonary resection by microwave tissue coagulator (MTC)--clinical application].

A 55 year old male with metastatic lung and liver cancer was subjected to pulmonary and hepatic resections using Microwave Tissue Coagulator (MTC). No adverse effects were observed in this patient after operation. The resected specimen of the lung had the bronchioli partially accompanied with cartilages. Coagulation for the bronchioli of at least lmm in size, by MTC, could be carried out resulting in no air leakage after operation.

Adenocarcinoma↗

PubMed1989

Histopathologic characteristics and nuclear DNA content as prognostic factors in medullary thyroid carcinoma. A nationwide study in Sweden. The Swedish MTC Study Group.

Complete follow-up for 4 to 27 years was achieved for virtually all 249 patients with medullary thyroid carcinoma (MTC) diagnosed in Sweden in a 23-year period. Tumor specimens from 241 patients were re-examined with regard to calcitonin immunoreactivity, amyloid content, argyrophil reaction, tumor capsule condition, and nuclear DNA content. In univariate analyses, these factors, with the exception of the argyrophil reaction, were strong predictors of survival. There were twofold-to-threefold differences in hazard rate between patients with a high (greater than 50%) and low (less than 10%) frequency of calcitonin-immunoreactive tumor cells, between those with amyloid-containing and amyloid-free tumors, and between those with an intact and a nonintact tumor capsule. Calcitonin immunoreactivity and the amyloid content also provided prognostic information in multivariate analyses that adjusted for all the other factors mentioned above and in the full multivariate model, which in addition considered age, sex, heredity, stage of the disease, tumor size, and treatment. The strong prognostic capacity of the nuclear DNA content found in univariate analyses became considerably weaker when other morphologic characteristics were considered.

Adult↗

PubMed1979

Results of regular study on radionuclidic purity of 99mTc obtained from 99Mo--99mTc generators.

A total of 39 99mTc eluates obtained from 9 99Mo--99mTc generators delivered by The Radiochemical Centre Amersham during one year was studied with regard to their radionuclide purity. Using a Ge(Li) spectrometer the contaminants 60Co, 103Ru, 131I, 134Cs, 140Ba, 140La and 188Re were found in 99mTc-eluates with average levels ranging from 2.9 X 10(-3) to 2.8 X 10(-1) per cent of 99mTc activity. The additional total body absorbed dose caused by these contaminants, as calculated from their average content in 99mTc eluates, was less than 1% of the dose due to 99mTc pertechnetate.

Radiation Dosage↗

PubMed1991

Magnetization transfer contrast (MTC) in flash MR imaging.

Magnetization transfer between bound and free protons was used as a source of contrast in high speed MR imaging using the FLASH technique. Contrast in FLASH MR images was found to depend upon the reduced magnetization and the spin lattice relaxation rate of free protons in the presence of bound proton radio-frequency saturation. MTC FLASH imaging was thus used to estimate the variation with saturation frequency of free proton spin-lattice relaxation during magnetization transfer.

Animals↗

PubMed1991

Cyclotron production of NCA 99mTc and 99Mo. An alternative non-reactor supply source of instant 99mTc and 99Mo----99mTc generators.

The direct production of no-carrier-added (NCA) 6.02 h 99mTc and of 66 h 99mMo using proton beams of natural Mo targets was investigated. The major objective of this work was to evaluate the potential of utilizing high-intensity proton accelerators as a supply source of 99mTc and 99Mo for use in diagnostic nuclear medicine. The excitation functions for the production of the directly-made 99mTc via the 100Mo(p, 2n)99mTc (Q = -7.85 MeV) reaction, and of its parent 99Mo via the 100Mo(p, pn) 99Mo (Q = -8.30 MeV) and 100Mo(p, 2p)99mNb(15 s)----99Mo (Q = -11.14 MeV) reactions, were measured in the 68-8 MeV energy range. Single and cumulative yields for 99mTc and 99Mo, and for other Tc, Mo, Zr, Nb and Y radiocontaminants were also determined. The prospects of integrating the use of enriched 100Mo targets with high-intensity, dual beam, H- accelerators was analyzed. The potential of this combined method to replace or complement the current reactor-based supply sources of 99Mo----99mTc generators, is also discussed. Finally, a brief analysis is made on the potential use of this combined technology to support the anticipated expansion of nuclear medicine in developing nations.

Molybdenum↗

PubMed1989

The development of a two-site enzyme immunometric assay (EIA) for calcitonin and its application in the measurement of the hormone in normal subjects, MTC-patients and post-menopausal women.

We have developed a sensitive, two-site enzyme immunometric assay (EIA) using high affinity monoclonal antibodies for the measurement of immunoreactive human calcitonin (i-hCT) and compared the performance of the assay with that of the conventional radioimmunoassay (RIA). The sensitivity of an overnight EIA (2 pmol/l) was comparable with the long incubation (7 days) RIA. Both, the EIA and the RIA have been applied for the measurement of i-hCT in three groups: normal volunteers (n = 53), post-menopausal women (n = 25) and patients with MTC (n = 20). The results showed that in all three groups, the level of i-hCT was somewhat lower than that measured by RIA due to its greater specificity. The EIA can provide an attractive alternative to the conventional RIA for both routine diagnostic work and physiological studies.

Antibodies, Monoclonal↗

PubMed1989

Magnetization transfer contrast (MTC) and tissue water proton relaxation in vivo.

In this study the exchange between 1H magnetization in "free" water (1Hf) and that in a pool with restricted motion (1Hr) was observed in tissues in vivo using NMR saturation transfer methods. Exchange between these two pools was demonstrated by a decrease in the steady-state magnetization and relaxation times of 1Hf with radiofrequency irradiation of 1Hr. The pseudo-first-order rate constant for the movement of magnetization from 1Hf to 1Hr was approximately 1 s-1 in kidney and approximately 3 s-1 in skeletal muscle in vivo. Proton NMR imaging demonstrated that this exchange was tissue specific and generated a novel form of NMR image contrast. The extent of exchange between 1Hf and 1Hr as well as the topological correlation of the exchange with relaxation weighted images suggests that this pathway is a major determinant of the observed relaxation properties of water 1H in vivo.

Animals↗