Methodological and biological aspects to be considered in acetylcholinesterase reactivation assays using 2-PAM

Kinetic and toxicological characteristics of fish (Odontesthes argentinensis) and crab (Callinectes sapidus) cholinesterases as well as methodological conditions to perform reactivation assays using pyridine 2-aldoxime (2-PAM) were established. According to kinetic and eserine sensitivity data, both cholinesterases can be considered as acetylcholinesterases. The concentration of eserine that inhibited 50% of enzyme activity (IC(50)) was estimated as 15.9x10(-8) and 4.6x10(-8) M for crab and fish, respectively. For purified eel acetylcholinesterase (V-S type), it was estimated as 4.2x10(-8) M. 2-PAM showed both to increase non-enzymatic hydrolysis of acetylthiocholine iodide and to inhibit activity of the acetylcholinesterases tested. The IC(50) of 2-PAM for crab acetylcholinesterase (8.2x10(-4) M) was significantly higher than that from O. argentinensis (2.5x10(-4) M) or eel (2.0x10(-4) M) acetylcholinesterase. Enzyme inhibition induced by 2-PAM showed to mask subtle inhibition due to malathion, suggesting that a previous characterization of 2-PAM inhibition must be done before its use in reactivation assays.

Thyroid tissue: US-guided percutaneous interstitial laser ablation-a feasibility study

PURPOSE

To evaluate percutaneous interstitial laser photocoagulation (ILP) as a palliative treatment of recurrent thyroid carcinoma untreatable with surgery or radioiodine administration.

MATERIALS AND METHODS

By using 18 resected thyroid glands, the volume and histologic pattern of ILP-induced thyroid damage were assessed. In vivo treatment feasibility was evaluated by using a low-energy laser in two volunteers before thyroidectomy for huge autonomously functioning nodules. With ultrasonographic (US) monitoring, a 21-gauge spinal needle was inserted into the thyroid nodules. A 300-microm quartz fiberoptic guide was inserted through the needle lumen, and the fiber tip was placed in direct contact with the tissue. Laser irradiation was performed with a 1.064-nm Nd:YAG laser in surgically resected glands, which were treated with 2, 3, 5, or 7 W.

RESULTS

Tissue ablation was well-defined histologically, and its area was related to laser irradiation parameters (range, 0-26 mm). No correlation was found between US images and the actual extent of laser-induced lesions. Large colloid or fluid collections did not permit regular heat diffusion within the tissue. In vivo low-energy ILP was performed without technical difficulties or complications.

CONCLUSION

ILP induces well-defined tissue ablation correlated with energy parameters in thyroid glands devoid of cystic areas. ILP could be a therapeutic tool for highly selected problems in thyroid tumor treatment.

Altered ligand binding and transcriptional regulation by mutations in the PML/RARalpha ligand-binding domain arising in retinoic acid-resistant patients with acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) is characterized by a specific translocation, t(15;17), that fuses the promyelocytic leukemia (PML) gene with the RA receptor RARalpha. Pharmacologic doses of retinoic acid (RA) induce differentiation in human APL cells and complete clinical remissions. Unfortunately, APL cells develop resistance to RA in vitro and in vivo. Recently, mutations in PML/RARalpha have been described in APL cells from patients clinically resistant to RA therapy. The mutations cluster in 2 regions that are involved in forming the binding pocket for RA. These mutant PML/RARalpha proteins have been expressed in vitro, which shows that they cause a diversity of alterations in binding to ligand and to nuclear coregulators of transcription, leading to varying degrees of inhibition of retinoid-induced transcription. This contrasts with the nearly complete dominant negative activity of mutations in PML/RARalpha previously characterized in cell lines developing RA resistance in vitro. Current data from this study provide additional insight into the molecular mechanisms of resistance to RA and suggest that alterations in the ability of mutants to interact with coregulators can be determinant in the molecular mechanism of resistance to RA. In particular, ligand-induced binding to the coactivator ACTR correlated better with transcriptional activation of RA response elements than the ligand-induced release of the corepressor SMRT. The diversity of effects that are seen in patient-derived mutations may help explain the partial success to date of attempts to overcome this mechanism of resistance in patients by the clinical use of histone deacetylase inhibitors.

Lipid peroxidation induced by Clinostomum detruncatum in muscle of the freshwater fish Rhamdia quelen

The effect of Clinostomum detruncatum metacercaria infection on the activities of the antioxidant enzymes superoxide dismutase and catalase in muscle of the freshwater fish Rhamdia quelen was analyzed. Tert-butyl hydroperoxide-initiated chemiluminescence, a measure of lipid peroxidation, was also investigated. Enzyme activities were similar in infected and uninfected fishes. However, the chemiluminescence was almost 2-fold higher in muscle of infected fishes than in muscle of uninfected ones. These results indicate that parasite infection induces oxidative stress and a higher level of membrane damage in the fish muscle due to an imbalance between pro-oxidants and non-enzymatic antioxidants. Our results suggest that fish response to parasite infection could involve, as in other vertebrates, reactive oxygen intermediates.

Effects of copper and zinc on growth, feeding and oxygen consumption of Farfantepenaeus paulensis postlarvae (Decapoda: Penaeidae)

The effect of chronic exposure (35 days) to sub-lethal concentrations of copper (17-212 ppb) and zinc (41-525 ppb) on growth of Farfantepenaeus paulensis postlarvae 17 days old (PL(17)) was analysed. The effects of acute exposure of PL(17) to the same metal on food ingestion and oxygen consumption were also evaluated. Studies were performed using copper and zinc singly, and in a mixture of equipotent concentrations (1:2.5). Chronic exposure to copper (85 and 212 ppb) and zinc (106, 212 and 525 ppb) reduced PL(17) growth. Acute exposure to copper (212 ppb) and zinc (525 ppb) reduced the number of Artemia sp. predated during 30 min and the positive feeding response induced by L-isoleucine. Despite of the lower positive feeding response when PL(17) were exposed to zinc, a significant difference from control condition was not seen. Oxygen consumption was reduced by all copper and zinc concentrations tested. The mean reduction was approximately 32%. The copper zinc-mixture did not modify food consumption and feeding response, or the oxygen consumption of the PL(17). The inhibition of food and oxygen consumption induced by copper and zinc could explain, at least in part, the long-term reduction of growth observed in chronically exposed PL(17). Our results also suggest that the inhibition of food consumption induced by copper is possibly due to an effect on chemosensory mechanisms. Finally, an antagonism between copper and zinc was observed, when were employed to analyse feeding behaviour and aerobic metabolism after acute exposure.

Oligomerization of RAR and AML1 transcription factors as a novel mechanism of oncogenic activation

RAR and AML1 transcription factors are found in leukemias as fusion proteins with PML and ETO, respectively. Association of PML-RAR and AML1-ETO with the nuclear corepressor (N-CoR)/histone deacetylase (HDAC) complex is required to block hematopoietic differentiation. We show that PML-RAR and AML1-ETO exist in vivo within high molecular weight (HMW) nuclear complexes, reflecting their oligomeric state. Oligomerization requires PML or ETO coiled-coil regions and is responsible for abnormal recruitment of N-CoR, transcriptional repression, and impaired differentiation of primary hematopoietic precursors. Fusion of RAR to a heterologous oligomerization domain recapitulated the properties of PML-RAR, indicating that oligomerization per se is sufficient to achieve transforming potential. These results show that oligomerization of a transcription factor, imposing an altered interaction with transcriptional coregulators, represents a novel mechanism of oncogenic activation.

Activation of the mitogen-activated protein kinase ERK1 during meiotic progression of mouse pachytene spermatocytes

Okadaic acid (OA) causes meiotic progression and chromosome condensation in cultured pachytene spermatocytes and an increase in maturation promoting factor (cyclin B1/cdc2 kinase) activity, as evaluated by H1 phosphorylative activity in anti-cyclin B1 immunoprecipitates. OA also induces a strong increase of phosphorylative activity toward the mitogen-activated protein kinase substrate myelin basic protein (MBP). Immunoprecipitation experiments with anti-extracellular signal-regulated kinase 1 (ERK1) or anti-ERK2 antibodies followed by MBP kinase assays, and direct in-gel kinase assays for MBP, show that p44/ERK1 but not p42/ERK2 is stimulated in OA-treated spermatocytes. OA treatment stimulates phosphorylation of ERK1, but not of ERK2, on a tyrosine residue involved in activation of the enzyme. ERK1 immunoprecipitated from extracts of OA-stimulated spermatocytes induces a stimulation of H1 kinase activity in extracts from control pachytene spermatocytes, whereas immunoprecipitated ERK2 is uneffective. We also show that natural G(2)/M transition in spermatocytes is associated to intracellular redistribution of ERKs, and their association with microtubules of the metaphase spindle. Preincubation of cultured pachytene spermatocytes with PD98059 (a selective inhibitor of ERK-activating kinases MEK1/2) completely blocks the ability of OA to induce chromosome condensation and progression to meiotic metaphases. These results suggest that ERK1 is specifically activated during G(2)/M transition in mouse spermatocytes, that it contributes to the mechanisms of maturation promoting factor activation, and that it is essential for chromosome condensation associated with progression to meiotic metaphases.

Direct effect of temperature on the catalytic activity of nitric oxide synthases types I, II, and III

The effect of temperature (between 5.0 and 45.0 degrees C) on the catalytic activity of nitric oxide synthases types I, II, and III (NOS-I, NOS-II, and NOS-III, respectively) has been investigated, at pH 7.5. The value of V(max) for NOS-I activity increases from 1.8 x 10(1) pmol min(-1) mg(-1), at 5.0 degrees C, to 1.8 x 10(2) pmol min(-1) mg(-1), at 45.0 degrees C; on the other hand, the value of K(m) (=4.0 x 10(-6) M) is temperature independent. Again, the value of V(max) for NOS-II activity increases from 8.0 pmol min(-1) mg(-1), at 7.0 degrees C, to 5.4 x 10(1) pmol min(-1) mg(-1), at 40.0 degrees C, the value of K(m) (=1.8 x 10(-5) M) being unaffected by temperature. Temperature exerts the same effect on NOS-I and NOS-II activity, as shown by the same values of DeltaH(V(max)) (=4.2 x 10(1) kJ mol(-1)), DeltaH(K(m)) (=0 kJ mol(-1)), and DeltaH((V(max))(/K(m))()) (=4.2 x 10(1) kJ mol(-1)). On the contrary, the value of K(m) for NOS-III activity decreases from 3.8 x 10(-5) M, at 10.0 degrees C, to 1.6 x 10(-5) M, at 40.0 degrees C, the value of V(max) (=6.8 x 10(1) pmol min(-1) mg(-1)) being temperature independent. Present results indicate that temperature influences directly NOS-I and NOS-II activity independently of the substrate concentration, the values of K(m) being temperature independent. However, when l-arginine level is higher than 2 x 10(-4) M, as observed under in vivo conditions, NOS-III activity is essentially unaffected by temperature, the substrate concentration exceeding the value of K(m). As a whole, although further studies in vivo are needed, these observations seem to have potential physiopathologic implications.

Inhibition of endothelial nitric-oxide synthase by ceruloplasmin

The plasma copper protein ceruloplasmin (CP) was found to inhibit endothelial nitric-oxide synthase activation in cultured endothelial cells, in line with previous evidence showing that the endothelium-dependent vasorelaxation of the aorta is impaired by physiological concentrations of ceruloplasmin. The data presented here indicate a direct relationship between the extent of inhibition of agonist-triggered endothelial nitric oxide synthase activation and CP-induced enrichment of the copper content of endothelial cells. Copper discharged by CP was mainly localized in the soluble fraction of cells. The subcellular distribution of the metal seems to be of relevance to the inhibitory effect of CP, because it was mimicked by copper chelates, like copper-histidine, able to selectively enrich the cytosolic fraction of cells, but not by copper salts, which preferentially located the metal to the particulate fraction.

Resistance to Bean Golden Mosaic Virus in Bean Genotypes

Bean lines MD 806, MD 807, MD 820, MD 829, MD 808, and MD 821, all with high levels of resistance to bean golden mosaic virus (BGMV), were selected under field conditions. On a 1 to 9 scale (1 = symptomless plant; 9 = severe symptoms), the mean disease severity of the MD lines ranged from 1.7 to 3.9 for mosaic symptom (foliar yellowing) and from 1.7 to 2.2 for malformation. In contrast, disease severity in the susceptible cultivars Carioca, Carnaval, and Iapar 20 ranged from 4.1 to 8.7 for mosaic and from 4.0 to 7.3 for malformation. Symptoms on the selected lines were expressed later than on susceptible controls. The MD lines yielded 1.2- to 5.9-fold the yield of the cultivars Carioca and Iapar 20. Under greenhouse conditions, reactions of the bean genotypes to BGMV were similar to those observed in the field. MD 806 and MD 807 were obtained from early crosses involving genotypes that reacted to BGMV infection with mild mosaic (Aeté 1/38 and TMD-1) and mild malformation (Porrillo Sintético and Turrialba 1). Parents of the lines MD 820 and MD 829 were Phaseolus coccineus (of unknown reaction to BGMV) and Carioca. Line MD 648 (DOR-selected line) was the ancestral parent of lines MD 808 and MD 821, which had the highest levels of resistance or tolerance to BGMV. Severity of all BGMV symptoms showed gradual reductions from the earliest parents to their later selected progenies. Responses of the parent genotypes and progenies to BGMV infection suggest a combination of resistance characters in the selected MD lines. MD 806, MD 820, and MD 821 were released in the state of Paraná under the names Iapar 57, Iapar 72, and Iapar 65, respectively.

Advantages of spinal anesthesia in abdominal gynecologic surgery

The advantages obtained in vaginal surgery and caesarean section using spinal anesthesia led us to test this anesthesia to verify feasibility, problems and advantages in abdominal surgery. Spinal anesthesia was performed in 60 patients between 21 and 87 years of age. Thirty-seven total abdominal hysterectomies with or without adnexectomy, 5 laparotomic miomectomies, 3 adnexectomies, 5 colposacropexies, 2 hysterectomies with lymphadenectomy, 7 Burch colposuspension with or without hysterectomy and 1 laparoscopy for sterilization were performed. No significant problems during surgery and the postoperative period were observed. Resumption of the different physiologic functions were more rapid, hospital stay shorter and compliance greater than with general anesthesia.

Some kinetic and toxicological characteristics of thoracic ganglia cholinesterase of Chasmagnathus granulata (Decapoda, Grapsidae)

In this study, some kinetic and toxicological parameters of the thoracic ganglia cholinesterase from the estuarine crab Chasmagnathus granulata were determined. Effects of the type and concentration of substrate, pH (6.80-8.50), incubation temperature (5-35 degrees C) and eserine on the enzyme activity were studied. Enzymatic activity was higher at pH 7.40 and 8.00 and significantly reduced at lower temperatures (5-10 degrees C). Employing acetylthiocholine iodide (ATCh) as substrate, the K(m) and Vmax were estimated as 0.28 mM and 1.75 mumol.mg protein-1.min-1, respectively. A 14.11 and 24.51% decrease in enzyme activity were registered at 4.62 and 9.24 mM of ATCh, respectively. Using propionylthiocholine iodide as substrate, the K(m) and Vmax were estimated as 0.16 mM and 0.91 mumol.mg protein-1.min-1, respectively. The IC50 for eserine was estimated as 5.3 x 10(-4) mM. The Ki estimated for eserine (8.10 mM-1.min-1) indicates that the thoracic ganglia cholinesterase from C. granulata showed a low ability to generate an irreversible enzyme-inhibitor complex. The higher enzymatic activity registered with ATCh and the enzyme inhibition observed at high concentration of this substrate, suggest that thoracic ganglia cholinesterase from C. granulata is an acetylcholinesterase.

Reducing clozapine-related morbidity and mortality: 5 years of experience with the Clozaril National Registry

The Clozaril National Registry (CNR) was created to help protect patients from developing potentially fatal agranulocytosis secondary to treatment with the antipsychotic medicine clozapine. The CNR, designed and maintained by the manufacturer of the branded Clozaril (clozapine), has the principal goals of (1) prophylaxis-preventing inappropriate retreatment, and (2) quality assurance-overseeing adherence to a "no blood, no drug" policy. This article reviews the estimated impact of the CNR on clozapine-related morbidity and mortality over the first 5 years of commercial experience in the United States.

METHOD

Complete data on leukopenia and agranulocytosis, gathered from the CNR database for the period of 1990-1994, were reviewed and compared with data from the pre-CNR period.

RESULTS

Use of clozapine in 99,502 patients according to package labeling requirements (distribution of the medicine linked to mandated white blood cell count testing) was associated with a total of 382 cases of agranulocytosis (0.38%) versus an expected cumulative total of 995 cases (based on the pre-CNR rate of 1% to 2%). Based on the expected agranulocytosis rate, up to 149 deaths might have been anticipated. Instead, there were only 12 deaths attributed to complications of agranulocytosis.

CONCLUSION

The CNR provides for universal rechallenge protection as well as controlled dispensing of clozapine. It also serves as an early warning system to promote the safe and effective use of clozapine. The CNR includes quality assurance mechanisms designed to enhance compliance. Despite the added logistic requirements this system places upon physician, pharmacist, and manufacturer, the CNR has helped to reduce substantially potential fatal outcomes. The CNR reinforces both patient and treatment system compliance. Based on this favorable experience concerning agranulocytosis and associated fatalities, the Neuropsychopharmacology Advisory Committee to the U.S. Food and Drug Administration has unanimously recommended a reduction in frequency of the white blood cell count testing requirement after 6 months to every 14 days, instead of weekly. Finally, the CNR database containing white blood cell count and demographic data on every patient in the United States who has received the medicine has served as a unique epidemiologic database.

Evaluation of the vascular pattern of hepatocellular carcinoma with dynamic computed tomography and its use in identifying optimal temporal windows for helical computed tomography

The aim of this work was to study the vascularization of hepatocellular carcinoma (HCC) by means of dynamic CT and to demonstrate the existence of optimal temporal windows for visualization of HCC in order to develop new protocols for helical CT of the liver. We studied, by means of dynamic CT, 42 histologically proved HCCs in 30 patients after injecting contrast medium (100 ml, 3 ml/s). We performed a time-density analysis of the aorta, liver, portal vein, spleen and lesion. We identified three temporal curves of attenuation of the neoplastic tissue. Curve 1 was three-phasic: hyperattenuation, isoattenuation and hypoattenuation; curve 2 was two-phasic: hyperattenuation and isoattenuation; curve 3 was two-phasic: isoattenuation and hypoattenuation. Thirty-two lesions were homogeneous (curve 1 in 22 cases, 68.7 %; curve 2 in 7 cases, 21.8 %; curve 3 in 3 cases, 9.4 %), whereas 10 lesions were non-homogeneous. Two optimal temporal windows were identified: the first, with predominantly hyperattenuating lesions (range 29-65 s, 90.4 % sensitivity); the second, with predominantly hypoattenuating lesions (range 132.1-360 s, 76.1 %). There is an interposed time range of reduced visualization (range 62-127 s, 54.7 %) in which lesions are isoattenuating. Combined CT study during the first and second temporal windows improves the detection of HCCs especially for homogeneous and small lesions. The intermediate isoattenuation time range does not increase lesion detection rate.

Parthenogenetic activation of mouse eggs by microinjection of a truncated c-kit tyrosine kinase present in spermatozoa

A truncated form of the c-kit tyrosine kinase receptor, corresponding to the phosphotransferase portion of the cytoplasmic catalytic domain and the carboxyterminus (tr-kit), is accumulated during late mouse spermiogenesis. Here we report that tr-kit is specifically localized in the residual sperm cytoplasm, with maximal accumulation in the midpiece of the flagellum, suggesting that it can enter the egg during fertilization. Microinjection of extracts from COS cells expressing a recombinant tr-kit protein into metaphase II-arrested mouse oocytes caused complete oocyte activation, including cortical granule exocytosis, completion of the 2nd meiotic division, formation of a parthenogenetic pronucleus and progression through cleavage stages. No activation above background levels was obtained with extracts from mock-transfected COS cells. Similar results were obtained by microinjection of in vitro synthesized tr-kit mRNA into metaphase II-arrested oocytes. Tr-kit-induced parthenogenetic egg activation was completely inhibited by oocyte preincubation with the Ca2(+)-chelating agent BAPTA-AM or with a specific inhibitor of phospholipase C activity. Tr-kit-induced egg activation was associated with a decrease in activity of mitogen-activated protein kinase, an essential component of the cytostatic factor. These results candidate tr-kit as a putative sperm factor required for triggering activation of mouse eggs at fertilization.

[Interstitial photocoagulation with laser in the treatment of liver metastasis]

Interstitial laser photocoagulation (ILP) causes tumor necrosis with local hyperthermia produced by laser light energy. We treated with US-guided ILP 14 patients (7 men and 7 women; mean age: 67 years) and 20 metastases: 9 of them were < 3 cm in max. diameter and 11 were > 3 cm (mean diameter: 2.9 cm); 14 metastases were from colon carcinoma, 5 from breast cancer and 1 from lung cancer. ILP was performed with 300 and 600 microns quartz fiberoptic guides advanced in 21-18G Chiba needles and a continuous-wave Nd: YAG laser with 1064 nm wavelength. We used single expositions of 5-6 minutes with an irradiation power of 5 watts and scheduled 3 treatment sessions, performing CT scans and biopsies at the end of each session. The extent of induced necrosis was classified as follows on the basis of CT findings: grade 1 = 100% necrosis; grade 2 = necrosis > 50%; grade 3 = necrosis < 50%. The average follow-up was 6 months. After the 3 scheduled treatment sessions, CT showed grade 1 necrosis in all the lesions < 3 cm in diameter and in 4/9 (44%) lesions > 3 cm and grade 2 and 3 necrosis in the remaining cases (necrosis > 50% in 95% of the lesions and 92% of the patients). The cytologic findings were in agreement with CT results in all grade 2 and 3 cases, but in one grade 1 necrosis cytology showed residual viable tumor. To conclude, ILP is a safe and well-tolerated procedure. Maximum efficacy was observed in the lesions < 3 cm, while lesion volume was markedly reduced in the lesions > 3 cm. US is a useful tool in the real-time monitoring of this procedure and CT is the most accurate imaging technique to assess treatment efficacy.