Teores de água no solo e eficácia do herbicida glyphosate no controle de Euphorbia heterophylla

Um experimento em casa de vegetação foi realizado com os objetivos de avaliar a eficácia do herbicida glyphosate no controle de Euphorbia heterophylla se desenvolvendo em solo com diferentes teores de água e determinar qual o menor teor de água do solo que não prejudica a ação desse herbicida no controle dessa planta daninha. O delineamento utilizado foi o de blocos casualizados em esquema fatorial 6 x 5, sendo seis intervalos entre a última irrigação e a aplicação do herbicida (0, 6, 12, 24, 48 e 72 horas) e cinco doses de glyphosate (0, 180, 360, 720 e 1.080 g ha-1). Quando as plantas atingiram estádio de três pares de folhas, foram aplicados 10 mm de chuva simulada, conforme tratamento previsto. Ao término do período de simulação de chuva, aplicou-se o herbicida com pulverizador costal pressurizado com CO2, utilizando-se volume de calda de 120 L ha-1. Aos 7, 20, 34 e 41 dias após aplicação (DAA), foram avaliados o controle (por escala visual) e, aos 41 DAA, a massa seca de raízes e da parte aérea. Após análise dos dados, verificou-se que a partir da dose de 720 g ha-1 de glyphosate obteve-se controle satisfatório de E. heterophylla, independentemente do intervalo entre a última irrigação e a aplicação do herbicida. Pulverizações de 360 g ha-1 de glyphosate a intervalos menores que 48 horas entre a última irrigação e sua aplicação e em solo com teor de água maior que 0,09 cm³ cm-3 não prejudicaram a eficácia do herbicida. A aplicação de 180 g ha-1 de glyphosate a intervalos menores que 12 horas entre a última irrigação e sua aplicação e em solo com teor de água superior a 0,14 cm³ cm-3 não afetou a eficácia do herbicida.

Influência de doses reduzidas do glyphosate no tomateiro (Lycopersicon esculentum)

O tomateiro (Lycopersicon esculentum) é cultivado em todas as regiões do Brasil devido à ampla utilização na culinária, tanto in natura quanto industrializado. A deriva do glyphosate vem sendo citada como um dos fatores que interferem negativamente sobre as culturas hortícolas, cultivadas nas adjacências das lavouras de arroz. Objetivou-se com esse verificar os efeitos de doses reduzidas do glyphosate sobre a cultura do tomateiro. O glyphosate foi aplicado a 0, 15, 30, 45, 60, 75 e 90% da dose de 1.260 g ha-1, aos 30, 50 e 70 dias após o transplante (DAT) da cultura. As variáveis analisadas foram fitotoxicidade, altura e número de cachos florais, flores e frutos por planta. Os dados experimentais foram submetidos à análise da variância e, sendo significativos, os efeitos de época de aplicação foram comparados pelo teste de Tukey, e os efeitos do fator dose, analisados por regressão. A aplicação do glyphosate, a partir de 378 g ha-1, afetou o desenvolvimento do tomateiro, independentemente do estádio de desenvolvimento.

Teores de água no solo e eficácia do herbicida fomesafen no controle de Amaranthus hybridus

Com os objetivos de avaliar a eficácia do herbicida fomesafen no controle de plantas de Amaranthus hybridus se desenvolvendo em solo com diferentes teores de água e determinar qual o menor teor de água do solo que não prejudica a ação desse herbicida no controle dessa espécie, foi realizado um experimento em casa de vegetação. O delineamento experimental utilizado foi o de blocos ao acaso em esquema fatorial 5 x 5, envolvendo cinco intervalos entre a última irrigação e a aplicação do herbicida (0, 6, 12, 24 e 48 horas) e cinco doses de fomesafen (0,0, 62,5, 125,0, 250,0 e 375,0 g ha-1). Quando as plantas atingiram estádio de quatro pares de folhas, foram aplicados 10 mm de chuva simulada, conforme tratamento previsto. Ao término do período de simulação de chuva, aplicou-se o herbicida utilizando pulverizador costal pressurizado com CO2, com volume de calda de 120 L ha-1. Aos 5, 22, 29 e 43 dias após a aplicação (DAA) do herbicida, foi avaliado o controle (por escala visual) de A. hybridus e, aos 43 DAA, foram avaliadas também a massa seca das raízes e a da parte aérea. A aplicação de 375,0 g ha-1 de fomesafen proporcionou controle satisfatório de A. hybridus, independentemente do intervalo entre a última irrigação e a aplicação do herbicida ou do teor de umidade do solo, dentro da faixa avaliada. Pulverizações de 250,0 g ha-1 de fomesafen a intervalos menores que 24 horas entre a última irrigação e sua aplicação e/ou em solo com teor de água maior que 0,12 cm³ cm-3 não afetaram a eficácia do herbicida sobre A. hybridus. Aplicações de 125,0 g ha-1 de fomesafen a intervalos menores que 12 horas entre a última irrigação e sua aplicação e/ou em solo com teor de água maior que 0,15 cm³ cm-3 não afetaram a eficácia do herbicida sobre A. hybridus.

Atividade residual de (imazethapyr+imazapic) sobre azevém anual (Lolium multiflorum), semeado em sucessão ao arroz irrigado, sistema clearfield®

Este trabalho teve por objetivo avaliar a atividade residual da mistura comercial (imazethapyr+imazapic) sobre azevém semeado em sucessão em áreas antes cultivadas com arroz Clearfield® (CL) por um, dois ou três anos consecutivos. Os experimentos foram conduzidos em campo, no município de Capão do Leão, RS. O arroz cv. IRGA 422 CL foi considerado cultura principal, e o azevém, variedade indefinida, cultura sucessora. O delineamento experimental utilizado foi o de blocos ao acaso, com quatro repetições. Os tratamentos foram arranjados em esquema fatorial, em que o fator A, dentro da mesma safra, comparou resíduos de (imazethapyr+imazapic) em um, dois e três anos de cultivo de arroz CL, e o fator B avaliou o efeito de dose sobre a atividade residual do herbicida. Os blocos foram constituídos por quatro unidades experimentais, que haviam recebido a mistura (imazethapyr+imazapic) nas doses de 0; 25+75; 37,5+112,5; e 50+150 g ha-1, acrescidos de Dash a 0,5% v/v. A análise conjunta dos dados, gerados nos três ambientes (A1, A2 e A3), acusou interação entre dose herbicida (imazethapyr+imazapic) e ambientes para as variáveis-resposta estatura de plantas e rendimento biológico. Para as variáveis peso de grãos e poder germinativo, as diferenças ocorreram somente entre as doses do herbicida. Os resultados demonstram que todas as variáveis-resposta avaliadas foram alteradas negativamente pela presença de resíduos da mistura (imazethapyr+imazapic) no solo, sendo maiores as injúrias com o incremento da dose. Foi observado que o cultivo de arroz irrigado no sistema CL deixa resíduos dos herbicidas (imazethapyr+imazapic) no solo, capazes de causar danos ao azevém cultivado em sucessão. Além disso, o sistema de sucessão envolvendo o arroz CL e azevém requer intervalos superiores a 180 dias entre a aplicação inicial do herbicida na primeira cultura e a semeadura do cultivo sucessor.

Milho (Zea mays) como espécie bioindicadora da atividade residual de (imazethapyr+imazapic)

Este estudo teve como objetivo avaliar a atividade residual, no solo, do herbicida (imazethapyr+imazapic) aplicado na cultura de arroz irrigado, instalado pelo sistema Clearfield® e tendo como planta bioindicadora o milho, cv. Biomatrix 2202. Os trabalhos foram realizados em casa de vegetação da Universidade Federal de Pelotas, Capão do Leão-RS. O arroz, cv. IRGA 422 CL, foi semeado em caixas de polietileno (60 x 40 x 20 cm). Quando o arroz estava em estádio de 3 a 4 folhas, foram aplicados os tratamentos com o herbicida (imazethapyr+ imazapic) a 0; 25+75; 37,5+112,5; e 50+150 g ha-1, que corresponderam a 0, 100, 150 e 200 g ha-1 no produto formulado. Após a colheita do arroz, o solo foi mantido sem irrigação por 45 dias, quando então foi semeada aveia-preta (Avena strigosa), colhida no início da primavera. Aos 360 e 540 dias após a aplicação dos tratamentos (DAA), foi transferido o solo das caixas de polietileno para dois conjuntos de vasos, onde foi semeado milho, os quais passaram respectivamente a ser identificados como experimentos safra (E1) e safrinha (E2). Nos primeiros 360 e 540 dias entre a aplicação dos herbicidas e a semeadura dos dois experimentos, o solo do E2 permaneceu sem irrigação. As plantas de milho foram colhidas, em estádios de 4 a 5 folhas. As variáveis avaliadas foram: massas secas dos sistemas radical e aéreo, altura de planta e índice de área foliar, sendo esta última avaliada somente no E2. Os dados experimentais foram submetidos à análise de variância (<0,05); havendo significância, eles foram testados por modelos de regressão polinomial. Foram observadas reduções significativas nas massas secas de raiz e parte aérea, altura de planta e área foliar do milho, cv. Biomatrix 2202, semeado até 540 DAA do herbicida (imazethapyr+imazapic) na cultura do arroz, demonstrando que o milho pode ser utilizado como indicador da atividade desse herbicida no solo.

Michelson interferometer with porch swing bearing for portable FTIR spectrometer

The interferometer for low resolution portable Fourier Transform middle infrared spectrometer was developed and studied experimentally. The final aim was a concept for a commercial prototype. Because of the portability, the interferometer should be compact sized and insensitive to the external temperature variations and mechanical vibrations. To minimise the size and manufacturing costs, Michelson interferometer based on plane mirrors and porch swing bearing was selected and no dynamic alignment system was applied. The driving motor was a linear voice coil actuator to avoid mechanical contact of the moving parts. The driving capability for low mirror driving velocities required by the photoacoustic detectors was studied. In total, four versions of such an interferometer were built and experimentally studied. The thermal stability during the external temperature variations and the alignment stability over the mirror travel were measured using the modulation depth of the wide diameter laser beam. Method for estimating the mirror tilt angle from the modulation depth was developed to take account the effect from the non-uniform intensity distribution of the laser beam. The spectrometer stability was finally studied also using the infrared radiation. The latest interferometer was assembled for the middle infrared spectrometer with spectral range from 750 cm−1 to 4500 cm−1. The interferometer size was (197 × 95 × 79) mm3 with the beam diameter of 25 mm. The alignment stability as the change of the tilt angle over the mirror travel of 3 mm was 5 μrad, which decreases the modulation depth only about 0.7 percent in infrared at 3000 cm−1. During the temperature raise, the modulation depth at 3000 cm−1 changed about 1 . . . 2 percentage units per Celsius over short term and even less than 0.2 percentage units per Celsius over the total temperature raise of 30 °C. The unapodised spectral resolution was 4 cm−1 limited by the aperture size. The best achieved signal to noise ratio was about 38 000:1 with commercially available DLaTGS detector. Although the vibration sensitivity requires still improving, the interferometer performed, as a whole, very well and could be further developed to conform all the requirements of the portable and stable spectrometer.

Die Beendigung von finnischen und deutschen Telefonaten. Eine interaktionslinguistische, kontrastierende Untersuchung

Suomalaisten ja saksalaisten arkikeskustelujen välillä on sekä yhtäläisyyksiä että eroja. Tässä saksalaisen filologian alaan kuuluvassa tutkimuksessa tarkastellaan yhtä keskeistä arkikeskustelun toimintoa, puhelinkeskustelun lopetusta, suomen- ja saksanpuhujien tuottamana. Aineistona on käytetty suomen- ja saksankielisten äidinkielisten puhujien tätä tutkimusta varten nauhoittamia henkilökohtaisia luonnollisia puhelinkeskusteluja. Aineistoon valikoitui 12 suomalaista ja 12 saksalaista puhelua. Nauhoitteiden käyttöön on saatu asianmukainen lupa kaikilta osapuolilta. Puhelut on litteroitu saksalaisella kielialueella vakiintuneen GAT-litterointisysteemin mukaan. Teoreettis-metodisena kehyksenä on kaksi tutkimusalaa, vuorovaikutuslingvistiikka ja kielten vertailu. Vuorovaikutuslingvistinen tarkastelu keskittyy havaintoihin vuorojen ja puheen sekvenssien rakenteesta. Vuorojen merkitysten tulkinnassa hyödynnetään systemaattisesti prosodian antamia vihjeitä. Tuloksena on yksittäisten lopetusten keskustelunanalyyttinen lähikuvaus, jonka pohjalta määritellään kulloisenkin lopetuksen sekvenssirakenne. Kaikki lopetukset olivat siltä osin yhteneväisiä, että niissä kaikissa havaittiin ainakin aloittava, tulevaan tapaamiseen viittaava sekä lopputervehdyksiin johtava sekvenssi. Sekvenssirakenteen variaatioiden pohjalta aineiston lopetukset voidaan kuitenkin jaotella ryhmiin. Sekä suomen- että saksankielisessä aineistossa havaittiin kolmentyyppisiä lopetuksia: kompakteja, komplekseja ja keskeytettyjä lopetuksia. Ryhmittely kolmeen tyyppiin on avuksi seuraavassa kuvausvaiheessa, jossa verrataan suomen- ja saksankielisiä lopetuksia toisiinsa. Samanaikaisesti kun tutkimus valottaa kohtia, joissa kaksi aineistosettiä yhtenevät ja eroavat, se myös esittää, mitkä vuorovaikutuksen tasot soveltuvat kieltenvälisen vertailun kohteiksi. Pohdintaa siitä, mitä vuorovaikutuksen tasoja kieltenväliseen vertailuun voidaan sisällyttää, onkin toistaiseksi esitetty verrattain vähän. Työ siis rakentaa siltaa vuorovaikutuslingvistisen ja kontrastiivisen kielitieteen välille.

Simulation of new p-type pixel strip detector with enhanced multiplication effect

This Master’s Thesis is dedicated to the simulation of new p-type pixel strip detector with enhanced multiplication effect. It is done for high-energy physics experiments upgrade such as Super Large Hadron Collider especially for Compact Muon Solenoid particle track silicon detectors. These detectors are used in very harsh radiation environment and should have good radiation hardness. The device engineering technology for developing more radiation hard particle detectors is used for minimizing the radiation degradation. New detector structure with enhanced multiplication effect is proposed in this work. There are studies of electric field and electric charge distribution of conventional and new p-type detector under reverse voltage bias and irradiation. Finally, the dependence of the anode current from the applied cathode reverse voltage bias under irradiation is obtained in this Thesis. For simulation Silvaco Technology Computer Aided Design software was used. Athena was used for creation of doping profiles and device structures and Atlas was used for getting electrical characteristics of the studied devices. The program codes for this software are represented in Appendixes.

Transient current technique simulation of semiconductor detectors

Nowadays advanced simulation technologies of semiconductor devices occupies an important place in microelectronics production process. Simulation helps to understand devices internal processes physics, detect new effects and find directions for optimization. Computer calculation reduces manufacturing costs and time. Modern simulation suits such as Silcaco TCAD allow simulating not only individual semiconductor structures, but also these structures in the circuit. For that purpose TCAD include MixedMode tool. That tool can simulate circuits using compact circuit models including semiconductor structures with their physical models. In this work, MixedMode is used for simulating transient current technique setup, which include detector and supporting electrical circuit. This technique was developed by RD39 collaboration project for investigation radiation detectors radiation hard properties.

Ydinvoimalaitosten vesikemia ja korroosionesto

Ydinvoimalaitosten vesikemian optimointi ja korroosionesto on välttämätöntä laitosten taloudellisen ja turvallisen käytön kannalta. Eri laitoksiin liittyvää vesikemiaa ja järjestelmissä havaittavia korroosion muotoja on tutkittu laajasti ja tutkitaan yhä edelleen. Monien prosessien ymmärtäminen vaatii usean eri tieteenalan osaamista, kuten kemiantekniikan, energiatekniikan sekä materiaalitekniikan. Tässä työssä kerrotaan yksinkertaistaen vesikemiaan ja korroosioon liittyviä prosesseja ja reaktioita. Työssä käsitellään kevytvettä jäähdytteenä sekä moderaattorina käyttävien ydinvoimalaitosten eri korroosiomuotoja sekä säteilyn vaikutusta näihin suoraan tai vesikemian kautta. Työssä kerrotaan korroosio- ja aktivoitumistuotteiden muodostumisesta ja kulkeutumisesta sekä näiden tuotteiden vaikutuksista laitosten toimintaan. Korroosion ja materiaalien aktivoitumisen pohjalta tarkastellaan kattavasti ydinvoimalaitosten tyypillisimpiä vesikemian muokkauskeinoja sekä korroosionhallintaa. Tärkeimpiin asioihin syvennytään hieman lähemmin. Tarkastelun kohteena ovat eniten käytetyt ydinvoimalaitokset, eli länsimaiset paine- ja kiehutusvesilaitokset sekä venäläisvalmisteiset VVER-laitokset. Tarkoituksena on ollut luoda tiivis tietopaketti opiskelijoiden käyttöön muun opintomateriaalin tueksi.

Sunflower response to repeated foliar applications of Paclobutrazol

Paclobutrazol (PBZ), a well-known growth retardant of the triazole family, is mostly used for controlling plant size and growth, resulting in more desirable compact plants for floricultural purposes; however, limited experimental data are available for use of PBZ in field sunflower. The objective of this study was to evaluate the effect of repeated foliar applications of PBZ at rates of 50 + 50 g ha-1(double application) and 50 + 50 + 50 g ha-1 (triple application) on sunflower morphology and productivity. PBZ applications corresponded to growth stages of four to five, five to six, and six to eight true leaves of sunflower plants, respectively. The double foliar application of PBZ reduced sunflower plant height at maturity by 4.4% (or by 11.7 cm). The triple foliar application of PBZ reduced sunflower plant height at maturity by 14.4% (or by 49.2 cm). However, PBZ either in the double or the triple application reduced achene yield per plant by 25.6% and 22.5% and the 100-achene weight by 11.4% and 25.0%, respectively, compared with the non-treated control. Overall, the repeated foliar applications of PBZ at the rates tested in this study, apart from providing a reduction of sunflower plant height, had major adverse effects on achene yield and weight. Thus, different application schemes of PBZ or perhaps different growth regulators should be investigated to control plant height in sunflower.

Vegetative propagation strategies of four rupestrian species of Leiothrix (Eriocaulaceae)

Leiothrix is endemic of South America and includes 37 species, 25 of which occur in the state of Minas Gerais. Nineteen of those occur in the "Serra do Cipó", a mountain chain, located in the southern portion of the Espinhaço mountain range. This study examines vegetative propagation strategies of four species of Leiothrix, endemic to the Minas Gerais portion of the Espinhaço mountain range. For each species we established permanent plots, where we marked 30 to 51 rosettes or clones, and then took morphological and phenological measurements. Leiothrix crassifolia (Bong.) Ruhland and L. curvifolia var. lanuginosa (Bong.) Ruhland are rhizomatous, forming compact clones. Leiothrix vivipara (Bong.) Ruhland does not produce rhizomes, but is pseudoviviparous, i.e., produces numerous ramets originating from inflorescences. These ramets are formed precociously, and the flower heads do not touch the ground. In Leiothrix spiralis (Bong.) Ruhland both of these strategies are seen: it is both rhizomatous and pseudoviviparous. In this species, the ramets are formed late, only after the flower head has touched the ground. One of the typical conditions of the rupestrian grasslands is soil water shortage in some periods of the year and nutrient scarcity all year round. These conditions might have created an ideal ecological scenario for the evolution of both pseudovivipary and rhizomatous clonal growth in Leiothrix.

The interplay of JNK and SCG10 during cortical development and in excitotoxic responses in brain

Initially identified as stress activated protein kinases (SAPKs), the c-Jun Nterminal kinases (JNKs) are currently accepted as potent regulators of various physiologically important cellular events. Named after their competence to phosphorylate transcription factor c-Jun in response to UVtreatment, JNKs play a key role in cell proliferation, cell death or cell migration. Interestingly, these functions are crucial for proper brain formation. The family consists of three JNK isoforms, JNK1, JNK2 and JNK3. Unlike brain specific JNK3 isoform, JNK1 and JNK2 are ubiquitously expressed. It is estimated that ten splice variants exist. However, the detailed cellular functions of these remain undetermined. In addition, physiological conditions keep the activities of JNK2 and JNK3 low in comparison with JNK1, whereas cellular stress raises the activity of these isoforms dramatically. Importantly, JNK1 activity is constitutively high in neurons, yet it does not stimulate cell death. This suggests a valuable role for JNK1 in brain development, but also as an important mediator of cell wellbeing. The aim of this thesis was to characterize the functional relationship between JNK1 and SCG10. We found that SCG10 is a bona fide target for JNK. By employing differential centrifugation we showed that SCG10 co-localized with active JNK, MKK7 and JIP1 in a fraction containing endosomes and Golgi vesicles. Investigation of JNK knockout tissues using phosphospecific antibodies recognizing JNK-specific phosphorylation sites on SCG10 (Ser 62/Ser 73) showed that phosphorylation of endogenous SCG10 was dramatically decreased in Jnk1-/- brains. Moreover, we found that JNK and SCG10 co-express during early embryonic days in brain regions that undergo extensive neuronal migration. Our study revealed that selective inhibition of JNK in the cytoplasm significantly increased both the frequency of exit from the multipolar stage and radial migration rate. However, as a consequence, it led to ill-defined cellular organization. Furthermore, we found that multipolar exit and radial migration in Jnk1 deficient mice can be connected to changes in phosphorylation state of SCG10. Also, the expression of a pseudo-phosphorylated mutant form of SCG10, mimicking the JNK1- phopshorylated form, brings migration rate back to normal in Jnk1 knockout mouse embryos. Furthermore, we investigated the role of SCG10 and JNK in regulation of Golgi apparatus (GA) biogenesis and whether pathological JNK action could be discernible by its deregulation. We found that SCG10 maintains GA integrity as with the absence of SCG10 neurons present more compact fragmented GA structure, as shown by the knockdown approach. Interestingly, neurons isolated from Jnk1-/- mice show similar characteristics. Block of ER to GA is believed to be involved in development of Parkinson's disease. Hence, by using a pharmacological approach (Brefeldin A treatment), we showed that GA recovery is delayed upon removal of the drug in Jnk1-/- neurons to an extent similar to the shRNA SCG10-treated cells. Finally, we investigated the role of the JNK1-SCG10 duo in the maintenance of GA biogenesis following excitotoxic insult. Although the GA underwent fragmentation in response to NMDA treatment, we observed a substantial delay in GA disintegration in neurons lacking either JNK1 or SCG10.

Ultrasonic and Electrokinetic Remediation of Low Permeability Soil Contaminated with Persistent Organic Pollutants

Electrokinetics has emerged as a potential technique for in situ soil remediation and especially unique because of the ability to work in low permeability soil. In electrokinetic remediation, non-polar contaminants like most organic compounds are transported primarily by electroosmosis, thus the process is effective only if the contaminants are soluble in pore fluid. Therefore, enhancement is needed to improve mobility of these hydrophobic compounds, which tend to adsorb strongly to the soil. On the other hand, as a novel and rapidly growing science, the applications of ultrasound in environmental technology hold a promising future. Compared to conventional methods, ultrasonication can bring several benefits such as environmental friendliness (no toxic chemical are used or produced), low cost, and compact instrumentation. It also can be applied onsite. Ultrasonic energy applied into contaminated soils can increase desorption and mobilization of contaminants and porosity and permeability of soil through developing of cavitation. The research investigated the coupling effect of the combination of these two techniques, electrokinetics and ultrasonication, in persistent organic pollutant removal from contaminated low permeability clayey soil (with kaolin as a model medium). The preliminary study checked feasibility of ultrasonic treatment of kaolin highly contaminated by persistent organic pollutants (POPs). The laboratory experiments were conducted in various conditions (moisture, frequency, power, duration time, initial concentration) to examine the effects of these parameters on the treatment process. Experimental results showed that ultrasonication has a potential to remove POPs, although the removal efficiencies were not high with short duration time. The study also suggested intermittent ultrasonication over longer time as an effective means to increase the removal efficiencies. Then, experiments were conducted to compare the performances among electrokinetic process alone and electrokinetic processes combined with surfactant addition and mainly with ultrasonication, in designed cylinders (with filtercloth separating central part and electrolyte parts) and in open pans. Combined electrokinetic and ultrasonic treatment did prove positive coupling effect compared to each single process alone, though the level of enhancement is not very significant. The assistance of ultrasound in electrokinetic remediation can help reduce POPs from clayey soil by improving the mobility of hydrophobic organic compounds and degrading these contaminants through pyrolysis and oxidation. Ultrasonication also sustains higher current and increases electroosmotic flow. Initial contaminant concentration is an essential input parameter that can affect the removal effectiveness.

Autoradiographic thyroid evaluation in short-term experimental diabetes mellitus

Previous studies have shown that in vitro thyroid peroxidase (TPO) iodide oxidation activity is decreased and thyroid T4-5'-deiodinase activity is increased 15 days after induction of experimental diabetes mellitus (DM). In the present study we used thyroid histoautoradiography, an indirect assay of in vivo TPO activity, to determine the possible parallelism between the in vitro and in vivo changes induced by experimental DM. DM was induced in male Wistar rats (about 250 g body weight) by a single ip streptozotocin injection (45 mg/kg), while control (C) animals received a single injection of the vehicle. Seven and 30 days after diabetes induction, each diabetic and control animal was given ip a tracer dose of 125I (2 µCi), 2.5 h before thyroid excision. The glands were counted, weighed, fixed in Bouin's solution, embedded in paraffin and cut. The sections were stained with HE and exposed to NTB-2 emulsion (Kodak). The autohistograms were developed and the quantitative distribution of silver grains was evaluated with a computerized image analyzer system. Thyroid radioiodine uptake was significantly decreased only after 30 days of DM (C: 0.38 ± 0.05 vs DM: 0.20 ± 0.04%/mg thyroid, P<0.05) while in vivo TPO activity was significantly decreased 7 and 30 days after DM induction (C: 5.3 and 4.5 grains/100 µm2 vs DM: 2.9 and 1.6 grains/100 µm2, respectively, P<0.05 ). These data suggest that insulin deficiency first reduces in vivo TPO activity during short-term experimental diabetes mellitus