Die in dieser Arbeit isolierten und hochaufgereinigten, humanen dermalen Mastzellen wurden mit UVB, UVA-1 und PUVA-1 bestrahlt und anschließend entweder mit Substanz P oder anti-IgE stimuliert. Dadurch sollten Einblicke in die unterschiedlichen Wirkmechanismen der bei zahlreichen mastzellassoziierten Erkrankungen eingesetzten UV Licht Therapie gewonnen werden. Ein Schwerpunkt dieser Arbeit lag in der Erforschung der Histamin-, Tryptase- und Zytokinfreisetzung von menschlichen Mastzellen. Zusätzlich wurde die Expression von Lysosomen-assoziierten Membran Proteinen (LAMPs) auf der Oberfläche dieser Zellen untersucht. Im Gegensatz zu der durch UV Licht induzierbaren spontanen Histaminfreisetzung zeigte sich die anti-IgE stimulierte Histaminausschüttung durch UVB, UVA-1 und PUVA-1 signifikant und dosisabhängig inhibierbar. Auch die durch Substanz P stimulierten Mastzellen gaben nach UVA-1 Bestrahlung deutlich weniger Histamin ab. Demgegenüber blieb die sezernierte Menge des Mediators nach UVB und PUVA-1 konstant. Analog zu den erhobenen Histaminergebnissen konnte eine signifikante Inhibition der anti-IgE induzierten Tryptasefreisetzung nachgewiesen werden. Ebenso zeigte sich eine signifikante Verringerung, der innerhalb von vierundzwanzig Stunden basal freigesetzten Menge an Interleukin-6 und Interleukin-8, nach UV Bestrahlung. Die spontane Ausschüttung vom Tumornekrosefaktor-a verblieb in dem Untersuchungszeitraum auf sehr geringem Niveau, so dass eine relevante Beeinflussung durch UV Licht nicht stattfand. Des weiteren konnte eine vermehrte basale Expression von CD107a und CD63 auf der Mastzellmembran durch UV Bestrahlung demonstriert werden. Auch die anti-IgE induzierte Mehrexpression der LAMPs konnte bei den drei Bestrahlungsarten nachweisbar supprimiert werden. Die in dieser Arbeit gewonnenen Erkenntnisse zeigen, dass die Auswirkungen der UV Licht Therapie auf Mastzellen sehr komplex sind. Zu beachten ist, dass unter physiologischen Bedingungen nicht nur isolierte Mastzellen, sondern auch weitere bestrahlte Zellverbände eine Veränderung erfahren. Erst durch das Zusammenspiel aller Zellen lassen sich Rückschlüsse auf Krankheitsbilder und die anzuwendende Therapien ziehen. Letztendlich soll diese Arbeit dazu beitragen, dass das Verständnis der unterschiedlichen Wirkungen von UV Licht begriffen und so ein sinnvolles und gezieltes Einsetzen im klinischen Alltag ermöglicht wird. / For all experiments highly purified dermal mast cells were used. The aim of the current study was to systematically investigate the effects of UVB, UVA-1 and PUVA-1 on skin derived human mast cells. Baseline and stimulated release of histamine, tryptase and of the proinflammatory cytokines IL-6, IL-8 and TNF-a were examined. Furthermore, the CD 107a and CD 63 surface levels in UV treated cells were investigated representing two members of lysosome associated membrane proteins which were found to appear on mast cell surface during degranulation. Prior treatment with UV resulted in a striking suppression of the anti-IgE induced release of preformed mediators such as histamine and tryptase in a dose dependent manner. This inhibition was accompanied by a diminished, anti-IgE mediated increase in CD 107a and CD 63 surface expression. In sharp contrast, UV-light slightly preactivates mast cells as indicated by a marginal but statistically significant direct UV-caused histamine release. Theses findings matched the observation of slightly enhanced CD 107a and CD 63 surface levels in UV treated but unstimulated cells. After UVA-1 treatment the histamine release of substance P stimulated mast cells is statistically significant reduced which contrasts to the unchanged liberation of this preformed marker after UVB and PUVA-1 irradiation. Furthermore the release of mediators that are not or only partially preformed was examined. In the present study all types of UV-irradiation inhibits baseline IL-6 and IL-8 secretion from mast cells. The very low baseline level of TNF-a remained unaffected. Taken together, the present findings identify cutaneous human mast cells as important targets of UV-induced immunomodulation. They help explain both the dose-dependent adverse effects of UV-light and the beneficial and desired antiinflammatory effects during therapy.

Die Haut ist das größte Organ des Menschen und stellt die primäre Barriere gegen Umwelteinflüsse und Pathogene dar. Eine Dysbalance der Hautbarriere birgt die Gefahr einer nachfolgenden Entzündungsreaktion. Bleibt diese bestehen, können sich Hautkrankheiten wie zum Beispiel die atopische Dermatitis (AD) entwickeln. Verschiedene Zytokine wie Thymic Stromal Lymphopoietin (TSLP) werden bei entzündlichen Hauterkrankungen eine bedeutende Rolle zugeschrieben. Die Bedeutung von TSLP wurde zunächst anhand mehrerer Knockout-Mausstämme untersucht. Hier zeigte sich, dass TSLPR-KO und TNF-TSLPR-DKO Mäuse im Gegensatz zu TNF-KO Mäusen keine bzw. weniger Zeichen einer Entzündungsreaktion in der Haut entwickeln. Die Rolle äußerer Einflüsse auf die TSLP-Produktion wurde anhand eines Irritationsmodells ebenfalls in Mäusen untersucht. Dabei führte die Hautirritation, ausgelöst durch Abtragen der oberen Hautschichten mittels eines Tesa-Abriss, zu einem signifikanten Anstieg von TSLP in der Haut?. Mit Hilfe von Agonisten und Inhibitoren konnte gezeigt werden, dass dieser Irritations-vermittelte TSLP-Anstieg über Interleukin-1 (IL-1) und Protease Activated Receptor 2 (PAR-2) vermittelt wird. In diesem Zusammenhang wurde auch gezeigt, dass die Aktivierung von IL-1- sowie PAR-2-abhängigen Signalwegen zu einer gesteigerten Aktivität des TSLP-Promotors führte. Die Untersuchung der Wirkung verschiedener Mastzellmediatoren auf die TSLP-Expression ergab, dass Tryptase, über die Aktivierung von PAR-2, der wichtigste Mediator für den Anstieg von TSLP nach der Degranulation von Mastzellen ist. Dieses Ergebnis wurde mittels verschiedener in vitro, in vivo und ex vivo Experimentalansätze belegt. So konnte in einem c48/80-abhängigen Degranulationsmodell in Mäusen gezeigt werden, dss PAR-2- sowie Mastzell-KO Mäuse im Vergleich zu Wildtypen nach Injektion von c48/80 signifikant weniger TSLP exprimierten. / The skin is the first line of defense against environmental or microbial pathogens. A deviation of the skin barrier homeostasis by any kind of insult can result in an inflammatory response. The inflammatory response in turn can promote the development of an eczemaincluding atopic eczema. Thymic stromal lymphopoietin (TSLP) due to its pleiotropic nature play an important role in inflammatory disorders. The major aim of this thesis was to better understand the underlying mechanisms of TSLP production in the context of skin irritation and mast cell (MC) mediators and their contribution in the development of atopic dermatitis (AD). The role of TSLP was studied using TSLPR-/- mice. The data show that TSLPR-/- and TNF-/-/TSLPR-/- mice were protected from AD development, by contrast TNF-/- mice exhibited severe AD. The role of exogenous triggers was studied using tape stripping mediated skin irritation mouse models. Skin irritation resulted in significant enhanced TSLP production. TSLP induction was identified to depend on interleukin (IL)-1 and protease activated receptor (PAR)-2 pathways proven by using exogenous activators or inhibitors of these pathways. Moreover, PAR-2 and IL-1 concomitantly promoted NF-κB binding to the human TSLP promoter which in turn resulted in an increased TSLP promoter activity. Additionally, the role of mast cell mediators in the context of TSLP induction was investigated. Tryptase turned out to be the trigger responsible for the enhanced TSLP response by activating the PAR-2 pathway. This finding was proven by employing in vitro, ex vivo and in vivo approaches. In detail PAR-2-/- and MC-/- mice were used in a compound 48/80 (C48/80) dependent MCs degranulation model. PAR-2-/- and MC-/- mice produced significantly less TSLP in comparison to control mice.

Die Haut ist das größte Organ des Menschen und bildet die Barriere gegenüber Einwirkungen aus der Umwelt. Die Störung der Hautbarriere durch exogene und endogene Reize führt zu einer Entzündungsreaktion in der Haut. In der Folge können Hauterkrankungen wie die irritative oder Atopische Dermatitis entstehen. Der Tumor Nekrose Faktor-α (TNF-α) ist ein pleiotrop wirksames Zytokin, das eine zentrale Rolle bei entzündlichen Prozessen spielt. Ziel der vorgelegten Promotionsarbeit war zu untersuchen, ob und wie TNF-α zu Entzündungsgeschehen, ausgelöst durch exogene und endogene Faktoren, beiträgt. Die Bedeutung von TNF-α wurde in TNF-ko Mäusen in verschiedenen Hautmodellen untersucht. Für das Irritationsmodell wurden chemische und physikalische Reize verwendet. TSLP (Thymic stromal lymphopoietin) wurde durch die verschiedenen Stimuli signifikant induziert. Diese Induktion war unabhängig von der endogenen TNF-α Produktion, gezeigt durch den Einsatz von TNF- ko Mäusen . Da endogenes TNF-α für die Hautirritation keine notwendige Bedingung darstellte, wurde die Bedeutung von TNF-α bei der atopischen Dermatitis (AD) untersucht. TNF-α defiziente Mäuse zeigen verstärkt Ekzeme im Vergleich zu Wildtyp Mäusen. Die Behandlung von TNF-ko Mäusen mit einem TSLP Antikörper führte zu einer Verminderung des Ekzems. Mastzellen wurden vermehrt in läsionaler Haut gefunden und korrelierten mit dem Schweregrad des atopischen Ekzems sowie der TSLP-Expression. / The skin is the largest organ of an individuum and builds the barrier for a host against the environment. Skin barrier disruption by exogenous or endogenous stimuli can lead to skin inflammation. As a consequence, irritant or atopic eczema, frequent skin diseases, may evolve. Tumor necrosis factor-α (TNF-α) is a pleiotropic cytokine which plays a central role in inflammatory processes. The main aim of this thesis was to clarify whether and how endogenous TNF-α is contributing to skin inflammation driven by exogenous and endogenous triggers. The role of endogenous TNF-α was studied using TNF knockout (-/-) mice. In an irritation model, chemical and physical stimuli were applied on to mouse skin. Thymic stromal lymphopoietin (TSLP) was significantly induced by the used irritants. This TSLP induction was independent from endogenous TNF-α proven by using TNF-/- mice. Next the role of TNF-α in atopic dermatitis (AD) promoting an allergic skin inflammation was investigated. TNF-/- mice developed more severe AD compared to the wildtype mice and TSLP was significantly increased and correlated with the severity of the eczema. To prove the pathophysiological role of TSLP for AD progression, TNF-/- mice were pretreated with an TSLP antibody. Indeed, these mice developed less AD symptoms compared to the control mice. Mast cells (MCs) were also significantly increased in lesional skin in the AD model and moreover, correlated with AD severity, but also with TSLP expression.

Die Synthese und -Freisetzung von FGF-2 aus humanen dermalen Mastzellen Fibroblast growth factor-2 (FGF-2) ist ein Mitglied einer großen Familie von Wachstumsfaktoren. FGF-2 fördert das Wachstum und die Entwicklung von Blutgefäßen (Angiogenese) und nimmt somit Einfluss auf Wundheilungsprozesse, Gewebeentwicklung, als auch verschiedene pathologische Vorgänge im Organismus. Mastzellen wurden lange Zeit allein als Effektorzellen der Typ I Allergiereaktion betrachtet. Mittlerweile betrachten man sie auch als wichtige Zellen für die Gewebe Homöostase und Wundheilung. In der vorliegenden Arbeit wurden MC aus humenen dermalen Gewebe isoliert, um deren FGF-2 Synthese und –Freisetzung zu untersuchen. Die Zellen wurden mit verschiedenen proinflammatorischen Mediatoren stimuliert. FGF-2 wurde mit ELISA und PCR Methoden bestimmt. Durch Stimulationen mit a–IgE, SP, IL–4, IL–6 und IL–8 wurde eine gesteigerte FGF–2–Synthese induziert. Weiterhin zeigten die vorliegenden Ergebnisse, dass bei der Degranulation der MC FGF-2 freigesetzt wird, auch wenn der zugrunde liegende Mechanismus für die Freisetzung weiterhin unklar bleibt. UVA1–und PUVA1–Bestrahlung hatten einen inhibieren Effekt auf die Sekretion des Proteins. / Synthesis and release of FGF-2 from human dermal mast cells Fibroblast growth factor-2 (FGF-2) is a member of a large family of proteins. FGF-2 stimulates the growth and development of new blood vessels (angiogenesis) that contribute to the pathogenesis of several diseases (i.e. atherosclerosis), normal wound healing and tissue development. Mast cells are traditionally viewed as effector cells of immediate type hypersensitivity reactions. There is, however, a growing body of evidence that the cells might play an important role in the maintenance of tissue homeostasis and repair. In this present investigation we isolated MC from human tissue to investigate their FGF-2 synthesis and release after stimulation with different proinflammatory mediators. To detect FGF-2 we used ELISA and PCR technique. We could show the up-regulation of FGF-2 synthesis after stimulation with a-IgE, SP, IL-4, IL-6 and IL-8. Within the degranulation of MC there was a release of FGF-2 even though the mode of release still remains unclear. Through UV-light radiation we could show a downregulation of FGF-2 release.

En raison des conflits maritimes qui s'étendent (piraterie, embargo,...), les besoins de communiquer et de détecter les menaces sont de plus en plus importants. Ceci conduit irrémédiablement à l'augmentation du nombre d'aériens à bord des plateformes navales. Afin de gérer au mieux cet accroissement du nombre d'antennes, qui conduit à des effets de couplage et à une augmentation de la signature radar du navire, les principales entreprises du secteur ont mis en place des structures de mâts intégrés. C'est dans un contexte d'amélioration de leur mâture intégrée compacte (Cmast™) que les Constructions Mécaniques de Normandie (CMN) de Cherbourg en collaboration avec l'IETR de Rennes et INEO Défense ont proposé cette thèse. Ces travaux ont pour objectifs le développement de deux systèmes antennaires intégrables au sein de cette mâture intégrée compacte : une antenne de communication en bande V/UHF et une antenne de radar de navigation à balayage électronique en bande X. Une première étude a permis le développement d'une antenne conique large bande (225-400MHz) dont les paramètres géométriques ont été optimisés pour assurer une communication entre les navires et des aéronefs. Un prototype de cette antenne a été réalisé et a permis une validation expérimentale de ses performances. Une seconde étude a permis le développement d'une antenne d'un radar de navigation à balayage électronique en bande X. Cette antenne est basée sur une technologie transmit-array comprenant une source illuminante et un réseau permettant la formation du diagramme. Un effort particulier a été porté sur la source illuminante qui doit éclairer, à des distances très courtes (<550mm), un réseau qui présente des dimensions particulières (1530mmx100mm). Plusieurs sources utilisant un principe de focalisation en zone champ proche ont été développées et validées expérimentalement. Enfin deux architectures d'antennes transmit-array ont été étudiées, utilisant respectivement une technologie imprimée et une technologie en guide. Le fonctionnement de l'antenne complète (source illuminante + réseau transmit-array) a été étudié théoriquement. / The need to communicate and detect potential enemies increases with the extension of maritime conflicts. This need impacts directly the number of antennas on naval platforms. However, this increase of aerials leads to several damaging effects: like coupling or high radar signature. To limit this effect, some companies have developed integrated mast design. This structure limits the coupling effect between aerials by a subdivision of the mast and provides an omnidirectional coverage for all antennas inserted inside the mast. The objective of the thesis is to design two antenna systems for the compact integrated mast (CmastTM) developed by the Constructions Mécanique de Normandie (CMN): a communication antenna in the V/UHF band and an electronically scanning antenna for a maritime navigation radar in X-band. For the communication in the V/UHF band, a broadband conical antenna has been developed (225-400MHz). This antenna provides an optimized radiation pattern to insure the communications between the ship and the aircrafts. An experimental validation has been done with a prototype. In the second study, we have developed an electronically scanning antenna for a navigation radar. This antenna is based on a transmit-array technology including an illuminating feed and an antenna which generates the appropriate radiation pattern. A large part of the study has been done on the feed, which illuminates an array with specific dimensions (1530mmx100mm). Three different near-field focusing feeds have been developed and some of them have been validated experimentally. Then, two architectures of transmit-array antennas have been studied, using two different technologies: printed technology and a mixed technology with waveguide and horn.

MT nucleation from γ-tubulin complexes, located at centrosome, is an essential step in the formation of MT cytoskeleton. In mammalian cells, -tubulin is encoded by two genes. We functionally characterized two γ-tubulin proteins and have found that both are functionally equivalent. γ-Tubulin 2 is able to substitute for γ-tubulin 1 in MT nucleation. However, we revealed that unlike TUBG1, TUBG2 expression is downregulated in mouse preimplantation development. Mast cells represent effectors of the allergy reaction. Their activation by antigen induces number of cellular processes such as degranulation, proliferation and cytoskeleton rearrangements. The regulatory mechanisms of MT reorganization during mast cell activation are unknown. We identified new signaling proteins, GIT1 and PIX that interact with - tubulin. Depletion of GIT1 or PIX leads to changes in MT nucleation. GIT1 is phosphorylated on tyrosine and associates with γ-tubulin in a Ca2+ -dependent manner. Our data suggested a novel signaling pathway for MT rearrangement in mast cells where tyrosine kinase-activated GIT1 and βPIX work in concert with Ca2+ signaling to regulate MT nucleation. We tested the capability of GIT1 and PIX to influence -tubulin function in more cell types. We found out that GIT1/βPIX signaling proteins together...

No description available.

S. aureus est un pathogène majeur de l’Homme capable de produire une grande variété de facteurs de virulence tels que les phénol-solubles modulines alpha (PSM) et l’hémolysine delta (Hld). La transmission de S. aureus est essentiellement manu-portée mais les éléments favorisant sa dissémination dans la population restent inconnus. Les mastocytes étant connus pour libérer des médiateurs pruritogènes, nous avons suspecté leur implication dans la physiopathologie et la transmission des infections cutanées staphylococciques. Sur une lignée de mastocytes humains, l’Hld et les PSM1, montrés pour être produits in vivo, déclenchaient la libération de tels médiateurs. Chez S. aureus, la production des toxines est sous la dépendance du système de régulation globale Agr. Les souches de S. aureus appartenant au type Agr1, produisant significativement plus d’Hld et de PSM que les autres souches, ont été les plus fréquemment retrouvées au cours de l’année 2017 dans les infections cutanées staphylococciques. Ceci corrobore l’hypothèse selon laquelle une souche de S. aureus produisant des toxines capables d’interagir avec les mastocytes et induisant un prurit, diffuse plus facilement dans la population. Nous avons ensuite étudié la modulation de l’expression des PSM et d’Hld par des concentrations sub-inhibitrices d’antibiotiques. L’oxacilline induisait une inhibition de l’expression des PSM et d’Hld alors que la clindamycine entraînait plus fréquemment une induction de leur expression. Ces observations nous ont interrogé sur l’utilisation de la clindamycine considérée habituellement comme anti-toxinique et sur l’effet bénéfique ou délétère de l’effet inhibiteur de l’oxacilline / S. aureus is a major human pathogen able to produce several virulence factors such as phenol-solublemodulins alpha (PSMalpha) and delta hemolysin (Hld). S. aureus is essentially spread through hand butthe elements promoting its spreading stay unsolved. Mast cells release several soluble mediatorstriggering itching behavior. We suspect the mast cell involvement in spreading of S. aureus strains andin physiopathology of staphylococcal skin infections. Upon human mast cell line, we showed thatPSMalpha1 and Hld induced the release of mediators triggering itching behavior. Moreover, these toxinswere produced in vivo during staphylococcal skin infections. Expression of staphylococcal virulencefactors is regulated by global regulatory system Agr. Interestingly, we observed that S. aureus strainsbelonging in Agr1 produced higher quantity of PSMalpha and Hld than those belonging to Agr2 and Agr3,and were more frequently responsible to skin infections during the last year. This observation supportsour hypothesis whereby a strain producing toxins able to trigger mast cell mediator inducingscratching behavior, spreads electively in the community. Thereafter, we studied modulation of PSMalphaand Hld expression by sub-inhibitory concentration of antibiotics. We reported that oxacillin inducedan inhibitory effect on PSMalpha and Hld expression, while clindamycin resulted in more frequently aninducer effect. These results are discordant with these observed with Panton-Valentine leucocidin andalpha hemolysin and interrogate on clindamycin use for its anti-toxin activity and on benefic ordeleterious effect of oxacillin inhibitory effect

No description available.

Recognition of text from camera-captured scene/born-digital images help in the development of aids for the blind, unmanned navigation systems and spam filters. However, text in such images is not confined to any page layout, and its location within in the image is random in nature. In addition, motion blur, non-uniform illumination, skew, occlusion and scale-based degradations increase the complexity in locating and recognizing the text in a scene/born-digital image. Text localization and segmentation techniques are proposed for the born-digital image data set. The proposed OTCYMIST technique won the first place and placed in the third position for its performance on the text segmentation task in ICDAR 2011 and ICDAR 2013 robust reading competitions for born-digital image data set, respectively. Here, Otsu’s binarization and Canny edge detection are separately carried out on the three colour planes of the image. Connected components (CC’s) obtained from the segmented image are pruned based on thresholds applied on their area and aspect ratio. CC’s with sufficient edge pixels are retained. The centroids of the individual CC’s are used as nodes of a graph. A minimum spanning tree is built using these nodes of the graph. Long edges are broken from the minimum spanning tree of the graph. Pairwise height ratio is used to remove likely non-text components. CC’s are grouped based on their proximity in the horizontal direction to generate bounding boxes (BB’s) of text strings. Overlapping BB’s are removed using an overlap area threshold. Non-overlapping and minimally overlapping BB’s are used for text segmentation. These BB’s are split vertically to localize text at the word level. A word cropped from a document image can easily be recognized using a traditional optical character recognition (OCR) engine. However, recognizing a word, obtained by manually cropping a scene/born-digital image, is not trivial. Existing OCR engines do not handle these kinds of scene word images effectively. Our intention is to first segment the word image and then pass it to the existing OCR engines for recognition. In two aspects, it is advantageous: it avoids building a character classifier from scratch and reduces the word recognition task to a word segmentation task. Here, we propose two bottom-up approaches for the task of word segmentation. These approaches choose different features at the initial stage of segmentation. Power-law transform (PLT) was applied to the pixels of the gray scale born-digital images to non-linearly modify the histogram. The recognition rate achieved on born-digital word images is 82.9%, which is 20% more than the top performing entry (61.5%) in ICDAR 2011 robust reading competition. In addition, we explored applying PLT to the colour planes such as red, green, blue, intensity and lightness plane by varying the gamma value. We call this technique as Nonlinear enhancement and selection of plane (NESP) for optimal segmentation, which is an improvement over PLT. NESP chooses a particular plane with a proper gamma value based on Fisher discrimination factor. The recognition rate is 72.8% for scene images of ICDAR 2011 robust reading competition, which is 30% higher than the best entry (41.2%). The recognition rate is 81.7% and 65.9% for born-digital and scene images of ICDAR 2013 robust reading competition, respectively, using NESP. Another technique, midline analysis and propagation of segmentation (MAPS), has also been proposed. Here, the middle row pixels of the gray scale image are first segmented and the statistics of the segmented pixels are used to assign text and non-text labels to the rest of the image pixels using min-cut method. Gaussian model is fitted on the middle row segmented pixels before the assignment of other pixels. In MAPS, we assume the middle row pixels are least affected by any of the degradations. This assumption is validated by the good word recognition rate of 71.7% on ICDAR 2011 robust reading competition for scene images. The recognition rate is 83.8% and 66.0% for born-digital and scene images of ICDAR 2013 robust reading competition, respectively, using MAPS. The best reported results for ICDAR 2003 word images is 61.1% using custom lexicons containing the list of test words. On the other hand, NESP and MAPS achieve 66.2% and 64.5% for ICDAR 2003 word images without using any lexicon. By using similar custom lexicon, the recognition rates for ICDAR 2003 word images go up to 74.9% and 74.2% for NESP and MAPS methods, respectively. In place of passing an image segmented by a method, manually segmented word image is submitted to an OCR engine for benchmarking maximum possible recognition rate for each database. The recognition rates of the proposed methods and the benchmark results are reported on the seven publicly available word image data sets and compared with these of reported results in the literature. Since no good Kannada OCR is available, a classifier is designed to recognize Kannada characters and words from Chars74k data set and our own image collection, respectively. Discrete cosine transform (DCT) and block DCT are used as features to train separate classifiers. Kannada words are segmented using the same techniques (MAPS and NESP) and further segmented into groups of components, since a Kannada character may be represented by a single component or a group of components in an image. The recognition rate on Kannada words is reported for different features with and without the use of a lexicon. The obtained recognition performance for Kannada character recognition (11.4%) is three times the best performance (3.5%) reported in the literature.