Clinical Development Strategies and Outcomes in First-in-Human Trials of Monoclonal Antibodies.

PURPOSE: We conducted a comprehensive review of the design, implementation, and outcome of first-in-human (FIH) trials of monoclonal antibodies (mAbs) to clearly determine early clinical development strategies for this class of compounds. METHODS: We performed a PubMed search using appropriate terms to identify reports of FIH trials of mAbs published in peer-reviewed journals between January 2000 and April 2013. RESULTS: A total of 82 publications describing FIH trials were selected for analysis. Only 27 articles (33%) reported the criteria used for selecting the starting dose (SD). Dose escalation was performed using rule-based methods in 66 trials (80%). The median number of planned dose levels was five (range, two to 13). The median of the ratio between the highest planned dose and the SD was 27 (range, two to 3,333). Although in 56 studies (68%) at least one grade 3 or 4 toxicity event was reported, no dose-limiting toxicity was observed in 47 trials (57%). The highest planned dose was reached in all trials, but the maximum-tolerated dose (MTD) was defined in only 13 studies (16%). The median of the ratio between MTD and SD was eight (range, four to 1,000). The recommended phase II dose was indicated in 34 studies (41%), but in 25 (73%) of these trials, this dose was chosen without considering toxicity as the main selection criterion. CONCLUSION: This literature review highlights the broad design heterogeneity of FIH trials testing mAbs. Because of the limited observed toxicity, the MTD was infrequently reached, and therefore, the recommended phase II dose for subsequent clinical trials was only tentatively defined.

Pedaling rate is an important determinant of human oxygen uptake during exercise on the cycle ergometer.

Estimation of human oxygen uptake (V˙o2) during exercise is often used as an alternative when its direct measurement is not feasible. The American College of Sports Medicine (ACSM) suggests estimating human V˙o2 during exercise on a cycle ergometer through an equation that considers individual's body mass and external work rate, but not pedaling rate (PR). We hypothesized that including PR in the ACSM equation would improve its V˙o2 prediction accuracy. Ten healthy male participants' (age 19-48 years) were recruited and their steady-state V˙o2 was recorded on a cycle ergometer for 16 combinations of external work rates (0, 50, 100, and 150 W) and PR (50, 70, 90, and 110 revolutions per minute). V˙o2 was calculated by means of a new equation, and by the ACSM equation for comparison. Kinematic data were collected by means of an infrared 3-D motion analysis system in order to explore the mechanical determinants of V˙o2. Including PR in the ACSM equation improved the accuracy for prediction of sub-maximal V˙o2 during exercise (mean bias 1.9 vs. 3.3 mL O2 kg(-1) min(-1)) but it did not affect the accuracy for prediction of maximal V˙o2 (P > 0.05). Confirming the validity of this new equation, the results were replicated for data reported in the literature in 51 participants. We conclude that PR is an important determinant of human V˙o2 during cycling exercise, and it should be considered when predicting oxygen consumption.

A human immune data-informed vaccine concept elicits strong and broad T-cell specificities associated with HIV-1 control in mice and macaques

Background: None of the HIV T-cell vaccine candidates that have reached advanced clinical testing have been able to induce protective T cell immunity. A major reason for these failures may have been suboptimal T cell immunogen designs. Methods: To overcome this problem, we used a novel immunogen design approach that is based on functional T cell response data from more than 1,000 HIV-1 clade B and C infected individuals and which aims to direct the T cell response to the most vulnerable sites of HIV-1. Results: Our approach identified 16 regions in Gag, Pol, Vif and Nef that were relatively conserved and predominantly targeted by individuals with reduced viral loads. These regions formed the basis of the HIVACAT T-cell Immunogen (HTI) sequence which is 529 amino acids in length, includes more than 50 optimally defined CD4+ and CD8+ T-cell epitopes restricted by a wide range of HLA class I and II molecules and covers viral sites where mutations led to a dramatic reduction in viral replicative fitness. In both, C57BL/6 mice and Indian rhesus macaques immunized with an HTI-expressing DNA plasmid (DNA.HTI) induced broad and balanced T-cell responses to several segments within Gag, Pol, and Vif. DNA.HTI induced robust CD4+ and CD8+ T cell responses that were increased by a booster vaccination using modified virus Ankara (MVA.HTI), expanding the DNA.HTI induced response to up to 3.2% IFN-γ T-cells in macaques. HTI-specific T cells showed a central and effector memory phenotype with a significant fraction of the IFN-γ+ CD8+ T cells being Granzyme B+ and able to degranulate (CD107a+). Conclusions: These data demonstrate the immunogenicity of a novel HIV-1 T cell vaccine concept that induced broadly balanced responses to vulnerable sites of HIV-1 while avoiding the induction of responses to potential decoy targets that may divert effective T-cell responses towards variable and less protective viral determinants.

Human papillomavirus (HPV) in mothers before and after delivery – a three year follow-up study.

Human papillomavirus (HPV) infections in mothers are important to consider since pregnancy may affect the outcome of the infection and the mother may transmit HPV to the child. This thesis is part of the 3-year Finnish Family HPV Study on HPV infection dynamics within 329 families. The presence of maternal HPV antibodies and HPV DNA in placenta, umbilical cord blood and breast milk was examined. In addition, genital and oral HR-HPV carriage was studied among mothers with one or two pregnancies. At enrollment, seropositivity to HPV 6, 11, 16, 18 and 45 was recorded in 53 %, 21 %, 35 %, 21 % and 9 % of the mothers, respectively. Age at sexual debut, number of sexual partners, a history of genital warts and antibodies to LR/HR-HPV predicted HR/LR-HPV-seropositivity. During follow-up 27 %, 14 %, 17 %, 17 % and 7 % of the mothers seroconverted to the tested HPV-types, respectively. Decay of HPV-antibodies was rare. The mother’s new pregnancy was of minor impact in the outcome of oral and cervical HR-HPV infections. HPV-DNA was present in 4.2 % and 3.5 % of the placentas and umbilical cord blood samples, and in 4.5 % and 19.7 % of the breast milk samples collected at day 3 and month 2 postpartum, respectively. HPV-positivity in placenta/cord blood was related to a history of abnormal pap-smears or genital warts, and raised the risk of the neonate being HPV-positive at birth. The mode of delivery did not predict the HPVstatus of neonate, placenta, or cord blood. HPV DNA in breast milk was associated with oral HPV status of the father, but not with HPV status of the neonate. The results indicate that exposure to HPV is common and that part of the exposure might take place already early in life. Contrary to the common claim, pregnancy is not a risk factor for HPV.

High performance thin layer chromatographic determination of nifedipine in human serum after liquid-liquid extraction

A method using HPTLC for quantitation of nifedipine in serum was developed and validated. It includes a liquid-liquid extraction, and carbamazepine as internal standard. Chloroform: ethyl acetate: cyclohexane (19:2:2, v/v/v) was the mobile phase. The method showed good relationship (r = 0.996) (2.00 to 25.00 ng/band, corresponding to 0.02 and 0.25 ng/µL in serum). The % RSD of intra-assay and inter-assay, were between 0.57 and 3.56 and 1.16 to 3.60, respectively. LOD and LOQ were 0.72 and 0.86 ng/band, respectively. The recovery values were between 93 and 102%. Rf for nifedipine and carbamazepine were 0.31 and 0.10, respectively.

UV determination of epinephrine, uric acid, and acetaminophen in pharmaceutical formulations and some human body fluids using multivariate calibration

In this work, a spectrophotometric methodology was applied in order to determine epinephrine (EP), uric acid (UA), and acetaminophen (AC) in pharmaceutical formulations and spiked human serum, plasma, and urine by using a multivariate approach. Multivariate calibration methods such as partial least squares (PLS) methods and its derivates were used to obtain a model for simultaneous determination of EP, UA and AC with good figures of merit and mixture design was in the range of 1.8 - 35.3, 1.7 - 16.8, and 1.5 - 12.1 µg mL-1. The 2nd derivate PLS showed recoveries of 95.3 - 103.3, 93.3 - 104.0, and 94.0 - 105.5 µg mL-1 for EP, UA, and AC, respectively.

Characterisation of Human Neutral and Lysosomal alpha-Mannosidases

Neutral alpha-mannosidase and lysosomal MAN2B1 alpha-mannosidase belong to glycoside hydrolase family 38, which contains essential enzymes required for the modification and catabolism of asparagine-linked glycans on proteins. MAN2B1 catalyses lysosomal glycan degradation, while neutral α-mannosidase is most likely involved in the catabolism of cytosolic free oligosaccharides. These mannose containing saccharides are generated during glycosylation or released from misfolded glycoproteins, which are detected by quality control in the endoplasmic reticulum. To characterise the biological function of human neutral α-mannosidase, I cloned the alpha-mannosidase cDNA and recombinantly expressed the enzyme. The purified enzyme trimmed the putative natural substrate Man9GlcNAc to Man5GlcNAc, whereas the reducing end GlcNAc2 limited trimming to Man8GlcNAc2. Neutral α-mannosidase showed highest enzyme activity at neutral pH and was activated by the cations Fe₂+, Co2+ and Mn₂+, Cu2+ in turn had a strong inhibitory effect on alpha-mannosidase activity. Analysis of its intracellular localisation revealed that neutral alpha-mannosidase is cytosolic and colocalises with proteasomes. Further work showed that the overexpression of neutral alpha-mannosidase affected the cytosolic free oligosaccharide content and led to enhanced endoplasmic reticulum associated degradation and underglycosylation of secreted proteins. The second part of the study focused on MAN2B1 and the inherited lysosomal storage disorder α-mannosidosis. In this disorder, deficient MAN2B1 activity is associated with mutations in the MAN2B1 gene. The thesis reports the molecular consequences of 35 alpha-mannosidosis associated mutations, including 29 novel missense mutations. According to experimental analyses, the mutations fall into four groups: Mutations, which prevent transport to lysosomes are accompanied with a lack of proteolytic processing of the enzyme (groups 1 and 3). Although the rest of the mutations (groups 2 and 4) allow transport to lysosomes, the mutated proteins are less efficiently processed to their mature form than is wild type MAN2B1. Analysis of the effect of the mutations on the model structure of human lysosomal alpha-mannosidase provides insights on their structural consequences. Mutations, which affect amino acids important for folding (prolines, glycines, cysteines) or domain interface interactions (arginines), arrest the enzyme in the endoplasmic reticulum. Surface mutations and changes, which do not drastically alter residue volume, are tolerated better. Descriptions of the mutations and clinical data are compiled in an α-mannosidosis database, which will be available for the scientific community. This thesis provides a detailed insight into two ubiquitous human alpha-mannosidases. It demonstrates that neutral alpha-mannosidase is involved in the degradation of cytosolic oligosaccharides and suggests that the regulation of this α-mannosidase is important for maintaining the cellular homeostasis of N-glycosylation and glycan degradation. The study on alpha-mannosidosis associated mutations identifies multiple mechanisms for how these mutations are detrimental for MAN2B1 activity. The α-mannosidosis database will benefit both clinicians and scientific research on lysosomal alpha‑mannosidosis.

Application of Computational Fluid Dynamics in Modeling Blood Flow in Human Thoracic Aorta

The aim of this study was to simulate blood flow in thoracic human aorta and understand the role of flow dynamics in the initialization and localization of atherosclerotic plaque in human thoracic aorta. The blood flow dynamics in idealized and realistic models of human thoracic aorta were numerically simulated in three idealized and two realistic thoracic aorta models. The idealized models of thoracic aorta were reconstructed with measurements available from literature, and the realistic models of thoracic aorta were constructed by image processing Computed Tomographic (CT) images. The CT images were made available by South Karelia Central Hospital in Lappeenranta. The reconstruction of thoracic aorta consisted of operations, such as contrast adjustment, image segmentations, and 3D surface rendering. Additional design operations were performed to make the aorta model compatible for the numerical method based computer code. The image processing and design operations were performed with specialized medical image processing software. Pulsatile pressure and velocity boundary conditions were deployed as inlet boundary conditions. The blood flow was assumed homogeneous and incompressible. The blood was assumed to be a Newtonian fluid. The simulations with idealized models of thoracic aorta were carried out with Finite Element Method based computer code, while the simulations with realistic models of thoracic aorta were carried out with Finite Volume Method based computer code. Simulations were carried out for four cardiac cycles. The distribution of flow, pressure and Wall Shear Stress (WSS) observed during the fourth cardiac cycle were extensively analyzed. The aim of carrying out the simulations with idealized model was to get an estimate of flow dynamics in a realistic aorta model. The motive behind the choice of three aorta models with distinct features was to understand the dependence of flow dynamics on aorta anatomy. Highly disturbed and nonuniform distribution of velocity and WSS was observed in aortic arch, near brachiocephalic, left common artery, and left subclavian artery. On the other hand, the WSS profiles at the roots of branches show significant differences with geometry variation of aorta and branches. The comparison of instantaneous WSS profiles revealed that the model with straight branching arteries had relatively lower WSS compared to that in the aorta model with curved branches. In addition to this, significant differences were observed in the spatial and temporal profiles of WSS, flow, and pressure. The study with idealized model was extended to study blood flow in thoracic aorta under the effects of hypertension and hypotension. One of the idealized aorta models was modified along with the boundary conditions to mimic the thoracic aorta under the effects of hypertension and hypotension. The results of simulations with realistic models extracted from CT scans demonstrated more realistic flow dynamics than that in the idealized models. During systole, the velocity in ascending aorta was skewed towards the outer wall of aortic arch. The flow develops secondary flow patterns as it moves downstream towards aortic arch. Unlike idealized models, the distribution of flow was nonplanar and heavily guided by the artery anatomy. Flow cavitation was observed in the aorta model which was imaged giving longer branches. This could not be properly observed in the model with imaging containing a shorter length for aortic branches. The flow circulation was also observed in the inner wall of the aortic arch. However, during the diastole, the flow profiles were almost flat and regular due the acceleration of flow at the inlet. The flow profiles were weakly turbulent during the flow reversal. The complex flow patterns caused a non-uniform distribution of WSS. High WSS was distributed at the junction of branches and aortic arch. Low WSS was distributed at the proximal part of the junction, while intermedium WSS was distributed in the distal part of the junction. The pulsatile nature of the inflow caused oscillating WSS at the branch entry region and inner curvature of aortic arch. Based on the WSS distribution in the realistic model, one of the aorta models was altered to induce artificial atherosclerotic plaque at the branch entry region and inner curvature of aortic arch. Atherosclerotic plaque causing 50% blockage of lumen was introduced in brachiocephalic artery, common carotid artery, left subclavian artery, and aortic arch. The aim of this part of the study was first to study the effect of stenosis on flow and WSS distribution, understand the effect of shape of atherosclerotic plaque on flow and WSS distribution, and finally to investigate the effect of lumen blockage severity on flow and WSS distributions. The results revealed that the distribution of WSS is significantly affected by plaque with mere 50% stenosis. The asymmetric shape of stenosis causes higher WSS in branching arteries than in the cases with symmetric plaque. The flow dynamics within thoracic aorta models has been extensively studied and reported here. The effects of pressure and arterial anatomy on the flow dynamic were investigated. The distribution of complex flow and WSS is correlated with the localization of atherosclerosis. With the available results we can conclude that the thoracic aorta, with complex anatomy is the most vulnerable artery for the localization and development of atherosclerosis. The flow dynamics and arterial anatomy play a role in the localization of atherosclerosis. The patient specific image based models can be used to diagnose the locations in the aorta vulnerable to the development of arterial diseases such as atherosclerosis.

Local control of human papillomavirus infection after anal condylomata acuminata eradication

OBJECTIVE: To verify whether the eradication of anal condylomata acuminata was effective for local control of HPV infection using anal colposcopy and anal brush cytology.METHODS: We evaluated 147 patients treated for anal margin and/or anal canal condyloma, with 108 HIV-positive and 39 HIV-negative individuals. The average age for males was 40 years for HIV-positive and 27.5 for HIV-negative. In females, the mean age was 37.5 years for HIV-positive and 31.5 for HIV-negative.RESULTS: Twenty-four patients (16.3%) had normal cytology and anal colposcopy, 16 (10.9%) normal cytology and altered anal colposcopy, 52 (35.4%) normal anal colposcopy and altered cytology, and 55 (37.4%) had altered cytology and anal colposcopy.CONCLUSION: the eradication of clinical lesions failed to locally control HPV infection.

Infection by Toxoplasma gondii in Neotropical non-human primates

Toxoplasma gondii (Nicolle et Manceaux, 1909) is an obligatory intracellular protozoan parasite of warm animals, including human and non-human primates. Domestic and wild felids are considered definitive hosts. Several authors have already identified lesions in New World primates caused by T. gondii. Nevertheless, little is known about serological studies on those animals. With this reason, New World non-human primates of the genera Cebus and Callithrix that were apprehended by governmental authorities and sent to the Wildlife Screening Center (Cetas)/IBAMA, at the municipality of Seropédica, state of Rio Janeiro, were bled and sera were submitted to the indirect hemagglutination test for detection of anti-T. gondii antibodies. From 21 sera of Cebus primates, 76.19% (16/21) had anti-T. gondii antibodies. Titles varied from 16 to 2048. In samples from 21 Callithrix, only 4.5% (1/22) had anti-T. gondii antibodies. Only one animal had a title of 32. During all the time those animals were clinical evaluated until sample was collected; none of them had any clinical sign or sequel related to infection by T. gondii. The fact that the origin of these primates is unknown and that there is no information about their feeding habits before captivity makes it difficult to determine the source of T. gondii infection.

Liminal Monster and the Conflict Between Human and Machine: The Shrike in Dan Simmons’ Hyperion and The Fall of Hyperion

Tarkastelen tutkielmassani Dan Simmonsin kaksiosaista tieteisfiktioteosta, joka koostuu romaaneista Hyperion ja The Fall of Hyperion. Keskityn teoksissa esiintyvään Shrike-hirviöön, joka edustaa ihmiskunnan pelkäämää potentiaalista konfliktia ihmisten ja koneiden välillä. Pelko ja konflikti ovat keskeisiä teemoja paitsi tieteisfiktiossa, myös hirviöteoksissa yleensä, ja näiden kahden käyttö samassa kertomuksessa luo otolliset edellytykset nyky-yhteiskunnan ahdistusten kuvaamiseen. Hirviöitä ja tieteisfiktiota on tätä nykyä tutkittu melko laajalti, mutta Shrike on aiemmin jäänyt vähälle huomiolle. Lähtökohtaisen teoreettisen viitekehyksen tutkimukselleni ovat luoneet Jeffrey Cohenin Monster Theory: Reading Culture, Stephen Asman On Monsters: An Unnatural History of Our Worst Fears sekä Holly Lynn Baumgartnerin ja Roger Davisin At the Interface: Hosting the Monster. Teoksista kokoamani hirviöteorian kautta tarkastelen sitä, miten Shriken puoliksi orgaaninen ja puoliksi keinotekoinen keho heijastaa niitä romaaneissa esiintyviä osa-alueita, joista tulevaisuudenpelko ja ihmisten ja koneiden väliseen konfliktin uhka koostuu. Koska Shrike on puoliksi orgaaninen ja puoliksi keinotekoinen, se on näiden ominaisuuksien kynnyksellä; tässä risteytyneessä kehossa yhdistyvät molemmat ääripäät, jolloin tämä keho myös symboloi osapuolten välistä konfliktia. Konfliktin lisäksi Shrike ilmentää niitä vastakkaisuuksia, joista ihmisten ja koneiden välisen konfliktin pelko rakentuu: itseyttä ja toiseutta, houkuttelevuutta ja luotaantyöntävyyttä, menneisyyttä ja tulevaisuutta sekä utopiaa ja dystopiaa.

Outcome of human papillomavirus infection among men in the Finnish Family HPV Study

Ihmisen papilloomaviruksen taudinkuva suomalaisperheiden seurantatutkimuksen mieskohortissa Tieto ihmisen papilloomaviruksen (HPV) yhteydestä eri anatomisten alueiden sairauksien syntyyn on lisännyt mielenkiintoa miehen papilloomavirustulehduksen taudinkulun selvittämiseksi. Tämä väitöskirjatyö on osa suomalaista seurantatutkimusta, jossa tutkitaan HPVinfektioiden tartuntareittejä 329 perheessä. Väitöstyössä keskitytään tutkimukseen osallistuneiden 131 miehen aineistoon. Suun limakalvonäytteet otettiin seitsemässä aikapisteessä. Lisäksi otettiin sukuelinalueen näytteet kahdella seurantakäynnillä. Riskitekijöitä kartoittava kyselytutkimus teetettiin tutkimuksen alkutilanteessa sekä viimeisellä seurantakäynnillä. Oireettomat HPV infektiot olivat alkutilanteessa yleisiä molemmilla sukupuolilla (miesten suu 18,3 % ja sukuelinalue 35,9 %, naisten suu 17,2 % ja kohdunsuu 18,8 %), mutta HPV:n genotyyppien vastaavuus partnerien välillä oli vähäinen. Naisen, mutta ei miehen, seksuaalinen riskikäyttäytyminen oli yhteydessä pariskunnan HPV tyyppien vastaavuuteen. Partnerin ja siviilisäädyn vaihtaminen lisäsivät miehen riskiä saada uusia HPV infektioita. Miehen suun limakalvonäytteistä löytyi kaikkiaan 17 eri HPV tyyppiä. Suun HPV-tulehduksen esiintyvyys vaihteli eri aikapisteissä 15 %:sta 31 %:iin. Uusien HPV tulehdusten ilmaantumisaika vaihteli 3,9 ja 25,7 kuukauden välillä. Suun HPV infektio parani valtaosalla miehistä. Suun krooninen HPV-infektio todettiin 14 %:lla miehistä. Näiden infektioiden keskimääräinen kesto vaihteli 6.0:sta 30.7:ään kuukauteen. Tupakointi lisäsi korkean riskin HPV tyyppien aiheuttamien suun kroonisten infektioiden riskiä, kun taas aikaisemmin sairastetut sukuelinten kondyloomat suojasivat siltä. Tuloksemme osoittavat, että miehen oireeton HPV tulehdus on yleinen suussa ja sukuelinten alueella. Vakaa parisuhde suojaa uusilta HPV tulehduksilta. Tupakoinnilla on keskeinen merkitys suun HPV-infektion kroonistumisessa.

Linear competitive inhibition of human tissue kallikrein by 4-aminobenzamidine and benzamidine and linear mixed inhibition by 4-nitroaniline and aniline

Hydrolysis of D-valyl-L-leucyl-L-arginine p-nitroanilide (7.5-90.0 µM) by human tissue kallikrein (hK1) (4.58-5.27 nM) at pH 9.0 and 37ºC was studied in the absence and in the presence of increasing concentrations of 4-aminobenzamidine (96-576 µM), benzamidine (1.27-7.62 mM), 4-nitroaniline (16.5-66 µM) and aniline (20-50 mM). The kinetic parameters determined in the absence of inhibitors were: Km = 12.0 ± 0.8 µM and k cat = 48.4 ± 1.0 min-1. The data indicate that the inhibition of hK1 by 4-aminobenzamidine and benzamidine is linear competitive, while the inhibition by 4-nitroaniline and aniline is linear mixed, with the inhibitor being able to bind both to the free enzyme with a dissociation constant Ki yielding an EI complex, and to the ES complex with a dissociation constant Ki', yielding an ESI complex. The calculated Ki values for 4-aminobenzamidine, benzamidine, 4-nitroaniline and aniline were 146 ± 10, 1,098 ± 91, 38.6 ± 5.2 and 37,340 ± 5,400 µM, respectively. The calculated Ki' values for 4-nitroaniline and aniline were 289.3 ± 92.8 and 310,500 ± 38,600 µM, respectively. The fact that Ki'>Ki indicates that 4-nitroaniline and aniline bind to a second binding site in the enzyme with lower affinity than they bind to the active site. The data about the inhibition of hK1 by 4-aminobenzamidine and benzamidine help to explain previous observations that esters, anilides or chloromethyl ketone derivatives of Nalpha-substituted arginine are more sensitive substrates or inhibitors of hK1 than the corresponding lysine compounds.

Narrow-band 1, 2, 3, 4, 8, 16 and 24 cycles/360º angular frequency filters

We measured human frequency response functions for seven angular frequency filters whose test frequencies were centered at 1, 2, 3, 4, 8, 16 or 24 cycles/360º using a supra-threshold summation method. The seven functions of 17 experimental conditions each were measured nine times for five observers. For the arbitrarily selected filter phases, the maximum summation effect occurred at test frequency for filters at 1, 2, 3, 4 and 8 cycles/360º. For both 16 and 24 cycles/360º test frequencies, maximum summation occurred at the lower harmonics. These results allow us to conclude that there are narrow-band angular frequency filters operating somehow in the human visual system either through summation or inhibition of specific frequency ranges. Furthermore, as a general result, it appears that addition of higher angular frequencies to lower ones disturbs low angular frequency perception (i.e., 1, 2, 3 and 4 cycles/360º), whereas addition of lower harmonics to higher ones seems to improve detection of high angular frequency harmonics (i.e., 8, 16 and 24 cycles/360º). Finally, we discuss the possible involvement of coupled radial and angular frequency filters in face perception using an example where narrow-band low angular frequency filters could have a major role.

The Shiga toxin 2 B subunit inhibits net fluid absorption in human colon and elicits fluid accumulation in rat colon loops

Shiga toxin (Stx)-producing Escherichia coli (STEC) colonizes the large intestine causing a spectrum of disorders, including watery diarrhea, bloody diarrhea (hemorrhagic colitis), and hemolytic-uremic syndrome. It is estimated that hemolytic-uremic syndrome is the most common cause of acute renal failure in infants in Argentina. Stx is a multimeric toxin composed of one A subunit and five B subunits. In this study we demonstrate that the Stx2 B subunit inhibits the water absorption (Jw) across the human and rat colonic mucosa without altering the electrical parameters measured as transepithelial potential difference and short circuit current. The time-course Jw inhibition by 400 ng/ml purified Stx2 B subunit was similar to that obtained using 12 ng/ml Stx2 holotoxin suggesting that both, A and B subunits of Stx2 contributed to inhibit the Jw. Moreover, non-hemorrhagic fluid accumulation was observed in rat colon loops after 16 h of treatment with 3 and 30 ng/ml Stx2 B subunit. These changes indicate that Stx2 B subunit induces fluid accumulation independently of A subunit activity by altering the usual balance of intestinal absorption and secretion toward net secretion. In conclusion, our results suggest that the Stx2 B subunit, which is non-toxic for Vero cells, may contribute to the watery diarrhea observed in STEC infection. Further studies will be necessary to determine whether the toxicity of Stx2 B subunit may have pathogenic consequences when it is used as a component in an acellular STEC vaccine or as a vector in cancer vaccines.