Splenectomy and experimental infection of mice by a virulent strain of trypanosoma cruzi

Splenectomy seems to increase susceptibility of mice to a jurther infection with a virulent strain of Trypanosoma cruzi. Parasitemia increases with splenectomy and the sooner the infection follows the operation, the greater the parasitemia. The mortality rate seems to have not been influenced by splenectomy.

Serial heart rate changes in rats inoculated by conjunctival instillation of Trypanosoma cruzi obtained from bug faeces

The cardiac effects of experimentally induced myocarditis, when the parasite is obtained from mouse blood, are well known. However, the consequences of the infection when the parasites are obtained from bug faeces are less well defined. In the present investigation, we have used the "Y" strain of Trypanosoma cruzi, which was maintained in Rhodnius prolixus by repeated passages in mice. The faeces of 30 infected bugs were collected, the number of parasites counted and 4,000 parasites inoculated by the conjunctival route in 60 rats. Twenty-nine other rats received faeces from noninfected bugs (sham-inoculated controls) and 40 were used as normal controls. The heart rate of the three groups of animals was recorded under general anesthesia with ether. The heart rate, at day 0 pre-inoculation, was similar in the three groups of animals (Controls: 379 ± 27 beats/min Mean ± SD; Sham-inoculated: 366 ± 31; Infected: 351 ± 29) (p> 0.05). In the infected animals, the mean heart rate began to increase significantly by day 12 following infection (375 ± 31), reaching the highest values between days 18 (390 ± 33) and 21 (403 ± 33) and returned to baseline by day 30 (359 ± 28) (p< 0.05). The heart rate changes were statistically different from those observed in the sham-inoculated controls and in the control animals. Therefore, these heart rate changes were provoked by the Trypanosoma cruzi-induced infection. Thus, it appears that irrespective of the source of the parasite and route of inoculation Trypanosoma cruziacute infection provokes a transient sinus tachycardia.

Clonal structure of Trypanosoma cruzi Colombian strain (biodeme Type III): biological, isoenzymic and histopathological analysis of seven isolated clones

The clonal structure of the Colombian strain of Trypanosoma cruzi, biodeme Type III and zymodeme 1, was analyzed in order to characterize its populations and to establish its homogeneity or heterogeneity. Seven isolated clones presented the basic characteristics of Biodeme Type III, with the same patterns of parasitemic curves, tissue tropism to skeletal muscle and myocardium, high pathogenicity with extensive necrotic-inflammatory lesions from the 20th to 30th day of infection. The parental strain and its clones C1, C3, C4 and C6, determined the higher levels of parasitemia, 20 to 30 days of infection, with high mortality rate up to 30 days (79 to 100%); clones C2, C5 and C7 presented lower levels of parasitemia, with low mortality rates (7.6 to 23%). Isoenzymic patterns, characteristic of zymodeme 1, (Z1) were similar for the parental strain and its seven clones. Results point to a phenotypic homogeneity of the clones isolated from the Colombian strain and suggest the predominance of a principal clone, responsible for the biological behavior of the parental strain and clones.

Flexible gastrointestinal motility pressure sensors based on aluminum thin-film strain-gauge arrays

This paper reports on an innovative approach to measuring intraluminal pressure in the upper gastrointestinal (GI) tract, especially monitoring GI motility and peristaltic movements. The proposed approach relies on thin-film aluminum strain gauges deposited on top of a Kapton membrane, which in turn lies on top of an SU-8 diaphragm-like structure. This structure enables the Kapton membrane to bend when pressure is applied, thereby affecting the strain gauges and effectively changing their electrical resistance. The sensor, with an area of 3.4 mm2, is fabricated using photolithography and standard microfabrication techniques (wet etching). It features a linear response (R2 = 0.9987) and an overall sensitivity of 2.6 mV mmHg−1. Additionally, its topology allows a high integration capability. The strain gauges’ responses to pressure were studied and the fabrication process optimized to achieve high sensitivity, linearity, and reproducibility. The sequential acquisition of the different signals is carried out by a microcontroller, with a 10-bit ADC and a sample rate of 250 Hz. The pressure signals are then presented in a user-friendly interface, developed using the Integrated Development Environment software, QtCreator IDE, for better visualization by physicians.

The effect of subminimal inhibitory concentrations of penicillin on growth rate and haemolysin activity of group G Streptococcus

The influence of the subminimal inhibitory concentrations (1/3 and 1/4 of the MIC) of penicillin on growth rate and on haemolysin production of a strain of group G Streptococcus was studied. It was shown that 1/3 of the MIC almost completely inhibited the bacterial growth, but it was not able to inhibit haemolysin activity in the culture supernate. The generation time of bacteria grown in 1/4 of the MIC was approximately twice longer than that of the control culture. In all cultures, the haemolysin, after being produced (or liberated), reached a peak and decreased to low levels, which could suggest that group G Streptococcus produces some end products of metabolism that are able to inhibit haemolysin activity.

Characterization of a Trypanosoma rangeli Strain of Colombian Origin

A Colombian strain of Trypanosoma rangeli was characterized by analyzing its behaviour in different axenic and cellular culture, its infection rate and the histopathological lesions produced in experimental animals. Although slight inflammatory infiltrations were shown in different histopathological sections, no pseudocysts could be observed. Grace's insect medium is better than liver infusion tryptose or artificial triatomine urine supplemented with proline when studying T. rangeli metacyclogenesis, with a peak of 32% trypomastigotes. High infection rates were found in VERO and J774 cells. Because of its 100% infectivity rates and adequacy of parasitemia levels, C23 strain is a suitable model of T. rangeli biology study

A non-circadian role for clock-genes in sleep homeostasis: a strain comparison.

BACKGROUND: We have previously reported that the expression of circadian clock-genes increases in the cerebral cortex after sleep deprivation (SD) and that the sleep rebound following SD is attenuated in mice deficient for one or more clock-genes. We hypothesized that besides generating circadian rhythms, clock-genes also play a role in the homeostatic regulation of sleep. Here we follow the time course of the forebrain changes in the expression of the clock-genes period (per)-1, per2, and of the clock-controlled gene albumin D-binding protein (dbp) during a 6 h SD and subsequent recovery sleep in three inbred strains of mice for which the homeostatic sleep rebound following SD differs. We reasoned that if clock genes are functionally implicated in sleep homeostasis then the SD-induced changes in gene expression should vary according to the genotypic differences in the sleep rebound. RESULTS: In all three strains per expression was increased when animals were kept awake but the rate of increase during the SD as well as the relative increase in per after 6 h SD were highest in the strain for which the sleep rebound was smallest; i.e., DBA/2J (D2). Moreover, whereas in the other two strains per1 and per2 reverted to control levels with recovery sleep, per2 expression specifically, remained elevated in D2 mice. dbp expression increased during the light period both during baseline and during SD although levels were reduced during the latter condition compared to baseline. In contrast to per2, dbp expression reverted to control levels with recovery sleep in D2 only, whereas in the two other strains expression remained decreased. CONCLUSION: These findings support and extend our previous findings that clock genes in the forebrain are implicated in the homeostatic regulation of sleep and suggest that sustained, high levels of per2 expression may negatively impact recovery sleep.

Vectorial competence of Aedes aegypti (Linnaeus 1762) Rio de Janeiro Strain, to Dirofilaria immitis (Leidy 1856)

Dirofilaria immitis (Leidy 1856), a nematode parasite, is the etiologic agent of canine heartworm disease and mosquitoes are essential intermediate hosts. Mosquito susceptibility to the worms differ with species, strains and also among individuals of the same strain. To evaluate the degree of susceptibility of Rio de Janeiro laboratory raised strain of Aedes aegypti, we fed mosquitoes on canine blood with different densities of microfilariae (mf). There was no significant difference in the rate of development among the three different densities of mf. Infective larvae were found in the head and proboscis of all mosquitoes provided bloodmeals with different densities of mf after the 11th day post-infection. The infection rate of mosquitoes after ingestion of blood containing 3,000 mf/ml, 5,000 mf/ml and 7,000 mf/ml were 55.3%, 66.7% and 100%, respectively. The vector efficiency indices ranged from 1.6 to 9.3. The finding of L3 stage larvae, high infection rates and vector efficiency indices suggest that Ae. aegypti, Rio de Janeiro laboratory strain, is a potential vector of D. immitis, although of low efficiency.

Isochorismate synthase (PchA), the first and rate-limiting enzyme in salicylate biosynthesis of Pseudomonas aeruginosa.

In Pseudomonas aeruginosa the extracellular metabolite and siderophore pyochelin is synthesized from two major precursors, chorismate and l-cysteine via salicylate as an intermediate. The regulatory role of isochorismate synthase, the first enzyme in the pyochelin biosynthetic pathway, was studied. This enzyme is encoded by pchA, the last gene in the pchDCBA operon. The PchA protein was purified to apparent electrophoretic homogeneity from a PchA-overexpressing P. aeruginosa strain. The native enzyme was a 52-kDa monomer in solution, and its activity strictly depended on Mg(2+). At pH 7.0, the optimum, a K(m) = 4.5 microm and a k(cat) = 43.1 min(-1) were determined for chorismate. No feedback inhibitors or other allosteric effectors were found. The intracellular PchA concentration critically determined the rate of salicylate formation both in vitro and in vivo. In cultures grown in iron-limiting media to high cell densities, overexpression of the pchA gene resulted in overproduction of salicylate as well as in enhanced pyochelin formation. From this work and earlier studies, it is proposed that one important factor influencing the flux through the pyochelin biosynthetic pathway is the PchA concentration, which is determined at a transcriptional level, with pyochelin acting as a positive signal and iron as a negative signal.

Construction and analysis of a new conditional ferritin H knockout mouse strain/

Résumé Le fer joue un rôle important dans la plupart des fonctions biologiques mais sa présence excessive provoque la production de molécules réactives d'oxygène (ROS) qui peuvent contribuer à diverses maladies. La protéine de stockage du fer, la ferritine H, capte l'excès en fer et le stocke sous forme non-toxique, ce qui empêche des dommages potentiels. La délétion de la ferritine H dans des souris knock-out a été essayée antérieurement, mais ces souris mouraient au stade précoce du développement embryonnaire. Pour étudier l'importance du fer, et en particulier son stockage dans la ferritine, et pour pouvoir mieux comprendre les fonctions de la ferritine H, nous avons créé un modèle de souris knock-out conditionnelles de la ferritine H, selon le système classique de Cre-LoxP. Le premier exon et la région du promoteur du gène de la ferritine H ont été entourés de sites loxP. La mortalité embryonnaire provoquée par la délétion constitutive du gène de la ferritine H a été confirmée en croisant nos souris avec des souris exprimant nestin-Cre1. En croisant nos souris avec des souris transgéniques Mx-Cre, nous avons observé que l'induction de Cre par injection de polyI-polyC provoque la délétion presque complète de la ferritine H dans le foie (> 99%) et la rate (> 88%). Ces tissus ont également perdu une grande partie de leur réserve de fer. Cette observation apporte pour la première fois la preuve in vivo que la ferritine H est indispensable pour le stockage du fer, que les fonctions de la ferritine H et de la ferritine L ne sont pas équivalentes, et que la ferritine L ne peut pas assumer seule la fonction de stockage du fer. Dans le foie des souris knock-out, l'expression de l'ARN messager de l'hepcidine a été induite après 10 jours. En même temps, l'expression de l'ARN messager des gènes codant pour des protéines de l'absorption de fer (DMT1, ferroportin, Dcytb1 et hephaestin) a été réprimée mais dans le duodénum seulement. L'expression d'hepcidine est inversément corrélée avec celle des gènes liés à l'absorption de fer. Cette observation corrobore des études antérieures. Mais, en plus, elle montre également que cette répression se produit seulement dans l'intestin. Nous pouvons ainsi tirer la conclusion suivante : ou bien l'hepcidine a un récepteur spécifique dans le duodénum ou bien les gènes liés à l'absorption de fer dans le duodénum ont un facteur spécifique de transcription sensible à l'hepcidine. Aucune répression de DMT1 et de ferroportin n'a été observée dans les macrophages de la rate après l'induction d'hepcidine. La délétion de ferritine H a entraîné une augmentation du taux de mortalité des cellules hépatiques, ainsi que des altérations dans l'architecture normale du tissu de la rate. Vu par l'immunohistologie, le nombre de lymphocytes B et T était réduit dans la rate, tendant à démontrer que la ferritine H et l'homéostase du fer jouent un rôle dans l'immunité. En conclusion, le modèle de souris knock-out conditionnelles de la ferritine H nous fournit un outil précieux pour l'étude in vivo du rôle joué par la ferritine dans l'homéostase du fer, dans les dommages créés par les ROS, ainsi que dans l'apoptose et l'immunité. Summary Iron plays an important role in most biological functions. However, excess of iron results in production of reactive oxygen species (ROS) which could substantially contribute to pathology of various diseases. Ferritin H scavenges excess of iron and stores it in non-toxic form and potentially prevents the damage. Fenitin H targeting in mice has been attempted before, however, straight knockout was lethal in early embryonic stage. To study the role of iron and its storage protein ferritin and to further elucidate ferritin H functions, we aimed at creating a conditional ferritin H knockout mouse model by classical Cre-LoxP system. First exon along with promoter region of the ferritin H gene was foxed. Embryonic lethality of the constitutive ferritin H deletion was confirmed by crossing the foxed mice with mice expressing nestin Cre-1 as transgene. Almost complete deletion was observed in liver (> 99%) and spleen (>88%) upon induction of Cre by injecting polyI-polyC in Fth Lox/Lox; MxCre mice. These tissues also lost substantial fraction of their iron stores. This provides first in vivo evidence that ferritin H is required for iron storage, ferritin H and L functions are not redundant and that ferritin L cannot perform iron storage function alone. Hepcidin mRNA expression was induced after 10 days in the livers of deleted mice and, simultaneously, mRNA expression of iron absorption related genes (DMT 1, ferroportin, Dcytb1 and hephaestin) was repressed in duodenum only. Hepcidin expression is inversely correlated with that of duodenal iron absorption related genes. This is in agreement with previous studies. However, we also show that this repression happens only in intestine. This leads to the conclusion that either hepcidin has a specific receptor in duodenum or the iron absorption related genes have duodenum specific transcription factor that is responsive to hepcidin. No repression of DMT1 and ferroportin was observed in spleen macrophages upon hepcidin induction. Ferritin H deletion showed increased cell death in liver and disruption of normal architecture of spleen. B lymphocytes were reduced in spleen on immunohistology which point towards a role of ferritin H and iron homeostasis in immunity. In conclusion, ferritin H conditional knockout mouse model provides us with an invaluable tool to study the in vivo role of ferritin H in iron homeostasis, ROS mediated damage, apoptosis and immunity.

Strain diversity of mycobacteria isolated from pulmonary tuberculosis patients at Debre Birhan Hospital, Ethiopia.

BACKGROUND: Ethiopia ranks seventh in the list of 22 high tuberculosis (TB) burden countries, with an incidence rate of 379 cases per 100 000 population for TB all forms. However, information on the genomic diversity of Mycobacterium tuberculosis in Ethiopia is limited. OBJECTIVE: To investigate the molecular characteristics of M. tuberculosis strains implicated in pulmonary TB in the study area. METHODS AND RESULTS: A cross-sectional study was conducted using socio-demographic, clinical and culture data combined with molecular typing analysis. The proportion of TB and M. tuberculosis isolates was not associated with risk factors (P > 0.05). Of 99 sputum samples, 80.8% were culture-positive. Speciation of isolates showed that 88.8% were M. tuberculosis. Further characterisation led to the identification of 27 different spoligotype patterns of M. tuberculosis; the most dominant shared types were SIT149, SIT53 and SIT54. Of the 27 strains, three strains were new and were reported to the SITVIT database. More than two thirds of the strains belonged to the Euro-American lineage. CONCLUSION: This study shows the presence of several clusters and new strains of M. tuberculosis circulating in pulmonary TB patients in the study area, suggesting recent transmission. Nationwide studies are recommended to map the population structure of M. tuberculosis and set control measures.

Rate and processes of river network rearrangement during incipient faulting: The case of the Cahabon river, Guatemala

Deeply incised river networks are generally regarded as robust features that are not easily modified by erosion or tectonics. Although the reorganization of deeply incised drainage systems has been documented, the corresponding importance with regard to the overall landscape evolution of mountain ranges and the factors that permit such reorganizations are poorly understood. To address this problem, we have explored the rapid drainage reorganization that affected the Cahabon River in Guatemala during the Quaternary. Sediment-provenance analysis, field mapping, and electrical resistivity tomography (ERT) imaging are used to reconstruct the geometry of the valley before the river was captured. Dating of the abandoned valley sediments by the Be-10-Al-26 burial method and geomagnetic polarity analysis allow us to determine the age of the capture events and then to quantify several processes, such as the rate of tectonic deformation of the paleovalley, the rate of propagation of post-capture drainage reversal, and the rate at which canyons that formed at the capture sites have propagated along the paleovalley. Transtensional faulting started 1 to 3 million years ago, produced ground tilting and ground faulting along the Cahabon River, and thus generated differential uplift rate of 0.3 +/- 0.1 up to 0.7 +/- 0.4 mm . y(-1) along the river's course. The river responded to faulting by incising the areas of relative uplift and depositing a few tens of meters of sediment above the areas of relative subsidence. Then, the river experienced two captures and one avulsion between 700 ky and 100 ky. The captures breached high-standing ridges that separate the Cahabon River from its captors. Captures occurred at specific points where ridges are made permeable by fault damage zones and/or soluble rocks. Groundwater flow from the Cahabon River down to its captors likely increased the erosive power of the captors thus promoting focused erosion of the ridges. Valley-fill formation and capture occurred in close temporal succession, suggesting a genetic link between the two. We suggest that the aquifers accumulated within the valley-fills, increased the head along the subterraneous system connecting the Cahabon River to its captors, and promoted their development. Upon capture, the breached valley experienced widespread drainage reversal toward the capture sites. We attribute the generalized reversal to combined effects of groundwater sapping in the valley-fill, axial drainage obstruction by lateral fans, and tectonic tilting. Drainage reversal increased the size of the captured areas by a factor of 4 to 6. At the capture sites, 500 m deep canyons have been incised into the bedrock and are propagating upstream at a rate of 3 to 11 mm . y(-1) deepening at a rate of 0.7 to 1 5 mm . y(-1). At this rate, 1 to 2 million years will be necessary for headward erosion to completely erase the topographic expression of the paleovalley. It is concluded that the rapid reorganization of this drainage system was made possible by the way the river adjusted to the new tectonic strain field, which involved transient sedimentation along the river's course. If the river had escaped its early reorganization and had been given the time necessary to reach a new dynamic equilibrium, then the transient conditions that promoted capture would have vanished and its vulnerability to capture would have been strongly reduced.

Pneumocystis jirovecii genotype associated with increased death rate of HIV-infected patients with pneumonia.

Pneumocystis jirovecii dihydropteroate synthase (DHPS) mutations have been associated with failure of sulfa prophylaxis; their effect on the outcome of patients with P. jirovecii pneumonia (PCP) remains controversial. P. jirovecii DHPS polymorphisms and genotypes were identified in 112 cases of PCP in 110 HIV-infected patients by using PCR single-strand conformation polymorphism. Of the 110 patients observed, 21 died; 18 of those deaths were attributed to PCP. Thirty-three percent of the PCP cases involved a P. jirovecii strain that had 1 or both DHPS mutations. The presence or absence of DHPS mutations had no effect on the PCP mortality rate within 1 month, whereas P.jirovecii type 7 and mechanical ventilation at PCP diagnosis were associated with an increased risk of death caused by PCP. Mechanical ventilation at PCP diagnosis was also associated with an increased risk of sulfa treatment failure at 5 days.

Modelling the curing process in magneto-sensitive polymers: Rate-dependence and shrinkage

This paper deals with a phenomenologically motivated magneto-viscoelastic coupled finite strain framework for simulating the curing process of polymers under the application of a coupled magneto-mechanical road. Magneto-sensitive polymers are prepared by mixing micron-sized ferromagnetic particles in uncured polymers. Application of a magnetic field during the curing process causes the particles to align and form chain-like structures lending an overall anisotropy to the material. The polymer curing is a viscoelastic complex process where a transformation from fluid. to solid occurs in the course of time. During curing, volume shrinkage also occurs due to the packing of polymer chains by chemical reactions. Such reactions impart a continuous change of magneto-mechanical properties that can be modelled by an appropriate constitutive relation where the temporal evolution of material parameters is considered. To model the shrinkage during curing, a magnetic-induction-dependent approach is proposed which is based on a multiplicative decomposition of the deformation gradient into a mechanical and a magnetic-induction-dependent volume shrinkage part. The proposed model obeys the relevant laws of thermodynamics. Numerical examples, based on a generalised Mooney-Rivlin energy function, are presented to demonstrate the model capacity in the case of a magneto-viscoelastically coupled load.

Isolation of a yeast strain able to produce a polygalacturonase with maceration activity of cassava roots

The objective of the present study was the isolation of a yeast strain, from citrus fruit peels, able to produce a polygalacturonase by submerged fermentation with maceration activity of raw cassava roots. Among 160 yeast strains isolated from citrus peels, one strain exhibited the strongest pectinolytic activity. This yeast was identified as Wickerhamomyces anomalus by 5.8S-ITS RFLP analysis and confirmed by amplification of the nucleotide sequence. The yeast produced a polygalacturonase (PG) in Erlenmeyer shake flasks containing YNB, glucose, and citrus pectin. PG synthesis occurred during exponential growth phase, reaching 51 UE.mL-1 after 8 hours of fermentation. A growth yield (Yx/s) of 0.43 gram of cell dry weight per gram of glucose consumed was obtained, and a maximal specific growth rate (µm) of 0.346 h-1 was calculated. The microorganism was unable to assimilate sucrose, galacturonic acid, polygalacturonic acid, or citrus pectin, but it required glucose as carbon and energy source and polygalacturonic acid or citrus pectin as inducers of enzyme synthesis. The crude enzymatic extract of Wickerhamomyces anomalus showed macerating activity of raw cassava. This property is very important in the production of dehydrated mashed cassava, a product of regional interest in the province of Misiones, Argentina.