Mechanisms of persistence and impact of ordinary heterotrophic organisms in aerobic granular sludge.

The stability of granules, contaminant removal and microbial structure of an aerobic granular sludge (AGS) process were investigated with a focus on ordinary heterotrophic organisms (OHOs). Long-term stable granules and high removals of COD (97 %), NH4+ (98 %), P (85 %) and total N (77 %) were achieved. Sequencing analyses identified 6.6 % of phosphorus-accumulating organisms in the sludge, concordant with the observed bio-P removal capacity. However, OHOs were the most abundant bacteria in the sludge (70-93 %) without resulting in unstable aggregates. Under current dogmas of microbial competition in activated sludge, it seemed contradictory that OHOs could persist in the long term in the AGS where COD was depleted beginning in the anaerobic phase. Microbial analyses showed that OHOs could survive in granules by micropredation, proteolysis, fermentation and EPS consumption. Heterotrophic-nitrification/ aerobic-denitrification was an active pathway in the AGS. These findings contribute to a better understanding of microbial competition in AGS and its stability.

A baseline assessment of hydrologic alteration degree for the Mexican catchments at gauged rivers (2016).

River regime has been modified in several freshwater bodies around the world. This alteration has led to species loss, water pollution, higher or lesser economic profits, changes in magnitude, timing, duration and rate change of flow, among others. Thus, hydrologic alteration assessment allows evaluating the regime parameters so that stakeholders, decision-makers, and dams managers may take efficient actions to mitigate or rehabilitate riparian ecosystems. In the present study, Hydrologic Alteration Indexes on Rivers (IAHRIS, for its acronym in Spanish) and the Mexican standard approach were considered to evaluate 1150 gauged catchments in Mexico and come up with an alteration baseline for 67.03% of the country surface. The comparison may assist stakeholders to propose potential changes in the Mexican standard approach. Results reveal that 232 analyzed catchments can be considered as non-altered according to IAHRIS. In stark contrast, there are 281 non-altered catchments in Mexico in agreement with the official standard approach. Altered catchments are mainly impacted by minimum flow metrics and connectivity discharge. Additionally, the correlation between alteration indexes and 5 socio-economic variables was checked to identify which variables may greatly impact hydrologic alteration evolution or mitigation. From the five selected variables, the Human Development Index is significatively correlated to extreme minimum metrics (p = 0.94) while the Gross Domestic Product to extreme maximum metrics (p = 0.90).

Mobilisation efficacy in young patients with different stages of degenerative disc disease.

BACKGROUND: Lumbar vertebrae carry the greatest load from the spinal column, often leading to several pathologies, including degenerative disc disease (DDD), potentially disturbing spinal movement patterns. Mobilisation increases hypomobile segment mobility, however there is little evidence on mobilisation in patients suffering from different types of DDD. OBJECTIVE: To assess the efficacy of mobilisation in young patients with DDD, as diagnosed by MRI. METHODS: Thirty patients (24-35 years) participated in this study, and were divided into two groups, based on progression levels of DDD diagnosed by MRI (protrusion-PRO/extrusion-EXT). Twenty sessions of sustained stretch mobilisation (grade III) were applied to both groups over four weeks. Numeric Rating Scale (NRS), Oswestry Disability Index (ODI), straight leg raise (SLR), passive lumbar extension (PLE) and lumbar range of motion (ROM) assessed outcome variables. Three trial stages were investigated: pre-therapy (1), post-therapy (2) and follow-up (3). RESULTS: Age (p= 0.007) and NRS (p= 0.002) were significantly different before therapy. Patient outcomes were significantly improved for all parameters in both groups, except SLR which improved in the EXT group only (p= 0.043). CONCLUSIONS: Applied treatments improved patient outcomes and were statistically significant in both groups, however, better outcomes were observed in the EXT group during follow-up. Mobilisation was a safe and effective procedure for the treatment of DDD.

Genetic structure and invasion history of the house mouse (Mus musculus domesticus) in Senegal, West Africa: a legacy of colonial and contemporary times.

Knowledge of the genetic make-up and demographic history of invasive populations is critical to understand invasion mechanisms. Commensal rodents are ideal models to study whether complex invasion histories are typical of introductions involving human activities. The house mouse Mus musculus domesticus is a major invasive synanthropic rodent originating from South-West Asia. It has been largely studied in Europe and on several remote islands, but the genetic structure and invasion history of this taxon have been little investigated in several continental areas, including West Africa. In this study, we focussed on invasive populations of M. m. domesticus in Senegal. In this focal area for European settlers, the distribution area and invasion spread of the house mouse is documented by decades of data on commensal rodent communities. Genetic variation at one mitochondrial locus and 16 nuclear microsatellite markers was analysed from individuals sampled in 36 sites distributed across the country. A combination of phylogeographic and population genetics methods showed that there was a single introduction event on the northern coast of Senegal, from an exogenous (probably West European) source, followed by a secondary introduction from northern Senegal into a coastal site further south. The geographic locations of these introduction sites were consistent with the colonial history of Senegal. Overall, the marked microsatellite genetic structure observed in Senegal, even between sites located close together, revealed a complex interplay of different demographic processes occurring during house mouse spatial expansion, including sequential founder effects and stratified dispersal due to human transport along major roads.

Impact of the Intra- and Inter-observer Variability in the Delineation of Parotid Glands on the Dose Calculation During Head and Neck Helical Tomotherapy.

The intra- and inter-observer variability in delineation of the parotids on the kilo-voltage computed tomography (kVCT) and mega-voltage computed tomography (MVCT) were examined to establish their impact on the dose calculation during adaptive head and neck helical tomotherapy (HT). Three observers delineated left and right parotids for ten randomly selected patients with oropharynx cancer treated on HT. The pre-treatment kVCT and the MVCT from the first fraction of irradiation were selected to delineation. The delineation procedure was repeated three times by each observer. The parotids were delineated according to the institutional protocol. The analyses included intra-observer reproducibility and inter-structure, -observer and -modality variability of the volume and dose. The differences between the left and right parotid outlines were not statistically significant (p > 0.3). The reproducibility of the delineation was confirmed for each observer on the kVCT (p > 0.2) and on the MVCT (p > 0.1). The inter-observer variability of the outlines was significant (p < 0.001) as well as the inter-modality variability (p < 0.006). The parotids delineated on the MVCT were 10% smaller than on the kVCT. The inter-observer variability of the parotids delineation did not affect the average dose (p = 0.096 on the kVCT and p = 0.176 on the MVCT). The dose calculated on the MVCT was higher by 3.3% than dose from the kVCT (p = 0.009). Usage of the institutional protocols for the parotids delineation reduces intra-observer variability and increases reproducibility of the outlines. These protocols do not eliminate delineation differences between the observers, but these differences are not clinically significant and do not affect average doses in the parotids. The volumes of the parotids delineated on the MVCT are smaller than on the kVCT, which affects the differences in the calculated doses.

[Serological and Behavioral Survey on HIV/AIDS among prisoners in Nouakchott (Mauritania)]. / Enquête comportementale et sérologique sur le VIH/sida chez les détenus à Nouakchott (Mauritanie).

In Mauritania, epidemiological data estimate national HIV prevalence to less than 1%. Our study is the first joint survey on HIV/AIDS conducted among prisoners in Mauritania. It is a cross-sectional survey with anonymity and informed consent. The study covered a sample of 296 prisoners enrolled in a population of 706 prisoners held in Nouakchott. The sex ratio was 14.6. The refusal rate of blood sample was 4.7%. HIV prevalence in the sample was 3.9%. 53.37% of prisoners knew the concept of seropositivity but only 7.4% had a perfect knowledge of the ways of HIV transmission untainted by false beliefs. The results showed that 99% of prisoners knew that the condom is a means of protection against HIV infection, but they also showed many false beliefs about protection against HIV in the majority of prisoners. Indeed, 98.49% of respondents said they protected themselves by avoiding sex with strangers and 94.97% of them thought that sex with young girls or virgins are protection against HIV. Nearly one quarter of the prisoners did not have a good perception of risk of contracting HIV in prison although homosexual relations between prisoners have been reported. This study showed that prisoners in Mauritania are a vulnerable group to HIV because the prevalence of HIV in this group was higher than the national prevalence and this sub-population was unfamiliar with the disease and adopt risk behaviors.

[Relationship between the obstructive character of the tonsils and the sagittal cephalometric measurements]. / Relations entre le caractère obstructif des amygdales palatines et les mensurations céphalométriques du sens sagittal.

INTRODUCTION: The role of obstructive tonsils in the sagittal dimension of the skeleton-dental abnormalities is widely discussed in the literature but remains controversial. Data on the probable relationship between obstructive tonsils and the presence of these abnormalities were subjective. The objective of this study was to quantify the relationship between the obstructive character of the tonsils and the sagittal cephalometric measurements. MATERIALS AND METHODS: A cross-sectional study was performed in children aged between 6 to 12 years divided into 2 groups (A and B) according to the obstructive character of the tonsils. Cephalometric measurements were recorded on each child. Data were analyzed using SPSS 20.0 for Windows. At Student test was used to compare quantitative variables according to the obstructive character of the tonsils. Significance was set at p = 0.05. RESULTS: Subjects with obstructive tonsils (group B) are significantly more trend to have a convex facial profile and a skeletal class II with more mandibular retrusion and retroclined incisor compared with subjects without obstructive tonsils (group A). CONCLUSION: Early evaluation of children with obstructive tonsils can prevent sagittal dimension of the squeleto-dental abnormalities caused by upper airway obstruction. Thus late and more aggressive treatments which are not always as efficient as when they were performed during childhood will be avoided.

[Sagittal photogrammetric evaluation of the soft tissue profile between two different racial groups: a comparative study]. / Caractéristiques photogrammétriques sagittales de profil des tissus mous chez deux groupes raciaux. Etude comparative.

INTRODUCTION: Facial soft-tissue analyses made from photographic records (photogrammetric analysis of the soft tissues) showed interracial dimorphism. Standard of these facial analyses, originally obtained from Caucasian might not be appropriate for the diagnosis and treatment planning of other groups of orthodontic patients. The purpose of this study was to compare the sagittal photogrammetric soft tissue profile characteristics between Senegalese and Moroccan adults. MATERIALS AND METHODS: A cross-sectional study was performed in a group of Senegalese and Moroccan students in the Faculty of Medicine, Pharmacy and Dentistry of Dakar. Standardized facial-profile photographs were taken with each student in natural head position, centric relation, and relaxed lip posture. Twenty four linear parameters were measured on paper sheet using a graduated ruler. For each variable mean and SD were calculated. In addition independent samples t-test was performed to detect sexual and racial dimorphism. Results were regarded as significant at p = 0.05. RESULTS: Senegalese subjects had significantly more lips protrusion than Moroccan who had significantly a more elongated and more anterior positioned nose, a more chin prominence and a tendency to cutaneous class II than Senegalese. CONCLUSION: Further studies including different age groups subjects would allow having longitudinal data according to age.

Lysophosphatidic acid mediates fibrosis in injured joints by regulating collagen type I biosynthesis.

OBJECTIVE: Articular cartilage is a highly specialized tissue which forms the surfaces in synovial joints. Full-thickness cartilage defects caused by trauma or microfracture surgery heal via the formation of fibrotic tissue characterized by a high content of collagen I (COL I) and subsequent poor mechanical properties. The goal of this study is to investigate the molecular mechanisms underlying fibrosis after joint injury. DESIGN: Rat knee joint models were used to mimic cartilage defects after acute injury. Immunohistochemistry was performed to detect proteins related to fibrosis. Human fetal chondrocytes and bone marrow stromal cells (BMSCs) were used to study the influence of the lipid lysophosphatidic acid (LPA) on COL I synthesis. Quantitative PCR, ELISA and immunohistochemistry were performed to evaluate the production of COL I. Chemical inhibitors were used to block LPA signaling both in vitro and in vivo. RESULTS: After full-thickness cartilage injury in rat knee joints, stromal cells migrating to the injury expressed high levels of the LPA-producing enzyme autotaxin (ATX); intact articular cartilage in rat and humans expressed negligible levels of ATX despite expressing the LPA receptors LPAR1 and LPAR2. LPA-induced increases in COL I production by chondrocytes and BMSCs were mediated by the MAP kinase and PI3 Kinase signaling pathways. Inhibition of the ATX/LPA axis significantly reduced COL I-enriched fibrocartilage synthesis in full-thickness cartilage defects in rats in favor of the collagen II-enriched normal state. CONCLUSION: Taken together, these results identify an attractive target for intervention in reducing the progression of post-traumatic fibrosis and osteoarthritis.

[Disease modifying antirheumatic drugs]. / Traitement de fond de la polyarthrite rhumatoïde.

The natural history of rheumatoid arthritis, previously burdened with high morbidity, has been strongly modified by appropriate treatment. Early diagnosis and treatment, and follow-up by a specialist, with the aim to achieve remission or low disease activity, are essential for the functional outcome of patients. Disease-modifying anti-rheumatic drugs include "conventional" treatments like methotrexate, biologic therapies such as TNF-inhibitors, abatacept, tocilizumab and rituximab, and targeted synthetic therapies such as tofacitinib (a JAK kinase inhibitor). New treatments currently under study should allow rheumatologists to successfully treat even more patients than nowadays.

Mechanical compressive force inhibits adipogenesis of adipose stem cells.

OBJECTIVE: The aim of this study was to investigate effects of mechanical compressive force on differentiation of adipose-derived stem cells (ASCs) in vitro. MATERIALS AND METHODS: Mice ASCs were treated with compressive force (2000 µÎµ, 1 Hz) for 2 or 6 h after adipogenic induction for 3 days, then oil red O staining was used to examine oil droplet-filled cells. Adipogenic genes, PPAR-γ1 and APN, were examined by real-time PCR and immunofluorescence (IF) staining was performed to test expression of de-PPAR-γ and ph-PPAR-γ at the protein level. RESULTS: Our data showed that mechanical compressive force reduced numbers of oil droplet-filled cells, and down-regulated mRNA levels of both PPAR-γ1 and APN and protein level of PPAR-γ, in ASCs. CONCLUSIONS: In culture medium containing adipogenic stimuli, mechanical compressive force inhibited adipogenesis of ASCs.

Effects of bone morphogenetic protein-4 (BMP-4) on adipocyte differentiation from mouse adipose-derived stem cells.

OBJECTIVES: As mesenchymal stem cells (MSCs) can be isolated easily from adipose tissues while retaining their self-renewal and multi-potential differentiation capacities, they hold promising possibilities for being applied extensively in tissue engineering. Bone morphogenetic protein (BMP) family members have been reported to provide instructive signals to MSCs for them to differentiate into several different cell lineages. The study described here aims to investigate whether BMP-4 could promote adipose-derived stem cell (ASC) differentiation into adipocytes under various concentrations. MATERIALS AND METHODS: ASCs were isolated from mouse inguinal adipose pads and cultured in vitro. 10 ng/ml and 50 ng/ml BMP-4 were added to adipogenic media for 8 days. Oil red-O staining, reverse transcription/polymerase chain reaction and immunocytofluorescence staining were performed to examine differentiation of the ASCs. RESULTS: As indicated by increased expression of adipogenic and lipogenic genes (PPAR-γ, APN and LPL) and proteins, 50 ng/ml BMP-4 seemed to induce mASCs to differentiate into the adipo-lineage compared to 10 ng/ml BMP-4, and control groups. In addition, lipid droplets accumulated within the adipocytes under 50 ng/ml BMP-4 stimulation, as shown by oil red-O staining. CONCLUSIONS: Our present study suggests that BMP-4, as an adipo-inducing factor, promoted adipogenesis of ASCs at higher concentrations (50 ng/ml) and can perhaps be considered as a candidate for use in adipose tissue engineering.

Low-intensity pulsed ultrasound induced enhanced adipogenesis of adipose-derived stem cells.

OBJECTIVE: The aim of this study was to investigate effects of low-intensity pulsed ultrasound (LIPUS) on differentiation of adipose-derived stem cells (ASCs), in vitro. MATERIALS AND METHODS: Murine ASCs were treated with LIPUS for either three or five days, immediately after adipogenic induction, or delayed for 2 days. Expression of adipogenic genes PPAR-γ1, and APN, was examined by real-time PCR. Immunofluorescence (IF) staining was performed to test for PPAR-γ at the protein level. RESULTS: Our data revealed that specific patterns of LIPUS up-regulated levels of both PPAR-γ1 and APN mRNA, and PPAR-γ protein. CONCLUSIONS: In culture medium containing adipogenic reagents, LIPUS enhanced ASC adipogenesis.

Osteogenic differentiation of adipose-derived stem cells prompted by low-intensity pulsed ultrasound.

OBJECTIVES: Based on in vivo studies, low-intensity pulsed ultrasound (LIPUS) stimulation has been widely used in the clinic for advancing bone growth during healing of non-union alignment, fractures and other osseous defects. In this study, we have investigated osteogenic differentiation of adipose stem cells (ASCs) regulated by LIPUS, and also in a preliminarily manner, we have discussed diverse effects of different duty ratio parameters. MATERIALS AND METHODS: Mouse adipose stem cells were isolated and osteogenically induced. Then they were treated with LIPUS for 10 min/day for 3 days, 5 days and 7 days, respectively. Finally, effects of LIPUS on osteogenic differentiation of the ASCs were analysed by real-time PCR, western blotting and immunofluorescence. RESULTS: Our data indicated that LIPUS promoted mRNA levels of runt-related transcription factor 2, osteopontin and osterix in the presence of osteo-induction medium; moreover, protein levels of runt-related transcription factor 2 and osteopontin were upregulated. CONCLUSIONS: We successfully demonstrated that LIPUS enhanced osteogenesis of ASCs, specially at the duty ratio of 20%.

[Relationships between the dental arches measurements and the peak nasal inspiratory flow (PNIF): a cross sectional study on 78 Senegalese teenagers]. / Relations entre les mensurations des arcades dentaires et le débit nasal inspiratoire de pointe: etude transversale sur 78 adolescents Senegalais.

INTRODUCTION: Upper airways obstruction can result in the reduction of the transversal dimensions of the maxillary arch which affect the vertical and the sagittal dimensions. The PNIF measure is an objec- tive and cheap way to assess the upper airways permeability. The aim of this study was to determine the relationship between PNIF and dental arch sizes. MATERIALS AND METHODS: Seventy eight patients (40 girls and 38 boys) age ranged 10-15 years were included in this cross sectional study. The PNIF was measured with a Youlten peak flow meter (Clement Clarke International, London, United Kingdom). The sagittal, vertical and transversal dimensions of the dental arches were evaluated on dental casts with a digital caliper (Mitutoyo Corporation, Tokyo, Japan). T test was used to assess differences in PNIF and dental arches variables between subjects grouped according to sex (male and female). The Pearson's correlation coefficient was used to analyze the relationship between the dental arches sizes and the PNIF. The significance was set at p < 0.05. RESULTS: PNIF rate was higher in girls than in boys but the difference was not significant. There were sexual dimorphism regarding the anterior and total lengths of the upper arch, the total length of the lower arch and the maxillary intermolar width which are significantly more important for boys (p respectively equal to 0.05; 0.03; 0.04 and 0.04). The PNIF was significantly and negatively correlated with the total length of the upper arch (r = -0.25). The others measurements did not show significant correlation with PNIF. CONCLUSION: Others parameters are needed to complement the peak nasal inspiratory flow rate for the respiratory disorders related dental arches sizes abnormalities diagnosis.

Trichosomoides nasalis (Nematoda: Trichinelloidea) in the murid host Arvicanthis niloticus: migration to the epithelium of the nasal mucosa after intramuscular development.

Knowledge of the biology of the trichinelloid subfamily Trichosomoidinae is poor. Trichosomoides nasalis is a common parasite of Arvicanthis niloticus (Muridae) in Senegal, and a procedure for experimental infections has been established. It has been demonstrated that larvae develop in striated muscle fibres, similar to Trichinella spp., but they are not arrested in the first stage, and they reach the adult stage within three weeks. In the present histological study it is shown that T. nasalis females and dwarf males migrate from the abdomen and thorax to the host's muzzle, moving through connective tissues and between muscles. A few migrating specimens were also found in the blood vessels of the nasal mucosa. While sexes were still separated in the lamina propria of the mucosa, females recovered from the epithelium contained intra-uterine males. Worms were found between the incisors in the mucosa of the anterior and median conchae which are rich in mucous cells. Only the pseudostratified epithelium was parasitized. Under natural conditions, the inflammation of the nasal mucosa that is induced by the parasites might reduce the competitiveness of infected rodents when foraging or looking for potential mates.

Jagged-1-mediated activation of notch signalling induces adipogenesis of adipose-derived stem cells.

OBJECTIVES: Notch signalling plays an important role in many cell activities, involving proliferation, migration, differentiation and cell death. The aim of this study was to investigate effects of such signalling on adipogenesis of mouse adipose-derived stem cells (mASCs). MATERIALS AND METHODS: Jagged1 (50 and 100 ng/ml) was added to mASCs to activate Notch signalling, 2 days before adipogenic induction. At 5 and 7 days after induction, oil red-O staining was performed to evaluate lipid accumulation. Then real-time PCR was performed to examine expression of Notch downstream genes (Notch-1, -2, Hes-1 and Hey-1) and adipogenic transcription factor (PPAR-γ). Expressions of Hes-1 and PPAR-γ at protein level were confirmed by immunofluorescence staining. RESULTS: Our data indicated that Jagged1 promoted adipogenic differentiation of mASCs. Moreover, Jagged1 also increased expression of Notch downstream genes and PPAR-γ. Expressions of Hes-1 and PPAR-γ were found to be enhanced in Jagged1 pre-treated mASCs when compared to controls. DISCUSSION: The results led to the conclusion that activation of Notch signalling had stimulated adipogenesis of mASCs in the presence of adipogenic medium by promoting expression of PPAR-γ.

COD fractionation and biological treatability of mixed industrial wastewaters.

This study was conducted at a centralized wastewater treatment plant that receives discharges from nearly 160 industries. The chemical oxygen demand (COD) was fractionated for two objectives: delineation of the limits of the activated sludge process being used at the plant, and evaluation of the potential environmental impact of the treated effluent. Physico-chemical analyses, respirometric and biodegradation tests, as well as COD fractionation were carried out. Molasses-wastewaters were determined to be the major contribution to the plant. The influent was dark brown in color, with a relatively high content of both organics (2503 mg/L COD) and salts (5459 µS/cm conductivity), but a low biochemical oxygen demand (568 mg/L BOD(5)) and BOD(5)/COD ratio (0.24). The degradability of the organics was limited by the high content of inert soluble COD (S(I)). The COD fractionation pattern was 40-20-40% for S(I), X(I) (inerts) and S(H) (soluble hydrolyzable), respectively. More than 90% BOD(5) removal was obtained, which was sufficient for the plant to meet the national Standards. However, the effluent discharged into the river was intensely colored and polluted (>1000 mg/L COD, >5000 µS/cm), emphasizing the need for legislation regulating COD, color and salinity, and for upgraded treatment methods worldwide for molasses wastewaters.

Initial-rate based method for estimating the maximum heterotrophic growth rate parameter (µHmax).

Currently, the method most used for measuring the maximum specific growth rate (µ(Hmax)) of heterotrophic biomass is by respirometry, using growth batch tests performed at high food/microorganism ratio. No other technique has been suggested, although the former approach was criticized for providing kinetic constants that could be unrepresentative of the original biomass. An alternative method (seed-increments) is proposed, which relies on measuring the initial rates of respiration (r(O2)(_ini)) at different seeding levels, in a single batch, and in the presence of excess readily biodegradable substrate (S(S)). The ASM1-based underlying equations were developed, which showed that µ(Hmax) could be estimated through the slope of the linear function of r(O2)(_ini)·(V(WW)+v(ML)) vs v(ML) (volume of mixed liquor inoculum); V(WW) represent the wastewater volume added. The procedure was tested, being easy to apply; the postulated linearity was constantly observed and the method is claimed to measure the characteristics of the biomass of interest.

Development of Trichosomoides nasalis (Nematoda: Trichinelloidea) in the murid host: evidence for larval growth in striated muscle fibres.

Trichosomoides nasalis (Trichinelloidea) is a parasite of Arvicanthis niloticus (Muridae) in Senegal. Female worms that harbour dwarf males in their uteri, occur in the epithelium of the nasal mucosa. Young laboratory-bred A. niloticus were either fed females containing larvated eggs or intraperitoneally injected with motile first-stage larvae recovered from female uteri. Both resulted in successful infection. Organs examined during rodent necropsy were blood and lymphatic circulatory systems (heart, large vessels, lymphnodes), lungs, liver, kidneys, thoracic and abdominal cavities, thoracic and abdominal muscular walls, diaphragm, tongue, and nasal mucosa. Development to adult nasal stages took three weeks. Recovery of newly hatched larvae from the peritoneal fluid at four-eight hours after oral infection suggests a direct passage from the stomach or intestinal wall to the musculature. However, dissemination through the blood, as observed with Trichinella spiralis, cannot be excluded even though newly hatched larvae of T. nasalis are twice as thick (15 µm). Developing larvae were found in histological sections of the striated muscle of the abdominal and thoracic walls, and larvae in fourth moult were dissected from these sites. Adult females were found in the deep nasal mucosa where mating occurred prior to worms settling in the nasal epithelium. The present study shows a remarkable similarity between T. nasalis and Trichinella species regarding muscle tropism, but the development of T. nasalis is not arrested at the late first-larval stage and does not induce transformation of infected fibres into nurse cells. T. nasalis seems a potential model to study molecular relations between trichinelloid larvae and infected muscle fibres.