An open-source musculoskeletal model of the lumbar spine and lower limbs: a validation for movements of the lumbar spine.

Musculoskeletal models of the lumbar spine have been developed with varying levels of detail for a wide range of clinical applications. Providing consistency is ensured throughout the modelling approach, these models can be combined with other computational models and be used in predictive modelling studies to investigate bone health deterioration and the associated fracture risk. To provide precise physiological loading conditions for such predictive modelling studies, a new full-body musculoskeletal model including a detailed and consistent representation of the lower limbs and the lumbar spine was developed. The model was assessed against in vivo measurements from the literature for a range of spine movements representative of daily living activities. Comparison between model estimations and electromyography recordings was also made for a range of lifting tasks. This new musculoskeletal model will provide a comprehensive physiological mechanical environment for future predictive finite element modelling studies on bone structural adaptation. It is freely available on https://simtk.org/projects/llsm/.

Floristic evidence for alternative biome states in tropical Africa.

The idea that tropical forest and savanna are alternative states is crucial to how we manage these biomes and predict their future under global change. Large-scale empirical evidence for alternative stable states is limited, however, and comes mostly from the multimodal distribution of structural aspects of vegetation. These approaches have been criticized, as structure alone cannot separate out wetter savannas from drier forests for example, and there are also technical challenges to mapping vegetation structure in unbiased ways. Here, we develop an alternative approach to delimit the climatic envelope of the two biomes in Africa using tree species lists gathered for a large number of forest and savanna sites distributed across the continent. Our analyses confirm extensive climatic overlap of forest and savanna, supporting the alternative stable states hypothesis for Africa, and this result is corroborated by paleoecological evidence. Further, we find the two biomes to have highly divergent tree species compositions and to represent alternative compositional states. This allowed us to classify tree species as forest vs. savanna specialists, with some generalist species that span both biomes. In conjunction with georeferenced herbarium records, we mapped the forest and savanna distributions across Africa and quantified their environmental limits, which are primarily related to precipitation and seasonality, with a secondary contribution of fire. These results are important for the ongoing efforts to restore African ecosystems, which depend on accurate biome maps to set appropriate targets for the restored states but also provide empirical evidence for broad-scale bistability.

Analytical models approximating individual processes: a validation method.

Upscaling population models from fine to coarse resolutions, in space, time and/or level of description, allows the derivation of fast and tractable models based on a thorough knowledge of individual processes. The validity of such approximations is generally tested only on a limited range of parameter sets. A more general validation test, over a range of parameters, is proposed; this would estimate the error induced by the approximation, using the original model's stochastic variability as a reference. This method is illustrated by three examples taken from the field of epidemics transmitted by vectors that bite in a temporally cyclical pattern, that illustrate the use of the method: to estimate if an approximation over- or under-fits the original model; to invalidate an approximation; to rank possible approximations for their qualities. As a result, the application of the validation method to this field emphasizes the need to account for the vectors' biology in epidemic prediction models and to validate these against finer scale models.

Dynamics of dengue epidemics in urban contexts.

Dengue, similar to other arboviral diseases, exhibits complex spatiotemporal dynamics. Even at town or village level, individual-based spatially explicit models are required to correctly reproduce epidemic curves. This makes modelling at the regional level (province, country or continent) very difficult and cumbersome. We propose here a first step to build a hierarchized model by constructing a simple analytical expression which reproduces the model output from macroscopic parameters describing each 'village'. It also turns out to be a good approximation of real urban epidermic outbreaks. Subsequently, a regional model could be built by coupling these equations on a lattice.

Early determination of the reproductive number for vector-borne diseases: the case of dengue in Brazil.

OBJECTIVE: To evaluate a new method of deriving the reproductive number for vector-borne diseases from the early epidemic curves for vector-borne diseases with incubations in the vectors and in the hosts. METHOD: We applied the model to several dengue epidemics in different climatic regions of Brazil: Brasilia, Belém, Fortaleza, Boa Vista. RESULTS: The new method leads to higher estimates of the reproductive number than previous models. CONCLUSION: At present, Aedes aegypti densities, the meeting of more compatible strains of viruses and mosquitoes, may lead to re-emergence of urban yellow fever epidemics.

Immortalized goat milk epithelial cell lines replicate CAEV at high level.

Primary milk epithelial cells were isolated from CAEV-uninfected goats and three cell lines designated TIGMEC-1, TIGMEC-2 and TIGMEC-3 were established. The three cell lines retained their morphological characteristics of epithelial cells and expressed specific epithelial cytokeratin marker as well as the immortalizing SV40 large T antigen. The kinetics of growth of TIGMEC1, TIGMEC2 and TIGMEC3 cell lines showed a doubling time of 24-48 hours while the parental cell lines became senescent after the passage 6 in cell culture. Like the parental primary cells, the three cell lines were found to be highly sensitive to CAEV-pBSCA, an infectious molecular clone of CAEV-CO strain, and to a French isolate CAEV-3112. TIGMEC cell lines infected with CAEV-pBSCA became chronically infected producing high virus titers in absence of cytopathic effects. These cell lines may be useful for study of the possible physiological alterations in mammary epithelial cells infected with small ruminant lentiviruses and their consequences on milk quality. On an other hand, these cell lines can be used to study their role in virus transmission and pathogenesis.

Lack of functional receptors is the only barrier that prevents caprine arthritis-encephalitis virus from infecting human cells.

Barriers to replication of viruses in potential host cells may occur at several levels. Lack of suitable and functional receptors on the host cell surface, thereby precluding entry of the virus, is a frequent reason for noninfectivity, as long as no alternative way of entry (e.g., pinocytosis, antibody-dependent adsorption) can be exploited by the virus. Other barriers can intervene at later stages of the virus life cycle, with restrictions on transcription of the viral genome, incorrect translation and posttranslational processing of viral proteins, inefficient viral assembly, and release or efficient early induction of apoptosis in the infected cell. The data we present here demonstrate that replication of caprine arthritis-encephalitis virus (CAEV) is restricted in a variety of human cell lines and primary tissue cultures. This barrier was efficiently overcome by transfection of a novel infectious complete-proviral CAEV construct into the same cells. The successful infection of human cells with a vesicular stomatitis virus (VSV) G-pseudotyped Env-defective CAEV confirmed that viral entry is the major obstacle to CAEV infection of human cells. The fully efficient productive infection obtained with the VSV-G-protein-pseudotyped infectious CAEV strengthened the evidence that lack of viral entry is the only practical barrier to CAEV replication in human cells. The virus thus produced retained its original host cell specificity and acquired no propensity to propagate further in human cultures.

Experimental infection of Mouflon-domestic sheep hybrids with caprine arthritis-encephalitis virus.

OBJECTIVE: To determine whether monocyte-derived macrophages from Mouflon-domestic sheep hybrids (Ovis musimon X Ovis spp) were susceptible to productive infection with caprine arthritis-encephalitis virus (CAEV) in vitro and whether experimental inoculation of Mouflon-domestic sheep hybrids with a molecularly cloned CAEV would result in persistent infection. ANIMALS: 5 Mouflon hybrids. PROCEDURE: Macrophage monolayers were inoculated with virus in vitro. Three animals were inoculated with virus intratracheally. RESULTS: Productive replication of CAEV was demonstrated in monocyte-derived macrophages following in vitro and in vivo inoculation. Titer of infectious cytopathic CAEV produced by macrophages from the Mouflon hybrids was similar to titers produced by macrophages from an infected goat or by synovial membrane cells. Isolation of virus from monocyte-derived macrophages and use of a semiquantitative polymerase chain reaction assay to amplify a portion of the viral genome demonstrated persistent virus replication in all 3 inoculated animals. Two weeks after inoculation of sheep, approximately 1 of 5,000 monocytes was harboring the virus. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicate that Mouflon-domestic sheep hybrids are susceptible to infection with isolates of CAEV that cause infection in domestic small ruminants.

Goat milk epithelial cells are highly permissive to CAEV infection in vitro.

The main route of small ruminant lentivirus dissemination is the ingestion of infected cells present in colostrum and milk from infected animals. However, whether only macrophages or other cell subtypes are involved in this transmission is unknown. We derived epithelial cell cultures, 100% cytokeratin positive, from milk of naturally infected and noninfected goats. One such culture, derived from a naturally infected goat, constitutively produced a high titer of virus in the absence of any cytopathic effect. The other cultures, negative for natural lentivirus infection, were tested for their susceptibility to infection with the CAEV-CO strain and a French field isolate CAEV-3112. We showed that milk epithelial cells are easily infected by either virus and produce viruses at titers as high as those obtained in permissive goat synovial membrane cells. The CAEV-CO strain replicated in milk epithelial cells in absence of any cytopathic effect, whereas the CAEV-3112 field isolate induced both cell fusion and cell lysis. Our results suggest that CAEV-infected milk epithelial cells of small ruminants may play an important role in virus transmission and pathogenesis.

Defective RNA packaging is responsible for low transduction efficiency of CAEV-based vectors.

Replication defective retroviral vectors are regularly used for transfer and expression of exogenous genes into dividing cells and in animals. Since lentiviruses are able to infect terminally differentiated and non-dividing cells, their use to produce replication defective vectors may overcome this limitation. We developed two replication-defective lentiviral vectors based on the genome of Caprine Arthritis Encephalitis Virus (CAEV). The first vector (pBNL2) carries the neo and lacZ marker genes. Neo gene is expressed from a genomic RNA and lacZ gene from a subgenomic RNA. The second vector (pCSHL) carries a single fusion gene encoding both phleomycin resistance and beta-galactosidase activity. Replication-competent CAEV was used as helper virus to provide the viral proteins for transcomplementation of these vectors. Our data demonstrated that the genomes of both vectors were packaged into CAEV virions and transduced into goat synovial membrane cells following infection. However, the vector titers remained 3 to 4 logs lower than those of CAEV. Further analysis showed a lack of accumulation of unspliced pBNL2 RNA into the cytoplasm of producer cells resulting in the packaging of pBNL2 sub-genomic RNA only. In contrast, RNA produced from pCSHL vector was correctly transported to the cytoplasm and more efficiently packaged than the pBNL2 sub-genomic RNA as revealed by slot-blot and quantitative RT/PCR analyses. However this higher packaging efficiency of pCSHL genome did not result in a higher transduction efficiency of lacZ gene.

Fecal beta-D-galactosidase production and Bifidobacteria are decreased in Crohn's disease.

Digestive bacterial microflora play a major role in the pathogenesis of Crohn's disease (CD). Bacterial enzyme activities, especially beta-D-galactosidase, are decreased in fecal extracts from CD patients. We hypothesized that an alteration of the colonic flora might be responsible for this decrease. Indeed, we demonstrate that beta-D-galactosidase production in supernates of anaerobic cultures was significantly (P < 0.01) reduced in feces from patients with active Crohn's disease (N = 7), when compared to healthy controls (N = 8). Therefore using X-gal and selective media, we enumerated bacteria able to release beta-D-galactosidase in feces from patients with active (N = 16) or quiescent disease (N = 5) and healthy controls (N = 14). Bifidobacteria numbers were significantly reduced in patients (P < 0.01 for active; P < 0.02 for quiescent disease) whereas Bacteroides and Lactobacilli counts remained unchanged. beta-D-Galactosidase activity and Bifidobacteria counts were significantly correlated (P < 0.03). Bifidobacteria are regarded as beneficial for the host. The reduction in Bifidobacteria is responsible for decreased beta-D-galactosidase activity. Thus oral administration of prebiotics that promote their growth might have potential therapeutic interest.

Bacterial enzymes used for colon-specific drug delivery are decreased in active Crohn's disease.

Enzymes produced by colonic microflora have been proposed for triggering local delivery of antiinflammatory azo-bond drugs and prodrugs to the colon. This approach could be advantageous in steroid treatment of inflammatory bowel diseases, thus sparing steroids' side effects. We recently demonstrated that the metabolic activity of digestive flora, assessed on the activity of fecal glycosidases, was decreased in patients with active Crohn's disease. In the present study, the azoreductase activity in feces of 14 patients with active Crohn's disease was decreased (11.39 +/- 7.93 mU/g F) as compared with 12 healthy subjects (51.13 +/- 21.39 mU/g F). beta-D-Glucosidase and beta-D-glucuronidase activities in fecal homogenates incubated under anaerobic conditions were also decreased in patients. These data bring into question the therapeutic usefulness for those patients of azo-bond drugs and glycoside prodrugs. They could explain the therapeutic failure of some of those drugs in active ileocolic and colic Crohn's disease.

Hypokalaemia related to acute chloroquine ingestion.

Large doses of chloroquine can cause poisoning. Our aim was to determine the possible relation between the plasma potassium concentration on admission with the severity of acute chloroquine poisoning and to assess the mechanism of chloroquine-induced hypokalaemia. We conducted a retrospective study of 191 consecutive cases. The main data included the occurrence of vomiting before admission, plasma, and urinary potassium concentration at admission, whole blood chloroquine concentration on admission, haemodynamic parameters and ECG, administration of catecholamines and outcome. Mean blood chloroquine level was 20.1 mumol/L (SD 14.3) (therapeutic level < or = 6 mumol/L). Mean plasma potassium concentration was 3.0 mmol/L (0.8) and was lower in the subjects who died than in those who survived (p = 0.0003). Plasma potassium varied directly with the systolic blood pressure and inversely with the QRS and QT. Plasma potassium varied inversely with the blood chloroquine (p = 0.0001; tau = -0.42). Acute chloroquine intoxication is responsible for a hypokalaemia which correlates with the gravity of the intoxication and may be due to a transport-dependent mechanism. Plasma potassium concentrations should be carefully observed, particularly among patients who also receive catecholamine infusions. We should keep in mind, however, that overzealous repletion invokes the risk of subsequent hyperkalaemia and thus should be avoided.

Surimi and native codfish contain a common allergen identified as a 63-kDa protein.

We have compared the allergenicity of codfish and surimi (prepared from codfish) by skin testing, specific IgE-RIA, and leukocyte histamine release (LHR) in six fish-allergic patients. Prick tests were positive for codfish and, to a lesser extent, surimi. The percentages of labeled anti-IgE bound to surimi-Sepharose were 1.55 +/- 0.19% and 3-6% with control and patient sera, respectively. Inhibition of the surimi protein-Sepharose IgE-RIA was greatest (80%) at protein concentrations of 13.4 and 408.5 micrograms/ml for codfish and surimi extract, respectively. The allergenic protein was isolated by gel filtration and subjected to SDS-PAGE. The eluate from codfish contained several proteins ranging from 13 to 63 kDa, while the eluate from surimi contained a single 63-kDa protein. It was concluded that surimi contained a single allergenic protein.

Different mechanism for insulin induced and contraction induced increases in skeletal muscle glucose uptake.

Glucose facilitated diffusion into cells depends on concentration gradients between intracellular and extracellular spaces and can be modified by several factors such as insulin and contractions. Calmodulin participates in the insulin induced recruitment of vesicles containing glucose transporter molecules and its inhibition by trifluoperazine blocks insulin increases in glucose uptake. In the present study we tested if calmodulin inhibition with trifluoperazine blocks hindlimb muscle glucose uptake increase induced by contractions. Trifluoperazine does not inhibit exercise induced increases in glucose uptake; therefore, the mechanisms by which insulin and functional activity increase glucose uptake are different.

[Differentiation of glucidolytic mycoplasmas isolated from goats by the API 50 CH system and electrophoresis]. / Différenciation par le système API 50 CH et électrophorèse des mycoplasmes glucidolytiques isolés chez la chèvre.

Carbohydrate metabolism of 62 glucidolytic strains of mycoplasma belonging to 4 species (M ovipneumoniae, M putrefaciens, M mycoides, M capricolum) has been studied using the API 50 Ch system for bacterial identification. This microtechnique and colony aspect were relevant in distinguishing M ovipneumoniae and M putrefaciens from the group M mycoides and M capricolum isolated from goats, but still presented a lack of specificity in distinguishing M mycoides from M capricolum. Similar results were obtained when the mycoplasma strains were tested by electrophoresis.

[Responses of kids to monocytes infected in vitro by the caprine arthritis-encephalitis virus]. / Réponses du chevreau à des monocytes infectés in vitro par le virus de l'arthrite et de l'encéphalite de la chèvre.

Retroviruses from small ruminants are spread between susceptible animals by mononuclear phagocytes which are also virus targets. Young seronegative goats were inoculated with in vitro infected monocytes producing caprine arthritis encephalitis virus (10(5) cells/animal) by intravenous route corresponding to 10(5) syncytia forming units. After 3 months the same goats received dexamethasone treatment (5 mg/animal each 2 days over a 10-day period). The observed immune response differed if the animal was infected with its own cells or with homologous cells. Before dexamethasone treatment, antibody production evaluated by gel precipitation, ELISA or western blot was delayed in autologous by comparison with homologous conditions. After dexamethasone treatment, the appearance of infectious monocytes in blood and subsequent arthritis were observed in all animals in homologous conditions and only in 1 animal out of 3 in autologous conditions. Host reaction to the infected cells determines virus expression at the time of contamination.

[Nasal and pulmonary flora in the goat]. / Flores nasale et pulmonaire de la chèvre.

On the basis of bacteriological examinations carried out on 75 intranasal swabs and 80 goat lung punctures, aerobic, aero-anaerobic respiratory microbes and mycoplasma were studied. Mycoplasma ovipneumoniae was isolated both from nasal flora (37%) and from the lungs (27.5%) as well as Pasteurella spp which accounted respectively for 24% and 12.5%. The nasal flora are characterised by the presence of a Gram-negative strain included in the genus Moraxella and connected with Moraxella bovis species.