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Biomedical subjects

J Casas

Publications and source records attributed to J Casas.

At least 19 recordsLinked to original sources
PubMed2006

Ontogeny of air-motion sensing in cricket.

Juvenile crickets suffer high rates of mortality by natural predators that they can detect using extremely sensitive air-sensing filiform hairs located on their cerci. Although a huge amount of knowledge has accumulated on the physiology, the neurobiology and the biomechanics of this sensory system in adults, the morphological and functional aspects of air sensing have not been as well studied in earlier life history stages. Using scanning electronic microscopy, we performed a survey of all cercal filiform hairs in seven instars of the wood cricket (Nemobius sylvestris). Statistical analyses allowed us to quantify profound changes in the number, the length and the distribution of cercal hairs during development. Of particular importance, we found a fivefold increase in hair number and the development of a bimodal length-frequency distribution of cercal hairs from the second instar onwards. Based on theoretical estimations of filiform hair population coding, we found that the cercal system is functional for a wide range of frequencies of biologically relevant oscillatory flows, even from the first instar. As the cricket develops, the overall sensitivity of the cercal system increases as a result of the appearance of new hairs, but the value of the best tuned frequency remains fixed between 150 and 180 Hz after the second instar. These frequencies nicely match those emitted by natural flying predators, suggesting that the development of the cercal array of hairs may have evolved in response to such signals.

Air Movements↗
PubMed2006

Air-flow sensitive hairs: boundary layers in oscillatory flows around arthropod appendages.

The aim of this work is to characterize the boundary layer over small appendages in insects in longitudinal and transverse oscillatory flows. The problem of immediate interest is the early warning system in crickets perceiving flying predators using air-flow-sensitive hairs on cerci, two long appendages at their rear. We studied both types of oscillatory flows around small cylinders using stroboscopic micro-particle image velocimetry as a function of flow velocity and frequency. Theoretical predictions are well fulfilled for both longitudinal and transverse flows. Transverse flow leads to higher velocities than longitudinal flow in the boundary layer over a large range of angles between flow and cylinder. The strong spatial heterogeneity of flow velocities around filiform-shaped appendages is a rich source of information for different flow-sensing animals. Our results suggest that crickets could perceive the direction of incoming danger by having air-flow-sensitive hairs positioned around their entire cerci. Implications for biomimetic flow-sensing MEMS are also presented.

Air Movements↗
PubMed2003

Lipogenesis in an adult parasitic wasp.

The goal of this study was to determine the extent of lipogenesis in the parasitoid Eupelmus vuilletti (Hymenoptera: Eupelmidae). Carbohydrate and lipid metabolism were followed in glucose-fed and starved females over 3 days. Fed females increased their glycogen level, while maintaining their lipid level. Starved females used most of their glycogen, while maintaining their lipid level too. Thus, females either use exclusively sugars to preserve their lipid reserves, or maintained a steady renewal of lipids through lipogenesis. The incorporation of radioactively marked glucose into lipids showed however that lipogenesis did not occur at a sufficient level to increase lipid reserves and to compensate for lipid use. This result has important implications for understanding nutrients allocation strategy in this species as the amount of lipids is almost totally fixed upon the emergence. From an evolutionary perspective, we call for detailed physiological studies of lipogenesis in a wide range of adult hymenopterans, as the absence of lipogenesis could be common to all of Aculatea.

Animals↗
PubMed2003

Antinociceptive effects of tricyclic antidepressants and their noradrenergic metabolites.

This study evaluates the antinociceptive effect of several tricyclic antidepressants in four nociceptive tests which employ either thermal (hot plate and tail flick tests) or chemical (formalin and acetic acid tests) stimuli. Forced swimming test was also performed as a model of depression and an activity test was also performed. Mixed antidepressants in current clinical use: amitriptyline, imipramine and clorimipramine and their respective main secondary metabolites which preferentially inhibit noradrenaline reuptake: nortriptyline, desipramine and desmethylclorimipramine, were tested (2.5-20 mg/kg, i.p.) in mice. The results show a stronger antinociceptive effect in chemical tests induced by all the drugs, compared with thermal tests. The doses needed to produce antinociception were lower than those inducing an antidepressive effect, both effects being mutually independent. The overall results show that preferentially noradrenergic tricyclics induced an antinociceptive effect comparable with that of mixed tricyclics, indicating that noradrenaline reuptake plays an important role in tricyclic-induced antinociception.

Analgesics↗
PubMed2003

NGF and TGF-beta mRNA expression during pregnancy in a rat corneal wound healing model.

BACKGROUND: Growth factors seem to play a major role in corneal wound healing and TGF-beta seems to be associated with abnormal healing after corneal surgical procedures. Few studies have analysed the role of NGF and TGF-beta on corneal wound healing during pregnancy. The aim of the present study was to create an animal model to evaluate the expression of NGF and TGF-betas during corneal wound healing in two groups: control and pregnant rats. METHODS: Corneal mRNA for NGF and the three isoforms of TGF-beta were analysed by RT-PCR, in a time-course experiment on different days after epithelial wounding (2, 7, 14 days) in pregnant and control groups RESULTS: The results show high corneal mRNA expression for NGF and TGF-beta1 without any variation throughout the healing process or pregnancy evolution. However, we detected a different expression of corneal mRNAs for TGF-beta2 and TGF-beta3 in the control group. This data was not detected in the pregnant group. DISCUSSION: Our results suggested that pregnancy could have a relevant role on TGF-beta2 and TGF-beta3 mRNA expression during the corneal wound healing process. Additional research should be performed to corroborate these findings.

Animals↗
PubMed2001

Matching host reactions to parasitoid wasp vibrations.

The sensory ecology of predator detection by prey has been little studied for any arthropod prey predator system, in contrast to the sensory ecology of prey finding by predators. The aim of this study was to quantify the foraging signals produced by the parasitoid Sympiesis sericeicornis (Hymenoptera: Eulophidae) and the sensory ecology of enemy detection and the avoidance behaviour of the leaf-mining host, Phyllonorycter spp. (Lepidoptera: Gracillariidae). We used synthetic vibrations approximating the signals generated by ovipositor insertions to stimulate the host in its mine. Tothe authors' knowledge, this is the first manipulative study to describe a match in the frequency range between a parasitoid foraging stimulus and a host behavioural response. We discuss our findings in relation to other predator-prey systems for which a coevolution between prey sensitivity and predator signal has been described.

Animals↗
PubMed2001

Lifetime allocation of juvenile and adult nutritional resources to egg production in a holometabolous insect.

In holometabolous insects reproductive success is strongly determined by the nutritional resources available to the females. In addition to nutrients derived from adult feeding, resources for egg production may come from the limited reserves accumulated during the larval stages. The pattern of allocation of these larval reserves to egg production is expected to be strongly linked to the nutritional ecology of the adult. We investigate the temporal pattern of allocation of larval reserves to reproduction in a host-feeding parasitoid wasp. As predicted by the dynamics of allocation of an adult meal, larval reserves are the main source of nutrients for four or five days after emergence. However, despite the high frequency of host feeding and the high nutrient content of a haemolymph meal, which we predicted would lead to larval reserves being conserved in the event of host deprivation, larval reserves contribute to egg production throughout the lifetime of the female. We propose several mechanistic and adaptive explanations for our results, including the possible existence of a limiting or key nutrient for egg production of exclusively larval origin. We make further predictions concerning the pattern of allocation of larval resources in parasitoids with different adult nutritional requirements.

Animal Nutritional Physiological Phenomena↗
PubMed2001

A one-year follow-up study in anorexia nervosa. Dietary pattern and anthropometrical evolution.

OBJECTIVE: To find out the modifications and the interrelationships between the energy and macronutrient intakes and anthropometric measurements of a group of anorexia nervosa patients (ANP), with homogenous diagnosis, age and treatment, during a 1 y follow-up. DESIGN: Longitudinal study design. SUBJECTS: Fourteen restricting-type ANP in the adolescent age (11-21 y) were recruited for the study and evaluated at four time intervals during 1 y of multidisciplinary treatment: (a) on admission (AN0); (b) after 1 month (AN1); (c) after 6 months (AN6); (d) after 1 y (AN12). MEASURES: Energy and macronutrient composition of the diet (48 h recall) and anthropometric measurements including skinfold thickness. RESULTS: Mean weight and BMI were under the 3rd percentile in AN0. All anthropometrical parameters increased significantly in AN1 compared to AN0 and did not change in AN6 and AN12. Energy and macronutrient intakes increased significantly in AN1. The dietary changes were not maintained in the subsequent time intervals and there was an overall tendency to turn back to AN0 results. Energy intake adequacy to Spanish Recommended Intakes (RI) showed only an acceptable ratio in AN1 (94% RI); however, a preserved protein intake was found throughout the study (mean intakes between 128.5% and 230.0% RI). Negative correlations were found at AN12 between size of arm's subcutaneous fat stores and energy and macronutrient intakes. CONCLUSION: In this 1 y follow-up study the decrease in the intake of energy and macronutrients after discharge seems to be related to anthropometric evolution, so that a return to restrictive eating behaviour had occurred in those subjects who had reached the highest values in their subcutaneous fat stores, probably related to dissatisfaction with self-body image.

Adolescent↗
PubMed2001

Phase reversal of vibratory signals in honeycomb may assist dancing honeybees to attract their audience.

Forager honeybees dancing on the comb are able to attract dance-followers from distances across the comb that are too remote for tactile or visual signals to play a role. An alternative signal could be the vibrations of the comb at 200-300 Hz generated by dancing bees but which, without amplification, may not be large enough to alert remote dance-followers. We describe here, however, an unexpected property of honeycomb when it is subjected to vibration at around 200 Hz that would represent an effective amplification of the vibratory signals for remote dance-followers. We find that, at a specific distance from the origin of an imposed vibration, the walls across a single comb cell abruptly reverse the phase of their displacement and move in opposite directions to one another. Behavioural measurements show that the distance from which the majority of remote dance-followers are recruited coincides with the location of this phase-reversal phenomenon relative to the signal source. We propose that effective signal amplification by the phase-reversal phenomenon occurs when bees straddle a cell across which the phase reversal is expressed. Such a bee would be subjected to a situation in which the legs were moving towards and away from one another instead of in the same direction. In this manner, remote dance-followers could be alerted to a dancer performing in their vicinity.

Animal Communication↗
PubMed2001

Femoral fractures in children from 4 years to 10 years: conservative treatment.

Some authors have widened the indications for surgical management of isolated femoral shaft fractures in children between 4 years and 10 years of age. We address this study to evaluate the results of such femoral fractures treated conservatively in 41 children. All fractures were closed, isolated, and diaphyseal. The mean age was 6.5 years (standard deviation, 1.7 years) and the mean follow-up was 2.3 years (standard deviation, 1.7 years). All fractures were managed conservatively with skin traction (mean hospitalization time, 20.7 days), alignment of the fragments was serially followed by X-ray, and a spica cast was applied (9.7 weeks), usually without a general anesthesia. Angular deformity was assessed by measurement of the fracture-site diaphyseal angle as well as by measurement of the interphyseal angle described by Wallace and Hoffman. No significant complications were recorded regarding leg-length discrepancy, deformity, refractures, etc. Mean cost is not a factor in determining method of treatment at our hospital. We feel that this type of fracture in the 4 years to 10 years age group can be safely treated with a conservative approach.

Casts, Surgical↗
PubMed2000

The role of leaf structure in vibration propagation.

The leaf and its structural components play a key role in the propagation of short transient signals produced by insects. In this paper, it is shown how the complex structure of an apple leaf could be modeled by a much simpler one for the analysis of vibratory signal propagation. Waves were produced by impacts of small spheres and the propagation studied using two laser vibrometers, followed by a wavelets analysis. Three components of the leaf were investigated: the midvein, minor veins, and the interspaced homogeneous regions making up the leaf lamina. The loss of signal energy over the leaf lamina and across minor veins and midvein was studied. For the midvein, the loss of energy decreased from 80% at the leaf base to 40% at the apex. For minor veins, the loss of energy decreased from 70% at the leaf base to 31% at the apex. The loss in homogeneous regions was 40%. A signal decomposition into two frequency ranges, above and below 1.7 kHz, showed that the midvein acted as a low-pass filter. As energy loss was mainly a function of vein diameter and not vein type, veins smaller or equal to 0.2 mm were considered as equivalent to homogeneous regions. Hence, a model leaf reduced to the leaf lamina and veins with a diameter >0.2 mm is retained for the study of signal propagation in a leaf.

Models, Biological↗
PubMed1999

In vitro modulation of macrophage phenotype and inhibition of polymer degradation by dexamethasone in a human macrophage/Fe/stress system.

A new in vitro accelerated biological model, the macrophage-FeCl2-stress system was used for the evaluation of dexamethasone (DEX)-polymer formulations. This model combines the effects of cells (macrophages), transition metal ions (Fe2+), and polymer stress to promote material biodegradation. The cell and material effects of DEX, either in solution or incorporated into a polyetherurethane matrix (DEX/PEU), were monitored. Cell morphology and hydroperoxide formation in the polymer during cell culturing were characterized. After a subsequent treatment with FeCl2 the development of environmental stress cracking in the polymer was evaluated. We attempted to duplicate the biodegradation of PEU in terms of environmental stress cracking (ESC). Our results support the direct involvement of macrophages in polyetherurethane oxidation, probably by inducing hydroperoxide formation in the polymer structure. Under the influence of stress or strain, polymers with sufficient hydroperoxides degrade in the presence of Fe2+ metal ions in a manner that closely resembles the stress cracking that is observed in vivo. By contrast, polymers treated with either agents that inhibit cell activation and/or the oxidative burst, or with cells with no oxidative burst did not show signs of the biodegradative process. We demonstrated a reduction in hydroperoxide formation and no later ESC development in macrophage-cultured PEU in the presence of DEX in solution or in DEX-loaded PEU. We believe the prevention of initial polymer oxidation by reducing the cell's potential to produce oxidative stress at the tissue-biomaterial interface can directly inhibit the ESC degradation of chronically implanted polymers. The in vitro macrophage-Fe-stress system is a valuable tool for reliable assessment and cost-effective evaluation of biomaterials.

Adult↗
PubMed1999

Vibratory stimuli in host location by parasitic wasps.

Parasitic wasps use a broad spectrum of different stimuli for host location and host acceptance. Here we review the published evidence for the use of mechanical stimuli, i.e. substrate born vibrations which are invariably regarded as vibrotaxis. We propose a set of criteria to class behavioural reactions as vibrotaxis or vibrokinesis and characterize 14 studies reporting the use of host-associated vibrations by parasitoids. The studies are compared concerning (i) experimental design; (ii) characterisation of vibrational signals; and (iii) progress of the parasitoid towards the host.The recent experimental development based on new measurement techniques shows the growing body of evidence that host-associated vibrations are exploited by parasitic wasps. Nevertheless a definite proof for vibrotaxis is still lacking. To assess the exact mechanisms by which parasitoids use vibrations bioassays comparing reactions to natural and artificially generated signals are needed. Vibrotaxis as well as vibrokinesis are both helpful host location strategies for parasitoids foraging in a multimodal environment. At the community level they may lead to niche differentiation.

Journal Article↗
PubMed1999

Biotransformations of putative phytoecdysteroid biosynthetic precursors in tissue cultures of Polypodium vulgare.

Incubation of calli and prothalli of Polypodium vulgare with different tritium-labelled ecdysteroids has led to modification of some previous assumptions about the biosynthesis of ecdysteroids in plants. Thus, 25-deoxy-20-hydroxyecdysone was transformed efficiently in both tissues into 20-hydroxyecdysone (20E), but no 25-deoxyecdysteroids such as pterosterone and inokosterone were formed. Likewise, incubation of 2-deoxyecdysone (2dE) produced exclusively ecdysone (E) and 20E, indicating a high 2-hydroxylase activity in both tissues, despite calli not producing phytoecdysteroids. This 2-hydroxylation was also evident in the transformation of 2,22-dideoxyecdysone (2,22dE) into 22-deoxyecdysone (22dE). Different ecdysteroids that do not occur in P. vulgare were formed in the incubation of 3-dehydro-2,22,25-trideoxyecdysone (3D2,22,25dE) by 3alpha-reduction and 3beta-reduction and 25-hydroxylation processes. The fact that 22,25-dideoxyecdysone and 22dE were the only 2-hydroxylated products formed in this case suggests that only compounds bearing a 3beta-hydroxyl group are substrates for the 2-hydroxylase. Surprisingly, 22-hydroxylation was never observed with either 2,22dE or 3D2,22,25dE, raising the possibility that it could occur at an early step in the biosynthetic pathway. In this respect, labelled 22R-hydroxycholesterol was efficiently converted into E and 20E, whereas 22S-hydroxycholesterol was not transformed into ecdysteroids, because of its unsuitable configuration at C22. Finally, the conversion of 25-hydroxycholesterol into E and 20E was greatly enhanced after thermal treatment of prothalli which induces the release of previously stored ecdysteroids. Thus, P. vulgare prothalli and calli appear to be particularly suitable models for the study of ecdysteroid biosynthesis and its regulation in plants.

Chromatography, High Pressure Liquid↗
PubMed1999

Unusual finding after contrast injection of a solitary bone cyst. A case report.

Injection of radiopaque contrast into a solitary bone cyst (SBC) prior to methylprednisolone acetate (MPA) injection has been previously reported. We report an unusual finding during the injection of radiopaque contrast in the treatment of one case of SBC of the femur: a bicameral appearance of the cyst was observed; no filling of the proximal cavity occurred and immediate perfusion of the femoral vein with contrast was noted. In cases of SBC such as this one, percutaneous autologous marrow or corticosteroid injection may fail to be effective. Furthermore there exists the potential risk of fat embolus secondary to bone marrow injection. Based on these findings in the case reported, we suggest that contrast injection should be performed prior to bone marrow or corticosteroid injection in order to evaluate both the venous drainage of the cyst and its degree of loculation.

Anti-Inflammatory Agents↗
PubMed1998

Clinical heterogeneity associated with mitochondrial DNA depletion in muscle.

We studied 10 patients with a variable degree of mtDNA depletion in muscle. Seven patients showed a clear-cut myopathic pattern, while the three remaining had brain involvement. There was no relationship between age at onset and relative mtDNA copy number in muscle, but we found an apparent correlation between clinical severity and degree of muscle mtDNA depletion. Muscle morphology showed that mtDNA depletion was associated with mitochondrial proliferation and cytochrome c oxidase negative fibers. Biochemical studies revealed single or combined defects of mtDNA-dependent respiratory chain complexes. Our data indicate that patients with mtDNA depletion may have a more variable age at onset and clinical evolution and wider phenotype than previously thought. The diagnosis of this condition, so far regarded as rare, may have been overlooked to some extent.

Age Factors↗