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Biomedical subjects

A Janssen

Publications and source records attributed to A Janssen.

At least 19 recordsLinked to original sources
PubMed2007

[Prolonged vascular complications with subsequent finger necrosis after humeral head luxation fracture in the elderly].

Fractures of the proximal humerus represent a typical injury of the elderly. Additional lesions of nerves or arteries are rare and there is only little information in the literature on the co-occurrence of proximal humerus fractures and compromised peripheral circulation which could lead to the loss of the upper extremity. To prevent damage to the injured limb, it is necessary to invent and initiate a standardized algorithm involving trauma care matching the special needs of this combined injury.

Aged, 80 and over↗
PubMed2006

The role of caspases in photoreceptor cell death of the retinoschisin-deficient mouse.

Early schisis cavities in the retinal bipolar cell layer accompanied by progressive loss of cone and rod photoreceptor cells are the hallmark of the retinoschisin-deficient (Rs1h(-/Y)) murine retina. With this study we aimed at elucidating the molecular events underlying the photoreceptor cell death in this established murine model of X-linked juvenile retinoschisis. We show that photoreceptor degeneration in the Rs1h(-/Y) mouse is due to apoptotic events peaking around postnatal day 18. Cell death is accompanied by increased expression of initiator and inflammatory caspases but not by downstream effector caspases. The strong induction of caspase-1 (Casp1) prompted us to explore its involvement in the apoptotic process. We therefore generated double knock-out mice deficient for both retinoschisin and Casp1. No direct influence of the Casp1 genotype on apoptosis could be identified although striking differences in the overall number of resident microglia were observed independent of the Rs1h genotype.

Animals↗
PubMed2005

[Fractures of the distal humerus].

The treatment of fractures of the distal humerus remains challenging due to the complex anatomy of the elbow joint. Satisfactory results can only be attained with the complete recovery of the function and stability of the joint. Open reduction and internal fixation following AO principles, therefore, represents the standard procedure for the treatment of distal humerus fractures. Unfavourable results can, however, not be avoided in all cases, especially if fractures are complicated by concomitant lesions of soft tissues, nerves or vessels.

Fracture Fixation, Internal↗
PubMed2005

Pulsatility index is better than ankle-brachial doppler index for non-invasive detection of critical limb ischaemia in diabetes.

BACKGROUND: Diabetic polyneuropathy of the feet and legs obscures the diagnosis of critical limb ischaemia (CLI) because of lack of pain sensation. Hence, the Fontaine classification does not apply to these patients. Furthermore, many of them will exhibit medial arterial calcification, which invalidates the application of sphygmomanometry. This study was done to evaluate the pulsatility index (P1) assessed at the ankle arteries by colour Doppler ultrasonography as a non-invasive method to diagnose CLI in diabetic polyneuropathy. PATIENTS AND METHODS: 140 legs of 106 diabetic patients were studied who presented with polyneuropathy and painlessness of the feet; of these, 117 feet displayed an ulcer or gangrene. CLI was defined as the need for arterial revascularisation, as indicated by the physicians in charge on the basis of a) a foot lesion Wagner grade 1-5, and b) a positive arteriography. All patients were subjected to 4 vascular assessment techniques: digital subtraction arteriography, ankle-brachial Doppler index, systolic ankle blood pressure, and PI. RESULTS: Of the 140 legs, 61 (44%) were affected by CLI, and 76 (54%) by medial arterial calcification. A PI < 1.2 indicated CLI with a sensitivity of 0.87 and a specificity of 0.62. The sensitivity and specificity of ankle-brachial index < 0.9, and of systolic ankle pressure < 70 mm Hg to predict CLI was 0.71 and 0.42, and 0.30 and 0.89, respectively. CONCLUSIONS: The pulsatility index is a better noninvasive technique than the ankle-brachial Doppler index or the systolic ankle pressure to assess critical limb ischaemia in diabetic polyneuropathy. A pulsatility index < 1.2 at the ankle arteries is a reliable criterion for diagnosis of CLI in diabetic patients with polyneuropathy.

Aged↗
PubMed2005

Design of laying nests in furnished cages: influence of nesting material, nest box position and seclusion.

(1) Preferences for three nesting materials and nest box positions were investigated simultaneously in two trials using a furnished cage: one with 18 individual laying hens and one with 18 groups of 5 hens. Following a habituation period in pre-test cages, every hen or group of hens was tested for 2 d: once without and once with plastic flaps at the entrance of the nest boxes. (2) Hens preferred peat and artificial turf to coated wire mesh for egg laying. (3) One nest box position was clearly preferred to both other nest boxes. The hens' choice of nest box position was influenced by the pre-test cage in which they had been habituated. (4) The presence of plastic flaps at the entrance of the nest boxes had no influence on the proportion of eggs laid on the different nesting materials or on the proportion of floor eggs. (5) Individual and group testing resulted in the same overall results despite the presence of a distinct group effect.

Animal Husbandry↗
PubMed2003

Tall stature and progressive overweight in mitochondrial encephalopathy.

We describe two children carrying an inherited T899C mutation in the mitochondrial ATPase 6 gene with mild encephalopathy and normal postnatal growth followed by tall stature and obesity. No familial tall stature, endocrine anomaly or advanced skeletal age were present. Failure to thrive is a characteristic finding in most patients with a mitochondrial disease. Our observations suggest that children with encephalomyopathy, even in the presence of a significant clinical overgrowth, should be screened for a possible defect in oxidative phosphorylation.

Adolescent↗
PubMed2003

Anti-epileptogenesis research: the clinical relevance.

In recent years, different research lines have examined the epileptogenic process in order to understand the different stages in this process, and with the hope that early recognition and intervention could prevent chronic epilepsy in patients with epileptic seizures. In animals, acquired epilepsy is studied most commonly with kindling models, status epilepticus models and traumatic brain injury models. Molecular genetic studies substantially help to understand age-specific channel and receptor abnormalities. Major progress has been made in recent years and we are now waiting for the first large scale multi-center clinical trials that test the possible anti-epileptogenic properties of anti-epileptic drugs or other compounds in well defined patient groups. In clinical practice, a structured diagnostic work-up in all patients with recurrent seizures is a first and necessary step in the recognition of patients at risk for developing chronic and refractory epilepsy.

Animals↗
PubMed2001

Habitat structure and population persistence in an experimental community.

Understanding spatial population dynamics is fundamental for many questions in ecology and conservation. Many theoretical mechanisms have been proposed whereby spatial structure can promote population persistence, in particular for exploiter-victim systems (host-parasite/pathogen, predator-prey) whose interactions are inherently oscillatory and therefore prone to extinction of local populations. Experiments have confirmed that spatial structure can extend persistence, but it has rarely been possible to identify the specific mechanisms involved. Here we use a model-based approach to identify the effects of spatial population processes in experimental systems of bean plants (Phaseolus lunatus), herbivorous mites (Tetranychus urticae) and predatory mites (Phytoseiulus persimilis). On isolated plants, and in a spatially undivided experimental system of 90 plants, prey and predator populations collapsed; however, introducing habitat structure allowed long-term persistence. Using mechanistic models, we determine that spatial population structure did not contribute to persistence, and spatially explicit models are not needed. Rather, habitat structure reduced the success of predators at locating prey outbreaks, allowing between-plant asynchrony of local population cycles due to random colonization events.

Animals↗
PubMed2001

Prenatal and postnatal development of peroxisomal lipid-metabolizing pathways in the mouse.

The ontogeny of the following peroxisomal metabolic pathways was evaluated in mouse liver and brain: alpha-oxidation, beta-oxidation and ether phospholipid synthesis. In mouse embryos lacking functional peroxisomes (PEX5(-/-) knock-out), a deficiency of plasmalogens and an accumulation of the very-long-chain fatty acid C(26:0) was observed in comparison with control littermates, indicating that ether phospholipid synthesis and beta-oxidation are already active at mid-gestation in the mouse. Northern analysis revealed that the enzymes required for the beta-oxidation of straight-chain substrates are present in liver and brain during embryonic development but that those responsible for the degradation of branched-chain substrates are present only in liver from late gestation onwards. The expression pattern of transcripts encoding enzymes of the alpha-oxidation pathway suggested that alpha-oxidation is initiated in the liver around birth and is not active in brain throughout development. Remarkably, a strong induction of the mRNA levels of enzymes involved in alpha-oxidation and beta-oxidation was observed around birth in the liver. In contrast, enzyme transcripts that were expressed in brain were present at rather constant levels throughout prenatal and postnatal development. These results suggest that the defective ether phospholipid synthesis and/or peroxisomal beta-oxidation of straight-chain fatty acids might be involved in the pathogenesis of the prenatal organ defects in peroxisome-deficient mice and men.

Animals↗
PubMed2001

Predatory mites avoid ovipositing near counterattacking prey.

Attacking prey is not without risk; predators may endure counterattack by the prey. Here, we study the oviposition behaviour of a predatory mite (Iphiseius degenerans) in relation to its prey, the western flower thrips (Frankliniella occidentalis). This thrips is capable of killing the eggs of the predator. Thrips and predatory mites - apart from feeding on each other - can also feed and reproduce on a diet of pollen. Because thrips may aggregate at pollen patches, such patches may be risky for oviposition by the predatory mites. We found that, in absence of thrips, predatory mites lay their eggs close to pollen, but further away when thrips are present. Predatory mite eggs near pollen were killed more frequently by thrips than when they were deposited further away. The oviposition behaviour of the predatory mite was also studied in absence of thrips, but in presence of the alarm pheromone of thrips. This pheromone is normally secreted upon contact with predators or competitors. When applied close to the pollen. predatory mites oviposited significantly further away from it. When the alarm pheromone was applied away from the food source, most eggs were found near the pollen. These results indicate that female predatory mites show flexible oviposition behaviour in response to the presence of their counterattacking prey.

Animals↗
PubMed2001

Phytoseiid predators as potential biological control agents for Bemisia tabaci.

Mites of the family Phytoseiidae are known to be predators of whiteflies in several agroecosystems, especially of Bemisia tabaci Gennadius, a pest with high resistance to chemical insecticides that occurs in greenhouses in temperate regions. We collected predatory mites that were found to co-occur with whiteflies in the Middle East for control of B. tabaci: Tvphlodromus athiasae (Porath and Swirski), Neoseiulus barkeri Hughes, Tvphlodromips swirskii (Athias-Henriot), Euseius scutalis (Athias-Henriot), Phytoseius finitimus Ribaga. As a first step in the evaluation of these species as biological control agents, we measured their life-history traits when feeding on whiteflies. The intrinsic rates of increase (rm) of the predatory mite species ranged between 0.131 and 0.215 per day and E. scutalis had the highest rm estimated. Comparisons with the rm of B. tabaci indicate that some of the species should be capable of suppressing local populations of whitefly. The ability of predators to use alternative food was also tested, since it facilitates the setup of mass cultures and it can promote their persistence in the crop, even if the prey is scarce. All predatory mite species tested were able to survive and reproduce on a diet of broad bean pollen.

Animals↗
PubMed2001

Prey preference, intraguild predation and population dynamics of an arthropod food web on plants.

The theory of intraguild predation (IGP) largely studies effects on equilibrium densities of predators and prey, while experiments mostly concern transient dynamics. We studied the effects of an intraguild (IG) predator, the bug Orius laevigatus, on the population dynamics of IG-prey, the predatory mite Phytoseiulus persimilis, and a shared prey, the phytophagous two-spotted spider mite Tetranychus urticae, as well as on the performance of cucumber plants in a greenhouse. The interaction of the predatory mite and the spider mite is highly unstable, and ends either by herbivores overexploiting the plant or predators exterminating the herbivores. We studied the effect of IGP on the transient dynamics of this system, and compared the dynamics with that predicted by a simple population-dynamical model with IGP added. Behavioural studies showed that the predatory bug and the predatory mite were both attracted to plants infested by spider mites and that the two predators did not avoid plants occupied by the other predator. Observations on foraging behaviour of the predatory bug showed that it attacks and kills large numbers of predatory mites and spider mites. The model predicts strong effects of predation and prey preference by the predatory bugs on the dynamics of predatory mites and spider mites. However, experiments in which the predatory bug was added to populations of predatory mites and spider mites had little or no effect on numbers of both mite species, and cucumber plant and fruit weight.

Animals↗
PubMed2000

Impact of a worker notification program: assessment of attitudinal and behavioral outcomes.

BACKGROUND: Hundreds of worker notification programs are conducted each year to communicate occupational risks to workers. However, few attempts have been made to evaluate their effectiveness and few have described how communication theories are applied in developing notification messages. We developed and assessed the effectiveness of a worker notification program at a beryllium machining plant. METHODS: We compared self-protective attitudinal and behavioral responses among workers in two plants: (1) an intervention plant that received beryllium risk notification and (2) a matched control plant that did not receive notification. RESULTS: Workers receiving notification reported significantly stronger perceptions of threat and efficacy, more positive attitudes toward safety practices, and engaged in more protective behaviors than the workers at the control plant. CONCLUSIONS: This study demonstrates the utility of applying communication theories in the development of notification messages and the results suggest that mass presentations may be just as effective, if not more so, than one-on-one notifications. Am. J. Ind. Med. 37:205-213, 2000. Published 2000 Wiley-Liss, Inc.

Adult↗
PubMed2000

Diet of a polyphagous arthropod predator affects refuge seeking of its thrips prey.

Antipredator behaviour of prey costs time and energy, at the expense of other activities. However, not all predators are equally dangerous to all prey; some may have switched to feeding on another prey species, making them effectively harmless. To minimize costs, prey should therefore invest in antipredator behaviour only when dangerous predators are around. To distinguish these from harmless predators, prey may use cues related to predation on conspecifics, such as odours released by a predator that has recently eaten conspecific prey or alarm pheromones released by attacked prey. We studied refuge use by a herbivorous/omnivorous thrips, Frankliniella occidentalis, in response to odours associated with a generalist predatory bug, Orius laevigatus, fed either with conspecific thrips or with other prey. The refuge used by thrips larvae is the web produced by its competitor, the two-spotted spider mite, Tetranychus urticae, where thrips larvae experience lower predation risk because the predatory bug is hindered by the web. Thrips larvae moved into this refuge when odours associated with predatory bugs that had previously fed on thrips were present, whereas odours from predatory bugs that had fed on other prey had less effect. We discuss the consequences of this antipredator behaviour for population dynamics. Copyright 2000 The Association for the Study of Animal Behaviour.

Journal Article↗