Environmental gradients structure Daphnia pulex × pulicaria clonal distribution.

The rarity of eukaryotic asexual reproduction is frequently attributed to the disadvantage of reduced genetic variation relative to sexual reproduction. However, parthenogenetic lineages that evolved repeatedly from sexual ancestors can generate regional pools of phenotypically diverse clones. Various theories to explain the maintenance of this genetic diversity as a result of environmental and spatial heterogeneity [frozen niche variation (FNV), general-purpose genotype] are conceptually similar to community ecological explanations for the maintenance of regional species diversity. We employed multivariate statistics common in community ecological research to study population genetic structure in the freshwater crustacean, Daphnia pulex × pulicaria. This parthenogenetic hybrid arose repeatedly from sexual ancestors. Daphnia pulex × pulicaria populations harboured substantial genetic variation among populations and the clonal composition at each pond corresponded to nutrient levels and invertebrate predator densities. The interclonal selection process described by the FNV hypothesis likely structured our D. pulex × pulicaria populations.

Ecological consequences of evolution in plant defenses in a metacommunity.

Dispersal can affect the assembly of local communities in a metacommunity as well as evolution of local populations in a metapopulation. These two processes may also affect each other in ways that have not yet been well studied and that may have novel effects on community structure. Here, we illustrate the interaction of these two processes on community structure with a model of adaptive evolutionary dynamics of plant defenses in a metacommunity food web involving multiple patches along a productivity gradient. We find an enhanced suite of adaptive plant types in our metacommunity model than is predicted in the absence of dispersal. We also find that this, and the movement of nutrients among patches via dispersal, alters patterns of food web architecture, trophic structure and diversity along the productivity gradient. Overall, our model illustrates that evolutionary and metacommunity dynamics may influence communities in complex interactive ways that may not be predicted by models that ignore either of these types of processes.

Concurrent criterion-related validity of physical examination tests for hip labral lesions: a systematic review.

Hip injuries are prevalent, especially within the athletic population. Of the hip injuries in this population, some 18-55% are lesions to the labrum of the hip. Clinical diagnosis of hip labral lesions is difficult because data on prevalence are varied. In addition, data on the prevalence of internal and external risk factors are absent as are data on the correlation of these risk factors with labral lesions, making it difficult to gauge the diagnostic utility. The mechanism of injury is often unknown or not specific to labral lesions. Internal risk factors may remain hidden to physical therapists because in most jurisdictions, ordering imaging tests is not within their scope of practice. Anterior inguinal pain seems highly sensitive for the diagnosis of patients with labral lesions but can hardly be considered specific; data on other pain-related and mechanical symptoms clearly have little diagnostic utility, making these data collected during the patient history almost irrelevant to diagnosis. By way of a comprehensive literature review and narrative and systematic analysis of the methodological quality of the retrieved diagnostic utility studies, this paper aimed to determine a diagnostic physical examination test or test cluster based on current best evidence for the diagnosis of hip labral lesions. Current best evidence indicates that a negative finding for the flexion-adduction-internal rotation test, the flexion-internal rotation test, the impingement provocation test, the flexion-adduction-axial compression test, the Fitzgerald test, or a combination of these tests provides the clinician with the greatest evidence-based confidence that a hip labral lesion is absent. Currently, research has produced no tests with sufficient specificity to help confidently rule in a diagnosis of hip labral lesion. Suggestions for future research are provided.

Work-related injuries to the foot. Data from an occupational injury/illness surveillance system.

In 1988, a total of 990 work-related injuries to the foot of employees from private-sector companies were characterized in an occupational injury/illness surveillance system maintained by a network of occupational health centers. The mean age of the worker with a foot injury was 34.2 years (+/- 12.0), with 83% occurring among men; 22.3% of the cases were fractures or sprains/strains. Jobs involving extensive manual material handling or vehicular operations were the most often listed occupations among those with work-related foot injuries. Across occupational groups, being struck by an object accounted for 58.4% of the foot injuries. Regardless of industry group, metal items and vehicles were related to 50.7% of all work-related foot injuries. Specifically, foot injuries were found to be associated with being struck by boxes, metals, or vehicles, or to being caught in, under, or between vehicles or machinery. A peak of work-related injuries involving the foot is observed during the summer months.

Non-invasive diagnosis of internal carotid artery dissections.

Arteriography is thought to be mandatory for the diagnosis of internal carotid artery (ICA) dissection. With the introduction of transcranial Doppler sonography (TCD) and magnetic resonance imaging (MRI), however, this is no longer the case. In 13 consecutive patients with ICA dissections the diagnosis was made by means of non-invasive tests including extracranial and transcranial Doppler sonography, contrast enhanced computed tomography (ceCT), and, in five patients, MRI. Intra-arterial digital subtraction angiography used as the gold standard in all cases was confirmative. Extracranial and transcranial ultrasound findings indicative of the diagnosis could be identified. MRI directly demonstrated the intramural haematoma and the false lumen of the dissected artery. These non-invasive techniques also allowed for repetitive follow up examinations. They were, however, unable to demonstrate false aneurysms in the chronic state. Results show that the diagnosis of carotid dissection can be made by means of cerebrovascular ultrasound and MRI.

[Dissections of the internal carotid artery--new diagnostic and pathogenetic aspects]. / Dissektionen der A. carotis interna--neue diagnostische und pathogenetische Aspekte.

Initial and follow-up investigations were done systematically in 15 cases of internal carotid artery (ICA) dissections by means of angiography, computerized tomography, Magnetic Resonance Imaging, extracranial and transcranial Doppler sonography, as well as B-mode imaging. Cerebral hemodynamic reserve was evaluated by means of both SPECT and CO2-dependent vasomotor reactivity. The findings are focussed on two major issues: Do modern diagnostic tools permit to make the diagnosis of ICA dissection without angiographical proof? What is the pathogenesis of brain infarctions due to ICA dissections? Our findings demonstrate that the diagnosis of carotid artery dissection can reliably be done noninvasively by means of ultrasound techniques and MRI. These methods also allow for frequent follow-up investigations without any inconvenience for the patient. Embolic brain infarctions caused by carotid artery dissections are equally frequent as low flow induced lesions. Acute and follow-up findings suggest that surgical intervention is contraindicated in the acute phase, but may be considered for chronic pseudoaneurysms. Initial anticoagulation with high dose heparin is safe and seems to be efficacious. In certain cases, subsequent cumarine therapy may be indicated for a maximum of six months. Measures improving hemodynamics, e. g. induced hypertension, are reasonable, as long as the vasomotor reserve is exhausted.

Infarctions and non-invasive diagnosis in moyamoya disease: two case reports.

An 31-year-old female and a 32-year-old male had clinical signs and angiographical confirmation of adult Moyamoya disease (MMD). Bilateral carotid siphon (C1), middle cerebral artery (M1), and anterior cerebral artery (A1) stenoses were diagnosed by means of transcranial Doppler sonography (TCD) and visualized during angio Magnetic Resonance Imaging (angio-MRI). In the woman, a 'rete mirabile' of dilated and tortuous lenticulostriate arteries could be visualized during proton weighted and T1-weighted MRI sequences. CO2-dependent vasomotor reactivity was bilaterally reduced and completely exhausted in the territory of right middle cerebral artery in both patients. Cerebral perfusion reserve, defined as the ratio of cerebral blood flow (CBF) to cerebral blood volume (CBV) was assessed by SPECT, and was found to be dramatically reduced in the anterior region of the male patient. Both patients had bilateral small subcortical infarctions in the corona radiata. TCD and MRI are important noninvasive techniques for a preliminary diagnosis of Moyamoya disease. Infarctions in Moyamoya disease may be hemodynamically produced low-flow infarctions.

Trophic interactions and habitat segregation between competing Daphnia species.

Two commonly coexisting species of Daphnia segregate by habitat in many stratified lakes. Daphnia pulicaria is mostly found in the hypolimnion whereas D. galeata mendotae undergoes diel vertical migration between the hypolimnion and the epilimnion. I examined how habitat segregation between these two potentially competing species might be affected by trophic interactions with their resources and predators by performing a field experiment in deep enclosures in which I manipulated fish predation, nutrient levels, and the density of epilimnetic Daphnia. The results of the experiment indicate that habitat use by D. pulicaria can be jointly regulated by competition for food from epilimnetic Daphnia and predation by fishes. Patterns of habitat segregation between the two Daphnia species were determined by predation by fish but not by nutrient levels: The removal of epilimnetic fish predators resulted in higher zooplankton and lower epilimnetic phytoplankton densities and allowed D. pulicaria to expand its habitat distribution into the epilimnion. In contrast, increased resource productivity resulted in higher densities of both Daphnia species but did not affect phytoplankton levels or habitat use by Daphnia. The two species exhibit a trade-off in their ability to exploit resources and their susceptibility to predation by fish. D. g. mendotae (the less susceptible species) may thus restrict D. pulicaria (the better resource exploiter) from the epilimnion when fish are common due to lower minimum resource requirements than those needed by D. pulicaria to offset the higher mortality rate imposed by selective epilimnetic fish predators. D. g. mendotae does not appear to have this effect in the absence of fish.

A model for occupational injury surveillance by occupational health centers.

Injuries account for more than 90% of the reported work-related health problems in the United States. However, a complete and standardized reporting system for occupational injuries does not exist in this country. This paper describes the first year's experience of a clinic-based occupational injury surveillance system involving occupational medicine clinics. During 1988, health and hazard information was collected on 14,156 work-related admissions. An analysis of these cases showed that most patients received care for minor trauma, with 78.4% of the cases classified as cuts or lacerations, sprains or strains, or contusions. Overall, 53.8% of the cases were caused by metal items, boxes, machines, or working surfaces. These preliminary results support the feasibility of conducting clinic-based occupational injury surveillance as a means of assisting employers with the control of work-related conditions.

[Dissections of the vertebral artery following cervical chiropractic manipulations]. / Dissektionen der Arteria vertebralis nach zervikalen chiropraktischen Manipulationen.

In a 37-year-old female patient complaining of increasing pain in the neck and occiput, chiropractic manipulations at the cervical vertebral column were associated with ischaemias of the brain stem presenting as vertigo, transient "locked-in" syndrome followed by vomiting, and sensorimotor hemiparesis. Digital subtraction angiography (DSA) revealed complete obstruction of the right and slight dissection of the left vertebral artery. The symptoms receded within a few days after heparinisation with 1000 IU/h intravenously. A 39-year-old female patient developed vertigo, nystagmus, tetraparesis and dysarthria two days after chiropractic intervention because of refractory pain in the neck and occiput. DSA showed embolism of the basilar artery and extensive dissections of the vertebral arteries. The basilar artery was completely recanalized after local intraarterial fibrinolysis with 50,000 IU urokinase. During the further course of treatment the symptoms receded under heparin and phenprocoumon over a period of 8 months, except for hemiparesis on the left side especially affecting the arm. Trivial traumas can result in dissections of the vertebral arteries. Severe neck pain is a frequent, typical early symptom. Hence, patients with cervical vertebral column syndromes should receive chiropractic treatment only after careful diagnosis.