Characterizing the phylogenetic specialism-generalism spectrum of mammal parasites.

The distribution of parasites across mammalian hosts is complex and represents a differential ability or opportunity to infect different host species. Here, we take a macroecological approach to investigate factors influencing why some parasites show a tendency to infect species widely distributed in the host phylogeny (phylogenetic generalism) while others infect only closely related hosts. Using a database on over 1400 parasite species that have been documented to infect up to 69 terrestrial mammal host species, we characterize the phylogenetic generalism of parasites using standard effect sizes for three metrics: mean pairwise phylogenetic distance (PD), maximum PD and phylogenetic aggregation. We identify a trend towards phylogenetic specialism, though statistically host relatedness is most often equivalent to that expected from a random sample of host species. Bacteria and arthropod parasites are typically the most generalist, viruses and helminths exhibit intermediate generalism, and protozoa are on average the most specialist. While viruses and helminths have similar mean pairwise PD on average, the viruses exhibit higher variation as a group. Close-contact transmission is the transmission mode most associated with specialism. Most parasites exhibiting phylogenetic aggregation (associating with discrete groups of species dispersed across the host phylogeny) are helminths and viruses.

ABCG2 loss-of-function polymorphism predicts poor response to allopurinol in patients with gout.

Many patients fail to achieve the recommended serum urate (SU) target (<6 mgdl-1) with allopurinol. The aim of our study was to examine the association of ABCG2 with SU target in response to standard doses of allopurinol using a cohort with confirmed adherence. Good response was defined as SU<6 mgdl-1 on allopurinol ⩽300 mgd-1 and poor response as SU⩾6 mgdl-1 despite allopurinol >300 mgd-1. Adherence was confirmed by oxypurinol concentrations. ABCG2 genotyping was performed using pre-designed single nucleotide polymorphism (SNP) TaqMan assays. Of 264 patients, 120 were good responders, 68 were poor responders and 76 were either non-adherent or could not be classified. The minor allele of ABCG2 SNP rs2231142 conferred a significantly increased risk of poor response to allopurinol (odds ratio=2.71 (1.70-4.48), P=6.0 × 10-5). This association remained significant after adjustment for age, sex, body mass index, ethnicity, estimated glomerular filtration rate, diuretic use and SU off urate-lowering therapy. ABCG2 rs2231142 predicts poor response to allopurinol, as defined by SU⩾6 mgdl-1 despite allopurinol >300 mgd-1.

The mismatch of narratives and local ecologies in the everyday governance of water access and mosquito control in an urbanizing community.

Mosquito-borne disease presents a significant threat to urban populations, but risk can be uneven across a city due to underlying environmental patterns. Urban residents rely on social and economic processes to control the environment and mediate disease risk, a phenomenon known as everyday governance. We studied how households employed everyday governance of urban infrastructure relevant to mosquito-borne disease in Bengaluru, India to examine if and how inequalities in everyday governance manifest in differences in mosquito control. We found that governance mechanisms differed for water access and mosquitoes. Economic and social capital served different roles for each, influenced by global narratives of water and vector control.

Critical patch size generated by Allee effect in gypsy moth, Lymantria dispar (L.).

Allee effects are important dynamical mechanisms in small-density populations in which per capita population growth rate increases with density. When positive density dependence is sufficiently severe (a 'strong' Allee effect), a critical density arises below which populations do not persist. For spatially distributed populations subject to dispersal, theory predicts that the occupied area also exhibits a critical threshold for population persistence, but this result has not been confirmed in nature. We tested this prediction in patterns of population persistence across the invasion front of the European gypsy moth (Lymantria dispar) in the United States in data collected between 1996 and 2008. Our analysis consistently provided evidence for effects of both population area and density on persistence, as predicted by the general theory, and confirmed here using a mechanistic model developed for the gypsy moth system. We believe this study to be the first empirical documentation of critical patch size induced by an Allee effect.

Chemical and biological microstructures as probed by dynamic processes.

The dynamic process of electronic energy transfer is shown to be an important tool for probing the microstructure of molecular systems, particularly those in which donors and acceptors occupy specifically labeled sites of spatially confining host matrices. Special attention is given to analyzing the temporal behavior of the direct energy transfer reaction for systems in which the dipolar coupling is between a donor and randomly distributed acceptors. This dynamic process is dependent on two competing lengths when the donor and acceptor distribution is determined by the microstructure of the confining system: Rp, the dominant length characterizing the size of the confinement, and R0, which scales the strength of the dipolar coupling. When energy transfer processes are viewed in the context of these two competing lengths, a picture emerges of the microstructure of the confinement that is consistent with and corroborated by other structural probes.

Upper limb motor function in young adults with spina bifida and hydrocephalus.

OBJECTIVE: The objective of the study was to measure upper limb motor function in young adults with spina bifida meningomyelocele (SBM) and typically developing age peers. METHOD: Participants were 26 young adults with SBM, with a Verbal or Performance IQ score of at least 70 on the Wechsler scales, and 27 age- and gender-matched controls. Four upper limb motor function tasks were performed under four different visual and cognitive challenge conditions. Motor independence was assessed by questionnaire. RESULTS: Fewer SBM than control participants obtained perfect posture and rebound scores. The SBM group performed less accurately and was more disrupted by cognitive challenge than controls on limb dysmetria tasks. The SBM group was slower than controls on the diadochokinesis task. Adaptive motor independence was related to one upper limb motor task, arm posture, and upper rather than lower spinal lesions were associated with less motor independence. CONCLUSIONS: Young adults with SBM have significant limitations in upper limb function and are more disrupted by some challenges while performing upper limb motor tasks. Within the group of young adults with SBM, upper spinal lesions compromise motor independence more than lower spinal lesions.

Ultrasonic motor-induced geometric distortions in magnetic resonance images.

Ultrasonic motors (USMs) are common actuators that can be safely used in the magnetic resonance imaging (MRI) environment. However, lack of MRI compatibility results in issues such as image distortion. This fact led researchers to shift focus from USMs to pneumatic and hydraulic actuators in development of surgical robots. The aim is to quantify and compensate the geometric distortion of MR images as generated by the presence of USMs. An ultrasonic motor was positioned in three orientations with respect to the bore axis. The induced distortions were compared across four image sequences. To reduce the distortions, three artifact reduction methods were employed. Geometric distortion is the only artifact in image slices farther from the motor. The various motor orientations lead to different distortions, with the lowest distortion for the z orientation. The maximum measured distortion of ten pixels occurred. This maximal distortion is equal to a 1-cm displacement of the displayed points relative to their actual locations and it is beyond the acceptable level for medical display standards. Bandwidth reduction reduced the distortion, with a 50% reduction for a doubled bandwidth. In conclusion, USMs can be preferred alternative because accurate targeting of pathologies can occur in free distorted images.

Design, Modelling and Teleoperation of a 2 mm Diameter Compliant Instrument for the da Vinci Platform.

This work explores the feasibility of creating and accurately controlling an instrument for robotic surgery with a 2 mm diameter and a three degree-of-freedom (DoF) wrist which is compatible with the da Vinci platform. The instrument's wrist is composed of a two DoF bending notched-nitinol tube pattern, for which a kinematic model has been developed. A base mechanism for controlling the wrist is designed for integration with the da Vinci Research Kit. A basic teleoperation task is successfully performed using two of the miniature instruments. The performance and accuracy of the instrument suggest that creating and accurately controlling a 2 mm diameter instrument is feasible and the design and modelling proposed in this work provide a basis for future miniature instrument development.

The constitutive properties of the brain parenchyma Part 1. Strain energy approach.

In this paper we study several constitutive equations for the brain based on the strain energy density function. We use the polynomial function and hyper-elastic Ogden model for the strain energy and include the energy dissipation by a Prony series expansion. The models are compared with known unconfined compression experimental results of the human brain tissue to obtain the best fitted model and brain mechanical parameters. Finite element simulations are also performed using the given constitutive equations, and numerical solutions match the analytical results very closely. The results are compared with other analytical and numerical calculations.

Reduced local cerebral blood flow in periventricular white matter in experimental neonatal hydrocephalus-restoration with CSF shunting.

The extent to which the reduction in CBF occurring in hydrocephalus is a primary or secondary event in the pathogenesis of the brain injury that ensues has not been clearly established. This is particularly true in neonatal hydrocephalus, where the disorder is most common, and where timing of the treatment of the developing nervous system is so important. We investigated the changes in local CBF (lCBF) in an animal model of severe progressive neonatal hydrocephalus before and after CSF shunting. Hydrocephalus was induced in 27 1-week-old kittens by percutaneous injection of 0.05 ml of 25% kaolin into the cisterna magna. Fourteen littermates acted as controls. The lCBF was measured by 14C-iodoantipyrine quantitative autoradiography after 1 week in 15 animals (8 hydrocephalic, 7 controls) and after 3 weeks in 26 animals (19 hydrocephalic, 7 controls) following induction of hydrocephalus. Twelve of the 3-week hydrocephalic group received a ventriculoperitoneal shunt 10 days following kaolin injection. At 1 week following induction of hydrocephalus, lCBF was globally reduced in cortical gray matter and white matter as well as deep subcortical structures. The maximum reduction was in the parietal white matter, to 37% of control levels. At 3 weeks a significant reduction in lCBF persisted only in the white matter (parietal, occipital, and corpus callosum; average, 42% of control levels), whereas cortical gray and deep subcortical structures had returned to normal levels spontaneously.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional injury of cholinergic, GABAergic and dopaminergic systems in the basal ganglia of adult rat with kaolin-induced hydrocephalus.

Structural and/or functional injury of the basal ganglia can lead to motor functional disabilities, abnormal gait and posture, and intellectual/emotional impairment, disorders also frequently seen in hydrocephalus. Previous reports have documented changes in dopamine levels in the neostriatum in experimental hydrocephalus. The present study was designed to investigate possible functional injury of cholinergic, GABAergic and dopaminergic systems in the basal ganglia immunohistochemically in a model of kaolin-induced hydrocephalus. Hydrocephalus was induced in 12 Wistar rats by intracisternal injection of 0.05 ml volume of 25% kaolin solution under microscopic guidance. Four controls received an equal volume of sterile saline. The animals were killed at 2, 4 and 8 weeks after injection. The numbers of choline acetyltransferase (ChAT)- and glutamic acid decarboxylase (GAD)-immunoreactive (IR) neostriatal neurons and tyrosine hydroxylase (TH)-IR nigral neurons, were counted in 60-micron thick representative sections and the IR cellular densities (counted cell number/neostriatal area) were calculated in the neostriatum. The number of total neostriatal neurons was also counted in 15-micron thick sections stained by cresyl violet (Nissl staining) to calculate the cellular density. The number and cellular density of neostriatal ChAT-IR neurons were significantly reduced at 2, 4, and 8 weeks after injection (P < 0.05), while those of GAD-IR neurons decreased at 4 and 8 weeks (P < 0.05). There was a linear correlation between degree of ventricular enlargement, and reduction in number of ChAT- and GAD-IR neurons (P < 0.001) as well as in the cellular density (P < 0.001). However, Nissl staining revealed no reduction in the cellular density of total neostriatal neurons (P < 0.001). TH immunoreactivity was reduced in neostriatal axons and in nigral compacta neurons, particularly in the medial portion of the dopaminergic nigrostriatal pathway. These findings suggest that progressive hydrocephalus results in functional injuries of cholinergic and GABAergic neurons in the neostriatum and dopaminergic neurons in the substantia nigra compacta by mechanical distortion. The disturbance in balance of these neurotransmitter systems in the basal ganglia may explain some of motor functional disabilities in hydrocephalus.

Fatal ethibloc embolization of vertebrobasilar system following percutaneous injection into aneurysmal bone cyst of the second cervical vertebra.

A 4-year-old boy developed progressive neck pain and an expansile osteogenic lesion of C2; the diagnosis was an aneurysmal bone cyst. An image-guided biopsy with 3D CT planning was performed followed by Ethibloc injection into the aneurysmal bone cyst. Subsequent CT and MR images demonstrated embolization material in the vertebrobasilar system, and the patient died of brain stem and cerebellar infarction 23 hours after the intervention. The course of events and technical considerations are discussed.

Retethering of sectioned fibrolipomatous filum terminales: report of two cases.

OBJECTIVE AND IMPORTANCE: The release of a tethered spinal cord by sectioning a thickened filum terminale is a straightforward surgical procedure that can prevent, arrest, or ameliorate neurological deficits. We recently recognized progressive neurological deterioration caused by filum retethering in two patients years after this procedure was performed. This sequela of a recurrent tethered cord after the sectioning of a filum terminale has not previously been described. CLINICAL PRESENTATION: Two female patients, each 13 years of age at presentation, had been previously operated on for tethered spinal cords secondary to fibrolipomatous (fatty) fila terminale. Both presented with bladder dysfunction and one with progressive paraparesis. Magnetic resonance images revealed a low-lying conus medullaris and a sectioned filum with the proximal stump adherent to the posterior dura. INTERVENTION: Each patient underwent neurosurgical exploration of the previous site of sectioning, with the recognition of a retethered proximal stump of the filum terminale. After rerelease of the fatty filum, the patient with only bladder dysfunction stabilized and a motor examination revealed normal results for the patient with progressive paraparesis. CONCLUSION: Retethering of the spinal cord is a rare sequela after the sectioning of a tight filum terminale. The clinical presentation is typical for recurrent cord tethering, and the radiographic findings are subtle. Careful surgical exploration should be offered for spinal cord untethering. Awareness of this rare and hitherto undescribed sequela is necessary for appropriate long-term management of tethered spinal cord caused by a fatty filum terminale.

Cerebrospinal fluid flow dynamics in children with external ventricular drains.

Fifty-five children had 64 external ventricular drains (EVDs) placed predominantly (95%) for cerebrospinal fluid (CSF) shunt infections. In 9 children, a computer monitoring system measured the CSF output each second continuously for up to 24 hours. The monitoring was repeated daily for up to 9 days. The state of arousal of the patients was recorded simultaneously. In all children, daily EVD outputs were related to age, sex, weight, method of establishing the EVD, height of the drip chamber, time since insertion, and type of infecting organism. Computer monitoring revealed wide fluctuations in flow rate, with peak rates frequently greater than 20 ml/h and periods of flow arrest. These changes were usually associated with increased arousal, but also occurred with sleep. The mean EVD flow rate for all children was 6.3 ml/h. EVD output increased with age and weight. EVD output decreased with Gram-negative or multiple-organism infections and with elevation of the drip chamber. Resolution of the infection, sex of the patient, and method of establishing the EVD had no effect on output. These results predict that CSF production increases with brain growth in humans: that CSF production is depressed by Gram-negative and multiple-organism infections: that implanted CSF shunts with standard valves flow at equivalent rates to an EVD in the supine position; and that the CSF drainage requirements in this group are approximately equal to their EVD outputs.

Computer- and robot-assisted resection of thalamic astrocytomas in children.

Six children ranging in age from 2 to 10 years who harbored deep benign astrocytomas were operated upon using a computer- and robot-assisted system. A radical excision was achieved in all cases with no significant morbidity nor any mortality. The system consists of an interactive, three-dimensional display of computed tomographic image contours and digitized cerebral angiograms taken using the Brown-Roberts-Wells stereotactic frame. The surgical retractor is held and manipulated using a PUMA 200 robot. The position and orientation of the surgical retractor is displayed on the three-dimensional display. Preoperative planning and simulation are important features of this system. Movement of the brain after removal of the tumor and cerebrospinal fluid is substantial, so the tumor removal is based on visually defined margins. Enhanced computer graphics and robotic devices are important adjuncts to neurosurgical procedures and will find increasing use in the future.

Functional obstruction of an antisiphon device by raised tissue capsule pressure.

The proper function of an antisiphon device (ASD) requires that it be exposed externally to atmospheric pressure and that its mobile membrane be free to move. A 4-year-old boy who had an ASD placed for postshunt subdural hematomas presented with functional obstruction of the ASD-symptomatic ventriculomegaly despite evidence of patency of the shunt system by radionuclide flow study. At surgery, the distal shunt system including the ASD was infused with normal saline before and after surgical exposure of the device. The pressures required to maintain a flow rate of 5 ml/h and 50 ml/h were 27 mm Hg and 30 mm Hg, respectively. After surgical exposure, these pressures fell to 0 mm Hg and 5 mm Hg, respectively, for the same infusion rates. Surgical exposure removes the effects of the tissue capsule, including the overlying skin and a collagenous sheath, restoring the external pressure to atmospheric pressure. Functional obstruction of ASDs occurs because of raised ambient pressure from the tissue capsule acting to depress the mobile membrane of the ASD, increasing its resistance to flow. This case confirms previously reported effects of subcutaneous implantation of ASDs in experimental animals and is the probable explanation for reported functional obstruction of ASDs in other patients.

Spinal hemangioblastoma, syrinx, and hydrocephalus in a two-year-old child.

A two-year-old child presented with an acute inability to bear weight. Radiological investigation revealed a large cervicothoracolumbar syrinx of no known cause. During investigation, acute communicating hydrocephalus developed, which required a shunt. At surgery, a small thoracic spinal cord hemangioblastoma was discovered and excised. Complete recovery with collapse of the syrinx followed. The clinical features of this rare childhood tumor and its associated effects are discussed.

Spontaneous intraparenchymal hemorrhage in full-term neonates.

OBJECTIVE: Spontaneous intraparenchymal hemorrhage is extremely rare in full-term newborns. Reports to date have been limited to descriptions of individual cases, small groups within larger studies of intracranial hemorrhage, and one series of four patients. Structural lesions are rarely identified, and the majority of patients described have been managed without surgical intervention. METHODS: Analysis of a computerized database of pediatric neurosurgical patients from January 1960 to February 2000 identified full-term newborns younger than 3 months of age with nontraumatic intraparenchymal hemorrhages. Prenatal histories, labor and delivery histories, clinical presentations, imaging studies, management, and outcomes were reviewed. RESULTS: Eleven full-term newborns with spontaneous intraparenchymal hemorrhages were identified. The majority had normal prenatal courses. Most presented within the first 2 days of life (6 of 11 patients), and the most common presenting sign was seizure (7 of 11 patients). No cause was identified in 6 of 11 patients; the remainder were attributed to coagulopathy (n = 3), ruptured intracranial aneurysm (n = 1), or hemorrhagic infarction (n = 1). Eight patients underwent surgical hematoma evacuation on the basis of radiographic evidence of significant mass effect, evidence of signs of elevated intracranial pressure, or both. Three patients did not receive surgical intervention. There were no subsequent hemorrhages or deaths during a mean follow-up period of 4.5 years (range, 1-16 yr). Four patients had normal neurological outcomes, four had motor deficits (one of whom additionally demonstrated cognitive delay), and three had delayed speech. CONCLUSION: No cause is identified in most newborns with spontaneous intraparenchymal hemorrhage. Radiographic evidence of mass effect or signs of elevated intracranial pressure may necessitate surgical hematoma evacuation. Outcome varies widely and may be normal, even in patients with sizeable intraparenchymal hemorrhages.

Primary leptomeningeal melanoma: an unusually aggressive tumor in childhood.

Primary malignant melanoma of the leptomeninges of the central nervous system is a rare and aggressive tumor in children. We report our experience from 1964 to 1990 with this tumor in eight children. The mean age at diagnosis was 4.9 years (range, 1.3 to 13 yr). Five children presented with signs and symptoms of raised intracranial pressure from hydrocephalus secondary to tumoral obliteration of the basal cisterns, but the time from the initial symptomatology to diagnosis was frequently delayed. Three patients in this series had hairy nevi in association with their leptomeningeal melanoma. Cerebrospinal fluid (CSF) analysis typically showed raised opening pressures, decreased glucose, and increased protein concentrations. Malignant melanoma cells were found in the CSF in three patients. Confirmatory radiographic examinations included air encephalography, myelography, and computed tomographic and magnetic resonance scanning. Four patients were treated with lumboperitoneal shunts, and one patient was treated with a ventriculoperitoneal shunt for hydrocephalus. Two patients underwent craniotomies and subtotal excisions of their tumors. In seven patients, a definitive diagnosis of leptomeningeal melanoma was made by pathological examination of tissues sent at surgery or at post mortem. In one case, the diagnosis was established by a detailed cytological analysis of the CSF. Four children died of fulminant disease and tumor spread before treatment could be instituted. The four children who received treatment had a combination of radiation therapy and chemotherapy. One child received intrathecal methotrexate. The two children with the longest survivals (2 and 3 yr, respectively) received cisplatinum and dimethyltriazenoimidazole carboxamide in addition to craniospinal irradiation.(ABSTRACT TRUNCATED AT 250 WORDS)

Lumboperitoneal shunting: a retrospective study in the pediatric population.

There is a shortage of data concerning the long-term follow-up of patients with lumboperitoneal (LP) shunts, especially in the pediatric population. A retrospective study of 143 patients who underwent LP shunting between 1974 and 1991 was therefore performed. The mean age at the time of shunt insertion was 3.3 years (range, 18 d to 17.8 yr), and the indication for shunting was: hydrocephalus (81%), cerebrospinal fluid fistula (12%), and pseudotumor cerebri (7%). The mean follow-up time was 5.7 years (range, 5 d to 17.5 yr), and during this period, there were five deaths of which one was shunt related (2.5 yr post-shunt insertion). Of the types of LP shunt used during the study period, the T-tube shunt (101 patients) fared significantly better (P = 0.003) than the percutaneous type (42 patients), and the overall survival characteristics for the T-tube shunt approximated those seen for ventriculoperitoneal shunts, with a 50% probability of remaining free of malfunctions for 5 years. A high rate of migration (19%) was partially responsible for the poor performance of the percutaneous-type shunts. By the end of the study, 40 patients (28%) had been converted to ventricular shunts, and this rate of conversion was similar for both shunt types. LP shunts have certain advantages over other forms of cerebrospinal fluid diversion and were successfully used for various clinical conditions during this study.(ABSTRACT TRUNCATED AT 250 WORDS)