Genetic evidence for panmixia in a colony-breeding crater lake cichlid fish.

Fine-scaled genetic structuring, as seen for example in many lacustrine fish, typically relates to the patterns of migration, habitat use, mating system or other ecological factors. Because the same processes can also affect the propensity of population differentiation and divergence, assessments of species from rapidly speciating clades, or with particularly interesting ecological traits, can be especially insightful. For this study, we assessed the spatial genetic relationships, including the genetic evidence for sex-biased dispersal, in a colony-breeding cichlid fish, Amphilophus astorquii, endemic to Crater Lake Apoyo in Nicaragua, using 11 polymorphic microsatellite loci (n = 123 individuals from three colonies). We found no population structure in A. astorquii either within colonies (no spatial genetic autocorrelation, r ~0), or at the lake-wide level (pairwise population differentiation FST = 0-0.013 and no clustering), and there was no sex-bias (male and female AIc values bounded 0) to this lack of genetic structure. These patterns may be driven by the colony-breeding reproductive behaviour of A. astorquii. The results suggest that strong philopatry or spatial assortative mating are unlikely to explain the rapid speciation processes associated with the history of this species in Lake Apoyo.

Genetic fingerprinting of salmon louse (Lepeophtheirus salmonis) populations in the North-East Atlantic using a random forest classification approach.

Caligid sea lice represent a significant threat to salmonid aquaculture worldwide. Population genetic analyses have consistently shown minimal population genetic structure in North Atlantic Lepeophtheirus salmonis, frustrating efforts to track louse populations and improve targeted control measures. The aim of this study was to test the power of reduced representation library sequencing (IIb-RAD sequencing) coupled with random forest machine learning algorithms to define markers for fine-scale discrimination of louse populations. We identified 1286 robustly supported SNPs among four L. salmonis populations from Ireland, Scotland and Northern Norway. Only weak global structure was observed based on the full SNP dataset. The application of a random forest machine-learning algorithm identified 98 discriminatory SNPs that dramatically improved population assignment, increased global genetic structure and resulted in significant genetic population differentiation. A large proportion of SNPs found to be under directional selection were also identified to be highly discriminatory. Our data suggest that it is possible to discriminate between nearby L. salmonis populations given suitable marker selection approaches, and that such differences might have an adaptive basis. We discuss these data in light of sea lice adaption to anthropogenic and environmental pressures as well as novel approaches to track and predict sea louse dispersal.

Precise control of osteogenesis for craniofacial defect repair: the role of direct osteoprogenitor contact in BMP-2-based bioprinting.

BACKGROUND: Success with bone morphogenetic protein-2 (BMP-2) has been widely reported in the osseous reconstruction of large calvarial defects. These efforts have required enormous doses of BMP-2 and are not sufficiently refined to facilitate the detail-oriented repair required for intricate craniofacial structures. We have previously shown that inkjet-based bioprinting technologies allow for precisely customized low-dose protein patterns to induce spatially regulated osteogenesis. Here, we investigate the importance of direct contact between bioprinted BMP-2 and the dura mater (a source of osteoprogenitors) in mediating calvarial healing. METHODS: Five-millimeter osseous defects were trephinated in mouse parietal bones (N=8). Circular acellular dermal matrix (ADM) implants were prepared such that 1 semicircle of 1 face per implant was printed with BMP-2 bio-ink. These implants were then placed ink-toward (N=3) or ink-away (N=5) from the underlying dura mater. After 4 weeks, osteogenesis was assessed in each of the 4 possible positions (BMP-2-printed area toward dura, BMP-2-printed area away from dura, unprinted area toward dura, and unprinted area away from dura) by faxitron. RESULTS: The BMP-2-printed portion of the ADM generated bone covering an average of 66.5% of its surface area when it was face-down (printed surface directly abutting dura mater). By comparison, the BMP-2-printed portion of the ADM generated bone covering an average of only 21.3% of its surface area when it was face-up (printed surface away from dura). Similarly, the unprinted portion of the ADM generated an average of only 18.6% osseous coverage when face-down and 18.4% when face-up. CONCLUSIONS: We have previously shown that inkjet-based bioprinting has the potential to significantly enhance the role of regenerative therapies in craniofacial surgery. This technology affords the precise control of osteogenesis necessary to reconstruct this region's intricate anatomical architecture. In the present study, we demonstrate that direct apposition of BMP-2-printed ADM to a source of osteoprogenitor cells (in this case dura mater) is necessary for bio-ink-directed osteogenesis to occur. These results have important implications for the design of more complex bioprinted osseous structures.

Force sensor in simulated skin and neural model mimic tactile SAI afferent spiking response to ramp and hold stimuli.

BACKGROUND: The next generation of prosthetic limbs will restore sensory feedback to the nervous system by mimicking how skin mechanoreceptors, innervated by afferents, produce trains of action potentials in response to compressive stimuli. Prior work has addressed building sensors within skin substitutes for robotics, modeling skin mechanics and neural dynamics of mechanotransduction, and predicting response timing of action potentials for vibration. The effort here is unique because it accounts for skin elasticity by measuring force within simulated skin, utilizes few free model parameters for parsimony, and separates parameter fitting and model validation. Additionally, the ramp-and-hold, sustained stimuli used in this work capture the essential features of the everyday task of contacting and holding an object. METHODS: This systems integration effort computationally replicates the neural firing behavior for a slowly adapting type I (SAI) afferent in its temporally varying response to both intensity and rate of indentation force by combining a physical force sensor, housed in a skin-like substrate, with a mathematical model of neuronal spiking, the leaky integrate-and-fire. Comparison experiments were then conducted using ramp-and-hold stimuli on both the spiking-sensor model and mouse SAI afferents. The model parameters were iteratively fit against recorded SAI interspike intervals (ISI) before validating the model to assess its performance. RESULTS: Model-predicted spike firing compares favorably with that observed for single SAI afferents. As indentation magnitude increases (1.2, 1.3, to 1.4 mm), mean ISI decreases from 98.81 ± 24.73, 54.52 ± 6.94, to 41.11 ± 6.11 ms. Moreover, as rate of ramp-up increases, ISI during ramp-up decreases from 21.85 ± 5.33, 19.98 ± 3.10, to 15.42 ± 2.41 ms. Considering first spikes, the predicted latencies exhibited a decreasing trend as stimulus rate increased, as is observed in afferent recordings. Finally, the SAI afferent's characteristic response of producing irregular ISIs is shown to be controllable via manipulating the output filtering from the sensor or adding stochastic noise. CONCLUSIONS: This integrated engineering approach extends prior works focused upon neural dynamics and vibration. Future efforts will perfect measures of performance, such as first spike latency and irregular ISIs, and link the generation of characteristic features within trains of action potentials with current pulse waveforms that stimulate single action potentials at the peripheral afferent.

Rapid evolution and selection inferred from the transcriptomes of sympatric crater lake cichlid fishes.

Crater lakes provide a natural laboratory to study speciation of cichlid fishes by ecological divergence. Up to now, there has been a dearth of transcriptomic and genomic information that would aid in understanding the molecular basis of the phenotypic differentiation between young species. We used next-generation sequencing (Roche 454 massively parallel pyrosequencing) to characterize the diversity of expressed sequence tags between ecologically divergent, endemic and sympatric species of cichlid fishes from crater lake Apoyo, Nicaragua: benthic Amphilophus astorquii and limnetic Amphilophus zaliosus. We obtained 24 174 A. astorquii and 21 382 A. zaliosus high-quality expressed sequence tag contigs, of which 13 106 pairs are orthologous between species. Based on the ratio of nonsynonymous to synonymous substitutions, we identified six sequences exhibiting signals of strong diversifying selection (K(a)/K(s) > 1). These included genes involved in biosynthesis, metabolic processes and development. This transcriptome sequence variation may be reflective of natural selection acting on the genomes of these young, sympatric sister species. Based on Ks ratios and p-distances between 3'-untranslated regions (UTRs) calibrated to previously published species divergence times, we estimated a neutral transcriptome-wide substitutional mutation rate of approximately 1.25 x 10(-6) per site per year. We conclude that next-generation sequencing technologies allow us to infer natural selection acting to diversify the genomes of young species, such as crater lake cichlids, with much greater scope than previously possible.

Using Force Sensors and Neural Models to Encode Tactile Stimuli as Spike-based Responses.

Tactile sensors will augment the next generation of prosthetic limbs. However, currently available sensors do not produce biologically-compatible output. This work seeks to illustrate that a force sensor combined with a bi-phasic, neural spiking algorithm, or spiking-sensor, can produce spiking patterns similar to that of the slowly adapting type I (SAI) mechanoreceptor. Experiments were conducted where first spike latency and inter-spike interval, in response to a rapidly delivered (100 ms) sustained displacement (1.1, 1.3, 1.5 mm for 5 s), were compared between the spiking-sensor and SAI recording. The results indicated that the predicted spike times were similar, in magnitude and increasing linear trend, to those observed with the SAI. Over the three displacements, average dynamic ISIs were 7.3, 4.2, 3.8 ms for the spiking-sensor and 6.2, 6.9, 4.1 ms for the SAI, while average static ISIs were 69.0, 45.2, 35.1 ms and 159.9, 69.6, 38.8 ms. The predicted first spike latencies (74.3, 73.9, 96.3 ms) lagged in comparison to those observed for the SAI (26.8, 31.7, 28.8 ms), which may be due to both the different applied force ramp-ups and the SAI's exquisite dynamic sensitivity range and rapid response time.

Applying new inter-individual approaches to assess fine-scale population genetic diversity in a neotropical frog, Eleutherodactylus ockendeni.

We assess patterns of genetic diversity of a neotropical leaflitter frog, Eleutherodactylus ockendeni, in the upper Amazon of Ecuador without a priori delineation of biological populations and with sufficiently intensive sampling to assess inter-individual patterns. We mapped the location of each collected frog across a 5.4 x 1 km landscape at the Jatun Sacha Biological Station, genotyped 185 individuals using five species-specific DNA microsatellite loci, and sequenced a fragment of mitochondrial cytochrome b for a subset of 51 individuals. The microsatellites were characterized by high allelic diversity and homozygote excess across all loci, suggesting that when pooled the sample is not a panmictic population. We conclude that the lack of panmixia is not attributable to the influence of null alleles or biased sampling of consanguineous family groups. Multiple methods of population cluster analysis, using both Bayesian and maximum likelihood approaches, failed to identify discrete genetic clusters across the sampled area. Using multivariate spatial autocorrelation, kinship coefficients and relatedness coefficients, we identify a continuous isolation by distance population structure, with a first patch size of ca. 260 m and apparently large population sizes. Analysis of mtDNA corroborates the observation of high genetic diversity at fine scales: there are multiple haplotypes, they are non-randomly distributed and a binary haplotype correlogram shows significant spatial genetic autocorrelation. We demonstrate the utility of inter-individual genetic methods and caution against making a priori assumptions about population genetic structure based simply on arbitrary or convenient patterns of sampling.

Enzyme-linked immunosorbent assay for detection of antibodies against simian hemorrhagic fever virus.

Better assays are needed for the detection of simian hemorrhagic fever virus (SHFV), which induces persistent infection without overt signs of disease in most old world monkeys, but causes a fatal hemorrhagic fever in macaques. An enzyme-linked immunosorbent assay (ELISA) is described here that is useful in identifying primates previously exposed to SHFV. This assay involves testing serum samples against SHFV and cell antigens to obtain an ODvirus-to-ODcell ratio that eliminates potential high background values associated with primate serum. High correlation was found using this assay, compared with that found with the current "gold standard" indirect immunofluorescence assay (IFA). However, this ELISA is less time consuming, less subjective, and not as prone to human error than the SHFV-IFA.

HAIR-AN syndrome: a multisystem challenge.

HAIR-AN syndrome is an acronym for an unusual multisystem disorder in women that consists of hyperandrogenism (HA), insulin resistance (IR) and acanthosis nigricans (AN). The precipitating abnormality is thought to be insulin resistance, with a secondary increase in insulin levels and subsequent overproduction of androgens in the ovaries. Long periods of hyperinsulinism and, some suspect, hyperandrogenism can result in the cutaneous manifestation of acanthosis nigricans. Patients are often concerned about the physical manifestations of this disorder, including virilization and acanthosis nigricans, and may be less aware of systemic problems. Physicians should assess women with these problems for an underlying endocrine abnormality. Although a treatment regimen for the HAIR-AN syndrome has not been established, antiandrogen therapy and weight loss are useful.

Therapeutic update: use of risperidone for the treatment of monosymptomatic hypochondriacal psychosis.

Monosymptomatic hypochondriacal psychoses such as delusions of parasitosis are often difficult to treat. For the past two decades, pimozide has been considered the drug of choice. Although a few controlled studies have been done to support the efficacy of pimozide, the recommendation of treatment of choice is largely based on case reports. Pimozide has significant side effects, including cardiac and extrapyramidal abnormalities, which are of most concern in the treatment of the elderly. Although pimozide does appear to be effective in some cases of somatic delusional disorders, newer antipsychotics such as risperidone have also been shown to be beneficial in treating this perplexing cluster of disorders. Risperidone is generally considered safer than pimozide and should be considered as first-line therapy for monosymptomatic hypochondriacal psychoses.

Contact urticaria to the MCU-2A/P gas mask.

A case of contact urticaria to the silicone rubber in the MCU-2A/P gas mask is presented. Contact urticaria is a type I hypersensitivity reaction mediated by immunoglobulin E that usually manifests as localized erythema, edema, pruritus, and urticarial plaques. It can also cause systemic reactions, including anaphylaxis. Allergic reactions to silicone rubber have been increasingly reported and are of importance in medical and military personnel. The implication of such a diagnosis in an active duty military member is significant because the individual cannot be worldwide-qualified. The correct diagnosis of allergic skin reactions to personal protective gear is critical to maintaining a strong fighting force and protecting military personnel from potentially life-threatening allergic reactions.

Herpes zoster in a 7-month-old infant: a case report and review.

Herpes zoster (HZ) is a cutaneous viral infection of the skin that presents in a dermatomal distribution. It represents reactivation of herpes varicella zoster virus that has continued to exist in a latent form in the neurons of the posterior root ganglia. Although it is rare to see HZ in children, cases have been reported after exposure to varicella zoster in utero or during the first months of life. We present a case of HZ in a healthy 7-month-old girl who had had chickenpox at age 4 months.

Cutaneous T-cell lymphoma presenting as benign dermatoses.

Cutaneous T-cell lymphoma, also known as mycosis fungoides, is a malignancy of the T helper (CD4+) cells. Diagnosis is difficult early in the course of this disease because it mimics several benign skin disorders, including eczema, psoriasis and contact dermatitis. Cutaneous T-cell lymphoma is also difficult to identify histologically, and multiple biopsies may be necessary to confirm the diagnosis. Treatment may require a combination of topical and systemic agents. Patients with limited skin disease have a good prognosis, but the prognosis is less hopeful in those with extracutaneous involvement. As the disease progresses, the normal T-cell population is eliminated, and the patient becomes significantly immunosuppressed. Infection is the primary cause of mortality in patients with cutaneous T-cell lymphoma.

Confirmation of reduced temporal limbic structure volume on magnetic resonance imaging in male patients with schizophrenia.

A structural deficit in the temporal lobes has been implicated in the pathogenesis of schizophrenia. A prospective magnetic resonance imaging (MRI) study was carried out in 20 young male patients with schizophrenia and 20 age-matched healthy male volunteers. Volumetric measurements were performed in all slices with temporal lobe cross-sections from the temporal pole to the tip of the Sylvian fissure. Volumetric assessment included the temporal lobe as a whole, hippocampal formation and amygdala complex, temporal horn and cella media of the lateral ventricle, the third ventricle, and hemispheric volume in all slices that showed temporolimbic structures. Brain structural deficit in the patients was most conspicuous in the posterior portion of the hippocampal formation. Significant effects of diagnosis were also found for the total temporal lobe and the third ventricle. Multiple regression analysis revealed posterior hippocampal volume to be significantly determined by diagnosis, but not by age or by temporal lobe or hemispheric volume. Significant correlations of morphologic and clinical parameters were restricted to negative correlations of temporal lobe volume with the global rating and sum score of the Scale for the Assessment of Negative Symptoms. The study confirms subtle temporolimbic deficit reported in previous MRI studies in patients with schizophrenia.

Intracerebral chloroma complicating acute monocytic leukemia.

We present the case of a 21-year-old woman with an acute monocytic leukemia. When she was in complete hematological remission, she developed rapid progressive hemiparesis on the right caused by a left frontoparietal chloroma as confirmed by surgery and histological examination. Postoperatively, the patient recovered completely, and x-ray therapy followed. Since intracerebral myeloblastic tumors are extremely rare and since the neurosurgeon may be involved in treatment of these lesions, we are encouraged to present our findings.

MRI findings in medial temporal lobe structures in schizophrenia.

In an MRI volumetric study of 10 young male schizophrenics (DSM-III-R 295.9x) a temporal lobe segment, corresponding hippocampal formation and parahippocampal gyrus were found smaller as compared with healthy controls while temporal horn was enlarged. Temporal lobe segment and parahippocampal gyrus were larger on the right in patients and controls, reversed asymmetry was found for the hippocampus.