The 185/333 gene family is a rapidly diversifying host-defense gene cluster in the purple sea urchin Strongylocentrotus purpuratus.

The genome of the purple sea urchin contains numerous large gene families with putative immunological functions. One gene family, known as 185/333, is characterized by extraordinary molecular diversity resulting from single nucleotide polymorphisms and the presence or the absence of 27 large blocks of sequences known as elements. The mosaic composition of elements, known as element patterns, that is present within the members of this gene family is encoded entirely in the second of two exons. Many of the elements correspond to one of six types of repeats that are present throughout the genes. The sequence diversity and variation in element patterns led us to investigate the evolution of the 185/333 gene family. The work presented here suggests that the element patterns are the result of both recombination and duplication and/or deletion of intragenic repeats. Each element is composed of a limited number of similar but distinct sequences, and their distribution among the 185/333 genes suggests frequent recombination within this gene family. Phylogenetic analyses of five 185/333 elements and two regions of the intron were performed using two tests: incongruence length difference and incongruence permutation. Results indicated that each pair of sequence segments was incongruent, suggesting that recombination occurs frequently along the length of the genes, including both the intron and the second exon, and that recombination is not restricted to intact elements. Paradoxically, the high level of similarity among the elements indicated that the 185/333 genes appear to be the result of a recent diversification. These results add to the growing body of evidence suggesting that invertebrate immune systems are not simple and static, but are dynamic and highly complex, and may employ group-specific mechanisms for diversification.

Low-bandwidth telephony for urban and rural access to nursing services for survivors of stroke and their caregivers.

Trends related to rapidly aging populations nationally and internationally, combined with shortages in skilled health professionals and rising health care costs have necessitated efficient and cost-effective technologies for improved access to health care services. This paper discusses the use of low-bandwidth telephonic technology for providing nursing and counseling services to stroke caregivers in urban and rural areas and addresses factors that affect adoption and utilization of technologies for their intended use. Twenty-one subjects with recent stroke and their caregivers and five nurses were enrolled in the study. Seventy-two telehealth visits (i.e. tele-visits) were made to urban and rural locations using standard plain-old-telephone-service (POTS). Eighty-three percent of televists experienced first-time completion success at a bandwidth of 27.6+3 kbps. Over one-third (36%) of visits were unsolicited and initiated by caregivers using the protocol. Each tele-visit lasted approximately 20 minutes. Televisit sessions ranged from providing health care instruction for caregivers to stroke-related education to caregiver counseling. Televists were widely accepted by stroke subjects and caregivers. Acceptance and utilization of telehealth services correlated with rapport between at-home users and nurses.

Expression of ARF6 mutants in neuroendocrine cells suggests a role for ARF6 in synaptic vesicle biogenesis.

ARF6 regulates membrane trafficking between the plasma membrane and endosomes. We investigated the role of ARF6 in synaptic vesicle biogenesis as this process occurs both at the plasma membrane and at endosomes. We used a synaptic vesicle marker protein, p-selectin-horseradish peroxidase (HRP), to follow the effects of ARF6 expression on synaptic vesicle biogenesis in PC12 neuroendocrine cells. Expression of a constitutively active ARF6 mutant increased, while expression of a nucleotide-free ARF6 mutant decreased, p-selectin-HRP levels in the synaptic vesicle peak. These results provide the first direct evidence for a role for ARF6 in synaptic vesicle biogenesis.

Long-term breastfeeding: nourishment or nurturance?

Mothers frequently describe the primary benefit of breastfeeding beyond a year as providing comfort rather than nourishment. Little is known about the effect of extended breastfeeding on the growth or nutritional status of children in the United States. Data collected on 38 long-term breastfeeding children (12 to 43 months old) included growth measurements, breastfeeding patterns, and dietary intake obtained through diaries and dietary recalls. Although the children's weight-for-age, length/height-for-age, and weight-for-length/height Z scores clustered below zero, they fell within two standard deviations of the median, suggesting normal growth. The daily time and frequency of breastfeeding were not different between the 1-year-old and 2-year-old age groups but were significantly lower in the 3-year-old age group. In an analysis of non-breast milk diets, the children would need an average intake of 100 to 460 mL of breast milk per day to meet the RDA for energy intake and nutrients that were lower in their diets compared to national food intake surveys.

Regulation of neuronal function by protein trafficking: a role for the endosomal pathway.

Protein trafficking plays a central role in many aspects of neuronal function, from the release of neurotransmitters by exocytosis and the recycling of synaptic vesicle proteins to the regulation of receptor signalling. Synaptic function can be significantly modified on a short time scale by alterations in the levels of receptors, ion channels and transporters both pre- and postsynaptically. In many cases, these alterations appear to be mediated by acute changes in the rates at which the proteins are endocytosed from and exocytosed to the cell surface from intracellular pools. While our current understanding of the signalling mechanisms and the intracellular pathways responsible for these acute changes is still in its infancy, intriguing details are beginning to emerge from a number of systems.

Evidence for a primary endocytic vesicle involved in synaptic vesicle biogenesis.

The regulated release of neurotransmitters at synapses is mediated by the fusion of neurotransmitter-filled synaptic vesicles with the plasma membrane. Continuous synaptic activity relies on the constant recycling of synaptic vesicle proteins into newly formed synaptic vesicles. At least two different mechanisms are presumed to mediate synaptic vesicle biogenesis at the synapse as follows: direct retrieval of synaptic vesicle proteins and lipids from the plasma membrane, and indirect passage of synaptic vesicle proteins through an endosomal intermediate. We have identified a vesicle population with the characteristics of a primary endocytic vesicle responsible for the recycling of synaptic vesicle proteins through the indirect pathway. We find that synaptic vesicle proteins colocalize in this vesicle with a variety of proteins known to recycle from the plasma membrane through the endocytic pathway, including three different glucose transporters, GLUT1, GLUT3, and GLUT4, and the transferrin receptor. These vesicles differ from "classical" synaptic vesicles in their size and their generic protein content, indicating that they do not discriminate between synaptic vesicle-specific proteins and other recycling proteins. We propose that these vesicles deliver synaptic vesicle proteins that have escaped internalization by the direct pathway to endosomes, where they are sorted from other recycling proteins and packaged into synaptic vesicles.

Membrane trafficking regulates the activity of the human dopamine transporter.

The trafficking of synaptic proteins is unquestionably a major determinant of the properties of synaptic transmission. Here, we present a detailed analysis of the downregulation and intracellular trafficking of the cocaine- and amphetamine-sensitive dopamine transporter (DAT), a presynaptic plasma membrane protein responsible for the regulation of extracellular DA concentrations. Using PC12 cells stably transfected with human DAT cDNA, we observe that phorbol ester activation of protein kinase C (PKC) results in decreased transporter capacity and a parallel decrease in the amount of DAT on the cell surface that is attributable to intracellular transporter sequestration. After internalization, DAT diverges to the recycling, as opposed to the degradative, arm of the endocytic pathway. This study demonstrates, for the first time, DAT endocytosis, establishes the pathways through which DAT traffics both at steady state and in response to PKC activation, and suggests that DAT recycling is likely to occur.

ECG data compression using cut and align beats approach and 2-D transforms.

A new electrocardiogram (ECG) data compression method is presented which employs a two dimensional (2-D) transform. This 2-D transform method utilizes the fact that ECG signals generally show two types of redundancies--between adjacent heartbeats and between adjacent samples. A heartbeat data sequence is cut and beat-aligned to form a 2-D data array. Any 2-D compression method can then be applied. Transform coding using the 2-D discrete cosine transform (DCT) [2-D DCT] is employed here as an example. Using selections from the MIT-BIH arrhythmia and Medtronic databases, results are presented that illustrate substantial improvement in compression ratio over one-dimensional methods for comparable percent root-mean-square difference (PRD).

Targeting of the synaptic vesicle protein synaptobrevin in the axon of cultured hippocampal neurons: evidence for two distinct sorting steps.

Synaptic vesicles are concentrated in the distal axon, far from the site of protein synthesis. Integral membrane proteins destined for this organelle must therefore make complex targeting decisions. Short amino acid sequences have been shown to act as targeting signals directing proteins to a variety of intracellular locations. To identify synaptic vesicle targeting sequences and to follow the path that proteins travel en route to the synaptic vesicle, we have used a defective herpes virus amplicon expression system to study the targeting of a synaptobrevin-transferrin receptor (SB-TfR) chimera in cultured hippocampal neurons. Addition of the cytoplasmic domain of synaptobrevin onto human transferrin receptor was sufficient to retarget the transferrin receptor from the dendrites to presynaptic sites in the axon. At the synapse, the SB-TfR chimera did not localize to synaptic vesicles, but was instead found in an organelle with biochemical and functional characteristics of an endosome. The chimera recycled in parallel with synaptic vesicle proteins demonstrating that the nerve terminal efficiently sorts transmembrane proteins into different pathways. The synaptobrevin sequence that controls targeting to the presynaptic endosome was not localized to a single, 10- amino acid region of the molecule, indicating that this targeting signal may be encoded by a more distributed structural conformation. However, the chimera could be shifted to synaptic vesicles by deletion of amino acids 61-70 in synaptobrevin, suggesting that separate signals encode the localization of synaptobrevin to the synapse and to the synaptic vesicle.

Identification of a somatodendritic targeting signal in the cytoplasmic domain of the transferrin receptor.

Neurons are highly polarized cells that must sort proteins synthesized in the cell body for transport into the axon or the dendrites. Given the amount of time and energy needed to deliver proteins to the distal processes, neurons must have high fidelity mechanisms that ensure proper polarized protein trafficking. Although a variety of proteins are localized either to the somatodendritic domain or to the axon (), the question of whether there are signal-dependent mechanisms that sort proteins to distinct neuronal domains is only beginning to be addressed. To determine sequence requirements for the polarized sorting of transmembrane proteins into dendrites, we expressed mutant transferrin receptors in cultured rat hippocampal neurons, using a defective herpes virus vector. Wild-type human transferrin receptor colocalized with the endogenous protein in dendritic endosomes and was strictly excluded from axons, despite overexpression. Polarized targeting was abolished by deletion of cytoplasmic amino acids 7-10, 11-14, or 19-28, but not 29-42 or 43-58. These deletions also increased the appearance of transferrin receptor on the plasma membrane, implying that endocytosis and dendritic targeting are mediated by overlapping signals and similar molecular mechanisms. In addition, we have characterized a specialized para-Golgi endosome poised to play a critical role in the polarized recycling of transmembrane proteins.

A sampling theorem for EEG electrode configuration.

An analytical tool to help in selecting the number of electrodes required for recording electroencephalogram (EEG) signals is presented. The main assumption made is that the scalp can be modeled as a hemispherical surface. The number of sensors required to sample a surface is derived by using a mean square error (MSE) measure to approximate the continuous potential functions on the hemispherical surface. An algorithm for selecting the number of electrodes for arbitrary head geometries is also proposed. A sampling theorem is then derived with conditions on the sampling points for electrode placement.

Calcium-dependent transmitter secretion from fibroblasts: modulation by synaptotagmin I.

Following endocytic uptake of acetylcholine (ACh), CHO fibroblasts exhibit Ca(2+)-dependent spontaneous quantal ACh release and depolarization-evoked ACh release, as detected by a whole-cell voltage-clamped myocyte in contact with the fibroblast. CHO fibroblasts transfected with synaptotagmin I, an integral membrane protein of synaptic vesicles, showed a reduced spontaneous quantal ACh release and an enhanced Ca(2+)-evoked ACh release, as compared with control cells. Biochemical and ultrastructural studies of endocytic activity using horseradish peroxidase as a marker further confirmed the inhibitory action of synaptotagmin I on spontaneous vesicular exocytosis and on elevated exocytosis induced by Ca2+. Through inhibition of exocytosis at the resting intracellular concentration of Ca2+ and removal of the inhibition upon depolarization-induced Ca2+ entry, synaptotagmin I could enhance the efficiency of excitation-secretion coupling.

EEG dipole localization bounds and MAP algorithms for head models with parameter uncertainties.

The Cramer-Rao bound for unbiased dipole location estimation is derived under the assumption of a general head model parameterized by deterministic and stochastic parameters. The expression thus characterizes fundamental limits on EEG dipole localization performance due to the effects of both model uncertainty and statistical measurements noise. Expressions are derived for the cases of multivariate Gaussian and gamma distribution priors, and examples are given to illustrate the derived bounds when the radii and conductivities of a four-concentric sphere head model are allowed to be random. The joint MAP estimate of location/model parameters is then examined as a means of achieving robustness to deviations from an ideal head model. Random variations in both the multiple sphere radii and the layer conductivities are shown, via the stochastic Cramer-Rao bounds and Monte Carlo simulation of the MAP estimator, to have the most impact on localization performance in high SNR regions, where finite sample effects are not the limiting factors. This corresponds most often to spatial regions that are close to the scalp electrodes.

Pulmonary lymphangiomyomatosis.

Lymphangiomyomatosis is a rare disease of unknown etiology characterized by hamartomatous proliferation of smooth muscle in the pulmonary lymphatics, blood vessels and airways. The disease occurs exclusively in women of reproductive age. Although the clinical course and radiographic findings may strongly suggest lymphangiomyomatosis, definitive diagnosis is made by obtaining open-lung biopsy. The clinical course of lymphangiomyomatosis is progressive, leading to pulmonary insufficiency and death within 10 years. Treatment with hormonal manipulation and/or oophorectomy has resulted in temporary improvement or stabilization of the disease process.

Robust adaptive microphone array processing for hearing aids: realistic speech enhancement.

The problem of combining the outputs of an array of microphones as a single input for a hearing aid is investigated. Emphasis is placed on the conservative prediction of realistically achievable performance gains provided by the array over a single microphone. Performance improvement is measured as a change in the speech reception threshold (SRT) between single microphone and multimicrophone conditions. Consistent with previous work, predictions of this change in SRT using intelligibility averaged gain, [symbol: see text] are shown to be good. Consequently, this measure is used, along with changes in signal-to-noise ratios (SNRs), to evaluate array performance. The results presented include the effects of acoustic headshadow, small room reverberation, microphone placement uncertainty, and desired speaker location uncertainty. It is in this context that realistic predictions of speech enhancement provided by robust adaptive microphone array processors are discussed. Performance improvements are demonstrated relative to the "best" single microphone in the array for three types of spatial filters: Fixed, robust block processed, and robust adaptive. The performance of the robust block processed arrays is shown to be attainable with adaptive implementations. One fundamental criterion employed in robust beamformer design directly limits the amount of cancellation of the desired signal that can occur.