A physicochemical perspective of aging from single-cell analysis of pH, macromolecular and organellar crowding in yeast

Cellular aging is a multifactorial process that is characterized by a decline in homeostatic capacity, best described at the molecular level. Physicochemical properties such as pH and macromolecular crowding are essential to all molecular processes in cells and require maintenance. Whether a drift in physicochemical properties contributes to the overall decline of homeostasis in aging is not known. Here, we show that the cytosol of yeast cells acidifies modestly in early aging and sharply after senescence. Using a macromolecular crowding sensor optimized for long-term FRET measurements, we show that crowding is rather stable and that the stability of crowding is a stronger predictor for lifespan than the absolute crowding levels. Additionally, in aged cells, we observe drastic changes in organellar volume, leading to crowding on the micrometer scale, which we term organellar crowding. Our measurements provide an initial framework of physicochemical parameters of replicatively aged yeast cells.

Loss of vacuolar acidity results in iron-sulfur cluster defects and divergent homeostatic responses during aging in Saccharomyces cerevisiae

The loss of vacuolar/lysosomal acidity is an early event during aging that has been linked to mitochondrial dysfunction. However, it is unclear how loss of vacuolar acidity results in age-related dysfunction. Through unbiased genetic screens, we determined that increased iron uptake can suppress the mitochondrial respiratory deficiency phenotype of yeast vma mutants, which have lost vacuolar acidity due to genetic disruption of the vacuolar ATPase proton pump. Yeast vma mutants exhibited nuclear localization of Aft1, which turns on the iron regulon in response to iron-sulfur cluster (ISC) deficiency. This led us to find that loss of vacuolar acidity with age in wild-type yeast causes ISC defects and a DNA damage response. Using microfluidics to investigate aging at the single-cell level, we observe grossly divergent trajectories of iron homeostasis within an isogenic and environmentally homogeneous population. One subpopulation of cells fails to mount the expected compensatory iron regulon gene expression program, and suffers progressively severe ISC deficiency with little to no activation of the iron regulon. In contrast, other cells show robust iron regulon activity with limited ISC deficiency, which allows extended passage and survival through a period of genomic instability during aging. These divergent trajectories suggest that iron regulation and ISC homeostasis represent a possible target for aging interventions.

Trajectories of Aging: How Systems Biology in Yeast Can Illuminate Mechanisms of Personalized Aging

All organisms age, but the extent to which all organisms age the same way remains a fundamental unanswered question in biology. Across species, it is now clear that at least some aspects of aging are highly conserved and are perhaps universal, but other mechanisms of aging are private to individual species or sets of closely related species. Within the same species, however, it has generally been assumed that the molecular mechanisms of aging are largely invariant from one individual to the next. With the development of new tools for studying aging at the individual cell level in budding yeast, recent data has called this assumption into question. There is emerging evidence that individual yeast mother cells may undergo fundamentally different trajectories of aging. Individual trajectories of aging are difficult to study by traditional population level assays, but through the application of systems biology approaches combined with novel microfluidic technologies, it is now possible to observe and study these phenomena in real time. Understanding the spectrum of mechanisms that determine how different individuals age is a necessary step toward the goal of personalized geroscience, where healthy longevity is optimized for each individual.

DNA damage checkpoint activation impairs chromatin homeostasis and promotes mitotic catastrophe during aging

Genome instability is a hallmark of aging and contributes to age-related disorders such as cancer and Alzheimer's disease. The accumulation of DNA damage during aging has been linked to altered cell cycle dynamics and the failure of cell cycle checkpoints. Here, we use single cell imaging to study the consequences of increased genomic instability during aging in budding yeast and identify striking age-associated genome missegregation events. This breakdown in mitotic fidelity results from the age-related activation of the DNA damage checkpoint and the resulting degradation of histone proteins. Disrupting the ability of cells to degrade histones in response to DNA damage increases replicative lifespan and reduces genomic missegregations. We present several lines of evidence supporting a model of antagonistic pleiotropy in the DNA damage response where histone degradation, and limited histone transcription are beneficial to respond rapidly to damage but reduce lifespan and genomic stability in the long term.

Rb analog Whi5 regulates G1 to S transition and cell size but not replicative lifespan in budding yeast

An increase in cell size with age is a characteristic feature of replicative aging in budding yeast. Deletion of the gene encoding Whi5 results in shortened duration of G1 and reduced cell size, and has been previously suggested to increase replicative lifespan. Upon careful analysis of multiple independently derived haploid and homozygous diploid whi5Δ mutants, we find no effect on lifespan, but we do confirm the reduction in cell size. We suggest that instead of antagonizing lifespan, the elongated G1 phase of the cell cycle during aging may actually play an important role in allowing aged cells time to repair accumulating DNA damage.

In vivo measurements reveal a single 5'-intron is sufficient to increase protein expression level in Caenorhabditis elegans

Introns can increase gene expression levels using a variety of mechanisms collectively referred to as Intron Mediated Enhancement (IME). IME has been measured in cell culture and plant models by quantifying expression of intronless and intron-bearing reporter genes in vitro. We developed hardware and software to implement microfluidic chip-based gene expression quantification in vivo. We altered position, number and sequence of introns in reporter genes controlled by the hsp-90 promoter. Consistent with plant and mammalian studies, we determined a single, natural or synthetic, 5'-intron is sufficient for the full IME effect conferred by three synthetic introns, while a 3'-intron is not. We found coding sequence can affect IME; the same three synthetic introns that increase mcherry protein concentration by approximately 50%, increase mEGFP by 80%. We determined IME effect size is not greatly affected by the stronger vit-2 promoter. Our microfluidic imaging approach should facilitate screens for factors affecting IME and other intron-dependent processes.

An inexpensive microscopy system for microfluidic studies in budding yeast

Recently, microfluidic technologies have been developed to allow higher throughput collection of yeast replicative lifespan data. Adoption of these devices has been limited, in part, due to the high cost of the motorized microscopy instrumentation from mainline manufacturers. Inspired by recent development of open source microscopy hardware and software, we developed minimal-cost hardware attachments to provide long-term focus stabilization for lower-cost microscopes and open source software to manage concurrent time-lapse image acquisition from multiple microscopes. We hope that these tools will help spur the wider adoption of microfluidic technologies for the study of aging in yeast.

Age-dependent deterioration of nuclear pore assembly in mitotic cells decreases transport dynamics

Nuclear transport is facilitated by the Nuclear Pore Complex (NPC) and is essential for life in eukaryotes. The NPC is a long-lived and exceptionally large structure. We asked whether NPC quality control is compromised in aging mitotic cells. Our images of single yeast cells during aging, show that the abundance of several NPC components and NPC assembly factors decreases. Additionally, the single-cell life histories reveal that cells that better maintain those components are longer lived. The presence of herniations at the nuclear envelope of aged cells suggests that misassembled NPCs are accumulated in aged cells. Aged cells show decreased dynamics of transcription factor shuttling and increased nuclear compartmentalization. These functional changes are likely caused by the presence of misassembled NPCs, as we find that two NPC assembly mutants show similar transport phenotypes as aged cells. We conclude that NPC interphase assembly is a major challenge for aging mitotic cells.

Transition between fermentation and respiration determines history-dependent behavior in fluctuating carbon sources

Cells constantly adapt to environmental fluctuations. These physiological changes require time and therefore cause a lag phase during which the cells do not function optimally. Interestingly, past exposure to an environmental condition can shorten the time needed to adapt when the condition re-occurs, even in daughter cells that never directly encountered the initial condition. Here, we use the molecular toolbox of Saccharomyces cerevisiae to systematically unravel the molecular mechanism underlying such history-dependent behavior in transitions between glucose and maltose. In contrast to previous hypotheses, the behavior does not depend on persistence of proteins involved in metabolism of a specific sugar. Instead, presence of glucose induces a gradual decline in the cells' ability to activate respiration, which is needed to metabolize alternative carbon sources. These results reveal how trans-generational transitions in central carbon metabolism generate history-dependent behavior in yeast, and provide a mechanistic framework for similar phenomena in other cell types.

Morphologically constrained and data informed cell segmentation of budding yeast

Motivation

Although high-content image cytometry is becoming increasingly routine, processing the large amount of data acquired during time-lapse experiments remains a challenge. The majority of approaches for automated single-cell segmentation focus on flat, uniform fields of view covered with a single layer of cells. In the increasingly popular microfluidic devices that trap individual cells for long term imaging, these conditions are not met. Consequently, most techniques for segmentation perform poorly. Although potentially constraining the generalizability of software, incorporating information about the microfluidic features, flow of media and the morphology of the cells can substantially improve performance.

Results

Here we present DISCO (Data Informed Segmentation of Cell Objects), a framework for using the physical constraints imposed by microfluidic traps, the shape based morphological constraints of budding yeast and temporal information about cell growth and motion to allow tracking and segmentation of cells in microfluidic devices. Using manually curated datasets, we demonstrate substantial improvements in both tracking and segmentation when compared with existing software.

Availability and implementation

The MATLAB code for the algorithm and for measuring performance is available at https://github.com/pswain/segmentation-software and the test images and the curated ground-truth results used for comparing the algorithms are available at http://datashare.is.ed.ac.uk/handle/10283/2002.

Contact

mcrane2@uw.edu.

Supplementary information

Supplementary data are available at Bioinformatics online.

Caenorhabditis elegans Genes Affecting Interindividual Variation in Life-span Biomarker Gene Expression

Genetically identical organisms grown in homogenous environments differ in quantitative phenotypes. Differences in one such trait, expression of a single biomarker gene, can identify isogenic cells or organisms that later manifest different fates. For example, in isogenic populations of young adult Caenorhabditis elegans, differences in Green Fluorescent Protein (GFP) expressed from the hsp-16.2 promoter predict differences in life span. Thus, it is of interest to determine how interindividual differences in biomarker gene expression arise. Prior reports showed that the thermosensory neurons and insulin signaling systems controlled the magnitude of the heat shock response, including absolute expression of hsp-16.2. Here, we tested whether these regulatory signals might also influence variation in hsp-16.2 reporter expression. Genetic experiments showed that the action of AFD thermosensory neurons increases interindividual variation in biomarker expression. Further genetic experimentation showed the insulin signaling system acts to decrease interindividual variation in life-span biomarker expression; in other words, insulin signaling canalizes expression of the hsp-16.2-driven life-span biomarker. Our results show that specific signaling systems regulate not only expression level, but also the amount of interindividual expression variation for a life-span biomarker gene. They raise the possibility that manipulation of these systems might offer means to reduce heterogeneity in the aging process.

Environmental Canalization of Life Span and Gene Expression in Caenorhabditis elegans

Animals, particularly poikilotherms, exhibit distinct physiologies at different environmental temperatures. Here, we hypothesized that temperature-based differences in physiology could affect the amount of variation in complex quantitative traits. Specifically, we examined, in Caenorhabditis elegans, how different temperatures (15°C, 20°C, and 25°C) affected the amount of interindividual variation in life span and also expression of three reporter genes-transcriptional reporters for vit-2, gpd-2, and hsp-16.2 (a life-span biomarker). We found the expected inverse relationship between temperature and average life span. Surprisingly, we found that at the highest temperature, there were fewer differences between individuals in life span and less interindividual variation in expression of all three reporters. We suggest that growth at 25°C might canalize (reduce interindividual differences in) life span and expression of some genes by eliciting a small constitutive heat shock response. Growth at 25°C requires wild-type hsf-1, which encodes the main heat shock response transcriptional activator. We speculate that increased chaperone activity at 25°C may reduce interindividual variation in gene expression by increasing protein folding efficiency. We hypothesize that reduced variation in gene expression may ultimately cause reduced variation in life span.

Distributing tasks via multiple input pathways increases cellular survival in stress

Improving in one aspect of a task can undermine performance in another, but how such opposing demands play out in single cells and impact on fitness is mostly unknown. Here we study budding yeast in dynamic environments of hyperosmotic stress and show how the corresponding signalling network increases cellular survival both by assigning the requirements of high response speed and high response accuracy to two separate input pathways and by having these pathways interact to converge on Hog1, a p38 MAP kinase. Cells with only the less accurate, reflex-like pathway are fitter in sudden stress, whereas cells with only the slow, more accurate pathway are fitter in increasing but fluctuating stress. Our results demonstrate that cellular signalling is vulnerable to trade-offs in performance, but that these trade-offs can be mitigated by assigning the opposing tasks to different signalling subnetworks. Such division of labour could function broadly within cellular signal transduction.

DOI:http://dx.doi.org/10.7554/eLife.21415.001

The faster we do tasks the harder it is to do them well. For example, when we wish to judge if, say, a cup, is too hot, we first quickly withdraw our hand after touching it: we know that the cup is hot but not how much. Next we hold a finger against the cup to accurately judge its temperature. Such speed-accuracy trade-offs are studied widely in fields ranging from neuroscience to engineering, but their consequences for single cells are unknown. This is despite the fact that when cells are exposed to stress they must respond both quickly (to survive) and accurately (to reduce how many resources they consume).

One way of stressing yeast cells is to place them in a syrupy substance called sorbitol. This causes the cells to lose water, shrink in size, and launch a stress response to regain volume. If the cells respond inappropriately to the situation, they may die.

The signalling network that produces the stress response is unusual in that it has a Y-shaped structure, where the two ‘arms’ of the Y are the input pathways. Although it was known that one input pathway responds to stress faster than the other, the advantages of having two inputs in the signalling network were not understood. Granados, Crane et al. thought that the differences in speed and the Y-shaped structure could allow the cell to respond to stress with both speed and accuracy.

To investigate this theory, Granados, Crane et al. used a microscope to study individual yeast cells that had been exposed to sorbitol. Combining these results with a mathematical model of the cell signalling network revealed that a mutant yeast cell that only has one of the input pathways specializes in speed but is inaccurate, similar to a reflex-like response. In contrast, a mutant with only the other pathway specializes in accuracy, being slower but matching the level of the cell’s response to the level of stress placed on it. This trade-off is reflected in rates of cell survival: the first mutant survives best in sudden shocks of stress; the second mutant survives best in gradually increasing stress. Normal yeast cells that have both input pathways survive more often than either mutant.

Overall, the results presented by Granados, Crane et al. reveal principles behind cellular decision-making that should hold true in more complex organisms and could be exploited by synthetic biologists to programme cells with new behaviours.

DOI:http://dx.doi.org/10.7554/eLife.21415.002

Transaldolase inhibition impairs mitochondrial respiration and induces a starvation-like longevity response in Caenorhabditis elegans

Mitochondrial dysfunction can increase oxidative stress and extend lifespan in Caenorhabditis elegans. Homeostatic mechanisms exist to cope with disruptions to mitochondrial function that promote cellular health and organismal longevity. Previously, we determined that decreased expression of the cytosolic pentose phosphate pathway (PPP) enzyme transaldolase activates the mitochondrial unfolded protein response (UPR^mt) and extends lifespan. Here we report that transaldolase (tald-1) deficiency impairs mitochondrial function in vivo, as evidenced by altered mitochondrial morphology, decreased respiration, and increased cellular H₂O₂ levels. Lifespan extension from knockdown of tald-1 is associated with an oxidative stress response involving p38 and c-Jun N-terminal kinase (JNK) MAPKs and a starvation-like response regulated by the transcription factor EB (TFEB) homolog HLH-30. The latter response promotes autophagy and increases expression of the flavin-containing monooxygenase 2 (fmo-2). We conclude that cytosolic redox established through the PPP is a key regulator of mitochondrial function and defines a new mechanism for mitochondrial regulation of longevity.

There are a growing number of studies linking mitochondrial dysfunction to enhanced longevity, especially in the nematode C. elegans. The reasons for these pro-longevity effects have been elusive, but one current model is that adaptive responses to mitochondrial inhibition promote organismal health and stress resistance. Here, we report an intriguing example of mitochondrial stress induced by inhibition of a cytosolic metabolic pathway that extends lifespan in worms. We find that inhibition of the pentose phosphate pathway, which is essential for cytosolic redox homeostasis, affects multiple parameters of mitochondrial function and activates a starvation-like response that promotes longevity through recycling of damaged cellular components and induction of the enzyme flavin-containing monooxygenase 2. These results establish novel links between the pentose phosphate pathway, mitochondrial function, redox homeostasis, and organismal aging.

Deep phenotyping unveils hidden traits and genetic relations in subtle mutants

Discovering mechanistic insights from phenotypic information is critical for the understanding of biological processes. For model organisms, unlike in cell culture, this is currently bottlenecked by the non-quantitative nature and perceptive biases of human observations, and the limited number of reporters that can be simultaneously incorporated in live animals. An additional challenge is that isogenic populations exhibit significant phenotypic heterogeneity. These difficulties limit genetic approaches to many biological questions. To overcome these bottlenecks, we developed tools to extract complex phenotypic traits from images of fluorescently labelled subcellular landmarks, using C. elegans synapses as a test case. By population-wide comparisons, we identified subtle but relevant differences inaccessible to subjective conceptualization. Furthermore, the models generated testable hypotheses of how individual alleles relate to known mechanisms or belong to new pathways. We show that our model not only recapitulates current knowledge in synaptic patterning but also identifies novel alleles overlooked by traditional methods.

Experimenter scoring of cellular imaging data can be biased. This study describes an automated and unbiased multidimensional phenotyping method that relies on machine learning and complex feature computation of imaging data, and identifies weak alleles affecting synapse morphology in live C. elegans.

Diffuse Cystic Endometrial Hyperplasia and Metastatic Endometrial Adenocarcinoma in a Vietnamese Pot-Bellied Pig (Sus Scrofa)

A 16-year-old female Vietnamese pot-bellied pig was euthanized after a period of inappetence and weight loss. Diffuse cystic endometrial hyperplasia and endometrial adenocarcinoma with metastasis to lymph nodes, liver, and lung were diagnosed. This report follows the recent description of cystic endometrial hyperplasia and uterine leiomyomas in 3 aged female Vietnamese pot-bellied pigs. The findings in this report and previous reports suggest that pigs may develop some similar age-related uterine lesions as do women.

Microfluidic technologies for yeast replicative lifespan studies

The budding yeast Saccharomyces cerevisiae has been used as a model organism for the study of aging for over 50 years. In this time, the canonical aging experiment-replicative lifespan analysis by manual microdissection-has remained essentially unchanged. Recently, microfluidic technologies have been developed that may be able to substitute for this time- and labor-intensive procedure. These technologies also allow cell physiology to be observed throughout the entire lifetime. Here, we review these devices, novel observations they have made possible, and some of the current system limitations.

Automated Processing of Imaging Data through Multi-tiered Classification of Biological Structures Illustrated Using Caenorhabditis elegans

Quantitative imaging has become a vital technique in biological discovery and clinical diagnostics; a plethora of tools have recently been developed to enable new and accelerated forms of biological investigation. Increasingly, the capacity for high-throughput experimentation provided by new imaging modalities, contrast techniques, microscopy tools, microfluidics and computer controlled systems shifts the experimental bottleneck from the level of physical manipulation and raw data collection to automated recognition and data processing. Yet, despite their broad importance, image analysis solutions to address these needs have been narrowly tailored. Here, we present a generalizable formulation for autonomous identification of specific biological structures that is applicable for many problems. The process flow architecture we present here utilizes standard image processing techniques and the multi-tiered application of classification models such as support vector machines (SVM). These low-level functions are readily available in a large array of image processing software packages and programming languages. Our framework is thus both easy to implement at the modular level and provides specific high-level architecture to guide the solution of more complicated image-processing problems. We demonstrate the utility of the classification routine by developing two specific classifiers as a toolset for automation and cell identification in the model organism Caenorhabditis elegans. To serve a common need for automated high-resolution imaging and behavior applications in the C. elegans research community, we contribute a ready-to-use classifier for the identification of the head of the animal under bright field imaging. Furthermore, we extend our framework to address the pervasive problem of cell-specific identification under fluorescent imaging, which is critical for biological investigation in multicellular organisms or tissues. Using these examples as a guide, we envision the broad utility of the framework for diverse problems across different length scales and imaging methods.

New technologies have increased the size and content-richness of biological imaging datasets. As a result, automated image processing is increasingly necessary to extract relevant data in an objective, consistent and time-efficient manner. While image processing tools have been developed for general problems that affect large communities of biologists, the diversity of biological research questions and experimental techniques have left many problems unaddressed. Moreover, there is no clear way in which non-computer scientists can immediately apply a large body of computer vision and image processing techniques to address their specific problems or adapt existing tools to their needs. Here, we address this need by demonstrating an adaptable framework for image processing that is capable of accommodating a large range of biological problems with both high accuracy and computational efficiency. Moreover, we demonstrate the utilization of this framework for disparate problems by solving two specific image processing challenges in the model organism Caenorhabditis elegans. In addition to contributions to the C. elegans community, the solutions developed here provide both useful concepts and adaptable image-processing modules for other biological problems.

Animal microsurgery using microfluidics

Small multicellular genetic organisms form a central part of modern biological research. Using these small organisms provides significant advantages in genetic tractability, manipulation, lifespan and cost. Although the small size is generally advantageous, it can make procedures such as surgeries both time consuming and labor intensive. Over the past few years there have been dramatic improvements in microfluidic technologies that enable significant improvements in microsurgery and interrogation of small multicellular model organisms.

Quantitative screening of genes regulating tryptophan hydroxylase transcription in Caenorhabditis elegans using microfluidics and an adaptive algorithm

Forward genetic screening via mutagenesis is a powerful method for identifying regulatory factors in target pathways in model organisms such as the soil-dwelling free-living nematode Caenorhabditis elegans (C. elegans). Currently manual microscopy is the standard technique for conducting such screens; however, it is labor-intensive and time-consuming because screening requires imaging thousands of animals. Recently microfluidic chips have been developed to increase the throughput of some of such experiments; nonetheless, most of these chips are multilayer devices and complicated to fabricate and therefore prone to failure during fabrication and operation. In addition, most sorting decisions are made manually and the criteria used for sorting are subjective. To overcome these limitations, we developed a simple single-layer microfluidic device and an adaptive algorithm to make sorting decisions. The one-layer device greatly improves the reliability, while quantitative analysis with the adaptive algorithm allows for the identification of mutations that generate subtle changes in expression, which would have been hard to detect by eye. The screening criterion is set based on the mutagenized population, not separate control populations measured prior to actual screening experiments, to account for stochasticity and day-to-day variations of gene expression in mutagenized worms. Moreover, during each experiment, the threshold is constantly updated to reflect the balance between maximizing sorting rate and minimizing false-positive rate. Using this system, we screened for mutants that have altered expression levels of tryptophan hydroxylase, a key enzyme for serotonin synthesis in a CaMKII gain-of-function background. We found several putative mutants in this screen. Furthermore, this microfluidic system and quantitative analysis can be easily adapted to study other pathways in C. elegans.

A conserved role for atlastin GTPases in regulating lipid droplet size

Lipid droplets (LDs) are the major fat storage organelles in eukaryotic cells, but how their size is regulated is unknown. Using genetic screens in C. elegans for LD morphology defects in intestinal cells, we found that mutations in atlastin, a GTPase required for homotypic fusion of endoplasmic reticulum (ER) membranes, cause not only ER morphology defects, but also a reduction in LD size. Similar results were obtained after depletion of atlastin or expression of a dominant-negative mutant, whereas overexpression of atlastin had the opposite effect. Atlastin depletion in Drosophila fat bodies also reduced LD size and decreased triglycerides in whole animals, sensitizing them to starvation. In mammalian cells, co-overexpression of atlastin-1 and REEP1, a paralog of the ER tubule-shaping protein DP1/REEP5, generates large LDs. The effect of atlastin-1 on LD size correlates with its activity to promote membrane fusion in vitro. Our results indicate that atlastin-mediated fusion of ER membranes is important for LD size regulation.

Sequentially pulsed fluid delivery to establish soluble gradients within a scalable microfluidic chamber array

This work presents a microfluidic chamber array that generates soluble gradients using sequentially pulsed fluid delivery (SPFD). SPFD produces stable gradients by delivering flow pulses to either side of a chamber. The pulses on each side contain different signal concentrations, and they alternate in sequence, providing the driving force to establish a gradient via diffusion. The device, herein, is significant because it demonstrates the potential to simultaneously meet four important needs that can accelerate and enhance the study of cellular responses to signal gradients. These needs are (i) a scalable chamber array, (ii) low complexity fabrication, (iii) a non-shearing microenvironment, and (iv) gradients with low (near zero) background concentrations. The ability to meet all four needs distinguishes the SPFD device from flow-based and diffusion-based designs, which can only achieve a subset of such needs. Gradients are characterized using fluorescence measurements, which reveal the ability to change the curvature of concentration profiles by simple adjustments to pulsing sequence and flow rate. Preliminary experiments with MDA-MB-231 cancer cells demonstrate cell viability and indicate migrational and morphological responses to a fetal bovine serum gradient. Improved and expanded versions of this technology could form the basis of high-throughput screening tools to study cell migration, development, and cancer.

Rabx-5 regulates RAB-5 early endosomal compartments and synaptic vesicles in C. elegans

Early endosomal membrane compartments are required for the formation and recycling of synaptic vesicles, but how these compartments are regulated is incompletely understood. We performed a forward genetic screen in C. elegans for mutations that affect RAB-5 labeled early endosomal compartments in GABAergic motoneurons. Here we report the isolation and characterization of one mutation, rabx-5. The rabx-5 mutation leads to decreased intensity of YFP::RAB-5 in the cell soma but increased intensity in the synaptic and intersynaptic regions of the axon. This effect is due to the bias of the cycling state of RAB-5, and results from a change in the organization of the early endosomal compartment as well as the membrane binding state of RAB-5. Synaptic vesicle accumulation is altered in rabx-5 mutants, and synaptic transmission from cholinergic neurons is decreased. Early endosomal membrane compartments show disorganization with ageing and rabx-5 mutant animals age faster. These results suggest that rabx-5 regulation of RAB-5 compartments is important for maintaining proper synaptic function throughout the lifetime.

A multispectral optical illumination system with precise spatiotemporal control for the manipulation of optogenetic reagents

Optogenetics is an excellent tool for noninvasive activation and silencing of neurons and muscles. Although they have been widely adopted, illumination techniques for optogenetic tools remain limited and relatively nonstandardized. We present a protocol for constructing an illumination system capable of dynamic multispectral optical targeting of micrometer-sized structures in both stationary and moving objects. The initial steps of the protocol describe how to modify an off-the-shelf video projector by insertion of optical filters and modification of projector optics. Subsequent steps involve altering the microscope's epifluorescence optical train as well as alignment and characterization of the system. When fully assembled, the illumination system is capable of dynamically projecting multispectral patterns with a resolution better than 10 μm at medium magnifications. Compared with other custom-assembled systems and commercially available products, this protocol allows a researcher to assemble the illumination system for a fraction of the cost and can be completed within a few days.

Real-time multimodal optical control of neurons and muscles in freely behaving Caenorhabditis elegans

The ability to optically excite or silence specific cells using optogenetics has provided a powerful tool to interrogate the nervous system. Optogenetic experiments in small organisms have mostly been performed using whole-field illumination and genetic targeting, but these strategies do not always provide adequate cellular specificity. Targeted illumination can be a valuable alternative but to date it has only been shown in non-moving animals without the ability to observe behavior output. We present a real-time multimodal illumination technology that allows both tracking and recording the behavior of freely moving Caenorhabditis elegans while stimulating specific cells that express Channelrhodopsin-2 or MAC. We use this system to optically manipulate nodes within the C. elegans touch circuit and study the roles of sensory and command neurons and the ultimate behavioral output. This technology significantly enhances our ability to control, alter, observe, and investigate how neurons, muscles, and circuits ultimately produce behavior in animals using optogenetics.

Microfluidics-enabled phenotyping, imaging, and screening of multicellular organisms

This paper reviews the technologies that have been invented in the last few years on high-throughput phenotyping, imaging, screening, and related techniques using microfluidics. The review focuses on the technical challenges and how microfluidics can help to solve these existing problems, specifically discussing the applications of microfluidics to multicellular model organisms. The challenges facing this field include handling multicellular organisms in an efficient manner, controlling the microenvironment and precise manipulation of the local conditions to allow the phenotyping, screening, and imaging of the small animals. Not only does microfluidics have the proper length scale for manipulating these biological entities, but automation has also been demonstrated with these systems, and more importantly the ability to deliver stimuli or alter biophysical/biochemical conditions to the biological entities with good spatial and temporal controls. In addition, integration with and interfacing to other hardware/software allows quantitative approaches. We include several successful examples of microfluidics solving these high-throughput problems. The paper also highlights other applications that can be developed in the future.

Computer-enhanced high-throughput genetic screens of C. elegans in a microfluidic system

Most visual screens based on fluorescent markers are currently limited in throughput and accuracy. Here we present the first genetic screen of a mutagenized population of C. elegans in a microfluidic device. Animal handling streamlined by a microfluidic device and intuitive control software enabled the identification of novel mutants and a large screening speed.

Automated on-chip rapid microscopy, phenotyping and sorting of C. elegans

Microscopy, phenotyping and visual screens are frequently applied to model organisms in combination with genetics. Although widely used, these techniques for multicellular organisms have mostly remained manual and low-throughput. Here we report the complete automation of sample handling, high-resolution microscopy, phenotyping and sorting of Caenorhabditis elegans. The engineered microfluidic system, coupled with customized software, has enabled high-throughput, high-resolution microscopy and sorting with no human intervention and may be combined with any microscopy setup. The microchip is capable of robust local temperature control, self-regulated sample-loading and automatic sample-positioning, while the integrated software performs imaging and classification of worms based on morphological and intensity features. We demonstrate the ability to perform sensitive and quantitative screens based on cellular and subcellular phenotypes with over 95% accuracy per round and a rate of several hundred worms per hour. Screening time can be reduced by orders of magnitude; moreover, screening is completely automated.

The Genetics of Generalized Osteoarthritis (GOGO) study: study design and evaluation of osteoarthritis phenotypes

PURPOSE

The primary goal of the Genetics of Generalized Osteoarthritis (GOGO) study is to identify chromosomal regions associated with increased susceptibility to generalized osteoarthritis (OA). Here we describe the study design and phenotype of the 2728 participants from the 1145 families recruited for this study.

METHODS

GOGO is an investigator-initiated collaboration involving seven clinical academic sites and sponsored by GlaxoSmithKline. Family ascertainment was carried out between 1999 and 2002. A qualifying family required self-reported Caucasian ethnicity and at least two affected siblings with clinical hand OA. We hypothesized that this clinical phenotype would facilitate identification of participants with multijoint radiographic OA (rOA) in and beyond the hand. The "gold standard" case definition, however, was based on rOA (Kellgren-Lawrence grade > or =2) involving > or =3 hand joints distributed bilaterally and including at least one distal interphalangeal joint, with two of the three involved joints within a joint group (distal interphalangeal, proximal interphalangeal, or carpometacarpal). Radiographs of hips, knees and spine were also obtained. Additional siblings and living parents from qualifying families, both affected and unaffected, were invited to participate.

RESULTS

A total of 2706 participants had complete clinical and radiological examination data. Of these, 2569 participants met clinical examination criteria for affected status; while 1963 (73%) participants met the prespecified radiographic criteria for affected status. This corresponded to a total of 707 families with at least two affected siblings that met the hand rOA criteria. Of those individuals with rOA of the hand, the frequency of rOA at other sites was highest for the knee (51%) and spine (54%), and less common for the hip (25%). Concordance rates among hand affected siblings were greatest for spine (36%) followed by knee (31%) and hip (9%); a total of 53% of the affected sib pairs were concordant for specific patterns of generalized rOA involving the hand and large joints (knees, hips or spine).

CONCLUSIONS

GOGO represents a large multicenter collection of families with multiple joint OA that have been characterized both clinically and radiographically. The GOGO study will employ a comprehensive strategy for genetic screening based upon both qualitative and quantitative radiographic trait analyses, circulating biomarkers in a quantitative trait-based analysis, fine mapping, and candidate gene analysis. This sample should provide sufficient power to detect linkage to OA associated genes.

In vitro inhibition of Salmonella organisms isolated from reptiles by an inactivated culture of microcin-producing Escherichia coli

OBJECTIVE

To determine whether an inactivated culture of a microcin-producing avian Escherichia coli was capable of killing Salmonella isolates from reptiles in an in vitro test system.

SAMPLE POPULATION

57 Salmonella isolate from reptiles.

PROCEDURE

A wild-type avian E. coli electrotransformed with a plasmid coding for the production of microcin 24 was tested in an in vitro microassay system for its ability to kill 57 Salmonella spp isolated from reptiles. The reptile population included snakes, iguana, frilled lizards, turtles, other lizards, and unspecified reptiles.

RESULTS

44 of the Salmonella isolates were inhibited strongly, compared with the in vitro assay controls; 12 had weak inhibition, and 1 was not inhibited by the microcin-producing E. coli. Thirteen of the 57 isolates had resistance to at least 1 antibiotic, primarily streptomycin. There were 9 O serogroups identified in the 57 isolates, with serogroup H being the most prevalent (18 to 57).

CONCLUSION AND CLINICAL RELEVANCE

Antibiotics are not recommended to eliminate Salmonella organisms from reptiles because of the development of antibiotic resistance. Further studies are necessary to determine whether the use of microcin-producing bacteria will be effective in controlling Salmonella infections in companion reptiles.

Acute appendicitis in children: the importance of family history

BACKGROUND/PURPOSE

Acute appendicitis is common, frequently atypical, challenging, and still associated with significant morbidity. Despite major technologic advances, appendicitis remains a primarily clinical diagnosis. Therefore, no relevant anamnestic information should be overlooked. Surprisingly, the relationship between heredity and appendicitis is seldom considered. Because of the potential clinical importance of the family history, the authors addressed this question prospectively over a 52-month period in a practice that includes the majority of pediatric patients with appendicitis in the region.

METHODS

Family histories were obtained in a standardized manner, focusing on first-degree relatives. Children with incomplete family information were excluded. Patients (ages 2(1/2) to 19 years) were divided into 3 groups: group A, children who underwent an appendectomy (n = 166); group B (first control), children who presented with an acute abdomen and suspected appendicitis but did not undergo an appendectomy (n = 117); group C (second control), children who were seen in the practice for unrelated conditions (n = 141).

RESULTS

A positive parental history was obtained from 59 patients (36%) in group A, 24 patients (21%) in group B, and 20 patients (14%) in group C, and the odds ratios (ORs) were 2.0 (P =.035) and 2.9 (P <.001) for groups A versus B and A versus C, respectively. Of the 13 patients whose sibling had had acute appendicitis, 9 were in group A versus 2 each in groups B and C, and the OR for any family history (siblings, parents) in groups A versus B was 1.9 (P =.028) and for groups A versus C was 2.9 (P < 0.001). Appendicitis was histologically confirmed in 93% of children in group A.

CONCLUSIONS

Heredity is a significant factor in pediatric patients who have appendicitis. Children who have appendicitis are twice as likely to have a positive family history than are those with right lower quadrant pain (but no appendicitis) and almost 3 times as likely to have a positive family history than are surgical controls (without abdominal pain). Because of its potential value in changing the threshold for intervention, a careful family history should be obtained for every child in whom acute appendicitis is suspected.

Comparison of implantation and pregnancy rates in African American and white women in an assisted reproductive technology practice

OBJECTIVE

To compare IVF outcomes between infertile African American and white women.

DESIGN

Retrospective cohort study.

SETTING

Hospital-based IVF practice.

PATIENT(S)

Women undergoing IVF procedures between November 1996 and June 2000.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Implantation and pregnancy rates.

RESULT(S)

There were 24 African American and 273 white women < or =40 years of age who underwent 25 and 333 IVF cycles, respectively. African American women were more likely to have had tubal factor as a primary diagnosis, to have had a child, and to have undergone fewer previous assisted reproductive technology (ART) cycles as compared to white women. No differences between the two groups for clinical variables were noted with the exception of body mass index (BMI [kg/m(2)], 27.1 in African Americans vs. 24.8 in whites). Implantation rates were higher in African American than in white women (35% vs. 23%, respectively). Pregnancy rates were 71% in African Americans and 48% in whites. After adjustment for tubal factor, BMI, and parity, the odds ratio for pregnancy in African American women versus white women increased from 2.6 to 3.3.

CONCLUSION(S)

This is the first study to demonstrate a significantly higher clinical pregnancy rate in African American women as compared to white women undergoing ART. These data strongly contradict a recent study comparing the same two groups of women undergoing ART. We urge other ART centers to report their data pertaining to race.

An analysis of limb-threatening lower extremity wound complications after 1090 consecutive coronary artery bypass procedures

The objective of this study was to examine and characterize limb-threatening lower extremity wound or soft tissue complications after coronary artery bypass (CABG) and determine risk factors for their cause. While minor wound problems of the leg after CABG are not uncommon, serious limb-threatening complications, though less frequent, do occur and are often de-emphasized in the surgical literature. A review of 1090 consecutive CABG procedures performed from January 1, 1995 through December 31, 1995 was instituted, which screened for limb-threatening lower extremity wound or soft tissue complications defined as wounds that: required additional surgery for treatment; prolonged the length of stay; or which required lengthy home health nursing for treatment. Minor lymph leaks, leg swelling, infections or wound problems treated as an outpatient were excluded. Of 1090 patients, 54 (5.0%) experienced a limb-threatening lower extremity complication. Complications were categorized as vein harvest incision non-healing (n = 36, 66.7%), decubitus ulceration (n = 11, 20.4%), forefoot ischemia/embolization (n = 10, 18.5%), groin hematoma/abscess (n = 6, 11.1%), severe cellulitis (n = 3, 5.6%), or a combination (n = 12, 22.2%). Statistically significant risk factors by univariate and bivariate analysis for a complication included older age (68 years vs 62 years, p = 0.007), female sex (57% vs 28%, p < 0.001), diabetes (57% vs 33%, p = 0.005) and longer pump time (129 min vs 114 min, p = 0.009). These complications necessitated five major lower extremity amputations and nine revascularization procedures. Chronic lower extremity ischemia from peripheral vascular disease (PVD) was a major contributing factor for the development of wounds in at least 23 (42.6%) of these patients, though suspected in only 10 (43.5%) preoperatively. A non-healing vein harvest incision below the knee of a patient retrospectively found to have inadequate distal circulation for healing occurred in 17 (31.5%) of the total 54 cases. It was concluded that non-healing vein incisions, decubitus ulcers and forefoot ischemic lesions frequently occurring in older diabetic females with undetected pre-existing PVD, comprise the majority of limb-threatening leg complications after CABG. Nearly one-third of the complications may have been avoided had the vein harvest incision not been made at the ankle of a patient with unappreciated PVD.

Electronic fetal heart rate monitoring: early neonatal outcomes associated with normal rate, fetal stress, and fetal distress

OBJECTIVE

The purpose of this study was to test the ability of a clearly defined classification system for electronic fetal heart rate monitoring to predict early neonatal outcome.

STUDY DESIGN

All labors of women with singleton pregnancies > or = 32 weeks' gestation electronically monitored at 2 institutions were examined. Tracings in the final hour before delivery were defined as normal, fetal stress, or fetal distress. After delivery, Apgar scores, cord blood gas values, and admission to the neonatal intensive care unit were examined as measures of early neonatal outcome.

RESULTS

Among the 898 patients who qualified for study, 627 (70%) had tracings classified as normal, 263 (29%) had tracings classified as fetal stress, and 8 (1%) had tracings classified as fetal distress. There was a significant worsening of neonatal outcome across these 3 groups with regard to depressed Apgar scores 1 minute (5.1%, 18.3%, and 75.0%; P <.05), depressed Apgar scores at 5 minutes (1.0%, 3.8%, and 37.5%; P <.05), and admission to the neonatal intensive care unit (5.6%, 10.6%, and 37.5%; P <.05). There was also a progressive worsening of cord blood pH (7.27 +/- 0.06, 7.21 +/- 0.08, and 7.06 +/- 0.14; P <.05), a progressive increase in PCO (2) (53.39 +/- 8.34 mm Hg, 58.51 +/- 10.55 mm Hg, and 78.31 +/- 20.35 mm Hg; P <.05), and a progressive decline in base excess (-3.18 +/- 2.02 mEq/L, -5. 11 +/- 3.11 mEq/L, and -9.07 +/- 4.59 mEq/L; P <.05).

CONCLUSION

This simple classification system for interpreting fetal heart rate tracings accurately predicts normal outcomes for fetuses as well discriminating fetuses in true distress. Further, it identifies an intermediate group of fetuses with a condition labeled fetal stress who might benefit from additional evaluation and possibly from expeditious delivery.

The pitfalls of establishing a statewide vascular registry: the South Carolina experience

Concerned about the inadequacy of a centralized database and the importance of low morbidity and mortality on carotid endarterectomy efficacy, the South Carolina Vascular Surgical Society prospectively instituted a computer registry for carotid procedures performed by its members, to establish a statewide standard of practice. From January 1994 through December 1997, 23 of the 30 physician members voluntarily registered data on 1652 carotid operations at 14 hospitals into a central database. Blinded results were reviewed biannually. Complete data (1995-1997) were available for 1199 cases. The patients tended to be >64 years old (72%), male (62%), and white (93%). Carotid endarterectomy was the most frequently performed operation (90%). Perioperative complications (< or = 30 days) occurred in 173 patients (14.4%), including stroke (n = 19; 1.6%), death (n = 8; 0.7%), and stroke/death (n = 25; 2.0%). Although 23 surgeons (77% of the society) contributed some data, only 10 surgeons (33%) contributed complete data on >10 patients/year. Despite biannual efforts to boost participation, case entry remained stable (1994, 358; 1995, 347; 1996, 425; and 1997, 427), representing about one-third of the estimated carotid procedures performed in the state during that period. The cost of the registry was approximately $11,500. Audit of 8 surgeons revealed a >95 per cent match against the statewide discharge database and low error rate versus independent medical record review. This experience confirms that excellent outcomes after carotid endarterectomy are not limited to a few select centers and can be accomplished by adequately trained surgeons in a variety of institutional settings. Incomplete physician participation, however, inevitably raises questions about the utility of such efforts. Until volunteer registries induce full participation by heightening perceived physician benefit, their role will remain limited for future outcomes research.

Nonendarterectomy procedures of the carotid artery: a five-year review

Although the efficacy of carotid endarterectomy has been well established, nonendarterectomy procedures of the carotid bifurcation have only sporadically been reported. Of 334 consecutive nontraumatic carotid procedures performed on 321 patients from July 1992 until May 1997, 306 (91.6%) were carotid endarterectomies, 14 (4.2%) were carotid-subclavian bypasses/transpositions, and 14 (4.2%) were nonendarterectomy procedures of the carotid artery. These latter 14 cases (nine females and five males; mean age, 63 years) were all symptomatic (neurological or painful mass) and included carotid kink/coil resection (n = 3; 0.9%), endarterectomy and vertebral transposition (n = 2; 0.6%), carotid aneurysm resection (n = 2; 0.6%), carotid body tumor resection (n = 2; 0.6%), carotid stump ligation/external endarterectomy (n = 1; 0.3%), infected/bleeding carotid patch removal with vein graft replacement (n = 1; 0.3%), saphenous vein graft replacement (n = 1; 0.3%), carotid dilatation for fibromuscular dysplasia (n = 1; 0.3%), and descending aorta to carotid bypass (n = 1; 0.3%). With 30 day follow-up complete for all 334 carotid operations, 10 perioperative strokes (2.9%) and five deaths (1.5%) occurred for a combined stroke/death rate of 3.3 per cent. Of the 14 nonendarterectomy carotid artery operations, there were no strokes or deaths; with mean follow-up of 13 months, 13 patients (92.9%) are asymptomatic, patent, and disease-free. Three severe transient cranial nerve (CN) neuropraxias (21.4%), one myocardial infarction (7.1%), and one late death (mesenteric ischemia at 2 months), however, occurred. Although no statistical differences in stroke, death, and stroke/death occurred between the endarterectomy versus the nonendarterectomy group, transient CN injury was more common in the nonendarterectomy group (21.4% versus 4.1%; P = 0.027). Although nonendarterectomy procedures of the carotid bifurcation are infrequently needed, they seem safe, effective, and indicated in selected patients, despite a higher incidence of transient CN injury.

Control of air quality in an assisted reproductive technology laboratory

OBJECTIVE

To investigate the effect of improved air quality on IVF and subsequent embryo development.

DESIGN

Retrospective cohort study.

SETTING

Hospital-based IVF facility composed of an anteroom, a cleanroom, and an adjacent operating room.

PATIENT(S)

Two-hundred seventy-five couples requesting IVF between 1993 and 1997.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Particle counts (sizes 0.3, 0.5, 1.0, and 5.0 microm); IVF rates; and embryo quality (stage and grade).

RESULT(S)

Clinical pregnancy rates decreased from 35% in 1993 to 16% in 1994 (numerous construction odors were detected during 1994) and increased steadily after the cleanroom was built (rates for 1995-1997 were 20%, 32%, and 59%, respectively). Fertilization rates decreased between 1993 (74%) and 1994 (60%) and then steadily increased after cleanroom installation (62% in 1995, 71% in 1996, and 69% in 1997). The proportion of embryos past the four-cell stage decreased from 66% in 1993 to 61% in 1994 but then increased steadily in the years after the cleanroom was built (78%, 77%, and 83% in 1995, 1996, and 1997, respectively). During the same 5-year period, there were no differences in embryo quality or number of embryos transferred.

CONCLUSION(S)

Construction of a Class 100 cleanroom improved air quality and IVF rate and increased the number of embryos past the four-cell stage available for transfer.

Validity and cost-effectiveness of antisperm antibody testing before in vitro fertilization

OBJECTIVE

To determine the usefulness of and cost-effectiveness of antisperm antibody testing in the prediction of poor fertilization rates in couples undergoing IVF.

DESIGN

Retrospective cohort study.

SETTING

A hospital-based reproductive endocrinology and infertility practice.

PATIENT(S)

Male partners of 251 couples undergoing IVF between 1992 and 1997.

MAIN OUTCOME MEASURE(S)

Fertilization rates in couples undergoing conventional IVF.

RESULT(S)

One hundred nineteen couples were evaluated for antisperm antibodies; fertilization rates were similar in those couples whose husbands were and were not tested (64% versus 68%). Antisperm antibodies were detected in 16 men. Four (25%) of the 16 couples whose husbands had antisperm antibodies fertilized < or = 50% of oocytes, compared with 31 (30%) of the 103 couples whose husbands did not have these antibodies. Overall, 21 couples (8.4%) experienced complete fertilization failure. In a program that included antisperm antibody testing for selected couples and intracytoplasmic sperm injection (ICSI) for those who tested positive, it would cost $11,735 to prevent a fertilization failure (assuming ICSI were 100% effective), whereas it would cost $9,250 to perform ICSI in a second IVF cycle for those who initially failed.

CONCLUSION(S)

In this practice setting, antisperm antibody testing has low sensitivity in predicting low or no fertilization and does not appear to be cost-effective when selectively ordered as part of an IVF workup.

Factors associated with limb loss despite a patent infrainguinal bypass graft

Lower-extremity limb salvage should parallel infrainguinal bypass graft patency. To determine factors associated with limb loss despite a patent bypass, we reviewed 191 consecutive infrainguinal bypasses in 158 patients followed prospectively over 42 months. In this series of 176 (92%) vein grafts, 15 (8%) expanded polytetrafluoroethylene grafts, 122 (64%) tibial artery bypasses, and 170 (89%) bypasses placed for limb salvage, 29 major lower-extremity (above-knee or below-knee) amputations were performed in 29 patients, 12 because of ischemia after graft thrombosis and 17 (9% of series) due to progression of soft tissue infection/necrosis despite a functioning bypass. Primary and secondary 36-month vein graft patencies by life-table analysis were 61 per cent and 81 per cent, respectively. When the 17 cases of limb loss were compared to the rest of the series, nonstatistically significant variables included male sex [11 (65%) vs 79 (56%); P = 0.608] and diabetes [12 (71%) vs 80 (57%); P = 0.310]. Statistically significant variables included black race [9 (53%) vs 39 (28%); P = 0.048]; chronic renal failure [6 (35%) vs 12 (9%); P = 0.005], placement to a tibial/pedal artery [15 (88%) vs 107 (62%); P = 0.034], distal anastomosis to the anterior tibial/dorsalis pedis (AT/DP) artery [8 (47%) vs 27 (16%); P = 0.004], and grafts requiring late revision [7 (41%) vs 22 (13%); P = 0.006]. Thirteen (76%) extremities had an intact pedal arch. Nine amputations were performed within 30 days (early group), and eight were performed from 45 days to 20 months (median, 8 months) after bypass placement (late group). The most common primary causes of limb loss in the early group were overwhelming progression of soft-tissue infection despite patent bypass (n = 4; 44%) and insufficient runoff in the foot (n = 3; 33%). In the late group, amputation most often followed long treatment of a chronic proximal diabetic neuropathic foot ulcer with osteomyelitis. Five (63%) grafts in this group were anastomosed to the AT/DP arteries. These data suggest that patients with chronic renal failure, chronic neuropathic heel ulcers, and an AT/DP bypass are at greater risk for amputation despite a working bypass, especially if the graft develops a hemodynamically significant stenosis. Careful judgment and patient selection under these circumstances are thus justified.

Superficial femoral artery eversion endarterectomy: a useful adjunct for infrainguinal bypass in the presence of limited autogenous vein

PURPOSE

To evaluate, in a group of technically high-risk patients, the results of infrainguinal revascularization using a conduit constructed with endarterectomized superficial femoral artery (SFA) and available arm or saphenous vein.

METHODS

Of 237 consecutive lower extremity vein graft bypass procedures performed in 195 patients from July 1992 through August 1996, 15 SFA eversion endarterectomies (in 10 men and five women; median age, 70 years) were performed and used as a composite bypass conduit with available autogenous vein for the treatment of limb-threatening ischemia. In each case, an occluded SFA was divided 8 to 15 cm distal to its origin, proximally endarterectomized, and sewn end-to-end to a segment of vein to provide adequate conduit length for bypass grafting. Indications for this technique were unavailability of vein as a result of failed previous bypass grafting (n = 10) or previous coronary artery bypass grafting (n = 5). Veins were sewn distally to a below-knee popliteal artery (n = 4; 27%) or tibial artery (n = 11; 73%).

RESULTS

Primary patency, secondary patency, and limb salvage rates at 36 months by life table analyses for the 237 grafts were 62.3%, 81.0%, and 77.2%, respectively. The 15 composite SFA-vein bypass grafts had 36-month primary patency, secondary patency, and limb salvage rates of 60.0%, 72.0%, and 65.9%, respectively (mean follow-up, 15 months). Currently, eight of these patients (53%) have patent bypass grafts; two (13%) died at 4 and 18 months after the operation with patent grafts; two (13%) underwent amputations for progressive foot gangrene despite a patent bypass graft; and three (20%) had grafts that thrombosed at 4, 5, and 10 months. Typical hyperplastic intrinsic graft-threatening stenoses developed in two patients (13%) in the SFA segment at 4 and 8 months; they were discovered by routine duplex scan surveillance.

CONCLUSION

Composite SFA eversion endarterectomy/vein graft conduits yield acceptable results, behave similarly to other autogenous conduits used for technically high-risk infrainguinal revascularization, and are beneficial when autogenous vein is limited.

Correlation between selected environmental exposures and karyotype in acute myelocytic leukemia

Many bone marrow cytogenetic abnormalities in acute myelogenous leukemia (AML) are tumor specific, clonal, nonrandom, and related to prognosis; it has been hypothesized that they may be markers of exposure to etiological agents. A previous report from our institution revealed several such associations; the purpose of the current study was to determine whether previous findings were present in a new group of patients. Subjects included 84 newly diagnosed AML patients (French-American-British M1 and M2); exposure data were gathered using self-report questionnaires at the time of registration. Two sets of comparisons were made: (a) patients with all (AA) or some (AN) cytogenetically abnormal cells versus those with normal karyotypes (NN) and (b) patients with specific abnormalities [-5/5q-, -7/7q-, +8, t(8;21)] versus all others. Odds ratios (ORs) were 4.64 for the association between prior cytotoxic therapy and -5/5q- and 6.38 for the association with -7/7q-, but were <1.00 for +8 and t(8;21). There were no ORs > 2.0 for specific abnormalities in any of the other exposures evaluated (cigarette smoking, alcohol use, occupational exposure to organic chemicals, paints, or pesticides/herbicides), with the exception of exposure to paints and -7/7q- (OR, 7.50). The ORs for AA/AN versus NN patients were 1.43 and 3.81 for smoking and alcohol use, and weak dose-response trends were present. The most consistent positive associations between the two series were for prior cytotoxic therapy (-5/5q-; -7/7q-), cigarette smoking (AA/AN versus NN) and alcohol use (AA/AN versus NN). Reasoning from the known association between prior cytotoxic therapy and -7/7q-, we would have predicted relatively high ORs (> 4.0) if specific abnormalities acted as markers for the exposures assessed, but none were present. However, in both series, AA/AN patients were more likely to smoke and use alcohol than were NN patients, and weak dose-response patterns were present for both. This finding suggests that both smoking and alcohol use may play a role in the pathogenesis of cytogenetic abnormalities in AML-M1/M2; however, the mechanism by which they work and whether they are involved in the etiology of these diseases remain unclear.

Benefits from a teen pregnancy program: neonatal outcomes potential cost savings

These data demonstrated that participants in our teen pregnancy program had better birth outcomes than comparable teens who did not participate in the program. Based on number of NICU admissions and lengths of stay, we estimate that this program provided, through the reduction of poor birth outcomes, potential cost savings of $890,000 over four years.

Antithrombin III and trauma patients: factors that determine low levels

A prospective (cohort) study was conducted to determine the incidence of low antithrombin III (AT III) levels and the association with selected clinical variables in adult trauma patients. One hundred sixty AT III levels were obtained on 50 consecutive trauma admissions to a community-based level I trauma center. Antithrombin III levels were drawn as soon after admission as possible and every other day thereafter. Thirty-one patients (62%) had at least one low AT III level (< 80%), whereas 15 concurrently drawn control levels were all > or = 90%. Low AT III levels were more common in patients with one or more of the following: base deficit less than -4 (39% vs. 0, p = 0.002); Injury Severity Score > 15 (48% vs. 16%, p = 0.04); and blood transfusion (32% vs. 5%, p = 0.04). All other variables (shock, surgical intervention, subcutaneous heparin, and sequential compression devices) were not statistically significant, although all six patients with shock had low levels. In conclusion, over 60% of adult trauma patients had low AT III levels at some time during hospitalization and these patients were clearly more severely injured. Further studies are required to determine if these patients are more susceptible to thromboembolic phenomena.

Zidovudine improves psoriasis in human immunodeficiency virus-positive males

BACKGROUND AND DESIGN

Patients with human immunodeficiency virus (HIV) infection can develop severe psoriasis, which is difficult to treat using conventional therapy. Anecdotal case reports have suggested that administration of zidovudine can improve psoriasis in the HIV-infected patient. An open-label study was conducted to determine the safety and effectiveness of zidovudine therapy in 24 patients with HIV-associated psoriasis and to correlate response with laboratory and clinical variables.

RESULTS

Of 19 evaluable patients, 90% had either partial (58%) or complete (32%) improvement of their HIV-associated psoriasis during zidovudine therapy. Greater than 75% reduction in the body surface area involved was positively associated with antigenemia and an age younger than 30 years.

CONCLUSIONS

Zidovudine therapy, at a dosage of 1200 mg/d, appears to be beneficial in the treatment of HIV-associated psoriasis, although long-term relapses occurred and the associated arthritis did not improve.

Effect of HIV transmission category and CD4 count on the occurrence of diarrhea in HIV-infected patients

This study was designed to assess the relative contributions of HIV transmission category and immunodeficiency to the risk of HIV-related diarrhea. We reviewed the medical records of 169 HIV-infected non-AIDS patients seen between 1986 and 1990 at the Houston VA Special Medicine Clinic. The prevalence of diarrhea at any given clinic visit ranged from 3% to 7%. Diarrhea was three times more common in homosexual/bisexual men [odds ratio = 3.0 (1.01-9.53)], and this pattern persisted when stratified by CD4 count. Previous studies have focused mainly on the detection of enteric organisms in patients with HIV-related diarrhea. Studies of the temporal relationships between sexual practices, enteric pathogens, diarrhea, and immunodeficiency are needed to clarify the pathogenesis of HIV-related diarrhea.

Cocaine use in women from a defined population: prevalence at delivery and effects on growth in infants

Adverse health effects associated with intrauterine cocaine exposure (prematurity and its associated morbidity, intrauterine growth retardation, possible risk of sudden infant death syndrome) are based on studies from large urban hospitals, but few data exist from other sources. The current study, set in a community hospital, was designed to (1) estimate the prevalence of maternal cocaine use at delivery, (2) describe neonatal outcomes, and (3) evaluate physiological growth in exposed children. The study was conducted over 30 months (total births were 14,074) at The Children's Hospital of Greenville Memorial Hospital, the major source of neonatal care for Greenville County, South Carolina (1990 population: 320,000). A child was considered exposed to cocaine if there was documented evidence of use in the mother's medical record or if one member of the pair had a positive urine drug screen. Growth data were abstracted from clinical records. Overall prevalence of exposure was 1.0%. Of the 137 subjects (89, positive urine drug screen; 48 self-reported exposure), 21 (15%, 95% confidence interval, 9% to 21%) were premature (gestational age < 37 weeks) and 2 died of sudden infant death syndrome. Mean age- and sex-adjusted percentiles for weight, length, and head circumference increased from 23%, 29%, and 18%, respectively, at birth to 43%, 49%, and 54% in children followed for 12 months; however, 50% of the cohort were lost to follow-up, and these children were smaller at birth than those under active follow-up. Rates of prematurity and infant death were similar to those reported in urban hospitals.(ABSTRACT TRUNCATED AT 250 WORDS)

A simple clinical staging system that predicts progression to AIDS using CD4 count, oral thrush, and night sweats

OBJECTIVE

To develop a simple clinical staging system based on CD4 count and clinical variables that predicts progression to AIDS in HIV-infected non-AIDS patients.

DESIGN

Retrospective cohort study.

SETTING

A primary care outpatient clinic for HIV-infected patients at a VA Medical Center.

PATIENTS

One hundred seventy-six HIV-infected non-AIDS patients seen at the Houston VA Special Medicine Clinic between January 1986 and December 1990 and followed for a mean of 22 months. Fifty-four patients (31%) progressed to AIDS during follow-up.

MEASUREMENTS

The medical records were reviewed, and data corresponding to the initial (baseline) clinic visit and subsequent six-month visits were extracted.

MAIN RESULTS

"Predictive" baseline variables (i.e., those associated with progression to AIDS) were first identified and then examined in Cox proportional hazards modeling. In the final model, CD4 category, oral thrush, and night sweats made significant independent contributions. A three-stage prognostic system was constructed by assigning points to the three variables: CD4 > 500 cells/mm3 = 0; 500 > or = CD4 > or = 200 = 1; CD4 < 200 = 2; presence of oral thrush = 1; presence of night sweats = 1. Stages were assigned as follows: stage I = 0 points, stage II = 1-2 points, and stage III = 3-4 points. The proportions of patients who progressed to AIDS were: stage I, 6/39 (15%); stage II, 31/106 (29%); and stage III, 17/31 (55%).

CONCLUSIONS

These results demonstrate that simple, clinically sensible prognostic staging systems that predict progression to AIDS can be constructed using CD4 count and clinical variables.