Attraction of immature stages of the American dog tick (Dermacentor variabilis) to 2,6-dichlorophenol.

To determine whether 2,6-dichlorophenol is solely a sex pheromone, the response to it by the various stages of the American dog tick, Dermacentor variabilis, were compared. In contrast to adults, 2,6-dichlorophenol was attractive to unfed nymphs and to unfed larvae. Use of this chemical also prompted the expression of a novel type of 'feeding' posture behavior in adults.

Agricultural genomics and subterranean plant-plant communications.

Agricultural genomics has the potential to dramatically enrich the availability and quality of food supplies worldwide. However, because thousands of different plant species are grown for food, the application of genomics to crop improvement faces issues distinct from those in medical research. The challenge to agricultural plant scientists is to exploit the databases being generated for rice, maize, and Arabidopsis toward the genetic improvement of non-model crop species.

Water requirements of terrestrial and epiphytic orchid seeds and seedlings, and evidence for water uptake by means of mycotrophy.

The use of endomycorrhizal fungi as an energy source (=mycotrophy) initiates seedling development and supplements or replaces photosynthesis in all orchids in nature. Fungus-infected and non-infected seeds of the monkey face orchid, Platanthera integrilabia, a US Federally-threatened terrestrial species, had a different set of water relations than seeds of the green fly orchid, Epidendrum conopseum, a subtropical epiphyte. Seeds of the terrestrial species had lower water loss rates, smaller activation energies for water loss and absorbed water from lower relative humidities.

Positive and negative selection of antigen-specific B cells in transgenic mice expressing variant forms of the V(H)1 (T15) heavy chain.

Four variant forms of the V1 (T15-H chain) gene are synthesized in mice. Each V1 variant pairs with a distinct L chain to produce a binding site having specificity for phosphocholine (PC). Transgenic mice expressing variant forms of the V1 gene were analyzed to elucidate the factors driving B cell selection into the peripheral repertoire.

Poliovirus RNA-dependent RNA polymerase (3Dpol): structural, biochemical, and biological analysis of conserved structural motifs A and B.

We have constructed a structural model for poliovirus RNA-dependent RNA polymerase (3D(pol)) in complex with a primer-template (sym/sub) and ATP. Residues found in conserved structural motifs A (Asp-238) and B (Asn-297) are involved in nucleotide selection. Asp-238 appears to couple binding of nucleotides with the correct sugar configuration to catalytic efficiency at the active site of the enzyme.

Immune-type diversity in the absence of somatic rearrangement.

Immunoglobulin gene diversity has been characterized to varying degrees in modern representatives of all of the major radiations of cartilaginous fish. A pattern of overall chromosomal relationships of the various types of joined and unjoined Ig gene clusters is suggested in which the essential features are: (a) both Ig heavy and light-chain gene clusters occur on multiple chromosomes, (b) various classes of Ig are interspersed, (c) not all individual gene loci appear to be closely linked (Fig. 2).

Expanding our understanding of immunoglobulin, T-cell antigen receptor, and novel immune-type receptor genes: a subset of the immunoglobulin gene superfamily.

The immunoglobulin superfamily (IgSF) is an extensively diversified multigene family whose members share a common structural feature, the Ig fold. Members of the Ig/T-cell antigen receptor (TCR) subset of the IgSF mediate antigen-specific recognition in adaptive immune responses. Antigen-binding receptors belonging to this subset are present in all species of jawed vertebrates.

Squalene: a naturally abundant mammalian skin secretion and long distance tick-attractant (Acari: Ixodidae).

Squalene is a naturally occurring lipid on mammalian skin and is an attractant to the lone star tick, Amblyomma americanum (L.). In this study, we compared squalene to the standard tick-attractants, benzaldehyde, isobutyric acid, methyl salicylate, nonanoic acid, and o-nitrophenol identified as active ingredients of tick aggregation-attachment pheromones and determined its effectiveness in field and laboratory settings at varying distances.

Palp-splaying behavior and a specific mouthpart site associated with active water vapor uptake in Amblyomma americanum (Acari: Ixodidae).

Ticks actively absorb water vapor from unsaturated air via their mouthparts. A wax technique was used to cover select areas of the mouthparts of the lone star tick, Amblyomma americanum (L.), to examine whether a specific site is involved in uptake.

Parasitic plant responses to host plant signals: a model for subterranean plant-plant interactions.

The ability of plants to fulfill nutritional needs by parasitizing neighboring plants has originated several times in angiosperm evolution. Molecular tools are now being exploited to investigate the evolutionary origins of plant parasitism and to dissect the genetic mechanisms governing parasitic plant-host plant interactions. Investigating the nature of signal exchanges between parasitic plants and their hosts serves as a tractable system for understanding how plants in general communicate in the environment.

Flavonoids promote haustoria formation in the root parasite triphysaria versicolor.

Parasitic plants in the Scrophulariaceae develop infective root structures called haustoria in response to chemical signals released from host-plant roots. This study used a simple in vitro assay to characterize natural and synthetic molecules that induce haustoria in the facultative parasite Triphysaria versicolor. Several phenolic acids, flavonoids, and the quinone 2,6-dimethoxy-p-benzoquinone induced haustoria in T.

Host-root exudates increase gene expression of asparagine synthetase in the roots of a hemiparasitic plant Triphysaria versicolor (Scrophulariaceae).

Triphysaria is a facultative root parasite in the Scrophulariaceae family. Similar to other related parasites, the development of the parasitic life cycle is initiated by molecular signals released from appropriate host roots. Using a differential display, we isolated cDNAs preferentially abundant in T.

The MEDIGATE graphical user interface for entry of physical findings: design principles and implementation. Medical Examination Direct Iconic and Graphic Augmented Text Entry System.

The solution to many of the problems of the computer-based recording of the medical record has been elusive, largely due to difficulties in the capture of those data elements that comprise the records of the Present Illness and of the Physical Findings. Reliable input of data has proven to be more complex than originally envisioned by early work in the field. This has led to more research and development into better data collection protocols and easy to use human-computer interfaces as support tools.

Insertional inactivation of the tomato polygalacturonase gene.

The site-selected insertion (SSI) procedure was used to generate insertional knockout mutations in the gene for tomato polygalacturonase (PG), a critical enzyme in fruit ripening. Previously, it had been shown that the Dissociation (Ds) elements in a select group of tomato plants frequently inserted into PG, at least in somatic tissues. DNA isolated from pollen produced by progeny of these plants was screened by SSI to identify plants likely to transmit the insertions in PG to progeny.

Sex-specific exons control DNA methyltransferase in mammalian germ cells.

The spermatozoon and oocyte genomes bear sex-specific methylation patterns that are established during gametogenesis and are required for the allele-specific expression of imprinted genes in somatic tissues. The mRNA for Dnmt1, the predominant maintenance and de novo DNA (cytosine-5)-methyl transferase in mammals, is present at high levels in postmitotic murine germ cells but undergoes alternative splicing of sex-specific 5' exons, which controls the production and localization of enzyme during specific stages of gametogenesis. An oocyte-specific 5' exon is associated with the production of very large amounts of active Dnmt1 protein, which is truncated at the N terminus and sequestered in the cytoplasm during the later stages of oocyte growth, while a spermatocyte-specific 5' exon interferes with translation and prevents production of Dnmt1 during the prolonged crossing-over stage of male meiosis.

A candidate mammalian DNA methyltransferase related to pmt1p of fission yeast.

Trace levels of 5-methylcytosine persist in the DNA of mouse embryonic stem cells that are homozygous for null mutations in Dnmt1 , the gene for the one previously recognized metazoan DNA methyltransferase. This residual 5-methylcytosine may be the product of a candidate second DNA methyltransferase, Dnmt2, that has now been identified in human and mouse. Dnmt2 contains all the sequence motifs diagnostic of DNA (cytosine-5)-methyltransferases but appears to lack the large N-terminal regulatory domain common to other eukaryotic methyltransferases.

Comparison and cross-validation of cycle ergometry estimates of VO2max.

The purpose of this study was to examine the accuracy and quality of a series of cycle ergometry tests used to estimate maximal aerobic capacity (VO2max). One-hundred nine males and 71 females participated in five tests: a maximal exercise test on the treadmill, three Air Force Cycle Ergometry Tests (AF1, AF2, AF3), and a Progressive cycle ergometry test (PROG). The VO2max value measured during the treadmill test was compared with the VO2max estimates from each ergometry test.

Cytosine methylation and the ecology of intragenomic parasites.

Most of the 5-methylcytosine in mammalian DNA resides in transposons, which are specialized intragenomic parasites that represent at least 35% of the genome. Transposon promoters are inactive when methylated and, over time, C-->T transition mutations at methylated sites destroy many transposons. Apart from that subset of genes subject to X inactivation and genomic imprinting, no cellular gene in a non-expressing tissue has been proven to be methylated in a pattern that prevents transcription.

Elective laparoscopic splenectomy for hematologic disorders.

Laparoscopic splenectomy has been reported to be the procedure of choice in selected patients with hematologic disorders. The purpose of this study is to review our experience with laparoscopic splenectomy in this patient population. The charts of all patients with hematologic disorders who presented for laparoscopic splenectomy over a 17-month period were reviewed.

DNA (cytosine-5)-methyltransferases in mouse cells and tissues. Studies with a mechanism-based probe.

The mechanisms that establish and maintain methylation patterns in the mammalian genome are very poorly understood, even though perturbations of methylation patterns lead to a loss of genomic imprinting, ectopic X chromosome inactivation, and death of mammalian embryos. A family of sequence-specific DNA methyltransferases has been proposed to be responsible for the wave of de novo methylation that occurs in the early embryo, although no such enzyme has been identified. A universal mechanism-based probe for DNA (cytosine-5)-methyltransferases was used to screen tissues and cell types known to be active in de novo methylation for new species of DNA methyltransferase.

Impact of feeding, molting and relative humidity on cuticular wax deposition and water loss in the lone star tick, Amblyomma americanum.

To determine whether there is a correlation between the amount of lipids on the surface of ticks and their permeability to water, we quantified cuticular surface wax and measured water-loss rates in the ixodid tick Amblyomma americanum from nonfed nymph to egg-laying female. Ticks deposited no extra cuticular lipids during feeding, permitting maximum transpiratory water loss that presumably helps to concentrate the bloodmeal; and ticks deposited additional cuticular wax after apolysis that reduced integumental water loss, which likely prepares ticks for off-host existence. A remarkable three-fold boost in surface wax deposition and extreme water retention were noted after host drop-off following feeding.

Awareness of deficit in Alzheimer's disease: relation to caregiver burden.

Patients with Alzheimer's disease (AD) show varying degrees of awareness of their deficits. To examine the impact of this phenomenon upon the distress experienced by family caregivers of AD patients, we analyzed caregiver burden in relation to patient awareness of deficit in three different functional domains. The relationship of burden to selected sociodemographic variables was also explored.