Biomedical subjects

Julie Clark

Publications and source records attributed to Julie Clark.

11 recordsLinked to original sources

PubMed2006

Long-term self-renewal and directed differentiation of human embryonic stem cells in chemically defined conditions.

Chemically defined medium (CDM) conditions for controlling human embryonic stem cell (hESC) fate will not only facilitate the practical application of hESCs in research and therapy but also provide an excellent system for studying the molecular mechanisms underlying self-renewal and differentiation, without the multiple unknown and variable factors associated with feeder cells and serum. Here we report a simple CDM that supports efficient self-renewal of hESCs grown on a Matrigel-coated surface over multiple passages. Expanded hESCs under such conditions maintain expression of multiple hESC-specific markers, retain the characteristic hESC morphology, possess a normal karyotype in vitro, as well as develop teratomas in vivo. Additionally, several growth factors were found to selectively induce monolayer differentiation of hESC cultures toward neural, definitive endoderm/pancreatic and early cardiac muscle cells, respectively, in our CDM conditions. Therefore, this CDM condition provides a basic platform for further characterization of hESC self-renewal and directed differentiation, as well as the development of novel therapies.

Activins↗

PubMed2006

Chemoprevention of lung cancer by tea.

Tea is the second only to water as the most consumed beverage in the world. Both green and black teas have been studied for their health benefits for a variety of diseases, particularly cancer. Lung cancer is the predominant cause of cancer mortality in developed countries. Smokers' risk of lung cancer is 20 times that of persons who have never smoked. Epidemiological studies on the cancer-preventive effects of tea produce inconsistent results, which could in part be attributed to the lack of a universal standard for tea preparations. However, most animal studies indicate that tea has strong chemopreventive effects against lung tumorigenesis. The reported mechanisms for chemopreventive activity of green tea are antioxidation, induction of phase II enzymes, inhibition of TNFalpha expression and release, inhibition of cell proliferation, and induction of apoptosis. Cell cycle arrest and apoptosis induced by green tea are probably the two most significant factors. Future studies are needed to determine how green tea affects the genes associated with cell cycle regulation and apoptosis during the mouse lung carcinogenesis process.

Animals↗

PubMed2006

Generation of RNAi libraries for high-throughput screens.

The completion of the genome sequencing for several organisms has created a great demand for genomic tools that can systematically analyze the growing wealth of data. In contrast to the classical reverse genetics approach of creating specific knockout cell lines or animals that is time-consuming and expensive, RNA-mediated interference (RNAi) has emerged as a fast, simple, and cost-effective technique for gene knockdown in large scale. Since its discovery as a gene silencing response to double-stranded RNA (dsRNA) with homology to endogenous genes in Caenorhabditis elegans (C elegans), RNAi technology has been adapted to various high-throughput screens (HTS) for genome-wide loss-of-function (LOF) analysis. Biochemical insights into the endogenous mechanism of RNAi have led to advances in RNAi methodology including RNAi molecule synthesis, delivery, and sequence design. In this article, we will briefly review these various RNAi library designs and discuss the benefits and drawbacks of each library strategy.

Journal Article↗

PubMed2005

Immunocytochemical localization of choline acetyltransferase and muscarinic ACh receptors in the antenna during development of the sphinx moth Manduca sexta.

Immunocytochemistry with monoclonal antibodies was used to investigate the locations of muscarinic acetylcholine receptors (mAChR) and choline acetyltransferase (ChAT) in sections of the developing antennae of the moth Manduca sexta. The results were correlated with a previous morphological investigation in the developing antennae which allowed us to locate different cell types at various stages of development. Our findings indicated that the muscarinic cholinergic system was not restricted to the sensory neurons but was also present in glial and epidermal cells. By day 4-5 of adult development, immunoreactivity against both antibodies was present in the axons of the antennal nerve, and more intense labeling was present in sections from older pupae. At days 4-9, the cell bodies of the sensory neurons in the basal part of the epidermis were also intensely immunolabeled by the anti-mAChR antibody. In mature flagella, large numbers of cells, some with processes into hairs, were strongly labeled by both antibodies. Antennal glial cells were intensely immunolabeled with both antibodies by days 4-5, but in later stages, it was not possible to discriminate between glial and neural staining. At days 4-9, we observed a distinctly labeled layer of epidermal cells close to the developing cuticle. The expression of both ChAT and mAChRs by neurons in moth antennae may allow the regulation of excitability by endogenous ACh. Cholinergic communication between neurons and glia may be part of the system that guides axon elongation during development. The cholinergic system in the apical part of the developing epidermis could be involved in cuticle formation.

Animals↗

PubMed2005

Moving beyond the keg party: a daily process study of college student drinking motivations.

Theoretical models of alcohol consumption assert that young adults endorse multiple drinking motives, including drinking to cope with negative experiences and to enhance positive experiences. Social contacts may be important to both pathways. This study applied daily process methodology to determine the relationship between college student drinking in different contexts and daily social contacts and moods. Each afternoon for 3 weeks, 122 undergraduates (43% men, 57% women) logged onto a secure Web site during specified hours to report daily activities, moods, and contacts. Hierarchical linear modeling analyses provided support for motivational models and the context-specific nature of motivated drinking. Individual differences were revealed for each motivation. These findings highlight the importance of studying within-person processes using daily process designs.

Adult↗

PubMed2005

Ki-67 expression in benign breast ductal cells obtained by random periareolar fine needle aspiration.

Ki-67 expression in ductal cells obtained by random periareolar fine needle aspiration (RPFNA) is currently being used as a response biomarker in phase II breast cancer chemoprevention trials; however, Ki-67 in RPFNA has not been well studied as a risk predictor for cancer, which would support its use as a response indicator. We examined the expression of Ki-67 in RPFNA specimens with hyperplasia +/- atypia obtained from 147 women at high risk for development of breast cancer. Median Ki-67 was 1.4% (range 0-24%). Ki-67 was higher in specimens from women < 50 versus those > or = 50 (median 2% versus 0.6%; P = 0.006) and from premenopausal women versus postmenopausal women (P = 0.037); however, hormone replacement therapy (predominately low-dose estrogen without progestins) had no effect. By univariate analysis, Ki-67 was positively correlated with ductal cell number (P = 0.001) and hyperplasia with atypia (P = 0.007). By multivariable analysis, the proportion of ductal cells expressing Ki-67 was again predicted by cell number, which, in turn, was predicted by cytologic atypia. The association of Ki-67 expression with cytologic atypia, a known risk factor for development of breast cancer, provides preliminary justification for its use as a response biomarker in phase II chemoprevention trials.

Adult↗

PubMed2005

Genomic studies in stem cell systems.

Stem cell research holds promise for future regenerative medicine. In recent years, much effort has been devoted to our understanding of stem cell self-renewal and differentiation at the molecular level. Important studies that have applied various genomic approaches, including genomics, functional genomics and proteomics, to gain molecular insights into stem cell development, are reviewed.

Expressed Sequence Tags↗

PubMed2004

Eimeria tenella sporozoites and merozoites differentially express glycosylphosphatidylinositol-anchored variant surface proteins.

Little is known about glycosylphosphatidylinositol (GPI)-linked surface proteins in the coccidian parasite Eimeria tenella. Examination of 28,550 EST sequences from the sporozoite and second merozoite developmental stages of the parasite led to the identification of 37 potential GPI-linked variant surface proteins, termed EtSAGs. Analysis of the complete nucleotide sequences of 23 EtSAG genes separated them into two multi-gene families. All the predicted EtSAG proteins (which vary in length from 228 to 271 residues) have an N-terminal hydrophobic signal peptide, a C-terminal hydrophobic GPI signal-anchor peptide and an extracellular domain organised around six cysteine residues, the positions of which are conserved within each family. Using specific antibodies against a small number of recombinant-expressed EtSAGs, the surface localisation and GPI-anchorage of members of both families was confirmed experimentally. Expression of EtSAGs is differentially regulated between the oocyst/sporozoite and second generation merozoite stages, with only one expressed specifically in the sporozoite, a small number expressed in both stages and the majority expressed specifically in the second generation merozoite. Preliminary data support a model in which multiple variant surface antigens are co-expressed on individual parasites, rather than a model of antigenic switching. The biological role(s) of EtSAGs and the effect(s) that expression of a complex repertoire of variant surface antigens by the second generation merozoite has on host adapted immunity are unknown.

Amino Acid Sequence↗

PubMed2003

Defining the protein repertoire of microneme secretory organelles in the apicomplexan parasite Eimeria tenella.

The apicomplexan pathogen Eimeria causes coccidiosis, an intestinal disease of chickens, which has a major welfare and economic impact on the poultry industry. There is an urgent need to identify molecules that are rational targets for drug design and novel vaccines against coccidiosis. Apicomplexan secretory organelles, including micronemes and rhoptries, are essential for invasion of the host intestinal epithelium and establishment of parasitism. However, relatively little is known about the precise molecular function of these organelles, partly because few organelle proteins have been characterized. In this study, proteomics tools have been harnessed to define the protein repertoire of micronemes. Purified microneme proteins from Eimeria tenella sporozoites were excised from two-dimensional (2-D) gels and analyzed using matrix-assisted laser desorption/ionization-time of flight-mass spectrometry (MALDI-TOF-MS) and chemically assisted fragmentation (CAF)-MALDI with de novo sequencing. Peptide mass profiles were searched against the NCBI non-redundant (nr) database and against Eimeria-specific databases using the Mascot search algorithm, resulting in the identification of 37 of 96 spots excised from the 2-D gels. In addition, we have found CAF-MALDI to be a useful adjunct for identifying proteins, without the need for tandem MS. This global approach to protein characterization will be vital to gain greater understanding of the processes involved in apicomplexan host cell invasion.

Animals↗

PubMed2002

Evidence for the association of FMRFamide-related peptides with the spermatheca of Locusta migratoria.

The association of FMRFamide-related peptides (FaRPs) with the spermatheca of Locusta migratoria was demonstrated using radioimmunoassay and immunohistochemical techniques. The physiological effects of various FaRPs on the neurally evoked contractions of the spermatheca were also examined. FMRFamide-like immunoreactivity (FLI) was demonstrated in processes and cell bodies situated in the VIIIth (terminal) abdominal ganglion. These included an anterior, central and posterior pair of ventral cell bodies positioned near the midline of the ganglion, in addition to two bilaterally paired dorsal cell bodies in the posterior region of the VIIIth abdominal ganglion. Two axons displaying FLI proceed down the ventral ovipositor nerve (VON) and into the receptaculum seminis nerve which innervates the anterior regions of the spermatheca. FLI was also noted in processes on the spermathecal muscle with the highest density occurring on the spermathecal sac and coil duct. FaRPs applied to the spermathecal muscle included GQERNFLRFamide, NFIRFamide, ADDRNFIRFamide, YGGFMRFamide, FMRFamide, ADVGHVFLRFamide and SchistoFLRFamide (PDVDHVFLRFamide). Dose-dependent physiological effects were only noted for FMRFamide, ADVGHVFLRFamide and SchistoFLRFamide. FMRFamide led to a dose-dependent increase in the amplitude of neurally evoked contractions with a threshold of approximately 5 x 10(-7) M. SchistoFLRFamide, and ADVGHVFLRFamide, had an inhibitory effect, decreasing the amplitude of neurally evoked spermathecal contractions.

Animals↗

PubMed2002

Yield of laboratory testing to identify secondary contributors to osteoporosis in otherwise healthy women.

Our purpose in this study was to determine the prevalence of undetected disorders of bone and mineral metabolism in women with osteoporosis and to identify the most useful and cost-efficient screening tests to detect these disorders. A cross-sectional study was conducted among 664 postmenopausal women with osteoporosis at the Osteoporosis and Metabolic Bone Disease Program at the Mount Sinai Hospital in New York between January 1992 and June 1996. Women without a history of diseases or medications known to adversely affect bone who completed extensive laboratory testing including complete blood count, chemistry profile, 24-h urinary calcium, 25(OH)vitamin D, and PTH were included. Among 173 women who met the inclusion criteria for the study, previously undiagnosed disorders of bone and mineral metabolism were identified in 55 women (32%). Disorders of calcium metabolism and hyperparathyroidism were the most frequent diagnoses. A testing strategy involving measurement of 24-h urine calcium, serum calcium, and serum PTH for all women and serum TSH among women on thyroid replacement therapy would have been sufficient to diagnose 47 of these 55 women (85%) at an estimated cost of $75 per patient screened. Previously undiagnosed disorders affecting the skeleton are common in otherwise healthy women with low bone density. A simple testing strategy is likely to identify most such disorders.

Aged↗