Search PubMed⌕ Search

Biomedical subjects

M Kennedy

Publications and source records attributed to M Kennedy.

At least 73 records · Page 4Linked to original sources
PubMed1999

Hematopoietic commitment during embryogenesis.

Hematopoiesis develops initially as discrete blood islands in the extraembryonic yolk sac of the embryo. These blood islands consist of clusters of primitive erythrocytes surrounded by developing angioblasts that ultimately form the yolk sac vasculature. The close developmental association of these early hematopoietic and endothelial cells has led to the hypothesis that they develop from a common precursor, a cell known as the hemangioblast. Using a developmental model system based on the in vitro differentiation capacity of embyronic stem (ES) cells, we have identified a precursor with the capacity to generate endothelial as well as primitive and definitive hematopoietic progeny. The developmental potential of this precursor population suggests that it represents the in vitro equivalent of the hemangioblast.

Animals↗
PubMed1999

Structure, G protein activation, and functional relevance of the cardiac G protein-gated K+ channel, IKACh.

The muscarinic-gated atrial potassium channel IKACh has been well characterized functionally, and has been an excellent model system for studying G protein/effector interactions. Complementary DNAs encoding the composite subunits of IKACh have been identified, allowing direct probing of structural and functional features of the channel. Here, we highlight recent approaches taken in our laboratory to determine the oligomeric structure of native cardiac IKACh, the mechanism of activation of IKACh by G proteins, and the relevance of IKACh to cardiac physiology.

Amino Acid Sequence↗
PubMed1999

The long and short of it: branch lengths and the problem of placing the New Zealand short-tailed bat, Mystacina.

The taxonomic position of the endemic New Zealand bat genus Mystacina has vexed systematists ever since its erection in 1843. Over the years the genus has been linked with many microchiropteran families and superfamilies. Most recent classifications place it in the Vespertilionoidea, although some immunological evidence links it with the Noctilionoidea (=Phyllostomoidea). We have sequenced 402 bp of the mitochondrial cytochrome b gene for M. tuberculata (Gray in Dieffenbach, 1843), and using both our own and published DNA sequences for taxa in both superfamilies, we applied different tree reconstruction methods to find the appropriate phylogeny and different methods of estimating confidence in the parts of the tree. All methods strongly support the classification of Mystacina in the Noctilionoidea. Spectral analysis suggests that parsimony analysis may be misleading for Mystacina's precise placement within the Noctilionoidea because of its long terminal branch. Analyses not susceptible to long-branch attraction suggest that the Mystacinidae is a sister family to the Phyllostomidae. Dating the divergence times between the different taxa suggests that the extant chiropteran families radiated around and shortly after the Cretaceous-Tertiary boundary. We discuss the biogeographical implications of classifying Mystacina within the Noctilionoidea and contrast our result with those classifications placing Mystacina in the Vespertilionoidea, concluding that evidence for the latter is weak.

Animals↗
PubMed1999

The cost of elective and emergency repair of AAA in patients under and over the age of 80.

BACKGROUND: As Australia's population ages, the number of elderly patients presenting for surgery of abdominal aortic aneurysms (AAA), both elective and ruptured, will increase. The aim of the present study was to compare the costs of treatment of patients with AAA, under and over the age of 80, in the elective and emergency settings in a hospital with a divisional structure in which the true costs can be accurately obtained. METHODS: A total of 40 patients were selected at random from a series of 267 patients treated with open surgery for AAA between January 1987 and December 1994, 10 in each of four groups: group A, elective repair in patients aged < 80 (171/267); group B, elective AAA repair in patients aged > 80 (25/267); group C, emergency AAA repair in patients aged < 80 (50/267); and group D, emergency AAA repair in patients aged > 80 (11/267). A retrospective analysis of the hospital costs of treatment of these patients at St George Hospital was conducted. These true costs were then compared to Australian National Diagnostic Related Group (AN-DRG) costs. RESULTS: Group A and B had no mortality. In Group C and D the mortality was 20 and 60%, respectively. The emergency treatment groups also had longer lengths of stay. A statistically significant difference in cost of AAA repair between elective and emergency groups in both age groups was seen; that is, group A cost less than group C and group B cost less than group D. Costs per survivor, however, showed a dramatic difference between the cost of group C patients ($30000) and group D patients ($60000). In comparison with AN-DRG calculated costs, the true costs of groups A and B were equivalent to AN-DRG costs. In the emergency groups, however, there were marked discrepancies between the true cost ($61000) and that calculated by the DRG ($25000) in group D, with similar differences seen in group C to a lesser extent. CONCLUSION: Emergency repair of AAA is significantly more expensive and has a high mortality in the over-80 age group. Also, there is a substantial shortfall between the true costs of treating these patients and the funds allocated for treatment in this group.

Aged↗
PubMed1999

Development of erythroid and myeloid progenitors in the yolk sac and embryo proper of the mouse.

In this study, we have mapped the onset of hematopoietic development in the mouse embryo using colony-forming progenitor assays and PCR-based gene expression analysis. With this approach, we demonstrate that commitment of embryonic cells to hematopoietic fates begins in proximal regions of the egg cylinder at the mid-primitive streak stage (E7.0) with the simultaneous appearance of primitive erythroid and macrophage progenitors. Development of these progenitors was associated with the expression of SCL/tal-1 and GATA-1, genes known to be involved in the development and maturation of the hematopoietic system. Kinetic analysis revealed the transient nature of the primitive erythroid lineage, as progenitors increased in number in the developing yolk sac until early somite-pair stages of development (E8.25) and then declined sharply to undetectable levels by 20 somite pairs (E9.0). Primitive erythroid progenitors were not detected in any other tissue at any stage of embryonic development. The early wave of primitive erythropoiesis was followed by the appearance of definitive erythroid progenitors (BFU-E) that were first detectable at 1-7 somite pairs (E8.25) exclusively within the yolk sac. The appearance of BFU-E was followed by the development of later stage definitive erythroid (CFU-E), mast cell and bipotential granulocyte/macrophage progenitors in the yolk sac. C-myb, a gene essential for definitive hematopoiesis, was expressed at low levels in the yolk sac just prior to and during the early development of these definitive erythroid progenitors. All hematopoietic activity was localized to the yolk sac until circulation was established (E8.5) at which time progenitors from all lineages were detected in the bloodstream and subsequently in the fetal liver following its development. This pattern of development suggests that definitive hematopoietic progenitors arise in the yolk sac, migrate through the bloodstream and seed the fetal liver to rapidly initiate the first phase of intraembryonic hematopoiesis. Together, these findings demonstrate that commitment to hematopoietic fates begins in early gastrulation, that the yolk sac is the only site of primitive erythropoiesis and that the yolk sac serves as the first source of definitive hematopoietic progenitors during embryonic development.

Animals↗
PubMed1999

5-aminosalicylic acid inhibits iNOS transcription in human intestinal epithelial cells.

The mechanism by which 5-aminosalicylic acid (5-ASA) reduces mucosal injury in colitis is undefined. In murine cells, 5-ASA modulates the expression of the inducible nitric oxide (NO) synthase, a potential mediator of colitic injury, but its effect on the human isoform is unknown. Given the lack of conserved regulation of iNOS expression in rodent and human systems, we sought to test the effect of 5-ASA on the expression of human iNOS in cultured enterocytes. Transformed human intestinal epithelial cells, DLD-1 and Caco-2BBe, were stimulated by IL-1beta and IFN-gamma and analyzed for iNOS upregulation and NO production in the presence of various aminosalicylates. 5-ASA, but not 4-ASA, dose-dependently inhibited NO production by both cell lines [IC50 (mM) DLD-1 =4.5, Caco-2BBe =2. 5]. 5-ASA also inhibited the expression of iNOS protein and mRNA and blocked cytokine-induced transcriptional upregulation of the iNOS gene. 5-ASA (1-5 mM) had no effect on cytokine-induced nuclear translocation of NF-kappaB or expression of IRF-1, transactivating factors which regulates the human iNOS enhancer. We conclude that 5-ASA inhibits iNOS expression and NO production at therapeutically relevant concentrations. The inhibition occurs at the level of transcriptional activation and is independent of IRF-1 and NF-kappaB. Since NO is an important final effector of mucosal injury in inflammatory bowel disease, these findings may have implications for the clinical efficacy of 5-ASA.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1999

Interobserver variability in subclassification of squamous intraepithelial lesions: Results of the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology.

OBJECTIVE: To determine whether, on a national cytology proficiency test, a competent cytologist can consistently distinguish grades of squamous intraepithelial lesions. DESIGN: Results for low- and high-grade squamous intraepithelial lesion referenced slides from the College of American Pathologists Interlaboratory Comparison Program in Cervicovaginal Cytology for 1996 and 1997 were analyzed including educational, nongraded vs graded validated slides. RESULTS: The discrepant rate between low- and high- grade lesions ranged from 9.8% to 15% for cytotechnologist, pathologist, laboratory, and all responses. There was a statistically significant difference in performance on graded, validated slides vs educational slides with better performance on validated slides. CONCLUSION: This significant interobserver variability in subclassification of squamous lesions should be considered in management guidelines for abnormal Papanicolaou test results and implementation of national cytology proficiency testing.

Carcinoma, Squamous Cell↗
PubMed1999

Glycolate metabolism by Hep G2 cells.

The pathways of oxalate synthesis in humans are not well defined despite their clinical significance in primary hyperoxaluria and idiopathic calcium oxalate nephrolithiasis. Furthermore, the functional roles, if any, of this synthesis have not been elucidated. This study examines pathways of oxalate synthesis from glycolate in Hep G2 cells, a human hepatoma cell line. Incubation of these cells with glycolate has revealed that a pathway may function to synthesize oxalate from glycolate that does not depend on the oxidation of glycolate to glyoxylate by glycolate oxidase. Labeling cells with 14C-glycolate and chromatographic analyses indicated that detectable amounts of 14C-glyoxylate were not formed. A radioactive peak that coeluted with oxalate on ion exclusion chromatography was the only peak yet identified. A detailed examination of glycolate metabolism in these cells should help clarify the terminal steps associated with oxalate synthesis and aid in our understanding of two-carbon metabolism.

Carcinoma, Hepatocellular↗
PubMed1999

Development and application of a minimal-adenoviral vector system for gene therapy of hemophilia A.

To achieve efficient delivery and sustained expression of the human factor VIII cDNA in vivo, a minimal-adenoviral (mini-Ad) vector system was developed. The system is composed of a mini-Ad vector with essential cis-elements (less than 1 kb) of the viral genome, an E1-deleted ancillary Ad with packaging attenuation, and an E1-complementing production cell line. Based on this system, MiniAdFVIII was generated to deliver a 27 kb expression cassette consisting of a full-length human factor VIII cDNA flanked by human albumin promoter and genomic sequences. The MiniAdFVIII vector mediated expression of functional human factor VIII in HepG2 and 293 cells. A single-dose intravenous injection of 10(11) viral particles in hemophilic mice of MiniAdFVIII produced a sustained high-level expression of human factor VIII (at 100-800 ng/ml up to 369 days) which corrected the FVIII-deficient phenotype. Safety studies of MiniAdFVIII showed that there were no significant toxic effects in mice and dogs after single intravessel doses of up to 3 x 10(11) and 6 x 10(12) viral particles, respectively. Studies for developing the MiniAdFVIII vector with a site-specific integration mechanism and progress in the development of a human factor VIII-tolerized mouse model for pre-clinical studies of MiniAdFVIII are reported. Further pre-clinical studies and product development of MiniAdFVIII for clinical trials are also discussed.

Adenoviridae↗
PubMed1999

Boning up on osteoporosis.

Osteoporosis may have once been considered just another harbinger of the aging process, like liver spots, gray hair and big ears. But few aging Americans today will stand for it, literally and figuratively, now that there are various treatment alternatives at hand, and more on the way, thanks to medical advances in diagnostics and therapeutics. Baby boomers will be not only the largest, oldest cohort this nation--perhaps the world--has ever seen, they will also be the most active. And, they will be insistent and vocal about receiving medical care that allows them to fulfill their elder years with myriad pursuits; activities which will require mobility and pain-free living as much as possible. "No doubt osteoporosis will become a bigger health care issue," said Dr. Fagan. "We still don't think of it in the same category as heart disease and cancer, I guess because it is not lethal right away. But we have to recognize that it has serious medical implications that can lead to a downward spiral of medical problems that can mean the need for extended nursing care or prolonged illness. Those who suffer from it acutely can hardly do anything for themselves. People with spinal fractures are miserable with pain and a good hip fracture will take eight weeks healing time. Preventing these types of fractures by controlling bone loss is a basic health issue--a real quality of life issue--that we need to be addressing."

Aged↗
PubMed1998

LeIF: a recombinant Leishmania protein that induces an IL-12-mediated Th1 cytokine profile.

We have evaluated the ability of the Leishmania protein LeIF to influence the Th1/Th2 cytokine responses and the generation of LeIF-specific T cell clones in the absence of adjuvant. We characterized LeIF-specific T cell responses in Leishmania major-infected and uninfected BALB/c mice. These mice develop a strong Th2 response during infection with L. major. When lymph node cells from infected BALB/c mice were stimulated in vitro with LeIF, only IFN-gamma (and no detectable IL-4) was found in the culture supernatant. In addition, LeIF down-regulated Leishmania Ag-specific IL-4 production by lymph node cells from infected BALB/c mice. Subsequently, Th responses were evaluated in naive BALB/c mice following immunization with LeIF. T cell clones derived from mice immunized with LeIF preferentially secreted IFN-gamma. Finally, to understand the basis for the preferential Th1 cytokine bias observed with LeIF, the ability of LeIF to influence the early cytokine profile was evaluated in splenocytes of SCID mice. We found that LeIF stimulated fresh spleen cells from naive SCID mice to secrete IFN-gamma by IL-12/IL-18-dependent mechanisms. The N-terminal half of the molecule (amino acid residues 1-226) maintained the ability to stimulate IFN-gamma from splenocytes of SCID mice. Finally, we also demonstrated that LeIF was able to provide partial protection of BALB/c mice against L. major. Thus, our results suggest the potential of LeIF as a Th1-type adjuvant and as a therapeutic and prophylactic vaccine Ag for leishmaniasis when used with other leishmanial Ags.

Adjuvants, Immunologic↗
PubMed1998

Does the ultrasonically activated scalpel release viable airborne cancer cells?

BACKGROUND: Viable cancer cells may implant at distant sites and cause tumor recurrence. One possible mechanism is the inadvertent exfoliation of viable tumor cells during dissection. The ultrasonically activated scalpel (UAS) uses ultrasonic energy to disrupt tissues by cavitation and produces a dense cloud of cellular debris that may contain viable cells. This study aimed to investigate the viability of airborne cells released during cancer dissection using the UAS and electrosurgery. METHODS: Flank tumors (n = 8) measuring 1 cm3 were induced in male WAG rats by subcutaneous injection of 2 x 10(6) CC531s colon cancer cells. Dissection was performed in cutting mode using the maximum power output of the respective devices. Electrosurgery was performed using a standard monopolar electrosurgical unit and a needle probe, and ultrasonic dissection was performed with the Harmonic Scalpel utilising the open surgical handset and the hooked spatula tip. The smoke plume was aspirated by a vacuum pump and bubbled under Hank's balanced salt solution to trap particulate matter. The viability of the cellular material was blindly assessed with the trypan blue test and by in vitro culture. The morphology of the cellular debris was studied by examination of cytospin preparations. RESULTS: Large quantities of cellular debris was trapped in the plume from both devices. However, no viable cells were isolated, nor did in vitro cell growth occur with either device. Examination of the debris from the UAS demonstrated a characteristic mixture of amorphous forms and very few morphologically intact cells. The cauterized tumor produced charred cells and tissue fragments. CONCLUSIONS: In conclusion, this study demonstrates that viable airborne cancer cells are not released after tumor ablation with the UAS or electrosurgery.

Animals↗