PubMed Health⌕ Search

Biomedical subjects

L Heath

Publications and source records attributed to L Heath.

15 recordsLinked to original sources
PubMed2001

Consistent land- and atmosphere-based U.S. carbon sink estimates.

For the period 1980-89, we estimate a carbon sink in the coterminous United States between 0.30 and 0.58 petagrams of carbon per year (petagrams of carbon = 10(15) grams of carbon). The net carbon flux from the atmosphere to the land was higher, 0.37 to 0.71 petagrams of carbon per year, because a net flux of 0.07 to 0.13 petagrams of carbon per year was exported by rivers and commerce and returned to the atmosphere elsewhere. These land-based estimates are larger than those from previous studies (0.08 to 0.35 petagrams of carbon per year) because of the inclusion of additional processes and revised estimates of some component fluxes. Although component estimates are uncertain, about one-half of the total is outside the forest sector. We also estimated the sink using atmospheric models and the atmospheric concentration of carbon dioxide (the tracer-transport inversion method). The range of results from the atmosphere-based inversions contains the land-based estimates. Atmosphere- and land-based estimates are thus consistent, within the large ranges of uncertainty for both methods. Atmosphere-based results for 1980-89 are similar to those for 1985-89 and 1990-94, indicating a relatively stable U.S. sink throughout the period.

Agriculture↗
PubMed2001

Direct activation of an inwardly rectifying potassium channel by arachidonic acid.

Arachidonic acid (AA) is an important constituent of membrane phospholipids and can be liberated by activation of cellular phospholipases. AA modulates a variety of ion channels via diverse mechanisms, including both direct effects by AA itself and indirect actions through AA metabolites. Here, we report excitatory effects of AA on a cloned human inwardly rectifying K(+) channel, Kir2.3, which is highly expressed in the brain and heart and is critical in regulating cell excitability. AA potently and reversibly increased Kir2.3 current amplitudes in whole-cell and excised macro-patch recordings (maximal whole-cell response to AA was 258 +/- 21% of control, with an EC(50) value of 447 nM at -97 mV). This effect was apparently caused by an action of AA at an extracellular site and was not prevented by inhibitors of protein kinase C, free oxygen radicals, or AA metabolic pathways. Fatty acids that are not substrates for metabolism also potentiated Kir2.3 current. AA had no effect on the currents flowing through Kir2.1, Kir2.2, or Kir2.4 channels. Experiments with Kir2.1/2.3 chimeras suggested that, although AA may bind to both Kir2.1 and Kir2.3, the transmembrane and/or intracellular domains of Kir2.3 were essential for channel potentiation. These results argue for a direct mechanism of AA modulation of Kir2.3.

Animals↗
PubMed1996

Effector mechanisms responsible for gamma interferon-mediated host resistance to Legionella pneumophila lung infection: the role of endogenous nitric oxide differs in susceptible and resistant murine hosts.

To facilitate identification of the effector mechanism(s) responsible for gamma interferon (IFN-gamma)-mediated host resistance to Legionella pneumophila, a murine model of legionellosis in BALB/c mice with a targeted disruption in the IFN-gamma gene (gamma knockout [GKO] mice) was developed. Immunocompetent BALB/c mice and GKO mice were inoculated intratracheally with virulent L. pneumophila (10(6) bacteria per mouse), and bacterial clearance and the pulmonary inflammatory response were assessed. L. pneumophila did not replicate in, and was rapidly cleared from, the lungs of immunocompetent BALB/c mice, demonstrating that immunocompetent BALB/c mice are resistant to replicative L. pneumophila pulmonary infections. In contrast, similarly infected GKO mice developed persistent, replicative intrapulmonary L. pneumophila infections with extrapulmonary dissemination of the bacteria to the spleen. Histopathologic and flow cytometric analysis of L. pneumophila-infected lung tissue demonstrated that while immunocompetent BALB/c mice develop multifocal pneumonitis which resolves, similarly infected GKO mice develop diffuse pneumonitis with persistent neutrophil recruitment into the lung. Intratracheal administration of exogenous IFN-gamma to L. pneumophila-infected GKO mice facilitated intrapulmonary clearance of the bacteria, confirming the pivotal role of IFN-gamma in innate host defenses to L. pneumophila lung infection in this murine host. The potential role of endogenous reactive nitrogen intermediates, including nitric oxide (NO), in IFN-gamma-mediated resistance to L. pneumophila pulmonary infections in immunocompetent BALB/c mice was subsequently assessed. Macrophage inducible nitric oxide synthetase (an enzyme responsible for the production of NO) was induced in alveolar cells from L. pneumophila-infected immunocompetent BALB/c mice (with maximal expression at 48 h postinfection) but was not induced in similarly infected GKO mice. However, administration of the NO synthetase inhibitor N-monomethyl-L-arginine did not significantly inhibit clearance of L. pneumophila from the lung of immunocompetent BALB/c mice (compared with that in similarly infected mice not administered N-monomethyl-L-arginine). In contrast, we have previously demonstrated that IFN-gamma-induced host resistance to replicative L. pneumophila lung infections in a susceptible murine host (A/J mice) is mediated, in part, by endogenous NO. Taken together, these studies identify a differing role of endogenous NO in IFN-gamma-mediated resistance to L. pneumophila pulmonary infection in susceptible and resistant murine hosts.

Animals↗
PubMed1996

Coinoculation with Hartmannella vermiformis enhances replicative Legionella pneumophila lung infection in a murine model of Legionnaires' disease.

The effect of inhaled amoebae on the pathogenesis of Legionnaires' disease was investigated in vivo. A/J mice, which are susceptible to replicative Legionella pneumophila infections, were inoculated intratracheally with L. pneumophila (10(6) bacteria per mouse) or were coinoculated with L. pneumophila (10(6) bacteria per mouse) and Hartmannella vermiformis (10(6) amoebae per mouse). The effect of coinoculation with H. vermiformis on bacterial clearance, histopathology, cellular recruitment into the lung, and intrapulmonary levels of cytokines including gamma interferon and tumor necrosis factor alpha was subsequently assessed. Coinoculation with H. vermiformis significantly enhanced intrapulmonary growth of L. pneumophila in A/J mice. Histopathologic and flow cytometric analysis of lung tissue demonstrated that while A/J mice inoculated with L. pneumophila alone develop multifocal pneumonitis which resolves with minimal mortality, mice coinoculated with H. vermiformis develop diffuse pneumonitis which is associated with diminished intrapulmonary recruitment of lymphocytes and mononuclear phagocytic cells and significant mortality. Furthermore, coinoculation of mice with H. vermiformis resulted in a fourfold enhancement in intrapulmonary levels of gamma interferon and tumor necrosis factor alpha compared with mice infected with L. pneumophila alone. The effect of H. vermiformis on intrapulmonary growth of L. pneumophila in a resistant host (i.e., BALB/c mice) was subsequently evaluated. While BALB/c mice do not develop replicative L. pneumophila infections following inoculation with L. pneumophila alone, there was an eightfold increase in intrapulmonary L. pneumophila in BALB/c mice coinoculated with H. vermiformis. These studies, demonstrating that intrapulmonary amoebae potentiate replicative L. pneumophila lung infection in both a susceptible and a resistant host, have significant implications with regard to the potential role of protozoa in the pathogenesis of pulmonary diseases due to inhaled pathogens and in the design of strategies to prevent and/or control legionellosis.

Animals↗
PubMed1992

Monoclonal antibodies raised against pre-migratory neural crest reveal population heterogeneity during crest development.

In order to address the problem of when heterogeneity arises within premigratory and early migratory neural crest cell populations, mouse monoclonal antibodies were raised against quail premigratory neural crest. Due to the limited availability of immunogen an intrasplenic route for immunization was used. Three monoclonal antibodies (referred to as LH2D4, LH5D3 and LH6C2) were subsequently isolated which recognized subpopulations in 24 h cultures of both quail and chick mesencephalic and trunk neural crest in immunocytochemical studies. Subsequent investigations using a range of six antibodies, including LH2D4, LH5D3 and LH6C2, showed that population heterogeneity (which was not cell cycle related) could be detected as early as 15 h following mesencephalic crest explantation, a stage at which all the neural crest cells were morphologically identical. However, premigratory neural crest from the same axial level of origin was homogeneous, as judged by immunoreactivity patterns with these antibodies. Significant differences were found in the proportion of immunoreactive cells between populations of mesencephalic and trunk neural crest cultures. Double immunofluorescence studies revealed the existence of at least four separate cell populations within individual crest cultures, each identified by their unique antibody reactivity pattern, thus providing some insight into the underlying complexity of subpopulation composition within the neural crest. Immunocytochemical studies on quail embryos from stages 7-22 showed that the epitopes detected by LH2D4, LH5D3 and LH6C2 were not necessarily confined to the neural crest or to cells of crest derivation. All three epitopes displayed a spatiotemporal regulation in their expression during early avian ontogeny. Since the differential epitope expression described in this investigation was detectable as early as 15 h after premigratory neural crest explantation, took place in vitro in the absence of any other cell type and changed progressively with time, we conclude that a certain degree of population heterogeneity can be generated very early in neural crest ontogeny and independently of the tissue interactions that normally ensue in vivo.

Animals↗
PubMed1990

Care of HIV-infected patients: nurses' concerns, opinions, and precautions.

The purpose of this study was to describe nurses' concerns, opinions, and precautions related to nursing patients infected with the human immunodeficiency virus (HIV). Of special interest was a comparison of responses by nurses who reported exposure to the HIV through broken skin or mucous membranes with the responses of nurses who reported no such exposure. The sample included all staff nurses employed in either the ambulatory/home health care unit or in one of seven inpatient critical care units of a large urban medical center. Of the 323 respondents, 64 (20%) reported HIV exposure, 77 (24%) reported no exposure, and 180 (56%) reported not knowing if they had been exposed. A 15-item Likert-type scale was used. More HIV-exposed nurses than non-exposed nurses reported: (a) worrying about becoming HIV-infected; (b) considering a change of specialty or profession because of the acquired immunodeficiency syndrome (AIDS) risk; and (c) favoring selected HIV-related policies. Of the total sample, nearly all subjects agreed that staff nurses should be involved in developing HIV-related policies affecting nurses; and over one-half said that, if the agency gave them the option, they would refuse assignment to HIV-infected patients. Nearly 30% said that they had considered changing their profession because of the AIDS risk. Some implications are that nursing administrators should involve well-informed staff nurses in formulating HIV-related policies that affect nurses. The HIV-exposed nurses may need support in dealing with their concerns resulting from HIV-exposure, and they may need more information about HIV-infection control and seroconversion rates of HIV-exposed nurses.

Attitude of Health Personnel↗
PubMed1989

Effects of media violence on children. A review of the literature.

The effects of media violence on the behavior of children are controversial. We examined and reviewed studies addressing this issue and identified many mediating variables. A small but genuine association appears to exist between media violence and aggression. However, many unanswered questions persist, and no interventions are clearly indicated.

Aggression↗
PubMed1987

Monoclonal antibodies and magnetic microspheres for the depletion of leukaemic cells from bone marrow harvested for autologous transplantation.

The use of a panel of monoclonal antibodies and anti-mouse immunoglobulin-coated microspheres is described for the depletion of leukaemic blasts from bone marrow. Marrow treated in this way rapidly reconstitutes haemopoietic function after high-dose consolidation chemoradiotherapy. The recovery of cells from bone marrow is similar but not identical to results obtained on removal of neuroblasts from marrow to be used for autologous transplant. This is probably a reflection of the cross-reactivity of 'anti-leukaemic' antibodies with a variety of haemopoietic progenitor cells. The study described here demonstrates the feasibility of using this method to purge leukaemic cells from bone marrow. A much larger randomised study between patients receiving either purged or non-purged bone marrow would be necessary to validate the need to remove small numbers of tumour cells from bone marrow.

Antibodies, Monoclonal↗
PubMed1986

Magnetic microspheres and monoclonal antibodies for the depletion of neuroblastoma cells from bone marrow: experiences, improvements and observations.

Improvements to the original procedure of using a panel of monoclonal antibodies and magnetic microspheres for the depletion of tumour cells from bone marrow are described. These include a completely disposable system for the magnetic depletion of tumour cells coated with magnetic microspheres. Properties of a new series of microspheres are compared with the old M330 beads in their ability to deplete neuroblasts from both model systems and 50 bone marrows harvested from Stage IV neuroblastoma patients. Using human neuroblastoma cell lines labelled with the DNA intercalating, Hoechst dye 33342 a 5% tumour contamination can routinely be removed from 5 X 10(6) - 5 X 10(7) nucleated cells. Analysis of the 50 purged marrows revealed that 10 were visibly contaminated with tumour (by conventional cytology and immunological procedures). In all but one case, tumour cells were removed. In this instance the tumour:bead ratio fell to 1:4 indicating the importance of maintaining a sufficient number of beads in the system. Red cell contamination of marrow was also kept extremely low so preventing possible physical blockade of bead:tumour cell interaction. Marrow engraftment was rapid in this group, apart from patients who had been exposed to high doses of alkylating agents prior to autografting.

Antibodies, Monoclonal↗
PubMed1986

Television and violent criminal behavior: beyond the Bobo doll.

This study builds on the research concerning television viewing and aggression by extending the external validity, or generalizability, of the dependent variable. We assess the relationship between self-reported television viewing at 8, 10, and 12 years of age and the subsequent commission of a violent criminal act. This study is based on interview data from 48 males incarcerated for violent crimes and 45 nonincarcerated, nonviolent males matched on age, race, and neighborhood of residence during adolescence. Results show that the extent of a respondent's reported television viewing was not, in and of itself, predictive of violent criminal acts. Instead, it was the interaction of heavy doses of television viewing and exposure to either maternal or paternal abuse that related to violent crime. These findings support the efforts of some recent scholars in their attempts to understand why television has a negative effect on only some viewers. The results are discussed in light of the cognitive formulations of neoassociationism, encoding specificity, and the double-dose effect.

Adolescent↗
PubMed1975

Anonychia with ectrodactyly.

A patient had congenital absence of thumb nails with associated absence of the distal phalanges of the thumbs. We reveiw the pertinent literature.

Humans↗
PubMedDate not supplied

Reducing waiting times in lung cancer.

BACKGROUND: Concern exists over delays in the management of lung cancer patients. Maximum waiting times and a multidisciplinary team (MDT) approach have been recommended in several recent national reports. OBJECTIVE: Having implemented a MDT approach, we wished to assess whether national recommendations were achievable and to identify the major factors causing delays. METHODS: Prospective survey over five months of all new referrals with suspected lung cancer, documenting waiting times at all stages from referral to definitive treatment. RESULTS: Of the total of 92 patients, 57 were outpatients (67% seen within one week, 89% within two weeks of receipt of referral) and 35 were inpatients (all seen within two working days). Patient age did not influence waiting times to first being seen or to investigation. The result of the initial diagnostic test was received within two weeks of first being seen in 86% of patients. All patients received definitive treatment within recommended times from diagnosis. Delays in the early part of the care pathway were largely due to potentially remediable service factors, but unavoidable patient related factors were important in some prolonged diagnostic delays. CONCLUSIONS: National recommendations on waiting times are achievable in a high proportion of cases. The probable importance of the MDT approach is discussed.

Aged↗