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Biomedical subjects

K Francis

Publications and source records attributed to K Francis.

At least 37 records · Page 2Linked to original sources
PubMed1998

Two new pseudopod morphologies displayed by the human hematopoietic KG1a progenitor cell line and by primary human CD34(+) cells.

A primitive human hematopoietic myeloid progenitor cell line, KG1a, characterized by high expression of the CD34 surface antigen has been observed to extend long, thin pseudopodia. Once extended, these pseudopods may take on one of two newly described morphologies, tenupodia or magnupodia. Tenupodia are very thin and form in linear segments. They adhere to the substrate, can bifurcate multiple times, and often appear to connect the membranes of cells more than 300 micrometer apart. Magnupodia are much thicker and have been observed to extend more than 330 micrometer away from the cell. Magnupods are flexible and can exhibit rapid dynamic motion, extending or retracting in a few seconds. During retraction, the extended material often pools into a bulb located on the pod. Both morphologies can adhere to substrates coated with fibronectin, collagen IV, and laminin as well as plastic. The CD34 and CD44 antigens are also present on the surface of these podia. Primary human CD34(+) cells from fetal liver, umbilical cord blood, adult bone marrow, and mobilized peripheral blood extend these podia as well. The morphology that these pseudopods exhibit suggest that they may play both sensory and mechanical roles during cell migration and homing after bone marrow transplantation.

Adult↗
PubMed1998

Detection of Chlamydia trachomatis cervical infection by urine tests among adolescents clinics.

PURPOSE: To compare urine ligase and polymerase chain reaction (LCR, PCR) tests for diagnosis of Chlamydia trachomatis cervical infection with PCR and nucleic acid probe (GPA) on cervical specimens in adolescents, as well as risk factors for C. trachomatis infection and prevalence of infection at enrollment. METHODS: Urine and cervical specimens were collected from women aged 13-20 years attending adolescent clinics, and interviews were administered. Urine specimens were tested by PCR and LCR, and cervical specimens by GPA and PCR. Prevalence rates of C. trachomatis infection and gonorrhea were compared by demographic, behavioral, and clinical risk factors. RESULTS: Of 415 women tested, 86 (20.7%) were infected with C. trachomatis as indicated by positive cervical PCR results. A higher prevalence of C. trachomatis infection was seen among adolescents who douched monthly or more frequently, or had gonorrhea; prevalence declined from 25.8% in the first 7 months to 16.3% in the last 14 months of the study (p = .017). A statistically significant protective effect for reported condom use was not observed. Sensitivity of urine PCR was 89.5% and specificity was 100% relative to cervical PCR, compared to 84.9% and 99.4% (urine LCR) and 65.4% and 98.0% (cervical GPA). Sensitivity of urine PCR was higher in women with discharge; urine LCR sensitivity was higher in women < 19 years of age. CONCLUSIONS: Polymerase chain reaction and LCR assays on urine specimens were sensitive, specific, and noninvasive tests in this population of adolescents with high C. trachomatis infection prevalence. Chlamydia trachomatis infection was associated with douching monthly or more frequently. Prevalence of infection declined over the period during which the study was conducted.

Adolescent↗
PubMed1998

The burden of physical inactivity & cardiovascular heart disease.

Heart disease exacts a tremendous toll each year in mortality and health care expenditures. Although physical activity reduces the risk of heart disease, the population remains inactive. The importance of physical activity in risk and health care cost reduction is discussed.

Exercise↗
PubMed1998

Effect of acute exercise on plasma homocysteine.

BACKGROUND: The aim this work was to study the effects of acute exercise on plasma homocysteine level. METHODS: Twenty healthy, physically active males aged 24-39 (X = 29) ran on treadmill at an intensity of 70% of their maximal heart for 30 minutes. Blood was taken before, immediately following and 30 minutes following the exercise bout. RESULTS: There was no statistically significant relationship between pre-exercise plasma homocysteine levels and VO2 max (r = -0.05). Plasma homocysteine significantly increased 11.5% from the pre-exercise to 11.6 +/- 3.3 mumol.L-1 immediate post exercise levels. Thirty minutes postexercise plasma homocysteine was still elevated from pre-exercise levels, however the mean of 11.2 +/- 2.9 mumol.L-1 was not statistically different from pre-exercise values. The increase in homocysteine that occurred with 30 minutes of exercise is thought to be the result of hemoconcentration as indicated by changes in plasma albumin. Plasma albumin likewise paralleled the changes observed for homocysteine. Mean pre-exercise plasma albumin values were 42.9 +/- 2.9 g.L-1. Plasma albumin significantly increased 6.9% to 45.8 +/- 2.4 g.L-1 immediately post-exercise. Thirty minutes post exercise plasma albumin was still elevated from pre-exercise levels at 44.8 +/- 5.4 g.L-1. When the homocysteine plasma levels were adjusted for changes in plasma albumin, there was no statistical difference between any of the time points. CONCLUSIONS: It was concluded that acute exercise does not have any effect on plasma homocysteine in young healthy men aged 24-39.

Adult↗
PubMed1997

Effective intercellular communication distances are determined by the relative time constants for cyto/chemokine secretion and diffusion.

A cell's ability to effectively communicate with a neighboring cell is essential for tissue function and ultimately for the organism to which it belongs. One important mode of intercellular communication is the release of soluble cyto- and chemokines. Once secreted, these signaling molecules diffuse through the surrounding medium and eventually bind to neighboring cell's receptors whereby the signal is received. This mode of communication is governed both by physicochemical transport processes and cellular secretion rates, which in turn are determined by genetic and biochemical processes. The characteristics of transport processes have been known for some time, and information on the genetic and biochemical determinants of cellular function is rapidly growing. Simultaneous quantitative analysis of the two is required to systematically evaluate the nature and limitations of intercellular signaling. The present study uses a solitary cell model to estimate effective communication distances over which a single cell can meaningfully propagate a soluble signal. The analysis reveals that: (i) this process is governed by a single, key, dimensionless group that is a ratio of biological parameters and physicochemical determinants; (ii) this ratio has a maximal value; (iii) for realistic values of the parameters contained in this dimensionless group, it is estimated that the domain that a single cell can effectively communicate in is approximately 250 micron in size; and (iv) the communication within this domain takes place in 10-30 minutes. These results have fundamental implications for interpretation of organ physiology and for engineering tissue function ex vivo.

Animals↗
PubMed1997

Atypical presentation of Henoch-Schoenlein purpura in two children.

Henoch-Schoenlein purpura (HSP) is a common vasculitic disorder of childhood. Patients with this disorder typically present with palpable purpura or petechia associated with one or more of the following signs and symptoms: abdominal pain, arthritis/arthralgias, and nephritis. The diagnosis may be difficult to make, however, when a patient presents with isolated symptoms such as abdominal pain without the typical rash. A high index of suspicion must be maintained to diagnose HSP in this setting and to avoid unnecessary interventions. This report describes two unusual patients with the presenting complaint of abdominal pain who had delayed onset of the purpuric rash, making the diagnosis of HSP difficult.

Abdominal Pain↗
PubMed1997

Responses of melanin-concentrating hormone mRNA to salt water challenge in the rainbow trout.

Melanin-concentrating hormone (MCH) is a structurally conserved neuropeptide, produced in the hypothalamus of all vertebrates where it probably serves as a central neurotransmitter/neuromodulator. In teleost fish it is also a neurohypophysial hormone with peripheral effects on skin colour but its central effects are less well understood. In mammals, MCH mRNA abundance changes in response to salt-loading or dehydration, suggesting an involvement in salt or water balance. The present study has used in situ hybridization to investigate the response of the MCH neurons in the rainbow trout (Oncorhynchus mykiss) to progressive changes in ambient salinity. In trout, MCH perikarya are found in two hypothalamic sites: predominantly in the nucleus lateralis tuberis (NLT) and, to a lesser extent, in neurons above the lateral ventricular recess (LVR). Immersion in 50% salt water (SW) for 24 h had no effects on MCH transcripts, plasma osmotic pressure (OP) or cortisol concentrations, but after 24 h in 80% SW, plasma OP and cortisol were raised and MCH transcripts in the NLT were significantly increased (159% of controls, p < 0.01). LVR-MCH neurons remained unaffected. However, after 24 h in 100% SW, MCH mRNA was significantly reduced in both groups of neurons (NLT -62% of controls, p < 0.001; LVR -33% of control, p < 0.001). These responses were transient and were no longer apparent after 6 days in 100% SW, despite the fact that plasma OP and cortisol levels continued to rise. The relative importance of osmotic disturbance and stress on the differential responses of the 2 groups of MCH neurons to changing salinity is discussed, together with a consideration of the potential role of MCH in osmoregulation.

Animals↗
PubMed1996

Physical activity in the prevention of cardiovascular disease.

Research during the past several decades confirms the health benefits of regular physical activity, including improved cardiovascular function and quality of life, with reduced risks of morbidity and mortality from cardiovascular heart disease (CHD). Health care professionals, including physical therapists, can assist the public by promoting physical activity and describing the type, quantity, and quality of activity that confers health benefits. Participation in vigorous physical activity for at least 30 minutes a day is recommended for cardiorespiratory fitness, but recent studies suggest that physical activity below this level can have benefits in reducing the risk for CHD. This article addresses the relationship between physical inactivity and the financial burdens on health care, the relationship between physical inactivity and the risks of developing CHD in different age groups, the health benefits associated with moderate levels of physical activity, and the amounts and types of physical activities that are needed to reduce the risk of CHD.

Adolescent↗
PubMed1995

Evidence for the stochastic acquisition of cytokine profile by CD4+ T cells activated in a T helper type 2-like response in vivo.

The diversity of cytokine production patterns displayed by T cells activated in vivo was investigated by analyzing short-term antigen-specific CD4+ T cell clones and single CD4+ T cells derived from draining lymph nodes of mice undergoing a T helper 2 (Th2)-like response to keyhole limpet hemocyanin (KLH). On average, 2.7% of CD4+ lymph node cells gave rise to clones in the presence of the immunizing antigen and, of these, about 90% secreted interleukin-4 (IL-4) and 20% secreted interferon-gamma (IFN-gamma) when restimulated after 2 weeks in vitro. Almost all IFN-gamma-producing clones co-produced IL-4. The definition of clones as positive or negative for cytokine synthesis depended on assay sensitivity, however, since their titers were distributed continuously from the threshold of detection over at least a 1000-fold range. Reverse-transcription polymerase chain reaction analysis of 59 clones revealed multiple patterns of co-expression of IL-2, IL-3, IL-4, IL-6, IFN-gamma and granulocyte-macrophage colony-stimulating factor (GM-CSF) mRNA. Although most clones contained detectable IL-4 and IL-6 mRNA and a minority contained IFN-gamma mRNA, only 1 clone expressed the canonical Th2 cytokine profile. The observed frequencies of mRNA co-expression for most of the six cytokines (including IL-4 with IFN-gamma), and the frequency of co-secretion of IL-4 and IFN-gamma, were not significantly different from those predicted for random association. Independent regulation of IL-4 and IFN-gamma mRNA expression was confirmed at the single-cell level in a polyclonal population of KLH-primed CD4+ cells, among which co-expression of these cytokines again occurred at the frequency predicted for a random event. The data suggest that the polarization of this immune response towards a Th2 cytokine profile is achieved by altering the probabilities of expression of the IL-4, IFN-gamma and other cytokine genes at the population level, rather than by selective expansion of a distinct T cell subset.

Animals↗
PubMed1995

Developmental changes in melanin-concentrating hormone in Rana temporaria.

Melanin-concentrating hormone (MCH) is a vertebrate neuropeptide produced in hypothalamic neurons. In bony fish, such as trout, MCH acts as a neurohypophysial hormone which, once released into the circulation, acts on pigmented skin cells with the result that the fish turns pale to camouflage itself against a light colored background. In other animals the role of MCH is not clearly established but it appears to be a neuromodulator/transmitter within the central nervous system rather than a hormone. The present study examines MCH function in the grass frog, Rana temporaria. Using immunocytochemistry the location and morphology of irMCH neurons were followed, from tadpole to adult frog. In adult R. temporaria a group of MCH neurons appeared to comprise small and large-celled populations located in the ventral and dorsal infundibular regions, respectively. A group of MCH neurons in the preoptic area is proposed, although the perikarya were rarely immunostainable. Immunoreactive fibers were seen in various areas of the brain, including the olfactory lobes, optic tecta, habenular nucleus, and spinal cord. Immunoreactive MCH cells were only visible in midmetamorphic climax stages, and cellular morphology suggested low secretory activity until the animal first emerged onto land at which time nuclear size and granulation increased significantly. No such increase was observed in equivalent stages of the South African clawed toad, Xenopus laevis, an animal which is fully aquatic throughout its life in contrast to R. temporaria which is terrestrial.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Distribution of ryanodine receptor-like immunoreactivity in mammalian central nervous system is consistent with its role in calcium-induced calcium release.

The distributions of ryanodine receptor-like immunoreactivity and Ca-ATPase-like immunoreactivity were identified in the guinea-pig and rat central nervous system using antibodies raised against the rabbit skeletal muscle ryanodine receptor and Ca-ATPase. In both guinea-pig and rat cerebellum, the ryanodine receptor-like immunoreactivity was restricted to the soma and dendrites of Purkinje cells. In the medulla, neuron somata in the hypoglossal nucleus were stained in both species, but in the dorsal motor nucleus of the vagus somata were stained in guinea-pigs but not in rats. This species difference in ryanodine receptor-like immunoreactivity is consistent with the species difference in expression of a ryanodine sensitive, calcium activated potassium conductance in neurons of the dorsal motor nucleus of the vagus. Immunoreactivity to Ca-ATPase was present in vagal motoneurons in both species with denser staining in the guinea-pig. The data further support the idea that, in neurons of the dorsal motor nucleus of the vagus, release of intracellular calcium stores via a ryanodine receptor activates a specific class of potassium channels, thereby modulating cell excitability.

Animals↗
PubMed1992

Measures of clinical agreement for nominal and categorical data: the kappa coefficient.

The desire to determine the extent inter-rater measurements obtained in a clinical setting are free from measurement error and reflect true scores has spurned a renewed interest in assessment of reliability. The kappa coefficient is considered the statistic of choice to analyze the reliability of nominal and categorical types of data recorded on the same patient by more than one clinician. This paper presents a simple computer program written in PASCAL that can be used in a clinical environment to quickly determine the reliability of nominal or categorical data. This computer program calculates both weighted and non-weighted kappa coefficients with their corresponding standard errors as well as bias-correcting jackknife estimates of kappa for use with small sample sizes.

Data Interpretation, Statistical↗
PubMed1992

A height-adjusted step test for predicting maximal oxygen consumption in males.

A suitable testing device that is generally favored for estimating maximal oxygen consumption (VO2max) under field conditions or in environments where testing equipment is limited is the step test. Recently a mathematical model was reported to standardize the height of stepping for individuals of various heights. The purpose of this study was to validate this model in males. Thirty-three men aged 18 to 47 (x = 28) performed each of three rate-specific step tests and a Bruce treadmill test. Direct measurements of VO2max obtained from the treadmill test were correlated with a 15 second recovery heart rates after three different step tests were performed at stepping frequencies of 22, 26 and 30 ascents/minute. The correlation coefficients for prediction of VO2max from the recovery heart rate and directly measured oxygen consumption were 0.77 at 22 and 0.81 at 26 and 30 ascents/minute. Each relationship was statistically significant at the p < 0.01 level. It can be concluded that the single-stage height adjusted step test provides an effective predictor of VO2max in males and can be used when more complex methods of clinical testing are unavailable or not feasible.

Adolescent↗