PubMed Health⌕ Search

Biomedical subjects

P Bartlett

Publications and source records attributed to P Bartlett.

At least 19 recordsLinked to original sources
PubMed2003

Molecular characterization of gentamicin-resistant Enterococci in the United States: evidence of spread from animals to humans through food.

We evaluated the molecular mechanism for resistance of 360 enterococci for which the gentamicin MICs were >/=128 micro g/ml. The aac(6')-Ie-aph(2")-Ia, aph(2")-Ic, and aph(2")-Id genes were identified by PCR in isolates from animals, food, and humans. The aph(2")-Ib gene was not identified in any of the isolates. Two Enterococcus faecalis isolates (MICs > 1,024 micro g/ml) from animals failed to generate a PCR product for any of the genes tested and likely contain a new unidentified aminoglycoside resistance gene. Pulsed-field gel electrophoresis (PFGE) analysis showed a diversity of strains. However, 1 human and 18 pork E. faecalis isolates from Michigan with the aac(6')-Ie-aph(2")-Ia gene had related PFGE patterns and 2 E. faecalis isolates from Oregon (1 human and 1 grocery store chicken isolate) had indistinguishable PFGE patterns. We found that when a gentamicin-resistant gene was present in resistant enterococci from animals, that gene was also present in enterococci isolated from food products of the same animal species. Although these data indicate much diversity among gentamicin-resistant enterococci, the data also suggest similarities in gentamicin resistance among enterococci isolated from humans, retail food, and farm animals from geographically diverse areas and provide evidence of the spread of gentamicin-resistant enterococci from animals to humans through the food supply.

Animal Diseases↗
PubMed2002

Response of intestinal epithelial cells to Trichuris suis excretory-secretory products and the influence on Campylobacter jejuni invasion under in vitro conditions.

We previously developed a swine animal model in which natural host resistance to Campylobacter jejuni is altered by experimental infection with low numbers of the nematode Trichuris suis. Pigs naturally colonized with C. jejuni experience colitis because of the invasion of the bacterium approximately 21 days after exposure to T. suis. To better understand the mechanism of T. suis-dependent C. jejuni colitis, we evaluated the effects of T. suis excretory-secretory products (ESPs) on intestinal epithelial cells (IECs) and the influence of ESP on C. jejuni invasion in IECs under in vitro conditions. Viability assays revealed a dose-dependent cytotoxic response in ESP-treated IECs, particularly IPEC-1 and INT407 cells. Transepithelial electrical resistance dropped significantly in IPEC-1 cells treated on apical and basolateral surfaces, but not in those treated only on apical surfaces. Using the gentamicin-killing assay, reduced numbers of intracellular C. jejuni were recovered from IECs treated with ESP at 1 mg protein/ml concentration. This observation can be at least partially explained by a novel antibacterial activity in ESP. Contrary to our hypothesis, ESP at subtoxic concentrations did not enhance invasion. In addition to mechanical damage from worms, these results suggest that soluble products released by T. suis contribute to IEC damage at the site of worm attachment.

Animals↗
PubMed2001

Direct measurements of colloidal friction coefficients.

The time-independent hydrodynamic forces operating between two hard spheres were studied as a function of the interparticle separation r. Two colloids were positioned a distance r apart using a dual-beam optical tweezer similar to that described by Meiners and Quake [Phys. Rev. Lett. 82, 2211 (1999)]. Brownian fluctuations in the positions of the two spheres were followed by recording the intensity of forward scattered laser light. The two particles move cooperatively as a result of hydrodynamic forces. The strength of the correlation increased strongly with decreasing separation r. We show that the temporal and spatial correlations in the particle displacements are determined by the distance dependence of the pair friction tensor xi. The distance and geometry dependence of the measured friction tensor is found to be in excellent agreement with the predictions of low-Reynolds number calculations.

Journal Article↗
PubMed2001

Nurse-led ear care: training needs and the latest techniques.

Patients requiring ear care have reported higher levels of satisfaction when this was provided by nurses. The wisdom of ear syringing, the traditional method of cleaning the ear, is now being questioned for many patients, and the aural toilet should be used as an alternative when appropriate. Nurses should remember that good communications skills are vital.

Cerumen↗
PubMed2000

Superlattice formation in mixtures of hard-sphere colloids

We report a detailed experimental study of the superlattice structures formed in dense binary mixtures of hard-sphere colloids. The phase diagrams observed depend sensitively on the ratio alpha=R(S)/R(L) of the radii of the small (S) and large (L) components. Mixtures of size ratio alpha=0.72, 0.52, 0.42, and 0.39 are studied. The structures of the colloidal phases formed were identified using a combination of light-scattering techniques and confocal fluorescent microscopy. At alpha=0.39, ordered binary crystals are formed in suspensions containing an equal number of large and small spheres which microscopy shows have a three-dimensional structure similar to either NaCl or NiAs. At the larger size ratio, alpha=0.52, we observe LS2 and LS13 superlattices, isostructural to the molecular compounds AlB2 and NaZn13, while at alpha=0.72 the two components are immiscible in the solid state and no superlattice structures are found. These experimental observations are compared with the predictions of Monte Carlo simulations and cell model theories.

Journal Article↗
PubMed1998

Radiologic versus surgical placement of vena cava filters: a comparative study of cost, time and complications.

OBJECTIVE: To compare the cost- and time-effectiveness of 2 methods of placement of vena cava filters for the prevention of pulmonary embolism: the radiologic percutaneous placement of the Vena Tech LGM filter and the surgical cutdown placement of the 24 Fr Greenfield filter. METHODS: Retrospective review of radiologic and clinical records for 15 consecutive patients who had the Vena Tech LGM filter placed radiologically and 15 consecutive patients who had the Greenfield filter placed surgically. Factors studied were cost, procedure time, waiting time and rates of immediate and delayed complications. The follow-up period ranged from 1 to 26 months (mean 7 months). RESULTS: The procedure cost for the radiologic method was $702 less than for the surgical method. The procedure time for the radiologic method was 30 minutes shorter, and the waiting time for placement was also shorter. There was no difference in the complication rates following each procedure. The higher cost of the Greenfield filter accounted for 80% of the total cost difference. CONCLUSION: The radiologic percutaneous method of filter placement is preferred over the surgical cutdown method because of its benefits in terms of cost and time with no increase in risk. However, when the difference in cost between filters is taken into account, there is little difference in overall costs for the 2 methods. Therefore, radiology and surgery departments can place a filter percutaneously at a similar cost. Other factors such as waiting times, complication rates, venography capabilities and physician interest in performing the procedure will dictate which department places the filter.

Adult↗
PubMed1997

Cytokines which signal through the LIF receptor and their actions in the nervous system.

A number of different cytokines, each initially characterized on the basis of very different biological activities, all have very similar signalling pathways and share a similar tertiary structure. These cytokines include leukaemia inhibitory factor, ciliary neuronotrophic factor, oncostatin M, growth-promoting activity and cardiotrophin 1. They all have been found to regulate a number of properties of cells of the developing and mature nervous system in vitro and thus are neuroregulatory cytokines. The actions of these cytokines include regulation of neurotransmitter phenotype, differentiation of neuronal precursor cells both in the peripheral nervous system and in the spinal cord, survival of differentiated neurons, and regulation of development of both astrocytes and oligodendrocytes. In addition, studies in animal models show that these factors can rescue sensory and motor neurons from axotomy-induced cell death, which suggests that they can act as trauma factors for injured neurons. Analysis of the expression patterns of the different neuroregulatory cytokines and their receptors reveals that the receptors are expressed throughout nervous system development and following trauma, whereas the cytokines show temporal and spatial specific expression patterns. This is consistent with the idea that specific cytokines have specific roles in neural development and repair, but that their signalling pathways are shared. The phenotypes of the receptor knockouts show clear deficits in nervous system development, indicating a crucial role for LIF receptor signalling. Knockouts of individual cytokines are less dramatic, but LIF and CNTF knockouts do reveal deficits in maintenance of motor neurons or following trauma. Thus, whereas LIF and CNTF have clear roles in maintenance and following trauma, it is unclear which of the cytokines is involved in nervous system development. In clinical terms, these findings add further support to the use of these cytokines in nervous system trauma and disease.

Animals↗
PubMed1996

Leukemia inhibitory factor and ciliary neurotrophic factor in sensory neuron development.

Leukemia inhibitory factor (LIF), ciliary neurotrophic factor (CNTF), and related proteins are potentially involved in several aspects of sensory neuron development. There is evidence that LIF promotes the differentiation of sensory neurons from progenitor cells of neural crest origin. Later in development, LIF, CNTF, oncostatin M and interleukin-6 promote the survival of cultured neurons. Some neurons, like those of the nodose ganglion, respond early in their development to these factors, whereas other neurons, like those of the trigeminal ganglion, respond much later. In addition to promoting sensory neuron survival, there is some evidence that LIF is able to influence neurotransmitter and neuropeptide expression in these neurons. These observations suggest that several kinds of sensory neurons may be influenced in various ways by LIF and related factors at different stages of their development.

Animals↗
PubMed1995

Role of leukaemia inhibitory factor (LIF) in rat peripheral nerve regeneration.

The cytokine leukaemia inhibitory factor (LIF) favours the survival and growth of axons in vitro. The efficacy of this factor in the in vivo model has been the aim of this study. Following nerve transection and immediate entubulation repair in the rat sciatic nerve, this study demonstrated that (1) LIF promotes the growth of a population of axons of greater cross-sectional area after 6 and 12 weeks in comparison to either saline (negative control) or basic fibroblast growth factor (bFGF) (positive control), (2) LIF improves the nerve conduction velocity of regenerating axons, (3) LIF has a positive effect on skeletal muscle mass following nerve repair, (4) the benefits of LIF on skeletal muscle appear to be somewhat independent of reinnervation as similar observations are made where there is no growth of a tissue bridge within the tube, and (5) the effects of LIF seem to be potentiated by the addition of fibronectin.

Animals↗