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Biomedical subjects

C P Davis

Publications and source records attributed to C P Davis.

At least 37 records · Page 2Linked to original sources
PubMed1995

Mycoplasma pneumoniae and Mycoplasma genitalium mixture in synovial fluid isolate.

A mycoplasma cultured from synovial fluid specimens from a patient with pneumonia and subsequent polyarthritis was identified initially as Mycoplasma pneumoniae. In retrospective studies, the culture was shown also to contain Mycoplasma genitalium. In this paper, the laboratory techniques employed in the identification and separation of the two species are presented, and evidence to implicate postinfectious autoimmunity is provided. An increasing number of reports of M. genitalium in human tissue sites and difficulties in isolation and identification of the organism in the clinical laboratory suggest the need for more extensive application of rapid and specific detection systems for both M. genitalium and M. pneumoniae in the clinical laboratory.

Animals↗
PubMed1995

Real-time biplanar needle tracking for interventional MR imaging procedures.

PURPOSE: To evaluate real-time biplanar tracking of a specially designed needle with magnetic resonance (MR) imaging guidance. MATERIALS AND METHODS: The needle is made of polyetheretherketone and has a miniature radio-frequency coil incorporated into the tip. Tracking software on two workstations is used to compute three-dimensional coordinates of the coil and to display the position as a moving symbol in two imaging planes. Validation of needle tracking was performed in a harvested human liver. T2-weighted fast spin-echo images were used to target a 1-cm cyst. Success of needle placement was confirmed with aspiration and with updated gradient-recalled-echo images. RESULTS: The cyst was successfully targeted from different approaches. Tracking procedures were monitored in real time simultaneously on two separate images. CONCLUSION: Real-time biplanar needle tracking may prove to be useful for both diagnostic and therapeutic interventional MR imaging procedures.

Artifacts↗
PubMed1995

In vivo reduction of bacterial populations in the urinary tract of catheterized sheep by iontophoresis.

PURPOSE: Iontophoresis kills microbes in vitro and, therefore, may be a useful method for eliminating microbial populations associated with catheter-induced urinary tract infections in vivo. MATERIALS AND METHODS: Catheters were modified to deliver current to platinum electrodes in the catheter tip. Female sheep were catheterized with this iontophoretic catheter and left ambulatory. In 5 sheep (experimental group) 400 microA was applied to the catheter and withheld in 4 sheep (control group) for 20 to 21 days. The animals were then sacrificed. During the study, types and concentrations of bacteria, and physical and chemical characteristics of the urine samples were determined. RESULTS: Throughout the study, bacteria levels were reduced in urinary tracts of the experimental group (10(3) to 10(4) microbes per ml.) compared with the control group (10(7) microbes per ml.), without extensive alterations to urine chemistry or the sheep urinary tract. CONCLUSIONS: Since iontophoresis safely reduced bacterial populations in catheterized sheep, this technology may reduce or eliminate nosocomial, catheter-induced urinary tract infections in humans.

Animals↗
PubMed1995

[Fast and ultra-fast MRI imaging of the heart].

Conventional magnetic resonance imaging (MRI) is capable of providing satisfactory morphological images of the heart and the surrounding structures. It has further evolved into a well accepted modality for functional cardiac studies such as flow quantification and volumetry. MRI has, however, been hampered by long image acquisition times. This combined with its non-real-time nature and the limited spatial resolution hs made it difficult to extend MRT to the study of small cardiac structures. Recent technical improvements have made breath-held or real-time MRI feasible and thus laid the foundations for further applications in the field of cardiovascular imaging, notably MR coronary angiography, imaging of cardiac valve leaflets, as well as first-pass perfusion studies. Moreover ultrafast MR techniques may eventually replace conventional data acquisition strategies and thus drastically increase patient throughput by shortening acquisition time. This article provides an overview of the technical advances in MRI and their application to the cardiovascular system and discusses possibilities of combined ultrafast and interventional strategies.

Echo-Planar Imaging↗
PubMed1994

Quantification, qualification, and microbial killing efficiencies of antimicrobial chlorine-based substances produced by iontophoresis.

The dependence of microbial killing on chloride ions present in solutions undergoing iontophoresis is addressed. A 400-microA current was applied to vials containing synthetic urine or saline, and the production of chlorine-based substances (CBSs) was detected by the N,N-diethyl-p-phenylene diamine colorimetric method. It was found that as the time of current application increased, the total concentration of CBSs also increased. The iontophoretic current converted (through oxidation) chloride ions present in the solutions into CBSs such as free chlorine, chlorine dioxide, chlorite, monochloramine, and dichloramine (the last two were produced by iontophoresis only when nitrogenous substances were present in the solution). Two of the CBSs (free Cl and ClO2), when they were separately added back to microbial suspensions (approximately 3 x 10(5) CFU/ml) at the same concentrations at which they were detected in either 0.46% (wt/vol) NaCl solution or synthetic urine iontophoresed for 4 h at 400 microA, reduced or eliminated bacterial genera and a fungus. However, when free Cl and ClO2 were jointly added back to microbial suspensions, bacterial and fungal killing was synergistic and more rapid and complete than when these chlorine-based biocides were added separately. Therefore, iontophoresis of solutions containing chloride ions produces chlorine-based biocides that are responsible for the antimicrobial effect of iontophoresis.

Bacteria↗
PubMed1994

Normal heart: evaluation with echo-planar MR imaging.

PURPOSE: To evaluate the appearance of the heart on spin-echo (SE) and gradient-echo (GRE) echo-planar magnetic resonance (MR) images. MATERIALS AND METHODS: Nine healthy volunteers were examined with an MR imager with transaxial echo-planar imaging (EPI) capabilities. SE EPI and GRE EPI sequences were used. Full k-space signal was obtained with readout time of 40 msec per image, and total image acquisition time was 72 and 52 msec, respectively, for SE EPI and GRE EPI. RESULTS: Delineation of cardiac structures was superior with SE EPI, reflective of significantly higher contrast between myocardial and intraluminal signal intensity (SI) (P < .001). The higher (P < .01) and more homogeneous (P < .001) intraluminal SI with GRE EPI allowed better assessment of intracardiac flow. Septal SI was significantly higher for GRE EPI (P < .01), but signal homogeneity was similar for both sequences (P > .2). CONCLUSION: Diagnostic images of the heart were obtained with both SE EPI and GRE EPI. GRE EPI is more suitable for flow studies because of the higher and more homogeneous intravascular SI.

Adult↗
PubMed1994

[MR angiography of pelvic and abdominal vessels].

The assessment of abdominal vessels with conventional methods is invasive and frequently does not yield an accurate diagnosis, particularly in the evaluation of the portal venous system. MR angiography is non-invasive and is well suited for the examination of abdominal vessels. Both vessel morphology and intravascular flow patterns can be characterized with this method. Clinical indications include portal hypertension, portal vein thrombosis, portosystemic shunts, assessment of congenital anomalies, thrombus, and tumor propagation into the inferior vena cava and the renal veins, proximal renal artery stenosis, and assessment of the pelvic arteries and veins. In the future, MR angiography may become an important part of the non-invasive evaluation of abdominal and pelvic vessels.

Abdomen↗
PubMed1993

[Trichomegaly in HIV infection].

Hypertrichosis of the eyelashes was first described as "trichomegaly" in the setting of rare congenital syndromes. Recently numerous cases of acquired trichomegaly of the eyelashes have been described, especially in patients with advanced human immunodeficiency virus type I infection. The pathomechanisms leading to acquired trichomegaly remain largely unknown. Direct effects of the virus on the hair follicle, immune dysregulation, and a multifactorial pathogenesis are discussed. We report a case of acquired trichomegaly in advanced HIV-I infection in order to present this unusual clinical finding and other hair problems in AIDS patients. It is suggested that acquired trichomegaly of the eyelashes may act as a useful clinical marker for assessment of severity of HIV-I infection.

AIDS-Related Opportunistic Infections↗
PubMed1993

Ketorolac as a rapid and effective treatment of migraine headache: evaluations by patients.

The objective of this study was to determine the speed and efficiency of ketorolac in reducing the symptoms of migraine headache. Twenty-three patients who presented in the emergency department during the period between April and July 1992 with a previous diagnosis of migraine headache were considered for the study. Patients subjectively evaluated parameters of their migraine headaches (eg, pain and nausea) with a numerical scale and were asked to re-evaluate these same parameters at 30, 60, and 360 minutes after a single injection of Ketorolac. Seventeen (74%) patients reported a decrease in headache symptoms that was significant (P < .005) after 1 hour. Relief lasted at least 6 hours after injection.

Acute Disease↗
PubMed1993

Iontophoresis and chloride-containing compounds: parameters required for killing.

Fungi, and gram-positive and gram-negative organisms were susceptible to iontophoretic killing in simple media. Iontophoresis did not depend on electrode type but did require chloride-containing compounds in the medium. All organisms could be killed efficiently if chloride-containing compounds (for example sodium chloride and calcium chloride) were present in physiological concentrations. Effectiveness of iontophoretic killing could be reduced by nonphysiologically elevated concentrations of other substances (for example creatinine and albumin). The data suggest that iontophoresis should function well in urine, since chloride-containing compounds are present in adequate concentrations even if some naturally occurring compounds, such as creatinine or albumin, are elevated.

Calcium Chloride↗
PubMed1992

Electrode and bacterial survival with iontophoresis in synthetic urine.

Urinary catheters, especially in patients with long-term catheter requirements, frequently are a source of infection. Iontophoresis has been proposed as a method to decrease or eliminate such infections. Several types of material were examined for their potential use as electrodes in an iontophoretic catheter system. Silver, copper and nickel electrodes did kill microorganisms but did not show longevity. Carbon and gold electrodes showed longevity and killing of microorganisms. Gold proved to be somewhat better than carbon in killing Klebsiella pneumoniae in a broth. Few organisms survived iontophoresis. Those few that survived (mainly Klebsiella in broth), when rechallenged by iontophoresis, did not show any striking resistance to iontophoresis. Our data support the proposition that inclusion of electrodes, depending on the electrode type, in a catheter probably will decrease or eliminate a bacterial population in urine and, thus, may help prevent catheter-related infections and their sequelae.

Bacteria↗
PubMed1992

Iontophoresis generates an antimicrobial effect that remains after iontophoresis ceases.

Iontophoresis required chlorine-containing compounds in the medium for effective microbial population reduction and killing. After iontophoresis ceased, the antimicrobial effect generated by iontophoresis remained but slowly decreased. Antimicrobial effects of iontophoresis may be related to the generation of short-lived chlorine-containing compounds.

Candida albicans↗
PubMed1991

Serum and urinary immunoglobulin in the rat model of acute urinary tract infection.

Total levels of urine and serum immunoglobulin IgM, IgG and IgA, and the E. coli-specific bacterial immunoglobulin response were determined by enzyme-linked immunosorbent assay (ELISA) in a rat model of acute urinary tract infection. High levels of urinary IgM were detected as early as day 3 post infection and then decreased to statistically insignificant levels. Peak levels of IgG occurred in the serum and urine on day 14. Urine and serum IgA levels remained low throughout the study period. The results demonstrate that in the rat model of acute urinary tract infection, IgM appears first in the urine and serum, and rapidly decreases. IgG then appears in the serum and urine followed by a late E. coli-specific immunoglobulin serum and urine response. Also, a non-specific component of the immunoglobulin response was noted in both the serum and urine. In the rat, IgA appears to play little or no role in the urine or in the serum response to the infection.

Acute Disease↗
PubMed1991

Urothelial hyperplasia and neoplasia. III. Detection of nitrosamine production with different bacterial genera in chronic urinary tract infections of rats.

Various agents have been implicated in inducing urothelial cancer. Although drugs, occupational and environmental carcinogens are more widely accepted as playing a major role as urothelial carcinogens, several investigations suggest that bacteria may play a role. The mechanism of how bacteria may interact with the host to augment the development of urothelial carcinoma is not well understood. Clinically, investigators have linked the development of infection, urinary stones and indwelling catheters with urothelial cancer. Other investigators have suggested that the mechanism may be related to the production of carcinogenic compounds (nitrosamines) which can be detected during urinary tract infection. In our laboratory, we showed that rats with chronic urinary tract infections produced increasing urinary levels of N,N dimethylnitrosamine over a 24 week period and that the production correlated with hyperplasia and early neoplasia of the bladder epithelium. Three bacterial genera were used and two of these (Escherichia coli and a protein sp.) showed production of increasing levels of urinary nitrosamine and correlated with infection. The purpose of this current study is to determine if other bacterial genera and strains can also produce similar increasing nitrosamine levels in the rat model of chronic urinary tract infection and thus provide evidence that a number of bacterial genera and strains can produce nitrosamines in vivo. Also, the histology of the chronically infected bladder was examined for hyperplasia and neoplasia.

Animals↗
PubMed1991

Bacterial and fungal killing by iontophoresis with long-lived electrodes.

Iontophoresis with gold, carbon, and platinum electrodes was shown to effectively reduce or eliminate gram-positive, gram-negative, and Candida albicans inocula in synthetic urine. Platinum and gold electrodes were more effective than carbon electrodes, but platinum showed the best longevity and may reduce or eliminate microbial colonization of catheters.

Bacterial Physiological Phenomena↗