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Biomedical subjects

J A Piper

Publications and source records attributed to J A Piper.

11 recordsLinked to original sources
PubMed2003

High average power, all-solid-state external resonator Raman laser.

As much as 3 W of average power at 1064 nm from a diode-pumped Nd:YAG laser, Q switched at 4 kHz, was used to pump an external-resonator, crystalline Ba(NO3)2 Raman laser generating a maximum of 1.3-W output at the first Stokes wavelength of 1197 nm. The slope efficiency was 63% with respect to the fundamental power incident on the Ba(NO3)2 crystal. A reduction in the beam quality of the Stokes output from M2 approximately 1.4 at lower Stokes powers to M2 approximately 3.4 at higher powers is attributed to thermal loading of the Raman-active crystal.

Journal Article↗
PubMed2001

Characterizing output beams for lasers that use high-magnification unstable resonators.

Laser beams generated from high-magnification on-axis unstable resonators by use of hard-edged optics typically have a doughnut-shaped distribution in the near field (i.e., a flat-top profile with a hole in the middle for an axially coupled beam). We derive analytical expressions describing this distribution by using the flattened Gaussian beams concept. The superposition of two flattened Gaussian beams whose flatness and steepness of edges are controlled by defined parameters (i.e., the beam width and the order) is used to analyze the output beam intensity along the propagation axis. Finally, experimental measurements of beam propagation from a copper-vapor laser fitted with a high-magnification unstable resonator show excellent agreement with theoretical predictions.

Journal Article↗
PubMed1999

Sutureless microvascular anastomoses by a biodegradable laser-activated solid protein solder.

A new sutureless technique to successfully anastomose the abdominal aorta of rats (1.3 mm in diameter) by using a fully biodegradable, laser-activated protein solder is presented. A total of 90 rats were divided into two groups randomly. In group one, the anastomoses were performed by using conventional microsuturing technique, whereas in group two, the anastomoses were performed by using a new laser welding technique. In addition, each of the two groups were divided into five subgroups and evaluated at different follow-up periods (10 minutes, 1 hour, 1 day, 1 week, and 6 weeks). At these intervals, the anastomoses were evaluated for patency and tensile strength. Three anastomoses in each subgroup were processed for light and electron microscopy. All anastomoses were found to be patent. The mean clamp time of the anastomoses performed with conventional suturing was 20.6 minutes compared with 7.2 minutes for the laser-activated welded anastomoses (p < 0.001). The strain measurements showed a stronger mechanical bond of the sutured anastomoses in the initial phase. However, at 6 weeks the tensile strength of the laser-welded anastomoses was higher compared with the conventional suture technique. Histologic evaluations revealed a near complete resorption of the solder after 6 weeks. The junction site of the vessel ends cannot be determined on the luminal side of the artery. In conclusion, a resorbable protein used as a solder, activated by a diode laser, can provide a reliable, safe, and rapid arterial anastomosis, which could be performed by any microsurgeon faster than conventional suturing after a short learning curve.

Anastomosis, Surgical↗
PubMed1998

Laser nerve repair by solid protein band technique. I: identification of optimal laser dose, power, and solder surface area.

Thirty-four tibial nerves in 17 adult male wistar rats were repaired by applying protein bands longitudinally across the nerve join. The bands were then irradiated with a fibre-coupled diode laser (lambda = 810 nm). The relations among the laser weld breaking force, the power, and the solder surface area were investigated, while maintaining a consistent ratio between the total mass of protein solder in a band and total laser energy delivered (the laser energy dose). When this laser energy dose was held constant, the average breaking force of the laser welds irradiated by 72 mW laser output power was weaker than that reached after 90 mW laser radiation. There is a linear relation between the solder breaking force and the solder surface area when band thickness, laser power, and laser dose are unvaried.

Animals↗
PubMed1998

Laser nerve repair by solid protein band technique. II: assessment of long-term nerve regeneration.

A total of 18 adult male Wistar rats had left tibial nerve repaired by either the laser-solder technique or a more conventional microsuture technique. The diode laser power was 90 mW and the radiation dose 16 J/mg. Three months postoperatively electrophysiology showed that the average compound muscle action potential (CMAP) of the laser repair group was not significantly different from the CMAP of the sutured nerves. Light microscopy confirmed regeneration of myelinated axons in both groups of animals. The laser-solder technique, when used with such parameters, proved to be a reliable method to achieve satisfactory peripheral nerve anastomosis and nerve regeneration.

Action Potentials↗
PubMed1997

A common strategic language for clinicians and senior managers.

Effective strategic analysis of existing and potential services requires a framework which is relevant and understandable to both clinicians and senior managers. Our work with NHS trusts has developed a framework based on analysis of services into four principal service streams--emergency general hospital, non-emergency general hospital, specialist general hospital and tertiary. Relating service streams to clinical specialties provides a matrix which can provide a basis for an initial analysis of the current and prospective clinical services portfolio, allowing drilling down into the detail and back up to the overall picture. Portfolio effectiveness is assessed by considering overall viability consisting of three interrelated elements--clinical, market and financial viability. The interrelationship of service streams, clinical specialties and viability allows the trust board and key clinicians to share insights into the current and potential systemic linkages between these three elements and to develop a vision of future strategic direction.

Communication↗
PubMed1996

Observation of single-cell fluorescence spectra in laser flow cytometry.

We report the first demonstration of directly recording fluorescence spectra of single cells in flow cytometry. An intensified, 512-element photodiode array was used in conjunction with a dispersing prism to capture the fluorescence emission spectra of Coulter ImmunoCheck calibration beads and Dictyostelium discoideum spores stained with the indocarbocyanine derivative CY3, fluorescein isothiocyanate, or R-phycoerythrin. The demonstration was made feasible by enhancing the signal-to-noise ratio of the detection process by using a fast gating technique applied to the detector. Results show that the complete fluorescence spectra of individual stained cells contain information that is normally not captured by conventional flow cytometers. By using the spectrographic flow cytometer, all this information is recorded, allowing small features and shifts in the fluorescence spectra of labelled particles to be studied.

Animals↗
PubMed1986

Beta-chain human chorionic gonadotropin-producing leiomyosarcoma of the small intestine.

A 22-year-old patient with primary leiomyosarcoma of the small bowel presented with symptoms including nausea and vomiting, a symptom complex similar to hyperemesis gravidarum in the pregnant female. She was found to have elevated levels of serum beta-HCG which were localized to the leiomyosarcoma cells utilizing an immunoperoxidase staining technique. Thus, this patient presents evidence that beta-HCG may be produced by sarcoma cells and, therefore, that beta-HCG may be used as a tumor marker in some sarcoma patients.

Adult↗
PubMed1985

Evaluation of dual-label simultaneous assays for lutropin and follitropin in serum.

We evaluated the analytical performance and clinical utility of three dual-label simultaneous assays for lutropin and follitropin by comparison with widely used individual assays for these analytes (Diagnostic Products Corp.; DPC). Of the three assays evaluated, "Cotropin" (Clinetics Corp.) and "Combostat" (Micromedics Systems, Inc.) compared favorably with the DPC assay with respect to recovery, linearity, intra- and inter-assay precision, and sensitivity for lutropin. The third assay evaluated, "Simultropin" (Becton Dickinson Immunodiagnostics), exhibited greater interassay variability for lutropin than did the DPC assay but otherwise compared favorably. Analytically the three assays were similar to one another for follitropin determinations and results compared favorably with those by the DPC assay. Intercorrelation of patients' results obtained with these assays is poor. However, using the same standards with each of the three assays improved intercorrelation of patients' data except for follitropin by Combostat. A universally accepted reference material for immunoassay of lutropin and follitropin is needed.

Cobalt Radioisotopes↗
PubMed1969

The differential sensitivity of cultured chick mesodermal cells to actinomycin D.

Cells were isolated from the somite mesoderm and from the unsegmented (presomite) mesoderm of early chick embryos and exposed to actinomycin D in single cell culture. Actinomycin D inhibited proliferation in cell cultures derived from the unsegmented mesoderm, although the same concentrations of this antibiotic did not inhibit cultures derived from the somite mesoderm. This differential sensitivity parallels the regionally specific necrosis and degeneration observed in the unsegmented mesoderm of intact chick embryos exposed to actinomycin D. In culture, both cell types exhibited approximately the same permeability to labeled actinomycin D and showed comparable inhibition of RNA, DNA, and protein syntheses in the presence of the antibiotic. However, freshly isolated mesodermal cells from the somite region had a higher content of RNA than did cells from the unsegmented region, and the somite cells maintained a higher rate of macromolecular synthesis in untreated cultures.

Animals↗