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Biomedical subjects

R Robinson

Publications and source records attributed to R Robinson.

At least 109 records · Page 6Linked to original sources
PubMed1996

Comparison of technetium-99m-HMPAO and technetium-99m-ECD cerebral SPECT images in Alzheimer's disease.

UNLABELLED: SPECT has shown increasing promise as a diagnostic tool in Alzheimer's disease (AD). Recently, a new SPECT brain perfusion agent, 99mTc-ethyl cysteinate dimer (99mTc-ECD) has emerged with purported advantages in image quality over the established tracer, 99mTc-hexamethylpropyleneamine oxime (99mTc-HMPAO). This research aimed to compare cerebral images for 99mTc-HMPAO and 99mTc-ECD in discriminating patients with AD from control subjects. METHODS: Twenty-four AD patients (mean age +/- s.d. = 68.9 +/- 8.2 yr) and 13 healthy subjects (68.4 +/- 8.0 yr) were scanned sequentially with 20 mCi of each tracer using the CERASPECT system within 1 mo. Scanning began on average 11.5 +/- 2.8 min after 99mTc-HMPAO injection and 41.8 +/- 10.1 min after 99mTc-ECD. A ratio, R, was derived of count densities in "typically affected" brain structures (parietal and temporal association cortices) to "unaffected" structures (cerebellum, basal ganglia, thalamus, occipital cortex, and sensorimotor cortex). RESULTS: Analysis of variance revealed significant interaction between diagnostic group and radiopharmaceutical (F = 4.71; df = 1.35; p = 0.04), with 99mTc-ECD demonstrating better separation of R values between AD patients and control subjects than 99mTc-HMPAO. Receiver operating characteristic (ROC) analysis, revealed no significant difference in the ability of the two tracers to correctly classify AD patients and control subjects. Both tracers showed high diagnostic accuracy (99mTc-ECD: sensitivity = 100%, specificity = 92%; 99mTc-HMPAO: sensitivity = 100%, specificity = 85%). CONCLUSION: Technetium-99m-ECD shows greater contrast than 99mTc-HMPAO between affected and unaffected brain structures in AD when patients are compared to age-matched control subjects. Both tracers perform equally well in correctly classifying patients and control subjects.

Aged↗
PubMed1996

Infection control in practice. Infection control and clinical efficiency: are they compatible?

A frequently expressed concern regarding infection control guidelines is that they require too much time, effort and expense. This paper will address those concerns by examining the relationship between infection control and clinical efficiency. Infection control procedures can be minimized if proper attention is given to the concept of Limited Surface Contamination. Adherence to a clearly defined Zone of Contamination is essential. Emphasis should be on prevention rather than elimination of contamination. By following well-established principles of Dental Assistant Utilization (DAU), or 'four-handed dentistry', clinical efficiency is enhanced and infection control improved. Proper infection control in the dental surgery is virtually impossible without the cooperation and involvement of a well-trained, committed dental chairside assistant.

Dental Assistants↗
PubMed1995

Isolation and photodynamic effects of hematoporphyrin derivative components: a chromatographic analysis of the starting materials.

Twenty different fractions of hematoporphyrin derivatives (HpD) and eight fractions of an HpD dimer mixture were isolated utilizing isocratic reversed-phase ion-pair high-performance liquid chromatography. These fractions were characterized by UV-visible and fluorescence spectrophotometry. Fluorescence quantum yields and photokill efficiency for each fraction in PTK2 epithelial cells were obtained. Results indicate that some part of the photoactivity exhibited by HpD may be due to impurities present in the HpD starting material, hematoporphyrin-IX dihydrochloride, depending on its source. It was also found that hematoporphyrin D, a commercial acetylated product formed during synthesis of HpD, contained a higher percentage of monomers than would be expected.

Animals↗
PubMed1995

Fillers.

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Periodicals as Topic↗
PubMed1995

Elimination of potential mutagenicity in platelet concentrates that are virally inactivated with psoralens and ultraviolet A light.

BACKGROUND: For virus sterilization of platelet concentrates (PCs), treatment with aminomethyltrimethyl psoralen (AMT) and long-wavelength ultraviolet A light (UVA) has shown efficacy. It has been found that treatment with 50 micrograms per mL of AMT and 38 J per cm2 of UVA in the presence of 0.35-mM rutin efficiently kills viruses while maintaining platelet integrity. There is, however, concern about the mutagenic potential of psoralens and UVA (PUVA)-treated PCs. STUDY DESIGN AND METHODS: Adsorption of PUVA-treated PCs with a hydrophobic resin containing C18 as the ligand was used for AMT removal, which was quantitated by the use of radioactive AMT. PUVA-treated PCs, with and without C18 treatment, were examined for solution pH and platelet aggregation response to agonists. In addition, residual AMT activity was determined by AMT's virucidal activity or incorporation into cellular DNA upon a second UVA irradiation and by its mutagenic potential in the Ames test. RESULTS: After PUVA treatment of PCs, residual AMT retained virucidal and adduct-forming ability upon re-exposure to UVA, but activities were less than those observed originally. As has been found previously, AMT had mutagenic potential following incubation in the dark with rat liver S9 microsomal enzymes. The PUVA treatment reduced this potential by 90 percent. C18 adsorption following PUVA treatment had no negative effect on platelet integrity and eliminated 50 percent of the added radioactive AMT. In addition, all detectable virucidal, nucleic acid-modifying, and mutagenic activities of AMT-treated PCs were removed by C18. CONCLUSION: These results suggest that hydrophobic resin adsorption of PUVA-treated PCs will conveniently remove functional psoralens and eliminates their mutagenic potential.

Adsorption↗
PubMed1995

Psoralen-mediated virus photoinactivation in platelet concentrates: enhanced specificity of virus kill in the absence of shorter UVA wavelengths.

Treatments with psoralens and long-wavelength ultraviolet radiation (UVA, 320-400 nm; PUVA) have shown efficacy for virus sterilization of platelet concentrates (PC). Our laboratory has employed the psoralen derivative 4'-aminomethyl-4,5',8-trimethylpsoralen (AMT), and we have found that platelet integrity is best preserved when rutin, a flavonoid that quenches multiple reactive oxygen species, is present during AMT/UVA treatment of PC. In this report, we examine the effects of different UVA spectra under our standard PC treatment conditions (i.e. 50 micrograms/mL AMT, 0.35 mM rutin and 38 J/cm2 UVA). Added vesicular stomatitis virus (VSV; > or = 5.5 log10) was completely inactivated with the simultaneous maintenance of the platelet aggregation response (> 90% of control) when a UVA light source with transmission mainly between 360 and 370 nm (narrow UVA1) was used. In contrast, with a broad-band UVA (320-400 nm; broad UVA) light source, the aggregation response was greatly compromised (< 50% of control) with only a minor increase in the rate of VSV kill. With this lamp, platelet function could be improved to about 75% of the control by adding a long-pass filter, which reduced the transmission of shorter (< or = 345 nm) UVA wavelengths (340-400 nm; UVA1). At equivalent levels of virus kill, aggregation function was always best preserved when narrow UVA1 was used for PUVA treatment. Even in the absence of AMT, and with or without rutin present, narrow UVA1 irradiation was better tolerated by platelets than was broad UVA.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Platelets↗
PubMed1995

Colonoscopy.

Colonoscopy is a procedure that more primary care physicians are performing. This article has attempted to provide such physicians the basic information needed regarding the indications, contraindications, and complications associated with colonoscopy. Patient issues such as preparation, education, and consent were also discussed.

Anemia↗
PubMed1995

Cardiovascular pressures with venous gas embolism and decompression.

Venous gas embolism (VGE) is reported with decompression to a decreased ambient pressure. With severe decompression, or in cases where an intracardiac septal defect (patent foramen ovale) exists, the venous bubbles can become arterialized and cause neurological decompression illness. Incidence rates of patent foramen ovale in the general population range from 25-34% and yet aviators, astronauts, and deepsea divers who have decompression-induced venous bubbles do not demonstrate neurological symptoms at these high rates. This apparent disparity may be attributable to the normal pressure gradient across the atria of the heart that must be reversed for there to be flow patency. We evaluated the effects of: a) venous gas embolism (0.025, 0.05 and 0.15 ml.kg-1.min-1 for 180 min.); b) hyperbaric decompression; and c) hypobaric decompression on the pressure gradient across the left and right atria in anesthetized dogs with intact atrial septa. Left ventricular end-diastolic pressure was used as a measure of left atrial pressure. In a total of 92 experimental evaluations in 22 dogs, there were no reported reversals in the mean pressure gradient across the atria; a total of 3 transient reversals occurred during the peak pressure gradient changes. The reasons that decompression-induced venous bubbles do not consistently cause serious symptoms of decompression illness may be that the amount of venous gas does not always cause sufficient pressure reversal across a patent foramen ovale to cause arterialization of the venous bubbles.

Altitude↗
PubMed1995

Fibroid growth in response to high-dose progestogen.

OBJECTIVE: To challenge the conventional belief that leiomyomata are estrogen-dependent tumors by presentation of a case report suggesting high-dose progestogen therapy is associated with a dramatic increase in size of a fibroid uterus. DESIGN: Case report. SETTING: British university hospital. PATIENT: One white woman treated with tamoxifen and high-dose megestrol acetate for breast carcinoma. INTERVENTIONS: Megestrol acetate therapy withdrawn. MAIN OUTCOME MEASURE: Uterine size. RESULTS: While taking tamoxifen and high-dose megestrol acetate, the patient suffered a dramatic increase in size of her fibroid uterus, which reversed when the progestogen was withdrawn. CONCLUSION: This case report suggests that P may be important in fibroid growth.

Breast Neoplasms↗