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Biomedical subjects

D M Taylor

Publications and source records attributed to D M Taylor.

At least 145 records · Page 8Linked to original sources
PubMed1989

Human excimer laser lamellar keratectomy. A clinical study.

The first ten blind human eyes in the United States to receive excimer laser (ArFl 193 nm) lamellar keratectomy (reprofiling) are presented. Seven of these patients were followed 6 to 12 months after ablation. All eyes are grossly clear in the region of ablation. Results of slit-lamp examination of all flattened ablated areas show mild superficial haze at the epithelial/stromal interface. This haze might not interfere significantly with vision in patients 7 to 10. Serial pachymetry and keratometry measurements, refraction, and digital keratoscopy show a progressive filling in of the excavated area by approximately two thirds but a loss of initial diopteric correction of only one third. Histopathologic analysis was obtained for four eyes. Transmission electron microscopy of three eyes enucleated 3 to 12 days after ablation shows 40-microns ablation depths through Bowman's layer and superficial stroma with minimal adjacent tissue damage and no inflammatory cells. The epithelium is increased in thickness by 50%, and firmly attached to the underlying stroma. A 4-month postablation specimen shows keratocyte activation with increased protein synthesis (presumed collagen and ground substance).

Blindness↗
PubMed1989

Experimental corneal studies with the excimer laser.

The excimer laser is potentially capable of achieving wide area central corneal reprofiling because of its extreme precision and limited penetration into adjacent tissues. A beam modifying system designed for this application is described. Initial clinical studies in monkeys and in ten human patients with blind eyes were performed. Long-term clinical data and interim histologic analyses are available from these studies. The results indicate that following ablation with an ultraviolet laser in both humans and primates, the ablated tissue shows a normal healing reaction resulting in a mild to moderate stromal interface haze. The effects of this healing on best corrected vision must be elucidated through additional research. Some loss of refractive effect was seen early in the healing process with apparent stabilization.

Animals↗
PubMed1989

The efficacies of pure LICAM(C) and DTPA on the retention of plutonium-238 and americium-241 in rats after their inhalation as nitrate and intravenous injection as citrate.

The pure carboxylated catechoyl amide LICAM(C) and the calcium and zinc salts of diethylenetriaminepenta-acetic acid (DTPA), were tested for efficacy for removing 238Pu and 241Am from rats after inhalation of the nitrate or intravenous injection of the citrate. The results were compared with the efficacy of methylated LICAM(C) used in previous experiments. It was shown that: (1) after inhalation of 238Pu nitrate, DTPA was far superior to pure LICAM(C); (2) after intravenous injection of 238Pu citrate, the infusion of DTPA plus LICAM(C) was only marginally more effective than DTPA alone; and (3) after inhalation or intravenous injection of 238Pu plus 241Am, the efficacy of pure LICAM(C) was only marginally more effective than the methylated form and neither form was effective for the decorporation of 241Am. It was concluded that DTPA, at present, remains the chelating agent of choice for treating persons accidentally contaminated with transportable forms of Pu and Am.

Aerosols↗
PubMed1989

Human excimer laser keratectomy. Short-term histopathology.

The first human trial utilizing the argon fluoride excimer laser at 193 nm to produce a superficial keratectomy in the initial three of 10 human eyes has been described with the clinical appearance and short-term (less than 14 days) histopathologic evaluation of these three eyes. The process of laser superficial keratectomy has proved one of the promising areas of surgical intervention for reconstructive or refractive keratoplasty in the future. Intensive investigations of corneal wound healing following laser ablation as well as the nature and long-term stability of the corneal excisions or induced refractive corrections are needed. It is essential that the optimal laser parameters be established for the various refractive corrections and other corneal surgical techniques and that pathophysiologic and histopathologic changes that have been induced by the excimer laser-corneal tissue interaction in animals and humans be critically and extensively analysed.

Adult↗
PubMed1988

Abnormal hyperexcitability of hippocampal slices from kindled rats is transient.

The anatomic substrates and mechanisms responsible for the development and permanence of kindling remain to be determined. One region believed to play an important role in kindling development is the hippocampus. Epileptiform activity (K+-induced spontaneous bursting) was recently shown to be enhanced in hippocampal slices from kindled rats studied 1 day after kindling from the lateral entorhinal cortex (LEC). Identical results one month after kindling raised the possibility that hippocampal excitability might be permanently increased in kindled animals. One goal of the present study was to confirm this finding, and also to extend it in terms of both the anatomic extent and the duration of this excitability increase. Stimulus train-induced bursting (STIB) is an in vitro model of hippocampal epileptogenesis. Parallels between STIB and kindling suggested STIB might prove useful for studying mechanisms underlying kindling. To strengthen the relation of STIB to kindling, we examined whether slices from kindled animals would behave as if they had undergone STIB during kindling. K+-induced bursting and STIB were studied in hippocampal slices from control and kindled rats one day and about 3 months after completion of kindling from the right LEC. Both K+-induced bursting and STIB development were enhanced one day after kindling. The enhancement of K+-induced bursting was present in both temporal and septal slices from both the ipsilateral and the contralateral hippocampus. Neither of these proepileptic changes was detected 3 months after kindling.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1988

Technetium-99m labeled renal function and imaging agents: III. Synthesis of 99mTc-MAG3 and biodistribution of by-products.

99mTc-MAG3, a new 99mTc radiopharmaceutical with biological properties similar to o-iodohippuric acid (OIH), is expected to find wide clinical application for renal function studies. Therefore it is important to make a kit formulation available which provides reproducibly the desired product in high radiochemical yields. Some differences between the biokinetic data of kit prepared 99mTc-MAG3 and HPLC-purified 99mTc-MAG3 were reported by different authors. The subject of this paper is the isolation of the by-products which are formed with our own kits, the evaluation of their biological behaviour and the comparison with the main product 99mTc-MAG3 in rats. The results suggest that the radiochemical purity of 99mTc-MAG3-preparations should be not less than 95%.

Animals↗
PubMed1988

Biochemical binding and distribution of protactinium-233 in the rat.

Following intravenous injection into male Sprague-Dawley rats 233Pa, like other elements, deposits predominantly in the skeleton (ca. 70-80 per cent), but unlike Pu and Am the liver deposition of 233Pa is low, about 2-3 per cent between 1 and 7 days. About 99 per cent of the injected 233Pa is lost from the plasma compartment in 3 days, a clearance comparable to that of Pu but much slower than that of Np, Am or Cm. On entering the liver cell cytosol 233Pa is bound rapidly to an unidentified protein of molecular mass 200 kDa and to a protein of 80 kDa, which is probably transferrin. Within a few hours the metal migrates to bind to a protein of greater than 400 kDa which has been tentatively identified as ferritin. Some 233Pa remains bound to small ligands until virtually all the intracellular 233Pa has been deposited in the lysosomes, or to a lesser extent in some other, as yet, unidentified organelles.

Animals↗
PubMed1988

The potential for irradiation of the lens and cataract induction by incorporated alpha-emitting radionuclides.

Data on the uptake and retention of Ra and Pu in ocular tissues are reviewed. These data were used to calculate alpha radiation doses to the lens of the eye for patients injected with 224Ra and for individuals exposed to one annual limit on intake (ALI) per year of 224Ra, 226Ra, 228Ra and 239Pu for a period of 50 y. On the basis of this analysis, it is concluded that the induction of lens opacity should not be the factor limiting intake of any radioisotope of Pu or for 224Ra or 226Ra. However, for 228Ra the dose lies within the range of doses received by 224Ra patients who have developed cataracts.

Alpha Particles↗
PubMed1988

Factors influencing the uptake of cadmium into cells in vitro.

The uptake of cadmium was studied in Chinese Hamster Ovary (CHO) cells. Cadmium accumulates rapidly against a concentration gradient and uptake is dependent on incubation temperature. The presence of serum or albumin results in a reduction in Cd uptake. Several substances known to influence certain metabolic steps of cell metabolism were used to influence Cd accumulation. Of these compounds, those that blocked the SH groups of the plasma membrane exerted the strongest influence. The effect of inhibitors of endocytosis was less pronounced.

Animals↗
PubMed1988

A shift from acute to chronic spontaneous pyelonephritis in male MM mice associated with a change in the causal micro-organisms.

Proteus mirabilis was the predominant cause of acute diabetes-associated pyelonephritis occurring spontaneously in male MM mice until they were segregated in a new environment. Thereafter Pasteurella pneumotropica and Streptococcus faecalis emerged collectively as the most common causal organisms, the pyelonephritis became more chronic and Proteus mirabilis isolates from faeces and urine produced atypical non-swarming colonies on blood agar plates. This did not account for the reduced pathogenicity of Proteus mirabilis; when MM males were returned to the original environment the pyelonephritis again became acute but was associated with the atypical type of Proteus mirabilis although the normal type was abundant in the environment. The MM mice were Caesarean-derived and cross-fostered shortly before their transfer to the second environment, which probably accounts for their changed microbial status, but the reason for the emergence of the atypical type of Proteus mirabilis is not understood. The acute nature of the male MM pyelonephritis when caused by Proteus mirabilis parallels the situation described in other animals and humans.

Acute Disease↗
PubMed1988

Altered clinical and histological features of male MM mouse pyelonephritis associated with a change in its microbiology.

Radical changes in the clinical, microbiological and histological features of spontaneous pyelonephritis in MM male mice occurred when they were transferred to a new environment after Caesarean derivation. Although the incidence of pyelonephritis remained the same, the survival age was increased. The renal histology indicated a shift to a more chronic form of pyelonephritis with renal amyloidosis as a common feature. At autopsy much more renal scarring was seen, resulting in the 'shrunken' kidney typical of chronic pyelonephritis. Renal lymphocytic accumulations were commonly found in MM mice, but they were also seen frequently in C57BL mice and in germfree stocks of both strains: no association was found between these lesions and pyelonephritis.

Amyloidosis↗
PubMed1988

Human excimer laser corneal surgery: preliminary report.

The first human trial utilizing the argon fluoride excimer laser at 193 nm to produce a superficial keratectomy in ten human eyes has been described with the histopathological evaluation of four eyes and the longer gross appearance of six eyes at intervals extending to 10 months post-excimer laser treatment. The process of laser superficial keratectomy has proved to be one of the promising areas of surgical intervention for reconstructive or refractive keratoplasty in the future. Intensive investigations need to be undertaken on the corneal wound healing process following laser ablation as well as the nature, and long-term stability of the corneal excisions or induced refractive corrections. It is essential that the optimal laser parameters be established for the various refractive corrections and other corneal surgical techniques, and that pathophysiologic and histopathologic changes that have been induced by the excimer laser-corneal tissue interaction in animals and humans be critically and extensively analyzed.

Adult↗
PubMed1987

Electrochemical characteristics of platinum electrodes coated with cytochrome b5-phospholipid monolayers.

Platinum electrodes can be coated with cytochrome b5-phospholipid monolayers by the Langmuir-Blodgett technique. Cyclic voltammetry of a series of dyes shows that the coated electrodes become selective for certain electroactive species. The electron transfer reactions of negatively charged species are inhibited at the modified electrode, whereas positively charged species show enhanced reactivity compared with that at a bare metal electrode.

Animals↗