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S R Thomas

Publications and source records attributed to S R Thomas.

At least 91 records · Page 5Linked to original sources
PubMed1992

Safety and efficacy of repeated sequential administrations of Re-186(Sn)HEDP as palliative therapy for painful skeletal metastases. Initial case reports of two patients.

Single intravenous injections of 30 to 35 mCi (1,110 to 1,295 MBq) of Re-186(Sn)HEDP previously have been shown to result in palliation of painful skeletal metastases from prostate cancer. There are no reports of patients receiving repetitive Re-186(Sn)HEDP therapy. We have followed two such patients who received multiple (five to seven) injections of Re-186(Sn)HEDP at 2-month intervals. Each experienced a sustained decrease in both pain and analgesic intake. The only evident clinical or biochemical toxicity was a mild progressive decline in their total platelet counts.

Adenocarcinoma↗
PubMed1992

Quantitation of perfluorocarbon blood substitutes in tissues using F-19 magnetic resonance spectroscopy.

F-19 Magnetic Resonance Spectroscopy (MRS) has been used to quantitate the biodistribution of perfluorocarbon (PFC) blood substitutes in porcine tissues following intraperitoneal administration of a 20% w/v perfluorotributylamine (FC-43) based emulsion. PFC tissue concentrations were determined for spleen, liver and lung tissues from juvenile pigs ranging in weight from 12 to 15 kg. Typical average values (mmoles FC-43/gram tissue) ranged from 0.23-0.39 for spleen; 0.09-0.13 for liver; and 0.09-0.12 for lung. A description of this spectroscopy based quantitation technique will be presented. F-19 MRS is a specific, rapid, and accurate method for measurement of PFC tissue concentrations.

Animals↗
PubMed1992

MIRD Pamphlet No. 14: a dynamic urinary bladder model for radiation dose calculations.

The constant-volume urinary bladder model in the standard MIRD phantom has recognized limitations. Various investigators have developed detailed models incorporating more physiologically realistic features such as expanding bladder contents and residual volume, and variable urinary input rate, initial volume and first void time. We have reviewed these published models and have developed a new model incorporating these factors. The model consists of a spherical source with variable volume to simulate the bladder contents and a wall represented by a spherical shell of constant volume. The wall thickness varies as the source expands or contracts. The model provides for variable urine entry rate (three different hydration states), initial bladder contents volume, residual volume and first void time. The voiding schedule includes an extended nighttime gap during which the urine entry rate is reduced to one-half the daytime rate. Radiation dose estimates have been calculated for the bladder wall surface (including photon and electron components) and at several depths in the wall (electron component) for [18F]FDG, 99mTc-DTPA, 99mTc-HEDP, [99mTc]pertechnetate 99mTc-RBCs, 99mTc-glucoheptonate, 99mTc-MAG3, [123I]/[124I]/[131I]OIH and sodium [131I]iodide(Nal). The initial bladder volume and first void time that provide the lowest radiation dose to the bladder wall are determined separately for each compound to give guidance for establishing dose reduction protocols.

Algorithms↗
PubMed1992

Radioiodine-131 therapy for well-differentiated thyroid cancer--a quantitative radiation dosimetric approach: outcome and validation in 85 patients.

For almost five decades, 131I treatment of thyroid cancer has been based empirically on administered activity rather than on actual radiation doses delivered. In 1983, we defined radiation dose thresholds for successful treatment. This report is concerned with the subsequent validation of those thresholds in 85 patients. The successful ablation of thyroid remnants occurred after a single initial 131I administration in 84% of inpatients and in 79% of outpatients when treatment was standardized to a radiation dose of at least 30,000 cGy (rad). Administered activities low enough to permit outpatient therapy could be used in 47% of the patients. Lymph node metastases were treated successfully in 74% of patients with a single administration of 131I calculated to deliver at least 8,500 cGy (rad). For athyrotic patients with nodal metastases only, success was achieved in 86% of patients at tumor doses of at least 14,000 cGy (rad). These success rates are equal to or better than those reported with empiric methods of 131I administration. The individualized treatment planning selectively allocates hospitalization and higher exposures to 131I to those patients who require them.

Adenocarcinoma↗
PubMed1991

Effect of varying salt and urea permeabilities along descending limbs of Henle in a model of the renal medullary urine concentrating mechanism.

Modelling studies have played an important role in research on the mechanism of urine concentration and dilution by the medulla of the kidney ever since Hargitay and Kuhn (1951, Z. Elektrochem. 55, 539-558) first proposed that the parallel tubular structures in the kidney medulla must function as a "countercurrent multiplication" system. Present-day models, in keeping with our considerably improved understanding of most aspects of medullary structure-function relationships, have evolved into rather sophisticated systems of parallel tubes. In spite of this increasing complexity, it has remained the case that "model medullas" do not concentrate as well as the real kidney, especially in the inner medulla where only passive, diffusional transport occurs. Inasmuch as these models take into account the majority of contemporary ideas making up our global hypothesis about the functioning of this system, their failure to behave physiologically indicates that our understanding remains incomplete. The purpose of the present modelling study was to evaluate the implications of some recent measurements showing that permeabilities of NaCl (Ps) and urea (Pu) vary along the length of the descending thin limbs of Henle (Imai et al., 1988, Am. J. Physiol. 254, F323-F328), rather than being constant throughout this segment as had been assumed earlier. It was hoped that these newly measured values might explain, by a passive, diffusional process, the net solute addition at the bend of Henle's loop observed under some circumstances and heretofore attributed (though without any supporting experimental evidence) to active transport into the descending limb. The results of the present study show that whereas incorporation of the new values for Ps and Pu in the descending limbs of short nephrons does indeed improve the concentrating power of the model, these new values are nonetheless not sufficient to allow the model to build an osmolarity gradient that increases all the way through the inner medulla. This failing, which is common to virtually all modelling studies to date using measured values from rat kidneys, probably points to a key role for preferential exchange supposed by some to exist among certain tubule segments within vascular bundles in species whose kidneys have the highest concentrating power.

Animals↗
PubMed1991

A simple method for fixation of mandibular fractures.

A useful but underused technique of mandibular fixation is described. Its main advantages over more traditional techniques are that it is easily and rapidly applied, suitable for both children and adults, and generally well tolerated. The method can be employed where only a few teeth are present and in displaced fractures together with an intraosseous buccal plate wire. It is a method that can be recommended for use in nonmaxillofacial units and in areas where only basic equipment and facilities are available.

Bone Wires↗
PubMed1991

Magnetic resonance imaging of rat brain following in vivo disruption of the cerebral vasculature.

Intravenous administration of hyperosmotic mannitol into rats produced a disruption of the blood-brain barrier (BBB). This was visualized by T1 weighted magnetic resonance (MR) imaging following intravenous administration of the MR contrast agent gadolinium diethylenetriamine pentaacetic acid (Gd-DTPA). Following administration of the Gd-DTPA there was an increase in signal intensity corresponding to the cerebral cortex. There was also an increase in signal intensity in features corresponding to the lateral ventricles. However, there was no increase in signal intensity within the striatum indicating that the vasculature within the striatum was resistant to disruption by the hyperosmotic mannitol. The tumors formed by C-6 glioma cells were isointense with rat brain on precontrast MR images. Following intravenous administration of Gd-DTPA, in a representative rat, the tumor was visualized as areas of high signal intensity. There was no enhancement of normal brain by Gd-DTPA. Thus, the tumor had different vascular properties than the host brain with respect to permeability of the contrast agent. Furthermore, Gd-DTPA did not enter the normal brain via the tumor. Thirty days following unilateral injection of kainic acid (KA: 5 nmol) into rat striatum, the shrinkage of the lesioned striatum and the concomitant enlargement of the lateral ventricles was visible on the precontrast MR images. Following administration of Gd-DTPA, there was no enhancement of any regions of the brain. Therefore, the structural perturbations of the striatum produced by KA lesions were not accompanied by disruption of the BBB. These studies demonstrate that MR imaging represents a useful technique for investigating in vivo the perturbation of the cerebral vasculature in rat models of neuropathologies.

Animals↗
PubMed1991

Software and hardware integration of a microprogrammable state machine for NMR imaging.

We have integrated a commercially available microprogrammable state machine (Tecmag PULSkit) for use as a magnetic resonance pulse programmer. Providing the capability for active research environment imaging protocols, it features timing resolution of 100 nsec, ten 16-bit loop counters, and individually addressable look-up tables. This integration involved hardware and software integration with a VAX 11/750 at several levels. Hardware: Each of the three gradient channels employs three digital-to-analog converters (DACs). An 8-bit, 4-quadrant, multiplying DAC generates the gradient waveform shape. A 12-bit DAC generates the multiplying DAC scaling voltage, controlling gradient amplitude and sign. A third 12-bit DAC produces a gradient offset (shim) voltage. An eddy current compensation network is present for each gradient channel. Software: The software design philosophy was to create a flexible interface (interactive window environment), while not constraining complex manipulation of the hardware (direct use of the pulse-sequence compiler primitives and microprogramming). The software levels include (a) pulse-sequence microprogramming, (b) pulse-sequence compiler, (c) interactive parameter specification, and (d) canned pulse-sequence microcode library.

Computer Systems↗
PubMed1991

Isolation and characterization of a tomato Acid phosphatase complementary DNA associated with nematode resistance.

The tomato (Lycopersicon esculentum) acid phosphatase-1 (Apase-1(1), EC 3.1.3.2) isozyme variant, genetically linked to the root-knot nematode resistance locus (Mi) on chromosome 6, has been purified by a rapid procedure from tomato cell suspension cultures. Peptide fragments of the purified enzyme were generated from trypsin and Lys-C endoprotease digests and separated by reverse-phase high-performance liquid chromatography. Amino acid sequences derived from the purified peptide fragments represented >50% of the total amino acid content of the protein and enabled the construction of degenerate oligonucleotide probes that were used to screen a tomato cell culture complementary DNA library. Clones corresponding to full-length coding sequences for Apase-1 have been isolated and sequenced. Southern blot analysis of DNA isolated from a number of tomato cultivars shows that the Apase-1(1) gene (aps1) is present at one copy per genome and that genotypes containing the aps1(1) allele have restriction fragment length polymorphisms that distinguish them from cultivars having the aps1(+) allele. Segregation analysis demonstrates that the restriction fragment length polymorphisms are associated with the aps1 locus. Tomato Apase-1(1) is also found to have significant homology at the amino acid sequence level to a class of vegetative storage proteins characterized in soybean.

Journal Article↗
PubMed1991

Rhenium-186(Sn)HEDP for treatment of painful osseous metastases: results of a double-blind crossover comparison with placebo.

Rhenium-186 (tin) hydroxyethylidene diphosphonate (HEDP) is a new radiopharmaceutical that simultaneously localizes in multiple skeletal metastases in patients with advanced cancer. A single intravenous administration of 30-35 mCi (1110-1295 MBq) is associated with a prompt, significant relief of osseous pain in about 80% of such patients. The efficacy of this new compound was evaluated further by utilizing a double-blind crossover comparison with 99mTc-methylene diphosphonate (MDP) as a radioactive placebo. The new rhenium compound resulted in a significantly (p less than 0.05) greater decrease in pain than did treatment with the radioactive placebo. Rhenium-186(Sn)HEDP appears to be a useful new compound for the palliation of painful skeletal metastases.

Aged↗
PubMed1990

T1 and T2 weighted magnetic resonance imaging of excitotoxin lesions and neural transplants in rat brain in vivo.

On T1- and T2-weighted magnetic resonance (MR) images obtained at 0.14 T the rat brain was visible in the rat head as an area of relative high signal intensity. The enlarged lateral ventricles produced by intrastriatal injections of the excitotoxin kainic acid (KA) were clearly visible as areas of low signal intensity in T1-weighted images but could not be differentiated from normal brain tissue on T2-weighted images for the protocols utilized. Repeated T1-weighted MR images of individual rats demonstrated a progression in the extent of the lesions over an approximately 14-week period following the injection of KA. On the T2-weighted images, areas of relatively high signal intensity corresponding to tissue on the lesioned side of the brain were evident. As the lesion progressed and the remaining tissue visible on the T1-weighted images decreased, the region of high signal intensity visible on the T2-weighted images diminished. This area of high signal intensity on the T2-weighted images appeared to correspond to tissue undergoing a neurodegenerative process. MR images from contiguous slices of brain demonstrated the extent of the KA-induced degeneration throughout the brain, although volume averaging of multiple brain structures was a possible confounding factor. Features apparently corresponding to fetal striatal tissue transplants growing within the enlarged lateral ventricle were visible on T1-weighted images but could not be discriminated on the T2-weighted images. MR imaging is useful for monitoring in vivo the anatomical location and progression of excitotoxin lesions and the location of fetal striatal tissue transplants in lesioned rat brain.

Animals↗
PubMed1990

Effect of short wavelength absorbing filters on Farnsworth-Munsell 100 Hue test and hue identification task performance.

The influence of four short wavelength absorbing filters (yellow filters) on performance of the Farnsworth-Munsell 100-Hue test and three hue identification tasks was assessed in 10 color-normal observers. The yellow filters included the NoIR 40% Amber, Vuarnet No. 4006, Corning CPF 550, and Blu Blocker. A neutral density filter and a no-filter condition served as comparisons. Results showed that the Vaurnet, CPF 550, and Blu Blockers significantly lowered performance on the Farnsworth-Munsell 100-Hue test and the color-dependent tasks below levels obtained in either the neutral-density filter or no-filter conditions.

Adult↗
PubMed1990

Re-186(Sn) HEDP for treatment of painful osseous metastases: initial clinical experience in 20 patients with hormone-resistant prostate cancer.

Rhenium-186(tin) hydroxyethylidene diphosphonate (HEDP) is a new radiopharmaceutical that localizes in areas of osseous metastases in a manner similar to that of standard bone-scanning agents. It also emits beta particles with sufficient energy to be therapeutically useful. A single intravenous injection of about 33 mCi (1,221 MBq) was given to each of 20 elderly patients with advanced skeletal metastases from hormonally resistant prostate cancer. Prompt, significant relief of pain occurred 80% of the time with no significant side effects and only minimal, transient marrow toxicity. Re-186(Sn) HEDP appears to be a useful new agent for the palliation of painful osseous metastases in prostate cancer.

Adenocarcinoma↗
PubMed1989

A magnetic resonance imaging contrast agent differentiates between the vascular properties of fetal striatal tissue transplants and gliomas in rat brain in vivo.

The tumors formed by rat C-6 glioma cells were isointense with the normal rat brain on precontrast T1 weighted magnetic resonance (MR) images. Following i.v. peripheral administration of the MR imaging contrast agent gadolinium (Gd)-DTPA, there was no significant change in the signal intensity from normal brain tissue. However, the tumor appeared as areas of high signal intensity demonstrating the abnormal vascular properties of the tumor. Fetal rat striatal tissue transplanted into unlesioned adult rat striatum appeared isointense with the host brain on precontrast T1 weighted images and there was no evidence for enhancement of the transplanted tissue relative to host brain following i.v. administration of Gd-DTPA. Using this technique we found no evidence with respect to permeability of the contrast agent of an abnormal blood-brain barrier within the striatal transplant in vivo.

Animals↗
PubMed1989

Magnetic resonance imaging of rat brain following kainic acid-induced lesions and fetal striatal tissue transplants.

Use of a small diameter (5.1 cm) radiofrequency coil provided relatively high resolution magnetic resonance (MR) images of rat heads at 0.14 Tesla. On T1-weighted images, the rat brain was clearly visible in the rat head as a region of high signal intensity. No structures were distinguished within the normal rat brain. In contrast, in the brains of rats receiving unilateral kainic acid lesions of the striatum, enlarged lateral ventricles, which are characteristic of the lesion, were clearly visible as dark areas of low signal intensity. Extrastriatal damage on the lesioned side of the brain was also evident in some of the images. Fetal striatal tissue transplants growing within the lesioned striata were also identified in the MR images. The transplanted tissue appeared as areas of high and intermediate signal intensity, similar to the host brain. MR imaging is a useful technique for monitoring excitotoxin lesions of brain and fetal striatal tissue transplants in vivo.

Animals↗