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Biomedical subjects

A G Williams

Publications and source records attributed to A G Williams.

At least 91 records · Page 5Linked to original sources
PubMed1985

Butyrate formation from glucose by the rumen protozoon Dasytricha ruminantium.

Production of butyrate by the holotrich protozoon Dasytricha ruminantium involves the enzymes of glycolysis, pyruvate:ferredoxin oxidoreductase, acetyl-CoA:acetyl-CoA C-acetyltransferase, 3-hydroxybutyryl-CoA dehydrogenase, 3-hydroxyacyl-CoA hydro-lyase, 3-hydroxyacyl-CoA reductase, phosphate butyryltransferase and butyrate kinase. Subcellular fractionation by differential and density-gradient centrifugation on sucrose gradients indicated that all those enzymes except pyruvate:ferredoxin oxidoreductase were non-sedimentable at 6 X 10(6) g-min. Butyrate kinase and phosphate butyryltransferase were associated with the large- and small-granule fractions. Thus, although metabolic reactions necessary for butyrate production proceed predominantly in the cytosol, hydrogenosomes play a key role in the conversion of pyruvate into acetyl-CoA.

Animals↗
PubMed1985

The insensitivity of 99mTc pertechnetate imaging for Kaposi's sarcoma.

A total of 13 technetium 99m (99mTc) pertechnetate image studies were performed on 7 patients with a histologic diagnosis of Kaposi's sarcoma. Five patients with peripheral edema had diffusely increased radionuclide activity in the same areas. The two patients without edema had normal radionuclide images. The primary cutaneous lesions were only identified in one of the patients. These findings suggest that previously reported "occult metastasis" are probably due to peripheral edema in most patients; therefore, the radionuclide study has a much lower sensitivity than has been previously reported.

Aged↗
PubMed1985

Thyroid radiation absorbed dose from diagnostic procedures in U.S. population.

According to a 1981 survey of thyroid imaging methods in the United States, radionuclide thyroid scans and uptake studies increased 250%-300% between 1966 and 1981, while the U.S. population increased only 17%. Collective absorbed dose decreased from 18 X 10(6) rad (18 X 10(4) Gy) in 1966 to 13.9 X 10(6) rad (13.9 X 10(4) Gy) in 1981. The decrease was due to the use of iodine 123 and technetium 99m pertechnetate rather than iodine 131 (I-131 was used for 100% of scans and uptake studies in 1966 and 10% and 54%, respectively, in 1981) and also to fewer free-standing thyroid uptake studies (150,000 in 1966 and 33,000 in 1981). Even with reduced usage, I-131 still accounted for 93% of the collective absorbed dose in 1981. If I-131 were eliminated from diagnostic procedures, the annual absorbed dose would decrease to 1.4 X 10(6) rad (1.4 X 10(4) Gy). The number of radiation-induced cancer cases would also be reduced.

Humans↗
PubMed1985

Trends and utilization of nuclear medicine in the United States: 1972-1982.

In the decade 1972-1982, in vivo nuclear medicine procedures in the United States increased from 3.3 million to about 7.5 million per annum. This growth has been the result of a markedly increased frequency in some types of examinations; particularly bone, liver, lung, and cardiovascular imaging. The only type of imaging in which a decrease in frequency has been observed has been in radionuclide brain imaging. Examination of these trends illustrates the difficulty in forecasting, even over time periods as short as 5 years. Competing tests have largely replaced radionuclide imaging in some areas; although in other areas, such as cardiac nuclear medicine, competing technologies appear to have been additive in terms of the frequency of examinations. Comparison with recent data from other countries indicates that the frequency of nuclear medicine procedures in the United States is probably the highest in the world.

Biliary Tract Diseases↗
PubMed1984

Radionuclide thyroid studies: a survey of practice in the United States in 1981. Special report.

A survey was conducted to determine the radiopharmaceuticals and radionuclide imaging methods used for thyroid studies in the U.S. in 1981. The final sample, made up of 299 hospitals, was taken from a random sample consisting of 10% (337) of U.S. hospitals performing nuclear medicine studies. The survey showed that over one half of thyroid scans were obtained with Tc-99m pertechnetate and over one half of uptake studies were performed with I-131. Uptake determinations accompanied 78% of scans. Only 8% of the uptake studies were performed without scans. I-123 was more commonly used on the west coast and in the northeast, and there was interest in a more readily available and less expensive supply of I-123. Thyroid studies accounted for 6.7% of all nuclear imaging procedures. Approximately 7,760,000 nuclear medicine imaging procedures were performed in the U.S. in 1981.

Hospitals↗
PubMed1983

Hydrogenosomes in a mixed isolate of Isotricha prostoma and Isotricha intestinalis from ovine rumen contents.

1. Both Isotricha intestinalis and I. prostoma possess microbody-like organelles, with a highly granular appearance. 2. These organelles, which are sedimentable at 10(5) g-min, bear no morphological similarity to mitochondria, but are enzymatically similar to organelles possessed by certain other anaerobic protozoa and termed hydrogenosomes. 3. The hydrogenosomes isolated from a preparation of mixed isotrichs bear a closer similarity to those isolated from the other rumen holotrich. Dasytricha ruminantium, than those recently identified in a mixed entodiniomorph preparation, or the trichomonads, in that the enzyme malate dehydrogenase (decarboxylating) is non-sedimentable and phosphoacetyl transferase together with acetate kinase are involved in the transformation of acetyl CoA to acetate. 4. The results enable a scheme of acetate, CO2 and H2 formation from carbohydrates to be proposed and extends the number of protozoa known to possess this organelle.

Animals↗
PubMed1983

Ascites causing a false-positive radionuclide liver image.

False-positive radionuclide liver images can occur due to impingement on the liver by adjacent normal anatomic structures or adjacent pathologic masses or fluid collections. A patient with ascites in the anterior subphrenic space had an apparent "cold" lesion in the left lobe of the liver. Ultrasonography demonstrated a normal left lobe and localized the fluid collection.

Ascites↗
PubMed1983

Sulfur colloid distribution in normal hips.

The normal distribution of Tc-99m sulfur colloid is described in 100 patients with no clinical or radiographic evidence of hip disorders. Two-thirds of the patients had uptake in the femoral neck and some uptake in the femoral head. In the other one-third, no uptake was detected in either femoral head. A high degree of symmetry was noted. Judging both the symmetry and pattern of uptake in both hips is important in evaluating femoral head vasculature after a fracture.

Adolescent↗
PubMed1983

Tc-99m PYP scanning following low voltage electrical injury.

An adolescent boy sustained low voltage electrical injury to his extremities when he inadvertently touched a low tension (440 volts) wire with a metal tube. Early in his hospital course, he was evaluated with Tc-99m pyrophosphate whole body scanning for the extent of his injuries. The scintigraphic findings correlated well with his subsequent clinical course.

Child↗
PubMed1982

Respiration of the rumen ciliate Dasytricha ruminantium Schuberg.

The endogenous respiration of the rumen ciliate Dasytricha ruminantium maintained under an O2 tension of 2kPa (approximately 0.02 atm) was partially inhibited by KCN (40% inhibition) and NaN3 (58% inhibition). The organisms lack cytochromes, and sensitivity of respiration to KCN, NaN3, chloroquine and quercetin suggest that the operation of flavoprotein-iron-sulphur-mediated electron transport. As in Tritrichomonas foetus, hydrogenosomal respiration can be stimulated by the addition of CoA in the presence of 0.025% Triton X-100; stimulation by ADP was not detected. Stimulation of pyruvate-supported O2 uptake by Pi suggests that acetate is produced via acetyl phosphate.

Acetate Kinase↗
PubMed1982

Intraspinal, extradural ependymoma.

Extradural ependymoma is a rare tumor arising most commonly in the soft tissues of the presacral area, less commonly in the soft tissues of the sacrococcygeal region dorsal to the sacrum, and rarely in the extradural portion of the spinal canal. The differential diagnosis varies with the location, but the natural history of the tumor is the same. If the tumor is not completely excised at surgery, it may recur. Distant metastases have been reported. A case of an extradural ependymoma arising within the spinal canal is reported with myelographic and computed tomographic findings at diagnosis and after therapy.

Adult↗
PubMed1982

Oxygen affinities of the hydrogenosome-containing protozoa Tritrichomonas foetus and Dasytricha ruminantium, and two aerobic protozoa, determined by bacterial bioluminescence.

Oxygen-dependent bioluminescence of Photobacterium (Vibrio) fischeri was used to measure oxygen affinities of four protozoa. The aerobic organisms Acanthamoeba castellanii and Tetrahymena pyriformis showed apparent Km values for O2 of 0.42 and 2.43 microM respectively. The aerotolerant anaerobe Tritrichomonas foetus, and the more strictly anaerobic rumen ciliate Dasytricha ruminantium, both of which have hydrogenosomes, respired with apparent Km values of 1.08 and 1.70 microM-O2. We conclude that mitochondrial respiration is not the only process conferring on organisms a high affinity for O2.

Amoeba↗
PubMed1982

Potential complications in myelography: I. Technical considerations.

Scanning electron microscopy demonstrated starch powder contamination on the stylet tip from a spinal needle after it was lightly touched with nonwashed surgical gloves. A sterile solution of Pantopaque was injected through the spinal needle after the stylet was withdrawn and carried particulate contaminants to a 0.2 micrometer millipore filter. Using both scanning electron microscopy and energy dispersive x-ray analysis, particles of various sized (mostly 5-10 microns) and variable compositions, including starch, talc, and other elements, were identified. Also, glass particles from the Pantopaque vial and plastic particles from the plastic syringe and tubing used in drawing up the Pantopaque were seen. These observations indicate that strict attention to proper technique in myelography is essential in order to eliminate potential cerebrospinal fluid contamination.

Arachnoiditis↗