Biomedical subjects

W A Williams

Publications and source records attributed to W A Williams.

At least 19 recordsLinked to original sources

PubMed2004

Resrad-recycle: a computer model for analyzing radiation exposures resulting from recycling radioactively contaminated scrap metals or reusing radioactively surface-contaminated materials and equipment.

RESRAD-RECYCLE is a computer code designed by Argonne National Laboratory (ANL) to be used in making decisions about the disposition of radioactively contaminated materials and scrap metals. It implements a pathway analysis methodology to evaluate potential radiation exposures resulting from the recycling of contaminated scrap metals and the reuse of surface-contaminated materials and equipment. For modeling purposes, it divides the entire metal recycling process into six steps: (1) scrap delivery, (2) scrap melting, (3) ingot delivery, (4) product fabrication, (5) product distribution, and (6) use of finished product. RESRAD-RECYCLE considers the reuse of surface-contaminated materials in their original forms. It contains representative exposure scenarios for each recycling step and the reuse process; users can also specify scenarios if desired. The model calculates individual and collective population doses for workers involved in the recycling process and for the public using the finished products. The results are then used to derive clearance levels for the contaminated materials on the basis of input dose restrictions. The model accounts for radiological decay and ingrowth, dilution and partitioning during melting, and distribution of refined metal in the various finished products, as well as the varying densities and geometries of the radiation sources during the recycling process. A complete material balance in terms of mass and radioactivity during the recycling process can also be implemented. In an international validation study, the radiation doses calculated by RESRAD-RECYCLE were shown to agree fairly well with actual measurement data.

Body Burden↗

PubMed2000

The suitability of [11C]-alpha-methyl-L-tryptophan as a tracer for serotonin synthesis: studies with dual administration of [11C] and [14C] labeled tracer.

The tracer [11C]-alpha-methyl-L-tryptophan (alphaMTP) has been used to measure brain serotonin synthesis rates with positron emission tomography (PET). To address questions about the accuracy of the kinetic model, [14C]alphaMTP was used to directly measure conversion to [14C]-alpha-methyl-serotonin (alphaM5HT) in monkeys that had been previously studied with PET and [11C]alphaMTP. Four male, fasted, isoflurane-anesthetized rhesus monkeys were studied with [11C]alphaMTP and PET. Immediately after the initial 3-hour scan, a second dose of [11C]alphaMTP was coinjected with 1 mCi of [14C]alphaMTP, and additional PET data were collected. Approximately 90 minutes after the second alphaMTP administration, the animals were killed with an overdose of phenobarbital, and brain samples from 21 regions were taken and analyzed by HPLC. Minimal conversion of alphaMTP to alphaM5HT occurred; HPLC analysis of 14C radioactivity showed that greater than 96% of the total counts were in fractions corresponding to the alphaMTP peak. Brain concentrations of serotonin, tryptophan, 5-hydroxyindole-3-acetic acid, and alphaMTP also were determined fluorometrically using external quantification. Patlak plots generated from PET images acquired over 3 hours showed no time period of linear increase, and final slopes were not significantly different from zero, consistent with the finding of minimal conversion to [14C]alphaM5HT. These data indicate that in the 3-hour period after injection, [11C]alphaMTP is acting predominantly as a tracer of tryptophan uptake, not serotonin synthesis.

Animals↗

PubMed1999

A new member of the endonuclease III family of DNA repair enzymes that removes methylated purines from DNA.

DNA is constantly exposed to endogenous andexogenous alkylating agents that can modify its bases,resulting in mutagenesis in the absence of DNA repair [1,2]. Alkylation damage is removed by the action of DNA glycosylases, which initiate the base excision repair pathway and protect the sequence information of the genome [3-5]. We have identified a new class of methylpurine DNA glycosylase, designated MpgII, that is a member of the endonuclease III family of DNA repair enzymes. We expressed and purified MpgII from Thermotoga maritima and found that the enzyme releases both 7-methylguanine and 3-methyladenine from DNA. We cloned the MpgII genes from T. maritima and from Aquifex aeolicus and found that both genes could restore methylmethanesulfonate (MMS) resistance to Escherichia coli alkA tagA double mutants, which are deficient in the repair of alkylated bases. Analogous genes are found in other Bacteria and Archaea and appear to be the only genes coding for methylpurine DNA glycosylase activity in these organisms. MpgII is the fifth member of the endonuclease III family of DNA repair enzymes, suggesting that the endonuclease III protein scaffold has been modified during evolution to recognize and repair a variety of DNA damage.

Amino Acid Sequence↗

PubMed1999

Effects of acute tryptophan depletion on plasma and cerebrospinal fluid tryptophan and 5-hydroxyindoleacetic acid in normal volunteers.

Brain serotonin synthesis and metabolism (turnover), as indicated by CSF concentrations of 5-hydroxyindoleacetic acid (5-HIAA), may depend on plasma concentrations of the essential amino acid L-tryptophan (TRP). We investigated the biochemical effects of acute plasma TRP depletion (ATD) in normal volunteers undergoing a 36-h CSF collection via lumbar drain. Six subjects who were in good health were put on a low-TRP diet (160 mg/day) 24 h before lumbar puncture; this diet was continued for the first 22 h of the CSF collection. At hour 22, subjects ingested a TRP-deficient 15-amino acid drink shown previously to deplete plasma TRP. Total plasma TRP, free plasma TRP, and CSF TRP subsequently decreased 86.3, 86.5, and 92.3%, respectively. CSF 5-HIAA decreased by 32.8%. Plasma total and free TRP concentrations were both decreased at approximately 2 h following ingestion of the TRP-free amino acid drink and were lowest approximately 6 h after ATD; CSF TRP and 5-HIAA were decreased at 2.5 h and approximately 4 h after ATD, respectively. CSF TRP was lowest 8.0 h later. CSF 5-HIAA continued to decrease 14 h after the TRP-deficient amino acid drink was given.

Adult↗

PubMed1997

A phylogenetic analysis of aerobic polychlorinated biphenyl-degrading bacteria.

Several bacterial isolates were characterized based on their abilities to degrade specific polychlorinated biphenyls (PCBs) and their 16S rRNA gene sequences. The members of one group of bacteria consisting of Alcaligenes species, including the PCB-degrading bacterium Alcaligenes eutrophus H850, had strong abilities to degrade a broad range of PCBs but not the di-para-chlorine-substituted congeners. The members of another group, which included the PCB-degrading bacterium originally classified as Corynebacterium sp. strain MB1, had strong abilities to degrade di-para-chlorine-substituted PCBs. These bacteria were most likely different members of Rhodococcus species.

DNA, Bacterial↗

PubMed1996

Changes in mood and hormone levels after rapid-rate transcranial magnetic stimulation (rTMS) of the prefrontal cortex.

Rapid-rate transcranial magnetic stimulation (rTMS) was administered to 10 healthy volunteers on different days over the right or left prefrontal cortex, midfrontal cortex, occipital cortex, or cerebellum. Mood (self-rated), reaction time, and hormone levels were serially measured. Consistent with a previous study, comparison of hemispheres revealed significant associations with decreased happiness after left prefrontal rTMS and decreased sadness after right prefrontal rTMS. Stimulation of all three prefrontal regions, but not the occipital or cerebellar regions, was associated with increases in serum thyroid-stimulating hormone. There was no effect on serum prolactin. rTMS applied to prefrontal cortex is safe and well tolerated and produces regionally and laterally specific changes in mood and neuroendocrine measures in healthy adults. rTMS is a promising tool for investigating prefrontal cortex functions.

Adult↗

PubMed1996

Response-dependent prechoice effects on foraging-related choice.

Three experiments explored the influence of prechoice events on pigeons' preference. In two of three studies, a fixed-interval 200-second prechoice period preceded the initial links of a concurrent chain in which outcomes differed either (a) in terms of the delay to food or (b) in terms of amount of food and delay to food. In Experiment 3, the prechoice period preceded the initial links that provided a choice between a small single food presentation and two identical, more delayed food presentations. In all three cases, obtained choice proportions did not vary as a function of prechoice duration. These results suggest that a local-contextual view adequately describes the foraging context; they also have implications for the appropriate formulation of the delay-reduction theory of conditioned reinforcement and rate-maximizing views of optimal foraging theory.

Journal Article↗

PubMed1995

Daily repetitive transcranial magnetic stimulation (rTMS) improves mood in depression.

Converging evidence points to hypofunction of the left prefrontal cortex in depression. Repetitive transcranial magnetic stimulation (rTMS) activates neurons near the surface of the brain. We questioned whether daily left prefrontal rTMS might improve mood in depressed subjects and report a pilot study of such treatment in six highly medication-resistant depressed inpatients. Depression scores significantly improved for the group as a whole (Hamilton Depression Scores decreased from 23.8 +/- 4.2 (s.d.) at baseline to 17.5 +/- 8.4 after treatment; t = 3.03, 5DF, p = 0.02, two-tailed paired t-test). Two subjects showed robust mood improvement which occurred progressively over the course of several weeks. In one subject, depression symptoms completely remitted for the first time in 3 years. Daily left prefrontal rTMS appears to be safe, well tolerated and may alleviate depression.

Affect↗

PubMed1994

Delay reduction and optimal foraging: variable-ratio search in a foraging analogue.

The present study investigated conditions under which the conditioned reinforcement principles of delay-reduction theory and views based on simple maximization of reinforcement rate make ordinally opposing predictions with respect to foraging-related choice behavior. The use of variable-ratio schedules in the choice phase also represents an extension of delay-reduction theory to schedules that may better mimic the effort involved in searching. Pigeons responded on modified concurrent-chains schedules in which equal variable-ratio schedules led to unequal variable-interval outcomes and unequal reinforcer amounts. All 4 subjects completed a minimum of two replications of conditions for which the predictions of delay-reduction theory and a simple rate-maximizing theory were opposed. Results were consistent with delay reduction's ordinal predictions in 11 of 11 replications of the divergent predictions favoring the smaller, more immediate alternative. The predictions of rate maximization were upheld only when they were consistent with those of delay reduction. Results are discussed in terms of conditioned reinforcement, sensitivity to reductions in delay to food, and possible rules of thumb that may be useful in characterizing foraging.

Animals↗

PubMed1992

Management of an outbreak of Norwegian scabies.

An outbreak of Norwegian scabies in a 170-bed acute care hospital was controlled through an organized plan for delivering treatment to those affected: four patients, 50 staff members, and 14 family members of staff members. Health departments in two counties were notified and found four additional cases in the long-term care facility at which the index patient lived. Contact isolation was used for the index patient and any other patients with nosocomial scabies. Staff members infested with Sarcoptes scabiei were released from work until they had been treated with lindane. Staff members who had been in contact with infested persons and staff members' families were treated prophylactically with lindane. This aggressive treatment plan resulted in rapid resolution of the outbreak.

Cross Infection↗

PubMed1991

Choice and conditioned reinforcement.

A potential weakness of one formulation of delay-reduction theory is its failure to include a term for rate of conditioned reinforcement, that is, the rate at which the terminal-link stimuli occur in concurrent-chains schedules. The present studies assessed whether or not rate of conditioned reinforcement has an independent effect upon choice. Pigeons responded on either modified concurrent-chains schedules or on comparable concurrent-tandem schedules. The initial link was shortened on only one of two concurrent-chains schedules and on only one of two corresponding concurrent-tandem schedules. This manipulation increased rate of conditioned reinforcement sharply in the chain but not in the tandem schedule. According to a formulation of delay-reduction theory, when the outcomes chosen (the terminal links) are equal, as in Experiment 1, choice should depend only on rate of primary reinforcement; thus, choice should be equivalent for the tandem and chain schedules despite a large difference in rate of conditioned reinforcement. When the outcomes chosen are unequal, however, as in Experiment 2, choice should depend upon both rate of primary reinforcement and relative signaled delay reduction; thus, larger preferences should occur in the chain than in the tandem schedules. These predictions were confirmed, suggesting that increasing the rate of conditioned reinforcement on concurrent-chains schedules may have no independent effect on choice.

Animals↗

PubMed1988

Pneumocystis carinii pneumonia complicated by lymphadenopathy and pneumothorax.

A case of generalized Pneumocystis carinii infection presented as hilar and mediastinal lymphadenopathy and was complicated by spontaneous pneumothorax. Extrapulmonary P carinii infection in patients with acquired immunodeficiency syndrome is rare, and pneumothorax is even rarer. The purpose of this report is to call attention to these atypical features of P carinii infection in patients with the acquired immunodeficiency syndrome.

AIDS-Related Complex↗

PubMed1986

A survey of the California Alliance for the Mentally Ill.

Family groups are becoming increasingly active in providing support to family members and in mental health advocacy. The authors report the results of a survey that assessed the concerns of members of the California Alliance for the Mentally Ill and the treatment history of disabled family members. The 199 respondents were typically the parents of a schizophrenic son between the ages of 24 and 34 whose illness was first noticed in the late teens and for whom assistance had been sought for at least a decade. The respondents indicated that medication, family support, socialization centers, community residential treatment, and locked facilities had most helped the family member to improve. The most important additional needs were housing, vocational, and social opportunities and research.

Adult↗

PubMed1984

Self-survey of family organization.

A self-survey was undertaken among 512 members of the California Alliance for the Mentally Ill (CAMI), a statewide family support organization. The typical CAMI member is the parent of a mentally disabled son or daughter who has been ill for an average of 13 years with multiple hospitalizations and therapists. The employment record of the disabled individuals was poor; more than two-thirds had been involuntarily committed at some time, and half had been in jail. Family members see the most serious unmet need to be social rehabilitation housing with planned programs.

Adaptation, Psychological↗

PubMed1982

Superficial thrombophlebitis of lower limbs.

In the absence of malignancy, thrombophlebitis of the lower limb is invariably associated with pre-existent varicose veins. Not until pulmonary embolism was reported to occur in superficial phlebitis did the clinician introduce anticoagulants and/or surgery in the management of this condition. In an effort to reach an effective approach to this problem, 1,000 consecutive cases of varicose veins of the lower limbs were reviewed. Of these patients, 779 were admitted for elective vein ligation and stripping and 221 presented with thrombophlebitis. The latter group was subdivided into four categories according to the mode of management: (1) local heat and anti-inflammatory agents, 60 cases; (2) anticoagulants, 22 cases; (3) phlebotomy, high saphenous ligation and anticoagulation, 4 cases; and (4) ligation and stripping, 135 cases. In category 4 the saphenous is removed in a routine fashion together wih all its tributaries. All perforators are exposed, evacuated of thrombus when present, and ligated subfascially. Thrombi were encountered in one or more perforating veins in 10 patients, but no pulmonary embolism was observed in this group of patients. All instances of documented pulmonary embolism (10 cases) occurred in category 1 with one fatality. The incidence of pulmonary embolism in the elective group of ligation and stripping (without phlebitis) was 0.5%. The data indicate that the surgical approach is safe and preferable to the other modalities for several reasons: (1) It eliminates the varicosities and the phlebitic process simultaneously, (2) a single hospitalization is necessary (cost effectiveness), and (3) no anticoagulants are needed. If, for any reason, surgery cannot be undertaken, then anticoagulants should be employed in an effort to avoid thromboembolism.

Adolescent↗

PubMed1979

Exposure of field workers to organophosphorus insecticides: sweet corn and peaches.

Plasma and red blood cell cholinesterase levels of professional agricultural workers engaged in packing sweet corn and thinning peaches were monitored. Workers with extensive contact with mechanically harvested sweet corn (the corn had been treated one or two days before harvest with a combination of ethyl and methyl parathion) exhibited significant depression of cholinesterase. Gloves, worn by 40% of the workers, provided some protection from absorption of pesticide residues. No significant cholinesterase depression was found in workers thinning peaches which had been previously treated with parathion.

Adult↗

PubMed1979

Exposure of field workers to organophosphorus insecticides: cotton.

The red blood cell and plasma cholinesterase (ChE) levels of cotton scouts inspecting foliage for insect infestation and damage were monitored. Group means for ChE activity were significantly depressed at one or more time(s) during four of the eight growing seasons studied. Although no symptoms of organophosphate poisoning were confirmed, several scouts exhibited ChE depressions over 50% of pre-exposure levels.

Agricultural Workers' Diseases↗

PubMed1977

Pediatric pesticide poisonings in North Carolina: epidemiologic observations.

In four years, 218 pesticide exposures were reported among North Carolina children. Epidemiologic follow-up revealed 50 symptomatic cases with nine fatalities. Mean age of exposed children was 27 months; boys were involved twice as frequently as girls. Agents most often implicated were anticoagulant rodenticides (17%) and organophosphate insecticides (16%). Sixty-eight percent of exposures were to products intended for household use. Special characteristics of pesticides that contribute to morbidity include exceptional toxicity, dermal penetration, and frequent application as food baits. Exposure histories indicate that high petroleum distillate content often adds to product toxicity.

Child↗