Biomedical subjects

G A Dawson

Publications and source records attributed to G A Dawson.

12 recordsLinked to original sources

PubMed1996

Selenium bioaccumulation and hazards in a fish community affected by coal fly ash effluent.

Bioaccumulation of selenium (Se) in the fish community of Pigeon River/Pigeon Lake, which receives inputs of Se from a coal fly ash disposal facility, was studied to assess potential hazards of Se to fish, wildlife, and humans. Se concentrations in fish from sites receiving seepage and effluents from fly ash disposal ponds were significantly greater than those in fish from upstream, where Se concentrations were near background concentrations. Se concentrations differed among fish species, and interspecific variation was greatest at the most contaminated locations. Differences in Se bioaccumulation among fish species were not consistently associated with differences in trophic status. Although Se concentrations in northern pike were consistently less than those in likely prey species, large yellow perch contained Se concentrations as great as those in spottail shiners, their likely prey. Se bioaccumulation may have been influenced by differences in habitat preferences, as limnetic species generally contained greater Se concentrations than benthic species. Se concentrations in fish from the lower Pigeon River and Pigeon Lake did not exceed lowest observable adverse effect concentrations (LOAECs) for Se in tissues of fish species, but exceeded LOAECs for dietary Se exposure of sensitive species of birds and mammals. Human consumption of moderate quantities of fish from the areas studied should not result in excessive Se intake.

Analysis of Variance↗

PubMed1992

Phenelzine therapy for headache patients with concomitant depression and anxiety.

Eleven patients with refractory chronic daily headache, associated depression, and generalized anxiety were treated with phenelzine. Ten patients (91%) had a greater than or equal to 50% improvement in headache frequency, seven (64%) had a similar degree of improvement in mood and headache intensity or activity level. Orthostatic hypotension was the most common side effect and necessitated discontinuation of therapy in two patients. One patient suffered a hypertensive crisis which was easily managed and caused no permanent sequelae. Based on these preliminary results, we conclude that phenelzine is effective in the treatment of chronic daily headache with associated depression and anxiety, but further investigations are needed to determine if there is selective efficacy of phenelzine for this subgroup of patients.

Adult↗

PubMed1992

Self-administration of parenteral ketorolac tromethamine for head pain.

Sixty-one separate self-injections of ketorolac tromethamine (Toradol) by 16 patients diagnosed with episodic migraine with or without aura were evaluated over a 90-day period for safety, efficacy of pain reduction, and the ability of this therapy program to prevent the necessitation of emergency room acute care. Prior to initiation of treatment, patients were formally instructed on intramuscular injection techniques by a member of our nursing staff. Patients were instructed to call upon the onset of a severe headache interfering with daily functioning and, then, were permitted to proceed with the injection. Headache intensity ratings were collected prior to injection and intermittently for the following twenty-four hours. The results demonstrate safety and efficacy of this form of therapy. A significant percent of ketorolac usages (64%) resulted in a good response and significant reduction in head pain. Twenty-three percent of ketorolac usages resulted in a mild response and only 13% of usages provided no relief. Furthermore, 13% of all usages failed to prevent the necessitation for emergency room treatment. The results are discussed in terms of the impact of self-injection on pain relief and substantial cost-reduction by decreasing emergency room utilization.

Analgesics↗

PubMed1992

Cluster headache following head injury: a case report and review of the literature.

A relation between head trauma and cluster headache is frequently described in the literature. The percentage of cluster patients with a history of head injury is approximately 16.5 when several large studies are reviewed. The present paper reports another case where there is close proximity between head injury and the onset of cluster headache. A review of the literature attempts to document the supposition that there is indeed a causal or precipitous role for head injury in cluster cephalgia pathogenesis.

Adult↗

PubMed1992

Radiation therapy of cancer in prosthetically augmented or reconstructed breasts.

The authors review the literature and report their experience with radiation treatment of 39 prosthetically augmented or reconstructed breasts in 37 patients with primary or recurrent breast cancer. Group 1 consisted of 10 patients (12 primary breast cancers), of whom six had undergone previous breast augmentation and were later treated with lumpectomy and radiation therapy. Four patients were treated with mastectomy, reconstruction, and postoperative irradiation. Local tumor control was achieved in all patients. Excellent or good cosmetic results were achieved in all but two patients. Group 2 consisted of 27 patients with recurrent breast cancer after mastectomy and reconstruction. Local tumor control was achieved in 78% (21 of 27), with a mean duration of 34 months. Excellent or good cosmetic results were achieved in 93% (25 of 27). Patients who develop primary or recurrent breast cancer in prosthetically augmented or reconstructed breasts can be offered radical radiation therapy, with satisfactory tumor control and aesthetic results.

Adult↗

PubMed1985

Brain function and writing with the unaccustomed left hand.

Twenty right-handed subjects were asked to handprint a passage containing all the letters of the alphabet once with each hand. The purpose was to describe the changes a document examiner can expect to find in handprinting done with the unaccustomed left hand and to offer a hypothesis as to why these changes occur. It was found that many of the writers displayed persistent differences between their right- and left-hand writings. It is suggested that these differences were due to both a lack of manual dexterity when writing with the unaccustomed left hand and to the fact that different neurophysiological processes are involved.

Brain↗

PubMed1983

Ribosomal 5S genes in relation to C-value in amphibians.

We have measured the amount of 5S-ribosomal DNA in the genomes of Xenopus laevis, Triturus cristatus carnifex and Ambystoma mexicanum, three species of Amphibians which have widely different C-values. Our best estimate is that these organisms have about 24,000, 32,000 and 61,000 5S-genes per haploid genome respectively. A trend to increasing 5S gene copynumber with increasing C-values in amphibians is apparent, probably linked to the need to supply more ribosomes to the larger cells which are associated with larger genomes, particularly during the critical phases of oogenesis and embryonic cleavage. The correlation between the two is poor however, and whilst C-value may determine a minimum gene copy-number, there appears to be little constraint on exceeding this minimum in some species. Certain problems encountered in measuring gene copy-numbers, i.e. the criterion dependance of such numbers and the effect of having pseudogenes, are highlighted.

Ambystoma↗

PubMed1979

The use of time and space by the Panamanian tamarin, Saguinus oedipus.

Tamarin activity patterns and habitat utilization strategies in the Tropical Dry Forest of the Panama Canal Zone were monitored quantitatively using radio-location telemetry. The daily tamarin activity pattern differed from that of other Neotropical primates in that early morning and late afternoon activity normally did not occur. Total daily activity time averaged 676 +/- 62 min. Sleeping trees, and behaviors associated with their use, were documented. Daily path length averaged 2,061 +/- 402 m. Mean travel distance was 468 +/- 66 m. Approximately one-third of the home range was utilized on a given day. Wet season home ranges for two social groups were 26 and 32 ha in area. Areas of low brush, forest edge, and vine-entangled second growth were heavily used by foraging tamarins. Large shade trees, particularly evergreens, were important as refuges from solar radiation. Open-canopy forest types and areas of grass were avoided. Social groups on resource-stable lowland sites defended territories; those on unstable upland sites used a system of time-space segregation. Upland groups became seminomadic during the dry season. Suitability of home range site may affect social group stability, natality, and infant survivorship.

Animals↗

PubMed1976

Physiologic responses of men 49 to 65 years of age to endurance training.

A study was made of the effects of training for 30 minutes, three days a week for 20 weeks on certain physiologic measures of sedentary men between 49 and 65 years of age. Twenty-two subjects volunteered for the experimental group, and 8 others for the control group. Exercise sessions were conducted on a quarter-mile track and consisted of continuous bouts of walking and jogging. The average daily energy expenditures progressed from 228 to 365 kilocalories between weeks 4 and 20. For the same period, average exercise heart rates (HRs) progressed from 149 beats/minute (83 per cent maximum HR) to 155 beats/minute (91 per cent maximum HR). The experimental group showed significant increases in maximum oxygen intake (VO2 max) from 2.47 to 2.90 liters/minute (18 per cent) and in maximum pulmonary ventilation (VE max) from 105 to 121 liters/minute (BTPS), and decreases in resting HR, diastolic blood pressure, body weight, skinfold fat, and abdominal girth. Serum cholesterol and triglyceride levels and heart volume remained unchanged. The control subjects showed no significant changes. Regression analysis, with use of age as a covariate, showed a small but significant inverse relationship with changes in VO2 max. It was concluded that men of the 49-65 age group respond favorably to endurance exercise and show a magnitude of change similar to that found in previous investigations of similar design with younger subjects.

Age Factors↗

PubMed1976

Reproductive characteristic of free-ranging Panamanian tamarins (Saguinus oedipus geoffroyi).

Field observations on reproductive activity in the Panamanian tamarin (Saguinus oedipus geoffroyi) were made in conjunction with the examination of 131 reproductive tracts collected at regular intervals over one year. Reproductive tract characteristics were compared over seasons. Embryonic and fetal development were also assessed. A distinct birth peak was observed from April to early June. Pregnancies in April and May point to a potential, but unrealized, birth peak in August and September. Despite the tendency toward birth peaks, reproductive activity occurred throughout the year. Reproduction was limited to a single female per social group. The average number of infants born per female was two. Groups inhabiting lowland areas appeared to be more successful in raising young than groups inhabiting upland areas.

Animals↗

PubMed1976

Trypanosome infections in the marmoset (Saguinus geoffroyi) from the Panama Canal Zone.

From August 1973 through May 1974 a total of 148 marmosets (Saguinus geoffroyi) were examined for blood parasites. Parasites were detected in 93.2% of the monkeys. Direct examination of blood revealed 82.4% infected with trypanosomes; Trypanosoma cruzi was seen in 1.3% of the animals examined T. minasense in 52.7% and T. rangeli in 25%. However, the use of several diagnostic tests (direct microscopic examination, hemoculture, xenodiagnosis, and animal inoculation) in 15 marmosets revealed T. cruzi in 40%, T. rangeli in 93% and T. minasense in 87%. The high rate of infection among marmosets suggests that they are important natural hosts of T. cruzi and T. rangeli in the Panama Canal Zone.

Animals↗

PubMedDate not supplied

An evaluation of line quality in photocopied signatures.

Qualified forensic document examiners from Canada, USA, Great Britain and Australia participated in this study. They were sent one photocopied signature, together with a set of original known standards to evaluate the line quality of the photocopied signature and compare these characteristics with the standards. They were asked to assess the photocopies for the presence of tremor, hesitation, pen lifts, patching, blunt initial or terminal strokes, and abrupt changes in direction. The authors compared the assessments with the corresponding original signatures. It was possible to determine which line quality characteristics were the most difficult to detect, which indicia of simulation were concealed and what anomalies were introduced by the photocopying process. Results indicated that line quality characteristics can be identified in average quality photocopies. Furthermore, accurate judgements can be made regarding similarities and differences in line quality when comparing a photocopied signature with original known standards. In a few instances, ink line morphology was problematic when striation patterns and ink gooping were misinterpreted as pen lifts, hesitation and patching on the photocopies.

Copying Processes↗