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Biomedical subjects

D Macdonald

Publications and source records attributed to D Macdonald.

70 records · Page 4Linked to original sources
PubMed1986

The effects of nicotine upon memory and problem solving performance.

This study examined the effects of 4 mg nicotine and placebo upon problem solving performance in word and number tasks, and subsequent recall and recognition of the answers to these problems. The results demonstrated that the drug had no effect upon the subject's ability to generate the correct answers to the problems, but that immediate and delayed recall and recognition were significantly impaired. These data clearly do not support the view that nicotine, without exception, enhances information processing, and it was suggested that the effects of nicotine upon information retrieval may be specific to tasks which assess episodic memory in the absence of retrieval cues or a problem solving context.

Adolescent↗
PubMed1982

Problems in the management of patients with artificial valves during pregnancy.

During the past 15 years, 12 patients with prosthetic valves were treated during 18 pregnancies in the four Dublin maternity hospitals. These patients were on long-term anticoagulants and their pregnancies were reviewed to assess the problems associated with anticoagulation. One baby had warfarin embryopathy, six pregnancies ended in spontaneous abortions and there were two intrauterine deaths. On the basis of the findings a policy on the most appropriate anticoagulant regimen in such cases was formulated.

Abortion, Spontaneous↗
PubMed1981

Analogues of red and white muscle in squid mantle.

In five species of squid, varying in life-style from fast-swimming pelagic predators to sluggish benthic forms, the circular muscle of the mantle was found to be metabolically and structurally differentiated into inner, middle, and outer zones. In the middle zone, mitochondrial abundance and the ratios of oxidative to glycolytic enzyme activities were low. This zone was sandwiched between thinner bands of muscle lining both the inner and outer edges of the mantle. In these bands, mitochondrial abundance and the ratios of oxidative to glycolytic enzyme activities were high. It is proposed that this metabolic differentiation is analogous to the development of red and white muscles in vertebrates and that it serves a similar function, white muscle mainly supporting burst-type swimming and red muscle sustaining steady-state oxidative work.

Journal Article↗
PubMedDate not supplied

Quantitative prediction of biodegradability, metabolite distribution and toxicity of stable metabolites.

An evaluation of the capability of organic chemicals to mineralize is an important factor to consider when assessing their fate in the environment. Microbial degradation can convert a toxic chemical into an innocuous one, and vice versa, or alter the toxicity of a chemical. Moreover, primary biodegradation can convert chemicals into stable products that can be difficult to mineralize. In this paper, we present some new results obtained on the basis of a recently developed probabilistic approach to modeling biodegradation based on microbial transformation pathways. The metabolic transformations and their hierarchy were calibrated by making use of the ready biodegradability data from the MITI-I test and expert knowledge for the most probable transformation pathways. A model was developed and integrated into an expert software system named CATABOL that is able to predict the probability of biodegradation of organic chemicals directly from their structure. CATABOL simulates the effects of microbial enzyme systems, generates the most plausible transformation pathways, and quantitatively predicts the persistence and toxicity of the biodegradation products. A subset of 300 organic chemicals were selected from Canada's Domestic Substances List and subjected to CATABOL to compare predicted properties of the parent chemicals with their respective first stable metabolite. The results show that most of the stable metabolites have a lower acute toxicity to fish and a lower bioaccumulation potential compared to the parent chemicals. In contrast, the metabolites appear to be generally more estrogenic than the parent chemicals.

Animals↗
PubMedDate not supplied

Restructuring clinical laboratories in Ontario--a '90s revolution.

The results of the first-ever province-wide survey of laboratory restructuring initiatives in Ontario, Canada are presented. These initiatives coincide with the historically largest financial cuts to the publicly funded health-care delivery system in Ontario, Canada's most populous province. The laboratory system includes both public hospital and commercial sectors. A survey was mailed to every laboratory director in the province, with a 73% response rate from the hospital sector. The results show that most hospital laboratories are restructuring, the bed count of the hospital is not a determinant of change, and downsizing and multiskilling of staff are the most frequent strategies. Many hospital laboratories were also considering regional alliances or contracting out part or all of their services. Also, the survey showed that the majority of laboratories in community hospitals did not have Laboratory Information Systems, in contract to the situation in teaching facilities. Most hospitals employed some form of utilization management, with the most popular being education of their users. Many respondents viewed the effect of these changes on staff morale with disquiet and expressed anxiety about the potential adverse effects on quality. In many ways, these findings mirror those reported in the United States.

Clinical Laboratory Information Systems↗