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Biomedical subjects

G Davies

Publications and source records attributed to G Davies.

At least 253 records · Page 14Linked to original sources
PubMed1986

Pathophysiology of coronary occlusion in acute infarction.

Coronary angiography has proved beyond doubt that complete coronary occlusion is the rule in the very early hours of infarction. The 60% to 80% rate of coronary recanalization after thrombolytic therapy has proved that thrombosis is a major component of the occlusion at the time when the procedure is performed a few hours after the onset of symptoms. However, the trigger for coronary thrombosis and the causes of failure of thrombolytic therapy are still a matter of speculation. The relatively rare occurrence of acute coronary occlusion in the life of an individual with even severe coronary disease can be explained on the basis of the necessity of either extremely powerful isolated stimuli, which only occurs rarely, or the casual simultaneous presence in one coronary arterial segment of multiple unfavorable events, such as plaque fissuring, enhanced reactivity of coronary smooth muscle to constrictor stimuli and displacement of the thrombotic-thrombolytic equilibrium toward thrombosis. Coronary artery constriction possibly caused by vasoconstrictor substances released by thrombus, represents the potential element of a vicious cycle causing persistent coronary occlusion and reocclusion when reflow occurs with thrombolysis.

Anticoagulants↗
PubMed1986

Calcitonin gene-related peptide: a potent dilator of human epicardial coronary arteries.

To investigate the action of calcitonin gene-related peptide (CGRP) on human epicardial coronary arteries, six patients received intracoronary CGRP at doses of 50,100, and 200 ng/min. The effect of CGRP was measured angiographically with a computerized analysis system. A dose-dependent increase in coronary arterial diameter was observed. At the highest dose there were 34%, 7%, 38%, and 40% mean increases in the diameters of the circumflex, proximal, mid, and distal left anterior descending arteries, respectively. No further increase in diameter was found after a subsequent dose of 1 mg intracoronary isosorbide dinitrate. Prior infusion of CGRP did not prevent coronary arterial spasm induced by ergonovine in two patients with variant angina, but a subsequent bolus of CGRP partially relieved the spasm. We propose that CGRP has a role in the regulation of coronary vascular smooth muscle tone.

Angina Pectoris↗
PubMed1986

Local coronary supersensitivity to diverse vasoconstrictive stimuli in patients with variant angina.

It has been shown in different groups of patients with variant angina that coronary spasm can be reproduced by physiologic maneuvers and pharmacologic agents. It is not known, however, to what extent different stimuli can induce spasm in the same patient. To investigate whether coronary arterial spasm results from specific abnormal agonist-receptor interactions or from a local nonspecific coronary supersensitivity to different stimuli, 28 patients with vasospastic angina were submitted to a series of diverse vasoconstrictive stimuli known to provoke coronary spasm. Ergonovine, hyperventilation, handgrip, cold pressor, and exercise-tests, were carried out in all 28 patients. In the last 15 patients histamine was also administered. Spasm was provoked by ergonovine in 96% of patients, by hyperventilation in 54%, by histamine in 47%, by exercise in 46%, and by the cold pressor and handgrip tests in 11% and 7%, respectively. No significant differences were found in the responses to provocative tests of patients with normal coronary arteries or nonsignificant stenoses and those with significant lesions. In the same individual, spasm was induced by at least two vasoconstrictive stimuli, although with a different mechanism of action, in 82% of patients and spasm was induced by three or more stimuli in 39%. Tests were repeated in at least 23 patients and short-term reproducibility paralleled sensitivity. These results suggest that in patients with variant angina, a local nonspecific supersensitivity rather than an abnormal specific agonist-receptor interaction plays a major role in the genesis of coronary arterial spasm.

Adult↗
PubMed1986

Guardianship: Alberta style.

The Alberta model of guardianship places a strong emphasis on least restrictive alternatives for the dependent adult. It is also designed to ensure that the needs, rights, and dignity of the individual are recognized and respected within the caring context. Both guardians and discharge planners must try to achieve these ends by striking a sensitive balance between political direction, societal trends, individual rights, and organizational values and realities. There are still more questions than answers in this area, more issues to be resolved. Guardianship has been well received in Alberta, and is demonstrating that it can and ought to be a key element in the case-planning process.

Adult↗
PubMed1986

Insulin secretion during intravenous glucose tolerance tests in non-insulin-dependent diabetes in the young.

The phasic response of insulin to intravenous glucose was studied in 9 patients with non-insulin-dependent diabetes in the young (NIDDY), with 3-generation transmission of the disease; and 9 age-, weight- and sex-matched reference subjects. Furthermore, 10 non-diabetic siblings of these diabetic patients were submitted to the same test procedure in an attempt to identify a prodrome of impaired glucose tolerance. In comparison to the controls and non-diabetic family members, the diabetics had no first phase insulin release. In addition, the non-diabetic siblings had insulin and glucose responses similar to those of the reference subjects. Therefore, it would appear that there is no prodromal phase in this discrete syndrome of NIDDY.

Adult↗
PubMed1986

Antiplatelet drugs and the incidence of thromboembolic complications of the St. Jude Medical aortic prosthesis in patients with rheumatic heart disease.

The incidence of thromboembolic complications after St Jude Medical aortic valve replacement was evaluated in patients who received antiplatelet drugs alone (aspirin and dipyridamole). This report includes 107 consecutive patients undergoing aortic valve replacement with the St. Jude Medical prosthesis from February, 1980, until December, 1983. There were three perioperative deaths (2.8%). Thirty-seven of these patients received life-time warfarin anticoagulation and therefore were excluded from further analysis. The remaining 67 patients receiving antiplatelet drugs were followed up for 22 +/- 8 months (range 5 to 54 months) with a total observation period of 123 patient-years. Group 1 consisted of 52 patients having single St. Jude Medical aortic valve replacement (mean age 27 +/- 10 years). Group 2 included 15 patients having St. Jude Medical aortic valve replacement with additional mitral valve replacement (mean age 27 +/- 11 years). There were no postoperative embolic events in Group 1, but two St. Jude Medical aortic prostheses became thrombotic (2.1 per 100 patient-years) 19 and 32 months after the operation. Emergency aortic valve replacement was done in one of these patients and aortic thrombectomy in the other. Both patients are alive and doing well. In Group 2, three patients (10 per 100 patients-years) had thrombosis of the St. Jude Medical aortic valve 10, 12, and 30 months after the operation, and two of them required emergency aortic value replacement. One of these patients also had a massive left coronary embolus and could not be weaned from cardiopulmonary bypass. The third patient, who was asymptomatic, was prescribed warfarin anticoagulation and has been well. None of the seven patients in this group with St. Jude Medical aortic and mitral prostheses has had a thromboembolic event. These results indicate that antiplatelet drugs alone are associated with a very low risk of embolism but are insufficient to prevent thrombosis of St. Jude Medical aortic valves, even when the patients have sinus rhythm.

Adolescent↗
PubMed1985

Art, science and mathematics: new approaches to animal health problems in the agricultural industry.

This article is about change; particularly the prospect for change in veterinary research during the last decade and a half of the 20th century. The title encapsulates the idea that veterinary medicine, if it is to be effective, periodically has to change its approach to solving animal health problems; that over the last century we have witnessed one major change, that from veterinary medicine as an art to veterinary medicine as a science, and that we are probably on the brink of another change, moving from a scientific or more correctly an experimental approach to a mathematical or observational approach.

Agriculture↗
PubMed1985

Mechanisms of ischemic cardiac pain and silent myocardial ischemia.

The mechanisms of cardiac ischemic pain remain obscure. It is unknown whether ischemia causes cardiac pain by the release of chemical substances or by mechanical stretching. It is also unknown whether ischemia activates specific nociceptors and pain fibers or mechanoreceptors and chemoreceptors. In patients who have both painful and painless ischemic episodes, a certain minimal duration and severity of ischemia are necessary but insufficient to explain the presence of pain, since very severe ischemia of long duration can be silent. Thus, central transmission of painful stimuli and the pain perception threshold appear to play major roles in determining the presence or absence of pain. The emotional state and psychologic expectations of patients may affect their perception and threshold of pain considerably.

Angina Pectoris↗
PubMed1985

Different susceptibility to myocardial ischemia provoked by hyperventilation and cold pressor test in exertional and variant angina pectoris.

Coronary constriction at the site of atherosclerotic stenoses has been suggested to play an important role in modulating the frequency of symptoms in patients with exertional angina. To investigate whether stimuli triggering coronary constriction have similar effects in patients with exertional and variant angina, responses to hyperventilation (HV) and cold pressor test (CPT) were evaluated. Twenty patients with chronic exertional angina, positive exercise test results and coronary heart disease were compared with 14 patients with variant angina and ST-segment elevation during an ergonovine test. In patients with exertional angina, the CPT produced diagnostic ST-segment depression in 6 of 20 patients (30%) at levels of rate-pressure product much lower than those during the exercise test; all patients had low effort tolerance and severe coronary artery disease. HV produced diagnostic ST-segment depression in only 1 of 20 patients (5%) (p less than 0.05 compared to that with CPT). Conversely, in patients with variant angina, HV produced ST-segment elevation in 11 of 14 patients (78%) and CPT produced elevation in only 2 of 14 (14%) (p less than 0.01). Thus, coronary constriction can provoke myocardial ischemia not only in patients with variant angina but also in some patients with exertional angina. Furthermore, the 2 groups of patients have a different susceptibility to stimuli known to produce coronary constriction.

Adult↗
PubMed1985

Effects of verapamil in preventing early postinfarction angina and reinfarction.

Because verapamil is effective in the treatment of "preinfarction" angina, a single-blind, placebo-controlled trial was performed in 17 patients admitted to the coronary care unit with transmural acute myocardial infarction (AMI) to assess the effects of verapamil on angina and reinfarction after AMI. The study was terminated because results obtained in the initial 17 patients indicated that verapamil is not as effective in treating angina after AMI as it is in angina before AMI and does not prevent reinfarction. Continuous electrocardiographic monitoring during the first 3 days after AMI showed the presence of transient episodes of ST-segment elevation in 4 patients taking verapamil and 4 patients taking placebo. The total number and duration of transient ischemic episodes was similar in the 2 groups (46 vs 41 and 23 +/- 22 vs 17 +/- 15 minutes, respectively). The percentage of transient ischemic episodes accompanied by chest pain was similar in both groups (10%). The ischemic episodes were never preceded by important increases of heart rate. Four patients taking verapamil and 4 taking placebo had reinfarction within the first 10 days after the incident AMI. These findings suggest that the prevailing mechanisms of myocardial ischemia in the immediate post-AMI period could be different from those operating in angina before AMI.

Aged↗
PubMed1985

Severity of asthma in skin test-negative and skin test-positive patients.

The standardized records of 144 asthmatic patients have been analyzed to determine whether the severity of their condition was correlated with the presence or absence of positive intradermal skin test reactions to a panel of seven allergen extracts (dust, feathers, Alternaria, Hormodendrum, mixed tree pollen, mixed grass pollen, and ragweed pollen). The skin tests were totally negative in 71 of the subjects, whereas in 73 subjects there was a strongly positive response to two or more allergens. The skin test-negative patients were older than the skin test-positive ones and had a shorter duration as well as a later onset of asthma. Also, they had lower serum-IgE levels and a lower frequency of a family history of atopic disease. Moreover, the skin test-negative group lost more time from their normal activities, required more visits to their doctor as a result of asthma, and were more frequently treated with oral corticosteroids. They additionally had greater air trapping on pulmonary function tests. However, when the groups were adjusted for the discordance in their age and duration of asthma, they tended to converge in the level of the variables that described the severity of their asthma. Thus the severity of asthma was found to be relatively similar in skin test-negative and skin test-positive patients.

Adult↗
PubMed1985

Tooth loss, attrition and temporomandibular joint changes in a Romano-British population.

Mandibular condyles and temporal fossae were studied in a large Romano-British collection of skulls. The size and shape of the condyles differed from those in previous populations studied. Changes in form or shape of the condyles were age-related and could be correlated to the number of teeth lost on the same side and on the contralateral side. No statistically significant correlations were seen between attrition and condylar form and surface change.

Adolescent↗
PubMed1985

Management of pituitary gigantism. The role of bromocriptine and radiotherapy.

True gigantism with overproduction of growth hormone (GH) and prolactin (PRL) was diagnosed in two boys, aged 13 years (case I) and 7 1/2 years (case II). Both had shown increased growth rates since early childhood (from 4 years and 1 1/2 years, respectively), but no skeletal acromegalic features were noted. However, both showed increased sweating and both had advanced pubic hair relative to testis volume. No other pituitary dysfunction was recorded. Case I underwent transsphenoidal surgery with only incomplete and temporary suppression of GH and PRL levels. However, in both patients bromocriptine administration promptly suppressed PRL levels. Following combined irradiation and bromocriptine treatment, GH also gradually normalized over a period of 2 years. Both boys are still on treatment, and both showed an increase in plasma GH concentrations when the dose of bromocriptine was reduced or discontinued, indicating that even 3 1/2-5 years after irradiation therapy (and during continuous treatment with bromocriptine) the disease was controlled but not cured. However, in these two boys bromocriptine has proved effective in controlling the PRL/GH oversecretion.

Body Height↗
PubMed1985

Longitudinal study of grain elevator and control workers with demonstration of healthy worker effect.

Changes in the respiratory symptoms and pulmonary function of 441 grain elevator workers and a control group of 180 civic workers during a three-year period were compared. The grain handlers who left their jobs during the interval between the first and second surveys were found to have shown a significantly higher prevalence of cough and shortness of breath at the beginning of the study period than those who remained employed; this difference was not observed among the civic workers. The grain and civic workers who were examined on both occasions showed similar longitudinal changes in their symptoms and pulmonary function. Nevertheless, the results of this study are biased by the healthy worker effect among the grain handlers.

Age Factors↗
PubMed1984

Spontaneous dissection of the cervical internal carotid artery.

Five patients with spontaneous dissection of the cervical internal carotid artery (CICA) are reported. The different patterns of clinical and radiological presentation are described and the frequently benign outcome is underlined. The need for diagnostic angiography is emphasized.

Aortic Dissection↗
PubMed1984

General practitioners and the pull of prevention.

Sociologists have often criticised notions of preventive health work advocated by doctors. This work has yielded important insights into victim-blaming and into ways the economic and political causes of ill-health have been mystified or denied. While this analytical strategy remains an important one, it needs extending in at least three directions. First, we must appreciate changes over time in the forms of arguments about preventive work; secondly, we must situate the argument both in terms of developments within the medical profession and in terms of the relationship of the medical profession to the wider society; finally, we need to make sense of the doctors' claims that these ideas are radical/progressive. The paper is based on a recent series of reports on prevention by the Royal College of General Practitioners, and focusses in particular on the one dealing with preventive care for children.

Child↗