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Biomedical subjects

L Chadwick

Publications and source records attributed to L Chadwick.

11 recordsLinked to original sources
PubMed1999

Social inertia in white-throated sparrows results from recognition of opponents.

Social inertia is a term for the stability of dominance relationships despite changes in the intrinsic dominating abilities of opponents. In a standard test for social inertia, low-ranking birds in an established hierarchy receive implants with testosterone (treated) and high-ranking birds receive empty implants (untreated). Social inertia occurs when the treated birds remain subordinate to untreated opponents in these groups, despite evidence that similarly treated birds dominate untreated strangers. In previous demonstrations of social inertia, however, treated and untreated birds were returned to their original aviaries and tested with familiar opponents, and thus the effects of familiarity with the location and those of familiarity with opponents were not separated. To address this issue, we investigated social inertia in 16 groups of white-throated sparrows Zonotrichia albicollis. When low-ranking treated birds were placed in new aviaries with familiar high-ranking, untreated opponents (treatment S, same opponents), dominance relationships showed social inertia. When such birds were placed in new aviaries with unfamiliar opponents (treatment N, new opponents), testosterone influenced dominance. When groups of high-ranking, untreated birds acquainted with each other were placed with unfamiliar treated opponents (treatment G, grouped dominants), 'coat-tail' effects (dominance by association with high-ranking individuals) sometimes outweighed the effects of testosterone. Social inertia in this species is thus a result of familiarity with opponents, rather than familiarity with locations of encounters. Measurements of aggressive tendencies confirmed a previous report that social inertia suppresses activation of aggression by testosterone. White-throated sparrows can thus recognize their opponents, and this ability affects the expression of both dominance and aggression. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed1997

Widespread neuroendocrine malignancy within the central nervous system: a diagnostic conundrum.

A 75 year old female presented with a sellar tumour, and was subsequently found also to have a cauda equina tumour, a parietal dural tumour, a pontine tumour, an intradural spinal tumour, and several vertebral body tumours. Histological examination revealed a neuroendocrine tumour forming cell nests surrounded by reticulin. There was moderate nuclear pleomorphism, prominent mitoses, and focal necrosis. Immunohistochemistry showed diffuse positive staining with cytokeratins, chromogranin and 5-hydroxytryptamine, and focal positive staining with S100. This case is an unusual and ultimately insoluble, diagnostic problem; however, the differential diagnoses include pituitary carcinoma, malignant paraganglioma, and atypical carcinoid.

Aged↗
PubMed1996

Localisation of immunoreactive factor VIII, nitric oxide synthase, substance P, endothelin-1 and 5-hydroxytryptamine in human postmortem middle cerebral artery.

This pre-embedding electron-immunocytochemical study investigated the localisation of endothelial (type III) and neuronal (type I) isoforms of nitric oxide synthase, substance P, endothelin-1 and 5-hydroxytryptamine in the human middle cerebral artery taken up to 40 h postmortem. To ¿recover' from the anoxic period some of the vessels were incubated in oxygenated Krebs solution prior to the immunoprocedure. At this long postmortem time, immunoreactivity to type III and type I nitric oxide synthase, substance P, endothelin-1 and 5-hydroxytryptamine was found in a subpopulation of intact cells present in the vessel intima; immunoreactivity to type I nitric oxide synthase was also observed in a subpopulation of adventitial perivascular nerve fibres. Cultures of the cells from the intima of the postmortem vessels showed that the cells were proliferating and positive immunoreactivity to factor VII identified them as endothelial cells. The results therefore indicate that even after up to 40 h postmortem, endothelium of human middle cerebral artery is immunoreactive for a number of vasoactive agents and perivascular nerve fibres show nitric oxide synthase immunoreactivity.

Aged↗
PubMed1991

Preoperative clinical evaluation as a predictor of cardiac complications after infrarenal aortic reconstruction.

This paper analyses cardiac risk factors in 93 consecutive patients undergoing elective infrarenal aortic reconstruction over a 2 year period. During the perioperative or postoperative period, 26 patients sustained a total of 42 cardiac complications. Eight patients had myocardial infarction, 14 left ventricular failure and 15 arrhythmias. There were five cardiac-related deaths. Angina was the only statistically significant risk factor in predicting postoperative cardiac problems. A multivariate analysis identified a high-risk group of patients in whom cardiac complications after operation were common.

Age Factors↗
PubMed1991

General surgery with a special interest in vascular surgery: is the tail starting to wag the dog?

Most general surgeons are expected to develop an interest in a surgical specialty in addition to their general surgical workload. Over a 2-year period we have prospectively analysed the type of patient admitted to a general surgical unit with a special interest in vascular surgery. Half of the admissions were emergencies, over which we had no control. Of the elective admissions, there was a steady increase in the proportion of patients with a vascular diagnosis. This was due to increasing numbers of arterial reconstructions and interventional radiological procedures being undertaken. As cutbacks are made in the numbers of available beds and operating sessions, the increasing number of patients requiring admission for the management of arterial disease can only be achieved at the cost of patients awaiting routine general surgical procedures.

England↗
PubMed1991

General surgery with a special interest in vascular surgery: an audit of relative workload.

In a district general hospital (DGH) almost all vascular surgery is provided by general surgeons with a vascular interest and training. There is a growing view, however, that vascular surgeons should be 'pure' to the exclusion of other surgery. In an attempt to define the relationship between general and vascular work in a DGH we have analysed, prospectively, out-patient, in-patient and theatre workload over a three-month period. Eight-hundred-and-forty-four patients (277 new, 567 follow-up) were seen in the clinics. Nine per cent of new vascular referrals and 33 per cent of new general referrals were booked for admission. There were 356 admissions (50 per cent 'emergencies') representing a wide spectrum of general surgery. Elective and emergency vascular cases stayed in hospital for twice and four times longer, respectively, than general patients. Vascular patients represented 26 per cent of the caseload but accounted for 46 per cent of the bed occupancy. Vascular operations made up only 21 per cent of the total theatre caseload (233 procedures) but consumed 34 per cent of theatre time. The vascular unit in a DGH deals with a substantial number and wide variety of general surgical cases. Vascular surgery, however, consumes disproportionately large amounts of out-patient and theatre time and hospital beds. This has implications both for the planning of vascular services and also for the resource allocation within the hospital.

Aged↗
PubMed1989

Accident and emergency abusers.

Inappropriate attendances at Accident and Emergency departments is a problem affecting all such services around the UK. Different approaches have been and are being tried. We report the results of a detailed study of this subject and discuss the main cause of the abuse of this facility.

Accidents↗