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Biomedical subjects

D W Sims

Publications and source records attributed to D W Sims.

8 recordsLinked to original sources
PubMed2005

Shifts in a fish's resource holding power during a contact paired interaction: the influence of a copper-contaminated diet in rainbow trout.

The influence of sublethal chronic dietary copper (Cu) exposure on the dominant-subordinate relationship between pairs of juvenile rainbow trout (Oncorhynchus mykiss) was examined. Fish were fed either a normal (11 mg Cu kg(-1) food) or Cu-contaminated (721 mg Cu kg(-1) food) diet for 8 wk. Paired interactions were observed--control versus control, Cu-exposed versus Cu-exposed, and control versus Cu-exposed fish--using a computer-aided video tracking system to measure duration of interactions, total distance moved, and the number of encounters during each contest. In concurrence with game theory, each interaction became escalated with a lesser size disparity between contestants. However, in Cu-exposed versus Cu-exposed fish interactions, the dominant-subordinate relationship was decided sooner and with less aggression than a control versus control fish interaction with fish of a similar relative body mass disparity. During control versus Cu-exposed fish interactions, control fish would normally dominate interactions (12 out of 16 bouts) unless the Cu-exposed fish had a 15% body mass advantage. Muscle glycogen and lactate levels after each contest reflected the duration of bouts and winners of the contests, irrespective of Cu exposure. We conclude that Cu-contaminated fish are less able to compete and have lower resource holding power than controls and will withdraw from a contest at a lower level of interaction, unless a size advantage in the Cu-exposed fish increases the probability of winning.

Analysis of Variance↗
PubMed2003

Shark skin: a function in feeding.

Dermal denticles are unique tooth-like structures embedded in the skin of sharks and rays that protect them from predators and ectoparasites, reduce mechanical abrasion and possibly minimize swimming-induced drag. Here, we show that juvenile lesser spotted dogfish (Scyliorhinus canicula) also use this body armour to anchor food items near their tail so that bite-sized pieces can be torn away by rapid jaw and head movements. This scale-rasp behaviour is novel among fishes and suggests a new role for skin in the feeding ecology of sharks. Scale rasping may be important ecologically because it could function to increase the dietary breadth and growth potential of juveniles.

Animals↗
PubMed2001

Timing of squid migration reflects North Atlantic climate variability.

The environmental and biotic conditions affecting fisheries for cephalopods are only partially understood. A problem central to this is how climate change may influence population movements by altering the availability of thermal resources. In this study we investigate the links between climate and sea-temperature changes and squid arrival time off southwestern England over a 20-year period. We show that veined squid (Loligo forbesi) migrate eastward in the English Channel earlier when water in the preceding months is warmer, and that higher temperatures and early arrival correspond with warm (positive) phases of the North Atlantic oscillation (NAO). The timing of squid peak abundance advanced by 120-150 days in the warmest years ('early' years) compared with the coldest ('late' years). Furthermore, sea-bottom temperature was closely linked to the extent of squid movement. Temperature increases over the five months prior to and during the month of peak squid abundance did not differ between early and late years, indicating squid responded to temperature changes independently of time of year. We conclude that the temporal variation in peak abundance of squid seen off Plymouth represents temperature-dependent movement, which is in turn mediated by climatic changes associated with the NAO. Such climate-mediated movement may be a widespread characteristic of cephalopod populations worldwide, and may have implications for future fisheries management because global warming may alter both the timing and location of peak population abundance.

Animal Migration↗
PubMed2000

Annual social behaviour of basking sharks associated with coastal front areas.

Comparatively little is known about reproductive behaviour in wild sharks as it has proved extremely difficult to study, especially in large pelagic sharks. Here we describe annual courtship-like behaviour in the second-largest fish species, the basking shark (Cetorhinus maximus), from 25 separate episodes observed and tracked during a five-year study period (1995-1999) off south-west England. Social behaviours observed between paired, or three or four, sharks were consistent with courtship behaviours seen in other shark species, namely nose-to-tail following, close following, close flank approach, parallel and echelon swimming. Mature individuals between 5 and 8 m total body length (L(T)) exhibited these behaviours whereas smaller sharks (3-4 m L(T)) did not. Lead individuals were identified as female on a number of occasions and interactions were prolonged; the longest continuous observation of socializing was 1.8 h, although intermittent track data indicates bouts may last for up to 5-6 h. Locations of courtship-like behaviour events were not distributed randomly and were significantly associated with thermal fronts. Our results indicate that putative courtship behaviour occurs between May and July along oceanographic fronts, probably as a consequence of individuals aggregating to forage in rich prey patches before initiating courtship. Thus, locating the richest prey patches along fronts may be important for basking sharks to find mates as well as food in the pelagic ecosystem. As courtship-like behaviours occur annually off south-west England we speculate that this region may represent an annual breeding area for this protected species, but mating itself probably takes place at depth as it was not seen at the surface.

Animals↗
PubMed1989

Urban trauma: a chronic recurrent disease.

Urban trauma, often presumed to be an acute episodic event, may actually be a chronic recurrent disease related to the lifestyle, environment, and other factors of its victims. To test this idea an attempt was made to obtain 5-year followup for 501 consecutive survivors of violent trauma seen at one hospital, 1980-1981. Followup information for these patients was obtained from medical records at four local Level I trauma centers, death certificates, Medical Examiner's records, and police crime computer files. Of the 501 patients, 263 had medical followup including 148 patients with one trauma and 115 patients with recurrent trauma. Of these 263 patients, 200 (76%) were unemployed and 164 (62%) abused alcohol or drugs. From 1982-1987 142 out of 263 patients were involved in 133 crimes and 52 died. These data suggest that urban trauma is a chronic disease with a recurrent rate of 44% and a 5-year mortality rate of 20%.

Adolescent↗
PubMedDate not supplied

Pre-operative ultrasonography guiding minimal, selective surgical approach in primary hyperparathyroidism.

BACKGROUND: The traditional surgical approach for the treatment of primary hyperparathyroidism (HPT) has been routine bilateral surgical exploration. Our aim was to evaluate pre-operative ultrasonography (U/S) in altering our practice to selective unilateral neck exploration. PATIENTS AND METHODS: A retrospective study was conducted involving 53 patients who had parathyroidectomy over a 5-year period (1989-1994), 41 of whom with the diagnosis of HPT had pre-operative neck U/S. RESULTS: Thirty-eight patients had a single adenoma, one had parathyroid cancer, and two had multiple adenomas. Thirty-six of 41 (88%) patients were true positives, two (5%) false positives, two (5%) false negatives and one (2%) was true negative. Based on the surgeon's personal preference and U/S results, 21/41 (51%) of patients had bilateral and 20/41 (49%) had unilateral neck exploration. All the 41 patients had resolution of the hypercalcemia postoperatively. Eighteen of 38 (47%) patients with a single adenoma had bilateral neck exploration and only in two patients was this necessary. CONCLUSIONS: Patients undergoing parathyroid surgery for HPT should have preoperative U/S and, if a single enlarged parathyroid gland is found, unilateral U/S guided neck exploration is safe and economical. In all the other patients, bilateral exploration is the preferred approach.

Adenoma↗