Communication and mutual resource exchange in north Florida hermit crabs

The patterns of shell exchange in three species of hermit crabs which overlap in distribution and shell use were observed in the laboratory. Crabs showed no tendency to initiate more exchanges with conspecifics as compared with nonconspecific individuals and there were no specific size dominance effects. Lack of common communicatory patterns between Clibararius vittatus and Pagurus pollicaris was correlated with minimal actual exchange, while Pagurus impressus exchanged with both species and executed patterns in common with both. The pattern of shell exchanges and preferences indicated that, in some cases, both individuals may gain in interspecific exchanges.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46904/1/265_2004_Article_BF00569198.pd

Human chondrocyte apoptosis in response to mechanical injury

AbstractObjective The effect of mechanical injury on chondrocyte viability and matrix degradation was studied. It was proposed that mechanical injury to human cartilage explants results in chondrocyte apoptosis with associated loss of glycosaminoglycans.Design Full thickness human cartilage explants, 5mm in diameter were subjected to a single static mechanical stress of 14MPa for 500ms under radially unconfined compression. Glycosaminoglycan (GAG) release and percentage of cells undergoing apoptosis were measured at 96h after injury. To establish the time course of apoptosis, explants were subjected to 30% strain and cultured for varying intervals up to 7 days after injury. A group of loaded explants were also treated with the broad spectrum aspase inhibitor z-Vad.fmk after injury.Results Internucleosomal DNA fragmentation as one indicator of apoptosis was observed in 34% (S.D.±11) of chondrocytes at 96h in response to mechanical loading at 14MPa, compared to 4% (S.D.±2) in the non-loaded explants. Evidence for cell death induction via apoptosis was also obtained by electron microscopy and caspase cleavage of cytokeratin. GAG release was also higher for the loaded explants, mean 1.9% (S.D.±0.14) of total GAG content, compared to control explants, mean 0.8% (S.D.±0.28). The percentage of apoptotic cells also correlated with the level of GAG release into the culture media. The percentage of apoptotic chondrocytes demonstrated a progressive increase from 6h to 7 days post-injury. When loaded explants were cultured in z-Vad.fmk after injury, a 50% reduction in apoptosis rates was seen.Conclusions These results demonstrate that mechanical injury induces chondrocyte apoptosis and release of GAG from the matrix. The time course suggests that a therapeutic window may exist where apoptosis could be inhibited. This potentially identifies a new approach to chondroprotection

Patient-Controlled Analgesia Versus Conventional Intramuscular Injection: A Cost Effectiveness Analysis

Background. In previous studies comparing patient-controlled-analgesia and intramuscular pain management have been unable to provide conclusive evidence of the benefits of either method of postoperative pain control. Aim. The purpose of the study was to compare the efficacy and cost-effectiveness of intravenous patient-controlled-analgesia with intermittent intramuscular morphine for Chinese women in the first 24 hours following elective gynaecological surgery. Methods. A randomized control design was used. The main outcomes were level of pain and cost for the two types of pain management. Participants indicated their level of pain at rest and when deep breathing or coughing on a 100 mm Visual Analogue Scale, on seven occasions within 24 postoperative hours. Costs for the two types of pain management were based on the costs of equipment, drugs and nursing time. Results. A total of 125 women participated in the study. Mean pain level over the 24 hours in the patient-controlled-analgesia group was significantly lower than in the intramuscular group (P < 0•001). Mean pain level over the seven occasions for the patient-controlled-analgesia group was 11•83 points (95% CI 7•1416•52) lower when at rest and 11•73 points (95% CI 5•9617•50) lower during motion than the intramuscular group. Cost per patient was $81•10 (Hong Kong) higher for patient-controlled-analgesia than for intramuscular pain management. Women in the patient-controlled-analgesia group had significantly greater satisfaction with pain management than those in the intramuscular group (P < 0•001), but reported significantly more episodes of nausea (P < 0•05). Conclusions. While patient-controlled-analgesia was more costly, it was also more effective than conventional on-demand intramuscular opioid injections after laparotomy for gynaecological surgery