The influence of stimulus and background colour on signal visibility in the lizard Anolis cristatellus.

Anoline lizards communicate with visual displays in which they open and close a colourful throat fan called the dewlap. We used a visual fixation reflex as an assay to test the effects of stimulus versus background chromatic and brightness contrast on the probability of detecting a moving coloured (i.e. dewlap-like) stimulus in Anolis cristatellus. The probability of stimulus detection depended on two additive visual-system channels, one responding to brightness contrast and one responding to chromatic contrast, independent of brightness. The brightness channel was influenced only by wavelengths longer than 450nm and probably received input only from middle- and/or long-wavelength photoreceptors. The chromatic contrast channel appeared to receive input from three, or possibly four, different classes of cone in the anoline retina, including one with peak sensitivity in the ultraviolet. We developed a multi-linear regression equation that described most of the results of this study to a reasonable degree of accuracy. In the future, this equation could be used to predict the relative visibility of different-coloured stimuli in different habitat light conditions, which should be very useful for testing hypotheses that attempt to relate habitat light conditions and visual-system response to the evolution of signal design.

Wolf spider predator avoidance tactics and survival in the presence of diet-associated predator cues (Araneae: Lycosidae).

Some prey can distinguish between chemical cues from predators fed different diets. Here we document the first evidence of diet-based chemical discrimination of predators in a terrestrial arthropod and measure the survival value of behavioural responses to predator chemical cues. We tested activity level and avoidance behaviour of the wolf spider, Pardosa milvina, to faeces and silk associated with the predatory wolf spider, Hogna helluo, fed either P. milvina or crickets (Acheta domesticus). We then measured survival of Pardosa in the presence of Hogna when placed on blank paper or paper previously occupied by Hogna fed either crickets or Pardosa. Filter paper previously occupied by Hogna from each diet treatment or a blank control were simultaneously presented to adult female Pardosa among four treatment pairs (N=15/treatment): (1) blank paper/blank paper, (2) Hogna fed crickets/blank, (3) Hogna fed Pardosa /blank and (4) Hogna fed Pardosa / Hogna fed crickets. Cues from Hogna fed either crickets or Pardosa elicited significantly less activity relative to blank controls. Cues from Hogna fed Pardosa elicited a significantly greater reduction in activity than Hogna fed crickets. When given a choice, Pardosa initially chose the blank substrate significantly more often than either substrate with Hogna cues. Spiders survived longer in the presence of cues from either Hogna diet treatment relative to blank paper, but there was no significant effect of predator diet on survival. Results suggest diet-based predator cues elicit different levels of activity in Pardosa that reduce predation in the presence of Hogna. Copyright 2001 The Association for the Study of Animal Behaviour.

Wolf spiders show graded antipredator behavior in the presence of chemical cues from different sized predators.

The wolf spider, Pardosa milvina, displays effective antipredator behavior (reduced activity) in the presence of silk and excreta cues from adults of another cooccurring wolf spider, Hogna helluo. However, Pardosa and Hogna engage in size-structured intraguild predation, where Pardosa may be either the prey or predator of Hogna. We tested the ability of adult female Pardosa to vary antipredator responses toward kairomones produced by Hogna that vary in size. Hogna were maintained on filter paper for 24 hr. We then presented the paper to adult female Pardosa simultaneously paired with a blank sheet of paper. One treatment had two sheets of blank paper to serve as a control. The Hogna stimulus treatments were as follows (N = 15/treatment): (1) 1 Hogna half the mass of Pardosa; (2) 1 Hogna of equal mass of a Pardosa; (3) 1 adult Hogna, 30 times the mass of Pardosa; and (4) 8 Hogna each 0.25 the mass of Pardosa. Pardosa decreased activity in the presence of kairomones from Hogna of equal or larger size, but showed no change in activity in the presence of a blank control or from a single Hogna smaller than itself. Pardosa showed a reduction in activity in the presence of cues from eight small Hogna. Pardosa avoided substrates with adult Hogna cues, but showed no avoidance response to any other treatment. These results suggest that Pardosa is showing graded antipredator behavior relative to the quantity of predator kairomones present rather than directly discriminating among the different sizes of the predator.

Deaths and injuries due to unexploded ordnance (UXO) in northern Lao PDR (Laos).

Xieng Khousang province in Lao PDR (Laos) is one of the most heavily bombed areas on earth due to the secret bombing during the Vietnam war. This study presents the community-based cumulative incidence of injuries related to unexploded ordnance (UXO) after the war. The data were collected by one of the UK based non-governmental organizations, Mines Advisory Group (MAG). Three districts in the province, reported to have the largest UXO load, were studied. Nearly half of the injuries and deaths involved children below age 15. The case-fatality rate was not different among children and adults. Males were significantly more likely to die of UXO injuries than females. We believe that UXO is an important public health problem in Laos for the following reasons: (1) 22 years after the end of the war, an average of one injury still occurs every other day (2) there is a high incidence among children below age 15 (3) the case-fatality rate is high (4) most injuries involve multiple fragments which usually require complex surgical and medical management skills.

Sensitivity to Nd:YAG induced laserthermia is a cell-type-specific feature not directly related to tumorigenic potential or proliferation rate.

BACKGROUND AND OBJECTIVE: Laser-induced hyperthermia, laserthermia, is a promising new method for treating neoplasms. The response of different cell types to conventional hyperthermia varies [Bhuyan, Cancer Res 1979; 39:2277-2284; Raaphorst et al., Cancer Res 1979; 39:396-401]. We investigated the possible relationship between sensitivity to laser treatment and tumorigenic potential of three closely related cell types. Non-tumorigenic cells PYS-2 and differentiated F9S1 were compared to tumorigenic cells F9S1. STUDY DESIGN/MATERIALS AND METHODS: The contact Nd:YAG laser was used in a continuous-wave mode with a power setting of 6W, exposure times were 2 and 4 min [Castrén-Persons et al., Lasers Surg Med 1991; 11:595-600; Castrén-Persons, unpublished data]. The frosted-end probe was placed in the middle of the well and a thermocouple was attached 5 mm from the tip of the probe. The total amount of energy was measured for each well. A 4 min, 44 degrees C water bath treatment was used as comparison. Untreated wells served as controls. May-Grünwald-Giemsa staining and 3H-thymidine labeling were used for the analysis. RESULTS: Laserthermia killed all three cell types significantly more effectively than the water bath. PYS-2 cells were the most sensitive to the laser treatment. At the same temperature, PYS-2 cells were only slightly affected by water bath induced heating; the differentiated F9 cells were the most sensitive to this treatment. During the laser treatments, the energy required for holding the temperature seemed to depend not only on the cell type but also on the amount of cells treated: the more cells in the well, the more energy was needed. CONCLUSION: Our results suggest that laser sensitivity is a cell-type specific feature which is not directly related to the proliferation rate or benign or malignant behavior of the cells.

Percutaneous interstitial laser hyperthermia in clinical use.

Twelve patients were treated with laser-induced hyperthermia. Eight had liver metastases from breast cancer or colorectal cancer, and four were treated for a primary tumour, two in the liver, one in the biliary tract and one in the pancreas. The mean diameter of the metastases was 2.5 cm and of the primary tumours 4 cm. One patient was given ethanol injections before the treatment, and seven were treated with chemotherapy before and two after the treatment. At the time of writing this report, all the patients are still alive. The follow-up times vary from six months to five years. Treatment was technically possible in all cases. The smallest metastasis disappeared totally and, with the exception of a few larger tumours, they were reduced in size. There were no serious complications. The patients were treated percutaneously under ultrasonographic imaging in real time. Only minor side effects were seen, and the method is safe. Technically, laserthermia is easy to perform. A skillful radiologist is needed, and the presence of an anaesthetist makes it possible to safely treat tumours that can be reached only when respiration is controlled mechanically. Controlled, randomized studies are now needed to evaluate the method in comparison with other palliative treatment modalities.

Laser-induced hyperthermia: comparison of two different methods.

The effectiveness of two different techniques of laser-induced hyperthermia was analyzed in healthy piglet livers. Hyperthermia was produced using a continuous-wave Nd:YAG laser with both a contact sapphire probe and a bare quartz fibre. In both methods the tip was inserted into the liver, and the temperature 1 cm from the tip was raised and held between 42 degrees C and 44 degrees C for 600 seconds. Specimens were taken 0, 7 and 14 days after the treatment. The tissue effects of 36 treatment sites were analysed using standard van Gieson's method. In addition, a histochemical method for demonstrating lactate dehydrogenase activity was employed to show damage not observable by routine methods. No statistically significant difference in the extent of the treatment sites at d 0 and after 7 days was seen when comparing the two laser methods. After 2 weeks, the diameter of the lesion with the bare fibre was significantly larger (3,7 mm with both analysing methods) than by using the contact probe (2,6 with LDH demonstration; P < 0.01 and 2.1 mm with van Gieson's staining; P < 0.001). It can be concluded that the simple fibre tip seems more effective in causing tissue necrosis than the sapphire tip.

The impact of a resident-directed survey on the education curriculum of a university surgical training program.

Surgical training programs use various objective and subjective means to evaluate housestaff performance. However it is less clear how to assess the quality of the educational experience the program itself provides. This study examines the use of a resident-directed survey as a means of identifying and rectifying weakness in a surgical training curriculum. Multiple choice questionnaires covering each of 14 senior rotations were prepared by chief residents and distributed to all senior surgical residents in April 1989 (year I). The survey covered factors considered vital to resident education, including operative experience, input into preoperative and postoperative decisions, autonomy, and time demands, and an overall rating (OR) of the educational quality of the rotations. Responses were numerically graded: 1, appropriate; 0, fair; -1, inadequate (or "excessive" for the variable "time demands"). The results, which were presented and discussed at a departmental retreat that spring, prompted specific curriculum changes for the 1989-1990 academic year. An identical survey was conducted the next spring (year II). Major reorganizational changes were made in three of the four negatively rated rotations from year I. The OR for each of the rotations improved dramatically in year II (average increase of 0.64/rotation; p less than 0.05). None of the eight favorably rated rotations in year I suffered a reduction in OR as a result of the changes. Case load, intraoperative involvement, and input in both preoperative and postoperative decisions correlated most frequently with favorable ORs in both years. This study shows that a resident survey is an effective tool for critically assessing the education curriculum of a surgical training program.

Contact Nd:YAG laser potentiates the tumor cell killing effect of hyperthermia.

This study was carried out to investigate the effects of Nd:YAG laser-induced hyperthermia on murine F9 embryonal carcinoma cells in vitro using various power settings, temperatures, and exposure times. F9 cells were plated on gelatin-coated dishes, treated on the following day, and cultured overnight. The following day the killing efficiency of the treatments was estimated by staining the dishes or by labeling the cells with 3H-thymidine. A contact Nd:YAG laser with a frosted-end probe was used. After laser treatments at 39 degrees C, no significant changes were observed in the viability of the cells. Laser treatment at 43 degrees C killed F9 cells, and the effect was related to the power setting used. Using 6 W, the quantity of viable cells progressively decreased after 1-, 2-, and 5-min treatments, and no viable cells were found after a 10-min treatment. Using 10 W, approximately 10% of the cells survived a 1-min laser treatment, but all cells were killed after a 2-min treatment. In the control wells, heated in a water bath for up to 40 min, all cells regularly survived at 43 degrees C. There were much less viable cells in those laser-treated wells where the temperature exceeded 44 degrees C than in those where the temperature was kept at 44 degrees C. In conclusion, the tumoricidic effect of hyperthermia can be potentiated by the use of the contact Nd:YAG laser. At a set temperature the cell killing effect of laser treatment is dependent on the power used and the duration of the treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Cognitive learning during surgical residency. A model for curriculum evaluation.

The program summary of the American Board of Surgery In-Service Training Exam (ABSITE) can be used to quantitate cognitive learning during a surgical residency and to identify areas of curricular weakness in a residency program. Knowledge on each question is categorized as high (known) or low (unknown) depending on the percentage of residents who answered correctly. Knowledge of Level 1 (entry) residents is then compared with Level 5 (exit) residents. Each ABSITE question can thus be categorized on entry versus exit as known-known, unknown-unknown, unknown-known, and known-unknown. Only about half of unknown knowledge on entry appears to become known on exit. Very little knowledge known on entry becomes unknown on exit. Weaknesses in specific subject areas can be readily identified by ranking questions according to the number of exiting residents who answer incorrectly. Use of this technique to quantitate cognitive learning in a residency program may allow objective assessment of changes in curriculum.