Erbium-YAG and holmium-YAG laser ablation of bone

Results are presented for the latent heat of ablation of bone using an erbium-YAG laser operating at 2.9m, and a holmium-YAG laser operating at 2.1m. The values are 8.2±1.0 kJ cm^–3 and 18±2.0 kJ cm^–3, respectively. Secondary damage to surrounding tissue is found to extend approximately 5m with the erbium laser and is greatly increased to 80m with significant charring in the case of holmium. These secondary damage zones are much smaller than those produced by the CO₂ laser.     

Development of sun compensation by honeybees: how partially experienced bees estimate the sun's course

Honeybees and some other insects, in learning the sun's course, behave as if they can estimate the sun's position at times of day when they have never seen it, but there are competing ideas about the computational mechanisms underlying this ability. In an approach to this problem, we provided incubator-reared bees with opportunities to fly and see the sun only during the late afternoon. Then, on a cloudy day, we allowed bees to fly for the first time during the morning and early afternoon, and we observed how they oriented their waggle dances to indicate their direction of flight relative to the sun's position. The clouds denied the bees a direct view of celestial orientation cues and thus forced them to estimate the sun's position on the basis of their experience on previous evenings. During the test days, experience-restricted bees behaved during the entire morning as if they expected the sun to be in an approximately stationary position about 180 degrees from the average solar azimuth that they had experienced on previous evenings; then from about local noon onward they used the evening azimuth. This pattern suggests that honeybees are innately informed of the general pattern of solar movement, such that they can generate an internal representation that incorporates spatial and temporal features of the sun's course that they have never directly seen.     

Measuring handicap: the London Handicap Scale, a new outcome measure for chronic disease.

OBJECTIVE--To develop a handicap measurement scale in a self completion questionnaire format, with scale weights allowing quantification of handicap at an interval level of measurement. DESIGN--Adaptation of the International Classification of Impairments, Disabilities and handicaps into a practical questionnaire incorporating the dimensions of handicap mobility, occupation, physical independence, social integration, orientation, and economic self sufficiency and scale weights derived from interviews with a general population sample, with the technique of conjoint analysis. SETTING--Two general practices in different areas of London. SUBJECTS--240 adults aged 55-74 years randomly selected from the practices, 101 (42%) of whom agreed to be interviewed, and 79 (78%) of whom completed the exercise. MAIN MEASURES--Rating of severity of handicap associated with 30 hypothetical health scenarios on a visual analogue scale, from which was derived a matrix of scale weights ("part utilities") relating to different levels of disadvantage on each dimension, with a formula for combining them into an overall handicap score. Severity scores measured directly for five scenarios not used to derive the scale weights were compared with those calculated from the formula to validate the model. RESULTS--The part utilities obtained conformed with the expected hierarchy for each dimension, confirming the validity of the method. The measured severities and those calculated from the formula for the five scenarios used to validate the model agreed closely (Pearson's r = 0.98, p = 0.0009; Kendall's tau = 1.00, p = 0.007). CONCLUSIONS--This interval level handicap measurement scale will be useful in assessing both specific therapies and health services, in clinical trials, in analyses of cost effectiveness, and in assessments of quality assurance.     

Comparison of Chinese and Western rifapentines and improvement of bioavailability by prior taking of various meals

Bioavailability was measured by rifapentine (RPE) serum concentrations and by the urinary ratio between RPE and creatinine, in specimens obtained 4-50 h after 600 mg RPE preceded by food. The bioavailabilities of RPEs manufactured in China and by a Western manufacturer were similar after a standard English breakfast, and serum concentrations were also similar to those obtained in an earlier Italian study following a complex meal. Although absorption of RPE was unsatisfactory after lipid-rich biscuits or shortbread, absorption after egges and toast was excellent and was nearly as good after a fast-food sandwich. The urinary measure of bioavailability at 26 h appeared as efficient as peak serum estimations at 6, 8 and 26 h. Fast-food sandwiches are being taken before RPE in a current clinical trial of Chinese RPE in Hong Kong.     

The infectious complications of anabolic-androgenic steroid injection

One million individuals in the United States alone are estimated to be current or past users of anabolic-androgenic steroids. In the United States fifty-percent of anabolic-androgenic steroid users administer their compounds intramuscularly, and twenty-five percent of adolescent anabolic-androgenic steroid users share needles, placing these young adults at risk for infections related to injection. To examine the medical literature for reports of infections attributable to anabolic-androgenic steroids, we conducted a MEDLINE (1966-1998) and AIDSLINE (1980-1998) world literature review to examine all references that attributed infections to anabolic-androgenic steroid injection. Infections associated with anabolic-androgenic steroid injection include three cases of HIV, one case of hepatitis B, one case of hepatitis C, eight abscesses, and a case of fungal endophthalmitis. No cross-sectional or prospective studies exist that document the risk of infections related to anabolic-androgenic steroid injection. These serious infectious complications of anabolic-androgenic steroid injection may be avoided with education and prevention techniques. Infections occurring in anabolic-androgenic steroid users are not as common as in intravenous drug users.     

Laser-tissue interaction with a high-power 2-microm fiber laser: preliminary studies with soft tissue

BACKGROUND AND OBJECTIVE: Recent developments in fiber laser technology have introduced highly efficient, compact sources with high output beam quality. The first laser-tissue interaction studies with a high-power 2-microm fiber laser were conducted. STUDY DESIGN/MATERIALS AND METHODS: Chicken breast and porcine muscle tissue samples were subjected to continuous wave (cw) irradiation at 800-mW and 5-W output power levels, with spot sizes of approximately 150 microm. After laser irradiation, samples were inspected with an optical microscope and prepared for histologic processing. RESULTS: Evaluation of surface changes in tissue samples indicated an interaction similar in nature to those previously demonstrated with other cw lasers, but with photothermal ablation characteristics typical of strongly absorbed lasers operating in the infrared wavelength region. An ablation velocity of 0.27 mm.sec(-1) in porcine tissue was determined at 800-mW incident power. Histopathologic analysis demonstrated the formation of lesions with minimal damage at boundaries and no evidence of carbonization. CONCLUSIONS: Results indicate that this fiber laser has the potential to fulfill applications in the medical field.     

Alcohol-specific socialization, parenting behaviors and alcohol use by children.

OBJECTIVE: This panel study examined the relations between alcohol-specific socialization by parents (monitoring of alcohol use by children, allowing alcohol use by children at home, communicating against alcohol use and setting rules against alcohol use), general dimensions of parenting behavior (responsiveness and demandingness) and alcohol use by children. METHOD: A sample of 488 fifth-grade children reported their perceptions of alcohol-specific socialization by parents, parental responsiveness and parental demandingness. These variables were used to predict alcohol use when children in the panel were in seventh grade. RESULTS: Nineteen percent of seventh-grade children reported alcohol use in the past 30 days. Logistic regression analyses indicated that, after accounting for children's age, sex, single parent status, prior use of alcohol and exposure to parental modeling of alcohol use, the odds of alcohol use were significantly greater among children who perceived no parental monitoring of alcohol use, who had been allowed by parents to have a drink with alcohol at home and who perceived relatively low levels of parental demandingness. Rules against alcohol use, parental communication against alcohol use and parental responsiveness were unrelated to the study outcome. CONCLUSIONS: Parental monitoring of alcohol use by children, family norms regarding alcohol use by children at home and parental ability to set and enforce behavioral rules merit consideration as factors that should be modified by prevention programs. There is a need, however, for additional research that further examines the relations between exposure to such parenting behaviors during childhood and alcohol use during adolescence.     

How to do it: utilizing risk stratification to evaluate outcomes in adult open-heart operations

The purpose of this study is to demonstrate that by using a proven method of stratifying open-heart operations into levels of predicted mortality, hospitals can closely monitor trends of their open-heart programs and possibly improve the health planning decisions for their institution. A proven method of uniform risk stratification utilizing objective and readily available preoperative patient data was implemented at our institution for a 12 month period (September 1, 1991 through August 31, 1992). A total of 367 patients were included in this study. The patients were categorized into four risk ranges (0 to 4% good risk, 5 to 9% fair risk, 10 to 14% poor risk, and greater than or equal to 15% high risk) indicating a predictive percent probability of operative mortality. The number of patients categorized as either 0 to 4% good risk, 5 to 9% fair risk, 10 to 14% poor risk, and greater than or equal to 15% high risk were 46, 74, 84 and 163, respectively. The patient's average post-operative length of stay in each risk category was 7.6 days, 8.2 days, 10 days, and 12 days, respectively. The patient's average total hospital charges in each risk category were $48,241, $53,531, $60,416 and $75,555, respectively. This information has helped our hospital administration make relevant and objective decisions concerning our open-heart program. Uniform risk stratification (outcomes research) should be incorporated into all adult open-heart surgery programs because it is simple, inexpensive, and can evaluate the outcomes and cost of open-heart surgery.