APS August/September journal hot picks

September 21, 2001

Highlights from peer-reviewed journals announced

Children with burn injuries and exercise, cloning a 200-million year old vertebrate for research on newborn liver disease, asthma and allergy sufferers and their bronchial responses, exercise studies on elite athletes, differences among black and white females exercisers, and effective techniques for teaching science are among the current research highlights published by the American Physiological Society (APS)

September 10, 2001 - Bethesda, MD-The American Physiological Society (APS) spotlights recent research findings designed to improve human well being and understanding of human health. The highlights have been selected from three of the l4 peer-reviewed journals the Society publishes each month. On an annual basis, APS publishes more than 3,800 articles. Highlights have been selected from the current editions of the Journal of Applied Physiology, American Journal of Physiology: Gastrointestinal and Liver Physiology, and Advances in Physiological Education, and are listed below.

CHILDREN WITH BURN INJURIES AND EXERCISE
Effects of a 12-Week Resistance Exercise Program on Skeletal Muscle Strength in Children with Burn Injuries


Summary: Post-traumatic response to burn injury leads to significant and prolonged skeletal muscle loss and weakness. Conventional rehabilitation programs do not provide the same benefits as resistance exercise programs.

Methodology: Post-traumatic response to burn injury leads to significant and prolonged skeletal muscle loss and weakness, which persist despite standard rehabilitation programs of occupational and physical therapy. In a study led by Oscar E. Suman, and jointly sponsored by the Shriners Hospitals for Children and The University of Texas Medical Branch, researchers investigated whether a resistance exercise program would attenuate muscle loss and weakness that is typically found in children with thermal injury. The researchers assessed the changes in leg muscle strength and lean body mass in children who suffered from severe burns over more than 40 percent of their total body surface area. The patients were randomly placed in either a 12-week standard hospital physical rehabilitation program -- supplemented with an exercise-training program -- or at a home-based rehabilitation program without exercise. Leg muscle strength was assessed both before and after the rehabilitation or training program at an isokinetic speed of 150 degrees per second. Lean body mass was assessed using dual-energy X-ray absorptiometry.

Conclusion: The researchers found that participation in a resistance exercise program resulted in a significant improvement in muscle strength, power, and lean body mass compared to a standard rehabilitation program without exercise.

Source: Journal of Applied Physiology, September 2001

A BABY STEP FORWARD IN UNDERSTANDING NEWBORN LIVER DISEASE
Cloning of A 200 Million-Year Old Evolutionary Relative May Shed Light on Liver Disease in Newborns


Summary: Bile secretion is a fundamental function of the liver of all vertebrates. The Bile Salt Export Pump (BSEP) is the major thoroughfare for excreting bile salts from the body and is responsible for production of bile flow. Mutations in the human BSEP result in a form of liver disease called progressive intrahepatic cholestasis, or PFIC Type II. PFIC Type II is characterized by persistent neonatal impaired bile flow, aspects of neonatal hepatitis, and subsequent cirrhosis of the liver caused by obstruction or infection. This study presents evidence that the BSEP evolved early in vertebrate evolution and that its functional properties have remained essentially unchanged despite 200 million years of evolution.

Methodology: To determine the evolutionary origin and structure-function relationship of the human BSEP, a full-length clone of a marine skate (Raja erinacea), a 200-million year old vertebrate that shares 68.5 percent of the identity of the human BSEP, was examined. Shi-Ying Cai, Lin Wang, and James L. Boyer of the Yale University School of Medicine, along with Nazzareno Ballatori of the University of Rochester School of Medicine, cloned DNA from a skate liver BSEP (sBSEP). The clone was subjected to Northern blot analysis, and comparisons made in Sf9cells.

Results: The researchers found that the sequences at the site of published mutations in human BSEP were conserved in sBSEP. When two of these mutations were introduced into the sBSEP DNA, a defective expression of the Sf9 cells occurred.

Conclusions: These findings suggest that mutations in human BSEP that result in PFIC-II during infancy might reside in sequences common to sBSEP. Moreover, as 32 percent of the sBSEP sequence is not conserved in human BSEP, and functional studies suggest that sBSEP and mammal BSEPs have identical properties, it is likely that the non-conserved sequences may not be essential for targeting. The possibility that sBSEP is misfolded and prone to degradation is also suggested and a comparative functional genomics approach should be considered.

Source: American Journal of Physiology: Gastrointestinal and Liver Physiology, August 2001

BREATHING DIFFERENCES BETWEEN ASTHMATICS AND ALLERGY SUFFERERS EXPOSED TO ALLERGENS
Do Allergy and Asthma Sufferers Breath Similarly When Exposed to Allergens?


Summary: It has been suggested that asthma and rhinitis (nasal allergy) represent two different combinations of the same disease. An important difference between asthma and rhinitis alone is the fact that a much greater dose of allergen is necessary to cause significant bronchoconstriction in allergy sufferers. This may explain why some individuals with allergies develop asthma symptoms on natural exposure to allergen, whereas others do not. But does allergen exposure provoke the same bronchial response in asthmatic individuals as in allergy sufferers?

Methodology: To answer the question, Emanuele Crimi and his colleagues in the Dipartimenti di Scienze Motorie e Riabilitative di Medicina Interna e di Oncologia Biolgica e Genentica, at the Universita¢ di Genova, Genoa, Italy, examined nine subjects with mild asthma and eight with only rhinitis (allergy). Each individual underwent methacholine challenges. They were also exposed to allergen inhalation challenges, which were preceded and followed by bronchoalveolar lavage and bronchial biopsy.

Results: The response to methacholine was positive in all asthmatic vs. two rhinitic subjects. The response to allergens was positive in all asthmatic vs. five rhinitic subjects. No significant differences between groups were found in airway inflammatory cells or basement membrane thickness either at baseline or after allergen exposure. However, the ability of deep inhalation to dilate methacholine-constricted airways was greater among allergy sufferers than asthmatic individuals, but it progressively reduced in rhinitis during exposure to allergens.

Conclusions: The researchers concluded that the allergy subjects may develop similar airway inflammation and remodeling as do asthmatic subjects. They also conclude that the difference in bronchial response to allergens between asthmatic individuals and allergy sufferers is associated with different airway mechanics.

Source: Journal of Applied Physiology, September 2001

EXERCISE
Evidence of LPL Gene-Exercise Interaction for Body Fat and LPL Activity: The HERITAGE Family Study


Summary: Evidence of a gene-exercise interaction for traits related to body composition is limited. As part of the HERITAGE Family Study, researchers examined the association between the lipoprotein lipase (LPL) S447X polymorphism, and changes in body mass index, fat mass, percent body fat, abdominal visceral fat (measured by computerized topography), and post-heparin plasma LPL activity.

Methodology: Christophe Garene and his colleagues studied 741 adult white and black subjects and their response to 20 weeks of endurance training. The researchers compared changes between carriers and non-carriers of the X447 allele after adjustment for the effects of age and pre-training values.

Results: No evidence of association was observed in men. However, white women carrying the X447 allele exhibited greater reductions of body mass index, fat mass and percent body fat. In black women, the carriers exhibited a greater reduction of abdominal visceral fat and a greater increase in post-heparin LPL activity.

Conclusions: These results suggest that the LPL S447X polymorphism influences the training-induced changes in body fat and post-heparin LPL activity in women but not in men.

Source: Journal of Applied Physiology, August 2001

"Living High-Training Low" Altitude Training Improves Sea-Level Performance In Male and Female Elite Runners

Summary: Acclimatization to moderate high altitude, accompanied by training at low altitude (living high-training low), has been shown to improve sea-level endurance performance in accomplished, but not elite, runners. Whether elite athletes achieve similar performance gains has been unclear.

Methodology: James Stray-Gundersen, Robert F. Chapman, and Benjamin D. Levine studied 14 elite men and 8 elite women before and after 27 days of living at 2,500 meters while performing high-intensity training at 1,250 meters. The altitude sojourn began one week after the USA Track and Field National Championships, when the athletes were close to their season's fitness peak.

Conclusions: One-third of the athletes achieved personal best times for the distance after the altitude training camp. The improvement in running performance was accompanied by a 3 percent improvement in maximal oxygen uptake. Circulating erythropoietin levels were near double initial sea-level values 20 hours after ascent. Soluble transferring receptor levels were significantly elevated on the 19th day at altitude, confirming a stimulation of erythropoiesis. The researchers concluded that four weeks of acclimatization to moderate altitude, accompanied by high-intensity training at low altitude, improves sea-level endurance performance even in elite runners.

Source: Journal of Applied Physiology, September 2001

LH Secretion and Testosterone Concentrations are Blunted After Resistance Exercise in Men

Summary: Researchers have hypothesized that exercise-induced changes in circulating testosterone would be centrally mediated via hypothalamic-pituitary release of luteinizing hormone (LH).

Methodology: In a study of 10 healthy young men, Bradley C. Nindl and colleagues examined overnight LH, total and free testosterone (TT and FT), and cortisol (C) concentrations during two experimental sessions: (1) a control and (2) an acute heavy-resistance exercise bout (50 total sets consisting of squats, bench press, leg press, and latissimus dorsi pull-down). The exercise was performed from 1500 to 1700 hours, and blood samples were taken beginning at 1700 and continuing until 0600 the next morning. Blood was sampled every 10 minutes for LH and every hour for TT, FT, and C.

Conclusions: Overnight post-exercise concentrations were compared with control concentrations; no statistically significant differences were observed for LH half-life, LH pulse frequency, interpulse interval, pulse amplitude, or pulse mass. Significant differences, however, were observed for LH production rate. For the ANOVA marginal main effect means due to condition C was significantly elevated, while TT and FT were significantly decreased for the exercise condition. The researchers concluded that the decline in overnight testosterone concentrations after acute heavy-resistance exercise is accompanied by a blunted LH production rate and elevated C concentrations.

Source: Journal of Applied Physiology, August 2001

TEACHING SCIENCE
Can Students Learn - and Like - Biology? Yes, If....

Summary: As evidenced by national and regional efforts, colleges are striving to improve their performance. One aspect of the effort involves science and the attainment of benchmarks proposed by the American Association for the Advancement of Science. Other efforts are designed to provide an understanding of the "scientific method" and development of scientific habits of mind. A study conducted R. Russell Wilke, Ph.D., at Angelo State University's Department of Biology, and William J. Straits, Ph.D., of the University of Texas at Austin's Science Education Center, investigates "discovery learning" and its effects on students' achievement and attitudes toward instruction in a college-level biology course.

Methodology: The course consisted of two semester-long (15-week) sections of sophomore-level biology, entitled, "Structure and Function of Organisms." Each section was taught by the same instructor, had similar numbers of students (160 each) and used similar exams. The course was primarily lecture-based interspersed with Socratic-type questioning episodes and taught in a large lecture hall. In addition, four "discovery learning" activities were used during the semester. Students' performance on the final exam was evaluated to determine the effectiveness of the discovery instruction on their content acquisition, science process skills, and experimental design capabilities. The exam was subdivided into categories and defined as (1) content learned through traditional lecture methods, (2) content learned through discovery methods, (3) discovery (science) process skills, and (4) experimental design questions. Three experts with advance degrees in biology determined that the questions were of comparable levels of difficulty.

Results: The results indicated that students performed best on those content questions learned through discovery methods and worst on experimental design questions learned through discovery methods.

Conclusion: Results indicate that students had greater achievement on the content they learned through discovery methods compared with lecture-based instruction. Moreover, the findings regarding students' attitudes toward discovery-based instruction suggest that students enjoyed active, discovery-based problems, believed that discovery helped them gain an understanding of the material and helped them to develop skills that could be used in other courses.

Source: Advances in Physiological Education, 25:62-69, 2001
-end-
The American Physiological Society (APS) was founded in 1887 to foster basic and applied science, much of it relating to human health. The Bethesda, MD-based Society has more than 10,000 members and publishes 3,800 articles in its 14 peer-reviewed journals every year.

American Physiological Society

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