Genetic Transformation Among Azotobacter Species

Previous methods for genetic transformation in Azotobacter vinelandii have employed poorly defined genetic markers or crude DNA extracts. An improved transformation technique has been developed for use in Azotobacter. The technique was used to transform several strains of Azotobacter with DNA carrying a defined genetic marker. A method for isolating pure, high molecular weight, biologically active DNA from Azotobacter is also presented. Purity of the extracted DNA was determined by standard chemical assays. The molecular weight was determined by boundary sedimentation techniques to be 18.2 megadaltons. DNA was obtained from several mutant strains of Azotobacter. Biological activity of these samples was demonstrated by using them to accomplish both intra- and interstrain transformation. Thermal denaturation profiles of several DNA samples are presented, from which guanine plus cytosine content was determined. Among the Azotobacter species examined, GC content ranged from 65.1 to 67.8%. The use of the new transformation and DNA isolation methods in taxonomic and mapping studies is discussed

The Effect of Hamstring Contractions in the Activation of the Abdominal Muscles during a Standard Abdominal Crunch

Purpose: The purpose of this study was to determine the effect of a hamstring contraction on the abdominal musculature during a standard crunch. Studies in the past have looked at abdominal and core strengthening, exercise equipment, and exercise techniques and their effect on abdominal electromyography (EMG). Few published studies have looked at the effect on the abdominals during a modified crunch, which is a hamstring contraction during a standard crunch. Methods: Participants (n=30) for this study were between the ages of 18 and 60 with no history of acute or chronic back pain or major abdominal surgery. EMG was used to record the activity of four muscle groups including the: upper rectus abdominus (URA), lower rectus abdominus (LRA), external obliques (EO), and the biceps femoris during a standard crunch and also during a modified crunch. Data analysis compared EMG output to each participant\u27s individual maximal voluntary contraction (MVC) for each muscle group analyzed. Results: There was a significant (p\u3c0.05) increase in the average mean difference in the LRA of + 26.89% and EO of +46.3% in EMG activity during the modified crunch. URA displayed an increase of +2.25%; however, it was not found to be statistically significant. Discussion: In this study there was an increase in abdominal EMG output for the modified crunch; however, other factors that need to be considered include: the effects of gender, age, previous abdominal training, influence of pathologies, and other musculature involvement

A Demographic Approach to Race and Ethnicity in Metropolitan and Non-Metropolitan Regions of Arkansas, 1990 and 1999

This manuscript provides an empirical portrait of emergent trends in the growth, distribution, and racial and ethnic composition of Arkansas’ resident population. Particular attention is given to variation in the racial and ethnic composition of the estimated population among different regions of the state. During the 1990’s, racial and ethnic diversity increased statewide due in large part to Hispanic population growth in all regions. Black population growth was greatest in central Arkansas while Asian and Native American population growth increased most rapidly in the northwest metropolitan regions of the state. Overall, both metropolitan and non-metropolitan Arkansas communities have a more diverse mix of ethnic populations than has been known in the past