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Biomedical subjects

B H Jones

Publications and source records attributed to B H Jones.

At least 55 records · Page 3Linked to original sources
PubMed1997

Injury among female and male army parachutists.

BACKGROUND: While military parachuting injuries have been well studied, the relationship between gender and risk of injury has not. Injuries among women may be different due to anatomic and physiologic differences, or due to exposure to different jump conditions. Training methods and equipment developed for men may not be as effective in preventing injuries among women. HYPOTHESIS: We hypothesize that the nature and distribution of parachute injuries will vary by gender. METHODS: This descriptive retrospective study used 10 yr of parachute injury data reported to the U.S. Army Safety Center at Fort Rucker, AL, and exposure data obtained from the Defense Manpower Data Center, Monterey, CA. RESULTS: Women appear to jump under less hazardous conditions (jump more often than men in daylight and in static-line, non-tactical environments), yet appear to be at greater risk of serious injury, particularly lower extremity fractures. Injured male parachutists are more likely to experience upper extremity injury. Women's injuries are more likely to be the result of an improper parachute landing fall or parachute malfunction, while men are more likely to be injured due to ground hazards. CONCLUSIONS: There are some provocative gender differences in patterns of injury. Further research is indicated starting with a comprehensive, prospective study, controlling for physical fitness and exposure differences, as well as for potential reporting bias, in order to better understand the apparent differences in reported injuries.

Adult↗
PubMed1996

Comparisons of methods of myocardial hypothermia for cardiac transplantation.

BACKGROUND: Myocardial hypothermia of less than 10 degrees C is an essential component of preservation of donor hearts before implantation. Here we report temperature changes and comparison of methods for maintenance of myocardial hypothermia during implantation. METHODS: Twenty patients were prospectively randomized into two equal groups. In one cohort myocardial hypothermia was maintained by the "Stanford method" of continuous lavage of the pericardium and left atrium with refrigerated saline solution. In the other a cooling jacket was used without saline lavage. Temperatures at multiple sites were measured at 30-second intervals from initiation of cardiac suturing until aortic cross-clamp removal. Comparisons were made between groups at each temperature site. RESULTS: The cooling jacket group temperatures were significantly lower at the left ventricular epicardium and endocardium than those of the Stanford method group. CONCLUSIONS: During cardiac implantation maintenance of myocardial hypothermia with a cooling jacket resulted in significantly deeper and more consistent hypothermia of the left ventricle than pericardial and left atrial lavage with refrigerated saline solution. Blood loss from aspirated saline lavage and perfusate dilution by the saline solution were eliminated.

Adult↗
PubMed1996

Insulin increases lipogenic enzyme activity in human adipocytes in primary culture.

Studies with human adipose tissue have demonstrated the presence of key enzymes of fat synthesis. However, long-term regulation of these enzymes has not been reported. To address this issue, we used human adipocytes in primary culture. Human adipose tissue was obtained from abdominal fat of patients undergoing abdominal surgery. Adipocytes were isolated by collagenase digestion and cultured in media supplemented with 1% fetal bovine serum. To evaluate metabolic activity of cultured cells, we assessed the following during the culture: DNA pattern, cell size, glucose consumption and activities for two lipogenic enzymes, fatty acid synthase (FAS) and glycerol-3-phosphate dehydrogenase (GPDH). Analysis of DNA pattern showed that human adipocytes cultured under the above condition did not undergo cell apoptosis. In addition, no significant change in the cell size occurred during 22 d of culture. Glucose consumption by cultured cells was also constant during the culture and was 60% greater in the presence of 10 nmol/L of insulin. Treatment of cultured human adipocytes with insulin for 3-22 d increased GPDH and FAS activity by 60% and 2.8-fold, respectively, compared to cells cultured without insulin. Furthermore, the increase in FAS activity due to insulin treatment was dose dependent and maximal at 10 nmol/L. Our studies show for the first time that human adipocytes can be maintained viable and metabolically active for 2-3 wk in culture. Interestingly, cultured cells remain responsive to insulin. Therefore, this system will allow further characterization of long-term regulation of lipogenesis in human adipocytes and will be useful for developing pharmacological treatments of obesity.

Adipocytes↗
PubMed1996

Lower limb morphology and risk of overuse injury among male infantry trainees.

The effect of anatomic variation on the risk of overuse injuries has not been adequately evaluated. To determine the association of several common anatomic characteristics (genu varum, genu valgum, genu recurvatum, and lower limb length differences) with risk of overuse injury, we made prospective morphologic measurements of young men prior to beginning 12 week of Army infantry training. The training included frequent running, marching, calisthenics, and other vigorous activities. Lower extremity anatomic landmarks were high-lighted, and front- and side-view photographic slides were taken of the 294 study volunteers. The slides were compute digitized, and the following measures calculated: pelvic width to knee width ratio (to assess genu valgum/varum), quadriceps angle (Q-angle), knee angle at full extension, and lower limb length differences. The cumulative incidence of lower limb overuse injury was 30%. Relative risk of (RR) of overuse injury was significantly higher among participants with the most valgus knees (RR = 1.9). Those with Q-angle of more than 15 degrees had significantly increased risk specifically for stress fractures (RR = 5.4). Anatomic characteristics were associated with several other types of injuries, including pain and nonacute muscle strain due to overuse. This pilot study provides evidence that some lower limb morphologic characteristics may place individuals at increased risk of overuse injuries.

Chi-Square Distribution↗
PubMed1996

Upregulation of adipocyte metabolism by agouti protein: possible paracrine actions in yellow mouse obesity.

Mutations leading to ectopic expression of the murine agouti gene (a) result in progressive obesity. To further characterize this model, we analyzed adipose and hepatic mRNA levels for fatty acid synthase (FAS) and stearoyl-CoA desaturase (SCD), two key enzymes in de novo fatty acid synthesis and desaturation, respectively. FAS and SCD mRNA in both tissues of obese (Avy) mice were dramatically increased relative to lean (ala) controls. Excessive expression of these genes in this model could be due to direct effects of the agouti gene product; to test this possibility we treated 3T3-L1 adipocytes in vitro with recombinant agouti protein. Agouti treatment increased FAS and SCD mRNA levels by 1.5- and 4-fold, respectively. In addition, FAS activity and triglyceride content were 3-fold higher in agoutitreated 3T3-L1 cells relative to controls; these effects were attenuated by simultaneous treatment with a calcium channel blocker (nitrendipine). These data demonstrate that the agouti protein can directly increase lipogenesis in adipocytes and suggest that these effects are mediated through an intracellular calcium-dependent mechanism.

Adipocytes↗
PubMed1996

Adipose tissue stearoyl-CoA desaturase mRNA is increased by obesity and decreased by polyunsaturated fatty acids.

Stearoyl-CoA desaturase (SCD) is a key regulatory enzyme in the synthesis of unsaturated fatty acids. Although regulation of hepatic SCD by obesity and polyunsaturated fatty acids (PUFA) has been well investigated, no studies have addressed whether similar regulation occurs in adipose tissue. We addressed these questions by feeding control (12% corn oil) and high-PUFA (48% corn oil) diets to lean and obese Zucker rats and analyzing SCD mRNA levels in adipose tissue and liver. We report that SCD mRNA content was dramatically elevated in adipose tissue of obese vs. lean rats on both diets and was significantly decreased by PUFA in both genotypes. Interestingly, we demonstrate that SCD expression was directly downregulated in a dose dependent manner by PUFA in 3T3-L1 adipocytes. We conclude that 1) obese Zucker rats overexpress the SCD gene in both liver and adipose tissue and 2) PUFA directly suppress SCD expression in adipocytes. Further studies will elucidate the mechanisms responsible for obesity- and PUFA-mediated regulation of SCD in adipose cells.

Adipocytes↗
PubMed1996

Parachuting injuries among Army Rangers: a prospective survey of an elite airborne battalion.

Injuries are common in sports and military parachuting. This paper presents results of a prospective survey of parachuting injuries in an airborne Ranger battalion. The Ranger regiment is the U.S Army's most elite airborne infantry, prepared for worldwide deployment without advanced notice. Average unit size was 556 Rangers for the 18 months of follow-up. Other variables examined were type of landing area and time of day. During the follow-up period, all injuries occurring in the battalion were documented, as were all airborne operations. During the survey period, 65 airborne operations were conducted (7,948 static-line and free-fall jumps), which caused 163 injuries to Rangers. Fifty-five percent of the operations and jumps were made at night, and 63, 23, and 14% of operations were onto fields, airports, and unimproved airplane landing strips, respectively. All operations were performed in a tactical environment with equipment. The "static-line" injury rate was 2.2%. The types of injuries were similar to those found in previous reports. Dirt landing strips (4.7% injured) and airports (2.3%) appeared to be more hazardous landing areas than fields (1.6%) and water (0%), and more injuries occurred during night operations (2.7%) than during the day (1.4%). Two and one-half times as many severe injuries occurred at night versus day. This type of information is important for combat airborne operations.

Adolescent↗
PubMed1996

Influence of boot-sock systems on frequency and severity of foot blisters.

This study examined the infleunce of three types of boot-sock systems on incidence and severity of foot blisters. Participants were 357 men undergoing U.S. Marine recruit training at Parris Island, South Carolina. Each participant was assigned to one of three treatment groups. The first group wore the standard military boot sock consisting of a wool-cotton-nylon-Spandex combination. The second group wore the standard military boot sock with a thin inner or liner sock consisting of polyester. The third group wore a very thick, dense, prototype outer sock consisting of a wool-polypropylene combination over the same liner sock as the second group. Foot blister incidence was lower among participants who wore the the prototype boot sock and liner than among those wearing the standard military sock (40 vs. 69%, p < 0.001) or among subjects wearing the standard military sock with liner (40 vs. 77%, p < 0.001). Foot blisters and cellulitis severe enough to require medical attention occurred with greater frequency in the standard military sock group compared to both the prototype boot-sock group (24 vs. 11%, p = 0.02) and the standard military sock with liner group (24 vs. 9%, p < 0.01); there was no difference between the latter two groups. Blister reduction was most apparent in the early weeks of recruit training. The standard military sock with a polyester liner reduced the incidence of severe blisters, but the dense sock with the polyester liner reduced the overall incidence of blisters as well as the incidence of severe blisters.

Adult↗
PubMed1995

Does glycemic control affect growth velocity in children with insulin-dependent diabetes mellitus.

To determine the effect of glycemic control on linear growth in children with insulin-dependent diabetes mellitus type 1, we studied 82 patients (40 male, 42 female) over a 6-year period. The mean +/-SD for age of onset and duration of IDDM were 7.3 +/- 3.9 years and 4.8 +/- 3.5 years, respectively. At each clinic visit, glycemic control was assessed by measuring glycosylated hemoglobin (GHb). For a total of 751 clinic visits, the mean +/- SD for chronologic age and GHb were 11.5 +/- 3.8 years and 10.2% +/- 2.3%, respectively. Good glycemic control was correlated with more frequent clinic visits (r= 0.219, P < 0.05). Growth was assessed by determining both weight and height, which were normalized for age and sex by calculating Z scores for weight and height and GHb. Moreover, regression analysis revealed no significant correlation between GHb levels and delta Z for either weight or height. While a significant correlation was observed between delta Z for weight and height (r = 0.30, P < 0.01), the relationship was not affected by glycemic control. Therefore, these data demonstrate that weight gain and growth rate do not seem to be significantly affected by glycemic control. This study also confirms that linear growth velocity is dependent on weight gain and suggests that in type 1 children, weight gain and level of growth-producing hormones such as insulin-like growth factor-1 (IGF-1) are more important regulators of linear growth than glycemic control.

Blood Glucose↗
PubMed1995

Friction blisters. Pathophysiology, prevention and treatment.

Blisters occur frequently, especially in vigorously active populations. Studies using respective rubbing techniques show that blisters result from frictional forces that mechanically separate epidermal cells at level of the stratum spinosum. Hydrostatic pressure causes the area of the separation to fill with a fluid that is similar in composition to plasma but has a lower protein level. About 6 hours after formation of the blister, cells in the blister base begin to take amino acids and nucleosides; at 24 hours, there is high mitotic activity in the basal cells; at 48 and 120 hours, new stratum granulosum and stratum corneum, respectively, can be seen. The magnitude of frictional forces (Ff) and the number of times that an object cycles across the skin determine the probability of blister development - the higher the Ff, the fewer the cycles necessary to produce a blister. Moist skin increases Ff, but very dry or very wet skin necessary to produce a blister. Moist skin increases Ff, but very dry or very wet skin decreases Ff. Blisters are more likely in skin areas that have a thick horny layer held tightly to underlying structures (e.g. palms of the hands or soles of the feet). More vigorous activity and the carrying of heavy loads during locomotion both appear to increase the likelihood of foot blisters. Antiperspirants with emollients and drying powders applied to the foot do not appear to decrease the probability of friction blisters. There is some evidence that foot blister incidence can be reduced by closed cell neoprene insoles. Wearing foot socks composed of acrylic results in fewer foot blisters in runners. A thin polyester sock, combined with a thick wool or polypropylene sock that maintains its bulk when exposed to sweat and compression reduces blister incidence in Marine recruits. Recent exposure of the skin to repeated low intensity Ff results in a number of adaptations including cellular proliferation and epidermal thickening, which may reduce the likelihood of blisters. More well-designed studies are necessary to determine which prevention strategies actually decrease blister probability. Clinical experience suggests draining intact blisters and maintaining the blister roof results in the least patient discomfort and may reduce the possibility of secondary infection. Treating deroofed blisters with hydrocolloid dressings provides pain relief and may allow patients to continue physical activity if necessary. There is no evidence that antibiotics influence blister healing. Clinical trials are needed to determine the efficacy of various blister treatment methods.(ABSTRACT TRUNCATED AT 250 WORDS)

Blister↗
PubMed1994

Ambulatory foot contact monitor to estimate metabolic cost of human locomotion.

The rate of metabolic energy expenditure during locomotion (Mloco) is proportional to body weight (Wb) divided by the time during each stride that a single foot contacts the ground (tc) (Nature Lond. 346: 265-267, 1990). Using this knowledge, we developed an electronic foot contact monitor. Our objective was to derive and cross-validate an equation for estimation Mloco from Wb/tc. Twelve males were tested [age = 19.4 +/- 1.4 (SD) yr, Wb = 78.4 +/- 8.0 kg] during horizontal treadmill walking (0.89, 1.34, and 1.79 m/s) and running (2.46, 2.91, and 3.35 m/s). Measured Mloco was defined as the total rate of energy expenditure, measured by indirect calorimetry, minus the estimated rate of resting energy expenditure. The equation to estimate Mloco was derived in six randomly selected subjects: Mloco = 3.702.(Wb/tc) - 149.6 (r2 = 0.93). Cross-validation in the remaining six subjects showed that estimated and measured Mloco were highly correlated (r2 = 0.97). The average individual error between estimated and measured Mloco was 0% (range -22 to 29%). In conclusion, Mloco can be accurately estimated from Wb and measurements of tc made by an ambulatory foot contact monitor.

Adult↗
PubMed1994

Consistency of visual assessments of arch height among clinicians.

Flat feet and high-arched feet have been cited as risk factors for musculoskeletal injury and functional problems among runners and other active individuals, although there are no established quantitative definitions or measures for assessing either condition. As part of a larger study, four-plane photographs were made of the weight-bearing right foot of 246 young male Army trainees. These photographs were independently evaluated by six clinicians and rated on a scale of clearly flat-footed (category 1) to clearly high arched (category 5). There was much interclinician variability in the assessments, even for extremes of foot type. The probability of a clinician assessing a foot as clearly flat, given that another clinician had rated the foot as clearly flat, ranged from 0.32 to 0.79, with a median probability of 0.57, while for clearly high-arched feet, probabilities ranged from 0.0 to 1.00, with a median of 0.17. These findings demonstrate the need for objective standards and quantitative methods of evaluating foot morphology.

Flatfoot↗
PubMed1994

Exercise, training and injuries.

Although exercise results in a number of well documented physical fitness and health benefits, accruing such benefits entails a risk of exercise-related injuries. Musculoskeletal injuries occur frequently among fitness programme participants, runners, athletes, military recruits and others who engage in routine vigorous exercise. The same parameters of exercise (intensity, duration and frequency) that determine the positive fitness and health effects of physical training also appear to influence the risk of injuries. Studies of runners and other physically active groups have consistently demonstrated that greater duration and frequency of exercise are associated with higher risks of injury. However, the sports medicine literature shows little association between exercise intensity and injuries, a finding which may be misleading. The strongest and most consistent association reported exists between greater total amounts of exercise and higher risks of injury. This is not surprising, since the total amount of exercise is the product of the intensity, duration and frequency of exercise. Recent military research confirms the finding that higher volumes of running are associated with higher rates of injury. Furthermore, the study of army recruits suggests that greater amounts of exercise not only result in greater risks of injury, but in some instances may also impart no additional increase in fitness, a finding consistent with an earlier study of civilian runners. Several military studies also demonstrate that those recruits who have been more physically active in the past are less likely to be injured during basic training. These military studies also document a number of other factors, such as older age, smoking, sedentary jobs and lifestyle, high or low flexibility and high arches of the feet, which may contribute to or modify the risks for exercise-related injuries. In conclusion, the present review suggest that, for activities such as running, specific parameters of exercise may contribute to the overall risk of injuries in rough proportion to their contribution to the total amount of activity performed. Also, better knowledge of the effects of the parameters of training and other factors on the risks of exercise-related injuries is necessary to make more judicious choices about how to best achieve the benefits of exercise and to prevent injuries.

Athletic Injuries↗
PubMed1993

Foot morphologic characteristics and risk of exercise-related injury.

OBJECTIVE: It is widely accepted that persons with flat or high-arched feet are at increased risk of exercise-associated injury, even though this purported association has not been scientifically evaluated. We evaluate the risk of exercise-associated injury among young men with flat, normal, and high-arched feet. DESIGN: A prospective study of 246 US Army Infantry trainees followed up over a rigorous 12-week training program. All subjects were evaluated prior to onset of training. Evaluation included photographs of the right, weight-bearing foot that were digitized and utilized to make several measures of arch height. SETTING: An army initial entry training center. SUBJECTS: All trainees beginning army training on 2 successive weeks were potential volunteers. There were no criteria for exclusion other than declining to participate (n = 3). The subjects were healthy, active young men with a mean age of 20.3 years. OUTCOME MEASURE: The occurrence of a lower-extremity musculoskeletal injury resulting in a visit to and a diagnosis by an army physician or physician assistant. Treating physicians and physician assistants were blind to participation status and were not study staff members. RESULTS: On univariate analysis, there was an association between arch height and risk of injury using several alternative operational definitions of foot type. The 20% with the flattest feet were at the lowest risk (reference group; odds ratio, 1.0), with adjusted odds ratios for any musculoskeletal injury of 3.0 (P < .05) for the middle 60% group and 6.1 (P < .05) for the highest 20% group. CONCLUSIONS: These findings do not support the hypothesis that low-arched individuals are at increased risk of injury, and they have implications for runners, exercise enthusiasts, and clinicians. It may be possible to prevent substantial morbidity among active populations by identifying individuals at high risk and advising alternate activities.

Adolescent↗
PubMed1993

Epidemiology of injuries associated with physical training among young men in the army.

It is widely acknowledged that musculoskeletal injuries occur as a result of vigorous physical activity and exercise, but little quantitative documentation exists on the incidence of or risk factors for these injuries. This study was conducted to assess the incidence, types, and risk factors for training-related injuries among young men undergoing Army infantry basic training. Prior to training we evaluated 303 men (median age 19 yr), utilizing questionnaires and measurements of physical fitness. Subjects were followed over 12 wk of training. Physical training was documented on a daily basis, and injuries were ascertained by review of medical records for every trainee. We performed univariate and multivariate analyses of the data. Cumulative incidence of subjects with one or more lower extremity training-related injury was 37% (80% of all injuries). The most common injuries were muscle strains, sprains, and overuse knee conditions. A number of risk factors were identified, including: older age, smoking, previous injury (sprained ankles), low levels of previous occupational and physical activity, low frequency of running before entry into the Army, flexibility (both high and low), low physical fitness on entry, and unit training (high running mileage).

Adult↗
PubMed1988

Influence of fasting on carbohydrate and fat metabolism during rest and exercise in men.

Metabolic effects of an overnight fast (postabsorptive state, PA) or a 3.5-day fast (fasted state, F) were compared in eight healthy young men at rest and during exercise to exhaustion at 45% maximum O2 uptake. Glucose rate of appearance (Ra) and disappearance (Rd) were calculated from plasma glucose enrichment during a primed, continuous infusion of [6,6-2H]glucose. Serum substrates and insulin levels were measured and glycogen content of the vastus lateralis was determined in biopsies taken before and after exercise. At rest, whole-body glucose flux (determined by the deuterated tracer) and carbohydrate oxidation (determined from respiratory exchange ratio) were lower in F than PA, but muscle glycogen levels were similar. During exercise, glucose flux, whole-body carbohydrate oxidation, and the rate of muscle glycogen utilization were significantly lower during the fast. In the PA state, glucose Ra and Rd increased together throughout exercise. However, in the F state Ra exceeded Rd during the 1st h of exercise, causing an increase in plasma glucose to levels similar to those of the PA state. The increase in glucose flux was markedly less throughout F exercise. Lower carbohydrate utilization in the F state was accompanied by higher circulating fatty acids and ketone bodies, lower plasma insulin levels, and the maintenance of physical performance reflected by similar time to exhaustion.

Adult↗