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Biomedical subjects

J R Hoffman

Publications and source records attributed to J R Hoffman.

At least 55 records · Page 3Linked to original sources
PubMed1999

Thrombospondin expression in nerve regeneration I. Comparison of sciatic nerve crush, transection, and long-term denervation.

Patterns of expression of the extracellular matrix molecule thrombospondin (TSP) were examined during peripheral nerve regeneration following sciatic nerve crush or transection. In noninjured nerve, was present in the axoplasm, Schwann cells, endoneurium, and perineurium of the adult mouse sciatic nerve. Following nerve crush or nerve transection, levels of TSP rapidly increased distal to the trauma site. Elevated levels of TSP were present distal to regenerating axons, while expression gradually returned to normal proximal to the regenerating axons. When reinnervation was blocked, TSP levels remained high in the endoneurium in excess of 30 days, but TSP was absent by 60 days. Following reanastomosis of the proximal and distal segments after 60 days of denervation, TSP was re-expressed in the distal nerve stump. These results indicate that TSP, which is involved in neuronal migrations in the embryo and neurite outgrowth in vitro, appears to play a role in axonal regeneration in the adult peripheral nervous system.

Animals↗
PubMed1999

Thrombospondin expression in nerve regeneration II. Comparison of optic nerve crush in the mouse and goldfish.

Expression of the extracellular matrix molecule thrombospondin (TSP) was examined following retrobulbar crush injury of the goldfish and mouse optic nerve. TSP was present within the glia limitans and surrounding axon fascicles of the control normal goldfish optic nerve, but was absent from the normal mouse optic nerve. Following crush injury of the goldfish optic nerve, TSP expression increased dramatically along the path of regenerating axons and returned to near normal levels following axonal outgrowth. In contrast, during the unsuccessful attempt at regeneration following crush injury of the mouse optic nerve, TSP expression was present only in glial fibrillary acidic protein (GFAP)-negative, macrophage-rich regions distal to ganglion cell axons. These results indicate that TSP expression is increased in a temporal pattern along the path of regenerating goldfish optic nerve axons and therefore may be involved in successful central nervous system regeneration. The absence of TSP in the environment encountered by damaged mouse optic nerve axons may correlate with the lack of regeneration observed in the mouse optic nerve.

Animals↗
PubMed1999

Impact of patient acuity on preference for information and autonomy in decision making.

OBJECTIVES: To test the hypotheses that ED patients' desires for medical information and for autonomy in decision making are inversely related to increasing acuity of illness, increasing age, and lower level of formal education. METHODS: The authors conducted a prospective study of ED patients who presented for care during seven nonconsecutive 24-hour periods. Of 804 patients approached, 665 completed a questionnaire that was administered by a trained research assistant. Patients rated their desire for medical information, and for participation in medical decision making, on two 10-cm visual analog scales. Patient acuity level was determined in routine fashion by trained triage nurses, who were unaware of the nature of this study. RESULTS: Desire for information was uniformly high, and did not vary statistically between triage groups (p = 0.41). The most acutely ill patients (level I) were more likely to be excluded by the research interviewer (p < 0.001). Of included level I patients, desire to participate was not decreased (p < 0.01). Higher level of formal education (p = 0.036) and younger age (p < 0.001) were associated with greater desire for autonomy in decision making. CONCLUSION: Among ED patients able to participate, higher acuity of illness was not associated with a decreased desire for medical information. Many very acutely ill patients preferred autonomy in medical decision making. Older patients and those with less formal education expressed a lesser desire for decision-making autonomy.

Adolescent↗
PubMed1999

The effect of leg strength on the incidence of lower extremity overuse injuries during military training.

This study examined the effects of strength, aerobic fitness, and activity profile on the incidence of overuse injuries, particularly stress fractures, during military training. A total of 136 military recruits were followed during 9 weeks of basic training. Maximal strength and aerobic fitness were determined by a one-repetition maximum leg press and a 2,000-m run, respectively. An activity profile was determined by the recruit's activity history. Twelve recruits (8.8%) were diagnosed with stress fractures. Recruits who were 1 SD below the population mean in both absolute (98.4 +/- 36.6 kg) and relative strength (1.72 +/- 0.61 kg/kg of body weight) had a five times greater risk for stress fracture (p < 0.05) than stronger recruits. Poor aerobic fitness did not appear to be related to any increased incidence of stress fracture. It appears that recruits with lower body strength levels, within 1 SD of the population mean, have a reduced incidence of stress fractures during military training.

Adolescent↗
PubMed1999

The relationship of physical fitness on pilot candidate selection in the Israel Air Force.

BACKGROUND: The purpose of this study was to examine whether physical fitness is an important component in the selection process of pilot candidates to the Israel Air Force (IAF) flight school. METHODS: There were 223 male pilot candidates who volunteered to participate in the study. All subjects were tested 1 - 12 wk prior to a week-long "bootcamp" for aerobic power (Astrand bicycle test), anaerobic power (vertical jump test), and percent body fat. In addition, an activity profile was established based on an activity history questionnaire. All fitness measures were correlated to a performance score based on the IAF selection criteria measure for each candidate. RESULTS: Candidates who were accepted to flight school had a higher aerobic capacity, anaerobic power output relative to body weight and a lower percent body fat than candidates who were not successful. Significant correlations were seen between the performance score and aerobic power (r = 0.31), anaerobic power (r = 0.17) and anaerobic power relative to body weight (r = 0.21). Linear regression analysis showed that aerobic power explained 9% of the variance in the performance score, while anaerobic power explained an additional 3%. The results of this study suggest that physical fitness has a positive influence on the success of pilot candidates in gaining admittance to the IAF flight school.

Aerospace Medicine↗
PubMed1999

An examination of mood changes and performance in a professional basketball team.

BACKGROUND: The purpose of this study was to examine the relationship between the Profile of Mood States (POMS) and performance in a professional basketball team. METHODS PARTICIPANTS: seven male professional basketball players playing for the defending champions of the Israel Basketball League participated in this study. EXPERIMENTAL DESIGN: the POMS was administered seven times (T1-T7) during the season. The initial POMS administration was performed three weeks following the start of preseason practice and one day prior to the first basketball game. Each of the other POMS administrations were performed two days following a game and no more than 2 days before the next game. RESULTS: Typical iceberg profiles were observed during T1, T2 and T3, which coincided with successful performance (winning percentages greater than 60% between each POMS administration). Subsequent decreases in performance between T3 and T4 (a 33% winning percentage) resulted in a decrease in vigor and an increase in anger. As team performance improved between T4 and T5 (winning percentage again above 60%), vigor returned to its original level. However, the mood states anger and depression remained elevated, even during successful team play. This may have been related to problems independent of basketball performance (coaching and financial). CONCLUSIONS: These results suggest that the mood state vigor may be reflective of team performance. In addition, mood states appear to be influenced more by performance or experience, rather than performance being influenced by changes in mood states.

Adult↗
PubMed1999

BDNF and NT4/5 promote survival and neurite outgrowth of pontocerebellar mossy fiber neurons.

The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3), and NT4/5 are all found in the developing cerebellum. Granule cells, the major target neurons of mossy fibers, express BDNF during mossy fiber synaptogenesis. To determine whether neurotrophins contribute to the development of cerebellar afferent axons, we characterized the effects of neurotrophins on the growth of mossy fiber neurons from mice and rats in vitro. For a mossy fiber source, we used the basilar pontine nuclei (BPN), the major source of cerebellar mossy fibers in mammals. BDNF and NT4/5 increased BPN neuron survival, neurite outgrowth, growth cone size, and elongation rate, while neither NT3 nor NGF increased survival or outgrowth. In addition, BDNF and NT4/5 reduced the size of neurite bundles. Consistent with these effects, in situ hybridization on cultured basilar pontine neurons revealed the presence of mRNA encoding the TrkB receptor which binds both BDNF and NT4/5 with high affinity. We detected little or no message encoding the TrkC receptor which preferentially binds NT3. BDNF and NT4/5 also increased TrkB mRNA levels in BPN neurons. In addition to previously established functions as an autocrine/paracrine trophic factor for granule cells, the present results indicate that cerebellar BDNF may also act as a target-derived trophic factor for basilar pontine mossy fibers.

Afferent Pathways↗
PubMed1998

Selective cervical spine radiography in blunt trauma: methodology of the National Emergency X-Radiography Utilization Study (NEXUS).

Fear of failure to identify cervical spine injury has led to extremely liberal use of radiography in patients with blunt trauma and remotely possible neck injury. A number of previous retrospective and small prospective studies have tried to address the question of whether any clinical criteria can identify patients, from among this group, at sufficiently low risk that cervical spine radiography is unnecessary. The National Emergency X-Radiography Utilization Study (NEXUS) is a very large, federally supported, multicenter, prospective study designed to define the sensitivity, for detecting significant cervical spine injury, of criteria previously shown to have high negative predictive value. Done at 23 different emergency departments across the United States and projected to enroll more than 20 times as many patients with cervical spine injury than any previous study, NEXUS should be able to answer definitively questions about the validity and reliability of clinical criteria used as a preliminary screen for cervical spine injury.

Cervical Vertebrae↗
PubMed1998

Interrater reliability of cervical spine injury criteria in patients with blunt trauma.

STUDY OBJECTIVE: To determine the interrater reliability of previously defined risk criteria for cervical spine injury. METHODS: Two emergency physicians independently evaluated patients with blunt trauma to determine whether they exhibited any of four risk criteria: (1) altered neurologic function; (2) evidence of intoxication; (3) spinous process or posterior midline cervical tenderness; or (4) distracting painful injury. Each criterion was explicitly described on study data forms. Physician concordance was measured, and the kappa statistic was calculated, for the combined risk criteria (based on the presence of any individual criterion), and for each individual criterion. RESULTS: There were 122 patients evaluated. Physicians agreed on overall classifications for 107 patients (87.7%; kappa, .73; confidence interval [CI], .61 to .86). Agreement for individual criteria were as follows: (1) altered neurologic function--102 patients (83.6%; kappa, .58; CI, .41 to .74); (2) intoxication--118 patients (96.7%; kappa, .86; CI, .72 to .99); (3) posterior midline tenderness--109 patients (89.3%; kappa, .77; CI .65 to .89); (4) distracting injury--112 patients (91.8%; kappa.77; CI, .64 to .91). CONCLUSION: The combined cervical spine injury criteria have substantial interrater reliability. Individual criteria are slightly less reliable.

Adolescent↗
PubMed1998

Plasma testosterone and cortisol responses to training-intensity exercise in mild and hot environments.

Seven endurance-trained and heat-nonacclimated men (Mean+/-SEM: 20+/-1 yr; VO2max = 67+/-2 ml x kg(-1) x min(-1)) ran in two environments (M: 23 degrees C, H: 38 degrees C; 7 days apart) at two absolute training-intensity velocities (S1: 240 m x min(-1); followed by S2: 270 m x min(-1); 10 min each) during the winter months. Blood samples were taken via cannula before (pre) S1 and after S1 and S2. Plasma testosterone (TEST) concentrations increased (p<0.05) above pre levels after S1 in M (19+/-3 versus 24+/-3 nmol x L(-1)) and H (18+/-2 versus 23+/-3 nmol x L(-1)), and after S2 in H (18+/-2 versus 24+/-1 nmol x L(-1)). Plasma cortisol (CORT) and the molar ratio of TEST/CORT were unchanged from pre levels after S1 and S2 during M and H. No differences were found in plasma TEST, CORT, or the molar ratio of TEST/CORT between M and H. These results indicated that circulating levels of TEST and CORT were not changed in endurance-trained, heat-nonacclimated athletes in response to short-duration running performed at the same absolute intensity in the heat, compared to mild environmental conditions. The lack of significant differences in the molar ratio of TEST/CORT, between the 23 degrees C and 38 degrees C trials, suggested that this short-duration exercise challenge performed in the heat was no more of an anabolic or catabolic stimulus for these athletes.

Acclimatization↗
PubMed1998

Doctoring: University of California, Los Angeles.

The Doctoring curriculum at the University of California, Los Angeles, UCLA School of Medicine covers all four years of medical school. Its goal is to train physicians to give care that is compassionate, humanistic, high-quality, and evidence-based through a longitudinal, interdisciplinary curriculum with integration of learning experiences within and between years and with more emphasis on certain topics that had been previously neglected (e.g., advanced physical diagnosis, nutrition, public health, ethics). The curriculum operates alongside the traditional one, but strong attempts are made to link the two curricula. The authors describe the gradual introduction of the Doctoring curriculum, the sometimes formidable barriers that were encountered and in some cases still exist (e.g., some faculty and student resistance, need to find funds, faculty recruitment and retention). Active, interested faculty are essential, and intensive faculty development is needed. A detailed description of each year's courses and teaching approaches is given. Year one focuses on interpersonal communication, the medical interview, human development and behavior, and the role of the community in health care; year two, on clinical reasoning, physical diagnosis skills, population medicine, and ethics; year three, on clinical problem solving, health services, professionalization issues, and prevention; and year four (which is elective), on medical education and leadership. The methods of evaluating students, faculty, and the curriculum itself are described and assessed. The authors conclude with a review of plans, prospects, and ongoing problems.

Curriculum↗
PubMed1997

The effect of environmental temperature on testosterone and cortisol responses to high intensity, intermittent exercise in humans.

The purpose of this study was to examine the testosterone, cortisol, and the molar ratio of testosterone to cortisol (T:C) blood concentration responses to intermittent, high intensity exercise in the heat. Eight active men [mean age 25 (SD 3) years, mass 71.1 (SD 5.5) kg, height 175.9 (SD 4.4) cm] performed two series of five 15-s Wingate anaerobic power tests in both hot (H, 35 degrees C) and thermoneutral (TN, 22 degrees C) environments. Each period of exercise was separated by 30-s of active recovery. Each series was separated by 60 min of passive recovery. Blood samples were obtained before (PRE), immediately post (IP), and 5(5R), 10(10R), 15(15R), 30(30R), 45(45R), and 60(60R) min following exercise. Peak power was significantly higher, during the first series of exercise, in the H compared to TN. No significant differences were seen in any of the variables between the first and second series of exercise in either environmental condition. Furthermore, no significant differences between these conditions were observed in heart rate, blood lactic acid concentration, or rectal temperature. A significant decrease in cortisol concentration was observed between PRE and IP, during both conditions. However, no significant interactions between TN or H were seen. No change from PRE was observed in testosterone or T:C during either TN or H. It would appear that testosterone and cortisol respond similarly to repeated periods of short duration high intensity exercise, in either thermoneutral or moderately hot environments.

Adult↗
PubMed1997

Thermal and circulatory responses during exercise: effects of hypohydration, dehydration, and water intake.

This investigation examined the distinct and interactive effects of initial hydration state, exercise-induced dehydration, and water rehydration in a hot environment. On four occasions, 10 men performed a 90-min heat stress test (treadmill walking at 5.6 km/h, 5% grade, 33 degrees C, 56% relative humidity). These heat stress tests differed in pretest hydration [2 euhydrated (EU) and 2 hypohydrated (HY) trials] and water intake during exercise [2 water ad libitum (W) and 2 no water (NW) trials]. HY+NW indicated greater physiological strain than all other trials (P < 0.05-0.001) in heart rate, plasma osmolality (Posm), sweat sensitivity (g/degrees C.min), and rectal temperature. Unexpectedly, final HY+W and EU+W responses for rectal temperature, heart rate, and Posm were similar, despite the initial 3.9 +/- 0.2% hypohydration in HY+W. We concluded that differences in pretest Posm (295 +/- 7 and 287 +/- 5 mosmol/kg for HY+W and EU+W, respectively) resulted in greater water consumption (1.65 and 0.31 liter for HY+W and EU+W, respectively), no voluntary dehydration (0.9% body mass increase), and attenuated thermal and circulatory strain during HY+W.

Adult↗