The associations between adolescent head-on-neck posture, backpack weight, and anthropometric features

STUDY DESIGN

A Cross-sectional, observational study, examining the effects of backpack weight on adolescent posture.

OBJECTIVES

To investigate the response of the craniovertebral angle to backpack load.

SUMMARY OF BACKGROUND DATA

There is a widely held belief that repeated carrying of heavy loads, such as school backpacks, places additional stress on rapidly growing adolescent spinal structures, making them prone to postural change.

METHODS

Ten volunteer state high schools in metropolitan Adelaide, South Australia, provided 985 students, aged 12 to 18 years and from five different high school years, for this study. Students' posture was measured with and without their school backpack. All data analyses were undertaken per school year level to account for specific load-carrying requirements and spinal development associated with the age group.

RESULTS

A significant change in craniovertebral angle was found at every year level, when comparing standing posture with no backpack with posture when carrying a backpack. The change was greatest for the youngest students. Incremental change in craniovertebral angle was not strongly associated with backpack loads. The association became stronger for the oldest girls when controlled for body mass index and for weight.

CONCLUSION

The results support a differential postural response per gender and per level of spinal development but also suggest that the craniovertebral angle may not be the most sensitive measure of head-on-neck postural change for adolescents.

Stress during pregnancy alters the offspring hypothalamic, pituitary, adrenal, and testicular response to isolation on the day of weaning

Subjecting pregnant female rats to situations that activate the hypothalamic-pituitary-adrenal (HPA) axis can have long-term effects on the development of the offspring. Restraint under bright lights is a common method of stressing pregnant females that results in consistent behavioral changes in the offspring. We investigated the effects of gestationally administered restraint, bright lights, and heat on the HPA axis response of 21-day-old offspring following exposure to isolation in a novel environment or under resting conditions. Corticotropin-releasing factor titers in the hypothalamus were unaffected following isolation. Nonetheless, adrenocorticotropin hormone (ACTH) was found to be lower in the gestationally stressed offspring prior to or following the isolation period. Corticosterone was attenuated in gestationally stressed offspring following the postnatal stressor and there was also a tendency for the gestationally stressed females to have lower concentrations of aldosterone. Plasmatic testosterone levels were higher in the gestationally stressed males following the period of isolation. The present data suggest that the HPA axis of the offspring is differentially affected by the gestational stress procedure, that is, it is attenuated at the level of the pituitary and adrenal, but not at the level of the hypothalamus. These data have implications for behavioral differences observed in gestationally stressed animals.

Changes in the hormonal concentrations of pregnant rats and their fetuses following multiple exposures to a stressor during the third trimester

Human and animal studies indicate that stress during pregnancy can exert long-term effects on the development of the offspring, effects that appear to be mediated in part by the hypothalamic-pituitary-adrenal (HPA) axis. In this experiment changes in levels of a variety of HPA and other hormones in both pregnant rats and their fetuses were investigated. Trunk blood was collected from pregnant females and fetuses following repeated 45-min presentations of restraint, bright lights, and heat during the third trimester. In addition, testes were harvested from the male fetuses. Hormone concentrations were determined by radioimmunoassay. Pregnant females had elevated titers of plasma corticosterone, aldosterone, and ACTH for approximately 15 min following termination of the stressor. No differences were found for beta-endorphin or prolactin. Fetuses showed a pattern of changes in plasma corticosterone and aldosterone that was similar to that of pregnant females, but no effect was observed for fetal ACTH titers. These results are consistent with a role of the HPA axis in the effects of gestational stress. Testicular levels of CRF on gestational day 21 were lower in fetuses of stressed females than in those of nonstressed females. The reduced levels of testicular CRF suggest that CRF may be involved in the altered pattern of sexual differentiation of males stressed during gestation.

Pre-matriculation program at the University of South Florida College of Medicine

Underrepresented-minority (URM) students at the University of South Florida College of Medicine increased from 4.9% to 10.5% of the total student body from 1991 to 1997. During that period it became clear that some majority and minority students had serious academic difficulties with the first-year curriculum and that a higher proportion of the minority matriculants had difficulties. In response, the college in 1997 created the Summer Pre-matriculation Program to reduce the number of first-year students who had academic difficulty. In the summer before they matriculate in the college, the students complete a six-week program of lectures, small-group discussions, compute-aided instruction, and laboratory instruction in biochemistry, human embryology, and gross anatomy. URM students, non-science majors, and students who have been away from the academic environment (e.g., pursuing medicine as a second career) are given priority for the 20 positions available each year. At the end of the first cohort's first medical school year, the academic performances of program participants and other students were compared, and it was clear that the program participants had performed as well as or slightly better than their counterparts in gross anatomy, biochemistry, and human embryology. Further, the program participants performed at or above the class average in medical school courses for which they had not had targeted instruction during the program. The College of Medicine is committed to diversifying its student body and realizes that diverse students bring varying levels of academic preparation as well as diversity in cultural and academic backgrounds. Concerted efforts such as the pre-matriculation program may be required to normalize the "playing field" at the very outset of medical school and to ensure that every matriculant has an equal opportunity to succeed.

Vitamin E and lipoic acid, but not vitamin C improve blood oxygenation after high-energy IMPULSE noise (BLAST) exposure

Exposure to high energy impulse noise (BLAST) caused by explosions, result in structural and functional damage to the hollow organs, especially to the respiratory and auditory systems. Lung damage includes alveolar wall rupture, edema and hemorrhage, and may be fatal. Previous observations at the molecular level using the rat model, suggested that secondary free radical-mediated oxidative stress occurs post exposure resulting in antioxidant depletion and hemoglobin (Hb) oxidation. This study examined whether a short period of pre-exposure supplementation with antioxidants would protect Hb from the effects of BLAST exposure. Six groups of male Sprague-Dawley rats (8/group) were gavaged with 800 IU vitamin E (VE) in 2 ml corn oil, 1000 mg vitamin C (VC) in 2 ml distilled water or 25 mg or (-lipoic acid (LA) in 2 ml corn oil for 3 days. Matched control groups were gavaged with the respective vehicles. On day 4, rats were deeply anesthetized and exposed to a simulated BLAST wave with an average peak pressure of 62 +/- 2 kPa. Rats were euthanized one hour post exposure and blood samples were obtained by cardiac puncture and analyzed using a hemoximeter. Post exposure oxygenation states (HbO2, O2 saturation, and O2 content) were markedly decreased, while reduced-Hb was increased. Supplementation with VE and LA reversed the trend and increased Hb oxygenation, but VC did not. This suggests that a brief dietary loading with pharmacological doses of VE or LA, but not VC shortly before BLAST exposure may be beneficial. Moreover, measurement of blood oxygenation may function as a simple semi-invasive biomarker of BLAST-induced injury applicable to humans.

The distribution of radiolabeled corticotropin-releasing factor in pregnant rats: an investigation of placental transfer to the fetuses

Stress during gestation can have serious consequences on the development of the fetus. Many of these effects appear to be mediated by hormones of the hypothalamic-pituitary-adrenal (HPA) axis. Corticotropin-releasing factor (CRF), released by the hypothalamus during times of stress serves to activate release of pituitary hormones and is also present in low levels in rat plasma. Moreover, the uterus contains significant quantities of CRF at implantation sites, probably from local sources. Therefore, the possibility exists that CRF may cross the placenta and activate the fetal HPA axis. However, the ability of CRF to cross the placenta has not been demonstrated. In the present study, pregnant rats were administered radiolabeled CRF intraperitoneally, and the distribution of the labeled product was determined in the fetuses and various maternal organs. High levels of activity were observed in the pregnant female's uterus, adrenals, heart and the placentae, but only background levels of activity were detected in the maternal brain. Very low levels of activity were observed in the fetuses, indicating that the transfer of CRF across the placenta is greatly restricted. These findings suggest that maternal CRF has little or no direct effect on the developing fetus during gestational stress.

Stress during pregnancy alters rat offspring morphology and ultrasonic vocalizations

Stress during pregnancy, or prenatal stress, is known to alter offspring behavior, morphology and physiology. We found that a heat, light and restraint stressor applied during the third trimester of pregnancy: 1) decreased the weight gain of adult female rats during pregnancy; 2) reduced the weight of pups, as well as the anogenital distance of male offspring, at birth; and 3) increased the number of ultrasonic vocalizations emitted by pups during isolation in a novel environment on Postnatal Day 14. These results closely approximate those we previously observed after peripheral administration of corticotropin-releasing factor to pregnant females during the third trimester. Together, the studies strongly suggest a role for corticotropin-releasing factor and/or other hormones of the hypothalamic-pituitary-adrenal system in mediating some of the effects of gestational stress.

Plasma cortisol levels of dogs at a county animal shelter

Plasmacortisol levels were examined to assess the stress of dogs in a county animal shelter. Groups of dogs confined in the shelter for their 1st, 2nd, or 3rd day had higher cortisol levels than did a group maintained in the shelter for more than 9 days. Dogs in the shelter for an intermediate period (Day 4-9) had intermediate levels of cortisol. The cortisol concentrations of dogs during their first day in the shelter were greater than either those of the same dogs on Day 4/5 in the shelter or those of a group of pet dogs sampled in their own homes. There was no overall effect of 20 min of social interaction with a human (e.g., petting) on the plasma cortisol levels of dogs in the shelter on Day 1-3. However, the gender of the petter did affect cortisol levels. Those dogs interacting with a female had lower cortisol concentrations at the end of the session than did dogs interacting with a male. The results suggest that confinement in a public animal shelter produces a prolonged activation of the hypothalamic-pituitary-adrenal axis. Further, it appears that some subtle aspect of interaction with a human may be capable of moderating this response. Possible implications for the welfare of confined dogs, and for the development of behavior problems in dogs obtained from shelters, are discussed.

Effects of peripherally administered corticotropin-releasing factor (CRF) and a CRF antagonist: does peripheral CRE activity mediate behavior of guinea pig pups during isolation?

Guinea pig pups vocalized and ambulated when first isolated in a test cage; at 1 and 24 hr, levels of these behaviors had waned, and pups frequently exhibited a crouched stance, eye-closing, and piloerection. Injection (s.c.) of corticotropin-releasing factor (CRF) prior to isolation diminished the initial vocalization and locomotor responses and induced pups to exhibit the crouched stance, eye-closing, and piloerection at the beginning of the isolation period. Pretreatment with a CRF-receptor antagonist reversed the behavioral effects of CRF. CRF had no effect on blood pressure. Thus, s.c. CRF produced the same behavioral profile as seen with the passage of time in untreated isolated pups. The behavioral effects appeared to be CRF-receptor-mediated events and were not secondary to hypotension. These results support the hypothesis that during prolonged isolation, high or sustained peripheral CRF activity modulates behavior.

Tuberculosis, AIDS, and death among substance abusers on welfare in New York City

BACKGROUND

In New York City, the incidence of tuberculosis has more than doubled during the past decade. We examined the incidence of tuberculosis and the acquired immunodeficiency syndrome (AIDS) and the rate of death from all causes in a very-high-risk group--indigent subjects who abuse drugs, alcohol, or both.

METHODS

In 1984 we began to study prospectively a cohort of welfare applicants and recipients 18 to 64 years of age who abused drugs or alcohol. The incidence rates of tuberculosis, AIDS, and death for this group were ascertained through vital records and New York City's tuberculosis and AIDS registries.

RESULTS

The cohort was followed for eight years. Of the 858 subjects, tuberculosis developed in 47 (5.5 percent), 84 (9.8 percent) were given a diagnosis of AIDS, and 183 (21.3 percent) died. The rates of incidence per 100,000 person-years were 744 for tuberculosis, 1323 for AIDS, and 2842 for death. In this group of welfare clients, the rate of newly diagnosed tuberculosis was 14.8 times that of the age-matched general population of New York City; the rate of AIDS was 10.0 times as high; and the death rate was 5.2 times as high. There was no significant difference in the rate of new cases of tuberculosis between subjects with positive skin tests and those with negative skin tests at examination in 1984.

CONCLUSIONS

Among indigent alcohol and drug abusers in New York City, the rates of tuberculosis, AIDS, and death are extremely high. In this population, a single positive or negative skin test does not predict the development of tuberculosis, probably because both anergy and new infections are common. If programs to control tuberculosis and AIDS are to be effective in groups of indigent substance abusers, health services must be integrated into the welfare delivery system.

Effects of peripherally administered corticotropin-releasing factor (CRF) and a CRF antagonist: does peripheral CRE activity mediate behavior of guinea pig pups during isolation?

Guinea pig pups vocalized and ambulated when first isolated in a test cage; at 1 and 24 hr, levels of these behaviors had waned, and pups frequently exhibited a crouched stance, eye-closing, and piloerection. Injection (s.c.) of corticotropin-releasing factor (CRF) prior to isolation diminished the initial vocalization and locomotor responses and induced pups to exhibit the crouched stance, eye-closing, and piloerection at the beginning of the isolation period. Pretreatment with a CRF-receptor antagonist reversed the behavioral effects of CRF. CRF had no effect on blood pressure. Thus, s.c. CRF produced the same behavioral profile as seen with the passage of time in untreated isolated pups. The behavioral effects appeared to be CRF-receptor-mediated events and were not secondary to hypotension. These results support the hypothesis that during prolonged isolation, high or sustained peripheral CRF activity modulates behavior.

CRF administered to pregnant rats alters offspring behavior and morphology

Pregnant rats injected with 20 micrograms of corticotropin-releasing factor (CRF) from day 14 through 21 gained less weight during gestation than did saline-injected controls. The offspring of CRF-injected females differed from the offspring of control females in several ways: males and females weighed less during the first 2 weeks of life, males had shorter anogenital distances at birth, and males and females emitted more ultrasonic vocalizations during isolation in tests at 6 and 14 days of age. These effects are similar to those that have been observed following exposure of pregnant females to stressors, and provide support for the notion that CRF and/or CRF activation of the hypothalamic-pituitary-adrenal axis mediate effects of gestational stress.

Effects of centrally administered corticotropin-releasing factor (CRF) and alpha-helical CRF on the vocalizations of isolated guinea pig pups

Intraventricular corticotropin-releasing factor (CRF) was administered to guinea pig pups both with a freehand injection technique and via indwelling cannula. Behavioral effects depended upon the technique used. The highest dose of CRF (5 micrograms) inhibited the vocalizing of pups in a subsequent isolation test only when CRF was given by freehand injection. The possibility that disturbance attendant to the freehand procedure can account for this difference is discussed. To determine the effect of endogenous CRF in the absence of additional disturbance, the CRF antagonist alpha-helical CRF (ahCRF) was administered with the indwelling cannula procedure. ahCRF enhanced vocalizing during the first 10 min, and enhanced locomotor activity during the last 10 min, of a 30-min isolation test. Overall, the results indicate that endogenous CRF reduces vocalizing and locomotion during social isolation and that under certain injection conditions exogenous CRF can exacerbate the behavioral effect. The results also demonstrate the potential impact of the technique used to administer exogenous CRF. Further, the prevailing view, that CRF mediates stress-related behavioral responses, is supported only if behavioral inhibition, rather than vocalizing or locomotor activity, is viewed as the stress-related response in this situation.

Cytochrome P450. Mechanisms of action and clinical implications

The term cytochrome P450 refers to a group of hemoproteins whose Fe(2+)-carbon monoxide complex shows an absorption spectrum with a maximum near 450 nm. There is a broad interest in the P450s because of their significance in a variety of disciplines ranging from medical genetics to inorganic chemistry. Cytochrome P450 enzymes are involved in the metabolism of drugs, carcinogens, steroids, pesticides, hydrocarbons and natural products. The toxicity of many of these products may be modulated, either via replacement or by the various oxidations catalyzed by the cytochrome P450 enzymes. In recent years the roles of cytochrome P450 enzymes in the metabolism of endogenous compounds have been partially elucidated. Physiological compounds such as steroids, fatty acids, prostanoids and other eicosanoids, fat-soluble vitamins and mammalian alkaloids have been shown to be substrates. Aside from their roles in metabolism, certain of these enzymes were found to be involved in the metabolic activation of a variety of chemical carcinogens and possibly in the overall process of chemical carcinogenesis. Studies show that alterations in cytochrome P450 activities toward various substrates have been implicated in diseases which affect human health. The roles are reviewed of the various cytochrome P450 enzymes in the metabolism of substrates which may be associated with clinical disease states.

Predicting length of stay in long-term treatment for chemically dependent females

Psychological and demographic variables were analyzed for 136 chemically dependent women treated in a residential therapeutic community. Cocaine users constituted 50% of the sample and were likely to drop out of treatment earlier (p less than .05). Of all the variables studied, only the Beck Depression Inventory scores were significantly higher for clients who terminated treatment prematurely compared to clients who completed treatment. The results point to the need for further research on the role of depression as a predictive factor of retention.

In vivo suppression of stearyl CoA desaturase activity by griseofulvin: evidence against the involvement of lipid peroxidation

Administration of a diet containing 2.5% (w/w) griseofulvin (GF) resulted in a significant decrease in hepatic microsomal stearyl CoA desaturase activity compared to desaturase activity in microsomes from animals fed a normal rat chow diet. Desaturase activities were 0.66 +/- 0.18 vs 0.16 +/- 0.09 nmoles oleyl CoA formed/min/mg protein for control and GF-fed animals, respectively. Examination of lipid peroxides in microsomes from control and GF-treated rats showed an approximate fivefold higher concentration of lipid peroxides in microsomes from GF-treated rats compared to that from controls. However, when rats were fed a diet containing GF and diphenyl-p-phenylenediamine an inhibitor of lipid peroxidation, stearyl CoA desaturase activity was still similar to that observed with GF alone, even though microsomal lipid peroxides were reduced to nondetectable levels. In vitro stimulation of microsomal lipid peroxidation using ADP-Fe and EDTA-Fe did not result in a significant decrease in desaturase activity. Results of our experiments show that dietary administration of GF results in a marked decrease in stearyl CoA desaturase activity in hepatic microsomes. Although GF feeding stimulates microsomal lipid peroxidation, increase in microsomal peroxidation does not appear to be the mechanism by which GF feeding decreases desaturase activity. GF appears to act by decreasing the terminal desaturase activity.

Liver microsomal inactivation of 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone as an inhibitor of ribonucleotide reductase

Studies were carried out to determine the effects of preincubation of 4-methyl-5-amino-1-formylisoquinoline thiosemicarbazone (MAIQ) with hepatic microsomes on the ability of MAIQ to inhibit CDP reductase activity in vitro. An aliquot from the 100,000 x g supernatant fraction from this incubation was used in the CDP reductase assay. MAIQ incubated in the absence of microsomes inhibited CDP reductase activity in a dose-dependent manner. At high MAIQ concentration (5 microM) CDP reductase activity was inhibited 95%. When MAIQ (5 microM) was first incubated in the presence of hepatic microsomes and NADPH, CDP reductase activity was inhibited only 30%. This attenuation of MAIQ inhibition was dependent on time of incubation and microsomal protein concentration and showed an obligatory requirement for NADPH or NADH. Significant attenuation was observed at pyridine nucleotide concentrations as low as 0.1 mM. Heat denaturation of microsomal proteins inactivated their ability to attenuate the MAIQ inhibition. Microsomes prepared from Ehrlich tumor cells were ineffective as inactivators of MAIQ. Results of our studies show that hepatic microsomes contain an enzyme(s) which can inactive MAIQ as an inhibitor of CDP reductase.

Policies and procedures for scheduling student nurses

A smoothly operating system for student clinical affiliations can save staff time and positively influence recruitment and retention. To ensure a systematic approach to scheduling students, the author shares her approach, policies, and procedures.