Altered brain phosphocreatine and ATP regulation when mitochondrial creatine kinase is absent

In cerebral gray matter, ATP concentration is closely maintained despite rapid, large increases in turnover and low substrate reserves. As seen in vivo by (31)P nuclear magnetic resonance (NMR) spectroscopy, brain ATP is stable early in seizures, a state of high energy demand, and in mild hypoxia, a state of substrate deficiency. Like other tissues with high and variable ATP turnover, cerebral gray matter has high phosphocreatine (PCr) concentration and both cytosolic and mitochondrial creatine kinase (UbMi-CK) isoenzymes. To understand the physiology of brain creatine kinases, we used (31)P NMR to study PCr and ATP regulation during seizures and hypoxia in mice with targeted deletion of the UbMi-CK gene. The baseline CK reaction rate constant (k) was higher in mutants than wild-types. During seizures, PCr and ATP decreased in mutants but not in wild-types. The k-value for the CK catalyzed reaction rate increased in wild-types but not in the mutants. Hypoxic mutants and wild-types showed similar PCr losses and stable ATP. During recovery from hypoxia, brain PCr and ATP concentrations returned to baseline in wild-types but were 20% higher than baseline in the mutants. We propose that UbMi-CK couples ATP turnover to the CK catalyzed reaction rate and regulates ATP concentration when synthesis is increased.

HIV-related behaviors and perceptions among adults in 25 states: 1997 Behavioral Risk Factor Surveillance System

OBJECTIVES

To assess the level of HIV-related risk behavior among the general US adult population, we analyzed data from the first sexual behavior questions available for states to use with the Behavioral Risk Factor Surveillance System.

METHODS

The Behavioral Risk Factor Surveillance System is a state-specific, population-based, random telephone survey. In 1997, 25 states collected sexual behavior data. Annual prevalence estimates for selected behaviors were calculated and examined by sociodemographic characteristics. The correlation between actual and perceived HIV risk also was determined.

RESULTS

Most (77.1%) of the respondents reported just 1 sexual partner in the past year; 26.0% reported using a condom at last intercourse. Males, persons who were younger, and Blacks were more likely to report 2 or more partners but also more likely to report using a condom at last intercourse. Only 4.1% of the respondents reported a risk factor for HIV infection; 7.7% reported that they were at medium or high risk for HIV. Actual and perceived HIV risk were positively associated.

CONCLUSIONS

Most US adults do not engage in HIV-related risk behavior; those that do are more likely to report protective behavior.

Reliability and validity of measures from the Behavioral Risk Factor Surveillance System (BRFSS)

OBJECTIVES

To assess the reliability and validity of measures on the BRFSS, to assist users in evaluating the quality of BRFSS data, and to identify areas for further research.

METHODS

Review and summary of reliability and validity studies of measures on the BRFSS and studies of measures that were the same or similar to those on the BRFSS from other surveys.

RESULTS

Measures determined to be of high reliability and high validity were current smoker, blood pressure screening, height, weight, and BMI, and several demographic characteristics. Measures of both moderate reliability and validity included when last mammography was received, clinical breast exam, sedentary lifestyle, intense leisure-time physical activity, and fruit and vegetable consumption. Few measures were of low validity and only one measure was determined to be of low reliability. Several other measures were of high or moderate reliability or validity, but not both. The reliability or validity could not be determined for some measures, primarily due to lack of research.

CONCLUSIONS

Most questions on the core BRFSS instrument were at least moderately reliable and valid, and many were highly reliable and valid. Additional research is needed for some measures.

Brain creatine kinase and creatine transporter proteins in normal and creatine-treated rabbit pups

Systemic creatine (Cr) supplementation increases brain phosphocreatine (PCr) and prevents hypoxic seizures in 15-day-old rabbits. Between 5 and 30 days of age during normal development, rabbit gray matter mitochondrial creatine kinase (Mi-CK) increases 400% while cytosolic CK (BB-CK) increases 60%. In white matter, both isoenzymes show smaller, similar increases (40%) during this period. The Cr transporter protein decreases 60% between 5 and 15 days in both regions. In vivo CK rate constants measured by (31)P nuclear magnetic resonance increase 30% between 10 and 20 days, and then fall 50% between 20 and 30 days in predominantly gray matter slices. Similar maturational changes are seen in predominantly white matter slices. Injecting Cr at 15 days does not significantly change BB-CK or Mi-CK isoenzymes or the in vivo CK reaction rate constants. Thus, the largest change in the CK system associated with suppression of hypoxic seizures in Cr-treated rabbits is increased PCr in gray and white matter.

Brain ATP metabolism in hypoxia resistant mice fed guanidinopropionic acid

Feeding beta-guanidinopropionic acid (GPA), a competitive inhibitor of creatine transport, decreases mortality and increases brain ATP stability in hypoxic mice. To study brain ATP metabolism in GPA-fed animals, respiratory rates were measured in grey matter and white matter slices as well as cerebral hemisphere mitochondria from GPA-fed mice and rats. Creatine kinase and adenylate kinase activities were measured in rat cerebral grey matter and white matter. Respiratory rates and oxidative phosphorylation were the same in GPA-fed mice and control mice. The adenylate kinase activity increased 50% and creatine kinase showed a small decrease in grey matter. In white matter, creatine kinase increased 50% while adenylate kinase decreased. Thus, GPA produces opposite adaptive changes in adenylate kinase and creatine kinase in grey matter and in white matter. These results suggest that the creatine kinase reaction in grey matter acts to regulate cellular ADP and ATP concentrations.

Multi-component apparent diffusion coefficients in human brain: relationship to spin-lattice relaxation

In vivo measurements of the human brain tissue water signal decay with b-factor over an extended b-factor range up to 6,000 s/mm(2) reveal a nonmonoexponential decay behavior for both gray and white matter. Biexponential parametrization of the decay curves from cortical gray (CG) and white matter voxels from the internal capsule (IC) of healthy adult volunteers describes the decay process and serves to differentiate between these two tissues. Inversion recovery experiments performed in conjunction with the extended b-factor signal decay measurements are used to make separate measurements of the spin-lattice relaxation times of the fast and slow apparent diffusion coefficient (ADC) components. Differences between the spin-lattice relaxation times of the fast and slow ADC components were not statistically significant in either the CG or IC voxels. It is possible that the two ADC components observed from the extended b-factor measurements arise from two distinct water compartments with different intrinsic diffusion coefficients. If so, then the relaxation results are consistent with two possibilities. Either the spin-lattice relaxation times within the compartments are similar or the rate of water exchange between compartments is "fast" enough to ensure volume averaged T(1) relaxation yet "slow" enough to allow for the observation of biexponential ADC decay curves over an extended b-factor range. Magn Reson Med 44:292-300, 2000.

State- and sex-specific prevalence of selected characteristics--Behavioral Risk Factor Surveillance System, 1996 and 1997

PROBLEM/CONDITION

High-risk behaviors (e.g., physical inactivity, cigarette smoking, and drinking and driving) and lack of preventive health care (e.g., screening for cancer) are associated with morbidity and mortality from chronic disease and injury. The Behavioral Risk Factor Surveillance System (BRFSS) collects state-specific information to determine the prevalence of such behaviors and preventive practices. By using the BRFSS, states can gain a better understanding of the factors that have a major affect on the health of their adult populations. The BRFSS is also used to monitor progress toward national health objectives.

REPORTING PERIOD COVERED

1996 and 1997.

DESCRIPTION OF SYSTEM

The BRFSS is a state-based telephone survey of the civilian, noninstitutionalized, adult (i.e., persons aged 18 years) population. In both 1996 and 1997, 50 states, the District of Columbia, and the Commonwealth of Puerto Rico participated in the BRFSS.

RESULTS

As in previous years, state- and sex-specific variations occurred in the prevalence of high-risk behaviors, awareness of certain medical conditions, use of preventive health services, and health-care coverage. For example, in 1997, the percentage of adults who reported being current cigarette smokers ranged from 13.8% to 30.7% among states (median: 23.2%), and the percentage of adults who reported driving after drinking too much alcohol ranged from 0.6% to 5.3% (median: 1.9%). Binge drinking varied substantially not only by state (range: 6.3%-23.3%; median: 14.5%) but also by sex (men: 22.3%; women: 6.7%). Similarly, the prevalence of overweight varied considerably by sex: 62.2% of men and 44.5% of women were overweight in 1997.

INTERPRETATION

The 1996 and 1997 BRFSS data demonstrate that U.S. adults engage in behaviors that are detrimental to their health. The data also demonstrate that many adults are making efforts to prevent chronic disease and injury. The prevalence of certain behaviors and health practices differs between states and between men and women. The reasons for these differences by state and sex are subjects for further analysis, but only through continued surveillance can the areas that need further study be identified.

PUBLIC HEALTH ACTIONS

Data from the BRFSS are useful in developing and guiding public health programs and policies. For many states, the BRFSS is the only source of state-level data on behaviors and practices related to chronic disease and injury; therefore, BRFSS data are vital for effective decision-making at the local level. States will continue to use these data to help prevent premature morbidity and mortality among their adult population and to assess progress toward national health objectives.

Lipoproteins in the central nervous system

Although the synthesis and metabolism of plasma lipoproteins are well characterized, little is known about lipid delivery and clearance within the central nervous system (CNS). Our work has focused on characterizing the lipoprotein particles present in the cerebrospinal fluid (CSF) and the nascent particles secreted by astrocytes. In addition to carrying lipids, we have found that beta-amyloid (A beta) associates with lipoproteins, including the discoidal particles secreted by cultured astrocytes and the spherical lipoproteins found in CSF. We believe that association with lipoproteins provides a means of transport and clearance for A beta. This process may be further influenced by an interaction between A beta and apoprotein E (apoE), the primary protein component of CNS lipoproteins. Specifically, we have investigated the formation and physiologic relevance of a SDS-stable complex between apoE and A beta. In biochemical assays, native apoE2 and E3 (associated with lipid particles) form an SDS-stable complex with A beta that is 20-fold more abundant than the apoE4:A beta complex. In cell culture, native apoE3 but not E4 prevents A beta-induced neurotoxicity by a mechanism dependent on cell surface apoE receptors. In addition, apoE and the inhibition of apoE receptors prevent A beta-induced astrocyte activation. Therefore, we hypothesize that the protection from A beta-induced neurotoxicity afforded by apoE3 may result from clearance of the peptide by SDS-stable apoE3:A beta complex formation and uptake by apoE receptors.

State-specific prevalence of selected health behaviors, by race and ethnicity--Behavioral Risk Factor Surveillance System, 1997

PROBLEM/CONDITION

In the United States, disparities in risks for chronic disease (e.g., diabetes, cardiovascular disease, and cancer) and injury exist among racial and ethnic groups. This report summarizes findings from the 1997 Behavioral Risk Factor Surveillance System (BRFSS) of the distribution of access to health care, health-status indicators, health-risk behaviors, and use of clinical preventive services across five racial and ethnic groups (i.e., whites, blacks, Hispanics, American Indians or Alaska Natives, and Asians or Pacific Islanders) and by state.

REPORTING PERIOD COVERED

1997.

DESCRIPTION OF SYSTEM

The BRFSS is a state-based telephone survey of the civilian, noninstitutionalized, adult (i.e., persons aged > or = 18 years) population. In 1997, all 50 states, the District of Columbia, and Puerto Rico participated in the BRFSS.

RESULTS

Variations in risk for chronic disease and injury among racial and ethnic groups exist both within states and across states. For example, in Arizona, 11.0% of whites, 26.2% of Hispanics, and 50.5% of American Indians or Alaska Natives reported having no health insurance. Across states, the median percentage of adults who reported not having this insurance ranged from 10.8% for whites to 24.5% for American Indians or Alaska Natives. Other findings are as follows. Blacks, Hispanics, American Indians or Alaska Natives, and Asians or Pacific Islanders were more likely than whites to report poor access to health care (i.e., no health-care coverage and cost as a barrier to obtaining health care). Blacks, Hispanics, and American Indians or Alaska Natives were more likely than whites and Asians or Pacific Islanders to report fair or poor health status, obesity, diabetes, and no leisure-time physical activity. Blacks were substantially more likely than other racial or ethnic groups to report high blood pressure. Among all groups, American Indians or Alaska Natives were the most likely to report cigarette smoking. Except for Asians or Pacific Islanders, the median percentage of adults who reported not always wearing a safety belt while driving or riding in a car was > or = 30%. The Papanicolaou test was the most commonly reported screening measure: > or = 81% of white, black, and Hispanic women with an intact uterine cervix reported having had one in the past 3 years. Among white, black, and Hispanic women aged > or = 50 years, > or = 63% reported having had a mammogram in the past 2 years. Approximately two thirds of white, black, and Hispanic women aged > or = 50 years reported having had both a mammogram and a clinical breast examination in the past 2 years; this behavior was least common among Hispanics and most common among blacks. Screening for colorectal cancer was low among whites, blacks, and Hispanics aged > or = 50 years: in each racial or ethnic group, < or = 20% reported having used a home-kit blood stool test in the past year, and < or = 30% reported having had a sigmoidoscopy within the last 5 years.

INTERPRETATION

Differences in median percentages between racial and ethnic groups, as well as between states within each racial and ethnic group, are likely mediated by various factors. According to published literature, socioeconomic factors (e.g., age distribution, educational attainment, employment status, and poverty), lifestyle behaviors (e.g., lack of physical activity, alcohol intake, and cigarette smoking), aspects of the social environment (e.g., educational and economic opportunities, neighborhood and work conditions, and state and local laws enacted to discourage high-risk behaviors), and factors affecting the health-care system (e.g., access to health care, and cost and availability of screening for diseases and health-risk factors) may be associated with these differences. ACTION TAKEN: States will continue to use the BRFSS to collect information about health-risk behaviors among various racial and ethnic groups. (ABSTRACT TRUNCATED)

Trends in pregnancy-related smoking rates in the United States, 1987-1996

CONTEXT

Rates of smoking are increasing among adolescents and young adults, but trends in smoking among pregnant women have not been studied.

OBJECTIVE

To assess pregnancy-related variations in smoking behaviors and their determinants among women of childbearing age in the United States.

DESIGN

Analysis of data collected between 1987-1996 from the Behavioral Risk Factor Surveillance System survey.

SETTING AND SUBJECTS

A total of 187302 (178499 nonpregnant and 8803 pregnant) noninstitutionalized women aged 18 to 44 years from 33 states.

MAIN OUTCOME MEASURES

Prevalence rates of smoking initiation and current smoking, median number of cigarettes smoked, and adjusted odds ratios for smoking stratified by pregnancy status; prevalence rate ratio for current smoking comparing pregnant with nonpregnant women.

RESULTS

The overall percentage of women who had ever initiated smoking decreased significantly from 44.1% in 1987 to 38.2% in 1996. During that 10-year period, the prevalence of current smoking also decreased significantly among both pregnant women (16.3% to 11.8%) and nonpregnant women (26.7% to 23.6%). Overall, pregnant women were about half (54%) as likely as nonpregnant women to be current smokers during 1987-1996. Over time, the median number of cigarettes smoked per day by pregnant smokers remained at 10, whereas among nonpregnant smokers it decreased from 19 to 15 (P<.05 for trend). In the same period, among young women (aged 18-20 years), prevalence rates of smoking initiation and current smoking increased slightly. Sociodemographic subgroups of women at increased risk for current smoking were the same for pregnant and nonpregnant women (ie, those with a completed high school education or less, whites, and those who were unmarried).

CONCLUSIONS

In this analysis, the decline in smoking over time among pregnant women was primarily due to the overall decline in smoking initiation rates among women of childbearing age, not to an increased rate of smoking cessation related to pregnancy. To foster effective perinatal tobacco control, efforts are needed to further reduce the number of young women who begin smoking. Clinicians should query all pregnant women and women of childbearing age about smoking and provide cessation and relapse interventions to each smoker.

The feminization of the female oedipal complex, Part I: a reconsideration of the significance of separation issues

Freud's insights about the oedipus complex have been universalized to include the psychology of the girl. The authors argue that this crucial developmental phase for girls has uniquely feminine characteristics that have not been fully recognized or cohesively incorporated into psychoanalytic theories. This paper addresses these differences, which are based on characteristic patterns of object relationships, typical defenses, and social considerations. The authors argue that "female oedipal" is an oxymoron, and propose that this constellation be named "the Persephone complex" after the Greek myth of Persephone, which seems to capture better the typical situation of the little girl. They focus on the issue of separation and its complicated and necessary role in the triangular situation of females. Using illustrations from clinical material, the authors argue that the frequent appearance of separation material linked to triangular heterosexual competitive fantasies can and should be differentiated from material in which ideas about separation stem from dyadic and earlier issues. Misunderstanding how these separation conflicts tie into triangular "oedipal" relationships can lead to a "preoedipalization" of the dynamics of girls and women.

In vivo development of brain phosphocreatine in normal and creatine-treated rabbit pups

To study the effects of creatine (Cr) on brain energy metabolism and on hypoxia-induced seizures, 5- to 30-day-old rabbit pups were given subcutaneous Cr (3 g/kg) for 3 days before exposure to 4% O2 for 8 min. In saline-treated controls, hypoxic seizures were most frequent at 15 days (80% of pups) and 20 days (60%) of age. Seizures were prevented at 15 days and reduced 60% at 20 days in Cr-treated pups. In surface coil-localized brain 31P nuclear magnetic resonance spectra, with signal from both cerebral gray (GM) and white (WM) matter, the phosphocreatine (PCr)/nucleoside triphosphate (NTP) ratio doubled between 5 and 30 days of age in controls. In all Cr-injected pups, brain PCr/NTP increased to values seen in 30-day-old controls. When spectra were acquired in predominantly GM and WM slices in vivo, the PCr/NTP ratio was very low in GM at 5 days but reached adult levels by 15 days in controls. In WM, the ratio increased steadily from 5 to 30 days of age. In Cr-injected pups, PCr/NTP increased to mature levels in WM and in GM at all ages. In conclusion, hypoxic seizures occur midway in the time course of brain PCr/NTP increase in rabbit pups as previously described in rat pups. In both altricial pups, systemic Cr increases brain PCr/NTP ratio and prevents hypoxic seizures. These results suggest that mature levels of PCr and/or Cr in brain limit EEG activation either directly or indirectly by preventing hypoxic metabolic changes.

Multi-component apparent diffusion coefficients in human brain

The signal decay with increasing b-factor at fixed echo time from brain tissue in vivo has been measured using a line scan Stejskal-Tanner spin echo diffusion approach in eight healthy adult volunteers. The use of a 175 ms echo time and maximum gradient strengths of 10 mT/m allowed 64 b-factors to be sampled, ranging from 5 to 6000 s/ mm2, a maximum some three times larger than that typically used for diffusion imaging. The signal decay with b-factor over this extended range showed a decidedly non-exponential behavior well-suited to biexponential modeling. Statistical analyses of the fitted biexponential parameters from over 125 brain voxels (15 x 15 x 1 mm3 volume) per volunteer yielded a mean volume fraction of 0.74 which decayed with a typical apparent diffusion coefficient around 1.4 microm2/ms. The remaining fraction had an apparent diffusion coefficient of approximately 0.25 microm2/ms. Simple models which might explain the non-exponential behavior, such as intra- and extracellular water compartmentation with slow exchange, appear inadequate for a complete description. For typical diffusion imaging with b-factors below 2000 s/mm2, the standard model of monoexponential signal decay with b-factor, apparent diffusion coefficient values around 0.7 microm2/ms, and a sensitivity to diffusion gradient direction may appear appropriate. Over a more extended but readily accessible b-factor range, however, the complexity of brain signal decay with b-factor increases, offering a greater parametrization of the water diffusion process for tissue characterization.

Creatine increases survival and suppresses seizures in the hypoxic immature rat

The incidence of clinical seizures is highest in the newborn period. At this developmental stage seizures have many causes, with hypoxia and ischemia thought to be the most common. In rat pups hypoxia produces seizures most frequently at 10-12 d of age. Brain cellular energy metabolism increases between 5 and 25 d of age in the rat, as indicated in vivo by the phosphocreatine (PCr)/nucleoside triphosphate (NTP) ratio measured by 31P nuclear magnetic resonance (NMR) spectroscopy. Brain PCr/NTP ratios are approximately the same in 10-12-d-old rats and human term newborns, the ages of high seizure susceptibility. Thus, low Cr or PCr may be important in susceptibility to hypoxic seizures in the metabolically immature brain. To test this hypothesis, rat pups were injected with Cr for 3 d before exposing them to hypoxia on postnatal d 10 or 20. Before and during hypoxia, the electrocortical activity or 31P nuclear magnetic resonance spectra were measured. At 10 but not 20 d, Cr injections increased brain PCr/NTP ratios, decreased hypoxia-induced seizures and deaths, and enhanced brain PCr and ATP recoveries after hypoxia. Thus, Cr protects the metabolically immature brain from hypoxia-induced seizures and, perhaps, from cellular injury. These results may be directly relevant to the human newborn.

In vivo phosphocreatine and ATP in piglet cerebral gray and white matter during seizures

The creatine kinase (CK) reaction is thought to be important in coupling ATP metabolism and regulating ADP concentration in tissues with high and variable ATP turnover, including cerebral gray matter (GM). There is low phosphocreatine (PCr), low CK reaction rates, and high mitochondrial CK (MiCK) isoenzyme activity in GM compared to white matter (WM). To compare the CK reaction in GM and WM when ATP metabolism is high, CK reactants and reaction rates were measured in predominantly GM and WM slices in vivo in 2 and 14-day old piglets during pentylenetetrazole (PTZ) seizures using 31P nuclear magnetic resonance (NMR) 1-dimensional chemical shift imaging (CSI). Arterial pressure, temperature, and blood gasses were stable at both ages. Before seizures, the PCr/nucleoside triphosphate (NTP) ratio was higher in WM than GM at both ages with a developmental increase seen in WM. The CK reaction rate constant increased in both regions between 2 and 14 days. During seizures, PCr/NTP increased in GM at 14 days due to increased PCr while the ratio and PCr decreased in WM. The NTP was more stable in WM and GM at both ages. The CK reaction rate decreased in both regions more at 2 than at 14 days. Thus, brain ATP, deduced from NTP, is stable during seizures in the piglet. In GM stable ATP is associated with a unique increase in PCR concentration.

Persephone, the loss of virginity and the female oedipal complex

The ancient myth of Persephone and her mother, Demeter, has been characterised as the most important myth about women and the mother-daughter relationship. Previous psychoanalytic interpretations of the myth have neglected its depiction of the girl's defence against a sense of agency over her sexuality. The authors present two examples of the use of this myth by an analytic patient and the writer, Edith Wharton. Both women consciously identified in childhood with the figure of Persephone. Aspects of the myth contributed to a central unconscious fantasy that illuminated their dynamics and sexual conflicts. The authors argue that the Persephone myth is essentially a portrayal of the oedipal dilemma that emphasises a conflict of loyalty towards father and mother, fear of loss of virginity and adult sexuality and a peaceful resolution. The female oedipal conflict is seen as different from that of the male, because the girl competes with the mother on whom she must depend as primary care-giver. Separation issues are encompassed within the female oedipal phase proper. It is proposed that the Persephone complex is better suited to representing women's issues than is the myth of Oedipus.

RARE imaging of PCr in human forearm muscles

Rapid acquisition with relaxation enhancement (RARE) sequences have been used to map the 31P phosphocreatine (PCr) signal in human forearms at 4.7 T. Signal-to-noise levels of approximately 10 were achieved from the major muscle groups in 5.5-minute scan times with a spatial resolution of 4 x 2 x 2 cm3. Exercise caused demonstrable reductions in PCr signal from activated muscles, which correlated with affected muscle groups in T2-weighted proton images. RARE imaging of the PCr signal at 4.7 T is feasible and, with technically achievable improvements in signal-to-noise ratio, should prove useful in studying energy metabolism in muscle and other organs.

Patterns of health risk behaviors for chronic disease: a comparison between adolescent and adult American Indians living on or near reservations in Montana

PURPOSE

To compare the chronic disease health risk behavior patterns of adolescents and adults among American Indians living on or near reservations in Montana.

METHODS

We analyzed data from the 1993 Youth Risk Behavior Survey of American Indians in Grades 9-12 living on or near Montana reservations. Risk factors included tobacco use, low physical activity, attempted weight loss, and low consumption of fruits, vegetables, and green salad. Similar data were analyzed from a 1994 Behavioral Risk Factor Survey of American Indian adults living on or near reservations in Montana.

RESULTS

The prevalence of most adolescent health risk behaviors was high, especially cigarette smoking (45% for males, 57% for females), smokeless tobacco use (44% for males, 30% for females), and infrequent consumption of salad or vegetables (59-76%). With the exception of daily cigarette smoking and inadequate fruit consumption among adolescents of both genders and physical inactivity among adolescent males, the prevalence of chronic disease health risk behaviors among adolescents was similar to or higher than the prevalence of the same risk behaviors among adults.

CONCLUSIONS

Many health risk behaviors for chronic diseases are common by the time this group of American Indians in Montana has reached adolescence. Possible reasons may include modeling of familial behaviors, peer pressure, advertising, or age cohort effects. If these risk behavior patterns continue into adulthood, morbidity and mortality from chronic diseases are likely to remain high. Substantial efforts are needed to prevent or reduce health risk behaviors among adolescents and adults in this population.

Multiecho approaches to spectroscopic imaging of the brain

Spectroscopic imaging (SI) with nuclear magnetic resonance (NMR) is one of the most powerful tools available for studying brain chemistry in vivo. Both proton (1H) and phosphorus (31P) NMR offer valuable biochemical information that can in principle be mapped throughout the entire brain, thereby enhancing our understanding of brain function. With the exception of protons from tissue water and the triglycerides of adipose tissue, however, nuclei contributing to the NMR signals of living tissue are in relatively small (millimolar) concentrations. The low concentration of metabolite nuclei reduces the overall sensitivity of conventional SI techniques, making high-quality metabolite mapping a lengthy procedure. This problem has led to the development and testing of nonconventional methods for reducing SI scan times, including techniques based on the collection of multiple spin-echoes. The extent to which multiecho methods can be used to decrease SI scan times and maintain high-quality metabolite mapping depends on several factors. These include the spectral transverse relaxation times, the spectral resolution required, and J-coupling interactions. We have discussed these various technical aspects of multiecho SI methods as applied to 1H and 31P spectroscopic imaging of the living brain.

In vivo brain phosphocreatine and ATP regulation in mice fed a creatine analog

Mitochondrial and cytosolic creatine kinase (CK) isozymes are active in cells with high and variable ATP metabolic rates. beta-Guanidinopropionic acid (GPA), a competitive inhibitor of creatine transport, was used to study the hypothesis that the creatine-CK-phosphocreatine (PCr) system is important in regulating brain ATP metabolism. The CK-catalyzed reaction rate and reactant concentrations were measured in vivo with 31P nuclear magnetic resonance spectroscopy during energy deficit (hypoxia) or high-energy turnover (seizures) states in urethane-anesthetized mice fed GPA, creatine, or standard chow (controls). Brain phosphagen (i.e., cellular energy reserves) or PCr plus phosphorylated GPA (GPAP) concentrations were equal. The phosphagen-to-NTP ratio was lower than in controls. In vivo CK reaction rate decreased fourfold, whereas ex vivo CK activity that was biochemically measured was doubled. During seizures, CK-catalyzed fluxes increased only in GPA-fed mice. Phosphagen increased in GPA-fed mice, whereas PCr decreased in controls. Survival was higher and brain phosphagen and ATP losses were less for hypoxic GPA-fed mice than for controls. In contrast to mice fed GPA, hypoxic survival and CK reactant concentrations during hypoxia and seizures were the same in creatine-fed mice and controls. Thus GPA, GPAP, or adaptive changes in ATP metabolism stabilize brain ATP and enhance survival during hypoxia in mice.

Brain creatine kinase reaction rates and reactant concentrations during seizures in developing rats

Brain creatine kinase (CK) catalyzed phosphorus fluxes between phosphocreatine (PCr) and ATP and changes in reactant concentrations were measured using [31P] nuclear magnetic resonance spectroscopy ([31P]NMR) before and during pentylenetetrazole-induced seizures in 7 and 21 day old rats. The CK rate constants measured before seizures were three times higher in the older than in the younger rats. The rate constants increased 60% during seizures in the older rats but did not change or decreased in the younger. Small decreases in PCr were seen during seizures at both ages. A small decrease in ATP was seen at 7 days but not at 21 days.

Multi-echo 31P spectroscopic imaging of ATP: a scan time reduction strategy

Spectroscopic imaging of 31P metabolites and adenosine triphosphate (ATP) in particular with multiple spin echoes may prove useful for reducing data acquisition times. The usual T2 decay processes that degrade multi-echo spectroscopic imaging methods, however, are further compounded by J-coupling modulations in the case of ATP. We determine how these modulations affect multi-echo spectroscopic imaging k-space data and produce systematic spatial misregistrations of the ATP resonances. The specific J-coupling modulations of ATP are determined to identify echo-spacing effects in multi-echo spectroscopic imaging of ATP and to determine appropriate post-processing correction schemes to address the spatial misregistration problem. An in vivo demonstration of the technique that offers a threefold reduction in scan time compared to conventional SI methods is provided and compared with the conventional SI approach.

Cerebral oxygenation measured by near infrared spectroscopy during cardiopulmonary bypass and deep hypothermic circulatory arrest in piglets

Near infrared spectroscopy (NIRS) shows large changes in cerebral oxyhemoglobin (Hbo2), deoxyhemoglobin (Hb), and oxidation state of cytochrome aa3 (Cyto2) in infants undergoing cardiopulmonary bypass and deep hypothermic circulatory arrest (CPB-DHCA). To evaluate the physiologic significance of these clinical NIRS measurements, we applied the technique in a piglet model of CPB-DHCA. After an initial stabilization period on CPB, animals (n = 8) were cooled to 15 degrees C, subjected to DHCA for 1 h, then reperfused with rewarming and monitored for 180 min. NIRS measurements were compared with determinations of cerebral blood flow (CBF). During cooling, Cyto2 decreased markedly, whereas Hbo2 increased. DHCA was associated with a sharp decrease in Hbo2, a corresponding increase in Hb, and a smaller, less consistent further decrease in Cyto2. NIRS measurements recovered toward baseline with reperfusion. CBF decreased during cooling and recovered to baseline levels with reperfusion. These findings are consistent with existing human data and show that 1) cooling is associated with increased oxygenation of cerebral hemoglobin despite a reduction in CBF; 2) Cyto2 becomes more reduced during cooling, consistent with a net cellular oxygen deficit; and 3) DHCA is associated with rapid cerebral hemoglobin deoxygenation and a small further reduction of Cyto2.

Cerebral metabolic recovery from deep hypothermic circulatory arrest after treatment with arginine and nitro-arginine methyl ester

BACKGROUND

Recent studies suggest that nitric oxide is important in the pathogenesis of ischemic brain injury and also has a role in controlling cerebrovascular tone. This study examines the net effects of nitric oxide on cerebral metabolic recovery after deep hypothermic circulatory arrest.

METHODS

Two-week-old piglets were supported by cardiopulmonary bypass and cooled to 15 degrees C followed by 1 hour of deep hypothermic circulatory arrest, 45 minutes of reperfusion and rewarming, and then 3 hours of normothermic perfusion. Groups of 10 piglets received one of four treatments before bypass; L-nitro-arginine methyl ester, inhibitor of nitric oxide synthesis, 10 mg/kg intravenously; L-arginine, to enhance nitric oxide synthesis, 30 mg/kg intravenously before bypass and then 10 mg/kg per minute during the first hour of reperfusion; a combination of L-nitro-arginine methyl ester plus L-arginine at these same doses; and no pretreatment (controls). Cerebral high-energy phosphates and pH were measured by magnetic resonance spectroscopy in half the animals. Cerebral blood flow, metabolic rates for oxygen and glucose, and the oxidation/reduction state of cytochrome aa3 and oxygenated and deoxygenated hemoglobin measured by near-infrared spectroscopy were assessed in the other half of the piglets.

RESULTS

L-nitro-arginine methyl ester significantly increased cerebral vascular resistance and markedly reduced recovery of high-energy phosphates, pH, and oxidation state of cytochrome aa3, L-arginine increased cerebral blood flow, cerebral glucose and oxygen consumption, and recovery of cytochrome aa3 oxidation and high-energy phosphates. L-Arginine did not reverse completely the effects of L-nitro-arginine methyl ester on cerebral metabolic recovery.

CONCLUSION

In a piglet model of deep hypothermic circulatory arrest, L-nitro-arginine methyl ester has a deleterious effect and L-arginine has a beneficial effect on cerebral metabolic recovery. The deleterious metabolic effects of L-nitro-arginine methyl ester are only partially reversed by L-arginine. This fact suggests that there may be mechanisms in addition to inhibition of nitric oxide synthesis contributing to the neurotoxicity of L-nitro-arginine methyl ester in this model.

Population estimates of household firearm storage practices and firearm carrying in Oregon

OBJECTIVES

To examine statewide data on exposure of adults and children to loaded and unlocked household firearms, and to estimate the prevalence of firearm carrying among adults in Oregon.

DESIGN

Analyses of 1992 and 1993 telephone survey data from 6202 adults aged 18 years and older using the Oregon Behavioral Risk Factor Surveillance System.

MAIN OUTCOME MEASURES

Number of adults and children exposed to household firearms always or sometimes stored loaded and unlocked. Adjusted odds ratios (ORs) for exposure to loaded and unlocked firearms and firearm carrying among adults by demographic and alcohol use patterns.

RESULTS

Ten percent of adults (197 400 persons) lived in households with firearms that were always or sometimes stored loaded and unlocked. An estimated 6.2% of households with children had firearms that were loaded and unlocked, and about 40 000 children lived in these households. Overall, 4.4% of adults carried loaded firearms in the past month. Rural residence, male sex, and less than a college education were associated with living in a household with loaded and unlocked firearms and with firearm carrying. Drinking 5 or more alcoholic beverages on 1 or more occasions in the past month (OR, 1.7; 95% confidence interval, 1.3-2.3) or drinking 60 or more alcoholic beverages in the past month (OR, 1.8; 95% confidence interval, 1.2-2.7) were independently associated with living in households with loaded and unlocked firearms.

CONCLUSIONS

Many adults and children are exposed to unsafely stored firearms in Oregon, and many adults carry loaded firearms. Improved public health surveillance of firearm storage and firearm carrying using standardized questions and definitions is needed at the national, state, and local levels.

Relative phosphocreatine and nucleoside triphosphate concentrations in cerebral gray and white matter measured in vivo by 31P nuclear magnetic resonance

Rates of ATP metabolism generally are higher in cerebral gray matter compared to white matter. In order to study the physiology of this regional difference in vivo, the 1-dimensional chemical shift imaging technique (1D-CSI) was used to acquire 31P nuclear magnetic resonance spectra from 2.5 mm slices of 4-week old piglet brains. Spectra from predominantly gray matter slices (estimated 76% gray matter, 7 mm below the scalp) were compared to predominantly white matter slices (56% estimated white matter, 13 mm below the scalp) as assessed by magnetic resonance images. The 1D-CSI technique introduced no systematic changes in the ratio of signals from a single chamber phantom containing a phosphocreatine (PCr) and ATP solution. Gray matter slices showed a PCr/NTP ratio of 0.93 +/- 0.11 (mean +/- S.D.) using a 2 s interpulse interval, a value very close to the ratio in surface coil localized spectra. The predominantly white matter slices showed a PCr/NTP ratio of 1.32 +/- 0.18 (P < 0.02 for gray versus white matter). Using the estimated percentages of gray and white matter in the two slices and calculated concentrations from fully relaxed spectra, the gray matter PCr/NTP ratio is approximately 0.77, while the ratio in white matter is approximately 2.18. The difference in PCr/NTP measured in vivo suggests that either the total NTP concentration is higher or the steady state PCr concentration is lower in gray matter than in white matter in the piglet brain.

Nevermore: the hymen and the loss of virginity

A major milestone in a woman's life is the loss of virginity, "defloration," with the breaking of the hymen. Psychoanalysis has paid little attention to the meaning of defloration to either women or men, and virtually none to the hymen as a part of the female genitalia. The reasons for this disregard or avoidance are explored. Utilizing the few psychoanalytic writings, mythology, literature, and anthropological studies in addition to numerous clinical examples, the authors find that the unconscious meanings of the loss of virginity and the hymen emerge clearly. The common theme is that of negation, never, never again, never seen, known or named. Theoretical considerations regarding female sexuality are discussed. Technical implications for analyst-patient are presented.

Phosphocreatine and creatine kinase in piglet cerebral gray and white matter in situ

Rates of adenosine triphosphate (ATP) metabolism are higher in cerebral gray matter than in white matter. Like other excitable tissues, brain contains a phosphocreatine (PCr)/creatine kinase (CK)/ATP system including cytosolic (B-CK) and mitochondrial (Mi-CK) isozymes. High B-CK activity is present in white and gray matter while Mi-CK is mostly in gray matter. An in situ localizing 31P-NMR technique, one-dimensional chemical shift imaging (1D-CSI), has been used to study the PCr/CK/ATP system in these regions. In the metabolically mature 4-week-old piglet, the PCr/nucleoside triphosphate (NTP) ratio measured by the 1D-CSI technique is at least 50% higher in white than gray matter. Total creatine (Cr), ATP, and total NTP concentrations are the same in rapidly frozen rat white and gray matter, suggesting that PCr/Cr ratio is much higher in white matter. The PCr increases more in gray than white matter between 4 days and 4 weeks of age in piglet brain. The CK catalyzed reaction rate constant, measured by combining the saturation transfer experiment with the 1D-CSI, is also much higher in white than gray matter at both ages. The postnatal maturational increase in the CK rate constant is greater in gray matter. In summary, these differences in PCr concentration and CK reaction rates and isozymes characterize two physiologically different PCr/CK/ATP systems in gray and white matter.

'Hot spots' of creatine kinase localization in brain: cerebellum, hippocampus and choroid plexus

Creatine kinase (CK) isoenzymes, with emphasis on the mitochondrial CK isoenzymes, were characterized and localized in chicken cerebellum. Chicken cerebellum extracts analyzed by two-dimensional gels, using antipeptide antibodies specific for sarcomeric muscle-type mitochondrial CK (Mib-CK) and revealed the presence of a Mib-CK variant in avian cerebellum. This CK isoform was localized by immunofluorescence staining exclusively in the Purkinje neurons. The co-expression of this Mib-CK together with cytosolic muscle-type MM-CK, as observed in the same Purkinje neurons, may reflect the specific energy requirements associated with highly fluctuating Ca2+ levels (Ca2+ spiking) in these specialized neurons. Ubiquitous brain-type mitochondrial Mia-CK was found together with cytosolic BB-CK mainly in the glomeruli structures of the cerebellar granular layer. BB-CK, but much less so Mia-CK however, was also very prominent in Bergmann glial cells of the two mitochondrial Mi-CK isoenzymes in the chicken cerebellum is demonstrated. Other hot spots of CK localization were the granule and pyramidal cells of the hippocampus in rat. There, a developmental stage-dependent immunofluorescence staining, especially with antibodies against Mia-CK was noted. Epithelial cells of the choroid plexus were also highly enriched in CK. The possible implications of a CK/PCr circuit at these various cellular locations of the brain are discussed with respect to normal brain physiology and pathology.

Creatine and nucleoside triphosphates in rat cerebral gray and white matter

In vivo localized nuclear magnetic resonance spectroscopy has shown three-fold higher phosphocreatine/nucleoside triphosphate (PCr/NTP) ratios in cerebral white compared to gray matter. To interpret these results, total creatine (Cr) and ATP concentrations were measured enzymatically in samples taken from rapidly frozen rat cerebral cortex and corpus callosum. Total Cr (PCr plus Cr) and ATP concentrations were the same in the two regions. High performance liquid chromatography showed similar concentrations of total NTP in the two regions. These results suggest that higher in vivo PCr/NTP ratios in white compared to gray matter may be due to a higher PCr/Cr ratio in white matter and/or higher percentages of non-adenine mono- or diphosphate nucleotides in gray matter.

Parent and peer communication effects on AIDS-related behavior among U.S. high school students

Data from a 1989 national probability sample of 8,098 high school students in the United States indicate that young people's discussions about the human immunodeficiency virus (HIV) with parents and with peers are highly correlated and have opposite effects on behavior. Students who discussed HIV with their parents were less likely than those who did not to have had multiple sex partners, to have had unprotected sexual intercourse and to have ever injected drugs; on the other hand, students who discussed HIV with their peers were more likely than those who did not to have had multiple partners and to have had unprotected sexual intercourse. Subgroup analyses show that young women were influenced more by HIV discussions with parents, while young men were influenced more by discussions with peers; some communication effects differed by race and ethnicity. Students who received HIV instruction in school were more likely to have talked about HIV with both parents and peers.

Enamel hypoplasia, bilateral cataracts, and aqueductal stenosis: a new syndrome?

We report on a 12-year-old girl who presented with generalized enamel hypoplasia, cataracts, and enlargement of the cerebral ventricles secondary to aqueductal stenosis. Previously described syndromes of enamel defects with or without cataracts were excluded on the basis of clinical criteria and appearance of the dentition. Metabolic conditions which could have caused cataracts were excluded clinically and by biochemical tests. The combination of signs in this patient may represent a new syndrome.

Trends in risk behaviors for HIV infection among U.S. high school students, 1989-1991

The objective of this study was to examine trends in rates of self-reported HIV-related instruction and behaviors among high school students in the United States. Self-administered questionnaires were completed by three independent, multistage national probability samples of public and private school students in grades 9 through 12 who were surveyed in the spring of 1989, 1990, and 1991, respectively. Controlling for demographic characteristics, we used logistic regression to test for trends from 1989 to 1991. From 1989 to 1991, the proportion of students who had received HIV instruction in school significantly increased from 53.7% in 1989 to 83.3% in 1991. At the same time, the proportion of students engaging in selected sexual behaviors generally decreased. We found significant declines in the proportion of students who had engaged in sexual intercourse (58.5% in 1989 to 54.1% in 1991), had two or more sex partners during their lifetime (40.1% in 1989 to 35.2% in 1991), and had four or more lifetime sex partners (23.6% in 1989 to 18.7% in 1991). School-based HIV instruction, which is reaching greater numbers of U.S. students, may be contributing to the decline in reported risk behavior. However, because the current level of HIV-related behavior is still too high, risk-reduction efforts for adolescents should be maintained and strengthened.

pH strategies and cerebral energetics before and after circulatory arrest

The pH-stat strategy compared with the alpha-stat strategy provides more rapid recovery of brain high-energy phosphate stores and intracellular pH after 1 hour of hypothermic circulatory arrest in pigs. Possible mechanisms for this difference are (1) improved oxygen delivery and homogeneity of brain cooling before deep hypothermic circulatory arrest and (2) greater cerebral blood flow and reduced reperfusion injury owing to extracellular acidosis during the rewarming phase. To identify which of these mechanisms is predominant, we studied 49 4-week-old piglets undergoing 1 hour of deep hypothermic circulatory arrest. Four groups were defined according to cooling/rewarming strategy: alpha/alpha, alpha/pH, pH/alpha, and pH/pH. In 24 animals cerebral high-energy phosphate levels and intracellular pH were measured by magnetic resonance spectroscopy (alpha/alpha group 7, alpha/pH group 5, pH/alpha group 7, pH/pH group 5). In 25 animals cerebral blood flow was measured by labeled microspheres, cerebral metabolic rate by oxygen and glucose extraction, and the redox state of cytochrome aa3 and hemoglobin oxygenation by near infrared spectroscopy (alpha/alpha group 7, alpha/pH group 5, pH/alpha group 7, pH/pH group 6). Cerebral blood flow was greater with pH-stat than alpha-stat during cooling (56.3% +/- 3.7% versus 32.9% +/- 2.1% of normothermic baseline values, p < 0.001). Cytochrome aa3 values became more reduced during cooling with alpha-stat than with pH-stat (p = 0.049). Recovery of adenosine triphosphate levels in the initial 45 minutes of reperfusion was more rapid in group pH/pH compared with that in the other groups (p = 0.029). Recovery of cerebral intracellular pH in the initial 30 minutes was faster in group pH/pH compared with that in group alpha/alpha (p = 0.026). Intracellular pH became more acidic during early reperfusion only in group alpha/alpha, whereas it showed continuous recovery in the other groups. This study suggests that there are mechanisms in effect during both the cooling and rewarming phases before and after deep hypothermic circulatory arrest that could contribute to an improved cerebral outcome with pH-stat relative to more alkaline strategies.

Phosphocreatine and ATP regulation in the hypoxic developing rat brain

Decreased brain ATP and phosphocreatine (PCr) concentrations and intracellular pH were compared in hypoxic 4-, 10-11, and 24-25-day-old rats. Surface coil 31P-nuclear magnetic resonance (NMR) spectra were acquired in vivo every minute before, during, and after 7 min of breathing 4% O2. At all ages PCr decreased rapidly. At the two younger ages, the nucleoside triphosphate signal was still 80-85% of pre-hypoxic values, indicating 20-30% decrease in ATP, when PCr was almost fully depleted. At 24-25 days, PCr initially decreased 40-50% with an ATP loss of about 30%. Then, PCr and ATP decreased simultaneously. The decrease in brain pH was greatest at 24-25 days. More electrocortical seizure activity during hypoxia was seen at 10-11 days than at other ages. Seizure activity was seen only when ATP was less than 20% depleted and was not associated with more rapid decreases in ATP or PCr. At all ages, loss of electrocortical activity occurred when ATP was about 30% depleted. Brain creatine kinase catalyzed flux, measured by the NMR saturation transfer experiment before the hypoxic period, was 4-fold higher at 24-25 days than at 4- or 10-11 days. In conclusion, the temporally coupled depletion of PCr and ATP during hypoxia, which is characteristic of the mature brain, is seen only after the maturational increase in brain CK activity.

Reduction of cytochrome aa3 measured by near-infrared spectroscopy predicts cerebral energy loss in hypoxic piglets

Near-infrared spectroscopy is a noninvasive monitoring technique that allows quantitative measurement of changes in cerebral oxygenated Hb (HbO2), deoxygenated Hb (Hb), total Hb, and oxidized cytochrome aa3 (CytO2). Changes in cerebral Hb oxygenation and CytO2 have been measured in human neonates and infants under a variety of conditions. However, the association of these measurements with cerebral high-energy phosphate loss is not known. We studied simultaneous changes in cerebral HbO2, Hb, total Hb, and CytO2 by near-infrared spectroscopy and changes in nucleoside triphosphate (NTP, mostly ATP) and phosphocreatine (PC) concentrations and intracellular pH by in vivo 31P-labeled magnetic resonance spectroscopy. Four-wk-old piglets (n = 8) underwent sequential hypoxic episodes of increasing severity (inspired O2 concentration, 12, 8, 6, 4, and 0%). Animals were anesthetized and mechanically ventilated. At all levels of hypoxia, cerebral HbO2 decreased, and Hb increased. Loss of PC or NTP was not observed until inspired O2 concentration was decreased to less than 12%. With such severe hypoxia, hypotension, intracellular acidosis, and increasingly severe PC and NTP depletions occurred. Decreases in PC and NTP correlated closely with decreased CytO2 and arterial blood pressure (p < 0.0001) but not with changes in HbO2 and Hb. In conclusion, cerebral hypoxemia is readily detected by near-infrared spectroscopy as a decrease in HbO2 and an increase in Hb. However, relative changes in cerebral HbO2 and Hb have low predictive value for cerebral energy failure. Reduction of CytO2 is highly correlated with decreased brain energy state and may indicate impending cellular injury.

Effects of cerebroplegic solutions during hypothermic circulatory arrest and short-term recovery

Previous studies have suggested that a simple crystalloid "cerebroplegic" solution may prolong the safe duration of hypothermic circulatory arrest. We tested the hypothesis that pharmacologic modification of the cerebroplegic solution would further enhance cerebral protection. Forty-six 4-week-old miniature piglets underwent core cooling to 15 degrees C nasopharyngeal temperature and 2 hours of hypothermic circulatory arrest. Twelve animals had a 50 ml/kg dose of saline infused into the carotid artery system at the onset of hypothermic circulatory arrest and repeat doses of 10 ml/kg every 30 minutes during arrest. Eleven animals received the same initial and repeat doses of University of Wisconsin organ preservation solution and 10 received University of Wisconsin solution with 7.5 mg/L of MK-801, an excitatory neurotransmitter antagonist. In 13 control animals blood was partially drained from the piglet before 2 hours of circulatory arrest at 15 degrees C and no cerebroplegic solution was infused. All solutions were delivered at 4 degrees C. Brain temperature (n = 24) at the onset of hypothermic circulatory arrest was 15.0 degrees +/- 0.1 degrees C (mean +/- standard error). Brain temperature after cerebroplegic infusion dropped to 13.0 degrees +/- 0.3 degrees C and stayed lower than brain temperature in the control group throughout the hypothermic circulatory arrest period. Recovery of cerebral adenosine triphosphate and intracellular pH determined by phosphorus 31 magnetic resonance spectroscopy (n = 22) was significantly improved by saline infusion and was further improved with University of Wisconsin solution and University of Wisconsin solution plus MK-801 (p < 0.001). Recovery of cerebral blood flow measured by microspheres (n = 24) also was augmented by University of Wisconsin solution (p < 0.001) but not in the presence of MK-801. The vascular resistance response to acetylcholine and nitroglycerin suggested that MK-801 has a direct vasoconstrictive effect. Recovery of cerebral oxygen consumption (n = 24) was increased by University of Wisconsin solution and University of Wisconsin solution with MK-801 (p = 0.002). Brain water content (n = 46) was significantly lower in all cerebroplegia-treated groups than in controls (p < 0.001).

CONCLUSION

Cerebroplegia improves short-term recovery after 2 hours of circulatory arrest in hypothermic piglets. Pharmacologic modification with University of Wisconsin solution further improves the recovery of cerebral blood flow and metabolism. MK-801 does not augment the protective effects of University of Wisconsin solution and reduces the recovery of cerebral blood flow by a direct vascular action. Modified cerebroplegia may provide a novel approach to improved cerebral protection when prolonged hypothermic circulatory arrest is necessary.

Substance use and HIV-related sexual behaviors among US high school students: are they related?

OBJECTIVES

This study was undertaken to examine whether use of alcohol, cigarettes, marijuana, cocaine, and other illicit drugs is related to the likelihood of sexual behaviors that increase risk for human immunodeficiency virus (HIV) infection among youth.

METHODS

The 1990 national Youth Risk Behavior Survey was used to collect self-reported information about a broad range of health risk behaviors from a representative sample of 11,631 high school students in the United States.

RESULTS

Students who reported no substance use were least likely to report having had sexual intercourse, having had four or more sex partners, and not having used a condom at last sexual intercourse. Adjusted for age, sex, and race/ethnicity, odds ratios for each of these sexual risk behaviors were greatest among students who had used marijuana, cocaine, or other illicit drugs. Students who had used only alcohol or cigarettes had smaller but still significant increases in the likelihood of having had sexual intercourse and of having had four or more sex partners.

CONCLUSIONS

HIV prevention programs for youth should recognize that substance use may be an important indicator of risk for HIV infection and acquired immunodeficiency syndrome through its association with unsafe sexual behaviors.

Changes in HIV-related information sources, instruction, knowledge, and behaviors among US high school students, 1989 and 1990

OBJECTIVES

Few data have been available among adolescents to determine behavioral changes that may prevent human immunodeficiency virus (HIV) infection. This analysis examines changes in the prevalence of self-reported HIV-related information sources, instruction, knowledge, and behaviors among high school students in the United States.

METHODS

Two independent, multistage national probability samples of students in grades 9 through 12 were surveyed in 1989 (n = 8098) and 1990 (n = 11,631) with self-administered, anonymous questionnaires that included similar items.

RESULTS

Compared with students surveyed in 1989, a significantly greater proportion of students surveyed in 1990 had received HIV instruction in school. Significant decreases were found in the proportion of White and female students who reported having had sexual intercourse, in the proportion of White students reporting two or more lifetime sex partners, and in the proportion of 15- and 16-year-olds, White students, and female students who reported having had four or more lifetime sex partners. For both years, students who had a greater level of HIV knowledge were less likely to have had multiple lifetime sex partners or to have injected illicit drugs.

CONCLUSIONS

The findings suggest that school-based HIV education and knowledge may be contributing factors in reducing certain risk behaviors that can lead to HIV transmission among secondary school youth.

Effects of MK-801 and NBQX on acute recovery of piglet cerebral metabolism after hypothermic circulatory arrest

Brain protection during open heart surgery in the neonate and infant remains inadequate. Effects of the excitatory neurotransmitter antagonists MK-801 and NBQX on recovery of brain cellular energy state and metabolic rates were evaluated in 34 4-week-old piglets (10 MK-801, 10 NBQX, 14 controls) undergoing cardiopulmonary bypass and hypothermic circulatory arrest at 15 degrees C nasopharyngeal temperature for 1 h, as is used clinically for repair of congenital heart defects. MK-801 (dizocilpine) (0.75 mg/kg) or NBQX [2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo(F)quinoxaline] (25 mg/kg) was given intravenously before cardiopulmonary bypass. Equivalent doses were placed in the cardiopulmonary bypass prime plus continuous infusions after reperfusion (0.15 mg kg-1h-1 and 5 mg kg-1h-1). Changes in high-energy phosphate concentrations and pH were analyzed by magnetic resonance spectroscopy in 17 animals until 225 min after reperfusion. Cerebral blood flow determined by radioactive microspheres as well as cerebral oxygen and glucose consumption were studied in 17 other animals. Cerebral blood flow and oxygen consumption were depressed relative to control by both MK-801 and NBQX at baseline. Recovery of phosphocreatine (p = 0.010), ATP (p = 0.030), and intracellular pH (p = 0.004) was accelerated by MK-801 and retarded by NBQX over the 45 min of rewarming reperfusion and the first hour of normothermic reperfusion. The final recovery of ATP at 3 h and 45 min reperfusion was significantly reduced by NBQX (46 +/- 26% baseline, mean +/- SD) versus control (81 +/- 19%) and MK-801 (75 +/- 8%) (p = 0.030). Cerebral oxygen consumption recovered to 105 +/- 30% baseline in group MK-801 and 94 +/- 31% in control but only to 61 +/- 22% in group NBQX (p = 0.070). Cerebral blood flow stayed significantly lower in group NBQX relative to control. Thus, MK-801 accelerates recovery of cerebral high-energy phosphates and metabolic rate after cardiopulmonary bypass and hypothermic circulatory arrest in the immature animal. At the dosage used NBQX exerts an adverse effect.

Recovery of cerebral blood flow and energy state in piglets after hypothermic circulatory arrest versus recovery after low-flow bypass

A miniature piglet model that replicates clinical hypothermic (14 degrees C nasopharyngeal) circulatory arrest and low-flow (50 ml/kg per minute) bypass was used to study carotid blood flow with electromagnetic flow probe, cerebral blood flow by microsphere injection, cerebral metabolic rate by arteriovenous oxygen and glucose extractions, lactate production by cerebral arteriovenous difference, and cerebral edema. Data from five animals that underwent circulatory arrest and five animals that underwent low-flow bypass (aged 28.8 +/- 0.4 [mean +/- standard error of the mean] days) were analyzed. The duration of circulatory arrest and low-flow bypass was 1 hour. In a parallel study with the same animal model, phosphorus 31 magnetic resonance spectroscopy was used to assess cerebral phosphocreatine, nucleoside triphosphate (adenosine triphosphate), and intracellular pH. Five animals (aged 31.8 +/- 1.1 days) underwent circulatory arrest, and five underwent low-flow bypass. A brief phase of hyperemic carotid blood flow was seen immediately after the onset of reperfusion in the circulatory arrest group but not in the low-flow group. In the circulatory arrest and low-flow bypass groups, cerebral blood flow (percentage of baseline 71.2% +/- 8.3% and 69.1% +/- 5.8%, respectively), cerebral oxygen consumption (45.6% +/- 10.0%, 44.5% +/- 7.6%), and cerebral glucose consumption (31.5% +/- 30.7%, 83.5% +/- 24.2%) remained depressed after 45 minutes of reperfusion and rewarming to normothermia. However, after 3 more hours of pulsatile normothermic reperfusion, cerebral oxygen consumption and cerebral glucose consumption had returned to baseline. Phosphocreatine, adenosine triphosphate, and pH were maintained at or above baseline levels throughout low-flow bypass and throughout 3 hours of normothermic reperfusion. In contrast, both phosphocreatine and adenosine triphosphate became undetectable 32 +/- 3.7 minutes after onset of circulatory arrest. During and early after circulatory arrest, pH decreased to a minimum of 6.506 +/- 0.129 at 40 minutes after reperfusion. After 3 hours of normothermic reperfusion, phosphocreatine and adenosine triphosphate recovered to 98.6% +/- 9.0% and 90.1% +/- 13.5% of baseline, respectively, and pH was 7.087 +/- 0.051, similar to baseline (7.1755 +/- 0.041). In the low-flow bypass group, the disparity between the depressed level of cerebral oxygen consumption and normal high-energy phosphate levels may reflect incomplete cerebral rewarming or decreased energy consumption. In the circulatory arrest group, the parallel recovery of oxygen consumption and high-energy phosphates eventually achieving baseline levels suggests that the degree of hypothermia used provides adequate protection for acute cerebral recovery after 1 hour of circulatory arrest.(ABSTRACT TRUNCATED AT 400 WORDS)

Profound, reversible energy loss in the hypoxic immature rat brain

The goal of this study was to compare the effects of oxygen deprivation on cellular energy state and pH in the developing and adult rat brain. Relative quantities of phosphocreatine (PC), inorganic phosphorus (P(i)), and nucleoside triphosphates (NTP), and intracellular pH, were determined using in vivo 31P NMR spectroscopy at different postnatal ages (postnatal day (P) 2-6, P9-13, P16-20, P23-27) in the hypoxic rat brain (7 min, 4% O2). While a significant increase in P(i) was seen at all ages during hypoxia, a severe but reversible reduction in concentrations of PC (80-100% decrease) and NTP (40-50% decrease) was observed only at P9-13. This dramatic response was not seen in older (> P16) or younger (< P6) animals. These latter groups responded with moderate decreases in brain PC (50-60% decrease) and NTP (20-40% decrease). In addition, the youngest animals showed much less intracellular brain acidosis than the other age groups. The transient period of development during which the brain exhibits heightened susceptibility to hypoxic energy failure coincides with known changes in brain energy production pathways and susceptibility to hypoxia-induced excitability.

Sports participation, age at smoking initiation, and the risk of smoking among US high school students

OBJECTIVE

To examine smoking patterns, smoking initiation, and the relationship of sports participation and age at smoking initiation to regular and heavy smoking among adolescents.

DESIGN

Survey.

PARTICIPANTS

A nationally representative sample of US high school students.

OUTCOME MEASURES

Prevalences of smoking patterns, prevalence and incidence of smoking initiation, and prevalences and odds of regular and heavy smoking in relation to sports participation and age at smoking initiation.

RESULTS

Seventy-two percent of students reported experimenting with, formerly, or ever smoking cigarettes, and 32% reported smoking in the past 30 days. Students who had participated in interscholastic sports were less likely to be regular and heavy smokers than were others who had not participated. Smoking initiation rates increased rapidly after age 10 years and peaked at age 13 to 14 years. Students who began smoking at age 12 years or younger were more likely to be regular and heavy smokers than were students who began smoking at older ages.

CONCLUSIONS

These data suggest that smoking initiation at a young age can increase the risk of nicotine addiction during adolescence and that sports participation may influence smoking behavior. Interventions to prevent smoking should be available before age 12 years to help combat the smoking epidemic among youth.