A Case of Guillain-Barré Syndrome With Multiple Causative Factors in a Young Male

Guillain-Barré syndrome (GBS), an immune-mediated disease of the peripheral nervous system, is mainly characterized by rapidly progressive ascending weakness of the limbs with reduced or absent deep tendon reflexes. The exact cause of GBS is unknown, but it often occurs after a gastrointestinal or respiratory infection. The present study represents a case of GBS in which multiple antecedent antigenic stimuli may have contributed to the development of GBS. The patient, a 28-year-old immunocompetent man with no significant medical history, presented to the emergency department (ED) with acute ascending flaccid paralysis that persisted for a few days. His initial symptoms included tingling in his legs, which started at his shin and calf and developed into numbness, which extended to his upper limbs and arms. A CT scan of the lumbar and cervical spine indicated minor L4-L5 and L5-S1 disc herniation as well as slight bulging in C5-C6 and C7. The patient was discharged but returned to the ED for urgent treatment the next day after he weakened rapidly, losing the ability to walk or maintain balance. Based on his clinical presentation of ascending weakness and generalized hyporeflexia, he was diagnosed with GBS. Abnormal liver function and positive blood tests for anti-cytomegalovirus (anti-CMV) and anti-Epstein-Barr virus (anti-EBV) IgG and IgM antibodies diagnosed hepatitis, CMV, and EBV, respectively. The patient was treated with intravenous immunoglobulin therapy (IVIG; 27 g/day) and antiviral medicine (ganciclovir; 340 mg IV/day) for five days. His nonexistent deep tendon reflexes began to improve two to three days following treatment. He was able to ambulate longer distances with a walker, and his upper extremities regained full strength. This case highlights the importance of a multiple-treatment approach to the treatment of GBS, wherein multiple antigenic triggering factors may be involved.

Epigenetic Mechanisms in Obesity: Broadening Our Understanding of the Disease

Now recognized as more than just the result of overeating or the consumption of poor-quality foods, obesity is understood to be a multifactorial disease, strongly correlated with a variety of environment-gene interactions. In addressing the complex public health issue of obesity, medical practitioners, along with their allied healthcare counterparts, face the challenge of reducing its prevalence by utilizing and sharing with patients the current, yet incomplete, scientific knowledge concerning the disease. While continued research is required to strengthen direct cause-effect relationships, substantial evidence links post-translational modifications such as DNA methylation and histone modifications of several candidate "obesity" genes to the predilection for obesity. Additional evidence supports the influence of maternal diet during the gestational period, individual diet, and other lifestyle and genetic factors in obesity. The purpose of this review is to synthesize the current information concerning epigenetic modifications that appear to support, or result from, the development of obesity. Such mechanisms may serve as therapeutic targets for developing novel prevention and/or treatment strategies for obesity or as epigenetic biomarkers for monitoring recovery.

Pheochromocytoma: A Troublesome Tumor

This report presents the case of a 45-year-old man with a history of episodic headaches, palpitations, and sweating for the past six months. His blood pressure on admission was 170/100 mmHg. The patient was diagnosed with pheochromocytoma confirmed by elevated levels of plasma catecholamines and metanephrines. CT imaging revealed a 3 cm mass in the left adrenal gland with evidence of local invasion into the surrounding tissues. The patient underwent a laparoscopic adrenalectomy and was discharged on the third postoperative day with normal blood pressure. Histopathological examination confirmed the diagnosis of pheochromocytoma. The patient was followed for six months postoperatively with the resolution of symptoms and no evidence of tumor recurrence on imaging. Recurrence involves complex environment-gene interactions that are poorly understood. The diagnosis of pheochromocytoma could take several weeks to several years mainly because the symptoms are nonspecific and episodic. Although sudden death is rare, the debilitations associated with pheochromocytoma are often multisystemic with cardiovascular, emotional, and metabolic components. This case report highlights the importance of early diagnosis, appropriate management, and follow-up for pheochromocytoma.

An Integrated Review of Carpal Tunnel Syndrome: New Insights to an Old Problem

Carpal tunnel syndrome (CTS) is a common entrapment neuropathy characterized by pain, numbness, and impaired function of the hand due to compression of the median nerve at the level of the wrist. Although CTS can develop from repetitive strain, injury, or medical conditions, there are also congenital and genetic risk factors that can predispose individuals to the condition. With respect to anatomical factors, some individuals are born with a smaller carpal tunnel, which increases their susceptibility to median nerve compression. Variations in specific genes, such as those encoding proteins involved in extracellular matrix remodeling, inflammation, and nerve function, have also been linked to an increased risk for CTS. CTS is associated with a high cost of health care maintenance and loss of work productivity. Therefore, it is vital that primary care physicians fully understand the anatomy, epidemiology, pathophysiology, etiology, and risk factors of CTS, so they can be proactive in prevention, diagnosing, and guiding proper treatment. This integrated review also provides insights into how biological, genetic, environmental, and occupational factors interact with structural elements to determine who is most likely to acquire and suffer from CTS. Keeping health practitioners abreast of all the factors that could impact CTS should go a long way in decreasing the health care and socioeconomic burden of CTS.

A Study of Diurnal Cortisol Adaptations in Sleep-Deprived Firefighters During a 72-Hour Work Shift: A Case Series

Seventy percent of US firefighters are overweight or obese. The combination of sleep deprivation and exposure to traumatic events during 72-hour work shifts, commonly employed in emergency responders, is thought to put firefighters at high risk for a variety of stress-related diseases and suicide. Previous studies suggest that the cortisol awakening response (CAR) may be increased in sleep-deprived emergency responders. This case series was designed to investigate the variations in CAR and associations with measurements of salivary cortisol and testosterone, blood glucose and triglyceride, and blood pressure during a 72-hour work shift. Measurements were made at 08:00 and 20:00 in five participants (one normal weight normotensive, three obese hypertensive, and one morbidly obese normotensive male). Data were characterized by the regression statistic R² computed from the relationship between diurnal measurement and concentration, with significance at R²≥0.4. The predominant AM CAR adaptation response consisted of no significant 72-h change (flat response) in salivary cortisol (R²<0.4), found in three of the five participants (60%). The normal-weight participant's 72-h AM CAR adaptation was characterized as incremental (R²=0.91), and markedly different than that of the four obese firefighters who exhibited either a flat response (R²<0.4, 60%) or, in one subject, a decremental response (R²=0.40, 20%). The predominant 72-h PM cortisol adaptation was found to be decremental (R²=0.78-0.97) in three of the five participants (60%), including the normal weight subject (R²=0.78). Diurnal salivary cortisol and testosterone exhibited normal physiological circadian variations (P=0.01, AM>PM and P=0.1, AM>PM, respectively). Blood glucose and triglyceride also showed physiological circadian variations (P=0.02 AM<PM and P=0.002 AM<PM, respectively). Diurnal variation of systolic BP was found to be not significant (P=0.2). The flat AM CAR adaptation exhibited in three of four obese hypertensive firefighters may represent a blunted adaptation response, akin to the responses reported for survivors of suicide. These findings suggest that diurnal variations in salivary cortisol and testosterone, blood glucose, and triglyceride may be useful biochemical markers for identifying stress-related adaptations to 72-hour work shifts. Future studies should be designed to correlate diurnal variations in biomarkers with the risk of developing stress-related diseases and suicide in firefighters.

Aldosterone Synthase Inhibitors and Dietary Interventions: A Combined Novel Approach for Prevention and Treatment of Cardiovascular Disease

Systemic hypertension (HTN) is the hallmark of cardiovascular disease and the forerunner of heart failure. These associations have been established over decades of research on essential HTN. Advancements in the treatment of patients diagnosed with HTN, consisting of alpha- or beta-adrenergic receptor blockers, calcium channel blockers, angiotensin-converting enzyme inhibitors, thiazide, or aldosterone receptor blockers known as anti-mineralocorticoids, in the presence or absence of low sodium salt diets, often fail to control blood pressure adequately to prevent morbidity and mortality. Low sodium diets have had limited success in controlling HTN because low sodium intake is associated with renin-angiotensin-aldosterone system upregulation. Therefore, upregulating aldosterone secretion, sodium, and water retention which, in turn, moves the blood pressure back toward the range of HTN dictated by the baroreceptor reset value, as a compensatory mechanism, especially in resistant HTN. These impediments to blood pressure control in HTN may have been effectively circumvented by the advent of a new class of drugs known as aldosterone synthase inhibitors, represented by baxdrostat. The mechanism of action of baxdrostat as an aldosterone synthase inhibitor demonstrates the inextricable linkage between sodium and blood pressure regulation. Theoretically, combining a low sodium diet with the activity of this aldosterone synthesis inhibitor should alleviate the adverse effect of renin-angiotensin-aldosterone system upregulation. Aldosterone synthesis inhibition should also decrease the oxidative stress and endothelial dysfunction associated with HTN, causing more endothelial nitric oxide synthesis, release, and vasorelaxation. To the best of our knowledge, this is the first systematic review to summarize evidence-based articles relevant to the use of a novel drug (aldosterone synthase inhibitor) in the treatment of HTN and cardiovascular disease. Making the current database of relevant information on baxdrostat and other aldosterone synthase inhibitors readily available will, no doubt, aid physicians and other medical practitioners in their decision-making about employing aldosterone synthase inhibitors in the treatment of patients.

Postprandial Hypotension: An Underreported Silent Killer in the Aged

Orthostatic hypotension (OH) is one of the most common autonomic dysfunctions, with high prevalence in populations of elderly, hypertensive, diabetic, or Parkinson's patients. Evidence is emerging that OH co-occurs with postprandial hypotension (PPH); a greater prevalence of PPH than of OH is reported for Parkinson's disease patients. OH is diagnosed by measuring the blood pressure changes associated with postural changes and often produces alterations in consciousness or other such bothersome symptoms as fainting. PPH is diagnosed by measuring the blood pressure changes associated with ingesting high carbohydrate test meals. Because of the time lag between food ingestion and absorption, PPH is often not reported as symptomatic and, therefore, not diagnosed as PPH. OH and PPH are independent predictors for all causes of mortality. Relative underdiagnosis may qualify PPH as a "silent killer" disease. This review is aimed at providing updates on the epidemiology, pathophysiology, and clinical aspects associated with the diagnosis and treatment of PPH. Highlighting the current gaps in knowledge and research about PPH is expected to make medical practitioners more cognizant of the dangers of underdiagnosis and motivate future research to identify individuals and populations at high risk for PPH and its sequelae.

Cardiac Rehabilitation and Cardiopulmonary Fitness in Children and Young Adults With Congenital Heart Diseases: A Critically Appraised Topic

Public health guidelines and a myriad of studies have proven that exercise is beneficial in the alleviation of various cardio-metabolic diseases. Congenital heart disease (ConHD) is one of the most frequently occurring congenital structural malfunctions in the pediatric population, affecting nine of every 1,000 live births. Only a few studies have established the impact of a structured exercise program on cardiopulmonary fitness in diverse groups of patients with ConHD. It is also alarming to know that a substantial number of these patients and their caregivers often remain very wary of exercise. Anxiety about exercise may increase the risk of developing morbid obesity and other long-term health complications of ConHD. The present review of a critically appraised topic is undertaken to answer the question, “Does structured exercise intervention (cardiac rehabilitation) improve cardiorespiratory fitness in children and young adults with ConHD?” Exercise science and the medical literature were searched for studies that engaged the use of aerobic exercise in patients with different ConHD diagnoses. The search yielded four studies after screening with the inclusion and exclusion criteria, which were further narrowed to three studies after a full-text review. These studies yielded results showing significant increments in peak exercise workload, duration, power output, peak oxygen uptake, or improved tissue oxygenation and muscle strength after an exercise training intervention. It is noteworthy that a group identified as “cyanotic palliated” exhibited the most significant impairment both at baseline and after the exercise intervention. This review provides level 1b medical evidence that a structured exercise program may improve cardiopulmonary fitness in patients with ConHD, which is likely to be beneficial to their overall physical, motor, and psychosocial development. The results of this review may be useful for alleviating the anxiety of patients and their caregivers about participation in structured exercise programs. This review should also motivate future research investigations to develop clinical guidelines for the management of patients with ConHD by adding exercise prescriptions to their daily therapeutic regimens.

Epigenetics and Pain: New Insights to an Old Problem

Physicians and neuroscientists have long observed that factors such as thoughts, emotions, and expectations can influence the perception of pain. Pain can be described as an unpleasant sensation that causes physical discomfort and emotional distress. It alerts an individual to seek help and is the main complaint that brings individuals to physicians. Though it is associated with probable tissue damage, such damage may be subtle, sometimes involving the release of algesic chemicals, and also influenced by attitudes, beliefs, personality, and social factors. The perception of pain may vary due to a multitude of these factors influencing the ascending sensory impulse propagation to the primary somatosensory cortex. The genetics and epigenetics of pain modulators have been previously studied, but there is a lack of application in the everyday management and treatment of pain due to the paucity of valid evidence-based data. We used the PubMed database as our primary tool for researching current literature on this topic. The MeSH terms used included: gene modification, epigenetics, genes, pain, analgesia, “types of pain, and theories of pain. The results were filtered as follows: publications within the last 10 years, generalized pain studies regarding the biopsychosocial aspect of pain, pertinent genes, and epigenetic modulation of those genes; 52 publications were selected for review. By addressing the external factorial causes and the appropriate application of epigenetic principles which affect pain perception, it is hoped that this review will motivate future advancements in the management of acute and/or chronic pain. 

Pancoast tumor presenting with multiple joint pains: a case report

Background

Pancoast tumors represent a unique subset of lung cancers wherein a primary neoplasm arises in the lung’s apex and invades the surrounding soft tissues. One of the main challenges in the diagnosis and treatment of these apical lung cancers is that they are usually not visualized on initial chest x-ray and, by the time the patient presents with symptoms, the tumor has almost always invaded nearby structures.

Case presentation

Herein we report a case of a 58-year-old nonsmoking African American male who presented to the neurology clinic with a history of multiple chronic joint pains. The patient complained of shoulder pain that traveled into his right arm and right finger and had worsened over the past 9 months. The patient also reported decreased right proximal strength and swelling of his right hand. Magnetic resonance imaging of the shoulder and cervical region showed mild cervical spondylosis and a questionable right apical mass. A subsequent high-resolution computed tomography scan of the chest revealed a large right apical lung mass, with chest wall invasion and erosion of the adjacent ribs. Biopsy of the mass confirmed poorly differentiated non-small cell lung cancer. Radiation therapy was initiated, and the patient’s pain improved significantly. Given the size of the tumor, chemotherapy was recommended by the oncology team. The patient decided against chemotherapy.

Conclusion

This case highlights the importance of early diagnosis by expanding the differential diagnosis in patients presenting with weakness, sensory loss, and shoulder pain beyond radiculopathy or joint-related diseases. A comprehensive history and careful examination may lead to an earlier diagnosis, more appropriate treatment, and better outcome in cases of Pancoast tumor presenting with neuropathic or musculoskeletal pain.

Epigenetic Influences on Wound Healing and Hypertrophic-Keloid Scarring: A Review for Basic Scientists and Clinicians

Primary care physicians and dermatologists are challenged by patients affected by keloid or hypertrophic scarring resulting from accidental wounding, surgical incisions, tattooing, or “branding” procedures to demonstrate their association with a specific culture, fraternity, or cult. The dysregulated wound healing associated with keloids and hypertrophic scarring adversely affects genetically susceptible individuals, especially persons of color with Fitzpatrick Skin types IV-VI. Although the specific mechanisms of bulky hypertrophic/keloid scarring and its association with oxidative stress and inflammation remain unclear, the current knowledge base is sufficient to provide some guidance to health practitioners who must serve, treat, and counsel affected individuals. This review focuses on providing insight to healthcare professionals about the role of epigenetics, oxidative stress, poor local oxygenation, and its relationship to impaired wound healing. The goal is to promote further research on bulky hypertrophic and keloid scarring for its prevention and to develop evidence-based clinical guidelines for optimal treatment.

Electroencephalographic Signature of Negative Self Perceptions in Medical Students

Frontal alpha asymmetry (fAA) is purported to be a neurophysiological marker for anxiety and depression. Higher left frontal alpha EEG voltage is associated with lower left and higher right frontal cerebral cortical activation, indicative of right-sided fAA. This pilot study tests the hypothesis that greater left-sided frontal alpha voltage is associated with negative thoughts about oneself. A group of eight healthy 28-41-year-old right-handed male medical students were subjected to an extensive interactive self-report inventory (ISI) evaluating perceptions of their psychosocial interactions. Quantitative EEG (qEEG) was performed with eyes closed. Computations of fAA and related parameters were based on measurements in the alpha bandwidth (8-13 Hz) at the left frontal F7 and right frontal F8 scalp electrodes. fAA was the percent difference between mean voltages at F8 minus that at F7. Significance of associations between fAA and the ISI scores was determined by Pearson’s product-moment correlation coefficient, at P≤0.05. “Depressed” scores were positively correlated with right-sided fAA (P=0.01). “Relaxed” (P=0.05), “regulated” (P=0.02), “cooperative” (P=0.05) and “dependent scores” (P=0.004) were negatively correlated with right-sided fAA. These findings imply that right-sided fAA may be associated with more perceptions of “depressed” psychosocial interactions involving negative thoughts about oneself, as well as, more reliance on others (“dependence” score), less sharing (“cooperative” ISI score), less trust (“regulated” ISI score) and less initiative (“relaxed” ISI score). These results support the hypothesis that right-sided fAA may identify individuals with a predilection for negative thoughts about themselves and other negatively-valenced perceptions of their psychosocial interactions.

Case Report: Ulcerative Colitis with Multiple Dural Venous Thrombosis

Background Cerebral sinus vein thrombosis (CVT) is a rare but serious complication associated with ulcerative colitis (UC), an idiopathic autoimmune inflammatory disease of the gastrointestinal tract. Management approaches for CVT remain unclear but may include anticoagulation and surgical thrombectomy. Herein, we report a case of a 23-year-old male who developed CVT with a history of UC. The patient was presented to Howard University Hospital when he slipped and fell. On arrival at the hospital, he complained of a headache with an aching sensation, associated with light/sound sensitivity. The patient had a history of uncontrolled UC. He had positive bloody diarrhea, lower abdominal pain, but denied any other neurological deficit. Computed tomography of the head showed left frontoparietal lobe hypodensities. Neurological exam was nonfocal. Vital signs were within normal range, but the patient experienced some memory loss and personality changes. Subsequent diagnosis of CVT was made with magnetic resonance angiography and magnetic resonance venography. Immediate treatment with low-molecular-weight intravenous heparin (18 IU/kg) was introduced. His UC was managed with methylprednisolone (60 mg IV daily), proton pump inhibitors, mesalamine, ciprofloxacin, and metronidazole. His condition gradually improved. On discharge, he was prescribed prednisone, azathioprine for his UC, levetiracetam for seizure, and warfarin with an INR goal of 2-3. In conclusion, the sudden onset and/or acute worsening of neurological status such as headache and mental confusion in a patient with UC should alert the treating physician about the possibility of CVT so that timely intervention could be employed to prevent disabling and potentially lethal sequelae of this disease.

Norepinephrine stabilizes translation-dependent, homosynaptic long-term potentiation through mechanisms requiring the cAMP sensor Epac, mTOR and MAPK

Neuromodulators regulate higher-order cognitive processes including learning and memory through modulation of synaptic transmission and plasticity. Norepinephrine is a neuromodulator that is secreted throughout the brain in response to novelty or increased arousal, which alters neural circuits by increasing the modifiability of CNS synapses. Norepinephrine activates metabotropic receptors, initiating complex intracellular signalling cascades that can promote enduring changes in synaptic strength including long-term potentiation (LTP). In particular, activation of beta-adrenergic receptors (β-ARs) by norepinephrine enhances LTP through downstream engagement of signalling cascades which upregulate protein synthesis at synapses. Here, we sought to determine the select signalling pathways recruited by norepinephrine to promote homosynaptic LTP at hippocampal synapses in mice. Application of norepinephrine initiated a long-lasting form of homosynaptic LTP that requires protein synthesis. Norepinephrine-mediated enhancement of LTP was reduced by inhibition of mammalian target of rapamycin and exchange protein directly activated by cAMP (Epac) but not cAMP-dependent protein kinase A, suggesting that the endogenous β-AR ligand norepinephrine may preferentially recruit Epac signalling to promote enduring changes in synaptic strength. These findings advance our understanding of the mechanisms through which norepinephrine regulates synaptic plasticity associated with formation of new memories.

Associations of Alpha and Beta Interhemispheric EEG Coherences with Indices of Attentional Control and Academic Performance

Introduction. Heretofore, research on optimizing academic performance has suffered from an inability to translate what is known about an individual's learning behaviors to how effectively they are able to use the critical nodes and hubs in their cerebral cortex for learning. A previous study from our laboratory suggests that lower theta-beta ratios (TBRs) measured by EEG may be associated with higher academic performance in a medical school curriculum.

METHODS

In this study, we tested the hypothesis that TBR and academic performance may be correlated with EEG coherence, a measure of brain connectivity. We analyzed the interhemispheric coherences of the subjects involved in our prior study. TBR and coherence measurements were made at 19 scalp electrode recording sites and 171 electrode combinations with eyes open and closed (EO, EC). Control data were acquired during a session of acclimation to the research protocol 3 d before an initial examination in anatomy-physiology (control exam) and were repeated five weeks later, 3 d before a second exam covering different anatomy-physiology topics (comparison exam).

RESULTS

Between the control and comparison exams, beta coherences increased significantly at the frontal pole, frontal, parietal, midtemporal, posterior temporal, and occipital recording sites under the EO condition and at the inferior frontal, central, midtemporal, and posterior temporal sites under the EC condition. Alpha coherences increased significantly at the same sites and under the same EO/EC conditions as found for the beta coherences. The beta coherences were negatively correlated with the TBR and were positively correlated with the comparison exam score at the midfrontal electrode site (F3-F4) but only under the EO condition. Beta and alpha coherences at the midfrontal, inferior frontal midtemporal, posterior temporal, and occipital sites were also negatively correlated with the average TBR under the EO condition.

CONCLUSIONS

Lower TBR, an indicator of attentional control, was associated with higher alpha and beta interhemispheric coherences measured with eyes open at sites overlying the frontal, temporal, and occipital cortices. Changes in EEG coherences and TBRs might be useful as neurophysiological measures of neuroplasticity and the efficacy of strategies for preventing academic underachievement and treatments for improving academic performance.

qEEG Measures of Attentional and Memory Network Functions in Medical Students: Novel Targets for Pharmacopuncture to Improve Cognition and Academic Performance

Objectives

Attentional and memory functions are important aspects of neural plasticity that, theoretically, should be amenable to pharmacopuncture treatments. A previous study from our laboratory suggested that quantitative electroencephalographic (qEEG) measurements of theta/beta ratio (TBR), an index of attentional control, may be indicative of academic performance in a first-semester medical school course. The present study expands our prior report by extracting and analyzing data on frontal theta and beta asymmetries. We test the hypothesis that the amount of frontal theta and beta asymmetries (fTA, fBA), are correlated with TBR and academic performance, thereby providing novel targets for pharmacopuncture treatments to improve cognitive performance.

Methods

Ten healthy male volunteers were subjected to 5–10 min of qEEG measurements under eyes-closed conditions. The qEEG measurements were performed 3 days before each of first two block examinations in anatomy-physiology, separated by five weeks. Amplitudes of the theta and beta waveforms, expressed in μV, were used to compute TBR, fTA and fBA. Significance of changes in theta and beta EEG wave amplitude was assessed by ANOVA with post-hoc t-testing. Correlations between TBR, fTA, fBA and the raw examination scores were evaluated by Pearson’s product-moment coefficients and linear regression analysis.

Results

fTA and fBA were found to be negatively correlated with TBR (P<0.03, P<0.05, respectively) and were positively correlated with the second examination score (P<0.03, P=0.1, respectively).

Conclusion

Smaller fTA and fBA were associated with lower academic performance in the second of two first-semester medical school anatomy-physiology block examination. Future studies should determine whether these qEEG metrics are useful for monitoring changes associated with the brain’s cognitive adaptations to academic challenges, for predicting academic performance and for targeting phamacopuncture treatments to improve cognitive performance.

Environmental Enrichment and Brain Neuroplasticity in the Kainate Rat Model of Temporal Lobe Epilepsy

Background and Purpose

Environmental enrichment (EE) improves brain function and ameliorates cognitive impairments; however, whether EE can reverse the learning and memory deficits seen following seizures remains unknown.

Methods

We tested the hypothesis that EE augments neurogenesis and attenuates the learning and memory deficits in rats subjected to kainate-induced seizures in hippocampus, amygdala and motor cortex. EE consisted of daily exposures immediately after KA lesioning (early EE) and after a 60-day period (late EE). Morphometric counting of neuron numbers (NN), dendritic branch-points and intersections (DDBPI) were performed. Spatial learning in a T-maze test was described as percent correct responses and memory in a passive-avoidance test was calculated as time spent in the small compartment where they were previously exposed to an aversive stimulus.

Results

EE increased NN and DDBPI in the normal control and in the KA-lesioned rats in all brain areas studied, after both early and late exposure to EE. Late EE resulted in significantly fewer surviving neurons than early EE in all brain areas (p < 0.0001). EE increased the percent correct responses and decreased time spent in the small compartment, after both early and late EE. The timing of EE (early vs. late) had no effect on the behavioral measurements.

Conclusions

These findings demonstrate that, after temporal lobe and motor cortex epileptic seizures in rats, EE improves neural plasticity in areas of the brain involved with emotional regulation and motor coordination, even if the EE treatment is delayed for 60 days. Future studies should determine whether EE is a useful therapeutic strategy for patients affected by seizures.

GABAergic Neurons as Putative Neurochemical Substrate Mediating Aversive Effects of Nicotine

Nicotine, the main addictive component of tobacco smoke, has both rewarding and aversive properties. Recent studies have suggested that GABAergic neurons, one of the main neurochemical components of the reward-addiction circuitry, may also play a role in the aversive responses to nicotine. In the present study of transgenic mice expressing Green Fluorescent Protein (GFP) in Glutamate Decarboxylase 67 (GAD67) neurons, we hypothesized that a subpopulation of GABAergic neurons in the Ventral Tegmental Area (VTA) are the targets of aversive doses of nicotine in the CNS. We tested this hypothesis using c-Fos immunohistochemical techniques to identify GAD67-GFP positive cells within the VTA, that are activated by a single intraperitoneal (i.p.) injection of a low (40 ug/kg) or a high (2 mg/kg) dose of nicotine. We also assessed the anatomical location of GAD67-GFP positive cells with respect to tyrosine hydroxylase (TH) Immunoreactive (IR) dopaminergic cells in VTA. Consistent with our previous studies low- and high-dose nicotine both induced c-Fos activation of various intensities at multiple sites in VTA. Double labeling of c-Fos activated cells with GAD67-GFP positive cells identified a subpopulation of GABAergic neurons in Substantia Nigra Compact part Medial tier (SNCM) that were activated by high- but not by low-dose nicotine. Of 217 GABAergic cells counted at this site, 48.9% exhibited nicotine induced c-fos immunoreactivity. GAD67-GFP positive cells in other regions of VTA were not activated by the nicotine doses tested. Double labeling of GAD67-GFP positive cells with TH IR cells showed that the GABAergic neurons that were activated by high-dose nicotine were located in close proximity to the dopaminergic neurons of substantia nigra compact part and VTA. Dose-dependent activation of GAD67-GFP positive neurons in SNCM, by a nicotine dose known to produce aversive responses, implies that GABAergic neurons at these sites may be an important component of the nicotine aversive circuitry.

Neuroanatomical Relationships between Orexin/Hypocretin-Containing Neurons/Nerve Fibers and Nicotine-Induced c-Fos-Activated Cells of the Reward-Addiction Neurocircuitry

Orexin/hypocretin-containing neurons in lateral hypothalamus (LH) are implicated in the neurobiology of nicotine addiction. However, the neuroanatomical relationships between orexin-neurons/nerve fibers and nicotine-activated cells within the reward-addiction neurocircuitry is not known. In the present study in mice, we first used c-Fos immunohistochemistry to identify CNS cells stimulated by an acute single injection of nicotine (NIC, 2 mg/kg, IP). Sequential double-labelling was then performed to identify the location of orexin-containing neurons and nerve fibers with respect to NIC-induced c-Fos activated cells and/or tyrosine hydroxylase (TH) immunoreactive (IR) cells of the mesocorticolimbic reward-addiction pathways. Orexin-IR nerve fibers and terminals were detected at multiple sites of the NIC reward-addiction circuitry in close apposition to, and intermingled with, NIC-induced c-Fos-IR cells of locus coeruleus (LC), ventral tegmental area (VTA), nucleus accumbens (Acb), LH and paraventricular thalamic nucleus (PVT). Double-labelling of orexin with TH showed frequent contact between orexin-IR nerve fibers and noradrenergic cells of LC. However, there was infrequent contact between the orexinergic fibers and the TH-expressing dopaminergic cells of VTA, dorsal raphe nucleus (DR), posterior hypothalamus (DA11), arcuate hypothalamic nucleus (DA12) and periventricular areas (DA14). The close anatomical contact between orexinergic nerve fibers and NIC-activated cells at multiple sites of the reward-addiction pathways suggests that orexinergic projections from LH are likely to be involved in modulating activity of the neurons that are directly impacted by acute administration of nicotine.

Nonlinear Conte-Zbilut-Federici (CZF) Method of Computing LF/HF Ratio: A More Reliable Index of Changes in Heart Rate Variability

Objectives:

Acupuncture treatments are safe and effective for a wide variety of diseases involving autonomic dysregulation. Heart rate variability (HRV) is a noninvasive method for assessing sympathovagal balance. The low frequency/high frequency (LF/HF) spectral power ratio is an index of sympathovagal influence on heart rate and of cardiovascular health. This study tests the hypothesis that from rest to 30% to 50% of peak oxygen consumption, the nonlinear Conte-Zbilut-Federici (CZF) method of computing the LF/HF ratio is a more reliable index of changes in the HRV than linear methods are.

Methods:

The subjects of this study were 10 healthy young adults. Electrocardiogram RR intervals were measured during 6-minute periods of rest and aerobic exercise on a cycle ergometer at 30% and 50% of peak oxygen consumption (VO_2peak).

Results:

The frequency domain CZF computations of the LF/HF ratio and the time domain computations of the standard deviation of normal-to-normal intervals (SDNN) decreased sequentially from rest to 30% VO_2peak (P < 0.001) to 50% VO_2peak (P < 0.05). The SDNN and the CZF computations of the LF/HF ratio were positively correlated (Pearson’s r = 0.75, P < 0.001). fast Fourier transform (FFT), autoregressive (AR) and Lomb periodogram computations of the LF/HF ratio increased only from rest to 50% VO_2peak.

Conclusion:

Computations of the LF/HF ratio by using the nonlinear CZF method appear to be more sensitive to changes in physical activity than computations of the LF/HF ratio by using linear methods. Future studies should determine whether the CZF computation of the LF/HF ratio improves evaluations of pharmacopuncture and other treatment modalities.

Cardiovascular Responses to an Isometric Handgrip Exercise in Females with Prehypertension

Background:

Hypertensive individuals are known to exhibit greater increases in blood pressure during an isometric handgrip exercise (IHE) than their normotensive counterparts.

Aim:

This study tests the hypothesis that, compared to normotensive individuals, prehypertensive individuals exhibit an exaggerated response to IHE.

Materials and Methods:

In this study, the effects of IHE were compared in matched prehypertensive vs. normotensive healthy African-American females. Six healthy young adult African–American female university students were screened in a physician's office for blood pressure in the range of prehypertension, systolic blood pressure (SBP) 120–139 mmHg and diastolic blood pressure (DBP) 80–89 mmHg. Six young adult African–American women were also recruited to serve as a healthy normotensive control group with SBP ≤119 mmHg and DBP ≤79 mmHg. Cardiovascular fitness was determined by peak oxygen uptake (VO₂ peak) measured during a progressive exercise test.

Results:

During the handgrip exercise, the prehypertensive group exhibited greater increases in SBP (from 139 ± 6 to 205 ± 11 mmHg, +48%) than the controls (from 132 ± 3 to 145 ± 3 mmHg, +10%); intergroup difference P < 0.001. The prehypertensive group also exhibited greater increases in DBP (from 77 ± 2 to 112 ± 5 mmHg, +46%) compared to the controls (from 72 ± 3 to 78 ± 4 mmHg, +8%); intergroup difference P < 0.001. The increase in systemic vascular resistance was also greater in the prehypertensive group (from 1713 ± 91 to 2807 ± 370 dyne.s.cm^-5, +64%) than in the controls (from 1668 ± 80 to 1812 ± 169 dyne.s.cm^-5, +9%); intergroup difference P < 0.05.

Conclusion:

These results suggest that blood pressure measurements performed during IHE may be a useful screening tool in evaluating prehypertensive individuals for antihypertensive treatments.

Relationship Between Aerobic Fitness, the Serum IGF-1 Profiles of Healthy Young Adult African American Males, and Growth of Prostate Cancer Cells

The growth of prostate tumors is mediated by the bioavailability of androgens and insulin-like growth factors. This study tested the hypothesis that healthy young adult African American men exhibiting low aerobic capacity (fitness) have serum insulin-like growth Factor-1 (IGF-1) and testosterone levels that promote growth of prostate cancer cells. A cross-sectional data research design was used to study groups of 18- to 26-year-old healthy men exhibiting low and moderate aerobic fitness, based on their peak oxygen consumption (VO_2peak). The individual serum levels of IGF-1, IGF-1 binding protein-3 (IGFBP-3), and testosterone were measured. In vitro growth of androgen-dependent LNCaP prostate tumor cells was measured after incubation in culture medium fortified with each subject's serum. Aerobic capacity was significantly greater in the moderate-fitness group than in the low-fitness group without an intergroup difference in body mass index. The serum IGF-1 concentration was significantly higher in the low-fitness group in the absence of an intergroup difference in serum testosterone. The serum IGFBP-3 concentration was significantly lower in the low-fitness group. Prostate tumor cell growth was significantly greater in the cultures incubated in media containing the sera of the low-fitness group than in the sera of the moderate-fitness group. These findings suggest that moderate aerobic fitness in young adults may decrease the circulating levels of free IGF-1 and lower the potential to support growth of prostate cancer cells.

The Sensory Impact of Nicotine on Noradrenergic and Dopaminergic Neurons of the Nicotine Reward - Addiction Neurocircuitry

The sensory experience of smoking is a key component of nicotine addiction known to result, in part, from stimulation of nicotinic acetylcholine receptors (nAChRs) at peripheral sensory nerve endings. Such stimulation of nAChRs is followed by activation of neurons at multiple sites in the mesocorticolimbic reward pathways. However, the neurochemical profiles of CNS cells that mediate the peripheral sensory impact of nicotine remain unknown. In the present study in mice, we first used c-Fos immunohistochemistry to identify CNS cells stimulated by nicotine (NIC, 40 μg/kg, IP) and by a peripherally-acting analog of nicotine, nicotine pyrrolidine methiodide (NIC-PM, 30 μg/kg, IP). Sequential double-labelling was then performed to determine whether noradrenergic and dopaminergic neurons of the nicotine reward-addiction circuitry were primary targets of NIC and NIC-PM. Double-labelling of NIC and/or NIC-PM activated c-Fos immunoreactive cells with tyrosine hydroxylase (TH) showed no apparent c-Fos expression by the dopaminergic cells of the ventral tegmental area (VTA). With the exception of sparse numbers of TH immunoreactive D11 cells, dopamine-containing neurons in other areas of the reward-addiction circuitry, namely periaqueductal gray, and dorsal raphe, were also devoid of c-Fos immunoreactivity. Noradrenergic neurons of locus coeruleus (LC), known to innervate VTA, were activated by both NIC and NIC-PM. These results demonstrate that noradrenergic neurons of LC are among the first structures that are stimulated by single acute IP injection of NIC and NIC-PM. Dopaminergic neurons of VTA and other CNS sites, did not respond to acute IP administration of NIC or NIC-PM by induction of c-Fos.

Neuroanatomical circuitry mediating the sensory impact of nicotine in the central nervous system

Direct actions of nicotine in the CNS appear to be essential for its reinforcing properties. However, activation of nicotinic acetylcholine receptors (nAChRs) on afferent sensory nerve fibers is an important component of addiction to, and withdrawal from, cigarette smoking. The aim of the present study was to identify the neuroanatomical substrates activated by the peripheral actions of nicotine and to determine whether these sites overlap brain structures stimulated by direct actions of nicotine. Mouse brains were examined by immunohistochemistry for c-Fos protein after intraperitoneal injection of either nicotine hydrogen tartrate salt (NIC; 30 and 40 μg/kg) or nicotine pyrrolidine methiodide (NIC-PM; 20 and 30 μg/kg). NIC-PM induced c-Fos immunoreactivity (IR) at multiple brain sites. In the brainstem, c-Fos IR was detected in the locus coeruleus, laterodorsal tegmental nucleus, and pedunculotegmental nucleus. In the midbrain, c-Fos IR was observed in areas overlapping the ventral tegmental area (VTA), which includes the paranigral nucleus, parainterfascicular nucleus, parabrachial pigmental area, and rostral VTA. Other structures of the nicotine brain-reward circuitry activated by NIC-PM included the hypothalamus, paraventricular thalamic nucleus, lateral habenular nucleus, hippocampus, amygdala, accumbens nucleus, piriform cortex, angular insular cortex, anterior olfactory nucleus, lateral septal nucleus, bed nucleus of stria terminalis, cingulate and medial prefrontal cortex, olfactory tubercle, and medial and lateral orbital cortex. NIC, acting through central and peripheral nAChRs, produced c-Fos IR in areas that overlapped NIC-PM-induced c-Fos-expressing sites. These neuroanatomical data are the first to demonstrate that the CNS structures that are the direct targets of nicotine are also anatomical substrates for the peripheral sensory impact of nicotine.

Calcitonin Gene-Related Peptide Regulates Cardiomyocyte Survival through Regulation of Oxidative Stress by PI3K/Akt and MAPK Signaling Pathways

CGRP and specific CGRP receptors are found in the heart where they produce positive-inotropic and anti-apoptotic effects, key adaptations to exercise and cardiovascular disease. PI3K/Akt and MAPK signaling imbalances are associated with cardiomyocyte pathologies; however, the effects of CGRP on these pathways are unclear. Therefore, we hypothesized that CGRP modulates inotropic and apoptotic adaptations of cardiomyocytes by regulating PI3K/Akt and MAPK/ERK signaling balances. We treated cardiomyocytes with combinations of CGRP, PI3K/Akt and MAPK signaling agonists and antagonists. We evaluated expression of the mRNA and proteins levels of survival signaling molecules related to the PI3K/Akt and MAPK and measured apoptosis by caspase 3/7 activity. CGRP_1-37 decreased Akt, NFκB, SOD-3 and increased ERK1/2 and p38 MAPK expressions, which was antagonized by CGRP_8-37. Akt-negative construct transfection, Ad.Akt(K179M), inhibited the CGRP_1-37-induced increment in MAPK expressions. A PI3K-antagonist treatment with LY294002 or CGRP_1-37/Ad.Akt(K179M) co-treatment alleviated the CGRP-increased caspase activity and -decrements in SOD-3. These findings demonstrate a CGRP negative effect on the PI3K/Akt signaling pathway and CGRP receptor-induced crosstalk between PI3K/Akt and MAPK in normal cardiomyocytes. Future studies to differentiate CGRP effects on intracellular signal transduction mechanisms in pathological conditions will elucidate the significance of CGRP in, and provide novel therapeutic targets for, heart failure.

Hemodynamic correlates of low umbilical cord vitamin D and ionized calcium

Vitamin D deficiency and hypocalcemia are associated with gestational hypertension. Therefore, we hypothesized that umbilical cord [Ca(2+)] and [vitamin D] are correlated with perinatal blood pressures. Mothers and newborns comprised vitamin D sufficient (vitamin D ≥ 50 nM, range 52-111 nM, n = 14), and vitamin D deficient groups (vitamin D < 50 nM, range 13-49 nM, n = 29). Cord [Ca²⁺] was negatively correlated with maternal systolic pressure (SBP) (r = -0.56, p < 0.01) and positively correlated with neonatal SBP (r = +0.55, p < 0.01) in the vitamin D deficient group. We conclude that low umbilical cord [vitamin D] and [Ca²⁺] may predispose mothers to higher and newborns to lower blood pressures.

Arterialization of Venous Blood for Differentiation of Sickle Cell Subjects in Vaso-occlusive Crisis

These studies were designed as two experiments. Experiment 1 was performed to validate the hypothesis that oxygen saturation of the venous blood may be a marker for vaso-occlusive crisis (VOC) in sickle cell patients undergoing hydroxyurea (HU) treatments. Experiment 2 was performed to test the hypothesis that an acute increase in the blood nitric oxide (NO) concentration by administering HU modulates the perception of pain in sickle cell subjects in VOC. The percent saturations of oxyhemoglobin (%O<PRE>2</PRE>Hb), reduced hemoblogin (%RHb), carboxy-hemoglobin (%COHb), met-hemoglobin (%MHb), fetal hemoglobin (HbF), and nitric oxide metabolites were measured in venous blood samples collected from sickle cell disease (SCD) who were on and off HU and O<PRE>2</PRE> at steady state and during VOC. The results showed the ratio of %O<PRE>2</PRE>Hb/RHb in VOC+HU was significantly higher than patients in the steady state who were on and off of HU (p<0.05). The %COHb was higher in all SCD groups, %COHb values were significantly different in SCD at steady state who were on HU. HU and O<PRE>2</PRE> treatment did not play important role on venous blood %O<PRE>2</PRE>Hb and pain scores in SCD during VOC. A single oral dose of HU was associated with a significant increase in the venous concentration of nitric oxide metabolites (NOx), p<0.05. These findings suggest that the ratio %O<PRE>2</PRE>Hb/RHb in venous blood and pain scores differentiate HU-untreated and HU-treated at steady state subjects from HU-treated subjects in VOC; however, the acute increase in venous NOx produced by administering HU to HU-treated subjects in VOC does not explain this difference.

Cardiorespiratory function associated with dietary nitrate supplementation

The advent of medical nutrition therapy and nutritional physiology affords the opportunity to link diet to specific cardiovascular mechanisms, suggesting novel treatments for cardiovascular disease. This study tests the hypothesis that beetroot juice increases the plasma nitric oxide (NO) concentration, which is associated with improvements in cardiorespiratory function at rest and during submaximal aerobic exercise. The subjects were 12 healthy, young adult, normotensive African-American females, with a body mass of 61 ± 2 kg, body fat of 28% ± 4%, and peak oxygen consumption of 26 ± 3 mL·kg(-1)·min(-1). The subjects were studied at rest and during cycle ergometer exercise at 40%, 60%, and 80% of peak oxygen consumption. Plasma NO concentration, respiratory quotient (RQ), minute ventilation, systolic and diastolic blood pressure (SBP and DBP), heart rate, and oxygen consumption were compared between isocaloric, isovolumetric placebo control orange juice and experimental beetroot juice treatments on separate days. The beetroot juice treatment increased plasma NO concentration and decreased oxygen consumption, SBP, and the heart rate-SBP product at rest and at 40%, 60%, and 80% of peak oxygen consumption in the absence of significant effects on RQ, minute ventilation, heart rate, and DBP. These findings suggest that, in healthy subjects, beetroot juice treatments increase plasma NO concentration and decrease cardiac afterload and myocardial oxygen demand at rest and during 3 submaximal levels of aerobic exercise. Future studies should determine the cellular and molecular mechanisms responsible for the improvement in cardiorespiratory function associated with dietary nitrate supplementation and whether they translate into better cardiovascular function and exercise tolerance in individuals with a compromised cardiovascular system.

Inotropic and lusitropic effects of calcitonin gene-related peptide in the heart

Previous studies have demonstrated positive-inotropic effects of calcitonin gene-related peptide (CGRP), but the mechanisms remain unclear. Therefore, two experiments were performed to determine the physiological correlates of the positive-inotropic effects of CGRP. Treatments designed to antagonize the effects of physiologically active CGRP₁₋₃₇ included posttreatment with CGRP₈₋₃₇ and pretreatment with LY-294002 (LY, an inhibitor of phosphatidylinositol 3-kinase), 17β-estradiol (E), and progesterone (P) were also used to modulate the effects of CGRP₁₋₃₇. Experiment 1 was in vitro studies on sarcomeres and cells of isolated adult rat cardiac myocytes. CGRP₁₋₃₇, alone and in combination with E and P, decreased sarcomere shortening velocities and increased shortening percentages, effects that were antagonized by CGRP₈₋₃₇, but not by LY. CGRP₁₋₃₇ increased resting intracellular calcium ion concentrations and Ca(2+) influxes, effects that were also antagonized by both CGRP₈₋₃₇ and LY. Experiment 2 was in vivo studies on left ventricular pressure-volume (PV) loops. CGRP₁₋₃₇ increased end-systolic pressure, ejection fraction, and velocities of contraction and relaxation while decreasing stroke volume, cardiac output, stroke work, PV area, and compliance. After partial occlusion of the vena cava, CGRP₁₋₃₇ increased the slope of the end-systolic PV relationship. CGRP₈₋₃₇ and LY attenuated most of the CGRP-induced changes. These findings suggest that CGRP-induced positive-inotropic effects may be increased by treatments with estradiol and progesterone and inhibited by LY. The physiological correlates of CGRP-induced positive inotropy observed in rat sarcomeres, cells, and intact hearts are likely to reveal novel mechanisms of heart failure in humans.

Exaggerated vasopressor response to exercise and cerebral blood flow velocity

We studied 10 young adults, normotensive at rest, comprising a control group (n = 5) with normal blood pressure responsiveness to exercise and an experimental group exhibiting greater percentage of body fat and body mass index (BMI) than the controls, with exaggerated blood pressure (vasopressor) responsiveness to exercise (EEBPR) (n = 5). Lower absolute and varying oxygen consumption/body weight normalized units of middle cerebral arterial blood flow velocity (MCAV) were found during exercise in the experimental group (P < .01). These findings support the hypothesis that the combination of EEBPR and high BMI is associated with low MCAV that may put such individuals at risk for cerebral hypoperfusion and cognitive deficits.

Epigenetics and hypertension

Epigenetics refers to mechanisms for environment-gene interactions (mainly by methylation of DNA and modification of histones) that do not alter the underlying base sequence of the gene. This article reviews evidence for epigenetic contributions to hypertension. For example, DNA methylation at CpG islands and histone acetylation pathways are known to limit nephron development, thereby unmasking hypertension associated with exposure to a high-salt diet. Maternal water deprivation and protein deficiency are shown to increase expression of renin-angiotensin system genes in the offspring. The methylation pattern of a serine protease inhibitor gene in human placentas is shown to be a marker for preeclampsia-associated hypertension. Mental stress induces phenylethanolamine n-methyltransferase, which may act as a DNA methylase and mimic the gene-silencing effects of methyl CpG binding protein-2 on the norepinephrine transporter gene, which, in turn, may exaggerate autonomic responsiveness. A disrupter of telomeric silencing (Dot1) is known to modulate the expression of a connective-tissue growth-factor gene associated with blood vessel remodeling, which could alter vascular compliance and elastance. Dot1a also interacts with the Af9 gene to produce high sodium channel permeability and silences the hydroxysteroid dehydrogenase-11β2 gene, thereby preventing metabolism of cortisol to cortisone and overstimulating aldosterone receptors. These findings indicate targets for environment-gene interactions in various hypertensive states and in essential hypertension.

Association of body fat percentage and heart rate variability measures of sympathovagal balance

AIMS

We tested the hypothesis that body fat percentage determines cardiac sympathovagal balance in healthy subjects.

MAIN METHODS

Heart rate variability (HRV) measurements were made of the standard deviation of the normal-normal RR intervals (SDNN) and the low frequency/high frequency (LF/HF) ratio, from time domain and fast Fourier transform spectral analysis of electrocardiogram RR intervals during trials of uncontrolled and controlled (paced) breathing at 0.2Hz. Body fat percentage was measured by dual energy x-ray absorptiometric (DEXA) scanning. Significance of differences between uncontrolled and controlled (paced) breathing was determined by analysis of variance and correlations between body fat percentage and HRV measurements by Pearson's coefficient at P<0.05.

KEY FINDINGS

Percent body fat was negatively correlated with LF/HF during the uncontrolled breathing (r=-0.56, two-tailed P<0.05, one-tailed P<0.01) but not during the paced breathing trial (r=-0.34, (P>0.1).

SIGNIFICANCE

We conclude that sympathetic activity produced by paced breathing at 0.2Hz can obscure the relationship between body fat percentage and sympathovagal balance and that high body fat percentage may be associated with low sympathetic modulation of the heart rate in healthy adolescent/young adult males.

Association of classroom participation and examination performance in a first-year medical school course

The advent of internet-based delivery of basic medical science lectures may unintentionally lead to decreased classroom attendance and participation, thereby creating a distance learning paradigm. In this study, we tested the hypothesis that classroom attendance/participation may be positively correlated with performance on a written examination for first-year medical school instruction. The study subjects consisted of 115 first-year medical students. The introductory respiratory structure-function instruction was designed to include one noncompulsory pretest, four short postinstruction noncompulsory self-evaluation tests that were unannounced as to date and time, and one compulsory comprehensive examination. The relationship between attendance/participation, measured by the number of noncompulsory tests taken, and performance on the comprehensive examination was determined by Pearson's correlation coefficient, one-way ANOVA, and a chi(2)-test of significance. The average score on the pretest was 28%; for the same items on the comprehensive examination (posttest), the average score was 73%. For the 80 students who took the pretest, this translated to an overall score increase of 161%. Attendance/participation in four or five of the noncompulsory tests resulted in an 83.3% pass rate on the comprehensive exam compared with a rate of 52.9% for attendance/participation in three, two, one, or none of the five noncompulsory tests; the overall pass rate was 60.9%. There was a significant association between a high rate of classroom attendance/participation and a high score on the comprehensive examination (Pearson's chi(2) = 8.599, P < 0.01). These findings suggest that classroom attendance/participation may be a significant determinant of performance of medical students on comprehensive examinations in first-year basic medical science courses. It is concluded that a substantial number of first-year medical students in this study could be at risk for poor performance because they may believe that there is an equivalency between internet- and classroom-based instruction in basic medical science courses.

Effects of high-carbohydrate and high-fat dietary treatments on measures of heart rate variability and sympathovagal balance

AIMS

We tested the hypothesis that respiratory quotient (RQ) determines sympathovagal balance associated with metabolism of stored and dietary energy substrates.

MAIN METHODS

Six 18-20 year-old African-American males were studied after two control pretreatments of fasting and post-treatments of metabolizing high-fat and high-carbohydrate beverages. RQ, heart rate (HR), energy expenditure (EE) and blood pressure (BP) were recorded at rest and repeated 1 h-3 h after ingesting isocaloric high-carbohydrate and high-fat beverages. Sympathovagal modulation of HR was quantified by the low frequency/high frequency (LF/HF) ratio from fast Fourier transform (spectral) analysis of the electrocardiogram RR intervals during paced breathing at 0.2 Hz. Significance of differences of peak post-treatment values from controls was evaluated by analysis of covariance and of correlations by linear regression at P<0.05.

KEY FINDINGS

The high-carbohydrate and high-fat treatments increased RQ, EE, HR and LF/HF with significant interactions between covariates. LF/HF values were not significant after eliminating covariance of RQ, EE and HR for the control vs. high-fat and for the high-fat vs. high-carbohydrate and after eliminating covariance of EE and HR for the control vs. high-carbohydrate treatments. Across the RQ values, correlations were significant for EE and LF/HF.

SIGNIFICANCE

These findings imply that high RQ and sympathetic modulation produced by metabolizing carbohydrate is associated with high resting energy expenditure. We conclude that respiratory quotient may be an important determinant of the LF/HF ratio in the heart rate variability spectrum, likely, by a respiratory chemosensory mechanism.

Effects of hydroxyurea and L-arginine on the production of nitric oxide metabolites in cultures of normal and sickle erythrocytes

Previous in vitro studies suggest that erythrocytes may be a source of nitric oxide (NO) produced by nitric oxide synthase (NOS) or by oxyhemoglobin-mediated oxidation of hydroxyurea (HU). This study was performed to determine the roles of HU and NOS in the production of NO by normal and sickle erythrocytes. Red blood cells (RBCs) from normal adult hemoglobin (HbAA) and homozygous sickle cell subjects (HbSS) were incubated with PBS containing 0.2 mM hydrogen peroxide (control) for 2 h at 37 degrees C in the presence and absence of l-arginine, the substrate for NOS, and with l-arginine plus HU in the presence and absence of l-NMMA, a specific inhibitor of NOS. The nitrate and nitrite metabolites of NO, expressed as [NOx], were measured. [NOx] in the HbAA and HbSS RBC cultures was not significantly different in the presence and absence of 1.0 mM l-arginine (p>0.1). [NOx] in the HbAA and HbSS cultures treated with a clinically relevant dose of HU (1.0 mM) plus 1.0 mM l-arginine was significantly greater than that in controls incubated with PBS and with l-arginine p < 0.01. However, [NOx] in the HbAA and HbSS cultures treated with 50 microg/ml l-NMMA was not significantly different than that in the cultures treated with HU plus l-arginine in the absence of l-NMMA. These findings suggest that NOx production by erythrocytes may be increased by treatment with HU and may not be decreased by inhibiting NOS. Therefore, we conclude that a therapeutic dose of HU may increase the plasma concentration of NO by a mechanism that does not require erythrocytes NOS activity.

Acute exercise and postexercise blood pressure in African American women

BACKGROUND

Limited data suggest that physical activity increases postexercise blood pressure in African-American women. The purpose of this study was to evaluate the postexercise blood pressure response to acute exercise in normotensive young adult African-American women.

METHODS

Eight healthy women (age 22.5+/-.9 years) performed a cycle ergometer bout of 30 minutes at 60% of peak ventilatory oxygen uptake (VO2 peak). Control arterial blood pressure, heart rate, lower leg blood flow, cardiac output, spectral analysis of blood pressure, heart rate variability, and baroreceptor sensitivity were measured for 5 minutes before exercise and were compared to postexercise measurements performed at rest intervals of 15-20, 35-40 and 55-60 minutes after exercise.

RESULTS

Exercise performed at 60% VO2 peak produced an arterial pressure of 172+/-10/ 70.1+/-4.0 mm Hg. Postexercise recovery values were not significantly different than the baseline control values.

CONCLUSION

These results do not support the hypothesis that acute physical activity exerts an adverse effect on postexercise blood pressure in African American women.

Dietary protein deficiency in pregnant mice and offspring

Previous studies suggest an association between dermal contact hypersensitivity and preterm delivery. We hypothesized that dietary protein deficiency produces cell-mediated immune hypersensitivity in pregnant animals and their offspring akin to those known to produce tissue damage. We compared the effects of feeding a 20% protein diet (controls) to those of feeding a 10% protein (deficient) diet ad libitum to pregnant BALB/c mice. We measured dermal contact sensitivity to 2,4-dinitrofluorobenzene (DNFB) by the increment in ear skin thickness (swelling) 72 h after immunization and parity by the number of viable pups delivered. Dams fed the protein-deficient diet ingested less food, gained less weight and delivered fewer viable pups than the dams fed the control diet. Greater DNFB-stimulated increment in ear skin thickness was found in the protein-deficient mothers and in their offspring than in the control mothers and their offspring. We conclude that dietary protein deficiency limits parity and induces immune hypersensitivity. These findings suggest the potential for dietary protein deficiency to activate a T-cell-mediated branch of the immune response that may put pregnant animals at risk for preterm delivery.

Alpha-7 and alpha-4 nicotinic receptor subunit immunoreactivity in genioglossus muscle motoneurons

In the present study, immunohistochemistry combined with retrograde labeling techniques were used to determine if hypoglossal motoneurons (HMNs), retrogradely labeled after cholera toxin B subunit (CTB) injection to the genioglossus muscle in rats, show immunoreactivity for alpha-7 and alpha-4 subunits of nicotinic acetylcholine receptors (nAChRs). CTB-positive HMNs projecting to the genioglossus muscle were consistently labeled throughout the rostrocaudal extent of the hypoglossal nuclei with the greatest labeling at and caudal to area postrema. Alpha-7 subunit immunoreactivity was found in 39.44+/-5.10% of 870 CTB-labeled motoneurons and the alpha-4 subunit in 51.01+/-3.71% of 983 CTB-positive neurons. Rostrally, the number of genioglossal motoneurons demonstrating immunoreactivity for the alpha-7 subunit was 45.85+/-10.04% compared to 34.96+/-5.11% at and caudal to area postrema (P>0.1). The number of genioglossal motoneurons that showed immunoreactivity for the alpha-4 subunit was 55.03+/-4.83% at and caudal to area postrema compared to 42.98+/-3.90% in rostral areas (P=0.074). These results demonstrate that nAChR immunoreactivity is present in genioglossal motoneurons and suggest a role for alpha-7 and alpha-4 subunits containing nAChRs in the regulation of upper airway patency.

Attenuation of exaggerated exercise blood pressure response in African-American women by regular aerobic physical activity

INTRODUCTION

A hyperreactive blood pressure response to exercise is a predictor of developing hypertension. The present study determined the influence of physical activity on an exaggerated exercise blood pressure response (EEBPR) in normotensive African-American women.

METHODS

We screened 36 women 18-26 years of age for EEBPR defined as a > or = 50 mm Hg difference in systolic blood pressure at rest and during exercise at 50% peak oxygen uptake (VO2peak). Seven subjects demonstrated an EEBPR and participated in the study. Study participants trained for eight weeks on a bicycle ergometer at a work intensity of 70% VO2peak. Blood pressure, heart rate, cardiac output (CO), stroke volume (SV), and total peripheral vascular resistance (TPR) were determined at baseline and during submaximal exercise at power outputs of 30 W and 50% VO2peak. Subjects served as their own controls, and data were evaluated by using a paired t test at P<.05.

RESULTS

Effectiveness of the intervention was shown by a significantly greater VO2peak associated with significant decrements in systolic and mean arterial pressures at power outputs of 30 W and 50% VO2peak. A significant decrement in heart rate was observed during exercise at 30 W. Significant increments in CO and SV and decrement in TPR were found during exercise at 50% VO2peak.

CONCLUSION

The reduction in TPR associated with regular aerobic physical activity may attenuate the EEBPR and decrease the risk for hypertension in normotensive, young-adult, African-American women.

Normal exercise blood pressure response in African-American women with parental history of hypertension

BACKGROUND

Genetic and environmental hypotheses may explain why normotensive persons at high risk of developing hypertension often exhibit greater cardiovascular reactivity to stressors than those at low risk.

METHODS

Pearson's correlation was used to evaluate reproducibility and independent t test to compare the cardiovascular responses to 30 W of exercise of normotensive young adult African-American women with positive and negative parental histories (PH) of hypertension (PH, n = 23; PH, n = 20).

RESULTS

Correlations were significant for duplicate measurements. The effects of PH on blood pressure measured at rest and during exercise were not statistically significant (P > 0.1). A nearly significant trend for greater resting (.-)VO(2) (P = 0.08) was detected in the PH than in the PH group (3.67 +/- 0.18 versus 3.26 +/- 0.14 mL/kg/min).

CONCLUSION

A hyper-reactive blood pressure response to exercise, characteristic of the evolution of hypertension, may not be present among the normotensive female offspring of hypertensive African Americans. The significance of an 11% intergroup difference in the mean resting (.-)VO(2) observed in this study is unclear.

Expression of α-7 nAChRs on spinal cord–brainstem neurons controlling inspiratory drive to the diaphragm

In the present study, we determined whether alpha-7 subunit containing nicotinic acetylcholine receptors (nAChRs) are expressed by neurons within the pre-Botzinger complex (pre-BotC), bulbospinal, and phrenic motor nuclei in the rat. alpha-7 Immunohistochemistry combined with cholera toxin B (CTB), a retrograde tracer was used to detect expression of alpha-7 nAChRs by phrenic motor and bulbospinal neurons. Neurokinin-1 receptor immunoreactivity was used as a marker for pre-BotC neurons. Of the CTB-positive neurons in the phrenic nuclei, 60% exhibited immunoreactivity for alpha-7 nAChRs. Of the bulbospinal neurons in the paramedian reticular nuclei (PMn), gigantocellular nuclei (Gi), raphe nuclei, rostral ventrolateral medulla (RVLM) and nucleus tractus solitarius, 20-50% were found to express alpha-7 nAChR immunoreactivity. Of the peudorabies virus (PRV) labeled bulbospinal neurons in PMn, Gi, raphe and RVLM, 9-12% co-expressed alpha-7 nAChRs. Immunoreactivity for alpha-7 nAChRs was also detected in 57% of the neurokinin-1 receptor containing neurons presumed to reside in pre-BotC. These findings suggest that nicotinic cholinergic regulation of the chest wall pumping muscles may occur at multiple levels of the central nervous system.

Arterialization of peripheral venous blood in sickle cell disease

Arterialization of the venous blood is thought to be indicative of cutaneous shunting, and occurs in patients with sickle cell disease (SCD) during vaso-occlusive crisis (VOC). We performed the present study to quantify the amount of shunting that occurs in sickle cell patients presenting at the Howard University Sickle Cell Center, Washington, D.C., as outpatients and for hospitalizations associated with sickle cell crisis. Peripheral venous blood was drawn anaerobically into heparinized syringes from 9 normal control subjects (NC), 24 outpatients (steady-state group), and 14 inpatients during crisis (VOC group). Spectrophotometric measurements were made for the following species of hemoglobin (Hb): oxy-Hb (O2Hb), reduced Hb (RHb), carboxy-Hb (COHb), and met-Hb (MHb). In addition, fetal hemoglobin (HbF) was measured by high-pressure liquid chromatography (HPLC). The O2Hb saturations of the steady state group were not significantly different than those of the NC group (55 +/- 4% vs. 40 +/- 6%). However, the O2Hb saturations of the VOC group were 73 +/- 3%, and this value was found to be significantly greater than those of both the steady-state and the NC groups (p < 0.05). Reduced hemoglobin saturations were inversely related to the O2Hb values, as expected. Compared to the NC group, the steady-state, and VOC groups had greater dyshemoglobin (COHb and MHb) levels (p < 0.05). These findings suggest that the percentages of venous O2Hb and dyshemoglobins may be increased in sickle cell disease even in the absence of VOC. Therefore, the venous O2Hb saturation may be a useful biochemical marker for the arteriovenous shunting and hemodynamic adaptations associated with sickle cell disease.