Mean Decrement Research Articles

Efficacy of Aspirin on Improvement of Peripheral Blood Circulation in Mice

An in vivo model for assessing the efficacy of aspirin on the improvement of peripheral circulatory was developed by obtaining the cold-induced peripheral blood flow in mice using laser Doppler flowmetry (LDF) and temperature-controlled chambers. ICR mice (w=6) were placed in a temperature-controlled chamber and anesthetized with 1.5% isoflurane. LDF was used to measure the peripheral blood flow during whole-body warming for 10 min (37°C, baseline) and cooling for 40 min (until 13°C). Peripheral blood flow ratio showed significant difference between baseline and whole-body cooling after a lapse of 20 (0.92±0.20) and 40 min (0.33±0.13, p<0.001). Peripheral blood flows of mice administered aspirin (100 mg/kg) or control substance (saline) were measured. Mean peripheral flow ratio decrement of the hind foot was significantly higher in aspirin (0.23±0.10, p<0.05) than the control substance (0.15±0.04). These findings indicate that whole-body cooling is characterized by peripheral circulatory disturbance, which also influences the efficacy of aspirin in improving the peripheral blood circulation.

Pancreas Transplant Alone as an Independent Risk Factor for the Development of Renal Failure: A Retrospective Study

Pancreas transplant alone (PTA) is a controversial procedure. Without clearly demonstrated patient survival, recipients report improved quality of life. Nephrotoxic immunosuppression (IS) may exacerbate diabetic renal injury post-PTA. A single institution retrospective review of patients receiving PTA over a 14-year period was completed. Patient and donor demographics, surgical outcomes, rejection, and patient or graft survival were analyzed. Pre- and Postoperative estimated glomerular filtration rates (eGFR) were calculated based on the modification of diet and renal disease. Multivariate analysis was performed. One hundred twenty-three patients undergoing 131 PTAs had an average age of 40.0 years. Seven patients were retransplanted and one received a third pancreas. Mean graft survival was 3.26 years (0-11.3 years) with 21 patients (17%) lost to follow-up. One- and 5-year patient survivals were 96.6% and 91.5%, respectively (mean, 7.15 year). Seventeen patients had an eGFR less than 50 mL/min/1.73 m preoperatively, whereas 64 patients did so post-PTA and 24 had an eGFR less than 30 mL/min. Mean eGFR pretransplantation was 88.9 vs. 55.6 posttransplantation (P<0.0001) with mean follow-up of 3.68 years. All but 16 (12%) patients showed a decrease in eGFR. Mean decrement was 32.1 mg/min/1.73 m. Thirteen developed end-stage renal disease chronic kidney disease (CKD 5) requiring kidney transplantation (KT) at a mean of 4.36 years. Eighty-three patients had an episode of rejection. In post-PTA RF, graft survival was 3.2 vs. 2.4 years (P=0.13). In those requiring KT, graft survival was 7.9 vs. 2.9 years (P<0.0001). Cold ischemia times, donor age, and preoperative eGFR for those with and without RF-requiring KT were not significant. Body mass index was statistically significant. Leukocyte-depleting agents was evaluated, but was not significant. All patients received calcineurin inhibitor IS. Patients who undergo PTA may be at increased risk for RF. After comparing patient and donor demographics, IS, and human leukocyte antigen mismatch, it seems that PTA is an independent risk factor for the development of renal failure. Patients with more successful pancreatic grafts demonstrated lower eGFR. Patients should be made aware of the risks of long-term IS. Only the most appropriate patients should be chosen for PTA.

Quantifying the Decrement in Utility from Perceived Side Effects of Combination Antiretroviral Therapies in Patients with HIV

Background The decrement in utility attributable to side effects from combination antiretroviral therapy (CART) is unknown and likely to influence clinical decisions regarding CART initiation and cost-effectiveness. Objective To quantify the decrement in utility attributable to side effects from CART. Methods We estimated SF-6D utilities (quality-of-life weights on a scale from 0.29 [worst possible health] to 1.00 [perfect health]) from SF-12 scores among patients with HIV in the Veterans Aging Cohort Study by using a published and validated conversion algorithm. We then compared utilities among patients who: 1) did not have bothersome symptoms while taking CART; 2) had bothersome symptoms that they thought might be due to CART; and 3) had bothersome symptoms that they were confident were due to CART; we controlled for other characteristics known to influence quality of life and stratified analyses by CD4 count. Results Among 1864 patients with available data, symptoms perceived to be attributable to CART were associated with a mean (95% confidence interval) decrement in utility of 0.06 (0.05, 0.08) points in univariate analyses and 0.08 (0.06, 0.10) in multivariable analyses, clinically significant differences that are comparable to utility decrements reported for partial impotence or mild angina. Other significant predictors of changes in SF-6D utilities were hazardous alcohol consumption, recent drug use, cigarette smoking, homelessness, and African American race ( R 2 = 0.12). Stratifying by CD4 count, symptoms attributable to CART side effects decreased utility by 0.03 to 0.08 points. Conclusions Symptoms perceived to be related to CART are associated with a substantial decrement in utility.

Relationship between brief and prolonged repeated sprint ability

Repeated sprint ability (RSA) is often assessed over a brief time period with limited recovery between sprints; however, it is not known how performance in such tests is related to the ability to perform repeated sprints over a more prolonged duration. Eighteen boys aged 15.3+/-0.5 years completed both a brief and prolonged RSA test on a non-motorised treadmill. The brief RSA test consisted of seven 5s sprints with 20s of recovery between sprints and the prolonged RSA test lasted for 42min and included a 5s sprint every 2min. There was a moderate but significant relationship between the mean speed in both tests (r=0.51, p<0.05). The maximal speed achieved in a single sprint provided strong relationships with both brief RSA speed (r> or =0.72, p<0.001) and prolonged RSA speed (r> or =0.77, p<0.001). Total work done during the brief protocol was significantly correlated to both total work (r=0.81, p<0.001) and total sprint distance (r=0.79, p<0.001) during the prolonged test. There were no significant relationships between percentage decrement scores across the two protocols (r< or =0.33, p>0.05). Maximal speed in a single sprint and total work done during repeated sprints represent general qualities related to RSA that are independent of the test protocol. The mean speed and decrements in performance represent specific RSA qualities, which are dependent on the frequency of sprints and duration of the test protocol.

Plasma amyloid-β, Aβ1-42, load is reduced by haemodialysis

Patients with chronic renal failure treated with haemodialysis have vascular risk factors that, in the general population, are associated with increased prevalence of Alzheimer's disease (AD). Patients in haemodialysis, however, present different kinds of dementia but they do not have an increased risk of AD. We have hypothesized that amyloid-beta (Abeta)1-42 is washed out from plasma during the dialysis and that this procedure enhances Abeta elimination and reduces the risk of AD. We have measured plasma Abeta1-42 levels in 11 patients with renal failure, before and after haemodialysis. A single procedure reduced the plasma Abeta levels in all subjects with a mean decrement of 30% of baseline. Since Abeta deposition could be altered by certain metals like Cu and Zn, we have also measured the effects of dialysis on the levels of these ions in plasma. We found no changes in levels of Cu and Zn after dialysis. Haemodialysis, therefore, reduces very effectively plasma Abeta without modifying Cu and Zn levels. The potential use of this strategy in patients with AD requires further investigation.

Healthcare costs and long-term outcomes after acute respiratory distress syndrome: A phase III trial of inhaled nitric oxide*

To determine the costs and long-term outcomes of acute respiratory distress syndrome (ARDS) in previously healthy adults. To determine whether treatment with inhaled nitric oxide affects these costs and outcomes. One-year follow-up of a randomized trial of inhaled nitric oxide. Hospital bills were collected, and follow-up was performed at hospital discharge, 6 months, and 1 year. Forty-six U.S. centers. Three hundred and eighty-five previously healthy adults with ARDS. Subjects were randomized to 5 ppm inhaled nitric oxide or placebo gas. One-year survival was 67.8%, with no difference by treatment arm (67.3% vs. 68.3% for inhaled nitric oxide vs. placebo, p = .71). Hospital costs from enrollment to discharge were high and similar in the inhaled nitric oxide and placebo arms ($48,500 vs. $47,800, p = 0.8). There were also no differences in length of stay or Therapeutic Intervention Scoring System points. Almost half (43.4%) of subjects were discharged to another healthcare facility or to home with professional help, and 24.1% were readmitted in 6 months, with no differences between groups. At 1 year, survivors reported low quality of life with no differences by treatment arm (Quality of Well-Being score [range 0-1], 0.61 vs. 0.64 for inhaled nitric oxide vs. placebo, p = .11) and poor function with no differences by treatment arm (32.5% returned to </=5 points of baseline Activities of Daily Living [range 0-100], 63.3% returned to </=10 points, and the remaining 36.7% suffered a mean decrement of 27 points). ARDS, even in previously healthy adults, not only is followed by poor survival, quality of life, and function but also is associated with high costs of care and postdischarge resource use. Inhaled nitric oxide at 5 ppm had no effect on these outcomes.

Mortality and airflow obstruction in asthma: a 17‐year follow‐up study

Asthma is associated with fixed airflow obstruction and an increased risk of death. The aim of this study was to relate asthma mortality and airflow obstruction to severity of asthma in a cohort of patients with chronic asthma studied over a 17-year period. In 1980, asthma severity based on symptoms, asthma duration, treatment and smoking habits were assessed and lung function was measured after maximal therapy in 89 patients. In 1997, mortality was recorded and 44 of 60 patients known to be alive were restudied. Eighteen patients had died: eight deaths were associated with asthma (seven occurred before and one after 1990). The risk of death was higher with decreased forced expiratory volume in 1 s (FEV1), increased FEV1 variability, age and treatment requirements but not symptom severity, at initial study. In the patients restudied, asthma severity and FEV1 variability decreased whereas the dose of inhaled corticosteriods increased 2.8-fold. Highest FEV1 was negatively related to treatment score and smoking history at initial study, but not at follow up and was <80% predicted in 19 (43%) patients, 11 of whom had never smoked. The mean (+/-standard deviation) decrement in FEV1 was 32 +/- 24 mL/year and correlated positively with FEV1 at initial study, smoking history, age of onset of asthma and treatment requirements at follow up. In this cohort study, asthma was associated with chronic airflow obstruction and that with increased risk of mortality. Symptoms and mortality risk improved in association with increased reported use of inhaled corticosteroids; however, there was ongoing chronic airflow obstruction.

Evidence for a Tetrahydrobiopterin Deficit in Schizophrenia

Tetrahydrobiopterin (BH₄) is a vital cofactor maintaining availability of the amine neurotransmitters [dopamine (DA), noradrenaline (NA), and serotonin (5-HT)], regulating the synthesis of nitric oxide (NO) by nitric oxide synthase (NOS), and stimulating and modulating the glutamatergic system (directly and indirectly). These BH₄ properties and their potential relevance to schizophrenia led us to investigate the hypothesis of a study group (healthy controls, n = 37; schizophrenics, n = 154) effect on fasting plasma total biopterin levels (a measure of BH₄). Study analysis showed a highly significant deficit of total biopterins for the schizophrenic sample after partialling out the effects of potential confounds of gender, age, ethnicity, neuroleptic use history and dose of current use, 24-hour dietary phenylalanine/protein ratio (a dietary variable relevant to BH₄ synthesis), and plasma phenylalanine (which stimulates BH₄ synthesis). A mean decrement of 34% in plasma total biopterins for schizophrenics from control values supports clinical relevance for the finding. In a subsample (21 controls and 23 schizophrenics), sequence analysis was done of the GTP cyclohydrolase I feedback regulatory gene and no mutations were found in the coding region of the gene. A deficiency of BH₄ could lead to hypofunction of the systems of DA, NA, 5-HT, NOS/NO, and glutamate, all of which have been independently implicated in schizophrenia psychopathology. Further, evidence has been accumulating which implicates the critical interdependence of these neurotransmitter systems in schizophrenia; this concept, along with the present study finding of a biopterin deficit, suggests that further study of the BH₄ system in schizophrenia is warranted and desirable.

Health-related quality of life measurements in elderly Canadians with osteoporosis compared to other chronic medical conditions: a population-based study from the Canadian Multicentre Osteoporosis Study (CaMos)

The objective of this research was to determine the relative decrement in health-related quality of life, as measured by the health utilities index mark 3 (HUI3), in osteoporosis compared to other chronic medical conditions. The impact of chronic medical conditions other than osteoporosis on HUI3 measurements had been previously established in the 1996/1997 Canadian National Population Health Survey (NPHS). The Canadian Multicentre Osteoporosis Study (CaMos) is a national population-based study in which regional participants were randomly recruited, regardless of presence of osteoporosis. We analyzed data from participants aged > or = 65 years who completed a baseline HUI3 questionnaire and provided information on their medical history (n=3,750). We determined the age- and gender-adjusted mean decrement in HUI3 for several chronic medical conditions, including osteoporosis. The mean changes in HUI3 adjusted for age and gender (with 95% confidence intervals) were as follows: arthritis -0.10 (-0.11, -0.09), chronic obstructive pulmonary disease (COPD) -0.07 (-0.09, -0.05), diabetes mellitus -0.05 (-0.08, -0.03), heart disease -0.06 (-0.08, -0.04), hypertension -0.02 (-0.03, -0.01), and osteoporosis -0.08 (-0.11, -0.06), respectively (model r2=0.17; P<0.0001). These findings were comparable to those observed in the NPHS, with the exception of osteoporosis, which had not been previously studied in this fashion. The decrement in HUI3 score seen in participants with osteoporosis was comparable to that observed in other chronic medical conditions, such as arthritis, COPD, diabetes mellitus or heart disease.

Impact of Immunosuppressive Treatment on Liver Fibrosis in Autoimmune Hepatitis

The impact of treatment on progression of fibrosis in autoimmune hepatitis (AIH) is unknown. We assessed the changes in liver fibrosis before and after treatment among these patients. Nineteen AIH patients who had paired liver biopsies were studied. Of these, seven had been treated with 6 months of cyclosporine A and the rest with 6 months of prednisolone for induction of remission. Thereafter all had been maintained on azathioprine. Biopsy specimens before and after treatment were reviewed by one pathologist and scored by the Ishak method. Mean fibrosis stages before and after treatment were compared. Also, factors predicting significant fibrosis (stage > or =3) and cirrhosis (stage > or =5) at presentation were assessed. Mean interval between biopsies was 3.38 years. Mean fibrosis stage decreased from 4.53 to 2.16 following treatment (P < 0.001). Mean decrement in inflammatory grade was 8 scores (range, 4-10) in patients in whom fibrosis improved, and 2 scores (range, 0-4) in patients in whom fibrosis did not decrease after treatment (P < 0.001). ALT-to-platelet ratio was the best predictor of significant fibrosis and also cirrhosis. Fibrosis commonly improves after immunosuppressive treatment in AIH. ALT-to-platelet ratio can predict accurately the presence of significant fibrosis and cirrhosis in AIH.

The Effect of Posterior Lumbar Interbody Fusion After Posterolateral Fusion in Degenerative Spondylolisthesis

Purpose: To determine the necessity of an additional posterior lumbar interbody fusion (PLIF) after a posterolateral fusion (PLF) for the treatment of degenerative spondylolisthesis (DS). Materials and Methods: A retrospective study, after a minimum follow-up of 2 years was conducted on forty patients who underwent a single level decompression and instrumented fusion for DS with spinal stenosis at the L4-5 level. A PLF was performed in 21 patients, and a circumferential fusion (CF) with an additional PLIF in 19 patients. According to the fusion methods and preoperative segmental mobility, the patients were divided into four groups; s-PLF group (PLF in the stable group, n=13), s-PLIF group (CF in the stable group, n=11), u-PLF group (PLF in the unstable group, n=8), and u-PLIF group (CF in the unstable group n=8). Clinical and radiographic comparisions between the PLF and PLIF groups were performed. Results: The mean decrements of Oswestry Disability Index (Visual Analog Scale) scores were 29% (5.5), 29% (5.9), 22% (2.6) and 42% (5.9) respectively for the s-PLF, s-PLIF, u-PLF and u-PLIF groups, and a statistical difference was found only between the u-PLF and u-PLIF groups (ODI: p=0.032, VAS: p=0.004). Fusion rates were 92%, 100%, 88% and 100% respectively. The mean slip angle increments were serially 2.5, -3.1, -1.5 and -0.3, and the mean percent slip decrements were 6.7%, 8.7%, 5.1% and 3.7%, and the mean disc height increments were -0.4 mm, 1.8 mm, 0.5 mm and 3.0 mm, and the mean lumbar lordosis increments were 8.6 4.7, -1.9 and 1.9 and the mean sacral tilt increments were 3.8, 3.4, -1.3 and 0.9. Statistical differences were found only between the s-PLF and s-PLIF groups in slip angle increments (p=0.029) and between the s-PLF and s-PLIF groups (p=0.043) and between the u-PLF and u-PLIF groups (p=0.042) in disc height increments. Conclusion: PLF alone provided successful clinical outcome in stable group, but CF provided better clinical outcomes in the unstable groups. This study suggests that preoperative segmental mobility may be a criterion to determine whether or not an additional PLIF is necessary in the treatment of lumbar DS.

Rapid neck muscle adaptation alters the head kinematics of aware and unaware subjects undergoing multiple whiplash-like perturbations

To examine whether habituation confounds the study of whiplash injury using human subjects, we quantified changes in the magnitude and temporal development of the neck muscle electromyogram and peak linear and angular head/torso kinematics of subjects exposed to sequential whiplash-like perturbations. Forty-four seated subjects (23F, 21M) underwent 11 consecutive forward horizontal perturbations (peak sled acceleration=1.5 g). Electromyographic (EMG) activity was recorded over the sternocleidomastoid (SCM) and cervical paraspinal (PARA) muscles with surface electrodes, and head and torso kinematics were measured using linear and angular accelerometers and a 3D motion analysis system. EMG onset occurred at reflex latencies (67–75 ms in SCM) and did not vary with repeated perturbations. EMG amplitude was significantly attenuated by the second perturbation in PARA muscles and by the third perturbation in SCM muscles. The mean decrement in EMG amplitude between the first trial and the mean of the last five trials was between 41% and 64%. Related kinematic changes ranged from a 21% increase in head extension angle to a 29% decrease in forward acceleration at the forehead, and were also significantly different by the second exposure in some variables. Although a wider range of perturbation intensities and inter-perturbation intervals need to be studied, the significant changes observed in both muscle and kinematic variables by the second perturbation indicated that habituation was a potential confounder of whiplash injury studies using repeated perturbations of human subjects.

Relationship Between the Right Ventricular Pressure Waveform and the Vasodilator Response of Pulmonary Artery Pressure in Pulmonary Artery Hypertension

Background and Objectives:This study was performed to discern whether the vasodilatory response of pulmonary artery pressure could be predicted by the right ventricular (RV) pressure waveforms, and therefore, from continuous wave Doppler signals of tricuspid regurgitant jet (CWTR). Subjects and Methods:Twelve patients with pulmonary hypertension who underwent cardiac catheterization were enrolled. Nitroprusside was infused at a dose of 0.5 μg/kg/min, with the dosage being increased by 0.5 μg/kg/min every 5 minutes to a maximum of 4 μg/kg/min. Cardiac output (CO), pulmonary vascular resistance (PVR), peak systolic RV pressure (Pp), RV pressure at the inflection point (Pi), ΔP (Pp-Pi) and CWTR were obtained before and at the end of the nitroprusside infusion. A positive response to the vasodilator was defined when there was ≥20% change in the mean pulmonary artery pressure at the end of the nitroprusside infusion. Results:Eight patients did not show a positive response (Group 1) while four patients did (Group 2). Mean decrements in Pp following the nitroprusside test were 4.1±7.7 mmHg in group 1 and 27.8±5.6 mmHg in group 2. There were no significant differences between groups 1 and 2 in baseline CO, PVR or Pp. However group 1 had a significantly higher ΔP than group 2 (29.0± 10.5 mmHg vs. 13.3±3.0 mmHg, p<0.05). In the configuration analysis of CWTR, the slope between the inflection point and peak velocity was linear in group 1, while there was an indentation in group 2. Conclusion:Patients with a small difference between Pp and Pi tend to be reactive to a vasodilator and this tendency can be predicted from the configuration of CWTR. (Korean Circulation J 2003;33 (11):1011-1017)

Exposure to indoor combustion and adult asthma outcomes: environmental tobacco smoke, gas stoves, and woodsmoke

Background: Because they have chronic airway inflammation, adults with asthma may be particularly susceptible to indoor air pollution. Despite widespread exposure to environmental tobacco smoke (ETS), gas stoves, and woodsmoke,...

Response properties of the refractory auditory nerve fiber.

The refractory characteristics of auditory nerve fibers limit their ability to accurately encode temporal information. Therefore, they are relevant to the design of cochlear prostheses. It is also possible that the refractory property could be exploited by prosthetic devices to improve information transfer, as refractoriness may enhance the nerve's stochastic properties. Furthermore, refractory data are needed for the development of accurate computational models of auditory nerve fibers. We applied a two-pulse forward-masking paradigm to a feline model of the human auditory nerve to assess refractory properties of single fibers. Each fiber was driven to refractoriness by a single (masker) current pulse delivered intracochlearly. Properties of firing efficiency, latency, jitter, spike amplitude, and relative spread (a measure of dynamic range and stochasticity) were examined by exciting fibers with a second (probe) pulse and systematically varying the masker-probe interval (MPI). Responses to monophasic cathodic current pulses were analyzed. We estimated the mean absolute refractory period to be about 330 micros and the mean recovery time constant to be about 410 micros. A significant proportion of fibers (13 of 34) responded to the probe pulse with MPIs as short as 500 micros. Spike amplitude decreased with decreasing MPI, a finding relevant to the development of computational nerve-fiber models, interpretation of gross evoked potentials, and models of more central neural processing. A small mean decrement in spike jitter was noted at small MPI values. Some trends (such as spike latency-vs-MPI) varied across fibers, suggesting that sites of excitation varied across fibers. Relative spread was found to increase with decreasing MPI values, providing direct evidence that stochastic properties of fibers are altered under conditions of refractoriness.

Hypersensitivity pneumonitis in a metal‐working environment

An outbreak of lung disease among workers in a metal-working plant included 16 biopsy-confirmed cases of hypersensitivity pneumonitis and additional patients with asthma, bronchiolitis and emphysema, usual interstitial pneumonitis, and sarcoidosis. Study design Clinical examination of patients; cross-sectional questionnaire survey of the outbreak plant and two control plant areas, one with and one without MWF exposures, in a separate facility; industrial hygiene survey with laboratory characterization of microbial flora; and immunological investigation. Patients with suspected hypersensitivity pneumonitis underwent a clinical examination including detailed lung function, imaging, and tissue studies. A plant walk-through identified metal-working processes, microbial aerosols, and work practices. Microbial characteristics of the three microbial aerosol-producing processes were characterized. Antibodies to those agents were determined in patient sera. A questionnaire survey was conducted in the case plant and in two areas of a control plant, one with and one without metal-working fluids exposure. Thirty-nine (79.6%) patients described symptoms consistent with work-related lung disease, eight received other diagnoses, and two did not complete their examinations. Sixteen patients had hypersensitivity pneumonitis confirmed on biopsy. Mean decrements in lung forced expiratory volume in 1 s and force vital capacity from before to after work were similar in the 16 biopsy-confirmed cases of hypersensitivity pneumonitis ( - 6.3%; - 7.2%) and the 19 symptomatic patients without biopsies ( - 11.2%, - 10.1%). Symptoms were more common in the case plant than in a non-MWF control plant area. Three sources of water-based aerosols were identified that grew similar microbial flora. Although machining increased airborne bacterial levels, the increase was not related to the concentration of viable bacteria in the sumps. Antibody testing did not identify a specific single organisms. Endotoxin levels were similar in case and MWF control plant. Lung disease in environments with water-based aerosols may be more common than usually recognized. Patients with HP often present with only subtle abnormalities and may be missed if multiple clinical abnormalities are required to document disease.

Outcome after unilateral hypogastric artery occlusion during endovascular aneurysm repair

Purpose: The purpose of this study was to determine the long-term functional outcome after unilateral hypogastric artery occlusion during endovascular stent graft repair of aortoiliac aneurysms. Methods: During a 41-month period, 157 consecutive patients underwent elective endovascular stent graft repair of aortoiliac aneurysms with the Medtronic AneuRx device. Postoperative computed tomography scans were compared with preoperative scans to identify new hypogastric artery occlusions. Twenty-three (15%) patients had unilateral hypogastric occlusion, and there were no cases of bilateral occlusions. Telephone interviews about past and current levels of activity and symptoms were conducted, and pertinent medical records were reviewed. All 23 (100%) patients were available for the telephone interview. A disability score (DS) was quantitatively graded on a discrete scale ranging from 0 to 10 corresponding to “virtually bed-bound” to “greater-than-a-mile” exercise tolerance. Worsening or improvement of symptoms was expressed as a difference in DS between two time points (–, worsening/+, improving). Results: Among the 23 patients, two groups were identified: 10 patients (43%) had planned and 13 patients (57%) had unplanned or inadvertent occlusions. The patients in the two groups did not differ significantly in the mean age (73.4 vs 73.7 years), sex (male:female, 9:1 vs 10:3), and duration of follow-up (15.6 vs 14.4 months). Nine (39%) of the 23 patients, five patients in the planned and four patients in the unplanned group, reported significant symptoms of hip and buttock claudication ipsilateral to their occluded hypogastric arteries. The mean decrement from baseline of these nine patients in their DS postoperatively was –3.3. The symptoms were universally noted on postoperative day 1. Although most patients improved (89%), one (11%) never got better. Among those whose symptoms improved, the mean time to improvement was 15 weeks, but with a plateau thereafter resulting in a net decrement of DS of –2.3 from baseline. Finally, when questioned whether they would undergo the procedure again, all 23 patients unanimously answered, “Yes.” Conclusions: A significant number (39%) of patients who sustain hypogastric artery occlusion after endovascular aneurysm repair have symptoms. Although most patients with symptoms have some improvement, none return to their baseline level of activity. Despite this, all patients in retrospect would again choose endovascular repair over conventional open repair. (J Vasc Surg 2001;33:921-6.)

Connections between the Cosmic Baryon Fraction, the Extragalactic Ionizing Background, and Lyman Break Galaxies

We reassess constraints on the cosmological baryon density from observations of the mean decrement and power spectrum of the Ly? forest, taking into account uncertainties in all free parameters in the simplest gravitational instability model. The uncertainty is dominated by that of the photoionizing background, but incomplete knowledge of the thermal state of the intergalactic medium also contributes significantly to the error budget. While current estimates of the baryon fraction from the forest do prefer values that are somewhat higher than the big bang nucleosynthesis value of ?b h2 = 0.02 ? 0.001, the discrepancy is at most about 3 ?. For instance, assuming the highest estimate of the ionizing background, as indicated by recent measurements of a large escape fraction from Lyman break galaxies by Steidel, Pettini, & Adelberger, we find ?bh2 = 0.045 ? 0.008. A recent measurement of the ionizing background from the proximity effect by Scott et al., on the other hand, implies ?bh2 = 0.03 ? 0.01. We provide an expression from which future likelihoods for ?b h2 can be derived as measurements of the ionizing background improve?consistency among constraints from the forest, nucleosynthesis, and the microwave background will provide a powerful test of the gravitational instability model for the forest and for large-scale structure in general. We also develop a formalism that treats lower bounds on the baryon density in a statistical manner, which is appropriate if only a lower bound on the ionizing background is known. Finally, we discuss the implications of the escape fraction measurement for the age, structure, and stellar content of Lyman break galaxies. We show that the observed hard spectrum from Lyman break galaxies requires a very young age (less than about 1 million years) and/or a top-heavy initial mass function. We also build a model in which an extended (non-disk-like) gas distribution allows a large escape fraction.

Essential tremor frequency decreases with time.

To quantify the extent to which tremor frequency changes with time in patients with essential tremor. Tremor frequency tends to be lower in older patients. The author's previous study of 18 patients with essential tremor produced evidence that tremor frequency decreases slowly over a period of 4 to 8 years. A decrement in frequency will increase tremor amplitude because there is less attenuation of lower-frequency tremor by the low-pass filtering properties of muscle and limb mechanics. Nineteen women and 25 men with essential tremor and no other neurologic conditions were followed for 4 years. Accelerometry and surface electromyography (EMG) were used to measure hand tremor and motor unit entrainment in the extensor carpi radialis brevis every 2 years. Tremor frequency was computed from the spectral peak in the rectified filtered EMG spectrum under the condition of 300-gram loading. The patients' mean +/- SD age was 68.0+/-9.95 years. The mean tremor frequency at baseline was 5.79+/-1.32 Hz. The mean decrement in tremor frequency over 4 years was 0.332 Hz (95% CI = 0.141 to 0.523) and was 0.270 Hz (95% CI = 0.122 to 0.418) when a 61-year-old outlier patient was excluded. Tremor frequency and patient age were linearly related: frequency = -0.061(age) + 9. 94 (r = 0.459; p<0.002). The frequency of essential tremor decreases by approximately 0.06 to 0.08 Hz/year. This decrement in frequency is consistent with the linear relationship between age and tremor frequency.

Aerobic performance of Special Operations Forces personnel after a prolonged submarine deployment

The US Navy's Sea, Air and Land Special Operations Forces personnel (SEALs) perform a physically demanding job that requires them to maintain fitness levels equivalent to elite athletes. As some missions require SEALs to be deployed aboard submarines for extended periods of time, the prolonged confinement could lead to deconditioning and impaired mission-related performance. The objective of this field study was to quantify changes in aerobic performance of SEAL personnel following a 33-day submarine deployment. Two age-matched groups of SEALs, a non-deployed SEAL team (NDST, n= 9) and a deployed SEAL team (DST, n= 10), performed two 12-min runs for distance (Cooper tests) 5 days apart pre-deployment and one Cooper test post-deployment. Subjects wore a Polar Vantage NVTM heart rate (HR) monitor during the tests to record exercise and recovery HR. Variables calculated from the HR profiles included mean exercise heart rate (HRmean), maximum exercise heart rate (HRmax), the initial slope of the HR recovery curve (HRreslope) and HR recovery time (HRrectime). The second pre-deployment test (which was used in the comparison with the post-deployment test) showed a 2% mean increase in the distance achieved compared with the first (n= 18, p< 0.05) with no difference in HRmean, HRmax, HRreslope and HRrectime. The test-retest correlation coefficient and 95% limits of agreement for the Cooper tests were 0.79 (p< 0.001) and −68.6±267.5 m, respectively. For the NDST there were no changes in any of the HR measures or the distance run between the pre- and post-deployment tests. When individual running performances were expressed as a percentage change in the distance run between the pre- and post-deployment tests, the DST performed significantly worse than the NDST (p< 0.01). The DST showed a 7% mean decrement in the distance run following deployment (p< 0.01). The decrement in performance of the DST was not associated with any changes in HRmean or HRmax; however, there was a 17% decrease in the HRrecslope (p< 0.05) and a 47% increase in HRrectime following the deployment (p< 0.05). In conclusion, prolonged confinement aboard a submarine compromises the aerobic performance of SEAL personnel. The resulting deconditioning could influence mission success.