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Biomedical subjects

D Baker

Publications and source records attributed to D Baker.

At least 55 records · Page 3Linked to original sources

Catheter angiography and angioplasty in patients with scleroderma.

The objectives of this study were (i) to identify patterns of angiographic disease in scleroderma patients with and without other vascular risk factors and (ii) to define patients with scleroderma in whom angiography and angioplasty is useful. The records of 26 patients with scleroderma who underwent angiography and angioplasty over an 8-year period were reviewed. Angiographic disease patterns were assessed using a modified Brewster classification. Angiography of the upper limb demonstrated distal disease alone in 86% of patients, both with and without other vascular risk factors such as smoking. In the lower limb there was a highly significant association between the presence of other vascular risk factors and macrovascular disease potentially amenable to angioplasty, and conversely between the absence of other vascular risk factors and distal disease in the lower limb. Good early but poor late clinical results were achieved in three of five patients who underwent angioplasty. Angiography of the upper limb is likely to demonstrate distal disease alone, and angiography and angioplasty of the lower limb may be useful only if other vascular risk factors are present.

Adult↗

Defusing the baby boomer time bomb: projections of after-tax income in the twenty-first century.

There has been a major national policy debate over the prospective tax burden facing future generations of workers as a result of the impending retirement of the baby boom generation. However, the real determinant of well-being is after-tax income, not the tax rate on before-tax income. This study constructs a series of projections of after-tax income, for workers and families at different points in the income distribution, to examine the effects of several different trends. The author first calculates the extent to which after-tax income can be expected to decline as the result of the aging of the baby boomers, then calculates the impact on after-tax income for families at different points in the income distribution of a continuation of recent trends in wage inequality. He also constructs a category of "after-tax, after-health-care spending" income, which examines the impact of the continued rapid growth in health care costs. The findings suggest that the continuation of recent trends in inequality and health care cost growth will have a much larger effect on future living standards than will the aging of the baby boomers.

Actuarial Analysis↗

Offshore medicine.

Offshore life can be refreshing for medics who are looking for a little change of pace; however, it is not for everyone. Working offshore can be the easiest or most boring job you'll ever have. It takes a specific type of medic to fit this mold. So, if you are considering a career in the offshore field, take all of the above into consideration. You are not just making a change in jobs, but a change in lifestyle. Once you become accustomed to this lifestyle, it will be hard to go back to the everyday hustle and bustle of the streets. For more information about working offshore, contact Acadian Contract Services at 800/259-333, or visit www.acadian.com.

Career Choice↗

Current surgical management of colorectal cancer.

Colorectal cancer is the leading cause of death from gastrointestinal malignancies in the United States. Recent emphasis on screening of high-risk and no-risk individuals in addition to careful postoperative surveillance has decreased the incidence and improved the quality of life of survivors. Although multimodality approaches to treating colorectal cancer are favored, surgical resection continues to be the mainstay for a cure. This article reviews current surgical approaches and advances based on evidence for best practice.

Adult↗

An evidence-based vector control strategy for military deployments: the British Army experience.

We describe the British Army's current strategy for controlling arthropod vectors of disease during overseas deployments. Military commanders and medical officers have different, but complementary responsibilities in achieving vector control. In this paper we define a hierarchy of evidence-based vector control guidelines. Field guidelines must be based on the best available research evidence, preferably that derived from pragmatic randomised controlled trials (RCTs), and from systematic reviews of trials. Assessing the effectiveness of different vector control measures involves a trade-off between the relative benefits and harm of different technology options. There is compelling scientific evidence that bed nets and screens treated with a pyrethroid insecticide are highly effective in protecting against nocturnally active, anthropophilic arthropods (including ectoparasites), and will reduce the incidence of malaria, leishmaniasis, lymphatic filariasis and Chagas' disease. Etofenprox and deltamethrin are the safest pyrethroids, and permethrin the least safe. Vector control strategies of probable effectiveness are the use of insecticide-treated clothing, the wearing of protective clothing, and the correct use of DEET-based topical insect repellents. Aerosol insecticides are of debatable effectiveness. Other effective vector control measures, of limited usefulness during deployments, include electric fans, mosquito coils/vaporising mats, and smoke. "Biological" vector control measures, and insect buzzers/electrocuters are ineffective. Practical insect avoidance measures, based on an understanding of vector biology, complete the military vector-control arsenal. We conclude that practical insect avoidance measures, combined with pyrethroid-treated nets and clothing, and DEET-based topical repellents, can achieve almost 100% protection against biting arthropods.

Animals↗

Patent medicine.

Explore the source record for details and available documents.

Drug Industry↗

The load that maximizes the average mechanical power output during explosive bench press throws in highly trained athletes.

The power output generated with different barbell loads and which resistance generated the maximum mechanical power output (Pmax) during explosive bench press-type throws (BT) in a smith machine device were investigated in power-trained athletes. Thirty-one rugby league players were tested for 1 repetition maximum (1RM) free-weight bench press strength (1RM BP). Maximal power output was assessed by the Plyometric Power System during BT using resistances of 40, 50, 60, 70, and 80 kg (BT P40, BT P50, BT P60, BT P70, and BT P80). It was found that BT Pmax occurred with resistance of 70.1 +/- 7.9 kg, representing 55 +/- 5.3% of 1RM BP of 129.7 +/- 14.3 kg. The power output with all loads except the BT P70 were different from the BT Pmax. The BT P70 and BT P80 were not different from each other. Furthermore, the BT P60 and BT P80 were not different from each other. This suggests that although resistances of 55% 1RM BP may maximize power output during explosive BT, loads in the range of 46-62% also allow for high power outputs. Resistances of 31-45% of 1RM BP resulted in significantly lower power outputs. Compared with previous research of BT in strength-trained athletes, the results of this investigation suggest that power-trained athletes may generate their Pmax at higher percentages of 1RM.

Adult↗

Comparison of upper-body strength and power between professional and college-aged rugby league players.

Levels of upper-body strength and power can distinguish between athletes of different levels in a number of sports. The purpose of this investigation was to compare the maximum upper-body strength and power of 22 professional National Rugby League (NRL) and 27 state- and city-league, college-aged (SRL) rugby league players. All players were from the same football club and had undergone the same preseason strength and power training program for the 8 weeks prior to testing. Maximum strength was assessed by a 1 repetition maximum bench press (1RM BP). Maximum power (Pmax) and power output with loads of 40, 50, 60, 70, and 80 kg (P40, P50, P60, P70, and P80) were assessed during BP throws using the plyometric power system (PPS). Despite no differences in body mass or height, the NRL players were significantly stronger and more powerful in every variable measured. Furthermore, the differences in power output between groups became more pronounced with increasing barbell loads. Overall strength and power were highly related (r = 0.82); however, the relationship between these variables was somewhat less in the stronger NRL group (NRL r = 0.58, SRL r = 0.85). The percentage 1RM which maximized power output was also significantly lower for the NRL group as well as for stronger subgroups within each group. The results suggest that maximum strength largely influences power output; however, once a strength plateau has been reached, the changing training emphasis toward power training or the negative effects of high-volume conditioning training may alter the extent of the relationship.

Adolescent↗

The load that maximizes the average mechanical power output during jump squats in power-trained athletes.

Three studies that used rugby league players experienced in power training methods as subjects were performed to investigate the resistance (percentage of 1 repetition maximum [1RM]) that maximized the average mechanical power output (Pmax) during the jump squat exercise. Maximum strength was assessed via 1RM (studies 2 and 3) or 3RM (study 1) during the full-squat exercise. Pmax was assessed during barbell jump squats, using resistances of 40, 60, 80, and 100 kg within the Plyometric Power System. All studies found that power output was maximized by resistances averaging circa 85-95 kg, representing 55-59% of 1RM full-squat strength. However, loads in the range of 47-63% of 1RM were often similarly effective in maximizing power output. The results of this investigation suggest that athletes specifically trained via both maximal strength and power training methods may generate their maximal power outputs at higher percentages of 1RM than those previously reported for solely strength-trained athletes and that there would appear to be an effective range of resistances for maximizing power output.

Adolescent↗

The effects of an in-season of concurrent training on the maintenance of maximal strength and power in professional and college-aged rugby league football players.

Fourteen professional (NRL) and 15 college-aged (SRL) rugby league players were observed during a lengthy in-season period to monitor the possible interfering effects of concurrent resistance and energy-system conditioning on maximum strength and power levels. All subjects performed concurrent training aimed at increasing strength, power, speed, and energy-system fitness, as well as skill and team practice sessions, before and during the in-season period. The SRL group significantly improved 1 repetition maximum bench press (1RM BP) strength, but not bench throw (BT Pmax) or jump squat maximum power (JS Pmax) over their 19-week in-season. The results for the NRL group remained unchanged in all tests across their 29-week in-season. The fact that no reductions in any tests for either group occurred may be due to the prioritization, sequencing, and timing of training sessions, as well as the overall periodization of the total training volume. Having athletes better conditioned to perform concurrent training may also aid in reducing the possible interfering effects of concurrent training. Correlations between changes in 1RM BP and BT Pmax suggest differences in the mechanisms to increase power between stronger, more experienced and less strong and experienced athletes.

Adult↗

A series of studies on the training of high-intensity muscle power in rugby league football players.

Maximal power (Pmax) levels and the effects of the manipulation of training variables on power output in rugby league football players were investigated in 5 studies. In study 1, players of 3 different ability levels were assessed for Pmax during explosive bench press throws. Pmax levels were a significant descriptor of playing ability within the sport. In study 2, the effect of contrast loading was investigated during jump squats. The result was a significant (p < 0.05) increase in power output in the investigated load. In study 3, the effect of an ascending vs. descending order of loads during explosive bench press throws was investigated. An ascending order resulted in a significantly higher power output for the heaviest load, whereas the descending order resulted in a significantly higher power output for the lightest load. In study 4, the relationship between measures of upper-body strength, power, and speed was investigated in athletes from 3 different levels of playing ability. Strength, power, and speed were significantly correlated overall; however, the relationships were greater in the more experienced training group. In study 5, it was found that stronger athletes utilized a lower percentage of 1 repetition maximum (1RM; 46-51%) to attain Pmax than less strong athletes (58-69%).

Adolescent↗

A role for near infrared spectroscopy in the assessment of intermittent claudication.

BACKGROUND: Near infrared spectroscopy (NIRS) can be used to monitor muscle oxyhemoglobin (HbO2), deoxyhemoglobin (Hb) and cytochrome oxidase (CytOx) oxidation. We evaluated the changes in NIRS in patients with intermittent claudication (IC) pre- and postexercise. Microalbuminuria is an index of endothelial dysfunction. Therefore, we also assessed whether the urinary excretion of albumin increased postexercise in patients with IC. METHODS: Each participant (14 patients with IC and 10 controls) underwent a treadmill test; NIRS was continuously recorded. The urinary albumin:creatinine ratio (ACR) and ankle: brachial systolic pressure index (ABPI) were measured pre- and postexercise. RESULTS: The ABPI in the claudicants dropped significantly (p<0.001) postexercise. The pre-exercise ACR did not differ between claudicants and controls but postexercise, the ACR increased significantly (p<0.001) in the claudicants. There was a significant (p<0.001) difference in the degree of HbO2 deoxygenation between claudicants and controls; the rate of deoxygenation was significantly higher in claudicants than in controls (-8.4 vs. -3.4 mol/L.min, p=0.024). The period of recovery of HbO2 postexercise was also significantly slower in claudicants (192 vs 68 sec, p=0.003). There was a significant correlation between the increase in the ACR and time of recovery of HbO2 levels postexercise (r=0.86, p<0.001, n=24). A similar pattern was seen with CytOx. CONCLUSIONS: NIRS may provide a simple, non-invasive assessment of the severity of IC. Furthermore, because the ACR is a marker of endothelial damage, it is possible that NIRS changes also reflect endothelial integrity. These applications of NIRS technique should be assessed in a larger study.

Aged↗

Endocannabinoids control spasticity in a multiple sclerosis model.

Spasticity is a complicating sign in multiple sclerosis that also develops in a model of chronic relapsing experimental autoimmune encephalomyelitis (CREAE) in mice. In areas associated with nerve damage, increased levels of the endocannabinoids, anandamide (arachidonoylethanolamide, AEA) and 2-arachidonoyl glycerol (2-AG), and of the AEA congener, palmitoylethanolamide (PEA), were detected here, whereas comparable levels of these compounds were found in normal and non-spastic CREAE mice. While exogenously administered endocannabinoids and PEA ameliorate spasticity, selective inhibitors of endocannabinoid re-uptake and hydrolysis-probably through the enhancement of endogenous levels of AEA, and, possibly, 2-arachidonoyl glycerol-significantly ameliorated spasticity to an extent comparable with that observed previously with potent cannabinoid receptor agonists. These studies provide definitive evidence for the tonic control of spasticity by the endocannabinoid system and open new horizons to therapy of multiple sclerosis, and other neuromuscular diseases, based on agents modulating endocannabinoid levels and action, which exhibit little psychotropic activity.

Amides↗

A multivariate analysis of factors associated with depression: evaluating the role of health literacy as a potential contributor.

BACKGROUND: High rates of low health literacy among elderly populations along with a high prevalence of chronic conditions may lead to increased levels of depression symptomatology. We sought to determine whether older adults with inadequate health literacy were more likely to report depressive symptoms and whether health literacy was an independent predictor of depression symptomatology. METHODS: A total of 3260 new Medicare enrollees 65 years or older were interviewed in person between June and December 1997 from 4 managed care plans (853 in Cleveland, Ohio, 498 in Houston, Tex, 975 in South Florida, and 934 in Tampa, Fla). Depression symptoms were measured by the Geriatric Depression Scale. RESULTS: Overall, 13% of respondents were classified as depressed. Individuals with inadequate health literacy had 2.7 times the odds (95% confidence interval, 2.2-3.4) of being depressed compared with individuals with adequate health literacy skills. However, after controlling for health status with multiple logistic regression, individuals with inadequate health literacy were not more likely to be depressed (adjusted odds ratio, 1.2; 95% confidence interval, 0.9-1.7). Individuals who had less social support, exercised less than twice a week, drank alcohol heavily, or had poor health status (at least 3 health conditions, physical limitations, or fair or poor self-rated health) had significantly higher odds of depression symptomatology. CONCLUSIONS: Although individuals with inadequate health literacy were more than twice as likely to report depressive symptoms, this was mostly explained by their worse health status. The strong relation between depression symptoms and poor health status suggests the need to research interventions to improve mental and physical health concurrently. The influence of particular interventions on depression, such as referral to community support contacts and recommendations for an exercise program, needs to be further evaluated. Arch Intern Med. 2000;160:3307-3314.

Activities of Daily Living↗

Sensory neuron-specific sodium channel SNS is abnormally expressed in the brains of mice with experimental allergic encephalomyelitis and humans with multiple sclerosis.

Clinical abnormalities in multiple sclerosis (MS) have classically been considered to be caused by demyelination and/or axonal degeneration; the possibility of molecular changes in neurons, such as the deployment of abnormal repertoires of ion channels that would alter neuronal electrogenic properties, has not been considered. Sensory Neuron-Specific sodium channel SNS displays a depolarized voltage dependence, slower activation and inactivation kinetics, and more rapid recovery from inactivation than classical "fast" sodium channels. SNS is selectively expressed in spinal sensory and trigeminal ganglion neurons within the peripheral nervous system and is not expressed within the normal brain. Here we show that sodium channel SNS mRNA and protein, which are not present within the cerebellum of control mice, are expressed within cerebellar Purkinje cells in a mouse model of MS, chronic relapsing experimental allergic encephalomyelitis. We also demonstrate SNS mRNA and protein expression within Purkinje cells from tissue obtained postmortem from patients with MS, but not in control subjects with no neurological disease. These results demonstrate a change in sodium channel expression in neurons within the brain in an animal model of MS and in humans with MS and suggest that abnormal patterns of neuronal ion channel expression may contribute to clinical abnormalities such as ataxia in these disorders.

Animals↗

Topology, stability, sequence, and length: defining the determinants of two-state protein folding kinetics.

The fastest simple, single domain proteins fold a million times more rapidly than the slowest. Ultimately this broad kinetic spectrum is determined by the amino acid sequences that define these proteins, suggesting that the mechanisms that underlie folding may be almost as complex as the sequences that encode them. Here, however, we summarize recent experimental results which suggest that (1) despite a vast diversity of structures and functions, there are fundamental similarities in the folding mechanisms of single domain proteins and (2) rather than being highly sensitive to the finest details of sequence, their folding kinetics are determined primarily by the large-scale, redundant features of sequence that determine a protein's gross structural properties. That folding kinetics can be predicted using simple, empirical, structure-based rules suggests that the fundamental physics underlying folding may be quite straightforward and that a general and quantitative theory of protein folding rates and mechanisms (as opposed to unfolding rates and thus protein stability) may be near on the horizon.

Amino Acid Sequence↗

Native protein sequences are close to optimal for their structures.

How large is the volume of sequence space that is compatible with a given protein structure? Starting from random sequences, low free energy sequences were generated for 108 protein backbone structures by using a Monte Carlo optimization procedure and a free energy function based primarily on Lennard-Jones packing interactions and the Lazaridis-Karplus implicit solvation model. Remarkably, in the designed sequences 51% of the core residues and 27% of all residues were identical to the amino acids in the corresponding positions in the native sequences. The lowest free energy sequences obtained for ensembles of native-like backbone structures were also similar to the native sequence. Furthermore, both the individual residue frequencies and the covariances between pairs of positions observed in the very large SH3 domain family were recapitulated in core sequences designed for SH3 domain structures. Taken together, these results suggest that the volume of sequence space optimal for a protein structure is surprisingly restricted to a region around the native sequence.

Amino Acid Sequence↗