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At least 1,765 records · Page 98Linked to original sources
PubMed1976

Modeling of the human leg in ski injuries.

This study establishes that the human lower extremity-ski system has a fundamental frequency of approximately 1 Hz. The fundamental mode dominates the system response when loading times are short compared to the first natural frequency. Consequently, the use of a single degree of freedom approximation and the use of impulse criteria can provide important insights into the problem of skiing injuries. Specifically, the sport of snow skiing develops forces with frequency content in the static, transition, and impulse regions of the leg-ski response spectrum. Therefore, ski release bindings must be designed to safely and effectively couple the leg to the ski throughout this loading environment. An important means of evaluating possible binding designs is by simulating their characteristics in a computer model. The model will apply realistic loading histories to the ski or binding, will evaluate the strain in the bones and ligaments of the lower extremity, and will determine the release point of the binding. The program presented in this discussion is one stage in the development of this total system capability.

Ankle Joint↗
PubMed2003

The triumph and tragedy of James Baxler Bean, MD, DDS (1834-1870).

In 1863, James Baxter Bean, a Southern physician and dentist, invented the interdental splint. This device was used to treat hundreds of Confederate soldiers who had received gun shot-related facial and jaw injuries during the Civil War. Made of vulcanized India-rubber, the splint provided a dramatic breakthrough in the treatment of maxillofacial wounds. In an Atlanta, Georgia hospital, Dr. Bean utilized his invention by establishing the first ward devoted exclusively to the treatment of jaw fractures. He also invented an apparatus that manufactured and administered nitrous oxide. Additionally, Bean's groundwork in casting aluminum as a denture base material led to Taggart's later invention (in 1907) of the casting machine. After the Civil War, Dr. Bean became a highly successful dentist, practicing in Baltimore, Maryland. In the fall of 1870, at age 36, Bean, representing the Smithsonian Institution in Washington, D.C., traveled to Europe to gather geological specimens. A short time after arriving, Bean decided to climb Mont Blanc with ten other men. The entire group perished in a raging 8-day snow storm on the mountain peak. This tragedy, a compelling drama, is legendary in the annals of mountaineering history. After Dr. Bean's passing, his wife lost her sanity and subsequently died. Later, the death of the couple's only child, Chapin, sadly ended the family line. Although his life was cut short, Bean's contributions to dentistry have been significant and far-reaching.

Anesthesia, Dental↗
PubMed2003

Pubertal development in patients with McCune-Albright syndrome or pseudohypoparathyroidism.

Gain or loss of function mutations of the GNAS1 gene lead to McCune-Albright syndrome (MAS) or pseudohypoparathyroidism Ia (PHP-Ia), respectively. Patients with MAS, caused by a post-zygotic missense mutation leading to constitutive activation of Gs alpha, suffer from gonadotropin-independent precocious puberty, and delayed or incomplete sexual development and reproductive dysfunction is found in women with PHP-Ia, an inherited disorder caused by deficient expression or function of the Gs alpha protein. In females with MAS, 50% developed precocious puberty by the age of 4 years, the remaining between 4 and 8 years. Peripheral precocious puberty is often atypical and characterized by alternate periods of rapid progression and regression of pubertal development; menstrual bleeding may occur before breast development. Ovarian cyst growth and regression is often described as a sign of ovarian follicle hyperactivation. Notwithstanding this clinical heterogeneity, a subset of patients with MAS develop relentlessly progressive precocious puberty ultimately resulting in premature epiphyseal fusion and reduced adult stature. Long-term information on reproductive function has been obtained in females: some patients had regular menses without ovarian cysts on pelvic US scan, whereas others were oligomenorrheic and showed recurrent ovarian cysts. In males with MAS, precocious puberty occurred in three patients between 4 and 9 years of age. In one patient, long-term follow-up demonstrated normal plasma testosterone and gonadotropin values at the age of 17 years. On testicular sonography, multiple hyperechogeneic spots were found in both testicles (snow-storm appearance). Female patients with PHP-Ia were oligomenorrheic or amenorrheic; more than half had delayed or incomplete sexual development, They were mildly hypoestrogenic with normal to slightly elevated serum gonadotropin levels. These clinical and biochemical findings indicate partial resistance of the theca and granulosa cells of the ovary to gonadotropins due to deficient Gs alpha activity. Responsiveness might be sufficient to promote some degree of follicular development and steroid secretion, but insufficient to induce ovulation

Amenorrhea↗
PubMed1992

Accidents in the Arctic. A psychological point of view.

The aim of this paper is to discuss the influence of arctic conditions on the occurrence of accidents especially from the point of view of the interaction between environment, activity and man. Special attention is paid to risk assessment, risk taking and risk compensation. According to the danger factor theory frostbites should be extremely common in arctic regions, but in reality serious frostbites appear rarely in accident statistics. This finding supports the interactive accident theories. Instead cold can be a contributing factor in accident and injury causation and the effect of cold is most often indirect. Frostbites can occur e.g. as a result of an accident, losing one's way because of darkness, snow storm etc., wet clothes, unexpected temperature changes, disease attack, alcohol-induced reasons such as immobility or excess risk taking etc. Temperatures below and above +20 degrees C increase unsafe behavior. In the Arctic it is impossible to remove all the potentially dangerous factors, because many typical features of working and living conditions are regulated by natural forces, the seasons etc. This makes accurate risk assessment and prediction especially important in accident prevention. If the person does not recognize the situations in which the risk factors exist, he/she cannot implement precautionary steps at the right moment and hence cannot avoid risks. Moreover, if better and safer machines, equipment and tools get people to take greater risks, the accident situation can even become worse.

Accident Prevention↗
PubMed1992

Relative activity of structural analogues of amsacrine against human leukemia cell lines containing amsacrine-sensitive or -resistant forms of topoisomerase II: use of computer simulations in new drug development.

Anilino analogues of amsacrine showed increased activity against amsacrine (AMSA)-resistant cell lines when compared with the parent compound, but the mechanisms of amsacrine resistance in these lines were unknown (Finlay, G. J., Baguley, B. C., Snow, K., and Judd, W., J. Natl. Cancer Inst., 82: 662-667, 1990). We tested the cytotoxic and DNA-cleaving activities of two amsacrine analogues which were derivatives of 9-anilinoacridine (1'-methylcarbamate and 1'-benzenesulfonamide) against an amsacrine-resistant human leukemia cell line (HL-60/AMSA) whose resistance is due to an amsacrine-resistant topoisomerase II. Neither agent could overcome the amsacrine resistance of HL-60/AMSA. Neither agent could induce HL-60/AMSA topoisomerase II-mediated cleavage of DNA in an isolated biochemical system, although at high concentrations the two analogues could inhibit HL-60/AMSA topoisomerase II-mediated DNA strand passage. Both analogues were at least as active, if not more active, than amsacrine against amsacrine-sensitive HL-60 and its topoisomerase II. Comparison of the cellular and biochemical results with those from computer simulation of the energy-minimized structures of amsacrine, its inactive isomer o-AMSA, and the two new active analogues suggests the following possibilities: (a) the positioning of the potential topoisomerase II-binding site (1'-anilino group) of the two new drugs resembles the positioning of this site in amsacrine; (b) the HL-60 topoisomerase II has a binding site which interacts with amsacrine and the two anilino analogues but not with o-AMSA, an analogue with altered positioning of the methoxy group; (c) the HL-60/AMSA topoisomerase II interacts with reduced affinity with amsacrine and the two anilino analogues, although HL-60/AMSA topoisomerase II still interacts with the structurally distinct topoisomerase II-reactive nonintercalator, etoposide; (d) because of their higher DNA binding affinity or the greater possible positions of their side groups in comparison to amsacrine, the two analogues can, at high concentrations, inhibit the strand-passing activity of HL-60/AMSA topoisomerase II.

Amsacrine↗
PubMed1992

Mechanical constraints on Nordic ski performance.

Skiers, coaches, and sports scientists must work within mechanical constraints to improve performance. If Nordic skiing is to be improved by mechanical means, it will be achieved by affecting one or more of the major constraints: gravity, mass, friction, aerodynamic or hydrodynamic lift and drag, and centripetal force. For example, the skier who assumes a tucked position, drafts a competitor, and wears a drag-reducing hood and body suit is reducing aerodynamic constraints. Sliding friction may also be reduced by using specially prepared skis and by selecting skis appropriate for the snow characteristics of the race course. Skin friction hydrodynamic drag may also be affected by ski selection and by special base preparations. Gravity and mass constraints are diminished by using lightweight components, by carrying them in the least costly way, and by minimizing swing weight. The toppling effect of centripetal forces is addressed by leaning into turns. All of these examples address mechanical constraints in a way that reduces physical power requirements, and thus decrease the metabolic power required to ski at a given speed, as well as increasing the maximal speed attainable.

Biomechanical Phenomena↗
PubMed1977

Proton inactivation of Ca2+ transport by sarcoplasmic reticulum.

The effects of acid on fragmented sarcoplasmic reticulum from rabbit white skeletal muscle have been studied. Brief exposure of sarcoplasmic reticulum membranes to pH values in the range 5.5 to 6.0 at 37 degrees caused rapid inactivation of calcium accumulation measured at 25 degrees in the presence of oxalate (calcium uptake) while (Ca2+, Mg2+)-ATPase (EC 3.6.1.3) activity was enhanced by 75%. ATPase activity, measured at 37 degrees in the absence of oxalate and in the calcium steady state, was unaltered when calcium uptake was inactivated. Calcium efflux from sarcoplasmic reticulum vesicles, previously loaded passibely with 45CaCl2, was only slightly increased when calcium uptake was abolished. At still lower pH values, 5.0 to 5.5, (Ca2+, Mg2+)-ATPase was inactivated while Mg2+ ATPase was more acid-resistant. Acid inactivation of calcium uptake followed simple first order kinetics for at least 80% of the time course. The rate constant, k, increased from 0.043 min-1 to 1.63 min-1 between pH 6.50 and pH 5.35. At pH 4.65, Ea, the energy of activation, was 31 kcal mol-1 between 24 degrees and 43 degrees. Inactivation, once initiated, was irreversible. Aged suspensions of sarcoplasmic reticulum were more sensitive to acid inactivation. Ethylene glycol bis(beta-aminoethyl ether)N,N'-tetraacetic acid enhanced inactivation, and calcium specifically protected against inactivation with half-maximal effect at 1 to 2 mM. The sulfhydryl reagent, dithiothreitol (1 mM), caused significantly increased rates of inactivation. Calcium binding was studied by dual wavelength spectrophotometry and stopped flow analysis. Acid inactivation distinguished two ATP-induced binding sites, previously described (Entman, M. L., Snow, T. R., Freed, D., and Schwartz, A. (1973) J. Biol. Chem. 248, 7762-7772) as a superficial Mg2+-independent Site A which binds and releases calcium rapidly and a deeper Mg2+-dependent Site B which binds and releases calcium more slowly. Rates of binding to both sites were decreased by acid inactivation. Binding of calcium to Site A increased, however, from 4.6 to 6.4 nmol mg of protein-1 whereas that to Site B decreased from 17.0 to 6.9 nmol mg of protein-1. Passive binding of calcium to sites of medium affinity (K = 7 X 10(4) M-1) was unaffected by acid inactivation of calcium uptake. Temperature dependence of (Ca2+, Mg2+)-ATPase was unchanged in the range 9-34 degrees. Above 34 degrees, the higher activation energy process (Ealpha = 33.7 kcal mol-1) observed in control sarcoplasmic reticulum and thought to arise from a conformational change in the ATPase (Inesi, G., Millman, M., and Eletr, S. (1973) J. Mol. Biol. 81, 483-504) was diminished by acid inactivation (Ealpha = 8.2 kcal mol-1) in a manner suggesting that it is related to active calcium transport. The ATP in equilibrium 32Pi exchange reaction was diminished by acid, but 25% of the activity remained when calcium uptake was completely abolished...

Adenosine Triphosphatases↗
PubMed1992

Injuries to the nervous system and spine in downhill skiing.

The authors describe injuries to the nervous system and spine from downhill skiing accidents through a review of the charts of downhill skiers admitted over 5 years to the three teaching hospitals of the University of Calgary. The office of the chief medical examiner provided details about accidental deaths from downhill skiing in which nervous system trauma occurred. During the study period, 145 downhill skiers suffered injury to the nervous system or spine. There were five deaths from nervous system trauma. The mean age of the injured skiers was 23.8 years, and these injuries were three times more common in men than in women. Eighty-eight skiers sustained a head injury, 25 had spinal fractures alone, 20 had spinal cord or nerve root injury and 12 had peripheral nerve injury. A simple fall on the hill was the commonest method of injury, followed in frequency by collision with a tree, which caused the most severe injuries. Reckless skiing, design of ski runs and man-made snow were contributing factors. The serious nature and number of these injuries must be recognized, and further study is needed on causal factors and preventive measures.

Adolescent↗
PubMedDate not supplied

[Mechanism of induction of cytogenetic damage in plant meristematic cells caused by combined effect of heavy natural radionuclides and heavy and alkaline metals].

The analysis of experimental data on the combined effect of 232Th and water from melted snow containing metal ions from industrally loaded territories on Tradescantia (clone 02) and on Allium shoenoprasum meristematic root tip cells treated with heavy natural radionuclides from natural water sources in the area of radioactive wastes storehouse is presented. It was demonstrated that plant meristematic cells response to heavy metals and heavy natural radionuclides, both from two-component model system and from natural water sources, have commom features.

Allium↗
PubMedDate not supplied

[Historical Archives of Italian Nephrology. Goldblatt, kidney and hypertension: three steps in the history of nephrology].

The existence of a clear relationship between renal ischemia and hypertension has been widely documented by Harry Goldblatt and his colleagues. In their original papers they showed that gross and persistent elevation of systolic blood pressure could be produced in dogs by clamping both renal artery, or one if the other kidney had been removed. If renal arteries constriction was not too severe, a stable hypertension unaccompanied by more than mild renal impairment was produced. Subsequently, Goldblatt showed that, with severe constriction, retinal changes, arteriolar impairment and left ventricular hypertension could occur. Goldblatt has remained steadily of the opinion that essential hypertension in man is similarly due to renal ischemia occasioned either by stenosis of a main artery, or by organic changes in the smaller renal arteries down to the size of the different glomerular arteries. At first sight, it might seem like a simple matter to correctly identify the chain of events that begins with renal artery constriction and ends with persistent hypertension. Observing that a link was missing in this chain of events, Goldblatt hypothesised that the link was a humoral mechanism. Tigersted and Bergman showed that renin was the missing link. Renal ischemia as cause of hypertension in dogs opened a new chapter in the connection between kidney circulation and blood pressure elevation. This quite unexpected connection is one of the most challenging issues today and clearly demonstrates that the development of Goldblatt's ideas on renal circulation is still important and has by no means ended. Goldblatt, in his epistemologic approach to hypertension scientific challenges, realised that ideas are the building blocks of science: not flights of fancy, not notions sculpted in snow, but enduring concepts. Goldblatt's lasting ideas are more than a function of time and place: they have inherent qualities that have survived up to the present day.

History, 20th Century↗
PubMed2003

The river Ganga of northern India: an appraisal of its geomorphic and ecological changes.

The Ganga is the most important perennial river originating from Gangotri in the snow-bound Himalayas about 3,900 m above mean sea level. Gorging a distance of about 220 km in the Himalayas, it enters the plain at Hardwar and after meandering and braiding over a distance of about 2,525 km through the Indo-Gangetic plains, ultimately joins the Bay of Bengal. The course of this river has been changed due to: (i) subsurface geotectonic movement leading to change in slope of the deltaic plain and subsidence of the Bengal basin; (ii) changing pattern of water discharge with time; (iii) variations in sediment load. The environment of Ganga basin is also deteriorating with time due to severe natural episodes of periodic floods and storms as well as anthropogenic factors such as population growth, deforestation, agricultural activities, urbanisation, fertiliser and fossil fuel consumption and construction activities such as dams and bridges. All these have inconceivable adverse impacts on the health and natural regeneration capacity of the river basin. The presence of micropollutants in water and sediments of this river turns the system into being unsustainable to the biota. The present study synthesises the available information on the changes of its geological, geomorphological and ecological aspects and suggests some remedial measures to be adopted now and in future.

Agriculture↗
PubMedDate not supplied

[Seasonal dynamics in a yeast population on the Oxalis acetosella L. leaves].

Analysis of an epiphytic yeast population on the leaves of the evergreen common wood sorrel Oxalis acetosella L. throughout a year showed that the density and the species composition of this population underwent regular seasonal changes. There were almost no yeasts on the young spring leaves. However, the yeast population on the mature leaves tended to increase in the autumn, reaching a maximum after the formation of continuous snow cover. Then the yeast population on the leaves tended to decrease, reaching a minimum in the spring. The species diversity of the yeasts was maximum in the autumn. The population of the epiphytic yeast species Cystofilobasidium capitatum, Rhodotorula fujisanensis, Leucosporium scottii, and Cryptococcus flavus peaked in the autumn. On the other hand, the population of the widespread epiphytic species Cryptococcus laurentii on the wood sorrel leaves peaked in January. The relative abundance of the red-pigmented phytobionts Rhodotorula glutinis and Sporobolomyces roseus virtually did not change throughout the year. The relative abundance of the euribiotic species Cryptococcus albidus showed irregular monthly variations. The data obtained show that the epiphytic microbial population of various plants can be comprehensively studied only by analyzing this population throughout the vegetative period of the plants.

Colony Count, Microbial↗
PubMed2004

Model simulations of the Arctic atmospheric boundary-layer from the SHEBA year.

We present Arctic atmospheric boundary-layer modeling with a regional model COAMPS, for the Surface Heat Budget of the Arctic Ocean (SHEBA) experiment. Model results are compared to soundings, near-surface measurements and forecasts from the ECMWF model. The near-surface temperature is often too high in winter, except in shorter periods when the boundary layer was cloud-capped and well-mixed due to cloud-top cooling. Temperatures are slightly too high also during the summer melt season. Effects are too high boundary-layer moisture and formation of too dense stratocumulus, generating a too deep well-mixed boundary layer with a cold bias at the simulated boundary-layer top. Errors in temperature and therefore moisture are responsible for large errors in heat flux, in particular in solar radiation, by forming these clouds. We conclude that the main problems lie in the surface energy balance and the treatment of the heat conduction through the ice and snow and in how low-level clouds are treated.

Arctic Regions↗
PubMed2004

Suspension of rotavirus vaccine after reports of intussusception--United States, 1999.

On July 16, 1999, CDC recommended that health-care providers suspend use of the licensed rhesus-human rotavirus reassortant-tetravalent vaccine (RRV-TV) (RotaShield, Wyeth Laboratories, Inc., Marietta, Pennsylvania) in response to 15 cases of intussusception (i.e., a bowel obstruction in which one segment of bowel becomes enfolded within another segment) among infants who received RRV-TV. The Vaccine Adverse Event Reporting System (VAERS) monitored for adverse events following licensure of RRV-TV on August 31, 1999. After the recommendation to suspend use of the vaccine, no additional cases were reported. This report describes the surveillance activities used to identify this vaccine adverse event, the emergency response, and follow-up investigations. Suspension of RRV-TV after the initial cases of intussusception parallels the removal of the Broad Street pump handle in response to John Snow's epidemiologic studies; both were decisive, life-saving public health actions.

Adverse Drug Reaction Reporting Systems↗
PubMed2004

An outbreak of norovirus gastroenteritis at a swimming club--Vermont, 2004.

John Snow's historic investigation of a severe epidemic of cholera traced the cause of infection to a common water source. Today, 150 years later, waterborne diseases remain a public health problem, and similar investigations are used to identify the source of infection. On February 3, 2004, the Vermont Department of Health (VDH) was notified of an outbreak of acute gastroenteritis among children whose only common exposure was attendance at a swimming club the previous weekend (January 31-February 1). This report summarizes the results of an investigation conducted by VDH and CDC, which determined the cause of the outbreak to be a combination of stool contamination, a blocked chlorine feed tube, and multiple lapses of pool-maintenance procedures. The findings underscore the importance of correct pool maintenance for rapid identification of water-quality problems to prevent outbreaks of swimming pool-associated illness.

Adolescent↗
PubMed1992

Treatment of unstable tibial shaft fractures by closed intramedullary nailing with flexible (Ender-type) pins.

Eighty patients with unstable tibial diaphyseal fractures were treated by closed intramedullary nailing with Ender-type flexible pins. The majority of injuries occurred from falling while snow skiing. Sixty-six fractures were closed and 14 were open. Fifty-eight fractures involved the distal, 21 fractures the middle, and one fracture the proximal one third of the tibial shaft. The average time to roentgenographic union was 15.5 weeks (range, ten to 34 weeks) for closed and open Grade I and II fractures. The time to union in Grade III fractures was 50 weeks (range, 36-64 weeks). There were two nonunions and two delayed unions. Both nonunions occurred in Grade IIIA open shaft fractures. Intramedullary stabilization with flexible, Ender-type pins provides good control of unstable tibial shaft fractures. The use of pins with a smaller diameter (3.5 or 4 mm) allows the surgeon to place more pins across the fracture site. The use of multiple pins and packing the intramedullary canal may provide better rotational stability. The use of Ender-type pins for fixation of Type IIIA open tibial shaft fractures is contraindicated.

Adolescent↗
PubMed2004

Impact of resistance to antiretroviral therapy in the minority community.

The development of resistance to antiretroviral therapies has become a formidable barrier to providing optimal treatment of HIV infection in the United States. The emergence of new mutations resistant to antiretroviral agents and a rise in transmission of resistant viruses contribute to an increased risk of treatment failure. Resistance testing of both treatment-experienced and treatment-naive patients i snow recommended for identification of the most effective treatment regimen; however, resistance testing is not universally available or easily interpreted. Furthermore, poor adherence to a treatment regimen or treatment with less potent antiretroviral agents can lead to exposure of virus to subinhibitory levels of drug and the development of resistance. In this article, we discuss several issues that specifically impact the development and transmission of resistant HIV in patients belonging to ethnic minorities and teh implementation of strategies that will overcome resistance as an obstacle to optimal treatment.

Anti-HIV Agents↗
PubMed2004

Effect of environment on extremely severe road traffic crashes: retrospective epidemic analysis during 2000-2001.

OBJECTIVE: To make an epidemiological analysis of the effect of environment on extremely severe road traffic crashes (RTCs). METHODS: Epidemiologic data of extremely severe RTCs associated with environmental factors, including weather, topography, road conditions and other traffic conditions in Mainland China during 2000-2001, were collected and analyzed. RESULTS: (1) During 2000-2001, there were 3365 extremely severe RTCs with 13666 deaths, 12204 injuries and a direct economical loss of 136 million RMB. (2) Most extremely severe RTCs occurred in fine weather days and in the daytime. The high occurrence sites were plain areas, horizontal and straight roads, Grade B and C roads, ordinary road segment, and asphalt, smooth and mixed roads. (3) Compared with other RTCs, extremely severe RTCs were more likely to happen under following conditions: on cloudy, snowing, misty and blustering days; in hill and mountainous areas; on crooked and sloping roads; on freeway, Grade A, B, and C roads; mixed roads; ordinary, bridge, narrow and transitional roads; sand and dirt-roads; without traffic control measures; night without lighting. (4) Extremely severe RTCs of mountainous area or crooked and sloping roads were most severe in terms of deaths and injures per crash. CONCLUSIONS: Extremely severe RTCs are closely related with environmental factors. Rational road programming, enhancing road establishment and improving road conditions are probably effective measures to reduce the road traffic injuries.

Accidents, Traffic↗