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At least 1,639 records · Page 91Linked to original sources

PubMed2003

Travel epidemiology: the Saudi perspective.

The Kingdom of Saudi Arabia occupies four-fifths of the Arabian Peninsula, with a land area of 2 million square kilometres. Saudi Arabia holds a unique position in the Islamic world, as the custodian of the two holiest places of Islam, in Mecca and Medina. Annually, some 2 million Muslims from over 140 countries embark on Hajj. This extraordinary en masse migration is a unique forum for the study of travel epidemiology since the Hajj carries various health risks, both communicable and non-communicable, often on a colossal scale. Non-communicable hazards of the Hajj include stampede and motor vehicle trauma, fire-related burn injuries and accidental hand injury during animal slaughter. Communicable hazards in the form of outbreaks of multiple infectious diseases have been reported repeatedly, during and following the Hajj. Meningococcal meningitis, gastroenteritis, hepatitis A, B and C, and various zoonotic diseases comprise some of the possible infectious hazards at the Hajj. Many of these infectious and non-infectious hazards can be avoided or averted by adopting appropriate prophylactic measures. Physicians and health personnel must be aware of these risks to appropriately educate, immunize and prepare these travellers facing the unique epidemiological challenges of Hajj in an effort to minimize untoward effects. Travel epidemiology related to the Hajj is a new and exciting area, which offers valuable insights to the travel specialist. The sheer scale of numbers affords a rare view of migration medicine in action. As data is continually gathered and both national and international policy making is tailored to vital insights gained through travel epidemiology, the Hajj will be continually safeguarded. Practitioners will gain from findings of travel related epidemiological changes in evolution at the Hajj: the impact of vaccinating policies, infection control policies and public health are afforded a real-world laboratory setting at each annual Hajj, allowing us to learn from this unique phenomenon of migration medicine.

Animals↗

PubMed1998

Recent advances in producing and selecting functional proteins by using cell-free translation.

Prokaryotic and eukaryotic in vitro translation systems have recently become the focus of increasing interest for tackling fundamental problems in biochemistry. Cell-free systems can now be used to study the in vitro assembly of membrane proteins and viral particles, rapidly produce and analyze protein mutants, and enlarge the genetic code by incorporating unnatural amino acids. Using in vitro translation systems, display techniques of great potential have been developed for protein selection and evolution. Furthermore, progress has been made to efficiently produce proteins in batch or continuous cell-free translation systems and to elucidate the molecular causes of low yield and find possible solutions for this problem.

Animals↗

PubMed2001

The familiar and the unexpected in structures of icosahedral viruses.

Viruses were the first large macromolecular assemblages to be visualized at high resolution. New virus structures continue to challenge our understanding of specificity in protein-protein "recognition". The evolution of virus structures has been even more opportunistic than previously imagined.

Biological Evolution↗

PubMed2003

[Meningioma: a model of cytogenetic evolution in tumoral initiation and progresion].

Meningiomas are tumors of the central nervous system with a great morphological heterogeneity. They are generally benign, and have the capacity to progress to a higher histological grade (atypical and anaplastic), which is associated with an increase in biological aggressivity and/or capacity to recur. Citogenetically this evolution is characterized by total or partial monosomy 22 in the early phase, continued by numerical and structural changes during tumor progression. In this study, we present a review of 85 cases of meningiomas: 43 benign, 28 atypical and 14 anaplastic. We study the clinical and histopathological features, and their correlation with cytogenetie abnormalities present in these tumors. Numerical aberrations such as monosomy of chromosome 10, 14 and 18, and structural abnormalities such as deletions on 1p are directly associated with a higher agressivity of tumors. An association of aberatons on 1p and chromosome 14 are more commonly found in atypical and anaplastic meningiomas. These facts imply that the presence of complex karyotypes progressively increases from grade I to grade III meningiomas. Furthermore, these karyotypes are common in recurrent tumors.

Adult↗

PubMed2001

Industrial biocatalysis.

The number of industrial processes for the synthesis of fine and commodity chemicals, pharmaceutical and agrochemical intermediates and drug substances utilizing biological catalysts continues to grow. The combination of new molecular biology techniques, such as directed evolution and pathway engineering, with new and efficient high-throughput screening methods is poised to bolster this field and further advance the contribution of biocatalysis to the chemical and the pharmaceutical industries.

Catalysis↗

PubMed1982

Attenuation of brain free fatty acid liberation during global ischemia: a model for screening potential therapies for efficacy?

Whole brain free fatty acids (FFA) continue to rise appreciably even 1 h after decapitation, which may reflect the evolution of ischemic brain injury at least during global ischemia. If so, the attenuation of FFA liberation by various drugs may reflect their efficacy in ischemic brain injury. Rats were pretreated with either 0.9% NaCl (controls), ketamine, halothane, lofentanil, etomidate, Y-9179, R41-468, Innovar-Vet, pentobarbital, thiopental, or phenytoin and decapitated 15 to 30 min thereafter. The brains were kept normothermic for 10 min until they were frozen in liquid nitrogen. Whole brain FFAs were quantitated gy gas-liquid chromatography. After 10 min of ischemia in controls, total FFAs and arachidonic, stearic, oleic, and palmitic acids increased by 8- to 10-fold. The drugs, in order of decreasing effectiveness in attenuating FFA liberation, fell into the following three groups: (1) phenytoin, thiopental, pentobarbital, and Innovar-Vet; (2) R41-468, Y-9179, and etomidate; and (3) lofentanil, halothane and ketamine. The three groups reduced total FFAs by about 23%, 13%, and 8%, respectively. The effectiveness of drugs in attenuating FFA liberation appears to correlate with their efficacy in ischemic brain injury. However, a cause and effect relationship between FAA liberation and the evolution of ischemic brain injury must be established before accurate predictions of efficacy can be made by this method. The limitations of the proposed method of evaluation are discussed.

Anesthetics↗

PubMed1996

Evolution of a specific fluorogenic derivatization of ivermectin for bioanalytical applications. A review.

The evolution of the fluorogenic derivatization of ivermectin is traced through a series of continual modifications that have resulted in improvements in speed and sensitivity. Since the original development of this selective analytical technique, the reaction time has been shortened from 24 h at 100 degrees C to < 30 s at room temperature and, through modifications of the derivatization reagent and catalyst, the sensitivity has also been increased 50-fold to 20 pg of analyte with no significant decrease in precision. A procedure is reported, based on the use of fluorescence derivatization, which eliminates the use of solid-phase columns for sample preparation and fluorophore isolation, and is faster and less cumbersome than previous methods. The method was evaluated with cattle and canine plasma samples over the concentration range 1.0-40 ng ml-1 of ivermectin. It has an accuracy of 1.9% (mean relative error) over this concentration range and a precision of 5.6% (RSD) at the 1 ng ml-1 ivermectin concentration level in a 1 ml plasma sample.

Animals↗

PubMed2001

Infancy is not a quiescent period of testicular development.

Postnatal evolution of the testis in most laboratory animals is characterized by the close continuity between neonatal activation and pubertal development. In higher primates, infancy, a long period of variable duration, separates birth from the beginning of puberty. This period has been classically considered as a quiescent phase of testicular development, but is actually characterized by intense, yet inapparent activity. Testicular volume increases vigorously shortly after birth and in early infancy due to the growth in length of seminiferous cords. This longitudinal growth results from active proliferation of infantile Sertoli cells which otherwise display a unique array of functional capabilities (oestrogen and anti-müllerian hormone secretion, increase of FSH receptors and maximal response to FSH). Leydig cells also show recrudescence after birth, possibly determined by an active gonadotrophic-testicular axis which results in increased testosterone secretion of uncertain functional role. This postnatal activation slowly subsides during late infancy when periodic phases of activation of the hypothalamo-pituitary-testicular axis are paralleled by incomplete spermatogenic spurts. The beginning of puberty is marked by the simultaneous reawakening of Leydig cell function and succeeding phases of germ cell differentiation/degeneration which ultimately lead to final spermatogenic maturation. The marked testicular growth in this stage is due to progressive increase at seminiferous tubule diameter. Sertoli cells, which have reached mitotic arrest, develop and differentiate, establishing the seminiferous tubule barrier, fluid secretion and lumen formation, and acquiring cyclic morphological and metabolic variations characteristic of the mature stage. All of these modifications indicate that, far from being quiescent, the testis in primates experiences numerous changes during infancy, and that the potential for pubertal development and normal adult fertility depends on the successful completion of these changes.

Animals↗

PubMed1995

Diffusion weighted imaging for acute cerebral infarction.

The diagnosis of acute cerebral ischemia remains difficult. Computed tomography and magnetic resonance tomography are not specific at early time points. Diffusion imaging a new technique for magnetic resonance imaging was introduced in experimental studies and shown to have much earlier sensitivity for acute ischemic infarction. Diffusion imaging demonstrated early hyperintensities within minutes after ischemic onset and correlated well with post-mortem studies of the final infarct size. On the basis of molecular motion of water, hyperintensities during ischemia on diffusion imaging are most likely related to the development of ischemia induced cytotoxic edema and to slower diffusional motion. Experimental treatment and reperfusion studies with diffusion imaging demonstrated lesion reversal in vivo. Continuous monitoring after induction of ischemia enables an in vivo demonstration of the evolution of the ischemic lesion. Quantitative analysis of the apparent diffusion coefficient may enable the differentiation of infarcted tissue in the core of the lesion from reversibly damaged tissue. Preliminary clinical studies demonstrated a superior sensitivity of diffusion imaging compared with T2-weighted imaging. Clinicians may be able in the near future to image early stroke and to assess therapy when the stroke is still evolving.

Acute Disease↗

PubMed1984

The master equation for neural interaction.

Based on neural interaction equations a random walk model for the stochastic dynamics of a single neuron is introduced. In this model the somatic potential corresponds to a state in the state space and action potentials provide the mechanism causing transitions. Time is made discrete, consisting of small finite increments delta t; assumptions are made about the transitions within such an increment and the associated probabilities are formulated. These quantities depend on delta t and on parameters derived from neural interaction equations. Moreover the model is chosen so that the sequence of somatic potentials is a Markov chain. By appropriately scaling the parameters, in the limit as delta t----0, a master equation for the probability in continuous time is obtained. Depending on the parameters, the master equation describes the evolution of a deterministic, a diffusion, or a discrete process. An interpretation for the diffusion and discrete processes is outlined. The conclusion is that the stochastic equations for neural interaction lead to a master equation representing a diffusion or a discrete process depending on the number, size of synaptic connectivity coefficients, and probability distribution of neural activity. An example is included describing how a master equation may be used to derive properties of the single neuron's output process.

Animals↗

PubMed2000

Photorefractive keratectomy.

In this chapter, we have reviewed important aspects of PRK. A thorough understanding of the preoperative assessments, techniques, and postoperative management is essential to achieve satisfactory visual outcomes. Laser safety checks are mandatory. A well-functioning excimer laser with good optics is required. The surgeon must avoid any decentration or global tilt. All aspects of the technique must be performed with attention to detail. The postoperative management requires frequent follow-up visits and psychological reinforcement of a healing process that is not instantaneous. PRK is a procedure in evolution. Although the results today are impressive, the complications in the future will continue to decrease with changes in lasers, techniques, and pharmacological management.

Humans↗

PubMed1991

Selective photothermolysis and removal of cutaneous vasculopathies and tattoos by pulsed laser.

The evolution of the laser as a medical device has been a process of continued improvement. Research into increasing our understanding of the optical characteristics of skin has made it possible to concentrate not on the effects of any particular laser system, but on basic biologic and physical principles of laser-tissue interaction. The lasers available in the 1960s and 1970s offered few possibilities for modification. However, modern technology allows us to manipulate the physical characteristics of lasers and design them for specific therapeutic purposes. Selective photothermolysis relies on chromophore-specific absorption of a brief pulse of light to generate and confine heat to certain targets within the skin without nonspecific thermal damage to adjacent structures. Thermally mediated target alterations can be confined from the level of large multicellular tissue structures (e.g., blood vessels) to individual microscopic pigmented structures (e.g., tattoo pigment granules). The purpose of this report is to describe the current progress being made and to summarize the present theories for achieving increasing selective removal, without scarring or other skin textural changes, of cutaneous vasculopathies and tattoo pigment by pulsed laser.

Adult↗

PubMed2004

Influence of the ions on the dynamical response of a nematic cell submitted to a dc voltage.

The influence of the ions present in a liquid crystal on the dynamical response of a nematic slab submitted to a dc voltage is studied. The evolution of the system toward the equilibrium state is investigated by solving the continuity equation for the electric charge, taking into account the current of drift and of diffusion. Our analysis shows that the formation of the double layers close to the electrodes strongly modifies the distribution of the electric field across the sample. We evaluate the surface polarization due to the ions movements and the contribution to the anisotropic part of the surface energy having a dielectric origin. We show also that, even if the optical response of the liquid crystal is a slow phenomenon, the distribution of the ionic charge is rather fast. Consequently, the presence of the ions cannot be neglected in the determination of the flexoelectric coefficients when the nematic sample is submitted to a square wave having a period of the order of 1 s.

Journal Article↗

PubMed2005

Temporal behavior of radiation-pressure-induced vibrations of an optical microcavity phonon mode.

We analyze experimentally and theoretically mechanical oscillation within an optical cavity stimulated by the pressure of circulating optical radiation. The resulting radio frequency cavity vibrations (phonon mode) cause modulation of the incident, continuous-wave (cw) input pump beam. Furthermore, with increasing cw pump power, an evolution from sinusoidal modulation to random oscillations is observed in the pump power coupled from the resonator. The temporal evolution with pump power is studied, and agreement was found with theory. In addition to applications in quantum optomechanics, the present work suggests that radiation-pressure-induced effects can establish a practical limit for the miniaturization of optical silica microcavities.

Journal Article↗

PubMed2005

Information transfer between dynamical system components.

We present a rigorous formalism of information transfer for systems with dynamics fully known. This follows from an accurate classification of the mechanisms for the entropy change of one component into a self-evolution plus a transfer from the other component. The formalism applies to both continuous flows and discrete maps. The resulting transfer measure possesses a property of asymmetry and is qualitatively consistent with the classical measures. It is further validated with the baker transformation and the Hénon map.

Journal Article↗

PubMed1972

Photorespiratory phenomena in maize: oxygen uptake, isotope discrimination, and carbon dioxide efflux.

Concurrent O(2) evolution, O(2) uptake, and CO(2) uptake by illuminated maize (Zea mays) leaves were measured using (13)CO(2) and (18)O(2). Considerable O(2) uptake occurred during active photosynthesis. At CO(2) compensation, O(2) uptake increased. Associated with this increase was a decrease in O(2) release such that a stoichiometric exchange of O(2) occurred. The rate of O(2) exchange at CO(2) compensation was directly related to O(2) concentration in the atmosphere at least up to 8% (v/v).When illuminated maize leaves were exposed to saturating CO(2) concentrations containing approximately equal amounts of (12)CO(2) and (13)CO(2), the latter was taken up more rapidly, thus depressing the atom% (13)C in the atmosphere. Moreover, upon exposure to CO(2) containing 96 atom% (13)C, there occurred a directly measurable efflux of (12)CO(2) from the leaves for at least 15 minutes. During this period an equimolar evolution of (16)O(2) and uptake of (13)CO(2) was observed. Thereafter, although the rate of (16)O(2) evolution remained unchanged, the rate of (13)CO(2) uptake declined markedly, suggesting continual (13)C enrichment of the photorespiratory substrate.It is concluded that a finite photorespiratory process occurs in maize and that the CO(2) generated thereby is efficiently recycled. Recycling maintains the internal CO(2) concentration at a level difficult to detect by most photorespiratory assays.

Journal Article↗

PubMed1980

The long-term culture of a diploid rat hepatocyte cell strain.

We have developed a cell culture system of cloned rat hepatocytes which is named RL-PR-C. This culture has been grown in culture for over 150 passages (560 p.d.). It remains diploid by modal number count for over 50 passages (183 p.d.) after which there is a variation in the modal number between 41 and 42. The culture becomes intrinsically (spontaneously) malignantly transformed at about this time whereas cells treated with aflatoxin B1, at subacute and subtoxic doses, from Passage 12(65 p.d.) were malignantly transformed at Passage 35(135 p.d.). Evidence indicates that not all cells in the population are malignantly transformed. Back injection of mixed population of malignantly transformed cells into isogenic rat pups, yield tumors which are histologically classified as mixed. That is, areas of the same tissue slice exhibit both carcinomas and sarcoma characteristics. Data obtained by injection of clones derived from malignantly transformed cells suggest that the cells injected are multipotent with respect to the type of tumor formed. Further investigations are continuing in this regard. This cultural system will be used to study the evolution and maintenance of the transformed state and to develop a test system for putative carcinogens and mutagens.

Aflatoxin B1↗

PubMed2004

The evolution of health education: the Kaiser Permanente Southern California experience.

This article conveys the history of establishing the health education program, the current delivery model, and the lessons learned from the process including practical applications for the practice setting. The evolution of health education in Kaiser Permanente reflects its history and describes the continued need for and relevance of health education. The era of the patient as the passive recipient of care is being replaced by an emphasis on the patient as a partner in care. Every health education program emphasizes shared responsibility and encourages active participation by the patient, family, and other social supports. Multiple modalities of self-care and/or self-management resources and services increase member access to needed health education, health promotion, and prevention information that facilitate lifestyle behavior changes for better health and simultaneously improve organizational clinical outcome measures. Ongoing efforts align health education with regulatory requirements and the organization's commitment to culturally and linguistically appropriate patient information.

Behavior Therapy↗