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PubMed2002

Visual function before and after the removal of bilateral congenital cataracts in adulthood.

Subject Peter Doyle (PD) had congenital bilateral cataracts removed at the age of 43. Pre-operatively PD's visual acuity was 20/80, with a resolution limit around 15 cpd, and he experienced monocular diplopia with high contrast stimuli. Post-operatively PD's visual acuity improved to approximately 20/40, with a resolution limit around 25 cpd. Using a variety of pre- and post-operative tests we have documented a wide range of neural adaptations to his limited and distorted visual input, and have found a limited amount of post-operative adaptation to his newly improved visual input. These results show that the human visual system is capable of significant adaptation to the particular optical input that is experienced.

Adaptation, Physiological↗
PubMed2002

What limits detection and resolution of short-wavelength sinusoidal gratings across the retina?

Peripheral resolution acuity for achromatic gratings is known to be limited by the density of the underlying ganglion cell sampling array. After confirming isolation of the short-wavelength sensitive (SWS) system using chromatic adaptation methods, we wished to determine if resolution is limited by blue/yellow ganglion cell sampling (evidenced by a superiority of detection over resolution acuity and the perception of aliasing) and thus directly related to SWS-driven ganglion cell density. We measured detection and resolution acuity between 0 degrees and 35 degrees, using blue sinusoidal gratings superimposed on a yellow adapting background which ranged in intensity from 2.5 to 4.7logTrolands. At all locations, a break could be observed in the acuity vs. illumination curves followed by a plateau. Detection and resolution acuity were the same for low background intensities, but resolution acuity was lower than detection at higher intensities, accompanied by observations of chromatic aliasing. SWS resolution is sampling-limited across the retina and agrees well with predicted performance based on anatomical estimates of small bistratified ganglion cell density.

Adolescent↗
PubMed2005

Molecular structure of the collagen triple helix.

The molecular conformation of the collagen triple helix confers strict amino acid sequence constraints, requiring a (Gly-X-Y)(n) repeating pattern and a high content of imino acids. The increasing family of collagens and proteins with collagenous domains shows the collagen triple helix to be a basic motif adaptable to a range of proteins and functions. Its rodlike domain has the potential for various modes of self-association and the capacity to bind receptors, other proteins, GAGs, and nucleic acids. High-resolution crystal structures obtained for collagen model peptides confirm the supercoiled triple helix conformation, and provide new information on hydrogen bonding patterns, hydration, sidechain interactions, and ligand binding. For several peptides, the helix twist was found to be sequence dependent, and such variation in helix twist may serve as recognition features or to orient the triple helix for binding. Mutations in the collagen triple-helix domain lead to a variety of human disorders. The most common mutations are single-base substitutions that lead to the replacement of one Gly residue, breaking the Gly-X-Y repeating pattern. A single Gly substitution destabilizes the triple helix through a local disruption in hydrogen bonding and produces a discontinuity in the register of the helix. Molecular information about the collagen triple helix and the effect of mutations will lead to a better understanding of function and pathology.

Amino Acid Sequence↗
PubMed1999

Denial: a conceptual analysis.

The term denial is used in nursing to describe a client's behavior. A random sample of 18 articles published in English from 1990 to 1999 was identified for conceptual analysis using Rogers' methodology. The 2 main definitions identified ranged from an adaptive to maladaptive coping process. Anxiety or perceived threats evolving from situational or maturational crises were antecedents. Events that followed typically resulted in either positive or negative outcomes. Related concepts used most often were avoidance, unrealistic hopefulness, and repression.

Adaptation, Psychological↗
PubMed2001

Inclusion compounds of tetrakis(4-nitrophenyl)methane: C-H...O networks, pseudopolymorphism, and structural transformations.

Tetrakis(4-nitrophenyl)methane is a new host material with considerable structural adaptability over a range of solvents. The crystal structures of 14 of these solvates have been determined and classified into three groups. The diamondoid group, wherein the host molecules form a 2-fold interpenetrated diamondoid network structure, is unprecedented in that network connections are made exclusively with weak C-H...O and pi...pi interactions. This group consists of the solvates of THF, dioxane, nitrobenzene, 4-bromoanisole, anisole, phenetole, p-xylene, and chlorobenzene. The rhombohedral group, which is characterized by specific host.guest interactions of the C-H...O and halogen...O2N type, consists of the solvates of CHCl3 and CHBr3 and somewhat surprisingly DMF, which shows an unusual 3-fold disorder mimicking in part the shape and size of the haloform molecules though not their orientation. The third group comprises solvent-rich solvates of the host with mesitylene, collidine, and o-xylene with quite different crystal structures. The THF solvate was found to lose solvent over limited temperature ranges transforming reversibly from the diamondoid structure to the rhombohedral structure. A mechanism for this process is outlined. Material from which solvent has been removed by heating was also found to resolvate upon soaking in appropriate solvents. In summary, the title compound forms a host network that is partially robust and in part flexible. It is possible that this fluxional nature of the host network derives from the weakness of the connecting interactions.

Journal Article↗
PubMed1999

The scaling of human grip configurations.

The many degrees of freedom of the hand and arm afford the wide range and rich adaptability of human grip configurations in action. Several classification schemes of human grip configurations have been proposed, but none is based on scaling laws of physical biology, which are well established for other categorizations of fundamental physical activities such as locomotion. This study examined the preferred human grip configurations used to displace to a new location cubes that varied systematically in length (L), mass (M), and density (ML-3). The body-scaled equation K = log L + (log M)/h (where h refers to anthropometric measures of the hand) predicted the grip configurations used to displace objects. The findings suggest that information about the dynamic scaling relation is picked up visually and organizes the many degrees of freedom of the hand-arm complex in the coordination of prehensile grip configurations.

Adult↗
PubMed2004

Beliefs and practices of patients with advanced cancer: implications for communication.

The aim of this study was to investigate the beliefs that patients with advanced cancer held about the curability of their cancer, their use of alternatives to conventional medical treatment, and their need to have control over decisions about treatment. Of 149 patients who fulfilled the criteria for participation and completed a self-administered questionnaire, 45 patients (31%) believed their cancer was incurable, 61 (42%) were uncertain and 39 (27%) believed their cancer was curable. The index of need for control over treatment decisions was low in 53 patients (35.6%) and high in only 17 patients (11.4%). Committed users of alternatives to conventional medical treatments were more likely to believe that their cancer was curable (P<0.001) and to have a higher need for control over decisions about treatment (P<0.004). The mean need for control scores were highest in patients who believed that their cancer was curable, or who were uncertain about the curability of their cancer, but who acknowledged that their oncologist had reported that the cancer was incurable. The diverse beliefs, attitudes and actions of these patients were consistent with a range of psychological adaptations to a life-threatening illness, some realistic and others illusory. Illusory responses influence what communication can achieve in daily oncology practice.

Attitude of Health Personnel↗
PubMed1970

A generalized system for automation of enzyme assays.

A flow system was developed, using a Technicon AutoAnalyzer, that is readily adaptable to a range of enzyme assays. The system includes lines for pumping substrate, cofactor, buffer and enzyme and for generating linear gradients. By using a variable-speed proportioning pump the incubation time may be continuously varied, and the system also allows for continuous variation in the pH, substrate or cofactor concentration, incubation temperature and enzyme concentration. A FORTRAN V program was written that uses instrument calibrations to calculate the flow rates in the individual lines, the incubation time and the characteristics of the gradient used. The computer then prints out instructions for preparation of reagents to give a required reaction mixture, weighing sheets for stock solutions and the results of the assay in international units in suitable tables and graphs. The flow system and computer program are designed to facilitate the automation of manual assays. A detailed example is given of the use of the system [the assay of three dehydrogenases in yeast: l(+)-lactate dehydrogenase, d(-)-lactate dehydrogenase and succinate dehydrogenase], and the general applications of the method are discussed. The program has been deposited as Supplementary Publication no. SUP 50002 at the National Library for Science and Technology, Boston Spa, Yorks. LS23 7BQ, U.K., from whom copies may be obtained on the terms indicated in Biochem. J. (1970), 116, 7.

Autoanalysis↗
PubMed1998

Growth characteristics and metabolic activities of the methanotrophic-heterotrophic groundwater community.

In this work the growth characteristics and metabolic activities of the methanotrophic-heterotrophic groundwater community (culture MM1) as well as of individual community members were studied. When growing in shake flasks, under various methane and oxygen tensions, culture MM1 revealed the capability of a stable association consisting of one obligate methanotroph with type II intracytoplasmic membranes as the dominant strain, and four or five heterotrophs of different morphological, physiological and metabolic characteristics. Coexistence of different populations and the stability of culture MM1 under various conditions suggested that complex relationships may exist between the community members. Most of these relationships seem to be beneficial for both the methanotroph and heterotrophs, making the community adaptable to a range of environmental conditions containing methane as the only carbon source. Furthermore, faster and more complete transformation of 2-[4-(sulphophenyl)]decane (2C10LAS) by the community than by any of the community members alone, illustrates the role and importance of methanotrophic-heterotrophic interactions in combined metabolic attack on complex linear alkylbenzenesulphonates molecules.

Bacteria↗
PubMed2002

Context-bound communication skills training: development of a new method.

OBJECTIVES: To examine how communication skills training might be integrated into everyday clinical practice in a manner that is acceptable to clinicians. DESIGN: General practitioners from 3 group practices agreed to take part, in turn, in a study of how to manage difficult consultations about antibiotic prescribing for acute respiratory infections. This provided the opportunity to conduct communication skills training in which lessons learned from one practice were taken into the next. SETTING: United Kingdom general practices. SUBJECTS: Three groups of general practitioners. FINDINGS: Difficulties with the acceptability of a traditional off-site workshop approach, using role play as the main teaching method, led to the development of a new training method (context-bound training), which proved to be practical and acceptable to experienced clinicians. The main features of the method were the delivery of training in the clinicians' place of work, and the transformation of their reported difficult cases into scenarios which they then encountered with a standardized simulated patient before and after brief seminars. Everyday clinical experience was kept in the foreground and 'communication skills' in the background. CONCLUSIONS: The method is acceptable to clinicians and adaptable to a range of clinical situations. It offers potential for improving the communication skills of clinicians both in hospital and primary care settings.

Communication↗
PubMedDate not supplied

Grafts of ovaries in males and females of Pleurodeles waltl (urodele amphibia): evidence of a long-term tolerance of allografts; application following a space biology experiment.

Ovary grafts were investigated in the salamander Pleurodeles using juveniles and adults as donors and hosts. Ovaries were provided by standard or histo-compatible strains and by standard females which had been submitted to a space flight. Laparotomy of the hosts was used to control viability of grafts. Entire juvenile ovaries transplanted into castrated juvenile females or males were tolerated and developed. Ovarian parts of adult females, which contained a majority of oogonies, could also be tolerated by juvenile animals. In addition, ovarian parts supported a better recovery and differentiation than parts that mainly included mature oocytes. About 24 months after the ovary grafts, some hosts (genetical females or males and standard or spatialized females) crossed with standard males provided progenies originating from oocytes of the grafted ovaries. The protocols applied offer a new range of potentialities, adapted to various experimental purposes such as life science research in space or sex differentiation studies.

Animals↗
PubMed2004

Evolution of p53 in hypoxia-stressed Spalax mimics human tumor mutation.

The tumor suppressor gene p53 controls cellular response to a variety of stress conditions, including DNA damage and hypoxia, leading to growth arrest and/or apoptosis. Inactivation of p53, found in 40-50% of human cancers, confers selective advantage under hypoxic microenvironment during tumor progression. The mole rat, Spalax, spends its entire life cycle underground at decidedly lower oxygen tensions than any other mammal studied. Because a wide range of respiratory adaptations to hypoxic stress evolved in Spalax, we speculated that it might also have developed hypoxia adaptation mechanisms analogous to the genetic/epigenetic alterations acquired during tumor progression. Comparing Spalax with human and mouse p53 revealed an arginine (R) to lysine (K) substitution in Spalax (Arg-174 in human) in the DNA-binding domain, identical to known tumor associated mutations. Multiple p53 sequence alignments with 41 additional species confirmed that Arg-174 is highly conserved. Reporter assays uncovered that Spalax p53 protein is unable to induce apoptosis-regulating target genes, resulting in no expression of apaf1 and partial expression of puma, pten, and noxa. However, cell cycle arrest and p53 stabilization/homeostasis genes were overactivated by Spalax p53. Lys-174 was found critical for apaf1 expression inactivation. A DNA-free p53 structure model predicts that Arg-174 is important for dimerization, whereas Spalax Lys-174 prevents such interactions. Similar neighboring mutations found in human tumors favor growth arrest rather than apoptosis. We hypothesize that, in an analogy with human tumor progression, Spalax underwent remarkable adaptive p53 evolution during 40 million years of underground hypoxic life.

Adaptation, Physiological↗
PubMed1990

Analysis of the relation between lithium clearance and sodium clearance in rats.

In rats on a normal or high sodium intake, lithium clearance (CLi) is thought to approximate fluid delivery to the end of the proximal tubule (Vprox), whereas in rats on a very low sodium intake CLi is lower than Vprox owing to significant reabsorption of lithium in the distal nephron. This paper examines the relation between CLi and sodium clearance (CNa) in animals adapted to a range of dietary sodium contents (5-300 mmol/kg). Measurements were performed in conscious, unoperated rats with hereditary diabetes insipidus, in which changes in urine flow rate (V) can be used as an index of changes in Vprox; stimulation of distal lithium reabsorption was identified by comparing changes in CLi with the corresponding changes in V. CLi exhibited a curved, positive relation with CNa, with considerable scatter and a sharp decrease of CLi at low values of CNa. Further analysis indicated that this relationship consisted of three elements: (i) an almost unaltered Vprox in response to variations in dietary sodium: taken alone, this would result in a horizontal regression of CLi on CNa. (ii) Distal reabsorption of lithium in rats on very low sodium intakes, bending the curve towards low CLi values at low values of CNa. (iii) Intra-individual variations in Vprox, causing covariation of CLi and CNa; the slopes of the regression lines linking the two depended on the level of sodium intake, but all the regression lines intercepted the CLi axis at a similar (low) value of CLi, making a major contribution to the curved shape of the relationship. It is concluded that observations of greatly reduced values of CLi at low values of CNa cannot be taken as unequivocal evidence, per se, of distal reabsorption of lithium. Nor should measured values of CLi be corrected for differences in CNa.

Absorption↗
PubMedDate not supplied

Screening for toxic activity of some marine benthic algae.

This research was carried out in order to show that certain substances of algal origin are toxic to animals, particularly to fish, and to determine if a relationship exists between toxicity and the latitude where the algae were collected. Twenty-nine species of algae were collected in different localities off the Pacific coast of Mexico. The samples were frozen shortly after collection and kept frozen until used. Crude ethanolic extracts of the algae were prepared and tested for ichthyotoxicity. The extracts were classified as nontoxic (NT), weakly toxic (WT) and highly toxic (with lethal effects) (T). The reactions exhibited by the fish to the presence of the algal extracts in their environment ranged from initial adaptative behaviour to death. Only four species (14%) out of the 29 algal species tested were highly toxic, 13 (45%) weakly toxic and 12 (41%) non-toxic. The high percentage of algal extracts that showed some degree of toxicity suggests that algae might have some kind of defence mechanism that could be noxious, thus being inedible by fish. The highest toxicity values were found among tropical algae. These results suggest that a relationship could exist between toxicity and the latitude of the collecting locality.

Animals↗
PubMed2006

Induction of decision trees using genetic programming for modelling ecotoxicity data: adaptive discretization of real-valued endpoints.

Recent literature has demonstrated the applicability of genetic programming to induction of decision trees for modelling toxicity endpoints. Compared with other decision tree induction techniques that are based upon recursive partitioning employing greedy searches to choose the best splitting attribute and value at each node that will necessarily miss regions of the search space, the genetic programming based approach can overcome the problem. However, the method still requires the discretization of the often continuous-valued toxicity endpoints prior to the tree induction. A novel extension of this method, YAdapt, is introduced in this work which models the original continuous endpoint by adaptively finding suitable ranges to describe the endpoints during the tree induction process, removing the need for discretization prior to tree induction and allowing the ordinal nature of the endpoint to be taken into account in the models built.

Decision Trees↗
PubMedDate not supplied

Health education goes Hollywood: working with prime-time and daytime entertainment television for immunization promotion.

This article presents an entertainment education strategy used to influence Hollywood prime-time and daytime television programs to add storylines on the importance of immunizations to their shows. Rather than giving information about immunizations to show producers, directors, actors, and writers, we furnished "log lines" and true stories about immunizations that could be used to inspire scripts that included immunization themes. By working through personal contacts within the entertainment television industry's closed system of networks, we were able to gain entree and some airtime for our campaign agenda. Embedded messages aired on eight popular shows in the 1996-1997 broadcast season, with five scheduled to air in the 1997-1998 season. These efforts were evaluated qualitatively, focusing on issues of personal networks, content of aired messages, and comparative costs for paid airtime. The strategy developed can be adapted for a range of entertainment education interventions.

Adolescent↗
PubMed2005

Human immunodeficiency virus dementia patients in Africa: How many? Who cares? And where to from here?

Dementia was a frequent consequence of human immunodeficiency virus (HIV) in developed countries before antiretroviral therapy (ART) became available and remains a common neurologic complication of acquired immunodeficiency syndrome (AIDS) among patients receiving appropriate therapy. The epidemiology of HIV dementia (HIV-D) in Africa remains unclear 20+ years into the AIDS epidemic. Early studies of cognitive impairment in HIV-positive populations in Africa were limited by vaguely defined criteria for cognitive impairment, inadequate assessment tools lacking ecologic validation, and the absence of normative population data. More recent studies have clarified definitions of impairment, utilized more sophisticated measures, and included normative comparisons. Unfortunately, these detailed neuropsychiatric assessments are not feasible for population-based studies or routine clinical implementation. Therefore, the prevalence data available for HIV-D in Africa represents rates found in people presenting to tertiary care centers and are unlikely to reflect HIV-D rates in the general population. As ART becomes available in Africa, future research efforts must provide a better understanding of the epidemiology of HIV-D, the effects of available ART regimens on HIV-D in this population, and the impact of HIV-D on ART adherence. Universally accepted terminology and criteria for HIV-D are needed. Population-based studies will require the development of neuropsychiatric batteries that can be adapted across a range of African environments. Ideally, these measures will be viable for nonphysician care providers to use as screening tools in the first stage of epidemiologic studies. Such screening tools could also serve as clinical indicators of possible HIV-related cognitive impairment facilitate implementation of ART adherence.

AIDS Dementia Complex↗