Tutorial: chaos theory--a primer for health care

Chaos theory, also called nonlinear systems theory, provides new insights into processes previously thought to be unpredictable and random. It also provides a new set of tools that can be used to analyze common administrative and clinical data. This tutorial provides an introduction to chaos theory. Subsequent articles will address applications of those principles to the administrative activities of health care organizations, implications of those principles for clinical data, and application of chaos theory concepts to our understanding of organizational dynamics.     

The effects of rest and subsequent training on selected physiological parameters in professional female classical dancers.

The purpose of this study was to assess the effects of a six-week summer break and of dance preparations at the beginning of the new season following the break, on selected physiological parameters. Seventeen professional ballerinas (mean age 27.2 +/- 1.4 years, mean height 160.2 +/- 6.2 cm) volunteered. They were assessed just before and immediately after their normal summer break, during which very little or no physical work was reported. Eight of these dancers were assessed for a third time, 2-3 months after the end of the break, while they were into preparing for the new season. More specifically, compared to pre-break data, the six-weeks of holiday was followed by a 15% overall increase in the three flexibility tests (from 334 to 386 degrees, P < 0.01), a 14% increase in peak anaerobic power (from 350 to 400 watts; P < 0.01), a 16% increase in leg strength (from 143 to 166 Nm; P < 0.01) (i.e. the mean performance of left and right knee extension added to the mean performance of left and right knee flexion), and a 10% increase in VO2max (from 41.2 to 45.2 ml/kg/min; P < 0.05). The third set of data, 2-3 months after the end of the break, revealed further significant increases by 24% in leg-strength (P < 0.005) and 17% in VO2max (P < 0.01) compared to pre-holiday data. Despite the lack of a control group, the present results fit with the hypothesis of a degree of "burnout" at the end of the season, which negatively affected the mechanisms of fitness and conditioning. A six-week summer-break can act as a restorer of these mechanisms. Two to three months into the new season, positive adaptations to exercise appeared to confirm recovery from the "burnout" or overtraining phenomenon. More research is required on the effects of demanding dance schedules on fitness and conditioning, and how such schedules might adversely affect dance performance and dancers' careers.     

Contrast agent neurotoxicity presenting as subarachnoid hemorrhage

A patient developed signs, symptoms, and radiologic findings compatible with acute subarachnoid hemorrhage after receiving a large dose of heparin and intravascular contrast medium for coronary angiography and stent placement. Subsequent CT indicated the subarachnoid enhancement was due to contrast. Neurotoxicity from contrast agents is well-known, however this is an unusual report of toxicity mimicking subarachnoid hemorrhage clinically and radiologically.     

Comorbidity of autistic spectrum disorders in children with Down syndrome

The aim of the study was to identify the comorbidity of autistic spectrum disorders in a population of children with Down syndrome (DS). All children with DS within a defined population of South Birmingham were identified. The Asperger Syndrome Screening Questionnaire and the Child Autism Rating Scale were completed and diagnosis made according to ICD-10 criteria following interview and observation. Thirty-three of 58 identified children completed the measures, four of whom received a diagnosis of an autistic spectrum disorder. This is equivalent to a minimum comorbid rate of 7%. The questionnaire items concerning social withdrawal, restricted or repetitive interests, clumsiness, and unusual eye contact were associated with an autistic disorder. Of the remaining 29 participating children, 11 also displayed marked obsessional and ritualistic behaviours. The comorbid occurrence of autism and DS is at least 7%. It is important that these children are identified and receive appropriate education and support. A full assessment of social, language, and communication skills and behaviour is crucial, particularly in children with DS who appear different from other children with DS. Potential mechanisms accounting for this comorbidity are discussed.     

Differential cellular expression of isoforms of inositol 1,4,5-triphosphate receptors in neurons and glia in brain

Inositol 1,4,5-trisphosphate receptors (IP3R) are mediators of second messenger-induced intracellular calcium release. Three isoforms are known to be expressed in brain, but their regional distributions and cellular localizations are little known. In order to better understand the roles of IP3 receptor isoforms in brain function, a first step is to define their distributions. We have used affinity-purified antibodies directed against peptides unique to each isoform to determine their sites of expression in rat brain. Type 1 IP3R (IP3R1) is dramatically enriched in Purkinje neurons in cerebellum and neurons in other regions, consistent with previous studies. By contrast, IP3R2 is only detected in glia, whereas IP3R3 is predominantly neuronal, with little detected in glia. IP3R3 is enriched in neuropil, especially in neuronal terminals (which often contain large dense core vesicles) in limbic and basal forebrain regions including olfactory tubercle, central nucleus of the amygdala, and bed nucleus of the stria terminalis. In addition, IP3R1 and IP3R3 have clearly distinct time courses of expression in developing brains. These data suggest separate roles for inositol 1,4,5-trisphosphate receptor isoforms in development, and for glial and neuronal function. The IP3R3 may be involved in regulation of neurotransmitter or neuropeptide release in terminals within specific nuclei of the basal forebrain and limbic system.     

Regulation of the angiotensin type-1 receptor by antisense oligonucleotides occurs through an RNase H-type mechanism

Multiple, diverse sites in the coding region of the angiotensin type-1 receptor mRNA were targeted with 2'-deoxyribonucleotide antisense oligonucleotides (ONs). The uptake of 1 microM concentration of these ONs into Chinese hamster ovary cells was facilitated by the use of cationic liposomes. The antisense sequences reduced binding of 125I-angiotensin II by 57-73%, while mismatch ONs and reverse sequence ONs produced little reduction in receptor binding. These reductions in AT1 receptor binding were accompanied by comparable decreases in AT1 receptor mRNA levels. Furthermore, mRNA cleavage fragments corresponding in size to 3'-cleavage fragments were observed with two of the antisense ONs, consistent with the involvement of an RNase H-type enzyme. When 2'-methoxyribonucleotide analogs of these same sequences were tested, AT1 receptor mRNA levels were unchanged even though small reductions in AngII binding were observed. Antisense effects seen with these 2'-methoxyribonucleotide sequences may have arisen through a translational arrest mechanism. Direct comparisons between 2'-deoxyribonucleotide analogs and their 2'-methoxyribonucleotide counterparts show that antisense effects are significantly larger when they are mediated through an RNase H-type mechanism. 2'-methoxyribonucleotide sequences were most effective when they were directed against the translation initiation codon.     

Artificial sapphire contact probes in Nd:YAG endometrial ablation: a quantitative in vitro and in vivo study

Artificial sapphire contact probes offer theoretical advantages in Nd:YAG endometrial ablation. To examine this, an in vitro and in vivo study of laser-tissue interaction was performed. In vitro, a linear correlation was found between applied energy and total depth of effect, that is, photovaporization and photocoagulation. Using a Round (MTR 1.5) contact probe, an applied energy of 30 joules gave a depth of myometrial effect of 3.3 mm. In vivo, there was a significant reduction in tissue effect (p less than 0.001) compared to in vitro. Difficulty of manipulation of the contact laser probe within the uterus also caused a significant reduction (p less than 0.001) in depth of tissue ablation achieved on the posterior uterine wall compared with that achievable at the uterine fundus, but this may be counteracted by increasing applied energy.