The mechanical properties of Saccharomyces cerevisiae

Cell-wall mechanical properties play an integral part in the growth and form of Saccharomyces cerevisiae. In contrast to the tremendous knowledge on the genetics of S. cerevisiae, almost nothing is known about its mechanical properties. We have developed a micromanipulation technique to measure the force required to burst single cells and have recently established a mathematical model to extract the mechanical properties of the cell wall from such data. Here we determine the average surface modulus of the S. cerevisiae cell wall to be 11.1 +/- 0.6 N/m and 12.9 +/- 0.7 N/m in exponential and stationary phases, respectively, giving corresponding Young's moduli of 112 +/- 6 MPa and 107 +/- 6 MPa. This result demonstrates that yeast cell populations strengthen as they enter stationary phase by increasing wall thickness and hence the surface modulus, without altering the average elastic properties of the cell-wall material. We also determined the average breaking strain of the cell wall to be 82% +/- 3% in exponential phase and 80% +/- 3% in stationary phase. This finding provides a failure criterion that can be used to predict when applied stresses (e.g., because of fluid flow) will lead to wall rupture. This work analyzes yeast compression experiments in different growth phases by using engineering methodology.

Review of the Bethesda System atlas does not improve reproducibility or accuracy in the classification of atypical squamous cells of undetermined significance smears

BACKGROUND

The Bethesda System (TBS) and its accompanying atlas were developed to promote uniform diagnosis and reporting of cervical and vaginal cytology, especially with respect to borderline abnormal smears. The authors assessed whether group study of TBS atlas improves the reproducibility and accuracy of the cytopathologic diagnosis of equivocal Papanicolaou smears.

METHODS

One hundred "atypical" smears were divided into pretest and posttest sets containing equal numbers of negative, atypical squamous cells of undetermined significance (ASCUS), and squamous intraepithelial lesion (SIL) diagnoses based on a five-member panel review. Two comparable teams of four pathologists from George Washington University Medical Center (Washington, DC) and Kaiser Permanente (Portland, OR), each comprised of two more experienced cytopathologists and two less experienced pathologists, independently reviewed the 50 pretest slides and classified the slides according to TBS as negative, ASCUS, or SIL. The teams then conducted group study sessions using TBS atlas. After the review, the pathologists independently classified the 50 posttest slides in a similar manner.

RESULTS

Pretest, pair-wise interobserver agreement ranged from 30% to 66% compared with 34-62% for posttest agreement. Absolute percent agreement of reviewers' diagnoses with a previously developed consensus diagnosis based on opinions of a five-expert panel (cytopathologic certainty scale) ranged from 44% to 62% for the pretest set and from 40% to 60% for the posttest set. Comparison of the detection of oncogenic human papilloma virus (HPV) DNA by hybrid capture tube test with smears classified as negative, ASCUS, or SIL revealed that seven of eight reviewers did not demonstrate a stronger association between HPV detection and cytologic diagnosis in the posttest set.

CONCLUSIONS

Review of TBS atlas by itself does not appear to improve the reproducibility or accuracy of cytologic diagnoses. The lack of improvement was similar among the pathologists involved regardless of experience level or whether they had a close working relation. Cancer (Cancer Cytopathol)

Perceived knowledge and training needs in adolescent pregnancy prevention: results from a multidisciplinary survey

OBJECTIVES

To examine health care professionals' knowledge and interest in training in adolescent pregnancy prevention and whether an association exists between perceived knowledge and interest in training.

DESIGN

A cross-sectional mailed survey.

PARTICIPANTS

Random, stratified sample design that identified 800 psychologists, 800 social workers, 1,000 nurses, and 400 pediatricians from national professional membership lists. Response rate to the mailed survey was 51%. After removing respondents who did not currently work with adolescents, 1,242 surveys (41%) were available for analyses.

MAIN OUTCOME MEASURES

Descriptive analyses were conducted on self-report data concerning perceived knowledge and interest in training about adolescent pregnancy prevention separately for each of the 4 disciplines. Within disciplines, perceived knowledge and interest in training were correlated for each of 3 content areas (ie, sex education and contraceptive counseling, adolescent pregnancy, and counseling after a negative pregnancy test) and for a summary measure of the content areas.

RESULTS

Less than half of the nursing, pediatrics, psychology, and social work professionals reported high perceived knowledge in the 3 content areas. Psychologists and social workers reported the lowest perceived knowledge. However, with the exception of psychologists, more than two thirds of the other respondents reported moderate or high interest in training in the 3 content areas. Interest in training was not strongly correlated with perceived knowledge within any discipline.

CONCLUSIONS

The need to integrate psychosocial components into adolescent health care is a core assumption in the field, yet these data indicate that psychologists and social workers perceive low levels of knowledge and interest in training. These disciplines may benefit from more targeted professional training about their role in preventing adolescent pregnancy.

Prevalence of home pregnancy testing among adolescents

OBJECTIVES

This study estimated the prevalence of home pregnancy testing among adolescents.

METHODS

A survey was administered in 11 urban clinics to 600 females aged 13 to 19 years.

RESULTS

The prevalence of home pregnancy test use was 34% among 474 sexually experienced youths; 77% of the users had received at least 1 negative pregnancy test result, and 48% took no further action for confirmation. Compared with those who had never used such tests, users were older, younger at sexual debut, less likely to consistently use effective birth control, and more likely to have ever been pregnant.

CONCLUSIONS

Health care clinics are important sources for pregnancy prevention, but clinics may have limited opportunity to intervene with some youths who use home pregnancy tests.

Vascular embolization of benign granulosa cells

OBJECTIVE(S)

Most conditions involving sex cord-stromal cells can be diagnosed on morphologic criteria alone. We describe a case of vascular embolization of benign granulosa cells in which immunohistochemistry was of value as a diagnostic tool.

METHODS

We reviewed the clinical history and gross pathologic findings from a 48-year-old patient who presented with abdominal pain and fullness. Formalin-fixed paraffin-embedded sections were examined by routine H&E and immunohistochemical stains.

RESULTS

Histologic examination of a grossly enlarged and cystic ovary revealed nests of cells within angiolymphatic spaces. Although the cells were cohesive and atypical, they were morphologically similar to the nearby graafian follicle. Immunohistochemistry showed positive labeling with antibodies to inhibin-alpha and cytokeratin in a pattern consistent with benign granulosa cells.

CONCLUSION(S)

Immunohistochemical stains for inhibin-alpha and cytokeratin are useful tools to help confirm granulosa cell origin, as demonstrated in this case involving an atypical histomorphologic picture of "embolization."

Domiciliary visits to the old and the mentally ill: how valuable?

In the early days of the British National Health Service, domiciliary visits were a continuation of the tradition whereby general practitioners (GPs) met consultants in the patient's home. The nature of domiciliary visits, which still attract a special fee, has since changed. We analysed the effectiveness of all domiciliary visits undertaken in a NHS trust providing primary care, mental health and elderly care services to a population of 470,000. Data were obtained from domiciliary visit claim forms and from questionnaires completed by the consultant, the referring GP and consultant peer reviewers. The largest number of visits (total 234) was in geriatric medicine 48.9%, followed by old-age psychiatry 44.9%. Geriatric medicine was more likely than psychiatry to admit patients to hospital (19%) after a visit. All domiciliary visits in old-age psychiatry were done during the day (9 am to 5 pm). Only 2% of GPs stated that they attended any of the domiciliary visits; almost all thought that the outcome of domiciliary visits was of value. Old-age-psychiatry peer reviewers believed that all visits in that specialty were appropriate; in geriatric medicine this figure was 77% and in other psychiatric specialties 65%. The findings indicate that domiciliary visits were not being used routinely as a pathway to hospital admission, though they were often used to expedite admission or gain a quick consultant opinion; the visits were valued by GPs. The practice of domiciliary visits differs greatly from the definition in NHS terms and conditions of service. One or other should be altered.

Bone mineral and geometric changes through the femur with immobilization due to spinal cord injury

This cross-sectional study describes bone mineral and geometric properties of the midshaft and distal femur in a control population and examines effects of immobilization due to spinal cord injury (SCI) at these skeletal sites. The subject populations were comprised of 118 ambulatory adults (59 men and 59 women) and 246 individuals with SCI (239 men and 7 women); 30 of these were considered to have acute injury (SCI duration <1 year). Bone mineral density (BMD) was assessed at the femoral neck, and midshaft and distal femur by dual energy absorptiometry. Geometric properties, specifically cortical area, polar moment of inertia, and polar section modulus, were estimated at the midshaft from cortical dimensions obtained by concurrent radiography. Reduction in BMD was noted in all femoral regions (27%, 25%, and 43% for femoral neck, midshaft, and distal femur, respectively) compared with controls. In contrast, although endosteal diameter was enlarged, geometric properties were not significantly reduced in the midshaft attributable to the age-related increase in periosteal diameter. These results suggest that simultaneous assessment of bone mineral and geometric properties may improve clinically relevant evaluation of skeletal status.

Genetic alterations in urinary bladder carcinosarcoma: evidence of a common clonal origin

The cellular origin of carcinosarcoma of the bladder is unknown. We addressed this issue by using microsatellite analysis for loss of heterozygosity (LOH) in both the carcinomatous and sarcomatous components of 6 bladder tumors. We tested 40 microsatellite markers from 19 human chromosomes and compared the genetic alterations between the two separately isolated components. The potential relevance of the E-cadherin pathway was also evaluated by immunohistochemistry. All 6 cases revealed identical LOH on chromosomal arms 9p, 9q, 8p, and 8q, corresponding to relatively early events in bladder carcinogenesis. Discordant losses between two alleles in the remaining chromosomes, associated with progression, were seen in all tumors with a trend toward a higher incidence in the more advanced tumors (N1M1 and N1Mx). E-cadherin was strongly expressed in the carcinomatous components (5 of 6), whereas most of sarcomatous elements displayed absence of the protein product (4 of 6). These results indicate that both the carcinomatous and sarcomatous components of carcinosarcoma are derived from a common stem cell. Downregulation of E-cadherin may define one of the pathways responsible for conversion of epithelial cells to the sarcomatous phenotype.

Do self-fulfilling prophecies accumulate, dissipate, or remain stable over time?

The authors examined whether self-fulfilling prophecies accumulate, dissipate, or remain stable over time by using data from more than 500 6th- through 12th-grade students in public school math classes. The authors used multiple regression analyses to assess the extent to which teacher perceptions predicted students' final math marks and standardized math-test scores from 6th through 12th grade. Control variables included 5 measures of student motivation and 2 measures of previous achievement. The results were consistent with both the dissipation and stability hypotheses. Implications for understanding the extent to which social perception creates social reality and the role of expectations in social problems are discussed.

Do self-fulfilling prophecies accumulate, dissipate, or remain stable over time?

The authors examined whether self-fulfilling prophecies accumulate, dissipate, or remain stable over time by using data from more than 500 6th- through 12th-grade students in public school math classes. The authors used multiple regression analyses to assess the extent to which teacher perceptions predicted students' final math marks and standardized math-test scores from 6th through 12th grade. Control variables included 5 measures of student motivation and 2 measures of previous achievement. The results were consistent with both the dissipation and stability hypotheses. Implications for understanding the extent to which social perception creates social reality and the role of expectations in social problems are discussed.

Optimal design for a study of butadiene toxicokinetics in humans

The derivation of the optimal design for an upcoming toxicokinetic study of butadiene in humans is presented. The specific goal of the planned study is to obtain a precise estimate of butadiene metabolic clearance for each study subject, together with a good characterization of its population variance. We used a two-compartment toxicokinetic model, imbedded in a hierarchical population model of variability, in conjunction with a preliminary set of butadiene kinetic data in humans, as a basis for design optimization. Optimization was performed using Monte Carlo simulations. Candidate designs differed in the number and timing of exhaled air samples to be collected. Simulations indicated that only 10 air samples should be necessary to obtain a coefficient of variation of 15% for the estimated clearance rate, if the timing of those samples is properly chosen. Optimal sampling times were found to closely bracket the end of exposure. This efficient design will allow the recruitment of more subjects in the study, in particular to match prescribed levels of accuracy in the estimate of the population variance of the butadiene metabolic rate constant. The techniques presented here have general applicability to the design of human and animal toxicology studies.

PEGylation of adenovirus with retention of infectivity and protection from neutralizing antibody in vitro and in vivo

Replication-defective recombinant adenovirus (Ad) vectors are under development for a wide variety of gene therapy indications. A potential limiting factor associated with virus gene therapy requiring repeated treatment is the development of a humoral immune response to the vector by the host. In animal models, there is a dose-dependent rise in neutralizing antibodies after primary vector administration, which can preclude effective repeat administration. The strategy we have developed to circumvent the neutralization of adenovirus vectors by antibodies is to mask their surface by covalent attachment of the polymer polyethylene glycol (PEG). Covalent attachment of PEG to the surface of the adenovirus was achieved primarily by using activated PEG tresylmonomethoxypolyethylene glycol (TMPEG), which reacts preferentially with the epsilon-amino terminal of lysine residues. We show that the components of the capsid that elicit a neutralizing immune response, i.e., hexon, fiber, and penton base, are also the main targets for PEGylation. Several protocols for PEGylation of an adenovirus vector were evaluated with respect to retention of virus infectivity and masking from antibody neutralization. We show that covalent attachment of polymer to the surface of the adenovirus can be achieved with retention of infectivity. We show further that PEG-modified adenovirus can be protected from antibody neutralization in the lungs of mice with high antibody titers to adenovirus, suggesting that PEGylation will improve the ability to administer Ad vectors on a repeated basis.

Novel role for E4 region genes in protection of adenovirus vectors from lysis by cytotoxic T lymphocytes

Target cells infected with adenovirus (Ad) vectors containing intact E3 and E4 regions were found to be relatively resistant to lysis by Ad-specific cytotoxic T lymphocytes. Elements from both the E3 and the E4 regions were required for this effect, leading to the identification of a previously undescribed role for E4 gene products in resistance to cytolysis.

An integrated assessment framework for climate change and infectious diseases

Many potential human health effects have been hypothesized to result either directly or indirectly from global climate change. Changes in the prevalence and spread of infectious diseases are some of the most widely cited potential effects of climate change, and could have significant consequences for human health as well as economic and societal impacts. These changes in disease incidence would be mediated through biologic, ecologic, sociologic, and epidemiologic processes that interact with each other and which may themselves be influenced by climate change. Although hypothesized infectious disease effects have been widely discussed, there have not yet been thorough quantitative studies addressing the many processes at work. In part this is because of the complexity of the many indirect and feedback interactions or mechanisms that bear on all aspects of the climate issue. It also results from the difficulty of including the multitude of always-changing determinants of these diseases. This paper proposes a framework for an integrated assessment of the impacts of climate change on infectious diseases. The framework allows identification of potentially important indirect interactions or mechanisms, identification of important research gaps, and a means of integrating targeted research from a variety of disciplines into an enhanced understanding of the whole system.

An integrated assessment framework for climate change and infectious diseases

Many potential human health effects have been hypothesized to result either directly or indirectly from global climate change. Changes in the prevalence and spread of infectious diseases are some of the most widely cited potential effects of climate change, and could have significant consequences for human health as well as economic and societal impacts. These changes in disease incidence would be mediated through biologic, ecologic, sociologic, and epidemiologic processes that interact with each other and which may themselves be influenced by climate change. Although hypothesized infectious disease effects have been widely discussed, there have not yet been thorough quantitative studies addressing the many processes at work. In part this is because of the complexity of the many indirect and feedback interactions or mechanisms that bear on all aspects of the climate issue. It also results from the difficulty of including the multitude of always-changing determinants of these diseases. This paper proposes a framework for an integrated assessment of the impacts of climate change on infectious diseases. The framework allows identification of potentially important indirect interactions or mechanisms, identification of important research gaps, and a means of integrating targeted research from a variety of disciplines into an enhanced understanding of the whole system.

Cationic lipid-mediated CFTR gene transfer to the lungs and nose of patients with cystic fibrosis: a double-blind placebo-controlled trial

BACKGROUND

We and others have previously reported significant changes in chloride transport after cationic-lipid-mediated transfer of the cystic fibrosis transmembrane conductance regulator (CFTR) gene to the nasal epithelium of patients with cystic fibrosis. We studied the safety and efficacy of this gene transfer to the lungs and nose of patients with cystic fibrosis in a double-blind placebo-controlled trial.

METHODS

Eight patients with cystic fibrosis were randomly assigned DNA-lipid complex (active) by nebulisation into the lungs followed 1 week later by administration to the nose. Eight control patients followed the same protocol but with the lipid alone (placebo). Safety was assessed clinically, by radiography, by pulmonary function, by induced sputum, and by histological analysis. Efficacy was assessed by analysis of vector-specific CFTR DNA and mRNA, in-vivo potential difference, epifluorescence assay of chloride efflux, and bacterial adherence.

FINDINGS

Seven of the eight patients receiving the active complex reported mild influenza-like symptoms that resolved within 36 h. Six of eight patients in both the active and placebo groups reported mild airway symptoms over a period of 12 h following pulmonary administration. No specific treatment was required for either event. Pulmonary administration resulted in a significant (p<0.05) degree of correction of the chloride abnormality in the patients receiving active treatment but not in those on placebo when assessed by in-vivo potential difference and chloride efflux. Bacterial adherence was also reduced. We detected no alterations in the sodium transport abnormality. A similar pattern occurred following nasal administration.

INTERPRETATION

Cationic-lipid-mediated CFTR gene transfer can significantly influence the underlying chloride defect in the lungs of patients with cystic fibrosis.

An evaluation of intelligent prognostic systems for colorectal cancer

In this paper we describe attempts at building a robust model for predicting the length of survival of patients with colorectal cancer. The aim of the research, reported in this paper, is to study the effective utilisation of artificial intelligence techniques in the medical domain. We suggest that an important research objective of proponents of intelligent prognostic systems must be to evaluate the additionality that AI techniques can bring to an already well-established field of medical prognosis. Towards this end, we compare a number of different AI techniques that lend themselves to the task of predicting survival in colorectal cancer patients. We describe the pros and cons of each of these methods using the usual metrics of accuracy and perspicuity. We then present the notion of intelligent hybrid systems and evaluate the role that they may potentially play in developing robust prognostic models. In particular we evaluate a hybrid system that utilises the k Nearest Neighbour technique in conjunction with Genetic Algorithms. We describe a number of innovations used within this hybrid paradigm used to build the prognostic model. We discuss the issue of censored patients and how this issue can be tackled within the various models used. In keeping with our objective of studying the additionality that AI techniques bring to building prognostic models, we use Cox's regression as a standard and compare each AI technique with it, attempting to discover their capabilities in enhancing prognostic methods in medicine. In doing so we address two main questions--which model fits the data best?, and are the results obtained by the various AI techniques significantly different from those of Cox's regression? We conclude this paper by discussing future enhancements to the work presented and lessons learned from the study to date.