Fetal diuretic responses to maternal hyponatremia: contribution of placental sodium gradient

Maternal hyponatremia induces fetal hyponatremia and increased fetal urine flow. We sought to examine the relative contributions of the placental Na(+) gradient vs. the absolute decrease in fetal plasma Na(+) in the fetal diuretic response to hyponatremia. Seven ewes with singleton fetuses (130 +/- 2 days) were prepared. Ewes received intravenous 1-desamino-8-D-arginine vasopressin (20 microg) and warm tap water (2 liters). Maternal plasma Na(+) was decreased to achieve two levels of maternal hyponatremia. Maternal and fetal blood volume were measured with radiolabeled red blood cells. In response to the first decrease in maternal plasma Na(+), fetal plasma Na(+) did not change initially. Subsequently, fetal plasma Na(+) decreased, normalizing the gradient. The second decrease in maternal plasma Na(+) similarly induced a reduced and normalized placental gradient at lower fetal plasma Na(+) values. Fetal urine flow increased in direct proportion to the degree of fetal hyponatremia (13, 38, 63, 100%, respectively). Maternal, although not fetal, blood volume significantly increased in response to hyponatremia. These results suggest that chronic fetal hyponatremia will result in a persistent diuresis, despite placental equilibration.

The relative influence of secondary versus primary prevention using the National Cholesterol Education Program Adult Treatment Panel II guidelines

OBJECTIVES

This study was undertaken to project the population-wide effect of full implementation of the Adult Treatment Panel (ATP) II guidelines of the National Cholesterol Education Program (NCEP).

BACKGROUND

The ATP II has proposed guidelines for cholesterol reduction, but the long-term epidemiologic influence of its components has not been fully examined.

METHODS

We used a calibrated, validated simulation of the U.S. population, aged 35 to 84 years to estimate the potential for the NCEP guidelines, under varying assumptions, to reduce coronary heart disease morbidity and mortality and overall mortality from the years 2000 to 2020.

RESULTS

Primary prevention would yield only about half of the benefits of secondary prevention despite requiring nearly twice as many person-years of treatment. The projected increase in quality-adjusted years of life per year of treatment for secondary prevention was 3- to 12-fold higher than for primary prevention. To yield population-wide epidemiologic benefits equivalent to NCEP recommendations for secondary prevention, primary prevention would require a nearly sixfold increase in the number of persons treated compared with NCEP recommendations. All benefits of universal success of the NCEP primary prevention "screen and treat" guidelines could be achieved by a 11 mg/dl (8%) population-wide reduction in low-density lipoprotein cholesterol levels among persons without preexisting coronary heart disease.

CONCLUSIONS

The NCEP guidelines for targeted primary prevention can be a useful component of a rational public health strategy, but only as a complement to the more appealing strategies of secondary prevention and "across-the-board" programs to lower all cholesterol levels.

The correspondence between intention to avoid childbearing and subsequent fertility: a prospective analysis

CONTEXT

Retrospective studies of pregnancy intendedness have revealed some characteristics that can help identify which women are more likely than others to experience an unintended birth. A comparison of these findings with those from a prospective analysis may shed greater light on the characteristics associated with unintended pregnancy.

METHODS

Data were taken from the 1988 National Survey of Fertility Growth and a telephone reinterview of respondents conducted in 1990. Separate analyses were conducted of women intending to postpone childbearing for at least three years and of women intending to forgo all future childbearing. Logistic regression models were used to identify the effects of social and demographic characteristics, as well as change in marital status and certainty of intentions, on the odds of experiencing a birth in the interval between interviews.

RESULTS

Only 10% of women intending to postpone pregnancy for more than three years and 8% of respondents seeking to forgo future childbearing had a birth in the interval between interviews. (These births, referred to as unpredicted births in this article, are roughly analogous to those labeled unintended in retrospective analyses.) Women with incomes below the poverty level were 2-3 times as likely as women with incomes between 100% and 199% of poverty to experience an unpredicted birth. Race was not a significant factor among women intending to avoid future childbearing, and became nonsignificant among those intending to postpone when change in marital status and contraceptive status were taken into account. Women aged 35 and older who wanted no more children were significantly less likely than women aged 20-29 to have an unpredicted birth. Women aged 30-34 who wanted to postpone childbearing were roughly 70% less likely than women aged 20-29 to experience an unpredicted birth. Overall, women who were at risk for a pregnancy but not practicing contraception were 2-3 times more likely than women using an effective method to have an unpredicted birth.

CONCLUSIONS

There are at least two potential explanations for instances where the correlates of unintended births in the prospective analysis differ from those identified in retrospective studies. Certain subgroups of women may be more likely to classify births as wanted when they are asked retrospectively; alternatively, they may be more likely to experience changes in their living conditions that alter their fertility intentions.

Acute tolerance to methylphenidate in the treatment of attention deficit hyperactivity disorder in children

OBJECTIVES

To evaluate the efficacy of several drug delivery patterns of methylphenidate and to determine whether acute tolerance develops to this widely used stimulant medication in the treatment of children with attention deficit hyperactivity disorder.

METHODS

Double-blind trials were conducted in a laboratory school setting in which multiple measures of efficacy were obtained frequently in the morning and afternoon across the school day. In study I, relative efficacy was determined for three dosing patterns of methylphenidate: a standard twice-daily profile, a flat profile, and an ascending profile. In study II, tolerance was assessed by comparison of three-times-a-day regimens in which the time of the middle dose varied.

RESULTS

In study I, the efficacy of the ascending treatment increased across the day, and in the afternoon it was equal to the efficacy of the twice-daily treatment, indicating that an initial bolus was not required for efficacy. The efficacy of the flat treatment declined across the day, and in the afternoon it was significantly less than in the twice-daily treatment, suggesting that tolerance may be developing. In study II, acute improvements in efficacy were reduced to the second of two closely spaced but not to two widely spaced bolus doses, suggesting that shortly after exposure to high concentrations, efficacy is reduced to given concentrations of methylphenidate. In a concentration-effect model, a tolerance term was needed to account for counterclockwise hysteresis.

CONCLUSIONS

Acute tolerance to methylphenidate appears to exist. This should be considered in the design of an optimal dosing regimen for the treatment of children with attention deficit hyperactivity disorder.

Different psychopathological models and quantified EEG in schizophrenia

BACKGROUND

This study compared the ability of two different models of psychopathology in schizophrenia to account for findings in the quantified electroencephalogram (qEEG) recorded from midline sites in a group of 40 subjects with schizophrenia. The first model was based on the positive and negative syndrome dichotomy, the second was a tripartite model that resembled Liddle's syndromes of psychomotor poverty, disorganization and reality distortion (Liddle, 1987a).

METHODS

A group of 40 subjects with predominantly chronic schizophrenia was assessed with the Positive and Negative Syndrome Scale (PANSS) prior to the acquisition of their quantified electroencephalogram. The relationship between EEG data and symptomatology was explored, initially with the PANSS positive and negative subscales and then with a tripartite model derived From a principal component analysis of the 14 positive and negative subscale items.

RESULTS

The tripartite syndrome model showed a greater concordance with the qEEG of the subjects than the dichotomous model. 'Psychomotor poverty' was significantly positively correlated with both delta and beta power and 'reality distortion' was significantly positively correlated with alpha-2 power. No significant correlations between the positive and negative syndrome dichotomy and the qEEG were observed.

CONCLUSIONS

This study lends support to the factor analysis of psychopathology, and specifically the tripartite syndrome model of schizophrenia, as a step in explicating the biological dimensions of the disorder.

A database designed for utilization management in diagnostic imaging

The methods and tools of health services research have been applied to a diverse number of health care areas. Surprisingly, they have been adopted only recently in diagnostic imaging, by a small number of professionals, in response to the severe fiscal constraints and widespread structural changes in the health industry, as well as to a growing concern that the value of social and individual investment in high-cost imaging services could not be validated objectively. As a result of the need for accountability for the use of scarce resources, regulators and payers of health services increasingly demand that a reasoned and objective evaluative process be adopted. To undertake a statistically driven evaluative approach that stands up to objective assessment of methodological rigour, an organized data-collection system is needed. Without this fundamental cornerstone, evaluators are left with little more than anecdotal evidence and professional and personal opinion to guide decision-making. It then becomes difficult to learn from both the successes and failures that are routinely experienced during times of rapid and fundamental change. This article describes the efforts made to integrate health services research in radiology into the routine daily activities and supporting systems of a large academic health system, the Hamilton Health Sciences Corporation and McMaster University Department of Radiology, in an attempt to move in the direction of evidence-based decision-making. The authors hope this will allow others to learn and improve on this work. Radiologists may then move the vast data systems and infrastructure associated with all imaging services to an evidence-based model for managing and guiding the vast resources entrusted to our collective stewardship.

A simple in vitro method for the evaluation of an ultrasonic nebulizer for drug delivery to intubated, ventilated patients and the effect of nebulizer and ventilator settings on the uptake of fluid from the nebulizer chamber

Little is known about the performance of ultrasonic nebulizers during different ventilation patterns when these nebulizers are used to deliver drugs to intubated, ventilated patients. A method that enables the performance of an ultrasonic nebulizer to be evaluated is described. We used an in vitro model to examine the performance of the DeVilbiss Ultra-Neb 2000 ultrasonic nebulizer under positive pressure ventilation. Performance was measured at different rates of nebulization and under changing conditions of positive end-expiratory pressure (PEEP), inspiratory flow rate, inspiratory time and minute volume. The volume of saline nebulized was unchanged by variations in positive end expiratory pressure from 0 to 5 cm to 10 cm H2O, in minute ventilation and in inspiratory flow rate. An increase in the inspiratory time resulted in an increase in the volume of saline nebulized and this volume was greater as the power setting of the nebulizer was increased. We conclude that ultrasonic nebulizers may be affected by different patterns of ventilation and that this simple in vitro assessment of nebulizer function in an intensive care setting may be of value prior to nebulizer use.

Should equine athletes commence training during skeletal development?: changes in tendon matrix associated with development, ageing, function and exercise

In human athletes, conditioning, training and competition are commenced before skeletal maturity. Yet in equine athletics, racing of young (age 2 years) horses remains contentious. Tendon injury persists as major causes of wastage in equine athletes. Minimising injury and associated welfare issues could involve a radical approach to the timing and implementation of conditioning and training. Tendons were examined from Thoroughbreds, Dutch Warmblood foals, working horses and also a group of wild horses to evaluate effects of age, function and exercise. Gross mechanical properties did not differ significantly with age or exercise, but showed a high variance within each group. Mechanical properties of tendon tissue showed significant differences as a function of age and location. The collagen fibril crimp angle and length showed a regional reduction in the central core with exercise and age, with a synergistic effect. Regional differences in collagen fibril diameter were seen in long-term exercised older horses, but not in short-term exercised, or younger, horses. The higher proportion of small fibrils in the central region of the long-term exercised horses did not correlate with new collagen formation and therefore appear to result from disassembly of the larger diameter fibrils. Fibril diameter distributions were influenced by exercise regimens in the growing foal. Changes in molecular composition occurred in longer-term exercise and older horses, in the centre of the tendon, with higher levels of type III collagen and changes in glycosaminoglycan (GAG) content. Cartilage Oligomeric Matrix Protein (COMP) levels also appear to be modulated by age, function and superimposition of exercise. These changes were all exacerbated with age and exercise, suggesting appropriate exercise in young horses may lead to a lower incidence of injury than in older horses. An hypothesis is advanced that immature tendon can respond to exercise while mature tendon has limited, if any, ability to do so. These findings support potentially controversial earlier conditioning and racing of younger, rather than older, equine athletes.

Monocyte adhesion and spreading on human endothelial cells is dependent on Rho-regulated receptor clustering

The GTPase Rho is known to mediate the assembly of integrin-containing focal adhesions and actin stress fibers. Here, we investigate the role of Rho in regulating the distribution of the monocyte-binding receptors E-selectin, ICAM-1, and VCAM-1 in human endothelial cells. Inhibition of Rho activity with C3 transferase or N19RhoA, a dominant negative RhoA mutant, reduced the adhesion of monocytes to activated endothelial cells and inhibited their spreading. Similar effects were observed after pretreatment of endothelial cells with cytochalasin D. In contrast, dominant negative Rac and Cdc42 proteins did not affect monocyte adhesion or spreading. C3 transferase and cytochalasin D did not alter the expression levels of monocyte-binding receptors on endothelial cells, but did inhibit clustering of E-selectin, ICAM-1, and VCAM-1 on the cell surface induced by monocyte adhesion or cross-linking antibodies. Similarly, N19RhoA inhibited receptor clustering. Monocyte adhesion and receptor cross-linking induced stress fiber assembly, and inhibitors of myosin light chain kinase prevented this response but did not affect receptor clustering. Finally, receptor clusters colocalized with ezrin/moesin/ radixin proteins. These results suggest that Rho is required in endothelial cells for the assembly of stable adhesions with monocytes via the clustering of monocyte-binding receptors and their association with the actin cytoskeleton, independent of stress fiber formation.

Epstein-Barr virus encodes a novel homolog of the bcl-2 oncogene that inhibits apoptosis and associates with Bax and Bak

The sequenced gammaherpesviruses each contain a single viral bcl-2 homolog (v-bcl-2) which may encode a protein that functions in preventing the apoptotic death of virus-infected cells. Epstein-Barr virus (EBV), a gammaherpesvirus associated with several lymphoid and epithelial malignancies, encodes the v-Bcl-2 homolog BHRF1. In this report the previously uncharacterized BALF1 open reading frame in EBV is identified as having significant sequence similarity to other v-bcl-2 homologs and cellular bcl-2. Transfection of cells with a BALF1 cDNA conferred apoptosis resistance. Furthermore, a recombinant green fluorescent protein-BALF1 fusion protein suppressed apoptosis and associated with Bax and Bak. These results indicate that EBV encodes a second functional v-bcl-2.

Physico-chemical analysis of Bordetella pertussis antigens

Physico-chemical methods are being developed for use in the control and standardization of acellular pertussis vaccines and their individual components. We have compared native and detoxified preparations of the B. pertussis antigens, pertussis toxin (PT), filamentous haemagglutinin (FHA), and the 69-kDa outer membrane protein (P69) using circular dichroism (CD), fluorescence spectroscopy, SDS-PAGE and FPLC gel filtration chromatography. Upon aldehyde detoxification, PT underwent a large change in its intrinsic fluorescence maximum (8-10 nm red-shift) and a large increase in its apparent size, detected by chromatography. Polyacrylamide gels showed individual subunits of the same apparent molecular weight (M(r)) as well as some polypeptides of higher M(r). FHA also changed conformation (5-nm red-shift in intrinsic fluorescence) upon aldehyde detoxification, with a resultant increase in the M(r)of its major constituent. The P69 protein appeared quite robust to formaldehyde treatment as measured by the same methods. Its near-UV CD spectrum contains a prominent tryptophan band; so this method may be more suitable for observing differences in conformation. We also examined an aluminium-desorbed DTaP preparation by these methods. When used in conjunction with immunochemical and toxicological assays, these methods are informative and useful in the characterization of candidate standards and should be valuable methods for ensuring the consistency of manufactured vaccines.

Evaluation of transmission electron microscopy for examination of components of acellular pertussis and combination vaccines

New acellular pertussis and combination vaccines vary in the concentration and presence or absence of specific components and in extent of adsorption to adjuvants. There is a pressing need to develop new control methods for acellular pertussis vaccines. Negative staining electron microscopy has been evaluated as a method for assessing the purity of individual vaccine components and the amount of adsorption to aluminium gels. Negative staining showed the characteristic morphology of vaccine components and permitted detection of contaminants and morphological changes. Reproducible results were obtained by use of a standardized negative staining technique and confidence in the technique was increased by comparison of previously unexamined specimens with a specimen that had been characterized by repeated observations. The degree of adsorption to aluminium adjuvants could only be assessed by observation of the amount of non-adsorbed material in the specimen. Negative staining electron microscopy can be used as one of a number of techniques for control of acellular pertussis combination vaccines.

An aerosol challenge model of Bordetella pertussis infection as a potential bioassay for acellular pertussis vaccines

Whole cell and five different types of acellular pertussis vaccine were assayed using a mouse aerosol challenge model which permitted delivery of a controlled, consistent dose of Bordetella pertussis to the lower respiratory tract. Using this system, the viable counts in the lungs of vaccinated mice were immunisation dose-dependent and allowed the protective capacity of different vaccine preparations to be distinguished. This model may thus provide the basis for a protection assay for pertussis vaccines. Comparison of acellular vaccines with a whole cell pertussis vaccine showed that the latter gave better active protection in mice but with a different dose-response relationship. Thus the two types of vaccine are not directly comparable in the same assay and require different reference standards. A pentavalent type acellular vaccine is suggested as a possible candidate standard for the acellular vaccine potency test. The results suggest that this aerosol challenge model has potential for use as a potency test for acellular pertussis vaccines.

Rape attitudes amongst British medical students

OBJECTIVES

To examine the rape attitudes of a sample of 252 British medical students.

DESIGN

A 20-item questionnaire was used.

SETTING

A London medical school.

SUBJECTS

Fourth-year medical students.

RESULTS

In general, students were well informed on legal and factual issues regarding rape and sexual assault. However, significant differences were found in the attitudes to rape between males and females. Female students were significantly more positive in their responses to victims.

CONCLUSIONS

These results support findings from previous studies of rape attitudes in other professional groups. Better knowledge and enlightened attitudes amongst health care staff can have a significant impact on the management of sexual assault and influence the likelihood of victims presenting for treatment. In conclusion, this study emphasizes the importance of teaching about sexual violence in British medical schools.

Trinucleotide (CAG) repeat length is positively correlated with the degree of DNA fragmentation in Huntington's disease striatum

Recent studies using DNA fragmentation assays suggest a role for apoptosis in cell death in Huntington's disease. In this study, we investigated the relationship between the degree of DNA fragmentation and the number of trinucleotide (CAG) repeats of the Huntington's disease gene in striatal tissue from Huntington's disease brains. We used frozen striatal tissue from 27 post mortem Huntington's disease brains (graded 0-4 on the Vonsattel classification, post mortem delay ranging from 4 to 41 h), plus control sections which were age, sex and post mortem delay matched from neurologically normal and Alzheimer's diseased striatal tissue. Our results show a significant positive correlation between the number of CAG repeats in the Huntington's disease gene and the degree of DNA fragmentation in Huntington's disease striatum. These results suggest that expanded CAG repeats in the Huntington's disease gene may lead to neuronal degeneration in Huntington's disease through an apoptotic mechanism.

Complement factor H or a related protein is a marker for transitional cell cancer of the bladder

The BTAstat and BTA TRAK tests are new immunoassays that detect and measure an antigen in the urine of individuals diagnosed with bladder cancer. As described in this report, the monoclonal antibodies used in these kits were developed by immunizing mice with partially purified protein preparations derived from the urine of patients with bladder cancer. The antigen that is recognized by the monoclonal antibodies was purified from the urine of bladder cancer patients by immunoaffinity chromatography and identified as being either complement factor H (FH) or a closely related protein (CFHrp) by partial amino acid sequence analysis. Like serum FH, the urine antigen was demonstrated to have a complement factor C3b binding site and to accelerate the degradation of C3b in the presence of complement factor I. The culture supernatants from several human bladder, cervical, and renal cancer cell lines contained antigen as determined by immunoassay, and antigen affinity-purified from HeLaS3 culture media was shown to have FH activity. Moreover, the cell lines were shown to make products of the expected sizes by reverse transcription-PCR using FH-specific primers. In contrast, normal human epithelial keratinocytes, a myeloid leukemia cell line, and the colon cancer line LS174T were negative for production of a FH-like protein (CFHrp). We propose that the expression of proteins with FH-like activities may confer a selective growth advantage to cancer cells in vivo by decreasing complement activity, thus aiding their escape from lysis by immune surveillance. Identification of these proteins as cancer products also suggests avenues of chemotherapy or immunotherapy of some cancers.

Multidimensional correlates of falls in older women

Older women who had fallen within the last year (n = 63) were compared with those who had not fallen (n = 67) on several psychological and motor measures. Both fallers and nonfallers demonstrated high levels of functioning. Discriminant analysis results indicated that a combination of variables, including physical activity and both psychological (general well-being, self-efficacy) and motor (functional reach, mobility) measures differentiated fallers and nonfallers. Results suggest that falling is a multidimensional phenomenon, that small declines on multiple factors may increase risk of falls, and that multifaceted interventions may help maintain high levels of functioning and prevent declines often associated with increased age.

Junctional adhesion molecule, a novel member of the immunoglobulin superfamily that distributes at intercellular junctions and modulates monocyte transmigration

Tight junctions are the most apical components of endothelial and epithelial intercellular cleft. In the endothelium these structures play an important role in the control of paracellular permeability to circulating cells and solutes. The only known integral membrane protein localized at sites of membrane-membrane interaction of tight junctions is occludin, which is linked inside the cells to a complex network of cytoskeletal and signaling proteins. We report here the identification of a novel protein (junctional adhesion molecule [JAM]) that is selectively concentrated at intercellular junctions of endothelial and epithelial cells of different origins. Confocal and immunoelectron microscopy shows that JAM codistributes with tight junction components at the apical region of the intercellular cleft. A cDNA clone encoding JAM defines a novel immunoglobulin gene superfamily member that consists of two V-type Ig domains. An mAb directed to JAM (BV11) was found to inhibit spontaneous and chemokine-induced monocyte transmigration through an endothelial cell monolayer in vitro. Systemic treatment of mice with BV11 mAb blocked monocyte infiltration upon chemokine administration in subcutaneous air pouches. Thus, JAM is a new component of endothelial and epithelial junctions that play a role in regulating monocyte transmigration.