A single growth cone is capable of integrating simultaneously presented and functionally distinct molecular cues during target recognition

A variety of cell recognition pathways affect neuronal target recognition. However, whether such pathways can converge at the level of a single growth cone is not well known. The RP3 motoneuron in Drosophila has previously been shown to respond to the muscle cell surface molecules TOLL and fasciclin III (FAS3), which are normally encountered during RP3 pathfinding in a sequential manner. TOLL and FAS3, putative "negative" and "positive" recognition molecules, respectively, affect RP3 antagonistically. Under normal conditions, TOLL and FAS3 together improve the accuracy of its target recognition. Here, we show that, when presented with concurrent TOLL and FAS3 expression, RP3 responds to both, integrating their effects. This was demonstrated most succinctly by single cell visualization methods. When a balance in relative expression levels between the two antagonistic cues is achieved, the RP3 growth cone exhibits a phenotype virtually identical to that seen when neither TOLL nor FAS3 is misexpressed. Thus, growth cones are capable of quantitatively evaluating distinct recognition cues and integrating them to attain a net result, in effect responding to the "balance of power" between positive and negative influences. We suggest that the ability to integrate multiple recognition pathways in real-time is one important way in which an individual growth cone interprets and navigates complex molecular environments.

Economic determinants and dietary consequences of food insecurity in the United States

This paper reviews recent research on the economic determinants and dietary consequences of food insecurity and hunger in the United States. The new Current Population Study (CPS) food insecurity and hunger measure shows that hunger rates decline sharply with rising incomes. Despite this strong relationship, confirmed in other national datasets, a one-to-one correspondence between poverty-level incomes and hunger does not exist. In 1995, 13.1% of those in poverty experienced hunger and half of those experiencing hunger had incomes above the poverty level. Panel data indicate that those who are often food insufficient are much more likely than food-sufficient households to have experienced recent events that stress household budgets, such as losing a job, gaining a household member or losing food stamps. Cross-sectional work also demonstrates the importance of food stamps because benefit levels are inversely related to food insufficiency. Concern for the dietary consequences of domestic food insufficiency is well placed; recent research shows that the odds of consuming intakes <50% of the recommended dietary allowance (RDA) are higher for adult women and elderly individuals from food-insufficient households. Preschoolers from food-insufficient households do not consume significantly lower amounts than those from food-sufficient households, but mean intakes for the rest of members in those very same households are significantly lower for the food insufficient. This research highlights the importance of food insecurity and hunger indicators, further validates the use of self-reported measures and points to areas of need for future research and interventions.

"Painting" the target: how local molecular cues define synaptic relationships

A majority of studies on neuronal growth cones focus on the features that particular groups of neurons share. In contrast, questions such as how specific growth cones respond very differently to the same extrinsic cues require cell-specific experimentation. The most succinct cell-specific growth cone responses occur during synaptic targeting. Recent studies have examined one specific growth cone, the Drosophila RP3 motoneuron growth cone, in variously altered microenvironments. In this review, we summarize how such studies are beginning to uncover the repertoire of extrinsic cues that influence the synaptic targeting of a single growth cone.

A nematode kinesin required for cleavage furrow advancement

Dividing cells need to coordinate the separation of chromosomes with the formation of a cleavage plane. There is evidence that microtubule bundles in the interzone region of the anaphase spindle somehow control both the location and the assembly of the cleavage furrow [1-3]. A microtubule motor that concentrates in the interzone, MKLP1, has previously been implicated in the assembly of both the metaphase spindle and the cleavage furrow [4-6]. To gain insight into mechanisms that might underlie interdependence of the spindle and the cleavage furrow, we used RNA-mediated interference (RNAi) to study the effects of eliminating MKLP1 from Caenorhabditis elegans embryos. Surprisingly, in MKLP1(RNAi) embryos, spindle formation appears normal until late anaphase. Microtubule bundles form in the spindle interzone and the cleavage furrow assembles; anaphase and cleavage furrow ingression initially appear normal. The interzone bundles do not gather into a stable midbody, however, and furrow contraction always fails before complete closure. This sequence of relatively normal mitosis and a late failure of cytokinesis continues for many cell cycles. These and additional results suggest that the interzone microtubule bundles need MKLP1 to encourage the advance and stable closure of the cleavage furrow.

Increasing prevalence of HIV antibody among blood donors monitored over 9 years in one blood bank

To determine the time trend of HIV infection among non-professional blood donors at the Christian Medical College and Hospital, Vellore, the annual HIV prevalence among them for the years 1993-1997 was compared with that of the previous 5 yr. Since confirmed number of HIV positive blood donors is required for calculation of prevalence, the serum samples which were reactive for HIV 1/2 antibody by ELISA, were confirmed by Western blot. The annual prevalence of HIV antibody gradually increased from 1.6 per 1000 in 1988-1989, to 3.8 per 1000 in 1996-1997. The mean tri-annual prevalences for the years 1988-91, 1991-94 and 1994-97 were 1.3, 2.7 and 3.6 per 1000 respectively, suggesting a slow but steady increase in HIV prevalence over time. Our findings provide an insight into the dynamics of HIV infection in the general population of our country, whom the nonprofessional blood donors at our hospital represent.

Motion perception: from phi to omega

When human observers view dynamic random noise, such as television 'snow', through a curved or annular aperture, they experience a compelling illusion that the noise is moving smoothly and coherently around the curve (the 'omega effect'). In several series of experiments, we have investigated the conditions under which this effect occurs and the possible mechanisms that might cause it. We contrast the omega effect with 'phi motion', seen when an object suddenly changes position. Our conclusions are that the visual scene is first segmented into objects before a coherent velocity is assigned to the texture on each object's surface. The omega effect arises because there are motion mechanisms that deal specifically with object rotation and these interact with pattern mechanisms sensitive to curvature.

Development of scales to measure psychosocial care needs of children with seizures and their parents. 1

There is little research and no self-report assessment instruments available to guide nurses in the provision of psychosocial care to children with seizures and their families. Information on the development of two instruments, Report of Psychosocial Care Scale and Child Report of Psycyhosocial Care Scale, and their use in a research study to measure psychosocial care of children with new-onset seizures and their parents are presented in three parts. This first article describes development and initial testing of their psychometric properties. The second article, Part 2, "Psychosocial Care Needs of Parents of Children with New-Onset Seizures," describes results from the use of the parent scale with mothers and fathers of children with new-onset seizures. The third article, Part 3, "Psychosocial Care Needs of Children with New-Onset Seizures," reports findings from the use of the child scale with children ages 8-14 years with new-onset seizures.

Household participation in the Food Stamp and WIC programs increases the nutrient intakes of preschool children

We examined the effects of household participation in the Food Stamp and WIC Nutrition Programs on the nutrient intakes of preschoolers using data from the 1989-1991 Continuing Survey of Food Intake by Individuals. Nonbreastfeeding children, 1-4 y of age, with 3 d of dietary data and whose households had incomes < 130% of the poverty level were included in the study sample (n = 499). Nutrient adequacy ratios for each of 15 nutrients were the dependent variables in multiple regression models that controlled for the following: age, sex and ethnicity of the individual; income, size and location of the household; schooling of the household head; home ownership; school lunch and breakfast participation; and season in which the interview was conducted. WIC benefits positively influenced (P < 0. 05) the intakes of 10 nutrients. For iron and zinc, the average increase due to WIC represented 16.6 and 10.6%, respectively, of the preschooler recommended dietary allowance (RDA) for these nutrients. The same analyses of the Food Stamp Program revealed increases in five nutrients. For iron and zinc, the average increase due to Food Stamps represented 12.3 and 9.2%, respectively, of the preschooler RDA. The effects of the WIC Program on the intakes of iron and zinc were greater than that of cash income, and neither program affected the intakes of fat, saturated fat or cholesterol.

Psychological and socio-medical aspects of HIV/AIDS: a reflection on publications in AIDS care (1989-1995)

It is necessary to consider the content and methods of AIDS social research publications for these represent research advances as well as current issues of concern for practitioners, communities and researchers alike. This article critically examines some of the research that has been conducted to date into social aspects of HIV and AIDS. It quantifies the content and major methodological style of publications in the journal AIDS Care from 1989 to 1995. The most commonly published topic area in AIDS Care, during this period was cultural and demographic issues (15.9%), followed by issues pertinent to the psychological impact of HIV (13.6%), sexual behaviour and condom use (11.3%) and policy and services (9.5%). Research and measurement issues were the least examined content area in AIDS Care 1989-1995 (2.6%). This article discusses possible variables that influence the style and topics that are published in AIDS Care and makes suggestions for authors to consider before embarking on future research projects or publications.

Environmental tobacco smoke exposure in the home and worksite and health effects in adults: results from the 1991 National Health Interview Survey

OBJECTIVE

To determine the effect of environmental tobacco smoke (ETS) exposure in the home and worksite on the health of adults in the United States.

DESIGN

Cross-sectional survey.

SETTING

Nationally representative population.

PARTICIPANTS

43,732 adults who completed the Health Promotion and Disease Prevention supplement in the 1991 National Health Interview Survey.

MAIN OUTCOME MEASURES

Rate of restricted activity, bed confinement, and work absence in the two weeks preceding the survey and self-reported health status among adults with and without exposure to ETS.

RESULTS

We found that only 20.2% of never-smokers and 23.1% of former smokers reported exposure to ETS at home or work, whereas 87.2% of current smokers reported exposure to ETS. Among never-smokers, after adjusting for covariates, people who were exposed to ETS were more likely to report one or more days of restricted activity (relative risk (RR) = 1.27, 95% confidence interval (CI) = 1.10 to 1.46), one or more days of bed confinement (RR = 1.43, 95% CI = 1.19 to 1.73), and one or more days of work absence (RR = 1.33, 95% CI = 1.05 to 1.73) in the two weeks before the survey than were people without such exposure. We detected smaller trends for one or more days of restricted activity among current and former smokers (RR = 1.16, 95% CI = 0.97 to 1.40; and RR = 1.11, 95% CI = 0.82 to 1.51), one or more days of bed confinement among current smokers (RR = 1.34, 95% CI = 0.95 to 1.88), and one or more days of work absence among former smokers (RR = 1.13, 95% CI = 0.84 to 1.50) in the two weeks before the survey than among people without such exposure, although the CIs were wide and chance cannot be excluded as an explanation for these findings. Never-smokers (RR = 1.47, 95% CI = 1.34 to 1.62), former smokers (RR = 1.22, 95% CI = 1.07 to 1.39) and current smokers (RR = 1.31, 95% CI = 1.10 to 1.56) exposed to ETS were all more likely to report a less than very good health status than were people without such exposure.

CONCLUSIONS

This study demonstrates that never-smoking adults exposed to ETS report more acute health effects than unexposed, never-smoking adults, and suggests similar findings in current and former smoking adults.

Nutrient intakes of individuals from food-insufficient households in the United States

OBJECTIVES

Understanding the nutritional consequences of food insufficiency is important for informed policy-making that addresses the problem of domestic hunger. This study estimated the extent to which individuals from food-insufficient households were likely to have low intakes of energy and 14 other nutrients.

METHODS

The diets of pre-schoolers, adult women, and the elderly were analyzed with 24-hour recall data from the 1989 through 1991 Continuing Survey of Food Intake by Individuals. Logistic regression analysis was used to study the association of self-reported household food insufficiency with nutrient intakes below 50% of the recommended daily allowance.

RESULTS

For adult women, food insufficiency was significantly associated with low intakes of eight nutrients, including energy, magnesium, and vitamins A, E, C, and B6. Elderly individuals in the food-insufficient group were also more likely to have low intakes of eight nutrients, including protein, calcium, and vitamins A and B6. Household food insufficiency was not significantly associated with low intakes among preschoolers.

CONCLUSIONS

The results validate the use of self-reported hunger measures in nutritional surveillance and highlight nutrients of concern for food assistance and nutrition education efforts targeted at individuals from food-insufficient households.

The ESRC review of government social classifications

In this article we first discuss the background to the ESRC Review of Government Social Classifications and the recommendations of the Review Committee's initial report to the Office for National Statistics in 1995. Second, we discuss the work of Phase 2 of the review, including the derivation of an interim version of a proposed revised government social classification schema and the criterion and construct validation work so far undertaken using this schema. Finally, we indicate the further work required to establish the schema in its ultimate recommended form for use by ONS and others. The main purpose of the paper is to introduce users of government social classifications both to the ideas underlying the review and to the revised version of the current classifications which we shall be recommending to ONS.

Prospective case-control study of role of infection in patients who reconsult after initial antibiotic treatment for lower respiratory tract infection in primary care

OBJECTIVE

To assess direct and indirect evidence of active infection which may benefit from further antibiotics in adults who reconsult within 4 weeks of initial antibiotic management of acute lower respiratory tract infection in primary care.

DESIGN

Observational study with a nested case-control group.

SETTING

Two suburban general practices in Arnold, Nottingham, over 7 winter months.

SUBJECTS

367 adults aged 16 years and over fulfilling a definition of lower respiratory tract infection and treated with antibiotics. 74 (20%) patients who reconsulted within 4 weeks for the same symptoms and 82 "control" patients who did not were investigated in detail at fallow up.

MAIN OUTCOME MEASURES

Direct and indirect evidence of active infection at the time of the reconsultation or the follow up visit with the research nurse for the controls. Investigations performed included sputum culture, pneumococcal antigen detection, serial serology for viral and atypical pathogens and C reactive protein, throat swabs for detecting viral and atypical pathogens by culture and polymerase chain reaction, and chest radiographs.

RESULTS

Demographic and clinical features of the groups were similar. Two thirds of the 74 patients who reconsulted received another antibiotic because the general practitioner suspected continuing infection. Any evidence of infection warranting antibiotic treatment was uncommon at reconsultation. The findings for the two groups were similar for the occurrence of identified pathogens; chest x ray changes of infection (present in 13%); and C reactive protein concentrations, which had nearly all fallen towards normal. Only three patients in the reconsultation group had concentrations > or = 40 mg/l. Pathogens identified at follow up in the 156 patients in both groups included ampicillin sensitive bacteria in six. Atypical infections diagnosed in 27 (Chlamydia pneumoniae in 22) and viral infections in 54 had probably been present at the initial presentation.

CONCLUSION

Our study suggests that active infection, which may benefit from further antibiotics, is uncommon in patients who reconsult after a lower respiratory tract infection, and a repeat antibiotic prescription should be the exception rather than the rule. Other factors, such as patients' perception of their illness, may be more important than disease and infection in their decision to reconsult.

Mental health. Heads and tales

Interviews conducted by other users can be a successful means of capturing mental health users' views on services. In this study, more than a third of those with severe mental health problems considered themselves over-medicated, and many wanted more 'talking therapies'. More than three-quarters were satisfied with their community psychiatric nurse but under half were satisfied with their consultant. A fifth did not know how to get help in a crisis.

Homophilic synaptic target recognition mediated by immunoglobulin-like cell adhesion molecule Fasciclin III

We demonstrate that the cell adhesion molecule Fasciclin III (FAS3) mediates synaptic target recognition through homophilic interaction. FAS3 is expressed by the RP3 motoneuron and its target muscles during synaptic target recognition. The RP3 growth cone can form synapses on muscles that ectopically express FAS3. This mistargeting is dependent on FAS3 expression in the motoneurons. In addition, when the FAS3-negative aCC and SNa motoneuron growth cones ectopically express FAS3, they gain the ability to recognize FAS3-expressing muscles as alternative targets. We propose that homophilic synaptic target recognition serves as a basic mechanism of neural network formation.

Invasive infections due to a fish pathogen, Streptococcus iniae. S. iniae Study Group

BACKGROUND

Streptococcus iniae is a pathogen in fish, capable of causing invasive disease and outbreaks in aquaculture farms. During the winter of 1995-1996 in the greater Toronto area there was a cluster of four cases of invasive S. iniae infection in people who had recently handled fresh, whole fish from such farms.

METHODS

We conducted a prospective and retrospective community-based surveillance for cases of S. iniae infection in humans. To obtain a large sample of isolates, we studied cultures obtained from the surface of fish from aquaculture farms. Additional isolates were obtained from the brains of infected tilapia (oreochromis species). All the isolates were characterized by pulsed-field gel electrophoresis (PFGE).

RESULTS

During one year, our surveillance identified a total of nine patients with invasive S. iniae infection (cellulitis of the hand in eight and endocarditis in one). All the patients had handled live or freshly killed fish, and eight had percutaneous injuries. Six of the nine fish were tilapia, which are commonly used in Asian cooking. Thirteen additional S. iniae isolates (2 from humans and 11 from infected tilapia) were obtained from normally sterile sites. The isolates from the nine patients were indistinguishable by PFGE and were highly related to the other clinical isolates. There was substantial genetic diversity among the 42 surveillance isolates from the surface of fish, but in 10 isolates the PFGE patterns were identical to those from the patients with S. iniae infection.

CONCLUSIONS

S. iniae can produce invasive infection after skin injuries during the handling of fresh fish grown by aquaculture. We identified a clone of S. iniae that causes invasive disease in both humans and fish.

Principles of an adaptive method for measuring the slope of the psychometric function

Recent developments in the efficient estimation of threshold are here extended to the problem of how best to estimate the slope of the psychometric function. An adaptive method is described for selecting stimulus intensities that are optimal for slope estimation. A two-dimensional array of probabilities of different thresholds and slopes is used to calculate the stimulus intensity for the next trial; this array is updated after the trial, using Bayes' theorem to incorporate information from the subject's response. The practical implementation and efficiency of the method are demonstrated and discussed.

Toll, a muscle cell surface molecule, locally inhibits synaptic initiation of the RP3 motoneuron growth cone in Drosophila

Toll, a transmembrane molecule with extracellular leucine-rich repeats, is dynamically expressed by the Drosophila embryonic musculature. Growth cones of RP3 and other motoneurons normally grow past Toll-positive muscle cells and innervate more distal muscle cells, which have down-regulated their Toll expression. In this study, we show that reciprocal genetic manipulations of Toll proteins can produce reciprocal RP3 phenotypes. In Toll null mutants, the RP3 growth cone sometimes innervates incorrect muscle cells, including those that are normally Toll-positive. In contrast, heterochronic misexpression of Toll in the musculature leads to the same growth cone reaching its correct target region but delaying synaptic initiation. We propose that Toll acts locally to inhibit synaptogenesis of specific motoneuron growth cones and that both temporal and spatial control of Toll expression is crucial for its role in development.

Expression of the invasive phenotype by MCF-7 human breast cancer cells transfected to overexpress protein kinase C-alpha or the erbB2 proto-oncogene

Transfection of the estrogen dependent and poorly invasive MCF-7 cell line to overexpress erbB2 was reported to increase athymic nude mouse mammary fat pad tumor growth; similar PKC-alpha overexpression produced a rapidly growing and metastatic transfectant. We investigated the invasive capacities of the two transfectants in vitro, their secretion of the proteolytic enzymes metalloproteinase (MMP)-9 and -2 and urokinase-type plasminogen activator (uPA), and plasminogen activator inhibitor-1 (PAI-1), together with membrane uPA receptor (uPAR) levels as determined by ELISA. Compared with the MCF-7 cells, the erbB2 transfectant was more invasive and secreted higher levels of MMP-9 and uPA; also there was a greatly enhanced PAI-1 secretion and cellular uPAR expression. The PKC-alpha transfectant cells secreted extremely high levels of uPA and some MMP-9 and MMP-2, with an intermediate increase in uPAR; however, they were so poorly adherent that it was not possible to assess invasiveness in vitro. Thus, erbB2-overexpressing MCF-7 cells possessed several features associated with the invasive phenotype. The reportedly aggressive metastatic phenotype induced by PKC-alpha overexpression, however, was notable only for its uPA hypersecretion.

Enduring stereoscopic motion aftereffects induced by prolonged adaptation

This study investigated the effects of prolonged adaptation on the recovery of the stereoscopic motion aftereffect (adaptation induced by moving binocular disparity information). The adapting and test stimuli were stereoscopic grating patterns created from disparity, embedded in dynamic random-dot stereograms. Motion aftereffects induced by luminance stimuli were included in the study for comparison. Adaptation duration was either 1, 2, 4, 8, 16, 32 or 64 min and the duration of the ensuing aftereffect was the variable of interest. The results showed that aftereffect duration was proportional to the square root of adaptation duration for both stereoscopic and luminance stimuli; on log-log axes, the relation between aftereffect duration and adaptation duration was a power law with the slope near 0.5 in both cases. For both kinds of stimuli, there was no sign of adaptation saturation even at the longest adaptation duration.

A mathematical model for analysis of pharmacologically induced changes in the kinetics of cardiac muscle

A mathematical model of the isometric contraction of cardiac muscle is developed and utilized to characterize the inotropic and lusitropic effects of cardioactive compounds in isolated guinea pig left atria. In contrast to metrics that are based on minima and maxima of an isometric twitch and its derivative function, the entire time course of the twitch is used to quantify the kinetics of the contraction-relaxation cycle. The model relates observed tension to a time-dependent activation function that describes generation of internal force and a coupling function that determines mechanical response to the activation function. The model is structured so that it is suitable for nonlinear curve fitting to observed data. Results obtained using the model for fitting experimental data from tissues treated with different classes of cardioactive compounds agree with more qualitative results presented by other authors. Experiments using the model to fit data over an extended (90 min) time course revealed differences in the kinetic profiles of milrinone and forskolin. Computer simulations that demonstrate the effect of each model parameter on twitch kinetics are presented, and the relationships between the model and other theoretical and empirical models of cardiac muscle are discussed. The mathematical model is useful to enable a more quantitative understanding of the kinetics of cardiac muscle contraction and relaxation and identify compounds that may be selective for inotropic or lusitropic effects.