TECRA Listeria Visual Immunoassay (TLVIA) for Detection of Listeria in Foods: Collaborative Study

A collaborative study involving 26 laboratories and 5 food types was performed to compare the TECRA Listeria Visual Immunoassay (TLVIA) with standard culture methods. Three foods (lettuce, ice cream, and fish fillets), under the jurisdiction of the U.S. Food and Drug Administration, and 2 foods (cooked chicken and cooked ground turkey), under the jurisdiction of the U.S. Department of Agriculture, were used to determine the effectiveness of the TLVIA. Of the 900 samples tested, 300 were inoculated with low levels (1-5 cells/25 g) of Listeria spp. and 300 were inoculated with high levels of Listeria spp. (10-50 cells/25 g). Method agreement between the conventional culture methods and TLVIA (visual) was 94.7%. Method agreement between the conventional culture methods and TLVIA (reader) was 93.6%. The colorimetric polyclonal enzyme immunoassay (TLVIA) for detection of Listeria in foods has been adopted first action by AOAC INTERNATIONAL.

Validation of a low field Rheo-NMR instrument and application to shear-induced migration of suspended non-colloidal particles in Couette flow

Nuclear magnetic resonance rheology (Rheo-NMR) is a valuable tool for studying the transport of suspended non-colloidal particles, important in many commercial processes. The Rheo-NMR imaging technique directly and quantitatively measures fluid displacement as a function of radial position. However, the high field magnets typically used in these experiments are unsuitable for the industrial environment and significantly hinder the measurement of shear stress. We introduce a low field Rheo-NMR instrument (¹H resonance frequency of 10.7MHz), which is portable and suitable as a process monitoring tool. This system is applied to the measurement of steady-state velocity profiles of a Newtonian carrier fluid suspending neutrally-buoyant non-colloidal particles at a range of concentrations. The large particle size (diameter >200μm) in the system studied requires a wide-gap Couette geometry and the local rheology was expected to be controlled by shear-induced particle migration. The low-field results are validated against high field Rheo-NMR measurements of consistent samples at matched shear rates. Additionally, it is demonstrated that existing models for particle migration fail to adequately describe the solid volume fractions measured in these systems, highlighting the need for improvement. The low field implementation of Rheo-NMR is complementary to shear stress rheology, such that the two techniques could be combined in a single instrument.

Phenotypic landscape of a bacterial cell

The explosion of sequence information in bacteria makes developing high-throughput, cost-effective approaches to matching genes with phenotypes imperative. Using E. coli as proof of principle, we show that combining large-scale chemical genomics with quantitative fitness measurements provides a high-quality data set rich in discovery. Probing growth profiles of a mutant library in hundreds of conditions in parallel yielded > 10,000 phenotypes that allowed us to study gene essentiality, discover leads for gene function and drug action, and understand higher-order organization of the bacterial chromosome. We highlight new information derived from the study, including insights into a gene involved in multiple antibiotic resistance and the synergy between a broadly used combinatory antibiotic therapy, trimethoprim and sulfonamides. This data set, publicly available at http://ecoliwiki.net/tools/chemgen/, is a valuable resource for both the microbiological and bioinformatic communities, as it provides high-confidence associations between hundreds of annotated and uncharacterized genes as well as inferences about the mode of action of several poorly understood drugs.

Features of the Value Function for Voice and Their Consistency across Participants from Four Countries: Great Britain, Mexico, The Netherlands, and the United States

This study investigated features of the value function for voice using subjects from four countries: Great Britain, Mexico, The Netherlands, and the United States. Across these four groups of subjects the shape of the value function was found to be similar, though differences in the estimated reference points were detected. Consistent with predictions derived from prospect theory (Kahneman & Tversky, 1979) the relationship between the value of voice and the magnitude of voice was found to be direct, monotonic, and nonlinear. The largest increment in value occurred when the magnitude of voice shifted from mute to some voice. Thereafter, increments in value tended to decline in magnitude suggesting diminishing marginal returns on the response measure of procedural fairness. An unexpected finding was that the final segment of the value function was convex indicating increasing marginal returns as the magnitude of voice shifted from its penultimate level to its maximum possible level. The study also investigated whether subjects' reported expectations of voice correspond to the value function reference point as theorized in the literature. Findings suggest that self-reported expectations of voice are higher than the estimated value function reference point.

Patterns of coping preferences for male and female caregivers of frail older adults

The similarities and differences in male and female caregivers' preferred strategies for coping and the perceived helpfulness of these strategies in managing caregiving stressors were examined in this study. Respondents were 170 caregivers (139 women and 31 men) who were primary caregivers for an elderly adult relative who was either cognitively impaired or physically frail. Results provide preliminary evidence that gender is related to frequency of use but not to the perceived helpfulness of specific coping strategies.

Patterns of coping preferences for male and female caregivers of frail older adults

The similarities and differences in male and female caregivers' preferred strategies for coping and the perceived helpfulness of these strategies in managing caregiving stressors were examined in this study. Respondents were 170 caregivers (139 women and 31 men) who were primary caregivers for an elderly adult relative who was either cognitively impaired or physically frail. Results provide preliminary evidence that gender is related to frequency of use but not to the perceived helpfulness of specific coping strategies.

Internal resourcefulness, task demands, coping, and dysphoric affect among caregivers of the frail elderly

Internal resourcefulness is defined as the repertoire of skills and behaviors individuals employ to deal with negative affective states. The relationships among caregivers' internal resourcefulness, demands of the caregiving situation, and caregivers' self-reported coping behaviors were examined relative to changes in dysphoric affect over time. Primary caregivers of the frail elderly (N = 143) completed the following measures, at two time periods, approximately four months apart: Rosenbaum's Self Control Schedule, assessing internal resourcefulness; Poulshock and Deimling's list of tasks carried out for the frail elder; Zarit et al.'s Memory and Behavior Problem Check List assessing caregiver burden; Moos et al.'s Indices of Coping; and Beck et al.'s Depression Inventory as a means of assessing dysphoric affect. Although caregivers' reactions to the care recipients' annoying behaviors predicted negative affect at time 1 and avoidant coping behavior predicted negative affect at times 1 and 2, internal resourcefulness was the only significant predictor of changes in dysphoric affect over time. Decreased dysphoric affect among caregivers was linked to possession of a larger initial set of internal resources to deal with negative internal experiences.

Involvement of Escherichia coli DNA polymerase II in response to oxidative damage and adaptive mutation

DNA polymerase II (Pol II) is regulated as part of the SOS response to DNA damage in Escherichia coli. We examined the participation of Pol II in the response to oxidative damage, adaptive mutation, and recombination. Cells lacking Pol II activity (polB delta 1 mutants) exhibited 5- to 10-fold-greater sensitivity to mode 1 killing by H2O2 compared with isogenic polB+ cells. Survival decreased by about 15-fold when polB mutants containing defective superoxide dismutase genes, sodA and sodB, were compared with polB+ sodA sodB mutants. Resistance to peroxide killing was restored following P1 transduction of polB cells to polB+ or by conjugation of polB cells with an F' plasmid carrying a copy of polB+. The rate at which Lac+ mutations arose in Lac- cells subjected to selection for lactose utilization, a phenomenon known as adaptive mutation, was increased threefold in polB backgrounds and returned to wild-type rates when polB cells were transduced to polB+. Following multiple passages of polB cells or prolonged starvation, a progressive loss of sensitivity to killing by peroxide was observed, suggesting that second-site suppressor mutations may be occurring with relatively high frequencies. The presence of suppressor mutations may account for the apparent lack of a mutant phenotype in earlier studies. A well-established polB strain, a dinA Mu d(Apr lac) fusion (GW1010), exhibited wild-type (Pol II+) sensitivity to killing by peroxide, consistent with the accumulation of second-site suppressor mutations. A high titer anti-Pol II polyclonal antibody was used to screen for the presence of Pol II in other bacteria and in the yeast Saccharomyces cerevisiae. Cross-reacting material was found in all gram-negative strains tested but was not detected in gram-positive strains or in S. cerevisiae. Induction of Pol II by nalidixic acid was observed in E. coli K-12, B, and C, in Shigella flexneri, and in Salmonella typhimurium.

Release of 5'-terminal deoxyribose-phosphate residues from incised abasic sites in DNA by the Escherichia coli RecJ protein

Excision of deoxyribose-phosphate residues from enzymatically incised abasic sites in double-stranded DNA is required prior to gap-filling and ligation during DNA base excision-repair, and a candidate deoxyribophosphodiesterase (dRpase) activity has been identified in E. coli. This activity is shown here to be a function of the E. coli RecJ protein, previously described as a 5'-->3' single-strand specific DNA exonuclease involved in a recombination pathway and in mismatch repair. Highly purified preparations of dRpase contained 5'-->3' exonuclease activity for single-stranded DNA, and homogeneous RecJ protein purified from an overproducer strain had both 5'-->3' exonuclease and dRpase activity. Moreover, E. coli recJ strains were deficient in dRpase activity. The hydrolytic dRpase function of the RecJ protein requires Mg2+; in contrast, the activity of E. coli Fpg protein, that promotes the liberation of 5'-->3'Rp residues from DNA by beta-elimination, is suppressed by Mg2+. Several other E. coli nucleases, including exonucleases I, III, V, and VII, endonucleases I, III and IV and the 5'-->3' exonuclease function of DNA polymerase I, are unable to act as a dRpase. Nevertheless, E. coli fpg recJ double mutants retain capacity to repair abasic sites in DNA, indicating the presence of a back-up excision function.

Dysphoric distress in childbearing women

Previous research on depression in childbearing women has focused on the presence or absence of clinical depression. Little attention has been paid to the distress caused by the presence of depressive symptoms in the absence of the full syndrome of clinical depression. A convenience sample of 202 healthy, married, primigravid women who were free of psychiatric symptoms were assessed at 10 to 14 weeks and 30 to 32 weeks of pregnancy and at 1 to 2 weeks and 14 weeks post partum. Depression symptoms were measured by using the Schedule of Affective Disorders and Schizophrenia, the standardized clinical interview for research and depression of The National Institute of Mental Health. Data from the Schedule of Affective Disorders and Schizophrenia indicated that only 5% of the women met criteria for clinical depression but approximately 50% of the sample reported clinical levels of three or more depressive symptoms. Anger, fatigue, psychic anxiety, and worry were the most frequently endorsed symptoms at each assessment point. The implications of these findings for symptom management and health promotion for childbearing women are discussed.

A standardized interview that differentiates pregnancy and postpartum symptoms from perinatal clinical depression

In a prospective longitudinal study, 202 primigravidas were assessed for depression using the National Institute of Mental Health's (NIMH) standardized clinical interview, the Schedule for Affective Disorders and Schizophrenia (SADS), and Research Diagnostic Criteria (RDC) at four periods: 10 to 14 weeks of pregnancy, 30 to 32 weeks of pregnancy, 1 to 2 weeks postpartum, and 14 weeks postpartum. Women's responses did not fit the SADS standardized questions and prescribed ratings because pregnancy and postpartum symptoms often mimicked depression symptoms. This was addressed by adding questions and scoring criteria to separate out pregnancy and postpartum symptoms from depression symptoms. Results showed that, after accounting for pregnancy-postpartum symptoms, women consistently claimed eight symptoms with high frequency and higher mean ratings: dysphoric mood, worrying, somatic and psychic anxiety, insomnia, fatigue, anger, and irritability. The findings suggest that 1) depression in pregnant and newly delivered women may be underdiagnosed if caregivers attribute their complaints or symptoms to time-limited somatic conditions; 2) depression may be overdiagnosed if clinicians use self-report measures solely, or without carefully interviewing women to separate the symptoms of depression from symptoms of pregnancy and postpartum; and 3) women's reactions to perinatal symptoms may have some bearing on the development of depression then or later. Simple clinical and social amelioration of the symptoms of distress might reduce their effect and diminish the rate of mistaken diagnoses of depression.

Retrospective assessment of marital adjustment and depression during the first 2 years of spousal bereavement

Two hundred twelve bereaved elders rated marital adjustment using items drawn from the Locke and Wallace (1959) Marital Adjustment Test and completed the Beck Depression Inventory 2 months, 12 months, and 30 months after the loss of their spouses. Their responses were compared with those of 162 nonbereaved individuals of comparable age who were tested at the same times. More positive ratings of marital adjustment were made by bereaved subjects than by nonbereaved subjects. Among nonbereaved elders, more severe ratings of depression were associated with lower ratings of marital adjustment. In the bereaved sample, however, the opposite was found: More severe ratings of depression were associated with higher ratings of marital adjustment. This pattern of results changed only slightly over the 2.5-year course of bereavement and was not influenced by gender. These results are discussed in terms of cognitive processes (e.g., idealization) that influence retrospective assessments of marital adjustment during bereavement.

Retrospective assessment of marital adjustment and depression during the first 2 years of spousal bereavement

Two hundred twelve bereaved elders rated marital adjustment using items drawn from the Locke and Wallace (1959) Marital Adjustment Test and completed the Beck Depression Inventory 2 months, 12 months, and 30 months after the loss of their spouses. Their responses were compared with those of 162 nonbereaved individuals of comparable age who were tested at the same times. More positive ratings of marital adjustment were made by bereaved subjects than by nonbereaved subjects. Among nonbereaved elders, more severe ratings of depression were associated with lower ratings of marital adjustment. In the bereaved sample, however, the opposite was found: More severe ratings of depression were associated with higher ratings of marital adjustment. This pattern of results changed only slightly over the 2.5-year course of bereavement and was not influenced by gender. These results are discussed in terms of cognitive processes (e.g., idealization) that influence retrospective assessments of marital adjustment during bereavement.

Prevalence of depression in family caregivers

Family caregivers who sought help to increase their coping skills (N = 158) and caregivers who volunteered for a longitudinal study of Alzheimer's disease (N = 58) were screened for depression. Among help-seekers, 46% had depression according to Research Diagnostic Criteria (RDC), but among non-help-seekers, only 18% met this criterion. In general, women were more depressed than men, but no major differences in the extent of depression were found in those who cared for more impaired persons.