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PubMed1978

Utilization of a specific in vitro lymphocyte immunostimulation assay as an aid in detection of brucella-infected cattle not detected by serological tests.

Studies using the in vitro lymphocyte stimulation test (LST) were conducted with cattle in a dairy herd with a high percentage of reactors to several serological tests for brucellosis. Lymphocytes were prepared from peripheral bovine blood by the Ficoll-diatrizoate technique. Lymphocytes were cultured using microtitration culture plates. Brucella abortus soluble antigen, at a concentration of 4.4 microgram/culture, was added to the appropriate wells of microtitration culture plates and incubated for 6 days. The lymphocyte stimulation responses were measured by assaying for [3H]thymidine incorporation into DNA. Seroagglutination tests were conducted simultaneously with the LST, and tissues were collected after slaughter of the cattle for bacteriological culture to isolate B. abortus. All 21 animals studied were serologically negative for anti-brucella antibodies. Two of the 21 animals were classified as infected with Brucella by the LST, and B. abortus biotype 1 was isolated from tissues of these same two animals. The LST exhibited significant sensitivity and specificity in this study, and more observations of this nature might strengthen the application of this assay as an aid in the diagnosis of brucellosis.

Animals↗
PubMed1975

In vitro detection of immune responses to MTV-induced mammary tumors: qualitative differences in response detected by time studies.

Both BALB/cfC3H females neonatally infected with mammary tumor virus (MTV) and MTV-free BALB/c females possess spleen cells capable of significant activity against target-MTV-induced mammary tumor cells in in vitro microcytotoxicity tests. The responses of the BALB/cfC3H and BALB/c females are different, however, on the basis of time studies. Further, the reactivity characteristic of virgin BALB/cfC3H females is increased in parous females, and part of this reactivity is subsequently lost in multiparous females bearing large tumors. BALB/cfC3H females possess reactive spleen cells as early as 3 weeks of age, indicating that response to MTV antigens develops soon after birth in these neonatally infected mice.

Age Factors↗
PubMed1992

Detection of combined frequency and amplitude modulation.

This article is concerned with the detection of mixed modulation (MM), i.e., simultaneously occurring amplitude modulation (AM) and frequency modulation (FM). In experiment 1, an adaptive two-alternative forced-choice task was used to determine thresholds for detecting AM alone. Then, thresholds for detecting FM were determined for stimuli which had a fixed amount of AM in the signal interval only. The amount of AM was always less than the threshold for detecting AM alone. The FM thresholds depended significantly on the magnitude of the coexisting AM. For low modulation rates (4, 16, and 64 Hz), the FM thresholds did not depend significantly on the relative phase of modulation for the FM and AM. For a high modulation rate (256 Hz) strong effects of modulator phase were observed. These phase effects are as predicted by the model proposed by Hartmann and Hnath [Acustica 50, 297-312 (1982)], which assumes that detection of modulation at modulation frequencies higher than the critical modulation frequency is based on detection of the lower sideband in the modulated signal's spectrum. In the second experiment, psychometric functions were measured for the detection of AM alone and FM alone, using modulation rates of 4 and 16 Hz. Results showed that, for each type of modulation, d' is approximately a linear function of the square of the modulation index. Application of this finding to the results of experiment 1 suggested that, at low modulation rates, FM and AM are not detected by completely independent mechanisms. In the third experiment, psychometric functions were again measured for the detection of AM alone and FM alone, using a 10-Hz modulation rate. Detectability was then measured for combined AM and FM, with modulation depths selected so that each type of modulation would be equally detectable if presented alone. Significant effects of relative modulator phase were found when detectability was relatively high. These effects were not correctly predicted by either a single-band excitation-pattern model or a multiple-band excitation-pattern model. However, the detectability of the combined AM and FM was better than would be predicted if the two types of modulation were coded completely independently.

Adult↗
PubMed1975

The detection of gratings by independent activation of line detectors.

1. The visibility of composite stimuli (double lines, multiple lines and sinusoidal gratings) is analysed in terms of the visibility of single lines. 2. The detection mechanisms for the composite stimuli were examined by measuring the probabilities for seeing these stimuli, the probabilites of "recognition" near their detection thresholds and by using the method of subthreshold summation. 3. The simplest composite stimulus consists of two lines spaced apart by 15 min; it was found that both the probability of seeing this stimulus and the probability of reporting either one or two lines may largely be explained by assuming independent detection of the two lines. For a 12 min spacing some antagonistic interaction was observed between the two lines, confirming the existence of an antagonistic surround in the line detector. 4. The probability of seeing a multiple line target (rectangular grating) of spacing 15 min is slightly greater than that predicted assuming independent detection of its component lines; this probability can be calculated from the probabilities of seeing a central line (near the fixation point) and pairs of lines spaced 15, 30, 45, 60, 75 and 90 min on either side of the fixation point. The observed threshold for the grating was about 0.05 log units less than the prediction. 5. The probability that a subject reports only one line from a rectangular grating was found to be consistent with independent detection of its component lines when the subject used a low (detection) threshold criterion but not for higher criteria. 6. The spatial frequencies involved in the detection of the rectangular grating were determined by subthreshold summation; the high spatial frequency selectivity was shown to be consistent with independent detection of the component lines. 7. The detection mechanism for a 4 c/deg sinusoidal grating was found to be similar to that for the 15 min rectangular grating. 8. Evidence is presented that the detection of finer and coarser gratings may be analysed in similar terms. 9. It is shown that lines are not detected by independent activation of sharply tuned grating detectors but that sub-units may be involved which are slightly more narrowly tuned than the line detector. 10. These sub-units contain both inhibitory and disinhibitory regions; the disinhibitory responses may be the basis of the deviations from probability summation noted in 4. 11. The properties of the proposed sub-units are in reasonable accord with the results of adaptation experiments.

Adult↗
PubMed2026

Assessment of differentially culturable tubercle bacteria assays for the detection of tuberculosis infection in asymptomatic household contacts and the implications for intra-household transmission: a longitudinal cohort study.

BACKGROUND: Conventional culture methods for tuberculosis diagnosis miss differentially culturable tubercle bacteria (DCTB), which grow only in liquid assays supplemented with growth-enhancing factors. This limitation, combined with inadequate contact tracing and screening, often fails to identify asymptomatic individuals, with live bacilli detectable by enhanced culture methods. This shortfall results in undiagnosed reservoirs of bacteria, potentially fuelling ongoing transmission. In this study, we aimed to investigate whether DCTB assays provide greater sensitivity by detecting more Mycobacterium tuberculosis infections than conventional culture and whether this enhanced detection improves the resolution of intrahousehold transmission mapping. In addition, we sought to evaluate whether DCTB populations can progress to conventional culture positivity, thereby highlighting their clinical and epidemiological relevance. METHODS: In this prospective observational longitudinal cohort study, drug-susceptible or rifampicin-resistant tuberculosis index participants aged 12 years or older, were recruited from primary healthcare clinics from two South African districts. Inclusion criteria were informed consent, Xpert MTB/RIF Ultra-positive results, tuberculosis symptoms (>2 weeks), provision of baseline samples, at least one consenting household contact, and documented HIV status. Household contacts of the index patients and control households were also recruited. Sputum specimens were collected at baseline and 2, 4, 8, 12, and 16 months from the index participants and household contacts. Samples were analysed by conventional mycobacterial growth indicator tube (MGIT) culture, and colony-forming unit assays to identify viable bacteria. Enhanced culture to detect DCTB involved serial dilution of sputum in liquid culture, supplemented with M tuberculosis culture filtrate as a source of growth stimulatory factors. Whole-genome sequencing (WGS) of cultured isolates was performed to trace household transmission. FINDINGS: Between June 1, 2020, and Feb 6, 2024, 293 index participants (183 [62%] male), 701 household contacts (453 [65%] female), and 122 control participants (67 [55%] female) were enrolled. At baseline, 249 (85%) of 293 index participants and 110 (16%) of 701 household contact sputum samples were positive for M tuberculosis by MGIT conventional culture. For baseline MGIT-negative specimens, DCTB assays detected M tuberculosis in an additional 21 (7%) of 293 index participants and 26 (4%) of 701 household contacts. Over 16 months of follow-up, DCTB assays identified 61 (8·7%) of 701 additional tuberculosis-positive household contacts not detected by conventional culture. WGS-guided transmission mapping using conventional culture identified transmission in 16 (15%) of 104 households, whereas DCTB assays detected an additional 19 (18%) of 104 transmission events. No evidence of intrahousehold transmission was found in the remaining 69 (66%) of 104 tuberculosis-positive households. Over the 16-month follow-up period, conventional culture identified 233 positive household contacts, of which 195 (84%) were asymptomatic. DCTB assays detected an additional 94 cases of M tuberculosis positivity in household contacts, of which 79 (84%) were asymptomatic. In control households, tuberculosis prevalence at baseline was two (2%) of 122, with an additional three (3%) of 122 identified during follow-up. INTERPRETATION: DCTB assays provide substantial value by detecting asymptomatic individuals missed by conventional culture, revealing a potentially important reservoir of subclinical infection, which could sustain transmission. In addition, DCTB detection uncovers transmission linkages missed by conventional culture, providing a more comprehensive understanding of M tuberculosis transmission dynamics and highlighting the need to incorporate enhanced culture methods into diagnostic and surveillance strategies, to strengthen early case identification and tuberculosis control efforts. FUNDING: National Institutes of Health.

Humans↗
PubMed2026

Evaluating sampling strategies for the detection of avian influenza viruses in the environment.

Highly pathogenic avian influenza (HPAI) viruses pose an increasing threat to wildlife, livestock and human health, underscoring the need for scalable and early-warning surveillance systems. Environmental RNA (eRNA) monitoring offers a non-invasive, cost-effective alternative to traditional host-based sampling by detecting viral genetic material shed into the environment. Despite its utility, the relative performance of different environmental sampling approaches for avian influenza virus (AIV) detection remains poorly resolved. Here, we conducted a longitudinal study with monthly sampling over approximately one year across two urban waterfowl ponds in Aotearoa New Zealand to evaluate four eRNA sampling strategies - fresh faeces, sediment, active-filtered water and passive-filtered water - for their ability to detect AIV. Using a combination of metagenomic sequencing and RT-qPCR, we show that all sample types can detect AIV, although detections were highly inconsistent across sampling methods, locations and time points. While metagenomic sequencing provided valuable genomic data, including subtype identification and phylogenetic context, RT-qPCR exhibited greater sensitivity, with active-filtered water yielding the highest detection rates, and is currently the more cost-effective approach for large-scale surveillance. Notably, AIV detections were asynchronous among sample types and frequently lacked temporal concordance, suggesting that environmental heterogeneity, RNA persistence, and methodological detection limits strongly influence surveillance outcomes. Despite these inconsistencies, phylogenetic analyses revealed that detected viruses belong to established Australasian lineages, highlighting the ability of environmental surveillance to capture ecologically relevant viral diversity. Our findings demonstrate that while eRNA-based surveillance holds substantial promise as a complementary tool for AIV monitoring, its effectiveness is highly dependent on the environmental sampling strategies and laboratory detection methods used.

Ducks↗
PubMed1992

The effect of breast self-examination on early detection and survival.

To investigate the effect of breast self-examination (BSE), we compared the stages, survival, and the risk of death for 355 patients with breast cancer detected by BSE with those for 1,327 patients with breast cancer detected by chance. The early stages of the disease were found to be more common among the symptomatic breast cancer patients detected by BSE than those by chance. The 5-year overall survival rate was 94.4% for the symptomatic patients detected by BSE, and was significantly higher by 8.7% than that (85.7%) for patients detected by chance (P less than 0.001). The 10-year survival rate was 81.6% for patients detected by BSE, and 76.6% for cases detected by chance (the difference was not significant). The overall difference between the two survival curves was statistically significant by the logrank test (P less than 0.01). A multivariate analysis using the Cox proportional hazards model showed that the risk of death for patients detected by BSE was smaller by 0.570 times than that for patients detected by chance, which was statistically significant (P less than 0.05). The effect of biases inherent to BSE in the survival analysis cannot be controlled completely even after conducting multivariate analysis. These results suggest that BSE may contribute to the reduction of the risk of death through early detection of breast cancer. However, further examination should be conducted by other methods to obtain conclusive evidence.

Breast Neoplasms↗
PubMed1977

Effects of phase-of-respiration on GSR detection.

Previous studies of visual and auditory signal detection (Flexman & Demaree, 1972; Flexman, 1974; Flexman, Demaree & Simpson, 1974) have found that signals occurring during exhalation are detected with greater sensitivity than are signals occuring during inhalation. The purpose of the present study was to make use of a use of a signal detection paradigm (Green & Swets, 1966) in extending these phase-of-respiration findings to internal event detection, specifically, to the detection of spontaneous galvanic skin responses (GSRs). A secondary purpose of the study was to re-examine Stern's (1972) finding that high magnitude GSRs were better detected than were low magnitude GSRs. It was found that the phase of respiration during which the GRS reached its peak significantly influenced GSR detection, but that unlike studies of external signal detection, detection was greater for GSRs peaking during the inhalation than for GSRs peaking during exhalation. Some possible artifactual sources of this finding are discussed. No significant effect of GSR magnitude on GSR detection was observed although differences were in the expected direction.

Awareness↗
PubMed1977

Human tactile detection thresholds: modification by inputs from specific tactile receptor classes.

1. Human detection thresholds for a vibratory stimulus applied to the volar surface of the index finger were examined under conditions where afferents from specific tactile receptor classes were simultaneously activated from the thenar eminence. The experiments were designed to test whether stimuli which have been shown previously to induce afferent inhibition of ;tactile' neurones in the cuneate nucleus of the cat could modify human subjective performance in a tactile detection task. Conditioning stimuli to the thenar eminence were usually of three forms; steady indentation to engage slowly adapting tactile receptors; 300 Hz vibration to engage Pacinian corpuscles; and 30 Hz vibration to engage the intradermal, rapidly adapting tactile receptors which are thought to be Meissner's corpuscles.2. In ten subjects the mean detection threshold for a 30 Hz test stimulus in the absence of conditioning stimulation was 8.6 +/- 1.0 mum (S.E.). Detection thresholds were increased substantially in the presence of a 300 Hz, 100 mum conditioning stimulus (mean increase 11.1 +/- 2.0 mum), whereas minor or insignificant effects were seen with conditioning stimuli consisting of (a) 30 Hz, 100 mum (mean increase 1.4 +/- 0.8 mum), (b) steady indentation, 1.5 mm in amplitude (mean increase 1.3 +/- 0.7 mum) or (c) 300 Hz, 100 mum to the contralateral thenar eminence (mean increase 0.4 +/- 0.5 mum).3. The 300 Hz conditioning stimulus to the ipsilateral thenar eminence caused a marked increase in detection thresholds at all test stimulus frequencies over the range 10-450 Hz. The effects of the conditioning stimulation therefore operated on inputs from Pacinian corpuscles, which are responsible for vibration detection at 80-450 Hz, and on inputs from the intradermal, rapidly adapting receptors which are responsible for vibration detection at 10-80 Hz.4. The band width of conditioning vibratory frequencies which was effective at amplitudes of 100 mum in bringing about increases in detection threshold extended from 50-80 Hz to 300 Hz, the maximum tested.5. Whereas amplitudes of 1-2 mum produced clear increases in detection thresholds with conditioning stimuli of 300 Hz, amplitudes of > 200 mum were needed at 30 Hz.6. The observed elevations in detection threshold are consistent with an afferent-induced inhibitory action exerted at synaptic relays of the sensory pathway by tactile inputs arising exclusively or predominantly from Pacinian corpuscles.

Adult↗
PubMed1992

Development of a biotin-streptavidin-enhanced enzyme-linked immunosorbent assay which uses monoclonal antibodies for detection of group C rotaviruses.

A biotin-streptavidin-enhanced enzyme-linked immunosorbent assay (ELISA) which uses monoclonal antibodies (MAbs) for the detection of group C rotaviruses was developed. An assay in which plates were coated with three pooled MAbs and biotinylated polyclonal immunoglobulin G (IgG) (polyclonal antibody [PAb]) was used as the detector (MAb capture-PAb detector) was found to be the most sensitive and specific of the assays when it was compared with assays in which plates were coated with polyclonal antiserum and detection was done with either biotinylated polyclonal antiserum (PAb capture-PAb detector) or biotinylated pooled MAbs (PAb capture-MAb detector). The MAb capture-PAb detector ELISA detected 83% of samples confirmed to be positive for group C rotaviruses, whereas the PAb capture-PAb detector assay detected 63% of positive samples and the PAb capture-MAb detector assay detected 65% of positive samples. All three procedures detected both of the bovine and the two human group C rotaviruses, but none of the three procedures detected fecal samples containing group A and B rotaviruses or fecal samples negative for group C rotaviruses used in this study. The sensitivity of the MAb capture-PAb detector ELISA was determined by serially diluting fecal group C rotaviruses; antigens were detected in maximal positive dilution ranges of 1:1,000 to 1:3,000 for the samples tested. On the basis of the cell culture immunofluorescence assay infectivity titer of semipurified cell culture-passaged Cowden group C rotavirus, the sensitivity of the MAb capture-PAb detection ELISA for detection of homologous group C rotavirus was 53 fluorescent focus units per ml. Epitope mapping by use of the biotinylated MAbs in competition assay suggested that our MAbs may bind to three different but overlapping epitopes. These results suggest that the MAb capture-PAb detector ELISA can be used to study the epidemiology of group C rotaviruses in humans and animals.

Animals↗