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Results for “selective sweep”

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PubMed1977

[External recording of His bundle electrical activity (author's transl)].

A noninvasive method to record His' potentials in man is described. In several patients who needed intracardiac recording, a bipolar lead was placed across the chest, directed as conveniently as possible for the recording of His bundle electrical activity. A signal filtered (70-300 Hz) and amplified (X 100.000), was processed by a multichannel analyzer for averaging. The temporal regime of the averager was determined by a trigger which established a fiducial point on the ECG. For this purpose a QRS detector fed to a normal peripheral bipolar lead was used. The temporal stability of the system was continually checked in order to reject the recordings over the limits of +/- 1 msec. The computer program was chosen in order to select a window (usually 200 msec) which occurred up to 150 msec prior and 50 msec after the trigger signal. The sampling rate was 5 KHz for 1024 samples and the sweep counts were fixed from 128 to 512. At the same time, the D1, D2 and D3 were recorded in the other three channels of the analyzer for a more accurate measurement of the HV interval. Then an example comparing the external and interval recording was presented. Finally several external recordings were measured and the exact reproducibility of the G wave was confirmed. In conclusion we can say that the G wave is significant and suggests the electrical activity of the bundle of His.

Bundle of His↗

PubMed1977

Receptive field characteristics of neurons in a visual area of the rabbit temporal cortex.

In a program of surveying the characteristics of visual receptive fields of neurons in rabbit brain, we have explored cortical sectors beyond the striate and occipital cortices and found cells in a part of the temporal lobe that were responsive to visual stimulation. Using evoked potential and unit-cluster methods, this temporal visual area was mapped to be roughly oval-shaped, 3 mm x 2mm in size, and at about the level posterior to the apex region of auditory area 1. It is located ventral to and continuous with visual area 11, at about the caudal half of M. Rose's temporal cortices 1 and 2 (T1 and T2). Only about two-thirds of 96 units studied responded to some sort of moving light stimulation. These motion-sensitive cells were divided into four groups. Cells in the first group (22) responded best to a large light spot or shadow sweeping quickly across the field. Cells in the second group (29) responded to slow moving, jerking spot. Nine cells responded to a narrow, dark bar thrusting into a lighted field. Four cells are "direction-selective," responding to light stimulus moving in one direction and showing either no response or decreased background discharges in the opposite direction. In addition, three cells required unusual stimulus features. Of the 38 cells tested, nine of them were found to be binocularly driven. These receptive field characteristics are quite different from those described for other visual centers of the rabbit. The significance of these results together with data on the anatomical connections of this cortical area as reported in the following paper were discussed.

Animals↗

PubMed1977

[M- and real-time b-scan diagnostic criteria and pit-falls in right ventricular volume overload (author's transl)].

The observation of a characteristic "see-saw" motion of the interventricular septum (IVS) in real-time B-scan (RTBS) in right ventricular volume overload (RVVO) reveals features which have not been taken into account in diagnostic M-scan echocardiography. From an investigation of 20 patients it became apparent that the criteria (1) increase in right ventricular internal diameter and (2) "paradoxical" septal motion, so far used for the M-scan diagnosis of RVVO, should be complemented by further criteria: (3) hypertrophy of the IVS in longstanding RVVO, (4) increase in septal amplitude of motion towards the cardiac apex, (5) selective increasing apical septal hypertrophy and (6) an apparent random septal motion without any resultant main direction as an indication of a displaced fulcrum of the septal "see-saw". All features may be visualised by carrying out a continuous sweep in M-scanning. The criteria 2-5 may be understood as a result of increased apical work load compensating for the haemodynamic loss of the reversed upper septal motion ("RUSM"). The diagnosis of RVVO can be made more readily and reliably with RTBS echocardiography, underlining the utility of a combined use of one- and two-dimensional ultrasonography in diagnostic cardiology.

Blood Volume↗

PubMed1977

Host feeding patterns of Connecticut mosquitoes (Diptera: Culicidae).

Blood-engorged Coquillettidia perturbans, Psorophora ferox, Culex, Culiseta, and Aedes mosquitoes were collected principally by sweep net from salt marsh and woodland habitats in Connecticut. Of the 570 mosquitoes tested, precipitin tests identified the origins of 517 blood meals and revealed distinct host feeding patterns. Aedes mosquitoes fed chiefly on mammals; A. abserratus, A. cantator, and A. vexans showed selectivity for cattle and (or) horses. A. cantator also obtained blood from avian hosts and, in some instances, showed mixed passerine-mammal blood meals. These findings increase the vector potential of this salt marsh mosquito for eastern equine encephalomyelitis virus. Feedings on deer by A. abserratus suggest potential involvement of this mosquito in the transmission of certain subtypes of California encephalitis. Culex-pipiens, C. restuans, Culiseta melanura, and Cs. morsitans dyari acquired blood almost exclusively from passeriform birds.

Aedes↗

PubMed1975

[The objective frequency decrement test (OFDT): a new objective EEG-test for determination of the difference limen for frequencies (author's transl)].

Subjective methods measuring the difference limen for frequencies (DLF) take a lot of time and are not reliable. You can find this fact not only while testing normal subjects, but also while testing patients with hearing loss combined with tinnitus. Therefore this new objective DLF-test has been developed. Apart from the testing function for clinical purpose, the different results of other studies can also be controlled. After 1080 msec a pure tone is changed to a lower frequency for a period of 670 msec. Immediately after the tone is finished a picture is presented. As a control pure tones of unvarying pitch are offered. This stimulus sequence is repeated for several times. The expectancies to the change of pitch and to the picture produce a negative slow potential shift (Walter's CNV) in the EEG. The perception of frequency change yields to a late evoked potential and to a DC-shift; as a result of the optimum conditions of the expectancy-situation and the appropriate recording-technique only 5-10 sweeps must be summed up to obtain a potential, sometimes it even can be seen in the "raw-EEG". The test makes a differentiation between a just believed and a real perception possible. A sample of subjects with normal hearing and a subgroup (musicians) were selected for the standardization. Because of objectivity, reliability and economy the test can be used for clinical application.

Electroencephalography↗

PubMed1978

Electron spin resonance in zero magnetic field of the reaction center triplet of photosynthetic bacteria.

The decay rates kx, ky, kz of the individual spin levels of the light-induced triplet state have been accurately measured by the zero-field resonance technique under conditions of very low light intensity and a microwave sweep rate of 2.5 MHz/microseconds, which is in excess of that commonly used in optical detection magnetic resonance experiments. The rates ku found correspond well with those previously determined under somewhat different conditions (Hoff, A.J. (1976) Biochim. Biophys. Acta 440, 765--771) and with those inferred from the decay at 4.2 degrees K of the triplet-triplet absorption after picosecond excitation (Parson, W.W. and Monger, T.G. (1977) Brookhaven Symp. Biology 28, 195--212). Thus there seems no reason to doubt that PR corresponds to the triplet state detected by ESR. In a recent publication Clarke and Connors (Clarke, R.H. and Conners, R.E. (1976) Chem. Phys. Lett. 42, 69--72) published values of the rates ku which differ substantially from ours and which lead to a mean lifetime in excess of that of PR. We show that erroneous rates are obtained when the microwave sweep rate is not made fast relative to the decay of the individual spin levels. Zero-field splitting parameters for a member of photosynthetic bacteria have been measured with an accuracy of better than 0.4% for D and 1% for E. The enhanced precision as compared to conventional ESR allows one to discriminate between species of one family. Deuteration reduces the ku values by a factor of about 2, with little spin selectivity. This effect is much larger than previously observed for chlorophyll a. The present results explain the decrease in fluorescence intensity observed on microwave saturation in zero-field optical detection magnetic resonance experiments, and they also show that the simple exciton model is inadequate to derive the geometry of the reaction center dimer from the observed zerofield splitting and decay rates.

Electron Spin Resonance Spectroscopy↗

PubMed1978

Efficacy...what's that??

We need to develop techniques for measuring the usefulness of medical services. If resources are limited, and we cannot do all the diagnostic tests we would like to do, we must be able to select those that are most useful. To do this we need to known how to weigh benefits against risks and how to measure the worth of a given outcome. This article discusses efficacy, in diagnosis, management, and outcome. Diagnostic efficacy of a test is measured by its ability to change the probability of disease (pre- versus post-test likelihood). Management efficacy is a measure of how the test changes patient management. Outcome efficacy, which may take years to evaluate, is the ultimate yardstick of usefulness. Even though there are many problems in estimating the likelihood of a disease (subjectivity, varying terminology, etc.), physicians can make reasonably close estimates, as shown by the American College of Radiology's Efficacy Study, which analyzed the diagnostic process in 9000 cases. Efficacy studies may be a mixed blessing, however, as they may result in overly strict criteria and sweeping economic changes. They may be ignored because of the difficulty in following the "perfect" protocol for a given clinical situation, and it remains to be shown that they themselves are efficacious. Nevertheless, we are finally coming to grips with the question of how useful our tests are in patient management.

Cost-Benefit Analysis↗

PubMed1975

Mercury vapor as an atmospheric contaminant of dental offices.

Airborne mercury from dental offices was selectively trapped by silber gauze elements in borosilicate glass obsorbers, followed by heat-desorption and spectrophotometric measurement at 2537A. As little as 0.4 ng of Hg could be accurately determined, which is equivalent to 49 ppt in a wone-L air sample on a v/v basis. Over 860 air samples were taken over a range of locations and working conditions at 88 different dental offices, and at the Dental Training Clinic of the University of Manitoba. The Hg vapor concentrations at the dental facilities ranged from 0.45 to 742 mug/m3 of air, 29% of the samples were within 0.45 to 5 mug; 37.8 were within 5.1 to 25mug;and 33.2% were above 25 mug. Mercury concentrations varied during the working day, depending on the time of sampling, the number of amalgams placed, and the interval between placements. The lowest concentrations were obtained in the morning. Disturbance of residual mercury droplets on floors or working areas by sweeping or dusting, or immediately after attempted clean-up of a mercury spill, sharply increased the amount of airborne mercury.

Air Pollutants↗

PubMed2026

REVIEW: CAUSES AND CONSEQUENCES OF DOING IT WITH ONESELF-SYNTHESIS AND META-ANALYSIS OF NEODERMATAN HERMAPHRODITIC MATING SYSTEMS.

Hermaphroditic mating systems profoundly influence evolution, yet in parasitic flatworms (Neodermata) they remain strikingly understudied. For decades, sweeping claims have oscillated between pervasive selfing and near-universal outcrossing, reflecting a lack of comprehensive synthesis. This review, the first in more than 40 yr, integrates nearly a century of research, from early observational studies to modern genetic analyses, to reveal a far more nuanced picture. Our meta-analysis of population-genetic data shows a sharp departure from the bimodal selfing patterns typical of plants and other hermaphroditic animals: neodermatan parasites are strongly skewed toward outcrossing. We link variation in mating systems to parasite demography and life-history traits, especially in species exhibiting mixed mating or elevated selfing. Current evidence suggests outcrossing is common, but taxonomic and life-history gaps preclude definitive conclusions. Beyond patterns and causes, we explore evolutionary consequences ranging from fitness costs such as inbreeding depression to trait evolution, including delayed selfing, sex allocation, and complex life cycles. Evidence for inbreeding depression is mixed and limited, yet emerging approaches using selfing-rate comparisons offer promising avenues for future research. Notably, demographic constraints, such as infection intensity and life-cycle architecture, often explain mixed mating without invoking selection, challenging classical models. Similarly limited in number, studies on sex allocation indicate that hermaphroditic mating systems can shape reproductive investment, with patterns consistent with local sperm competition in some taxa. By consolidating historical observations with modern genetic insights, this review provides the most comprehensive synthesis of hermaphroditic mating systems in the Neodermata to date. We highlight critical gaps in taxonomic coverage and experimental data and point to future opportunities for integrating genomic approaches with ecological and demographic frameworks. Such integration will be essential to illuminate how mating systems shape parasite evolution and to resolve long-standing questions about the persistence of mixed mating despite theoretical expectations.

Animals↗