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D S Weiss

Publications and source records attributed to D S Weiss.

At least 91 records · Page 5Linked to original sources
PubMed1992

Voltage-dependent gating mechanism for single fast chloride channels from rat skeletal muscle.

1. A voltage-dependent gating mechanism for the fast Cl- channel was developed from the analysis of single-channel current records obtained with the patch clamp technique from primary cultures of rat skeletal muscle. Up to 10(6) open and shut intervals were analysed from each of five different excised patches of membrane containing a single fast Cl- channel. 2. Rate constants for a kinetic scheme with six closed and two open states (scheme I) were estimated at a given voltage by maximum likelihood fitting of open and closed dwell-time distributions obtained at that voltage. This procedure was then repeated for data obtained at each of three to eight different membrane potentials for each channel. 3. Plots of the estimated rate constants against membrane potential typically appeared linear on semilogarithmic co-ordinates, consistent with rate constants that are exponentially dependent on voltage. 4. Regression analysis of these plots yielded two parameters for each rate constant: the value of the rate constant at -50 mV (B) and its voltage sensitivity (A). The dwell-time distributions predicted with these parameters and scheme I gave a good description of the experimental dwell-time distributions at all the studied voltages, lending further support for an exponential dependence of rate constants on membrane potential. 5. Estimates of A and B were also obtained by simultaneously fitting dwell-time distributions obtained at three to eight different voltages, in order to better define these parameters. Predicted dwell-time distributions obtained with these estimates and scheme I could approach the theoretical best description of the data for discrete-state Markov models. 6. Eight to twelve of the fourteen rate constants in scheme I appeared voltage sensitive, with effective gating charges ranging from about -1.5 to +1.0 units of electronic charge. 7. The estimated rate constants and their voltage sensitivities for the five analysed channels were generally similar, but showed some heterogeneity. 8. Gating mechanisms which had fewer kinetic states than scheme I, or equal and opposite effective gating charges over each transition barrier, or four or five identical and independent voltage-dependent subunits, all gave poorer descriptions of the data than scheme I. These simpler mechanisms were also ranked below scheme I by the Schwarz criterion, which applies a heavy penalty for additional free parameters. 9. These findings indicate that the voltage dependence of the fast Cl- channel is consistent with a kinetic scheme with six closed and two open states, in which a majority of transitions among the states are voltage dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1992

Actions of ethanol on gamma-aminobutyric acid-activated chloride channels.

Ethanol appears to exert its intoxicating effects, at least partly, by potentiating gamma-aminobutyric acid (GABA) mediated inhibitory synaptic transmission in the brain. Work over the past decade using mouse lines selected for different ethanol sensitivities has implicated GABA-activated chloride channels as a potential target of ethanol. More recently, molecular biological techniques have identified a subunit (gamma 2L) of the GABA channel which appears to be required for the effects of ethanol on GABA channels. The presence of this subunit, however, cannot account for the full degree of potentiation of GABA responses observed in native GABA channels. Ongoing research is directed at identifying other factors which might be involved in the effects of ethanol on GABA channels and in understanding ethanol's molecular mechanism of action. Such information could be vital for designing drugs to combat ethanol intoxication.

Animals↗
PubMed1992

The cosleeping habits of military children.

Cosleeping is a topic frequently of concern to parents; however, little objective evidence exists to support the historical prohibition against children sleeping in the same bed with their parents. Surveys from the parents of 86 children in the clinics of pediatrics and child psychiatry were analyzed to describe patterns of cosleeping in a group of military dependents aged 2 to 13 years. Shown is a significant increase in cosleeping with father absence and that cosleeping is less frequent in the psychiatric subpopulation.

Beds↗
PubMed1991

The phosphorylated form of the enhancer-binding protein NTRC has an ATPase activity that is essential for activation of transcription.

The NTRC protein of enteric bacteria is an enhancer-binding protein that activates transcription in response to limitation of combined nitrogen. NTRC activates transcription by catalyzing formation of open complexes by RNA polymerase (sigma 54 holoenzyme form) in an ATP-dependent reaction. To catalyze open complex formation, NTRC must be phosphorylated. We show that phosphorylated NTRC has an ATPase activity, and we present biochemical and genetic evidence that NTRC must hydrolyze ATP to catalyze open complex formation. It is likely that all activators of sigma 54 holoenzyme have an ATPase activity.

Adenosine Triphosphatases↗
PubMed1991

Prokaryotic transcriptional enhancers and enhancer-binding proteins.

A number of prokaryotic enhancer-binding proteins activate transcription by specialized forms of RNA polymerase. The enhancer-binding proteins catalyse isomerization of the initial complex formed between RNA polymerase and a promoter from the closed to the open state. To do so, one class of enhancer-binding proteins contacts its cognate polymerase by DNA loop formation but the other, which is represented by a single member, does not. Despite this difference, both classes of enhancer-binding proteins must hydrolyse ATP to catalyse open complex formation.

Amino Acid Sequence↗
PubMed1990

Identifying kinetic gating mechanisms for ion channels by using two-dimensional distributions of simulated dwell times.

Ion channels are integral membrane proteins that regulate ionic flux through cell membranes by opening and closing (or gating) their pores. The gating can be monitored by observing step changes in the current flowing through single channels. Analysis of the durations of the open and closed intervals and of the correlations among the interval durations can give insight into the gating mechanism. Although it is well known that the correlation information can be essential to distinguish among possible gating mechanisms, it has been difficult to use this information because it has not been possible to correct the predicted correlations for the distortion of the single-channel data because of filtering and noise. To overcome this limitation we present a method based on a comparison of simulated and experimental two-dimensional dwell-time distributions constructed by analysing simulated and experimental single-channel currents in an identical manner. The simulated currents incorporate the true effects of filtering and noise, the two-dimensional distributions retain the correlation information, and the identical analysis allows direct maximum-likelihood comparison of the simulated and experimental two-dimensional distributions. We show that the two-dimensional simulation method has a greatly increased ability to distinguish among models, compared with methods that use one-dimensional distributions.

Animals↗
PubMed1990

A bacterial enhancer functions to tether a transcriptional activator near a promoter.

The nitrogen regulatory protein NtrC of enteric bacteria activates transcription of the glnA gene by catalyzing isomerization of closed complexes between RNA polymerase and the glnA promoter to open complexes. NtrC binds to sites upstream of glnA that have properties of eukaryotic transcriptional enhancers. NtrC-binding sites were found to facilitate open complex formation when these sites and the glnA promoter were located on different rings of a singly linked catenane, but not when the two rings were decatenated. The results provide evidence that NtrC contacts RNA polymerase-promoter complexes in a process mediated by formation of a DNA loop. NtrC-binding sites serve to tether NtrC near the glnA promoter, thereby increasing the frequency of collisions between NtrC and polymerase-promoter complexes.

Bacterial Proteins↗
PubMed1990

Estimating kinetic parameters for single channels with simulation. A general method that resolves the missed event problem and accounts for noise.

Analysis of currents recorded from single channels is complicated by the limited time resolution (filtering) of the data which can prevent the detection of brief intervals. Although a number of approaches have been used to correct for the undetected intervals (missed events) when identifying kinetic models and estimating parameters, none of them provide a general method which takes into account the true effects of noise and limited time resolution. This paper presents such a method. The approach is to use simulated single-channel currents to incorporate the true effects of filtering and noise on missed events and interval durations. The simulated currents are then analyzed in a manner identical to that used to analyze the experimental currents. An iterative search process using likelihood comparison of two-dimensional dwell-time distributions obtained from the simulated and experimental single-channel currents then allows the most likely rate constants to be determined. The large errors and false solutions that can result from the more typically applied assumptions of no noise and an absolute dead time (idealized filtering) are excluded by the iterative simulation method, and the correlation information contained in the two-dimensional distributions should increase the ability to distinguish among different gating mechanisms. The iterative simulation method is generally applicable to channels which typically open to a single conductance level. For these channels the method places no restrictions on the proposed gating mechanism or the form of the predicted dwell-time distributions.

Ion Channel Gating↗
PubMed1990

Ichthyosis follicularis in two girls: an autosomal dominant disorder.

Ichthyosis follicularis (IF) is a rare disorder of keratinization that has been described primarily in males and proposed as a possible X-linked disorder. We report two black girls with nonscarring alopecia; photophobia; follicular hyperkeratoses; hyperkeratosis of the extensor aspects of the hands, knees, and elbows; fixed, erythematous, perineal plaques; and angular cheilitis who seem to fit the clinical criteria for IF. One girl also had gingival hypertrophy and a hearing deficit. One child's father had identical symptoms. We propose that these girls may have a variant of IF that is inherited as an autosomal dominant trait.

Alopecia↗
PubMed1990

Voltage dependence and stability of the gating kinetics of the fast chloride channel from rat skeletal muscle.

1. The voltage dependence and stability of the gating kinetics of the fast Cl-channel in excised patches of membrane from cultured rat skeletal muscle were studied with the patch clamp technique. Up to 10(6) open and shut intervals were analysed from each of five different patches containing a single fast Cl-channel. 2. To test for kinetic stability, plots of the mean durations of consecutive groups of 5-500 open and shut intervals were examined at each voltage. After excluding infrequent entries into both an apparent subconductance state and a long-lived (inactive) shut state, there were no abrupt and sustained changes in the moving means, indicating the absence of obvious shifts to other kinetic modes. The moving means did, however, fluctuate about the overall mean. 3. A comparison of experimental and simulated data indicated that most, but not all, of the fluctuation in the moving means was due to the stochastic variation inherent in the gating process. The fluctuation not accounted for by stochastic variation was mainly expressed as a slow, low-amplitude, component of drift about the mean. This slow component was unlikely to have arisen from measurement errors. 4. To examine whether the slow drift reflected detectable changes in kinetic modes, the data were divided into consecutive groups of 50,000 intervals. The exponential components describing the distributions were remarkably similar among the different groups, with stochastic variation accounting for most of the observed differences. This finding implies a single kinetic mode throughout the experiment. Thus, any changes in channel activity associated with the slow drift would have little effect on the analysis of gating kinetics presented here. 5. Depolarization increased channel open probability, Popen, for all five channels. This increase had a voltage sensitivity of 17 +/- 4 mV per e-fold change (effective gating charge of 1.6 +/- 0.32 electronic charges at 23 degrees C). Popen was 0.5 at -31 +/- 4 mV. 6. The depolarization-induced increase in Popen typically arose from a decrease in the mean shut time (19 +/- 4 mV per e-fold change; effective gating charge of 1.3 +/- 0.3 at 23 degrees C) and an increase in the mean open time (109 +/- 61 mV per e-fold change; effective gating charge of -0.24 +/- 0.13). 7. Neither plots of Popen versus voltage nor plots of the mean open and mean shut time versus voltage were completely described by a single Boltzmann distribution, suggesting multiple voltage-sensitive steps in channel gating.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Electrical stimulation and wound healing.

Living tissues possess direct current surface electropotentials that regulate, at least in part, the healing process. Following tissue damage, a current of injury is generated that is thought to trigger biological repair. In addition, exogenous electrical stimuli have been shown to enhance the healing of wounds in both human subjects and animal models. Intractable ulcers have demonstrated accelerated healing and skin wounds have resurfaced faster and with better tensile properties following exposure to electrical currents. This article examines the bioelectric properties of living systems and reviews the existing literature on electrical stimulation and wound healing.

Animals↗
PubMed1989

Exogenous electric current can reduce the formation of hypertrophic scars.

Exogenous electric current has been shown to influence the healing of wounds in both human subjects and animal models. We examined the effect of positive polarity electrical stimulation on the resultant scar thickness of surgically induced wounds, and report that electrotherapy can reduce scar thickness and hypertrophic scar formation.

Adult↗
PubMed1989

Psychometric properties of Loevinger's Sentence Completion Test in an adult psychiatric outpatient sample.

Little research has been conducted on Loevinger's Washington University Sentence Completion Test of Ego Development in adult psychiatric outpatients. The measure is a promising method of assessing a construct of personality and character functioning that should be useful in research on psychopathology and in choosing treatment modalities. The data presented in this study address the question of the psychometric adequacy of the measure in this segment of the subject population. Specifically, estimates of interrater reliability, internal consistency, and test-retest reliability are presented for a sample of 42 adult outpatients. In addition, the relationship between total protocol ratings and item sum scores is explored.

Adult↗
PubMed1989

Gating scheme for single GABA-activated Cl- channels determined from stability plots, dwell-time distributions, and adjacent-interval durations.

To study the gating of a GABA-activated Cl- channel, currents from single channels activated by 1.0 microM GABA were examined in patches of membrane excised from cultured chick cerebral neurons. The distributions of open and shut interval durations were each described by the sum of 3 exponential components, suggesting that the channel normally enters at least 3 open and 3 shut states. Five different 6-state gating schemes were found that could describe, all equally well, the observed distributions of open and shut interval durations. Plots of the mean duration of open intervals adjacent to shut intervals of specified durations revealed that, on the average, openings of brief duration were adjacent to closings of long duration. This observation indicated 2 or more independent transition pathways between the open and shut states. Examination of the distributions of open intervals adjacent to shut intervals of specified durations revealed that the time constants of the exponential components describing these conditional open-interval distributions were independent of the durations of the adjacent shut intervals. In contrast, the areas changed in a manner consistent with open states of briefer mean lifetimes typically making transitions to shut states of longer mean lifetimes. Four of the 5 gating schemes considered were rejected because they did not predict the relationship between adjacent intervals or because they predicted that the channel should switch between 2 gating modes with markedly different mean open and shut times, which was not a characteristic of the experimental data. The single remaining kinetic scheme could account for the observed kinetic properties of the GABA channel.

Animals↗
PubMed1988

Mass correlograms of multiple neuronal activity in the cat's extrastriate cortex.

Electrical activity of a population of visually responsive cells located in the vicinity of a single functionally defined neuron was recorded in the area 18 of the cat's cerebral cortex with a single tungsten microelectrode. The correlograms calculated from the mass activity record showed an existence of a rhythmic neuronal firing with an average interval near to 3 ms. When the system was activated by a visual stimulus, a line at an optimal angle moving in an optimal direction, the rhythmic activity became regular, acquiring an oscillatory sinusoidal character. This rhythmic pattern cannot be easily recognized when the activity of a single neuron is recorded. It is possible that such rhythmic activity involving large numbers of neurons contributes to the recognition of the velocity and position of the visual stimulus.

Animals↗
PubMed1988

Lack of homogeneity of receptive fields of visual neurons in the cortical area 18 of the cat.

The receptive fields of "complex" neurons within area 18 of the cerebral cortex of the cat were determined by a computer-assisted method using a moving light bar substantially shorter than the long diameter of the receptive field as a visual stimulus. The visual cells repeatedly generated nerve impulses when the stimulus crossed well-defined "active points" within their receptive fields. Outside of these active points, the cells remained silent. It is suggested that the receptive fields are formed by a discontinuous accumulation of such active points. When the electrical activities of two neighbouring visual neurons are recorded simultaneously, their active points do not coincide. In addition, some active points were located outside the most prominent excitatory part of the receptive field of the studied cells. Individual visual cells typically differ in the number and distribution of active points. Since these cells best respond to a stimulus moving in a certain direction, it is suggested that they may act as direction of movement and/or velocity detectors. Alternate firing of a number of neighboring cells connected to a distributed pattern of peripheral receptors may form a system which is able to code for velocity and direction of the moving stimulus.

Action Potentials↗