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PubMed1997

Low-amplitude oscillations in the inferior olive: a model based on electrical coupling of neurons with heterogeneous channel densities.

The mechanism underlying subthreshold oscillations in inferior olivary cells is not known. To study this question, we developed a single-compartment, two-variable, Hodgkin-Huxley-like model for inferior olive neurons. The model consists of a leakage current and a low-threshold calcium current, whose kinetics were experimentally measured in slices. Depending on the maximal calcium and leak conductances, we found that a neuron model's response to current injection could be of four qualitatively different types: always stable, spontaneously oscillating, oscillating with injection of current, and bistable with injection of current. By the use of phase plane techniques, numerical integration, and bifurcation analysis, we subdivided the two-parameter space of channel densities into four regions corresponding to these behavioral types. We further developed, with the use of such techniques, an empirical rule of thumb that characterizes whether two cells when coupled electrically can generate sustained, synchronized oscillations like those observed in inferior olivary cells in slices, of low amplitude (0.1-10 mV) in the frequency range 4-10 Hz. We found that it is not necessary for either cell to be a spontaneous oscillator to obtain a sustained oscillation. On the other hand, two spontaneous oscillators always form an oscillating network when electrically coupled with any arbitrary coupling conductance. In the case of an oscillating pair of electrically coupled nonidentical cells, the coupling current varies periodically and is nonzero even for very large coupling values. The coupling current acts as an equalizing current to reconcile the differences between the two cells' ionic currents. It transiently depolarizes one cell and/or hyperpolarizes the other cell to obtain the regenerative response(s) required for the synchronized oscillation. We suggest that the subthreshold oscillations observed in the inferior olive can emerge from the electrical coupling between neurons with different channel densities, even if the inferior olive nucleus contains no or just a small proportion of spontaneously oscillating neurons.

Animals↗

PubMed1999

Models of respiratory rhythm generation in the pre-Bötzinger complex. II. Populations Of coupled pacemaker neurons.

We have proposed models for the ionic basis of oscillatory bursting of respiratory pacemaker neurons in the pre-Bötzinger complex. In this paper, we investigate the frequency control and synchronization of these model neurons when coupled by excitatory amino-acid-mediated synapses and controlled by convergent synaptic inputs modeled as tonic excitation. Simulations of pairs of identical cells reveal that increasing tonic excitation increases the frequency of synchronous bursting, while increasing the strength of excitatory coupling between the neurons decreases the frequency of synchronous bursting. Low levels of coupling extend the range of values of tonic excitation where synchronous bursting is found. Simulations of a heterogeneous population of 50-500 bursting neurons reveal coupling effects similar to those found experimentally in vitro: coupling increases the mean burst duration and decreases the mean burst frequency. Burst synchronization occurred over a wide range of intrinsic frequencies (0.1-1 Hz) and even in populations where as few as 10% of the cells were intrinsically bursting. Weak coupling, extreme parameter heterogeneity, and low levels of depolarizing input could contribute to the desynchronization of the population and give rise to quasiperiodic states. The introduction of sparse coupling did not affect the burst synchrony, although it did make the interburst intervals more irregular from cycle to cycle. At a population level, both parameter heterogeneity and excitatory coupling synergistically combine to increase the dynamic input range: robust synchronous bursting persisted across a much greater range of parameter space (in terms of mean depolarizing input) than that of a single model cell. This extended dynamic range for the bursting cell population indicates that cellular heterogeneity is functionally advantageous. Our modeled system accounts for the range of intrinsic frequencies and spiking patterns of inspiratory (I) bursting cells found in the pre-Bötzinger complex in neonatal rat brain stem slices in vitro. There is a temporal dispersion in the spiking onset times of neurons in the population, predicted to be due to heterogeneity in intrinsic neuronal properties, with neurons starting to spike before (pre-I), with (I), or after (late-I) the onset of the population burst. Experimental tests for a number of the model's predictions are proposed.

Animals↗

PubMed1996

Synchronized action of synaptically coupled chaotic model neurons.

Experimental observations of the intracellular recorded electrical activity in individual neurons show that the temporal behavior is often chaotic. We discuss both our own observations on a cell from the stomatogastric central pattern generator of lobster and earlier observations in other cells. In this paper we work with models with chaotic neurons, building on models by Hindmarsh and Rose for bursting, spiking activity in neurons. The key feature of these simplified models of neurons is the presence of coupled slow and fast subsystems. We analyze the model neurons using the same tools employed in the analysis of our experimental data. We couple two model neurons both electrotonically and electrochemically in inhibitory and excitatory fashions. In each of these cases, we demonstrate that the model neurons can synchronize in phase and out of phase depending on the strength of the coupling. For normal synaptic coupling, we have a time delay between the action of one neuron and the response of the other. We also analyze how the synchronization depends on this delay. A rich spectrum of synchronized behaviors is possible for electrically coupled neurons and for inhibitory coupling between neurons. In synchronous neurons one typically sees chaotic motion of the coupled neurons. Excitatory coupling produces essentially periodic voltage trajectories, which are also synchronized. We display and discuss these synchronized behaviors using two "distance" measures of the synchronization.

Action Potentials↗

PubMed2005

African American couples merging strengths to successfully cope with breast cancer.

PURPOSE/OBJECTIVES: To explore the process of coping with breast cancer among African American women and their spouses. DESIGN: Exploratory, qualitative study using grounded theory methods. SETTING: Large metropolitan area in the mid-Atlantic United States. SAMPLE: 12 African American couples (N = 24). METHODS: African American women and their spouses were asked to complete a background data sheet and participate in a face-to-face semistructured interview. Qualitative data were audiotaped and transcribed verbatim. Themes were identified using the constant comparative method. Quantitative data were analyzed with descriptive statistics. MAIN RESEARCH VARIABLES: The process of coping with breast cancer among African American couples. FINDINGS: The basic social concern was living through and beyond a breast cancer diagnosis. The core variable was merging strengths to cope with and survive a breast cancer diagnosis. Six main categories emerged to describe how African American couples actively worked together to cope with a breast cancer diagnosis: walking together, praying together, seeking together, trusting together, adjusting together, and being together. CONCLUSIONS: African American couples described the importance of combining their strengths and working together as a couple to cope with a breast cancer diagnosis. IMPLICATIONS FOR NURSING: Nurses must understand the importance of developing culturally sensitive and culturally relevant interventions to assist African American couples with effectively coping with a breast cancer diagnosis. When providing care to African American couples, nurses should incorporate the six categories of walking, praying, seeking, trusting, adjusting, and being together to help couples cope with the various phases of the breast cancer experience.

Adaptation, Psychological↗

PubMed2000

Prevalence of extradyadic sex in male couples of mixed HIV status and its relationship to psychological distress and relationship quality.

This study assessed the prevalence of extradyadic sex and the relationship between such activity and psychological distress and relationship quality in male couples of mixed HIV serostatus. Sixty-three couples were interviewed and had sufficient data for inclusion in all analyses. With regard to sexual activity during the year prior to being interviewed, 19 (30%) couples were monogamous, 18 (29%) described themselves as "open," 13 (21%) kept extradyadic sex a secret from their partners, and in 13 couples there was only partial knowledge of extradyadic sex. Though not statistically significant, monogamous and open couples consistently scored lower numerically on measures of psychological distress and higher on measures of relationship quality, compared to "partial knowledge" and "secretive" couples. When pooled, monogamous and open couples scored significantly higher on measures of dyadic consensus, affectional expression, dyadic satisfaction, and sexual satisfaction compared to the combined subgroup of partial knowledge and secretive couples.

Adult↗

PubMed2002

Polarization-mode coupling in birefringent fiber gratings.

Polarization-mode coupling in birefringent fiber gratings is analyzed. The general expression for coupling coefficient components is also derived. It indicates that the polarization-mode coupling between any two linearly polarized (LP) core modes is possible by appropriately adjusting the grating parameters such as the grating tilt angle, the grating length, the orientation of the grating plane, the grating period, the birefringence, and the birefringent axis. It is analytically found that the complete LP01x-to-LP01y mode coupling and LP01x-to-LP11y mode coupling occur when fiber is pressed periodically. The LP01x-to-LP11y mode coupling in the linearly birefringent gratings created by pressing a two-mode fiber with a groove plate with a period of 80 microm at a tilt angle between 81.5 degrees and 83.5 degrees has also been experimentally demonstrated. The resonant LP01x-to-LP11y mode coupling in the birefringent gratings and their experimental transmission spectra were reasonably well predicted by the coupled-mode analysis.

Journal Article↗

PubMed2004

Analytical solutions of coupled-mode equations for multiwaveguide systems, obtained by use of Chebyshev and generalized Chebyshev polynomials.

A novel approach is proposed for obtaining the analytical solutions of the coupled-mode equations (CMEs); the method is applicable for an arbitrary number of coupled waveguides. The mathematical aspects of the CMEs and their solution by use of Chebyshev polynomials are discussed. When mode coupling between only adjacent waveguides is considered (denoted weak coupling), the first and second kinds of the usual Chebyshev polynomials are appropriate for evaluating the CMEs for linearly distributed and circularly distributed multiwaveguide systems, respectively. However, when one is considering the coupling effects between nonadjacent waveguides also (denoted strong coupling), it is necessary to use redefined generalized Chebyshev polynomials to express general solutions in a form similar to those for the weak-coupling case. As concrete examples, analytical solutions for 2 x 2, 3 x 3, and 4 x 4 linearly distributed directional couplers are obtained by the proposed approach, which treats the calculation as a nondegenerate eigenvalue problem. In addition, for the 3 x 3 circularly distributed directional coupler, which gives rise to a degenerate eigenvalue problem, an analytical solution is obtained in an improved way. Also, for comparison and without loss of generality, to clarify the difference between the two coupling cases, analytical solutions for a 5 x 5 circularly distributed directional coupler are obtained by use of the usual and the redefined generalized Chebyshev polynomials.

Journal Article↗

PubMed2005

Treating attachment injured couples with emotionally focused therapy: a case study approach.

This paper compared the attachment injury resolution process in two distressed couples undergoing ten sessions of Emotional Focused Therapy (EFT), a short-term empirically validated treatment for relational distress. An attachment injury is a newly coined clinical construct that denotes a specific type of betrayal within the couple's relationship. The incident is so potent that it calls into question assumptions about the safety of the relationship. The task analytic method was used to examine the pathways of change as related to attachment injury of each couple. Several outcome and process measures were employed in order to differentiate the therapeutic process between the resolved versus non-resolved couple. Results indicated that the couple who resolved their identified attachment injury at the outset of therapy adhered to the attachment injury resolution model, while the non-resolved couple showed marked deviations from the expected pathways of change. Findings suggest that the resolved couple tended to show more differentiation of interactional positions and greater levels of experiencing throughout the therapeutic process in relation to the non-resolved couple. It is recommended that further research is necessary to examine the clinical utility of the attachment injury resolution model in the context of a larger number of case studies.

Adult↗

PubMed2005

Electrical coupling between interneurons with different excitable properties in the stratum lacunosum-moleculare of the juvenile CA1 rat hippocampus.

Electrical coupling among GABAergic interneurons is believed to play an essential role in shaping synchronized brain network activity related to cognition and behavior. We have studied the rules governing the electrical coupling between hippocampal interneurons located in stratum lacunosum-moleculare of the CA1 hippocampus. The most frequently recorded interneuron subtype had short multipolar dendrites and a dense local axonal arborization, typical of neurogliaform cells. Electrical excitability in this class of interneurons was heterogeneous. Although injection of small current steps evoked late spiking, larger steps triggered different types of firing patterns. Trains of action potentials ranged from clearly adapting to highly irregular, with clustered or mostly regular spikes. Electrotonic and action potentials could be propagated to the coupled cells; the coupling coefficient for electrotonic signals was 0.035, which compared with 0.005 for action potentials. Electrical coupling was reversibly blocked by application of carbenoxolone. Multiple simultaneous recordings indicated that interneurons with similar and different firing patterns were electrically coupled. This visual impression was quantitatively confirmed by principal component analysis applied to variables related to membrane excitability. In fact, the probability of finding electrically coupled neurons in our sample was not dependent on the excitable properties of the cells tested and was approximately 0.34. The presence of diffuse electrical coupling among hippocampal interneurons of stratum lacunosum-moleculare with different excitability is a novel finding with important implications. For example, the promiscuity of electrical connections may endow inhibitory networks with a large degree of flexibility and regulate the computational power of the hippocampus during different synchronized states.

Action Potentials↗

PubMed2005

Gap-junctional coupling and absolute sensitivity of photoreceptors in macaque retina.

We investigated gap-junctional coupling of rods and cones in macaque retina. Cone voltage responses evoked by light absorption in neighboring rods were briefer and smaller than responses recorded in the rods themselves. Rod detection thresholds, calculated from noise and response amplitude histograms, closely matched the threshold for an ideal detector limited by quantal fluctuations in the stimulus. Surprisingly, cone thresholds were only approximately two times higher. Amplitude fluctuations in cones could be explained by a Poisson distribution of photoisomerizations within a pool of seven or more coupled rods. Neurobiotin coupling between rods and cones was consistent with our electrical recordings, with approximately six rods labeled per injected cone. The spatial distribution of tracer-coupled rods matched the light-evoked cone receptive field. The gap junction inhibitor carbenoxolone abolished both electrical and tracer coupling. Amplitude fluctuations in most rods were accounted for by the expected rate of light absorption in their outer segments. The fluctuations in some rods, however, were consistent with a summation pool of up to six rods. When single rods were injected with Neurobiotin, up to 10 rods were labeled. Rod-rod and rod-cone electrical coupling is expected to extend the range of scotopic vision by circumventing saturation at the rod to rod-bipolar cell synapse; however, because coupling also renders the rod synapse less effective at separating out photon signals from dark noise, coupling is expected to elevate the absolute threshold of dark-adapted observers.

Animals↗

PubMed1993

Behavioral marital therapy with and without additional couples relapse prevention sessions for alcoholics and their wives.

This study evaluated whether alcoholics who received couples relapse prevention (RP) sessions in the year after short-term behavioral marital therapy (BMT) did better than those who did not receive additional RP. Couples (n = 59) with an alcoholic husband, after participating in weekly BMT couples sessions for 5 months, were assigned randomly to receive or not receive 15 additional conjoint couples relapse prevention (RP) sessions over the next 12 months. Outcome measures were collected before and after BMT and at quarterly intervals for the year after BMT. Significant improvements in the alcoholics' drinking and the couple's marital adjustment occurred from before to after BMT replicating results of our own and other's earlier studies of BMT with alcoholics, and outcomes remained significantly improved through 12-months follow-up independent of the amount of aftercare received. Given these favorable outcomes overall, the present study provided a stringent test of the hypothesized utility of RP. As predicted, alcoholics who received RP after BMT had more days abstinent and fewer days drinking, maintained their improved marriages better and used behaviors targeted by BMT more than those who received BMT alone. The prediction that greater continued use of behaviors targeted by BMT would be associated with better outcomes irrespective of the amount of aftercare received also was supported. The final prediction that couples with more severe alcohol and marital problems at study entry would show the greatest additional benefit from RP was not supported. The relatively clear-cut findings favoring RP may be due to the fact that RP in this study was an intensive, multifaceted booster maintenance intervention delivered in a couples format over a lengthy period of time. Moreover, the present results occurred during the time that couples were still getting RP. Limitations to the generalizability and interpretation of the results are discussed.

Adult↗

PubMed2006

Dynamic interreceptor coupling: a novel working mechanism of two-dimensional ryanodine receptor array.

Ryanodine receptors (RyRs) usually form two-dimensional regular array in sarcoplasmic reticulum membranes in muscle cells. The inter-RyRs coupling may be essential for the maintenance of quiescent Ca2+ release in resting state, as well as for the coordinated activation and rapid termination of RyR-mediated Ca2+ release during excitation-contraction coupling. In our previous work, we have reported that the inter-RyRs interaction is modulated by RyR channel's functional state, which inspired us to propose a novel working mechanism of RyR array: "dynamic inter-RyR coupling". In this work, we built a simple model based on cellular automata and the Monte-Carlo method to quantitatively investigate the roles of intermolecular coupling and its modulation in regulating the signaling capabilities of RyR array. Our simulation results showed that with a suitable inter-RyR coupling strength, the combination of rest stability and high response efficiency, namely optimal signal/noise ratio, of Ca2+ signaling could be achieved. Moreover, we also found the continued coupling between open RyRs would delay the system termination rate. The coacquisition of robust termination of array opening relied on the proper decrease of coupling strength between activated RyRs. Obviously, such temporally asymmetric coupling would simultaneously endow the system with physiologically relevant resting stability and fast termination.

Calcium↗

PubMed1985

Augmentation of anti-tumor activity by immunization with Mycobacterium tuberculosis (Tbc) and tuberculin-coupled tumor cells.

The anti-tumor effect of immunization with heat-killed Mycobacterium tuberculosis (Tbc) and Tuberculin (PPD)-coupled syngeneic tumor cells was examined in vivo. Three tumor cell lines were employed. Immunization of Tbc-primed BALB/c mice with PPD-coupled syngeneic Meth-A tumor cells displayed a potent anti-tumor effect on viable Meth-A cells inoculated subcutaneously. Neither PPD-coupled LLC (Lewis Lung Carcinoma) cells nor sonicated PPD-coupled Meth-A cells were capable of immunizing these mice. PPD-coupled syngeneic whole tumor cells were indispensable for induction of this tumor-specific resistance. Immunization of Tbc-primed C3H/He mice with PPD-coupled syngeneic MH134 tumor cells did not elicit anti-tumor activity against MH134, but additional pretreatment of mice with cyclophosphamide brought on an anti-tumor effect. Antimetastatic reactivity was investigated in C57BL/6 mice bearing LLC, with a reduction in metastases noted. This antimetastatic effect was observed even when the mice were immunized with PPD-coupled LLC cells three days after removal of the initial tumor. Immunization with Tbc and PPD-coupled Meth-A cells together with intraperitoneal administration of murine or rat interleukin 2 (IL 2) further augmented anti-Meth-A resistance. Murine IL 2 further inhibited tumor growth during the early stage, while rat IL 2 showed an anti-tumor effect throughout the course of tumor growth.

Animals↗

PubMed1992

Attitudes about infertility interventions among fertile and infertile couples.

BACKGROUND: There has been marked progress in the development of infertility interventions. This paper reports attitudes about 11 interventions for infertility. METHODS: Face-to-face interviews were conducted with each member of 185 infertile and 90 presumed fertile couples in southeastern Michigan. RESULTS: Seven of these interventions were generally viewed favorably and four were generally viewed negatively, regardless of the couple's fertility status. Infertile couples viewed all interventions, except for adoption, more favorably than did fertile couples. Multidimensional scaling was used to cluster the interventions according to similarity in endorsement. These clusters form a continuum from interventions that allow only one member of the couple to be a biological parent to the most noninvasive techniques. All clusters remain roughly equidistant from adoption, in which neither member of the couple is a biological parent. CONCLUSIONS: Interventions that produce a child who is biologically related to only one member of the couple were viewed most negatively. Members of couples who were receiving fertility treatment made finer discriminations among infertility interventions than did individuals who had not received treatment.

Adoption↗

PubMed2001

Marital relationship in late adulthood: synchronous versus asynchronous couples.

The article presents a study on marital relations in late adulthood, conducted among a sample of 469 Israeli couples, who were divided into four groups based on occupational status and spousal timing of retirement. Two of the groups were categorized as synchronous: pre-retired couples (both partners are close to retirement); and retired couples (both partners are retired), and two of the groups were categorized as asynchronous: employed husband/retired wife and retired husband wife/employed husband. Differences between the groups were examined in three areas: Division of tasks in the home; marital power relations; and quality of marriage. Regarding division of tasks in the home, feminine tasks were usually more egalitarian among retired couples and retired husbands/employed wives than among pre-retired couples and employed husbands/retired wives. In addition, synchronous-retired couples were found to be more egalitarian than synchronous-pre-retired and asynchronous employed husbands/retired wives with regard to general tasks, while masculine tasks were usually carried out by husbands in all four groups. With respect to quality of marriage, the pre-retired couples expressed more marital complaints than did the retired couples, while no differences were found between either of the asynchronous groups. Nonetheless, marital power relations were generally egalitarian in all four groups.

Aged↗

PubMedDate not supplied

Sex ratio of male sex preselected children born to couples with exclusively female offspring.

The present study was undertaken to determine if couples with exclusively female children had a decreased probability of a male child after using male sex preselection. Selection criteria for subjects necessitated that couples have had only female children previously and had produced a child at one of 14 centers after using protocol 3 (n = 70) and modified 3 (n = 28) male sex preselection. Prior to sex selection, protocol 3 couples produced a combined total of 135 female children for an average of 2.01 (range 1-4) females per couple; modified 3 couples produced a combined total of 62 female children for an average of 2.21 (range 1-4) females per couple. The normal approximation to the binomial distribution was used to determine significant differences between the sex ratios prior to and after male sex preselection. For couples using protocol 3 there were significant differences in the sex ratio prior to sex preselection (0%) and after sex preselection (73.0%) (p less than .00003). There were also significant differences between the sex ratio prior to modified 3 (0%) and after sex preselection (86%) (p less than .00003). Couples using male sex preselection do not have a decreased probability of a male child if they have had exclusively female children.

Female↗

PubMed1995

Patterns of psychological distress in infertile couples.

The present investigation used a sample of 104 infertile couples to examine patterns of distress among couples. Couples were separated on the basis of which spouse(s) experienced distress: Both non-distressed (33%), Male distressed (18%), Female distressed (22%), Both distressed (27%). Most couples tended to exhibit parallel functioning (60%) with both spouses functioning at similar levels, while the remainder experienced complementary patterns with one distressed and the other not. Of particular note is the finding that a substantial number of infertile couples (18%) have a distressed husband paired with a non-distressed wife, which is counter to the general assumption that infertility is more distressing to women than to men. The Both non-distressed couples had the least overall psychological distress, with higher estimates of marital satisfaction. They and the couples from the Male distressed group had been in the treatment process less time and were drawn primarily from infertility clinics. The Female distressed group and Both distressed group had been in treatment for the longest time and were primarily recruited through RESOLVE, Inc. (a national non-profit organization for infertile people). These data illustrate the importance of considering the contextual pattern of distress in couples when considering women or men being treated for infertility.

Adaptation, Psychological↗

PubMed1998

[Dye coupling between visual cortical (area 17) neurones of adult rat--a study on brain slices].

With intracellular injection of biocytin, forty-nine neurones were successfully labeled in in vitro visual cortex (area 17) slices of the adult rat. Out of the sample dye coupling was found in 21 cases, for each injection the number of the coupled cells varying from 2 to 5 (mean 2.8 +/- 1.1). Eighteen couplings were pyramidal-pyramidal, two were pyramidal-nonpyramidal, and one was seen among non-pyramidal cells. In most cases, the coupled cells were apart from each other with a certain distance among their cell bodies (mean 43.1 +/- 24 microns). The longest distance was up to 635 microns. Most couplings (19/21) were observed within the same lamina; only two in different laminae. The dye couplings were found in laminae II/III, IV and V, but mostly in laminae II/III. We have measured membrane potential and response properties to white matter and intracellular stimulation for the coupled and non-coupled cells; no significant difference was found between them.

Animals↗