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PubMedDate not supplied

The relationship of the postcoital test and semen characteristics to pregnancy rates in 200 presumed fertile couples.

OBJECTIVE: To evaluate the postcoital test (PCT) and semen analysis (SA) in the prediction of pregnancy in 200 potentially fertile couples. METHODS: 200 couples without risk for infertility were prospectively followed for 1 year. Couples were attempting pregnancy for 12 menstrual cycles. In the first three cycles, the women underwent monthly PCTs and collected daily urines while the men provided bimonthly semen analyses. For the next nine cycles, the couples were monitored for pregnancy. The PCT included hours post-coitus, amount of mucus, spinnbarkeit, number of motile sperm, and percent of motile sperm. Since multiple PCTs and SAs were available for each couple, values were averaged to provide one mean value per couple. The Wilcoxon ranked sum test was used to detect differences in PCT and SA. RESULTS: Pregnancy occurred in 163/200 couples (82%) in 12 cycles. Mean sperm count per high-power field (p = 0.01) and mean number of highly motile sperm (p = 0.03) were higher among women in whom pregnancy occurred. Amount of mucus and spinnbarkeit were similar between women who became pregnant and those who did not. Semen concentration, motile sperm count, and percent motile sperm were significantly higher among men whose partner conceived (P < .02). Only 93 couples (47%) had PCTs that were correctly timed. CONCLUSIONS: Measures predictive of pregnancy included vigorously moving sperm per high-power field, sperm concentration, motile sperm count, and percent motility. Mucus characteristics were not predictive of pregnancy. Additionally, a high number of sperm seen in the PCT correlated with a high number of motile sperm in the SA. These results support the use of the PCT for initial evaluation of the infertile couple.

Adult↗

PubMed1998

The psychological effects of work experiences and disagreements about gender role beliefs in dual-earner couples: a longitudinal study.

Using an economically diverse random sample of 300 full-time employed men and women in dual-earner couples from two communities in the Northeast, we estimated the relation between the direction and magnitude of disagreement about gender role ideology (GRI) within couples and psychological distress. We conceptualized GRI within couples as both the couple mean or stable gender-role ideology (the "couple ideology") and as each partner's deviation from the other partner's score. Moreover, for each partner, we estimated the relation between both the stable (i.e., mean) component and the change (i.e., time-varying) component of GRI and distress. Finally, for each partner we estimated the moderating effect of GRI on the relation between job-role quality and distress. Findings are: (a) the more egalitarian the husband's average GRI is relative to his wife's, the less distressed he is; (b) if over time a wife's GRI becomes less egalitarian relative to her husband's, then her distress will be more affected by changes in her job-role quality; (c) for husbands, as the couple's average GRI becomes more egalitarian over time, the effect of job-role quality on distress is lessened; and (d) for a man in a couple with a more egalitarian stable GRI, the effects of change in job-role quality on distress are less pronounced than for a man in a couple with a less egalitarian stable GRI. Results are discussed in terms of new conceptions of GRI revealing the dynamic interaction of within-couples' gender-role ideologies.

Adult↗

PubMed1979

Tryptic proteolysis of coupling factor-latent ATPase from mycobacterium phlei. Theoretical modeling of structure-function relationships.

Trypsin treatment of solubilized coupling factor-latent ATPase from Mycobacterium phlei alters its subunit structure and functional properties. This coupling factor exhibits ATPase activity following trypsin treatment. Concurrently, both the ability of the enzyme to rebind to membranes depleted of coupling factor and its capacity for coupled phosphorylation are lost. The native alpha (64 000 dalton) subunit undergoes limited proteolytic digestion, and the delta (14 000 dalton) subunit is partially lost. During the course of tryptic proteolysis, the coupling factor molecule may exist in one of ten unique structural state (e.g. the native, ATPase-inactive molecule exists in the alpha alpha alpha state). Rigorous analysis of the experimental data by theoretical modeling provided information concerning the intermediate structural states leading to the fully ATPase-activated alpha" alpha" alpha" state under different conditions of trypsin treatment. The theoretical models of structure-function relationships that best-represented the experimental data predicted that the native coupling factor molecule contains three copies of the alpha (64 000 dalton) form of the alpha subunit, that the alpha" (58 000 dalton) alpha subunit species contributes maximally and the alpha' (61 000 dalton) form about half-maximally to ATPase activity, that membrane rebinding ability is proportional to the number of native alpha subunits in the enzyme, and that at least one native alpha subunit/molecule is required for full expression of coupled phosphorylation. These results indicate an essential role for the alpha subunit in the regulation of ATPase activity and in the ability of the solubilized coupling factor to rebind to depleted membranes.

Adenosine Triphosphatases↗

PubMed2006

Comparative localization of leucine-rich repeat-containing G-protein-coupled receptor-7 (RXFP1) mRNA and [33P]-relaxin binding sites in rat brain: restricted somatic co-expression a clue to relaxin action?

Relaxin is a polypeptide hormone with established actions associated with reproductive physiology, but until recently the precise nature of the relaxin receptor and its transmembrane signaling mechanisms had remained elusive. In 2002 however, the leucine-rich-repeat-containing G-protein-coupled receptor-7 (now classified as RXFP1) was identified as a cognate receptor for relaxin, with activation resulting in stimulation of intracellular cAMP production. These findings, along with the presence and putative actions of relaxin within the CNS and earlier descriptions of relaxin binding sites in brain, suggest the importance and feasibility of determining if these relaxin binding sites represent leucine-rich-repeat-containing G-protein-coupled receptor-7 and their precise comparative distribution. Thus, the current study reports the distribution of leucine-rich-repeat-containing G-protein-coupled receptor-7 mRNA throughout the rat brain using in situ hybridization histochemistry of [(35)S]-labeled oligonucleotides and the comparative distribution of [(33)P]-human relaxin binding sites. The extensive, topographical distribution of leucine-rich-repeat-containing G-protein-coupled receptor-7 mRNA throughout the adult rat brain correlated very closely to that of [(33)P]-relaxin binding sites. Leucine-rich-repeat-containing G-protein-coupled receptor-7 mRNA was expressed by neurons in several brain regions, including the olfactory bulb, cerebral cortex, thalamus, hippocampus, hypothalamus, midbrain, pons and medulla. Receptor transcripts were most abundant in areas such as the basolateral amygdala, subiculum, deep layers of the cingulate, somatosensory and motor cortices and intralaminar/midline thalamic nuclei. These areas also contained very high densities of [(33)P]-relaxin binding sites, suggesting a largely somatic localization of leucine-rich-repeat-containing G-protein-coupled receptor-7 protein and site of action for relaxin peptide. The central distribution of relaxin-producing neurons has been described, while data on the topography of nerve terminals that contain and secrete the peptide are currently lacking; but overall these findings strongly suggest that leucine-rich-repeat-containing G-protein-coupled receptor-7 is the cognate receptor for relaxin in the rat brain, and support a role for relaxin-leucine-rich-repeat-containing G-protein-coupled receptor-7 signaling in various somatosensory, autonomic and neurohumoral pathways, which warrants further investigation.

Animals↗

PubMed2003

Constitutively active Gq/11-coupled receptors enable signaling by co-expressed G(i/o)-coupled receptors.

Co-expression of guanine nucleotide-binding regulatory (G) protein-coupled receptors (GPCRs), such as the G(i/o)-coupled human 5-hydroxytryptamine receptor 1B (5-HT(1B)R), with the G(q/11)-coupled human histamine 1 receptor (H1R) results in an overall increase in agonist-independent signaling, which can be augmented by 5-HT(1B)R agonists and inhibited by a selective inverse 5-HT(1B)R agonist. Interestingly, inverse H1R agonists inhibit constitutively H1R-mediated as well as 5-HT(1B)R agonist-induced signaling in cells co-expressing both receptors. This phenomenon is not solely characteristic of 5-HT(1B)R; it is also evident with muscarinic M2 and adenosine A1 receptors and is mimicked by mastoparan-7, an activator of G(i/o) proteins, or by over-expression of Gbetagamma subunits. Likewise, expression of the G(q/11)-coupled human cytomegalovirus (HCMV)-encoded chemokine receptor US28 unmasks a functional coupling of G(i/o)-coupled CCR1 receptors that is mediated via the constitutive activity of receptor US28. Consequently, constitutively active G(q/11)-coupled receptors, such as the H1R and HCMV-encoded chemokine receptor US28, constitute a regulatory switch for signal transduction by G(i/o)-coupled receptors, which may have profound implications in understanding the role of both constitutive GPCR activity and GPCR cross-talk in physiology as well as in the observed pathophysiology upon HCMV infection.

Animals↗

PubMed2005

Prediction of the coupling specificity of GPCRs to four families of G-proteins using hidden Markov models and artificial neural networks.

MOTIVATION: G-protein coupled receptors are a major class of eukaryotic cell-surface receptors. A very important aspect of their function is the specific interaction (coupling) with members of four G-protein families. A single GPCR may interact with members of more than one G-protein families (promiscuous coupling). To date all published methods that predict the coupling specificity of GPCRs are restricted to three main coupling groups G(i/o), G(q/11) and G(s), not including G(12/13)-coupled or other promiscuous receptors. RESULTS: We present a method that combines hidden Markov models and a feed-forward artificial neural network to overcome these limitations, while producing the most accurate predictions currently available. Using an up-to-date curated dataset, our method yields a 94% correct classification rate in a 5-fold cross-validation test. The method predicts also promiscuous coupling preferences, including coupling to G(12/13), whereas unlike other methods avoids overpredictions (false positives) when non-GPCR sequences are encountered. AVAILABILITY: A webserver for academic users is available at http://bioinformatics.biol.uoa.gr/PRED-COUPLE2

Animals↗

PubMed1998

Reliability of self-reported sexual behavior in human immunodeficiency virus (HIV) concordant and discordant heterosexual couples in northern Thailand.

A partner study was conducted in northern Thailand between March 1992 and June 1996 which included data that allowed an assessment of the reliability of self-reports of sexual behavior and contraceptive use among heterosexual couples. The authors enrolled 529 couples among whom all male subjects were human immunodeficiency virus (HIV) seropositive voluntary blood donors and their female sexual partners were either HIV infected (n=246) or HIV seronegative (n=283). The levels of agreement within couples were assessed for recency of last sexual intercourse, sexual activity in the prior year, and contraceptive practices. For HIV discordant couples, a prospective study was conducted to examine risk factors for HIV transmission, the primary goal of the study. This allowed assessment of reliability of inter-partner reports over 6-12 months. Overall, agreement among couples was good for common sexual practices, especially vaginal intercourse and time since last intercourse, but was lower for condom use. Anal and oral sex were infrequently reported by these couples and there was greater disagreement for the occurrence of these practices. Partner agreement for contraceptive histories was good to excellent. Prospective data showed less frequent intercourse and more condom use but reliability remained good. Common sexual practices may be reliable for both HIV concordant and discordant couples in studies estimating prevalent infection. Estimates of incident heterosexually transmitted HIV may be made with greater reliability by studies which include assessment of reports of risk behavior by each member of a couple than studies of individuals.

Adult↗

PubMed1998

Long-term use of the female condom among couples at high risk of human immunodeficiency virus infection in Zambia.

BACKGROUND: Few studies have measured female condom use for more than a 6-month period or among persons at high risk of STD. OBJECTIVE: To measure long-term use of the female condom among couples at high risk of HIV infection and to evaluate the effect of female condom use on unprotected coital acts. STUDY DESIGN: Ninety-nine Zambian couples with symptomatic sexually transmitted diseases (STD) received female condoms, male condoms, and spermicides and were counseled to use either condom plus spermicide for each coital act. Couples were followed up at 3-, 6-, and 12-month visits. Barrier contraceptive use was measured prospectively by coital log. RESULTS: Among the 99 couples enrolled, 51, 38, and 30 couples were successfully followed up for 3, 6, and 12 months, respectively. Female condoms were reportedly used in 24%, 27%, and 23% of coital acts and by 86%, 79%, and 67% of the returning couples during each time interval. Higher-level female condom users used male condoms less often but had fewer unprotected coital acts (5% vs. 14%; p < 0.05) than lower-level female condom users. CONCLUSION: A majority of couples at high risk of HIV infection used the female condom in conjunction with other barrier methods over a 1-year period. The addition of female condoms accompanied by appropriate counseling to the barrier method mix may reduce unprotected sex among couples at high-risk of HIV infection.

Adult↗

PubMed2006

Current status and future directions in couple therapy.

Couple therapy research affirms that various approaches to couple treatment produce statistically and clinically significant improvement for a substantial proportion of couples in reducing overall relationship distress. Recent studies have extended these findings in indicating the effectiveness of couple-based interventions for a broad range of coexisting emotional, behavioral, or physical health problems in one or both partners. In contrast to these encouraging results, research also indicates that a sizeable percentage of couples fail to achieve significant gains from couple therapy or show significant deterioration afterward. Research on processes of change and predictors of treatment outcome in couple therapy provides preliminary evidence regarding factors potentially contributing to variable treatment response. The chapter concludes with 12 recommendations regarding future directions in couple therapy research and clinical training.

Anxiety Disorders↗

PubMed1998

Therapy with lesbian couples: the issues and the interventions.

OBJECTIVE: To highlight difficulties that are unique to lesbian couples by reviewing the data that contrast lesbian and heterosexual couples and exploring the theories that explain the observed differences in couple dynamics. METHOD: A review of the literature contrasting demographics and relationship characteristics in lesbians and heterosexual couples was conducted, and a review of lesbian psychotherapy literature was performed. RESULTS: The differences in couple dynamics may be attributed to female relational styles and the stresses of being in a relationship that is not socially sanctioned (homophobia). CONCLUSIONS: Therapists should not use heterosexual standards when evaluating lesbian relationships because this may lead to misconstruance of a couple's emotional intensity as pathological. They should, however, recognize the problems that stem from pathological levels of fusion. When evaluating a couple, clinicians must assess the level of internalized homophobia so as to understand when the couple's difficulties originate from unresolved conflicts over sexual orientation.

Couples Therapy↗

PubMed2004

Couple characteristics and outcome of therapy in vaginismus.

OBJECTIVE: To describe couple characteristics and outcome of therapy in vaginismus. DESIGN: A prospective before-after intervention descriptive study. SETTING: Department of Physiology, Faculty of Medicine, Colombo, Sri Lanka. METHODS: Fifty six couples with vaginismus, mostly self referrals and referrals from gynaecologists and general practitioners, were treated with a standard cognitive behaviour therapy protocol with before-after assessments of the degree of vaginismus and individual partner self-ratings of the relationship and psychological status (GHQ-30). OUTCOME MEASURES: Success at the end of the therapy was equated to the absence of or only mild vaginismus and, improvement in the couple relationship and psychological status scores. RESULTS: Twenty seven (48%) of the 52 (93%) couples with non-consummation reported failure of coitus following previous non-surgical and surgical interventions. Love marriages (70%), frequent attempts at sex (75%, 3 or 4 times/week) and sexual arousal (women = 86%, men = 89%) characterised couples. Ten men developed sexual problems, mostly erectile failure and premature ejaculation secondarily. Couple therapy enabled penetrative sex in 45 (80.3%). The single prognostic indicator of outcome was the degree of vaginismus at first visit, those with mild and moderate vaginismus (77%) being significantly more likely to establish coitus (p<0.001) and complete the therapy (p<0.001). The couple relationship improved marginally (women p<0.01, men 0.025 0.01) but the psychological status remained unchanged. Dropouts and referrals for psychiatric and marital counselling failed to complete therapy. INTERPRETATION: Couple sex therapy is effective in the management of vaginismus. Health professionals, especially gynaecologists and general practitioners, need to be aware of the problem and the satisfactory outcome of sex therapy.

Adult↗

PubMed2006

Defective vasodilatory mechanisms in hypertension: a G-protein-coupled receptor perspective.

PURPOSE OF REVIEW: The purpose of this article is to review recent evidence relating to the regulation of vasodilatation and alterations in these mechanisms in the hypertensive state. In particular, we will focus on signaling systems regulating nitric oxide synthase and intracellular cyclic AMP - the two principal mechanisms mediating vasodilatation. RECENT FINDINGS: G-protein-coupled-receptor-mediated, endothelial-dependent processes are increasingly being seen as critical vasodilatory mechanisms. Impairment of endothelial responses to G-protein-coupled receptor activation is a key component of the decrease in G-protein-coupled-receptor-mediated vasodilatation in hypertension. In addition, an 'uncoupling' of the G-protein-coupled receptor/G-protein complex is the principal mechanism underlying impaired G-protein-coupled-receptor-mediated vasodilatation in hypertension. Alterations in G-protein-coupled receptor kinase function have a central role underlying this defect. Finally, the importance of the expression of genetic variants of G-protein-coupled receptors and G-proteins underlying the defect in vasodilatation in hypertension remains contentious. SUMMARY: G-protein signaling pathways in the vasculature play an important role in both the development and the maintenance of the hypertensive state. It is unlikely, however, that any single defect in the G-protein-linked vasodilatory pathway will ever be shown to be the sole cause of hypertension.

Adenylyl Cyclases↗

PubMed2000

Functional coupling of mammalian receptors to the yeast mating pathway using novel yeast/mammalian G protein alpha-subunit chimeras.

The expression of mammalian G protein coupled receptors (GPCRs) in S. cerevisiae provides a powerful assay system for functional analysis, ligand identification and pharmaceutical screening. However, relatively few receptors have been coupled to the pheromone response pathway via the yeast G(alpha), Gpa1p, or chimeric yeast/mammalian G(alpha) subunits containing long C-terminal regions of mammalian G(alpha) proteins. We tested an extended range of seven such chimeras for G(alpha) sub-types of three major classes (G(alphai/o), G(alphas) and G(alphaq)), against eight human GPCRs (SST(2), SST(5), 5-HT(1A), 5-HT(1Dalpha), ML(1B), P2Y(1) and P2Y(2)). Although the G(alphai/o) chimeras increased the range of receptors that coupled efficiently, the G(alphas) and G(alphaq) chimeras were inactive when expressed using the GPA1 promoter. We describe 10 novel Gpa1p chimeras, designated 'transplants', in which the C-terminal five amino acids of Gpa1p were exchanged with mammalian residues. Coupling efficiency and ligand sensitivity improved significantly using the transplants. For the P2Y purinergic receptors, coupling could only be detected with the transplants; this is the first report of G(q) specificity coupling in yeast. Thus, the transplants offer major advantages over previously described approaches, in terms of both the range of receptors coupled and the efficiency of coupling.

GTP-Binding Proteins↗

PubMed2000

Long-term effect of prospective detection of high genetic risk on couples' reproductive life: data for thalassaemia.

Prospective risk detection with availability of prenatal diagnosis is the best service currently available for couples at high genetic risk Here we describe the long term effect of this service on the reproductive life of 102 couples at risk of thalassaemia, whose risk was detected prospectively by carrier screening, who made use of prenatal diagnosis, and where the woman is now over 40. Overall outcome for couples is described in terms of number of favourable versus unfavourable pregnancy outcomes. (A favourable pregnancy outcome = unaffected livebirth, or affected livebirth resulting from informed parental choice.) The 102 couples had a total of 356 pregnancies, including 302 viable pregnancies, and 88% achieved a family unburdened by thalassaemia. 68% of viable pregnancies had a favourable outcome, but only 43% of couples had only favourable outcomes, and 26% lost two or more viable wanted pregnancies. When early losses are included 58% of pregnancies had a favourable outcome, but only 30% of couples had only favourable outcomes, and 41% lost two or more pregnancies. Even with the best available service, at risk couples remain victims of chance, and a significant minority experience great difficulty in obtaining even one healthy child. Research is needed on approaches that may allow couples better control of reproductive outcomes.

Adult↗

PubMed2003

Single versus double intrauterine insemination (IUI) in stimulated cycles for subfertile couples.

BACKGROUND: Intra uterine insemination (IUI), with or without controlled ovarian hyperstimulation (COH), is one of the treatment modalities offered to couples who have tried to conceive for at least one year (subfertile couples). It has been suggested that increasing the number of inseminations from one per cycle to two might increase the probability of conception. OBJECTIVES: To determine if there is a difference in live birth or pregnancy rates for subfertile couples using single or double intrauterine insemination in stimulated cycles. SEARCH STRATEGY: We searched the Cochrane Menstrual Disorders and Subfertility group trials register (searched 8 July 2002), the Cochrane Controlled Trials Register (Cochrane Library Issue 1, 2002), MEDLINE (January 1966 to July 2002), EMBASE (January 1988 to July 2002), SCIENCE Direct Database (January 1966 to July 2002), Confsci (January 1973 to 15 July 2002), Pascal (January 1984 to July 2002) and reference lists of articles. We also contacted researchers in the field. SELECTION CRITERIA: Randomised controlled, parallel trials of single versus double intrauterine inseminations in simulated cycles in subfertile couples. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial quality and extracted data. Study authors were contacted for additional information. MAIN RESULTS: Three studies involving 386 women were included. There was no data for the main outcome measure of live birth per couple or ongoing pregnancy rates, and none presented comparative data for adverse events. The results of two studies that reported pregnancy rate per couple did not show a significant effect of using double insemination (Peto OR 1.45, 95% CI 0.78-2.70). REVIEWER'S CONCLUSIONS: Based on the results of pregnancy rate per couple of two trials, double intrauterine insemination showed no significant benefit over single intrauterine insemination in the treatment of subfertile couples with husband semen. There are no meaningful data to offer advice regarding clinical practice on the basis of this review.

Female↗

PubMed1983

Subsequent reproductive outcome in couples with repeated pregnancy loss.

While the role of cytogenetic study in couples with repeated pregnancy loss is well-established, little information is available for counseling these couples concerning future reproductive outcome. Couples evaluated by chromosome analysis for recurrent abortion between 1972 and 1979 were contacted by phone in 1981. Of those studied cytogenetically, 195 couples (50.1%) could be located, and information concerning outcome of subsequent pregnancies were obtained. Couples (91) with two consecutive pregnancy losses at the time of initial investigation had a 31.3% subsequent abortion rate, but most (68%) had at least one liveborn child. The rate of infertility following evaluation was slightly increased (18.7%), but that of prematurity (11.2%) and congenital anomalies (2.5%) was not. In contrast, couples with greater than or equal to 3 consecutive losses (84) experienced abortion in 45.7% of subsequent pregnancies, and only 54.8% of them eventually had a liveborn child. Again, the rate of infertility was increased (26.2%), but that of prematurity (10%) and congenital defects (3.2%) was not. Nine couples in which one individual was found to have a chromosome abnormality (two inversions and seven translocations) were considered separately. Of these, seven couples had nine liveborn offspring. Amniocentesis was performed in eight cases, with karyotypes showing a balanced translocation identical to that of the parent in 2. All children were phenotypically normal.

Abortion, Habitual↗

PubMed2004

Impact on couple relationships of predictive testing for Huntington disease: a longitudinal study.

Since predictive testing has been available for Huntington disease (HD) and similar adult-onset neurodegenerative disorders, research into the psychosocial impact of test results has focussed on those receiving results, and to a lesser extent, on their partners. Few studies have examined the impact of predictive testing on the couple relationship, particularly from the perspective of family systems theory. This longitudinal study compared the level of marital adjustment of 23 couples in which the at-risk partner is undergoing predictive testing for HD (the testing group) with that of 20 couples in which the at-risk partner is not undergoing testing (the non-testing group). Participating couples completed a relationship measure, the Dyadic Adjustment Scale, at baseline and on two subsequent occasions. Using non-parametric tests, comparisons were made at each phase between the couple scores of the testing and non-testing groups but no significant differences were found in the levels of marital adjustment. Within the testing group the same comparisons were made for the carrier and non-carrier subgroups, and a significant difference was found at the final phase. There was an increase in the level of marital adjustment for the carrier group and a decrease for the non-carrier group. Together with trends observed in the data, this finding suggests a need for greater attention to be given to the potential impact of predictive testing on the couple relationship. Offering couples pre-result relationship assessment and referral for couple therapy, if warranted, may enhance the quality of professional support during the predictive testing process.

Adaptation, Psychological↗

PubMed2003

Vibronic coupling in molecules and in solids.

We utilize the experience gained in our previous studies on the "chemistry of vibronic coupling" in simple homonuclear and heteronuclear molecules to begin assembling theoretical guidelines for the construction of potentially superconducting solids exhibiting large electron-phonon coupling. For this purpose we analyze similarities between vibronic coupling in isolated molecules and in extended solids. In particular, we study vibronic coupling along the antisymmetric stretch coordinate (Q(as)) in linear symmetric AAA molecules, and along the optical phonon "pairing" mode coordinate (Q(opt)) in corresponding one-dimensional [A]( infinity ) chains built of equidistant A atoms. This is done for a broad range of chemical elements (A). The following similarities between vibronic coupling in molecules and phonon coupling in solids emerge from our calculations: 1) The HOMO/LUMO electronic energy gap in an AAA molecule increases along Q(as), and the highest occupied crystal orbital/lowest unoccupied crystal orbital gap in [A]( infinity ) chain increases along Q(opt). 2) The maximum vibronic instability is invariably obtained for a half-filled, singly occupied molecular orbital in AAA molecules, and for a corresponding half-filled band in [A]( infinity ) chains. 3) The vibronic stability of an AAA molecule increases with a decrease of the AA bond length, as does the vibronic stability of [A]( infinity ) chains (external pressure may lead to a reversal of a Peierls distortion). 4) The high degree of s-p mixing and ionic/covalent forbidden curve crossing dramatically enhance the vibronic instability of both AAA molecules and [A]( infinity ) chains. We also introduce one quantitative relationship: The parameter log(R) (where R is molar refractivity, a parameter used by Herzfeld to prescribe the conditions for the metallization of the elements) correlates with a parameter f(AA) (defined as twice the electronegativity of A, divided by the equilibrium AA bond length), used by two of us previously to describe vibronic coupling in AAA molecules for a broad range of elements (A=halogen, H, or an alkali metal). We hope to illustrate that key chemical aspects of vibronic coupling in simple molecules may thus be profitably transferred to corresponding materials in the solid state.

Journal Article↗