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PubMed1992

Postnatal development of dye-coupling among astrocytes in rat visual cortex.

Intercellular coupling among astrocytes was studied in rat visual cortex slices from animals aged 1 week to 4 months. Cell coupling via gap junctions was determined by the dye spread of the low molecular weight dye Lucifer Yellow CH injected into electrophysiologically identified cells to adjacent cells. Coupling among glial cells was first detected at postnatal day 11 and was thereafter consistently observed until adulthood. Dye spread was observed up to 300 microns radially from the injected cell covering multiple cortical layers. Following dye injection into a single cell up to several hundred Lucifer Yellow-positive cells could be observed. Quantitative analysis revealed a similar extent of dye spread at different developmental stages including a quite constant number of dye-coupled astrocytes from the end of the second postnatal week to adulthood. Double labelling of Lucifer Yellow-filled cells with an antiserum against the glial fibrillary acidic protein confirmed the astrocytic nature of the injected and coupled cells. Comparison of the density of dye-coupled cells in a given area and the total number of astrocytes as revealed by immunocytochemical staining suggests that dye-coupling includes the entire local astrocytic population. It is concluded that coupling among astrocytes via gap junctions in rat visual cortex occurs shortly after birth and reflects one of the first steps in astroglial maturation.

Animals↗

PubMed1995

Transcription-coupled repair removes both cyclobutane pyrimidine dimers and 6-4 photoproducts with equal efficiency and in a sequential way from transcribed DNA in xeroderma pigmentosum group C fibroblasts.

We investigated the contribution of the global and the transcription-coupled nucleotide excision repair pathway to the removal of structurally different DNA lesions. The repair kinetics of UV-induced cyclobutane pyrimidine dimers (CPDs) and pyrimidine (6-4) pyrimidone photoproducts (6-4PPs) were determined in an active and inactive gene in normal human fibroblasts and in xeroderma pigmentosum group C (XP-C) fibroblasts. Previously we have shown that in normal human cells exposed to a UV dose of 10 J/m2 repair of CPDs takes place via two pathways: global repair and transcription-coupled repair, the latter being responsible for accelerated repair of CPDs in the transcribed strand of active genes. So far, no clear evidence for transcription-coupled repair of 6-4PPs has been presented. Here we demonstrate that 6-4PPs really form a target for transcription-coupled repair. In XP-C cells, exposed to 30 J/m2 and only capable of performing transcription-coupled repair, CPDs as well as 6-4PPs are removed selectively and with similar kinetics from the transcribed strand of the adenosine deaminase (ADA) gene. The non-transcribed strand of the ADA gene and the inactive 754 gene are hardly repaired. In contrast to XP-C cells, normal cells exposed to 30 J/m2 lack strand-specific repair of both 6-4PPs and CPDs, suggesting that transcription-coupled repair is overruled by global repair, probably due to severe inhibition of transcription at this high UV dose. The much more rapid repair of 6-4PPs compared with CPDs in normal cells may be related to higher affinity of the global repair system for the former lesion. In XP-C cells the similarity of the rate of repair of both 6-4PPs and CPDs in the transcribed strand at 30 J/m2 indicates that transcription-coupled repair of photolesions takes place in a sequential way. Our results strongly suggest that the significance of transcription-coupled repair for removal of lesions depends on the type of lesion and on the dose employed.

Cells, Cultured↗

PubMed2007

Lipopolysaccharide reduces electrical coupling in microvascular endothelial cells by targeting connexin40 in a tyrosine-, ERK1/2-, PKA-, and PKC-dependent manner.

Electrical coupling along the endothelium is central in the arteriolar conducted response and in control of vascular resistance. It has been shown that exposure of endothelium to lipopolysaccharide (LPS, an initiating factor in sepsis) reduces intercellular communication in vitro and in vivo. The molecular basis for this reduction is not known. We examined the effect of LPS on electrical coupling in monolayers of cultured mouse microvascular endothelial cells (MMEC) derived from the mouse hindlimb skeletal muscle. To assess coupling, we measured the spread of electrical current injected into the monolayer and computed the monolayer intercellular resistance (inverse measure of coupling). LPS (10 microg/ml, 1 h) reduced coupling (i.e., increased resistance) in MMEC isolated from wild-type, connexin37 (Cx37) null and Cx43(G60S) (nonfunctional mutant) mice, but not in MMEC derived from Cx40 null mice. LPS also activated JNK1/2, p38 and ERK1/2 MAP kinases. Pretreatment of WT monolayers with ERK1/2 inhibitor U0126 (20 microM, 1 h) prevented the LPS-induced decrease in coupling, while inhibition of JNK1/2 with SP600125 (20 microM, 1 h) and p38 with a p38 inhibitor (10 nM, 1 h) had no effect. Furthermore, inhibition of tyrosine kinases with PP-2 (10 nM, 1 h), activation of PKA by 8-bromo-cAMP (1 mM, 5 min), and activation of PKC by bryostatin-2 (10 nM, 1 h) also prevented the reduction in coupling. We propose that LPS reduces inter-endothelial electrical coupling via tyrosine-, ERK1/2-, PKA-, and PKC-dependent signaling that targets Cx40. We suggest that this mechanism contributes to compromised arteriolar function following LPS exposure.

Animals↗

PubMed2006

Substitution and protonation effects on spin-spin coupling constants in prototypical aromatic rings: C6H6, C5H5N and C5H5P.

Ab initio equation-of-motion coupled cluster calculations have been carried out to evaluate one-, two-, and three-bond 13C-13C, 15N-13C, 31P-13C coupling constants in benzene, pyridine, pyridinium, phosphinine, and phosphininium. The introduction of N or P heteroatoms into the aromatic ring not only changes the magnitudes of the corresponding X-C coupling constants (J, for X = C, N, or P) but also the signs and magnitudes of corresponding reduced coupling constants (K). Protonation of the heteroatoms also produces dramatic changes in coupling constants and, by removing the lone pair of electrons from the sigma-electron framework, leads to the same signs for corresponding reduced coupling constants for benzene, pyridinium, and phosphininium. C-C coupling constants are rather insensitive to the presence of the heteroatoms and protonation. All terms that contribute to the total coupling constant (except for the diamagnetic spin-orbit (DSO) term) must be computed if good agreement with experimental data is to be obtained.

Benzene↗

PubMed1995

A theory of the transition to parenthood of infertile couples.

A theoretical synthesis of the transition to parenthood of infertile couples is presented. The theory was derived from three studies of infertility the author conducted between 1985 and 1993. The theory is grounded in the experiences of infertile couples, and locates these experiences conceptually in the comparative context of normally fertile couples' transition to parenthood and in the domains of life transitions and illness work. Infertile couples exhibited some of the same processes as their fertile counterparts, varying in the phasing and intensity of these overlapping processes; and, they exhibited processes exclusive to them. There were also intragroup differences in the infertile couples: between adopting and childbearing couples, couples conceiving biomedically and spontaneously, and between couples conceiving with their own or donor gametes.

Adoption↗

PubMed2006

Core concerns of couples living with early stage breast cancer.

STUDY OBJECTIVES: Although clinicians and scientists have a growing awareness of breast cancer as a couple's joint experience, no one has studied the concerns couples choose to address with a professional coach to better manage the impact of the cancer. The purpose of the current study was to describe illness-related concerns couples worked on together with masters-educated professional coaches during the first eleven months of the wife's treatment for early stage breast cancer. SETTING AND PARTICIPANTS: Intervention sessions were conducted with twenty-nine couples in their homes in the Pacific Northwest. DESIGN: Data were obtained from single occasion case intensive interviews with couples. MAIN RESULTS: Inductive coding of the audiorecorded intervention sessions yielded four domains of core concerns: dealing with tension in the relationship; needing to be together as a couple; wondering about the children; and managing the threat of breast cancer. CONCLUSION: Over half the couples chose to address and do something about the stress, tension and dissatisfaction they were feeling in their relationship that each attributed to the breast cancer. Future family-focused cancer care needs to include services that assist couples to address these core concerns.

Adaptation, Psychological↗

PubMed1994

Na(+)-dependent transport of aminopeptidase-resistant sugar-coupled tripeptides in rat intestine.

Aminopeptidase-degradable tripeptide, tyrosylglycylglycine (TGG, a part of aminopeptidase-degradable enkephalines), was coupled with sugars (cellobiose, maltose, lactose, gentiobiose and glucose). These sugar-coupled TGGs were stable enough to be transported from the mucosal to the serosal side in rat everted small intestine, while TGG was not stable enough to be transported. The transport of sugar-coupled TGGs was decreased in the absence of Na+, indicating the Na(+)-dependent transport of sugar-coupled TGG in rat intestine. Cellobiose-coupled TGG and glucose-coupled TGG did not mutually inhibit their transport. It was suggested that the intestinal Na(+)-dependent transporter for disaccharide-coupled tripeptides, which have a pyranose ring, was different from that of monosaccharide-coupled tripeptide, which has no pyranose ring.

Amino Acid Sequence↗

PubMed1996

Rules for coupled expression of regulator and effector genes in inducible circuits.

The induction of effector genes that encode enzymes is often controlled by the protein product of a regulator gene that is directly involved in the control of its own expression. This coupling of elementary gene circuits can lead to three patterns of regulator and effector gene expression. As effector gene expression increases, regulator gene expression can increase, remain the same, or decrease, and these are referred to as directly coupled, uncoupled, or inversely coupled patterns. To determine the relative merits of each pattern, we have constructed appropriate mathematical models for the alternative gene circuits and made well-controlled comparisons using a priori criteria to evaluate their functional effectiveness. We have considered both negatively and positively controlled systems that are induced by an intermediate of the regulated pathway. Different results are obtained in the two cases. Our results indicate that direct coupling is better than inverse coupling or uncoupling for negatively controlled systems, while inverse coupling is better than the other two patterns for positively controlled systems. These optimal forms of coupling promote a fast response to inducer. Our results also indicate that realization of the optimal forms of coupling is influenced by the subunit structure of regulator proteins and requires a low capacity for induction, i.e. the ratio of maximal to minimal level of effector gene expression is small. These results lead to testable predictions, which we have compared with experimental data from over 30 systems.

Enzyme Induction↗

PubMed1997

Completely uncoupled and perfectly coupled gene expression in repressible systems.

Two forms of extreme coupling have been documented for the regulation of gene expression in repressible systems governed by a regulator protein. The first form, complete uncoupling, is distinguished by a constant level of regulator protein. The second form, perfect coupling, is distinguished by a level of regulator protein that varies coordinately with the level of the regulated enzyme. To determine how these two forms of coupling influence the performance of a system, so that we might predict the conditions under which each evolves through natural selection, we have used a mathematical approach to compare systems with complete uncoupling and perfect coupling. Our comparisons, which are controlled so that alternative systems are free from irrelevant differences, are based on a priori criteria that are related to various aspects of a system's performance, such as temporal responsiveness. By examining the influence of physical constraints that are related to the subunit structure of regulatory proteins and that limit the cooperativity of regulatory interactions, we have extended an early theory of gene circuitry for repressible systems. We obtain new results and testable predictions that can be summarized as follows. For typical systems with a low gain, performance is better with perfect coupling than with complete uncoupling if the mode of regulation is negative and better with complete uncoupling than with perfect coupling if the mode of regulation is positive. For systems with a high gain, these preferred forms of coupling are prevented by the physical constraints on cooperativity, and other forms of coupling can be expected. Tests of our predictions are illustrated by using data available in the literature.

Animals↗

PubMed1999

Measurement of Magnitude and Sign of Heteronuclear Coupling Constants in Transition Metal Complexes.

Sets of specifically tailored E.COSY-type correlation experiments and double-quantum/zero-quantum (DQ/ZQ) experiments are presented which enable the determination of sign and size of small heteronuclear coupling constants across the metal center of transition metal complexes. For the octahedrally coordinated complexes, [Ru(TPM)(H)(CO)(PPh3)]+[BF4]- (1) and [Ir(TPM)(H)(CO)(CO2CH3)]+[BF4]- (2), 14 of 15 and 15 of 15 possible two-bond scalar coupling constants across the metal center were measured, respectively, using 15N and 15N/13C enriched samples (TPM = tris(1-pyrazolyl)methane)). The reduced coupling constants 2KX-M-Y = 4pi2 2J/(hgammaXgammaY) were found to be positive when the coupled nuclei X and Y were trans with respect to the metal center, and negative when the coupled nuclei were in cis position. The validity of this sign rule was verified for JCC, JNN, JPN, JPC, JCN, JHP, JHC, and JHN couplings. Idiosyncracies associated with 2D NMR spectra for the sign determination of coupling constants with 15N which lead to corrections for the signs of JHN, JPN, and JCN couplings reported previously are discussed. Copyright 1999 Academic Press.

Journal Article↗

PubMed2000

Comparison and use of vector and quantum representations of J-coupled spin evolution in an IS spin system during RF irradiation of one spin

A comprehensive survey is provided of the analytical expressions for the orthogonal product operator states arising from any initial state of an IS J-coupled spin system during arbitrary RF irradiation of one spin. These equations exactly characterize the effect of J coupling during the application of the RF field. The survey differentiates two kinds of spin rotation, classical and nonclassical, where the second kind comprises any interconversion that includes the transverse two-spin coherence states, 2S(y)I(x) or 2S(y)I(y), as initial, transient, or final states, and the first kind comprises all other rotations. Classical rotations are defined as linear rotations of the nuclear spin magnetization vectors around effective fields and there is an exact correspondence between the resulting vector model and the quantum mechanical (QM) equations at all RF field strengths. The effect of scalar coupling can be neglected for B(1) > 5J. Nonclassical rotations are nonlinear in time for a constant RF field. At high field (B(1) > 50J), the effect of J modulation is negligible, and the rotation of magnetizations is classical to a very good approximation. At intermediate strengths (5J < B(1) < 50J), a semi-classical vector model of I-spin irradiation is applicable in which the J-coupled precession of the S spins is determined from a reduced coupling constant, but the effect of the S spins on the I spins is ignored (this model has previously been used to determine the effect of coupling during adiabatic pulses). At lower powers, the exact QM-derived equations must be used for nonclassical rotations, but continuous pictorial descriptions of the rotation of magnetizations determined from the vector sum of the product operator states are helpful in designing novel NMR applications. At all powers it is proven that the instantaneous reduced coupling constant acting on the S spins is J cosφ, where φ is the polar angle of the I-spin magnetizations, thus establishing the central tenet of the semi-classical model applicable at moderate power. Several spinstate transformations that combine the effects of RF and scalar coupling to produce the overall rotation can be generated in 100% yield using low power irradiation. Analogous transformations are also available using classical rotations and, in combination with their nonclassical counterparts, form a general class of frequency-selective pulses that we call J pulses. Any combination of a 90 degrees pulse and a consecutive (2J)(-1) delay period can be replaced with a J pulse, and some initial approaches to designing shaped J pulses with improved offset profiles are explored. Copyright 2000 Academic Press.

Journal Article↗

PubMed1996

Longitudinal body wall muscles are electrically coupled across the segmental boundary in the third instar larva of Drosophila melanogaster.

Longitudinal body wall muscles in the third instar larva of the fruitfly, Drosophila melanogaster, were systematically examined for electrical and dye coupling. These muscle cells were found to be electrically coupled but rarely dye-coupled across the segmental boundary. The inter-segmental coupling coefficients between muscle #6s and muscle #7s across the segmental boundary were 0.33 +/- 0.09 (mean +/- S.D., n = 12) and 0.43 +/- 0.09 (n = 5), respectively, which are much larger than values previously reported in Drosophila but similar to those reported in the blowfly and hawkmoth. By contrast, the intra-segmental coupling coefficient between muscles #6 and #7 was smaller, 0.16 +/- 0.08 (n = 28). Other muscle cells which had apparent physical contacts with these longitudinal muscles were examined but were not electrically coupled to them. Nerve-evoked as well as miniature excitatory junctional potentials were found also electrotonically spread across the segmental boundary. The inter-segmental coupling between muscle #6s was not blocked by the gap junction inhibitors halothane or 1-octanol. Functional significance of this electrical coupling is apparently in coordination of larval body movements.

1-Octanol↗

PubMed1984

Physiological and pathophysiological implications of ventricular/vascular coupling.

The purpose of this paper is to consider "ideal" ventricular/vascular coupling, and how this may be manifest in the time domain and in the frequency domain. The paper will also consider how such "ideal" coupling is achieved, and how it might be disturbed. The arterial system plays a crucial role in ventricular/vascular coupling since it separates the smallest vessels where flow is almost perfectly continuous from the ventricle, whose output is intermittent. Ventricular/vascular coupling can be assessed from measurements of pressure and flow in the ascending aorta (AA) (for left ventricle/systemic circulation), and in the main, pulmonary artery (MPA) (for right ventricle/pulmonary circulation). Ideal coupling is manifest as low pressure fluctuation in AA and MPA. Low pressure fluctuation results in pressure during systole being only slightly greater than pressure throughout the whole cardiac cycle, and pressure during diastole being only slightly less. This is desirable because pressure during systole determines ventricular output (when inotropic state and ventricular filling are constant), and ventricular metabolic requirement, while pressure during diastole in AA is a major determinant of coronary blood flow. In the frequency domain, "ideal" coupling is manifest as a correspondence between minimal values of impedance modulus in AA and MPA with maximal values of flow harmonics in AA and MPA, respectively. Factors responsible for "ideal" coupling have been identified as high distensibility of proximal arteries (with decreasing distensibility in peripheral arteries), wave reflection at arterial terminations, and a "match" between heart rate on the one hand and arterial length and wave velocity on the other. This favourable "match" results in the heart operating for both systemic and pulmonary circulations close to a node of pressure and antinode of flow; this match is improved under conditions which simulate flight and fight. While ventricular/vascular coupling appears to be close to ideal in most large mammals, it appears to be less than ideal in adult humans and some small mammals including guinea pigs, rats, and mice. The cause for mismatch in small mammals is unclear. In humans however, findings are attributable to progressive arterial degeneration which is known to commence in childhood and is apparent in the elderly as dilated tortuous arteries, high pulse pressure, and high likelihood of developing ventricular failure.

Aorta↗

PubMed2003

Agonist-specific coupling of a cloned human alpha1A-adrenoceptor to different second messenger pathways.

The agonist-specific coupling properties of the three cloned human alpha(1)-adrenoceptor subtypes have been compared, when expressed at similar levels in Chinese hamster ovary (CHO) cell lines, using noradrenaline and the (+/-)- meta- and (+/-)- para- structural isomers of octopamine as agonists. The alpha(1A)- and the alpha(1B)-adrenoceptor subtypes coupled to both the release of arachidonic acid and to the accumulation of inositol phosphates, whereas the alpha(1D)-adrenoceptor subtype only coupled effectively to the accumulation of inositol phosphates. The rank order of potencies of the three agonists tested was the same for all the three receptor subtypes when coupled to either signalling pathway: noradrenaline > meta-octopamine > para-octopamine. Meta-octopamine was a partial agonist of the alpha(1A)-adrenoceptor subtype when coupled to arachidonic acid release, whereas para-octopamine was a full agonist of this pathway. In contrast, meta-octopamine was a full agonist at the alpha(1B)-adrenoceptor subtype when coupled to arachidonic acid release, whereas para-octopamine was a partial agonist of this pathway. Neither meta-octopamine, nor para-octopamine acted as full agonists when coupling any of the three alpha(1)-adrenoceptor subtypes to the accumulation of inositol phosphates. Para-octopamine was only a weak partial agonist of this pathway for all three receptor subtypes. The results show that the modulation of arachidonic acid release and inositol 1,4,5-trisphosphate production occurs in both a subtype- and agonist-specific manner for the alpha(1A)-, alpha(1B)- and alpha(1D)-adrenoceptor subtypes. In addition, the alpha(1A)-adrenoceptor exhibits agonist-specific coupling (agonist trafficking) to the different second messenger pathways.

Adrenergic alpha-Agonists↗

PubMed1986

Comparison of coupling intervals that induce clinical and nonclinical forms of ventricular tachycardia during programmed stimulation.

Coupling intervals of extrastimuli that induced 57 previously documented unimorphic ventricular tachycardias (VTs) were compared with coupling intervals that induced 57 episodes of polymorphic VT or ventricular fibrillation (VF) in patients without a documented or suspected history of polymorphic VT or VF. Programmed stimulation was performed with the patient in the drug-free state, with 1 to 3 extrastimuli and 2 basic drive cycle lengths (600 or 500 ms, and 400 ms) at 2 right ventricular sites; stimuli were twice diastolic threshold. The mean coupling intervals of the first, second and third extrastimuli that induced nonclinical VT/VF (241 +/- 19, 185 +/- 19 and 173 +/- 24 ms, respectively, mean +/- standard deviation) were significantly shorter than the corresponding coupling intervals that induced the clinical VTs (266 +/- 25, 228 +/- 32 and 214 +/- 27 ms, respectively, p less than 0.001 for each). Regardless of the basic drive cycle length, the shortest coupling interval required to induce a clinical VT was 180 ms. Depending on the drive cycle length, 29 to 70% of nonclinical VT/VF induced by 3 extrastimuli required a coupling interval of less than 180 ms to induce. Therefore, a lower limit of coupling intervals may be identified below which only nonclinical VT/VF is induced by programmed stimulation. Restriction of coupling intervals to this lower limit may allow for significant improvement in specificity without compromise in the sensitivity of programmed ventricular stimulation protocols.

Aged↗

PubMed1984

Differential effects of N-acetylglutamate on citrulline synthesis by coupled and uncoupled mitochondria.

When rats were placed on a low-protein (5%) diet for 24 h or less, liver mitochondrial acetylglutamate decreased rapidly, carbamyl phosphate synthetase (ammonia) and ornithine transcarbamylase decreased little, and carbamyl phosphate synthesis (measured as citrulline) by isolated mitochondria occurred at very low rates. The matrix acetylglutamate content of these mitochondria, whether coupled or uncoupled, was increased similarly by preincubating them with added acetylglutamate, but citrulline synthesis increased from less than 1 to 2.3 nmol min-1 mg-1 in the coupled state, and from less than 1 to 35 nmol min-1 mg-1 in the uncoupled state. However, when coupled mitochondria were incubated with the substrates required for the synthesis of acetylglutamate in the matrix, citrulline synthesis increased to 48 nmol min-1 mg-1; this rate was similar to that of mitochondria from control rats (fed a normal diet). When mitochondria from controls were incubated with up to 5mM acetylglutamate, citrulline synthesis by coupled mitochondria was increased by 10 to 40%, while synthesis by uncoupled mitochondria was 1.5 to 4 times higher than that observed with the coupled mitochondria; matrix acetylglutamate in both conditions rose to levels similar to those in the medium. The reason for the different behavior of carbamyl phosphate synthetase (ammonia) in coupled and uncoupled mitochondria was not apparent; neither oxidative phosphorylation nor ornithine transport were limiting in the coupled system. These observations are an example of the restrictions imposed upon enzymatic systems by the conditions existing in the mitochondrial matrix, and of the different behavior of carbamyl phosphate synthetase in situ and in solution. In addition, they show that conclusions about the characteristics of the enzyme in coupled mitochondria based on observations made in uncoupled mitochondria are not necessarily justified.

Animals↗

PubMed1990

Activation of excitatory amino acid inputs to supraoptic neurons. II. Increased dye-coupling in maternally behaving virgin rats.

Electrical stimulation of the lateral olfactory tract (LOT) has been shown to excite, monosynaptically, supraoptic nucleus (SON) neurons in slices of hypothalamus taken from male, virgin female or lactating rats. Only in the last of these, however, did 10 min of 10 Hz stimulation produce an increase in the incidence of Lucifer yellow dye-coupling, an indicator of electrotonic interactions. This coupling is virtually exclusively dendrodendritic. Since virgin females that have been induced to show full maternal behavior have altered dendritic morphology reminiscent of lactating animals (but different from males and untreated virgins) we investigated the effects of LOT stimulation in slices from maternally behaving virgins. Similar to the data for lactating rats, electrical stimulation of this tract, the terminals of which release excitatory amino acid transmitter, increased the incidence of dye-coupling by 112% (P less than 0.01). Also similar to lactating rats, the coupling was dendrodendritic and the increase was due entirely to increasing the number of neurons coupled to the injected neuron. No increase in coupling was seen in stimulated slices from pup-exposed control rats. We conclude that the maternal behaviors engaged in by both real mothers and induced virgins 'primes' the supraoptic neurons to increase coupling in response to olfactory system stimulation. This priming may occur via olfactory and vomeronasal stimulation during such behaviors as sniffing and anogenital licking of the pups. That coupling increased in tissue from maternally behaving virgins comparably to that from nursing mothers further suggests that SON neurons may play a role in maternal behavior independent of its well-documented role in the milk ejection reflex.

Action Potentials↗

PubMed1985

Metabolic, fluorescent dye and electrical coupling between hamster oocytes and cumulus cells during meiotic maturation in vivo and in vitro.

Heterologous intercellular communication was determined qualitatively by lucifer yellow dye transfer and quantitatively by transfer of radiolabeled uridine metabolites and electrical current in hamster oocyte-cumulus complexes during meiotic maturation in vitro and in vivo. In addition, changes in cell resting potentials during maturation were recorded. Significantly less time was required for germinal vesicle breakdown (GVBD) in oocytes matured in vitro than in oocytes stimulated in vivo (1.81 +/- 0.06 hr, N = 13 vs 2.46 +/- 0.07 hr, N = 18, respectively, P less than 0.001). Resting potentials of the oocyte (RP-o) and cumulus cells (RP-c) significantly increased contemporaneously with GVBD in vitro (RP-o: from -18.9 +/- 3.2 mV to -33.2 +/- 2.9 mV, P less than 0.001; RP-c: from -16.3 +/- 1.9 mV to -27.5 +/- 2.6 mV, P less than 0.001) and in vivo after hCG injection (RP-o: from -16.8 +/- 5.9 mV to -30.1 +/- 3.9 mV, P less than 0.001; RP-c: from -15.5 +/- 3.8 mV to -26.3 +/- 3.2 mV, P less than 0.001). RP-o and RP-c progressively increased with time of culture up to 7 hr (maximum time examined) while the values reached maxima in in vivo matured oocytes 4.5 hr post-hCG and subsequently declined concomitant with the onset of cumulus expansion. Cumulus to oocyte coupling decreased progressively with time after release from meiotic arrest both in vitro and in vivo, as assessed by a progressive reduction in transfer of either uridine marker or lucifer yellow from the cumulus cell to the oocyte. By 4.5 hr after hCG injection, cumulus expansion had begun in 100% of complexes examined. Expansion was extensive by 7 hr post-hCG and spread of lucifer yellow from a cumulus cell was limited to very few adjacent cumulus cells. Oocyte to cumulus cell metabolic coupling also decreased progressively with time in both treatment groups. Examination of the extent of heterologous ionic coupling revealed that ionic coupling exhibited biphasic and, bidirectionally parallel, increases during meiotic maturation. While these temporal changes were observed in both groups, the coupling ratios were much greater in those complexes matured in vitro than in vivo. These results show that dye, metabolic, and electrical coupling exist between the immature hamster oocyte and its surrounding cumulus cells but that during the early stages of meiosis, metabolic and dye coupling decrease, while electrical coupling increases biphasically.

Action Potentials↗