Influence of the characteristics of pulses of gonadotrophin releasing hormone on the dynamics of luteinizing hormone release from perifused sheep pituitary cells

McIntosh, Rosalind P.; McIntosh, J. E. A.

doi:10.1677/joe.0.0980411

Cited by 60 publications

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“…*P<0·05; n=6. (McIntosh & McIntosh 1983, Baird et al 1984, Kamel et al 1987. For instance, treatment of perifused pituitary cells with LHRH, as given one 2-min pulse every 16 min, caused an initial important release of LH, followed by a decrease within 2-3 h (McIntosh & McIntosh 1983).…”

Section: Discussionmentioning

confidence: 99%

“…(McIntosh & McIntosh 1983, Baird et al 1984, Kamel et al 1987. For instance, treatment of perifused pituitary cells with LHRH, as given one 2-min pulse every 16 min, caused an initial important release of LH, followed by a decrease within 2-3 h (McIntosh & McIntosh 1983). It is to be noted that, in Experiment 2 during the initial 2-3 h of treatment with the highest dose of sulpiride, high concentrations of LH with low-amplitude pulses suggestive of a high LHRH frequency were found, and it is likely that LH pulses were poorly detected in this situation.…”

Section: Discussionmentioning

confidence: 99%

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Implication of D2-like dopaminergic receptors in the median eminence during the establishment of long-day inhibition of LH secretion in the ewe

Bertrand

Thiéry²,

Picard³

et al. 1999

Journal of Endocrinology

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In ewes, photoperiod modulates LH release and dopaminergic terminals in the median eminence (ME) have a critical role in the establishment of long-day inhibition of LH secretion. This study was undertaken to determine the type of dopaminergic receptors, D1-like or D2-like, that mediate the action of dopamine on LH secretion at the ME level in this situation. This was assessed, in ovariectomized and estradiol-treated ewes, with the use of reverse microdialysis in the ME in three experiments: first, when LH secretion was stimulated by short days, by determining the response to three doses (0·01, 0·1 or 1 mg/ml) of a D1-like (SKF38393) and a D2-like (quinpirole) agonist; secondly, during early long-day inhibition of LH secretion, by determining the ability of SKF38393 and quinpirole (1 mg/ml) to mimic the inhibitory effects of dopamine, after a blockade of its synthesis with -methyl-paratyrosine ( MPT; 2 mg/ml); and thirdly, during early long-day inhibition of LH secretion, by determining the response to three doses (0·009, 0·09 or 0·9 mg/ml) of a D1-like (SCH23390) and a D2-like (sulpiride) antagonist.In none of the conditions was effect of the D1-like analogs on LH secretion found, compared with the control treatments. In contrast, the D2-like analogs caused changes in LH secretion. First, with short days, quinpirole in the highest dose significantly reduced mean LH concentration (P<0·05) and LH pulse frequency (P<0·01). Secondly, with long days, addition of quinpirole to MPT caused a significant decrease in LH secretion relative to MPT alone (P<0·05). Thirdly, with long days, sulpiride at the highest dose significantly increased mean LH concentration (during the first 3 h of treatment, P<0·05) and LH pulse frequency (P<0·05). Prolactin secretion was also determined in these experiments, and D2-like agonist and antagonist caused an inhibition and a stimulation of prolactin secretion, respectively. These results demonstrate that, in the ME, inhibitory action of dopamine on LH secretion, critical for the initiation of long-dayinduced inhibition, is mediated by D2-like, not D1-like, dopaminergic receptors.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Implication of D2-like dopaminergic receptors in the median eminence during the establishment of long-day inhibition of LH secretion in the ewe

Bertrand

Thiéry²,

Picard³

et al. 1999

Journal of Endocrinology

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“…The multi-column perifusion system, as described previously and with modifications (McIntosh & McIntosh 1983, Evans et al 1985, 1988, 1996, allows for the simultaneous perifusion of up to 15 cell chambers, or columns. Through the use of a solenoid switching system various trains of peptide hormones and pharmacological agents can be applied to the cells.…”

Section: Multi-column Perifusion Experimentsmentioning

confidence: 99%

Desensitization of the adrenocorticotrophin responses to arginine vasopressin and corticotrophin-releasing hormone in ovine anterior pituitary cells

Hassan

Chacko²,

Mason

2003

Journal of Endocrinology

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Following repeated or prolonged exposure to either corticotrophin-releasing hormone (CRH) or arginine vasopressin (AVP), pituitary adrenocorticotrophin (ACTH) responsiveness is reduced. This study compared the characteristics of desensitization to CRH and AVP in perifused ovine anterior pituitary cells. Desensitization to AVP occurred at relatively low AVP concentrations and was both rapid and readily reversible. Treatment for 25 min with AVP at concentrations greater than 2 nM caused significant reductions in the response to a subsequent 5 min 100 nM AVP pulse (IC 50 =6·54 nM). Significant desensitization was observed following pretreatment with 5 nM AVP for as briefly as 5 min. Desensitization was greater following a 10 min pretreatment, but longer exposures caused no further increase. Resensitization was complete within 40 min following 15 min treatment with 10 nM AVP. Continuous perifusion with 0·01 nM CRH had no effect on AVP-induced desensitization. Treatment with 0·1 nM CRH for either 25 or 50 min caused no reduction in the response to a subsequent 5 min stimulation with 10 nM CRH. When the pretreatment concentration was increased to 1 nM significant desensitization was observed, with a greater reduction in response occurring after 50 min treatment. Recovery of responsiveness was progressive following 50 min treatment with 1 nM CRH and was complete after 100 min. Our data show that in the sheep AVP desensitization can occur at concentrations and durations of AVP exposure within the endogenous ranges. This suggests that desensitization may play a key role in regulating ACTH secretion in vivo. If, as has been suggested, CRH acts to set corticotroph gain while AVP is the main dynamic regulator, any change in responsiveness to CRH may significantly influence the overall control of ACTH secretion.

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“…The perifusion apparatus is an experimental in vitro tool used by endocrinologists to model information transfer in endocrine systems (Mcintosh & Mcintosh, 1983;Mcintosh, Mcintosh, & Kean, 1984;Evans et al, 1985). The major drawback of the perifusion system derives from the dispersion, diffusion and mixing of the hormone within the apparatus which distort the original released hormone concentration profile.…”

Section: Introductionmentioning

confidence: 99%

Signal restoration after transmission through an advective and diffusive medium

Shorten

Wall

2004

Proc. R. Soc. Lond. A

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ABSTRACT. Inverse problem, regularisation, singular perturbation, wave splitting, wave propagators, square root operator, inverse mass transport This paper considers an inverse problem associated with mass transport in a pipe. It illustrates how wave splitting techniques can be utilised for an inverse problem associated with one-dimensional mass transport processes. This is done by using a generalisation of Fick's law which introduces a relaxation parameter into the problem, so converting the parabolic partial differential equation by a singular perturbation into a hyperbolic one. This generalised law by ensuring finite mass flux propagation speeds, enables a stable equation to be utilised to reconstruct the interior boundary condition; so providing a regularised solution to the inverse problem. Theoretical results for the solution of the inverse problem are also developed. INTRODUCTIONThe perifusion apparatus is an experimental in vitro tool used by endocrinologists to model information transfer in endocrine systems (Mcintosh & Mcintosh, 1983;Mcintosh, Mcintosh, & Kean, 1984;Evans et al., 1985). The major drawback of the perifusion system derives from the dispersion, diffusion and mixing of the hormone within the apparatus which distort the original released hormone concentration profile. Recently mathematical techniques have been applied to improving this situation (Shorten & Wall, 2001). This paper presents another approach to the inverse problem of concentration signal restoration after signal transmission through an advective and diffusive medium, with applications to perifusion.The problem considered here has direct application to a related problem involving the estimation of secretion of adrenocorticotropic hormone (ACTH) from the pituitary gland. In this problem, assays of the blood flow are taken downstream from the pituitary in a horse, which is secreting ACTH, and it is then required to estimate the concentration of ACTH at the pituitary, (Alexander, Irvine, Liversey, & Donald, 1988). This in vivo experimental technique poses similar problems to the perifusion apparatus mentioned previously, but the flow situation is more complicated.When a mass concentration of a material is transported within a fluid of a different material, the estimation of the final temporal profile, downstream of the injection point, from the knowledge of the initial injection temporal profile, is a relatively straight-forward problem; it is required Date: September 9, 2002. 1991. to solve a well-posed parabolic partial differential equation. This is termed a direct problem. However, when a mass concentration of a material flowing and diffusing within an advecting fluid is measured downstream of the injection point, the estimation of the initial injection profile is a difficult problem. This is termed an inverse problem; in particular an inverse source problem. This problem is difficult because it is ill-posed and besides the difficulty of problem formulation, it must also be made well-posed.It is assumed throughout this paper ...

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Influence of the characteristics of pulses of gonadotrophin releasing hormone on the dynamics of luteinizing hormone release from perifused sheep pituitary cells

Cited by 60 publications

References 0 publications

Implication of D2-like dopaminergic receptors in the median eminence during the establishment of long-day inhibition of LH secretion in the ewe

Implication of D2-like dopaminergic receptors in the median eminence during the establishment of long-day inhibition of LH secretion in the ewe

Desensitization of the adrenocorticotrophin responses to arginine vasopressin and corticotrophin-releasing hormone in ovine anterior pituitary cells

Signal restoration after transmission through an advective and diffusive medium

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