The physiological role of calcitonin assessed through chronic calcitonin deficiency in rats

Kumar, M. Sunil; Sturtridge, W. C.

doi:10.1113/jphysiol.1973.sp010295

Cited by 9 publications

(3 citation statements)

References 15 publications

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“…This is probably because of the small number of animals studied. DISCUSSION The thyroid is the major source of calcitonin in the rat (11). Therefore, surgical thyroparathyroidectomy deprives the animal not only of thyroxine but also of calcitonin and parathyroid hormone.…”

Section: Introductionmentioning

confidence: 99%

Evidence for physiological importance of calcitonin in the regulation of plasma calcium in rats.

Kalu¹,

Hadji-Georgopoulos²,

Foster³

1975

J. Clin. Invest.

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A B S T R A C T To determine the physiological importance of calcitonin in the regulation of plasma calcium, studies were carried out in fasting animals to (a) assess the acute effects of thyroparathyroidectomy (TPTX) and thyroidectomy (TX) on plasma and urinary calcium; (b) investigate whether the changes in plasma calcium produced by removal of the glands were dependent on the presence of the kidney; and (c) determine if the effect of TPTX on plasma calcium is affected by age. Except where otherwise indicated, all studies were carried out on fasting male Wistar rats weighing over 300 g. The following observations were made. (a) TPTX and TX caused an increase in plasma calcium in nephrectomized animals. (b) This increase was not dependent on nephrectomy since in intact animals bearing autoparathyroid transplants TX also caused a significant rise in the mean plasma calcium level (0.37 mg/100 ml at 1i h). (c) Urinary calcium increased twofold in the 3-h period immediately after TX. (d) In unnephrectomized immature (50-g) rats, TPTX caused a progressive decrease in plasma calcium in contrast to old (360-g) rats, where a significant fall observed at 6 h was preceded by an increase in plasma calcium (0.5 mg/100 ml at 11 h). From these observations we conclude that: (a) calcitonin must play an important physiological role in the regulation of plasma calcium since the termination of its basal secretion caused an immediate but transient increase in plasma calcium in old unfed rats; (b) the relative importance of calcitonin and parathyroid hormone in the acute regulation of plasma calcium is agerelated; and (c) the action of parathyroid hormone on bone may be modified by changes in ambient calcitonin concentration.

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Section: Introductionmentioning

confidence: 99%

Evidence for physiological importance of calcitonin in the regulation of plasma calcium in rats.

Kalu¹,

Hadji-Georgopoulos²,

Foster³

1975

J. Clin. Invest.

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“…The fact that B = 0 is a direct consequence of assuming isothermal gas. If the gas is not isothermal then B 0 (see Kumar 1988).…”

Section: Appendix A: Higher Order Viscosity Coefficientsmentioning

confidence: 99%

“…Note that in this anisotropic case, B 0. This means that the diffusion of tilt governed by the ν 2 term in (1) becomes an advection-diffusion term (see Kumar 1988) and this must be included for a complete picture.…”

Section: Appendix C: Higher Order Viscosity Coefficients In the Anisomentioning

confidence: 99%

Accretion disc viscosity: a limit on the anisotropy

Nixon¹

2015

Monthly Notices of the Royal Astronomical Society

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Observations of warped discs can give insight into the nature of angular momentum transport in accretion discs. Only a few objects are known to show strong periodicity on long timescales, but when such periodicity is present it is often attributed to precession of the accretion disc. The X-ray binary Hercules X-1/HZ Herculis (Her X-1) is one of the best examples of such periodicity and has been linked to disc precession since it was first observed. By using the current best-fitting models to Her X-1, which invoke precession driven by radiation warping, I place a constraint on the effective viscosities that act in a warped disc. These effective viscosities almost certainly arise due to turbulence induced by the magneto-rotational instability. The constraints derived here are in agreement with analytical and numerical investigations into the nature of magneto-hydrodynamic disc turbulence, but at odds with some recent global simulations.

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The development of half‐eyes in Xenopus tadpoles

Feldman¹,

Gaze²,

MacDonald³

1975

J of Comparative Neurology

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When the nasal or temporal half of a developing eye in Xenopus larvae between stages 32 and 38 was removed, the remaining fragment became rounded up and subsequently developed into a normal eye by mid-larval stages. The contralateral retinotectal projection was normal in approximately twothirds of the animals, when mapped in later tadpole life. The remaining animals showed either some form of mirror reduplication in the visual map or else some degree of lack of order, as compared with a map taken from a normal tadpole of equivalent age. We conclude that the regulative powers of the larval Xenopus eye extend to much later stages (stage 38) than was previously thought; and a possible mechanism for the production of reduplicated maps from half-eyes is considered.In 1957 Szekely produced half-eyes by surgical operation on Triturus vulgaris embryos. The poles of the cut edge of the eye were apposed until healing took place, and the small, rounded, reconstructed eyes were then transferred to a host embryo. Operations were performed at a time when the naso-temporal axis was known to be determined, whereas the dorsoventral axis was as yet undetermined. Nasal and temporal half-eyes were transplanted with reversed nasotemporal polarity: the original nasal pole of the nasal half-eye was placed temporally and the original temporal pole of the temporal half-eye was placed nasally. When tested later by food-taking and optokinetic reflexes, the original nasal or temporal pole of the half-eye was found to have retained its original positional characteristics (or neuronal specificity) and the rest of the eye developed so as to form a normally organized eye, polarized dorsoventrally in proper relation to the orbit and polarized nasotemporally in accordance with the position of the original nasal or temporal pole.Straznicky, Gaze and Keating (unpublished observations) made half-eyes in Xenopus embryos at a time when both nasotemporal and dorsoventral axes had been established (Jacobson, '68). In these experiments of Straznicky et al., the edges of the remaining half-eye were surgically apposed (that is, the eye was rounded up) at the time of operation. The polarity J. COMP. NEUR., 162: 1s22 and connections of these eyes were later assessed by mapping the retinotectal projections and the results have been summarized by Gaze ('70). Various patterns of connection were found. Some of the eyes showed a normal projection. Some showed reduplication of the field projection resembling that seen in surgically produced double-nasal "compound" eyes (Gaze et al., '63, '65, '70). Other animals gave projections from the operated eyes which showed curling of the visual field contours (Gaze, '70). If the formation of the retinotectal projection is discussed in terms of the hypothesis of neuronal specificity (Sperry, '43, '45, '51, '65), we can say that these curling projection contours are what might be expected had the position-related specificities of the retinal ganglion cells remained unaltered after the operation. In this simplest case...

show abstract

The physiological role of calcitonin assessed through chronic calcitonin deficiency in rats

Cited by 9 publications

References 15 publications

Evidence for physiological importance of calcitonin in the regulation of plasma calcium in rats.

Evidence for physiological importance of calcitonin in the regulation of plasma calcium in rats.

Accretion disc viscosity: a limit on the anisotropy

The development of half‐eyes in Xenopus tadpoles

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