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The distribution and development of gonadotropic activity in the pituitary of Xenopus laevis
GENERAL
AND
COMl'ARATlW
The
ENUO(‘RINOLOGY
Distribution Activity
Assays of the pituitary 1 and 3% months after gland.
16, 606-614
and
(l%l)
Development
in the Pituitary
of Senopus metamorphosis,
have
of Gonadotropic
of Xenopus
shown that LH and is distributed
It has been possible to distinguish the different cell types in the pars distalis of the pituitary on the basis of their different staining properties. The distribution of these cell types can also be inferred from the results of assaying different regions of the pituitary for their contained hormones, and this approach was made for LH activity in Senopus pituitaries. LH activity was studied using t’he oocyte meiosis test (Thornton, 1971). For this assay mature oocytes are removed from a Senopus toad and incubated in Ringer’s solution containing the substance under test. After 18-24 hr the oocytes are examined for signs that the meiotic division has occurred. The oocytes respond to hormones similar in action to mammalian LH, and in the circumstances of the present experiments their sensitivity to certain steroid hormones can be disregarded. It has been generally accepted that the type 2 basophils are the likely source of follicle-stimulating hormone in the amphibian pituitary, while it has been suspected that the type 3 basophils secrete a hormone similar in action to mammalian LH (Kerr, 1965; van Oordt, 1968). On the other hand, van Kemenade (1969) has suggested a corticotropic function for the type 3 basophils in Ranu. Kerr (1965) has described the distribution of the cell types in the distal lobe of Xenopus; the type 3 basophils are distributed in a crescent-shaped zone around the anterior 606
laevis
activity arises between throughout the adult
border of the distal lobe, an observation which enables the supposed function of these cells to be examined. Pituitary glands from five adult male Senopus were cut into approximately equal anterior and posterior portions, and each half homogenised in 0.5 ml of frog Ringer solution and assayed separately for its LH activity using 25 test oocytes. For each incubation the number of oocyte$ undergoing meiosis after 24 hr at 19” was recorded. The results are summarized in Table 1. The LH activity was not significantly different in each half of the gland (p > .7) ; such a dist’ribution of activity thus fails to support the contention that the type 3 basophils are the source of LH. Observations on the time of appearance of LH activity in the pituitary during development also strengthened the conTABLE THE
Xmopus No.
Toad
Anterior portion of distal lobe 14 13
3
13
4
5
3 14
ACTIVJTY
IN
PITUITARIES
of oocytes
2
1
1 OF LH
DISTRIBUTION
undergoing
meosis/Zd
Posterior portion of distal lobe 17 1:: 13
0 18
607
NOTES
elusion that the type 3 basophils are not the cells responsible for the secretion of thid hormone. In a single experiment we tested for meiosis-inducing activity in 15 pituitaries taken from tadpoles (stage 56 according to Niewkoop and Faber, i956), in 10 piLuitaries from young Xenopus 1 month after metamorphosis, and in 5 pituitaries from toads 3l/rL months after metamorphosis. The pituitaries of each group were pooled, homogenised in 0.5 ml of Ringer’s solution, and incubated with 25 test oocytes. Incidence of meiosis was determined after 24 hr. No activity was detected in the pituitaries from tadpoles or from toads 1 month after metamorphosis. However, activity present in pituitaries from toads 31/z months after metamorphosis was sufficient to cause meiosis in 16 out of 25 oocytes. Clearly, detectable meiosis-inducing activity does not arise in the pituitary until some time after metamorphosis has taken place. Since Kerr (1966) has shown that type 3 basophils are present in the pituitary before metamorphosis, from around stage 52, it seems unlikely that these cells produce LH. Alternatively, the observed charactcristics of LH activity in the pituitary compare well with Kerr’s observations on the type 2 basophils. These cells occur distributed throughout the adult Xenopus pars distalis and first appear some months after metamorphosis (Kerr, 1965, 1966). While it is necessary to consider the possibility that yet another cell type is responsible for the secretion of LH, there is no clear indication that two gonadotropic hormones exist in the Amphibia; it is t’hus
Hormones
and
possible that the type 2 basophils secrete a gonadotropic hormone with both LHand FNSH-like properties. REFERENCES T. (1965). Histology of the distal lobe of the pituitary of Xenopus laevks Daudin. Gen. Comp. Endocrinol. 5, 232-240. IiEEtR, T. (1966). The development of the pituitary in Xenopu laevis Daudin. Gen. Comp. KERR,
Endocrinol. NIEWKOOP,
AND
FABER,
Table of Xenopus Znevis Holland, Amsterdam. THORNTON. V. F. (1971). A gesterone and gonadotrapins meiotic division of Xenopus Gen. Comp. Endocrinol. 16, VAN
KEIMENADE,
J.
A.
M.
J. (1956). “Normal Daudin.” Northbioassay for probased on the oocytes
in
vitro.
599-605.
(1969).
The
effects
of
Metopirone and Aldactone on the pars distalis of the pituitary, the interrenal tissue and the interstitial tissue of t,he testis in the common frog, Rann tempornrirt. Z. Zelljorsch. 96, 466477. OORDT, P. G. W. J. (1968). The analysis and identification of the hormone-producing cells of the adenohypophysis. In “Perspectives in Endocrinology” (Barrington. E. J. W.. and BarkerJergensen, C.. eds.). Academic Press. New York.
VAN
P. J. V. F.
EVENNETT THORNTON’
Department of Zoologz~ University of Leeds Leeds LSU” 9JT, England Received June 29, 1970
’ Present address: Department of Anatomy, Kinq College. London WC. 2. England.
Crayfish
Crayfish in both intermolt and premolt (eyestalkless) stages showed no blood sugar responseto glucagon-free insulin (2.0 IU) over a 6-hr period, while animals in both tht\se stages showed a significant hy-
6, 303-311.
P. D.,
Blood
Sugar
perglycemia within 2 hr after injection of 5.0 and 50.0 pg epinephrine. Glucagon (0.5 mg) induced hyperglycemia in 2 hr in intact intermolt stage animals only. Diverse results have been reported for
AND
COMl'ARATlW
The
ENUO(‘RINOLOGY
Distribution Activity
Assays of the pituitary 1 and 3% months after gland.
16, 606-614
and
(l%l)
Development
in the Pituitary
of Senopus metamorphosis,
have
of Gonadotropic
of Xenopus
shown that LH and is distributed
It has been possible to distinguish the different cell types in the pars distalis of the pituitary on the basis of their different staining properties. The distribution of these cell types can also be inferred from the results of assaying different regions of the pituitary for their contained hormones, and this approach was made for LH activity in Senopus pituitaries. LH activity was studied using t’he oocyte meiosis test (Thornton, 1971). For this assay mature oocytes are removed from a Senopus toad and incubated in Ringer’s solution containing the substance under test. After 18-24 hr the oocytes are examined for signs that the meiotic division has occurred. The oocytes respond to hormones similar in action to mammalian LH, and in the circumstances of the present experiments their sensitivity to certain steroid hormones can be disregarded. It has been generally accepted that the type 2 basophils are the likely source of follicle-stimulating hormone in the amphibian pituitary, while it has been suspected that the type 3 basophils secrete a hormone similar in action to mammalian LH (Kerr, 1965; van Oordt, 1968). On the other hand, van Kemenade (1969) has suggested a corticotropic function for the type 3 basophils in Ranu. Kerr (1965) has described the distribution of the cell types in the distal lobe of Xenopus; the type 3 basophils are distributed in a crescent-shaped zone around the anterior 606
laevis
activity arises between throughout the adult
border of the distal lobe, an observation which enables the supposed function of these cells to be examined. Pituitary glands from five adult male Senopus were cut into approximately equal anterior and posterior portions, and each half homogenised in 0.5 ml of frog Ringer solution and assayed separately for its LH activity using 25 test oocytes. For each incubation the number of oocyte$ undergoing meiosis after 24 hr at 19” was recorded. The results are summarized in Table 1. The LH activity was not significantly different in each half of the gland (p > .7) ; such a dist’ribution of activity thus fails to support the contention that the type 3 basophils are the source of LH. Observations on the time of appearance of LH activity in the pituitary during development also strengthened the conTABLE THE
Xmopus No.
Toad
Anterior portion of distal lobe 14 13
3
13
4
5
3 14
ACTIVJTY
IN
PITUITARIES
of oocytes
2
1
1 OF LH
DISTRIBUTION
undergoing
meosis/Zd
Posterior portion of distal lobe 17 1:: 13
0 18
607
NOTES
elusion that the type 3 basophils are not the cells responsible for the secretion of thid hormone. In a single experiment we tested for meiosis-inducing activity in 15 pituitaries taken from tadpoles (stage 56 according to Niewkoop and Faber, i956), in 10 piLuitaries from young Xenopus 1 month after metamorphosis, and in 5 pituitaries from toads 3l/rL months after metamorphosis. The pituitaries of each group were pooled, homogenised in 0.5 ml of Ringer’s solution, and incubated with 25 test oocytes. Incidence of meiosis was determined after 24 hr. No activity was detected in the pituitaries from tadpoles or from toads 1 month after metamorphosis. However, activity present in pituitaries from toads 31/z months after metamorphosis was sufficient to cause meiosis in 16 out of 25 oocytes. Clearly, detectable meiosis-inducing activity does not arise in the pituitary until some time after metamorphosis has taken place. Since Kerr (1966) has shown that type 3 basophils are present in the pituitary before metamorphosis, from around stage 52, it seems unlikely that these cells produce LH. Alternatively, the observed charactcristics of LH activity in the pituitary compare well with Kerr’s observations on the type 2 basophils. These cells occur distributed throughout the adult Xenopus pars distalis and first appear some months after metamorphosis (Kerr, 1965, 1966). While it is necessary to consider the possibility that yet another cell type is responsible for the secretion of LH, there is no clear indication that two gonadotropic hormones exist in the Amphibia; it is t’hus
Hormones
and
possible that the type 2 basophils secrete a gonadotropic hormone with both LHand FNSH-like properties. REFERENCES T. (1965). Histology of the distal lobe of the pituitary of Xenopus laevks Daudin. Gen. Comp. Endocrinol. 5, 232-240. IiEEtR, T. (1966). The development of the pituitary in Xenopu laevis Daudin. Gen. Comp. KERR,
Endocrinol. NIEWKOOP,
AND
FABER,
Table of Xenopus Znevis Holland, Amsterdam. THORNTON. V. F. (1971). A gesterone and gonadotrapins meiotic division of Xenopus Gen. Comp. Endocrinol. 16, VAN
KEIMENADE,
J.
A.
M.
J. (1956). “Normal Daudin.” Northbioassay for probased on the oocytes
in
vitro.
599-605.
(1969).
The
effects
of
Metopirone and Aldactone on the pars distalis of the pituitary, the interrenal tissue and the interstitial tissue of t,he testis in the common frog, Rann tempornrirt. Z. Zelljorsch. 96, 466477. OORDT, P. G. W. J. (1968). The analysis and identification of the hormone-producing cells of the adenohypophysis. In “Perspectives in Endocrinology” (Barrington. E. J. W.. and BarkerJergensen, C.. eds.). Academic Press. New York.
VAN
P. J. V. F.
EVENNETT THORNTON’
Department of Zoologz~ University of Leeds Leeds LSU” 9JT, England Received June 29, 1970
’ Present address: Department of Anatomy, Kinq College. London WC. 2. England.
Crayfish
Crayfish in both intermolt and premolt (eyestalkless) stages showed no blood sugar responseto glucagon-free insulin (2.0 IU) over a 6-hr period, while animals in both tht\se stages showed a significant hy-
6, 303-311.
P. D.,
Blood
Sugar
perglycemia within 2 hr after injection of 5.0 and 50.0 pg epinephrine. Glucagon (0.5 mg) induced hyperglycemia in 2 hr in intact intermolt stage animals only. Diverse results have been reported for