and experimental conditions when the production and secretion of a particular hormone
changes. In this wayan assessment of the role of each type of cell in the secretion of a certain
hormone can be made . An interesting new approach to this problem has been described by
EMMART, PICKFORD and WILHELMI (1966) using prolactin antibodies to which are attached
a fluorescent material, fluorescein isothiocyanate. Such fluorescent antibodies were allowed
to react with frozen sections of the pituitary of the teleost, Fundulus heteroclitus, while the
subsequent serial sections were stained by classical methods. The fluorescent antigen-antibody material was found to be localized near the eta cells which are thought to be the site
of origin of prolactin.
Direct measurements of the concentration of the hormones in endocrine glands and in
the circulating blood afford the most satisfactory way of assessing the level of endocrine
activity. Such procedures are not always feasible, and a histological examination of the secretory tissue may provide some information about this . Observations that can provide criteria of activity include ; the size and number of the secretory cells, their mitotic activity,
the appearance of the cytoplasm, nuclei, nucleoli, mitochondria, GOLGI apparatus, granules
and stainable secretory products that are present. The correlation of such changes with direct
measurements of the quantities of hormone present facilitates the physiological interpretation of such cytological observations. Histologically the activity of the thyroid gland
can be judged from measurements of its secretory cells, the greater their height, the greater
their activity, while the density of the neurosecretory material present in the neurohypophysis can be assessed and related to the function of the tissue . Endocrine activity may
also be judged, in some instances , from the histological condition of their target tissues;
reproductive organs like the uterus, testis and ovary afford the clearest examples of this.
Adequate interpretation of histological observation on endocrine function can be difficult,
especially with regard to the related hormone levels in the circulation. It thus may be difficult
to judge, whether accumulation of secretory material in a tissue reflects increased production, or decreased release of the hormone into the blood, alternatives that may indicate contrasting physiological conditions.
e) Identification and Measurement of Hormones
These procedures provide a veritable host of problems that have resulted in a multitude of
methods. Many of the difficulties arise from the necessity to identify and measure the active
materials, not only in the glandular tissues, but also in body fluids like blood and urine where
the concentrations may be very low (of the order 1012M).
This results in a two-fold problem; firstly how to handle and measure so little material, and secondly how to differentiate
it from other substances of similar chemical nature (like proteins) which are present at a
10
6
to 10
9
higher concentration. A battery of biological, physico-chemical and immunological methods are used.
Initial endocrinological investigations usually utilize biological methods for identification and measurement of the material present. In the first instance, a hormonal activity
is usually identified by its effects on an animal or tissue and these afford the criteria for its
presence . If the hormone has several demonstrable actions so much the better, as this provides a characteristic profile that can be used to aid in distinguishing it from other substances.
More precise assessment of the amounts of material present can be made by measuring the
magnitude of its effects on a particular biological system(s), such methods of measurement
being called bioassays. Two recently identified candidates for hormone status in fishes are
paralactin (a homologue of tetrapod prolactin), and a principle that can be extracted from
the caudal urophysis. Paralactin (and mammalian prolactin) increase the ability of hypophysectomized fish (kept in fresh water) to maintain adequate plasma sodium levels, and this
function has been used as a basis of measuring its concentration in the pituitary (ENSOR
and BALL, 1968a). Plasma sodium concentrations in such fish are used as an index of the
amount of hormone suspected to be in an injected extract. Ovine prolactin is used as astandard' preparation for comparison with the 'unknown'. In the instance of the urophysis, tissue
extracts increase water transfer across the urinary bladder of toads and also contract the
trout's urinary bladder (LACANILAO, 1969; LEDERIS, 1969), and these responses may not
only be used to help identify the material but could also provide a basis for its bioassay.
44
changes. In this wayan assessment of the role of each type of cell in the secretion of a certain
hormone can be made . An interesting new approach to this problem has been described by
EMMART, PICKFORD and WILHELMI (1966) using prolactin antibodies to which are attached
a fluorescent material, fluorescein isothiocyanate. Such fluorescent antibodies were allowed
to react with frozen sections of the pituitary of the teleost, Fundulus heteroclitus, while the
subsequent serial sections were stained by classical methods. The fluorescent antigen-antibody material was found to be localized near the eta cells which are thought to be the site
of origin of prolactin.
Direct measurements of the concentration of the hormones in endocrine glands and in
the circulating blood afford the most satisfactory way of assessing the level of endocrine
activity. Such procedures are not always feasible, and a histological examination of the secretory tissue may provide some information about this . Observations that can provide criteria of activity include ; the size and number of the secretory cells, their mitotic activity,
the appearance of the cytoplasm, nuclei, nucleoli, mitochondria, GOLGI apparatus, granules
and stainable secretory products that are present. The correlation of such changes with direct
measurements of the quantities of hormone present facilitates the physiological interpretation of such cytological observations. Histologically the activity of the thyroid gland
can be judged from measurements of its secretory cells, the greater their height, the greater
their activity, while the density of the neurosecretory material present in the neurohypophysis can be assessed and related to the function of the tissue . Endocrine activity may
also be judged, in some instances , from the histological condition of their target tissues;
reproductive organs like the uterus, testis and ovary afford the clearest examples of this.
Adequate interpretation of histological observation on endocrine function can be difficult,
especially with regard to the related hormone levels in the circulation. It thus may be difficult
to judge, whether accumulation of secretory material in a tissue reflects increased production, or decreased release of the hormone into the blood, alternatives that may indicate contrasting physiological conditions.
e) Identification and Measurement of Hormones
These procedures provide a veritable host of problems that have resulted in a multitude of
methods. Many of the difficulties arise from the necessity to identify and measure the active
materials, not only in the glandular tissues, but also in body fluids like blood and urine where
the concentrations may be very low (of the order 1012M).
This results in a two-fold problem; firstly how to handle and measure so little material, and secondly how to differentiate
it from other substances of similar chemical nature (like proteins) which are present at a
10
6
to 10
9
higher concentration. A battery of biological, physico-chemical and immunological methods are used.
Initial endocrinological investigations usually utilize biological methods for identification and measurement of the material present. In the first instance, a hormonal activity
is usually identified by its effects on an animal or tissue and these afford the criteria for its
presence . If the hormone has several demonstrable actions so much the better, as this provides a characteristic profile that can be used to aid in distinguishing it from other substances.
More precise assessment of the amounts of material present can be made by measuring the
magnitude of its effects on a particular biological system(s), such methods of measurement
being called bioassays. Two recently identified candidates for hormone status in fishes are
paralactin (a homologue of tetrapod prolactin), and a principle that can be extracted from
the caudal urophysis. Paralactin (and mammalian prolactin) increase the ability of hypophysectomized fish (kept in fresh water) to maintain adequate plasma sodium levels, and this
function has been used as a basis of measuring its concentration in the pituitary (ENSOR
and BALL, 1968a). Plasma sodium concentrations in such fish are used as an index of the
amount of hormone suspected to be in an injected extract. Ovine prolactin is used as astandard' preparation for comparison with the 'unknown'. In the instance of the urophysis, tissue
extracts increase water transfer across the urinary bladder of toads and also contract the
trout's urinary bladder (LACANILAO, 1969; LEDERIS, 1969), and these responses may not
only be used to help identify the material but could also provide a basis for its bioassay.
44