646
I L S E
L A S N I T Z K I
the parathyroid tissue or the PCF were derived. Thus, parathyroid fragments from young mice, from 9-12-day chick embryos and from newly
born humans, or PCF in which glands from a human foetus, from 10-day
chick embryos and a human parathyroid carcinoma had been grown
previously, produced identical changes (Gaillard, 1955b). Control
cultures of parietal bone showed deposition of fresh PAS-negative bone
matrix and the presence of osteoblasts. In the treated explants, osteoblasts were absent and no new bone was laid down. The pre-existing
matrix became PAS-positive after the first day in culture; but after
3-4 days the PAS-reaction changed again and varied from highly
positive to negative. At this time extensive lysis of the bone substance
could be observed which was, usually, but not always accompanied
by the appearance of giant multi-nucleate osteoclasts. Cinematographic observations of the living bone showed increased motility of
connective tissue cells between the bone trabeculae, and also large
osteoclasts in close contact with or in the immediate vicinity of the
dissolving area. They were either moving fast in various directions over
a wide area of dissolving matrix or made circumscribed "waggling"
movements on the same spot. In some treated cultures, resorption
occurred in the absence of osteoclasts while in others bone lysis was
absent although osteoclasts were present (Vol. 2, Chapter 16).
The PCF was still active at high dilutions (Gaillard, 1959). Dilutions
of 1 :25 and 1 :250 of a fluid in which 200 explants had been grown
produced an intense lysis in the majority of explants with the appearance
of a great number of osteoclasts and a dilution of 1 : 2500 still induced
a slight effect in about half the cultures. In experiments in which
parathormone (PTH) was used, 0-4 i.u./ml medium produced extensive
resorption in nearly all cultures with a high number of osteoclasts,
while doses below and above it were less effective.
Using the extent of bone resorption seen after a given concentration
of P T H and PCF as a guide, Gaillard (1959) deduced the amount of
hormone released by the gland into the medium and found it to be
approximately 0*25 i.u. for each individual explant.
The effect of the hormone is not confined to parietal bone; in limbbone rudiments which consist of three tissues, it affects cartilage and
connective tissue as well (Gaillard, 1960). In radii of 14-16-day-old
mouse embryos, a sub-periosteal layer of bone, a cartilaginous epiphysis
and a diaphysis with a strong azurophilic ground substance can be
distinguished. Within 3-6 days of cultivation in control medium the
rudiments elongate slightly and the cartilage in the shaft is gradually
replaced by connective tissue while osteoblasts appear at the inner side
of the surrounding layer of freshly laid down periosteal bone.
Limb-bone rudiments grown for 3-6 days in the presence of 2 i.u.
I L S E
L A S N I T Z K I
the parathyroid tissue or the PCF were derived. Thus, parathyroid fragments from young mice, from 9-12-day chick embryos and from newly
born humans, or PCF in which glands from a human foetus, from 10-day
chick embryos and a human parathyroid carcinoma had been grown
previously, produced identical changes (Gaillard, 1955b). Control
cultures of parietal bone showed deposition of fresh PAS-negative bone
matrix and the presence of osteoblasts. In the treated explants, osteoblasts were absent and no new bone was laid down. The pre-existing
matrix became PAS-positive after the first day in culture; but after
3-4 days the PAS-reaction changed again and varied from highly
positive to negative. At this time extensive lysis of the bone substance
could be observed which was, usually, but not always accompanied
by the appearance of giant multi-nucleate osteoclasts. Cinematographic observations of the living bone showed increased motility of
connective tissue cells between the bone trabeculae, and also large
osteoclasts in close contact with or in the immediate vicinity of the
dissolving area. They were either moving fast in various directions over
a wide area of dissolving matrix or made circumscribed "waggling"
movements on the same spot. In some treated cultures, resorption
occurred in the absence of osteoclasts while in others bone lysis was
absent although osteoclasts were present (Vol. 2, Chapter 16).
The PCF was still active at high dilutions (Gaillard, 1959). Dilutions
of 1 :25 and 1 :250 of a fluid in which 200 explants had been grown
produced an intense lysis in the majority of explants with the appearance
of a great number of osteoclasts and a dilution of 1 : 2500 still induced
a slight effect in about half the cultures. In experiments in which
parathormone (PTH) was used, 0-4 i.u./ml medium produced extensive
resorption in nearly all cultures with a high number of osteoclasts,
while doses below and above it were less effective.
Using the extent of bone resorption seen after a given concentration
of P T H and PCF as a guide, Gaillard (1959) deduced the amount of
hormone released by the gland into the medium and found it to be
approximately 0*25 i.u. for each individual explant.
The effect of the hormone is not confined to parietal bone; in limbbone rudiments which consist of three tissues, it affects cartilage and
connective tissue as well (Gaillard, 1960). In radii of 14-16-day-old
mouse embryos, a sub-periosteal layer of bone, a cartilaginous epiphysis
and a diaphysis with a strong azurophilic ground substance can be
distinguished. Within 3-6 days of cultivation in control medium the
rudiments elongate slightly and the cartilage in the shaft is gradually
replaced by connective tissue while osteoblasts appear at the inner side
of the surrounding layer of freshly laid down periosteal bone.
Limb-bone rudiments grown for 3-6 days in the presence of 2 i.u.