DIFFERENTIATION OF KIDNEY MESENCHYME
271
may indicate enhanced synthetic activities in cell aggregates. Therefore a
study was made of the location of any new products of differentiating
kidney mesenchyme, whether in the cells of the aggregates and the
tubules, in the loose mesenchymal cells, or in both.
Observations with the aid of electron microscopy revealed a change in
the endoplasmic reticulum of aggregated cells and of early tubule cells,
which suggests a change in the synthetic activity of these cells (Wartiovaara, 1966a). The basement membrane around the tubules seemed to
be secreted by the tubule cells; no signs of such a membrane were observed around nondifferentiating cells. The change appeared as cisternal
distensions of the endoplasmic reticulum. The cisternae subsequently
came to lie in the peripheral cytoplasm of the developing pretubules, and
this shift was followed by the appearance of basement membrane material on the tubule surface (Fig. 12).
In other experiments new protein species were histochemically localized in the mesenchyme undergoing differentiation (Rapola and Niemi,
1965). A battery of cytochemical techniques was employed; the appearance of a certain new enzyme activity in the cytoplasm may be conjectured to be the end result of the synthetic chain activated in differentiating cells.
At the condensation phase, reduced nicotinamide adenine dinucleotide
(NADH)-tetrazolium reductase activity markedly increased in the condensates, and the activity increased in the course of tubule maturation
(Fig. 13). Thiamine pyrophosphatase activity appeared in the Golgi
apparatus of the cells during their organization into tubule epithelium
and the formation of a lumen. A subsequent increase in the acid phosphatase activity of the apical cytoplasm was noticed during the formation
of the tubule lumen (Fig. 14). After 7 days of cultivation, the first
adenosine triphosphatase (ATPase) activity appeared both in the cell
membranes and in the cytoplasm of the tubule cells (Fig. 15).
When the properties characterizing kidney cells were mapped out,
using immunological methods to demonstrate the appearance of antigenic
vesicles (V) are located in the cytoplasm of the cells. A beginning accumulation of
extracellular material (EM) on the pretubule surface can be detected, (b) A local
accumulation of extracellular material (EM) is found on the surface of a pretubule
cell. A large cisternal distension (C) of the endoplasmic reticulum is seen in the
periphery of the cell and a vesicle (V) filled with dense material is located just
beneath the cell surface, (c) A large cisterna (C) filled with homogeneous material is
seen close to the outer surface of a pretubule. Fibrillar extracellular material (EM)
is detectable on the cell surface. (From Wartiovaara, 1966a.)
271
may indicate enhanced synthetic activities in cell aggregates. Therefore a
study was made of the location of any new products of differentiating
kidney mesenchyme, whether in the cells of the aggregates and the
tubules, in the loose mesenchymal cells, or in both.
Observations with the aid of electron microscopy revealed a change in
the endoplasmic reticulum of aggregated cells and of early tubule cells,
which suggests a change in the synthetic activity of these cells (Wartiovaara, 1966a). The basement membrane around the tubules seemed to
be secreted by the tubule cells; no signs of such a membrane were observed around nondifferentiating cells. The change appeared as cisternal
distensions of the endoplasmic reticulum. The cisternae subsequently
came to lie in the peripheral cytoplasm of the developing pretubules, and
this shift was followed by the appearance of basement membrane material on the tubule surface (Fig. 12).
In other experiments new protein species were histochemically localized in the mesenchyme undergoing differentiation (Rapola and Niemi,
1965). A battery of cytochemical techniques was employed; the appearance of a certain new enzyme activity in the cytoplasm may be conjectured to be the end result of the synthetic chain activated in differentiating cells.
At the condensation phase, reduced nicotinamide adenine dinucleotide
(NADH)-tetrazolium reductase activity markedly increased in the condensates, and the activity increased in the course of tubule maturation
(Fig. 13). Thiamine pyrophosphatase activity appeared in the Golgi
apparatus of the cells during their organization into tubule epithelium
and the formation of a lumen. A subsequent increase in the acid phosphatase activity of the apical cytoplasm was noticed during the formation
of the tubule lumen (Fig. 14). After 7 days of cultivation, the first
adenosine triphosphatase (ATPase) activity appeared both in the cell
membranes and in the cytoplasm of the tubule cells (Fig. 15).
When the properties characterizing kidney cells were mapped out,
using immunological methods to demonstrate the appearance of antigenic
vesicles (V) are located in the cytoplasm of the cells. A beginning accumulation of
extracellular material (EM) on the pretubule surface can be detected, (b) A local
accumulation of extracellular material (EM) is found on the surface of a pretubule
cell. A large cisternal distension (C) of the endoplasmic reticulum is seen in the
periphery of the cell and a vesicle (V) filled with dense material is located just
beneath the cell surface, (c) A large cisterna (C) filled with homogeneous material is
seen close to the outer surface of a pretubule. Fibrillar extracellular material (EM)
is detectable on the cell surface. (From Wartiovaara, 1966a.)