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T K Borg

Publications and source records attributed to T K Borg.

83 records · Page 5Linked to original sources
PubMed1978

Correlation of freeze-fracture and scanning electron microscopy of epiphyseal chondrocytes.

Chondrocytes in epiphyseal cartilage were examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) using freeze-fracture techniques. Freeze-fracture replicas showed large numbers of fingerlike, 0.11-0.15 micrometer diameter, projections from the chondrocyte surface, with numerous 95-180 A diameter intramembranous particles associated with both the cell membrane surface and these projections. With SEM, these cytoplasmic projections were also obvious, but appeared collapsed into clusters of globular-shaped projections on the surface of the chondrocytes. With freeze-fracture techniques, in which shrinkage artifacts were essentially eliminated, the cytoplasmic projections were often seen in intimate contact with the extracapsular matrix. However, with chondrocytes prepared by both SEM and conventional TEM, there was evidence of shrinkage, the cytoplasmic projections having little contact with the extracapsular matrix. These findings show that the cytoplasmic processes are not artifacts of tissue processing and provide morphological evidence in support of the hypothesis that matrix vesicles are of cellular origin.

Animals↗
PubMed1977

Ultrastructure of the neurosecretory cells in the brain of diapausing pupae of the tobacco hornworm, Manduca sexta (L).

The ultrastructure of seven different types of neurosecretory cells (NSC) found in the medial and lateral areas of the brain of diapausing Manduca sexta is described. The five different types of NSC in the medial area have characteristic differences in their shape, size, neurosecretory granules (NSG), and the morphology of their organelles. The cell types of the medial area accumulated the NSG, but did not appear to be synthesizing and packaging new NSG, whereas the NSC in the lateral region were synthesizing and packaging NSG during diapause. The possible significance of the relationship between the lateral and medial cells is discussed.

Animals↗
PubMed1977

Ultrastructure of the protocerebral neurosecretory cells of larval Galleria mellonella, in situ and after culture of the brain in vitro.

Three major groups of neurosecretory cells are described in the larval brain of Galleria mellonella at two different times during the last larval instar and in larval brains after 72 hr of culture in vitro. The medial group in vivo consists of four distinct neurosecretory cell types, based on characteristic size and morphology, while the posterior and lateral groups each contain a single distinct type of neurosecretory cell. Morphological differences between the same neurosecretory cells at the different times during the last instar are most apparent in the lateral L-1 cells and in the medial M-2 cells, where pleiomorphism is particularly evident in the size, density and accumulations of neurosecretory granules. The only neurosecretory cells in which apparent synthesis of neurosecretory granules is still observed after culture of the brain in vitro are the medial M-2 cells. The other neurosecretory cell types show no accumulation of neurosecretory granules nor new synthesis of neurosecretory material, but are similar to neurosecretory cells in the brain in vivo in all other respects. The morphology of the neurosecretory cells in the larval brain in vivo and in vitro is discussed in relation to their appearance at the light microscopic level and to a known neurohormonal function of the brain which is maintained during 72 hr in vitro.

Animals↗
PubMed1975

Morphological and histochemical evidence of mitoribosomes in Manduca sexta.

The mitochondria found in the neurons of the frontal ganglion of Manduca sexta contained numerous mitoribosomes. The mitochondria of the glial and perineural cells did not contain mitoribosomes. The mitoribosomes were digested in RNase whereas phospholipase C digested the cellular membranes but had no effect on the mitoribosomes.

Animals↗
PubMed1974

Intracellular distribution of hydroperoxide isomerase.

Differential centrifugation of several plant extracts indicates that the majority of the hydroperoxide isomerase activity is present in the cytoplasm of the cell. However, lesser amounts of isomerase activity were found in the mitochondrial and microsomal fractions of sunflower seedlings. Sucrose density gradient centrifugation of extracts from sunflower, watermelon, and flax seedlings and from cauliflower buds showed that isomerase activity was associated with the mitochondria. There was no evidence for presence of hydroperoxide isomerase activity in the microbodies.

Journal Article↗