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Biomedical subjects

S Ellis

Publications and source records attributed to S Ellis.

At least 181 records · Page 10Linked to original sources
PubMed1984

Regulation of mitotic activity and the cell cycle in primary chick muscle cells by neurotransferrin.

We previously demonstrated that neurotransferrin (NTF), a transferrin extracted from adult chicken peripheral nerves, promotes growth of primary chick muscle cells in the absence of embryo extract. NTF was shown to stimulate DNA synthesis and cell proliferation. In the present study, we demonstrate that NTF is a mitogen using two independent methods; counts of orcein-stained mitotic figures and analysis of cell cycle kinetics with a fluorescence-activated cell sorter. In low-density cultures mitotic activity increases with increasing doses of NTF followed by a plateau at concentrations greater than 6 micrograms/ml. Residual, embryonic mitotic activity progressively declines with time after plating muscle cells in the absence of NTF. Absence of NTF for 2 days causes cells to lose irreversibly their myogenic potential. In the presence of NTF, mitotic activity increases for 2 days followed by a decline concurrent with myoblast fusion and formation of myotubes. Cell cycle analysis showed that NTF addition causes cell populations to shift from G1 to S and G2 + M within 18.5 hr. Muscle cells, plated at high densities in the absence of NTF, show mitotic activities similar to those plated at low densities in the presence of NTF. Addition of NTF to high-density cultures is ineffective in stimulating mitosis. These studies show that at typical cell plating densities, NTF is a required mitogen for primary chick muscle cell cultures.

Animals↗
PubMed1984

Ultrastructural cytochemical localization of carbonic anhydrase activity in rat peripheral sensory and motor nerves, dorsal root ganglia and dorsal column nuclei.

Some of the myelinated axons in rat peripheral nerves possess marked axoplasmic carbonic anhydrase activity [Riley, Ellis and Bain (1982) J. Histochem. Cytochem. 30, 1275-1288; Riley and Lang (1984) J. Hand Surg. 9A, 112-120]. A mixture of reactive and nonreactive neurons was a general observation in cervical, thoracic and lumbar ganglia. Nonmyelinated axons in lumbar dorsal roots were nonreactive; this was consistent with the lack of carbonic anhydrase in small sensory neurons. The carbonic anhydrase cytochemical method marked the larger afferent or sensory neurons and distinguished them from the smaller sensory neurons which were devoid of carbonic anhydrase activity. Nonmyelinated axons in the lumbar ventral roots were also nonreactive. Examination of muscle spindle innervation revealed staining of the primary sensory and gamma motor endings. This was strongly suggestive that some of the reactive sensory neurons were primary afferents and a portion of the reactive ventral root axons were gamma motor. The reactive central processes of spinal neurons sent collaterals into the grey matter of the spinal cord, entered the dorsal funiculi, and terminated in synaptic glomeruli in the cuneate and gracilis nuclei. Oligodendroglial cells appeared to be the only intrinsic cellular elements of the brain stem and spinal cord that exhibited high carbonic anhydrase activity. Both oligodendroglial and Schwann cells exhibited intense carbonic anhydrase activity in thin pockets of cytoplasm internal to compact myelin. The subcellular distribution of reaction product within sensory neurons and oligodendroglial cells agreed with biochemical reports of cytosol and membrane-bound forms of carbonic anhydrase. A general staining of the cytoplasm was suggestive of soluble carbonic anhydrase fixed in situ by the glutaraldehyde. Clumps of reaction product on the cytoplasmic surface of the endoplasmic reticulum possibly represented membrane-bound enzyme. Most of the membrane-bound carbonic anhydrase was associated with the internal membranes rather than the axolemma or limiting plasma membrane of the axon. In contrast to biochemical reports, a small fraction of neuronal mitochondria exhibited staining in the intracristal spaces. We suggest that the association of carbonic anhydrase with endoplasmic reticulum and mitochondria implicates the enzyme in regulating intracellular calcium because both organelles are known to sequester calcium.

Animals↗
PubMed1984

Pituitary gonadotrophins in Booroola and control Merino sheep.

Pituitary content of FSH and LH, using radioreceptor assay methods, was determined in control and Booroola Merino ewes on the 3rd day of the oestrous cycle and in adult rams slaughtered in winter. Significantly more pituitary FSH (as per gland or per g wet wt) was found in the Booroola than in the control ewe. No significant differences were found in LH content although the difference in FSH/LH ratio between Booroola and control ewes was significant (P less than 0.001). Pituitary FSH content was similar in the rams of the two genotypes. A good correspondence between FSH values by the radioreceptor assay and by radioimmunoassays using anti-ovine and anti-human serum was observed for the Booroola ewes. However, radioimmunological estimates of FSH activity were significantly higher than radioreceptor estimates in control ewes and in Booroola and control rams in which the pituitary FSH values were 5-6% of that of the ewe. This over-estimation is attributed to differences in specificity between methods. Fractionation of pituitary extracts by electrofocussing indicated a similar pI profile of FSH for ewes and rams of both genotypes. It is concluded that quantitative rather than qualitative differences in pituitary FSH occur in Booroola and control Merino ewes. It is suggested that increased FSH levels contribute to the hormonal basis for the increased ovulation rate of the Booroola Merino.

Animals↗
PubMed1984

A monoclonal antibody to an antigen present on the microvillous membrane of the trophectoderm of the preimplantation blastocyst of the pig.

Immunization of BALB/c mice with 14-day pig preimplantation blastocyst material followed by fusion of spleen cells with NS-0 myeloma cells resulted in a clone, SN 1/38, which secreted IgG1 which reacted specifically with the microvillous border of the pig trophectoderm and trophoblast as assessed by immunohistology. SN 1/38 did not react with other fetal tissues, or with blastocysts from other animal species. It was shown by absorption studies and by enzyme-linked immunoabsorbent assay that SN 1/38 was not directed against the placental form of pig alkaline phosphatase. The location of this antigen and its apparent presence throughout gestation indicate a functional role in the materno-fetal interaction.

Animals↗
PubMed1984

Activity of calcium activated protease in skeletal muscles and its changes in atrophy and stretch.

The reduction of protein content in skeletal muscle undergoing disuse-induced atrophy is correlated with accelerated rates of protein degradation and reduced rates of protein synthesis. It is not known in what manner myofibers are partially disassembled during disuse atrophy to fibers of smaller diameter; nor is it known which proteases are responsible for this morphological change in contractile protein mass. Dayton and colleagues have suggested that the Ca(2+)-activated protease (CaP) may initiate myofibril degradation. The discovery of a form of CaP that is activatable by nanomolar concentrations of Ca2+ indicates that CaP activity may be regulated by physiological concentrations of Ca2+. The enhancement of proteolysis by the Ca2+ ionophore A23187, reported by Etlinger, is consistent with a significant role for CaP in protein degradation. It was of interest, therefore, to measure the levels of CaP activity and the CaP inhibitor in extracts obtained from skeletal muscles of rat and chicken limbs undergoing disuse atrophy or stretch hypertrophy, respectively.

Animals↗
PubMed1984

The arousal of ingestive behaviors by chemical injection into the brain of the suckling rat.

Three neurochemical agents known to arouse ingestion in adult rats were studied in milk-sated rat neonates ingesting fluids away from their dams. All were given intracerebroventricular (ICV) injection. Drinking of both milk and water by 2-day-olds injected with angiotensin II (Ang II) was confirmed. The characteristic adult dipsogenic response, intake of water greater than that of milk, appeared at 8 days. ICV carbachol (Carb), on the other hand, did not elicit drinking before 4 days, despite the fact that these dipsogens (Carb and Ang II) may both affect receptors in the subfornical organ. ICV norepinephrine (NE) increased milk intake beginning at 9 to 10 days, which coincides with the age at which central adrenergic receptors believed to mediate NE's orexigenic effect are appearing in the developing forebrain. NE had no effect on water intake at any age. The effects of all three agents on ingestive behaviors were dose-dependent. These data suggest that the neural systems utilized by Ang II, Carb, and NE are competent for mediation of specific ingestive behaviors before they reach full anatomical and biochemical maturity. Last, NE did not increase milk intake of pups suckling from their dam at any age. The noradrenergic system that is developing in the rat brain during the suckling period appears to be a nascent control of subsequent adult feeding rather than a functioning control of ongoing suckling.

Angiotensin II↗