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Biomedical subjects

P Morell

Publications and source records attributed to P Morell.

At least 109 records · Page 6Linked to original sources
PubMed1979

Axonal transport and metabolism of [3H]fucose- and [35S]-sulfate-labeled macromolecules in the rat visual system.

The axonal transport of labeled macromolecules in retinal ganglion cells of rats was investigated from 1 to 20 days following intraocular injection of [3H]fucose and [35S]sulfate. Maximal incorporation of [3H]fucose into acid insoluble material in the retina was at 8 h, followed by a biphasic decline. Transported [3H]fucose (98% as glycoprotein) was in the optic nerve at 1 h, the optic tract and lateral geniculate body by 2 h, and the superior colliculus by 3 h after injection, indicating a rate of transport of approximately 200 mm/day. Radioactivity continued to accumulate in the superior colliculus for at least 8 h and began to decline rapidly by 24 h. Between 3 and 6 days levels rose again in both optic tract and superior colliculus before starting a gradual decline, indicating that a wave of rapidly transported material was delayed in leaving the retina. When proteins in the superior colliculus were fractionated by gel electrophoresis, the composition of the two fucosylated protein transport phases could be partially resolved. Radioactivity in individual gel peaks represented primarily in the first phase decayed with an average half-life of one day, althouth that in one prominent protein of molecular weight 280,000 turned over with a half-life of the order of 12 h. Radioactive peaks primarily in the second phase decayed with an average half-life of more than a week. Incorporation of [35S]sulfate into acid insoluble material in the retina was maximal at 1-2 h, after which there was a rapid loss of label. The appearance of [35S]sulfate in the optic tract, lateral geniculate body and superior colliculus preceded by a short time that of the [3H]fucose; indicating a shorter retinal processing time for this label. The total transported [35S]sulfate in the superior colliculus peaked by 4-8 h and had fallen by 65% at one day; no prominent second wave of transport was observed as was the case for [3H]fucose. Acid insoluble [35S]sulfate in the superior colliculus was equally divided between glycopeptides and glycosaminoglycans at all times examined, indicating that these macromolecules are transported at the same rate. [35S]Sulfate incorporated into various proteins fractionated by gel electrophoresis had heterogeneous turnover rates, the average being around 12 h. Radioactivity in one group of proteins, of molecular weight around 90,000, decayed with a half-life of only a few hours.

Animals↗
PubMed1978

Experimental lead encephalopathy in the suckling rat: concentration of lead in cellular fractions enriched in brain capillaries.

Five-day old rats subjected to short-term (2-day) lead exposure by gastric gavage of aqueous lead acetate at the highest non-lethal dosage (1mgPb/g body weight/day) developed a hemorrhagic encephalopathy. Capillaries and microvessels isolated from brains of these rats showed abnormal morphology consisting of an increased number of irregularly dispersed endothelial nuclei and swollen, vacuolated endothelial cells. Lead was concentrated in isolated brain capillary-microvessel fractions, as demonstrated by both atomic absorption and 210Pb tracer methods. When lead exposure was continued for 20 days (at the maximal dosage regime compatible with a 60% survival rate), the rats recovered from the initial encephalopathy and capillaries and microvessels isolated from brains of these rats appeared morphologically normal. This recovery occurred despite continued high levels of lead in the blood and in the isolated capillary-microvessel fractions, suggesting that, as capillary endothelial cells mature, they are able to adapt to the presence of large amounts of lead.

Animals↗
PubMed1976

Myelin synthesis during postnatal nutritional deprivation and subsequent rehabilitation.

Newborn Long-Evans rats were undernourished by maternal deprivation so that by 20 days of age their body and brain weights were about 45 and 80%, respectively, of the values obtained for control (well-nourished) values. Proteins from myelin of undernourished and control rats were separated by polyacrylamide gel electrophoresis in buffers containing sodium dodecyl sulfate. At 15 and 20 days of age the proportion of basic and proteolipid protein was reduced in the starved animals relative to controls, indicative of a delay in maturation. However, by 30 days of age the composition of myelin from starved and control animals appeared similar. At all ages the yield of myelin from brains of starved rats was less than 25% of that obtained from control animals. A series of isotope labeling experiments, using a double label design, was carried out to compare relative rates of incorporation of radioactive amino acids into individual proteins of various brain subcellular fractions. In 20-day-old rats the incorporation of [3H] OR [14C] leucine or glycine into myelin proteins, relative to incorporation into proteins of other subcellular fractions, is preferentially depressed (about 60%) in starved animals. Synthesis of all the myelin proteins was depressed, supporting the hypothesis that the high molecular weight proteins isolated with myelin are true myelin constituents. Similar experiments were conducted using [3H]-and [14C] acetate, choline, or glycerol as precursors of lipids. Incorporation of isotope into lipids of myelin, relative to lipids of other subcellular fractions, was also depressed by about 60% in starved animals. In several experiments we studied synthesis during rehabilitation (ad libitum feeding) following 20 days of postnatal starvation. After 6 days of rehabilitation, incorporation of radioactive precursors into myelin, relative to other subcellular fractions, was still depressed. This result was true for both proteins and lipids, and was interpreted as evicence against the initiation of a process leading to a net recovery of myelin (i.e., an irreversible deficit of myelin synthesis is induced by this regime of nutritional deprivation).

Animals↗
PubMed1975

Glycoproteins released into the culture medium of differentiating murine neuroblastoma cells.

C-1300 murine neuroblastoma cells release glycoproteins into the culture medium. The process was studied by prelabeling spinner cultures for 12 to 60 hours with [3H]glucosamine. Then, the medium was removed and replaced with fresh medium lacking radioactive isotope. Soluble material released into the medium during the subsequent 2-hour incubation was collected by trichloroacetic acid precipitation. The released proteins were then separated by discontinuous polyacrylamide gel electrophoresis in buffers containing sodium dodecyl sulfate. The electrophoretograms of glycoproteins obtained from cultures labeled for different lengths of time were very similar; three major radioactive regions centered about molecular weights 87,000, 66,000, and 55,000 were present. When spinner cells were transferred to monolayer culture in the presence of N6,O2' dibutyryl adenosine 3':5'-monophosphate (Bt2cAMP), differentiation (extension of neurites twice the diameter of the perikaryon) was observed. Monolayer cultures grown in the presence of Bt2cAMP and [3H]glucosamine for 12 hours released glycoproteins which gave a gel electrophoresis pattern similar to that obtained using spinner cultures. However, after 60 hours in the presence of Bt2cAMP and [3H]glucosamine, the released radioactive material consisted almost exclusively of glycoproteins of the 66,000 molecular weight class. Similar results were obtained if [3H]fucose was substituted for [3H]glucosamine, or if bromodeoxyuridine (which also induced differentiation) was substituted for Bt2cAMP. Similar experiments using radioactive amino acids were conducted with both spinner and monolayer cultures. Much of the released radioactive material was contained in the same three molecular weight classes as the glycoproteins released by spinner cells prelabeled with [3H]glucosamine, and this pattern did not vary with length of labeling period or type of culture. These results may imply that the glycosylation of released proteins is influenced by agents which can induce differentiation. The origin of this released material is discussed. [3H]Glucosamine-labeled glycoproteins of the molecular weight class centered about 55,000 (discussed above) were isolated by preparative gel electrophoresis. They co-migrated with authentic mouse brain microtubular protein as two closely spaced bands on a number of different electrophoretic systems. This protein fraction was also characterized as complexing with a monospecific antitubulin antibody.

Bromodeoxyuridine↗
PubMed1975

Appearance of myelin proteins in rat sciatic nerve during development.

Rats between 5 and 45 days of age were sacrificed and their sciatic nerves dissected. Myelin was prepared from these sciatic nerves by a procedure involving purification on discontinuous sucrose gradients. The proteins of whole sciatic nerves at different ages and the proteins derived from the myelin isolated from these sciatic nerves were examined by discontinuous polyacrylamide gel electrophoresis in buffers containing sodium dodecyl sulfate. Over half of the proteins of sciatic nerve myelin migrated in a single band on the gel (P0). There were only minor changes in the protein distribution of sciatic nerve mylein during development. In contrast, the polyacrylamide gel patterns of whole sciatic nerve homogenate changed markedly during development between 5 and 15 days of age. The amount of P0 protein as a proportion of the total sciatic nerve protein increased from 3% at 5 days of age to 13% at 15 days of age after which it remained constant. Several other proteins which were also characteristic of the isolated myelin increased in relative importance during this time period. Parallel experiments dealing with a metabolic parameter of myelinogenesis, incorporation of intraperitoneally injected [35S]sulfate into sulfatide, were conducted. The maximum synthesis of sulfatide occurred between 6 and 16 days of age, coincident with the marked accumulation of myelin proteins in sciatic nerve.

Age Factors↗