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PubMed1986

Reorganization of synaptic ultrastructure at facilitated lobster neuromuscular terminals.

Prolonged stimulation of the single excitor axon to the lobster distal accessory flexor muscle in the presence of ouabain caused long-term facilitation at its neuromuscular synapses. Hence the extracellularly recorded synaptic potentials failed less frequently and increased their mean amplitude, compared to the non-facilitated (control) potentials from homologous sites in the contralateral muscle. The fine structure of synaptic terminals between matched pairs of facilitated and control preparations was compared with the aid of serial section electron microscopy. Differences between facilitated and control preparations were similar both when the latter were bathed in normal saline or ouabain-containing saline, suggesting that the changes were related to the electrical stimulation rather than to the presence of ouabain. First, the facilitated terminals were smaller in surface area than the control. Second, the number and size of synaptic contacts in the facilitated terminals resembled those in the control. Third, presynaptic dense bodies or active sites increased in number although their sizes remained unaltered in the facilitated terminal. This increase is attributed to the addition of dense bodies at existing synaptic contacts since synaptic contacts remained constant in number between facilitated and control preparations. Fourth, the number and size of synaptic vesicles were unaffected by prolonged stimulation although there was a redistribution of vesicles such that they appeared to be channelled in distinct streams to synaptic contacts. Fifth, mitochondria increased in number and were situated closer to the dense bodies at facilitated nerve terminals than at control terminals. Overall, these changes denote considerable reorganization of the synaptic terminals associated with elevated transmitter release.

Animals↗
PubMed1985

The mouse muscle creatine kinase cDNA and deduced amino acid sequences: comparison to evolutionarily related enzymes.

The nucleotide sequence of cloned DNA corresponding to full-length mouse muscle creatine kinase mRNA has been determined. This 1415 base pair DNA sequence and the deduced 381 amino acid sequence of the protein have been compared to creatine kinase sequences from other vertebrate species and to invertebrate guanidino kinase sequences. These comparisons show that the vertebrate muscle creatine kinases constitute a remarkably conserved protein family with a unit evolutionary period of 30. The creatine kinases also retain marked sequence similarity with the more distantly related invertebrate guanidino kinases. A portion of the sequence, presumably part of the ATP binding site, shows similarity to other nucleotide binding proteins with diverse functions. Comparisons of the untranslated regions of the creatine kinase cDNA sequences show that the 5' untranslated regions are more highly conserved than are the 3' untranslated regions; this may point to some regulatory function in the 5' region.

Amino Acid Sequence↗
PubMed1976

Nondestructive neutron activation analysis of marine organisms collected from ocean dump sites of the middle eastern United States.

The concentrations of eight metals were determined by a nondestructive neutron activation technique for eleven species of fish and shellfish. The marine organisms were collected from ocean dump sites off New York City, off New Haven, Connecticut, and off Delaware Bay. Antimony was not detected in most of the organisms examined in thid study; the detection limit was about 0.02 to 0.05 ppm. Antimony levels ranged from 0.01 to 0.129 ppm in fish that had detectable levels. Cobalt levels were low in all samples with most levels in the range of 0.1 to 0.3 ppm. Chromium concentrations at 0.3 to 1.0 ppm were only roughly quantitated by the procedure employed. Most marine organisms examined had chromium levels at or below these values. Nickel was not detected in any of the organisms examined; the detection limit was in the 3 to 6 ppm range. Rubidium concentrations were 0.6 to 1.5 ppm for most organisms; only rough quantitative measurement was possible at these levels. Selenium levels ranged from about 0.3 to 3.8 ppm in all samples. Silver concentrations were below 0.3 ppm in most organisms. Silver concentrations as high as 10 to 30 ppm, however, were found in the digestive gland of rock crab. Zinc levels in windowpane flounder liver were about 6 to 9 times greater than the 4 to 10 ppm levels found in muscle. Zinc concentrations in rock crab muscle, on the other hand, were only slightly higher than the 15 to 32 ppm concentration found in the digestive gland. Fish other than windowpane flounder had zinc levels that ranged from 4 to 9 ppm in the muscle and 14 to 42 ppm in the liver. Shellfish other than rock crab had zinc levels of 15 to 30 ppm in muscle and 17 to 40 ppm in the digestive gland.

Animals↗
PubMed1975

Sterols of the lobster (Homarus americanus) and the shrimp (Pandalus borealis).

In this study we have analyzed the sterol compositions of two continental shelf species of crustacea, the lobster (Homarus americanus) and the shrimp (Pandalus borealis). Cholesterol was found to be the most abundant sterol in these two species with smaller amounts of desmosterol, 24-methylcholesterol, 24-ethylcholesterol, 24-methylenecholesterol and 22-dehydrocholesterol.

Animals↗
PubMed1987

Polarity orientations of microtubules in squid and lobster axons.

Polarity orientations of microtubules in periaxolemmal and internal regions of squid and lobster axons were determined in order to test the hypothesis that regional differences in particle transport are produced by differentially distributed microtubule subclasses. Over 95% of the microtubules in all regions of the axons investigated were oriented with plus ends located distally, pointing away from axonal somata, and there were no significant differences in orientation ratios in periaxolemmal and internal axoplasm. In axonal sheath glial cells of lobsters, microtubules were found to be oriented parallel to axonal microtubules and to have approximately equally mixed polarities. The results for axonal microtubules did not support the possibility of subclasses of axonal microtubules.

Animals↗