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Aspergillus nidulans is able to grow on oleic acid as sole carbon source. Characterization of the oleate-induced beta-oxidation pathway showed the presence of the two enzyme activities involved in the first step of this catabolic system: acyl-CoA oxidase and acyl-CoA dehydrogenase. After isopicnic centrifugation in a linear sucrose gradient, microbodies (peroxisomes) housing the beta-oxidation enzymes, isocitrate lyase and catalase were clearly resolved from the mitochondrial fraction, which contained fumarase. Growth on oleic acid was associated with the development of many microbodies that were scattered throughout the cytoplasm of the cells. These microbodies (peroxisomes) were round to elongated, made up 6% of the cytoplasmic volume, and were characterized by the presence of catalase. The beta-oxidation pathway was also induced in acetate-grown cells, although at lower levels; these cells lacked acyl-CoA oxidase activity. Nevertheless, growth on acetate did not cause a massive proliferation of microbodies in A. nidulans.

The Aspergillus nidulans acuH gene, required for growth on acetate and long-chain fatty acids, was cloned by complementation of the acuH13 mutation. Northern blotting analysis showed that transcription of the acuH gene occurs in acetate-grown mycelium and at higher levels in oleate-grown mycelium, but not during growth on glucose minimal medium. The acuH gene encodes a protein of 326 amino acids that belongs to the mitochondrial carrier family. The ACUH protein contains three related segments of approximately 100 amino acids in length, each segment comprising two hydrophobic domains that are probably folded into two transmembrane alpha-helices linked by an extensive polar region. Sequence comparisons suggest that the acuH gene of A. nidulans encodes the homologue of the carnitine/acylcarnitine carrier of rat and man. The uncharacterised proteins YOR100C of Saccharomyces cerevisiae, COLT of Drosophila melanogaster, and DIF-1 of Caenorhabditis elegans also seem to be homologues of ACUH. In addition to the motifs present in all members of the mitochondrial carrier family, we propose the highly conserved motif R(A,S)(V,F)PANAA(T,C)F within the sixth hydrophobic domain of these proteins as the characteristic feature of the carnitine carrier subfamily. The proposed function of the ACUH protein is the transport of acetylcarnitine molecules from the cytosol to the mitochondrial matrix, a process required during growth on acetate or on long-chain fatty acids.

Morphological studies suggest that there are several types of decapod hemocytes; however, distinguishing criteria based on conventional staining techniques are often subtle or ambiguous. Cytochemical features of ridgeback prawn (Penaeidae: Sicyonia ingentis) hemocytes were studied using specific stains for lysosomes, cytoplasmic contents, and granule enzymes. This approach facilitates the differentiation of cell types in the ridgeback prawn and provides information on the functions of and relationships among different cell types.Agranular hemocytes and a subgroup of small granule hemocytes contain extensive cytoplasmic glycoprotein deposits which display smudgy, intense staining with Sudan black B. As previously shown, coagulogen the clotting material in decapods stains with Sudan black B when extracted from lysed hemocytes. Other hemocyte types display light staining limited to granule membranes.Lysosomes are not observed in agranular cells and are rarely present in small granule hemocytes with glycoprotein deposits. Small granule hemocytes without deposits and large granule hemocytes contain numerous lysosomes as shown by the presence of acid phosphatase, /3-glucuronidase, and nonspecific esterase. Acid phosphatase is observed in the Golgi body of these cells, within small vesicles, and in small granules. The granules in large granule hemocytes rarely show acid phosphatase reaction, yet small acid phosphatase-positive vesicles fuse with the large granules. The acid phosphatase in the large granules may exist in an inactive form. Prophenoloxidase activity is localized only in large granules. The physiological significance of hemocyte cytochemistry is also discussed.