Intraspecies composition difference in collagen from cuticle and body of Ascaris and Lumbricus

Serum fetuin-A is an independent marker of insulin resistance in Japanese men

AIM

Fetuin-A, also known as alpha2-Heremans Schmid glycoprotein, is an abundant plasma protein synthesized predominantly in the liver. Fetuin-A inhibits insulin receptor autophosphorylation, which is mediated by its intrinsic tyrosine kinase activity. In this study, we examined the association between the serum fetuin-A level and insulin resistance in Japanese men.

METHODS

We recruited 300 unrelated Japanese men without known chronic diseases, such as diabetes mellitus, or a history of regular drug use, and who underwent health examinations. From a 75-g oral glucose tolerance test, the study population included 194 individuals with normal glucose tolerance, 91 with impaired glucose tolerance and/or impaired fasting glucose, and 15 with diabetes mellitus. Serum fetuin-A concentrations were measured using an ELISA kit.

RESULTS

Serum fetuin-A concentrations were positively correlated with fasting insulin levels (r = 0.269, p<0.001), HOMA-IR (r = 0.274, p<0.001) and LDL-cholesterol (r = 0.172, p<0.01), and negatively correlated with HDL-cholesterol concentrations (r = -0.191, p<0.001). Fetuin-A concentrations were also positively correlated with serum leptin (r = 0.150, p<0.01) and negatively with adiponectin concentrations (r = -0.208, p<0.001). Stepwise regression analyses confirmed that the fetuin-A concentration was independently associated with the fasting insulin level and HOMA-IR, as were body mass index, triglyceride, LDL-cholesterol, leptin and adiponectin concentrations.

CONCLUSION

Our data suggest that increased serum fetuin-A levels constitute an independent marker of insulin resistance and an atherogenic lipid profile in Japanese men.

Amino acid metabolism in helminths

Amino acids are major constituents of biological material. Chemically they are extremely stable and combine a relatively simple molecular structure with a wide range of properties and functions. In general, amino acid metabolism in helminths has been relatively neglected and the information available is often uneven and of uncertain quality. However, the search for new target sites for anthelmintic development has led to a renewed interest in this area. The amino acid composition of helminths is similar to that of other invertebrates and no unique amino acids have been reported. With the possible addition of tyrosine, helminths seem to require the same 10 essential amino acids as mammals and, where studied in detail, the pathways of amino acid synthesis in helminths are similar to those of mammals. Although amino acids are not a significant energy source in parasites, helminths are able to catabolize amino acids by pathways which, again, appear identical to those found in mammals. Helminths have also been shown to carry out a number of oxidative reactions associated with amino acid metabolism, including cysteine dioxygenase, proline hydroxylase and tryptophan hydroxylase. There are, however, differences in detail between the pathways of amino acid metabolism in helminths and mammals, particularly in the metabolism of the sulphur amino acids and arginine and proline. These differences may be exploitable in anthelmintic design and proline analogues and proline biosynthesis inhibitors show some potential as fasciolicides (Sheers et al., 1982). Differences in metabolism between parasites and their hosts may be the result of parasitic adaptation or they may merely reflect general features of the invertebrate phyla as a whole. Thus a comparison of amino acid metabolism in parasitic helminths with that of their free-living relatives may give some insight into the biochemical basis of parasitism.

Invertebrate collagens

The collagens of all major invertebrate phyla have been studied, but characterization has been thorough in only a few classes and in no case in the detail (such as sequence analysis) known for vertebrate collagen. Biochemical data on insect collagen are particularly sparse. Invertebrate and vertebrate collagens are strikingly similar, with some notably unique features in annelids and nematodes. Present data do not support the suggestion that invertebrate collagens resemble vertebrate basement membrane collagen. In invertebrates, as in vertebrates, collagens of specific tissues show differenes that probably reflect individual tissue requirements.

Ultrastructural observations on the body wall of the leech, Batracobdella picta

A series of closely spaced annulations surround the surface of the body of Batracobdella picta. The epidermis is covered by a thin cuticle which is composed of several layer of orthogonally arranged, fibrous bundles. Numerous fine projections carpet the surface of the cuticle and appear to be derived from microvillar processes which extend through the cuticle from subjacent epithelial cells. Septate junctions occur between adjacent epithelial cells, and hemidesmosomes with associated tonofilaments appear to anchor the epithelium to the overlying cuticle and to the basal connective tissue. The epithelial cells contain abundant organelles including granular endoplasmic reticulum, mitochondria and Golgi complexes. The cytology of the body wall of B. picta is compared with that of other annelids.

A radioautographic study of collagen synthesis by earthworm epidermis

Secreation by the epidermis of two oligochaetes (Eisenia and Enchytraeus) was investigated radioautographically following administration of 3H-proline, 3H-tryptophan or Na2(35)SO4. Regionally epidermal columnar cells of Enchytraeus synthesize the overlying, probably collagenous, cuticle. Eisenia epidermis does not recordably synthesize the cuticle until after wounding (first eight segments removed). By two days postoperative the epidermal columnar cells of Eisenia synthesize the collagenous cuticle and, later in regeneration, the epidermis may simultaneously synthesize the different collagen of the underlying basement lamella. The epidermis of Enchytraeus, but not of Eisenia, synthesizes some sulfated material associated with the cuticle surface.