Troponin in embryonic chick skeletal muscle cells in vitro. An immunoelectron microscope study

The fine structurel distribution of troponin on thin filaments in developing myofibrils was investigated by the use of immunoelectron microscopy. Embryonic chick skeletal muscle cells grown in vitro were treated with antibodies against each of the troponin components (troponin T, I, and C) from adult chicken muscles. Each antibody was distributed along the thin filaments with a period of 38 nm. It is concluded that these newly synthesized regulatory proteins are assembled at their characteristic position from the initial phases of myofibrillogenesis.     

Screening method for prolidase deficiency

Summary A simple procedure was developed to determine prolidase activity in dried blood specimens. One thousand dried blood specimens from newborns were examined by this new method. Prolidase activities ranged from 140 to 370 nmol per 3 mm disc per hour (233±43, mean ± SD), and less than 2% of the samples overlapped the heterozygote values. This method should be useful in the mass screening for prolidase deficiency.This research was supported by a Research Grant from the Ministry of Education Japan 1979     

Freeze-Fracture images on filipin-sterol complexes in the thyroid follicle epithelial cell of mice with special regard to absence of cholesterol at the site of micropinocytosis

Summary In order to clarify the distribution of cholesterol in the plasma-and cyto-membranes of the thyroid follicle cell, freeze-fracture images of the filipin-treated tissues of normal and TSH-treated mice were observed. The filipin-sterol complexes, 25 to 30 nm protuberances or pits are distributed densely and almost homogeneously on the fractured plasma membrane, though the small depressions showing aggregates of intramembrane particles lack the complexes. Each depression corresponds to the coated pit, which might be an initial site for micropinocytosis of the luminal colloid. The limiting membranes of all the large colloid droplets reabsorbed are generally very rich in the complexes, but some small regions on the limiting membrane of the droplet are less in their density. The membranes of the rough endoplasmic reticulum, of the nucleus and of the Golgi apparatus are almost free from the complexes, though small clusters consisting of 2–5 complexes are rarely scattered. In thin sections, the membranes which are rich in the filipinsterol complexes become obscure in their fine structure after treatment with filipin for 12–14 h.This study was supperted by grants from the Japan Ministry of Education     

Urinary oligosaccharides of fucosidosis. Evidence of the occurrence of X-antigenic determinant in serum-type sugar chains of glycoproteins.

Urine of a fucosidosis patient contained a large amount of fucosyl oligosaccharides and fucose-rich glycopeptides. Six major oligosaccharides were purified by a combination of Bio-Gel P-2 and P-4 column chromatographies and paper chromatography. Structural studies by sequential exoglycosidase digestion and by methylation analysis revealed that their structures were as follows: Fucalpha1 leads to 6GlcNAc, Fucalpha1 leads to 2Galbeta1 leads to 4(Fucalpha1 leads to 3)GlcNAcbeta1 leads to 2Manalpha1 leads to 3Manbeta1 leads to 4GlcNAc, Galbeta1 leads to 4(Fucalpha1 leads to 3)GlcNAcbeta1 leads to 4Manalpha1 leads to 4GlcNAc, Galbeta1 leads to 4(Fucalpha1 leads to3)GlcNAcbeta1 leads to 2Manalpha1 leads to 6Manbeta1 leads to 4GlcNAc, and Galbeta1 leads to 4(Fucalpha1 leads to 3)GlcNAcbeta1 leads to 4Manalpha1 leads to 6Manalpha1 leads to 6Manbeta1 leads to 4GlcNAc. In additon, the structure of a minor decasaccharide was found to be Galbeta1 leads to (Fucalpha1 leads to)GlcNAcbeta1 leads to Manalpha1 leads to [Galbeta1 leads to (Fucalpha1 leads to)GlcNAcbeta1 leads to Manalpha1 leads to]Manbeta1 leads to 4GlcNAc.     

Mating type specific induction of cell wall lytic factor by agglutination of gametes in Chlamydomonas reinhardtii

When mt⁺ and mt^– gametes of Chlamydomonas reinhardtiiwere mixed, shedding of cell walls took place in both matingtypes during massive agglutination and/or pairing. This wascaused by a cell wall lytic factor that had been induced byflagellar agglutination and excreted into the medium by cellsconcurrently with their cell wall release. When glutaraldehyde-fixed gametes and isolated flagella of onemating type caused isoagglutination of live gametes of the othermating type, the live mt⁺ gametes induced the lytic factor andshed their walls, whereas none of the live mt^– did this.The cell walls of mt^– gametes were lost only when thelytic factor, which had been excreted by mt⁺ gametes into themedium, acted from the outside. These data imply that mt⁺ gametesare responsible for the induction of the lytic factor by agglutination,which acts on cell walls of both mating types either endogenouslyor exogenously. (Received February 28, 1978; )     

Developmental appearance of myosin heavy and light chain isoforms in vivo and in vitro in chicken skeletal muscle

Three myosin heavy chain isoforms with unique peptide maps appear sequentially in the development of the chicken pectoralis major muscle. An embryonic isoform is expressed early and throughout development in the embryo. A second isoform appears just after hatching and predominates by 10 days ex ovo. A third isoform, indistinguishable from adult myosin heavy chain, predominates by 8 weeks after hatching. This sequence of myosin isoform change does not, however, appear during myogenesis in vitro. In cultures prepared from embryonic myoblasts only embryonic myosin heavy chain is expressed. This is true even in cultures maintained for 30 days. Myosin light chain expression also changes in vivo with a progressive increase in fast light chain 3 accumulation. In vitro, however, this shift to increasing fast light chain 3 accumulation does not occur. The results indicate that the myosin heavy chain and light chain pattern observed in vitro is identical to that of the embryonic muscle and that the conditions necessary for the shift in expression to a more mature myosin phenotype are not present in myogenic cultures. These cultures are therefore potentially of great value in probing further the neural and humoral determinants of muscle fiber maturation and growth.