Cartilage proteoglycan aggregate formation. Role of link protein.

Cartilage proteoglycan aggregate formation was studied by zonal rate centrifugation in sucrose gradients. Proteoglycan aggregates, monomers and proteins could be resolved. It was shown that the optimal proportion of hyaluronic acid for proteoglycan aggregate formation was about 1% of proteoglycan dry weight. The reaggregation of dissociated proteoglycan aggregate A1 fraction was markedly concentration-dependent and even at 9 mg/ml only about 90% of the aggregates were reformed. The lowest proportion of link protein required for maximal formation of link-stabilized proteoglycan aggregates was 1.5% of proteoglycan dry weight. It was separately shown that link protein co-sedimented with the proteoglycan monomer. By competition with isolated hyaluronic acid-binding-region fragments, a proportion of the link proteins was removed from the proteoglycan monomers, indicating that the link protein binds to the hyaluronic acid-binding region of the proteoglycan monomer.     

Ultrastructure of the lateral-line sense organs of the ratfish,Chimaera monstrosa

Summary The ultrastructure of the lateral-line neuromasts in the ratfish, Chimaera monstrosa is described. The neuromasts rest at the bottom of open grooves and consist of sensory, supporting, basal and mantle cells. Each sensory cell is equipped with sensory hairs consisting of a single kinocilium and several stereocilia. There are several types of sensory hair arrangement, and cells with a particular arrangement form patches within the neuromast. There are two types of afferent synapse. The most common afferent synapse has a presynaptic body and is typically associated with an extensive system of anastomosing tubules on the presynaptic side. When the tubules are absent, vesicles surround the presynaptic body. These synapses are often associated into synaptic fields, containing up to 35 synaptic sites. The second type of afferent synapse does not have a presynaptic body and is not associated with the tubular system. The afferent synapses of the second type do not form synaptic fields and are uncommon. The efferent synapses are either associated with a postsynaptic sac or more commonly with a strongly osmiophilic postsynaptic membrane. The accessory cells are similar to those in the acoustico-lateralis organs of other aquatic vertebrates. A possibility of movement of the presynaptic bodies and of involvement of the tubular system in the turnover of the transmitter is discussed. A comparison of the hair tuft types in the neuromasts of Ch. monstrosa with those in the labyrinth of the goldfish and of the frog is attempted.     

The relationship between the nuage and the chromatoid body during spermatogenesis in the Rat

Summary Cytoplasmic structures ultrastructurally similar to the nuage are present in the cytoplasm of all spermatogenic cells in adult rats. The nuage is a discrete organelle which should not be confused with the chromatoid body. In step 7–8 spermatids transient contact is established between the nuage and the chromatoid body. This indicates a very specific recognition of the nuage by the chromatoid body. It is suggested that the nuage and the chromatoid body are separate cell organelles the functions of which are somehow related to each other.     

Physicochemical properties of salt-soluble,unsheared chromatin

The mass per unit length of and the corresponding DNA packing ratio of about 14 for the chromatin soluble at moderate ionic strengths has been determined by light scattering. With the increase in ionic strength and corresponding release of histone H1 the DNA packing ratio has been found to decrease down to 4.4. The data obtained are consistent with the idea suggested previously that the salt-soluble chromatin is organized in double nucleosome chains arranged side-by-side and stabilized by H1. With salt-induced H1 release the double chain dissociates and the nucleosomal DNA partially unravels.     

Visna Virus Meningoencephalomyelitis in Goats

A progressive paresis was encountered in herds of Swedish goats. The symptoms developed during a period of weeks or months, and were initially often seen as a weakness of the hind limbs before the animals became paralytic. The development and the histopathological lesions of the disease in the GNS and the lungs were similar to those of visna in sheep. In vitro grown choroid plexus cells, prepared from affected goats, showed foci of polykaryocytes. Electron microscopy revealed the presence of particles morphologically similar to those of sheep visna virus (SVV). Goats experimentally infected with the goat visna virus (GVV) developed GNS lesions similar to those of visna in sheep and became seropositive to SVV. The results of complement fixation tests, carried out on sera from 11 goat herds, showed a coincidence between seropositiveness and the occurrence of disease in one and the same herd. Using the ELISA method, an average of 80 % of the goats in 5 herds were found to be seropositive to GVV.     

Interference of Mycotoxins with Prenatal Development of the Mouse

The prenatal effects of mycotoxins were investigated in GBA mice given by stomach tube a single dose of either aflatoxin B1 (4 mg/kg), ochratoxin A (8 mg/kg) or zearalenone (20 mg/kg) on pregnancy day 8 or 9. Aflatoxin caused foetal anomalies (exencephaly, open eyes, and protrusion of intestines) after exposure on gestation day 8 but not on day 9. The effects (increased prenatal mortality, reduced foetal growth, and a wide variety of malformations) caused by ochratoxin were much more severe and occurred after treatment on either of the 2 days of gestation. Among the spectrum of malformations, predominantly involving the craniofacial complex and the axial skeleton, the most striking was the total aplasia/dysplasia of the upper facial structures. These defects were always accompanied by exencephaly and anophthalmia. Zearalenone caused no effects. It is concluded that of the 3 mycotoxins screened with the technique used, ochratoxin is the most potent teratogen in mice.     

Studies on immobilized α-glucosidase from brewers yeastSaccharomyces carlsbergensis

Summary -Glucosidase isolated from brewer's yeast (Saccharomyces carlsbergensis) was immobilized using hydroxymethacrylate activated by cyanogen bromide as a carrier. Up to a hundred-fold increase in the stability of the enzyme was observed after immobilization. The yield in activity (bound/applied) was up to 30%. Before developing the process of enzymatic cleavage of maltose further we evaluated the kinetic properties of the enzyme catalyst, as we had observed earlier that the soluble enzyme is strongly inhibited by the product glucose. This is even more pronounced with the immobilized -glucosidase leading in this case to a linear relation between initial rate and substrate concentration, so K_M (approx.) values can no longer be defined due to the dominating influence of the product inhibition.     

Influence of manganese on enzyme synthesis and citric acid accumulation inAspergillus niger

Summary A comparison of citric acid fermentations in manganese-deficient and manganese-containing media showed that manganese strongly influences idiophase metabolism. In the presence of manganese, cell growth increases, sugar consumption is diminished and acidogenesis decreases drastically. An investigation of the key enzymes of glycolysis, the pentosephosphate pathway, TCA-cycle, nitrogen metabolism, and gluconeogenesis indicated that manganese deficiency was accompanied by a repression of anabolic and TCA-cycle-enzymes with the exception of citrate synthase. The activity of this enzyme and the enzymes of glycolysis paralleled the sugar consumption rate. In the presence of manganese, no repression of enzyme synthesis was observed. Activities of 2-oxoglutarate dehydrogenase and isocitrate lyase could not be detected in either case. The results support the hypothesis that manganese deficiency mainly affects the operation of biosynthetic reactions inAspergillus niger, thus leading to an overflow of citric acid as an end product of glycolysis.