Collagen: the organic matrix of bone

Collagen is the principal organic matrix in bone. The triple helical region of the molecule is 1014 amino acids long. In fibrils these molecules are staggered axially by integers of 234 residues or 68 nm (D). This axial shift occurs by self-assembly and can be understood in terms of a periodicity in the occurrence of apolar and polar residues in the amino acid sequence. Because the molecular length L = 4.47 D, there are gaps 1.5 X 36.5 nm regularly arrayed throughout the fibrils. The three-dimensional molecular arrangement is a quasi-hexagonal lattice with three distinct values for the principal interplanar spacings. Analysis of the intensity distribution in the medium-angle X-ray diffraction patterns from tendons has produced the following picture of the molecular arrangement in fibrils (Fraser et al. 1983). The molecular helices have a coherent length of 32 nm and are tilted parallel to a specific place within the lattice. A regular azimuthal interaction exists between these helices. This crystalline region could be the overlap region with a non-crystalline gap region. However, the gap is still regular axially and the molecular helices retain their structure; their lateral packing is perturbed although they retain a 'gap'. Neutron and X-ray scattering experiments have shown that calcium hydroxyapatite crystals occur in the gap and are nucleated at a specific though unknown location within the gap. The c-axis of the apatite crystals is parallel to the fibril axis and its length c = 0.688 nm is close to the axial periodicity in a protein with an extended beta-conformation. If the telopeptides at the end of a collagen molecule do have this conformation they would either have a highly heterogeneous conformation or exist in a folded manner because the overall length of the telopeptides is shorter than a regular collagen repeat of 0.029 nm would allow.     

Relation between electrokinetic potentials and growth in callus cultures ofTrigonella foenum-graecum

Callus cultures ofTrigonella foenum-graecum were initiated from radicle or cotyledon portions of seedlings and young leaves and maintained on modified 1-B5 medium. The callus mass was disaggregated by mechanical agitation and the discrete cells thus obtained were used to measure their electrokinetic potential. Studies pertaining to the effects of ageing on electrokinetic potential and growth index revealed a relationship between these two parameters. Thus, the rate of change of electrokinotie potential with age could be employed as a parameter to study the growth kinetics of cells in callus cultures.     

Comparative study of electrokinetic potentials and binding affinity of lipopolysaccharides-chitosan complexes

Electrokinetic properties of complexes of chitosan (Ch) with lipopolysaccharides (LPSs) from Escherichia coli O55:B5, Yersinia pseudotuberculosis 1B 598, and Proteus vulgaris O25 (48/57) and their size distribution were investigated using zeta-potential distribution assay and quasi-elastic light scattering. The interaction of LPS from different microorganisms with chitosan at the same w/w ratio of components (1:1) resulted in the formation of complexes in which the negative charge of LPS was neutralized (LPS from E. coli) or overcompensated (Y. pseudotuberculosis and P. vulgaris). The changing in size of the endotoxin aggregates during binding with chitosan was observed. The binding constants of chitosan with LPSs were determined by a method with using the anionic dye Orange II. The LPS from E. coli possess higher affinity to chitosan in comparison with the two others samples of endotoxin.     

The fluoric origin of the bone lesion in the Pithecanthropus erectus femur

The femur of a patient autopsied 11 years ago is presented in which an osteophyte comparable to the one of the Pithecanthropus Erectus femur can be observed. Their analogous anatomopathological disposition is due to the fact that both are caused by the ossification of the tendinous insertion of the adductors of the thigh. The orifices they both present correspond to the channel of the perforating arteries which normally pierce them. This type of osteophyte is only present as a result of bone fluorosis. The autopsied patient presents a bone fluorosis of the Periostitis deformans' type, as described by the author in 1952. The femur of the Pithecanthropus was found by Eugene Dubois in some geological strata composed mainly of volcanic ash. In the Pithecanthropus, the fluoric intoxication came from the ingestion of fruits and plants impregnated with the fluorine filled volcanic ash. This volcanic fluorisis, known as Gaddur, is now seen among animals living on the volcanic region of Iceland. For these reasons we assume that the Pithecanthropus erectus suffered a bone fluorosis of the type of the Periostitis deformans, which would be the first disease known in man.     

The microlocalization of natural uranium in bone tissue

The author experimentally confirms the presence of a large share of uranium within the organic matrix of bone tissue and its uniform distribution within the bone mineral. It was shown in the powder-typed stratum bone cuts that the bone uranium is uniformly distributed within the bone mineral. The same is with the organic fraction of bone where uranium is uniformly distributed as well. This conclusion simplifies the calculation of the dose rate of irradiation of bone cells and red bone marrow cells with alpha-particles from the incorporated uranium, the event that these cells are plunged into a "cloud" of alpha-particles being proposed.     

The cytoplasmic origin of variability in the timing of S phase in mammalian cells.

The time at which S phase begins in mammalian cells is highly variable with respect to cell age. Evidence is presented that this variability does not arise because the initiation of DNA synthesis depends on the stochastic interaction of an initiator substance with a rare initiation site. Instead, the signal responsible for starting S phase must appear at random in the cytoplasm and may be transient.