Biomedical subjects

M Tzaphlidou

Publications and source records attributed to M Tzaphlidou.

29 records · Page 2Linked to original sources

PubMed1997

Influence of low doses of gamma-irradiation on mouse skin collagen fibrils.

The structure of mouse skin collagen fibrils after treatment with 0.5, 1 and 2.5 Gy gamma-irradiation was studied by electron microscopy. Animals were sacrificed 1, 4 and 8 weeks after irradiation. Although there were areas where the normal parallel packing of fibrils was retained in some regions packing was interrupted by abnormal fibrils and in some cases helical twisting was apparent. Irradiated collagen fibrils had a lower mean diameter compared with normal and a large variability in width. The diameter of 0.5 Gy irradiated fibrils returned to normal by 4 or 8 weeks after irradiation. Clusters of abnormal fibrils were found when viewed in cross-sections. Their number and size was reversibly dependent on the dose level. All fibrils retained normal banding periodicity. Computer analysis of irradiated and control patterns led to the conclusion that 0.5-2.5 Gy gamma-irradiation had no considerable effect in modifying the charge distribution along the mouse skin collagen fibril.

Animals↗

PubMed1995

Morphological alterations caused by lithium in various cell lines.

Lithium is being used for the treatment of mental diseases and for the attenuation of muelosuppression during chemotherapy. As during long term lithium treatment kidney damage has been reported, we studied morphological alterations in cells of kidney origin after exposure to lithium chloride. Above the level of 4 mmol, lithium has fatal effects in CV1 cells while HeLa cells that are not originating from kidneys, tolerate higher lithium concentrations. Cellular morphology alters during treatment duration. At early stages, cells become flatter on their substrate and upon longer than 4 days treatment begin to detach from their substrate and eventually cell death comes in a concentration dependent manner. The only morphological alteration observed in a lymphoblastoid cell line was a statistically significant cellular swelling.

Animals↗

PubMed1995

An electron microscopic study of collagen fibril structure after lithium treatment--II. The effects of low lithium dose and short treatment on mouse skin collagen.

The structure of mouse skin collagen fibrils, after treatment with lithium chloride at a dose of 0.7 meq/kg of body weight, was studied by electron microscopy. Animals were sacrificed 1-day, 1-, 2- and 6-months after the end of 30 consecutive days experimental period. Fibrils in disarray interspersed with normal ones were seen, although there were areas where the normal parallel packing of fibrils was completely replaced by a random arrangement. In some regions this packing was interrupted by fibrils forming a 'hairpin loop' and in some others helical twisting was apparent. Lithium treated collagen fibrils had a marked decrease in mean diameter compared to normal with a high variability in width. Clusters of abnormal fibrils were found when viewed in cross-sections, constituted approximately 10% of the whole population with an irregular outline. A shorter experimental period (7 days) leads to the same features in collagen disorganization as with the longer experimental period (30 periods). However, in short lithium treatment, there is no high variability in fibril width and although fibrils are smaller than the control, the decrease in mean diameter is not so pronounced as with longer treatment. In general, fibril diameter becomes altered progressively with experimental time. Lower dose, 0.3 meq Li/kg, in short treatment (7 days), leads to a normal collagen organization although in some areas fibril twisting is observed. Fibril diameter is not considerably affected.

Animals↗

PubMed1994

An electron microscopic study of collagen fibril structure after lithium treatment--I. The effect of different lithium doses on mouse skin collagen.

The structure of mouse skin collagen fibrils after treatment with lithium chloride at doses of 1.5 and 6 meq/kg of body weight was studied by electron microscopy. Animals were sacrificed 1 day, 1, 2 and 6 months after the end of a 30 consecutive days experimental period. With the first dose, which is commonly used clinically, although there were areas with normal collagen fibrils there were also regions where the characteristic parallel packing of fibrils was lost completely or it was preserved for a part of the area. With high doses, in most regions the normal packing of fibrils was replaced by an anarchic arrangement. In both cases, collagen fibrils had a marked decrease in mean diameter and showed a higher degree of variability in width and shape than collagen fibrils from controls. Also, many clusters of abnormal fibrils were found with a diameter of up to 260 nm vs 109 nm and a highly irregular outline when viewed in cross-sections. The periodicity D as well as the banding pattern were normal.

Animals↗

PubMed1992

Abnormal collagen fibril structure as studied by electron microscopy.

Transmission electron microscopy has emerged as an ideal tool for the study and diagnosis of various disorders that involve collagen, since the information obtained by this technique is at the ultrastructural level. Structural alterations of collagen fibrils brought about by these disorders are discussed. The positive staining pattern of such fibrils is also investigated. In addition, this review describes how quantitative studies of electron-optical images from abnormal collagen fibrils can lead to information about the changes produced by collagen defects which relate to molecular or fibril architecture.

Animals↗

PubMed1990

The collagen fibril--a model system for studying the staining and fixation of a protein.

A collagen fibril is made up of long rod-like molecules regularly D-staggered with respect to one another. This means that (i) its axially projected fine structure, resolvable to approximately 2 nm in electron micrographs, repeats D-periodically (D = 67 nm), and (ii) the amino acid residues contributing to each element of the fine structure can be inferred from sequence data. Electron-optical data from a fibril D-period can can therefore be correlated directly with chemical data. Such correlations confirm the electrostatic nature of the staining reaction when a fibril is positively stained. After negative staining, the principal factor determining the small-scale distribution of stain is local exclusion by 'bulky' amino acid side-chains. ('Bulkiness' is the average cross-sectional area, or 'plumpness', of a side-chain.) A small superimposed positive staining contribution can also be detected. Fixation of collagen by aldehydes and diimidoesters occurs via an initial reaction with lysyl (and hydroxylsyl) side-chains and alpha-amino groups, followed by secondary cross-linking reactions that differ from fixative to fixative. These secondary reactions determine the nature and abundance of the cross-links and the extent to which they influence subsequent staining behaviour.

Amino Acid Sequence↗

PubMed1988

The effect of elevated temperature on the aggregation of African green monkey kidney cells.

The aggregation kinetics of African green monkey kidney cells CV1 and of the SV40 transformed derivative COS1 cells that had been incubated at 37 degrees C or 43.5 degrees C was studied using the shaking flask system. COS1 cells show a three fold decrease in aggregation rate compared to CV1 cells when both cell types were incubated and aggregated at 37 degrees C. When these cell types were incubated at 43.5 degrees C for 5 hours, then aggregated at 37 degrees C showed a faster aggregation kinetics than before. Their aggregation at 43.5 degrees C with prior incubation at 37 degrees C or 43.5 degrees C reached the aggregation kinetics of 43.5 degrees C incubated cells aggregated at 37 degrees C. The addition of serum in the aggregation medium did not influence extensively the aggregation rates of both cell types.

Animals↗

PubMed1983

The effects of fixation by combination of glutaraldehyde/dimethyl suberimidate. Use of collagen as a model system.

The fixative behavior of glutaraldehyde/dimethyl suberimidate in combination was studied using reconstituted fibrils of type I calf skin collagen as a model system and comparing electron-optical data and chemical data by a computer-aided correlation procedure. The results confirm that the structural preservation of collagen obtained using prefixation in glutaraldehyde followed by dimethyl suberimidate fixation is less than when using dimethyl suberimidate and postfixation in glutaraldehyde. Furthermore, glutaraldehyde preserves the structure of collagen to a lesser degree than dimethyl suberimidate. With the combination of the two fixatives, the preservation of fine structure of collagen obtained is less than that when using dimethyl suberimidate alone.

Aldehydes↗

PubMedDate not supplied

A computer method for the comparison or the quantitative similarity between normal and abnormal collagen or between sequence data and experimental data.

In this paper, a method is described to correlate collagen structural data obtained by electron microscopy with chemical sequence data, or to compare two experimental sets of data. In this respect, collagen provides a valuable model system, firstly for studying the chemical basis of ultrastructure and the mechanisms of various treatments on a protein, and secondly for detecting and locating the alterations in collagen fibril structure produced by a collagen disorder.

Amino Acid Sequence↗

PubMedDate not supplied

The effect of lithium treatment on collagenous tissues: an electron microscope study.

Structural alterations of mouse skin collagen fibrils brought about by treatment with lithium chloride at various doses, as studied by electron microscopy, are discussed. The effect of the duration of treatment on such fibrils is also investigated. An analysis of positive staining patterns from fibrils from mice treated with lithium is included. In addition, this review describes how computer analyses of electron-optical images from collagen fibrils can lead to information about the changes produced by lithium on the molecular architecture of the fibril.

Animals↗

PubMedDate not supplied

The effects of inflammation-mediated osteoporosis (IMO) on the skeletal Ca/P ratio and on the structure of rabbit bone and skin collagen.

The relationships between the skeletal Ca/P ratio (used as an index of bone quality) and structural changes in the bone and skin was studied in inflammatory mediated osteoporosis (IMO). The bone Ca/P ratio in IMO rabbits was significantly lower than in controls. Also, severe alterations were detected at the ultrastructural level in bone and skin collagen fibrils from IMO rabbits.

Absorptiometry, Photon↗