PubMed Health⌕ Search

Biomedical subjects

M Tzaphlidou

Publications and source records attributed to M Tzaphlidou.

At least 19 recordsLinked to original sources
PubMed2001

Diameter distributions of collagenous tissues in relation to sex. A quantitative ultrastructural study.

A number of factors have been implicated in the regulation of collagen fibril diameter. Electron microscopy analysis was used to investigate the role of sex on fibril diameter. Female mouse skin collagen fibrils' mean diameter values were significantly smaller than those from the male, independent of age. In addition, the female rabbit collagen fibrils had a marked decrease in the mean diameter compared to male, in all the tissues examined (skin, liver, and bone). These data suggest that the collagen fibril diameter is related to sex.

Animals↗
PubMed2001

Structural variations of collagen in normal and pathological tissues: role of electron microscopy.

The spectrum of ultrastructural appearances assumed by collagen in normal and pathological tissues is illustrated using techniques of thin section transmission electron microscopy and computer-assisted analysis. The normal fibrillar collagen types are described in order to provide a basis for comparing other normal and abnormal forms. In normal tissues, the anchoring fibril and basal lamina (basement membrane) represent tissue structures largely containing collagen but differing significantly in organisation from normal types I to III fibrillar collagen. In pathological tissue, deviations from normal fine structure are reflected in abnormal aggregates of collagen fibrils (amianthoid and skeinoid fibres) and abnormalities in fibril diameter and cross-sectional profile. Fibrous and segment long-spacing collagen represent two further organisational variants of collagen, the former found widely in pathological tissues, the latter very rarely. Much remains to be discovered about these abnormal collagen variants-their mode of formation, the cells that produce them, and their roles. They also present a challenge for the collagen biologist formulating hypotheses of collagen fibril assembly and molecular organisation.

Animals↗
PubMed2000

Influence of nutritional factors on bone collagen fibrils in ovariectomized rats.

The influence of both vitamin D(3) and Ca:P ratio on bone collagen fibrils was investigated in ovariectomized rats. Six weeks after ovariectomy the rats were maintained for 80 days with diets containing vitamin D(3) and calcium supplementation. Age-matched ovariectomized animals were fed a normal diet. When vitamin D(3) was increased in the diet, although no effect in fibril organization was observed in relation to that from ovariectomized rats with the normal diet, a highly significant effect in fibril diameter was detected. When the calcium:phosphorus (Ca:P) ratio was increased from 1:1 to 2:1 (without vitamin D(3) supplementation) both structural fiber parameters were significantly affected. The results were closer to normal (i.e., collagen fibrils from animals without ovariectomy) when vitamin D(3) and Ca:P ratios were combined.

Animal Nutritional Physiological Phenomena↗
PubMed2000

Structural alterations in rat skin and bone collagen fibrils induced by ovariectomy.

In this study, the influence of ovariectomy in rat skin and bone (trabecular and cortical) collagen fibrils is examined using electron microscopy. Structural changes (fibril architecture and diameter) were detected, at the ultrastructural level, in skin and bone specimens from ovariectomized rats. The overall collagen fibril architecture was disturbed as compared with normal animals. Treated collagen fibrils' mean diameter values were significantly smaller than those from controls, in all tissues examined. The banding patterns of fibrils were normal in all cases; however, measurements by a computerized method of measuring axial periodicity of fibrils indicated significantly lower values for treated samples than untreated samples. Our results show a correlation between the effects induced by ovariectomy in skin and bone collagen. But, the question of whether these changes play a role in the pathogenesis of ovarian hormone deficiency in osteoporosis remains to be demonstrated.

Animals↗
PubMed1999

In vivo measurement of radius calcium/phosphorus ratio by X-ray absorptiometry.

We describe a new method for assessing the skeletal Ca/P ratio in vivo using X-ray absorptiometry. By placing cerium (Ce) and samarium (Sm) filters in the X-ray beam from a commercial X-ray source (Norland), mean photon energies of 39 and 89 keV were obtained. The instrument was designed to take measurements of the forearm, at a site located at the distal 1/3 of the radius. The system was calibrated with three bone phantoms: Ca10(PO4)6(OH)2, Ca(HPO4)(H2O)2 and Ca(HPO4)2(H2O)). The precision for measuring the Ca/P ratio in the human radius was 2.3% CV for a skin dose to the forearm ranging from 0.3 to 0.4 mGy, depending on the width of the arm. The Ca/P ratio of the radius was significantly lower in patients with postmenopausal osteoporosis than in premenopausal controls.

Absorptiometry, Photon↗
PubMed1999

Image processing of collagen: role in medicine.

This article describes how quantitative studies of electron-optical images from collagen fibrils, used as a model system can provide information not only about the molecular architecture of the fibril but also about the structural alterations produced by a treatment or disorder.

Animals↗
PubMed1999

Side effects of lithium treatment on collagenous tissues.

Structural alterations of collagen fibrils induced by treatment with lithium chloride at various doses and durations, are investigated. In addition, this article 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↗
PubMed1998

The influence of inflammation-mediated osteopenia (IMO) on the structure of rabbit bone and skin collagen fibrils.

The influence of Inflammation Mediated Osteopenia (IMO) on rabbit skin and bone (trabecular and cortical) collagen fibrils was studied by electron microscopy. Severe abnormalities in collagen fibril structure were detected, at the ultrastructural level, in skin and bone specimens from IMO rabbits. In treated animals the arrangement of fibrils is anarchic. The overall collagen fibril architecture is disturbed compared to normal. IMO collagen fibrils' mean diameter values were significantly larger than those from controls, in all examined tissues. However, the banding patterns of fibrils were normal in all cases. Computer analysis shows no differences in charged amino acid composition between IMO and untreated samples. Our results show a correlation between the effects induced by osteopenia on skin and bone collagen.

Animals↗
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↗