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Biomedical subjects

A S Craig

Publications and source records attributed to A S Craig.

At least 37 records · Page 2Linked to original sources
PubMed1991

The in vivo release of 90Y from cyclic and acyclic ligand-antibody conjugates.

Yttrium binding ligands DOTA, caDTPA and CT-DTPA were each conjugated to monoclonal antibody B72.3, labelled with 90Y and injected into mice in order to assess the in vivo inertness of the antibody-linked 90Y-ligand complexes. Levels of 90Y in femur shafts of the DOTA-B72.3 mice were low, being approximately 7 and 44%, respectively, of levels in the femur shafts of the caDTPA-B72.3 and CT-DTPA-B72.3 treated mice. This finding demonstrates the greater inertness and by implication the greater suitability for immunotherapy of the DOTA-90Y complex.

Animals↗
PubMed1989

An estimate of the mean length of collagen fibrils in rat tail-tendon as a function of age.

A theoretical expression has been derived for the mean collagen fibril length in tendon based on the assumption that collagen fibrils originate in cell surface invaginations and terminate either at some remote cell surface or another collagen fibril bundle. The expression thus determined requires knowledge of the effective lengths of the fibrocytes (or fibrocyte assemblies) and the cellular content of the tendon. Both of these parameters have been measured experimentally as a function of age for rat-tail tendon using a combined light microscope and electron microscope approach. The results obtained for immature tendon suggest that the mean collagen fibril length is at least equal to the critical length required to maintain the appropriate tensile properties. In the most mature tissue studied, however, the mean-collagen fibril length is in excess of 100 times the critical length.

Aging↗
PubMed1988

Ovine ceroid-lipofuscinosis II: Pathologic changes interpreted in light of biochemical observations.

Ceroid-lipofuscinosis is studied in a breed of sheep and the histochemical and ultrastructural changes are interpreted in light of the known chemical composition of cytosomes. It is concluded that the ovine disease is a lysosomal proteinosis. It is postulated that the multilamellar arrays reflect a complex three-dimensional structure of alternating lipid and protein with the proteinaceous component being specific polypeptides. This is supported by powder X-ray diffractions at 10A implying a repeating proteinaceous unit in the structures. The coherent size of diffracting units was remarkably similar to the periodicity of lamellae observed in electron micrographs of lipopigment cytosomes. The fluorescent and staining characteristics of lipopigment can be explained by the above conclusion and postulate.

Animals↗
PubMed1987

Ultrastructural organization of skin: classification on the basis of mechanical role.

In our previous developmental study on skin we reported that correlations existed between the collagen fibril diameter distribution, glycosaminoglycan content and composition, and mechanical role. In this work we present new but related electron microscope data on the ultrastructure of skins from flounder, marlin, cod, frog, toad, caiman, viper, pigeon, whale and opossum. It is shown that mammalian and avian body skins generally contain relatively sharp unimodal distributions of fibril diameter consistent with a "passive" mechanical role. In contrast most reptilian and fish skins have broad, right-skewed (or bimodal) distributions of fibril diameters compatible with the exotendinous attributes required of an "active" skin. A study of the changing form of the collagen fibril diameter distribution with depth in the dermis is also reported.

Alligators and Crocodiles↗
PubMed1985

Obstetric consultations during labor and delivery in a university-based family practice.

This study retrospectively examined the use of obstetrical consultants by family medicine residents and faculty at the University of Washington Hospital from July 1, 1980, to June 30, 1981. Of 125 deliveries, 104 (83 percent) were vaginal deliveries, 99 percent of which were performed by the family physician involved. There were 21 (17 percent) cesarean sections. Before the audit began, 13 complications of labor and delivery were established as criteria suggesting the need for consultation. Medical records were retrospectively examined for complications meeting these criteria. Formal consultations occurred in 32 percent of all deliveries. Of the patients with at least one of the 13 complications, 75 percent had consultations obtained. Patients with these complications had intrapartum risk scores that were significantly higher than patients without the listed complications. Apgar scores at 1 and 5 minutes were significantly lower in the group of patients meeting the consultation criteria (7.0 vs 8.0 at 1 minute; 8.3 vs 9.0 at 5 minutes). The criteria successfully identified a group of high-risk patients and could be an appropriate guide for decision making in the specific setting studied. Patients without one of the predetermined complications had a low rate of surgical intervention (cesarean section or midforceps deliveries); the negative predictive value was 98 percent.

Adult↗
PubMed1984

Crystalline fibril structure of type II collagen in lamprey notochord sheath.

We report here the existence of a crystalline molecular packing of type II collagen in the fibrils of the lamprey notochord sheath. This is the first finding of a crystalline structure in any collagen other than type I. The lamprey notochord sheath has a composition similar to that of cartilage, with type II collagen, a minor collagen component with 1 alpha, 2 alpha and 3 alpha chains, and cartilage-like proteoglycan. The high degree of orientation of fibrils in the notochord makes it possible to use X-ray diffraction to determine collagen fibril organization in this type II-containing tissue. The low angle equatorial scattering shows the fibrils are all about 17 nm in diameter and have an average center-to-center separation of 31 nm. These results are supported by electron microscope observations. A set of broad equatorial diffraction maxima at higher angles represents the sampling of the collagen molecular transform by a limited crystalline lattice, extending over a lateral dimension close to the diameter of one fibril. This indicates that each 17 nm fibril contains a crystalline array of molecules and, although a unit cell is difficult to determine because of the broad overlapping reflections, it is clear that the quasi-hexagonal triclinic unit cell of type I collagen in rat tail tendon is not consistent with the data. The meridional diffraction pattern showed 26 orders with the characteristic 67 nm periodicity found for tendon. However, the intensities of these reflections differ markedly from those found for tendon and cannot be explained by an unmodified gap/overlap model within each 67 nm period. Both X-ray diffraction and electron microscope data indicate a low degree of contrast along the fibril axis and are consistent with a periodic binding of a non-collagenous component in such a way as to obscure the gap region.

Animals↗
PubMed1984

Collagen fibril diameters and glycosaminoglycan content of skins--indices of tissue maturity and function.

Samples of anatomically and functionally distinct regions of the skin of a variety of altricial and precocial animals were taken at various stages of development from birth to beyond maturity. The glycosaminoglycan (GAG) content and composition of the tissues were determined by chemical analysis and the collagen fibril diameters measured by transmission electron microscopy. The fibril diameters of the skins of two fish and a bird were also assessed for comparison. Analysis and comparison of the data collected show that there was a significant correlation between collagen fibril diameter distribution, GAG type and amount, and functional load-bearing of the various skins, and that the variations in the biochemical and physical composition of the tissues at different stages of development could be related to both their post-conceptual maturity and their prospective functional loading.

Actin Cytoskeleton↗
PubMed1982

A role for glycosaminoglycans in the development of collagen fibrils.

Extensive data on the glycosaminoglycan (GAG) composition and the collagen fibril diameter distribution have been collected for a diverse range of connective tissues. It is shown that tissues with the smallest diameter collagen fibrils (mass-average diameter less than 60 nm) have high concentrations of hyaluronic acid and that tissues with the largest diameter collagen fibrils (mass-average diameter approximately 200 nm) have high concentrations of dermatan sulphate. It is suggested that the lateral growth of fibrils beyond a diameter of about 60 nm is inhibited by the presence of an excess of hyaluronic acid but that this inhibitory effect may be removed by an increasing concentration of chondroitin sulphate and/or dermatan sulphate. It is also postulated that high concentrations of chondroitin sulphate will inhibit fibril growth beyond a mass-average diameter of approximately 150 nm. Such an inhibition may in turn be removed by an increasing concentration of dermatan sulphate such that it becomes the dominant GAG present in the tissue.

Aging↗
PubMed1981

Growth and development of collagen fibrils in immature tissues from rat and sheep.

The collagen fibril diameter distribution of four immature tissues from both rat and sheep have been determined from the transverse sections observed in the transmission electron microscope. In many instances before birth, the form of the distribution for the tissues is both unimodal and sharp and the mean diameters of the distributions lie close to a multiple of 80 A. For some tissues, the collagen fibril diameter distributions may be resolved into a number of components, each of which represents a population of fibrils with a diameter close to a multiple of 80 A (8 nm). These data confirm and extend previous observations by the authors that small collagen fibrils growth occurs by the accretion of 80 A units. The form of the collagen fibrils diameter distribution at birth is broad for the sheep tissues but narrow for the rat tissues, thus confirming that the range of fibril diameters at this stage of life reflects the differing degree of development of precocious and altricious animals.

Aging↗
PubMed1979

Electron microscope evidence for an 80 A unit in collagen fibrils.

Connective tissues are composite structures containing collagen, elastin, glycosaminoglycans, minerals, water and other minor components. In all cases the collagen exists predominantly in fibrillar form. The size distribution of the fibrils does, however, vary markedly with both age and the mechanical requirements of the tissue. Little is known about the mechanism of fibril formation in vivo, although some information is now available form in vitro polymerisation studies. We have now collected new and extensive electron microscope data on the size of collagen fibrils from tendon, skin, cornea and other tissues from both fetal and immature animals. The results reported here show that the diameters of the collagen fibrils thus measured lie close to a multiple of 80 A, a result which may be simply and readily interpreted in terms of the collagen microfibril and its mode of packing.

Animals↗
PubMed1975

Spontaneous arteritis and glomerulitis in mice. A comparison of light and electron microscopic renal changes in PN/n, NZB/BL, 101/MAC, and CBA/MAC mice.

Four PN/n mice between 12 and 17 months of age had fibrinoid necrosis of the renal arteries, but 32 mice up to the age of 17 months showed no consistent change in the media or intima of the renal arteries although perivascular cuffing with round cells was prominent from 9 months of age. Glomerulitis, indicated by increase in the mesangium on light microscopy, affected most mice over 7 months of age, and dense deposits on electron microscopy were present in most mice from 7 months of age. These changes occurred significantly more frequently than in CBA/MAC mice; the 101/MAC showed an intermediate frequency, and the pattern in a small sample of NZB/BL mice resembled that of the PN/n mice. Basement membrane thickening increased with age from 3 weeks in all of the strains but more often included dense deposits in PN/n mice. Splitting of the glomerular basement membrane in very young mice in all strains was not considered relevant and may have been developmental. Failure consistently to detect glomerulitis earlier by electron microscopy than by light microscopy was attributed to the greater sampling error of the former. Unidentified dense bodies in glomerular epithelial cells occurred at all ages in all strains, so the suggestion that they were virus particles relevant to the disease was not sustained. Intraobserver variation studies showed satisfactory repeatability for light microscopy and for dense deposits and basement membrane thickening, but the dense bodies were not detected with acceptable reproducibility, a difficulty partly due to technical variation.

Age Factors↗