Fred W. Keeley

Bio: Fred W. Keeley is an academic researcher from University of Toronto. The author has contributed to research in topics: Elastin & Tropoelastin. The author has an hindex of 42, co-authored 96 publications receiving 6786 citations. Previous affiliations of Fred W. Keeley include St. Michael's Hospital & University of Sydney.

Durability of regenerated articular cartilage produced by free autogenous periosteal grafts in major full-thickness defects in joint surfaces under the influence of continuous passive motion. A follow-up report at one year.

Abstract: An autogenous graft of tibial periosteum was sutured (with its cambium layer facing into the joint) to the base of a five by ten-millimeter full-thickness defect in the patellar groove of each of forty-five adolescent rabbits. The rabbits were randomly treated postoperatively by either four weeks of immobilization in a cast, intermittent active motion in a cage, or two weeks of continuous passive motion. One year postoperatively, the regenerated tissue from each rabbit was analyzed macroscopically, histologically, histochemically, and biochemically. Gross degenerative changes were seen in 57 per cent of the rabbits that had been immobilized in a cast, in 73 per cent of the rabbits that had been allowed intermittent active motion, and in 22 per cent of the rabbits that had been subjected to continuous passive motion (p less than 0.05). Out of a possible score of 7.0 points for the nature of the regenerated tissue, the scores for the three groups were: immobilization in a cast, 4.1 points; intermittent active motion, 4.0 points; and continuous passive motion, 5.9 points (p greater than 0.05). Out of a possible perfect combined score of 10.0 points for the structural characteristics of the regenerated tissue, the cast-immobilization group scored 3.8 points; the intermittent active-motion group, 2.5 points; and the continuous passive-motion group, 6.4 points (p less than 0.001). The total scores for freedom from cellular changes of degeneration, a perfect score being 5.0 points, were: immobilization in a cast, 2.4 points; intermittent active motion, 2.3 points; and continuous passive motion, 3.9 points (p less than 0.01). Degenerative changes in the adjacent cartilage, which were noted in 42 and 46 per cent of the knees in the immobilization and intermittent active-motion groups, respectively, were not found in the knees that had been subjected to continuous passive motion (p less than 0.05). The total indices, which were derived by combining the scores for all categories (maximum, 24.0 points), revealed that the index for the continuous passive-motion group was significantly better than the index for either of the other two groups: immobilization in a cast, 12.9 points; intermittent active motion, 11.2 points; and continuous passive motion, 19.2 points (p less than 0.0005).(ABSTRACT TRUNCATED AT 400 WORDS)

The chondrogenic potential of free autogenous periosteal grafts for biological resurfacing of major full-thickness defects in joint surfaces under the influence of continuous passive motion. An experimental investigation in the rabbit.

Abstract: A rectangular graft of autogenous tibial periosteum was sutured (with its cambium layer facing into the joint) onto the base of a five by ten-millimeter full-thickness defect in the patellar groove of each of 143 adolescent and adult rabbits. The rabbits were managed postoperatively by either immobilization, intermittent active motion, continuous passive motion for two weeks, or continuous passive motion for four weeks. When the animals were killed four weeks postoperatively, the contour of the patellar groove had been restored in all of the rabbits in the group that had had four weeks of continuous passive motion, and the newly formed tissue in all of the defects in this group had the gross, histological, and histochemical appearance of smooth, intact hyaline articular cartilage. Histologically, the nature of the tissue that had formed, as well as its surface regularity, structural integrity, and bonding to the adjacent cartilage, were significantly better in the group that had had four weeks of continuous passive motion than in any of the other groups. The results were significantly worse when the orientation of the periosteal graft was reversed (that is, when it had been sutured into the defect with the cambium layer of the graft facing the subchondral bone rather than into the joint) or when no periosteal graft was used. Biochemical analyses revealed that, in the group that had had four weeks of continuous passive motion, the total hexosamine content, the levels of chondroitin sulphate and keratan sulphate, and the ratio of galactosamine to glucosamine were all comparable with the values for normal articular cartilage. In contrast, in the groups that were treated by immobilization, intermittent active motion, or two weeks of continuous passive motion, as well as in the adult rabbits, the content of the first three of these substances was significantly less than normal. In the groups that were treated by immobilization, intermittent active motion, or two weeks of continuous passive motion, 32 to 47 per cent of the total collagen was type II, while in the group that had had four weeks of continuous passive motion, 93 per cent of the total collagen was type II. These results demonstrate that, under the influence of continuous passive motion, free autogenous periosteal grafts can repair a large full-thickness defect in a joint surface by producing tissue that resembles articular cartilage grossly, histologically, and biochemically, and that contains predominantly type-II collagen.

Adaptations of carotid arteries of young and mature rabbits to reduced carotid blood flow

Abstract: Adaptive responses of rabbit common carotid arteries were examined after 70-80% reductions in blood flow produced by ipsilateral external carotid artery ligation. These flow reductions elicited growth inhibition of arterial wall tissue in immature rabbits. Specifically, experimental carotid arteries exhibited DNA levels significantly lower, by 35%, than contralateral control arteries 1 mo after external carotid ligation. Lower elastin contents (38%) were also observed, although collagen contents were not affected. These changes were accompanied by a relative reduction in wall mass of 30% and a 31% reduction in internal diameter. Adult rabbits exhibited decreased internal diameter (21%) after flow reduction, but no significant change in vessel mass or wall constituents was observed. Early diameter reductions were vasoconstrictor in origin, but the vessel functioned as a smaller artery rather than as a partially constricted normal vessel after 1 mo, i.e., both maximally dilated and maximally constricted diameters were reduced. A reduction in endothelial cell number was detected for the narrowed vessels. Manipulation of local flow conditions indicated that the vessels responded to changes in mean blood flow rather than the pulsatile component of flow.

Collagen Structure and Stability

Abstract: Collagen is the most abundant protein in animals. This fibrous, structural protein comprises a right-handed bundle of three parallel, left-handed polyproline II-type helices. Much progress has been made in elucidating the structure of collagen triple helices and the physicochemical basis for their stability. New evidence demonstrates that stereoelectronic effects and preorganization play a key role in that stability. The fibrillar structure of type I collagen—the prototypical collagen fibril—has been revealed in detail. Artificial collagen fibrils that display some properties of natural collagen fibrils are now accessible using chemical synthesis and self-assembly. A rapidly emerging understanding of the mechanical and structural properties of native collagen fibrils will guide further development of artificial collagenous materials for biomedicine and nanotechnology.

Liquid phase condensation in cell physiology and disease.

Abstract: BACKGROUND Living cells contain distinct subcompartments to facilitate spatiotemporal regulation of biological reactions. In addition to canonical membrane-bound organelles such as secretory vesicles and endoplasmic reticulum, there are many organelles that do not have an enclosing membrane yet remain coherent structures that can compartmentalize and concentrate specific sets of molecules. Examples include assemblies in the nucleus such as the nucleolus, Cajal bodies, and nuclear speckles and also cytoplasmic structures such as stress granules, P-bodies, and germ granules. These structures play diverse roles in various biological processes and are also increasingly implicated in protein aggregation diseases. ADVANCES A number of studies have shown that membrane-less assemblies exhibit remarkable liquid-like features. As with conventional liquids, they typically adopt round morphologies and coalesce into a single droplet upon contact with one another and also wet intracellular surfaces such as the nuclear envelope. Moreover, component molecules exhibit dynamic exchange with the surrounding nucleoplasm and cytoplasm. These findings together suggest that these structures represent liquid-phase condensates, which form via a biologically regulated (liquid-liquid) phase separation process. Liquid phase condensation increasingly appears to be a fundamental mechanism for organizing intracellular space. Consistent with this concept, several membrane-less organelles have been shown to exhibit a concentration threshold for assembly, a hallmark of phase separation. At the molecular level, weak, transient interactions between molecules with multivalent domains or intrinsically disordered regions (IDRs) are a driving force for phase separation. In cells, condensation of liquid-phase assemblies can be regulated by active processes, including transcription and various posttranslational modifications. The simplest physical picture of a homogeneous liquid phase is often not enough to capture the full complexity of intracellular condensates, which frequently exhibit heterogeneous multilayered structures with partially solid-like characters. However, recent studies have shown that multiple distinct liquid phases can coexist and give rise to richly structured droplet architectures determined by the relative liquid surface tensions. Moreover, solid-like phases can emerge from metastable liquid condensates via multiple routes of potentially both kinetic and thermodynamic origins, which has important implications for the role of intracellular liquids in protein aggregation pathologies. OUTLOOK The list of intracellular assemblies driven by liquid phase condensation is growing rapidly, but our understanding of their sequence-encoded biological function and dysfunction lags behind. Moreover, unlike equilibrium phases of nonliving matter, living cells are far from equilibrium, with intracellular condensates subject to various posttranslational regulation and other adenosine triphosphate–dependent biological activity. Efforts using in vitro reconstitution, combined with traditional cell biology approaches and quantitative biophysical tools, are required to elucidate how such nonequilibrium features of living cells control intracellular phase behavior. The functional consequences of forming liquid condensates are likely multifaceted and may include facilitated reaction, sequestration of specific factors, and organization of associated intracellular structures. Liquid phase condensation is particularly interesting in the nucleus, given the growing interest in the impact of nuclear phase behavior on the flow of genetic information; nuclear condensates range from micrometer-sized bodies such as the nucleolus to submicrometer structures such as transcriptional assemblies, all of which directly interact with and regulate the genome. Deepening our understanding of these intracellular states of matter not only will shed light on the basic biology of cellular organization but also may enable therapeutic intervention in protein aggregation disease by targeting intracellular phase behavior.