Biomedical subjects

T J Sims

Publications and source records attributed to T J Sims.

At least 37 records · Page 2Linked to original sources

PubMed1998

Schwann cell invasion of ventral spinal cord: the effect of irradiation on astrocyte barriers.

This study examines a radiation-induced invasion and spread of Schwann cells into ventral gray regions of the lumbar spinal cord. The prevalence of these cells within the gray matter and the time course of their appearance in the ventral spinal cord is quite different from the pattern of Schwann cell development in dorsal spinal cord reported previously. The focus is on 2 possible pathways, each involving astrocytic barriers, by which Schwann cells access the ventral gray matter. The first of these is the glia limitans covering the ventral surface of the spinal cord and the possibility that its integrity has been disrupted by the exposure to x-rays. Comparisons of the glia limitans, including its thickness, between irradiated and nonirradiated rats revealed that exposure to radiation did not result in any morphologically discernible alterations. The second barrier examined was the astrocytic covering of blood vessels. In irradiated animals the astrocyte processes that normally surround blood vessels were missing in some instances, and Schwann cells were observed at these sites. The difference between the dorsal and ventral occurrence of Schwann cells is that, whereas Schwann cells primarily follow axons, specifically dorsal root axons, to access the dorsal spinal cord, it appears that the presence of Schwann cells in the ventral portion of the spinal cord where their location is primarily in the gray matter is associated with the vasculature.

Aging↗

PubMed1998

Antigenic variation in Bacteroides forsythus detected by a checkerboard enzyme-linked immunosorbent assay.

Evidence indicating that multiple serotypes of Bacteroides forsythus participate in rapidly progressing periodontal infections has not been reported previously. Our aim was to develop an assay for detecting subsets of B. forsythus clinical isolates which differ in serogroup membership and subsets of patients with immunoglobulin G (IgG) responses which differ in serogroup recognition. A checkerboard enzyme-linked immunosorbent assay (ELISA) was used to assess variation in the IgG binding profiles of 22 clinical isolates in sera from 28 patients with early-onset rapidly progressive periodontitis. To accommodate the maximum number of isolates and sera in a given assay run, a multiplate assay grid with standard 96-well microtest plates was established. Single dilutions of individual sera were placed in rows crossing columns of isolate-coated wells, and antigen-specific IgG immobilized in the wells was measured as ELISA absorbance. Pooled sera and isolates were assayed in parallel to serve as negative controls for variation in IgG binding profiles. Correlation and hierarchical cluster analysis of the absorbance data matrix showed that the isolates could be sorted into at least four clusters based on variations in their IgG binding profiles across different sera. Furthermore, at least two patient clusters were defined by variations in their serum IgG antigen recognition profiles across different isolates. We conclude that multiple serogroups of B. forsythus exist and that different serogroups are dominant in the antibody response of different patients. The method applied here could be used to serologically classify clinical isolates of other species which evoke a serum antibody response in patients.

Adult↗

PubMed1997

Schwann cells can misdirect regrowing neuronal processes.

Studies of potentials for dorsal spinal nerve root axons to regrow into the spinal cord involved placement of the tracer HRP/WGA-HRP on the cut end of the nerve root. Following this procedure, labeled neurons were found within the spinal dorsal gray matter. Analyses revealed that spinal neurons influenced by the presence of radiation-induced intraspinal Schwann cells extend misdirected processes into the dorsal root.

Animals↗

PubMed1997

Astrocytes in the aged rat spinal cord fail to increase GFAP mRNA following sciatic nerve axotomy.

Aging in the brain is associated with specific changes in the astrocyte population. The present study establishes that similar changes occur in the aging spinal cord. The levels of glial fibrillary acidic protein (GFAP) mRNA were significantly increased 0.4-fold in aged 8- to 17-month-old rats compared to young 2-month-old rats. The ability of astrocytes in the aging spinal cord to respond to a non-invasive CNS injury was compared to young rats 4 days following sciatic nerve axotomy. The level of GFAP mRNA was significantly increased 0.5-fold in the young rats in response to axotomy. In contrast, the level of GFAP mRNA in aged rats did not increase following injury above that present in non-axotomized rats of the same age.

Aging↗

PubMed1997

Microglial development is altered in immature spinal cord by exposure to radiation.

Previous studies in this laboratory have documented that the microglial environment of the immature spinal cord is altered by exposure to ionizing radiation. As a result, the lumbosacral spinal cord is markedly depleted of both oligodendrocytes and astrocytes, while leaving axons and the overall cytoarchitecture intact. The status of the microglia in the irradiated region is unknown and is of interest given the interactions between microglia and astrocytes recently elucidated by others. This study uses both in vivo and in vitro approaches to examine the microglial population in normal and irradiated immature spinal cord. The lectin, Griffonia (Bandeiraea) simplicifolia, was selected since it marks microglia both in paraffin embedded sections and in cell cultures. Light microscopic examinations of spinal cord sections revealed a reduced microglial population in the irradiated region when compared to littermate controls, and a change in morphology of the remaining microglia to that described by others as "activated". Cultures prepared from lumbosacral spinal cords harvested from 3-day-old rats within 2-4 hr following irradiation were compared with cultures derived from their non-irradiated littermates after 8 days in vitro. Cultures from the irradiated spinal cords revealed trends similar to those observed in vivo, i.e. a reduced microglial population and altered morphology. Although all glial cell types were reduced in cultures from irradiated spinal cords, the few microglia present were usually positioned atop astrocytes. The consistency of reduction in all glial populations in this model shows the microglia to be a novel microenvironment for further studies of roles of microglial within the spinal cord.

Animals↗

PubMed1997

Biomechanical and biochemical study of a standardized wound healing model.

Standardized protocols were developed for use in a detailed investigation into the biomechanical and biochemical properties of a dermal wound healing model in the rat. The use of a rapid freezing method at -80 degrees C minimized the detrimental effects of freezing on the biomechanical properties of the tissue and also allowed for convenient inter-laboratory collaboration to be performed. The methodology described allowed for the simultaneous and reproducible measurement of tensile strength, collagen cross-linking and proteolytic enzyme activity. Increases in the tensile properties of the tissue with time were consistent with an active process of remodelling process as indicated by changes in the cross-link and enzyme profiles. Initially the granulation tissue was comparatively rich in the keto-imine cross-link hydroxylysino-keto-norleucine, which was later replaced by the aldimine cross-link dehydro-hydroxy-lysinonorleucine. The mature cross-link histidino-hydroxy-lysinonorleucine was not observed within the granulation tissue at any stage and was also absent in aged control skin. A peak of matrix metalloproteinase-9 activity was observed at early timepoints (48 hr) and then decreased rapidly to normal levels and is consistent with an acute inflammatory response. In contrast matrix metalloproteinase-2 activity peaked later (3 days) and then decreased gradually, consistent with its role as one of the predominant enzymes involved in the remodelling process. The results described validate the animal model used and emphasize its potential for use in combined biomechanical and biochemical studies of acute wound healing.

Animals↗

PubMed1997

Glial-glial and glial-neuronal interfaces in radiation-induced, glia-depleted spinal cord.

This review summarises some of the major findings derived from studies using the model of a glia-depleted environment developed and characterised in this laboratory. Glial depletion is achieved by exposure of the immature rodent spinal cord to x-radiation which markedly reduces both astrocyte and oligodendrocyte populations and severely impairs myelination. This glia-depleted, hypomyelinated state presents a unique opportunity to examine aspects of spinal cord maturation in the absence of a normal glial population. An associated sequela within 2-3 wk following irradiation is the appearance of Schwann cells in the dorsal portion of the spinal cord. Characteristics of these intraspinal Schwann cells, their patterns of myelination or ensheathment, and their interrelations with the few remaining central glia have been examined. A later sequela is the development of Schwann cells in the ventral aspect of the spinal cord where they occur predominantly in the grey matter. Characteristics of these ventrally situated intraspinal Schwann cells are compared with those of Schwann cells located dorsally. Recently, injury responses have been defined in the glia-depleted spinal cord subsequent to the lesioning of dorsal spinal nerve roots. In otherwise normal animals, dorsal nerve root injury induces an astrocytic reaction within the spinal segments with which the root(s) is/are associated. Lesioning of the 4th lumbar dorsal root on the right side in irradiated or nonirradiated animals results in markedly different glial responses with little astrocytic scarring in the irradiated animals. Tracing studies reveal that these lesioned dorsal root axons regrow rather robustly into the spinal cord in irradiated but not in nonirradiated animals. To examine role(s) of glial cells in preventing this axonal regrowth, glial cells are now being added back to this glia-depleted environment through transplantation of cultured glia into the irradiated area. Transplanted astrocytes establish barrier-like arrangements within the irradiated cords and prevent axonal regrowth into the cord. Studies using other types of glial cultures (oligodendrocyte or mixed) are ongoing.

Animals↗

PubMed1997

Recognition of antigenic epitopes in lipopolysaccharide and protein from Actinobacillus actinomycetemcomitans by serum antibodies in untreated rapidly progressive periodontitis patients.

Actinobacillus actinomycetemcomitans has been associated with early-onset periodontitis, including the localized juvenile and rapidly progressive forms. The immunodominant antigens of A. actinomycetemcomitans recognized by rapidly progressive periodontitis patients remain unidentified. Sera from 22 patients with rapidly progressive periodontitis and 20 periodontally normal subjects were tested by enzyme-linked immunosorbent assay (ELISA) for immunoglobulin G antibodies to whole-cell sonicate, protein, purified lipopolysaccharide and lipopolysaccharide fractions of A. actinomycetemcomitans. The median titers of rapidly progressive periodontitis patients and control subjects to whole-cell sonicate were 25.0 and 14.5 ELISA units, respectively (not significantly different). Binding of antibody from patient sera occurred to both the lipopolysaccharide and the protein fractions, with greater binding to lipopolysaccharide than to protein. We show for the first time that patient sera contain antibodies that bind specifically to antigenic epitopes in lipid A and in the core carbohydrate of lipopolysaccharide that were previously considered to be inaccessible and unavailable, as well as to epitopes in the O side chains. Sera manifesting antibody titers 2-fold or greater than the median titer for control sera were judged to be seropositive. More patients were seropositive for lipid A than for any of the other antigen preparations studied, and the median titer for patient sera to lipid A but to none of the other purified lipopolysaccharide fractions was significantly elevated relative to control values. Of 22 patients, 10 were seropositive to whole-cell sonicate, 7 to protein, 8 to lipopolysaccharide, 7 to the high-molecular-weight lipopolysaccharide-polysaccharide fraction rich in O side chains, and 16 to lipid A. The core carbohydrate did not adhere to the test plate surface, and this precluded ELISA measurements. However, when the core carbohydrate was used in the ELISA inhibition assay, it reduced antibody binding to lipopolysaccharide-coated plates by up to 45%, thereby demonstrating antibody binding to core carbohydrate. The core carbohydrate fraction from the Re mutant of Salmonella minnesota known to contain no O-side chains also inhibited binding of specific antibody to plates coated with A actinomycetemcomitans lipopolysaccharide. Overall, there was extreme variation in responses among patients to the various antigen preparations, with no single pattern dominating. Lipopolysaccharide and its components appear to be the immunodominant epitopes, since most rapidly progressive periodontitis patients are seropositive for lipopolysaccharide and/or its components and they have titers relative to those for proteins.

Adult↗

PubMed1997

Analysis of collagen status in premenopausal nulliparous women with genuine stress incontinence.

OBJECTIVE: To determine if differences exist in the collagen status of premenopausal nulliparous women with genuine stress incontinence compared with continent controls. DESIGN: Thirty-six premenopausal nulliparous women with urodynamically-proven genuine stress incontinence were compared with 25 controls. All the women studied had a periurethral vaginal biopsy taken of approximately 30-50 mg in wet weight. This biopsy was then analysed to determine the collagen content, the type I:III collagen ratio and the collagen cross-link content. SETTING: A tertiary referral urodynamic unit. RESULTS: The nulliparous women with genuine stress incontinence had significantly less collagen in their tissues (P < 0.0001) compared with the continent controls. In addition, there was a decreased ratio of type I to type III collagen (P = 0.0008), and the cross-link content was also significantly reduced in the women with genuine stress incontinence (P < 0.0001). CONCLUSION: Genuine stress incontinence is present in a significant number of women before childbirth. The aetiology of their incontinence appears to be due to a defect in their connective tissue, with both a quantitative and qualitative reduction in their collagen.

Adolescent↗

PubMed1996

The role of glycation cross-links in diabetic vascular stiffening.

Previous studies have shown that biomechanical analysis of aorta from diabetic subjects reveals a marked increase in stiffness compared to aorta from age-matched control subjects. In the present paper we have proposed that this increased stiffness can be attributed to glycation-induced inter-molecular cross-links based on a direct analysis of the two known glycation cross-links, the fluorescent pentosidine and the non-fluorescent NFC-1. There was a significant difference in the increase in concentration of both cross-links with increasing age for both the intima (p < 0.0025) and the media (p < 0.0005) from the diabetic compared to the control subjects, but no correlation with the mature enzymic cross-link hy droxylysyl-pyridinoline. Finally, we have obtained a significant correlation of stiffness with both glycation cross-links (NFC-1, r = 0.86; p < 0.005 and pentosidine r = 0.75, p < 0.05), but the concentration of NFC-1 is about 50 times greater than that of pentosidine, indicating that it is the major glycation cross-link responsible for the stiffening of the aorta.

Adult↗

PubMed1996

Shared antigens of Porphyromonas gingivalis and Bacteroides forsythus.

Periodontitis in humans is caused by a group of predominantly gram-negative, anaerobic bacteria among which Porphyromonas gingivalis and Bacteroides forsythus are prominent. A similar group is present and presumably plays a similar role in experimental periodontitis in the primate Macaca fascicularis. Nevertheless, immunization using a vaccine containing only killed P. gingivalis suppresses the progress of experimental periodontitis in M. fascicularis. We investigated the hypothesis that gram-negative periodontopathic bacterial may share antigens, and immunization with one species may induce antibodies reactive with other gram-negative species. Using enzyme-linked immunosorbent assay (ELISA), Western and dot immunoblots with nonabsorbed and absorbed and immune and preimmune sera we show that monkeys immunized with P. gingivalis produce antibodies reactive not only with antigens of P. gingivalis but also with those of B. forsythus. Similarly, rabbits immunized with P. gingivalis or with B. forsythus produce antibodies that react with antigens of both bacteria. Cross-reactive antibodies bind to epitopes in lipid A and possibly in core carbohydrate of lipopolysaccharide. Using complexes of lipopolysaccharide with polymyxin B, bovine serum albumin and apolipoprotein A1 specificity of binding was documented. Using sera from monkeys immunized with P. gingivalis, cross-reactivity with Actinobacillus actinomycetemcomitans could not be demonstrated by ELI-SA, although binding to lipopolysaccharide but not to lipid A was demonstrated by Western and dot immunoblots. Antibodies to shared lipopolysaccharide epitopes of periodontopathic bacteria may account, at least in part, for the immune protection observed in immunized monkeys, and shared epitopes may have potential as a vaccine for periodontitis in humans.

Animals↗

PubMed1996

Schwann cell-neuron relationships in spinal cord gray matter.

Schwann cells develop within the ventral gray matter following exposure of lumbosacral spinal cords to x-rays in early postnatal rats. These ventral gray matter Schwann cell aggregates occurred in about 40% of the animals 8 or more weeks following irradiation. Light microscopically these cells appeared to be apposed to somata of large motor neurons, raising a question regarding the fate of axo-somatic synapses. This study focused on neuron-Schwann cell relationships and demonstrated ultrastructurally that the intraspinal Schwann cells established a variety of relationships with the neuronal somata and primary dendrites. These relationships ranged from direct contact without an intervening basal lamina to the presence of synaptic contacts intervening between neuron and Schwann cell basal lamina. Occasionally, the Schwann cells occupied an intermediate position between neurons and blood vessels, suggesting functions similar to those carried out by astrocytes. In these instances, as in all cases of Schwann cell-blood vessel contact, the vessels lacked their normal investiture by astrocytes. Light microscopic evaluation of synaptophysin-immunostained sections revealed decreased immunoreactivity in neuropil occupied by the Schwann cells but confirmed the presence of synapses on neuronal somata. Possible mechanisms underlying Schwann cell induction in the ventral gray matter are discussed. An understanding of the interactions between Schwann cells and the cellular constituents of the gray matter is important in light of attempts to enhance repair in the central nervous system by transplanting Schwann cells into that environment.

Animals↗

PubMed1995

Non-enzymic glycation of fibrous collagen: reaction products of glucose and ribose.

Non-enzymic glycation of collagen involves a series of complex reactions ultimately leading to the formation of intermolecular cross-links resulting in changes in its physical properties. During analysis for the fluorescent cross-link pentosidine we identified the presence of an additional component (Cmpd K) in both glucose and ribose incubations. Cmpd K was formed more quickly than pentosidine in glucose incubations and more slowly than pentosidine in ribose incubations. Cmpd K represented 45% of the total fluorescence compared with 15% for pentosidine in glucose incubations and 25% of the total fluorescence compared with 30% for pentosidine in the ribose incubations. Cmpd K is not an artefact of in vitro incubations, as it was shown to be present in dermal tissue from diabetic patients. Subsequent high-resolution h.p.l.c. analysis of glucose-incubated collagen revealed Cmpd K comprise two components (K1 and K2). Further, a similar analysis of Cmpd K from the ribose incubations revealed two different components (K3 and K4). These differences indicate alternative mechanisms for the reactions of glucose and ribose with collagen. The amounts of these fluorescent components and the pentosidine cross-link determined for both glucose and ribose glycation were found to be far too low (about one pentosidine molecules per 200 collagen molecules after 6 months incubation with glucose) to account for the extensive cross-linking responsible for the changes in physical properties, suggesting that a further additional series of cross-links are formed. We have analysed the non-fluorescent high-molecular-mass components and identified a new component that increases with time of in vitro incubation and is present in the skin of diabetic patients. This component is present in sufficient quantities (estimated at one cross-link per two collagen molecules) to account for the changes in physical properties occurring in vitro.

Adolescent↗

PubMed1995

Abnormal collagen cross-linking in the cartilage of a diastrophic dysplasia patient.

The abnormal organization of the cartilage collagen in diastrophic dysplasia is not generally reflected in the levels of the major stabilizing cross-link, hydroxylysyl-pyridinoline. However, in one case there was a marked decrease in the pyridinoline concomitant with the appearance of two unknown components in the cross-link region of the chromatogram. A decrease in cross-linking of this magnitude could lead to mechanically weakened cartilage. Insufficient material was available to characterize these unknown components. The disorganization of cartilage in some cases of diastrophic dysplasia could therefore be due to post-translational modifications, including defective cross-linking.

Amino Acids↗

PubMed1994

Regrowth of dorsal root axons into a radiation-induced glial-deficient environment in the spinal cord.

Exposure of the lumbosacral spinal cord of early postnatal rats to X-rays reduces the glial populations within the irradiated region. The present study examines the ability of axons of a dorsal root subjected to a crush-freeze lesion to grow back into this glial-deficient spinal cord environment, in contrast to the non-irradiated rat. Ultrastructural examination of the dorsal root entry zone (DREZ) 60 days after root injury revealed a well-formed astrocytic scar in this zone and adjacent regions of spinal cord in non-irradiated rats. In contrast, scar formation did not occur in irradiated root-lesioned animals in which the astrocytic response was quite limited. Axons were present in the DREZ and underlying spinal cord in irradiated root-lesioned rats at this time but were absent from these regions in the non-irradiated lesioned controls. These ultrastructural findings are highly suggestive that axons are capable of regrowth into the irradiated spinal cord. Axonal regrowth was assessed further by tracing techniques after application of a combination of peroxidase-labeled wheat germ agglutinin and horseradish peroxidase to the cut end of the root distal to the previously injured site. Labeled axons were readily identified within the spinal gray matter in irradiated lesioned but not in the non-irradiated lesioned rats. These data, together with the ultrastructural observations, are supportive of regrowth of the dorsal root axons into the spinal cord. The radiation-induced changes in the glial populations are discussed with regard to conversion of a normally non-permissive environment into one conducive for axonal regrowth.

Animals↗

PubMed1994

Glial development in primary cultures established from normal and X-irradiated neonatal spinal cord.

The glial population of the lumbosacral spinal cord of the rat can be markedly depleted by exposure to ionizing radiation during the first postnatal week. Identification of specific cell populations which survive the exposure to radiation is difficult in situ; therefore, the present investigation used in vitro approaches to address issues related to specific phenotypes and maturational states of glia in cultures derived from non-irradiated (control) and irradiated (experimental) lumbosacral spinal cords of 3-day-old rats. Cultures were established from the spinal cords 2 to 4 hours following irradiation and were compared to cultures from non-irradiated, littermate controls. By 4 days in vitro (DIV) the numbers of cells in experimental cultures were profoundly reduced when compared to controls, and this reduction persisted through the termination of the study (8 DIV). In addition to reduction in numbers, astrocyte phenotypes were altered in experimental cultures, with greater proportions of the astrocyte population being constituted by the flat angular, large angular, and pancake types and a lesser proportion by stellate cells. The non-astrocytic cell types were dramatically reduced as evidenced by the paucity of oligodendrocytes immunoreactive for galactocerebroside and of small, non-process bearing cells binding the lectin, Griffonia (Bandeiraea) simplicifolia, a marker for microglia. Experimental cultures contained an increased incidence of binucleate astrocytes, an increase not restricted to a particular astrocyte phenotype. This study established the feasibility of utilizing this combined in vivo/in vitro approach in assessment of glial populations in immature spinal cords, and further investigations are in progress using this model.

Animals↗

PubMed1994

Regeneration of dorsal root axons into experimentally altered glial environments in the rat spinal cord.

Exposure of the lumbar spinal cord of rats to X-rays 3 days after birth results in changes in the composition of central glia. Shortly after irradiation, there is both retardation of central myelin formation and a loss of integrity of the astrocyte-derived glia limitans on the dorsal surface of the cord. Subsequently, Schwann cells invade, undergo division and myelinate axons in the dorsal funiculi in the irradiated region of the cord, creating there an environment similar to that of peripheral nerve. The present study was undertaken to compare the ability of lesioned dorsal root axons to grow back into the altered glial environments that exist within the spinal cord after irradiation. This regrowth was assessed by injecting Fluoro-Gold into the spinal cord and subsequently examining neurons in the dorsal root ganglia (DRG) for the presence of this label. Numbers of retrogradely labeled neurons were counted in the DRG in both injured and contralateral non-injured sides. Non-irradiated control rats had almost no labeled DRG neurons on the injured side, whereas Fluoro-Gold labeled neurons were observed in substantial numbers in the DRG on the injured side of irradiated rats. There was a definite trend in the data, indicating that the longer the interval between irradiation and root injury, the greater the number of labeled neurons. Since the Fluoro-Gold labeling technique does not allow for visualization of the labeled axons within the spinal cord, a few animals were used to assess anterograde labeling with wheat germ agglutinin-conjugated horseradish peroxidase (WGA-HRP/HRP) from the dorsal root into the spinal cord.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

The continuous elongation technique for severe Dupuytren's disease. A biochemical mechanism.

Continuous extension of Dupuytren's contracture prior to fasciectomy results in a softening of the tissue, allowing straightening of the fingers. The observed change in cross-link profile indicates an increase in newly synthesised collagen due to increased turnover. This was confirmed by demonstration of the increases in levels of the degradative enzymes, the neutral metalloproteinases, collagenase and gelatinase and the acidic cathepsins B and L. Both types of enzyme effectively depolymerize the collagen fibres, albeit by different mechanisms, leading initially to loss of tensile strength and ultimately to solubilization. We suggest that the increase in enzyme activity is generated by tension on the fibroblasts of this metabolically active tissue produced during the continuous extension of the retracted fingers. The weakening of the fibres by degradation and the increase in newly synthesized collagen provide an explanation for the extension of the tissue without trauma.

Amino Acids↗