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K M Miller

Publications and source records attributed to K M Miller.

At least 55 records · Page 3Linked to original sources
PubMed1998

Matrix metalloproteinase expression during experimental autoimmune neuritis.

Experimental autoimmune neuritis (EAN) is an animal model of Guillain-Barré syndrome. We have shown recently that BB-1101, a broad-spectrum matrix metalloproteinase (MMP) inhibitor, prevents development of EAN when given from the day of immunization and, more important clinically, reduces disease severity when given from symptom onset. This suggests the involvement of MMP activity in the pathogenesis of EAN. However, the exact function and expression patterns of MMPs in acute inflammation of the PNS have not been investigated. MMP-like enzymes are also involved in the processing of tumour necrosis factor-alpha (TNF-alpha), which has been implicated previously in the pathology associated with EAN. In the present study we investigated the profile of MMP and TNF-alpha expression and their localization in sciatic nerve tissue during EAN, using a semiquantitative competitive reverse transcriptase-coupled polymerase chain reaction and immunohistochemistry. In the normal rat PNS, four of the 10 MMPs studied were constitutively expressed and four MMPs were differentially regulated during EAN. Expression of TNF-alpha was elevated at peak disease severity and localized to Schwann cells, macrophages and endoneurial blood vessels. Expression levels of 92 kDa gelatinase and stromelysin-1 were significantly increased early in the development of EAN and continued to rise, peaking at day 15 coincident with maximum disease severity. Schwann cells and endothelial cells were the main cellular source of these enzymes. Prominent infiltration of inflammatory cells into the sciatic nerve was concordant with a significant increase in the expression levels of matrilysin and macrophage metalloelastase. Both matrilysin and macrophage metalloelastase were detected in invading macrophages, T lymphocytes and resident Schwann cells. The selective upregulation of specific MMPs during EAN and their varied cellular localization suggests that MMPs play a multifactorial role in the aetiology of EAN. Activity of MMPs could participate in the disruption of the blood-nerve barrier, breakdown of the myelin sheath, the release of TNF-alpha, and facilitate leukocyte invasion into the PNS. These observations highlight MMPs as potential targets for therapeutic intervention in acute peripheral neuropathies, such as Guillain-Barré syndrome.

Animals↗
PubMed1998

An alternative approach to hot spot identification using in situ gamma spectrometry measurements on a grid.

We describe the application of a computer code developed to analyze data from a series of in situ gamma spectrometry measurements on a grid. The code was designed to be used as a tool when evaluating compliance with regulations that set limits on the size and magnitude of elevated activity areas (also known as "hot spots"). It calculates location and magnitude of potential elevated activity areas consistent with the data, and for each potential elevated area it generates a corresponding distribution of radionuclides in the soil. The algorithm uses a maximum entropy deconvolution of the data, followed by further analysis. A test case using data from actual field measurements is presented.

Entropy↗
PubMed1998

The salmonid class I MHC: limited diversity in a primitive teleost.

Three MHC class I genes have been characterized in salmonids: A, B, and UA. Levels of polymorphism vary among the genes, but they all share one common feature: a lack of sequence diversity. Although individual species can carry over 30 alleles at a given locus (A), intraspecific diversity is generally less than 5% in Pacific salmon (genus Oncorhynchus), and less than 10% in Atlantic salmon (genus Salmo). These levels of diversity suggest that few ancient allelic lineages have persisted within species, and that most of the allelic radiation has occurred during or since speciation. Also apparent is the greater retention of allelic lineages in Atlantic salmon than Pacific salmon, which reflects historic differences of the two genera. Comparison of the salmonid class I sequences with those of other teleosts reveals two well supported groups: one containing the Cypriniformes and the salmonid UA, and the other containing the neoteleosts and the salmonid A and B. There is no homology between known Cypriniformes and neoteleostean sequences. If this relationship is borne out, it offers strong support for the hypothesis that the higher teleosts diverged more recently from the Salmoniformes than the Cypriniformes. The salmonid MHC may provide a snapshot of the neoteleostean MHC prior to the extensive class I duplication that has taken place in at least some of the more advanced species.

Animals↗
PubMed1997

Mouse model of GM2 activator deficiency manifests cerebellar pathology and motor impairment.

The GM2 activator deficiency (also known as the AB variant), Tay-Sachs disease, and Sandhoff disease are the major forms of the GM2 gangliosidoses, disorders caused by defective degradation of GM2 ganglioside. Tay-Sachs and Sandhoff diseases are caused by mutations in the genes (HEXA and HEXB) encoding the subunits of beta-hexosaminidase A. The GM2 activator deficiency is caused by mutations in the GM2A gene encoding the GM2 activator protein. For degradation of GM2 ganglioside by beta-hexosamindase A, the GM2 activator protein must participate by forming a soluble complex with the ganglioside. In each of the disorders, GM2 ganglioside and related lipids accumulate to pathologic levels in neuronal lysosomes, resulting in clinically similar disorders with an onset in the first year of life, progressive neurodegeneration, and death by early childhood. We previously have described mouse models of Tay-Sachs (Hexa -/-) and Sandhoff (Hexb -/-) diseases with vastly different clinical phenotypes. The Hexa -/- mice were asymptomatic whereas the Hexb -/- mice were severely affected. Through gene disruption in embryonic stem cells we now have established a mouse model of the GM2 activator deficiency that manifests an intermediate phenotype. The Gm2a -/- mice demonstrated neuronal storage but only in restricted regions of the brain (piriform, entorhinal cortex, amygdala, and hypothalamic nuclei) reminiscent of the asymptomatic Tay-Sachs model mice. However, unlike the Tay-Sachs mice, the Gm2a -/- mice displayed significant storage in the cerebellum and defects in balance and coordination. The abnormal ganglioside storage in the Gm2a -/- mice consisted of GM2 with a low amount of GA2. The results demonstrate that the activator protein is required for GM2 degradation and also may indicate a role for the GM2 activator in GA2 degradation.

Animals↗
PubMed1997

Enhanced expression of MMP-7 and MMP-9 in demyelinating multiple sclerosis lesions.

The pathology of multiple sclerosis (MS) is characterised by breakdown of the blood-brain barrier accompanied by infiltration of macrophages and T cells into the central nervous system (CNS). Myelin is degraded and engulfed by the macrophages, producing lesions of demyelination. Some or all of these mechanisms might involve proteinases, and here we have studied the cellular localisation and distribution of two matrix metalloproteinases (MMPs), MMP-7 (matrilysin) and MMP-9 (92-kDa gelatinase), in the normal human CNS and active demyelinating MS lesions. Cryostat sections of CNS samples were immunostained with antisera to MMP-7 and MMP-9. In addition, non-radioactive in situ hybridisation (ISH) was performed using a digoxygenin-labelled riboprobe to detect the expression of MMP-7. MMP-7 immunoreactivity was weakly detected in microglial-like cells in normal brain tissue sections, and was very strong in parenchymal macrophages in active demyelinating MS lesions. This pattern of expression was confirmed using ISH. MMP-7 immunoreactivity was not detected in macrophages in spleen or tonsil indicating that it is specifically induced in infiltrating macrophages in active demyelinating MS lesions. MMP-9 immunoreactivity was detected in a few small blood vessels in normal brain tissue sections, whereas many blood vessels stained positive in CNS tissue sections of active demyelinating MS lesions. The up-regulation of MMPs in MS may contribute to the pathology of the disease.

Adult↗
PubMed1997

Corneal endothelial toxicity of topical anesthesia.

PURPOSE: To determine the relative corneal endothelial toxicities of the following topical anesthetic agents: bupivacaine HCl 0.75%, unpreserved lidocaine HCl 4%, proparacaine HCl 0.5%, and tetracaine HCl 0.5%. METHODS: The experiment was conducted using pigmented rabbits. Approximately nine animals each were randomly assigned to eight groups. Right eyes received injections of 0.2 ml of one of the four anesthetic agents at one of two concentrations and left eyes received injections of 0.2 ml of balanced salt solution. Corneal thickness and clarity were measured before surgery and on postoperative days 1, 3, and 7. RESULTS: A statistically significant increase (P < 0.05) in corneal thickness and opacification over preoperative measurements was noted with injections of bupivacaine, lidocaine, and proparacaine, controlling for changes occurring in control eyes from surgery alone. Proparacaine was statistically more toxic than were the others. The toxicity of tetracaine was statistically indistinguishable from balanced salt solution, although mild toxicity was evident clinically. Injection of 1:10 dilutions of the same anesthetic agents failed to produce a statistically significant increase in corneal thickness or opacification on any postoperative examination. CONCLUSIONS: Anterior chamber injection of bupivacaine HCl 0.75%, unpreserved lidocaine HCl 4%, and proparacaine HCl 0.5% produces corneal thickening and opacification that is clinically and statistically significant. Tetracaine HCl 0.5% injection produces corneal thickening and opacification that is clinically apparent in some eyes but statistically insignificant. Ophthalmic surgeons should be aware of the potential for endothelial cell injury if anesthetic agents enter or are injected into the eye during cataract surgery in the concentrations supplied commercially.

Administration, Topical↗
PubMed1997

Matrix metalloproteinases, tumor necrosis factor and multiple sclerosis: an overview.

The matrix metalloproteinases (MMPs) are a family of at least 14 zinc-dependent enzymes which are known to degrade the protein components of extracellular matrix. In addition, MMPs and related enzymes can also process a number of cell surface cytokines, receptors, and other soluble proteins. In particular we have shown that the release of the pro-inflammatory cytokine, tumor necrosis factor-alpha, from its membrane-bound precursor is an MMP-dependent process. MMPs are expressed by the inflammatory cells which are associated with CNS lesions in animal models of multiple sclerosis (MS) and in tissue from patients with the disease. MMP expression will contribute to the tissue destruction and inflammation in MS. Drugs which inhibit MMP activity are effective in animal models of MS and may prove to be useful therapies in the clinic.

Animals↗
PubMed1997

Matrix metalloproteinase expression during experimental autoimmune encephalomyelitis and effects of a combined matrix metalloproteinase and tumour necrosis factor-alpha inhibitor.

Matrix metalloproteinases (MMPs) are a large family of Zn2+ endopeptidases that are expressed in inflammatory conditions and are capable of degrading connective tissue macromolecules. MMP-like enzymes are also involved in the processing of a variety of cell surface molecules including the pro-inflammatory cytokine TNF-alpha. MMPs and TNF-alpha have both been implicated in the pathology associated with neuro-inflammatory diseases (NIDs), particularly multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). We have shown that BB-1101, a broad spectrum hydroxamic acid-based combined inhibitor of MMP activity and TNF processing, reduces the clinical signs and weight loss in an acute EAE model in Lewis rats. However, little is known about which MMPs are involved in the neuroinflammatory process. In order to determine the optimum inhibitory profile for an MMP inhibitor in the treatment of NID, we investigated the profile of MMP expression and activity during EAE. The development of disease symptoms was associated with a 3-fold increase in MMP activity in the cerebrospinal fluid (CSF), which could be inhibited by treatment with BB-1101, and an increase in 92 kDa gelatinase activity detected by gelatin substrate zymography. Quantitative PCR analysis of normal and EAE spinal cord revealed the expression of at least seven MMPs. Of these, matrilysin showed the most significant change, being elevated over 500 fold with onset of clinical symptoms and peaking at maximum disease severity. Of the other six MMPs detected, 92 kDa gelatinase showed a modest 5 fold increase which peaked at the onset of clinical signs and then declined during the most severe phase of the disease. Matrilysin was localised by immunohistochemistry to the invading macrophages within the inflammatory lesions of the spinal cord. Matrilysin's potent broad spectrum proteolytic activity and its localisation to inflammatory lesions in the CNS suggest this enzyme could be particularly involved in the pathological processes associated with neuro-inflammatory disease.

Animals↗
PubMed1997

Molecular evolution at Mhc genes in two populations of chinook salmon Oncorhynchus tshawytscha.

The DNA sequences of four exons of the MHC (major histocompatibility complex) were examined in chinook salmon (Oncorhynchus tshawytscha) from an interior (Nechako River) and a coastal (Harrison River) population in the Fraser River drainage of British Columbia. Mhc class I A1, A2 and A3 sequences and a class II B1 sequence were obtained by PCR from each of 16-20 salmon from each population. The class I A1 and a pair of linked A2-A3 exons were derived from two different classical salmonid class I genes, Sasa-A and Onmy-UA, respectively. Allelic variation for B1, A1 and A2 was characterized by the high levels of nonsynonymous substitution indicative of the effects of natural selection on Mhc domains that contain peptide binding regions. The number of alleles detected at each of the four exons ranged from three (B1) to 22 (A1), but levels of nucleotide sequence divergence at all four exons were low relative to classical mammalian Mhc genes. The nucleotide similarity among alleles ranged between 89 and 99% over all exons, and all four domains possessed only two major sequence motifs. Allelic distributions at B1, A1 and A3 confirmed the genetic distinctiveness of the Harrison and Nechako chinook salmon populations revealed in previous studies. The two major allelic motifs of B1 and A1 segregated strongly between the populations. In spite of evidence that allelic diversity at these chinook salmon Mhc exons has been generated by selection, the level and distribution of diversity in the two salmon populations strongly reflected the demographic history of the species, which has been characterized by repeated bottlenecks and isolation-by-distance in glacial refugia.

Alleles↗
PubMed1997

Mhc diversity in Pacific salmon: population structure and trans-species allelism.

Geographic variation at an Mhc class I A1 exon was surveyed in 14 populations of coho salmon (Oncorhynchus kisutch) and 15 populations of chinook salmon (O. tshawytscha) inhabiting rivers of British Columbia, Canada. A total of 2,504 fish were sampled using denaturing gradient gel electrophoresis (DGGE), which distinguished 17 alleles in coho salmon and 20 alleles in chinook salmon. Heterozygosity at the A1 locus was moderately high for both coho (0.7) and chinook (0.6) salmon, but sequence divergence was low, with mean inter- and intraspecific nucleotide similarities of approximately 0.96. In a maximum parsimony tree, all of the observed alleles clustered into two trans-specific lineages. Within each lineage, coho and chinook alleles tended to fall into species-specific subclusters. Much of the intraspecific allelic variation within each lineage could be accounted for by nonsynonymous point mutation, indicative of balancing selection. The FST values for both coho (0.11) and chinook (0.13) salmon indicated that much of the allelic diversity was partitioned among populations. Neighbor-joining analyses of A1 allelic frequencies among coho and chinook salmon populations showed strong patterns of geographic differentiation similar to those based on neutral genetic markers such as microsatellite loci. Both natural selection and the salmonid zoogeographic history of frequent population bottlenecks have shaped the patterns of diversity observed at this and other Mhc exons in Pacific salmonids.

Alleles↗
PubMed1997

Differential matrix metalloproteinase expression in cases of multiple sclerosis and stroke.

Multiple sclerosis (MS) and stroke pathology are characterized blood-brain barrier breakdown, leucocyte emigration, and tissue destruction. Each process is thought to involve the matrix metalloproteinases (MMP), but little is known of their expression. We undertook to investigate whether MMP expression is dependent on the nature of the CNS lesion and whether expression would coincide with the histopathology. MS or cerebral-infarct tissue was examined for the presence of gelatinase-A, gelatinase-B, matrilysin and stromelysin-1. Gelatinases A and B and matrilysin expression was found to be up-regulated in microglia/macrophages within acute MS lesions. In active-chronic MS lesions, matrilysin and gelatinase-A expression was pronounced in the active borders. In chronic MS lesions, the expression of matrilysin was confined to macrophages within perivascular cuffs. The pattern of MMP expression in infarct lesions differed considerably. Gelatinase-B was strongly expressed by neutrophils in tissue from patients up to 1 week after an infarct, whereas gelatinase-A and matrilysin staining was much less marked. From 1 week to 5 years, neutrophils were absent and the large number of macrophages present were expressing matrilysin and gelatinase A. Only a low level of gelatinase-A and matrilysin expression was observed in normal brain controls. Thus, MMPs are expressed in inflammatory lesions in the CNS, but their individual expression is dependent on the nature and chronicity of the lesion. However, the general pattern of expression, in perivascular cuffs and in active lesions, supports a role for these enzymes as mediators of blood-brain barrier breakdown and tissue destruction, both in MS and in cerebral ischaemia.

Acute Disease↗
PubMed1996

Sequence analysis of a polymorphic Mhc class II gene in Pacific salmon.

Polymorphism of the nucleotide sequences encoding 149 amino acids of linked major histocompatibility complex (Mhc) class II B1 and B2 peptides, and of the intervening intron (548-773 base pairs), was examined within and among seven Pacific salmon (Oncorhynchus) species. Levels of nucleotide diversity were higher for the B1 sequence than for B2 or the intron in comparisons both within and between species. For the codons of the peptide binding region of the B1 sequence, the level of nonsynonymous nucleotide substitution (dN) exceeded the level of synonymous substitution (dS) by a factor of ten for within-species comparisons, and by a factor of four for between-species comparisons. The excess of dN indicates that balancing selection maintains diversity at this salmonid Mhc class II locus, as is common for Mhc loci in other vertebrates. Levels of nucleotide diversity for both the exon and intron sequences were greater among than within species, and there were numerous species-specific nucleotides present in both the coding and noncoding regions. Thus, neighbor-joining analysis of both the intron and exon regions provided phylogenies in which the sequences clustered strongly by species. There was little evidence of shared ancestral (trans-species) polymorphism in the exon phylogeny, and the intron phylogeny depicted standard relationships among the Pacific salmon species. The lack of shared allelic B1 lineages in these closely related species may result from severe bottlenecks that occurred during speciation or during the ice ages that glaciated the rim of the north Pacific Ocean approximately every 100000 years in the Pleistocene.

Amino Acid Sequence↗
PubMed1996

Corneal astigmatism after phacoemulsification and lens implantation through unsutured scleral and corneal tunnel incisions.

PURPOSE: We compared the changes in corneal astigmatism after phacoemulsification and intraocular lens implantation in 93 consecutive eyes with unsutured 4-mm superior scleral tunnel incisions to those through 105 consecutive eyes with unsutured 3.2- to 3.5-mm temporal corneal tunnel incisions. METHODS: Keratometry measurements were obtained preoperatively and at postoperative day 1, week 1, and week 6. Group differences in scalar and vector astigmatism were compared by using analysis of variance methods. RESULTS: Mean scalar astigmatism in the scleral incision group changed from preoperative astigmatism by 0.65 diopter at postoperative day 1, 0.37 diopter at postoperative week 1, and 0.13 diopter at postoperative week 6. Mean scalar astigmatism in the corneal incision group changed from preoperative astigmatism by 0.39 diopter at postoperative astigmatism by 0.39 diopter at postoperative day 1, 0.21 diopter at postoperative week 1, and 0.13 diopter at postoperative week 6. Mean vector astigmatism in the scleral incision group changed 1.26 diopters at 80 degrees at postoperative day 1, 1.05 diopters at 83 degrees at postoperative week 1, and 0.42 diopter at 103 degrees at postoperative week 6. Mean vector astigmatism in the corneal incision group changed 0.77 diopter at 90 degrees at postoperative week 1, and 0.61 diopter at 89 degrees at postoperative week 6. The differences were statistically significant (P = .003) only by vector analysis at the postoperative day 1 examination. CONCLUSIONS: We found significantly greater with-the-rule change in astigmatism in the scleral incision group than in the corneal incision group on the first postoperative day. The effect disappeared by the sixth postoperative week.

Astigmatism↗
PubMed1996

Quantitation of matrix metalloproteinases in cultured rat astrocytes using the polymerase chain reaction with a multi-competitor cDNA standard.

Matrix metalloproteinases (MMPs) are a family of Zn2+ endopeptidases that are expressed in many inflammatory conditions and that contribute to connective tissue breakdown and the release of the pro-inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha). There is emerging evidence that MMPs have a role in inflammatory disorders of the central nervous system (CNS) such as multiple sclerosis. However, little is known about the expression of MMPs by inflamed tissue within the CNS or by the glia, neurones, and leucocytes which participate in the inflammatory response. To address this issue we have developed a polymerase chain reaction (PCR)-based method for the quantitation of rat MMP mRNA levels, which we have applied to astrocyte cultures with and without inflammatory stimulation. The technique relies on a competition reaction in which a synthetic standard cDNA is co-amplified with the target cDNA in the same PCR reaction. Standard multi-competitor cDNAs, containing priming sites for nine MMPs, and two housekeeping genes were constructed. We have shown that MMP activity is increased over three-fold in neonatal rat astrocyte cultures following stimulation with lipopolysaccharide (LPS). At the mRNA level, MT-MMP-1, 72 kDa gelatinase, and stromelysin-3 were constitutively expressed and unaffected by LPS treatment, whereas 92 kDa gelatinase, and stromelysin-1 were strongly induced (1,000-fold). Stromelysin-2, rat collagenase, and macrophage metalloelastase were modestly upregulated by LPS treatment. Matrilysin was not expressed. This technique is suitable for quantifying MMP expression in the cells which contribute to inflammation in the CNS and could also be applied directly to tissue samples from animal models of disease.

Animals↗
PubMed1995

Recovery of thresholds and temporal integration in adult chickens after high-level 525-Hz pure-tone exposure.

Three adult, female chickens, previously trained to detect pure tones using a positive reinforcement paradigm, were exposed to pure tones at 525 Hz at 120-dB sound-pressure level for 48 h. Immediately after exposure, pure-tone thresholds were elevated between 10 and 56 dB compared to pre-exposure values. The configuration of the initial hearing loss was essentially flat between 500 and 2000 Hz, with slightly less loss at lower and higher frequencies. Over the course of 100 to 600 h, depending on subject and test frequency, thresholds returned to preexposure levels. The slopes of the threshold-duration functions measured shortly after exposure were shallower than normal, but returned to the normal slope of approximately 3 dB per doubling of duration as hearing loss resolved to less than 15 to 20 dB. The cochleas from additional chickens examined by scanning electron microscopy (SEM) and fluorescence microscopy between 0 and 1512 h post-exposure showed extensive damage to the tectorial membrane over the middle two-thirds of the cochlea, with mild to moderate hair cell loss in the region of the cochlea associated with the exposure frequency.

Animals↗