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Biomedical subjects

D J Miller

Publications and source records attributed to D J Miller.

At least 127 records · Page 7Linked to original sources
PubMed1995

Spontaneous CNS remyelination in beta 2 microglobulin-deficient mice following virus-induced demyelination.

Animal models with selective genetic immunodeficiencies are useful tools to identify pathogenic mechanisms of disease. Resistant (C57BL/6F 129/J) (H-2b) mice are rendered susceptible to Theiler's murine encephalomyelitis virus-induced demyelination by genetic disruption of the beta 2 microglobulin gene [beta 2 m(-l-)]. The absence of beta 2 m prevents the expression of major histocompatibility complex class I molecules and normal levels of functional CD8+ T cells. We tested whether genetic depletion of beta 2 m would permit CNS remyelination after chronic demyelination induced by the Daniel's strain of Theiler's virus. In contrast to the minimal spontaneous remyelination observed in SJL/J mice after infection with the Daniel's strain of Theiler's virus, chronically infected beta 2 m(-I-) mice showed extensive and progressive spontaneous CNS remyelination at 6, 12, and 18 months after infection. Spontaneous remyelination by both oligodendrocytes and Schwann cells occurred despite the presence of persistent virus antigen and RNA, but was associated with diminished virus-specific humoral and delayed-type hypersensitivity responses. These experiments support the hypothesis that the immune response inhibits myelin regeneration after virus-induced CNS demyelination.

Animals↗
PubMed1994

Nucleotide sequence of a cDNA clone encoding the precursor of the peridinin-chlorophyll a-binding protein from the dinoflagellate Symbiodinium sp.

mRNA from the dinoflagellate Symbiodinium sp. isolated from the staghorn coral Acropora formosa was used for the construction of cDNA libraries. A cDNA clone was identified which encoded the precursor of peridinin-chlorophyll a-binding protein (PCP), including a 52 amino acid transit peptide and the 313 amino acid mature protein. The deduced amino acid sequence clearly contains an internal duplication, implying that amongst dinoflagellates the M(r) 35,000 form of PCP has arisen by duplication and fusion of genes encoding the M(r) 15,000 form. This is the first reported sequence of a dinoflagellate light-harvesting protein. The anatomy of the mature protein and the transit peptide are discussed.

Amino Acid Sequence↗
PubMed1994

Effects of the reactive oxygen species hypochlorous acid and hydrogen peroxide on force production and calcium sensitivity of rat cardiac myofilaments.

Neutrophil activation occurs after myocardial infarction/ischaemia. They produce the reactive oxygen species (ROS) hypochlorous acid (HOCl) and hydrogen peroxide (H2O2) which could contribute to contractile dysfunction upon reperfusion. The myofilaments of 'skinned' rat cardiac muscle were exposed to ROS in various states of activation. Isometric force was measured at controlled degrees of activation. A single application of 10 microM HOCl for 1 min increased log [Ca2+] for half-maximal activation (log K1/2) from 5.23 to 5.32, initial maximum Ca-activated force (FCa, max) was reduced by 18.8 +/- 5.8% and resting tension increased to 15.4 +/- 8.0% of FCa, max. At 50 microM, a 1-min exposure to HOCl produced a greater increase in Ca-sensitivity (log K1/2 increased from 5.23 to 5.47), a greater reduction in FCa, max (falling by 42.3 +/- 23.2%) and a greater increase in resting tension (to 25 +/- 10.7% of FCa, max). The nature of the resting tension rise was examined by reducing pH before and during exposure to HOCl; the results are consistent with 'rigor-like' cross-bridges being involved. H2O2 was without effect on the myofilaments at physiologically relevant (< 10 microM) concentrations. These results suggest that ROS associated with inflammation could contribute to post-ischaemic myocardial dysfunction.

Actin Cytoskeleton↗
PubMed1994

Nucleotide sequence of an Onchocerca volvulus cDNA clone encoding an antigen homologous with the intermediate filament protein family.

A series of clones were isolated from an O. volvulus lambda gt11 cDNA library on the basis of strong recognition by sera from both Onchocerca volvulus or Wuchereria bancrofti patients. Several of these clones encoded a protein which clearly belonged to the intermediate filament (IF) class, and had most similarity with A1IF-A from Ascaris lumbricoides and a number of IF proteins from molluscs. Western blotting experiments implied that the first coiled domain appears to be markedly less antigenic in vivo than the remainder of the O. volvulus protein.

Amino Acid Sequence↗
PubMed1994

Identification and characterisation of a novel repetitive antigen from Onchocerca spp.

A novel repetitive antigen from the cattle parasite Onchocerca gibsoni was shown to be recognised by sera from humans infected with Onchocerca volvulus, Wuchereria bancroftii or Brugia malayi. The O. gibsoni protein was produced in a recombinant form, and antibodies raised to this protein used to screen cDNA libraries for O. volvulus. A series of clones were isolated which encoded repetitive regions very similar to those in O. gibsoni, but interspersed between these were longer repeating units which we have not so far found in O. gibsoni. The repetitive antigen was shown to be of high molecular weight and present only in the insoluble (membrane) fraction of O. gibsoni microfilariae. Immunofluorescence techniques demonstrated that the antigen was associated both with muscle and with specific membrane layers, including a peripheral layer which corresponds to either the outer hypodermis or an inner region of the cuticle in adult female O. gibsoni. In many respects, the proteins encoded by the O. gibsoni and O. volvulus cDNA clones resembled repetitive antigens from several distantly related eukaryotic parasites, and a possible common role in immune evasion is discussed.

Amino Acid Sequence↗
PubMed1994

Immune promotion of central nervous system remyelination.

Remyelination by oligodendrocytes is the normal response to injury of the central nervous system following experimental demyelination by toxins and viruses in rodents. By contrast, in immune-mediated myelin disorders such as human MS, Theiler's virus-induced demyelination or EAE, remyelination is incomplete. We have considered two hypotheses to explain why myelin repair is incomplete in these disorders. Hypothesis I is that myelin repair is the normal consequence of primary myelin injury but there are immune factors which prevent its full expression. To test hypothesis I, we depleted T cells in Theiler's virus infected mice with cyclophosphamide or with monoclonal antibodies to CD4, CD8, or immune response gene products (Ia). Enhanced remyelination and proliferation of glial cells was observed in mice depleted of CD4+ or CD8+ T cells. Hypothesis II is that there are immune factors within some demyelinated lesions which, when present, promote new myelin synthesis. We envision these factors to be present in those lesions showing remyelination but absent in those lesions that remain demyelinated. To test hypothesis II, we generated polyclonal immunoglobulins directed against normal CNS antigens. Transfer of immunoglobulins from mice immunized repeatedly with spinal cord homogenate resulted in 4-5-fold enhancement of remyelination in Theiler's virus infected mice. We have also generated a series of monoclonal antibodies directed against normal autoantigens which also promote CNS remyelination. These experiments support the concept that full CNS remyelination is possible in human demyelinating diseases such as MS. Manipulation of the immune response either by inhibiting the function of T cells or by treatment with immunoglobulins (possibly normal autoantibodies) appears to promote remyelination. These experiments provide hope for patients with fixed neurological deficits for whom there are currently no available therapies.

Adjuvants, Immunologic↗
PubMed1994

Overexpressing sperm surface beta 1,4-galactosyltransferase in transgenic mice affects multiple aspects of sperm-egg interactions.

Sperm surface beta 1,4-galactosyltransferase (GalTase) mediates fertilization in mice by binding to specific O-linked oligosaccharide ligands on the egg coat glycoprotein ZP3. Before binding the egg, sperm GalTase is masked by epididymally derived glycosides that are shed from the sperm surface during capacitation. After binding the egg, sperm-bound oligosaccharides on ZP3 induce the acrosome reaction by receptor aggregation, presumably involving GalTase. In this study, we asked how increasing the levels of sperm surface GalTase would affect sperm-egg interactions using transgenic mice that overexpress GalTase under the control of a heterologous promoter. GalTase expression was elevated in many tissues in adult transgenic animals, including testis. Sperm from transgenic males had approximately six times the wild-type level of surface GalTase protein, which was localized appropriately on the sperm head as revealed by indirect immunofluorescence. As expected, sperm from transgenic mice bound more radiolabeled ZP3 than did wild-type sperm. However, sperm from transgenic animals were relatively unable to bind eggs, as compared to sperm from wild-type animals. The mechanistic basis for the reduced egg-binding ability of transgenic sperm was attributed to alterations in two GalTase-dependent events. First, transgenic sperm that overexpress surface GalTase bound more epididymal glycoside substrates than did sperm from wild-type mice, thus masking GalTase and preventing it from interacting with its zona pellucida ligand. Second, those sperm from transgenic mice that were able to bind the zona pellucida were hypersensitive to ZP3, such that they underwent precocious acrosome reactions and bound to eggs more tenuously than did wild-type sperm. These results demonstrate that sperm-egg binding requires an optimal, rather than maximal, level of surface GalTase expression, since increasing this level decreases sperm reproductive efficiency both before and after egg binding. Although sperm GalTase is required for fertilization by serving as a receptor for the egg zona pellucida, excess surface GalTase is counterproductive to successful sperm-egg binding.

Acrosome↗
PubMed1994

Effects of oxidants on the sarcoplasmic reticulum of saponin treated rat ventricular trabeculae.

OBJECTIVE: The aim was to determine the effects of the superoxide anion, hydrogen peroxide, and hypochlorous acid on in situ cardiac sarcoplasmic reticulum. METHODS: Simultaneous measurement of caffeine induced calcium release from the sarcoplasmic reticulum and subsequent myofilament tension generation was made on saponin permeabilised rat ventricular trabeculae before, during, and after exposure to various reactive oxygen species. The superoxide anion (O2.-) was generated using the xanthine-xanthine oxidase system, hypochlorous acid (HOCl) was prepared from NaOCl, and hydrogen peroxide (H2O2) was added from a 30% stock solution. RESULTS: At [O2.-] sufficient to abolish tension generation by the myofilaments completely, the associated caffeine induced calcium release was unaffected. Both H2O2 and HOCl diminished caffeine induced calcium release but had differential effects on the associated tension response. Exposure to HOCl favoured the occurrence of spontaneous calcium releases from the sarcoplasmic reticulum. CONCLUSIONS: The reactive oxygen species H2O2 and HOCl reduced the amount of calcium release from the sarcoplasmic reticulum while O2.- was without effect. In some preparations it was observed that HOCl favoured spontaneous calcium release which might additionally reduce the calcium content of the sarcoplasmic reticulum.

Actin Cytoskeleton↗
PubMed1994

Promotion of remyelination by polyclonal immunoglobulin in Theiler's virus-induced demyelination and in multiple sclerosis.

Spontaneous remyelination occurs in experimental models of demyelination and in patients with multiple sclerosis, although to a limited extent. This enables the search for factors that promote remyelination. Using the Theiler's virus model of central nervous system demyelination, promotion of remyelination was observed after passive transfer of CNS-specific antiserum and transfer of CNS-specific purified immunoglobulin. Mouse polyclonal immunoglobulin from normal non-syngeneic mice, comparable with the human immunoglobulin preparation, also promotes CNS remyelination in the Theiler's virus model of multiple sclerosis. These experimental findings further bridge the gap with a pilot study that suggests clinical improvement after polyclonal immunoglobulin administration, possibly due to remyelination, in some multiple sclerosis patients with stable, steroid-unresponsive optic neuritis. In view of these experimental and clinical data, the physiological role of myelin in demyelination and remyelination is discussed, and the role of IgG solely as a deleterious molecule in the pathophysiology of multiple sclerosis and experimental demyelination is addressed.

Animals↗
PubMed1994

Hospital dentistry. Window on total family health care.

A confused and complicated medical history reported by the patient may signal the need for additional medical treatment and behavioral counseling. The issue of dentistry as a primary care health profession is explored, and two cases are presented to illustrate this principle in action.

Adult↗
PubMed1994

Monoclonal autoantibodies promote central nervous system repair in an animal model of multiple sclerosis.

Susceptible strains of mice infected intracerebrally with Theiler's murine encephalomyelitis virus develop a chronic, progressive, immune-mediated CNS demyelinating disease similar both pathologically and clinically to multiple sclerosis. Previous reports indicated that polyclonal immunoglobulins from mice injected with homogenized spinal cord promote CNS remyelination when given to SJL/J mice chronically infected with Theiler's virus. To explore further both the mechanism(s) and potential therapeutic usefulness of antibodies in the treatment of CNS demyelinating diseases, we made a panel of monoclonal antibodies derived from splenocytes of SJL/J mice injected with homogenized spinal cord, and screened them for their autoantigen-binding capability. Monoclonal IgM autoantibodies from two clones, designated SCH94.03 and SCH94.32, promoted fourfold more CNS remyelination than controls when given to chronically infected SJL/J mice. CNS remyelination, assessed morphologically by the presence of abnormally thin myelin sheaths relative to axonal diameter, correlated with the absence of clinical disease progression. In titration experiments, treatment with SCH94.03 and remyelination had a positive dose-response relationship, and as little as 10 micrograms of antibody promoted remyelination. Both SCH94.03 and SCH94.32 showed multiorgan autoreactivity, and recognized both surface and cytoplasmic determinants on glial cells. We propose that this model provides a unique system to elucidate the mechanism(s) and test the reparative potential of autoantibodies in the treatment of CNS injury.

Animals↗
PubMed1994

Comparison of activity levels using the Caltrac accelerometer and five questionnaires.

The purpose of this study was to compare the physical activity levels of physical therapists using five activity questionnaires and one electronic motion sensor (Caltrac). Thirty-three physical therapists (26 female, seven male) were monitored for seven consecutive days. The Caltrac data were compared with five questionnaires, including the Baecke (Baecke); Godin and Shephard (Godin); Ross and Jackson (NASA); 3-d record (3-d); and 7-d recall (7-d). A significant (P < 0.01) Spearman rank order correlation coefficient was observed between the Caltrac reading and the 7-d recall (r = 0.79). A significant correlation was also observed between the Caltrac and the Godin (r = 0.45, P < 0.01). Three of the questionnaires were also significantly (P < 0.01) correlated with each other, including the NASA with the Baecke (r = 0.52), the NASA with the Godin (r = 0.54), and the Godin with the Baecke (r = 0.61). The 3-d record was not significantly correlated with any of the other measures. The strong, significant correlation observed between the Caltrac data and the 7-d recall suggests adequate validity for the 7-d recall. The 7-d recall questionnaire would be quicker, easier, and less expensive to use in a large population study than the Caltrac.

Adult↗
PubMed1993

Nucleotide sequence of the histone gene cluster in the coral Acropora formosa (Cnidaria; Scleractinia): features of histone gene structure and organization are common to diploblastic and triploblastic metazoans.

We report the nucleotide sequence of the core histone gene cluster from the Cnidarian Acropora formosa. This is the first histone gene cluster to be sequenced from a diploblastic organism and the predicted amino acid sequences most resemble those of sea urchin equivalents. Each of the Cnidarian histone genes has two conserved regions 3' of the coding sequences and these closely resemble those of the metazoan alpha-class histone genes. In A. formosa the core histone genes are arranged as opposed (H3/H4 and H2A/H2B) pairs, a pattern common to the nondeuterostome metazoa, and tandem repetition is the predominant pattern of organization in the Cnidarian. With the recent identification of several classes of homeobox genes in Cnidarians these features clearly align the Cnidaria with triploblastic metazoans, supporting a monophyletic origin of the metazoa.

Amino Acid Sequence↗
PubMed1993

Egg cortical granule N-acetylglucosaminidase is required for the mouse zona block to polyspermy.

The mammalian egg must be fertilized by only one sperm to prevent polyploidy. In most mammals studied to date, the primary block to polyspermy occurs at the zona pellucida, the mammalian egg coat, after exocytosis of the contents of the cortical granules into the perivitelline space. The exudate acts on the zona, causing it to lose its ability to bind sperm and to be penetrated by sperm previously bound to the zona. However, the cortical granule components responsible for the zona block have not been identified. Studies described herein demonstrate that N-acetylglucosaminidase is localized in cortical granules and is responsible for the loss in sperm-binding activity leading to the zona block to polyspermy. Before fertilization, sperm initially bind to the zona by an interaction between sperm surface GalTase and terminal N-acetylglucosamine residues on specific oligosaccharides of the zona glycoprotein ZP3 (Miller, D. J., M. B. Macek, and B. D. Shur. 1992. Nature (Lond.). 357:589-593). These GalTase-binding sites are lost from ZP3 after fertilization, an effect that can be duplicated by N-acetylglucosaminidase treatment. Therefore, N-acetylglucosaminidase, or a related glycosidase, may be present in cortical granules and be responsible for ZP3's loss of sperm-binding activity at fertilization. Of eight glycosidases assayed in exudates of ionophore-activated eggs, N-acetylglucosaminidase was 10-fold higher than any other activity. The enzyme was localized to cortical granules using immunoelectron microscopy. Approximately 70 or 90% of the enzyme was released from cortical granules after ionophore activation or in vivo fertilization, respectively. The isoform of N-acetylglucosaminidase found in cortical granules was identified as beta-hexosaminidase B, the beta, beta homodimer. Inhibition of N-acetylglucosaminidase released from activated eggs, with either competitive inhibitors or with specific antibodies, resulted in polyspermic binding to the zona pellucida. Another glycosidase inhibitor or nonimmune antibodies had no effect on sperm binding to activated eggs. Therefore, egg cortical granule N-acetylglucosaminidase is released at fertilization, where it inactivates the sperm GalTase-binding site, accounting for the block in sperm binding to the zona pellucida.

Animals↗
PubMed1993

Attitudes of physicians toward elderly drivers and driving policy.

OBJECTIVE: To examine physicians' attitudes toward and knowledge concerning driving in older persons. DESIGN: Questionnaire survey. MEASUREMENTS: A questionnaire was sent to physician members of the American Geriatrics Society (n = 5009). The questionnaire explored physicians' practice characteristics, general approach to record keeping, frequency of behavior toward educating, counseling, and reporting patients to authorities when deemed appropriate, and their personal understanding of driving issues and physician responsibilities within the state in which they practice. RESULTS: A response rate of 48% was obtained. There was a lack of consensus among physicians, with a broad range of attitudes and practices dealing with this growing public health concern. Physicians generally believed that they had a legal responsibility to assess driving ability but were uncertain about how to assess driving competence and their responsibility toward their senior patients who drive. CONCLUSIONS: Physician practices concerning the appropriate management of older drivers vary widely. Physicians should be aware that medical literature is available to aid in the evaluation of the elderly driver with medical impairments. In addition, physicians should consider referring their elderly patients to driver refresher courses to improve or maintain their driving skills. More research is needed to help guide health professionals in assessing the frail elder with multiple medical impairments and decreasing the crash risk for the older driver.

Aged↗