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Biomedical subjects

M C Graves

Publications and source records attributed to M C Graves.

At least 19 recordsLinked to original sources
PubMed1992

Monoclonal IgM antibodies from cytomegalovirus-infected mice recognize the GlcNAc-containing receptor determinant of murine CMV as well as neutralizing anti-CMV IgG antibodies.

This study examines monoclonal antibodies derived from mice at different time points after infection with attenuated murine cytomegalovirus (MCMV). The antibodies obtained from mice at 3 weeks p.i. were of IgG type (designated V-antibodies) and several could neutralize the virus. Those obtained at 5 weeks p.i. were of the IgM class (designated R-antibodies), bound to uninfected (MEF, mouse embryo fibroblast) cells, and thereby blocked MCMV plaque formation. In ELISA, the IgM monoclonals (R-antibodies) bound to GalB1-3GlcNAc and GalB1-4GlcNAc, the receptor determinants for MCMV. Similarly, these GlcNAc-containing residues blocked the binding of purified IgM monoclonal antibodies (MAbs) to MEF. The R- and V-series of antibodies showed mutual binding activities; for example, IgM MAb R-2D8 bound specifically to four (V-8C4, V-1C7, V-8C7, V-9C5) of six neutralizing IgG MAbs in ELISA. The same neutralizing IgG MAbs bound to antireceptor IgM antibodies in an immunoblot assay. This suggests that the IgM monoclonals directed against the known cell surface receptor determinant are anti-idiotypic antibodies against neutralizing antiviral IgG antibodies. The neutralizing antiviral IgG MAbs bound to 60- and 66-kDa MCMV polypeptides on Western blots, suggesting that these viral polypeptides may be important in MCMV binding to this receptor. The R-series might represent anti-idiotype antibodies capable of down-regulating antiviral V-antibodies and may also represent a mechanism for the induction of IgM autoantibodies directed at cell surface glycolipids present in autoimmune CMV-associated neuropathies.

Acetylglucosamine↗
PubMed1992

Bilateral thyroarytenoid denervation: a new treatment for laryngeal hyperadduction disorders studied in the canine.

Adductor spasmodic dysphonia is a vocal disorder of uncertain etiology with no satisfactory long-term treatment. Recently, injection of botulinum toxin (Botax) into the thyroarytenoid (TA) muscle has been used as an effective temporary treatment. A surgical counterpart to bilateral TA Botox injection is described in this article. Bilateral thyroarytenoid denervation was performed through a window in the thyroid cartilage in seven canines, including four that were studied 3 months after the procedure. No serious complications occurred in the animals, each maintaining full vocal fold abduction and adduction. In all cases, anticipated physiologic changes in laryngeal function were observed, including the inability to generate high subglottic pressures during high levels of laryngeal nerve (RLN) stimulation. In two of the surviving animals, the ansa cervicalis was used to reinnervate the TA muscle, thereby preventing the possibility of reinnervation from the proximal RLN stump while limiting TA atrophy and fibrosis. Bilateral TA denervation represents a hopeful new long-term approach to spasmodic dysphonia treatment.

Animals↗
PubMed1992

Physiologic motion after vocal cord reinnervation: a preliminary study.

This study attempted to reestablish physiologic vocal cord motion, rather than synkinesis, to a reinnervated vocal cord. One mongrel dog underwent a division and reanastomosis of the anterior branch of the right recurrent laryngeal nerve and simultaneous separation and reimplantation of a posterior division nerve-muscle pedicle into the posterior cricoarytenoid muscle. After 21 weeks, spontaneous physiologic vocal cord movement and electromyographic (EMG) activity were recorded during respiratory obstruction and laryngeal mechanical stimulation. Acoustic measures and histologic data are also presented from the reinnervated and normal vocalis muscle and from the recurrent laryngeal nerve. This study demonstrated that physiologic vocal cord motion can be achieved after laryngeal reinnervation using this technique.

Anastomosis, Surgical↗
PubMed1992

Autoimmune disease and the nervous system. Biochemical, molecular, and clinical update.

Autoimmunity in the central and peripheral nervous system can manifest as the result of cellular or humoral immune responses to autoantigens. There is evidence that multiple sclerosis is a cell-mediated autoimmune disease of the central nervous system in which both myelin and the cell that produces the myelin are destroyed. Diseases such as acute inflammatory demyelinating polyneuropathy (also called Guillain-Barré syndrome) and myasthenia gravis are considered antibody-mediated diseases of the peripheral nervous system and neuromuscular junctions, respectively. We review these diseases and explore mechanisms of immune-mediated destruction of these nervous system components. We specifically focus on one effective therapy aimed at countering the immune attack, that of thymectomy in patients with myasthenia gravis.

Autoimmune Diseases↗
PubMed1991

A functional evaluation of ansa cervicalis nerve transfer for unilateral vocal cord paralysis: future directions for laryngeal reinnervation.

There are a variety of methods for treating unilateral vocal cord paralysis, but to date there are few objective studies that evaluate the functional results of nerve transfer from the ansa cervicalis. Six dogs underwent unilateral recurrent laryngeal nerve section with immediate reanastamosis to the sternothyroid branch of the ansa cervicalis. After 5 to 6 months, measurements of vocal efficiency and acoustic parameters, videolaryngoscopy, videostroboscopy, and evoked electromyography were performed. Identical measurements were made in eight control dogs during normal electrically induced phonation and a simulated unilateral recurrent laryngeal nerve paralysis. Histologic analysis of both vocalis muscles, recurrent laryngeal nerves, ansa cervicalis, and the ansa-recurrent laryngeal nerve anastamosis site was performed. Evidence of reinnervation was found in all of the animals that underwent nerve transfer. The vocal efficiency and acoustic quality after ansa cervicalis nerve transfer were dependent on the degree of electrical stimulation from the transferred nerve to the reinnervated cord during phonation. In the absence of electrical stimulation to the nerve transfer, physiologic vocal cord motion could not be elicited from the reinnervated cord.

Anastomosis, Surgical↗
PubMed1990

Identification of a human immunodeficiency virus-1 protease cleavage site within the 66,000 Dalton subunit of reverse transcriptase.

The human immunodeficiency virus-1 reverse transcriptase is a heterodimer of related 51 and 66 kDa subunits. The smaller subunit arises by viral protease-catalyzed cleavage of the carboxy-terminal domain of the 66 kDa species. Comparison of the amino acid composition analyses of the isolated 51 kDa and 66 kDa subunits indicates that the carboxyl terminus of 51 kDa is Phe440. This site was confirmed in vitro using purified recombinant protease and a peptide spanning the postulated cleavage area. The sequence surrounding this site does not show significant homology to other protease cleavage sites in the viral gag and pol precursors; thus, this new information may contribute to our understanding of the sequence specificity of the viral protease.

Amino Acid Sequence↗
PubMed1990

Human immunodeficiency virus type 1 protease cleaves the intermediate filament proteins vimentin, desmin, and glial fibrillary acidic protein.

The intermediate filament proteins vimentin, desmin, and glial fibrillary acidic protein are cleaved in vitro by human immunodeficiency virus type 1 protease (HIV-1 PR). Microsequencing showed that HIV-1 PR cleaved both human and murine vimentin between leucine-422 and arginine-423 within the sequence between positions 418 and 427, Ser-Ser-Leu-Asn-Leu/Arg-Glu-Thr-Asn-Leu (SSLNL/RETNL). Minor cleavages at other sites were also observed. Heat-denatured vimentin was cleaved by HIV-1 PR less efficiently than native vimentin. A decapeptide containing the sequence SSLN-LRETNL was also cleaved in vitro by HIV-1 PR as predicted. The presence of a charged residue (arginine) at the primary cleavage site distinguishes this from other known naturally occurring cleavage sites. Microinjection of HIV-1 PR into cultured human fibroblasts resulted in a 9-fold increase in the percentage of cells with an altered and abnormal distribution of vimentin intermediate filaments. Most commonly, the intermediate filaments collapsed into a clump with a juxtanuclear localization. These results support the possibility that intermediate filament proteins may serve as substrates within HIV-1-infected cells.

Amino Acid Sequence↗
PubMed1990

Attenuated murine cytomegalovirus binds to N-acetylglucosamine, and shift to virulence may involve recognition of sialic acids.

Treatment of cells with lectins specific for N-acetylglucosamine (GlcNAc) blocked infection by mouse cytomegalovirus (MCMV), and GlcNAc pretreatment of the lectin blocked this effect. MCMV failed to infect N-acetylglucosaminidase (GlcNAcase)-treated mouse embryo fibroblasts (MEF). GlcNAc and GlcNAc-containing synthetic oligosaccharides directly inhibited viral infectivity. Ulex lectin inhibition of infection was shown to be due to inhibition of surface adsorption of 35S-labeled virus. Also, GlcNAcase eluted 35S-labeled virus adsorbed to MEF at 4 degrees C and inhibited plaque formation if added after adsorption at this temperature. These findings indicate that GlcNAc binding is involved in attachment rather than in some later step in infection. High-performance thin-layer chromatography overlay of [35S]MCMV indicated that it binds to a GlcNAc-containing asialoglycolipid. Analogous experiments indicated that MCMV made virulent by in vivo salivary gland passage binds to sialic acids in addition to GlcNAc. Treatment of MEF with sialic acid-binding lectins blocked infectivity. Incubation of virus with sialic acids also prevented infection. N-acetylneuraminic acid was 10(3)-fold more potent than N-glycolylneuraminic acid. Sialidase-treated target cells were not efficiently infected by the virus. Thus, MCMV binds to GlcNAc on the cell surface, and the shift to virulence (by in vivo salivary gland passage) correlates with viral recognition of sialic acids.

Acetylglucosamine↗
PubMed1990

Necrotizing retinopathy after intraocular inoculation of murine cytomegalovirus in immunosuppressed adult mice.

A light microscopic study was done to investigate retinal changes in healthy and immunosuppressed mice after intraocular inoculation of murine cytomegalovirus (MCMV). A 0.01-ml inoculum containing 10(5) plaque-forming units of MCMV was placed behind the lens in 138 4-week-old Swiss Webster mice. Ninety-eight mice were immunosuppressed with 0.2 mg/g of cyclophosphamide given intraperitoneally at the time of inoculation and 0.1 mg/g of cyclophosphamide every 5 days thereafter. Selected eyes were examined on postinoculation days 5, 10, 15, and 16-20. Evidence of viral infection was most prominent in uveal tissue. Uveal infection developed whether or not animals received cyclophosphamide, but retinal necrosis developed only in immunosuppressed mice. Focal retinal necrosis, primarily involving the outer retinal layers and retinal pigment epithelium, was first observed in an eye examined on day 10. Retinopathy from MCMV was present in three of five eyes (60%) examined on day 15, and in six of 16 eyes (37.5%) examined between days 16-20. Retinal disease was characterized by full-thickness retinal necrosis, scattered cytomegalic cells, intranuclear and intracytoplasmic viral inclusions, and acute and chronic inflammation. These results indicate that MCMV can produce a necrotizing retinopathy in mice and that immunosuppression facilitates infection. Although ocular MCMV infection in immunosuppressed adult mice is a potential model for study of human CMV retinopathy, many differences exist between human CMV and MCMV and between the ocular diseases they produce.

Animals↗
PubMed1990

Characterization of the recombinant Clostridium pasteurianum ferredoxin and comparison of its properties with those of the native protein.

Ferredoxins (Fds) constitute an important class of nonheme iron-sulfur proteins. One of the most studied Fds is the [8Fe-8S] Fd from Clostridium pasteurianum. The gene for this Fd has previously been cloned and sequenced. We report the expression of this Fd in Escherichia coli, and the characterization and comparison of this recombinant protein to the native Fd. We have found that the purified recombinant protein has the same enzymatic, redox, magnetic and electronic properties as the native Fd isolated from C. pasteurianum, which indicates that the two [4Fe-4S] clusters present in the Fd were correctly formed in E. coli.

Bacterial Proteins↗
PubMed1989

Effective blocking of HIV-1 proteinase activity by characteristic inhibitors of aspartic proteinases.

Inhibitory constants (Ki) between 5 and 35 nM were derived (under different conditions of pH and ionic strength) for the interaction of HIV-1 proteinase with acetyl-pepstatin and H-261, two characteristic inhibitors of aspartic proteinases. Thus this enzyme, essential for replication of the AIDS virus, may be classified unequivocally as belonging to this proteinase family.

Aspartic Acid Endopeptidases↗
PubMed1989

A placebo-controlled, randomized, double-masked, variable dosage, clinical trial of azathioprine with and without methylprednisolone in multiple sclerosis.

Ninety-eight patients with multiple sclerosis (MS) in the chronic progression phase entered a 3-year clinical trial to determine if azathioprine (AZ) alone or with adrenal cortical steroids stabilizes the course of MS. In group AM, the patients took AZ throughout and methylprednisolone (MP) for the first 36 weeks. Group AP received AZ and placebo instead of MP. Group PP took placebos for both drugs. We adjusted the AZ to maintain the total white blood cell count within 3,000 to 4,000/mm3; we gave the MP in a fixed dose "pulse" and alternate-day regimen. The "intent-to-treat" groups had no statistically significant differences in the rates of progression among the 3 treatments. Subgroup analysis suggests that patients in the AM group who completed treatment exactly according to protocol did statistically significantly better than the placebo recipients using the sum of Standard Neurological Examination scores, slightly better using the quantitative neuro-performance tests, but no better using Mickey's Illness Severity Scores or Kurtzke's Disability Status Scale. Also, the AZ-treated groups had half the relapse rate of the placebo-treated group. Adverse reactions to AZ accounted for most withdrawals. Hematologic and hepatic abnormalities were significantly associated with AZ, but serious non-MS abnormalities were uncommon and were equally distributed among the 3 groups. Addition of MP to the AZ slightly improved the efficacy of the treatment, but also increased the adverse effects. The benefits of AZ with or without steroids did not outweigh the risks, and therefore we do not recommend this treatment for patients with chronic progressive MS.

Adolescent↗
PubMed1988

Theiler's virus-associated antigens on the surfaces of cultured glial cells.

Infection of the central nervous system by Theiler's murine encephalomyelitis virus (TMEV), a picornavirus, produces chronic demyelinating disease in susceptible mice. In this immunoelectron microscopic study of TMEV infection of neonatal mouse brain cells in culture, TMEV antigen was found on the surfaces of infected oligodendrocytes and astrocytes by labeling with hyperimmune serum from TMEV-infected mice or with rabbit antiserum to purified inactivated DA strain TMEV. Brain-derived macrophages had no TMEV-specific antigen on their surfaces and were not able to maintain productive TMEV infection, even though TMEV antigen was present in the cytoplasm. The presence of TMEV antigens on the surfaces of oligodendrocytes (myelin-producing cells) was unexpected because picornaviruses are nonenveloped viruses and do not bud from cell surfaces. The finding is consistent with the hypothesis that demyelination follows damage of infected oligodendrocytes by immune cells or immunoglobulins that recognize surface virus antigen.

Animals↗