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Biomedical subjects

F H Lin

Publications and source records attributed to F H Lin.

At least 73 records · Page 4Linked to original sources
PubMed1985

Cerebral biochemical abnormalities in experimental maternal phenylketonuria: gangliosides and sialoglycoproteins.

The present study sought a biochemical explanation for retarded brain development in the heterozygous offspring of the phenylketonuric (PKU) mother. Two rat models of simulated maternal PKU, one induced by p-chlorophenylalanine and phenylalanine and the other by phenylacetate, were employed in this investigation. Maternal PKU had no influence on cerebral concentrations of DNA, protein, and cholesterol, which were normal in the 2 d old pup. However, there was a noticeable disruption of the normal ganglioside pattern and a significant reduction of sialoglycoproteins. Concomitant with a delayed drop in the gangliosides Q1b and D3, was a slower rise in M1 and D1a. At least 66% of sialoglycoproteins located on SDS-PAGE gel chromatograms, by radioactivity incorporated in vivo from radiolabeled N-acetylmannosamine and by (3H) sialic acid released by Neuraminidase from periodate-(3H)borohydride labeled glycoproteins, have mobilities of the cell adhesion molecules N-CAM and D-CAM. Whether the reduction of the sialoglycoproteins induced by maternal PKU is mainly in these cell adhesion molecules requires further investigation. Interference with the function of gangliosides and certain sialoglycoproteins during cerebral development may contribute to the brain dysfunction observed in the offspring of PKU mothers not on diet control during pregnancy.

Animals↗
PubMed1983

Presence of oligoclonal immunoglobulin G bands and lack of matrix protein antibodies in cerebrospinal fluids and sera of ferrets with measles virus encephalitis.

Young adult ferrets were immunized with measles vaccine and 5 to 6 weeks later inoculated intracerebrally with Vero cells persistently infected with cell-associated strain D.R. of measles virus isolated from a patient with subacute sclerosing panencephalitis. Of nine ferrets which survived the infection for 3 weeks or longer, five showed neurological signs. At the time of death they had widespread inflammation in their brains, and cell-associated virus was isolated from three ferrets sacrificed from 5 weeks to 7 months after inoculation. Four ferrets did not develop clinical signs, but two of these had mild inflammation in the brain 7 months and 2 1/2 years after inoculation, respectively. Cerebrospinal fluids drawn by cisternal puncture from infected ferrets at the time of sacrifice had neutralizing titers against measles virus similar to the titers found in sera, but antibody against the measles virus matrix protein was not detectable. Cerebrospinal fluid showed increased immunoglobulin G (IgG) and had distinct measles virus-specific oligoclonal IgG bands. The intensity of the bands correlated with the neutralizing titers of the fluids. These results confirm and extend earlier findings and indicate that persistent measles virus infection in ferrets is similar to human subacute sclerosing panencephalitis and can be used to study certain aspects of persistent brain infections leading to subacute encephalitis.

Animals↗
PubMed1982

Precipitation of measles virus proteins by immunoglobulin G fractions containing groups of oligoclonal bands isolated from sera of patients with subacute sclerosing panencephalitis.

Groups of oligoclonal immunoglobulin G (IgG) bands were isolated from sera of patients with subacute sclerosing panencephalitis by employing preparative isoelectric focusing. Six IgG fractions containing two to three oligoclonal bands with different isoelectric points were used to precipitate the proteins from Vero cells infected with measles virus. The results showed that all of the measles virus proteins except the M protein were precipitated by all of the IgG fractions and that the precipitation of viral proteins by the fractions containing groups of oligoclonal IgG showed slightly different patterns in some sera, whereas other sera showed no significant differences. The present study indicates that oligoclonal IgGs in subacute sclerosing panencephalitis sera are not specific to individual measles virus proteins.

Antibody Specificity↗
PubMed1980

Absence of M protein in a cell-associated subacute sclerosing panencephalitis virus.

Measles virus has been suggested to cause subacute sclerosing panencephalitis (SSPE), a slow central nervous system disease of children. However, several questions remain about the pathogenesis of SSPE. For example, it is not known whether alteration of the measles virus genome has a role in the initiation and persistence of the disease. Several studies have compared the RNA and protein composition of wild-type (wt) and SSPE strains of measles virus in a search for markers characteristic of the latter. All the studies used SSPE strains that had reverted to the budding, virion-producing form, similar to wt. We have shown, however, that only cell-associated non-budding strains of SSPE virus cause an SSPE-like persistent infection in young ferrets. Strong cell association and cell-fusing activity were essential for the virulence of measles virus in the brains of experimental animals and possibly humans. We have, therefore, compared the protein composition of virulent SSPE strains to that of the budding, non-virulent SSPE and wt strains. We report here that the M protein was not detectable in non-budding SSPE strains D.R., Biken and IP-3, and strain D.R. contained very little H protein.

Animals↗
PubMed1980

Immunolabeling of SSPE and wild-type measles viruses in ferret brain cell culture.

Immunocytochemical studies using horseradish peroxidase labeled antibody were undertaken in an attempt to determine whether there are detectable antigenic differences which correlate with the biological properties of differences which correlate with the biological properties of different strains of SSPE and wild-type measles virus grown in ferret bran cell cultures. The rabbit anti-measles hyperimmune serum used in this experiment contained antibodies to all the measles virus proteins when tested by immunoprecipitation. When cells infected with the wild-type measles or productive SSPE virus strains were treated with this serum, heavy deposits of reaction product were seen on the cell membrane and virion envelope. When SSPE serum which contained relativly little antibody to the M protein was applied, a clear unlabeled area was evident just beneath the surface label. Cells infected with the non-productive SSPE strains were labeled by both sera in a spotty or discontinuous pattern on the outer surface of the cell membrane. The differences in membrane labeling seem to reflect differences in the expression of viral membrane proteins by the various SSPE and measles virus strains.

Animals↗
PubMed1980

Cellular immune response in rabbits immunized with purified Visna virus.

Visna virus-sensitized lymphocytes were demonstrated in the peripheral blood of rabbits following immunization with purified, concentrated visna virus. Lymphocytes sensitization was maximal at about 2 weeks and fell to control levels in 5 weeks. A delayed-type cutaneous hypersensitivity to the virus was observed at 2 weeks and lasted for at last 9 weeks. Both reactions increased after a booster injection. Although sera from immunized rabbits had precipitating antibodies against visna virus protein P25, their lymphocytes were not stimulated by P25. However, there was a slight reaction to P25 in the skin test. Therefore, in contrast to the humoral immune response, P25 is apparently not the most active viral antigen in the CMI response in rabbits.

Animals↗
PubMed1979

Evidence for two forms of RNA-dependent DNA polymerase in Visna virus.

The visna viral RNA-dependent DNA polymerase has been resolved into two forms by affinity chromatography. Glycerine gradient centrifugation of the two forms showed that one form sedimented at 6.9 S corresponding to an apparent molecular weight of 135 000 and the other at 6.3 S corresponding to 118 000. Sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis of the two forms indicated that the 6.9 S enzyme is composed of 2 molecules of 68 000 mol. wt. chain and the 6.3 S is a single chain enzyme. The latter form has been identified as a glycoprotein. The 6.9 S form can be completely inactivated in 20 min at 45 degrees C, prefers poly(rC) over poly(rA) as template and has high efficiency in utilizing visna 70 S RNA as template. The 6.3 S form is stable at 45 degrees C, active with 70 S viral RNA as template, prefers poly(rA) over poly(rC), and requires higher concentration of Mn2+ (0.4 mM) for maximum activity than the 6.9 S form does (0.1 mM) with synthetic homopolymers as templates. However, both 6.9 S and 6.3 S forms prefer Mg2+ over Mn2+ regardless of the nature of the templates.

Isoenzymes↗
PubMed1979

Precipitation of visna viral proteins by immune sera of rabbits and sheep.

Eighteen polypeptides equivalent to 1.2 x 10(6) daltons of visna virus were specifically precipitated by immune sera from rabbits and sheep. The hyperimmunized rabbit antisera contained high concentrations of antibodies against p25 and p14, whereas the sera from sheep actively infected with visna virus showed a large quantity of anti-gp115 antibody. The results indicate that almost all the polypeptides reported previously (F. H. Lin, J. Virol. 25:207--214, 1978) are virus-specific components of visna. The presence of anti-gp115 antibody in sera of infected sheep may offer a simple and sensitive diagnostic procedure for visna.

Animals↗
PubMed1978

Polyacrylamide gel electrophoresis of visna virus polypeptides isolated by agarose gel chromatography.

The proteins of visna are separated into nine major peaks by agarose gel chromatography in 6 M guanidine hydrochloride (GuHCl). The polypeptides in eack peak were isolated by acid precipitation and analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). The patterns of SDS-PAGE show that the excluded material from the GuHCl column contains an aggregate of 10 non-glycosylated polypeptides. It is shown that this aggregate represents virus substructures that are not completely solubilized by GuHCl. Two glycoproteins, gp175 and gp115, were isolated from the column eluate. The major glycoprotein gp115 was coeluted with P90, P68, and P61 in GuHCl 4. Each of the four major peaks (GuHCl 5 to 8) contains more than one nonglycosylated polypeptide. However, a small polypeptide, P12, can be isolated in a homogeneous form in the last peak, GuHCl 9. Analysis of the virus proteins (100 microgram) by SDS-PAGE shows that 20 radioactive bands can be recognized. During fractionation of the protein on agarose gel columns followed by analysis with SDS-PAGE, a number of minor polypeptides that were not detected before became clearly recognizable. Thus, the combined use of column chromatography and SDS-PAGE shows that visna virus is composed of 25 proteins.

Chromatography, Agarose↗
PubMed1977

Changes in macromolecular synthesis in Xanthomonas oryzae infected with bacteriophage XP-12.

Phage XP-12, which has complete substitution of the cytosine residues in its DNA with 5-methylcytosine residues, was shown to inhibit incorporation of uracil into host DNA and RNA during the latent period. This apparent inhibition of host macromolecular synthesis was not accompanied by extensive degradation of the host chromosome. Phage DNA synthesis in infected cells occurred at a faster rate than host DNA synthesis in analogous uninfected cells. However, phage DNA synthesis could not be accurately monitored by incorporation of [methyl-3H]thymidine into DNA because, soon after infection, there was a marked inhibition of utilization of exogenous thymidine for DNA synthesis. Phage infection conferred upon a thymine auxotrophic host the ability to synthesize thymine nucleotides for phage DNA synthesis. It is suggested that a phage-induced thymidylate synthetase activity is partially responsible for the inhibition of thymidine incorporation.

Bacteriophages↗
PubMed1976

Antigenic analysis of isolated polypeptides from Visna virus.

The antigenic activity of 10 Visna polypeptides separated by gel filtration in the presence of 6 M guanidine hydrochloride (GuHCl) was examined with rabbit antisera made specific for Visna virus. The results showed that the first (GuHCl 1) and the ninth (GuHCl 9) polypeptide peak reacted with the antisera when examined in immunodiffusion, passive hemagglutination, and complement fixation tests. Whole virus, GuHCl 1, and GuHCl 9, when tested with the antisera, appeared to be immunologically identical in the immunodiffusion test. However, GuHCl 1 reacted weakly with the antisera by all three techniques as compared with GuHCl 9 and whole virus. GuHCl 9, when subjected to polyacrylamide gel electrophoresis containing 0.1% sodium lauryl sulfate, revealed the presence of one polypeptide with a molecular weight of 25,000. By the same method, GuHCl 1 was found to contain an aggregate of four different polypeptides, the major one having a molecular weight of 25,000. The results indicate that the antigenic activity of both GuHCl 1 and GuHCl 9 was associated with a single polypeptide having a molecular weight of 25,000.

Antigens, Viral↗
PubMed1974

Substructures and polypeptides of Visna virus.

The protein of Visna virus, disrupted by 8 M guanidine hydrochloride and heating, was resolved into 10 polypeptides by agarose gel column chromatography in 6 M guanidine hydrochloride. Two of the peaks contained glycopolypeptides. Nonidet-disrupted virions were resolved into two fractions by potassium tartrate gradient centrifugation, with densities of 1.08 and 1.24 g/ml, respectively. About 70% of the viral DNA polymerase directed by added template was released into the light fraction, in which very little endogenous enzyme activity was detected. Also released into the light fraction were all of the glycopolypeptides, 50% of the viral RNA, and a part of each of the other viral protein components. The data indicate that extensive degradation of subviral structures occurred, even under mild conditions for virion disruption. The 1.24-g/ml fraction was composed of 50% of the viral RNA, most of the endogenous DNA polymerase activity (80%), and a major internal polypeptide (GuHCl6) with an estimated mol wt of 28,000. Two other polypeptides were also consistently detected in the heavy fraction, but they constituted less than 25% of the ribonucleoprotein complex, compared with 75% for GuHCl6.

Amino Acids↗
PubMed1972

Properties of maedi nucleic acid and the presence of ribonucleic acid- and deoxyribonucleic acid-dependent deoxyribonucleic acid polymerase in the virions.

Maedi virus contains a ribonucleic acid (RNA) which can be resolved into three major components, namely, 62S, 33S, and 13S, by sucrose gradient centrifugation. The presence of RNA- and deoxyribonucleic acid (DNA)-dependent DNA polymerase in virions of maedi virus was demonstrated. The enzyme product could be converted into acid-soluble form by pancreatic deoxyribonuclease, but was resistant to digestion by pancreatic ribonuclease and to hydrolysis by NaOH.

Animals↗