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T Hovi

Publications and source records attributed to T Hovi.

At least 19 recordsLinked to original sources
PubMed1992

Genetic variation in vivo and proposed functional domains of the 5' noncoding region of poliovirus RNA.

Poliovirus has a single-stranded RNA genome of about 7,440 nucleotides (nt) with an unusually long 750-nt noncoding region in the 5' end (5'NCR). Several regulatory functions have been assigned to the 5'NCR. We sequenced the 5'NCRs of 33 wild-type 3 poliovirus strains to study the range and distribution of naturally occurring sequence variations. In this regard, the 5'NCR can be divided into a conserved part (nt 1 to 650) and a hypervariable part (nt 651 to 750). In the conserved part, altogether 234 unevenly distributed nucleotide positions (36%) showed variation. When these positions were plotted against the predicted secondary-structure models, it was found that the existence of most of the proposed stem-loop structures was supported by extensive structure-conserving substitutions in the stems. Regions with conserved sequences, as well as mutational hot spots, were observed. The hypervariable part of the 5'NCR varied up to 56% between the strains studied. The A + U percentage was significantly higher than in the conserved part. The number of AUG codons varied between 5 and 15 in the conserved part of the 5'NCR, while none was found in the hypervariable part. These results provide information that can be used in site-directed mutagenesis and other approaches targeted to reveal the functional domains of the 5'NCR.

Base Sequence↗
PubMed1992

Serology versus clinical signs or symptoms and main laboratory findings in the diagnosis of exanthema subitum (roseola infantum).

Twenty-five patients with clinical exanthema subitum (roseola infantum) were enrolled into a study, where acute-phase and convalescent sera were examined for antibodies to human herpesvirus 6 (HHV-6), several other viruses, and other microbes. In addition, an acute-phase fecal specimen was examined for viruses by electron microscopy. Confirmative or suggestive serologic evidence for recent HHV-6 infection was obtained in 23 (92%) cases. Conversion to HHV-6 was found in 19 (76%), a diagnostic (greater than or equal to 4-fold) titer rise in 2, a twofold titer rise in 1, and a stable relatively high titer in 1 of the patients; only 2 (8%) individuals remained negative. The other microbial assays produced only two slight mycoplasma antibody rises and one rotavirus identification in the fecal specimen. It is concluded that if the clinical diagnosis of exanthema subitum is deemed doubtful, HHV-6 infection is verifiable in about 75% of the cases by serology.

Antibodies, Viral↗
PubMed1979

Suppression of the formation of polyamines and macromolecules by DL-alpha-difluoromethylornithine and methylglyoxal bis(guanylhydrazone) in phytohaemagglutinin-activated human lymphocytes.

1. The activation of human peripheral blood lymphocytes by phytohaemagglutinin in vitro was accompanied by striking increases in the concentrations of the natural polyamines putrescine, spermidine and spermine. 2. The enhanced accumulation of polyamines could be almost totally abolished by dl-alpha-difluoromethylornithine, a newly discovered irreversible inhibitor of l-ornithine decarboxylase (EC 4.1.1.17), or by methylglyoxal bis(guanylhydrazone) {1,1'-[(methylethanediylidene)dinitrilo]diguanidine}, an inhibitor of S-adenosyl-l-methionine decarboxylase (EC 4.1.1.50). The inhibition of polyamine accumulation was associated with a marked suppression of DNA synthesis, which was partially or totally reversed by low concentrations of exogenous putrescine, spermidine, spermine and cadaverine and by higher concentrations of 1,3-diaminopropane. 3. In contrast with some earlier studies, we found that methylglyoxal bis(guanylhydrazone), at concentrations that were sufficient to prevent polyamine accumulation, also caused a clear inhibition of protein synthesis in the activated lymphocytes. Similar results were obtained with difluoromethylornithine. The decrease in protein synthesis caused by both compounds preceded the impairment of DNA synthesis. The inhibition of protein synthesis by difluoromethylornithine was fully reversed by exogenous putrescine, spermidine and spermine, and that caused by methylglyoxal bis(guanylhydrazone) by spermidine and spermine. In further support of the idea that the inhibition of protein synthesis by these compounds was related to the polyamine depletion, we found that difluoromethylornithine caused a dose-dependent decrease in the incorporation of [(14)C]leucine into lymphocyte proteins which closely correlated with the decreased concentrations of cellular spermidine. 4. Difluoromethylornithine and methylglyoxal bis(guanylhydrazone) also elicited a variable depression in the incorporation of [(3)H]uridine and [(14)C]adenine into total RNA. The apparent turnover of lymphocyte RNA remained essentially unchanged in spite of severe polyamine depletion brought about by difluoromethylornithine. 5. The present results, as well as confirming the anti-proliferative action of the inhibitors of polyamine biosynthesis, suggest that polyamine depletion may interfere with reactions at different levels of gene expression.

Blood Proteins↗
PubMed1979

OC43 strain-related coronavirus antibodies in different age groups.

Serum antibodies against human coronavirus OC43 in different age groups were measured by complement fixation (CF), haemagglutination inhibition (HI), radial diffusion haemolysis-in-gel (HIG), and solid-phase radioimmunoassay (RIA) methods. Antigen grown in suckling mouse brain was used in all tests. Results obtained by the CF and HIG tests, and the RIA, were in good agreement with regard to the presence or absence of antibodies. Similar results were also obtained with the HI test if nonspecific haemagglutination inhibitors were first removed by treatment with phospholipase C and only titers of 1:20 or greater were considered positive. Children 6--23 months of age (n = 45) were without measurable coronavirus antibodies in all four assays. A rapid increase in the prevalence of antibodies then occurred in subsequent age groups, and practically all persons 6 years of age or older were found to have OC43 antibodies as measured by the HIG test or the RIA. The mean antibody levels determined by these two methods continued to increase, however, up to the age group of 10--14 years. This increase in antibody levels after the initial antibody incidence plateau may be due to boosting effects caused by related coronavirus strains, since OC43 antigens are known to cross-react with antibodies induced by other human coronaviruses. Taken together, these data suggest that OC43 virus, or an antigenically related coronavirus strain, is very common in Finland.

Adolescent↗
PubMed1979

The effect of air ionization on the air-borne transmission of experimental Newcastle disease virus infections in chickens.

The effect of artificial air-ionization on air-borne transmission of Newcastle disease virus (NDV) infection in chickens was studied in an isolated system consisting of two side-by-side cages with solid walls and a wire-gauze roof. During a 3-week observation period more than 90% of the uninoculated indicator chickens, housed in one of the cages, contracted the virus shed to the air by the NDV-inoculated, diseased birds in the neighbouring cage. This air-borne transmission of NDV was completely prevented by increasing the ion concentration in the test room by a constant negative corona discharge above the wire-gauze roof. On the other hand, spreading of the infection within a group of chickens housed in a single cage was not affected by air ionization. These and other results suggest that artificial air-ionization may protect animals from certain air-borne infections by interfering with microbial aerosol formation and/or by facilitating their decay.

Air Ionization↗
PubMed1978

Nonspecific inhibitors of coronavirus OC43 haemagglutination in human sera.

Antibodies against the human coronavirus OC43 in human sera were measured by haemagglutination inhibition (HI), complement fixation (CF), and radial diffusion-haemolysis in gel (HIG) techniques. The apparent HI titres in a fraction of sera with no antibodies detectable by the two other methods were found to be reduced considerably after treating the sera with phospholipase C (PLC). The PLC treatment also reduced the apparent HI titres in some sera containing variable amounts of CF and/or HIG antibodies, but did not affect antibody determinations by the two latter methods. These results suggest that false positive results can be obtained in the OC43 HI test unless the sera are treated with phospholipase C before the assay.

Antiviral Agents↗
PubMed1978

Rotavirus infections in adults in association with acute gastroenteritis.

During an epidemic of acute gastroenteritis in Helsinki, in March--May 1976, 18 out of 40 adult patients showed electron microscopic and/or serologic evidence for rotavirus infection. Rotavirus was most frequently seen in the fecal suspensions from 2 to 6 days after the onset of the symptoms but persisted in one patient for as long as 10 days. An increase in the complement-fixing (CF) serum antibody titers against the related Nebraska calf diarrhea virus (NCDV), or an initially high titer and subsequent significant decrease, was seen in all but one patient with rotavirus-positive feces, and in 6 additional patients. This suggests that using electron microscopy as the only diagnostic procedure a considerable number of rotavirus infections in adults remain undetected. Immune response against autologous or homologous rotavirus was also documented by immunoelectron microscopy. Complement-fixing antibody titers against NCDV decreased significantly from the convalescence values over a half-year observation period, but still remained clearly above the titers of a gastroenteritis-negative control population.

Acute Disease↗
PubMed1978

Defective defences.

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Adenosine Deaminase↗
PubMed1977

Cultured human monocytes synthesize and secrete alpha2-macroglobulin.

alpha2-Macroglobulin levels in the supernates of cultures of different subpopulations of human peripheral blood mononuclear leukocytes were assayed by a radioimmunoassay. Unfractionated mononuclear leukocytes produced greater amounts of the macroglobulin (4.0 vs. 0.8 ng/10(6) cells) than did subpopulations enriched in T or B+T lymphocytes, by passage through nylon wool or cotton wool columns, respectively. Still higher concentrations of alpha2-macroglobulin (40 ng/10(6) cells) were measured in the supernates of glass-adherent mononuclear leukocyte cultures. These results suggest that cells of monocyte-macrophage lineage are mainly, if not exclusively, responsible for the appearance of alpha2- macroglobulin in the supernate of human peripheral blood leukocyte cultures. The de novo synthesis and release of alpha2-macroglobulin by cultured monocytes was demonstrated by immunoprecipitation of radioactivity from supernates of 32S-methionine-labeled glass-adherent cells. Antiserum against purified alpha2-macroglobulin was used in both Ouchterlony double diffusion and double antibody precipitation tests. SDS-polyacrylamide gel electrophoresis of immunoprecipitates showed that most of the radioactivity comigrated with authentic alpha2-macroglobulin subunit at about 160,000 daltons.

B-Lymphocytes↗
PubMed1977

The role of de novo purine synthesis in lymphocyte transformation.

Genetic defects in purine metabolism are associated with severe immunodeficiency. Adenosine deaminase deficiency impairs the function of both B- and T-lymphocytes whereas in purine nucleoside (inosine) phosphorylase deficiency there is more severe impairment of T-lymphocyte functions than of B-lymphocyte functions. The relative unimportance of the salvage pathway catalysed by hypoxanthine-guanine phosphoribosyltransferase is shown by the normal responses of T-lymphocytes from patients with the Lesch-Nyhan syndrome to antigenic and mitogenic stimulation. A mild deficiency of B-lymphocyte function is found in these patients. Agents inhibiting the de novo pathway of purine synthesis, including azaserine, 6-mercaptopurine and azathioprine in low doses, block the responses of normal human lymphocytes to mitogenic stimulation. These observations emphasize the importance of the de novo pathway of purine synthesis in lymphocyte responses to antigenic and mitogenic stimulation. There is considerable heterogeneity in the amount of labelled uridine incorporated into human and rat lymphocytes. This does not appear to reflect only a difference between T- and B-lymphocytes

Adenine Phosphoribosyltransferase↗
PubMed1977

Purine metabolism and control of cell proliferation.

Exposure of normal lymphocytes to phytohaemagglutinin or other lectin mitogens results in increased concentrations of 5-phosphoribosyl-1-pyrophosphate (PP-ribose-P) within minutes. Subsequently, synthesis of purine nucleotides by both the de novo and the salvage pathways is facilitated. This change is prevented by proliferation-inhibiting concentrations of exogenous adenosine. The capacity of lymphocytes to metabolize both adenine and adenosine is increased several-fold by incubation with phytohaemagglutinin but the specific activities of the respective first-step enzymes are not significantly altered. These results suggest that the relatively low quantity of PP-ribose-P available in normal lymphocytes is a major factor limiting the synthesis of purine nucleotides and may be important for the maintenance of the quiescent state. Increased availability of PP-ribose-P may also be associated with proliferative activation of fibroblast-like cells: chick embryo fibroblast cultures released from density-dependent inhibition of growth by insulin, trypsin or serum rapidly increase the rate of adenine incorporation into nucleotides. Chick embryo fibroblasts transformed by Rous sarcoma virus, but not cells infected with the respective non-transforming leukosis virus, show PP-ribose-P concentrations higher than those observed in normal cells.

Adenine↗