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Biomedical subjects

P Toivanen

Publications and source records attributed to P Toivanen.

At least 217 records · Page 12Linked to original sources
PubMed1981

Enhancing effect of surgical bursectomy on antibody response.

Effect of surgical bursectomy on antibody response was studied in chicks injected intrabursally with sheep red blood cells (SRBC) and Brucella abortus on day 2 of life and challenged intravenously with the same antigens on day 9. Bursectomy performed 2 days after the priming resulted in a significantly decreased anti-SRBC plaque-forming cell (PFC) response, whereas bursectomy performed 4 or 5 days after the priming clearly enhanced the PFC response. The enhancing effect of bursectomy on the PFC response was also observed if the priming was made intravenously. In antibody titers against SRBC the enhancing effect was observed only if a secondary and tertiary challenge was performed at the age of 28 and 36 days, respectively. Titers of Brucella antibodies were either reduced by the bursectomy (performed 2 or 4 days after the intrabursal priming) or left unaffected (bursectomy performed 5 days after the priming). These findings are discussed in relation to bursa-derived suppressor cells.

Animals↗
PubMed1981

T cell dependent B cell differentiation in the chicken.

Transplantation of bursa cells into surgically thymectomized (STx), cyclophosphamide(CY)-treated and X-irradiated (X) newly hatched chicks resulted in a morphological and functional reconstitution of the bursa-dependent immune system only when the transplanted bursa cells were supplemented with thymus cells. Without supplementation with thymus cells, morphological restoration of the bursa, antibody formation to sheep red blood cells and Brucella abortus, and germinal center formation remained deeply deficient. Bursa cells alone induced a full reconstitution of the bursa-dependent immunity in non-thymectomized. CY-treated and X-irradiated cell recipients. The incomplete restoration of STx-CY-X chickens after transplantation of bursa cells was not due only to lack of T helper cells, as indicated by the incomplete restoration of the bursal morphology and of antibody formation against Brucella abortus, a thymus-independent antigen. It is concluded that T cells are necessary for the B cell differentiation in the bursa of Fabricius. The mechanism behind this phenomenon remains unclear but our results indicate that a complete T cell function is not a prerequisite for this, since STx-CY-X birds reconstituted with bursa and thymus cells together did not have their mitogen (PHA, Con A) responses normalized.

Animals↗
PubMed1981

Effect of trimethoprim or trimethoprim/sulphamethoxazole usage on the emergence of trimethoprim resistance in urinary tract pathogens.

The frequency of trimethoprim (TMP)-resistant bacteria isolated from urine was studied in hospitals, in Stockholm, Sweden, and Turku, Finland. TMP has been in clinical use in Finland since 1973, whereas in Sweden TMP was available only in combination with sulphamethoxazole (SMZ) at the time for this study. All samples were collected solely from in-patients at 4 different occasions during a 20-month period 1977-78. The frequency of TMP-resistant strains (MIC greater than or equal to 8 micrograms/ml) in Turku increased from 31 to 49%, whereas it remained at a low level (1.6-3.6%) in Stockholm during the whole period. Also the frequency of TMP/SMZ-resistant strains (MIC greater than or equal to 64 micrograms/ml) increased in Turku from 24 to 45% but remained at the same level, 0-4% in Stockholm. In Turku there was also an increased frequency of resistance to SMZ (MIC greater than or equal to 512 micrograms/ml), ampicillin (MIC greater than or equal to 32 micrograms/ml) and nitrofurantoin (MIC greater than or equal to 64 micrograms/ml), while these frequencies remained at their initial levels in Stockholm. The distribution of bacteria was different in the two areas. In Turku there was also a change towards more nosocomial strains during the observation period. Since antibacterial agents are used more frequently in Turku than in Stockholm, this might be one explanation to the increase of resistance in Turku.

Ampicillin↗
PubMed1980

Trimethoprim resistance in Finland after five years' use of plain trimethoprim.

A total of 1388 urinary bacterial pathogens were tested for resistance to plain trimethoprim after five years' use of this drug for prophylaxis against urinary tract infections. Samples were obtained in Turku, Finland, where use of the drug is much greater than in other parts of Finland. Resistance to trimethoprim (greater than 8 mg/l; agar-dilution method) occurred in 20.3% of strains isolated from outpatients and 39.8% of strains isolated from inpatients. Escherichia coli and Micrococcus showed low incidences of resistance (11% and 13% respectively in ouptatients and 23% and 19% respectively in inpatients); Enterobacter, Streptococcus faecalis, and Staphylococcus epidermidis occupied an intermediate position; and Proteus mirabilis and Klebsiella were resistant in 41-76% of cases. Similar incidences of resistance were observed to sulphamethoxazole-trimethoprim, sulphamethoxazole, ampicillin, and nitrofurantoin. These findings together with the rare occurrence of side effects and convenient dosage confirm the usefulness of plain trimethoprim for urinary tract infection.

Bacteria↗
PubMed1980

Lymphoid stem cells in the intraembryonic mesenchyme of the chicken.

Chromosomally marked cells from the 7-day intraembryonic mesenchyme were transplanted into 14-day-old irradiated chick embryos. At the age of 6 weeks donor-derived T and B lymphocytes were shown to be present in the thymus, spleen and bone marrow, indicating that cells in the 7-day intraembryonic mesenchyme are capable of developing into functional T and B lymphocytes. In addition to the sex chromosome marker, IgG allotype was used as a marker; the results demonstrate that cells from intraembryonic haemopoietic sites develop into mature IgG-producing cells. In similar experiments, the 7-day yolk sac also proved to contain lymphoid stem cells. Since lymphoid cell progenitors are not present in the 2-day yolk sac, as has been shown previously in the yolk sac-embryo chimaeras and since circulation is established from day 2 of incubation onwards, lymphoid stem cells present in the 7-day yolk sac are most likely secondary immigrants originating in the intraembryonic mesenchyme.

Animals↗
PubMed1980

Effects of intrauterine thymectomy on mitogen response in guinea pig.

Intrauterine thymectomy was carried out on days 36, 40, 48 and 68 (neonatal) of foetal life to investigate the role of thymus and emigration of thymocytes in the development of mitogenic (PHA, Con A, DxS) responses in the guinea pig. The results provide further evidence that emigration of thymocytes is a continuous process which takes place already at the time of demarcation between thymic cortex and medulla (before day 36 of gestation) and again immediately after birth. In the lymph nodes of guinea pigs thymectomized on day 36 in utero a small PHA and Con A responding cell population exists at the time of birth but not any more 3-4 mth later. This population is considered to depend on the transplacental thymic product(s). However, spleen and blood lymphocytes of animals thymectomized on day 36 in utero respond to PHA and Con A to some extent at the age of 3-4 mth, suggesting that the population emigrating before day 36 has a longer survival in the spleen and blood than in lymph nodes. Thymectomy at 40 days of gestation leaves an additional population which can express a good PHA and Con A response even in lymph nodes without a direct thymic influence. Responses to DxS were not significantly affected by the intrauterine thymectomy. Thus, intrauterine thymectomy at 36 days of gestation induces a severe but not complete T cell depletion in the guinea pig.

Animals↗
PubMed1979

Intraembryonic origin of lymphoid stem cells in the chicken: studies with sex chromosome and IgG allotype markers in histocompatible yolk sac-embryo chimaeras.

Two-day-old chick embryonic bodies were transplanted onto the area vasculosa of age-matched histocompatible blastoderms, resulting in the development of yolk sac-embryo chimaeras. Eighteen of these succeeded in hatching and became adults. Differences in the sex chromosomes and in IgG allotype between the embryo and the yolk sac were used to study the contribution of these two components to the lymphoid cell development. At 5-7 weeks of age the chimaeras proved to be completely normal in the IgM and IgG antibody production against human gamma globulin and Brucella abortus and in the lymphocyte responses to phytohaemagglutinin and concanavalin A. For the sex chromosome analyses bursa cells and specifically stimulated B and T lymphocytes were used. The latter was achieved by stimulating thymus, spleen, and bone marrow cells in vitro with anti-Ig and Con A. Only four out of 1498 mitoses analysed belonged to the sex opposite to that of the bird. Among the chimaeras eleven were marked through IgG allotypes. At the age of 3-20 weeks all eleven chimaeras showed serum IgG of the embryo allotype and none of the yolk sac type. These results, based on the use of two different markers, indicate that lymphoid stem cells in the chicken are originally derived from an intraembryonic source and not from the yolk sac.

Animals↗
PubMed1979

Cell-mediated lympholysis by human maternal and neonatal lymphocytes: mother's reactivity against neonatal cells and vice versa.

Maternal reactivity in cell-mediated lympholysis (CML) against cells from her own child is, in average, half of the maternal reactivity against unrelated adult cells. This finding remains the same when cells from a newborn or from an older child are used, suggesting that the reduced maternal reactivity is based rather on the one haplotype identity between the mother and child than on the occurrence of specific maternal tolerance. Consistently, CML-capacity of the child, directed against cells of own mother, is half of the control values, again independently of the child's age.

Adolescent↗
PubMed1979

Prebursal stem cells in the intraembryonic mesenchyme of the chick embryo at 7 days of incubation.

Cyclophosphamide-treated 18-day-old chick embryos were transplanted with cells from 7-day intraembryonic mesenchyme; the recipients and donors were identical at the major histocompatibility locus. At the age of 35 days, the cell recipients were studied to determine the reconstitution capacity of the transplanted cells. The transplantation resulted in a complete restoration of IgM and IgG class antibody production against human gammaglobulin and Brucella abortus, and of microscopic morphology of the bursa of Fabricius and of the germinal center formation in the spleen. These findings demonstrate that 7-day intraembryonic mesenchyme of the chick embryo harbor prebursal stem cells. These findings confirm our previous observations in the yolk sac-embryo chimeras indicating that lymphoid stem cells originate in the intraembryonic hematopoietic sites.

Aging↗