PubMed Health⌕ Search

Biomedical subjects

A C Kroes

Publications and source records attributed to A C Kroes.

At least 55 records · Page 3Linked to original sources
PubMed1991

Significance of isolated hepatitis B core antibodies detected by enzyme immunoassay in a high risk population.

Serum samples, which were found positive for anti-HBc and negative for HBsAg and anti-HBs during routine testing with Abbott enzyme immunoassays (EIA), were collected prospectively. The samples were obtained from patients with a high risk of hepatitis B. Further analysis was carried out using radioimmunoassays and tests for additional markers of hepatitis B. 84 of the 203 initially collected samples (41.4%) were found positive for anti-HBs by RIA. Of the 119 samples negative for anti-HBs by RIA, 103 were available for further investigation, and 35 (34.0%) of these were negative for anti-HBc by RIA. This indicates that low sensitivity of the anti-HBs EIA and non-specificity of the anti-HBc EIA may account for about 60% of the cases presenting with isolated anti-HBc at initial testing. Fifty-two samples positive for anti-HBc by RIA, with isolated anti-HBc confirmed after RIA testing for HBsAg and anti-HBs, were examined further: anti-HBe was detected in 16 sera, anti-HDV in one serum and HBV-DNA in 5 sera by PCR. Additional testing of serum samples with isolated anti-HBc is warranted.

Base Sequence↗
PubMed1990

[Aids caused by HIV-2 in The Netherlands].

In four patients in Rotterdam AIDS was diagnosed, and it was subsequently demonstrated that they were infected with HIV type 2. One of the patients was an immigrant from the Cape Verde islands, two of the others had heterosexual contacts with persons of this area, and the fourth patient was a male homosexual without known contacts with Africans. The Cape Verde islands are one of the areas in which HIV-2 infection occurs, and because of immigration into The Netherlands and in particular to Rotterdam, the possibility of HIV-2 infection should be considered in persons of this population group and their sexual contacts. Furthermore, problems with serologic investigations should be avoided by the application of HIV-2 specific confirmatory assays.

Acquired Immunodeficiency Syndrome↗
PubMed1990

Anti-leukemic potential of methyl-cobalamin inactivation by nitrous oxide.

Myelo-cytotoxicity of extended nitrous oxide (N2O) inhalation was described almost forty years ago and then incidentally applied already with temporary success for suppressing leukemia. In 1948 the accompanying megaloblastic maturation arrest was explained by inactivation of the methylcobalamin coenzyme and subsequent folate deficiency. We studied the anti-leukemic effect of N2O on a transplantable acute leukemia in B(rown) N(orway) rats. Progression of this B,N,M(yelocytic)L(eukemia) was measured as spleen and liver weights, and leukemic blood cell counts. The deoxyuridine (dU)-suppression test provided in vitro indication of the functional folate activity of leukemic cells. Breathing of N2O-oxygen considerably reduced but did not eradicate, BNML-proliferation. Addition of anti-metabolites, interfering with some enzyme in the folate metabolism beyond the methylcobalamin co-enzyme dependent methionine synthase step, acted at least synergistically. The anti-leukemic effect of cycloleucine, which reduces S-adenosyl-methionine synthesis by inactivation of methionine adenosyltransferase, was moderate but became much stronger with N2O inhalation. Methotrexate, a potent anti-leukemic agent by inhibiting tetrahydrofolate (THF) generation through inactivation of di-HF reductase, became highly anti-BNML, even in low dosage when combined with or preceded by N2O. 5-Fluorouracil, which inhibits methylene-THF dependent thymidilate synthase, itself was surprisingly anti-BNML, but also became much more potent with previous or concomitant N2O exposure. Preliminary dU-suppression test results with human acute leukemia cells, exposed to N2O and/or folate antagonists in vitro, correlated well with the in vivo BNML-experiments. Combining the anticobalamin activity of N2O with an anti-folate therefore seems to be a promising chemotherapeutic approach.

Animals↗
PubMed1990

Acute ulcerative proctocolitis associated with primary cytomegalovirus infection.

The case is reported of a 39-year-old pregnant woman who presented with fever, abdominal complaints, and diarrhea. Laboratory investigation revealed mononucleosis in the peripheral blood. All microbiological studies were negative, with the exception of finding cytomegalovirus (CMV). Seroconversion was documented; the virus was cultured from urine and subsequently was demonstrated to be present in the inflamed mucosa of the rectum and distal sigmoid, which was found at sigmoidoscopy. This woman was delivered of a neonate with congenital CMV infection but without apparent malformations. The patient experienced recurrences of the bowel disease, in the first of which CMV could still be cultured from a biopsy specimen. In the follow-up period, an otherwise aspecific chronic inflammatory bowel disease remained present. No immunological abnormalities were found, and antibodies to human immunodeficiency virus were negative. This case demonstrates that inflammatory bowel disease can develop as a result of primary infection with CMV.

Acute Disease↗
PubMed1990

Acute HIV-infection: report of a case and a review of recent developments.

A patient is reported with a typical acute HIV-infection. He presented with an infectious mononucleosis-like illness, which included fever, malaise, sore throat, myalgia, swollen glands and a rash. Seroconversion, documented by serial immunoblotting, occurred within a period of four days. If a patient with a glandular fever-like illness belongs to one of the risk groups, an acute HIV-infection should be seriously considered. In a recent study an association was found between the clinical course of acute HIV-infection and the subsequent course. Treatment of asymptomatic HIV-infected patients is discouraged, except if included in a clinical trial.

Acute Disease↗
PubMed1989

Uptake of transcobalamin II-bound cobalamin by HL-60 cells: effects of differentiation induction.

Binding and uptake of transcobalamin II-bound cobalamin by HL-60 promyelocytic leukemia cells proceed through receptor-mediated endocytosis. The affinity constant of the receptor for transcobalamin II-cobalamin was found to be 6.1 liter/nmol and the maximal rate of uptake 12 pmol/10(9) cells/h. This uptake is mediated by about 3000 receptor sites per cell. Evidence is presented that the receptor recirculates from the cell surface to the lysosomes and vice versa. Upon differentiation induction of the cells by either DMSO in granulocytic direction or by 1,25-dihydroxy-vitamin D3 in monocytic direction a rapid decline in cellular uptake and cell surface binding of the protein-bound vitamin ensues. In particular the internalization of the complex decreases faster than all other observed signs of the ongoing differentiation process, such as reduction in the OKT9-reactive transferrin receptor, increase in lineage-specific surface markers, and decrease in [3H]thymidine incorporation and actual cell proliferation. The transcobalamin II receptor on the cell surface appears to be a proliferation-associated membrane component in human leukemic cells.

Calcitriol↗
PubMed1988

The reduction of intracellular polyamines by sequential inhibition of the synthesis of decarboxylated S-adenosylmethionine: effects on rat leukemia.

Decarboxylated S-adenosylmethionine (SAM) is an aminopropyl donor in the synthesis of the polyamines, spermidine and spermine. The decarboxylation of SAM is inhibited by the toxic cytostatic drug methylglyoxalbis-(guanylhydrazone) (MGBG). To achieve more specific and less toxic effects of MGBG, this drug was combined with cycloleucine, which inhibits SAM synthesis, and with nitrous oxide, which inhibits methionine synthetase. This treatment thus aimed at sequential inhibition of the synthesis of decarboxylated SAM, and was studied in a rat leukemia model (BNML). Combined treatment further decreased the level of spermine, but not of spermidine, in leukemic cells, compared to the effects of MGBG alone. The therapeutic effects of this combination were additive or less than additive, however. MGBG was not very effective in reducing leukemic growth and severely toxic, although less with combined treatment. Another inhibitor of SAM decarboxylase, berenil, was also used, and although this drug was about equally active in inhibition of leukemic growth, alterations in intracellular polyamines were not observed. The combination of nitrous oxide and cycloleucine, which effectively reduced leukemic growth at non-toxic dosages, selectively inhibited spermine synthesis, and therefore may be used to interfere with polyamine metabolism. The relevance of this polyamine deprivation to the treatment of leukemia could not be demonstrated.

Adenosylmethionine Decarboxylase↗
PubMed1988

Effect of cobalamin inactivation on folate metabolism of leukemic cells.

Exposure to nitrous oxide inactivates the cobalamin coenzyme of methionine synthetase, an essential enzyme in folate metabolism. Hemopoietic cells are especially dependent on the function of cobalamin for the folate-dependent synthesis of thymidylate (dTMP). Inhibition of methionine synthetase may therefore be of potential value in the treatment of hematological malignancies. In the present study we investigated the effect of nitrous oxide induced cobalamin inactivation on folate metabolism of fresh leukemic cells and the human myelomonocytic cell line U937. Cells were exposed to nitrous oxide for 20 h. Subsequently they were subjected to the deoxyuridine suppression test (dU test), which measures the disturbance of folate-dependent dTMP synthesis. In all bone marrow samples, cobalamin inactivation resulted in a 200% increase of the dU test value, implicating a decreased de-novo synthesis of dTMP. Incubation of leukemic cells with methotrexate, 5-fluorouracil or cycloleucine induced similar increases of the dU test values which could be further raised to 400% with the addition of N2O exposure. Prolonged experiments with U937 cells revealed that the disturbance of folate metabolism aggravated up to 48 h of nitrous oxide exposure. It can be concluded that cobalamin inactivation in human leukemic cells results in disturbed folate-dependent dTMP synthesis. Moreover, effects of several drugs interfering with folate metabolism can be enhanced.

Bone Marrow↗
PubMed1986

Enhanced therapeutic effect of methotrexate in experimental rat leukemia after inactivation of cobalamin (vitamin B12) by nitrous oxide.

Exposure to nitrous oxide interferes selectively with the coenzyme function of vitamin B12 and causes inactivation of methionine synthetase, with subsequent impairment of folate metabolism and reduction of cellular proliferation. In a rat leukemia model (BNML) we investigated the combined administration of nitrous oxide, inactivating vitamin B12, and methotrexate (MTX), a folate antagonist inhibiting the enzyme dihydrofolate reductase. Through different mechanisms, both agents decrease the availability of tetrahydrofolate, and subsequently of other reduced folates, with increased impairment of folate-dependent synthesis of thymidylate. Effects on leukemic growth and on hematological values in rats demonstrated enhancement of the therapeutic effect of MTX by exposure to nitrous oxide. With several treatment schedules, the results of combined treatment were seen to be better than additive when compared with the effects of single agents. In particular, pretreatment of leukemic rats with nitrous oxide for 3 days before administration of MTX appeared effective. With higher doses of MTX, concomitant exposure to nitrous oxide even resulted in toxic effects. These findings were in accordance with the results of some metabolic studies performed in leukemic rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Nitrous oxide reduces growth of experimental rat leukemia.

The ability of nitrous oxide to inhibit the in vivo growth of hematological neoplasms was investigated in a rat model for acute myeloid leukemia (BNML). Nitrous oxide, administered in a concentration of 67% with 33% oxygen, resulted in a reduction of spleen and liver weights of approx. 30%, as compared with leukemic rats kept in ambient air. Peripheral white cell counts were also considerably lower in the treated rats. Plasma levels of vitamin B12 were found to be elevated in untreated leukemia, but fell to about normal levels after nitrous oxide exposure. On the contrary, folic acid levels were low in untreated leukemic rats, and significantly higher in animals exposed to nitrous oxide. The observed effects of nitrous oxide appeared to be dose-dependent. The deoxyuridine suppression test performed with leukemic cells became abnormal after nitrous oxide inhalation, in accordance with the effect on normal bone marrow. These results indicate that the interference of nitrous oxide with vitamin B12-related metabolism, which leads to impairment of de novo thymidine synthesis, has the potency to reduce leukemic proliferation in vivo.

Animals↗
PubMed1984

Synergistic growth inhibiting effect of nitrous oxide and cycloleucine in experimental rat leukaemia.

Nitrous oxide (N2O) inactivates the vitamin B12-dependent enzyme methionine synthetase with subsequent impairment of folate metabolism and a reduction of cellular proliferation. Indications exist that this effect is antagonized by S-adenosylmethionine (SAM), and it was investigated whether combination with an inhibitor of SAM synthesis, cycloleucine, would result in increased inhibition of growth in rat leukaemia model (BNML). Leukaemic growth was compared in untreated rats, in rats treated with either nitrous oxide/oxygen (1:1) or cycloleucine (50 mg kg-1 i.p.), and in rats receiving both agents. Combined treatment resulted in the strongest reduction of leukaemic infiltration in spleen and liver, and this reduction often was more than the added effects of single treatments. Peripheral leukocyte counts were also lowest after combined treatment. The deoxyuridine suppression test, measuring folate-dependent de novo synthesis of thymidine, was more severely disturbed with combined treatment. Levels of vitamin B12 in plasma were reduced in rats receiving N2O, but an increase in plasma folate occurred in all treated rats. These results indicate that a reduction of SAM synthesis by cycloleucine can increase the disturbance of folate metabolism that is caused by nitrous oxide, with a potentiation of the effects on leukaemic growth.

Amino Acids↗
PubMedDate not supplied

Infections after auxiliary partial liver transplantation. Experiences in the first ten patients.

In ten auxiliary partial liver transplant recipients selective bowel decontamination (SBD) was used to reduce infections due to gram-negative microorganisms and fungi. During SBD no gram-negative infections occurred. Candida peritonitis was observed in one patient. After discontinuation of SBD serious infections of gram-negative origin did occur and three fungal infections were seen. SBD seems to have a favourable effect in reducing infections by gram-negative microorganisms and fungi. Most striking was the number of enterococcal infections that occurred. Five out of ten patients developed enterococcal infections which in two cases contributed to a fatal outcome. These infections occurred after increase of the number of enterococci in faeces and concomitant positive cultures of bile, ascites or wound drains. This increase could be due to the use of SBD. Also, the kind of biliary anastomosis may play an important role in the relatively high incidence of enterococcal infections. In the postoperative period, recurrence of hepatitis B infection in the liver graft was observed in all patients with cirrhosis due to this virus. Problems caused by other viral infections or protozoal infections remained limited in these ten patients.

Adolescent↗