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J H Meuwissen

Publications and source records attributed to J H Meuwissen.

At least 19 recordsLinked to original sources
PubMed2001

A 1-year comparison of the efficacy and clinical tolerance in postmenopausal women of two hormone replacement therapies containing estradiol in combination with either norgestrel or trimegestone.

This double-blind, randomized, multi-center study compared the efficacy and clinical tolerance of a combined formulation containing 2 mg estradiol (E2) and 0.5 mg trimegestone (TMG) with a standard hormone replacement therapy containing estradiol valerate (E2V) and norgestrel (NG) in the treatment of climacteric symptoms. The study was conducted over 13 cycles, each of 28 days, and involved 634 subjects, of whom 481 completed the study. The primary efficacy variable was the percentage of subjects who showed at least a 50% reduction from baseline in the mean daily number of hot flushes in cycle 3. This was observed in 98.5% of the subjects in the E2 + TMG group and 93.3% of the subjects in the E2V + NG group (95% confidence interval of the difference, -8.6, -1.9). Significant differences in favor of the E2 + TMG combination were observed in the reduction in the mean daily number and severity of hot flushes, and in the percentage of subjects who had hot flushes at baseline but no hot flushes during treatment. There were no significant differences between the treatments in the Kupperman index and in urogenital signs or symptoms. Treatment with the E2 + TMG combination was well tolerated and the incidences of adverse events were similar in the two treatment groups. Breast pain was the main adverse event, possibly related to treatment that resulted in discontinuation. The mean number of bleeding days per cycle was significantly lower with the E2 + TMG combination than with the E2V + NG combination. The incidences of endometrial hyperplasia were low and comparable in both treatment groups. It was concluded that the E2 + TMG combination was either equivalent or superior to the E2V + NG combination in the treatment of hot flushes and other climacteric symptoms, and that its bleeding profile was favorable.

Double-Blind Method↗
PubMed1997

Prenatal diagnosis and treatment of congenital Toxoplasma gondii infections: an experimental study in rhesus monkeys.

The efficacy of treatment in fetuses in whom congenital Toxoplasma gondii infection has ben established has been investigated using rhesus monkeys as a model for humans. A polymerase chain reaction has been developed for the detection of Toxoplasma gondii. Using this polymerase chain reaction congenital infection can be established within 2 days of receiving an amniotic fluid sample. The polymerase chain reaction has subsequently been used to monitor the effect of treatment on fetal infection. The results show that early treatment with the combination of pyrimethamine and sulfadiazine was clearly effective in reducing the number of parasites in the infected fetus. The parasite was no longer detectable in the amniotic fluid 10 to 13 days after treatment was started. Spiramycin, on the other hand, has to be administered for at least 3 weeks to achieve the same effect. Moreover, pharmacokinetic studies revealed that spiramycin does not reach the brain. Pyrimethamine and sulfadiazine are able to pass the blood-brain barrier. Pyrimethamine appears to accumulate in the brain tissue and reaches concentrations which are also effective in vitro.

Amniotic Fluid↗
PubMed1996

Endometrial thickness assessed by transvaginal ultrasound insufficiently predicts occurrence of hyperplasia during unopposed oestrogen use.

In the present study, unopposed oestrogens were given to 184 non-hysterectomized women, for a duration varying from four weeks to 24 months, while the endometrial responses were monitored by transvaginal sonography (TVS) and backed up by endometrial sampling (conducted when the endometrial thickness reached 8 mm (double layer) or more, vaginal bleeding occurred during oestrogen administration, or after one year of unopposed oestrogen use). In cases where the endometrial thickness reached 8 mm or more, progestogens were administered for 12 days. In 64% of the women, administration of progestogen could be postponed until at least the fourth month of treatment under the pre-defined decision criteria. Eleven percent of the patients used oestrogens continuously during the two year study period, without any need of additional progestogen. In total, 338 endometrial biopsies were performed; 16 cases of hyperplasia were detected. In three cases, the corresponding endometrial thickness was below 8 mm (in one case, 5 mm). Endometrial thickness could not consistently predict occurrence of hyperplasia. In eight cases, hyperplasia occurred within 4 months of treatment, and in four cases, within only 2 months (of which only one case could possibly be attributed to previous hormone use and none to endogenous oestrogen production). The rapid occurrence of hyperplasia should be taken into account in studies of quarterly progestogen administration with hormone replacement therapy. It is concluded that postponement of progestogen administration with hormone replacement therapy under guidance of TVS only (without biopsies) would not be adequately safe to be recommended for clinical practice.

Adult↗
PubMed1996

Absence of relationships between selected human factors and natural infectivity of Plasmodium falciparum to mosquitoes in an area of high transmission.

The effects of sex, age of the human host, patency of asexual and sexual stages and seasonality on infectiousness of Plasmodium falciparum to mosquitoes were investigated in a rural village in southern Tanzania between 1992 and 1994. Villagers from randomized subgroups of households were surveyed for malaria parasites. Gametocyte and trophozoite prevalences were age dependent and fluctuated without any clear pattern of seasonality. A sample of 107 participants, selected to include an excess of gametocyte carriers, slept under bednets with holes cut into the sides for 3 weeks. A total of 3837 Anopheles gambiae s.l. and 5403 A. funestus recovered from these bednets, was examined for all oocysts 5-7 days after feeding or for oocysts less than 17.5 microns in diameter 2-3 days after feeding. Additional blood slides from participants were taken twice weekly. The 5-7 day oocyst rates were 12.1% in A. gambiae s.l. and 10.9% in A. funestus and 2-3 day rates were 3.6 and 4.9%, respectively. The higher rates using the former method were attributed to previous infection. There were strong correlations in the levels of infection in both vectors when they fed on the same hosts. However, patent gametocytaemia was only weakly associated with the development of oocysts in the mosquito. Infectiousness was not related to host age, sex, or the season.

Adolescent↗
PubMed1995

Plasmodium falciparum: a comparison of the activity of Pfs230-specific antibodies in an assay of transmission-blocking immunity and specific competition ELISAs.

The activity of monoclonal antibodies (mAbs) that specifically recognize the Plasmodium falciparum sexual stage-specific protein Pfs230 was analyzed. All mAbs reacted with the surface of extracellular sexual forms of the parasite in a suspension immunofluorescence antibody reaction and precipitated the Pfs230 protein from an NP-40 extract of surface radioiodinated macrogametes/zygotes. Only mAb that bound complement blocked transmission, whereas mAb that did not bind complement but competed with the complement-binding mAb for binding to the same epitope did not block transmission. These mAbs were used to develop Pfs230-specific competition ELISAs to analyze epitope diversity and to analyze the binding characteristics of anti-Pfs230 antibodies in human serum. Transmission-blocking (TB) antibodies in test/field sera competed in the competition ELISA for binding with epitope-specific, labeled mAbs against Pfs230. At least five different epitope regions could be defined with the competition ELISAs. All 46 sera from gametocyte carriers immunoprecipitated the Pfs230 molecule, while 19 of these sera blocked transmission in the bioassay. Five of the transmission-blocking and one of the nonblocking sera competed with monoclonal antibodies. A method comparison analysis was used to determine agreement between reactions in a competitive ELISA and the TB activity examined in the bioassay. The index of agreement kappa between outcomes of the bioassay and ELISA was fair to poor (kappa = 0.25) but since its range includes values below 0 the relation between the data obtained by the bioassay and the competition ELISA can be explained by chance alone. The serological data did not reveal a correlation between immunoprecipitation of Pfs230 and TB activity.

Adolescent↗
PubMed1995

Regression of endometrial thickness in combination with reduced withdrawal bleeding as a progestational effect of tibolone in postmenopausal women on oestrogen replacement therapy.

For 176 postmenopausal women on HRT with progestogen addition 'on demand' medroxyprogesterone acetate (MPA), noresthisterone and tibolone were used to protect the endometrium in 214 cases. Tibolone is a gonadomimetic steroid with combined progestogenic and estrogenic effects. In this study tibolone has been used as a progestogen. The results of these three progestogens were compared. The endometrial thickness before and after the use of progestogen was determined by vaginosonography. In 175 out of 214 cases progestogen addition during oestrogen therapy caused endometrial regression. Withdrawal bleeding was observed 166 times. If the endometrial thickness on the onset of progestogen addition was 5 mm or more, in nearly all cases withdrawal bleeding occurred when MPA or norethisterone was used. If tibolone was used, no withdrawal bleeding occurred in over half the cases studied. We report the first observation of induced endometrial regression without withdrawal bleeding.

Adult↗
PubMed1995

Susceptibility to Plasmodium berghei infection in rats is modulated by the acute phase response.

Brown Norway (BN) and Sprague Dawley (SD) rats are known to differ in their susceptibility to infection with sporozoites of Plasmodium berghei, as measured by the density of liver schizonts. Because of the known inhibitory effect of non-specific immunomodulators on schizont development, we compared some aspects of the acute phase response in these two rat strains. LPS induced IL-6 production was measured in supernatants of spleen cells and peritoneal macrophages of both strains. SD rats, which are the least susceptible to P. berghei sporozoites, showed significantly higher IL-6 production by macrophages from both sources. When LPS was administered in vivo, SD rats also had a significantly higher IL-6 response. Hepatocytes from both strains were cultured in the presence of IL-6. After three days of culture, alpha 2-Macroglobulin concentrations in the supernatants of SD hepatocytes were much higher than those from BN rats. Kupffer cell depletion in both BN and SD rats was correlated with a significant increase in liver schizont density, but did not abrogate the difference in susceptibility. From these results we conclude that the higher cytokine production capacity of SD rats compared to BN rats, may contribute to the difference in susceptibility to P. berghei sporozoites between these strains, but that other yet unknown factors are also involved.

Acute-Phase Proteins↗
PubMed1995

A comparison of transmission-blocking activity with reactivity in a Plasmodium falciparum 48/45-kD molecule-specific competition enzyme-linked immunosorbent assay.

Monoclonal antibodies (MAbs) 32F1 and 32F3 react with two independent epitopes of a protein doublet with molecular weights of 48 and 45 kilodaltons (kD) expressed on the surface of Plasmodium falciparum (Pfs48/45) macrogametes and zygotes; only 32F3 blocks transmission. These MAbs were used to develop a Pfs48/45-specific competition enzyme-linked immunosorbent assay (ELISA) using 32F1 to capture antigen and labeled 32F3 for quantification and analysis of the contribution of antibodies in human serum to transmission-blocking activity. A comparison analysis was used to determine agreement of competition ELISA titers and transmission-blocking activity as observed in the bioassay in three groups of serum samples: 37 from European travelers with previous exposure to malaria, 56 from gametocyte carriers, and 66 from schoolchildren from a malaria-endemic area in Cameroon. The index of agreement between outcomes of the ELISA and transmission-blocking assay in gametocyte carriers and in travelers was specifically defined as fair-to-moderate; in schoolchildren the agreement was not significant. The combined analysis of all sera showed a significant and fair-to-moderate agreement between the results of the competition ELISA and the transmission-blocking assay, with a relative specificity of 94% (of 105 cases negative in the transmission-blocking assay, 99 were also negative in the competition ELISA) and a relative sensitivity of 44% (of 54 cases positive in the transmission-blocking assay, 24 were also positive in the competition ELISA). This study shows that a positive C48/45-ELISA is indicative for transmission-blocking activity in the mosquito assay, while a negative result does not exclude transmission-blocking activity.

Adolescent↗
PubMed1994

Ultrasound determination of the effect of progestogens on the endometrium in postmenopausal women receiving hormone replacement therapy.

Progestogen challenge tests were performed in 81 postmenopausal women receiving hormone replacement therapy (HRT) with progestogen addition as required. The number of tests carried out totalled 159. The effect of progestogen use on endometrial thickness was determined by vaginosonography. The endometrial shedding caused by progestogen was correlated with the withdrawal bleeding pattern. As expected, in the majority of cases (145 out of 159), progestogen brought about endometrial shedding. In most but not all cases, shedding was attended by withdrawal bleeding. The intensity and the duration of withdrawal bleeding were positively correlated with endometrial shedding. No correlation was found between endometrial shedding and the onset of withdrawal bleeding.

Adult↗
PubMed1994

Transmission blocking immunity as observed in a feeder system and serological reactivity to Pfs 48/45 and Pfs230 in field sera.

Monoclonal antibodies (mAbs) and human sera from gametocyte carriers were applied in the bio-assay to test for their transmission-blocking capacity. Competition ELISA's have been developed for the detection of natural transmission blocking antibodies. Approximately 55% of the sera blocking in the bio-assay gave positive results in these competition ELISA's.

Adult↗
PubMed1994

Malaria chemosuppression during pregnancy. VI. Some epidemiological aspects of malaria in infants.

The possible influence of maternal malaria prophylaxis on infancy malaria was assessed in 241 infants. Mothers of 91 infants (PROG-cohort), 99 infants (CQ-cohort) and 51 infants (CQ+PROG-cohort) had received prophylaxis with daily proguanil, once weekly chloroquine, and the two drug combination respectively. Blood smears of infants were examined for parasitaemia once fortnightly. Parasitaemias were treated with either amodiaquine, Fansidar, or Fansidar-quinine combination. In all cohorts, the incidence of malaria parasitaemias within 3 months of age was high (overall mean = 63%). Chloroquine released from its tissue bound form in the CQ and CQ+PROG-cohorts did not have significant chemosuppressive effects on the parasitaemias. Acknowledging that the CQ-prophylaxis group simulated the hypothetical control group, the cohorts similarity in the pattern of parasitaemias suggested that effective maternal malaria chemoprophylaxis during pregnancy did not significantly influence infancy malaria. A sharp rise in incidence around 3 months was indicative of the waning effect of passive immunity. Sole dependence on sub-optimal active immunity led to another sharp rise in incidence from 9 months onwards. The high incidence of infancy malaria parasitaemias calls for increased vigilance in their early detection and effective treatment. Social-cultural factors within the communities may constrain effective disease management.

Age Factors↗
PubMed1993

[Ultrasonographic diagnosis of endometrial disorders: correlation with the histological results in 112 patients].

The diagnosis of endometrial lesions hitherto was mainly made on the basis of histological examination. The objective of this study was the assessment of the diagnostic accuracy of transvaginal ultrasound investigation by comparison with the usual histological investigation, which implies painful endometrial sampling. 112 perimenopausal women with irregular vaginal blood loss were examined by transvaginal ultrasound. Shortly afterwards endometrial sampling was performed by means of aspiration, conventional curettage or hysteroscopically guided biopsies. The group of 112 patients included 11 women who had previously received hormone substitution therapy (10%). The other patients (without previous hormone substitution therapy) were divided into a premenopausal group (n = 47) and a postmenopausal group (n = 54). In case of an endometrial thickness (single layer) of less than 3 mm in postmenopausal patients, no (pre)malignant lesions were found. In the pre- and postmenopausal group, using this cut-off-level two of the five endometrial hyperplasias were ultrasonographically missed. All fourteen endometrial carcinomas in 112 patients were ultrasonographically detected by an endometrial thickness > or = 4 mm. In the postmenopausal group specificity was 73% (16/22) using a cut-off-level of 3 mm, in the premenopausal patients it was only 36% (11/31). Regular echo-density or a clear alignment between endo- and myometrium hardly had any value in the diagnosis of (pre)malignant lesions of the endometrium. If our patients with an endometrial thickness of less than 3 mm would not have had an endometrial curettage, 38 of 112 (34%) endometrial samplings might have been avoided. According to our view, transvaginal endometrial examination can be of distinct value in the detection of (pre)malignant endometrium.

Biopsy, Needle↗
PubMed1993

Plasmodium berghei: recombinant interferon-gamma and the development of parasitemia and cerebral lesions in malaria-infected mice.

Mice infected with Plasmodium berghei K173-parasitized erythrocytes develop severe hypothermia followed by death as a consequence of murine cerebral malaria early in the second week after infection. A single intraperitoneal injection of 10(5) Units of IFN-gamma given between Day 4 and Day 6 postinfection results in a transient decrease of body temperature. No effect on parasitemia and cerebral malaria is obtained by this treatment. Daily injections of relatively low doses of IFN-gamma delays the patency of the infection for 2 days. Furthermore the proliferation rate of the parasites is reduced and the development of cerebral malaria is also delayed for 2 days. The reduction of body temperature, as found in untreated infected mice, is absent. Administration of IFN-gamma by means of a continuous delivery from intraperitoneally inserted osmotic pumps (1.2 x 10(4) Units of IFN-gamma/24 hr) also delays patency and inhibits parasitemia. Body temperature decreases during infection but mice are protected against the development of cerebral malaria. In nude mice, this treatment inhibits parasitemia to the same extent. However, reduction of body temperature was also prevented. High doses of IFN-gamma delivered by osmotic pumps (2.5 x 10(4) or 10(5) Units of IFN-gamma/24 hr) appear to be lethally toxic in conventional as well as in nude mice, independently of infection. Cerebral malaria-like symptoms are found in these mice. Treatment of infected C57BL/6J mice with antibody to IFN-gamma 4 days before and after infection as well as on the day of infection enhances parasitemia but does not affect the development of murine cerebral malaria. Single injections of anti-IFN-gamma-antibody 6 hr prior to infection or 7 days after infection have no effect. In CBA/Ca mice, treatment with anti-IFN-gamma-antibody enhances parasitemia; furthermore protection against cerebral malaria was obtained in part of the mice.

Animals↗
PubMed1993

Tumour necrosis factor-alpha and macrophages in Plasmodium berghei-induced cerebral malaria.

The effect of tumour necrosis factor-alpha on malaria-infected mice was studied. C57Bl/6J mice infected with Plasmodium berghei K173 exhibited an increased sensitivity to exogenous TNF. Injection of 15 micrograms TNF was lethal to some of the animals when given 5-7 days after infection, while when given later on in the infection (i.e. days 8-10) amounts as low as 2.5 micrograms TNF appeared to be lethal in all mice. The pathology in infected mice treated with TNF resembled that found in the brains of infected mice dying with cerebral malaria. Infected mice treated with TNF, however, also developed severe pathological changes in other organs. On the contrary, treatment with sublethal amounts of TNF (1.0 micrograms or less) given on days 8 and 9 after infection, protected mice against the development of cerebral malaria. In addition, infected mice exhibited and enhanced sensitivity for treatment with lipopolysaccharide (LPS). Sublethal amounts of LPS, however, did not prevent mortality as in TNF-treated mice (LPS-treated mice died at about the same time as infected mice that developed cerebral malaria), but no cerebral haemorrhages were found in the majority of LPS treated, infected animals. Treatment with dexamethasone during infection protected mice against the development of cerebral malaria, but did not suppress their increased sensitivity to exogenous TNF. Treatment of mice with liposome-encapsulated dichloromethylene diphosphonate (lip-Cl2MDP), used to eliminate macrophages (an important source of TNF), prevented the development of cerebral malaria, but only when given before day 5 of infection. Mice protected by treatment with lip-Cl2MDP, however, remained sensitive for LPS on the eighth day of infection.

Animals↗
PubMed1993

Kupffer cell elimination enhances development of liver schizonts of Plasmodium berghei in rats.

We investigated the development of exoerythrocytic forms (EEF) of Plasmodium berghei in livers of normal and macrophage-depleted Brown Norway rats. Macrophages were depleted by use of liposome-encapsulated dichloromethylene diphosphonate. Upon inoculation of sporozoites, macrophage-depleted rats had significantly larger numbers of EEF than untreated rats. We also investigated the effect of macrophage impairment by silica treatment on the development of EEF and confirmed that silica induces a significant reduction of EEF development. Intravenous administration of silica induced high levels of interleukin-6 in plasma within a few hours. The seemingly contradictory results for EEF development may be explained by our previous observation that interleukin-6 strongly inhibits sporozoite penetration and EEF development in vivo. We conclude that in experimental infections with sporozoites, Kupffer cells inhibit rather than enhance EEF development.

Animals↗
PubMed1993

Experimental infections of Anopheles gambiae with Plasmodium falciparum of naturally infected gametocyte carriers in Cameroon: factors influencing the infectivity to mosquitoes.

Factors which could influence the success of experimental infections of Anopheles gambiae with Plasmodium falciparum were investigated in Cameroon. 139 experimental infections with different gametocyte carriers were performed. 86 (62%) gave rise to mosquito infection after dissection of at least 20 mosquitoes. Among succeeding infections, the mean percentage of infected mosquitoes was 18.6% and mean oocyst load per positive midgut was 2.56. Only gametocyte density was identified as a factor which determined the success and the level of mosquito infection. No significant influence was found for sex and age of the gametocyte carrier, body-temperature, presence of asexual erythrocyte stages, rhesus factor, blood group and use of antimalarial drugs (chloroquine and amodiaquine).

ABO Blood-Group System↗
PubMed1993

Malaria chemosuppression during pregnancy. IV. Its effects on the newborn's passive malaria immunity.

The effect of malaria prophylaxis during pregnancy on the levels of cord blood anti-sporozoite antibodies was investigated in 203 newborns in Muheza, Tanzania. Mothers of 76 newborns had received prophylaxis with proguanil daily (PROG), 66 chloroquine once weekly (CQ), and 61 got a combination of the two drugs (CQ+PROG). Prophylaxis with PROG or CQ+PROG was more efficacious than with CQ. The mean antibody titres were comparable in all three groups, despite titres being significantly low in mothers of the CQ+PROG group. In 93% of 167 paired maternal-cord sera, maternal titres were higher than cord titres. The correlation between maternal and cord titres was low. Parity, placental malaria, and baby maturity showed little influence on titres. Titres of babies delivered by Caesarean section or whose placenta weighed between 0.75 and 1 kg were comparatively low. The first occurrence of a malaria parasitaemia in infants was independent of the levels of cord titres at birth. The results suggested that chemoprophylaxis as effective as PROG or CQ+PROG in holoendemic areas, insignificantly affects maternal-foetal transfer of anti-sporozoite antibodies, and that levels of these antibodies at birth do not modulate the first occurrence of infancy malaria parasitaemia. Interference with the maternal-foetal transfer of this antibody and possibly other component antibodies of passive immunity should not limit the selection of PROG or CQ+PROG for chemoprophylaxis.

Animals↗