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Biomedical subjects

R de Boer

Publications and source records attributed to R de Boer.

At least 19 recordsLinked to original sources
PubMed1995

The decay of house dust mite allergens, Der p I and Der p II, under natural conditions.

BACKGROUND: Fluctuations in the level of mite allergens in domestic house dust are the result of changes in the balance between synthesis, removal and decay. Purely physical forces as well as enzymatic degradation, mediated by house dust inhabiting microbes, may contribute to the decay of allergens in domestic dust. Knowledge about the speed of decay is essential for an understanding of the dynamics of allergen levels. OBJECTIVE: The present study is a quantitative assessment of the speed of decay at nine combinations of temperature (15 degrees C, 20 degrees C and 25 degrees C) and relative humidity (33%, 55% and 75%). METHODS: Samples of mite infested material of an old rug were stored at these temperature/relative humidity-combinations for 6, 12 or 18 months, after the mites were killed by either a freezing treatment or an acaricide (lindane). The microbes living in the rug presumably survive these treatments. Concentrations of Der p I and Der p II + Der f II, in extracts of the rug material, were measured by radio immunoassay. RESULTS: No significant changes in the levels of der p I and Der p II + Der f II, could be detected even after 1 1/2 year at a high temperature and humidity. CONCLUSION: These findings indicate that mite allergens can be extremely stable under normal domestic circumstances.

Allergens↗
PubMed1995

Genotypic and phenotypic analysis of Borrelia burgdorferi isolates from The Netherlands.

Sixty-three Borrelia burgdorferi isolates recovered from Ixodes ricinus ticks collected in 17 locations in The Netherlands and three Dutch human skin isolates were characterized by rRNA gene restriction fragment length polymorphism, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and Western blotting (immunoblotting). All three human isolates belonged to B. burgdorferi group VS461. Of the tick isolates, 29 (46%) were B. burgdorferi sensu stricto, 2 (3%) were group VS461, 19 (30%) were Borrelia garinii, and 13 (21%) were different from any previously described genomic species. On the basis of the criteria described, 12 isolates formed a distinct genomic group, designated M19. rRNA gene restriction patterns of the group M19 isolates resembled but were not identical to the B. garinii patterns. Hybridization of digested DNA with a flagellin probe confirmed the separation of group M19 from the B. garinii isolates. One isolate, M63, was different from all the others. In conclusion, the occurrence of B. burgdorferi sensu stricto, B. garinii, and B. burgdorferi group VS461 in ticks from The Netherlands corresponds with the occurrence of these genomic species among tick isolates from other European countries. However, our findings suggest that B. burgdorferi sensu lato probably contains more than three genomic species.

Animals↗
PubMed1992

The colonisation of new houses by house dust mites (Acari: Pyroglyphidae).

House dust mites, Dermatophagoides species (Acari: Pyroglyphidae), produce allergens, known for the provocation of asthma and other allergic reactions. To determine the time needed for complete colonisation of a new house by house dust mites, dust samples were collected from carpets of houses varying from 2 weeks to 2 years in age. In contrast to the expectation, no relation was found between age of the houses on the one hand and average levels of mite-allergens Der pI and Der pII and mite numbers on the other. However, presence of dogs appeared to be positively related to allergen levels. Furthermore, carpets in bedrooms appeared to contain more allergens than carpets in living-rooms. Finally, the age of the mattress was not related to allergen levels of bedroom floors.

Allergens↗
PubMed1991

The effect of customized beam shaping on normal tissue complications in radiation therapy of parotid gland tumors.

The impact of customized beam shaping was studied for five patients with parotid tumors treated with a paired wedged field technique. For each patient two plans were generated. The standard plan had unblocked portals with field sizes defined by the largest target contour found in any CT slice. In the second plan customized beam's eye view (BEV) designed blocks were added to both beams. The differences in the dose distributions between the two types of plans were evaluated using dose-volume histograms (DVH). As expected, the dose distribution within the target volume showed no difference. However, a considerable sparing of normal tissue was observed for the plans with customized blocks. The volume of unnecessary exposed normal tissue that received more than 90% of the prescribed dose, was reduced by a factor of about 4: from 165 to 44% on average, if the volume is expressed as a percentage of the target volume in each patient. In particular, the homolateral mandible showed a mean decrease of 21% of integral dose when blocks were used. Normal tissue complication probabilities (NTCP) were calculated. For a tumor dose of 70 Gy, the average bone necrosis probability was reduced from 8.4% (no blocks) to 4.1% (blocks). For other normal tissues such as nervous tissue, other soft tissues and bones a substantial reduction of integral dose was found for all patients when individual blocks were used.

Dose-Response Relationship, Radiation↗
PubMed1990

[Occurrence of Borrelia burgdorferi in Ixodes ricinus in The Netherlands].

In a 1989 surveillance to study the infection rate of Ixodes ricinus ticks with Borrelia burgdorferi, a total of 1838 nymphal and adult Ixodes ricinus ticks were collected from 20 locations in The Netherlands. By means of a culture method using modified Barbour-Kelly-Stoenner medium nymphs were examined in pools of 4 and adults were examined individually. With 63 out of 75 isolates propagation and serological identification were possible. All of these 63 isolates were identified as Borrelia burgdorferi by means of an indirect immunofluorescence assay. In nymphs the minimal infection rate was 2.4%. The rate of infection for adults was shown to be 14.3%. These results are in agreement with the percentages found by other investigators in West-Europe. In all locations examined Ixodes ricinus were found to be infected with Borrelia burgdorferi, although the infection rate varied. The results indicate that the infection is widespread among ticks in The Netherlands and the potential risk of acquiring Lyme borreliosis after a tick bite is serious.

Animals↗
PubMed1990

House-dust mite (Pyroglyphidae) populations in mattresses, and their control by electric blankets.

A reduction in house-dust-mite populations of 19-84% in beds in regular use could be achieved by heating the mattresses with electric blankets, when the beds were not being slept on. The effect of the heating treatment on the temperature and relative humidity inside the mattress is discussed. House-dust mites in the heated portions of the mattress migrated deeper inside the mattress to a depth of 3.5-5.0 cm. Evidence was also found that house-dust mites in non-heated mattresses do not only live near the surface, but that they are also present deep inside the mattress.

Animals↗
PubMed1990

Effect of heat treatments on the house-dust mites Dermatophagoides pteronyssinus and D. farinae (Acari: Pyroglyphidae) in a mattress-like polyurethane foam block.

The behaviour and survival of the house-dust mites Dermatophagoides pteronyssinus and D. farinae were studied under laboratory conditions in a mattress-like polyurethane foam block that was heated by an electric blanket. Mites obtained from a laboratory culture were introduced into the foam block which was sliced into seven horizontal layers and covered with an electric blanket. Measurements of temperature and relative humidity were taken between the layers and the number of living mites was established using the heat-escape method.

Animals↗
PubMed1990

Very early prolonged premature rupture of membranes and survival.

Fetal survival is possible even with very premature rupture of membranes followed by persisting oligohydramnios, secondary Potter facies and limb deformities. A case history is given with continuous amniotic fluid loss starting at 11+4 weeks, without development of pulmonary hypoplasia.

Abnormalities, Multiple↗
PubMed1990

Estrogenic effect of gestodene- or desogestrel-containing oral contraceptives on lipoprotein metabolism.

In a randomized comparative study, changes in lipoprotein metabolism during the use of two low-dose oral contraceptives with similar doses of ethinyl estradiol but with different progestogenically active compounds were evaluated for their effective estrogen/androgen balance. Sixty-eight healthy women who did not take hormonally active drugs or were pregnant the previous 3 months took either 75 micrograms of gestodene + 30 micrograms of ethinyl estradiol or 150 micrograms of desogestrel + 30 micrograms ethinyl estradiol during 12 cycles. During the first three cycles serum levels of the following parameters increased: triglycerides, cholesterol in high-density lipoprotein, and apolipoproteins A1, A2, and B. Additional increase was observed in apolipoprotein B only after three and six cycles. The induced changes were not significantly different in the two groups, and the levels generally remained within normal limits. The changes seen with both pills reflect a mild estrogenic dominance. On the basis of current knowledge, moderately altered lipoprotein metabolism is not expected to impose an extra risk of atherosclerosis.

Adult↗
PubMed1990

Effects of oral contraceptives on lipid metabolism.

A randomized, comparative study of two low-dose oral contraceptives was carried out in 60 nonpregnant women for 12 cycles. Twenty-eight women took a preparation containing 150 micrograms of desogestrel and 30 micrograms of ethinyl estradiol; 32 took 75 micrograms of gestodene and 30 micrograms of ethinyl estradiol. Baseline values in the two groups were in good agreement. During the first three cycles, serum cholesterol levels remained unchanged, but triglyceride and high-density lipoprotein cholesterol levels increased significantly and to the same extent (about 20%). Low-density lipoprotein cholesterol levels decreased slightly. Apolipoproteins A1 and A2 and low-density lipoprotein B increased significantly and similarly. Except for continued increases in low-density lipoprotein B, no further changes were noted during subsequent cycles. We concluded that the two contraceptives have the same impact on lipid metabolism, with all lipid and apolipoprotein values remaining within the normal range. The changes with both pills reflect a mild estrogenic dominance. Implications for coronary artery atherosclerosis appear to be minimal.

Adult↗
PubMed1990

Elevated folate levels in amniotic fluid after oral supplementation.

During oral supplementation of 5 mg folic acid and 1 microgram vitamin B12, the daily folate levels in plasma, red cells and midtrimester amniotic fluid were significantly higher in ten pregnant women during the 15th-18th week of menstrual age as compared to ten non-supplemented women serving as controls. In the control group as well as in the supplemented group, the folate concentrations in amniotic fluid were found to be lower than in the corresponding maternal plasma and red cells. Of all women investigated there was a significant positive correlation between maternal plasma folate concentrations and amniotic fluid levels (r = 0.72, p less than 0.001) and no correlation between red cell folate concentrations and amniotic fluid levels (r = 0.30, p = 0.22). Oral supplementation of vitamin B12 did not elevate maternal blood concentrations and amniotic fluid levels. Vitamin B12 levels in amniotic fluid in this group and controls were always higher than in plasma. These data suggest that the orally administrated dosages of folic acid unlike those of vitamin B12 augment both plasma, red cells and amniotic fluid levels.

Administration, Oral↗
PubMed1990

The control of house dust mite allergens in rugs.

Used rugs were vacuum cleaned, "wet cleaned," "shampooed," or heated in an autoclave. The effects on the live-mite population, on the allergen (Dermatophagoides pteronyssinus, Der p I and Der p II; and Dermatophagoides farinae, Der f II) content, and on the suitability of the rugs as a habitat for house dust mites was studied. Autoclaving was most effective in all three aspects. The cleaning methods were quite inefficient for killing the mites, but a significant reduction of allergens and deterioration of the habitat quality was established. "Wet cleaning" appears particularly promising.

Allergens↗
PubMed1990

[Fetal and neonatal outcome prolonged ruptured membranes in a gestational age of less than 24 weeks].

The view appears to be generally held that the survival chances of fetuses in cases of very early rupture of the membranes are low. We report a retrospective study of 12 pregnancies with prolonged rupture of the membranes less than or equal to 24 weeks menstrual age. There was no significant maternal morbidity. After birth special attention was given to respiratory problems, deformities and infections. Four children were born at menstrual age less than 26 weeks. In all cases an intrauterine infection was found (chorioamnionitis). The eight children born greater than or equal to 26 weeks had good chances of survival despite oligohydramnios (all) and deformities (four). Severe intrauterine infections were not present in this group. An expectant obstetric management in cases of very early prolonged rupture of the membranes seems justified.

Asphyxia Neonatorum↗
PubMed1987

Pregnancy and functional paraganglioma.

The association of pregnancy with a catecholamine-secreting tumor is rare. The high maternal and fetal mortality rate is significantly reduced when the diagnosis is made antepartum and adequate management is started. In 1979 Burgess reviewed 42 cases with antepartum diagnosis, demonstrating the benefits of alpha-blockade (Obstet Gynecol 1979; 53:266-270). When diagnosis was made in the third trimester of pregnancy, a combined procedure of cesarean section and tumor resection was best. The best surgical approach in first- and second-trimester diagnosis, however, remains controversial. A case with second-trimester diagnosis is described. Following a period of alpha- and beta-blockade, a combined surgical procedure in the third trimester resulted in a healthy mother and infant. Follow-up procedures included a meta-iodobenzylguanidine scan of the mother. Postpartum, ultrasonography of the child's brain revealed periventricular leucomalacia. The prognosis associated with this finding is poor. Some more recent information about certain aspects of these tumors is also discussed.

Adult↗