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Biomedical subjects

E de Boer

Publications and source records attributed to E de Boer.

At least 19 recordsLinked to original sources
PubMed2006

Does subfertility explain the risk of poor perinatal outcome after IVF and ovarian hyperstimulation?

BACKGROUND: The primary objective of this study was to investigate whether subfertility explains poor perinatal outcome after assisted conception. A secondary objective was to test the hypothesis that ovarian hyperstimulation rather than the IVF procedure may influence the perinatal outcome. METHODS: Using data from a Dutch population-based historical cohort of women treated for subfertility, we compared perinatal outcome of singletons conceived after controlled ovarian hyperstimulation (COHS) and IVF (IVF + COHS; n = 2239) with perinatal outcome in subfertile women who conceived spontaneously (subfertile controls; n = 6343) and in women who only received COHS (COHS only; n = 84). Furthermore, we compared perinatal outcome of singletons conceived after the transfer of thawed embryos with (Stim + Cryo; n = 66) and without COHS (Stim - Cryo; n = 73). RESULTS: The odds ratios (ORs) for very low birthweight (<1500 g) and low birthweight (1500-2500 g) were 2.8 [95% confidence interval (95% CI) 1.9-3.9] and 1.6 (95% CI 1.2-1.8) in the IVF + COHS group compared with the subfertile control group. The ORs for very preterm birth (<32 weeks) and for preterm birth (32-37 weeks) were 2.0 (95% CI 1.4-2.9) and 1.5 (95% CI 1.3-1.8), respectively. Adjustment for confounders did not materially change these risk estimates. The difference in risk between the COHS-only group and the subfertile group was significant only for very low birthweight (OR 3.5; 95% CI 1.1-11.4), but the association became weaker after adjustment for maternal age and primiparity (OR 3.1; 95% CI 1.0-10.4). No significant difference in birthweight and preterm delivery was found between the group of children conceived after ovarian stimulation/ovulation induction and (Stim + Cryo) and the group of children conceived after embryo transfer of thawed embryos in a spontaneous cycle without ovarian stimulation/ovulation induction (Stim - Cryo). CONCLUSIONS: The poor perinatal outcome in this database could not be explained by subfertility and suggests that other factors may be important in the known association between assisted conception and poor perinatal outcome.

Adult↗
PubMed2006

Differences between hospital- and community-acquired blood exposure incidents revealed by a regional expert counseling center.

OBJECTIVE: One year (2003) regional analysis of all blood exposure incidents from hospitals as well as from the community. DESIGN: Establishment of an easily accessible regional expert counseling center, operating 24 h a day, for all accidental blood exposures. Tasks of the center were to register incoming calls, to inform and counsel the victim, to assess the risk of the incident, and to provide a plan of further actions, including prophylactic measures. SETTING: A Dutch region (Northeast Brabant) with 500,000 inhabitants and two major hospitals (1,786 beds). RESULTS: A total of 454 incidents (1.2 per day) were recorded. Only half of the incidents occurred in the hospital setting (n = 234), whereas the others (n = 220) took place in the community setting. Nearly all (95%, n = 432) incidents occurred during work, and most of them (84%, n = 385) were related to health care activities. In the hospital setting injuries occurred with physicians (13%), nursing staff (45%), operating room (OR) staff (13%), ancillary (18%), others (10%). In the community setting, incidents took place among healthcare workers (48%), detention and police officers (10%), civilians (10%), general practitioners/dentists and their staff (8%), cleaning staff (4%) and work-related incidents not falling into any of the above categories (7%). More low risk incidents took place outside the hospital (87% vs. 68% in hospital), while high-risk incidents predominantly occurred within the hospital setting (23% vs. 6%). The hepatitis-B immunization rate was significantly lower in victims from the community than in those working in hospitals (38% vs. 96%). Reports from incidents in the community setting were delayed. CONCLUSIONS: Incidents that expose individuals to blood-borne pathogens occur equally frequent in the hospital and non-hospital (community) setting. Therefore, a regional expert counseling center, accessible around-the-clock, for all types of blood-exposure incidents is needed. Blood-exposure prevention programs should aim at a reduction of high-risk incidents within hospitals, and at increasing the awareness for vaccination and early reporting within the community setting.

Accidents, Occupational↗
PubMed2006

Shiga toxin-producing Escherichia coli (STEC) O157 outbreak, The Netherlands, September-October 2005.

In September 2005, the first national food-related outbreak of Shiga toxin (Stx)-producing Escherichia coli (STEC) O157 was investigated in the Netherlands. A total of 21 laboratory-confirmed cases (including one secondary case), and another 11 probable cases (two primary and nine secondary cases) were reported in patients who became ill between 11 September and 10 October 2005. Preliminary investigation suggested consumption of a raw beef product, steak tartare (in the Netherlands also known as "filet americain"), and contact with other symptomatic persons as possible risk factors. A subsequent case-control study supported the hypothesis that steak tartare was the source of the outbreak (matched odds ratio (OR) 272, 95% confidence interval (CI) 3-23,211). Consumption of ready-to-eat vegetables was also associated with STEC O157 infection (matched OR 24, 95% CI 1.1-528), but was considered a less likely source, as only 40% of the cases were exposed. Samples of steak tartare collected from one chain of supermarkets where it is likely that most patients (67%) bought steak tartare, all tested negative for STEC O157. However, sampling was done three days after the date of symptom onset of the last reported case. Since 88% of the cases became ill within a two week period, point source contamination may explain these negative results. It is concluded that steak tartare was the most likely cause of the first national food-related outbreak of STEC O157 in the Netherlands.

Disease Outbreaks↗
PubMed2004

[The central-venous compression syndrome: rare, but adequately treatable with endovascular stenting].

Two patients, women aged 30 and 29, had severe chronic pain in the left leg, and a woman aged 36 had pain in the left flank. On the grounds of the clinical symptoms, phlebography and venous-duplex ultrasonography, a central-venous compression syndrome was diagnosed: compression of the left common iliac vein between the crossing right common iliac artery and the body of the fifth lumbar vertebra (May-Thurner syndrome). The patient with left flank pain also had haematuria. Angiography, computed tomography and phlebography revealed that these symptoms were due to compression of the left renal vein between the abdominal aorta and the superior mesenteric artery (nutcracker phenomenon). The treatment of all 3 patients consisted of venous endovascular stenting. At follow-up after 12, 30 and 15 months, respectively, the complaints had subsided considerably.

Adult↗
PubMed2004

Spontaneous basilar membrane oscillation and otoacoustic emission at 15 kHz in a guinea pig.

A spontaneous otoacoustic emission (SOAE) measured in the ear canal of a guinea pig was found to have a counterpart in spontaneous mechanical vibration of the basilar membrane (BM). A spontaneous 15-kHz BM velocity signal was measured from the 18-kHz tonotopic location and had a level close to that evoked by a 14-kHz, 15-dB SPL tone given to the ear. Lower-frequency pure-tone acoustic excitation was found to reduce the spontaneous BM oscillation (SBMO) while higher-frequency sound could entrain the SBMO. Octave-band noise centered near the emission frequency showed an increased narrow-band response in that frequency range. Applied pulses of current enhanced or suppressed the oscillation, depending on polarity of the current. The compound action potential (CAP) audiogram demonstrated a frequency-specific loss at 8 and 12 kHz in this animal. We conclude that a relatively high-frequency spontaneous oscillation of 15 kHz originated near the 15-kHz tonotopic place and appeared at the measured BM location as a mechanical oscillation. The oscillation gave rise to a SOAE in the ear canal. Electric current can modulate level and frequency of the otoacoustic emission in a pattern similar to that for the observed mechanical oscillation of the BM.

Acoustic Stimulation↗
PubMed2002

Escherichia coli O157 infection associated with a petting zoo.

A young child was admitted to hospital with haemolytic-uraemic syndrome caused by infection with a Shiga toxin 2-producing strain of Escherichia coli (STEC) O157. Five days before he became ill, the child had visited a small petting zoo. STEC O157 strains were isolated from faecal samples from goats and sheep housed on the farm. The human and the animal isolates were indistinguishable by molecular subtyping. The petting zoo voluntarily closed temporarily to prevent further cases of infection. Two out of 11 other, randomly selected petting zoos (including one deer park) visited subsequently, tested positive. Furthermore, during the study period there was one more notification of STEC O157 infection possibly linked with a farm visit. Although STEC O157 was indeed found in the petting zoo associated with this patient, transmission through animal contact could not be confirmed because the human isolate was not available for subtyping. The case study and the results of the other on-farm investigations highlight the risk of acquiring severe zoonotic infections during visits to petting zoos.

Animals↗
PubMed2001

Vero cytotoxin binding to polymorphonuclear leukocytes among households with children with hemolytic uremic syndrome.

Hemolytic uremic syndrome (HUS), the leading cause of acute renal failure in childhood, can be caused by different serotypes of vero cytotoxin (VT; i.e., Shiga toxin)-producing Escherichia coli (VTEC). Recently, VT was shown to bind to polymorphonuclear leukocytes (PMNL) in the systemic circulation of patients with HUS. This study investigated whether VT bound to PMNL could be detected in persons in households with patients with HUS. Serum antibodies against E. coli O157 and, when available, fecal samples from patients with HUS and household members were studied for the presence of VTEC infection. The circulating PMNL of 82% of the household members were positive for VT, whereas stool and/or serum examination showed only 21% positivity. Thus, current methods underestimate the number of infected persons in households with patients with HUS.

Adult↗
PubMed2001

Zero-tolerance for faecal contamination of carcasses as a tool in the control of O157 VTEC infections.

The Dutch government, the meat producers organisation and the meat industry have recognised O157 VTEC as an important public health hazard, and agreed on the necessity to improve the hygiene in Dutch cattle- and calf-slaughtering establishments. This paper reports activities within a national action programme to achieve this objective, "Zero-tolerance for faecal contamination during slaughter of cattle and calves". The study included inspection of hygienic performances in slaughterhouses, and visual and microbiological (aerobic plate counts, Enterobacteriaceae counts and O157 VTEC presence/absence on visually clean cattle and calf carcasses) assessment of carcass cleanliness. Initial studies concluded that the hygienic performances in the Dutch cattle and calf slaughterhouses should be immediately improved. In 52% of the slaughterhouses inspected, carcasses were observed to be contaminated with hide, hair or faeces. Around 45% of the slaughterhouses had constructural deficiencies likely to lead to structural cross-contamination of carcasses, by direct carcass-carcass contact, or by indirect contacts with floors, walls or steps. In 39% of the slaughterhouses, cleaning and disinfection procedures were inadequate. Visual inspection of chilled carcasses found that in 11 of the 27 slaughterhouses visited, more than 10% of the carcasses were visibly contaminated. In 6 of the 27 slaughterhouses visited, more than 50% of the carcasses inspected were visibly contaminated. Microbiological analysis of visually clean carcasses noted contamination levels similar to those reported from other countries. O157 VTEC were not isolated during this study. Circulation of these findings lead to increased efforts by all parties to fulfil the requirements of the statutory "Zero-tolerance" programme. A follow-up study noted a significant decrease in the proportions of faecally contaminated carcasses, i.e., 7% of chilled carcasses were visibly contaminated with faeces, as opposed to 22% contamination during the initial study. The follow-up study also noted a greater awareness of the importance of good hygienic practices among slaughterhouse personnel and government meat inspectors.

Abattoirs↗
PubMed2001

Spatio-temporal expression of a gene encoding a putative RNA-binding protein during the early larval development of the mollusc Patella vulgata.

In the mollusc Patella vulgata a cDNA clone named Esther 32 (E32) was found to be expressed in a specific spatio-temporal pattern. DNA sequence analysis showed that E32 represents a putative RNA-binding protein containing a KH domain. In early trochophore larvae, expression of E32 was found in all cells except the already differentiated trochoblasts and the apical tuft cells. Later on in development, expression was also abolished in the presumptive shell gland and restricted to specific areas, among which were the head and foot anlage. This suggests that E32 is involved in maintaining cells in an undifferentiated state via a post-transcriptional mechanism.

Amino Acid Sequence↗
PubMed2001

Electrically evoked otoacoustic emissions from apical and basal perilymphatic electrode positions in the guinea pig cochlea.

Stimulation of the cochlea with sinusoidal current results in the production of an otoacoustic emission at the primary frequency of the stimulus current. In this study we test the hypothesis that the wide frequency response from round window (RW) stimulation is due to the involvement of a relatively large spatial segment of the organ of Corti. Tonotopically organized group delays would be evident from perilymphatic electrode locations that restrict the spatial extent of hair cell stimulation. Monopolar and bipolar-paired stimulus electrodes were placed in perilymphatic areas of the first or third cochlear turns and the electrically evoked otoacoustic emissions (EEOAE) produced by these electrodes were compared to that from the RW monopolar electrode in the anesthetized guinea pig. Current stimuli of 35 microA RMS were swept across the frequency range between 60 Hz and 100 kHz. The EEOAE was measured using a microphone coupled to the ear canal. It was found that the bandwidth of EEOAEs from RW stimulation extended to at least 40 kHz and was a relatively insensitive to electrode location on the RW. The group delay of the EEOAE from stimulation at the RW membrane (corrected to stapes motion) was about 53 micros. First and third turn stimulations from electrode placements in perilymph near the bony wall of cochlea yielded narrower band EEOAE magnitude spectra but which had the same short group delays as for RW stimulation. A confined current (from a bipolar electrode pair) applied close to the basilar membrane (BM) in the first turn produced the narrowest frequency-band magnitude emissions and a mean corrected group delay of 176 micros for a location approximately 3 mm from the high frequency end of the BM (corresponding to about the 18 kHz best frequency location). Bipolar electrodes in the third turn scala tympani produced low pass EEOAE magnitude functions with corrected group delays ranging between approximately 0.3 and 1 ms. The average phase slopes did not change with altered cochlear sensitivity and postmortem. These data indicate that the EEOAE from RW stimulation is the summed response from a wide-tonotopic distribution of outer hair cells. A preliminary model study indicates that short time delayed emissions are the result of a large spatial distribution of current applied to perilymphatic locations possibly giving rise to "wave-fixed" emissions.

Animals↗
PubMed2001

The short-wave model and waves in two directions.

In the region where a sinusoidal wave in the cochlea reaches its maximum amplitude, the long-wave (or one-dimensional) model of the cochlea is deficient. In this region a short-wave model is more appropriate. However, in its current form, the short-wave model supports only waves in one direction. Therefore, it cannot cope with reflection effects associated with, e.g., inhomogeneities. Theoretical explorations of creation and internal reflection of otoacoustic emissions have almost exclusively been based on the long-wave model. In this article the road is paved for future explorations on a generalized form of the short-wave model, one that supports forward as well as backward waves, and thus can include internal reflections.

Cochlea↗
PubMed2000

The mechanical waveform of the basilar membrane. II. From data to models--and back.

Mechanical responses in the basal turn of the guinea-pig cochlea are measured with low-level broad-band noise as the acoustical stimulus [for details see de Boer and Nuttall, J. Acoust. Soc. Am. 101, 3583-3592 (1997)]. Results are interpreted within the framework of a classical three-dimensional model of the cochlea that belongs to a very wide class of nonlinear models. The use of linear-systems analysis for this class of nonlinear models has been justified earlier [de Boer, Audit. Neurosci. 3, 377-388 (1997)]. The data are subjected to inverse analysis with the aim to recover the "effective basilar-membrane impedance." This is a parameter function that, when inserted into the model, produces a model response, the "resynthesized" response, that is similar to the measured response. With present-day solution methods, resynthesis leads back to an almost perfect replica of the original response in the spatial domain. It is demonstrated in this paper that this also applies to the response in the frequency domain and in the time domain. This paper further reports details with regard to geometrical properties of the model employed. Two three-dimensional models are studied; one has its dimensions close to that of the real cochlea, the other is a stylized model which has homogeneous geometry over its length. In spite of the geometric differences the recovered impedance functions are very similar. An impedance function computed for one model can be used in resynthesis of the response in the other one, and this leads to global amplitude deviations between original and resynthesized response functions not exceeding 8 dB. Discrepancies are much larger (particularly in the phase) when a two-dimensional model is compared with a three-dimensional model. It is concluded that a stylized three-dimensional model with homogeneous geometric parameters will give sufficient information in further work on unraveling cochlear function via inverse analysis. In all cases of a sensitive cochlea stimulated by a signal with a stimulus level of 50 dB SPL per octave or less, the resulting basilar-membrane impedance is found to be locally active, that is, the impedance function shows a region where the basilar membrane is able to amplify acoustic power or to reduce dissipation of power by the organ of Corti. Finally, the influence of deliberate errors added to the data is discussed in order to judge the accuracy of the results.

Animals↗
PubMed2000

The mechanical waveform of the basilar membrane. III. Intensity effects.

Mechanical responses in the basal turn of the guinea-pig cochlea were measured with broad-band noise stimuli and expressed as input-output cross-correlation functions. The experiments were performed over the full range of stimulus intensities in order to try to understand the influence of cochlear nonlinearity on frequency selectivity, tuning, signal compression and the impulse response. The results are interpreted within the framework of a nonlinear, locally active, three-dimensional model of the cochlea. The data have been subjected to inverse analysis in order to recover the basilar-membrane (BM) impedance, a parameter function that, when inserted into the (linearized version of that) model, produces a model response that is similar to the measured response. This paper reports details about intensity effects for noise stimulation, in particular, the way the BM impedance varies with stimulus intensity. In terms of the underlying cochlear model, the decrease of the "activity component" in the BM impedance with increasing stimulus level is attributed to saturation of transduction in the outer hair cells. In the present paper this property is brought into a quantitative form. According to the theory [the EQ-NL theorem, de Boer, Audit. Neurosci. 3, 377-388 (1997)], the BM impedance is composed of two components, both intrinsically independent of stimulus level. One is the passive impedance Zpass and the other one is the "extra" impedance Zextra. The latter impedance is to be multiplied by a real factor gamma (0 < or = gamma < or = 1) that depends on stimulus level. This concept about the composition of the BM impedance is termed the "two-component theory of the BM impedance." In this work both impedances are entirely derived from experimental data. The dependence of the factor gamma on stimulus level can be derived by using a unified form of the outer-hair-cell transducer function. From an individual experiment, the two functions Zpass and Zextra are determined, and an approximation (Zpass + gamma Zextra) to the BM impedance constructed. Next, the model response (the "resynthesized" response) corresponding to this "artificial" impedance is computed. The same procedure is executed for several stimulus-level values. For all levels, the results show a close correspondence with the original experimental data; this includes correct prediction of the compression of response amplitudes, the reduction of frequency selectivity, the shift in peak frequency and, most importantly, the preservation of timing in the impulse response. All these findings illustrate the predictive power of the underlying model.

Animals↗
PubMed1999

Isolation and characterization of verocytotoxin-producing Escherichia coli O157 from slaughter pigs and poultry.

Rectal contents and tonsils from Dutch slaughter pigs collected immediately after slaughter were examined for the presence of verocytotoxin (VT)-producing Escherichia coli (VTEC) of serogroup O157 (O157 VTEC). In addition, fresh fecal material from poultry layer flocks and turkey flocks collected on poultry farms was examined for the presence of O157 VTEC. E. coli O157 strains were isolated from two (1.4%) of 145 pigs. The strains were isolated from samples of rectal contents, all samples of tonsils being negative. While all 501 fecal samples from chicken flocks were found negative, E. coli O157 strains were isolated from six (1.3%) of 459 pooled fecal samples from turkey flocks. One of the porcine isolates and one of the turkey isolates contained the VT2 gene, the E. coli attaching-and-effacing gene, as well as the enterohemorrhagic E. coli hemolysin gene. Production of VT was confirmed by cytotoxicity tests on Vero cells. Based on these characteristics, the two stains were regarded as potentially pathogenic for humans. The porcine and the turkey isolate were further characterized as being of phage types 4 and 14, respectively. While biochemically typical of E. coli O157, the remaining six isolates were nonverocytotoxigenic and negative for both the E. coli attaching-and-effacing gene and the enterohemorrhagic E. coli hemolysin gene. All eight E. coli O157 isolates did not carry genes that encode E. coli heat-labile and heat-stable enterotoxins. It was concluded that pigs and poultry can be a source of O157 VTEC strains characteristic of those causing illness in man. The extent to which pigs and poultry play a role in the epidemiology of human O157 VTEC infection needs further research.

Abattoirs↗
PubMed1999

Methodology for detection and typing of foodborne microorganisms.

Over the past decade many improvements have been seen in both conventional and modern methods for the detection of pathogenic bacteria in foods. Modifications and automation of conventional methods in food microbiology include sample preparation, plating techniques, counting and identification test kits. ATP bioluminescence techniques are increasingly used for measuring the efficiency of cleaning surfaces and utensils. Cell counting methods, including flow cytometry and the direct epifluorescent filter technique are suitable techniques for rapid detection of microorganisms, especially in fluids. Automated systems based on impedimetry are able to screen high numbers of samples based on total bacterial counts within 1 day. Immunoassays in a wide range of formats make rapid detection of many pathogens possible. Recently, there have been important developments in the use of nucleic acid-based assays for the detection and subtyping of foodborne pathogens. The sensitivity of these methods has been significantly increased by the use of the polymerase chain reaction and other amplification techniques. Alternative and rapid methods must meet several requirements concerning accuracy, validation, speed, automation, sample matrix, etc. Both conventional and rapid methods are used within hazard analysis critical control point programs. Further improvements especially in immunoassays and genetic methods can be expected, including the use of biosensors and DNA chip technology.

Bacterial Typing Techniques↗
PubMed1999

Risk of persistent cobalamin deficiency in adolescents fed a macrobiotic diet in early life.

BACKGROUND: Cobalamin deficiency has been described in children consuming macrobiotic diets. OBJECTIVE: We investigated whether moderate consumption of animal products is sufficient for achieving normal cobalamin function in 73 adolescents who had received a macrobiotic diet until 6 y of age and had then switched to a lactovegetarian, lactoovovegetarian, or omnivorous diet (macrobiotic adolescents). DESIGN: Hematologic indexes and serum concentrations of methylmalonic acid (MMA), total homocysteine (tHcy), and folate were measured. Current consumption frequency of animal products and cobalamin intake from dairy products were assessed by questionnaire. Data from 94 age-matched adolescents who received an omnivorous diet from birth were used as a reference. RESULTS: Serum cobalamin concentrations were significantly lower and concentrations of MMA and folate and mean corpuscular volume (MCV) were significantly higher in macrobiotic adolescents than in control adolescents: of macrobiotic adolescents, 21% had abnormal MMA concentrations (>0.41 micromol/L), 37% had abnormal cobalamin concentrations (<218 pmol/L), 10% had abnormal tHcy concentrations (> 12.8 micromol/L), and 15% had abnormal MCV (> 89 fL). In macrobiotic adolescents, dairy products (200 g milk or yogurt and 22 g cheese/d) supplied on average 0.95 microg cobalamin/d; additionally, these adolescents consumed fish, meat, or chicken 2-3 times/wk. In girls, meat consumption contributed more to cobalamin status than the consumption of dairy products, whereas in boys these food groups were equally important. CONCLUSIONS: A substantial number of the formerly strict macrobiotic adolescents still had impaired cobalamin function. Thus, moderate consumption of animal products is not sufficient for restoring normal cobalamin status in subjects with inadequate cobalamin intake during the early years of life.

Adolescent↗