Biomedical subjects

R de Graaf

Publications and source records attributed to R de Graaf.

72 records · Page 4Linked to original sources

PubMed1990

Ambulatory 24-hour pH-metry in the diagnosis of gastroesophageal reflux disease. Determination of criteria and relation to endoscopy.

The results of ambulatory 24-h esophageal pH monitoring in 67 patients with gastroesophageal reflux symptoms (endoscopic esophagitis, n = 44; normal endoscopy, n = 23) were compared with those of 27 normal subjects without reflux symptoms. Patients with reflux symptoms had significantly increased gastroesophageal reflux compared with normal subjects. Acid reflux time was significantly (p less than 0.001) correlated with the severity of endoscopic esophagitis. Linear discriminant analysis was used to differentiate, for each reflux variable, between patients and controls. When the percentage of overall time at pH below 4 was used as a single determinant of gastroesophageal reflux, the sensitivity and specificity were 81% and 85%, respectively, with 4% as upper limit of normal. Pathologic reflux was found in 61% of the patients with negative endoscopy. Long-term ambulatory pH-metry is of clinical value in detecting pathologic reflux in symptomatic patients with negative endoscopy.

Acids↗

PubMed1989

Anteroposterior drawer measurements in the knee using an instrumented test device.

A newly developed instrumented knee laxity tester was used to measure anteroposterior (AP) drawer parameters (Lachmann test) in populations of normal subjects and patients with anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL) insufficiencies. The AP drawer tester features a differential electronic measuring procedure of displacements between patella and tuberosity over a continuous range between 180 and -180 N of AP forces. In the statistical evaluation, shift and compliance (or stiffness) parameters at various forces are considered. In a representative normal population, all relevant parameters were established, thus creating a normal data base for future reference. The average normal AP drawer shift between maximal anterior and posterior forces (180 N) was 6.4 +/- 1.7 mm. Right-left differences and male-female differences were found not to be statistically significant in any of the parameters. The validity of the instrumented drawer tester was confirmed relative to a group of patients with acute documented ligament insufficiencies. Measurements in two groups of patients with chronic postoperative knee instabilities revealed that although the diagnosis of instability could be confirmed, the results could hardly discriminate between ACL and PCL insufficiencies, probably due to unrecognized associated lesions at the time of operation and/or gradual postoperative developments of insufficiencies and deformities. An unexpected finding was that the mean laxities of the uninjured contralateral knees were significantly extended relative to the normal reference group, suggesting that these patients could have been classified as a high-risk group even before the time of injury.

Biomechanical Phenomena↗

PubMed1987

Accuracy and reproducibility of instrumented knee-drawer tests.

Instrumented devices for knee-drawer tests have become popular in orthopaedics relatively recently. The objective of the present study was to document the effects of several parameters on the accuracy and reproducibility of anterior-posterior (AP) drawer measurements. An instrumented knee-drawer tester for AP laxity evaluations was constructed, based on the differential displacement method, measuring shifts of the tuberosity relative to the patella. The accuracy of the AP-shift was determined with the parallel use of a highly accurate roentgen stereo photogrammetric (RSP) measurement system on two postmortem leg specimens. The effects of relative motion between patella and femur were negligible. In addition to AP shifts, significant knee flexion and tibial rotations occurred, although the foot and the thigh were fixed as well as possible. The differential displacement method was effective in circumventing this problem. The accuracy of the AP shift was greater than 10%. The reproducibility of the AP drawer parameters (shifts and compliances) was determined in normal subjects and patients. Tests were made to evaluate the effects of different observers, time sequences, and different days. In addition, effects of muscle relaxation were studied. Overall, the shift parameters at different forces were found to be reproducible to between 5 and 15%. The slopes (compliances) of the laxity curves, at different forces, were found to be reproducible between 20 and 40%. The reproducibility was principally affected by deviations in the subject positioning procedure.

Biomechanical Phenomena↗

PubMed1987

The maturation of the central auditory conduction in preterm infants until three months post term. III. The middle latency auditory evoked response (MLR).

Middle latency auditory evoked responses (MLRs) were recorded in 64 premature infants; serially in 54 of them. The last recording sessions occurred at 50-52 weeks conceptional age (CA), defined as the gestational age (GA) added to the chronological age. The MLRs were analyzed for the components PO, Na and Pa, and the interpeak latency difference (IPLD) Na-PO. The detectability rate of PO and Na reached 80-90% at about 30 weeks CA. Pa reached the highest rate of about 60% at 52 weeks CA. The degree of prematurity did not result in clear differences with respect to the parameter values. Also, the side of stimulation did not influence the MLR parameter values. The latency values of the MLR components are strongly age dependent. Topographic differences were found between the sides ipsi- and contralateral to stimulation. They are, however, different for PO, Na and Pa. The influence of the state of vigilance on the parameter values could generally only be established at CA levels of about 32 and 52 weeks CA. The amplitude values at 52 weeks CA are especially sensitive for sleep or awake state. The particular pattern of age dependency of the different components and their topographic differences are consistent with a differential generation of bilateral nature. The early appearance of the response supports the generation of an early functioning subcortical structure in the auditory pathway.

Arousal↗

PubMed1987

The maturation of the central auditory conduction in preterm infants until three months post term. V. The auditory cortical response (ACR).

Auditory cortical evoked responses (ACRs) were recorded in 65 preterm infants, at least on 3 occasions in 48 of them. The infants were divided into 5 groups according to their gestational age (GA). The recording sessions were performed at 8 conceptional age (CA) levels, defined as the gestational age added to the chronological age. The last recordings were obtained at 50-52 weeks CA. The ACRs were analyzed for the primary complex containing middle latency components (MLR) and the secondary complex, containing the slow late components. The ACR records first appear at about 25 weeks CA, initiating the premature stage followed by a transitional stage around term date and the gradual development into the mature stage, achieved at 50-52 weeks CA. The detectability rate of the various components generally increased with increasing conceptional age, for some of the components, especially N2p and N2, this rate achieved a value of about 80%. The degree of prematurity did not influence appreciably the development of the ACR. The waveforms, and to a lesser extent the latency and amplitude values, are strongly age dependent. Remarkable topographic differences between the ACR parameter latency and more importantly amplitude values are found between the derivations from the vertex and the central temporal areas, supporting the theory of different generation sites for the ACR components. The premature and mature ACR appeared relatively insensitive to changes in the states of vigilance. The ACR in premature infants are useful in developmental studies with respect to the central audition in premature infants and might contribute in the clinical assessment on the quality of the premature central auditory system.

Cerebral Cortex↗

PubMed1987

The maturation of the central auditory conduction in preterm infants until three months post term. II. The auditory brainstem responses (ABRs).

Auditory evoked brainstem responses (ABRs) were recorded in 65 preterm infants (serially in 55 of them), divided into 5 groups, according to their gestational age (GA). The recording sessions were performed at 8 conceptional age levels (CA = GA + chronological age), of which the last two were about 40 and 52 weeks CA. The number of recording sessions varied from one to seven. A full set of ABR latency and amplitude parameters was analyzed including peaks I, II, IIN, III, V and IIc, IIINc and Vc as well as some interpeak latency differences (IPLDs), and the amplitude ratios. The detectability of the different components in the ABR tests at 70 dB reached 80-100% at about 32 weeks CA. The side of stimulation nor the state of vigilance influences the detectability. The degree of prematurity in the 5 GA groups did not influence the development of the parameters. Neither the side of stimulation nor generally the state of vigilance give rise to different parameter values. The thresholds show an age dependent decrease, which is also determined by central maturation. The differential development of the latency decrease of the ABR parameters with increasing conceptional age can be associated with morphological maturational processes and may add weight to the arguments in the delineation of the sources of the ABR. The ipsi- and contralateral central conduction V-II and Vc-IIc do not show latency differences at any CA level. The components IIc and Vc, however, lagged behind in absolute latency compared with II and V. It is concluded that the ABR is a powerful instrument for the study of the maturation of the human auditory pathway in the brainstem. In view of the variability, the detectability and the complex changes within the ABR during the preterm period, its application for clinical purposes during this period has a limited value.

Analysis of Variance↗

PubMed1987

Cortisol and loss of malaria immunity in human pregnancy.

The concentration of both total (bound to corticoid-binding-globulin plus free) and free cortisol was determined in sera from two groups of pregnant women in Tanzania. One group consisted of 152 pregnant women (57 nulliparas and 95 multiparas) exhibiting clinical malaria during pregnancy, and the other group comprised 527 pregnant women (105 nulliparas and 422 multiparas), who did not have a record of malaria during pregnancy. The serum concentration of total cortisol was significantly higher in women with clinical malaria than in women without recorded malaria, and this is true for both nulliparae and multiparae. Free cortisol fractions did not differ significantly between these groups. Indications were obtained that higher total cortisol levels cause loss of malaria immunity rather than being concomitant with malaria infection only. The data are compatible with those of a murine malaria model.

Female↗

PubMed1986

Cortisol levels in human pregnancy in relation to parity and age.

Data are presented of a study on the relationship between cortisol, amenorrhea, parity, and age among pregnant women. Total cortisol concentrations were measured by a radioimmunoassay in healthy pregnant women (n = 527), including 105 nulliparas and 422 multiparas. The serum concentration of total cortisol increased linearly with progression of amenorrhea. Significantly higher cortisol levels were found in nulliparas compared to multiparas and independent of amenorrhea. Since parity and age are strongly correlated, age-dependent changes may contribute to the difference in cortisol level between nulliparas and multiparas. Analysis of the age-dependent changes on this difference in cortisol level showed no significant influence.

Adolescent↗

PubMed1986

The central auditory conduction at term date and three months after birth. II. Auditory brainstem response.

This communication describes the results of auditory brainstem responses (ABRs) obtained in 25 healthy mature newborns with a follow-up at 3 months of age. The combination of ipsi- and contralateral recordings, the intensity series and the comparison with the composite group averages are useful for the identification of the separate ABR components. Differences between the records after right or left ear stimulation were not observed. Comparing our data with those obtained by others, we conclude that the interpeak latency differences (IPLDs) offer a more consistent measure of ABR latency values than the peak latencies measured from stimulus onset. The simultaneously recorded ABRs ipsi- and contralateral to stimulation show both at term, and at 3 months, an equal central conduction time. The ABR II-V complex shows contralaterally a significant shift compared with the ipsilateral II-V complex. The significant latency changes observed between term and at 3 months are due mainly to the latency decrease in the II-III IPLD.

Age Factors↗

PubMed1986

The central auditory conduction at term date and three months after birth. III. Middle latency responses (MLRs).

Middle latency responses (MLRs) were obtained in 25 healthy newborns with a follow-up recording at 3 months in all but three. A four-channel recording provided topographic information. Linkage of the ear references reduced the myogenic contamination of the recordings. P0 and Na proved to be the most consistent components in the sinusoidal MLR wave sequence. Topographic differences suggest a generation of P0 and Na contralateral to stimulation. A significant latency decrease was found for P0 and na between term and 3 months. The most important latency and amplitude changes may occur before term date and immediately thereafter. The MLRs are the link between the auditory brainstem responses (ABRs) and the auditory cortical responses (ACRs), and it may be possible to use them for recordings in newborn infants. They provide information about the generation of specific components as well as regarding the auditory afference in the stimulus propagation between the brainstem and the cortical auditory areas.

Auditory Cortex↗

PubMed1986

The central auditory conduction at term date and three months after birth. IV. Auditory cortical responses.

Auditory cortical responses (ACRs) were recorded in 25 healthy mature newborns with a follow-up at 3 months. The waveform, latencies and amplitudes for the ACRs for this time period are studied. Topographic differences between the central and central-temporal derivations and changes between term and 3 months are found with respect to latencies and amplitudes for different peaks and troughs. The ACRs, obtained as a part of a protocol covering the entire auditory afference, offer consistent parameters, which can be used to study developmental neurophysiological properties of audition and which are potential diagnostic tools for the detection of deviant sensory or mental development.

Auditory Cortex↗

PubMed1986

Feasibility of a concanavalin A-peroxidase labeling method to detect cancerous and precancerous lesions of the uterine cervix.

For the detection of cancerous and precancerous lesions in cervical cytopathology, the feasibility of a concanavalin A-peroxidase labeling procedure was tested and compared with the Papanicolaou method. To this end, the percentage of labeled flattened epithelial cells with a morphologically normal appearance present in cervical cell suspensions was determined. It was found that the mean labeling percentage of the control group was 71% (SD, 11%). The means for mild, moderate, and severe dysplasia groups were, respectively, 54% (SD, 19%), 48% (SD, 13%), and 44% (SD, 16%). The mean for the carcinoma in situ group was 32% (SD,11%), and for the squamous cell carcinoma group 16% (SD, 5%). It appeared that the labeling percentage gradually decreases with increasing atypia of the epithelium as confirmed by histological observation. A complete dissimilarity was found between healthy individuals and cancer patients. In a follow-up study it was found that the mean labeling percentage did not alter in cases of an unchanged stage of disease. A reestablishment of the normal concanavalin A-peroxidase labeling percentage often appeared once the cancerous or precancerous lesion was treated. In conclusion, the concanavalin A-peroxidase labeling method can be considered as a supplementary technique to the Papanicolaou method for the early detection of cervical cancer. It reduces the effect of sampling and screening errors of the Papanicolaou method, and it allows a more objective cytological diagnosis. In addition, it may possess prognostic significance.

Carcinoma in Situ↗

PubMed1985

Concanavalin A-peroxidase labeling in cervical exfoliative cytopathology. II. Routine assessment of labeling results.

Concanavalin A-peroxidase (Con A-HRP) labeling of exfoliated cells of the uterine cervix have been shown to possess clinical significance in the detection of cancer. In the present study, a more simple method is used instead of the earlier applied complicated method. These two procedures for the assessment of the labeling results are compared. The first method is an objective machine-aided assessment procedure, consisting of a light microscope connected with a video system used in the sliced mode. The second is a more subjective method using human visual assessment with a light microscope only. The latter method would be suitable for routine use, if it shows similar Con A-HRP labeling results as obtained with the machine-aided procedure. In comparison with the machine-aided assessment procedure, the visual assessment procedure is less accurate. Moreover, the visual assessment is accompanied by intraobserver (between day) and interobserver variations. Although the discriminatory capacity in the detection of cancer patients is significantly lower for the human visual assessment procedure, this difference is small. It is of clinical relevance that in general a complete discrimination of healthy individuals and cancer patients is still possible. Therefore, visual assessment with a light microscope only, is preferred because of its simple equipment, which allows this procedure to be used as a routine method.

Carcinoma, Squamous Cell↗

PubMed1984

Use of the enzyme-linked immunosorbent assay for the early diagnosis of Mycoplasma pneumoniae infection.

IgM and IgG antibodies to Mycoplasma pneumoniae were measured in 147 sera from four groups of patients by means of an indirect enzyme-linked immunosorbent assay (ELISA) and the results compared with those obtained by other methods. A good correlation was demonstrated between the complement fixation test and ELISA-IgM and to a lesser extent ELISA-IgG; for the metabolic inhibition test the reverse was the case. The indirect haemagglutination test appeared to detect mainly IgM antibodies. Low levels of IgM antibodies were detected by ELISA in 60 sera of children not suffering from pneumonia. However, if only high titres (greater than 800) were regarded as indicative of Mycoplasma pneumoniae infection, a presumptive diagnosis could have been made in 42 of 73 single acute phase sera from patients. Comparable results were obtained with IHA. The diagnostic level of IgM antibodies. was reached during the second week of the disease. It is concluded that examination of a single serum sample by either ELISA-IgM or IHA may assist in early diagnosis of Mycoplasma pneumoniae infection.

Antibodies, Bacterial↗

PubMed1979

EEG spectra in children aged 8, 9 and 10 years. Reference values.

In a group of normal children aged 8, 9 and 10 years power density spectra of a 100-second EEG period were made over four different brain regions. All children had to undergo medical and psychological examinations prior to this EEG and the criteria for normality were based on these examinations. Reference values of the power density distribution for children between 8 and 10.5 years are given.

Age Factors↗

PubMedDate not supplied

Cortisol and Plasmodium falciparum infection in pregnant women in Kenya.

Women living under holoendemic conditions of malaria in Kenya exhibited an increased prevalence of clinical malaria during pregnancy. In addition parasite rate and density were higher in primigravidae compared to multigravidae. Higher serum cortisol concentrations were found in women with patent malaria during pregnancy and the levels were higher before, during and after the malaria episode. A causal relation between serum cortisol levels and suppression of malaria immunity during pregnancy is discussed.

Adolescent↗

PubMedDate not supplied

Detectability of auditory evoked response components in preterm infants.

In determining the detectability of brainstem, middle latency and cortical auditory evoked responses in preterm newborns, one has to deal with the ongoing maturation of the auditory system. In the preterm period the detectability of evoked responses is closely related to the appearance of the individual evoked response components. The detectability of the individual evoked response components in preterm infants is important, because low detectability rates make the absence of a particular evoked response component irrelevant with respect to the clinical-neurophysiological correlation. In a longitudinal study we determined the detectability and cumulative detectability, i.e. the presence of individual evoked response components in one or more recordings of evoked response components in 37 low risk preterm infants between 30 and 41 weeks conceptional age (CA). On the basis of their detectability it is concluded that evoked response components, determined between 30 and 34 weeks CA, are generally of limited use for clinical application, except for auditory brainstem response (ABR) components I, IIn, V and Vc and middle latency response (MLR) component Na. Our study made clear that improvement can be achieved by performing more than one examination within a period of approximately 4 weeks between the recording sessions. The cumulative detectability rates after two recordings showed improvement for all components involved in this study. The cumulative detectability rates of ABR components I, II, IIN, III, V, IIc, IIINc, Vc, MLR components Na and P0, and auditory cortical response (ACR) components PbP1 and N2p are sufficient to use as measures in the neurophysiological judgement of functional integrity of the central auditory pathway in preterm infants.

Auditory Cortex↗

PubMedDate not supplied

Urinary excretion of hydroxylysine and its glycosides in normal persons of different ages--influence of maturation.

Basement membrane collagen is relatively rich in hydroxylysine and the glycosides of hydroxylysine, glucosylgalactosylhydroxylysine and galactosylhydroxylysine. In this paper a modified procedure for analysis of these substances in urine is described, using a purification-step with the cation-exchange resin Amberlite CG-120 type II and a modified program for amino acid analysis. Values are obtained from 75 healthy persons of different ages ranging from prematurity to adulthood. The influence of maturation is studied. Prematures and young children have a high and rather variable excretion of all components, whereas adults have low and similar excretion rates. Neither the ratio glucosylgalactosylhydroxylysine/galactosylhydroxylysine nor the percentage of glycosylated hydroxylysine can be shown to be age-dependent. These data are important for the study of collagen disorders, especially in childhood.

Adolescent↗