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Biomedical subjects

J Groen

Publications and source records attributed to J Groen.

At least 55 records · Page 3Linked to original sources
PubMed1999

On the performance and accuracy of 2D navigator pulses.

The purpose of this study was to investigate and to optimize the performance of two-dimensional spatially selective excitation pulses used for navigator applications on a clinical scanner. The influence of gradient imperfections, off-resonance effects, and incomplete k-space covering on the pencil beam-shaped spatial excitation profile of the 2D RF pulse was studied. The studies involved experiments performed on phantoms and in vivo. In addition, simulations were carried out by numerical integration of the Bloch equations. The accuracy of positioning of the pencil beam was increased by a factor of three by employing a simple correction scheme for the compensation of gradient distortions. The spatial selectivity of the 2D RF pulse was improved by taking sampling density corrections into account. The 2D RF pulse performance was found to be sufficient to monitor the diaphragm motion even at moderate gradient strength. For applications, where a high spatial resolution is required or a less characteristic contrast is present a strong gradient system is recommended.

Artifacts↗
PubMed1999

Diagnostic value of dengue virus-specific IgA and IgM serum antibody detection.

The diagnostic value of dengue virus (DV)-specific immunoglobulin A (IgA) serum antibody detection, by an indirect immunofluorescence assay (IFA) was evaluated. For this study, the kinetics of DV-specific IgA serum antibodies was analysed in two experimentally immunised macaques, paired samples from 35 patients suspected of a primary or secondary DV infection, paired sera from patients with high levels of IgA specific antibodies against influenza virus (n = 15), sera from patients with other viral infections (n = 40) and healthy blood donors (n = 10), which served as controls. The presence of DV-specific IgA serum antibodies in humans and in monkeys was compared with that of DV-specific IgM demonstrated in a capture enzyme-linked immunosorbent assay (ELISA). The development of DV-specific IgA and IgM antibodies in macaques proved to be similar to that observed in humans with a DV infection. In sera obtained from suspected primary DV patients during the acute phase and convalescent phase, DV-specific IgA was detected in 1/6 (17%) and 6/6 (100%), whereas IgM was detected in 4/6 (67%) and 5/6 (83%), respectively. In sera from suspected secondary DV patients during the acute phase and convalescent phase, DV-specific IgA was detected in 18/29 (62%) and 28/29 (97%), whereas IgM was detected in 20/29 (69%) and 28/29 (97%), respectively. The control group consisted of five paired serum samples from yellow fever vaccinated individuals and a patient with acute tick-borne encephalitis, 15 paired serum samples from patients with high levels of IgA antibodies specific for influenza virus and 40 serum samples from patients with specific IgM antibodies against other viruses. Ten serum samples from healthy blood donors were included. Among the control serum samples, in one patient, both DV-specific IgA and IgM antibodies were present, and in three sera DV-specific IgM antibodies could be demonstrated. These data suggest that detection of DV-specific IgA serum antibodies by IFA may have additional value for the diagnosis of DV infection.

Animals↗
PubMed1999

IgM antibodies in hospitalized children with febrile illness during an inter-epidemic period of measles, in Somalia.

BACKGROUND: In the context of the measles elimination programme, endorsed by the expanded programme on immunization of the World Health Organization, the identification of infections which may be confused with measles is a major challenge. OBJECTIVE: To determine the causes of febrile illness in children in an inter-epidemic period of measles in a Somalian hospital. STUDY DESIGN: Serological tests were performed on sera from 23 Somali children with febrile illness and from 23 age matched children, to measure the specific IgM and IgG antibodies against measles virus, mumps virus, rubella virus, human herpes-6 virus, Epstein Barr virus, parvovirus B19, dengue virus, Mycoplasma pneumoniae and Rickettsia conorii. RESULTS: In about one third of the cases of febrile illness viral, mycoplasmal and rickettsial agents could be identified serologically as the probable cause of the disease. CONCLUSIONS: Although febrile illness with rash in children needing hospitalization is usually assumed to be due to measles, there are several other important virological causes of this condition which need to be considered in the differential diagnosis. Moreover there is a growing need to develop a simple, sensitive, specific and ready to use test to identify each case of measles, if this disease is to be eliminated.

Antibodies, Bacterial↗
PubMed1999

Evaluation of a fully automated glycoprotein G-2 based assay for the detection of HSV-2 specific IgG antibodies in serum and plasma.

BACKGROUND: Ranking after infections with Chlamydia trachomatis and human papillomavirus, genital herpesvirus is the third most common sexually transmitted disease. The majority of recurrent genital herpes infections are caused by herpes simplex virus type-2 (HSV-2). Seroepidemiological studies on the prevalence of HSV-2 specific IgG antibodies are especially important to study the impact of this infection among risk groups. OBJECTIVE: To evaluate the sensitivity and specificity of the Cobas Core HSV-2 IgG specific assay (available for research use only), that can be run on the Cobas Core fully automated immuno-analyzer. STUDY DESIGN: The Cobas Core HSV-2 specific IgG EIA is based on macro-beads coated with affinity purified glycoprotein G-2 antigen from HSV-2 infected cells. The Cobas Core HSV-2 IgG specific assay was compared with the Chiron rapid immunoblot assay (RIBA), the Gull enzyme-linked immunosorbent assay (EIA) and the Centocor EIA. The respective assays were tested, using 1219 serum samples, from 612 females and 607 males attending the outpatient clinic for sexually transmitted diseases of the Erasmus Medical Center Rotterdam (EMCR). RESULTS: The consensus value, obtained by a concordant result with three out of four assays, demonstrated 350 positive samples (28.7%), 851 negative samples (69.8%) and 18 (1.5%) serum samples with a discordant result. The overall agreement of the Cobas Core HSV-2 EIA against the consensus value was 95.8% and the sensitivity and specificity proved to be 100 and 97.1% respectively. CONCLUSION: The results obtained with the Cobas Core HSV-2 EIA indicate that this is a useful, specific and sensitive assay for the detection of HSV-2 specific IgG antibodies in serum. The advantage of the Cobas Core HVS-2 EIA compared to the other assays, is that this assay can be performed in a fully automated process.

Adolescent↗
PubMed1999

Low prevalence of antibodies against the zoonotic agents Brucella abortus, Leptospira spp., Streptococcus suis serotype II, hantavirus, and lymphocytic choriomeningitis virus among veterinarians and pig farmers in the southern part of The Netherlands.

Serum samples from 102 veterinarians and 191 pig farmers from the southern part of the Netherlands were investigated for antibodies against Brucella abortus, Leptospira spp, Streptococcus suis serotype II, Hantavirus (HV), and lymphocytic choriomeningitis virus (LCMV). All samples were collected in 1993 and stored until this study was performed. The prevalence of antibodies against B.abortus in veterinarians (4.5%) was significantly higher (P = 0.01) than in pig farmers (0%). None of the veterinarians (0%) and only one pig farmer (0.5%) had antibodies against Leptospira spp. Furthermore, significantly (P = 0.015) more veterinarians (6%) than pig farmers (1%) had antibody titres against muramidase-released protein (MRP),a protein of pathogenic S. suis serotype II strains. None of the veterinarians and a total of 3 (1.6%) pig farmers had antibody titres against HV. The prevalence of antibodies against LCMV tended to be higher in pig farmers (2.6%) than in veterinarians (0%) (P = 0.10). It can be concluded that the prevalence of antibodies against the investigated zoonotic agents in veterinarians and pig farmers is low.

Agriculture↗
PubMed1999

An outbreak of West Nile fever among migrants in Kisangani, Democratic Republic of Congo.

In February 1998, an outbreak of acute febrile illness was reported from the Kapalata military camp in Kisangani, the Democratic Republic of Congo. The illness was characterized by an acute onset of fever associated with severe headache, arthralgia, backache, neurologic signs, abdominal pain, and coughing. In 1 individual, hemorrhagic manifestations were observed. The neurologic signs included an altered level of consciousness, convulsions, and coma. Malaria was initially suspected, but the patients showed negative blood films and failed to respond to antimicrobial drugs. A total of 35 sera collected from the military patients in the acute phase were tested for the presence of IgM against vector-borne agents. Serum IgM antibodies against West Nile fever virus were found in 23 patients (66%), against Chikungunya virus in 12 patients (34%), against dengue virus in 1 patient (3%), and against Rickettsia typhi in 1 patient (3%). All sera were negative for IgM antibody against Rift Valley fever virus, Crimean Congo hemorrhagic fever virus, and Sindbis virus. These data suggest that infections with West Nile fever virus have been the main cause of the outbreak.

Adolescent↗
PubMed1998

Fatal cerebral oedema associated with primary dengue infection.

Encephalopathy associated with dengue fever is considered to be a rare condition in adults. We describe a patient with a primary dengue infection who, in the absence of overt signs of dengue shock syndrome, died due to progressive cerebral oedema. Autopsy findings demonstrated loss of integrity of cerebral vascular endothelium and involvement of complement activation.

Adult↗
PubMed1998

Neuromodulation: urodynamic effects of sacral (S3) spinal nerve stimulation in patients with detrusor instability or detrusor hyperflexia.

The aim of this study was to determine the urodynamic effects of sacral (S3) nerve stimulation in patients with urge incontinence due to detrusor overactivity which has been refractory to conservative treatment. A total of 24 patients with idiopathic detrusor instability and five with neurogenic hyperreflexia were studied urodynamically before and 6 months after a permanent S3 foramen electrode implant. The urodynamic studies at follow-up were done with the stimulus on. Clinically, the average voiding frequency, the number of leakage episodes and pad use per 24 h decreased significantly. Improvement in several urodynamic parameters was noted. In the idiopathic as well as in the neurogenic group, the correlation between symptomatic and urodynamic improvement was incomplete. Neuromodulation leads to improvement of several urodynamic parameters in patients with urge incontinence due to detrusor overactivity which has been refractory to conservative treatment and appears to be a valuable treatment option in these patients.

Adult↗
PubMed1998

Occupational risks of zoonotic infections in Dutch forestry workers and muskrat catchers.

Lyme borreliosis (LymeB), Hemorrhagic fever with renal syndrome (HemoFRS), Lymphocytic choriomeningitis (LymphoCM), Tick-borne encephalitis (TickBE), Q Fever (QFever), and Weil's leptospirosis (Lepto) are known to be occupational diseases for rural outdoor workers. We investigated the occupational infection risks for these diseases in greater detail. Antibodies to these agents were assessed in 312 forestry workers and muskrat catchers, and in 356 matched office workers. Three levels of occupational exposure were distinguished: high for active forestry workers, low for supervisory forestry staff and muskrat catchers and zero for office workers. At high exposure the prevalence odds ratios (with 95% CI between brackets) were: LymeB 15 (5.5-42), HemoFRS 11 (1.3-501), LymphoCM 5.4 (1.0-50), TickBE 1.0 (0.3-3.0), QFever 1.0 (0.4-2.1), and Lepto 0 (0.0-33). No significant risk of infection was found at low exposure. Part of the present group had also been studied in 1989 and 1990. Within this cohort the conversion rates to Borrelia burgdorferi have been estimated for the periods 1989-1990 and 1990-1993 as 0.23 and 0.066 year(-1), respectively, and the reversion rate as 0.44 year(-1). The corresponding values for HemoFRS were 0.031, 0.018 and 1.42 year(-1). Active forestry workers in the Netherlands are at high risk of infection by LymeB, HemoFRS and LymphoCM. Prevalence of antibodies to LymeB and HemoFRS appeared to reflect the levels of these infection hazards in recent history.

Animals↗
PubMed1998

Diagnosis and grading of detrusor instability using a computerized algorithm.

PURPOSE: Detrusor instability and hyperreflexia are characterized by involuntary detrusor contractions in the filling phase of the voiding cycle. The diagnosis is made when urodynamic evaluation reveals such contractions. To compare patients and evaluate treatment a method is needed to quantify the degree of instability. We developed an instability parameter based on the area under the curve of involuntary detrusor contractions on conventional filling cystometry. MATERIALS AND METHODS: We developed an automatic method to calculate the area under the curve of involuntary detrusor contractions in conventional filling cystometry. Logistic regression was used to construct decision rules to differentiate stable from unstable bladders. These rules, derived from a group of 100 children, were applied to a second group of 77 who were independently assessed by 3 urodynamics experts. RESULTS: Typically 88% of the second group were correctly classified as stable or unstable by the automatic procedure. In the unstable subgroup there was poor correlation between the calculated instability parameter and the instability score assigned by the experts. Most likely this difference occurred because the experts based their opinion mainly on the amplitude of the highest unstable contraction and the percentage of filling time that instability was found. CONCLUSIONS: The proposed method of automatically grading detrusor instability based on the area under detrusor contractions differs from the intuitive method used by experts. Since no standard is available, it cannot be concluded which method is better. Our proposed method is objective and it results in a single physical value.

Algorithms↗
PubMed1998

Use of recombinant nucleoproteins in enzyme-linked immunosorbent assays for detection of virus-specific immunoglobulin A (IgA) and IgG antibodies in influenza virus A- or B-infected patients.

The nucleoprotein genes of influenza virus A/Netherlands/018/94 (H3N2) and influenza virus B/Harbin/7/94 were cloned into the bacterial expression vector pMalC to yield highly purified recombinant influenza virus A and B nucleoproteins. With these recombinant influenza nucleoproteins, enzyme-linked immunosorbent assays (ELISAs) were developed for the detection of influenza virus A- and B-specific immunoglobulin A (IgA) and IgG serum antibodies. Serum samples were collected at consecutive time points after the onset of clinical symptoms from patients with confirmed influenza virus A or B infections. Nucleoprotein-specific IgA antibodies were detected in 41.2% of influenza virus A-infected patients and in 66. 7% of influenza virus B-infected patients on day 6 after the onset of clinical symptoms. In serum samples taken on day 21 (influenza virus A-infected patients) or day 28 (influenza virus B-infected patients), nucleoprotein-specific IgA antibodies could be detected in 58.8 and 58.3% of influenza virus A- and B-infected patients, respectively. At the same time, IgG antibody rises were detected in 88.2% of influenza virus A-infected patients and in 95.8% of influenza virus B-infected patients. On comparison, hemagglutination inhibition assays detected antibody titer rises in 81.3 and 72.7% of patients infected with influenza viruses A and B, respectively. In contrast to the detection of nucleoprotein-specific IgG antibodies or hemagglutination-inhibiting antibodies, the detection of nucleoprotein-specific IgA antibodies does not require paired serum samples and therefore can be considered an attractive alternative for the rapid serological diagnosis of influenza.

Animals↗
PubMed1998

Comparison of two enzyme-linked immunosorbent assays and one rapid immunoblot assay for detection of herpes simplex virus type 2-specific antibodies in serum.

The sensitivities and specificities of three immunoassays for the detection of herpes simplex virus type 2 (HSV-2)-specific immunoglobulin G antibodies in serum, including the one-strip rapid immunoblot assay (RIBA; Chiron Corporation) and two indirect enzyme immunosorbent assays (EIA; Gull Laboratories and Centocor), were compared by testing a panel of 1,250 serum samples from individuals attending an outpatient clinic for sexually transmitted diseases. A qualitative agreement among the three assays was observed with 1,080 serum samples (86.4%); 291 of the serum samples (23.3%) were positive, 789 samples (63.1%) were negative, and 170 serum samples (13.6%) gave a discordant result. Results were considered conclusive when a concordant result was obtained with two of three assays. The sensitivities and specificities of the RIBA, the Gull EIA, and the Centocor EIA proved to be 99.2, 99.7, and 89.9% and 97.1, 96.7, and 99.3%, respectively. These results indicate that the Chiron RIBA and the Gull EIA are especially useful and reliable for the detection of HSV-2-specific antibodies in serum.

Adolescent↗
PubMed1997

Respiratory syncytial virus specific serum antibodies in infants under six months of age: limited serological response upon infection.

The decline of maternal respiratory syncytial virus (RSV) specific serum antibodies was studied in 45 children during the first 6 months of life, using a virus neutralization assay and competition ELISAs measuring fusion protein and glycoprotein specific antibodies. In all children RSV neutralizing antibodies were demonstrated at birth, with titers ranging from 33 to 1382. The calculated mean half life of these antibodies was 26 days. Furthermore, in a group of 38 children with suspected RSV infection, all younger than 6 months of age on admission, the diagnostic value of serological assays was evaluated. In 32 children RSV infection was confirmed by virus isolation, direct immune fluorescence and RT-PCR. In 7 patients of this group a significant titer rise in virus neutralization assay was demonstrated. Six additional RSV infected children could be identified by showing the presence of RSV-specific IgM or IgA serum antibodies or by showing an increase in fusion protein or glycoprotein specific antibodies. All serological tests together identified 13 (41%) of the 32 RSV infected patients. It is concluded that in children of this age group, which represent the majority of patients hospitalized with RSV infections, serological assays not only have a limited diagnostic value but are of limited value for sero-epidemiological studies.

Antibodies, Viral↗
PubMed1997

Impaired cellular immune response in rats exposed perinatally to Baltic Sea herring oil or 2,3,7,8-TCDD.

While the immunotoxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) has been well established, the effects of complex environmental mixtures of polyhalogenated aromatic hydrocarbons (PHAHs) are poorly understood. Many PHAHs, including the polychlorinated-biphenyls (PCBs), -dibenzofurans (PCDFs), and dibenzo-p-dioxins (PCDDs), possess 'dioxin-like' activities, and accumulate in the aquatic food chain. Organisms occupying high trophic levels may therefore be exposed to concentrations which may present an immunotoxic risk. In this study, pregnant PVG rats were administered a daily oral dose of 1 ml of the following during pregnancy and lactation: (1) oil extracted from herring caught in the relatively uncontaminated Atlantic Ocean; (2) oil extracted from herring caught in the contaminated Blastic Sea; or (3) the Atlantic herring oil extract spiked with 2,3,7,8-TCDD. The daily intakes of aryl hydrocarbon (Ah)-receptor dependent toxic equivalents (TEQ) for mothers were 0.3 in the Atlantic group, 2.1 in the Baltic group, and 134 ng/kg body wt. in the 2,3,7,8-TCDD positive control group. Immune function and host resistance to rat cytomegalovirus (RCMV) were assessed in offspring aged 11, 25, 46 or 59 days. Rat pups in the positive control TCDD-spiked group exhibited immunosuppression characterized by reduced thymus weight and cellularity, reduced thymocyte and splenocyte proliferative responses to T-dependent mitogens in vitro, reduced virus-associated natural killer (NK) cell and specific antibody responses. While less pronounced, a similar pattern of effects was observed in the rat pups exposed only to the Baltic Sea herring oil. These immunotoxic effects were transient in both exposure groups, with a time-related recovery in immune function possibly due to the half-life of TCDD in rats and the waning exposure levels in the rapidly growing pups. We previously demonstrated that the same Baltic Sea herring led to impaired natural killer cell and T-lymphocyte function in harbour seals during the course of a long-term captive feeding study. The collective results of these studies in rats and seals indicate the immunotoxic potential of environmental mixtures at current levels in the aquatic environment, and suggest that the developing immune system of young mammals may be at particular risk.

Animals↗