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Biomedical subjects

J Nagel

Publications and source records attributed to J Nagel.

At least 37 records · Page 2Linked to original sources
PubMed1994

Neural-network classification of normal and Alzheimer's disease subjects using high-resolution and low-resolution PET cameras.

UNLABELLED: Neural-network classification methods were applied to studies of FDG-PET images of the brain acquired from a total of 77 "probable" Alzheimer's disease and 124 normal subjects at two different centers. METHODS: Classification performances, as determined by relative-operating-characteristic (ROC) analyses of cross-validation experiments, were measured for FDG PET images obtained with either a 15-mm FWHM PETT V or a 6-mm FWHM Scanditronix PC-1024-7B camera for various methods of data representation. Neural networks were trained to distinguish between normal and abnormal subjects on the basis of regional metabolic patterns. For both databases, classification performance could be improved by increasing the "resolution" of the representation (decreasing the region size) and by normalizing the regional metabolic values to the value of a reference region (occipital region). RESULTS: The optimal classification performance for Scanditronix data (ROC area = 0.95) was higher than that for PETT V data (ROC area = 0.87). Under Bayesian theory, the classification performance with Scanditronix data corresponded to an ability to change a pre-test probability of disease of 50% to a post-test probability of either 90% for a positive classification or 10% for a negative classification. CONCLUSION: This classification can be used to either strongly confirm or rule out the presence of abnormalities.

Aged↗
PubMed1993

Serological evaluation of a simplified immunization schedule using quadruple DPT-polio vaccine in Burkina Faso.

The immunogenicity of quadruple DPT-polio vaccine used in a two-dose regimen was investigated in a cross-sectional serological survey involving 355 children under 5 years of age. This schedule is currently applied in the EPI programme in three provinces in Burkina Faso, West Africa. It was found that two doses of quadruple DPT-polio vaccine induced antibodies at protective levels to diphtheria and tetanus toxin, and to the three types of polioviruses in over 90% of 179 children. The persistence of antibodies to tetanus and polioviruses is good, since over 90% of the children studied still had antibodies more than 2 years after their last vaccination. The antibodies to diphtheria toxin tend to decline in the first 6 months after vaccination, which is not uncommon. However, our data indicate clearly that a very high percentage (98%) of children have been primed to diphtheria toxin. Of 176 non-vaccinated children, up to 25% of the older ones had antibodies to polioviruses, most of them only to one type. This appears to be a sensitive parameter for the circulation of wild polioviruses in the environment. As the vaccination coverage in the study area was low (< 60%), it was to be expected that the circulation of polioviruses in the community could not be interrupted. The present study demonstrates the applicability of a two-dose strategy for primary immunization with a quadruple DPT-polio vaccine especially for poliovirus components and the toxoids. To induce pertussis immunity, however, a third vaccination is recommended.

Antibodies, Bacterial↗
PubMed1993

The cold pressor test: vascular and myocardial response patterns and their stability.

The purposes of the present study were to compare the cardiovascular response patterns evoked by three versions of the cold pressor test (either forehead stimulation or hand or foot immersion) and to determine the reproducibility of the responses over a 2-week interval. Blood pressure, heart rate, stroke volume, cardiac output, total peripheral resistance, and systolic time intervals were obtained during rest and during the cold pressor test in 42 young men. Across conditions, the pressor response was supported by peripheral resistance increases with concomitant stroke volume decreases. Although the response patterns were generally similar across sites, exceptions were apparent for heart rate. Forehead stimulation was characterized by no significant change in heart rate, whereas limb (hand or foot) immersion was associated with significant heart rate acceleration. The responses elicited by the three cold pressor test conditions were reliable and showed little evidence of attenuation over the test-retest interval.

Adolescent↗
PubMed1992

Quantitation of human IgG subclass antibodies to Haemophilus influenzae type b capsular polysaccharide. Results of an international collaborative study using enzyme immunoassay methodology.

An international collaborative study was conducted at ten sites to examine the performance of enzyme immunoassays (EIAs) for the quantitation of IgG1, IgG2, IgG3, IgG4 and total IgG anti-Haemophilus influenzae type b (Hib) capsular polysaccharide in human serum. All groups used the same reagents: microtiter plates coated with polyribosylribitol phosphate (PRP) conjugated to poly-L-lysine (PLL), reference, control and test human sera, biotin-conjugated International Union of Immunological Societies (IUIS)-documented monoclonal anti-human IgG1-4 and IgG Pan detection antibodies, avidin-peroxidase and TMB substrate. Initial mixing of soluble PRP antigen or an equal volume of buffer with the 20 test sera prior to analysis confirmed PRP antigen specificity in all five EIAs with greater than 80% competitive inhibition at most sites. Positive correlation between the total IgG anti-Hib and sum of IgG1-4 anti-Hib was demonstrated (r2 = 0.99, Y = 1.13X -0.15). Good agreement was shown between the total IgG anti-Hib as measured by EIA and the total Hib-specific antibodies measured by the current radiolabeled antigen binding assay (r2 = 0.97, Y = 4.6X -5.8). Assay parallelism was demonstrated with an average interdilutional %CV of 22% and parallel dose-response curve slopes. The interdilutional %CVs were calculated as an average per sample of the variation of microgram/ml (corrected for dilution) at different dilutions per laboratory for all participating sites. The interlaboratory variation was the only performance parameter studied that exceeded the target level of 35% CV in all IgG1-4 and total IgG anti-Hib assays. IgG subclass distributions in the test sera demonstrated a predominance of IgG1 anti-Hib in the pediatric serum pools and IgG2 anti-Hib in the adult sera, with low but detectable levels of IgG3 and IgG4 anti-Hib in each group.

Adult↗
PubMed1992

Neurovascular effects of reactive oxygen intermediates produced by photoradiation.

These experiments examined the effect of reactive oxygen intermediates, produced by laser illumination of the photosensitizer hematoporphyrin derivative, on the accumulation and release of norepinephrine from sympathetic nerve terminals. Using an isolated, spirally cut, superfused caudal artery of the rat, basal overflow of norepinephrine (NE) was significantly increased both during and after generation of reactive oxygen intermediates. Generation of reactive oxygen intermediates increased overflow of NE in vascular preparations in which release of NE had previously been elevated by the continuous superfusion of Krebs' solution, containing high concentrations of potassium (40 mM). Calcium free solutions did not block the overflow of norepinephrine augmented by reactive oxygen intermediates. This increase in overflow was due both to an increase in release of NE and an inhibition of accumulation of NE.

Animals↗
PubMed1992

Transgenic plants of tall fescue (Festuca arundinacea Schreb.) obtained by direct gene transfer to protoplasts.

Chimeric hygromycin phosphotransferase (hph) and phosphinothricin acetyltransferase (bar) genes were introduced, using polyethylene glycol treatment, into protoplasts isolated from embryogenic cell suspension cultures of tall fescue (Festuca arundinacea Schreb.), a graminaceous plant that is an important forage crop in temperate pastures. Colonies resistant to either 200 mg/l hygromycin or 100 mg/l phosphinothricin, respectively, were recovered upon selection using bead-type culture systems. Stable integration of the transgenes in the genomes of plants regenerated from resistant callus clones was shown by Southern hybridization analysis. In situ hybridization of a labeled transgene-probe to metaphase chromosomes is shown for one transgenic primary regenerant. Expression of the transgenes in mature plants was demonstrated by HPH enzyme assay or by phosphinothricin-herbicide spraying.

Acetyltransferases↗
PubMed1992

Erythroid colony formation by fetal rat liver and spleen cells in vitro: inhibition by a low relative molecular mass component of fetal spleen.

Liver and spleen hematopoietic cell suspensions from 20-day-old-fetal rats were fractionated on Percoll gradients. A granulocyte-rich splenic fraction inhibited CFUe production by cultures of a CFUe-enriched liver fraction, and by cultures of unfractionated liver and spleen hematopoietic cells. Conditioned medium from the spleen cell fraction contained an inhibitor of relative molecular mass, Mr, 25-35 x 10(3). The sensitivity of spleen cells to the inhibitor varied with the age of the fetus from which they were derived (20-day-old less than 18-and 19-day-old). No such age-dependence was found for liver cells. The inhibitor affects cycling CFUe, blocks the lethal effect of AraC, does not appear to be lineage-specific and its influence can be reversed by washing.

Animals↗
PubMed1992

[Diagnosis of activity in Crohn's disease and ulcerative colitis: scintigraphy with TC-99m glucoheptonate labelled leukocytes].

We evaluated a pre-tinning leukocyte labeling technique using Glucoheptonate-Sn lyophilized kit, in the detection of activity in 15 patients with clinical and laboratory signs of active inflammatory bowel disease (IBD). 25 patients, without gastrointestinal disease were the control group. In 7/8 patients with Crohn's disease and in 7/7 with Ulcerative Colitis the study was positive. The negative study corresponded to a patient who has only involvement of the duodenum, an area of difficult evaluation due to the high liver uptake. 3/25 patients of the control group had activity in the intestine at 4 hour images. In spite of the small group evaluated, we believe that this labeling technique is a promising procedure for evaluation of activity in patients with IBD (Sensitivity 93.3%, Specificity 88.0%).

Adult↗
PubMed1992

Epidemiological experience in the mission of the United Nations Transition Assistance Group (UNTAG) in Namibia.

Epidemiological data have rarely been generated during United Nations (UN) missions to Third World countries, even in situations where there is hardly any combat involvement. Continuous surveillance was therefore carried out during the 12-month stay of UN personnel in Namibia in 1989-90. In this population of 7114 persons, mostly young men, the mortality rate was 255 per 100,000; death was mainly due to traffic accidents. Hospitalization was chiefly because of fever of unknown origin or trauma. Repatriation to the country of origin was necessary in 46 patients, frequently for psychiatric reasons including alcoholism. Over this one-year period there were, on average, 2.7 new consultations per person for treatment (mostly for dental problems), and 0.8 per person for prophylactic measures. The extremely high mortality due to traffic accidents indicates a need for prevention. In the selection process for future missions, more emphasis should be given to the psychological and dental health of volunteers. All military contingents and civilian groups should learn about effective preventive measures prior to their arrival, and adhere to them.

Accidents, Traffic↗
PubMed1992

Evaluation of a neural-network classifier for PET scans of normal and Alzheimer's disease subjects.

The value of PET as an objective diagnostic tool for dementia may depend on the degree to which abnormal metabolic patterns can be detected by quantitative classification methods. In these studies, a neural-network classifier based on coarse region of interest analyses was used to classify normal and abnormal FDG-PET scans. The performance of neural networks and of an expert reader were evaluated by cross-validation testing. When the "abnormal" class was represented by subjects with clinical diagnoses of "Probable Alzheimer's," the areas under the relative-operating-characteristic (ROC) curves were 0.85 and 0.89 for the neural network and the expert reader, respectively. When testing with abnormal subjects represented by "Possible AD" cases, ROC areas for both the network and the expert were 0.81. The neural network out-performed discriminant analysis. It is concluded that PET has potential for the detection of abnormal brain function in dementing diseases, and that the combination of neural networks and PET is a useful diagnostic tool. Despite the low-resolution "view" afforded the neural network, its performance was nearly equivalent to that of an expert reader.

Adult↗
PubMed1991

Evaluation of immunization policies for peacekeeping missions.

This article first examines data bases available to assess the risk of vaccine-preventable diseases (VPD). In the second part, immunization recommendations and practices are briefly evaluated in view of the risk of exposure to VPD and of the efficacy and safety of available vaccines.

Cost-Benefit Analysis↗
PubMed1990

Description of a hybridoma bank towards Bordetella pertussis toxin and surface antigens.

This paper describes the development of a murine bank of monoclonal antibodies against Bordetella pertussis toxin, filamentous hemagglutinin (FHA), pili, lipopolysaccharide (LPS), or outer membrane proteins (OMPs). Subunits S1, S2, S3 of pertussis toxin (PT) bound immunoglobulins and glycoproteins such as fetuin and haptoglobin in an unspecific manner. The specificity of monoclonal antibodies towards subunits S1, S2, S3 or S4 of PT could be demonstrated by using purified immunoglobulins or their Fab2 fragments. A set of FHA-specific monoclonal antibodies could be differentiated on the basis of their binding to the various breakdown products present in FHA preparations. Pili-specific monoclonal antibodies reacted with either native pili or denatured pilin, and both demonstrated serotype specificity. Monoclonal antibodies to Bordetella pertussis OMPs were directed to either the virulent phase-regulated trypsin-sensitive, detergent-extractable OMPs 92 kDa, 32 kDa, and 30 kDa or the non-virulent phase-expressed, not-trypsin sensitive OMPs 38 kDa, 33kDa, and 18 kDa.

Animals↗
PubMed1989

[Uvulopalatopharyngoplasty without complications: a Fujita complication].

In 17 illustrations, a modification of Fujita's technique of UPPP is presented. This operation consists of excising redundant velar tissues from the free margin of the soft palate, tonsillar pillars, and uvula without reducing the muscles of the velum. In addition, the uvula muscle is almost completely preserved. Seventy patients, with habitual snoring or with obstructive sleep apnea syndrome, who underwent this surgery were followed-up from six to 24 months and did not show any palatal insufficiency with air and liquid escape through the nose. Additional remarks are made concerning the difficulties encountered during intubation of 60 percent of patients with chronic rhonchopathy.

Follow-Up Studies↗
PubMed1989

[Biliary scintigraphy in patients with functional disorders of Oddi's sphincter].

The appearance of biliary pain after cholecystectomy in patients with normal ultrasonic and cholangiographic studies has been attributed to functional alterations of the Sphincter of Oddi. We performed dynamic cholescyntigraphic studies of the biliary tract in 32 cholecystectomized patients, at least six months after the operation: 27 were asymptomatic (control group) and 5 had clinical and laboratory findings suggesting temporary functional obstruction of the Sphincter of Oddi. In this group we demonstrated an emptying delay of the biliary tract that was modified by the IV infusion of Cholecystokinin Octapeptide. Biliary Cholescintigraphy appears as a good screening method to evaluate functional alterations of the Sphincter of Oddi.

Abdominal Pain↗
PubMed1989

Selective inhibitory effects of ethylketocyclazocine on reflex pathways to the external urethral sphincter of the cat.

In the ventral horn of the sacral spinal cord of the cat, opioid terminals are preferentially localized in Onuf's nucleus, an area containing motor neurons that innervate the striated muscle of the external urethral sphincter. The present study was undertaken to 1) compare the effects of selective opioid agonists on sphincter reflex pathways with the effects of these drugs on hindlimb reflexes and urinary bladder reflexes and 2) determine if the physiological inhibition of sphincter reflexes, which accompany bladder contractions, is mediated by endogenous opioids. The effects of intrathecal (i.t.) and i.v. drug administration on bladder activity, sphincter reflexes and reflexes to the hindlimb musculature were monitored in chloralose-anesthetized cats. Ethylketocyclazocine (0.05-500 micrograms i.t.) produced a dose-dependent, naloxone-sensitive, inhibition of sphincter reflexes to less than 10% of control amplitude while having no consistent effects on hindlimb reflexes or bladder activity. D-Ser2-leu5-enkephalin-thr6 (DSLET; 0.1-2.0 micrograms i.t.) abolished rhythmic bladder activity, while having no effects on sphincter or hindlimb reflexes. Larger doses of DSLET (5.0-10 micrograms i.t.) produced a modest reduction of sphincter reflexes (to 60% of control amplitude), without affecting hindlimb reflexes. Naloxone (50 micrograms i.t.) reversed DSLETs marked inhibition of bladder activity, whereas large doses (greater than 250 micrograms i.t.) only partially antagonized DSLETs weak inhibition of sphincter reflexes. Morphine (5-500 micrograms i.t.) had no consistent effect on any of the measures.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The toxin binding inhibition test as a reliable in vitro alternative to the toxin neutralization test in mice for the estimation of tetanus antitoxin in human sera.

A method for the screening of human sera for tetanus antibodies has been developed and evaluated. The toxin binding inhibition test (ToBI-test) is based on inhibition of the binding of tetanus toxin to an antitoxin-coated immunoassay microtitre plate by tetanus antibodies. Serum samples from 191 healthy adults with different vaccination histories have been titrated for tetanus antibodies by the toxin neutralization (TN) test in mice, by toxoid-ELISA and by the ToBI-test. In every respect, the ToBI-test proved to be the best in vitro alternative to the TN-test in mice. Comparisons showed a higher degree of correlation between the ToBI-test and the TN-test than between the toxoid-ELISA and the TN-test. Furthermore, no overestimation of antibody content was seen in titrating low titre sera by the ToBI-test. In contrast, several false positive results were seen when using the toxoid-ELISA. It is concluded that the ToBI-test is a reliable and precise alternative to the TN-test and can be performed under simple laboratory conditions in a short time.

Animals↗
PubMed1988

Detection of IgA antibodies and quantification of IgA antibody-producing cells specific for ovalbumin or Trichinella spiralis in the rat.

This report describes procedures to quantify IgA responses in the rat sensitized to ovalbumin or infected with the parasite Trichinella spiralis: an ELISPOT detecting specific IgA antibody-producing cells in lymph nodes, and an ELISA demonstrating IgA antibody in serum and gut mucosal scrapings. For this purpose a mouse monoclonal anti-rat IgA antibody was produced. This IgG1-kappa 1 antibody recognized rat IgA but not rat IgM, IgG, or IgE. It proved very suitable in both assays. Using this reagent we could demonstrate large numbers of IgA anti-ovalbumin-producing cells in the mesenteric lymph nodes 15 days after sensitization to ovalbumin via the Peyer's patches. At 28 days after sensitization the numbers were much lower. IgA antibody titres to ovalbumin in serum were maximal between days 14 and 21 after immunization. Maximal numbers of IgA anti-T. spiralis-producing cells were found in the mesenteric lymph nodes 12 days after infection with muscle larvae, followed by a sharp decrease at 15 days. Maximal IgA anti-T. spiralis antibody titres in serum and mucus scrapings of small intestines were found on days 10 and 12 after oral infection with the parasite.

Animals↗