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J Lampinen

Publications and source records attributed to J Lampinen.

10 recordsLinked to original sources

Bayesian approach for neural networks--review and case studies.

We give a short review on the Bayesian approach for neural network learning and demonstrate the advantages of the approach in three real applications. We discuss the Bayesian approach with emphasis on the role of prior knowledge in Bayesian models and in classical error minimization approaches. The generalization capability of a statistical model, classical or Bayesian, is ultimately based on the prior assumptions. The Bayesian approach permits propagation of uncertainty in quantities which are unknown to other assumptions in the model, which may be more generally valid or easier to guess in the problem. The case problem studied in this paper include a regression, a classification, and an inverse problem. In the most thoroughly analyzed regression problem, the best models were those with less restrictive priors. This emphasizes the major advantage of the Bayesian approach, that we are not forced to guess attributes that are unknown, such as the number of degrees of freedom in the model, non-linearity of the model with respect to each input variable, or the exact form for the distribution of the model residuals.

Algorithms↗

Determinants of parental decisions after the prenatal diagnosis of Down syndrome.

We evaluated demographic factors and factors specific to the current pregnancy, and their relationship to the decision to continue or terminate a pregnancy after prenatal diagnosis of Down syndrome. All cases of Down syndrome (DS) managed at a tertiary care center from 1989-1997 were retrospectively analyzed with respect to maternal age, parity, gestational age, sonographic findings, insurance status, and race. Of 145 cases of trisomy 21, 19 (13.1%) of women chose continuation of pregnancy, while 126 (86.9%) chose termination. There were no differences between groups in parity, sonographic findings, insurance status, or race at the time of diagnosis. However, patients who chose termination were significantly older and earlier in gestation than those electing to continue their pregnancy. When Down syndrome is diagnosed prenatally, the choice of termination is related to maternal age and gestational age, but only gestational age is a significant independent predictor of pregnancy termination.

Abortion, Eugenic↗

What is an anomaly?

Explore the source record for details and available documents.

Congenital Abnormalities↗

Neuropathologic findings in a case of OFDS type VI (Váradi syndrome).

Oral-facial-digital syndrome type VI (OFDS VI) or Váradi syndrome is a rare autosomal-recessive disorder distinguished from other oral-facial-digital syndromes by metacarpal abnormalities with central polydactyly and by cerebellar abnormalities. Histopathologic characterization of the cerebellar abnormalities has not been described previously. We describe the neuropathologic findings in a stillborn, 21-week estimated gestational age (EGA) male fetus diagnosed antenatally with signs of OFDS VI. Autopsy findings included: facial abnormalities, postaxial central polydactyly of the right hand, bilateral bifid toes, and absence of cerebellar vermis with hypoplasia of the hemispheric cortex. Microscopic analysis of the cerebellum demonstrated absence of the subpial granular cell layer and disruption or dysgenesis of the glial architecture. These histopathologic findings suggest that a primary neuronal or glial cell defect, rather than an associated Dandy-Walker malformation, may account for the cerebellar abnormalities in this form of oral-facial-digital syndrome.

Cerebellar Diseases↗

Aneuploidy among prenatally detected neural tube defects.

We have reported previously a 10% aneuploidy detection rate among 39 cases of fetal neural tube defects (NTD). Subsequently we amassed an additional experience of over 17,000 prenatal diagnosis cases over a 5-year period. During this period 106 cases of NTDs were identified; 44 with anencephaly, 62 with open spina bifida. The average maternal age of this population with NTDs was 29 years (15-40); 6 patients declined amniocentesis. Six of 100 cytogenetic studies were aneuploid; one anencephalic fetus had inherited a maternal marker chromosome, and 5 NTD cases had trisomy 18. The average maternal age of the aneuploid cases was 31 (19-40); 3 were 35 years or older. Four of 5 trisomy 18 cases had multiple congenital anomalies (MCA). The overall aneuploidy detection rate in our cohort was 5-6%, while aneuploidy occurred in 2% of the isolated NTD cases, and 24% of the MCA cases. Combining the earlier experience, 4/39 aneuploidy (2 trisomy 18, 4p+, del 13q) yields an aneuploidy detection frequency of 10/145 (7%), of which most (7/10) had trisomy 18. These data support fetal karyotyping for accurate diagnosis, prognosis, and recurrence-risk counseling.

Adolescent↗

Use of controlled luciferase expression to monitor chemicals affecting protein synthesis.

In this article, we present a new bioluminescent test system for the screening of chemical compounds with an inhibitory effect on protein synthesis. The test is based on the measurement of real-time in vivo light production by Escherichia coli strains expressing different luciferase genes. The eukaryotic lucGR gene from Pyrophorus plagiophthalamus was found to be the best of three types of luciferase genes tested. Chemicals with known inhibitory effects on protein synthesis were used as test chemicals together with some general toxicants. The incubation of a test chemical with cells was performed either prior to or after the induction of protein synthesis, and the difference in the results of the two methods distinguishes the possible influence on protein synthesis from direct metabolic inhibition. Using lyophilized bacteria, the test is performed in less than an hour without any bacterial cultivation, which makes the test suitable for rapid and sensitive screening of chemicals or environmental samples. Compared with the standardized 50% inhibitory concentration calculation method of the bioluminescent cytotoxicity test, the more direct approach of calculation developed in this study proved to be more convenient than and as reliable as the standard method.

Journal Article↗

Expression of luciferase genes from different origins in Bacillus subtilis.

A group of vectors for luciferase expression in Bacillus subtilis was constructed. So far, only bacterial luciferases have been expressed in Bacillus, but in this study we wanted also to express genes encoding eukaryotic luciferases to perform direct comparisons of the light levels produced by the two different systems in B. subtilis. The vectors constructed can replicate both in Escherichia coli and B. subtilis, and the luciferase expression is strictly regulated due to the dual plasmid system used. Nearly a 100-fold increase in light production compared to previous results was achieved when genes encoding bacterial luciferase were inserted into the constructs and transformed into B. subtilis. An additional tenfold increase in light production was obtained when luciferase genes from the North American firefly (Photinus pyralis) or a click beetle (Pyrophorus plagiophtalamus) were introduced in a similar fashion into B. subtilis. Measurement of the light emission was performed without disruption of bacterial cells in a real-time manner, which is a common feature when working with all of these constructions. Structures of the shuttle vector constructs and results from light emission measurements are presented.

Amino Acid Sequence↗

Evaluation of Abbott TESTPACK ROTAVIRUS with clinical specimens.

TESTPACK ROTAVIRUS was compared with the Pathfinder Rotavirus assay for the detection of rotaviral antigens in feces from 137 patients. The symptomatology and ages of the patients varied from no symptoms to watery diarrhea and from less than 3 months to greater than 60 years of age. The sensitivity and specificity, before resolution, were 89.2 and 90.0%, respectively. After resolution with a blocking reagent, the results were 100% sensitivity and 98.9% specificity. The performance was similar for all age groups and in both symptomatic and asymptomatic patients. Abbott TESTPACK ROTAVIRUS is a rapid (10-min), easy-to-perform assay for the detection of rotaviral antigens and has the sensitivity and specificity of enzyme-linked immunosorbent assays that require several hours to perform.

Antigens, Viral↗