The "c" phase in continuous flow analysis.
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Autoanalysis↗
Biomedical subjects
K Spencer
Publications and source records attributed to K Spencer.
Flow cell modification of a filter fluorimeter producing improved throughput and precision.
A modification of a Corning-EEL 244 filter fluorimeter to take a Hellma fluoronephelometric flow cell is described, and the characteristics of a standard flow cell and the Hellma flow cell are compared by the use of a continuous flow fluorimetric calcein-calcium method. The study shows that by this modification a considerable improvement in precision, carryover, and throughput is possible. The kinetically better Hellma flow cell enables speeds in excess of 70 per hour to be achieved with carryover and precision better than that obtained at 40 per hour with the standard flow cell. Curve regeneration of signals using the Hellma flow cell can also be carried out, enabling a further increase in analytical rate to be obtained.
Calcium↗
Influence of reagent quality and reaction conditions on the determination of serum albumin by the bromcresol green dye-binding method.
In an age of reference methodologies and sophisticated quality control techniques it is surprising that so little attention is paid to the quality of the reagents that are used. This paper reports on an investigation of the bromcresol green dye-binding procedure for the estimation of serum albumin in which particular attention has been paid to changes in the reagent components that contribute to the performance of the method. It has been shown that detailed attention to the quality control of the reagents can improve the precision and interlaboratory comparison in the estimation of serum albumin.
Bromcresol Green↗
Problems associated with measuring sweat chloride concentration with an ion-specific electrode.
The measurement of sweat chloride concentration was investigated by using the Orion 417 skin chloride electrode. The effects of variation in pilocarpine concentration, iontophoresis period, and sweat collection period were also investigated. The results show that the sweat chloride concentration is directly related to the amount of sweat produced. When the amount of sweat collected falls below a certain level, there is an apparent increase in sweat chloride concentration. A procedure is recommended for the measurement of sweat chloride concentration which offers good precision (coefficient of variation 9.8%) and the minimum of inconvenience to the patient.
Adult↗
A study of factors influencing continuous flow kinetics: the use of serum calcium estimation as a model.
Previous studies of continuous flow kinetics have described an "AutoAnalyzer" peak in terms of two time constants, lag constant "a" and exponential constant "b". Further investigations described here define some of the factors which affect these constants and hence peak shape and analytical performance. This communication outlines the application of this information to the development of an automated method for the determination of serum calcium, having a carry-over of less than 1% and an analytical rate greater than 100/hour. The instaneous colour reaction, simple hydraulics, removal of the dialysis step, and the use of an integral debubbling flow cell have enabled small kinetic constants to be achieved. Over a period of three months' routine use between-batch co-efficient of variation (C.V.) was 1.4%.
Autoanalysis↗
Is English a dyslexic language?
McGuinness has suggested that there 'is no diagnosis and no evidence for any special type of reading disorder like dyslexia', and that poor teaching accounts for low levels of English literacy performance, rather than inherent personal deficits. Implicit in this is the assumption that some languages have simple grapheme-phoneme codes in which there is a one-to-one mapping, making them easy to teach and learn, while others have more complicated structures and are more difficult for teachers and students. There is now an increasing number of studies which demonstrate that readers in more transparent orthographies such as Italian, Spanish, Turkish, Greek and German have little difficulty in decoding written words, while English children have many more problems. Increasingly, lack of orthographic transparency in English is seen as having a powerful negative effect on the development of reading skills in English-speaking children. There is evidence that English-speaking children who fail to acquire reading skills may fall into two distinct categories: those who would succeed in languages, other than English, that have greater orthographic consistency; and those who would still have problems even with perfect orthographic transparency. The first, larger, group is let down by the interaction of poor teaching methods and an incomprehensible system of orthography. The present study examines word factors associated with poor spelling and reading that have been identified. Three factors account for the relative ease with which pupils can spell words: frequency of the word in the English language; length of the word; and the presence of 'tricky' letters or letter combinations. Data are presented illustrating the predictive model of spelling and reading which enables word difficulty to be calculated from the characteristics of English words. The implications the model has for teaching and learning English are elaborated, with reference to the possible benefits to be derived from mother-tongue teaching in British schools.
Dyslexia↗
Differential effects of orthographic transparency on dyslexia: word reading difficulty for common English words.
Orthographic transparency is increasingly being recognised as an important factor in determining the manifestation of dyslexic tendencies in individuals. Recent evidence has shown that normal English-speaking children have reading deficits in the range associated with same age dyslexic German-speaking children for less frequently used words, and English orthography has been identified as a contributing factor. Spencer (Reading (1999) 33(2), 72-77; Journal of Research in Reading (1999) 22(3), 283-292) has proposed a predictive model for English children's reading and spelling deficits, based on orthographic features. Two main factors have been identified: consistency of sound representation and inclusion of redundant letters in English words. Using new data for reading, a unified model will be discussed which incorporates measures of depth of orthographic transparency and relates these to recent positron emission tomography (PET) research. Implications for the relative frequency and severity of dyslexia in both deep and shallow orthographies is considered in the light of such studies.
Brain↗
Semantic disturbance in schizophrenia and its relationship to the cognitive neuroscience of attention.
We view schizophrenia as producing a failure of attentional modulation that leads to a breakdown in the selective enhancement or inhibition of semantic/lexical representations whose biological substrata are widely distributed across left (dominant) temporal and frontal lobes. Supporting behavioral evidence includes word recall studies that have pointed to a disturbance in connectivity (associative strength) but not network size (number of associates) in patients with schizophrenia. Paralleling these findings are recent neural network simulation studies of the abnormal connectivity effect in schizophrenia through 'lesioning' network connection weights while holding constant network size. Supporting evidence at the level of biology are in vitro studies examining N-methyl-D-aspartate (NMDA) receptor antagonists on recurrent inhibition; simulations in neural populations with realistically modeled biophysical properties show NMDA antagonists produce a schizophrenia-like disturbance in pattern association. We propose a similar failure of NMDA-mediated recurrent inhibition as a candidate biological substrate for attention and semantic anomalies of schizophrenia.
Attention↗
Nuclear weapons and nuclear power stations: what is the connection?
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Accidents↗
Ureteral duplication and its complications.
Duplication of the ureters is a common anomaly and is frequently encountered by radiologists. Duplication may be either complete or incomplete and is often accompanied by various complications. Incomplete duplication is most often associated with ureteroureteral reflux or ureteropelvic junction obstruction of the lower pole of the kidney. Complete duplication is most often associated with vesicoureteral reflux, ectopic ureterocele, or ectopic ureteral insertion, all of which are more common in girls than in boys. Vesicoureteral reflux affects the lower pole and can be outgrown, as in nonduplicated systems. Ectopic ureterocele and ectopic ureteral insertion affect the upper pole. The ectopic ureterocele produces a filling defect of variable size in the bladder; it can be identified with contrast material studies or ultrasound. Ectopic ureters may function poorly, be difficult to detect, and cause enuresis in girls. A fourth complication, ureteropelvic junction obstruction, occurs only in the lower pole and is seen in more boys than girls. Anatomic variants or anomalies as well as suboptimal imaging techniques can either simulate or obscure duplication, making diagnosis difficult. However, familiarity with the embryology of duplication and an awareness of the potential pitfalls of excretory urography and voiding cystourethrography will foster an understanding of the varied appearances and associated complications of both incomplete and complete duplication.
Diagnostic Imaging↗
Coelomic fluid leptin concentration in normal first-trimester pregnancies and missed miscarriages.
OBJECTIVE: Investigation of the possible role of leptin in early pregnancy failure. METHODS: Leptin concentration was measured in maternal serum, coelomic fluid and amniotic fluid from 15 singleton pregnancies with live fetuses and 7 missed miscarriages at 7-10 weeks of gestation. RESULTS: In the pregnancies with live fetuses, the median leptin concentration was significantly higher in coelomic fluid (median 33.1 ng/ml) than in maternal serum (median 8.1 ng/ml) or amniotic fluid (median 0.5 ng/ml). In the pregnancies with missed miscarriage, compared to those with live fetuses, the median leptin concentration in coelomic fluid was higher (median 45.3 ng/ml), but in maternal serum it was not significantly different (median 5.5 ng/ml). CONCLUSIONS: The high coelomic fluid leptin concentration suggests that embryonic death may be preceded by impaired oxygenation of the placenta that stimulates production of leptin.
Abortion, Missed↗
Prenatal diagnosis of trisomy 21 in monozygotic twins with increased nuchal translucency and abnormal serum biochemistry.
We present a case of a monozygotic twin pregnancy who underwent routine screening for chromosomal abnormalities at 14 weeks of gestation by ultrasonographic measurement of nuchal translucency and biochemical analysis of maternal serum alpha fetoprotein and free beta human chorionic gonadotrophin levels. Both screening methods indicated the pregnancy to be at increased risk of Down syndrome, with the ultrasound findings suggesting both fetuses to be affected. An amniocentesis was performed, and karyotype analysis revealed trisomy 21 in both fetuses; the mother subsequently opted for a termination of pregnancy. This case illustrates that screening for trisomy 21 in twin pregnancies is possible by both nuchal translucency measurement and maternal serum markers.
Adult↗
Antenatal maternal serum profiles.
Since the late 1970s antenatal biochemical screening for pregnancies associated with neural tube defects has become a routine part of obstetric practice in the UK. More recently, biochemical screening programmes for chromosomal anomalies such as trisomy 21 (Down's syndrome) and trisomy 18 (Edward's syndrome) have moved on from the research stage and have begun to be implemented.
Biomarkers, Tumor↗
[Comment on the contribution by Benz et al.: Serum screening for Down syndrome in women under 35 years of age with an age independent index].
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Adult↗