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Biomedical subjects

K C Chen

Publications and source records attributed to K C Chen.

At least 91 records · Page 5Linked to original sources
PubMed1991

An unusual Alu repeat sequence within the CAD gene.

There are several hundred thousand members of the Alu repeat family in the human genome. Those Alu elements sequenced to date appear to fit into subfamilies. A novel Alu has been found in an intron of the human CAD gene: it appears to be due to rearrangement between Alu repeats belonging to two different subfamilies. Further sequence data from this intron suggest that the Alu element may have rearranged prior to its entry into the CAD gene. Such findings indicate that, in addition to single nucleotide substitutions and deletions, DNA rearrangements may be a factor in generating the diversity of Alu repeats found in primate genomes.

Animals↗
PubMed1991

Complementary colors' effect on closure speed.

Contour closure of complementary colors as figure/ground (measured as RT and correct recognition) was difficult for 20 subjects. Perhaps this involves opponent cells in lateral geniculate nucleus.

Adult↗
PubMed1991

Pregnancy outcome in patients undergoing long-term hemodialysis.

Three uremic patients receiving hemodialysis for more than 5 years became pregnant and proceeded to the third trimester. A variety of complications were noted, including threatened abortion, vanished twin, preterm premature rupture of membranes, polyhydramnios, intra-uterine fetal death, intra-uterine growth retardation, premature labor and hypertension. Two of these 3 mothers gave birth to healthy babies under the management of the high-risk pregnancy team.

Adult↗
PubMed1991

[Primary mesencephalic hemorrhage: report of four cases].

Spontaneous intracerebral hemorrhage rarely occurs in the mesencephalon (midbrain), though thalamic or pontine hemorrhage may extend into that location. The neurologic manifestations and outcome in patients with primary mesencephalic hemorrhage (PMH) are different from those with thalamic or pontine hemorrhage. We report 4 patients (2 men and 2 women) with nontraumatic and non-neoplastic hemorrhages confined to the mesencephalon. One young patient, a 37-year-old woman, had no detectable risk factors for stroke, and her cerebral angiogram was normal. The other 3 elderly patients (73-85 years of age) all had a history of hypertension. The neurologic manifestations of patients with PMH are characterized by disturbance of ocular movements and cerebellar signs. Two patients with tegmental hematoma showed Claude's syndrome, i.e., ipsilateral oculomotor palsy and contralateral cerebellar signs. One patient with a small central midbrain hematoma showed bilateral oculomotor palsy. Another patient with a relatively large central midbrain hematoma presented with bilateral ptosis, bilateral internuclear ophthalmoplegia, upward gaze palsy, and bilateral cerebellar signs. The prognosis after conservative treatment for our patients with PMH was good.

Adult↗
PubMed1991

The epidemiology of diarrhoeal diseases in southeastern China.

In a community survey of 19,410 people for 12 months in southeastern China (Fujian Province), the overall annual incidence rate of diarrhoea was 729.9 episodes/1,000 population. The incidence varied with different age groups; children aged under five years had the highest rate, 2.25 episodes per child per year. A bacterial pathogen was isolated from 883 cases (44.03%), and 147 (14.76%) strains from 996 healthy controls. Enterotoxigenic Escherichia coli, enteropathogenic E. coli, and Shigella species were the most frequently isolated bacterial pathogens. Isolation was highest during the hot summer months. The investigation showed that the diarrhoea incidence was related to the status of economy, education, healthy, hygiene, food, and water.

Adolescent↗
PubMed1990

Analysis of the kinetic hairpin transfer model for parvoviral DNA replication.

All linear DNA molecules face special problems in replicating their 5' ends, as DNA polymerases add nucleotides only to pre-existing strands with free 3'-OH groups. Parvoviruses, a group of small animal viruses with a linear single-stranded DNA genome, cope with this problem by having palindromic terminal sequences that can fold back on themselves to form hairpin structures essential in priming DNA replication. The 3' terminal sequence that initiates replication becomes reversed in orientation during the process, and if the palindrome is imperfect, two different, reverse-complementary terminal sequences are generated. The relative abundances of the terminal sequence orientations at each end of the DNA molecules can be measured and give information about the replication process. From such clues, we developed a "kinetic hairpin transfer model" based on differential rates of hairpin formation and inversion processes depending on the conformations of the 3' termini. Numerical studies showed that this simple idea can account for the diverse pattern of DNA distributions observed in the family Parvoviridae. In this paper, we simplify the model to a set of coupled linear first-order ordinary differential equations in order to delineate its essential properties by Perron-Frobenius theory. Secondly, we examine our assumption of linear kinetics by modeling enzyme catalysis of the component steps of the hairpin transfer process. We show that the rate-determining step of the process is the binding of initiation complex to the self-priming hairpin structures. Furthermore, we find that if the replication machinery is saturated by DNA substrate late in an infection, the differential equations become non-linear but the steady-state DNA distribution is still given by the solution of our original linear equations.

Computer Simulation↗
PubMed1990

Recognition of altered shapes by hearing and hearing-impaired subjects.

In the present study, we explored whether mental transformation or feature detection is involved in visual processing of shape recognition; another purpose was to compare the visual processing of hearing subjects with that of hearing-impaired subjects. Deprivation of hearing, according to Myklebust (1964), impedes perceptual functioning in some respects and enhances such functioning in other respects. An experiment was conducted using two-dimensional random shapes under similarity transformations in Euclidean space. Reaction time served as the behavioral measure. The analysis of variance results showed significant main effects of orientations, isometries, and shapes, but not of groups and sizes. There were significant linear trends for orientations and sizes. Both groups demonstrated mental isometric transformation.

Adult↗
PubMed1990

Organization and nucleotide sequence of the 3' end of the human CAD gene.

Aspartate transcarbamylase (ATCase) is found as a monofunctional protein in prokaryotes and as a part of a multifunctional protein in fungi and animals. In mammals, this enzyme along with carbamyl phosphate synthetase II and dihydroorotase (DHOase) is encoded by a single gene called CAD. To determine the relationship between gene structure and the enzymatic domains of human CAD, we have isolated genomic clones of the human gene and sequenced the region corresponding to the 3' end of the gene. This includes exons encoding the end of the domain for DHOase, the complete domain for ATCase, and the bridge region connecting the two enzymatic domains. Three findings emerged. First, in comparing the human coding sequence to that obtained for other species that have a CAD gene, the length of the bridge region is conserved but its sequence is not. This is in contrast to the strong degree of positional identity observed for the segments of CAD encoding the DHOase and ATCase domains. Second, sets of exons appear to correspond to specific domains and subdomains of the encoded protein. Third, while overall there is a strong conservation of protein sequence among the ATCases of all species, reflecting conservation in catalytic function, two particular regions of the enzyme are more highly conserved among species where ATCase is a domain of a multifunctional protein as opposed to species where it is a monofunctional protein. Such findings may indicate regions of the ATCase domain that provide important structural contacts or functional channels when part of a multifunctional protein.

Amino Acid Sequence↗
PubMed1990

A cross-sectional study on the skeletal development of the hand and wrist from preadolescence to early adulthood among Chinese in Taiwan.

In order to study the skeletal development of the hand-wrist among Chinese in Taiwan, a total of 1,679 hand-wrist radiographs were collected from the files in the Division of Orthodontics, School of Dentistry, National Taiwan University and the Orthodontic Clinic of the National Taiwan University Hospital. The ages of the subjects ranged from 6.3 years to 22.7 years. The nine commonly used ossification events, PP2 = ,MP3 = ,S, MP3cap, DP3u, MP3u, Riu, Rau and Rcu, were used in this study. It was found that the sequence of the nine skeletal maturation stages did not differ between males and females and was generally in agreement with similar studies among other ethnic groups. A statistically significant difference did exist between the males and females in the mean ages of onset of the skeletal maturation stages. All of the skeletal stages were more advanced in the females than in the males. The mean ages of the nine skeletal maturation stages obtained in this study could be used as a reference for daily pedodontic and orthodontic practice as well as for related studies. Although there was no intention of making a statistical comparison of the data for the Chinese with those of other ethnic groups, some diagrammatic illustrations for comparison were made.

Adolescent↗
PubMed1989

A kinetic hairpin transfer model for parvoviral DNA replication.

The DNAs encapsidated by parvoviruses show distinctly different patterns with respect to the ratio of plus-to-minus strands and sequence heterogeneity at the ends. A kinetic model, based on differential rates of hairpin transfer at 3' termini, is described and shown to account for all known parvoviral DNA distributions.

Base Sequence↗
PubMed1989

Mapping of the gene encoding the multifunctional protein carrying out the first three steps of pyrimidine biosynthesis to human chromosome 2.

The CAD gene encodes a trifunctional protein that carries the activities of the first three enzymes (carbamyl phosphate synthetase II, aspartate transcarbamylase, and dihydroorotase) of de novo pyrimidine biosynthesis. Genomic fragments of the human CAD gene have been obtained by screening a human genomic library in bacteriophage lambda using a Syrian hamster cDNA clone as a probe. These human genomic clones have been used to assign the CAD gene to human chromosome 2 using in situ hybridization to human metaphase chromosomes and Southern blot hybridization analysis of DNA isolated from a panel of Chinese hamster/human hybrid cells. In situ hybridization analysis has allowed further localization of this gene to the chromosomal region 2p21-p22.

Amidohydrolases↗
PubMed1989

Identical ends are not required for the equal encapsidation of plus- and minus-strand parvovirus LuIII DNA.

Sequence analyses of the left and right termini of LuIII virus show they are nonidentical imperfect palindromes of 122 and 211 nucleotides, respectively. The left terminus of the minus strand of LuIII DNA, uniquely in the flip conformation, can assume a T-shaped structure. The right terminus of the minus strand of LuIII DNA can assume a U-shaped structure, and it exists in either the flip or flop conformation. The termini of LuIII shared a high degree of sequence homology and showed conserved secondary structure with those of the rodent parvoviruses MVMp and H-1. LuIII, like adeno-associated virus, encapsidates equal amounts of plus- and minus-strand DNA. However, the sequence data for LuIII virus demonstrate that identical termini are not required for this encapsidation pattern.

Base Sequence↗
PubMed1989

[The vector analysis of the anteroposterior relationship among the apical bases and the incisors].

Using the lateral cephalometric radiographs, the points A, B, maxillary incisor tip (U) and mandibular incisor tip (L) were projected onto the Frankfort horizontal plane and the projected points were defined as a, b, u and 1, respectively. According to the principle of the vector analysis, the vector formula ab - ul = au - bl can always stand irrespective of how the locations of the points a, b, u and 1 vary. The vectors ab, ul, au and bl represent the anteroposterior linear relationship between the upper jaw and the lower jaw, the upper incisor and the lower incisor (overjet), the upper jaw and the upper incisor, and the lower jaw and the lower incisor, respectively with reference to the FH plane. The lateral cephalometric radiographs taken from a total of 863 class I subjects, including 422 males and 441 females, were submitted for the study. The four vector values were obtained from the tracing of each radiograph and the mean values were computed according to sex and age. If a positive value was given to the vector ab, it denoted that point "a" was anterior to point "b", while a negative value denoted that "a" was posterior to "b". Both sexes of the subjects were divided according to their ages into junior primary (JP, 6-8 years), senior primary (SP, 9-11 years), junior high (JH, 12-14 years), and senior high (SH, 15-18 years) groups. No substantial or significant mean difference of each vector between the males and the females in each age group was noted. The mean values of the vector ab were 7.4, 6.8, 6.1 and 4.7 mm in JP, SP, JH and SH groups, respectively with the male and the female data pooled together. This indicates that there was a gradual catching up tendency of mandibular versus maxillary growth. The mean values of the vector ul were 1.4, 2.8, 2.9 and 2.8 mm in each successive age group, respectively showing that the overjet was rather constant with age except in the youngest group. The corresponding mean values were -0.4, -3.9, -5.2 and -6.1 mm for the vector au and -6.3, -8.0, -8.4 and -8.0 mm for the vector bl in JP, SP, JH and SH groups, respectively. The data indicate that both upper and lower incisors were relatively more upright in the youngest group when compared with the other age groups. In the remaining groups the upper incisors exhibited a tendency of gradual labial tipping with age, whereas the lower incisors kept stable in the procumbency.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1989

[Large food poisoning of Salmonella typhi-murium caused by ice drinks].

A large number of patients with fever, diarrhea and abdominal pain outbreaks in Yongan, Fujian in late Aug. 1987. 1113 patients fell ill in 5 days. S. typhi-murium were isolated from patients feces. Related HA-antibodies were detected in sera. All patients complained that they had eaten ice drink. Through investigating one of ice-bar, S. typhi-murium were detected from ice-cream and frozen cream, eggs and containers. A lot of contaminated bacteria were detected in ice cream containing 2.2 10(5)-1.5 10(8) and 2.9 10(5) in ice-brick per piece respectively. It was demonstrated that food poisoning outbreak was due to S. typhi-murium. Mean of patient's incubation period were 24.15 hrs., 78% diarrhea were less than 10 episodes. The incubation period, symptom were possessed of closed relation with the number of bacteria which patients taken in. After 4 months, a part of patients, poultry, eggs and polluted water were investigated, it was showed that S. typhi-murium were detected from 5% polluted water. Due to the potential danger has been existing. We should pay attention to surveillance and to prevent epidemic outbreak again.

Adult↗
PubMed1989

[The epidemiological investigation on diarrhea caused by bacteria in Fujian province].

Surveillance of diarrhea was conducted in five villages of Fujian Province with a total population of 20,488 from May 1986 to April 1987 and 14,168 cases of diarrhea were reported during this period, averaging 0.69 time per person, and the incidence in children under five years old being 2.25 times higher. 16 kinds of pathogens were isolated. ETEC was the most common and Shigella the next. The isolation rate was 44.03%. It was shown that the incidence of diarrhea was closely related with income, education, sanitary conditions, family sanitation and health condition.

Adolescent↗
PubMed1989

Production of isoamylase by Pseudomonas amyloderamosa mutant strain JD210.

Nutritional requirements for the production of isoamylase by Pseudomonas amyloderamosa mutant strain JD210 were investigated. The optimal initial pH for enzyme production in shake-flask cultivation was 5.0. Maltose and soybean protein hydrolyzate were found to be the best carbon source and nitrogen source, respectively. The enzyme production was drastically inhibited by Zn+2 and Cu+2. Other metal ions phosphates and surfactants exhibited no significant inhibitory or accelerating effect on enzyme production. According to auxanography and single omission experiments, proline and isoleucine were required for growth. The supplement of 0.1% proline increased enzyme production by around 30% compared with no addition.

Amino Acids↗
PubMed1988

Analysis of the termini of the DNA of bovine parvovirus: demonstration of sequence inversion at the left terminus and its implication for the replication model.

The distribution of terminal-sequence orientations in the viral DNA of bovine parvovirus (BPV), an autonomous parvovirus, was studied by end labeling and restriction enzyme digestion and also by cloning. The left (3') end of the minus strand of BPV was found in two alternative sequence orientations (designated as flip and flop, which are reverse complements of each other), with a 10-fold excess of flip. This is in contrast to the autonomous rodent parvoviruses which encapsidate minus-strand DNA with only the flip orientation at this end. The right (5') end of the minus strand of BPV contained both sequence orientations with equal frequencies, as in the rodent parvoviruses. Sequence inversions were also detected at both ends of the plus strand, which makes up about 10% of the encapsidated BPV DNA. Each terminus of BPV DNA had a characteristic ratio of flip to flop forms, and this ratio was restored in the progeny DNA resulting from transfection with genomic clones of different defined terminal conformations. Replicative-form DNA showed the same distribution of terminal-sequence orientations as the reannealed plus and minus virion DNAs, suggesting that the distribution of flip and flop forms observed in virion DNA is not due to selective encapsidation, but rather to the specific distribution of replicative forms. The current replication model for autonomous parvoviruses, which was based on the available data for the rodent parvoviruses, cannot account for the observed distribution of BPV DNA. An alternative model is suggested.

Animals↗