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Biomedical subjects

E Chen

Publications and source records attributed to E Chen.

250 records · Page 14Linked to original sources
PubMed1980

Different pattern of codon recognition by mammalian mitochondrial tRNAs.

Analysis of an almost complete mammalian mitochondrial DNA sequence has identified 23 possible tRNA genes and we speculate here that these are sufficient to translate all the codons of the mitochondrial genetic code. This number is much smaller than the minimum of 31 required by the wobble hypothesis. For each of the eight genetic code boxes with four codons for one amino acid we find a single specific tRNA gene with T in the first (wobble) position of the anticodon. We suggest that these tRNAs with U in the wobble position can recognize all four codons in these genetic code boxes either by a "two out of three" base interaction or by U.N wobble.

Animals↗
PubMed1975

Acute calcium nephrotoxicity. An electron microscopical and semiquantitative light microscopical study.

Rats were infused for three hours with doses of calcium gluconate to elevate serum calcium level and were killed either immediately after infusion or after 24 hours. Necrosis of proximal tubular cells was observed when serum calcium level was 16.0 mg/dl or higher. Above 16.0 mg/dl, an additional 5% of renal tubular profiles contained damaged cells for each 1 mg/dl in serum calcium. No difference in extent of damage was found in rats killed immediately or after 24 hours. Initial changes were formation of granular dense bodies in mitochondria, cell swelling, rupture, and extensive mitochondrial calcification. Renal tubular basement membrane changes appeared to be initiated by protrusion of cytoplasmic buds, forming ovoid bodies, which became embedded in the basement membrane. These ovoid bodies then appeared to serve as a nidus for further extensive basement membrane calcification.

Acute Disease↗
PubMedDate not supplied

Pharmacokinetics of scutellarin and its aglycone conjugated metabolites in rats.

Scutellarin, a flavonoid glycoside, is the primary active ingredient in breviscapine that is a mixture of flavonoid glycosides extracted from a Chinese herb Erigeron breviscapus (Vant.) Hand.-Mazz. The pharmacokinetics of scutellarin and its aglycone conjugated metabolites after intraperitoneal injection and oral administration of breviscapine was investigated in rats. The plasma concentration of scutellarin and scutellarein conjugates in serial samples was measured by validated high-performance liquid chromatography methods. The pharmacokinetic results indicated that scutellarin underwent rapid and extensive biotransformation in vivo. After intraperitoneal injection, scutellarin was absorbed rapidly. The profiles of scutellarin and scutellarein conjugates were fitted to a two-compartment open model. Scutellarin and scutellarein conjugates showed a similar time course. No significant difference in tmax, t0.5(alpha) and t0.5(beta) was observed between scutellarin and scutellarein conjugates (p>0.05). After oral administration, fluctuations were observed in the concentration-time profiles of both scutellarin and scutellarein conjugates and the pharmacokinetics could not be explained by classical compartment model. The relative bioavailability of oral administration was very low, 10.67 % +/- 4.78% for scutellarin and 7.92% +/- 1.90% for scutellarein conjugates.

Animals↗
PubMedDate not supplied

Structural alteration of viral homologue of receptor proto-oncogene fms at carboxyl terminus.

A role for proto-oncogenes in the regulation and modulation of cell proliferation has been suggested by the findings that the B-chain of platelet-derived growth factor (PDGF) is encoded by the proto-oncogene sis and that the erb-B oncogene product is a truncated form of the epidermal growth factor (EGF) receptor. Furthermore, the product of the proto-oncogene fms (c-fms) may be related or identical to the receptor for macrophage colony-stimulating factor (CSF-1). v-fms is the transforming gene of the McDonough strain of feline sarcoma virus (SM-FeSV) and belongs to the family of src-related oncogenes which have tyrosine-specific kinase activity. Furthermore, nucleotide sequence analysis of the v-fms gene product revealed topological properties of a cell-surface receptor protein. To elucidate the features involved in the conversion of a normal cell-surface receptor gene into an oncogenic one, we have now determined the complete nucleotide sequence of a human c-fms complementary DNA. The 972-amino-acid c-fms protein has an extracellular domain, a membrane-spanning region, and a cytoplasmic tyrosine protein kinase domain. Comparison of the feline v-fms and human c-fms sequences reveals that the proteins share extensive homology but have different carboxyl termini.

Amino Acid Sequence↗
PubMedDate not supplied

Children's memories for painful cancer treatment procedures: implications for distress.

Children (ages 3 to 18, N = 55) diagnosed with leukemia were tested for their memories of lumbar punctures (LPs), a repeated and painful part of the cancer treatment protocol. Memory for both event details and the child's emotional responses was assessed one week after the LP. Children of all ages displayed considerable accuracy for event details, and accuracy increased with age. Overall recall accuracy for event details and emotional responses was similar. Recall among children given oral Versed was similar to that among children not given Versed. Finally, higher distress predicted greater exaggerations in negative memory 1 week later (although controlling for age weakened this relationship); moreover, greater exaggerations in negative memory predicted higher distress at a subsequent LP. These results indicate that children's memories play an important role in their experience of distress during repeated stressful events.

Adolescent↗
PubMedDate not supplied

Universal opacity standard for Scheimpflug photography.

PURPOSE: To develop a universal standard for comparison of the results from different studies using Scheimpflug photography. MATERIAL AND METHOD: A suspension including polystyrene spheres was selected as the universal standard. The polystyrene suspension was diluted into 10 concentrations by adding spectroscopic quality water. An artificial eye chamber was designed to hold the diluted suspension for photography. Each concentration was photographed by both a Topcon SL-45 slit-lamp camera and a Nidek EAS-1000 system. The intensity of back-scattered light was analyzed statistically. RESULTS: The relationship between the concentration of the polystyrene suspension and the internal gray scale step within the Topcon SL-45 camera can be described by a second-order polynomial. The relationship between the concentration of the polystyrene suspension and the measurement of the Nidek EAS-1000 system can also be expressed by a second-order polynomial. The relationship between the Topcon SL-45 camera and the Nidek EAS-1000 system is linear. CONCLUSIONS: The results of lens nuclear opacity measured with different Scheimpflug cameras can be compared using the method established in the study. The linear relationship between the Topcon SL-45 and Nidek EAS-1000 systems can be used to convert measurements from one system to the other.

Anterior Chamber↗
PubMedDate not supplied

An urban community-based cancer prevention screening and health education intervention in Chicago.

Most types of cancer are disproportionately present in black populations. Among all ethnic and racial groups, black people have the highest incidence of all types of cancer combined, experiencing the highest mortality and the worst survival rate. A major intervention effort has begun in Chicago, targeting women living in 10 south side community areas whose populations are almost all black and among the poorest in the city. The purposes of the intervention are to develop and evaluate ways to reduce morbidity and mortality from breast and cervical cancer. Three outcome measures are being used, the proportion of women who receive Papanicolaou smears, breast examinations, and mammograms; the scores derived from a knowledge, attitudes, and practices survey; and the stage of diagnosed cancer. The results are being evaluated in three locations, the 10 target community areas, a Chicago Health Department clinic located in the community, and Fantus Clinic at Cook County Hospital. The intervention consists of reducing barriers to care at both public clinic sites and delivering education and information within the community. Public health outreach workers who are culturally sensitive to the population bring word of the program to places frequented by women, including local businesses (such as beauty shops, grocery stores, pharmacies, and currency exchanges), public housing developments (one being the largest in the country), and facilities belonging to city services programs. The intervention was developed to permit its ready adoption in similar environments should the evaluation results prove its usefulness.

Black or African American↗
PubMedDate not supplied

A nurse-delivered intervention to reduce barriers to breast and cervical cancer screening in Chicago inner city clinics.

An 18-month intervention was implemented to increase breast and cervical cancer screening among poor African-American women in Chicago. Breast and cervical cancer screening programs were set up in two public clinics, one community-based and the other hospital-based. Nurse clinicians and public health workers were used in these programs to recruit women in the clinics and in targeted community institutions to receive free breast and cervical cancer screening. The following barriers were specifically addressed by the intervention: accessibility of screening, knowledge about breast and cervical cancers, access to followup screening examinations, and access to treatment. A computerized followup system was specifically designed to track patients. During the 18 months of the intervention, 10,829 visits were made by 7,654 low-income women. A total of 84 cases of breast cancer and 9 cases of cervical cancer were detected. Awareness of the program, as measured by a survey after the completion of the intervention, increased in both clinics compared with baseline results. Knowledge about breast and cervical cancers also increased, as measured by scores on tests given before and after a class on breast and cervical cancers. Followup rates were 86 percent for women attending the programs. More than 90 percent of the women referred for evaluation of breast abnormalities kept an appointment. In summary, the intervention was successful in reducing barriers to breast and cervical cancer detection and in attracting a high-risk group of women.

Adult↗
PubMedDate not supplied

p53 influences mice skeletal development.

The p53 tumor suppressor gene encodes a transcriptional activator whose targets include genes that regulate cell cycle progression and apoptosis. Since we have shown that a critical event in the life history of the chondrocyte is programmed cell death, we asked the question: does loss of the p53 gene influence skeletogenesis? Female p53(+/-) mice were mated with p53(+/-) male mice and 17-day-old fetal mice were studied. Exencephaly was the most profound skeletal defect of the p53 null mutation. This defect was due to failure of formation of the bones that comprise the mouse calvarium. There was also loss of the hyoid bone, and defective mineralization of the manubrium sternum and the terminal phalanges. In the homozygous state (-/-), in the absence of exencephaly, the number of skeletal deformities was markedly reduced. Aside from the gross changes associated with null status, the mutants exhibited alterations in bone length and width. Small differences in the size and orientation of the mineral crystals in embryonic bone, as evaluated by small-angle X-ray scattering, were found to disappear after birth. To explain these observations, we evaluated the extent of apoptosis in the tibial growth plates using the TUNEL stain. In the growth plate of the p53(-/-) homozygote, there was minimal labeling of the hypertrophic layer. Since the p53(-/-) TUNEL stain pattern at 17 days was very similar to the pattern of labeling of the p53(+/+) at 15 days, we concluded that the growth defect reflected a delay in cartilage maturation rather than a change in chondrocyte phenotype. On this basis, we predict that after birth, in mice that survive, differences in bone length would become minimal, and at maturity, the length of the long bones of (+/+) and (-/-) mice would be similar.

Animals↗