Anomalies in the cyclotron resonance of quasi-two-dimensional electrons in silicon at low electron densities.
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Journal Article↗
Biomedical subjects
J Cheng
Publications and source records attributed to J Cheng.
Homozygous deletion of the retinoblastoma gene in an acute lymphoblastic leukemia (T) cell line.
Human leukemia cell lines were examined for the status of the retinoblastoma (RB) protein by immunoblotting analysis using antibodies raised against the TrpE-RB fusion protein. One of 16 cell lines examined, the T-cell acute lymphoblastic leukemia (ALL) line HSB-2, lacked the 110-Kd RB protein. Southern blot analysis of genomic DNA extracted from HSB-2 cells showed a large homozygous deletion of the RB gene, stretching from exon 18 beyond exon 27. Northern blot analysis showed multiple, abnormal RB transcripts in HSB-2. A truncated protein (72 Kd) was detected with 35S-methionine labeling but not with 32P-orthophosphate labeling of the HSB-2 cells. The genomic deletion of greater than 85 kb DNA at the RB locus (13q14) was not detectable in the karyotype of the HSB-2 cells. Among the 16 human leukemia cell lines examined for the status of the RB gene, only one, the HSB-2 line, showed an abnormal RB protein. Further study of primary leukemia and lymphoma samples appears to be warranted.
Blotting, Northern↗
Ultrastructural comparative study on endometrium of Chinese women using intrauterine devices of stainless steel ring, copper T220, and releasing levonorgestrel: morphometry of microvessels.
An electron microscopic morphometric study was performed for three kinds of IUDs, the stainless steel ring (SS), the copper T220 (TCu) and the WHO levonorgestrel IUD (LNG), for comparison of their effects on microvessels of the endometrium of women wearing the devices. The morphometry of plasmolemmal vesicles (PV) of the endothelial cell as well as the contracted and degenerated endothelial cell were undertaken. The results showed that all three IUDs led to significant changes in blood vessels, i.e., a higher percentage of contracted and degenerated cells than in the control group (p less than 0.01), and an increase in PV after insertion of the devices (p less than 0.01). The TCu caused more contracted endothelial cells than the SS (p less than 0.01) and the LNG (p less than 0.05). The levonorgestrel-releasing IUD resulted in a higher increase of PV than the SS and the TCu. For the differences between bleeding and non-bleeding groups, only the TCu showed a higher percentage of contracted cells (p less than 0.05).
Adult↗
New Taxanes from Taxus chinensis.
Two new taxane diterpenes, decinnamoyltaxagifine ( 3) and decinnanioyltaxagifine acetate ( 2), have been isolated from the leaves and stems of TAXUS CHINENSIS. Their structures were elucidated by spectroscopic methods. Their (13)C-NMR chemical shifts were assigned.
Journal Article↗
Autoantibodies to keratin in Sjögren's syndrome.
In order to determine which components of the salivary duct cells are recognized by the antisalivary duct antibodies, sera of patients with Sjögren's syndrome were screened for immunoreactivity to keratin by using an ELISA test and a Western blot analysis. The autoantibodies which reacted with keratin were demonstrated in 8 of 9 definite cases of Sjögren's syndrome and in 3 of 6 probable cases, and they reacted with different keratin peptides in each case. The results suggest that the antisalivary duct antibodies include antibodies against keratin, which exists ubiquitously as a cytoskeleton in the salivary gland epithelial cells. Detection of antikeratin antibody might be a useful aid for diagnosis of Sjögren's syndrome.
Adult↗
Immunolocalization of basement membrane molecules in the stroma of salivary gland pleomorphic adenoma.
In order to determine the participation of basement membrane molecules in formation of its characteristic stroma, 30 cases of salivary gland pleomorphic adenoma were examined by immunohistochemical staining for type IV collagen, laminin, heparan sulfate proteoglycan, and entactin. The stroma was histopathologically classified into four types: hyaline, fibrous, myxoid, and chondroid. Immunohistochemically, type IV collagen and laminin were more intensively localized in hyaline, fibrous and chondroid types of stroma, whereas heparan sulfate proteoglycan was more prominent in myxoid areas. The results suggest that the stroma contains these basement membrane components, which are possibly biosynthesized by epithelial tumor cells, and that histological variety of the stroma depends on proportion of local contents of each basement membrane molecule.
Adenoma, Pleomorphic↗
Feedback mechanisms and dynamics of atrioventricular node propagation.
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Arrhythmias, Cardiac↗
Translation to near the distal end of the penultimate exon is required for normal levels of spliced triosephosphate isomerase mRNA.
The translation of human triosephosphate isomerase (TPI) mRNA normally terminates at codon 249 within exon 7, the final exon. Frameshift and nonsense mutations within the TPI gene that cause translation to terminate prematurely at or upstream of codon 189, within exon 6, result in a decreased level of TPI mRNA (I.O. Daar and L.E. Maquat, Mol. Cell. Biol. 8:802-813, 1988). For all mutations in this group, the decrease is to the same extent, i.e., to approximately 20% of the normal level. We show here that a second group of nonsense mutations that cause translation to terminate prematurely at or downstream of codon 208, in exon 6, did not affect TPI mRNA abundance. Deletion analysis demonstrated that the abundance of translationally active TPI mRNA is a function of both the distance and the polarity of the nonsense codon relative to the final intron in TPI pre-mRNA. Our results indicate that if translating ribosomes are unable to progress to at least a certain position within the penultimate exon relative to the final intron, then the level of the corresponding mRNA will be abnormally low. Studies inhibiting RNA synthesis with dactinomycin demonstrated that a block in translation does not affect the half-life of mature TPI mRNA. The simplest interpretation of our data is that the translation of TPI mRNA in the cytoplasm facilitates the splicing of TPI pre-mRNA or the transport of TPI mRNA across the nuclear envelope or both.
Base Sequence↗
Frequent mutations in the p53 tumor suppressor gene in human leukemia T-cell lines.
Human T-cell leukemia and T-cell acute lymphoblastic leukemia cell lines were studied for alterations in the p53 tumor suppressor gene. Southern blot analysis of 10 leukemic T-cell lines revealed no gross genomic deletions or rearrangements. Reverse transcription-polymerase chain reaction analysis of p53 mRNA indicated that all 10 lines produced p53 mRNA of normal size. By direct sequencing of polymerase chain reaction-amplified cDNA, we detected 11 missense and nonsense point mutations in 5 of the 10 leukemic T-cell lines studied. The mutations are primarily located in the evolutionarily highly conserved regions of the p53 gene. One of the five cell lines in which a mutation was detected possesses a homozygous point mutation in both p53 alleles, while the other four cell lines harbor from two to four different point mutations. An allelic study of two of the lines (CEM, A3/Kawa) shows that the two missense mutations found in each line are located on separate alleles, thus both alleles of the p53 gene may have been functionally inactivated by two different point mutations. Since cultured leukemic T-cell lines represent a late, fully tumorigenic stage of leukemic T cells, mutation of both (or more) alleles of the p53 gene may reflect the selection of cells possessing an increasingly tumorigenic phenotype, whether the selection took place in vivo or in vitro. Previously, we have shown that the HSB-2 T-cell acute lymphoblastic leukemia cell line had lost both alleles of the retinoblastoma tumor suppressor gene. Taken together, our data show that at least 6 of 10 leukemic T-cell lines examined may have lost the normal function of a known tumor suppressor gene, suggesting that this class of genes serves a critical role in the generation of fully tumorigenic leukemic T cells.
Amino Acid Sequence↗
Clogging of biliary endoprostheses: a new perspective.
Endoscopic palliation with biliary endoprostheses is now an established treatment for benign and malignant strictures of the biliary tree. These endoprostheses, however, tend to clog with time. We investigated this problem by undertaking in vitro studies on stents of different designs made of different polymer materials. The stent that performed best was then tested in an in vivo trial. There was a direct relation in vitro between the frictional coefficient of a polymer and the amount of encrusted material. Catheters perfused in bacterially contaminated bile, irrespective of material and design, accrued significantly more sludge than catheters perfused with sterilised bile. The presence of side holes significantly increased the amount of sludge in the stents, but eliminated any differences between the various materials. We therefore investigated the effect of omitting side holes in a clinical trial which consisted of two groups of 20 patients each. The group treated with conventional stents accrued significantly more sludge in the stents than the group treated with experimental stents without side holes (p less than 0.05). The absence of side holes did not cause incomplete drainage or increase morbidity. Side holes are detrimental to stent patency, which is adversely affected by other factors including bacteria and proteins.
Aged↗
Effects of the spatial dispersion of acetylcholine release on the chronotropic responses to vagal stimulation in dogs.
We determined the effects of changing the spatial dispersion of acetylcholine release on the phase-dependent chronotropic responses to vagal stimulation in anesthetized dogs. We stimulated the vagus nerves with one brief burst of electrical pulses each cardiac cycle, and we changed the timing of the stimulus by a small, constant amount each cardiac cycle to scan the entire cycle. To vary the heterogeneity of acetylcholine release, we changed the voltage of the stimulus pulses over a range of submaximal values. To achieve the maximum homogeneity of acetylcholine release, we used supramaximal voltages, and we varied the level of acetylcholine release from each excited fiber by changing the number of pulses per burst. We used the average cardiac cycle length of the phase-response curve to assess the overall vagal effect, independent of its timing within the cardiac cycle. We found that the amplitude of the phase-response curve varied directly and the minimum-to-maximum phase difference varied inversely with the overall efficacy of vagal activity. However, for any given alteration in the overall efficacy, the specific changes in the characteristics of the phase-response curve did not depend on whether the alteration was achieved by varying the number of pulses per burst or by varying the stimulus voltage. Therefore, we conclude that although the cardiac chronotropic response is very sensitive to changes in the timing of vagal stimulation, it is not influenced appreciably by the spatial dispersion of acetylcholine release from the vagal nerve endings over a wide range of stimulation strengths.
Acetylcholine↗
Recombinant bivalent live vaccines against neonatal colibacillosis in piglets.
The genes of colonization factor K88 and avirulent heat-labile enterotoxin LT A-B+ of enterotoxigenic E. coli (ETEC) have been ligated, and a vaccine strain containing recombinant plasmid that efficiently expresses two antigens has been obtained. Using the activity of beta-galactosidase as a selection marker instead of drug resistance, another bivalent vaccine strain with the same expression level has also been constructed. The vaccine strains have no toxicity and do not cause any adverse reactions. In challenge study and field trials, a high degree of protection from colibacillosis was afforded to piglets when their dams were immunized orally or parenterally. Practice of bivalent live vaccines including colonization factor and enterotoxin antigens and without antibiotic resistance gene shows effective.
Adhesins, Escherichia coli↗
[Effects of amino acids on the membrane potential of toad oocytes and the underlying mechanism].
Of the 23 amino acids tested for their effect on the membrane potential of incubated toad oocyte, alanine, leucine and lysine were found to cause a decrease of polarization (depolarization) and K+ permeability, while tryptophan causes an increase of potential (hyperpolarization) and K+ permeability. For the rest 19 amino acids, no membrane effects were observed. Accompanying the alanine, leucine and lysine caused depolarization, the oocyte progesterone content became doubled and the maturation process hastened. These effects could be completely blocked by 1 mmol/L dibutyryl cAMP (db-cAMP) or 50 mumol/L estradiol. Tryptophan on the other hand could block the progesterone (10 mumol/L) induced depolarization but had no effect on the db-cAMP induced hyperpolarization. The regulatory function of the amino acids and steroid hormones underlying oocyte maturation is discussed.
Alanine↗
The construction of a non-antibiotic resistant ETEC vaccine strain containing K88ac and LT-B antigens.
By inserting the LacZ gene into the plasmid containing ETEC LT-B antigen gene we obtained a recombinant plasmid which could express the beta-galactosidase and LT-B antigen, but has the Tc resistant gene. The K88ac antigen gene was then inserted into the BamHI site of the Tc resistant region in the above plasmid. The final recombinant plasmid has no antibiotic resistance gene but can stably express both LT-B and K88ac antigens, as well as the beta-galactosidase as a tracking marker.
Antigens, Bacterial↗
[HPTLC densitometric determination of free bile acids in bezoar].
Cholic acid (CA), chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA) which are extracted with CH3OH from Bezoar can be separated on HPTLC silica gel plate (made in China) with isooctane-n-butyl acetate-acetic acid (4:2:1), and the three bile acids were determined by TLC densitometry.
Animals↗
Phonon modes in corrugated planes.
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Journal Article↗
The effect of intrauterine devices, the stainless steel ring, the copper T220, and releasing levonorgestrel, on the bleeding profile and the morphological structure of the human endometrium--a comparative study of three IUDs. A morphometric study of 96 cases.
Thirty-four women using the stainless steel ring (SS), 43 women using the Copper T220 (TCu), and 19 women using levonorgestrel-releasing intrauterine devices (LNG) were admitted to the study. The light microscopic biopsy material was subjected to morphometric studies including 8 indices of endometrial activity before (Control) and after 24 months of exposure to the SS and TCu device and 3-10 months of exposure to the LNG device. The women were grouped into subjects with and without intermenstrual and prolonged bleeding. The results revealed that there were highly significant differences between the IUDs at the endometrial level as displayed by morphometry. However, the difference between bleeders and non-bleeders was not significant in any of the three types of IUDs. Although the mode of action of these IUDs at the endometrial level is different, the mechanism responsible for the irregular endometrial bleeding needs to be further investigated.
Adult↗
The effect of intrauterine devices (stainless steel ring, copper-T220 and levonorgestrel) on the DNA content in isolated human endometrial cells.
The effect of three different intrauterine devices on the DNA content in human endometrial cells has been studied in 29 women before and after the insertion of an IUD; a stainless steel ring (9 subjects), Copper-T220 (11 subjects) and a medicated IUD releasing levonorgestrel at a rate of 2 micrograms/day (9 subjects). The material was grouped into "bleeders" (having more than 8 days of bleeding and spotting per month) and "non-bleeders" (having less than 8 days of bleeding and spotting per month). The DNA content was assessed on isolated endometrial cells smeared from thin biopsies and the amount of DNA per cell nucleus was measured by means of a Feulgen microspectrophotometric method. No significant difference was found between the "bleeders" and the "non-bleeders" as to the DNA content. Nevertheless, when the total number of subjects were pooled together, a significant increase in the DNA content was found in the post-insertion specimens in the groups of women using the SS and the T-Cu IUDs. Furthermore, a significant decrease in the DNA content was also found when the specimens obtained after the insertion of the LNG IUD were compared with those obtained after 24 months' use of the stainless steel ring and the Copper-T220 device (p less than 0.01 and p less than 0.002, respectively). It is concluded that the insertion of an inert IUD or an T-Cu IUD, induces significant alterations in the DNA content of the human endometrium adjacent to the device, whereas the use of the LNG device does not significantly modify the DNA synthesis when used for 3-10 months. No correlation was found between the DNA content per cell and the number of days of bleeding and spotting.
Adult↗