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W H Li

Publications and source records attributed to W H Li.

At least 145 records · Page 8Linked to original sources
PubMed1991

Is the guinea-pig a rodent?

The guinea-pig (Cavia porcellus), traditionally classified as a New World hystricomorph rodent, often shows anomalous morphological and molecular features in comparison with other eutherian mammals. For example, its insulin differs from that of other mammals in anabolic and growth-promoting activities and in its capability to form hexamers. Indeed, the literature about the molecular evolution of guinea-pigs abounds in references to 'convergent evolution', 'extremely rapid rates of substitution', and 'unique evolutionary mechanisms'. These claims are based on the assumption that the guinea-pig is a rodent. Our phylogenetic analyses of amino-acid sequence data, however, imply that the guinea-pig diverged before the separation of the primates and the artiodactyls from the myomorph rodents (rats and mice). If true, then the myomorphs and the caviomorphs do not constitute a natural clade, and the Caviomorpha (or the Histricomorpha) should be elevated in taxonomical rank and regarded as a separate mammalian order distinct from the Rodentia. If, as suggested by recent data, the myomorphs branched off before the divergence among the carnivores, lagomorphs, artiodactyls and primates, then the new order would represent an early divergence in eutherian radiation.

Animals↗
PubMed1991

Cloning and sequencing of bovine apolipoprotein E complementary DNA and molecular evolution of apolipoproteins E, C-I, and C-II.

Apolipoprotein (apo) E, a major protein component of plasma lipoproteins, is a physiological ligand for the low density lipoprotein (LDL) receptor as well as for a specific apoE receptor; it is therefore an important modulator of lipoprotein metabolism. In this study we cloned and sequenced bovine apoE complementary DNA. Comparison of nucleotide substitution rates shows that apoE is less conservative than apoA-I and evolves about 30% faster than an average mammalian protein. Although apoE is not a conservative protein, several regions have been well conserved among all eight mammalian sequences now available. These include a 33-amino-acid block immediately upsteam from the third intron/exon junction and the LDL receptor binding region. We have also compared published apoC-I and apoC-II sequences. Both proteins are less conservative than apoE. In particular, apoC-I shows no well-conserved region except for a small region in the common 33-amino-acid block, suggesting that the function of apoC-I does not have stringent structural requirements. On the other hand, in apoC-II the region encoded by exon 4, which consists of the last 29 amino acids of the polypeptide, has been rather well conserved, probably because this region is important for the activation of lipoprotein lipase and chylomicron and very low density lipoprotein metabolism.

Amino Acid Sequence↗
PubMed1991

Necessary and sufficient conditions for the existence of certain quadratic invariants under a phylogenetic tree.

Invariants are functions of the probabilities of state configurations among lineages, with expected values equal to zero under certain phylogenies. For two-state sequences, the existence of certain quadratic invariants requires a symmetric substitution model. For sequences with more than two states, the necessary condition for the existence of certain quadratic invariants in terms of independent events is much stronger than symmetry. For DNA sequences, only three parameters are allowed in the substitution model, which includes Kimura's two-parameter model as a special case.

Base Sequence↗
PubMed1991

Low nucleotide diversity in man.

The nucleotide diversity (pi) in humans is studied by using published cDNA and genomic sequences that have been carefully checked for sequencing accuracy. This measure of genetic variability is defined as the number of nucleotide differences per site between two randomly chosen sequences from a population. A total of more than 75,000 base pairs from 49 loci are compared. The DNA regions studied are the 5' and 3' untranslated regions and the amino acid coding regions. The coding regions are divided into nondegenerate sites (i.e., sites at which all possible changes are nonsynonymous), twofold degenerate sites (i.e., sites at each of which one of the three possible changes is synonymous) and fourfold degenerate sites (i.e., sites at which all three possible changes are synonymous). The pi values estimated are, respectively, 0.03 and 0.04% for the 5' and 3' UT regions, and 0.03, 0.06 and 0.11% for nondegenerate, twofold degenerate and fourfold degenerate sites. Since the highest pi value is only 0.11%, which is about one order of magnitude lower than those in Drosophila populations, the nucleotide diversity in humans is very low. The low diversity is probably due to a relatively small long-term effective population size rather than any severe bottleneck during human evolution.

Animals↗
PubMed1991

[Orthotopic xenotransplantation of human lung giant cell carcinoma and study on its invasion and metastasis].

Human lung giant cell carcinoma cell strains were implanted into the lungs of nude mice via an intrabronchial procedure. Tumorigenicity, invasion and metastasis of the xenografts, and their morphological features, including the findings by light and electronic microscopy and immunohistochemistry were investigated. Dissemination of xenografts within the airway (2/8), invasion to diaphragm (5/8), and development of bloody hydrothorax (5/8), were discovered. Metastasis via lymphatic and blood vessel routes as well as seeding metastasis occurred in all the tumor-bearing animals. The morphological features of xenografts were consistent with those of the parental giant cell carcinoma. These results indicate that lung cancer cell strains grow autonomously and the behavior of invasion and metastasis of the xenografts imitates more closely the clinical manifestation of lung cancer than their subcutaneous counterparts. Since microenvironment influences the biological behavior of the transplants, this model seemed to be more ideal for further investigation experimentally.

Animals↗
PubMed1991

[An ultrastructural and immunohistochemical observation of squamous cell carcinoma of the lung with neuroendocrine differentiation].

Thirteen cases (10.5%) of squamous cell carcinoma of the lung with neuroendocrine differentiation were identified ultrastructurally in 124 cases of resected pulmonary carcinoma. In addition to the features of epidermoid differentiation, i.e. presence of tonofilaments and desmosones, a small amount of cancer cells containing neurosecretory granules were found in all the 13 cases. Ultrastructures indicated that both epidermoid and neuroendocrine differentiations were present simultaneously in individual cancer cell. Immunohistochemical staining for NSE was performed in 12 cases. Positive reaction was obtained in all but one (91.7%). NSE positive cancer cells distributed focally or in single cell scattered in the cancer cell nests. The results suggest that biphasic differentiation of pulmonary squamous cell carcinoma diagnosed by light microscopy may not originate from different cells of different derms, but may be derived from a common stem cell of the bronchial epithelium which possesses the ability of multipotential differentiation.

Carcinoma, Squamous Cell↗
PubMed1991

Effects of berbamine on hemodynamics and myocardial reperfusion injury in isolated working rabbit hearts.

The isolated working rabbit hearts perfused with Tyrode's buffer solution persisted working in good condition at least up to 70 min. Berbamine (Ber) 3 mumol.L-1 significantly changed the hemodynamic parameters and reduced cardiac functions. The effects of Ber appeared in a dose-dependent manner. Reperfusion following 30-min of global ischemia aggravated the myocardial damages induced by ischemia, and the parameters of cardiac functions in working hearts markedly reduced and did not restore even at 20 min of reperfusion. Ber 1 mumol.L-1 reduced the myocardial ischemic reperfused damages and restored all parameters to the level of preischemia within 10 min of reperfusion, and this situation of working hearts also lasted 40-50 min. The present results showed that Ber could protect myocardium against ischemic reperfused damages, promote the recovery of cardiac functions and prolong the efficient working period in isolated working rabbit hearts.

Alkaloids↗
PubMed1991

No severe bottleneck during human evolution: evidence from two apolipoprotein C-II deficiency alleles.

The DNA sequences of a Japanese and a Venezuelan apolipoprotein (apo) C-II deficiency allele, of a normal Japanese apo C-II gene, and of a chimpanzee apo C-II gene were amplified by PCR, and their nucleotide sequences were determined on multiple clones of the PCR products. The normal Japanese sequence is identical to--and the chimpanzee sequence differs by only three nucleotides from--a previously published normal Caucasian sequence. In contrast, the two human mutant sequences each differ from the normal apo C-II gene sequence by several nucleotides, including deletions. The data suggest that both mutant alleles arose greater than 500,000 years ago. It is shown that a defective allele can persist in a population for only a short time if a bottleneck occurs. Therefore, the antiquity of the two alleles suggests no severe bottleneck during human evolution. Moreover, the fact that one allele is from Japan and the other is from a Venezuelan Caucasian family is more consistent with the multiregional evolution model of modern human origins than with the complete replacement or "out of Africa" model.

Alleles↗
PubMed1990

Apolipoprotein B mRNA editing. Validation of a sensitive assay and developmental biology of RNA editing in the rat.

Apolipoprotein B (apoB) 48 mRNA is the product of a C----U conversion of the first base of the codon CAA for Gln-2153 in apoB-100 mRNA, changing it to an in-frame stop codon (UAA). Methods for measuring the ratio of apoB-48 to apoB-100 mRNA that have been authenticated with standard mixtures of the two apoB mRNA species have not been described. Using RNA mixtures consisting of known proportions of in vitro transcripts of apoB-100 and apoB-48, we directly compared four different assays. We found that a procedure based on the polymerase chain reaction, cDNA cloning, and oligonucleotide colony hybridization was the most sensitive and accurate assay. Total RNAs isolated from adult rat small intestine, adult liver, Day 15 and term placentas, and term fetal membranes were found to contain apoB mRNA in the following relative amounts: 100, 59.8, 0.9, 6.96, and 1087, respectively. They all contained both apoB-48 and apoB-100 mRNAs, with the former constituting 95.8, 59.2, 4.6, 1.3, and 0.8%, respectively, of the apoB mRNA. We examined the ontogeny of apoB-48 mRNA biogenesis in the liver and intestine in the rat prenatally on Days 17, 19, and 20 of gestation, and postnatally on Days 1, 3, 7, 13, 20, 24, and 37 after birth. Slot-blot hybridization demonstrated that apoB mRNA showed a peak at birth (Days 1-3 in the liver and Days 1-7 in the small intestine) and then decreased on Days 7 (in the liver) and 13 (in the intestine) before it increased again on Day 20 toward the adult level. Quantitation of the ratio of apoB-48 to apoB-100 mRNA at the different time points showed that RNA editing became highly competent prenatally on Day 19 of gestation in the small intestine, but postnatally on Day 24 after birth in the liver. The asynchronous nature for this developmentally regulated process in the liver and small intestine of the rat has implications for the mechanism of RNA editing and lipid homeostasis in this animal.

Age Factors↗
PubMed1990

The cDNA and protein sequences of mouse lactate dehydrogenase B. Molecular evolution of vertebrate lactate dehydrogenase genes A (muscle), B (heart) and C (testis).

Mouse lactate dehydrogenase-B cDNAs were isolated from cDNA libraries of macrophage (ICR strain) and thymus (F1 hybrid of C57BL/6 and CBA strains), and their nucleotide sequences determined. The lactate dehydrogenase-B cDNA insert of thymus clone mB188 consists of the protein-coding sequence (1002 nucleotides), the 5' (46 nucleotides) and 3' (190 nucleotides) non-coding regions, and poly(A) tail (19 nucleotides), while macrophage clone mB168 contains a partial lactate dehydrogenase cDNA insert from codon no. 55 to the poly(A) tail. Seven silent nucleotide substitutions at codon no. 142, 143, 186, 187, 241, 285 and 292, as well as a single nucleotide change in the 3' non-coding region, were found between these different strains of mice. The predicted sequence of 333 amino acids, excluding initiation methionine, was confirmed by sequencing and/or compositional analyses of a total of 103 (31%) amino acids from tryptic peptides of mouse lactate dehydrogenase-B protein. The nucleotide sequence of the mouse coding region for lactate dehydrogenase B shows 86% identity with that of the human isoenzyme, and only eight of the 139 nucleotide differences resulted in amino acid substitutions at residues 10, 13, 14, 17, 52, 132, 236 and 317. The rates of nucleotide substitutions at synonymous and nonsynonymous sites in the mammalian lactate dehydrogenase genes are calculated. The rates of synonymous substitutions for lactate dehydrogenase genes A (muscle) and B (heart) are considerably higher than the average rate computed from human and rodent genes. The rates of nonsynonymous substitutions for lactate dehydrogenase genes A (muscle) and B (heart), particularly the latter, are highly conservative. The rates of synonymous and nonsynonymous substitutions for the lactate dehydrogenase-C gene are about the same as the average rates for mammalian genes. A phylogenetic tree of vertebrate lactate dehydrogenase protein sequences is constructed. In agreement with the previous results, this analysis further indicates that lactate dehydrogenase-C gene branched off earlier than did lactate dehydrogenase-A and lactate dehydrogenase-B genes.

Amino Acid Sequence↗
PubMed1990

Molecular phylogeny of Rodentia, Lagomorpha, Primates, Artiodactyla, and Carnivora and molecular clocks.

Phylogenetic analysis of DNA sequences from primates, rodents, lagomorphs, artiodactyls, carnivores, and birds strongly suggests that the order Rodentia is an outgroup to the other four mammalian orders and that Artiodactyla and Carnivora belong to a superordinal clade. Further, there is strong evidence against the Glires concept, which unites Lagomorpha and Rodentia. The radiation among Lagomorpha, Primates, and Artiodactyla--Carnivora is very bush-like, but there is some evidence that Lagomorpha has branched off first. Thus, the branching sequence for these five orders of mammals seems to be Rodentia, Lagomorpha, Primates, Artiodactyla, and Carnivora. The branching date for Rodentia could be as early as 100 million years ago. The rate of nucleotide substitution in the rodent lineage is shown to be at least 1.5 times higher than those in the other four mammalian lineages.

Animals↗
PubMed1990

Cloning and sequencing of bovine apolipoprotein A-I cDNA and molecular evolution of apolipoproteins A-I and B-100.

We have cloned and sequenced bovine apoA-I cDNA. Comparison with the apoA-I sequences of six other vertebrates shows the bovine gene to be most similar to that of the dog. Estimates of substitution rates show that apoA-I evolves approximately 25% faster than an average gene in mammalian lineages. All portions of the coding region evolve at roughly similar rates, suggesting that global conformation is conserved. However, a region of the rat protein has evolved rapidly both relative to other portions of the rat sequence and relative to homologous regions in other mammals. To extend our analysis to other apolipoproteins, we compared four vertebrate apoB-100 sequences. Conserved regions were found to include two putative LDL receptor binding domains, in addition to several regions of unidentified function. Comparison of the apoA-I sequences and the apoB-100 sequences indicates that the latter evolve approximately 40% faster than the former and at twice the average rate for mammalian proteins.

Amino Acid Sequence↗
PubMed1990

[Ultrastructure of renal cell carcinoma (RCC)].

The ultrastructural characteristics of 30 cases of RCC, (including 16 clear, 7 granular, 1 spindle and 6 mixed RCC) were compared. There was no difference in biological behavior between clear, granular and spindle RCC, except for the contents of lipid, glycogen and mitochondria. It was considered that the degree of ultrastructural differentiation may be helpful in evaluating the prognosis.

Carcinoma, Renal Cell↗
PubMed1990

[Studies of synthesis and structure-activity relationships of analogs of the muscle relaxant--baclofen].

In an effort to study the structure-activity relationship of analogs of baclofen and to search for more potent and less toxic muscle relaxants and analgesics, fifteen 3-substituted pheny-4-aminobutyric acids and their derivatives were synthesized. Preliminary pharmacological tests in albino mice showed that some of the target compounds exhibited muscle relaxant and analgesic effects. Compounds Ib, IIb, IIIa, IIIc and compounds Ib, IIb, IIIa, IIIb were, respectively, more potent in hot plate tests and morphine-induced straub tail reaction tests than other analogs, but they were still less potent than baclofen. The structure-activity relationship showed that the effects of baclofen were strongly structure specific, and the results also suggested that at least three groups in baclofen-phenyl, amino and carboxy--take important parts in the combination of baclofen with GABAB receptor.

Animals↗
PubMed1990

[LM, EM and immunohistochemical observations on 10 cases of atypical carcinoid of the lung].

Twenty-two cases of neuroendocrine tumor comprising neurosecretory granules were identified ultrastructurally in 124 cases of resected pulmonary carcinoma. Among these, 10 cases of atypical carcinoid of the lung were examined by LM, EM and immunohistochemical staining for NSE. The diagnosis of atypical carcinoid is difficult by LM alone. Therefore light microscopic observation is required in combination with electron microscopic findings for obtaining an accurate diagnosis of atypical carcinoid of the lung. Based on the data observed in these 10 cases, the diagnostic criteria of atypical carcinoid of lung are as follows: Microscopically: Increased cellularity with organoid architecture and rosette formation. Patchy necrosis at the center of cancer nests. Pleomorphism and irregularity of nuclei with hyperchromatism. Presence of abundant mitotic figures. NSE is positive immunohistochemically. Ultrastructurally: Various amount of neurosecretory granules found in cancer cells. Rich organelles, such as mitochondria, RER and ribosomes found in cytoplasm. Presence of basal lamina and desmosomes.

Carcinoid Tumor↗
PubMed1990

[Comparison of the distribution sites and diagnostic significance of three antibodies as the melanoma markers].

S-100 and its subunits have subsequently been shown to be present in a wide variety of human neoplastic tissues. Three antibodies, monoclonal S-100, polyclonal S-100 and HMB-45, were used for comparison of the positive rates of different sites of melanomas. The results showed that HMB-45 was positive for those melanoma cells in epidermis and negative for those in dermis. Monoclonal S-100 was negative for melanoma cells in epidermis and positive for those in dermis. They are useful for the diagnosis of melanoma in surgical pathology.

Antibodies, Monoclonal↗