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Biomedical subjects

M H Le

Publications and source records attributed to M H Le.

8 recordsLinked to original sources
PubMed2001

A pregnane steroid from Aglaia lawii and structure confirmation of cabraleadiol monoacetate by X-ray crystallography.

The pregnane steroid, (E)-aglawone, along with four known triterpenes, and a known sterol mixture were isolated from the bark of Aglaia lawii (Wight) Saldanha ex Ramamoorty (Meliaceae). The structural determination/identification was accomplished by a combination of 1D- and 2D-NMR spectroscopic techniques. The relative stereochemistry of the known triterpene, 20S,24S-epoxydammarane-3alpha,25-diol acetate, was also unequivocally determined for the first time by X-ray crystallography. The isolates were not active against various human cancer cell lines.

Crystallography, X-Ray↗
PubMed2001

Antimalarial compounds from Rhaphidophora decursiva.

Bioassay-directed fractionation led to the isolation of 14 compounds, six of which possess antimalarial activity, from the dried leaves and stems of Rhaphidophora decursiva. Polysyphorin (1) and rhaphidecurperoxin (6) showed strong activities against Plasmodium falciparum. Rhaphidecursinol A (2), rhaphidecursinol B (3), grandisin (4), and epigrandisin (5) were less active against the same organism. Among the isolates, rhaphidecursinol A (2) and rhaphidecursinol B (3) were determined to be new neolignans, and rhaphidecurperoxin (6) is a new benzoperoxide. Known compounds isolated include polysyphorin (1), grandisin (4), epigrandisin (5), (+)-medioresinol, (-)-pinoresinol, (-)-syringaresinol, (+)-glaberide I, (+)-dehydrovomifoliol, (-)-liliolide, (-)-hydroxydihydrobovolide, and N-butylbenzamide, of which compound 1 appears worthy of further evaluation as an antimalarial agent. Structure elucidation and identification were accomplished by spectroscopic means including 1D and 2D NMR analyses.

Animals↗
PubMed1999

Lymphoma presenting as a soft tissue mass. A soft tissue sarcoma simulator.

Lymphoma presenting as a soft tissue mass is rare and thus may be confused with the more common soft tissue sarcoma. No previous analysis of the clinical and radiologic features of lymphomas presenting as soft tissue masses is available because most of the cases reviewed are from the pathology literature. Four patients with diagnoses of extranodal lymphomas of the soft tissues were reviewed retrospectively with respect to their clinical features, primary tumor characteristics, stage, radiographic characteristics, treatment, and followup. Mean age was 72.5 years (range, 52-85 years). The soft tissue mass occurred in the thigh (three cases) and shoulder (one case). The median size of the soft tissue mass was 6.7 cm (range, 2-15 cm) in the largest dimension, as measured on magnetic resonance imaging. These patients each had evidence of lymphadenopathy at the time of diagnosis. Lactate dehydrogenase was increased significantly in two cases and increased slightly in two other cases. One case was Stage II(E) at presentation, one was Stage III(E), and two were Stage IV. All were B cell immunophenotype. All patients died between 2 and 24 months after diagnosis, despite the use of Cytoxan, vincristine, adriamycin, and prednisone chemotherapy in each case. Clinical and radiographic features that favor extranodal soft tissue lymphoma over sarcoma include pain and tenderness, lymphadenopathy (particularly when confluent radiologically), ipsilateral extremity swelling, and elevated lactate dehydrogenase.

Aged↗
PubMed1998

Isolation of erythropoietin receptor agonist peptides using evolved phage libraries.

Cyclic peptides capable of activating the erythropoietin receptor (EPOR) were isolated from phage display libraries by screening with a novel EPOR-IgG fusion protein reagent. A parental clone ERB1 (EPO Receptor Binder 1) was first isolated from a phage display library displaying 38 random amino acids as an N-terminal fusion with the M13 minor capsid protein, pill. An evolved library was then produced from the parental sequence using an oligonucleotide saturation mutagenesis strategy which yielded EPOR binding sequences with 20 times the relative affinity of ERB1. Two synthetic peptides were constructed from these sequences both of which bind the EPO receptor in specific ELISA, and act as full agonists in EPO dependent cell proliferation assays. These peptides are 18 amino acids in length, disulfide-bonded, and have a minimum consensus sequence of CXXGWVGXCXXW, where X represents positions tolerant of several amino acids.

Amino Acid Sequence↗
PubMed1996

Centric heterochromatin and the efficiency of achiasmate disjunction in Drosophila female meiosis.

The chromosomal requirements for achiasmate (nonexchange) homolog disjunction in Drosophila female meiosis I have been identified with the use of a series of molecularly defined minichromosome deletion derivatives. Efficient disjunction requires 1000 kilobases of overlap in the centric heterochromatin and is not affected by homologous euchromatin or overall size differences. Disjunction efficiency decreases linearly as heterochromatic overlap is reduced from 1000 to 430 kilobases of overlap. Further observations, including rescue experiments with nod kinesin-like protein transgenes, demonstrate that heterochromatin does not act solely to promote chromosome movement or spindle attachment. Thus, it is proposed that centric heterochromatin contains multiple pairing elements that act additively to initiate or maintain the proper alignment of achiasmate chromosomes in meiosis I. How heterochromatin could act to promote chromosome pairing is discussed here.

Animals↗
PubMed1995

Islands of complex DNA are widespread in Drosophila centric heterochromatin.

Heterochromatin is a ubiquitous yet poorly understood component of multicellular eukaryotic genomes. Major gaps exist in our knowledge of the nature and overall organization of DNA sequences present in heterochromatin. We have investigated the molecular structure of the 1 Mb of centric heterochromatin in the Drosophila minichromosome Dp1187. A genetic screen of irradiated minichromosomes yielded rearranged derivatives of Dp1187 whose structures were determined by pulsed-field Southern analysis and PCR. Three Dp1187 deletion derivatives and an inversion had one breakpoint in the euchromatin and one in the heterochromatin, providing direct molecular access to previously inaccessible parts of the heterochromatin. End-probed pulsed-field restriction mapping revealed the presence of at least three "islands" of complex DNA, Tahiti, Moorea, and Bora Bora, constituting approximately one half of the Dp1187 heterochromatin. Pulsed-field Southern analysis demonstrated that Drosophila heterochromatin in general is composed of alternating blocks of complex DNA and simple satellite DNA. Cloning and sequencing of a small part of one island, Tahiti, demonstrated the presence of a retroposon. The implications of these findings to heterochromatin structure and function are discussed.

Animals↗
PubMed1991

[Cataract surgery and implantation in diabetics. Apropos of 92 eyes].

We examined 92 eyes (63 patients) who underwent extracapsular cataract extraction with implantation of a posterior chamber intraocular lens. Visual acuity improved by two lines or more in 65% of cases. Follow-up examination (6 months and 2 years) showed posterior capsule opacification in 30% of cases. Progression of diabetic retinopathy was mild but cystoid macular edema was present in 70% of cases with non proliferative retinopathy. Proliferative retinopathy was treated postoperative by pan retinal photocoagulation. One neovascular glaucoma occurred, secondary to a ruptured capsule.

Aged↗