Biomedical subjects
Publications and source records attributed to J R Dai.
Two novel human cytomegalovirus protease inhibitors, cytonic acids A (1) and B (2), have been isolated from the solid-state fermentation of the endophytic fungi Cytonaema sp. Their structures as p-tridepside isomers were elucidated by MS and NMR methods.
Bioassay-guided fractionation of the organic extracts of whole plants of Mostuea brunonis (Loganiaceae), using the National Cancer Institute's (NCI) human tumor-based in vitro antitumor screen, led to the isolation and identification of camptothecin 20-O-beta-D-glucoside (1) and three moderately cytotoxic alkaloids, the known deoxypumiloside (2) and strictosamide (3), and the new 2'-O-acetylstrictosamide (4), from the cytotoxic alkaloid fractions. While the previously unknown 20-O-beta-D-glucopyranosyl camptothecin exhibited greater solubility in alcohol, DMSO-H(2)O and H(2)O than camptothecin, it was essentially inactive in the NCI's in vitro 60-cell line primary antitumor screen. However, it could be vulnerable to de-glucosidation in vivo, and may, therefore, merit additional evaluation as a potential prodrug of camptothecin that could be more readily formulated than the parent agent.
The purpose of this work is to investigate algorithms for the delivery of intensity-modulated fields using independent collimators (IC). Two heuristic algorithms are proposed to calculate jaw-setting sequences for arbitrary 2D intensity distributions. The first algorithm is based on searching the whole intensity matrix to find the largest nonzero rectangular area as a segment while the second algorithm is to find a nonzero rectangular area as a segment which makes the complexity of the remaining intensity matrix minimum. After a sequence is obtained, the delivery order of all its segments is optimized with the technique of simulated annealing to minimize the total jaw-moving time. To evaluate these two algorithms, randomly generated intensity matrices and three clinical cases of different complexity have been tested, and the results have been compared with one algorithm proposed for MLC technique. It is shown that the efficiency of IC technique becomes increasingly lower than that of MLC technique, and the relative efficiency of two algorithms proposed here is related to machine dose rate and jaw speed. Assuming the prescribed dose is 200 cGY per fraction, machine dose rate is 250 MU/min, and jaw speed is 1.5 cm/s, the treatment can be delivered within about 20 min for all three cases with the first algorithm. The second algorithm requires longer delivery time under such assumptions. The delivery time can be further reduced through increasing machine dose rate and jaw speed, and developing more efficient algorithms. The use of IC for intensity-modulation radiotherapy has some potential advantages over other techniques.
The segregation, integration and stability of the transgene-Bt (Bacillus thuringensis) in eight transformants created by three ways of transformation were studied by means of PCR (Polymerase chain reaction) and DNA molecular hybridization. The results are as follows: (1) The transgene-Bt in most of the progenies of the transformants showed simple Mendelian segregation. Although some deviation from Mendelian fashion existed in the early generations, the normal Mendelian segregation would be found after R3 generations and the transgene could fix in the populations. (2) The integration patterns of the transgene varied to the some extent in the different transformants, but they were characterized by either smaller band and copy numbers or cascade integration or closely linked integration in all transformants. (3) Changes of the Southern land pattern were found in some families of some transformants, especially, in the two families of Ding 4R5.
Three new oligostilbenes, malibatols A (1) and B (2) and dibalanocarpol (3), together with one known oligostilbene balanocarpol (4), were isolated from the organic extract of the leaves of Hopea malibato. The structure elucidation of these compounds was based on the interpretation of their chemical and spectral data. Compounds 3 and 4 exhibited very modest HIV-inhibitory activity, while compounds 1 and 2 were cytotoxic to the host cells (CEM SS) in the antiviral assay.
New monomeric (korupensamine E, 6) and dimeric (michellamines D-F, 7-9) naphthylisoquinoline alkaloids have been isolated from exracts of the tropical liana Ancistrocladus korupensis. Structures were determined by spectroanalytical methods, and stereochemistry was defined through NOE correlations, chemical degradation, and CD spectroscopy. Michellamines D-F exhibited in vitro HIV-inhibitory activity comparable to michellamine B, and korupensamine E exhibited in vitro antimalarial activity comparable to korupensamines A-D.
A new C43 acetylenic alcohol, vasculyne (1), was isolated by cytotoxicity-guided fractionation of the Caribbean sponge Cribrochalina vasculum. The structure of 1 was determined by spectroscopic methods.
Nine new polyacetylenes, triangulynes A-H (1-8) and triangulynic acid (9), have been isolated from the marine sponge Pellina triangulata (Oceanapiidae) through cytotoxicity-guided fractionation. Structural elucidations and stereochemistry assignments were based on chemical and spectral studies.
During the reisolation of the trimeric naphthoquinone derivative conocurvone [1] from an extract of the Australian shrub Conospermum incurvum, six monomeric naphthoquinones were isolated. These include three novel 1,4-naphthoquinone derivatives: 3-methyl-14,15-dihydro-15-hydroxyteretifolione B [3], 3-methyl-14,15-dihydro-15-hydroxyteretifolione B methyl ether [4], and 2,3-dimethyl-6-hydroxy-7-methoxy-1,4-naphthoquinone [5]. In addition, the previously reported compounds 3-methylteretifolione B [6], 3-methylteretifolione B methyl ether [7], and 8-geranyl-2,7-dihydroxy-3-methyl-1,4-naphthoquinone [8] were isolated and identified. The structures of the novel 1,4-naphthoquinones were elucidated by spectral methods. While conocurvone [1] is a potent inhibitor of HIV-1-induced cell killing, all of the monomeric naphthoquinone derivatives were inactive against HIV-1.
CT of the retroperitoneum in 70 patients (98 scans) who had undergone previous nephrectomy for renal cell carcinoma was reviewed. The interval between surgical operation and CT scanning were 15 days-7 years. In 59 cases (84%), CT scans were performed within the first 2 years. After nephrectomy, the emptied renal fossae were filled with adjacent organs, such as colon (27), small intestine (21), liver (14), inferior vena cava (3), adrenal gland (2) on the right side, and spleen (28) small intestine (33), colon (15), tail of pancreas (11), adrenal gland (2) on the left. In 47 cases, where CT scans were done within 4 months after operation, there were abscess/hematoma (8) and soft tissue thickening caused by post-operative edema and or inflammation (6). Most of the early post-operative complications gradually reduced in size in the follow-up scans. Local recurrences or metastases were detected by CT scan in 15 cases, with recurrence at the excision site (5), renal bed (6), adrenal gland (4), retroperitoneal lymph nodes (7) and contralateral kidney (1). 7 patients had solitary lesions and 8 patients had multiple recurrences. In 2 patients, local recurrences were detected by routine follow-up CT scanning. In 4 cases, recurrences were proved by surgery, and the others by clinical follow-up. Local recurrences were assessed within 2 years in 10/15 cases (67%), and 4 cases within 6 months. 9 cases had venous thrombosis (IVC 9, renal vein 3), the size of which was reduced after radiotherapy in 1 case. CT is the most preferred imaging technique in evaluating post-nephrectomy patients for renal cell carcinoma.
CT findings of retroperitoneal neoplasma in 50 cases (51 tumors) were reviewed. There were 28 (55%) malignant tumors and 23 (45%) benign ones. MFH and liposarcoma were the most common malignant tumors and neural origin tumors were the most common benign ones. Differentiation is difficult on the basis of CT features alone. Benign tumors were usually smooth and well defined, and malignant ones ill-defined, irregular in shape, heterogenous in density with massive necrosis. The characteristic CT appearance of liposarcoma is the CT attenuation value by fat density. Neural origin tumors are usually located near the spine. They may have thick wall cystic appearance or are dumbbell shaped, showing expansion or extrinsic pressure to the adjacent bone structures. MFH, hemangiopericytoma and other malignant tumors may have marked enhancement after contrast administration. Non-resectability is shown as: 1. big vessels encased by tumor over 90 degrees, 2. adjacent organs or structures invaded by tumor, 3. multiple masses, and 4. huge tumor invading into the pelvis. Local recurrence is common after surgery. Follow-up CT scans every 6 months in a 2 year period is suggested for early detection of recurrence.
Seven cases (8 tumors) of small renal carcinoma (less than 3 cm in diameter) proven by pathology were reviewed. It accounted for 7% of patients with renal cell carcinoma during the same period. Sonogram was hypoechogenic in 3 tumors, isoechogenic in 2 and slightly hyperechogenic in 3. Heteroechogenicity was shown in 3 cases and homoechogenicity in 5. None of the margins was sharp. CT scan showed 4 isodense, 1 hypodense and 1 slightly hyperdense masses. After contrast enhancement, increased attenuation to different degrees but still lower than the normal renal parenchyma was observed. The sensitivity of IVP was low because of the small size of the tumor, peripheral location and rare involvement of the renal calyces and pelvis. MRI is helpful in differential diagnosis of hilar adenopathy and small vessels for tumor staging. Yet, the value of MRI for renal masses should be further studied. On cost benefit, sonography and CT are more practical in the diagnosis of renal carcinoma.
Clinical, X-ray and pathological materials of 21 cases of primary non-Hodgkin's lymphoma (NHL) of the stomach were reviewed. According to NHL classification--working formulation for clinical usage sponsored by NCI, USA, there were 13 (61.9%) intermediate grade, 6 (28.6%) high grade and 2 (9.5%) low grade malignant lymphomas. By X-ray manifestations, they were classified into 5 types: multinodular type (4 cases), infiltrative (4), ulcerative (3), giant rugal (1) and mixed (9). Clinically, 10 lesions were stage I, 4 stage II, 1 stage III and 4 stage IV, 2 unclassified. The median survivals were 101 months for stage I, 15 months for stage II and less than 6 months for stages III and IV. The 5 and 10 year survival rates were 70% and 40% in stage I patients. The prognosis is related to clinical stage, depth of the tumor infiltration and histology type but not related to the tumor size or X-ray manifestations.
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