Search PubMed⌕ Search

Biomedical subjects

D Chen

Publications and source records attributed to D Chen.

At least 847 records · Page 47Linked to original sources
PubMed1990

[Comparison of bacteriostatic ability of oleum of Perilla frutescens (L.) Britt., Cinnamomum cassia Presl and Nipagin A].

A comparison of bacteriostatic ability has been carried out among oleum of Perilla frutescens and Cinnamomum cassia, benzoic acid and nipagin A. The result shows that the inhibiting effect of Perilla frutescens and Cinnamomum cassia on microorganisms inoculated and spontaneously contaminated is similar to or obviously superior to nipagin A and benzoic acid.

Aspergillus niger↗
PubMed1990

Malaria chemoprophylaxis among European tourists in tropical Africa: use, adverse reactions, and efficacy.

In order to determine knowledge, attitudes and practices towards malaria prophylaxis, as well as its side-effects and efficacy, a self-administered questionnaire was distributed to European travellers on return flights from tropical Africa to Europe. Between 1985 and 1988 the questionnaire was completed by 44,472 passengers (80.1% of those on board) on 242 flights. A follow-up questionnaire was completed by 42,202 (94.9%) of the same travellers 3 months later. Almost all knew about the risk of malaria, but 10% relied solely on advice from nonmedical sources. While 55.6% had taken at least one measure against mosquito bites, only 4.5% adopted three such measures (used repellents and insecticides and wore long clothing after dusk). Compliance with chemoprophylaxis use was reported by 57.0% of travellers who spent less than 3 months in Africa, compared with 29.2% who stayed 3-12 months. Depending on the antimalaria regimen taken, 11-44% of the travellers experienced adverse effects, while four deaths were attributed to the chemoprophylaxis. The incidence of malaria per month of exposure for travellers who took no chemoprophylaxis was 15.2 per 1000 in East Africa and 24.2 per 1000 in West Africa. In East Africa, the prophylactic efficacy of the currently recommended antimalaria regimens (relative to that of no chemoprophylaxis) was zero for a chloroquine dosage of 300 mg base per week (4 malaria fatalities), 64.1% for a chloroquine dosage of 600 mg base per week (P = 0.03), and 94.0% for mefloquine (P = 0.003).

Adult↗
PubMed1989

Amphiphilic networks: II. Biocompatibility and controlled drug release of poly[isobutylene-co-2-(dimethylamino)ethyl methacrylate].

Biocompatibility and diffusional characteristics of recently synthesized unique amphiphilic networks, i.e., copolymers of methacryloyl-capped polyisobutylene (MA-PIB-MA) with 2-(dimethylamino)-ethyl methacrylate (DMAEMA) have been examined. Excellent biocompatibility and biostability were obtained after 7 weeks with films containing 53-58% MA-PIB-MA implanted dorsally or abdominally in rats. In contrast, networks with higher or lower MA-PIB-MA contents showed decreased biocompatibility. These amphiphilic networks were also studied as potential implantable drug release systems. Bromophenol blue and folic acid were used as model compounds for drug release. Diffusion of these chemicals from loaded networks into water showed a marked pH dependence. Under specific well-defined conditions (MA-PIB-MA/DMAEMA content, pH, time range) release was observed to be independent of time (zero-order release).

Acrylates↗
PubMed1989

Biological and immunological characterization of a simian rotavirus SA11 variant with an altered genome segment 4.

We have studied a variant virus isolated from a stock of SA11 virus (H. G. Pereira, R. S. Azeredo, A. M. Fialho, and M. N. P. Vidal, 1984, J. Gen. Virol. 65, 815-818). This virus, designated 4F, was initially identified by its faster electrophoretic mobility for genome segment 4. The variant was analyzed to determine if the altered electrophoretic mobility of genome segment 4 could be correlated with phenotypic changes. Comparison of our standard laboratory SA11 virus (clone 3) with the 4F variant showed the following: (i) The 4F variant possesses a viral hemagglutinin (VP4) with a higher apparent molecular weight than clone 3. (ii) The 4F variant produces large plaques when assayed in vitro, as compared to clone 3. (iii) The 4F variant produces plaques in the absence of proteolytic enzymes, whereas clone 3 does not. (iv) The 4F variant reacts with serotype-specific neutralizing monoclonal antibodies to VP7, but fails to react with several neutralizing anti-VP4 monoclonal antibodies generated to SA11 clone 3. (v) The 4F variant grows to a higher titer and is more stable than clone 3. (vi) The 4F variant produces a VP4 that appears to be more susceptible to cleavage by trypsin than is the VP4 of clone 3. Further analyses with the 4F variant may lead to an understanding of the molecular basis for these altered phenotypes that appear to be related, at least in part, to the product of genome segment 4.

Antigens, Viral↗
PubMed1989

Phenotypes of rotavirus reassortants depend upon the recipient genetic background.

We have previously characterized the biological and immunological properties of a simian rotavirus SA11 variant (4F) with an altered genome segment 4. The SA11-4F variant formed large plaques in the presence of protease, formed small clear plaques in the absence of protease, and grew to high titer in the presence of protease when compared to our standard wild type (SA11 clone 3). To determine the genome segment of the rotavirus SA11 variant 4F that encoded the unique protease-associated phenotypes of the variant, reassortants were generated that segregated the outer capsid genes of 4F onto a genetic background derived from either the bovine rotavirus B223 or our standard SA11 wild type (clone 3), both of which have contrasting protease-associated phenotypes. The parental and reassortant viruses were examined to determine which genes from the 4F variant encoded the ability (i) to form large plaques in the presence of protease, (ii) to form small clear plaques in the absence of exogenous protease, and (iii) to grow to significantly higher titer in the presence of protease. These phenotypes could be transferred to a clone 3 genetic background by a single genome segment from the 4F variant segment 4. However, in the 4F/B223 reassortants a different and unexpected situation was found. On a B223 genetic background the same phenotypes segregated with a combination of a minimum of two 4F genome segments, segments 4 and 9. These results indicate that the recipient genetic background onto which the genes of a donor rotavirus are reassorted can affect the phenotypes conferred by the presence of the donor segments. Thus, the results of segregation mapping experiments using reassortant viruses should be interpreted with caution.

Cell Line↗
PubMed1989

The parascapular flap for treatment of lower extremity disorders.

The parascapular flap was used as a free microvascular transfer for soft-tissue resurfacing of 11 lower extremities. The diagnoses included four cases of osteomyelitis, three cases of vascular ulceration, one case of combined osteomyelitis and vascular ulceration, two cases of posttraumatic heel defects, and one case of extensive soft-tissue contracture overlying a posttraumatic defect of the femur. All cases were successful clinically. Anatomically, the parascapular flap is supplied by the cutaneous parascapular artery, a branch of the circumflex scapular artery, which itself derives from the subscapular artery. Flap territory may reach 15 x 30 cm, and the vascular pedicle can extend 14 cm if the subscapular artery is taken. Advantages of this flap include the constancy, length, and caliber of the vascular pedicle; the length and width attributes, which allow both coverage of large wounds and primary closure of the donor defect; and an absence of disruption of musculoskeletal function.

Adolescent↗
PubMed1989

Analysis of reassortment and superinfection during mixed infection of Vero cells with bluetongue virus serotypes 10 and 17.

The reassortment of genome segments during mixed infection of Vero cells with bluetongue virus (BTV) serotypes 10 and 17 was investigated, using non-selective conditions for analysis of the progeny of mixed infections. Reassortment was found to be an early event in the BTV replication cycle, indicating that progeny BTV genomes undergo a single round of reassortment. Non-random segregation of individual genome segments was observed in crosses at equal multiplicity of infection, and was confirmed in crosses performed at unequal multiplicity. Asynchronous infections showed that superinfection exclusion resulted in the failure of the superinfecting virus to contribute genome segments to reassortants if the second virus followed the first by more than 4 h. The significance of these results for the evolution and epidemiology of BTV is discussed.

Animals↗
PubMed1989

Atheromatous embolism: varied clinical presentation and prognosis.

Microemboli composed of atheromatous debris can produce sudden failure of one or many organ systems. The soft tissues of the lower extremity are almost always involved, and may sustain the only significant injury. Atheromatous embolization occurs more commonly than is recognized, and its incidence may be increasing. We report ten cases that demonstrate the variability in presentation and prognosis. These data and a review of the existing literature suggest an extremely grave prognosis in patients with generalized organ system involvement, as opposed to those patients with involvement of the lower extremity only. Treatment consists of general supportive care. Anticoagulation or lytic therapy appears to be of no benefit, and may actually contribute to embolization. We discuss new pharmacologic agents as possible treatment for the intense local ischemia, and recommend selective use of lumbar sympathectomy in cases of impending loss of lower extremity tissue.

Aged↗
PubMed1988

Molecular properties of p-(dimethylamino)benzaldehyde bound to liver alcohol dehydrogenase: a Raman spectroscopic study.

We have studied the binding nature of an aromatic aldehyde to the catalytic site of liver alcohol dehydrogenase from horse (LADH) using preresonance Raman spectroscopy. The compound p-(dimethylamino)benzaldehyde (DABA) is converted to the corresponding alcohol in the presence of nicotinamide adenine dinucleotide (NADH) and a catalytic amount of enzyme at neutral pH. A stable ternary complex of LADH/NADH/DABA can be formed if enzyme and coenzyme are in excess at high pH [Jagodzinski, P. W., Funk, G. F., & Peticolas, W. L. (1982) Biochemistry 21, 2193-2202]. We have obtained the preresonance Raman spectrum of bound DABA by subtracting the contribution of the binary complex of LADH/NADH from the spectrum of this stable ternary complex. In order to understand the normal mode patterns of DABA, four isotopically labeled DABA derivatives were synthesized and their Raman spectra, in solution and in the ternary complex, were measured. Three of these compounds contain substitutions in the functionally important aldehyde moiety: (i) In one such substitution, the aldehydic hydrogen atom was replaced by a deuterium; (ii) in another, this hydrogen atom was replaced by deuterium, and the aldehydic carbon atom was replaced by 13C; and (iii) in the third derivative, only the carbon atom was replaced by 13C. The fourth derivative has had the two hydrogen atoms at the 3- and 5-positions of the DABA ring replaced by deuterium atoms. We find that many of the spectral modes are fairly extended, involving both stretching and bending motions of the entire molecule, although a few modes are quite localized. We find that the normal mode structure of DABA changes considerably when it binds to LADH/NADH. As a model for the bound DABA, we have examined the zinc complexes of DABA (and all four isotopically labeled samples) in anhydrous diethyl ether and methylene chloride. A striking correspondence between the Raman spectra of the enzyme-bound DABA and DABA-Zn complexes in solution is found, which extends to all the isotopically labeled derivatives. This suggests that one of the major roles of LADH in the binding of DABA is to provide a divalent zinc ion to form a first-sphere Lewis acid complex. The data also suggest other interactions between enzyme-bound DABA with its protein surroundings and with the coenzyme NADH are quite minor. An estimate of the carbonyl bond character of bound DABA had been made on the basis of the response of Raman bands to isotopic labeling and on trends observed in spectra of DABA in solvents of various polarities.(ABSTRACT TRUNCATED AT 400 WORDS)

Alcohol Dehydrogenase↗
PubMed1988

Respiratory criteria of fitness for surgery and anaesthesia.

A retrospective analysis has been undertaken of 53 operations in 42 patients with severe chronic obstructive airway disease. All patients had a forced expiratory volume in 1 second between 0.3 and 1 litre, but the outcome of surgery was successful after their first operations, all of which were elective; 38 of the 42 had uneventful anaesthesia and surgery together with a normal postoperative period, while four had artificial ventilation of the lungs. The best predictors of the use of postoperative ventilation were the arterial PO2 and whether the patient was dyspnoeic at rest.

Aged↗