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Biomedical subjects

D C Lee

Publications and source records attributed to D C Lee.

At least 145 records · Page 8Linked to original sources
PubMed1986

An infrared spectroscopic study of metastable and stable forms of hydrated cerebroside bilayers.

Fourier transform infrared spectroscopy has been used to study the stable and metastable forms of a range of cerebrosides in aqueous systems. The spectra provide evidence for different degrees of inter- and intra-molecular hydrogen bonding, involving principally the amide group, in these different states. A comparison has been made with the spectra of a cerebroside containing an alpha-hydroxyl group in the fatty acyl chain. This cerebroside does not show metastability and its hydrogen bonding characteristics are shown to be different.

Cerebrosides↗
PubMed1986

Biomembranes as models for polymer surfaces. III. Characterization of a phosphorylcholine surface covalently bound to glass.

A surface layer of phosphorylcholine has been chemically linked with the surface hydroxyl groups present on glass and silica by reaction with mono- and bifunctional reagents. Evidence for the structural integrity of the deposited group was provided by the equimolar association of phosphorus and choline with the reacted surfaces. Modified glass surfaces yielded contact angles which are consistent with those found previously for other models of biological membranes. Covalent modification of the treated surfaces was demonstrated by i.r. spectroscopy via the removal of surface hydroxyl groups. The modified surfaces were thermostable at temperatures up to 375 degrees C for extended periods. The relevance of these results to the generation of new biomaterials is discussed.

Biocompatible Materials↗
PubMed1986

Isolation of cDNA clones coding for the catalytic subunit of mouse cAMP-dependent protein kinase.

mRNA coding for the catalytic (C) subunit of cAMP-dependent protein kinase (ATP: protein phosphotransferase, EC 2.7.1.37) was partially purified from bovine testis by polysome immunoadsorption and oligo(dT)-chromatography. This enriched mRNA preparation was used to prepare and differentially screen a cDNA library. One of the selected cDNA clones was shown to hybrid-select mRNA coding for a 40-kDa protein that was specifically precipitated with antibodies to the C subunit. This bovine cDNA clone was then used to isolate a series of mouse cDNA clones that are complementary to the entire mouse C subunit mRNA. The mouse clones code for a protein of 351 amino acids that shows 98% homology to the bovine C subunit and hybridize to a single mRNA of 2.4 kilobases in mouse heart and brain. Southern blot analysis of total genomic DNA suggests that there is a single mouse gene coding for the C subunit. mRNA levels for both the C subunit and the type I regulatory subunit in various mouse tissues and cell lines were quantitated and compared by using single-stranded RNA probes prepared with SP6 polymerase.

Animals↗
PubMed1985

Second-derivative infrared spectroscopic studies of the secondary structures of bacteriorhodopsin and Ca2+-ATPase.

The resolution of minor amide components in the infrared spectra of membrane proteins has, in the past, been limited by the small differences in frequency compared to the large half-widths of the bands that are assigned to different secondary conformations. Here, second-derivative calculations are used to resolve the relatively weak bands that are associated with the beta-sheet conformation and the vibrations of some amino acid side chains in the infrared spectra of bacteriorhodopsin and Ca2+-activated adenosine-5'-triphosphatase (Ca2+-ATPase). The spectra presented indicate that bacteriorhodopsin in the purple membrane contains an appreciable amount of beta structure in addition to the predominant alpha II-helical structure. Both sarcoplasmic reticulum and purified Ca2+-ATPase in native lipids contain alpha-helical and random coil conformations together with a small amount of beta structure. In 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) Ca2+-ATPase adopts a secondary conformation similar to that in the sarcoplasmic reticulum, and this structure is unaffected by the phospholipid phase transition. A shift to a predominantly random coil conformation is associated with solubilization of both bacteriorhodopsin and Ca2+-ATPase in 20% Triton X-100. Second-derivative analysis of the carbonyl stretching vibrations of DMPC bilayers indicates that below the phase-transition temperature (Tm) both bacteriorhodopsin and Ca2+-ATPase perturb the interface region such that the sn-2 carbonyls adopt a conformation similar to the sn-1 carbonyls. Above Tm, these integral proteins have no effect on the static order of the interface region, and the conformational inequivalence of the sn-1 and sn-2 carbonyls is similar to that found in a pure lipid bilayer.

Animals↗
PubMed1985

Active myocarditis in the spectrum of acute dilated cardiomyopathies. Clinical features, histologic correlates, and clinical outcome.

We studied the clinical features and course (average follow-up time, 18 months) of 27 patients with acute dilated cardiomyopathy (symptoms for less than 6 months) who were referred for endomyocardial biopsy. Almost 40 per cent of the patients subsequently had a rise in left ventricular ejection fraction (on average, from 0.21 to 0.41) and substantial improvement in heart failure; the remainder died or had chronic dilated cardiomyopathy. Biopsy revealed myocarditis in 18 patients, and this finding was especially common (89 per cent) in patients who had been ill for less than four weeks. But the biopsy specimen was negative in four patients whose clinical features and later course were diagnostic of myocarditis. Nine patients received immunosuppressive drugs, and four improved--a rate that did not differ from the rate of spontaneous improvement. Neither the histologic features of the biopsy specimen nor the clinical features at presentation were clearly correlated with subsequent improvement, whether or not immunosuppressive drugs were given. We conclude that many cases of unexplained dilated cardiomyopathy result from myocarditis. Definitive histologic confirmation depends on the duration of illness. The efficacy of immunosuppressive treatment must still be established.

Acute Disease↗
PubMed1985

An analysis of physicians' reasons for prescribing long-term digitalis therapy in outpatients.

We examined by medical-record review why long-term digitalis therapy was prescribed in 150 outpatients, the reasons were: supraventricular tachyarrhythmias (35): supraventricular tachyarrhythmias and heart failure (33); and heart failure with sinus rhythm (82). In the patients without supraventricular tachyarrhythmias we scrutinized the diagnosis of heart failure using a clinicoradiographic scoring system and found the diagnosis unlikely in 32 patients. When these 32 patients are combined with the 31 patients who had only one occurrence of supraventricular tachyarrhythmias or heart failure, 42% of the patients were on long-term digitalis therapy for a questionable reason. We conclude that a substantial fraction of general medical outpatients might benefit from digitalis withdrawal, if evidence for heart failure is lacking or if the reason prompting digitalis therapy is isolated to the distant past.

Aged↗
PubMed1985

Developmental expression of rat transforming growth factor-alpha mRNA.

Expression of the gene encoding transforming growth factor-alpha (TGF alpha) was examined in developing rat embryos by using a cloned TGF alpha cDNA as a hybridization probe. Northern blot analysis of RNA isolated from whole fetuses revealed that TGF alpha mRNA was present at relatively high levels in 8- through 10-day-old embryos and then declined to the low or undetectable level, which is characteristic of adult tissues before birth. The level of TGF alpha mRNA present during early gestation was similar to that present in retrovirus-transformed cells in culture, suggesting that TGF alpha expression is not highly localized in the embryo. These observations are consistent with the hypothesis that TGF alpha plays a role in development, possibly as a fetal growth factor.

Animals↗
PubMed1984

A difference infrared spectroscopic study of gramicidin A, alamethicin and bacteriorhodopsin in perdeuterated dimyristoylphosphatidylcholine.

Difference infrared spectroscopy has been used to study the way in which the intrinsic molecules gramicidin A, alamethicin and bacteriorhodopsin perturb their environment when present within a lipid bilayer structure. Dimyristoylphosphatidylcholine containing perdeuterated chains has been used to enable the lipid chain C-2H stretching absorption band to be separated from the C-H bands arising from the intrinsic polypeptide or protein. The C-2H stretching bands of the phospholipid are sensitive to two different types of chain conformation. The C-2H stretching frequency provides information about the static order of the lipid chains, whilst the half-maximum bandwidth provides a measure of chain librational and torsional motion. From the measurements it is concluded that: (1) Above the lipid phase transition temperature tc, low concentrations of either gramicidin A or alamethicin cause a small decrease in lipid chain gauche isomers whilst bacteriorhodopsin in the lipid bilayer has no effect. At higher concentrations each intrinsic molecule causes an increase to occur in lipid chain gauche isomers. (2) The lipid acyl chain motion, as deduced from the bandwidths is increased by the presence of a low concentration of gramicidin A within the lipid bilayer. The presence of the other intrinsic molecules studied have little effect. A higher concentration of alamethicin causes a decrease in chain motion whilst gramicidin A and bacteriorhodopsin have no effect. (3) Below tc each of the intrinsic molecules when present in the lipid bilayer causes an increase in gauche isomers to occur as well as an increase in the lipid chain motion. A broadening of the lipid phase transition occurs as the concentration of the polypeptide increases.

Alamethicin↗
PubMed1984

Silicone implant correction of pectus excavatum: indications and refinement in technique.

Pectus excavatum is the most common deformity of the chest wall. The overwhelming majority of patients with pectus excavatum have no physiologic compromise. Adolescents beyond their growth spurt and adults who are asymptomatic are best served by placement of a silicone implant to correct the chest-wall defect. We have treated 12 patients in this manner. The initial 7 were treated with placement of a subcutaneous implant. Despite patient satisfaction, we noted several problems that compromised the aesthetic result. In the last 5 patients, the implant has been placed subpectorally, and room temperature vulcanizing silicone has been used to augment the preformed silicone implant if necessary. Subpectoral placement of a preformed silicone implant is a relatively minor procedure with a short hospital stay and minimum morbidity. It avoids a major reconstruction of the chest wall with its inherent risks and complications and provides a pleasing aesthetic result. All 5 patients, 4 of whom had severe deformity, have had good results with postoperative follow-ups of between 8 months and 2 years.

Adolescent↗
PubMed1983

Isolation of a cDNA clone for the type I regulatory subunit of bovine cAMP-dependent protein kinase.

A cDNA clone for the type I regulatory subunit (RI) of cAMP-dependent protein kinase (ATP:protein phosphotransferase, EC 2.7.1.37) was isolated from bovine testis by a differential screening method. mRNA coding for RI was enriched 50- to 100-fold by polysome immunoadsorption chromatography with affinity-purified rabbit anti-RI and protein A-Sepharose. Poly(A)+ RNA from these polysomes was utilized to construct a cDNA library in pBR322, and this library was screened for hybridization to 32P-labeled cDNAs synthesized from either total or RI-enriched poly(A)+ RNA. Plasmids isolated from colonies showing preferential hybridization to the latter probe were further characterized by hybrid selection and DNA sequence analysis. One of these plasmids (designated 62C12) contains a 1,350-nucleotide insert that hybridized to RI mRNA; partial nucleotide sequence analysis confirmed its identity and indicated that it may contain the entire RI coding region. We also have identified a recombinant plasmid with a 1,550-nucleotide insert that selected through hybridization a mRNA coding for a 55,000-dalton protein that crossreacts with anti-RI antibodies. The function of this latter protein is unknown.

Amino Acid Sequence↗
PubMed1983

Effects of dimethyl sulfoxide and acupuncture on the cardiovascular system of dogs.

The intravenous administration of dimethyl sulfoxide (100 mg/kg) resulted in a significant increase in cardiac output, stroke volume, central venous pressure, and a significant decrease in heart rate. Acupuncture by electrocautery at Jen Chung (Go-26) produced a significant increase in cardiac output, stroke volume, heart rate, mean arterial pressure, and pulse pressure and a significant decrease in total peripheral resistance in dogs under 0.75% halothane anesthesia. Both DMSO and acupuncture elicit an analgesic effect and enhance cardiovascular function as exemplified by an increase in the cardiac output.

Acupuncture Therapy↗
PubMed1982

Heart failure in outpatients: a randomized trial of digoxin versus placebo.

The view that digitalis clinically benefits patients with heart failure and sinus rhythm lacks support from a well-controlled study. Using a randomized, double-blind, crossover protocol, we compared the effects of oral digoxin and placebo on the clinical courses of 25 outpatients without atrial fibrillation. According to a clinicoradiographic scoring system, the severity of heart failure was reduced by digoxin in 14 patients; in nine of these 14, improvement was confirmed by repeated trials (five patients) or right-heart catheterization (four patients). The other 11 patients had no detectable improvement from digoxin. Patients who responded to digoxin had more chronic and more severe heart failure, greater left ventricular dilation and ejection-fraction depression, and a third heart sound. Multivariate analysis showed that the third heart sound was the strongest correlate of the response to digoxin (P less than 0.0001). These data suggest that long-term digoxin therapy is clinically beneficial in patients with heart failure unaccompanied by atrial fibrillation whose failure persists despite diuretic treatment and who have a third heart sound.

Adult↗
PubMed1982

Inhibition of the cardiovascular effects of lysine acetylsalicylate by propranolol in dogs during halothane anaesthesia.

The cardiovascular effects of lysine acetylsalicylate and/or propranolol were studied in 26 dogs. All animals were maintained under anaesthesia with halothane 0.75 per cent, supplemented by the intravenous administration of succinylcholine to allow controlled ventilation during a two hour period of monitoring. Cardiac output, stroke volume, heart rate, mean arterial pressure, pulse pressure, central venous pressure, total peripheral resistance, pH, Paco2, pao2 and base deficit were measured in each dog. Lysine acetylsalicylate 50 mg . kg-1, administered alone as a single bolus, significantly (P less than 0.05) increased the cardiac output and stroke volume and significantly decreased the heart rate, central venous pressure and total peripheral resistance in dogs under halothane anaesthesia. Propranolol hydrochloride 0.5 mg . kg-1 as a single intravenous bolus was followed by a significant decrease in cardiac output, heart rate and mean arterial pressure and a significant increase in central venous pressure and total peripheral resistance. The administration of propranolol prior to lysine acetylsalicylate resulted in a significant decrease in cardiac output and heart rate. Pretreatment with propranolol was effective in inhibiting the positive inotropic effect of lysine acetylsalicylate.

Anesthesia, General↗
PubMed1982

DNA sequences affecting specific initiation of transcription in vitro from the EIII promoter of adenovirus 2.

We have identified those sequences affecting the level of specific initiation of transcription in vitro from the EIII promoter of adenovirus 2. Mutants containing deletions in and around the initiation sites were constructed in cloned viral DNA fragments and assayed for their ability to initiate transcription in vitro. Three classes of mutants were studied with deletions in the following regions: -38 to -268, -21 to -71 (which includes the T-A-T-A-A box), and -29 through the cap sites (+1 and +3). Deletions that remove some or all of the area from -28 to several nucleotides downstream from the cap sites essentially abolished specific transcription. Small deletions in the region -30 to -41 reduced transcription to approximately 60% of wild type; larger deletions in the region -35 to -268 reduced transcription to 30-40% of wild type. Deletions beginning from approximately +10 to +25 and extending further downstream reduced transcription to 20-40% of wild type, whereas a deletion beginning at +31 had little or no effect. Our results suggest that the region including the T-A-T-A-A box and extending to the area immediately beyond the cap sites is essential for specific transcription in vitro from the EIII promoter. However, sequences upstream from the T-A-T-A-A box and those downstream from the cap sites appear to significantly modulate the levels of transcription.

Adenoviruses, Human↗
PubMed1981

Reversal by acupuncture of cardiovascular depression induced with morphine during halothane anaesthesia in dogs.

The cardiovascular effects of morphine sulphate and/or acupuncture by means of electrocautery at Jen Chung (Go-26) were studied in 35 dogs. All animals were maintained under anaesthesia with halothane 0.75 per cent supplemented by the intravenous administration of succinylcholine to allow controlled ventilation during a two hour period of monitoring. Cardiac output, stroke volume, heart rate, mean arterial pressure, pulse pressure, central venous pressure, total peripheral resistance, [H+] (pH) PaCO2, PaO2 and base deficit were measured in each dog. Morphine 0.5 mg . kg-1, administered alone as a single bolus, significantly (P less than 0.05) decreased cardiac output, heart rate, mean arterial pressure, and significantly increased stroke volume and pulse pressure in dogs under halothane anaesthesia. Acupuncture by electrocautery alone induced a significant increase in cardiac output, stroke volume, heart rate, mean arterial pressure and pulse pressure with a significant decrease in total peripheral resistance following halothane. Acupuncture at Jen Chung (Go-26) for 10 minutes following the intravenous administration of morphine caused a significant increase in cardiac output, heart rate and mean arterial pressure with a significant decrease in central venous pressure and total peripheral resistance during halothane anaesthesia. The depressant effect of morphine on cardiac output, heart rate and mean arterial pressure in dogs under halothane anaesthesia appears to be reversed by acupuncture by electrocautery at Jen Chung (Go-26). Stimulation of this acupuncture locus could be helpful in resuscitating patients whose cardiovascular system is depressed by morphine and/or halothane anaesthesia.

Acupuncture Therapy↗
PubMed1981

Transcription of adenovirus type 2 genes in a cell-free system: apparent heterogeneity of initiation at some promoters.

We examined the transcription of a variety of adenovirus type 2 genes in a cell-free system containing purified ribonucleic acid polymerase II and a crude extract from cultured human cells. The early EIA, EIB, EIII, and EIV genes and the intermediate polypeptide IX gene, all of which contain a recognizable TATAA sequence upstream from the cap site, were actively transcribed in vitro, albeit with apparently different efficiencies, whereas the early EII (map position 74.9) and IVa2 genes, both of which lack a TATAA sequence, were not actively transcribed. A reverse transcriptase-primer extension analysis showed that the 5' ends of the in vitro transcripts were identical to those of the corresponding in vivo ribonucleic acids and that, in those instances where initiation was heterogeneous in vivo, a similar kind of heterogeneity was observed in the cell-free system. Transcription of the polypeptide IX gene indicated that this transcript was not terminated at, or processed to, the polyadenylic acid addition site in vitro. We also failed to observe, using the in vitro system, any indication of transcriptional regulation based on the use of adenovirus type 2-infected cell extracts.

Adenoviruses, Human↗