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Biomedical subjects

D C Lee

Publications and source records attributed to D C Lee.

At least 73 records · Page 4Linked to original sources
PubMed1996

Applications of tritium NMR to macromolecules: a study of two nucleic acid molecules.

We have tritium labeled two nucleic acid molecules, an 8 kDa DNA oligomer and a 20 kDa 'hammer-head' RNA for tritium NMR investigations. The DNA sequence studied has been previously used in homonuclear studies of DNA-bound water molecules and tritium NMR was expected to facilitate these investigations by eliminating the need to suppress the water resonance in tritium-detected 3H-1H NOESY experiments. We observed the anticipated through-space interactions found in B-form DNA in the NOESY experiments and an unexpected 'antiphase' cross-peak at the water frequency. T1 measurements on the tritiated DNA molecule indicated that relaxation rates were also accelerated for tritium and protons. Tritium NMR spectra of the hammerhead RNA molecule indicated conformational dynamics in the conserved region of the molecule in the absence of Mg2+ and spermine, two components necessary for cleavage. The dynamics were also investigated by 15N-correlated 1H spectroscopy and persisted after the addition of Mg2+ and spermine.

Base Sequence↗
PubMed1996

Sudden severe barotrauma from self-inflating bag-valve devices.

Self-inflating bag-valve devices are commonly used for the ventilation of intubated patients, especially during resuscitation and transport. These devices are generally safe, but minor deviations in their recommended use can expose patients to airway pressures greater than 135 cm H2O. We present a patient in whom a sudden tension pneumothorax developed during ventilation with a bag-valve device. We believe that this complication resulted from high airway pressures generated in the bag-valve device. The ability of the device in question to cause barotrauma was confirmed by bench-top measurements of the peak airway pressures generated by minor deviations from proper use of the device.

Barotrauma↗
PubMed1996

A new model of uncontrolled hemorrhage that allows correlation of blood pressure and hemorrhage.

OBJECTIVE: To compare hemodynamics, mortality rates, and bleeding rates at 3 severities of hemorrhage in a new model of uncontrolled intra-abdominal bleeding that uses an injury of varying severity and geometry unfavorable to thrombosis. METHODS: Ten swine were bled through a flow-monitored shunt placed between the femoral artery and the peritoneal cavity. The shunt was connected to catheters of varying diameters placed in the femoral artery to create 3 rates of hemorrhage. Blood flow through the shunt was measured with an in-line Doppler probe. Arterial pressures, cardiac output (CO), and ECGs were monitored. Survival and blood loss were calculated. RESULTS: The model successfully produced 3 hemorrhage severities. At all 3 rates of bleeding, blood flow was linearly related to mean arterial pressure, with R2 > 0.72. Bleeding was continuous in all groups. The mean numbers of minutes until death were 53, 45, and 25, respectively, at the increasing shock severities. Blood pressure (BP) and CO decreased continuously in all groups, but did so more rapidly with increasing severity of hemorrhage. CONCLUSIONS: In this model of uncontrolled hemorrhage, bleeding was continuous and linearly related to BP. The hemodynamic response to uncontrolled bleeding in this model differs markedly from those in previous wire aortotomy models where wound geometry is favorable to thrombosis. Hence, when injury geometry is favorable to thrombosis (as in aortotomy), thrombosis formation affects hemorrhage rates and hemodynamic responses.

Analysis of Variance↗
PubMed1996

Effect of permissive hypotension in continuous uncontrolled intra-abdominal hemorrhage.

OBJECTIVE: To determine the effects of aggressive fluid administration vs permissive hypotension on survival, blood loss, and hemodynamics in a model of uncontrolled hemorrhage in which bleeding has been shown to be continuous. METHODS: In this porcine model, 10 animals were bled through a flow-monitored shunt placed between the femoral artery and the peritoneal cavity. The animals received either no fluid (n = 5) or 80 mL/kg lactated Ringer's solution (n = 5) during a resuscitation phase between 10 and 20 minutes postinjury, followed by a 40-minute evaluation phase. Arterial pressures, cardiac output (CO), and hemorrhage rate were measured. Survival and blood loss were calculated outcome measures. RESULTS: The difference in survival between the animals left hypotensive (40%) and those receiving normotensive resuscitation (20%) was not significant (p = 0.49). In the animals receiving fluid resuscitation, mean arterial pressure (MAP) and CO increased during the resuscitative phase, but all the animals suffered the same pattern of hemodynamic deterioration in the evaluation phase. Rate of hemorrhage during the resuscitative phase was 20 +/- 5 mL/min in the animals not receiving fluid and 56 +/- 9 mL/min in the animals receiving fluids. Total blood loss was subsequently 20 mL/kg greater in the animals receiving fluids than in the animals without fluid resuscitation. CONCLUSIONS: In this model of continuous uncontrolled hemorrhage, the difference in survival between the animals left hypotensive and the animals receiving fluid resuscitation was not statistically significant. Increases in MAP and CO with fluid resuscitation were transient and were offset by larger volumes of blood loss. In contrast to the aortotomy model (where thrombosis is likely and hypotensive resuscitation has proven beneficial), this model suggests that in continuous bleeding avoiding fluid resuscitation has a much smaller effect on outcome. Much of the benefit from hypotensive resuscitation may depend on having an injury that can stop bleeding.

Animals↗
PubMed1996

Falsely elevated lithium levels in plasma samples obtained in lithium containing tubes.

CASE REPORT: We present a case of lithium poisoning in a 15-month-old child. Delayed elevation of the plasma lithium concentration at 13 hours after admission to a hospital was noted. This appeared to be factitiously related to the collection of samples in a speckled green top tube which contains lithium heparin as an anticoagulant. CONCLUSION: This type of false elevation has not been reported in the medical literature. A follow-up study in five healthy volunteers showed that the lithium concentrations of plasma samples obtained in speckled green top tubes are increased by approximately 1.5 mEq/L (1.5 mmol/L).

Adult↗
PubMed1996

A new long acting formulation of the luteinizing hormone-releasing hormone analogue goserelin: results of studies in prostate cancer.

PURPOSE: To assess the pharmacodynamic equivalence of the new 10.8 mg. goserelin depot with the current 3.6 mg. depot 3 studies were performed in patients with advanced prostate cancer. MATERIALS AND METHODS: In 2 comparative studies 160 patients were randomized for dosing every 12 weeks using the 10.8 mg. depot or every 4 weeks using the 3.6 mg. depot. In the noncomparative study 35 patients received the 10.8 mg. depot. Blood sampling for serum testosterone and evaluation of toxicity was done during the 48-week study period. RESULTS: Serum testosterone profiles of the 10.8 and 3.6 mg. goserlin depots were similar with testosterone levels decreasing into the castrate range by day 21 after depot administration. The safety profile of 10.8 mg. goserelin is comparable to that of the current monthly depot with the main side effects related to androgen deprivation. CONCLUSIONS: The new long acting depot was pharmacologically equivalent, and well tolerated locally and systemically, and will offer added convenience to patients and health care personnel.

Aged↗
PubMed1996

Characterization of the mouse transforming growth factor alpha gene: its expression during eyelid development and in waved 1 tissues.

The spontaneous mouse waved 1 (wa1) mutation is allelic with the transforming growth factor alpha (TGF-alpha) gene and produces phenotypes similar to those of TGF-alpha knockout mice. Here, we show that TGF-alpha mRNA and protein levels are measurable in wa1 tissues but reduced 5- to 30-fold relative to wild type. Because the wa1-coding sequence is identical to that of the normal mRNA, wa1 is not a null mutation. Nuclear run-on analyses revealed decreased transcription of the TGF-alpha gene in wa1 tissues, but the sequence of a 3.2-kb 5' flanking fragment containing the promoter was unaltered. Moreover, pulsed field gel electrophoresis analysis did not reveal alterations within 750 kb upstream or 350 kb downstream of the gene, and chromosome 6 was karyotypically normal. Hence, we speculate that the wa1 mutation may be subtle and/or reside at a greater distance from the TGF-alpha gene. TGF-alpha deficiency elicits a spectrum of variably penetrant eye anomalies in wa1 and knockout mice that are associated with open eyes at birth. We found that late-gestation wa1 and TGF-alpha-null embryos display a significant delay in eyelid closure, although the eyes of most embryos fuse prior to birth. In situ hybridization localized TGF-alpha expression to the advancing margins of the eyelid epithelium and epidermal growth factor receptor expression throughout the eyelid and corneal epithelia. These results suggest that eye problems observed in TGF-alpha-deficient adult mice arise from premature exposure and trauma to open eyes during or following parturition.

Amino Acid Sequence↗
PubMed1995

Inhibition of mammary gland involution is associated with transforming growth factor alpha but not c-myc-induced tumorigenesis in transgenic mice.

Deregulated expression of transforming growth factor alpha (TGF-alpha) or c-myc has been implicated in the genesis of human breast cancer. To better characterize the role of these molecules in this disease, we generated transgenic mice that express TGF-alpha or c-myc under control of the mouse whey acidic protein (WAP) promoter. We then compared the resulting mammary gland neoplasia in these mice and in previously described mice expressing a metallothionein-driven TGF-alpha transgene. Nonvirgin female mice in all transgenic lineages developed mammary tumors with 100% incidence but variable latency. Among TGF-alpha lines, mean survival time correlated with the level of transgene expression, and the average life spans of high-expressing WAP-TGF-alpha and WAP-c-myc mice were similarly reduced. The majority of TGF-alpha-induced tumors were relatively well-differentiated adenomas and adenocarcinomas; in contrast, WAP-c-myc tumors were poorly differentiated, solid carcinomas with a minority of adenocarcinomas. Most TGF-alpha and all c-myc-induced tumors were transplantable, but lung metastases were infrequently observed in all transgenic lines. WAP-TGF-alpha-induced tumors, in marked contrast to those induced by WAP-c-myc, displayed frequent induction of cyclin D1 mRNA, suggesting that expression of this gene may complement that of TGF-alpha during mammary tumor development. Expression of TGF-alpha also induced precocious development of pregnant glands and delayed or inhibited mammary involution. As a result, multiparious MT-TGF-alpha and especially WAP-TGF-alpha females accumulated large numbers of hyperplastic alveolar nodules that resembled the more differentiated TGF-alpha-induced tumors. Finally, coexpression of WAP-c-myc and WAP-TGF-alpha transgenes markedly decreased tumor latency, increased tumor growth, and even induced mammary tumors in virgin female and male mice. These findings provide further evidence for the importance of deregulated TGF-alpha expression in multistage carcinogenesis, and they suggest that in the mammary gland the mechanism of TGF-alpha-induced transformation may depend on postlactational survival of differentiated epithelium. They also provide evidence of a potent tumorigenic collaboration between TGF-alpha and c-myc in mammary epithelium.

Animals↗
PubMed1995

Mouse chromosomal location of three EGF receptor ligands: amphiregulin (Areg), betacellulin (Btc), and heparin-binding EGF (Hegfl).

The products of five distinct loci, Egf, Tgfa, Areg, Btc, and Hegfl act as ligands for the epidermal growth factor receptor. Egf and Tgfa have previously been mapped to mouse chromosomes 3 and 6, respectively, but the mouse chromosomal locations of Areg, Btc, and Hegfl have not been reported. Here, we show that Areg and Btc are tightly linked on mouse chromosome 5, while Hegfl maps to mouse chromosome 18. We also provide evidence that a putative sixth family member, Sdgf, is in fact a species variant of Areg. These results confirm and extend known relationships between mouse and human chromosomes, and they also provide new information regarding the evolution of this important gene family.

Amphiregulin↗
PubMed1995

A comparison of infrared spectra of proteins in solution and crystalline forms.

Fourier transform infrared spectroscopy has been used to compare the structure of a range of proteins in solution and in the form of single crystals. An infrared microscope was used to record the spectra of single crystals of the proteins. The proteins studied in this way were hen egg white lysozyme, bovine pancreatic ribonuclease A, bovine gamma-II crystallin, human serum amyloid P component, Endothia parasitica pepsin and Mucor pusillus pepsin. The amide I and amide II bands in the FTIR spectra of these proteins were analysed using derivative procedures thereby providing information on the secondary structure. The crystals were held under a vapour of mother liquor to reduce the effects of dehydration. A comparison of the spectra revealed that spectra recorded from crystals of lysozyme, ribonuclease A and gamma-II crystallin are nearly identical to those recorded from the proteins in solution. However, differences are observed between the spectra of serum amyloid P component, Endothia parasitica pepsin and Mucor pusillus pepsin in solution compared with that of the crystalline form These differences are suggested to be due to rearrangements of turn structures within the protein structure.

Animals↗
PubMed1995

Proliferative zones of postnatal rat brain express epidermal growth factor receptor mRNA.

Two ligands for the epidermal growth factor receptor (EGF-R), EGF and transforming growth factor-alpha (TGF alpha), have recently been shown to influence the proliferation, differentiation or survival of diverse populations of fetal and neonatal neuronal and glial cells in culture. These findings suggest that EGF, TGF alpha, or another EGF-R ligand play a role in the regulation of similar cellular developmental events in vivo. In the present study, in situ hybridization with an 35S-labeled cRNA probe was used to determine if mRNA for EGF-R is expressed in two principal germinal zones of the postnatal rat brain, the forebrain ventricular/subventricular zone and the cerebellar external granule layer. Cells labeled with the EGF-R cRNA were distributed throughout the subventricular zone, particularly in the dorsolateral aspect, from birth to adulthood, although the numbers of labeled cells as well as the density of hybridization diminished during development. In the developing cerebellum, virtually all cells in the external granule layer were densely labeled with the EGF-R cRNA, as were numerous perikarya throughout the molecular layer. EGF-R mRNA was also transiently expressed at lower levels by neurons of the internal granule layer and deep cerebellar nuclei. By adulthood, cerebellar expression of EGF-R mRNA was not detected. These results demonstrate prominent expression of EGF-R mRNA within germinal zones of the developing brain and indicate a role for EGF, TGF alpha, or another member of the EGF-related family in regulating the activities of neuronal and glial progenitor cells in vivo.

Animals↗
PubMed1995

Aggregation state and neurotoxic properties of Alzheimer beta-amyloid peptide.

The behaviour of synthetic batches of beta-amyloid (beta A) 1-40 peptide in solution has been studied. The effects of beta A1-40 on a PC12 cell toxicity assay was dependent upon the time of preincubation of an aqueous solution of the peptide before application to the cells. Fibrillization of the beta A1-40, quantitatively assessed by the binding of Congo red to amyloid fibrils, also increased in a time dependent manner over the 168 h incubation period studied. The degree of Congo red binding, in the absence of any preincubation, differed between two synthetically distinct batches of the peptide. The rate of development of fibril formation during subsequent incubation also differed between the two batches and appeared to parallel the effects on cell viability. Infra-red spectroscopic analysis revealed beta-sheet formation for both batches and other more subtle conformational differences between the peptides. Electron microscope examination of the batches of beta A1-40 confirmed the difference in occurrence and development of fibrils. At high magnification, fibrils of both batches exhibited a helical structure. The results suggest that the development of neurotoxicity of beta A1-40 is related to the fibrillar state of the peptide.

Alzheimer Disease↗
PubMed1995

Elevated 8-hydroxydeoxyguanosine in hepatic DNA of rats following exposure to peroxisome proliferators: relationship to mitochondrial alterations.

Recent studies have indicated a lack of correlation between hepatic 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels and the carcinogenicity of peroxisome proliferators (PP) and suggested that DNA in intact hepatic nuclei may be insensitive to increases in 8-OHdG resulting from PP exposure. The possibility that PP-induced elevations in acyl CoA oxidase (ACO) activity might result in oxidative damage to mitochondrial DNA (mtDNA) was therefore investigated by feeding male F344 rats the hepatocarcinogenic PP Wy-14,643 (Wy, 0.1% in the diet) for 3, 6, 11, or 22 weeks, or clofibric acid (CA, 0.5% in the diet) for 22 weeks. Following the respective PP exposures, hepatic peroxisomal acyl CoA oxidase activity was determined and DNA isolated from either mitochondria or unfractionated liver homogenates and analysed for the presence of 8-OHdG. PP treatment caused an increase in ACO activity (10- to 15-fold) at all time points examined and an increase of 8-OHdG (1.5- to 2-fold) in DNA isolated from unfractionated liver homogenates following PP treatment for 11 or 22 weeks. No increase of 8-OHdG in mtDNA was detected. However, quantitation of a PCR amplified region from the D-loop of mtDNA demonstrated a 2- to 3-fold increase in the relative amount of mtDNA in DNA isolated from unfractionated liver homogenates following 3, 11, and 22 weeks exposure to Wy or CA (22 weeks only). In addition, a slight increase in the mitochondrial volume density (1.4-fold) was observed in electron micrographs of liver samples from rats exposed to Wy for 22 weeks. These results (i) demonstrate that PP treatment, at levels which cause an increase in ACO activity, does not cause oxidative damage to mtDNA, and (ii) suggest that one reason for the observed increase of 8-OHdG in DNA from unfractionated liver homogenates may be an increase in the amount of mtDNA present in these samples. Furthermore, these studies provide additional evidence against a role of oxidative DNA damage, measured as 8-OHdG, in PP-induced rodent hepatocarcinogenesis and suggest that alterations in mitochondria or other effects may be more pertinent to PP-related carcinogenesis.

8-Hydroxy-2'-Deoxyguanosine↗