Biomedical subjects

J Lee

Publications and source records attributed to J Lee.

At least 541 records · Page 30Linked to original sources

PubMed2000

Activity and immobilization after eccentric exercise: II. Serum CK.

PURPOSE: The purpose of the present study was to examine the effect of muscle activity level on serum creatine kinase (CK) activity after high-force eccentric exercise of the elbow flexors. METHODS: Twenty-six male volunteers were randomly assigned to one of three groups for a 4-d treatment period after exercise: immobilization (N = 9), control (N = 8), and light exercise (N = 9). During the treatment period, the immobilization group had their arm casted and supported in a sling at 90 degrees. The control group had no restriction of their arm activity. The light exercise group performed a daily exercise regimen of 50 biceps curls with a 5-lb dumbbell. Serum CK activity was obtained by venipuncture for three consecutive days before eccentric exercise and during the 4-d treatment period. To quantify activity of the arm, CSA (Computer Science and Applications, Inc.) activity-monitoring devices were worn. RESULTS: Serum CK measurements revealed that there was a significant group by time interaction in the analysis of variance (P < 0.05). Peak serum CK activity of the immobilized group (668 IU) was lower than either the control (4230 IU) or light exercise (2740 IU) group. During the treatment period, activity level among the three groups was significantly different from each other (P < 0.001): 529 counts x min(-1) for the immobilization group, 944 counts x min(-1) for the control group, and 1334 counts x min(-1) for the light exercise group. CONCLUSIONS: These results suggest that immobilization of exercised damaged muscle during recovery significantly blunted serum CK activity, which may be due to attenuated removal of CK from the muscle and/or decrease lymphatic transport.

Adult↗

PubMed2000

Venoarterial extracorporeal membrane oxygenation impairs basal nitric oxide production in cerebral arteries of newborn lambs.

OBJECTIVE: Based on previous studies in our laboratory showing that exposure of newborn lambs to venoarterial extracorporeal membrane oxygenation (ECMO) alters cerebral blood flow autoregulation, we postulated that this altered vascular reactivity is mediated through changes in endothelial function caused by the pumping systems used in venoarterial ECMO. We tested that hypothesis in this study. DESIGN: Prospective, controlled, laboratory trial. SETTING: Animal research laboratory. SUBJECTS: Two groups of newborn lambs. INTERVENTIONS: One group of animals was exposed to venoarterial ECMO (n = 6) and another group of control animals (n = 5) was maintained under similar conditions for 2 hrs on the ventilator without ECMO. MEASUREMENTS AND MAIN RESULTS: Third-order branches of the middle cerebral arteries (140-300 microm diameter) were isolated from animals at the end of the experiment, mounted on glass cannulae in an arteriograph, and superfused with Krebs-Ringer buffer. Decrease in the diameter of the arteries induced by exposure of the vessels to nitric oxide synthase inhibitor NG-nitro-L-arginine methyl ester (200 micromol/L) for 30 mins was significantly less (p <.05) in arteries from lambs exposed to ECMO compared with control animals. There were no significant differences between the two groups in myogenic response or in the contractile activity of the arteries to increasing concentrations of serotonin. CONCLUSIONS: These results demonstrate that 2 hrs of exposure of newborn lambs to venoarterial ECMO leads to a decrease in basal production of nitric oxide in cerebral arteries, and suggest that venoarterial ECMO selectively impairs cerebral arterial endothelial function.

Journal Article↗

PubMed2000

Exact zeros of the partition function for a continuum system with double gaussian peaks

We calculate the exact zeros of the partition function for a continuum system where the probability distribution for the order parameter is given by two asymmetric Gaussian peaks. When the positions of the two peaks coincide, the two separate loci of the zeros that used to give a first-order transition touch each other, with the density of zeros vanishing at the contact point on the positive real axis. Instead of the second-order transition of the Ehrenfest classification as one might naively expect, one finds a critical behavior in this limit.

Journal Article↗

PubMed2000

Structure of the Ca2+-regulated photoprotein obelin at 1.7 A resolution determined directly from its sulfur substructure.

The crystal structure of the photoprotein obelin (22.2 kDa) from Obelia longissima has been determined and refined to 1.7 A resolution. Contrary to the prediction of a peroxide, the noncovalently bound substrate, coelenterazine, has only a single oxygen atom bound at the C2-position. The protein-coelenterazine 2-oxy complex observed in the crystals is photo-active because, in the presence of calcium ion, bioluminescence emission within the crystal is observed. This structure represents only the second de novo protein structure determined using the anomalous scattering signal of the sulfur substructure in the crystal. The method used here is theoretically different from that used for crambin in 1981 (4.72 kDa) and represents a significant advancement in protein crystal structure determination.

Aequorin↗

PubMed2000

"Artificial lymphatic system": a new approach to reduce interstitial hypertension and increase blood flow, pH and pO2 in solid tumors.

A mechanical drainage system, the "artificial lymphatic system" (ALS), consisting of a vacuum source and drain, is evaluated for its ability to aspirate the interstitial fluids responsible for the elevated interstitial fluid pressure (IFP) observed in solid tumors. IFP, pH, and pO2 radial profiles were measured before and after aspiration using wick-in-needle (WIN) probes, needle pH and oxygen electrodes, respectively. Laser Doppler flowmetry measured temporal changes in blood flow rate (BFR) at the tumor surface during aspiration. The WIN probe and IFP profile data were analyzed using numerical simulation and distributed mathematical models, respectively. The model parameter, P(E), reflecting central tumor IFP, was reduced from 15.3 to 5.7 mm Hg in neuroblastoma and from 13.3 to 12.1 mm Hg in Walker 256, respectively, following aspiration. The simulation demonstrated that spatial averaging inherent in WIN measurements reduced the calculated magnitude of the model parameter changes. IFP was significantly lower (p<0.05), especially in regions surrounding the drain, and BFR was significantly higher (p<0.05) following 25 and 45 min of aspiration, respectively; pH and pO2 profiles increased following aspiration. The experimental and mathematical findings suggest that ALS aspiration may be a viable way of reducing IFP and increasing BFR, pO2, and pH and should enhance solid tumor chemo and radiation therapy.

Animals↗

PubMed2000

Enhancing the uptake of chemotherapeutic drugs into tumors using an "artificial lymphatic system".

This paper presents findings from uptake studies to evaluate the ability of an "artificial lymphatic system" (ALS) to enhance large and small molecular weight drug transport into solid tumors and the therapeutic effect of the additional drug on their growth. These studies also served to test the effectiveness of an implantable multidrain ALS. Walker 256, Neuroblastoma, and Sarcoma dual-tumor models were used to evaluate the effect of ALS aspiration on the uptake of 3F8 monoclonal antibody, and doxorubicin. A tumor shrinkage experiment using Walker 256 dual tumors was used to evaluate the efficacy of an implantable ALS with cyclophosphamide chemotherapy. Drug uptake significantly increased in all aspirated tumors; 3F8 uptake was enhanced 37.4% in the Walker and 93.1% in the Neuroblastoma tumor lines (p<0.05). Doxorubicin uptake increased 23.2% in Sarcoma tumor (p<0.05). The shrinkage study demonstrated that one-drain aspirated tumors shrank 90% faster (p<0.01) than control tumors, while three-drain aspirated tumors shrank 123% faster than control tumors (p<0.01).

Animals↗

PubMed2000

Phosphorylation-induced signal propagation in the response regulator ntrC.

The bacterial enhancer-binding protein NtrC is a well-studied response regulator in a two-component regulatory system. The amino (N)-terminal receiver domain of NtrC modulates the function of its adjacent output domain, which activates transcription by the sigma(54) holoenzyme. When a specific aspartate residue in the receiver domain of NtrC is phosphorylated, the dimeric protein forms an oligomer that is capable of ATP hydrolysis and transcriptional activation. A chemical protein cleavage method was used to investigate signal propagation from the phosphorylated receiver domain of NtrC, which acts positively, to its central output domain. The iron chelate reagent Fe-BABE was conjugated onto unique cysteines introduced into the N-terminal domain of NtrC, and the conjugated proteins were subjected to Fe-dependent cleavage with or without prior phosphorylation. Phosphorylation-dependent cleavage, which requires proximity and an appropriate orientation of the peptide backbone to the tethered Fe-EDTA, was particularly prominent with conjugated NtrC(D86C), in which the unique cysteine lies near the top of alpha-helix 4. Cleavage occurred outside the receiver domain itself and on the partner subunit of the derivatized monomer in an NtrC dimer. The results are commensurate with the hypothesis that alpha-helix 4 of the phosphorylated receiver domain of NtrC interacts with the beginning of the central domain for signal propagation. They imply that the phosphorylation-dependent interdomain and intermolecular interactions between the receiver domain of one subunit and the output domain of its partner subunit in an NtrC dimer precede-and may give rise to-the oligomerization needed for transcriptional activation.

Bacterial Proteins↗

PubMed2000

Nonstructural protein 5A of hepatitis C virus inhibits the function of karyopherin beta3.

It has been suggested that nonstructural protein 5A (NS5A) of hepatitis C virus (HCV) plays a role in the incapacitation of interferon by inactivation of RNA-dependent protein kinase PKR. In order to further investigate the role of NS5A, we tried to identify cellular proteins interacting with NS5A by using the yeast two-hybrid system. The karyopherin beta3 gene was isolated from a human liver cell library as a protein interacting with NS5A. The protein-protein interaction between NS5A and karyopherin beta3 was confirmed by in vitro binding assay and an in vivo coimmunoprecipitation method. The effect of NS5A on the karyopherin beta3 activity was investigated using a yeast cell line containing mutations in both PSE1 and KAP123, genes that are homologous to the human karyopherin beta3 gene. Human karyopherin beta3 complemented the loss of the PSE1 and KAP123 functions, supporting growth of the double mutant cells. However, expression of NS5A hampered the growth of the double mutant cells supplemented with human karyopherin beta3. On the other hand, expression of NS5A by itself had no effect on the growth of the double mutant expressing wild-type yeast PSE1. This indicates that NS5A may inhibit karyopherin beta3 function via protein-protein interaction. The role of NS5A in HCV replication is discussed.

Animals↗

PubMed2000

Envelope glycoprotein determinants of increased fusogenicity in a pathogenic simian-human immunodeficiency virus (SHIV-KB9) passaged in vivo.

Changes in the envelope glycoprotein ectodomains of a nonpathogenic simian-human immunodeficiency virus (SHIV-89.6) that was serially passaged in vivo have been shown to be responsible for the increased pathogenicity of the resulting virus, SHIV-KB9 (G. B. Karlsson, et al., J. Exp. Med. 188:1159-1171, 1998). The 12 amino acid changes in the envelope glycoprotein ectodomains resulted in increased chemokine receptor-binding and syncytium-forming abilities. Here we identify the envelope glycoprotein determinants of these properties. A single amino acid change in the gp120 third variable (V3) loop was both necessary and sufficient for the observed increase in the binding of the SHIV-KB9 gp120 glycoprotein to the CCR5 chemokine receptor. The increased syncytium-forming ability of SHIV-KB9 involved, in addition to the V3 loop change, changes in the second conserved (C2) region of gp120 (residue 225) and in the gp41 ectodomain (residues 564 and 567). The C2 and gp41 ectodomain changes influenced syncytium formation in a cooperative manner. Changes in the V1/V2 gp120 variable loops exerted a negative effect on syncytium formation and chemokine receptor binding, supporting a previously described role of these changes in immune evasion. The definition of the passage-associated changes that determine the efficiency of chemokine receptor binding and membrane fusogenicity will allow evaluation of the contribution of these properties to in vivo CD4-positive lymphocyte depletion.

Animals↗

PubMed2000

BF-1 interferes with transforming growth factor beta signaling by associating with Smad partners.

The winged-helix (WH) BF-1 gene, which encodes brain factor 1 (BF-1) (also known as foxg1), is essential for the proliferation of the progenitor cells of the cerebral cortex. Here we show that BF-1-deficient telencephalic progenitor cells are more apt to leave the cell cycle in response to transforming growth factor beta (TGF-beta) and activin. We found that ectopic expression of BF-1 in vitro inhibits TGF-beta mediated growth inhibition and transcriptional activation. Surprisingly, we found that the ability of BF-1 to function as a TGF-beta antagonist does not require its DNA binding activity. Therefore, we investigated whether BF-1 can inhibit Smad-dependent transcriptional responses by interacting with Smads or Smad binding partners. We found that BF-1 does not interact with Smads. Because the identities of the Smad partners mediating growth inhibition by TGF-beta are not clearly established, we examined a model reporter system which is known to be activated by activin and TGF-beta through Smads and the WH factor FAST-2. We demonstrate that BF-1 associates with FAST-2. This interaction is dependent on the same region of protein which mediates its ability to interfere with the antiproliferative activity of TGF-beta and with TGF-beta-dependent transcriptional activation. Furthermore, the interaction of FAST-2 with BF-1 is mediated by the same domain which is required for FAST-2 to interact with Smad2. We propose a model in which BF-1 interferes with transcriptional responses to TGF-beta by interacting with FAST-2 or with other DNA binding proteins which function as Smad2 partners and which have a common mode of interaction with Smad2.

Activins↗

PubMed2000

Qualitative interview study of communication between parents and children about maternal breast cancer.

OBJECTIVE: To examine parents' communication with their children about the diagnosis and initial treatment of breast cancer in the mother. DESIGN: Qualitative interview study within a cross-sectional cohort. SETTING: Two breast cancer treatment centers. PARTICIPANTS: 32 women with stage I or stage II breast cancer with 56 school-aged children. Main outcome measures Semistructured interview regarding timing and extent of communication with children about the diagnosis and initial treatment of the mother's illness, reasons for talking to children or withholding information, and help available and requested from health professionals. RESULTS: Women were most likely to begin talking to their children after their diagnosis had been confirmed by biopsy, but a few waited until after surgery or said nothing at all. Family discussion did not necessarily include mention of cancer. There was considerable consistency in the reasons given for either discussing or not discussing the diagnosis. The most common reason for not communicating was to avoid children's questions, particularly those about death. Although most women had helpful discussion with a physician concerning their illness, few were offered help with talking to their children; many would have liked help, particularly the opportunity for both parents to talk to a health professional with experience in understanding and talking to children. CONCLUSION: Parents diagnosed with cancer or other serious illnesses should be offered help to think about whether, what, and how to tell their children and about what children can understand, especially as they may well be struggling themselves to come to terms with their illness.

Adolescent↗

PubMed2000

In the african lungfish Met-enkephalin and leu-enkephalin are derived from separate genes: cloning of a proenkephalin cDNA.

A full-length proenkephalin cDNA (accession number: AF232670) was cloned from an African lungfish (Protopterus annectens) brain cDNA library. The 1,351-bp African lungfish proenkephalin contains an open reading frame that codes 266 amino acids and a stop codon. Within the sequence of lungfish proenkephalin there are 5 pentapeptide opioid sequences (all YGGFM), 1 octapeptide opioid sequence (YGGFMRSL) and 1 heptapeptide opioid sequence (YGGFMGY). A Leu-enkephalin sequence was conspicuously absent in lungfish proenkephalin. These results, coupled with observations on the organization of amphibian proenkephalin and mammalian proenkephalin, indicate that among the Sarcopterygii (lobed finned fish and tetrapods), the appearance of a Leu-enkephalin sequence in proenkephalin may have evolved in either the ancestral amniotes or the ancestral mammals, but not earlier in sarcopterygian evolution. Furthermore, the detection of neurons in the lungfish CNS that are only immunopositive for Met-enkephalin, coupled with earlier anatomical studies on the presence of neurons in the lungfish CNS that are only immunopositive for Leu-enkephalin, indicates that a Leu-enkephalin-coding opioid gene must be present in the CNS of the lungfish. This gene may be the lungfish form of prodynorphin. Given the phylogenetic position of the lungfish in vertebrate evolution, the putative Leu-enkephalin-coding gene must have evolved in the ancestral sarcopterygian vertebrates, or in the ancestral gnathostomes. The apparent slow rate of lungfish evolution makes these organisms interesting models for investigating the evolution of the opioid/orphanin gene family.

Amino Acid Sequence↗

PubMed2000

Pharmacokinetics, pharmacodynamics, and safety of microencapsulated octreotide acetate in healthy subjects.

The pharmacokinetics, pharmacodynamics, and safety of the marketed formulation of microencapsulated octreotide acetate were evaluated in an open-label study in 22 healthy cholecystectomized subjects. Each subject received a single 30 mg dose of microencapsulated octreotide acetate intramuscularly (i.m.). Concentrations of octreotide, growth hormone (GH), insulin-like growth factor binding protein 3 (IGFBP-3), and insulin-like growth factor 1 (IGF-1) as well as clinical safety were evaluated over a period of 112 days (16 weeks). After the injection, mean serum octreotide concentration initially increased rapidly, reached the maximum (Cmax, day 1 = 0.96 +/- 0.25 ng/ml) approximately 1.5 hours after dosing, and declined thereafter until 24 hours postdose (Cmin, 24 h = 0.088 +/- 0.093 ng/ml). The octreotide concentration then increased and started a sustained release from day 7 onward. Plateau concentrations were maintained through day 70 and gradually declined to below the lower limit of quantification (LLOQ) by day 112. The plateau height (Cplateau (2-112d, 60%)) was 1.68 +/- 0.88 ng/ml, and the duration (delta plateau, 60%) was 30.2 +/- 15.7 days. The integrated concentration-time curve, AUC0-112d, was 2819 +/- 782 (ng.h/ml), and the apparent half-life (t1/2) was 169 hours. To assess the variability, the drug concentrations were determined hourly for 8 hours on day 28, and the mean octreotide concentration, Cavg, day 28' was 1.55 +/- 1.26 ng/ml. The suppression of IGF-1 was statistically significant compared to the baseline (p < 0.05) through day 63; however, there were no appreciable changes in GH and IGFBP-3 concentrations after a single injection of microencapsulated octreotide acetate. Simulation of a 28-day dose schedule suggested that steady-state octreotide concentrations would be reached by the third injection with steady-state concentrations about twofold greater than the first injection. There were no serious adverse events or clinically meaningful changes in vital signs, ECGs, or laboratory evaluations observed in this study, indicating that the 30 mg i.m. dose of microencapsulated octreotide acetate was well tolerated in this population.

Abdominal Pain↗

PubMed2000

Stage-specific expression of pituitary adenylate cyclase-activating polypeptide type I receptor messenger ribonucleic acid during ovarian follicle development in the rat.

Expression of pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide with considerable homology to vasoactive intestinal peptide, has been shown to be stimulated by gonadotropins in the ovary. The present studies further evaluated the cell-type specific expression and gonadotropin regulation of PACAP type I receptor (PACAPR) messenger RNA in immature rat ovaries and in cultured preovulatory follicles. Northern blot analysis of ovaries obtained from prepubertal rats revealed the increased expression of PACAPR during prepubertal development. The major cell types expressing PACAPR messenger RNA were granulosa cells of large preantral follicles. Treatment of immature rats with PMSG caused a decrease in ovarian PACAPR expression. In contrast, treatment with human (h) CG at 2 days after PMSG treatment stimulated ovarian PACAPR messenger RNA within 3-6 h in granulosa cells of preovulatory follicles. Treatment of cultured preovulatory follicles in vitro with LH further confirmed the time- and dose-dependent stimulation of PACAPR by gonadotropins in granulosa cells of preovulatory follicles. Moreover, RNase protection assay revealed that the short variant of ovarian PACAPR was the predominant form stimulated during prepubertal development and by gonadotropins. These results demonstrate the expression of PACAPR messenger RNA in granulosa cells of growing follicles and of preovulatory follicles stimulated by gonadotropins, and suggest that PACAP may play a role in the growth of developing follicles and in ovulation as an autocrine/paracrine factor.

Aging↗

PubMed2000

Stimulation of gonadotropin-releasing hormone surges by estrogen. II. Role of cyclic adenosine 3'5'-monophosphate.

Release of GnRH surges in female rats is directed by a daily neural signal and occurs only after exposure of the hypothalamus to sustained, elevated estrogen (E2) levels in serum. We have proposed that preovulatory E2 couples the daily neural signal to the circuitry governing GnRH release by a two-step process, which includes stimulation of neuronal progesterone receptors (PRs) by E2 and subsequent activation of PRs by the daily neural signal. In the preceding report we documented that PR activation is obligatory for the stimulation of GnRH surges by E2. In these studies we assess the validity of a second essential feature of this model, that neural signals can activate PRs and thereby prompt the release of GnRH and LH surges. Our efforts specifically focused on the role of cAMP in mediating neural PR trans-activation leading to GnRH surges. To assess whether cAMP may function as a daily neural signal, cAMP levels were examined via a competitive binding assay in anteroventral periventricular nucleus (AVPV) homogenates obtained at 0900, 1200, 1500, 1800, and 2100 h on all days of the estrous cycle. A significant rise in cAMP concentrations was observed at 1500 h on all estrous cycle days. A similar rise at the same time was observed in AVPV tissues of ovariectomized (OVX) rats regardless of steroid treatment. No significant increase in cAMP levels was observed at any time point in homogenates of ventromedial nucleus or cerebral cortex. In a second experiment, female rats were OVX on the afternoon of diestrous day 2 and simultaneously administered 30 microg estradiol benzoate or oil vehicle. On the following day of presumptive proestrus, rats received intracerebroventricular infusions of the cAMP analog, 8-bromo-cAMP, or saline vehicle at 0900 h. Rats treated with 8-bromo-cAMP exhibited LH surges that were advanced by 3 h compared with those in saline-treated controls. This advance did not occur in 8-bromo-cAMP-treated rats not primed with E2, or in E2-treated rats given the antiprogestin RU486. In a third experiment, OVX, estradiol benzoate-primed rats received intracerebroventricular infusions of saline vehicle or the adenylyl cyclase inhibitor SQ22536; although saline-treated rats exhibited normal LH surges, no surges were observed in the rats receiving SQ22536. In additional SQ22536-treated animals, however, LH surge release was rescued and greatly augmented by a pharmacological dose of progesterone. These results demonstrate that 1) cAMP levels in the AVPV are significantly elevated at 1500 h on a daily basis; 2) cAMP elevations in the AVPV can prematurely evoke LH surges by a mechanism that requires PR activation; 3) inhibition of adenylyl cyclase activity in the AVPV blocks LH surges, an action that can be reversed by progesterone; and 4) cAMP generation leads to PR transactivation in the AVPV. Our observations thus provide support for the hypothesis that an increase in intracellular cAMP in the AVPV acts as a component of the daily neural signal required to initiate GnRH and subsequent LH surges, and that transmission of this signal is mediated by cAMP-induced PR trans-activation in the AVPV.

8-Bromo Cyclic Adenosine Monophosphate↗

PubMed2000

Development of a web-based picture archiving and communication system using satellite data communication.

Using the JAVA language we have developed a Web-based picture archiving and communication system (PACS) which allows a remote hospital to access medical images. An asymmetric satellite data communication system (ASDCS) provided a receive-only link for data delivery and a conventional terrestrial link (which could be the conventional telephone network) allowed data transmission. The satellite communication link was 10-30 times faster than the conventional terrestrial link. To increase image transmission speeds over the Internet connection, JPEG and wavelet compression methods were used. The resulting images were evaluated quantitatively by measuring the peak signal:noise ratio and qualitatively by radiologists. Compression ratios of 10:1 or less were deemed acceptable for diagnostic purposes. The system appears to be suitable for teleradiology and telemedicine.

Computer Communication Networks↗

PubMed2000

Cloning and sequence analysis of the estA gene encoding enzyme for producing (R)-beta-acetylmercaptoisobutyric acid from Pseudomonas aeruginosa 1001.

The estA gene encoding the enzyme that catalyzes the production of (R)-beta-acetylmercaptoisobutyric acid from (R,S)-ester from Pseudomonas aeruginosa 1001, was cloned in Escherichia coli and its nucleotide sequence was determined, revealing the presumed open reading frame encoding a polypeptide of 316 amino acid residues (948 nucleotides). The overall A + T and C + G compositions were 32.59% and 67.41%, respectively. The amino acid sequence of the estA gene product showed a significant similarity with that of the triacylglycerol lipase from Psychrobacter immobilis (38% identity), triacylglycerol lipase from Moraxella sp. (36% identity), and two forms of carboxyl esterases from Acinetobacter calcoaceticus (17% and 17% identities). The deduced amino acid sequences have a pentapeptide consensus sequence, G-X-S-X-G, having an active serine residue, and another active site, dipeptides H-G, located at 70-100 amino acids upstream of the G-X-S-X-G consensus sequence.

Journal Article↗

PubMed2000

Recovery from surgery: grappling with an elusive concept.

When we ask our patients 'How are you?', can we quantify the answer? There is no ideal measure for every circumstance. This article will discuss the issues in measuring postsurgical recovery, describe different approaches, and consider future research.

Humans↗