Biomedical subjects

B H Lee

Publications and source records attributed to B H Lee.

At least 163 records · Page 9Linked to original sources

PubMed1996

Alteration in mucin gene expression and biological properties of HT29 colon cancer cell subpopulations.

Previous studies from our laboratory have shown that HT29 cells selected by adaptation to methotrexate (HT29-MTX) express mature mucins that differ in their immunoreactivity to antibodies against gastric mucin and in the level of one of two major gastric mucin MUC5AC (MUC5) mRNA compared with parental HT29 cells. In this study, we examined the expression of another major gastric mucin, MUC6 mRNA, as well as that of MUC2, -3 and -5 mRNAs in HT29-MTX cells. We also examined their relationship to mucin-related antigen expression and biological properties of the cells such as adhesion to matrigel and E-selectin and in vitro invasiveness, liver colonising activity and degree of differentiation of nude mouse xenograft. Slot blot and Northern analysis revealed markedly increased levels of MUC5 mRNA but no change in MUC6 mRNA level in HT29-MTX cells compared with parental HT29 cells which express barely detectable levels of MUC6 mRNA. A nuclear run-on study showed that MUC5 mRNA was up-regulated at the transcriptional level. The marked increase in MUC5 mRNA was associated with a significant increase in the expression of human gastric mucin and apomucin antigens in HT29-MTX cells. When the adhesive capacity of two cell lines was compared, HT29-MTX cells showed significantly lower adhesion to E-selectin consistent with their lower expression of sialyl Le(x) and sialyl Le(a) antigens compared with HT29 cells. HT29-MTX cells also showed lower adhesive capacity to matrigel than HT29 cells. Interestingly, HT29-MTX cells exhibited significantly decreased liver colonisation capacity in nude mice following splenic vein injection. Furthermore, nude mouse xenograft tumours produced by HT29-MTX cells exhibited a significantly greater degree of differentiation, consisting of mucin-secreting glands than those produced by HT29 cells. In conclusion, these results indicate a shift of predominantly colonic-type mucins to the gastric type, specifically the surface epithelial cell type (MUC5) but not the mucous neck cell or antral gland type (MUC6) in HT29-MTX cells and strongly suggest that altered regulation of mucin genes and the degree of differentiation in cancer cells may be responsible for the altered biological behaviour of these cells.

Animals↗

PubMed1996

Bitterness in cheese: a review.

Bitterness, the necessary consequence of proteolysis, has been under investigation from different perspectives. This review attempts to give more up-to-date information on the definition of some principal aspects, the relationship between the proteolytic activity and bitter peptide accumulation in cheese, and methods of isolation and detection of bitter peptides. Further knowledge on the physicochemical properties of bitter peptides in cheese as well as in synthetic peptides and the possible control methods for bitterness are discussed. Particular interest in using some strains of lactobacilli or their enzymes as an adjunct in accelerated ripened cheese (ARC) and enzyme-modified cheese (EMC) without bitterness is also described in detail.

Amino Acid Sequence↗

PubMed1996

Okadaic acid increases fibronectin synthesis in MC3T3-E1 cells.

Okadaic acid, a potent specific inhibitor of serine/threonine protein phosphatases type 1 and 2A, affects several gene expressions in various cells. To determine whether okadaic acid affects the expression of fibronectin in MC3T3-E1 cells, we measured mRNA level and synthesis of fibronectin by Northern blot hybridization and immunoprecipitation methods, respectively. Okadaic acid (10-50 ng/ml) increased both mRNA level and synthesis of fibronectin in a dose-dependent manner. The increase of fibronectin mRNA by okadaic acid was strongly attenuated by the inhibition of new protein synthesis. The results indicate that okadaic acid, inhibitor of protein phosphatases, increases fibronectin synthesis in MC3T3-E1 cells.

Animals↗

PubMed1996

Stimulation of fibronectin synthesis through the protein kinase C signalling pathway in normal and transformed human lung fibroblasts.

We examined the role of the protein kinase C (PKC) signaling pathway in the stimulation of fibronectin synthesis in both normal and transformed human lung fibroblasts. Phorbol myristate acetate (PMA), a potent PKC activator, stimulated fibronectin synthesis in both normal and transformed fibroblasts in a time and dose dependent fashion. Down-regulation of PKC by prior exposure of cells to a high concentration of PMA blocked the increase in fibronectin synthesis and mRNA levels induced by PMA. Bisindolylmaleimide, a specific inhibitor of PKC, also abolished the PMA-induced fibronectin synthesis. 4 alpha-phorbol didecanoate, an inactive phorbol ester, failed to affect fibronectin synthesis. These data suggest that PMA stimulates fibronectin synthesis and gene expression through the PKC signaling pathway in both normal and transformed human lung fibroblasts.

Carcinogens↗

PubMed1996

Kinetic and cross-linking studies on the interactions of negative patch mutant plastocyanin from Silene pratensis with photosystem I complexes from cyanobacteria, green algae, and plants.

The site-directed mutants of negative patches on silene plastocyanin (PC) were used to investigate the change of interactions between photosystem I (PSI) and PC during the course of evolution from cyanobacteria to plants. The net charges of two highly conserved negative patches (#42-45 and #59-61) on silene PC were systematically modified from -4 to +1. PSI complexes from cucumber and Chlamydomonas reinhardtii were efficient electron acceptors for silene PC. The increase of net charge on the negative patch (#42-45) of silene PC decreased the reduction rates of PSI from cucumber and Chlamydomonas, while the modification of the other negative patch (#59-61) had no effect. Though the addition of MgCl2 decreased the reduction rate of cucumber PSI, the decrease was severely diminished in the case of Chlamydomonas PSI, and the reduction rate increased with increasing concentration of MgCl2 when the net charge of the negative patch (#42-45) was modified to +1. The PSI complexes from Anabaena variabilis and Synechosystis sp. PCC 6803 were inefficient electron acceptors for silene PC and their rates were almost independent of the net charge of the negative patches, as well as the ionic strength of the reaction mixtures. Silene PC specifically cross-linked to the PsaF subunit of PSI complexes from cucumber, Chlamydomonas, Anabaena, and Synechosystis sp. PCC 6803. Modification of the negative patch (#42-45) inhibited the formation of cross-linked adducts in all the cases examined, whereas modification of the other negative patch (#59-61) had essentially no effect. Based on these results, the changes of electrostatic interactions between PC and PSI during the course of evolution from cyanobacteria to plants are discussed.

Amino Acid Sequence↗

PubMed1996

The clinical evaluation of an outbreak of aseptic meningitis in children.

BACKGROUND: Aseptic meningitis is a common disease in children; The present report describes the clinical and laboratory studies of 62 children involved in an outbreak of aseptic meningitis. METHODS: Sixty-two children with aseptic meningitis having been hospitalized from February to June 1993 were evaluated. The clinical data were obtained by review of the medical records. Initial cerebrospinal fluid (CSF) laboratory values were recorded, and CSF specimens were submitted to determine the viral etiology. RESULTS: Thirty-three percent of the cases were aged 2-5 years. Echovirus 30 was isolated from CSF specimens in 17 children, this is the only virus isolated from CSF during this period. The illness was characterized by transient fever, headache and vomiting. There was wide variation in the number of leukocyte from 14 to 2333 cell/mm3 in the spinal fluid. CSF protein ranged from 19 mg/dL to 114 mg/dL, and CSF sugar was normal in all specimens. Virus isolation was related to the cell count in CSF. There was no significant relationship between CSF cell count and protein content (r = 0.162, p = 0.2237). Hospital stay ranged from 1 to 14 days with an average of 3.9 days. CONCLUSIONS. The disease was mild and self-limiting without death or complication. Enterovirus isolation from CSF can substantially establish the diagnosis and the subsequent management, therefore, early discharge is expectable.

Adolescent↗

PubMed1995

Transcription factors RFX1/EF-C and ATF-1 associate with the adenovirus E1A-responsive element of the human proliferating cell nuclear antigen promoter.

The proliferating cell nuclear antigen (PCNA) is an adenovirus E1A-inducible factor that is intimately linked to the processes of DNA replication and cell cycle regulation. Previously, we defined a novel cis-acting element, the PCNA E1A-responsive element (PERE), that confers induction by the E1A 243R oncoprotein upon the human PCNA promoter. To better understand the regulation of PCNA expression by E1A 243R, we have identified cellular transcription factors that associate with the PERE. In electrophoretic mobility shift assays, the PERE formed three major complexes (P1, P2 and P3) with proteins in nuclear extracts from HeLa or 293 cells. Formation of complexes P2 and P3, which correlates with PCNA promoter activity in vivo, requires the activating transcription factor (ATF) binding site found within the PERE [Labrie et al. (1993) Mol. Cell. Biol., 13, 1697-1707]. Antibody interference experiments and mobility shift assays performed with in vitro-synthesized protein indicated that the transcription factor ATF-1 is a major component of these complexes. Similar assays demonstrated that the hepatitis B virus enhancer-associated protein RFX1 constitutes a major component of the P1 complex. In addition, we examined the binding of proteins to the minimal E1A-responsive promoter to identify other factors important for transcription from the PCNA promoter. Mobility shift assays revealed that a fragment encompassing the region from -87 to +62 relative to the transcription initiation site forms at least five complexes, EH1-EH5, with HeLa cell nuclear extracts. The transcription factor YY1 associates with the initiator element of the PCNA promoter. The identification of these transcription factors will allow their roles in the activation of PCNA by E1A to be evaluated.

Activating Transcription Factor 1↗

PubMed1995

Phase I/II study of neoadjuvant intraarterial chemotherapy with mitomycin-C, vincristine, and cisplatin in patients with stage IIb bulky cervical carcinoma.

BACKGROUND: Stage IIb bulky cervical carcinomas have been considered difficult to treat successfully by radiation and/or surgery, compared with smaller lesions. This study was designed to evaluate the efficacy of neoadjuvant pelvic intraarterial chemotherapy (IAC) and to determine the optimal dosage of cisplatin for reducing tumor volume in these patients. METHODS: Twenty-one previously untreated patients with primary cervical carcinoma of more than 4 cm in greatest dimension and parametrial invasion were included in this study. Pelvic IAC was administered using a combination of mitomycin-C, 10 mg/m2; vincristine, 1 mg/m2; and cisplatin, 50 mg/m2 (MVC; group 1, 8 patients) or 75 mg/m2 (group 2, 13 patients). Tumor volumes were measured three-dimensionally by magnetic resonance imaging (MRI) before and after three courses of IAC. Clinical responses were evaluated with gynecologic examination and MRI; pathologic responses were evaluated with histologic examinations of surgical specimens. RESULTS: The mean volume reduction rate (74.2% vs. 97.2% in groups 1 and 2, respectively, P = 0.0022), the clinical complete response rate (0% vs. 69.2%, P = 0.0033), and the pathologic complete response rate (0% vs. 46.2%, P = 0.0445) were significantly higher in group 2. Type III radical hysterectomy was possible in 19 patients (90.5%). Toxicities of grades 2-3 (World Health Organization criteria) were nausea and/or vomiting (38.1%), leukopenia (33.3%), and fever (14.2%). CONCLUSIONS: These preliminary results suggest that neoadjuvant pelvic IAC with MVC (especially with cisplatin at a dose of 75 mg/m2) is effective in reducing tumor volume, increasing the clinical and pathologic complete response rate, and improving the operability in most patients with Stage IIb bulky cervical carcinoma, generally considered inoperable.

Adult↗

PubMed1995

Domain closure in the catalytic chains of Escherichia coli aspartate transcarbamoylase influences the kinetic mechanism.

The closure of the two domains of the catalytic chains of Escherichia coli aspartate transcarbamoylase, which is critical for completion of the T-->R transition, is stabilized by salt-bridges between Glu-50 and both Arg-167 and Arg-234. Mutation of Glu-50 to Ala shifts the enzyme toward a low activity, low affinity state (Newton, C. J., and Kantrowitz, E. R. (1990) Biochemistry, 29, 1444-1451). Kinetic isotope effects (KIE) and equilibrium isotope exchange kinetics (EIEK) have been used to probe the dynamic properties of the Glu-50-->Ala enzyme. Unlike the behavior of the wild-type enzyme, the observed kinetic isotope effect for 13C versus 12C at the carbonyl group of carbamoyl phosphate (CP) increased upon the binding of ligands which promote the formation of the R-state (Asp, N-phosphonacetyl-L-aspartate (PALA), or ATP). The maximum rate for the [14C]Asp<-->Carbamoyl aspartate (CAsp) exchange with the Glu-50-->Ala enzyme was 500-fold slower than for the wild-type enzyme; however, the rate for the [14C]CP<-->CAsp exchange was only 50-fold slower, reversing the relative rates observed with the wild-type enzyme. In addition, upon variation of substrate pairs involving Asp or CAsp, loss of inhibition effects in the CP<-->CAsp exchange indicated that the Glu-50-->Ala substitution caused the kinetic mechanism for the mutant enzyme to shift from ordered to random. Computer simulations of the EIEK data indicate that the Glu-50-->Ala mutation specifically causes strong decreases in the rates of catalysis and association-dissociation for Asp and CAsp, with minimal effects on the CP and Pi on-off rates. With substrates bound, the Glu-50-->Ala enzyme apparently does not attain a full R-state conformation. The PALA-activated Glu-50-->Ala enzyme, however, exhibits substrate affinities comparable to those for the wild-type enzyme, but fails to restore the preferred order substrate binding. Unlike the wild-type enzyme, both the T and R-states of the Glu-50-->Ala enzyme contribute to catalysis. A third state, I, is proposed for the Glu-50-->Ala enzyme, in which random order substrate binding is exhibited, and the catalytic step contributes significantly to overall rate limitation.

Adenosine Triphosphate↗

PubMed1995

L-aspartate association contributes to rate limitation and induction of the T-->R transition in Escherichia coli aspartate transcarbamoylase. Equilibrium exchanges and kinetic isotope effects with a Vmax-enhanced mutant, Asp-236-->Ala.

Equilibrium isotope exchange kinetics (EIEK) and kinetic isotope effects have been used to determine the mechanistic basis for the altered kinetic characteristics of a mutant version of Escherichia coli aspartate transcarbamylase in which Asp-236 of the catalytic chain is replaced by alanine (Asp-236-->Ala). The [14C]Asp<--> N-carbamyl-L-aspartate (CAsp) and [14C]CP<-->CAsp exchange rates, observed as a function of various reactant-product pairs, exhibited dramatic increases in maximal rates, along with decreases in substrate half-saturation values and cooperativity. The carbon kinetic isotope effect, 13C versus 12C at the carbonyl group of carbamoyl phosphate, for the Asp-236-->Ala enzyme decreased toward unity as [Asp] increased, as observed for the wild-type enzyme. Both the kinetic isotope effects and EIEK results indicate that the Asp-236-->Ala enzyme operates by the same ordered kinetic mechanism as the wild-type enzyme. Although activation effects by ATP and N-phosphonacetyl-L-aspartate are lost, inhibition by CTP was apparent in equilibrium exchanges. Simulation of the EIEK data indicated that the best fit to the observed changes in saturation curves was obtained by preferentially increasing the rate of the T-->R transition, kappa T-->R, thereby destabilizing the T-state and increasing the equilbrium constant for the T<-->R transition. A multistep model for Asp bindng to aspartate transcarbamoylase is proposed, in which Asp induces the initial conformational changes that in turn trigger the T-->R transition, followed by stepwise filling of the remaining active sites.

Alanine↗

PubMed1995

Sequences of the 18S rDNAs from two Collembolan insects: shorter sequences in the V4 and V7 regions.

The complete 18S rDNA sequences were determined for Hypogastrura sp. and Crossodonthina koreana (Insecta: Collembola) using PCR cloning and Taq dideoxy sequencing. These two wingless insects show high sequence similarity to each other, without large insertions and/or deletions, and are clearly distinguished from the two dipteran insects Drosophila melanogaster and Aedes albopictus by shorter sequences in the V4 (61-76 bp) and in the V7 (89-104 bp). regions.

Animals↗

PubMed1995

Identification of new enzyme activities of several strains of Thermus species.

New thermostable enzyme activities of seven Thermus strains were compared using the API ZYM system. All the strains exhibited high levels of alpha- and beta-glycosidases, esterase (C4) and esterase-lipase (C8) activities intracellularly. Only T. thermophilus HB8 (ATCC 27634) showed alpha-glucosidase and esterase activities in the supernatant. According to the intensity of beta-galactosidase activity, Thermus strains were divided in three groups. Group 0, which showed a weak beta-galactosidase activity, included Thermus spp. ATCC 31674 (T351) and 27978 (X-1) as well as T. thermophilus ATCC 27634 (HB8). Group I which consisted of T. aquaticus ATCC 25104 (YT-1), ATCC 25105 (Y-VII-51B) and Thermus sp. ATCC 27737 (T2), had a specific activity of approximately 40.0 U mg-1 and galactose as inducer. T. aquaticus ATCC 31558 (group 2) was particularly effective for beta-galactosidase production (2840 U) with a specific activity of 98 U mg-1. For each strain, galactose (0.5%) was a better inducer of beta-galactosidase production than lactose (1%). The detection of beta-galactosidase activity was dependent on the derivative chromogenic substrates used (naphthyl or nitrophenol coupled to sugar). Oligosaccharides were synthesized from cellobiose, lactulose, maltose or lactose as substrates at high temperature in some strains of Thermus.

Esterases↗

PubMed1995

Expression and characterization of Met92Gln mutant plastocyanin from Silene pratensis.

To investigate the role of the copper-ligand Met92 in the structural and functional properties of silene plastocyanin (PC), Met92 was replaced with Gln, which is the purposed fourth copper-ligand in another blue copper protein, stellacyanin. By use of the recently developed expression system [Hibino et al. (1994) J. Biochem. 116, 826-832], the Met92Gln mutant of intermediate precursor plastocyanin was successfully expressed in Escherichia coli and accumulated in the periplasmic space as a mature protein. In contrast to the wild type, most of the Met92Gln mutant PC accumulated as an apoprotein. After purification, mutant apoprotein could incorporate copper ions, although less efficiently than the wild-type apoprotein. The absorption peak of Met92Gln mutant PC was blue-shifted from 597 nm in the wild type to 591 nm. The rhombic type EPR spectrum was obtained for the mutant in place of the axial spectrum in the wild type. Compared with that of the wild-type PC, the oxidation-reduction potentials of the Met92Gln mutant PC were lower by about 35 mV over the whole pH range examined. These results indicate that the Met92Gln mutant exhibited "stellacyanin-like" spectroscopic properties. Interestingly, the electron-transfer activities of the mutant PC with the physiological electron donor (cytochrome f) and acceptor (Photosystem I) were similar to that of the wild-type PC. Since Met92 is conserved in all the plastocyanins whose primary structures are known, we propose that the primarily function of Met as a copper-ligand is in the uptake of copper ions during folding rather than in electron-transfer activities.

Base Sequence↗

PubMed1995

Site-directed mutagenetic study on the role of negative patches on silene plastocyanin in the interactions with cytochrome f and photosystem I.

To investigate the role of two highly conserved negative patches, residues #42-45 and #59-61, on the surface of plant plastocyanin, six mutants were constructed by site-directed mutagenesis of the intermediate precursor gene from Silene pratensis. The mutants were designed systematically to incorporate positive charges into the negative patches, and the net charge on negative patches was modified from -4 to +1. Upon expression in Escherichia coli, the mutant proteins were correctly processed to the mature size and accumulated as holo-proteins. Absorption spectra, EPR, and redox potentials of the purified mutant proteins were almost indistinguishable from those of the wild-type. It was found that the electron transfer rate from cytochrome f to plastocyanin decreased exponentially as the net charge on the negative patch (#42-45) was increased, whereas the modification of the other negative patch (#59-61) had no effect. Ionic strength dependence studies indicated that the rate constants at infinite ionic strength did not change significantly among the wild-type and the six mutants, and the electrostatic attraction energies between plastocyanin and cytochrome f decreased when residues #42-45 were modified, whereas the modification of residues #59-61 had no effect. These results clearly indicated that only one (#42-45) of the two negative patches is involved in the transient complex formation with cytochrome f. Essentially similar results were observed for the electron transfer from plastocyanin to the photosystem I reaction center (P700), although in this case, slight participation of the negative patch (#59-61) is suggested.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗

PubMed1995

Evaluation of embolization effect of hepatocellular carcinoma by hepatic arterial flow study with Tc-99m MAA SPECT.

The degree of hepatocellular carcinoma vascularity in eight patients was assessed with Tc-99m MAA radionuclide angiography before and after treatment. For chemoembolization therapy, lipiodol and doxorubicin hydrochloride were administered intraarterially along with Gelfoam particles. The ratio of radioactivity in the hepatocellular carcinoma compared to that in the surrounding uninvolved tissue before therapy was 6.5-19.0 with a mean of 12.0. After therapy, the ratio dropped to 0.5-1.3. Because survival improved significantly after the therapeutic regimen used in these patients, radionuclide Tc-99m MAA angiography appears to be an accurate method for demonstrating successful embolization of the vascular supply in hepatocellular carcinoma.

Adult↗

PubMed1995

Cultural conditions for production of glucoamylase from Lactobacillus amylovorus ATCC 33621.

Lactobacillus amylovorus ATCC 33621 is an actively amylolytic bacterial strain which produces a cell-bound glucoamylase (EC 3.2.1.3). Conditions of growth and glucoamylase production were investigated using dextrose-free de Man-Rogosa-Sharpe (MRS) medium in a 1.5 l fermenter, with varying dextrin concentration (0.1-1.5% (w/v)), pH (4.5-6.5) and temperature (25-55 degrees C). Cell extracts were prepared by subjecting cells to treatment with a French Pressure cell in order to release intracellular proteins. Glucoamylase activity was then assayed. The effects of pH (4.0-9.0), temperature (15-85 degrees C) and substrate (dextrin and starch, 0-2% w/v) concentration on crude enzyme activity were investigated. Optimal growth was obtained in MRS medium containing 1% (w/v) dextrin, at pH 5.5 and 37 degrees C. Glucoamylase production was maximal at the late logarithmic phase of growth, during 16-18 h. Crude enzyme had a pH optimum of 6.0 and temperature optimum of 60 degrees C. With starch as the substrate, maximal activity was obtained at a concentration of 1.5% (w/v). The effects of ions and inhibitors on glucoamylase activity were also investigated. Enzyme activity was not significantly influenced by Ca2+ and EDTA at 1 mmol l-1 concentration; however Pb2+ and Co2+ were found to inhibit the activity at concentrations of 1 mmol l-1. The crude enzyme was found to be thermolabile when glucoamylase activity decreased after about 10 min exposure at 60 degrees C. This property can be exploited in the brewing of low calorie beers where only mild pasteurization treatments are used to inactivate enzymes. The elimination of residual enzyme effect would prevent further maltodextrin degradation and sweetening during long-term storage, thus helping to stabilize the flavour of beer.

Culture Media↗

PubMed1995

Increased fall rates in nursing home residents after relocation to a new facility.

OBJECTIVE: To examine the change in fall rates after relocation of nursing home residents from one facility to another and to identify resident risk factors for changes in falls following relocation. DESIGN: Retrospective review of incident reports to identify falls, followed by chart review of a longitudinal cohort. SETTING: An academic nursing home whose residents and programs moved from a 125-year-old, 233-bed facility to a newly constructed 255-bed facility. PATIENTS: A total of 210 nursing home residents were moved from one facility to the other. Of these, 133 individuals who lived in the old facility for 9 months before the move and in the new facility for 6 months after the move formed the longitudinal cohort. RESULTS: In the 3 months after the move, the fall rate increased from 0.34 to 0.70 falls per resident per quarter in the entire nursing home population (P < .001) and subsequently returned to baseline. In the longitudinal subgroup the fall rate went from 0.26 to 0.60 (P < .005). Fall-related injuries in the longitudinal subgroup went from 0.058 injuries per resident per quarter at baseline to 0.15 (P < .001). However, the injury rate per fall did not change. There were no characteristics associated with being a faller in the quarter before the move. Dementia and not being bedbound were associated with being a faller after the move. Individuals who were ambulatory or wheelchair mobile had a significant risk of increasing the number of falls after the move, and individuals with dementia had a strong but insignificant trend in this direction. CONCLUSIONS: The incidence of falling doubled after relocation of nursing home residents to a new facility. An increase in falls was seen in individuals who were not bedbound. Although nursing home relocation may be a relatively uncommon occurrence, it is reasonable to infer that older individuals who change their living environments are at increased risk for falls and fall-related injuries.

Accidental Falls↗

PubMed1995

PR interval behavior during exercise stress test.

OBJECTIVES: The PR interval on the electrocardiogram represents conduction time from the onset of atrial activation through His-Purkinje conduction system during a normal cardiac cycle. While its behavior at rest and during exposure to various cardioactive drugs is well documented, there exist few reports which describe PR interval variations during exercise in normal control and patient groups. In the present study, we examined the behavior of the PR intervals during various stages of exercise, and at the same time we observed whether the changes of PR interval during exercise could suggest that implanted cardiac pacemaker algorithms may be constructed to maximize hemodynamic benefits in patients requiring physiological cardiac pacemaker. METHODS: A retrospective analysis of the exercise treadmill test was performed on 148 healthy control group (148 males, mean age of 42.7 +/- 11.7) and 134 patient group (95 males & 39 females, mean age of 47.1 +/- 11.7) which had complained of non-specific chest symptoms but were identified as normal in the exercise treadmill test. During the test, we used the standard Bruce protocol. The results were expressed as mean +/- standard deviation, and differences in the mean value of each standard deviation, and differences in the mean value of each group were evaluated by the student's t-test. A P value of less than 0.05 was regarded as significant. RESULTS: 1) The control group showed 6.9msec reduction rate of the PR interval whenever their heart rate increased by 10 beats per minute. 2) The entire patients group showed 5msec reduction rate of the PR interval whenever their heart rate increased by 10 beats per minute. 3) The male patients group showed 5.2msec reduction rate of the PR interval whenever their heart rate increased by 10 beats per minute. 4) The female patient group showed 4.3msec reduction rate of the PR interval whenever their heart rate increased by 10 beats per minute. 5) There were significant differences of the PR interval changes between the entire or male patient group and the control group within the same range of heart rates. CONCLUSIONS: This study shows that PR interval changes corresponding to heart rate increments were linearly decreased. These changes of PR interval during exercise suggest that implanted cardiac pacemaker algorithms may be constructed to maximize hemodynamic benefits in patients requiring physiological cardiac pacemakers.

Adult↗