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At least 145 records · Page 8Linked to original sources
PubMed1989

A comparison of amplitude-modulated and frequency-modulated ambulatory monitoring systems.

To compare the results of monitoring for ischemia with amplitude-modulated (AM) and frequency-modulated (FM) ambulatory recorders, 22 patients with coronary artery disease were monitored during exercise and during 24 to 48 hours of daily activities. Simultaneous recordings were obtained with Oxford Medilog 4000-II and Medilog MR-35 systems from the same 2 bipolar leads. Each potential ischemic episode was interpreted blindly by 2 investigators. Significant ST depression was strictly defined as greater than or equal to 1 mm of horizontal or down-sloping ST depression persisting for 0.06 second beyond the J point and lasting greater than or equal to 1 minute. Of 82 episodes reviewed, 63 (77%) were either positive (37) or negative (26) for ischemia by both systems. However, 17 episodes were interpreted as positive on AM tracings but negative on FM tracings; the converse was true for only 2 episodes (p less than 0.01). For episodes read as positive with both systems, there were close correlations between recorders for duration (r = 0.80) and magnitude (r = 0.90) of ST depression. Because of the greater number of positive AM events, however, the mean total duration of ST depression for patients with ischemia during daily activities was greater on AM than on FM recordings (74 +/- 77 vs 39 +/- 42 minutes, p less than 0.10). Discrepancies between AM and FM tracings were invariably due to small differences in ST-segment morphology or in the magnitude of ST-segment depression. In summary, AM monitors generate complexes similar in appearance to those produced by FM devices in most instances.(ABSTRACT TRUNCATED AT 250 WORDS)

Activities of Daily Living↗
PubMed1989

Modulation of the Ca2+- or Pb2+-activated K+-selective channels in human red cells. II. Parallelisms to modulation of the activity of a membrane-bound oxidoreductase.

Modulation of Ca2+-activable K+ permeability was compared with modulation of a membrane-bound oxidoreductase activity in human erythrocytes. Changes in the K+ permeability were monitored by flux measurements and single-channel recordings. The enzyme activity was detected by measuring reduction of ferricyanide. Pb2+, Atebrin and menadione had parallel effects on the channel protein and the enzyme. In contrast, propranolol stimulates K+ permeability, but is without effect on enzyme activity. The results demonstrate that the K+ channel and the enzyme are distinct membrane proteins but that the enzyme activity may influence channel gating.

Calcium↗
PubMed1986

Modulation of the rabbit chondrocyte phenotype by retinoic acid terminates type II collagen synthesis without inducing type I collagen: the modulated phenotype differs from that produced by subculture.

The differentiated phenotype of rabbit articular chondrocytes can be characterized by the synthesis of high levels of cartilage specific proteoglycan and collagen (type II). Treatment of these cells in primary monolayer culture for periods of up to 18 days with 0.03 to 3.0 micrograms/ml retinoic acid (RA) resulted in suppression of colony formation, altered morphology, and decreased (eightfold) proteoglycan and collagen synthesis. With the exception of collagen synthesis, these changes were complete with all doses after 4 days of treatment. Collagen synthesis declined more slowly; it was dose dependent after 4 days and maximally inhibited by all doses by 9 days. Detailed analysis of the collagen phenotype was performed using SDS-PAGE of intact chains and 2-D CNBr peptide analysis. RA caused cessation of type II synthesis, and transient stimulation of type III and type I trimer collagen synthesis, without induction of type I collagen. Essentially identical results were obtained with retinol. The resultant collagen phenotype differed significantly from the type I-containing phenotype induced by subculture. Thus, suppression of this differentiated program did not elicit a common modulated phenotype. The results are discussed in the context of direct and indirect mechanisms of RA-dependent modulation of chondrocyte gene expression.

Animals↗
PubMed1989

Antigenic modulation induced by four monoclonal antibodies adsorbed on gold particles (specificity anti-CD4, anti-CD5, anti-CD7, and anti-150-kDa antigen): relationship between modulation and cytotoxic activity of immunotoxins.

The present study concerns the antibody-induced antigenic modulation of CD4, CD5, CD7, and 150-kDa antigens present on cells of the CCRF-CEM human T line. The immunogold electron microscopy method was used, and it was found that the entry routes associated with the various antigen-antibody complexes were different. Thus, the anti-CD7 monoclonal antibody (MoAb) was frequently internalized via the coated structures of the cell membrane, whereas anti-CD5 MoAb was rarely internalized via those structures and anti-CD4 and anti-150-kDa antigens never used this route. The delay required for 50% internalization of the labeled MoAb-receptor complexes was 30 min. 1 h, 2 h, and 9 h for anti-CD7, anti-CD5, anti-CD4, and anti-150-kDa antigen MoAbs, respectively. A shedding of complexes from the cell surface was never observed. The internalized labeled MoAbs were sequentially transferred into endocytic vacuoles, then into fine anastomosed tubulovesicular structures, and then into lysosomes. However, the anti-150-kDa antigen MoAb proceeded directly from endocytic vacuoles to lysosomes. Among the four MoAbs studied, anti-CD7 MoAb was the most abundant in the endosomal compartment (up to 34% of internalized particles) before it proceeded to the lysosomes. The overall valency of the anti-CD7 MoAb-labeled beads (from 3.8 to 14 MoAb molecules per bead) did not modify the intracellular routing. These results suggested that the subcellular fate of MoAbs was an intrinsic property of each MoAb-antigen complex. More importantly, the comparison between the MoAb-induced modulation and the cytotoxic level of the immunotoxin built with the same MoAb suggested that receptor-mediated endocytosis via coated pits, along with an abundant occurrence of the antigen-MoAb complex within the endosomal complex, could correspond to the best set of conditions for the transfer of the toxin moiety of the immunotoxin to the cytosol.

Antibodies, Monoclonal↗
PubMed1992

Substrate-specific modulation of Src-mediated phosphorylation of Ras and caseins by sphingosines and other substrate modulators.

It is important for the understanding of protein kinase action to differentiate between regulation at the enzyme and at the substrate levels. For example, the inhibitors dinitrophenol-tyrosine and tyrphostins act at the enzyme level to inhibit phosphorylation of all substrates by c-Src and v-Src kinases. In contrast, polylysine acts at the substrate level to stimulate Src-mediated phosphorylation of beta-casein but to inhibit phosphorylation of alpha-casein. Here we demonstrate novel enzyme-specific and substrate-specific modulations of Src kinase activity of potential physiological significance. At the enzyme level, we observed that c-Src kinase preferentially phosphorylates alpha-casein, while the v-Src kinase prefers beta-casein. At the substrate level we observed substrate-specific modulation by physiological factors including sphingosine, sphingosine derivatives and the ganglioside GM3. Galactosyl-sphingosine (psychosine) was more effective in stimulating phosphorylation of beta-casein and poly(E1A1Y1) than sphingosine. Glucosyl- and lactosyl-sphingosine were ineffective. Rat was extensively phosphorylated by c-Src in the presence of polylysine, and to a lesser extent in the sphingosine and galactosyl-sphingosine. These unexpected differences point out another potential mechanism for regulation of c-Src and v-Src kinase activities and may help to explain some of the pleotyptic manifestations of protein tyrosine kinase actions.

Animals↗
PubMed1998

Is heart rate variability a reliable method to assess autonomic modulation in left ventricular dysfunction and heart failure? Assessment of autonomic modulation with heart rate variability.

Autonomic dysfunction seems to be involved in the progression and prognosis of congestive heart failure. Measurement of heart rate variability (HRV) provides a noninvasive method to obtain reliable and reproducible information on autonomic modulation of heart rate, but there is a difficulty in using HRV as a quantitative estimate of autonomic dysfunction in heart failure. This study was aimed at testing the hypothesis that abnormal modulation of heart rate assessed by power spectrum analysis may be present also in asymptomatic patients with left ventricular dysfunction and progress in patients with overt symptoms of congestive heart failure. HRV was measured in three groups of subjects: Group 1: 30 patients with chronic heart failure; Group 2: 21 patients with asymptomatic left ventricular dysfunction; and Group 3: 25 healthy volunteers as control group. HRV was evaluated by autoregressive spectral analysis with 600-beat ECG samples, while subjects were quietly recumbent (BSI), in conditions of controlled breathing (15 acts/min) (RSC) and passive orthostatism after tilting (80 degrees) (TLT). Patients in group 1 showed a reduction in the standard deviation of the R-R intervals (SDRR) (p<0.0003) and in the low frequency component (LF) (p<0.0001) compared to normal subjects. Low frequency component was not detectable in 11 patients of group I (p<0.0008). On RSC and TLT, group 1 failed to show any modification in the low frequency and high frequency components (HF) under any stimulation. Group 2 showed no modification at baseline evaluation, no increase in the high frequency component on RSC and in LF during TLT compared to controls (p<0.01 and p<0.0001 respectively). At baseline, group 1 had a lower SDRR (p<0.03) and LF (p<0.0001) vs. group 2, whereas during stimulation the two groups exhibited the same behaviour. In conclusion, reduced heart rate variability is specific for both asymptomatic and symptomatic post-ischemic left ventricular dysfunction. Our results suggest that frequency domain analysis of heart rate variability during a stimulation test allows a more accurate definition of the degree of autonomic control of heart rate.

Autonomic Nervous System↗
PubMed2002

Intensity modulated versus non-intensity modulated radiotherapy in the treatment of the left breast and upper internal mammary lymph node chain: a comparative planning study.

BACKGROUND AND PURPOSE: To compare and evaluate intensity modulated (IMRT) and non-intensity modulated radiotherapy techniques in the treatment of the left breast and upper internal mammary lymph node chain. MATERIALS AND METHODS: The breast, upper internal mammary chain (IMC), heart and lungs were delineated on a computed tomography (CT)-scan for 12 patients. Three different treatment plans were created: (1) tangential photon fields with oblique IMC electron-photon fields with manually optimized beam weights and wedges, (2) wide split tangential photon fields with a heart block and computer optimized wedge angles, and (3) IMRT tangential photon fields. For the IMRT technique, an inverse planning program (KonRad) generated the intensity profiles and a clinical three-dimensional treatment planning system (U-MPlan) optimized the segment weights. U-MPlan calculated the dose distribution for all three techniques. The normal tissue complication probabilities (NTCPs) for the organs at risk (ORs) were calculated for comparison. RESULTS: The average root mean square deviation of the differential dose-volume histogram of the breast planning target volume was 4.6, 3.9 and 3.5% and the average mean dose to the IMC was 97.2, 108.0 and 99.6% for the oblique electron, wide split tangent and IMRT techniques, respectively. The average NTCP for the ORs (i.e. heart and lungs) were comparable between the oblique electron and IMRT techniques ( or=2%) for the ORs. CONCLUSIONS: The lowest NTCP values were found with the oblique electron and the IMRT techniques. The IMRT technique had the best breast and IMC target coverage.

Breast Neoplasms↗
PubMed1999

Smart (simultaneous modulated accelerated radiation therapy) boost: a new accelerated fractionation schedule for the treatment of head and neck cancer with intensity modulated radiotherapy.

PURPOSE: To report the initial experience in the definitive treatment of head and neck carcinomas using SMART (Simultaneous Modulated Accelerated Radiation Therapy) boost technique. Radiation was delivered via IMRT (Intensity Modulated Radiotherapy). The following parameters were evaluated: acute toxicity, initial tumor response, clinical feasibility, dosimetry and cost. METHODS AND MATERIALS: Between January 1996 and December 1997, 20 patients with primary head and neck carcinomas were treated with SMART boost technique. The treatment fields encompassed two simultaneous targets. The primary target included palpable and visible disease sites. The secondary target included regions at risk for microscopic disease. Daily fractions of 2.4 Gy and 2 Gy were prescribed and delivered to the primary and secondary targets to a total dose of 60 Gy and 50 Gy, respectively. Lower neck nodes were treated with a single conventional anterior portal. This fractionation schedule was completed in 5 weeks with 5 daily fractions weekly. Toxicity was evaluated by RTOG acute toxicity grading criteria, evidence of infection at immobilization screw sites, subjective salivary function, weight loss, and the need for treatment split. Mean follow-up was 15.2 months. Initial tumor response was assessed by clinical and radiographical examinations. Clinical feasibility was evaluated by the criteria: time to treat patient, immobilization, and treatment planning and QA time. In dosimetry, we evaluated the mean doses of both targets and normal tissues and percent targets' volume below goal. To evaluate cost, Medicare allowable charge for SMART boost was compared to those of conventional fractionated and accelerated radiotherapy. RESULTS: ACUTE TOXICITY: None of the patients had a screw site infection and all patients healed well after completion of radiotherapy. Sixteen of 20 patients (80%) completed the treatment within 40 days without any split. Sixteen patients (80%) had RTOG Grade 3 mucositis while 10 patients (50%) had Grade 3 pharyngitis. Three of 20 patients (15%) had weight loss greater than 10% of their pretreatment weight. Ten patients (50%) required intravenous fluids, tube feeding or both. Nine patients (45%) reported moderate xerostomia with significant relief reported within 6 months. INITIAL TUMOR RESPONSE: 19 patients (95 %) had complete response (CR) while one had partial response (PR). The patient with PR had stable disease on imaging at 12 months follow-up. Two patients were found to have lung metastases at 2 months and 5 months follow-up. To date, there have been two local recurrences in the complete responders. Both patients had nasopharyngeal primary; one was retreated with radioactive Cesium-137 implant and the other died from the disease. CLINICAL FEASIBILITY: The average treatment time for a three-arc treatment was 17.5 minutes and 2.5 minutes for each additional arc. Eleven patients (55%) had four-arc treatment while six patients (30%) had five-arc treatment and three patients (15%) had three-arc treatment. Immobilization was reproducible within less than 2 mm. The treatment planning, QA and documentation prior to treatment averaged 2 days. DOSIMETRY: The mean doses to the primary and secondary targets were 64.4 Gy and 54.4 Gy, respectively; 8.9% of the primary target volume and 11.6% of the secondary target volume were below prescribed dose goal. The mean dose delivered to the mandible was 30 Gy, spinal cord 17 Gy, ipsilateral parotid 23 Gy, and contralateral parotid 21 Gy. COST: Total Medicare allowable charge for SMART boost was $7000 compared to $8600 (conventional) and $9400 (accelerated fractionation). CONCLUSIONS: SMART boost technique is an accelerated radiotherapy scheme that can be delivered with acceptable toxicity. It allows parotid sparing as evidenced both clinically and by dosimetry. Initial tumor response has been encouraging. It is clinically feasible and cost saving. A larger population of patients and a long-term fol

Aged↗
PubMed2001

Simulated hair cell transduction of quasi-frequency-modulated and amplitude-modulated tones.

This paper describes a method for calculating the effect of simulated hair cell transduction on (i) a quasi-frequency-modulated (quasi-FM) tone and on (ii) an amplitude-modulated (AM) tone. The main finding is that the effect of the transduction on AM and quasi-FM (which have the same power spectra but whose phase spectra differ), is to produce different power spectra.

Animals↗
PubMed1998

[The diagnosis and imaging of the a. hepatica after orthoptic liver transplantation--a comparison of frequency-modulated and amplitude-modulated color Doppler sonography].

PURPOSE: We examined whether amplitude-modulated color Doppler (power Doppler) sonography provides a better anatomic imaging of the vascular course of the hepatic artery after liver transplantation. PATIENTS AND METHODS: 82 patients were examined with Doppler sonography after liver transplantation. The distal section of the hepatic artery was imaged both with frequency-modulated color Doppler (color Doppler) and power Doppler and a Doppler spectrum derived from each mode for determination of the flow velocity. RESULTS: Native imaging of the hepatic artery was possible in 78/82 patients, in 2/82 patients only after administration of Levovist, and in 2/82 patients it could not be seen. In these two patients the diagnosis of hepatic artery occlusion was confirmed by angiography. The anatomic course was demonstrated more longitudinally by power Doppler than by color Doppler (p < 0.001; chi 2 test) which made the angle correction easier. A disadvantage of power Doppler was the lack of image contrast to the portal veins; thus evaluation of the vascular course in this section was better possible with color Doppler by means of a specifically generated aliasing in the flow of the hepatic artery (p < 0.001; chi 2 test). Determination of the flow velocity showed no significant differences between color and power Doppler supported duplex sonography. CONCLUSIONS: The combined use of color Doppler and power Doppler improves visualization of the hepatic artery after liver transplantation. The lack of visualization of the vessel after administration of Levovist is diagnostic for occlusion of the vessel.

Adult↗
PubMed1996

A hydrophobic domain of Ca2+-modulating cyclophilin ligand modulates calcium influx signaling in T lymphocytes.

Ca2+-modulating cyclophilin ligand (CAML) was originally described as a cyclophilin B-binding protein whose overexpression in T cells causes a rise in intracellular calcium, thus activating transcription factors responsible for the early immune response. As reported here, structure-function analysis of the CAML gene in Jurkat T cells indicates that two of CAML's putative membrane-spanning domains are necessary and sufficient for the modulation of intracellular calcium. We propose that the hydrophobic C-terminal tail of CAML forms its effector domain, thus implicating the N-terminal hydrophilic domain in a regulatory role. These findings define a novel protein motif that functions in intracellular calcium signaling.

Adaptor Proteins, Signal Transducing↗
PubMedDate not supplied

High-performance photoelastic modulator for polarization modulation spectrometer.

A high-performance photoelastic modulator (PEM) has been built. It consists of a home-made PEM head and a home-built PEM driver that is based on the principle of the phase-locked loop (PLL) (PLL PEM driver). It was installed in our new type circular dichroism (CD) spectrometer for visible light region and its performance was evaluated. With the phase angle being set exactly to zero, the PEM is found to be about eight times more efficient than commercially available one. The efficiency of PEM depends not only on the efficiency of PEM driver but also on the quality of PEM head. The latter can be estimated from admittance-parameter measurements without installing it into a spectrometer. With substituting the PLL PEM driver for a conventional one, the PEM drive voltage can be reduced from one-half to one-third and the baseline shift for air blank that is a measure of the total performance of polarization modulation spectrometers becomes quite small.

Journal Article↗
PubMed2003

A comparative dosimetric study on tangential photon beams, intensity-modulated radiation therapy (IMRT) and modulated electron radiotherapy (MERT) for breast cancer treatment.

Recently, energy- and intensity-modulated electron radiotherapy (MERT) has garnered a growing interest for the treatment of superficial targets. In this work. we carried out a comparative dosimetry study to evaluate MERT, photon beam intensity-modulated radiation therapy (IMRT) and conventional tangential photon beams for the treatment of breast cancer. A Monte Carlo based treatment planning system has been investigated, which consists of a set of software tools to perform accurate dose calculation, treatment optimization, leaf sequencing and plan analysis. We have compared breast treatment plans generated using this home-grown treatment optimization and dose calculation software forthese treatment techniques. The MERT plans were planned with up to two gantry angles and four nominal energies (6, 9, 12 and 16 MeV). The tangential photon treatment plans were planned with 6 MV wedged photon beams. The IMRT plans were planned using both multiple-gantry 6 MV photon beams or two 6 MV tangential beams. Our results show that tangential IMRT can reduce the dose to the lung, heart and contralateral breast compared to conventional tangential wedged beams (up to 50% reduction in high dose volume or 5 Gy in the maximum dose). MERT can reduce the maximum dose to the lung by up to 20 Gy and to the heart by up to 35 Gy compared to conventional tangential wedged beams. Multiple beam angle IMRT can significantly reduce the maximum dose to the lung and heart (up to 20 Gy) but it induces low and medium doses to a large volume of normal tissues including lung, heart and contralateral breast. It is concluded that MERT has superior capabilities to achieve dose conformity both laterally and in the depth direction, which will be well suited for treating superficial targets such as breast cancer.

Breast Neoplasms↗
PubMed1994

Acute effects of levodopa on wrist movement in Parkinson's disease. Kinematics, volitional EMG modulation and reflex amplitude modulation.

Acute changes in motor performance due to levodopa were evaluated by a series of four motor tests unified by their focus on wrist flexion-extension movements. Subjects with idiopathic Parkinson's disease were evaluated with this battery of tests before (OFF) and after their usual morning dose of levodopa (ON). The test battery consisted of (i) repetitive self-paced movement in which velocity was to be maximized; (ii) visually guided tracking of a sinusoid and a square wave; and (iii) an assay of stretch reflex modulation during volitional sinusoidal tracking. The maximal wrist joint velocity of self-paced reciprocating flexion and extension movements increased after levodopa (ON), without significant changes in the movement period or amplitude. In the two tracking tasks, some subjects improved as evident by a lower root mean square (rms) error, but in similar numbers of subjects the rms error increased. Overall, the rms error, peak velocity or peak movement amplitude did not change after levodopa in either tracking task. Significant and consistent changes did occur after levodopa in an assay of reflex modulation during error-constrained tracking (Johnson et al., Brain 1991; 114: 443-60). The amplitude of volitional EMG increased after levodopa, with a concurrent reduction in reflex EMG. These changes are consistent with the noted increase in movement velocity. These results show that the effects of levodopa on movement velocity were not consistently translated into increased accuracy. The changes in the long latency reflex gain argue for a central control of this reflex, mediated by structures sensitive to levodopa. Finally, the results show that the quantitative evaluation of levodopa therapy cannot be unidimensional, but requires a battery of motor tests as undertaken in this study.

Aged↗
PubMed1988

The expression of CR1 and CR3 on non-modulated and modulated granulocytes of healthy blood donors as measured by flow cytofluorometry.

Complement receptors, CR1 and CR3, on neutrophils increase their cellular spontaneously at 37 degrees C or after mechanical stress during the cell preparation. We have established a cell preparation procedure and a cytofluorometric immunoassay method to evaluate the receptor expression in vivo in this study. The expression of CR1 and CR3 was studied after haemolysis in NH4Cl at different temperatures and incubation intervals. It was shown that cell preparation and receptor analysis must be performed at 15 degrees C or lower to avoid up-regulation of the receptor structures. Two minutes' incubation at 20 degrees C was sufficient to modulate the cells in this regard. Granulocytes from healthy blood donors were analysed and the mean fluorescence intensity (MFI), which reflects the number of receptors on the cell surface, showed a normal distribution for the CR1 (n = 158) and CR3 (n = 76) expression in the healthy population. The MFI of the two receptors showed a correlation (r = 0.71). Granulocytes from all donors could be modulated at 37 degrees C to a similar degree for both receptors (r = 0.76), despite the fact that they are supposed to be mobilized from different intracellular pools. A group of patients with localized inflammatory processes, such as sinusitis, differed from the healthy controls. In this group, the CR1 expression was not normally distributed, but 15 out of 26 patients (58%) had granulocytes with a CR1 expression exceeding the mean +/- SD of the normal population.

Adolescent↗
PubMed1996

Purinoceptor modulation of noradrenaline release in rat tail artery: tonic modulation mediated by inhibitory P2Y- and facilitatory A2A-purinoceptors.

1. The effects of analogues of adenosine and ATP on noradrenaline release elicited by electrical stimulation (5 Hz, 2700 pulses) were studied in superfused preparations of rat tail artery. The effects of purinoceptor antagonists, of adenosine deaminase and of adenosine uptake blockade were also examined. Noradrenaline was measured by h.p.l.c. electrochemical detection. 2. The A1-adenosine receptor agonist, N6-cyclopentyladenosine (CPA; 0.1-100 nM) reduced, whereas the A2A-receptor agonist 2-p-(2-carboxyethyl)phenethylamino-5'-N-ethylcarboxamidoadenosine (CGS 21680; 3-30 nM) increased evoked noradrenaline overflow. These effects were antagonized by the A1-adenosine receptor antagonist, 8-cyclopentyl-1,3-dipropylxanthine (DPCPX; 20 nM) and the A2-adenosine receptor antagonist, 3,7-dimethyl-1-propargylxanthine (DMPX; 100 nM), respectively. The P2Y-purinoceptor agonist, 2-methylthio-ATP (1-100 microM) reduced noradrenaline overflow, an effect prevented by the P2-purinoceptor antagonist, cibacron blue 3GA (100 microM) and suramin (100 microM). 3. Adenosine deaminase (2 u ml-1), DMPX (100 nM) and inhibition of adenosine uptake with S-(p-nitrobenzyl)-6-thioinosine (NBTI; 50 nM) decreased evoked noradrenaline overflow. DPCPX alone did not change noradrenaline overflow but prevented the inhibition caused by NBTI. The P2Y-purinoceptor antagonist, cibacron blue 3GA (100 microM) increased evoked noradrenaline overflow as did suramin, a non-selective P2-antagonist. 4. It is concluded that, in rat tail artery, inhibitory (A1 and P2Y) and facilitatory (A2A) purinoceptors are present and modulate noradrenaline release evoked by electrical stimulation. Endogenous purines tonically modulate noradrenaline release through activation of inhibitory P2Y and facilitatory A2A purinoceptors, whereas a tonic activation of inhibitory A1 purinoceptors seems to be prevented by adenosine uptake.

Adenosine↗
PubMed2001

Lipase and its modulator from Pseudomonas sp. strain KFCC 10818: proline-to-glutamine substitution at position 112 induces formation of enzymatically active lipase in the absence of the modulator.

A lipase gene, lipK, and a lipase modulator gene, limK, of Pseudomonas sp. strain KFCC 10818 have been cloned, sequenced, and expressed in Escherichia coli. The limK gene is located immediately downstream of the lipK gene. Enzymatically active lipase was produced only in the presence of the limK gene. The effect of the lipase modulator LimK on the expression of active lipase was similar to those of the Pseudomonas subfamily I.1 and I.2 lipase-specific foldases (Lifs). The deduced amino acid sequence of LimK shares low homology (17 to 19%) with the known Pseudomonas Lifs, suggesting that Pseudomonas sp. strain KFCC 10818 is only distantly related to the subfamily I.1 and I.2 Pseudomonas species. Surprisingly, a lipase variant that does not require LimK for its correct folding was isolated in the study to investigate the functional interaction between LipK and LimK. When expressed in the absence of LimK, the P112Q variant of LipK formed an active enzyme and displayed 63% of the activity of wild-type LipK expressed in the presence of LimK. These results suggest that the Pro(112) residue of LipK is involved in a key step of lipase folding. We expect that the novel finding of this study may contribute to future research on efficient expression or refolding of industrially important lipases and on the mechanism of lipase folding.

Bacterial Proteins↗