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Biomedical subjects

E S Lin

Publications and source records attributed to E S Lin.

At least 19 recordsLinked to original sources
PubMed2000

Nucleotide binding and sulfation catalyzed by phenol sulfotransferase.

The sulfation of a nucleotide is an indispensable step for the sulfuryl group transfer in a biological system. The product and cosubstrate of sulfotransferase in physiological condition are adenosine 3',5'-bisphosphate (PAP) and 3'-phospho adenosine 5'-phosphosulfate (PAPS), respectively. We find that ribose and adenine, two major parts of the adenosine nucleotide, bind tightly to phenol sulfotransferase (PST) separately, and various nucleotides also bind tightly to PST. We determine the dissociation constants of a variety of nucleotides and examine their potential as cofactors or cosubstrates of PST. Using 4-nitrophenyl sulfate as the sulfuryl group donor, three nucleotides, adenosine 5'-monophosphate (AMP), adenosine 2',5'-bisphosphate (2',5'-PAP), and adenosine 2':3'-cyclic phosphate 5'-phosphate (2':3'-cyclic PAP), are shown here for the first time to be sulfated at 5'-phopho position by a PST catalyzed reaction. Spectrophotometry, HPLC, and (31)P NMR are used to determine the activity of PST and identify the sulfated nucleotides. The V(max) of PST and K(m) of these nucleotides are determined when they are used as cofactors or cosubstrates for the sulfuryl group transfer. The existence and possible physiological significance of these newly reported binding and sulfation of nucleotides by PST in biology is yet to be discovered.

Adenosine Diphosphate↗
PubMed1998

Colorimetric determination of the purity of 3'-phospho adenosine 5'-phosphosulfate and natural abundance of 3'-phospho adenosine 5'-phosphate at picomole quantities.

This work presents novel colorimetric methods not only to measure 3'-phospho adenosine 5'-phosphate (PAP) and 3'-phospho adenosine 5'-phosphosulfate (PAPS) in the range of picomoles, but also to determine the purity of PAPS or PAP contaminants in PAPS in the range of nanomoles. These methods exploit the availability of overexpressed phenol sulfotransferase (PST) and the fact that sulfuryl group transfer requires the use of PAP or PAPS as a cofactor or cosubstrate. Experimental results indicate that absorption at 400 nm due to the production of 4-nitrophenol (pNP) is catalyzed by PST when the sulfuryl group transfers from 4-nitrophenylsulfate (pNPS) to PAP or to 2-napthol. In the absence of an acceptor substrate, PAPS is hydrolyzed to PAP by PST and is determined by sulfation with pNPS before and after this reaction. The change of absorption of pNP at 400 nm corresponds to the amount of PAP that is hydrolyzed from PAPS. Moreover, a standard curve is constructed using authentic PAP and PAP-free PST. Furthermore, this curve is used to determine the amount of PAP in extracts of pig liver, rat liver, and Escherichia coli.

Adenosine Diphosphate↗
PubMed1998

Effects of 3'-phosphoadenosine 5'-phosphate on the activity and folding of phenol sulfotransferase.

Known spectroscopic and kinetic data are used to formulate pathways of the physiological and transfer reactions and the substrate inhibition of phenol sulfotransferase. Kinetic mechanisms indicate that release of PAP from enzyme complex is required for the physiological reaction but not for the transfer reaction. The pathways explain rate difference between the physiological and transfer reactions since the release of PAP is the rate-limiting step of the former reaction. Two enzyme species of phenol sulfotransferase which distinguish the physiological and transfer reaction were found to involve the binding of PAP. Differences between two forms of phenol sulfotransferase, alpha and beta, indicate that they assemble through different folding process. It is demonstrated that only alpha enzyme renatures in the presence of PAP and beta enzyme renatures only in the absence of PAP in vitro. In the over-expressed system, formation of alpha and beta phenol sulfotransferase is also dependent on the availability of PAP in Escherichia coli. It is concluded that folding of phenol sulfotransferase is assisted by PAP to form alpha enzyme. In the absence of PAP, beta form of phenol sulfotransferase is produced.

Animals↗
PubMed1996

Configuration of the SCOTI device with different tracheal tubes.

We have evaluated the Sonomatic Confirmation of Tracheal Intubation device (SCOTI) by testing its ability to be correctly configured with a variety of tracheal tubes of differing internal diameter and length. The device only configured correctly for RAE tubes with internal diameter of 7.0 mm or greater and for armoured tubes of internal diameter 8.5 mm. For conventional tubes of varying internal diameter cut to different lengths, configuration was only successful with certain dimensions. The inability to configure the device correctly with all types and lengths of tracheal tubes limits its usefulness as a indicator of tracheal intubation.

Calibration↗
PubMed1995

Leukotriene B4 as a marker of cerebral dysfunction.

It has been postulated that leukotriene B4 is involved in the pathogenesis of postischaemic cerebral oedema. We set out to determine if a relationship exists between jugular bulb leukotriene B4 and other indicators of cerebral ischaemia. No association could be demonstrated for either intracranial pressure, jugular bulb blood oxygen saturation or lactate oxygen index. Our results provide insufficient evidence to suggest that measurement of leukotriene B4 has any place in the management of head-injured patients.

Adolescent↗
PubMed1992

Resistance and additional inspiratory work imposed by the laryngeal mask airway. A comparison with tracheal tubes.

Laryngeal mask airways and tracheal tubes were studied to determine both their resistance to constant gas flows and additional inspiratory work during simulated inspiration. Laryngeal mask airways imposed less resistance and required lower additional inspiratory work compared with the corresponding sized tracheal tubes. If inspiratory loading during anaesthesia is an important consideration, then the laryngeal mask airway may be preferable to a tracheal tube.

Airway Resistance↗
PubMed1991

Plasma catecholamines and oxygen consumption during weaning from mechanical ventilation.

Previous studies on oxygen consumption (VO2) during weaning from mechanical ventilation assumed that an increase in VO2 (delta VO2) reflected oxygen consumption by respiratory muscles (VO2RESP), and proposed delta VO2 as a weaning predictor. We measured VO2 CO2 production (VCO2) and plasma catecholamines in 20 short-term ventilated patients during weaning by SIMV and CPAP. delta VO2 as a percentage of VO2 during spontaneous ventilation (delta VO2%) ranged from 4.8% to 41.5%. VCO2 also increased and correlated with VO2. Plasma adrenaline and noradrenaline increased significantly to levels known to produce considerable increases in metabolic rate. Mean arterial pressure and heart rate concomitantly increased, but spontaneous minute ventilation decreased. Thus, since the increased plasma catecholamines are calorigenic, the assumption that delta VO2 represents VO2RESP is incorrect. Although mean delta VO2% of successfully weaned patients was significantly less than that of failure-to-wean patients, the wide scatter of individual values in the latter group excludes delta VO2% as an accurate weaning predictor.

Adult↗
PubMed1991

Resistance of humidifiers, and inspiratory work imposed by a ventilator-humidifier circuit.

The pressures and resistances of a bubble humidifier (Bennett Cascade) and a blow-by humidifier (Fisher and Paykel) were measured and computed at gas flow rates from 4.5 to 100 litre min-1. Pressures increased with flows, with the Bennett pressures being greater at all flows. The resistance of the Fisher-Paykel increased with flows, but remained less than that of the Bennett. An inverse resistance-flow relationship was seen with the Bennett up to a flow of 35 litre min-1. The work of breathing through a Servo 900C ventilator-humidifier circuit was computed, using a lung model. Work was performed by the Servo 900C on the lung, especially with the Fisher-Paykel circuit. The Bennett circuit required considerably greater (3.7 times more) inspiratory work. Thus the Bennett Cascade humidifier may present an unacceptable inspiratory load during spontaneous breathing.

Anesthesiology↗
PubMed1991

Systems analysis applied to intracranial pressure waveforms and correlation with clinical status in head injured patients.

Intracranial pressure waveforms (ICPWF) in head injured patients vary with the nature and severity of injury. Clinical interpretation of ICPWF shape is not defined. Spectral analysis provides an objective method of measuring changes in waveform shape, but the indices most suitable for clinical use remain unknown. Spectral analysis has been applied to ICPWF recorded from 30 patients with head injury, classified on clinical grounds into good, poor and intermediate groups. Normalized indices derived from ratios of certain characteristics of the ICP waveform to those of the arterial pressure (AP) waveform, were different (P less than 0.05) in all groups. A simple index examined was the harmonic count ratio (Nc:Na) which decreased with increasing severity of injury. ICP/AP harmonic transfer functions were derived, and demonstrated a peaked response in the range 10-12 Hz. Increasing attenuation of this peaked response occurred with increasing severity of injury. These results suggest that transfer functions may be a clinically useful index of intracranial conditions.

Blood Pressure↗
PubMed1991

Intra-arterial blood sampling for clotting studies. Effects of heparin contamination.

Prothrombin time and activated partial thromboplastin time were measured in two groups of 30 patients each. Blood sampled from an arterial line after various discard volumes and from a central venous line were compared with direct venipuncture control samples. The arterial line flushing solution contained 1 unit of heparin per ml in group 1 and 2 units per ml in group 2. Our results confirmed that clotting studies carried out on blood samples from an arterial line or central venous line correlate well with those obtained from a venipuncture sample. The only exception was activated partial thromboplastin time in group 2 patients when the discard volume from the arterial line is only 2.5 ml above the deadspace volume of the connecting line. At least 5 ml of discard volume must be withdrawn before sampling, to obtain reliable results.

Blood Coagulation Tests↗
PubMed1991

Inspiratory work imposed by demand valve ventilator circuits.

The inspiratory work (WI) imposed by three commonly used demand valve ventilator circuits was studied using a lung model to simulate spontaneous ventilation. The CPU-1 and Engstrom Erica circuits recorded WI of 379 mJ/l and 190 mJ/l respectively. A negative WI of -32 mJ/l was recorded for the Servo 900C, denoting that the circuit performed work on the lung. The demand valves recorded a time delay between inspiratory effort and onset of gas flow, of 300 ms (CPU-1), 190 ms (Servo 900c) and 160 ms (Engstrom Erica). Both the Servo 900C and Engstrom Erica demand valves were able to generate a high inspiratory gas flow response, but the CPU-1 lacked such a flow compensation. Expiratory work was also greatest with the CPU-1 (156 mJ/l) with 141 mJ/l and 90 mJ/l recorded for the Servo 900C and Engstrom Erica. Of the three ventilators studied, the Servo 900C appears to be the ventilator circuit of choice for spontaneous ventilation.

Humans↗
PubMed1990

Relationship between resonance and gas exchange during high frequency jet ventilation.

We have studied the relationship between gas exchange and mechanical frequency response during high frequency jet ventilation (HFJV) at 0.5-5.0 Hz in anaesthetized pigs. The mechanical gain curve showed a minimal "anti-resonant" response at 0.8 Hz (f1) and a maximal "resonant" response at 5.0 Hz (f2). This finding may be explained by modelling the thorax and abdomen as a system of coupled masses and compliances which undergo two different modes of forced oscillation in the frequency range studied. Gas exchange was optimal in the frequency range between the minimal and maximal responses. The tidal volumes produced were greater than anatomical deadspace, suggesting that gas transport was mainly convective in this range.

Animals↗
PubMed1990

Measurement of entrainment ratio during high frequency jet ventilation.

We have measured tidal (VT), entrained (Ve) and "blowback" (Vbb) volumes during high frequency jet ventilation (HFJV) through a Mallinckrodt Hi-Lo Jet tracheal tube in anaesthetized patients. The above volumes were calculated by digital integration of the appropriate regions of flow curves derived from a pneumotachograph placed between the bias flow tubing and the tracheal tube. At a driving pressure of 1 bar, lung minute ventilation increased with increasing ventilatory frequency, whilst tidal volumes decreased. The contribution of entrainment to tidal volume (Ve/VT) remained constant, although the volumes entrained were relatively small and varied widely from subject to subject. Blowback volumes were considerable, especially at ventilatory frequencies used clinically (1-2 Hz). We conclude that it is not possible to entrain predictable concentrations of volatile agents from the low pressure bias flow during HFJV.

Adult↗
PubMed1990

Factors influencing humidification in high-frequency jet ventilation.

A new method of water nebulization for high-frequency jet ventilation (HFJV) using a coaxial saline infusion is described. A bench study was performed to investigate how alteration of the HFJV variables affects humidity using this method of humidification. The variables examined included the water flow rate (0.1, 0.25, 0.5, and 1.0 ml/min), cannula OD 2.1 mm (14 ga) and 1.4 mm (17 ga), ventilation rate (60, 80, 100, and 120 beat/min), inspiratory/expiratory (I/E) ratio (0.25, 0.67, and 1.5), and driving pressure (600, 900, 1200, and 1500 torr). Increasing water flow rate increased humidity. Humidity decreased with increased driving pressure, I/E ratio, and cannula OD. Humidity is not much affected by ventilation rate.

Evaluation Studies as Topic↗
PubMed1989

Resonance in the mechanical response of the respiratory system to high frequency jet ventilation.

Eight normal domestic pigs (Large White breed) of body weights 17 kg to 62 kg were subjected to high frequency jet ventilation (HFJV) at frequencies of 1 to 10 Hz (60-600 breaths/min). Six animals survived the study. The gain response curves and phase shift response curves obtained for these animals indicate that respiratory system resonance can be excited at HFJV frequencies. Post-mortem examinations of the nonsurvivors' lungs suggested pulmonary barotrauma. These findings and their clinical implications are discussed.

Animals↗
PubMed1988

The pharmacokinetics of oral and intravenous nalbuphine in healthy volunteers.

The pharmacokinetics of nalbuphine were studied in 10 healthy volunteers on two separate occasions following administration by either the intravenous (20 mg) or oral (60 mg) route. After administration, serum concentrations of nalbuphine were measured for 12 h using a high pressure liquid chromatography assay, and pharmacokinetic parameters were derived using a three compartment model. After i.v. administration, elimination half-life was 222 (111-460) min (mean and range) and total body clearance was 1.5 (0.8-2.3) 1 min-1.Cmax after oral administration was 21.4 (6.0-36.2) ng ml-1 and tmax was 46.6 (15.3-89.0) min. Bioavailability of the oral preparation was 11.8 (6.1-20.1)%.

Administration, Oral↗
PubMed1988

Transcription of the celE gene in Thermomonospora fusca.

The steady-state level of celE mRNA (coding for cellulase E5) in Thermomonospora fusca YX was measured by Northern (RNA blot) hybridization under conditions causing induction or repression of cellulase synthesis. A good correlation was found between the mRNA level and the level of cellulase E5, suggesting that the T. fusca celE gene is regulated at the level of mRNA and, most likely, at the level of transcription. The 5' and 3' ends of the celE gene transcription unit were determined by S1 mapping with single-stranded DNA probes. These results showed that there were three species of celE mRNA in T. fusca YX with closely spaced 5' ends and identical 3' ends. The size of each mRNA was about 1.5 kilobases, from both the Northern and S1 data. This size is only slightly longer than that required to code for the 45-kilodalton E5 protein. In Escherichia coli D318 (celE), the 5' ends of the celE mRNAs are identical to those in T. fusca, but the 3' ends are located ca. 300 base pairs upstream of the T. fusca 3' end. The region where the putative celE promoters were located had some interesting features, including a 60-base-pair A + T-rich sequence and sequences resembling sigma 60 promoters.

Base Sequence↗