Effect of temperature on rate of left ventricular pressure fall in humans

The time constant (T) of left ventricular pressure fall is widely used as an index of ventricular "relaxation". It is not known whether its rate limiting step is deactivation, an enzymic energy consuming reaction whose rate is therefore sensitive to temperature, or elastic recoil. To distinguish between these possibilities, the time constant was measured by simple logarithmic (Tlog) and exponential (Texp) methods in 12 patients during cooling before coronary artery grafting. Ventricular loading conditions were altered by transfusion from bypass to maintain arterial and left atrial pressures constant in individual patients, though heart rate fell from 86 (8.4) to 68 (10) beats/min. Tlog increased from 49 (10) ms mean (SD), at 37 degrees C to 86 (15) ms at 31 degrees C, and Texp from 63(14) at 37 degrees C to 112 (23) ms at 31 degrees C with intermediate values at 34 degrees C. Texp proved sensitive to "noise" at low temperatures, but the overall change in Tlog with temperature was 9% per degree C--considerably less than that observed experimentally for the rate of tension decline of isolated myocardium, and possibly itself an overestimate because of the concomitant fall in heart rate. The relatively small effect of temperature on Tlog in humans, associated with a considerable load sensitivity appearing under hypothermic conditions, does not favour simple dependence on deactivation as the rate limiting step of left ventricular pressure fall, but suggests that its determinants may be complex.     

Effect of temperature on rate of left ventricular pressure fall in humans.

The time constant (T) of left ventricular pressure fall is widely used as an index of ventricular "relaxation". It is not known whether its rate limiting step is deactivation, an enzymic energy consuming reaction whose rate is therefore sensitive to temperature, or elastic recoil. To distinguish between these possibilities, the time constant was measured by simple logarithmic (Tlog) and exponential (Texp) methods in 12 patients during cooling before coronary artery grafting. Ventricular loading conditions were altered by transfusion from bypass to maintain arterial and left atrial pressures constant in individual patients, though heart rate fell from 86 (8.4) to 68 (10) beats/min. Tlog increased from 49 (10) ms mean (SD), at 37 degrees C to 86 (15) ms at 31 degrees C, and Texp from 63(14) at 37 degrees C to 112 (23) ms at 31 degrees C with intermediate values at 34 degrees C. Texp proved sensitive to "noise" at low temperatures, but the overall change in Tlog with temperature was 9% per degree C--considerably less than that observed experimentally for the rate of tension decline of isolated myocardium, and possibly itself an overestimate because of the concomitant fall in heart rate. The relatively small effect of temperature on Tlog in humans, associated with a considerable load sensitivity appearing under hypothermic conditions, does not favour simple dependence on deactivation as the rate limiting step of left ventricular pressure fall, but suggests that its determinants may be complex.     

Measured and estimated sinoatrial conduction during variations in rhythm. Microelectrode study of the isolated rabbit atrium

Strips of isolated atrium were obtained from 10 rabbits to study the validity of indirect methods of estimating sinoatrial conduction time during variations of the sinus rhythm. Direct recordings of the trans-membrane action potential of the sinus node were made. Mapping of the sinus region was undertaken to determine the site of the dominant pacemaker. A quadripolar surface electrode was positioned on the lower part of the crista terminalis for stimulation and recording of the atrial potential. This enabled a comparison to be made between the indirect estimated and the directly measured conduction times. An intrasinusal shift of the dominant pacemaker was obtained by cooling from 38 degrees C to 35 degrees C. This shift occurs progressively in the cranino-candal direction. The estimated and measured conduction times were compared under basal conditions and after cooling. The sinus cycle was significantly longer (p less than 0.001) at 35 degrees C (318 +/- 68 ms) than at 38 degrees C (255 +/- 48 ms). The mean measured anterograde conduction time also decreased from 36 to 31 ms (p less than 0.01) and the mean measured retrograde conduction time also decreased from 39 to 33 ms (p less than 0.02); the total conduction time decreased from 75 to 64 ms (p less than 0.001). The results of the total estimated conduction times were discordant. The associated effects of stimulation and cooling can cause conduction defects and an overestimation of the conduction time.(ABSTRACT TRUNCATED AT 250 WORDS)     

New studies on the heat resistance of hamster-adapted scrapie agent: threshold survival after ashing at 600 degrees C suggests an inorganic template of replication

One-gram samples from a pool of crude brain tissue from hamsters infected with the 263K strain of hamster-adapted scrapie agent were placed in covered quartz-glass crucibles and exposed for either 5 or 15 min to dry heat at temperatures ranging from 150 degrees C to 1,000 degrees C. Residual infectivity in the treated samples was assayed by the intracerebral inoculation of dilution series into healthy weanling hamsters, which were observed for 10 months; disease transmissions were verified by Western blot testing for proteinase-resistant protein in brains from clinically positive hamsters. Unheated control tissue contained 9.9 log(10)LD(50)/g tissue; after exposure to 150 degrees C, titers equaled or exceeded 6 log(10)LD(50)/g, and after exposure to 300 degrees C, titers equaled or exceeded 4 log(10)LD(50)/g. Exposure to 600 degrees C completely ashed the brain samples, which, when reconstituted with saline to their original weights, transmitted disease to 5 of 35 inoculated hamsters. No transmissions occurred after exposure to 1, 000 degrees C. These results suggest that an inorganic molecular template with a decomposition point near 600 degrees C is capable of nucleating the biological replication of the scrapie agent.     

Calcium induced reversible alterations in excitation-contraction coupling in verapamil treated rat myocardium

We studied the effects of a calcium channel blocking agent, verapamil (V) (2 to 10 micrograms/ml), in the presence of increasing external calcium on simultaneously recorded transmembrane electrophysiological properties and mechanical function of rat myocardium. Left ventricular papillary muscles from male Fischer 344 rats were studied electrically, by standard microelectrode techniques, and mechanically in an isolated tissue bath at 30 degrees C. Control (0 micrograms/ml V + 2.4 mM Ca2+) = C, action potential duration at 50% and 75% repolarization (D50ap and D75ap) recorded from papillary muscles were short (14.1 +/- 0.75 ms; 33.3 +/- 2.7 ms) compared with recordings from papillary muscles subjected to increasing doses of verapamil (2, 4, 6, 8, or 10 micrograms/ml) + 2.4 mM Ca2+ = V, (17.3 +/- 0.77 ms; 121.4 +/- 8.9 ms: 10 micrograms/ml) (P less than 0.001). Upon augmentation of external calcium [10 micrograms/ml Verapamil + augmented Ca2+ (4.8, 7.2, or 9.6 mM] = VCa, D50ap and D75ap decreased but still remained significantly longer than control D50ap and D75ap (15.1 +/- 0.77 ms; 110.1 +/- 7.9 ms). Developed tension (Td), time to peak developed tension (TPT), time to one-half relaxation (T1/2R) and resting tension (Tr) decreased as a function of verapamil concentration. Although TPT and T1/2R returned toward C values when external calcium was increased, Tr continued to decrease while Td increased above control levels. A significant correlation was found between measured parameters of contraction and transmembrane action potential for C and VCa muscles. However, in V muscles no significant correlation was observed between these same mechanical and electrical parameters.(ABSTRACT TRUNCATED AT 250 WORDS)     

Intracellular and extracellular recordings of sinus node activity: comparison with estimated sinoatrial conduction times during pacemaker shifts in rabbit heart

Sinoatrial conduction times, estimated by premature atrial stimulation, were compared with direct measurement of the sinoatrial conduction time in 15 isolated rabbit sinus node preparations before and after intrasinusal pacemaker shifts induced by cooling. Transmembrane potentials and surface electrograms were recorded from the sinus node and crista terminalis. Extracellular sinus node activity was recorded in five preparations. Mapping was performed at 38 degrees C and 35 degrees C to determine the site of the dominant pacemaker. The sinus cycle was significantly longer at 35 degrees C (319.4 ms vs 258.1 ms). Intracellular measured conduction time was significantly shorter (63.8 ms vs 70.4 ms) because of caudal shift of the dominant pacemaker. Estimated sinoatrial conduction time was significantly longer (110.3 ms vs 85.4 ms) owing to the depression of automaticity by the extrastimulus. Extracellular measured conduction time did not differ significantly from intracellular measured conduction time. These results suggest that intrasinusal pacemaker shift may explain inaccuracies in indirect estimations of sinoatrial conduction time by atrial pacing techniques. Extracellular recordings appear to be a better method of evaluating sinoatrial conduction times.     

Imaging of thermal activation of actomyosin motors

We have developed temperature-pulse microscopy in which the temperature of a microscopic sample is raised reversibly in a square-wave fashion with rise and fall times of several ms, and locally in a region of approximately 10 micrometers in diameter with a temperature gradient up to 2 degrees C/micrometers. Temperature distribution was imaged pixel by pixel by image processing of the fluorescence intensity of rhodamine phalloidin attached to (single) actin filaments. With short pulses, actomyosin motors could be activated above physiological temperatures (higher than 60 degrees C at the peak) before thermally induced protein damage began to occur. When a sliding actin filament was heated to 40-45 degrees C, the sliding velocity reached 30 micrometers/s at 25 mM KCl and 50 micrometers/s at 50 mM KCl, the highest velocities reported for skeletal myosin in usual in vitro assay systems. Both the sliding velocity and force increased by an order of magnitude when heated from 18 degrees C to 40-45 degrees C. Temperature-pulse microscopy is expected to be useful for studies of biomolecules and cells requiring temporal and/or spatial thermal modulation.     

Heat shock proteins of higher plants

The pattern of protein synthesis changes rapidly and dramatically when the growth temperature of soybean seedling tissue is increased from 28 degrees C (normal) to about 40 degrees C (heat shock). The synthesis of normal proteins is greatly decreased and a new set of proteins, "heat shock proteins," is induced. The heat shock proteins of soybean consist of 10 new bands on one-dimensional NaDodSO(4) gels; a more complex pattern is observed on two-dimensional gels. When the tissue is returned to 28 degrees C after 4 hr at 40 degrees C, there is progressive decline in the synthesis of heat shock proteins and reappearance of a normal pattern of synthesis by 3 or 4 hr. In vitro translation of poly(A)(+)RNAs isolated from tissues grown at 28 and 40 degrees C shows that the heat shock proteins are translated from a new set of mRNAs induced at 40 degrees C; furthermore, the abundant class mRNAs for many of the normal proteins persist even though they are translated weakly (or not at all) in vivo at 40 or 42.5 degrees C. The heat shock response in soybean appears similar to the much-studied heat shock phenomenon in Drosophila.     

Detection of one slowly exchanging substrate water molecule in the S3 state of photosystem II

The exchangeability of the substrate water molecules at the catalytic site of water oxidation in photosystem II has been probed by isotope-exchange measurements using mass spectrometric detection of flash-induced oxygen evolution. A stirred sample chamber was constructed to reduce the lag time between injection of H2(18)O and the detecting flash by a factor of more than 1000 compared to the original experiments by R. Radmer and O. Ollinger [(1986) FEBS Lett. 195, 285-289]. Our data show that there is a slow (t1/2 approximately 500 ms, 10 degrees C) and a fast (t1/2 <25 ms, 10 degrees C) exchanging substrate water molecule in the S3 state of photosystem II. The slow exchange is coupled with an activation energy of about 75 kJ/mol and is discussed in terms of a terminal manganese oxo ligand, while the faster exchanging substrate molecule may represent a water molecule not directly bound to the manganese center.     

Evidence of left ventricular contractile asynchrony by echocardiographic phase imaging in patients with type 2 diabetes mellitus and without clinically evident heart disease

Left ventricular electromechanical asynchrony has been shown to predict cardiac events in patients with heart failure. This study investigated whether left ventricular asynchrony is present in patients with type 2 diabetes mellitus (DM) with no clinically evident heart disease and normal QRS durations. Asynchrony was evaluated in 24 patients with DM, 15 nondiabetic control subjects, and 20 patients with left bundle branch block (LBBB) due to cardiomyopathy serving as positive controls by conventional tissue Doppler imaging and by a novel method, echocardiographic phase imaging. Asynchrony was significantly higher in patients with DM than in controls and significantly lower than in patients with LBBB. This was shown by tissue Doppler imaging: the SD of time to peak myocardial velocity was 13 +/- 10 ms in controls, compared with 30 +/- 19 ms in patients with DM (p <0.01) and 68 +/- 28 ms in those with LBBB (p <0.001). Similar data were obtained using echocardiographic phase imaging: the SD of phase degrees was 25 degrees +/- 8 degrees in controls, compared with 44 degrees +/- 21 degrees in patients with DM (p = 0.02) and 76 degrees +/- 25 degrees in those with LBBB (p <0.001). Tissue Doppler imaging correlated with echocardiographic phase imaging (r = 0.79, p <0.0001) but was more time consuming (15.5 +/- 4.5 vs 4.5 +/- 2.2 min/patient, p <0.05) and showed higher intraobserver variability (5.6% vs 3.2%, p <0.05). In conclusion, this is the first study showing increased left ventricular asynchrony in patients with DM and no clinical evidence of heart disease.     

Tsutsugamushi disease found in the northern districts of Awaji Island--epidemiological study of the outbreak season temperature

Ten cases of tsutsugamushi disease which were diagnosed and treated among the outpatients from 1987 through 1999 in a clinic of internal medicine locating at the northern districts of Awaji Island were investigated. The patients were consisted of 8 males and 2 females and their ages ranged from 6 to 69 years old. The infected areas were distributed in hilly districts extending over three towns. The outbreak season was from November through December. The following two facts seemed to be worthy of notice. 1) There was a time lag on the patient's onset among the different years. 2) When the incidences were more than two cases a year, the time difference of onset was within a few days each other. Then the relationship between atmospheric temperature and the date of onset was studied. Meterological observing records at Gunge Ichinomia Town near the northern districts of Awaji Island were investigated into the temperature every 10 days from 1987 to 1999. Average temperature every 10 days including the presumable day when each patient was infected with Orientia tsutsugamushi (O.T) ranged between 9.1 degrees C and 13.3 degrees C and in 7 of 10 cases ranged between 11.6 degrees C and 13.3 degrees C. The maximum temperature ranged between 11.3 degrees C and 17.5 degrees C, the minimum one between 6.6 degrees C and 9.1 degrees C. It is likely that the seasonal occurrence of tsutsugamushi disease greatly depends upon the optimum temperature for the activity of tsutsugamushi mites in these areas. The high titer of serum IgM and IgG antibody to Karp, Gilliam Kato type O. tsutsugamushi was detected by an immunofluorescense assay (IF) in all cases. IgG antibody, titers fell drastically to 20 or 10 times within a few years but 10 times titer was still detected in three cases in more than ten years. It is suggested that IgG antibody titer more than 10 times in healthy people indicates the infection in the past and titer more than 20 times implies the infection during the past few years.     

Products of neutrophils and eosinophils increase the responsiveness of human isolated bronchial tissue

This study examines the possibility that products of neutrophils and eosinophils could increase the responsiveness of human isolated bronchial tissue. Neutrophils and eosinophils were isolated from the peripheral blood of healthy volunteers. The cells were incubated with 1 microM calcium ionophore A23187 for 10-15 min then centrifuged, the supernatant collected and stored at -70 degrees C. Human bronchial rings (2-3 mm diameter, 3-4 mm long) were prepared from specimens resected at thoracotomy. The tissues were suspended in organ baths under a 1 g load and changes in tension measured isometrically. Stable contractions to bolus doses of histamine (0.1-10 microM) or to electrical field stimulation (40-100 V, 4-16 Hz, 1 ms for 20 s) were established. Supernatant from 106 neutrophils or 105 eosinophils was then added and tissue responsiveness reassessed. Neutrophil supernatant increased tissue responsiveness to histamine and electrical field stimulation by 54 +/- 17% (n = 5, p less than 0.05) and 18 +/- 7% (n = 6, p less than 0.05), respectively. Eosinophil supernatant increased the histamine response by 60 +/- 23% (n = 8, p less than 0.05) while tissue responsiveness to electrical field stimulation was unchanged (n = 3). Thus, as neutrophils and eosinophils can change the responsiveness of human bronchus in vitro it is possible that they do this in vivo and may not simply be temporally related to the development of bronchial hyperresponsiveness.     

Major cold shock protein of Escherichia coli.

When exponentially growing Escherichia coli cell cultures were transferred from 37 degrees C to 10 degrees C or 15 degrees C, the production of a 7.4-kDa cytoplasmic protein (CS7.4) was prominently induced. The rate of CS7.4 production reached 13% of total protein synthesis within 1-1.5 hr after a shift to 10 degrees C and subsequently dropped to a lower basal level. Regulation of CS7.4 expression was very strict, such that synthesis of the protein was undetectable at 37 degrees C. We have cloned the gene encoding this protein and have completed the nucleotide sequence analysis, which revealed that the gene encodes a hydrophilic protein of 70 amino acid residues.     

Coenzyme Q10 exogenous administration attenuates cold stress cardiac injury

The influence of coenzyme Q10 (CoQ10) in cold stress test (-15 degrees C for 4 hours) cardiac functional impairment was studied in isolated isovolumic heart of control rats (C; n=12) and of placebo (P; n=11) and treated rats (CoQ10; n=10). In addition, electron microscopic evaluation of left ventricular (LV) slices (n=3 in each group) allowed us to analyze the myocardial ultrastructure. Maximal values of developed pressure (DPmax) were similarly decreased in cold stressed animals (C=129+/-3.9 mmHg; P=106+/-6.7 mmHg; CoQ10=91+/-3.9 mmHg); however, volume-induced enhancement of pressure generation (slope of DP volume relations: C=0.248+/-0.0203 mmHg / microl; P=0.2831+/-0.0187 mmHg / microl; CoQ10=0.2387 ( 0.0225 mmHg / microl; p > 0.05), and the duration of systole (C=80+/-1.6 ms; P=78+/-1.3 ms; CoQ10=80+/-2.7 ms) were not altered. Myocardial relaxation, evaluated by the relaxation constant (C=39+/-1.9 ms; P=42+/-3.4 ms; CoQ10=51+/-6.0 ms), as well as resting stress / strain relations were unaffected by cold stress. Myocardial samples showed that pretreatment with CoQ10 attenuates myofibrillar and mitochondrial lesions, and prevents mitochondrial fractional area increase (P: 53.11%>CoQ10: 38.78%=C: 33.87%; p< 0.005) indicating that the exogenous administration of CoQ10 can reduce cold stress myocardial injury.     

Conventional transport assays underestimate sugar transport rates in human red cells

The time course of protein-mediated 3-O-methylglucose uptake by human red cells and by red cell ghosts containing or lacking 4 mM MgATP was measured at ice temperature and sub-saturating sugar levels by conventional sampling procedures and at 20 degrees C by use of a quench-flow apparatus. The temporal resolution of the quench-flow apparatus (as fast as 5-ms sample times) was confirmed by analysis of alkaline hydrolysis of dinitrophenolacetate. Red cell sugar uptake at 4 degrees C is consistent with two processes [fast (tau = 120 s) and slow (tau = 1100 s)] that occur in series. Intracellular ATP increases the size and the rate of equilibration of the fast compartment and slows the rate of filling of the slow compartment. Red cell ghost volume and protein content are unaffected by lysis/resealing in the presence of ATP. Uptake at 20 degrees C is also consistent with two processes [fast (tau = 10 ms) and slow (tau = 15 s)] that occur in series. ATP increases the size of both compartments and the rate of filling of the small compartment at 20 degrees C. Preliminary estimates indicate that the sugar uptake capacity of human red cells at 20 degrees C is underestimated by as much as 8-fold by measuring sugar uptake over 2 s vs. 26 ms. We discuss the implications of multiphasic sugar uptake in the context of models for protein-mediated sugar transport.     

A climatologic investigation of the SARS-CoV outbreak in Beijing, China

The first cases of severe acute respiratory syndrome (SARS) were identified in November 2002, in Guangdong Province, China. The epidemic spread rapidly within China and internationally, with 8454 recorded infections and 792 deaths by June 15, 2003. Temperature, relative humidity, and wind velocity were the three key meteorological determinants affecting the transmission of SARS. The peak spread of SARS occurred at a mean temperature of 16.9 degrees C (95% CI, 10.7 degrees C to 23.1 degrees C), with a mean relative humidity of 52.2% (95% CI, 33.0% to 71.4%) and wind speed of 2.8 ms(-1) (95% CI, 2.0 to 3.6 ms(-1)). In northern China, these conditions are most likely to occur in the spring and suggest that SARS has a seasonal nature akin to viruses such as influenza and the common cold. A regression equation (Y=218.692-0.698X(t)-2.043X(h)+2.282X(w)) was derived to represent the optimal climatic conditions for the 2003 SARS epidemic. Further investigations in other regions are necessary to verify these results.     

Effects of lutropin (LH) receptor internalization and recycling on the apparent numbers of LH receptors in rat testis Leydig cells at different temperatures

The effect of different temperatures on the Scatchard analysis of binding studies with 125I-hCG and intact rat testis Leydig cells has been investigated. The results show that at temperatures greater than 4 degrees C an overestimation of the number of receptors/cell is likely to occur. A one-site analysis of the data gives values of 13,573, 61,924 and 3802 LH receptors/cell at 34 degrees C, 21 degrees C and 4 degrees C respectively. At 34 degrees C and 21 degrees C (but not at 4 degrees C) a two-site analysis of the data is possible, giving similar high affinity binding components at both temperatures (KD 1 X 10(-10) M) but with dissimilar low affinity binding components (34 degrees C, 2.17 X 10(-9) M and 21 degrees C, 6.3 X 10(-8) M). The calculated total number of LH receptors using a two-site analysis at 21 degrees C is equal to 114,766 receptors/cell, and at 34 degrees C it is 37,987 receptors/cell. It is proposed that the differences in the level of binding at different temperatures and the associated changes in the value of KD, reflect the temperature sensitivity of the endocytic pathway of the 125I-hCG/LH receptor complex within the rat testis Leydig cell. From previous studies it is known that at 34 degrees C and 21 degrees C, a large part of the cell-associated hormone is not receptor bound but rather it represents 'processed' hormone before it is released from the cell. At 4 degrees C the cell-associated 125I-hCG remains bound only to cell surface LH receptors and thus gives a more accurate measure of total receptor numbers/cell.     

Canine model of Brugada syndrome using regional epicardial cooling of the right ventricular outflow tract

INTRODUCTION: Myocardial cooling can induce J point elevation (Osborn wave) as seen on ECG of the Brugada syndrome by activating transient outward current (Ito) and causing a spike-and-dome configuration of the monophasic action potential (MAP) in the ventricular epicardium in isolated canine ventricular wedge preparations. We determined the effect of regional epicardial cooling of the right ventricular outflow tract (RVOT) on surface ECG and ventricular vulnerability in the dog. METHODS AND RESULTS: In 12 dogs, a cooling device (20-mm diameter) was attached to the RVOT epicardium, and surface ECG, epicardial MAP, and endocardial MAP were recorded. Regional cooling (29.7 degrees C +/- 2.2 degrees C) elevated the J point from 0.05 +/- 0.06 mV to 0.12 +/- 0.11 mV and induced T wave inversion (from 0.02 +/- 0.12 mV to -0.27 +/- 0.20 mV) in lead V1 in association with "spike-and-dome" configuration of the epicardial MAP. Cooling prolonged MAP duration in the RVOT epicardium from 172 +/- 27 ms to 213 +/- 30 ms (P < 0.01) but not in the RV endocardium and increased transmural dispersion of MAP duration from 9 +/- 8 ms to 44 +/- 21 ms (P < 0.01). Cooling also prolonged the QT interval in lead V1 from 191 +/- 19 ms to 212 +/- 23 ms (P < 0.05), but not in lead V5, and increased spatial dispersion of QT interval from 7 +/- 5 ms to 20 +/- 10 ms (P < 0.01). QT interval in lead V1 correlated positively with MAP duration in the RVOT epicardium (r = 0.75). T wave amplitude in lead V1 correlated inversely with transmural dispersion of MAP duration in the RVOT (r =-0.74). Vagal nerve stimulation accentuated the cooling-induced changes. During cooling, ventricular fibrillation was induced by a single extrastimulus in 2 of 4 dogs, and additional vagal nerve stimulation during isoproterenol administration induced spontaneous ventricular fibrillation in one dog. CONCLUSION: Localized epicardial cooling of the RVOT could be an in vivo experimental model of Brugada syndrome.     

A sieving method for collecting the metacercariae of trematode parasites from freshwater fish

This study describes a sieving method for the collection of metacercariae from frozen (-20 degrees C) freshwater fish. Digested fish tissue is filtered through a series of sieves; the crude filtrate is then centrifuged. Centrifugation produces a sediment from which metacercariae can be removed. Half of the metracercariae that were obtained from the fish meat that had been frozen for 10 days (-20 degrees C) were dead; the other half were alive and some larvae were moving slowly.     

Some factors affecting Stellantchasmus falcatus metacercaria in laboratory

Killing factors, various temperatures and solutions were studied in the laboratory on Stellantchasmus falcatus metacercaria in half-beaked fish (Dermogenus pusillus). Killing criteria followed the Movability Index from 1.000 within 24 hours. The metacercariae were collected from Chiang Mai moat. They were incubated in 0.85 % NaCl at -20 degrees C, room temperature, 4 degrees, 37 degrees, and 65 degrees C. The in vitro investigation showed that at -20 degrees C and 65 degrees C, the worms were killed within 18 and 2 hours, respectively, while other temperatures produced no effect. The solutions investigated were NaCl (10, 20, 30, and 40%), lemon juice (25, 50, 75, and 100%), acetic acid (5, 10, 20, and 30%), vinegar (1, 3, and 5%) and water as a control. The worms were killed in NaCl at 20, 30, and 40% within 12, 6, and 2 hours, respectively. Acetic acid at 5% and 10% killed the metacercaria within 12 and 6 hours while at 20% and 30%, within 2 hours. The killing effect of 3% vinegar was found within 18 hours and of 5% vinegar within 12 hours. Lemon juice showed no killing effect.