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At least 235 records · Page 13Linked to original sources
PubMed2004

Rectal temperature reflects tympanic temperature during mild induced hypothermia in nonintubated subjects.

INTRODUCTION: Mild induced hypothermia holds promise as an effective neuroprotective strategy following acute stroke and cardiac arrest. Dependable noninvasive measurements of brain temperature are imperative for the investigation and clinical application of therapeutic hypothermia. Although the tympanic membrane temperature correlates best with brain temperature, it is a cumbersome location to record from continuously in the clinical setting. Data are lacking regarding the relationship between rectal and tympanic temperatures in nonintubated humans undergoing induced hypothermia via surface cooling. METHODS: We induced mild hypothermia in healthy volunteers using a novel surface cooling method (Arctic Sun Temperature Management System, Medivance, Inc., Louisville, CO). Core temperatures were recorded at the tympanic membrane (Ttym) and rectum (Trec). The gradient was defined as (Ttym-Trec). Controlled hypothermia was maintained for up to 300 minutes with a target Ttym of 34 degrees C to 35 degrees C; subjects were then actively rewarmed to a target Ttym of 36 degrees C over 1.5 to 3 hours. RESULTS: Twenty-two volunteers (10 males and 12 females) 31 +/- 8 years of age were studied. Subjects showed a triphasic temperature response: induction, maintenance, and rewarming. The mean gradient at baseline was -0.1 +/- 0.3 degrees C and the maximum gradient increased to -0.6 +/- 0.4 degrees C at 105 minutes. During maintenance of hypothermia (from 150 to 300 minutes), the mean gradient was -0.3 +/- 0.5 degrees C (95% confidence limits, -1.2 degrees C to 0.6 degrees C). CONCLUSIONS: : Our data suggest that Ttym and Trec are not related during the induction of hypothermia via surface cooling but correlate during the maintenance phase, with a -0.3 degrees C gradient. These findings support the use of rectal temperature as a measure of tympanic and, therefore, brain temperature during maintenance of induced hypothermia in nonintubated humans.

Acetaminophen↗
PubMed1994

Influence of temperature on growth rate and competition between two psychrotolerant Antarctic bacteria: low temperature diminishes affinity for substrate uptake.

The growth kinetics of two psychrotolerant Antarctic bacteria, Hydrogenophaga pseudoflava CR3/2/10 (2/10) and Brevibacterium sp. strain CR3/1/15 (1/15), were examined over a range of temperatures in both batch culture and glycerol-limited chemostat cultures. The maximum specific growth rate (mu max) and Ks values for both bacteria were functions of temperature, although the cell yields were relatively constant with respect to temperature. The mu max values of both strains increased up to an optimum temperature, 24 degrees C for 2/10 and 20 degrees C for 1/15. Strain 1/15 might therefore be considered to be more psychrophilic than strain 2/10. For both bacteria, the specific affinity (mu max/Ks) for glycerol uptake was lower at 2 than at 16 degrees C, indicating a greater tendency to substrate limitation at low temperature. As the temperature increased from 2 to 16 degrees C, the specific affinity of 1/15 for glycerol increased more rapidly than it did for 2/10. Thus 1/15, on the basis of this criterion, was less psychrophilic than was 2/10. The steady-state growth kinetics of the two strains at 2 and 16 degrees C imply that 1/15 would be able to outgrow 2/10 only at relatively low substrate concentrations (< 0.32 g of glycerol.liter-1) and high temperatures (> 12 degrees C), which suggests that 1/15 has a less psychrotolerant survival strategy than does 2/10. Our data were compared with other data in the literature for bacteria growing at low temperatures. They also showed an increase of substrate-specific affinity with increasing temperature.(ABSTRACT TRUNCATED AT 250 WORDS)

Antarctic Regions↗
PubMed1977

Physiological effects of growth of an Escherichia coli temperature-sensitive dnaZ mutant at nonpermissive temperatures.

The physiological effects of incubation at nonpermissive temperatures of Escherichia coli mutants that carry a temperature-sensitive dnaZ allele [dnaZ(Ts)2016] were examined. The temperature at which the dnaZ(Ts) protein becomes inactivated in vivo was investigated by measurements of deoxyribonucleic acid (DNA) synthesis at temperatures intermediate between permissive and nonpermissive. DNA synthesis inhibition was reversible by reducing the temperature of cultures from 42 to 30 degrees C; DNA synthesis resumed immediately after temperature reduction and occurred even in the presence of chloramphenicol. Inasmuch as DNA synthesis could be resumed in the absence of protein synthesis, we concluded that the protein product of the dnaZ allele (Ts)2016 is renaturable. Cell division, also inhibited by 42 degrees C incubation, resumed after temperature reduction, but the length of time required for resumption depended on the duration of the period at 42 degrees C. Replicative synthesis of cellular DNA, examined in vitro in toluene-permeabilized cells, was temperature sensitive. Excision repair of ultraviolet light-induced DNA lesions was partially inhibited in dnaZ(Ts) cells at 42 degrees C. The dnaZ(+) product participated in the synthesis of both Okazaki piece (8-12S) and high-molecular-weight DNA. During incubation of dnaZ(Ts)(lambda) lysogens at 42 degrees C, prophage induction occurred, and progeny phage were produced during subsequent incubation at 30 degrees C. The temperature sensitivity of both DNA synthesis and cell division in the dnaZ(Ts)2016 mutant was suppressed by high concentrations of sucrose, lactose, or NaCl. Incubation at 42 degrees C was neither mutagenic nor antimutagenic for the dnaZ(Ts) mutant.

Alleles↗
PubMed1984

Characterization of a temperature-sensitive defect of enterovirus 70: effect of elevated temperature on in vitro transcription.

A crude replication complex prepared from enterovirus 70-infected cells was used to study the temperature-sensitive characteristic of the virus. The complex showed a temperature sensitivity in the in vitro incorporation of radiolabeled ribonucleoside triphosphate. The endonuclease itself did not account for the restricted RNA synthesis at the nonpermissive temperature. Analyses of the in vitro products by both gel electrophoresis and sucrose density gradient centrifugation showed that the complex synthesized three types of viral RNA only when incubated for a short period of time at the nonpermissive temperature. When the replication complex was treated with a detergent (deoxycholic acid), incorporation of ribonucleoside triphosphate into RNA at the permissive temperature was reduced to the level of that at the nonpermissive temperature. In addition, the in vitro RNA synthesis by the enterovirus 70 replication complex at the permissive temperature required a higher concentration of ATP than of other ribonucleoside triphosphates, whereas such a preference for ATP was not found in the reaction at the nonpermissive temperature. The results indicate that the initiation step of RNA synthesis by the complex is blocked at the nonpermissive temperature. The possible implications of these findings are discussed.

Adenosine Triphosphate↗
PubMed1999

Tympanic membrane temperature as a measure of core temperature.

BACKGROUND: Ear thermometers are becoming popular as a method for measuring deep body (core) temperature. AIM: To determine the variability of a single user's tympanic membrane (ear) temperature measurements. SUBJECTS: Forty-two, afebrile, healthy children, and 20 febrile children with acute burns. RESULTS: In afebrile children measurements made in both ears (and within just a few minutes of each other) differed by as much as 0.6 degree C. Operator measurement error, sw of three consecutive measurements, in the same ear, was 0.13 degree C. In the group of febrile, burned children, core temperature was measured hourly at a number of sites (ear, rectum, axilla, bladder). A peak in core temperature occurred approximately 10-12 hours after the burn. Measurement error was calculated in 14 febrile, burned children with a peak temperature in excess of 38 degrees C. For the left ear, measurement error was 0.19 degree C and for the right ear, 0.11 degree C. In the febrile children agreement between the ears was poor. The limits of agreement were 0.4 degree C to -0.8 degree C. It was not possible to predict the occasions when the temperature differences between the ears would be large or small. CONCLUSIONS: The measurement error of one recording from the next is probably acceptable at about 0.1 to 0.2 degree C. To limit the variations in temperature of one ear to the other, measurements should be restricted to one of the ears whenever possible and the same ear used throughout the temperature monitoring period. Nurses and parents should take more than one temperature reading from the same ear whenever possible.

Adolescent↗
PubMed1996

Reexamination of tympanic membrane temperature as a core temperature.

Controversies surrounding tympanic temperature (Tty) itself and techniques for measuring it have dampened the potential usefulness of Tty in determining core temperature (operationally defined here as the body temperature taken at a deep body site). The present study was designed to address the following questions. 1) Can a tympanic membrane probe be made that is safer and more reliable than its predecessors? 2) Why is the effect of facial cooling and heating on Tty so inconsistent in reports from different laboratories? 3) Is Tty still useful as a measure of core temperature? Data from this study, obtained with a modified thermocouple probe, suggest that the widely reported facial skin cooling effect on Tty is most probably due to thermal contamination from the surrounding ear canal wall and/or suboptimal contact of the probe sensor with the tympanic membrane because 1) Tty that fell during facial cooling was increased to the precooling level by the repositioning of the probe sensor; 2) Tty determined by using a probe with a larger sensor area (the sensor soldered to a steel wire ring)tended to fall in response to facial cooling, whereas Tty determined with a thermally insulated probe ring did not; and 3) Tty obtained under careful positioning of the insulated probe was relatively insensitive to facial cooling or heating. Because Tty was practically identical to esophageal temperature (Tes) in the steady state, i.e., 36.83 +/- 0.20 (SD) degrees C for Tty and 36.87 +/- 0.16 degrees C for Tes at room temperature (n = 11), and because facial cooling had little effect on both Tty and Tes (36.86 +/- 0.17 degrees C for Tty and 36.86 +/- 0.26 degrees C for Tes during facial or scalp skin cooling), we support the postulate that Tty is a good measure of core temperature. The temperature transient in response to foot warming was detected 5 min (n = 2) faster with Tty than with Tes. Thus, with further improvements in the design of the probe. Tty can become a standard for determination of core body temperature.

Adult↗
PubMed2006

Molecular beacon-based temperature control and automated analyses for improved resolution of melting temperature analysis using SYBR I green chemistry.

BACKGROUND: Melting temperature analysis of products amplified with SYBR I Green chemistry is a cheap and effective method for identification of sequence differences. When used in conventional quantitative real-time PCR instruments (qPCR), this method is limited by temperature variations over the heating block and low numbers of fluorescence measurements during the dissociation step, which hamper the ability of most instruments to report accurate and precise melting temperatures. METHODS: We designed a molecular beacon-based temperature indicator probe (Tm-probe) to control for variations in temperatures over the heating block of the instrument. In addition, we wrote an automated curve-fit analysis algorithm of dissociation data to use multiple data points with a gaussian curve fit to extrapolate precise melting temperatures. RESULTS: Use of the Tm-probe in conjunction with the analysis algorithm and multiple dissociations improved SDs of melting temperatures over a 96-well plate from 0.19 to 0.06 degrees C. CONCLUSIONS: Melting temperature analyses with SYBR I Green chemistry on conventional qPCR instruments can be improved by the use of a Tm-probe in conjunction with curve-fit analysis of data. Resolution improvement up to 3-fold is possible and allows additional melting temperatures to be identified.

Algorithms↗
PubMed1994

The effect of incubation temperature on recovery of mesophilic bacteria from broiler chicken carcasses subjected to temperature abuse.

The optimum temperature to recover mesophilic organisms from temperature-abused broiler chicken carcasses was determined. Twenty broiler carcasses were collected from a commercial processing plant in each of three trials. Ten carcasses were sampled immediately (Day 0 control); 8 carcasses were sampled after holding at 3 C for 3 d, temperature abusing at 25 C for 12 h, and holding them at 3 C for an additional 3 d (temperature abused); and the remaining 2 carcasses were sampled after holding at 3 C for 7 d (Day 7 control). Whole carcass rinses were analyzed using total aerobic plate counts (TPC) and impedimetric detection times (DT) at incubation temperatures of 41, 42, 43, and 44 C. Total plate counts decreased (P < .05) and DT increased (P < .05), at all incubation temperatures tested, for carcasses held under refrigeration (Day 7 control). This demonstrates that mesophilic bacteria, rather than psychrotrophic bacteria, are being enumerated, because psychrotrophs increase on chicken skin upon cold storage. Total plate count was greater (P < .05) and DT was significantly lower for temperature-abused vs Day 7 control birds (5.7 vs 3.6 log10 cfu/mL and 3.7 vs 6.5 h), respectively. These results indicate that temperature-abused carcasses can be microbiologically distinguished from nonabused controls at all incubation temperatures tested. Recovery of mesophiles was optimal at 41 and 42 C for TPC and 41, 42, and 43 C for DT. Because there were no differences between DT at 41, 42, and 43 C, and because 42 C has been successfully used in the past, either 42 C or 43 C can be used when determining DT.

Animals↗
PubMed2002

Use of an infrared temperature monitoring system to determine optimal temperature for laser-solder tissue repair.

Thermal damage of tissue is a major concern for all laser tissue repair techniques where the resulting strength of a repair is sensitive to slight alterations in tissue temperature as well as changes in the duration of exposure of the tissue to the laser beam. Too low of a temperature will prevent proper bonding between the surfaces while prolonged exposure of the tissue to the laser beam results in collateral thermal damage and decreased flexibility and strength of the repair. Temperature feedback systems that monitor the surface temperature of the repair site and adjust the laser irradiance accordingly increase the success rate of the technique. Knowledge of an optimal temperature for tissue soldering will also increase the reliability of the technique. The choice of solder material has been another challenge to the reproducibility of strong repairs. The emerging use of solder-doped polymer membranes as surgical adhesives offers numerous advantages over more traditional liquid and solid solders. Poly (L-lactic-co-glycolic acid) (PLGA), when used as a polymer scaffold, is porous enough to absorb serum albumin and can also be doped with various hemostatic and thrombogenic agents to aid tissue healing. An in vitro study was performed to correlate tissue temperature with the tensile strength of repairs formed using the solder-doped polymer membranes. Previous studies by our group indicate that a solder/tissue interface temperature of 65 degrees C is optimal. Using this parameter as a bench mark, laser irradiance was varied and the solder surface and solder/tissue interface temperatures were monitored by an IR temperature monitoring system, designed by the researchers, and a type K thermocouple, respectively.

Animals↗
PubMed1976

Effects of altering spinal cord temperature on temperature regulation in the Adelie Penguin, Pygoscelis Adeliae.

In 6 Adelie penguins, thermodes were implanted in the cervical and upper thoracic spinal canal. At thermoneutral (+8 to +16 degrees C) and cold (-18 to -22 degrees C) ambient conditions, the effects of spinal canal heating and cooling on the surface temperature of one flipper (skin blood flow), oxygen consumption (metabolic heat production) and esophageal (core) temperature were observed in the conscious animals.- At thermoneutral ambient conditions, spinal cord cooling reduced and spinal heating increased skin blood flow. Only very strong spinal cooling induced small increases of oxygen consumption, while spinal heating had no effect at all. The relation between spinal canal temperature and metabolic heat production at thermoneutral ambient conditions could be described by a linear regression with a slope of -0.05 W. KG-1 . DEGREES C-1. -At cold ambient conditions, the skin vessels of the flippers were permanently constricted and an increase of metabolic heat production by 5-50% of the resting rate developed within 1-3 h of cold exposure. Spinal cord cooling augmented metabolic heat production. Spinal heating reduced heat production but did not release skin vasoconstriction even at high stimulus intensities. The relation between spinal canal temperature and metabolic heat production in the cold could be described by a linear regression with a slope of -0,52 W. kg-1 . degrees C-1. -It is concluded that temperature sensors with specific functions in temperature regulation are located in the spinal cord of the Adelie penguin. These sensors contribute to the central temperature signal input in the hypothermic and hyperthermic ranges of core temperature. The peripheral thermal conditions strongly influence the responsiveness of the various thermoregulatory effectors to the spinal thermal stimulus.

Animals↗
PubMed1976

Effects of altering rostral brain stem temperature on temperature regulation in the Adelie penguin, Pygoscelis adeliae.

In 4 Adelie penguins, thermodes were implanted in the rostral brain stem. Two animals were additionally equipped with spinal canal thermodes. At thermoneutral (+8 to +16 degrees C) and cold (-18 to -22 degrees C) ambient conditions, the effects of hypothalamic heating and cooling on the surface temperature of one flipper (skin blood flow), oxygen consumption (metabolic heat production) and esophageal (core) temperature were observed in the conscious animals.- Heating the rostral brain stem induced heat defence responses: Heat production was reduced in the cold and skin vasodilatation was evoked at thermoneutral ambient conditions. As a rule, core temperature fell during rostral brain stem heating.- Cooling the rostral brain stem did not induce clear-cut cold defence responses. On the contrary, strong cooling at thermo-neutral ambient conditions induced vasodilation in the skin. In the cold, even slight degrees of rostral brain stem cooling decreased metabolic heat production. As a rule, core temperature fell when the rostral brain stem was cooled.- It is concluded from the results that thermosensitive structures in the stimulated section of the rostral brain stem of the Adelie penguin contribute to the central temperature signal input in the range of normal to elevated core temperatures. These hypothalamic warm signals appear to be at least as effective as spinal warm signals in controlling skin blood flow and metabolic heat production. The inhibition of ongoing thermoregulatory effector activity by rostral brain stem cooling suggests positive temperature coefficients of the integrative and/or efferent neurons in the hypothalamic temperature regulation center of the Adelie penguin.

Animals↗
PubMed2003

Ambient temperature influences core body temperature response in rat lines bred for differences in sensitivity to 8-hydroxy-dipropylaminotetralin.

Agonist-induced decrease in core body temperature has commonly been used as a measure of serotonin1A (5-HT(1A)) receptor sensitivity in mood disorder. The thermoregulatory basis for 5-HT(1A) receptor agonist-induced temperature responses in humans and rats remains unclear. Therefore, the influence of ambient temperature on 5-HT(1A) receptor-mediated decreases in core body temperature were measured in rat lines bred for high (HDS) or low (LDS) sensitivity to the selective 5-HT(1A) receptor agonist 8-hydroxy-dipropylaminotetralin (8-OH-DPAT). HDS and LDS rats were injected with either saline, 0.25 or 0.50 mg/kg 8-OH-DPAT at ambient temperatures of 10.5, 24, 30, or 37.5 degrees C, and core temperature was measured by radiotelemetry. For both lines, the thermic response to acute 8-OH-DPAT was greatest at 10.5 degrees C and decreased in magnitude as ambient temperature increased to 30 degrees C, consistent with hypothermia. HDS rats displayed a greater hypothermic response than LDS rats at 10.5, 24, and 30 degrees C. At 37.5 degrees C, LDS rats showed a lethal elevation of temperature in response to 0.50 mg/kg 8-OH-DPAT. All thermic responses to 8-OH-DPAT, including the lethality, were effectively blocked by pretreatment with the 5-HT(1A) receptor antagonist WAY100635, suggesting line differences in thermoregulatory circuits that are influenced by 5-HT(1A) receptor activation. Following repeated injection of 8-OH-DPAT, the magnitude of the hypothermic response decreased in both lines at 10.5 degrees C, but increased in HDS rats treated with 0.50 mg/kg 8-OH-DPAT at 30 and 37.5 degrees C. This pattern was reversed in HDS rats following 8-OH-DPAT challenge at 24 degrees C, suggesting that a compensatory thermoregulatory response accounts for changes in the hypothermic response to chronic 8-OH-DPAT.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed1998

[Study of skin temperature, microclimate and comfort of clothing of old females at rest--ambient temperature x humidity: 30 degrees C. R.H.80%, 30 degrees C. R.H.45%, 20 degrees C. R.H.45%].

Old females are compared to young females for the purpose of studying the difference in comfort caused by the environmental variables of temperature and humidity as well as the form of clothing. Eight experiments were performed in three settings: (a) 30 degrees C R.H.80%; 30 degrees C R.H.45%; and 20 degrees C R.H.45%. The ages of the subjects range from 62 to 68 (Mean = 65.17, S.D. = 1.68) among old females and from 20 to 23 (Mean = 20.83, S.D. = 0.76) among young females. The following results were obtained: (1) The young females were sensitive to hot temperatures, while the old females were not. On the other hand, the old females were more sensitive to cold temperatures, under 20 degrees C R.H.45%, than the young females. In temperatures under 30 degrees C R.H.80%, the heat radiation from the young females was higher than that of the old females. Under 20 degrees C R.H.45%, the heat radiation from the old females was higher than from the young females. The old females are thought to decline in physiogenic function due to enduring both hot and cold temperatures. (2) The correlation between the temperature in clothes and comfort among the old females is not different from the same correlation among the young females. This conclusion agrees with previously published studies of the young females. (3) Skin temperature and bloodstream are measured, according to clothing form. As a result, a long skirt is the highest in thermal insulation, long pants the next highest, and a short skirt is the lowest. (4) The effect of thermal insulation provided by a lap robe was tested in both groups. The lap robe was found to be more effective for the older group than the younger in temperatures under 20 degrees C R.H.45%. Hence, the role of clothes in offsetting for the decline in the thermoregulation function that compensates for environmental change is more important for old females than for young.

Aged↗
PubMed1992

[The effect of the ambient temperature and motor activity on brain temperature in bullfinches].

In increasing of the ambient temperature, the difference between the brain and body temperatures diminished from 1.4 degrees C (at the ambient temperature 0 degree C) to 0.5 degrees C (at the ambient temperature +37 degrees C) in bullfinches, the brain temperature being always the lower one. In combination of high ambient temperature and locomotor activity the brain-body temperature difference increased as the body temperature had raised higher than the brain one.

Animals↗
PubMed2005

Nitrogen partitioning in the photosynthetic apparatus of Plantago asiatica leaves grown under different temperature and light conditions: similarities and differences between temperature and light acclimation.

Effects of growth temperature and irradiance on nitrogen partitioning among photosynthetic components were studied. Plantago asiatica was grown under different temperature and light conditions. Growth conditions were regulated such that the Chl a/b ratio in leaves grown at a low temperature with a low irradiance was similar to that in leaves grown at a high temperature with a high irradiance, suggesting that the balance between acquisition and utilization of light energy in the photosynthetic apparatus was similar between the two growth conditions. When plotted against the leaf nitrogen content, the RuBP (ribulose-1,5-bisphosphate) carboxylase content did not significantly differ depending on growth conditions. Both high irradiance and low temperature decreased nitrogen partitioning to Chl-protein complexes. Low temperature increased nitrogen allocation to stroma FBPase (fructose-1,6-phosphatase) irrespective of growth irradiance. Gas exchange measurement indicated that the ratio of the electron transport (J(max)) to the maximum carboxylation rate (V(cmax)) was not affected by growth irradiance but by growth temperature. It is concluded that nitrogen partitioning between acquisition and utilization of light energy responds to both growth temperature and irradiance, while nitrogen partitioning between carboxylation and regeneration of RuBP responds only to growth temperature.

Adaptation, Physiological↗
PubMed1987

A thermographic study of the effect of body composition and ambient temperature on the accuracy of mean skin temperature calculations.

The problem associated with using measurements from a small number of sites to determine mean skin temperature was investigated by studying variations in distributions of skin temperatures of the bare torsos of humans exposed to ambient temperatures of 18, 23, and 28 degrees C. Following a 60 minute equilibration period the temperatures of four regions (chest, abdomen, upper back, and lower back) were measured using both thermistors and an infra-red thermographic system. Regions of the torso usually represented by a single temperature exhibited significant point-to-point temperature variations especially in chilled subjects. Also an earlier finding was confirmed: in that larger variations in skin temperature distributions occur as body fat content increases. Caution must therefore be used in applying the concept of a mean skin temperature derived from a few select sites, especially with nude subjects who are chilled or have a high body fat content.

Adipose Tissue↗