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J R Hazel

Publications and source records attributed to J R Hazel.

At least 19 recordsLinked to original sources
PubMed2004

The substrate specificity of hormone-sensitive lipase from adipose tissue of the Antarctic fish Trematomus newnesi.

Antarctic fishes of the suborder Notothenioidei characteristically possess large stores of neutral lipids that have been shown to be important both in conferring buoyant lift and as a caloric resource for energy metabolism. Previous work has established that the aerobic energy metabolism of Antarctic fish is fueled predominantly by the catabolism of fatty acids, with the catabolic machinery displaying a preference for the oxidation of unsaturated fatty acids. The composition of the fatty acids released from adipose tissue of Antarctic fish during lipolysis, however, has not previously been demonstrated. Employing a substrate competition assay, we have characterized the substrate specificity of hormone-sensitive lipase (HSL) from adipose tissue of the Antarctic fish Trematomus newnesi. Rates of oleic acid release from radiolabeled triolein were quantified in the presence and absence of a nonradiolabeled cosubstrate. Polyunsaturated species of triacylglycerols (TAGs) containing 18:2 or 20:4 depressed rates of oleate release by 70-75% below control values. Most of the molecular species of TAG containing monoenoic fatty acids (i.e. those containing 14:1, 16:1 or 20:1) had no significant effect on rates of oleate release. By contrast, oleate release from triolein was actually stimulated (by 2-4-fold) by both saturated species of TAG (i.e. those containing 14:0, 16:0 and 18:0) and those possessing long-chain (22:1 and 24:1) monoenes (by 1.2-1.5-fold). Thus, the rank order of substrate preference for adipose tissue HSL was: polyunsaturates > monoenes > saturates. Degree of fatty acid unsaturation had a more marked effect on rates of hydrolysis than did fatty acid chain length. In addition, the enzyme displayed a preference for the hydrolysis of sn-1,2 rather than sn-1,3 diacylglycerols. These data indicate that the substrate specificity of adipose tissue HSL may be an important factor in determining which fatty acids are mobilized during stimulated lipolysis and which are made available for catabolism by other tissues of Antarctic fishes. Our data further suggest that TAGs containing some saturated fatty acids may be sufficiently poor substrates for catabolism by HSL to explain their disproportionate accumulation in adipose tissue. Such a mechanism could also contribute to the ontogenetic accumulation of fats that has been reported as an underlying basis for the positive correlation of buoyancy with increasing body mass in this group.

Adipose Tissue↗
PubMed2000

Membrane physical properties do not explain increased cyclic AMP production in hepatocytes from rats fed menhaden oil.

To study the effect of altering plasma membrane fatty acid composition on the glucagon signal transduction pathway, cAMP accumulation was measured in hepatocytes from rats fed diets containing either menhaden oil (MO) or coconut oil (CO). Hepatocytes from MO-fed animals produced significantly more cAMP in response to glucagon and forskolin compared to CO-fed animals. Glucagon receptor number and affinity were similar in MO- and CO-fed rats. Liver plasma membranes from MO-fed animals were enriched in long-chain n-3 fatty acids and contained significantly lower amounts of saturated C10-C16 and 18:1n-9 than CO-fed animals. Membrane physical properties were examined using both Fourier transform infrared spectroscopy (FTIR) and the fluorescent probe 1,6-diphenyl-1,3,5-hexatriene (DPH). FTIR analysis revealed that below 34 degrees C, CO membranes were more ordered than MO membranes. However, as assay temperature approached 37 degrees C, MO and CO membranes became similarly ordered. DPH polarization values indicated no differences in membrane order at 37 degrees C, whereas membrane order was decreased in CO-fed animals at 25 degrees C. These data indicate the importance of assay temperature in assessing the influence of membrane physical properties on the activity of signal transduction pathways. Whereas increased signal transduction activity has been correlated to reduced membrane order in MO-fed animals, these data indicate that at physiological temperatures membrane order did not vary between groups. Enhanced cAMP accumulation in response to forskolin indicates that adenylate cyclase activity or content may be elevated in MO- vs. CO-fed rats. Enhanced adenylate cyclase activity may result, in part, from changes in specific fatty acids in hepatocyte plasma membranes without demonstrable changes in membrane physical properties.

Animals↗
PubMed2000

Is fluid-phase endocytosis conserved in hepatocytes of species acclimated and adapted to different temperatures?

Our primary objective was to determine if rates of fluid-phase endocytosis (FPE) were conserved in hepatocytes from organisms acclimated and adapted to different temperatures. To this aim, the fluorescent dye Lucifer yellow was employed to measure FPE at different assay temperatures (AT) in hepatocytes from 5 degrees C- and 20 degrees C-acclimated trout, Oncorhynchus mykiss (at 5 and 20 degrees C AT), 22 degrees C- and 35 degrees C-acclimated tilapia, Oreochromis nilotica (at 22 and 35 degrees C AT), and the Sprague-Dawley rat (at 10, 20, and 37 degrees C AT). FPE was also studied in rats fed a long-chain polyunsaturated fatty acid (PUFA)-enriched diet (at 10 degrees C AT). Despite being temperature dependent, endocytic rates (values in pl. cell(-1). h(-1)) in both species of fish were compensated after a period of acclimation. For example, in 20 degrees C-acclimated trout, the rate of endocytosis declined from 1.84 to 1.07 when the AT was reduced from 20 to 5 degrees C; however, after a period of acclimation at 5 degrees C, the rate (at 5 degrees C AT) was largely restored (1.80) and almost perfectly compensated (95%). In tilapia, endocytic rates were also temperature compensated, although only partially (36%). Relatively similar rates obtained at 5 degrees C in 5 degrees C-acclimated trout (1.8), at 20 degrees C in 20 degrees C-acclimated trout (1.84), and at 22 degrees C in 22 degrees C-acclimated tilapia (2.2) suggest that endocytic rates are somewhat conserved in these two species of fish. In contrast, the rate in rat measured at 37 degrees C (16.83) was severalfold greater than in fish at their respective body temperatures. A role for lipids in determining rates of endocytosis was supported by data obtained at 10 degrees C in hepatocytes isolated from rats fed a long-chain PUFA-enriched diet: endocytic rates were higher (5.35 pl. cell(-1). h(-1)) than those of rats fed a standard chow diet (2.33 pl. cell(-1). h(-1)). The conservation of endocytic rates in fish may be related to their ability to conserve other membrane characteristics (i.e., order or phase behavior) by restructuring their membrane lipid composition or by modulating the activities of proteins that regulate endocytosis and membrane traffic, whereas the lack of conservation between fish and rat may be due to differences in metabolic rate.

Acclimatization↗
PubMed2000

Hyperthermia impairs liver mitochondrial function in vitro.

The effects of temperature on the relationships among the rates of pyruvate carboxylation, O(2) uptake (J(o)), oxidative phosphorylation (J(p)), and the free energy of ATP hydrolysis (G(p)) were studied in liver mitochondria isolated from 250-g female rats. Pyruvate carboxylation was evaluated at 37, 40, and 43 degrees C. In disrupted mitochondria, pyruvate carboxylase maximal reaction velocity increased from 37 to 43 degrees C with an apparent Q(10) of 2.25. A reduction in ATP/ADP ratio decreased enzyme activity at all three temperatures. In contrast, in intact mitochondria, increasing temperature failed to increase pyruvate carboxylation (malate + citrate accumulation) but did result in increased J(o) and decreased extramitochondrial G(p). J(p) was studied in respiring mitochondria at 37 and 43 degrees C at various fractions of state 3 respiration, elicited with a glucose + hexokinase ADP-regenerating system. The relationship between J(o) and G(p) was similar at both temperatures. However, hyperthermia (43 degrees C) reduced the J(p)/J(o) ratio, resulting in lower G(p) for a given J(p). Fluorescent measurements of membrane phospholipid polarization revealed a transition in membrane order between 40 and 43 degrees C, a finding consistent with increased membrane proton conductance. It is concluded that hyperthermia augments nonspecific proton leaking across the inner mitochondrial membrane, and the resultant degraded energy state offsets temperature stimulation of pyruvate carboxylase. As a consequence, at high temperatures approaching 43 degrees C, the pyruvate carboxylation rate of intact liver mitochondria may fail to exhibit a Q(10) effect.

Adenosine Triphosphate↗
PubMed2000

Does membrane fluidity contribute to thermal compensation of beta-adrenergic signal transduction in isolated trout hepatocytes?

The potential role of compensatory adjustments to membrane components in determining the function of the (&bgr;)-adrenergic receptor/adenylyl cyclase ((&bgr;)-AR/AC) signal-transduction system was studied in isolated hepatocytes of 5 degrees C- and 20 degrees C-acclimated rainbow trout Oncorhynchus mykiss. Rates of epinephrine-stimulated cyclic AMP (cAMP) production, although slowed (by a factor of 1.6- to 2.4-fold) by an acute drop in assay temperature from 20 to 5 degrees C, were significantly temperature-compensated, being approximately twofold higher in hepatocytes of 5 degrees C- than of 20 degrees C-acclimated trout. Membrane order in the bilayer interior of hepatocyte plasma membranes (as assessed by fluorescence polarization of 1, 6-diphenyl-1,3,5-hexatriene) was consistently lower in cold- than in warm-acclimated trout, reflecting an efficacy of homeoviscous adaptation of approximately 50 %. Temperature-induced changes in plasma membrane fatty acid composition (i.e. an increase in the proportions of polyunsaturated fatty acids with acclimation to 5 degrees C) were consistent with both the observed changes in the order of the bilayer interior and the extent of homeoviscous adaptation. However, isothermal fluidization of the bilayer interior by the addition of benzyl alcohol (30 mmol l(-)(1)) decreased rather than increased the rate of cAMP production. Significantly more (1. 81-fold) beta-adrenergic receptors were present in plasma membranes of hepatocytes from 5 degrees C-acclimated (6. 23x10(4)+/-4206 receptors per cell; mean +/- s.e.m., N=3) than 20 degrees C-acclimated fish (3.44x10(4)+/-4360 receptors per cell; N=3) when assayed at the acclimation temperature, whereas the equilibrium dissociation constants (K(d)) (13.73+/-4.33 nmol l(-)(1) at 5 degrees C; 9.75+/-3.29 nmol l(-)(1) at 20 degrees C; N=3) were similar. On the basis of a strong correlation between beta-adrenoceptor number and the rate of cAMP production (r(2)=0. 956), regardless of assay or acclimation temperature, we conclude that modulation of receptor number is the primary acclimatory response of this signal-transduction pathway to temperature change in trout liver.

Adenylyl Cyclases↗
PubMed1999

Dietary fat type alters glucose metabolism in isolated rat hepatocytes.

Dietary fat type can influence the regulation of carbohydrate metabolism in multiple tissue types. The influence of feeding high-fat (40% of kilocalories) diets containing either menhaden oil (MO) or coconut oil (CO) on hepatic glycogenolytic and gluconeogenic capacities was studied in isolated rat hepatocytes. Estimates of both glycogenolytic and gluconeogenic capacities were performed on hepatocytes isolated from fed and fasted animals, respectively. In MO-fed animals, both basal and hormone-stimulated rates of glucose production were significantly greater than those in CO-fed animals. However, both groups displayed a similar maximal increase in glucose production above basal for glucagon and epinephrine (2.3- and 1.9-fold, respectively). Basal rates of adenosine 3',5'-cyclic phosphate (cAMP) production were not different between groups whereas glucagon-stimulated cAMP production was increased twofold in the MO-fed group. In both MO and CO groups, the addition of 10 nM insulin reduced glucose production in fed animals to similar absolute rates. In animals fasted for 24 hours, gluconeogenic capacity was estimated using 10 mM pyruvate, lactate, or glycerol. Glucose production from all substrates was significantly greater in CO-fed animals. In addition to increased gluconeogenic rates, maximal phosphoenolpyruvate carboxykinase (PEPCK) activity was increased in the CO-fed group. Insulin reduced glucose production in both dietary groups, but the absolute rate of glucose production was 28% greater in the CO-fed group relative to the MO-fed group. In summary, dietary fat type can markedly influence the regulation of hepatic glucose metabolism in multiple metabolic pathways. MO feeding promoted glycogenolysis and sensitivity to insulin whereas CO feeding favored gluconeogenesis and reduced insulin sensitivity.

Journal Article↗
PubMed1998

Thermal acclimation of phase behavior in plasma membrane lipids of rainbow trout hepatocytes.

The fluorescent probes laurdan (6-dodecanoyl-2-dimethylaminonapthalene) and N-[7-nitrobenz-2-oxa-1, 3-diazol-4-yl] dipalmitoyl-L-alpha-phosphatidylethanolamine (NBD-PE) in addition to Fourier transform infrared spectroscopy (FTIR) were employed to measure the phase behavior and physical properties of hepatocyte plasma membranes isolated from the livers of thermally acclimated (5 and 20 degreesC) rainbow trout (Oncorhynchus mykiss). The primary objective was to determine the extent to which the phase behavior of membrane lipids is conserved at different growth temperatures. Arrhenius plots of laurdan-generalized polarization revealed a single discontinuity believed to reflect either the onset of the gel-fluid phase transition or the formation of gel phase microdomains, and this discontinuity occurred at significantly higher temperatures in membranes of 20 degrees C (13.2 +/- 0.7 degrees C)- than 5 degrees C (7.2 +/- 0.1 degrees C)-acclimated trout. Similarly, acclimation from 5 to 20 degrees C increased both the onset temperature (from 2.0 +/- 0.3 to 7.2 +/- 0.6 degrees C) and the thermal range (from 10.9 +/- 0.5 to 16.0 +/- 1.0) of the gel-fluid transition as assessed by FTIR. The gel-fluid transition midpoint (approximately -2 degrees C) and completion temperatures (-9 degrees C) were unchanged by thermal acclimation. The anisotropy of NBD-PE fluorescence displayed a distinct minimum in membranes of both warm- and cold-acclimated trout (reflecting alterations in lipid packing that in pure lipid membranes ultimately lead to the formation of nonlamellar phases) in the range of 56-58 degrees C; only membranes of 5 degrees C-acclimated trout displayed an additional minimum at significantly lower temperatures (24.5 +/- 1.7 degrees C). Collectively, these data suggest that the regulation of both the temperature at which gel phase lipids begin to form in response to cooling as well as the propensity of membrane lipids to form nonlamellar phases at higher temperatures may be key features of membrane organization subject to adaptive regulation.

2-Naphthylamine↗
PubMed1998

Differential responses to endurance training in subsarcolemmal and intermyofibrillar mitochondria.

To examine the effect of endurance training (6 wk of treadmill running) on regional mitochondrial adaptations within skeletal muscle, subsarcolemmal (SS) and intermyofibrillar (IMF) mitochondria were isolated from trained and control rat hindlimb muscles. Mitochondrial oxygen consumption (VO2) was measured polarographically by using the following substrates: 1 mM pyruvate + 1 mM malate (P+M), 10 mM 2-oxoglutarate, 45 microM palmitoyl-DL-carnitine + 1 mM malate, and 10 mM glutamate. Spectrophotometric assays of cytochrome-c reductase and NAD-specific isocitrate dehydrogenase (IDH) activity were also performed. Maximal (state III) and resting (state IV) VO2 were lower in SS than in IMF mitochondria in both trained and control groups. In SS mitochondria, training elicited significant 36 and 20% increases in state III VO2 with P+M and glutamate, respectively. In IMF mitochondria, training resulted in a smaller (20%), yet significant, increase in state III VO2 with P+M as a substrate, whereas state III VO2 increased 33 and 27% with 2-oxoglutarate and palmitoyl-DL-carnitine + malate, respectively. Within groups, cytochrome-c reductase and IDH activities were lower in SS when compared with IMF mitochondria. Training increased succinate-cytochrome-c reductase in both SS (30%) and IMF mitochondria (28%). IDH activity increased 32% in the trained IMF but remained unchanged in SS mitochondria. We conclude that endurance training promotes substantial changes in protein stoichiometry and composition of both SS and IMF mitochondria.

Animals↗
PubMed1995

Sensitive assay for cholesterol in biological membranes reveals membrane-specific differences in kinetics of cholesterol oxidase.

Quantification of cholesterol in biological membranes from a variety of sources is an important step toward understanding cholesterol's roles in membrane function. We extend to biological membranes the fluorometric/enzymatic approach (cholesterol oxidase) to measure cholesterol, originally described for whole cells (Heider and Boyett [1978] J. Lipid Res., 19:514-518; Gamble et al. [1978] J. Lipid Res., 19:1068-1070) and serum (Huang et al. [1975] Clin Chem., 21:1605-1608). This method has a detection limit of 0.3 microgram cholesterol. As revealed by comparison with high-performance liquid chromatography, the fluorometric/enzymatic method with biological membranes is accurate (within 4% and 8% for intestinal and hepatic plasma membranes, respectively). The assay may be completed within 3 to 4 hours and requires neither lipid extraction nor chromatographic techniques. Kinetics of the cholesterol oxidase reaction are membrane-specific, and first-order rate constants (k) are positively correlated with membrane order.

Animals↗
PubMed1995

Cholesterol content of trout plasma membranes varies with acclimation temperature.

Involvement of cholesterol in thermally induced restructuring of biological membranes was investigated in several tissues of rainbow trout (Oncorhynchus mykiss). Cholesterol-rich plasma membranes (PM) were isolated from erythrocytes, liver, kidney, and gill of fish acclimated to 5 and 20 degrees C. Mean PM cholesterol-to-phospholipid molar ratios (C/P) from warm-acclimated animals were significantly higher than those of cold-acclimated fish in liver (0.26 vs. 0.18; P < 0.01), kidney (0.49 vs. 0.40; P < 0.02), and gill (0.66 vs. 0.60; P < 0.05); erythrocyte C/P did not differ significantly with acclimation temperature (0.28 vs. 0.25; P = 0.25). In light of the ordering effects of cholesterol on fluid-phase membranes, these results are consistent with a role for cholesterol in the homeoviscous response of some poikilotherm PMs. Tissue differences in both PM cholesterol levels and the magnitude of thermally evoked cholesterol changes may reflect tissue-specific membrane functions. Lower PM C/P of trout tissues relative to corresponding data available for homeotherms also support a possible evolutionary relationship between cholesterol content and thermal adaptation of the PM.

Acclimatization↗
PubMed1994

Membrane fluidity and hemilayer temperature sensitivity in trout hepatocytes during brief in vitro cold exposure.

Fluorescent membrane probes were used to assess the fluidity of hepatocyte plasma membranes (PM) from 20 degrees C-acclimated trout after exposure to 20 and 5 degrees C. PM isolated from cells after 6 h at 5 degrees C were significantly more fluid [fluorescence depolarization of 1,6-diphenyl-1,3,5-hexatriene (DPH)] than control membranes at both temperatures. The increased fluidity was sufficient to offset 45-50% of the cold-induced membrane ordering. In contrast, the fluidity of PM in intact cells from 20 degrees C-acclimated fish remained constant when exposed to 5 degrees C for a similar period. In addition, the fluidity of the inner hemilayer [1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene, p-toluenesulfonate (TMA-DPH)] was significantly less sensitive to temperature change than was the fluidity of the outer hemilayer [3-(p-(6-phenyl)-1,3,5-hexatrienyl)phenylpropionic acid (PA-DPH)]. Because the isolated membrane preparation was most likely enriched with canalicular membranes (based on 5'-nucleotidase recovery), these results suggest that the canalicular domain of the plasma membrane is preferentially modified during short-term cold exposure and that the fluidity of the inner hemilayer of the plasma membrane of intact cells is relatively temperature insensitive, thus requiring fewer modifications than the outer hemilayer during temperature acclimation.

Adaptation, Physiological↗
PubMed1991

Thermal adaptation in biological membranes: functional significance of changes in phospholipid molecular species composition.

Quantities of 1-palmitoyl 2-docosahexaenoyl phosphatidylcholine (16:0/22:6-PC or PDPC) increase from 24 to 40 weight percent as a consequence of cold acclimation in mitochondrial membranes of rainbow trout liver (J. Comp. Physiol. 156, 665-674, 1986). The present study was undertaken to assess the impact of such a large change in the proportions of a single molecular species on the fluidity, lateral packing (as sensed by phospholipase A2), and permeability of biological membranes. These properties were examined in multilamellar liposomes prepared from binary mixtures of dipalmitoyl phosphatidylcholine (DPPC) and PDPC in proportions increasing from 10 to 40 mole% PDPC. Glucose permeability was positively correlated with both assay temperature and PDPC content. The temperature dependence of Na+ permeability declined steadily as the mole fraction of PDPC increased; consequently, sodium permeability was positively correlated with PDPC content at 5 degrees C, but inversely correlated at 20 degrees C. Phospholipase A2 activity was independent of both assay temperature and vesicle composition. Vesicles of all compositions displayed a single transition in the temperature dependence of 1,6 diphenyl-1,3,5-hexatriene (DPH) fluorescence polarization, which shifted to lower temperature and broadened as proportions of PDPC increased. At temperatures below the transition, fluidity was positively correlated with the mole fraction of PDPC, but interfacial and deeper regions of the bilayer were affected differently by variations in PDPC content. Nonelectrolyte permeability was the only index of membrane structure or function to be significantly correlated with the fluidity of the bilayer interior. The tendencies of PDPC to both fluidize the membrane and to reduce the temperature sensitivity of electrolyte permeation may promote the adaptation of membrane function to low temperature.

Acclimatization↗
PubMed1990

The role of alterations in membrane lipid composition in enabling physiological adaptation of organisms to their physical environment.

It is clear from the literature reviewed that modifications in membrane lipid composition play a major role in the adaptation of diverse organisms to specific environments and physiological circumstances. Acyl chain and molecular species restructuring in phospholipids are the most ubiquitous adaptations to environmental insult, being implicated in membrane adjustments to temperature, pressure, water activity, pH and salinity. In contrast, other adaptations (e.g. modulation of anionic phospholipids (salinity adaptation), trehalose content (dehydration) and the PC/PE ratio (temperature acclimation] appear to be more context specific. Although the volume of correlative data relating membrane composition to environmental state is impressive, several questions must be explicitly addressed in future research if a mechanistic understanding of the role of lipids in fine tuning membrane function is to be achieved. These include: (1) Adaptation thresholds--How much environmental variation is required before an acclimatory response is initiated, and is the extent of membrane perturbation induced by such minimally effective stimuli similar for different stress vectors? Interspecific comparisons of the Na+/K(+)-ATPase of fish collected at different depths indicate that species must be separated in depth by a distance corresponding to a pressure difference of 20 MPa before pressure adaptation is evident. Assuming a dT/dP value of 0.23 (Table 1), a 20 MPa change in pressure corresponds to ca. a 5 degrees C change in temperature, which agrees well with the minimal temperature change required to elicit changes in the lipid composition of plasma membranes in kidney tissue of thermally-acclimating trout. A pressure of 20 MPa also corresponds approximately to the maximum depth from which deep sea animals survive being brought to the surface. Collectively, these observations suggest that the minimally effective stimuli for both temperature and pressure adaptation are similar. Comparable data are not available for other environmental variables. (2) Signal transduction--What signals are being sensed and how are they transduced into an adaptational response? In some cases, it is clear that the enzymes of lipid metabolism respond directly (either by a variation in catalytic rate or substrate preference) to variations in the physical environment in an apparently adaptive manner (e.g. refer Sections VI.A.1 and VI.B.2). It seems unlikely, however, that such direct effects can explain the totality of the adaptive capacity of organisms, especially given the evidence for the induction of desaturase synthesis in cold adaptation (refer to Section VI.A.2).(ABSTRACT TRUNCATED AT 400 WORDS)

Adaptation, Physiological↗
PubMed1990

Adaptation to temperature: phospholipid synthesis in hepatocytes of rainbow trout.

De novo phospholipid biosynthesis was assayed in isolated hepatocytes of rainbow trout (Oncorhynchus mykiss) both fully acclimated to 5 or 20 degrees C and undergoing acclimation from one temperature extreme to the other. Incorporation of [14C]choline, [3H]ethanolamine, and [3H]serine into phosphatidyl-choline (PC), phosphatidylethanolamine (PE), or both, was followed to assess metabolic capacity. PE biosynthesis rates exceeded those for PC four- to fivefold. Methylation of PE accounted for 10 (20 degrees C)-17% (5 degrees C) of the synthetic capacity for PC, whereas 6 (20 degrees C-acclimated)-27% (5 degrees C-acclimated) of PE synthesis was derived from phosphatidylserine (PS) decarboxylation. Several factors may contribute to the altered proportions of PE and PC or unsaturated molecular species of phospholipids characteristic of thermally acclimated animals. 1) Activities of choline and ethanolamine phosphotransferase pathways were significantly higher, and decarboxylation activity lower, in 20 degrees C than in 5 degrees C-acclimated trout, resulting in maintained PE synthesis despite a general depression of lipid biosynthesis at cold temperatures. 2) PC biosynthesis depended more on temperature (Q10 = 2.6-3.0) than that of PE (Q10 = 1.8-2.2), causing the ratio of PC/PE synthesis to be positively correlated with temperature. 3) Contribution of methyltransferase pathway to the synthesis of PC was higher at 5 than 20 degrees C. 4) The percentage of ethanolamine incorporation recovered in PC increased threefold in the early stages of warm acclimation. However, not all adjustments in biosynthetic capacity (most notably a 10-fold stimulation of PC synthesis 2 days after transfer of warm-acclimated trout to 5 degrees C) influence membrane lipid composition, implicating other processes in the regulation of this parameter.

Acclimatization↗
PubMed1989

Diagnosing dislocation of the hip in infancy.

In evaluating the diagnosis of dislocation of the hip in childhood by orthopedists in Oregon in 1985, we identified 36 dislocations in 32 patients, an incidence of 0.9 per 1,000 live births. In 12 patients, 12 dislocations (33%) were diagnosed after the neonatal period, 5 of which were diagnosed at walking age. Of the 12 children with a late diagnosis, 10 had normal hips when examined in the neonatal period. Neonatal screening will not detect all cases of congenitally dislocated hip. If dislocation of the hip in childhood is to be diagnosed in a timely manner, it is essential that children's hips be examined at the time of routine well-baby evaluations until a normal gait has been established.

Female↗
PubMed1988

Time course of thermal adaptation in plasma membranes of trout kidney. I. Headgroup composition.

The phospholipid composition of plasma membranes from the kidney of rainbow trout, Salmo gairdneri, was determined over a period of 21 days as fish were acclimating between temperatures of 5 and 20 degrees C. Proportions of phosphatidylethanolamine (PE) were significantly higher (29.03 vs. 23.26%) in membranes of 5 degrees C- than 20 degrees C-acclimated trout, whereas levels of phosphatidylcholine (PC) were similar. During acclimation, changes in headgroup composition were restricted primarily to PE and PC, with proportions of the former increasing and the latter decreasing on cold exposure. Headgroup composition changed rapidly as indicated by variations in PC/PE, which dropped from 1.71 +/- 0.13 to 0.78 +/- 0.11 within 8 h of cold acclimation and rose from 1.31 +/- 0.15 to 2.0 +/- 0.13 by the 2nd day of warm acclimation. Differences between warm- and cold-acclimating fish in the proportion of both PC and PE attained during the acclimation time course exceeded the magnitude of the differences between fully acclimated fish. Because of differences in molecular geometry and physical properties between PC and PE, the observed changes in headgroup composition may result in thermal compensation of membrane function, and the more rapid response to cold as opposed to warm stress suggests a primary role in adaptation to cold temperatures. However, headgroup modulation is most likely to contribute to homeoviscous adaptation only during the initial stages of the acclimatory response.

5'-Nucleotidase↗
PubMed1988

Time course of thermal adaptation in plasma membranes of trout kidney. II. Molecular species composition.

The molecular species composition of phosphatidylcholine (PC) was determined in plasma membranes of kidney for rainbow trout, Salmo gairdneri, undergoing thermal acclimation between 5 and 20 degrees C. Species of PC from 5 degrees C-acclimated trout were characterized by significantly higher values of unsaturation ratio (8.78 vs. 3.15), unsaturation index (2.32 vs. 1.84), and average chain length (34.18 vs. 33.12 carbons) than those of 20 degrees C-acclimated trout, primarily because of elevated proportions of 16:0/20:4 (8.67 vs. 4.42%) and 16:0/22:6 (15.61 vs. 7.18%) and reduced levels of 14:0/16:0 (3.34 vs. 12.41%). Proportions of saturated and monoenoic species responded most rapidly (within 16-48 h) to temperature change, whereas species containing long-chain, polyunsaturated fatty acids increased only after 10-21 days of cold acclimation. The combined results of the present and preceding paper [Hazel and Landrey, Am. J. Physiol. 255 (Regulatory Integrative Comp. Physiol. 24): R352-R357, 1988] indicate that the metabolic adaptation responsible for the thermal compensation of membrane structure differ in response times, which range from rapid adjustments in both headgroup and molecular species composition to considerably slower changes in the proportions of species containing long-chain polyunsaturated fatty acids. Furthermore, the restructuring of phospholipid molecular species composition modifies membrane structure in different ways at different times during the acclimation response.

Acclimatization↗