The magnetic structures of GdCuSn, GdAgSn and GdAuSn

We have determined the magnetic structures of GdCuSn, GdAgSn and GdAuSn using a combination of [Formula: see text]Gd Mössbauer spectroscopy and neutron powder diffraction. Each compound shows the same antiferromagnetic ordering of the Gd sublattice. The magnetic cell is doubled along the crystallographic a-axis (propagation vector [Formula: see text]) with the moments aligned along the hexagonal c-axis, forming alternating ferromagnetic sheets of up/down Gd moments along the a-axis.

Magnetic properties of Ln2CoGe4O12 and LnBCoGe4O12 (Ln = Gd, Tb, Dy, Ho, Er; B = Sc, Lu)

Polycrystalline samples of Ln₂CoGe₄O₁₂ (Ln = Gd, Tb, Dy, Ho or Er) and LnBCoGe₄O₁₂ (B = Sc or Lu) have been prepared and characterised by a combination of magnetometry, ¹⁵⁵Gd Mössbauer spectroscopy and, in the case of Tb₂CoGe₄O₁₂ and TbScCoGe₄O₁₂, neutron diffraction. The holmium- and erbium-containing compositions remain paramagnetic down to 2 K, those containing dysprosium behave as spin glasses and the terbium and gadolinium-containing compounds show long-range magnetic order with transition temperatures below 4 K in all cases. The data can be rationalized qualitatively in terms of the interplay between magnetic anisotropy and crystal field effects.

Changes in Rat Adipocyte and Liver Glucose Metabolism Following Repeated Restraint Stress

Rats exposed to repeated restraint weigh less than controls even 8 weeks after stress. Stress-induced weight loss is lean tissue, but the post-stress difference in weight between control and restrained rats is lean and fat mass. Whole-body glucose clearance is enhanced 1 day after stress, but adipocyte glucose utilization is inhibited and muscle glucose transport is unchanged. The studies described here demonstrated that glucose transport was increased in both restrained and pair-fed rats, but that glycogen synthesis was increased only in restrained rats, which may account for the improved whole-body glucose clearance. Adipocyte glucose transport was inhibited and adipose plasma membrane β-adrenergic receptor number was increased 1 day post-stress in restrained rats when weight loss was lean tissue, but were not different from control rats 5 days post-stress, when both fat and lean tissue were reduced. Thus, repeated restraint induces reversible changes in adipocyte metabolism that may represent a transition from the catabolic state of stress to a new energetic equilibrium in rats that maintain a reduced body weight for an extended period of time.

Complex incommensurate helicoidal magnetic ordering of EuNiGe3

(151)Eu Mössbauer spectroscopy and neutron powder diffraction are combined to show that the tetragonal (I4mm #107) compound EuNiGe3 orders magnetically below [Formula: see text] K and adopts a complex incommensurate helicoidal magnetic structure at 3.6 K, with a propagation vector [Formula: see text] and a Eu moment of 7.1(2) [Formula: see text]. On warming through 6 K an incommensurate sinusoidal modulation develops and dominates the magnetic order by 12 K.

Europium and manganese magnetic ordering in EuMn2Ge2

The antiferromagnetic structures of both the manganese and europium sublattices in EuMn2Ge2 have been determined using thermal neutron diffraction. T(N)(Mn)  =  714(5) K with the 3.35(5) μ(B) (at 285 K) Mn moments ordering according to the I4'/m'm'm space group. The Eu order is incommensurate with the 6.1(2) μ(B) (at 3.6 K) Eu moments oriented parallel to the c-axis with a propagation vector of k  =  [0.153(2) 0 0]. Both neutron diffraction and (151)Eu Mössbauer spectroscopy reveal evidence of magnetic short-range ordering of the Eu sublattice around and above T(N)(Eu)  ∼ 10 K. The ordering temperature of the Eu sublattice is strongly affected by the sample's thermal history and rapid quenching from the melting point may lead to a complete suppression of that ordering.

The magnetic structure of EuCu₂Sb₂

Antiferromagnetic ordering of EuCu2Sb2 which forms in the tetragonal CaBe2Ge2-type structure (space group P4/nmm #129) has been studied using neutron powder diffraction and (151)Eu Mössbauer spectroscopy. The room temperature (151)Eu isomer shift of -12.8(1) mm s(-1) shows the Eu to be divalent, while the (151)Eu hyperfine magnetic field (B(hf)) reaches 28.7(2) T at 2.1 K, indicating a full Eu(2+) magnetic moment. B(hf)(T) follows a smooth S = 7/2 Brillouin function and yields an ordering temperature of 5.1(1) K. Refinement of the neutron diffraction data reveals a collinear A-type antiferromagnetic arrangement with the Eu moments perpendicular to the tetragonal c-axis. The refined Eu magnetic moment at 0.4 K is 7.08(15) μ(B) which is the full free-ion moment expected for the Eu(2+) ion with S = 7/2 and a spectroscopic splitting factor of g = 2.

Determination of the magnetic structure of Gd₂Fe₂Si₂C by Mössbauer spectroscopy and neutron diffraction

We have determined the magnetic structure of the intermetallic compound Gd2Fe2Si2C using neutron powder diffraction, (155)Gd and (57)Fe Mössbauer spectroscopy. This compound crystallizes in a monoclinic (C2/m) structure and its magnetic structure is characterized by antiferromagnetic order of the Gd sublattice along the b-axis, with cell-doubling along the c-axis. The propagation vector is k = [0 0 ½]. At 3.6 K the Gd moment reaches 6.2(2) μ(B). Finally, (57)Fe Mössbauer spectroscopy shows no evidence of magnetic ordering of the Fe sublattice.

Racial disparities in cardiovascular risk factor control in an underinsured population with Type 2 diabetes

AIM

To investigate the race-specific trend in attainment of the American Diabetes Association cardiovascular risk factor control goals (HbA1c <53 mmol/mol (7.0%), blood pressure <130/80 mmHg and LDL cholesterol <2.6mmol/l) by patients with Type 2 diabetes.

METHODS

The study sample included 14 946 African-American and 12 758 white patients who were newly diagnosed with Type 2 diabetes between 2001 and 2009 in the Louisiana State University Hospital system. The race-specific percentages of patients' attainment of American Diabetes Association goals were calculated using the baseline and follow-up measurements of HbA1c , blood pressure, and LDL cholesterol levels. Logistic regression was used to test the difference between African-American and white patients.

RESULTS

The percentage of patients who met all three American Diabetes Association goals increased from 8.2% in 2001 to 10.2% in 2009 (increased by 24.4%) in this cohort. Compared with African-American patients, white patients had better attainment of the following American Diabetes Association goals: HbA1c (61.4 vs. 55.1%), blood pressure (25.8 vs. 20.4%), LDL cholesterol (40.1 vs. 37.7%) and all three goals (7.3 vs. 5.1%). African-American and white patients generally had a better cardiovascular disease risk factor profile during follow-up when we assessed attainment of the American Diabetes Association goals by means of HbA1c , blood pressure and LDL cholesterol.

CONCLUSIONS

During 2001-2009, the present low-income cohort of people with Type 2 diabetes generally experienced improved control of cardiovascular disease risk factors. White patients had better attainment of the American Diabetes Association cardiovascular risk factor control goals than their African-American counterparts.

Ferrimagnetism in GdCo(12-x)Fe(x)B6

The effects of iron substitution on the structural and magnetic properties of the GdCo(12-x)Fe(x)B6 (0 ≤ x ≤ 3) series of compounds have been studied. All of the compounds form in the rhombohedral SrNi12B6-type structure and exhibit ferrimagnetic behaviour below room temperature: T(C) decreases from 158 K for x = 0 to 93 K for x = 3. (155)Gd Mössbauer spectroscopy indicates that the easy magnetization axis changes from axial to basal-plane upon substitution of Fe for Co. This observation has been confirmed using neutron powder diffraction. The axial to basal-plane transition is remarkably sensitive to the Fe content and comparison with earlier (57)Fe-doping studies suggests that the boundary lies below x = 0.1.

A TDPAC study of static and dynamic magnetic behaviour

The a-FexHf100-x system is used to explore the application of TDPAC (the time differential perturbed γ-γ angular correlation technique) to non-trivial anisotropic magnetic relaxation. The effect of fluctuations in this system is primarily to cause a decay of the zero-frequency component, which is characterized by the phenomenological decay rate λ. The zero-field magnetic phase diagram, constructed from both static and dynamic features of the data, and the temperature dependence of λ are both fully consistent with the physics of partial bond frustration. The results demonstrate that the magnetic fluctuations are meaningfully characterized by simple spectrum features, and are not obscured by large static fields or severe disorder.

The magnetic structure of EuPdSn

The TiNiSi-type structure, antiferromagnetic ordering and divalent state of europium in EuPdSn have been confirmed by neutron powder diffraction. The Néel temperature is 16.2(3) K. The magnetic diffraction peaks can be indexed with a propagation vector k = [0, 0.217, q(z)] (q(z) ≤ 0.02) at 13.2 K, and k = [0, 0.276, 0] at 3.6 K, indicating an incommensurate antiferromagnetic structure at both temperatures. At 13.2 K, the best refinement is obtained with a sinusoidally modulated magnetic structure and europium magnetic moments oriented in the (a,b) plane with an azimuthal angle ϕ of 66(4)°relative to the a-axis. By 3.6 K, the magnetic structure of EuPdSn has transformed to an (a,b) planar helimagnetic structure (a 'flat spiral').

Diet type and changes in food cravings following weight loss: findings from the POUNDS LOST Trial

Few well-controlled trials have evaluated the effects that macronutrient composition has on changes in food cravings during weight loss treatment. The present study, which was part of the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial, investigated whether the fat and protein content of four different diets affected changes in specific food cravings in overweight and obese adults. A sample of 811 adults were recruited across two clinical sites, and each participant was randomly assigned to one of four macronutrient prescriptions: 1) low fat (20% of energy), average protein (15% of energy); 2) moderate fat (40%), average protein (15%); 3) low fat (20%), high protein (25%); 4) moderate fat (40%), high protein (25%). With few exceptions, the type of diet that participants were assigned did not differentially affect changes in specific food cravings. Participants assigned to the high-fat diets, however, had reduced cravings for carbohydrates at month 12 (p<0.05) and fruits and vegetables at month 24. Also, participants assigned to high-protein diets had increased cravings for sweets at month 6 and month 12 (ps<0.05). Participants in all four dietary conditions reported significant reductions in food cravings for specific types of foods (i.e., high fat foods, fast food fats, sweets, and carbohydrates/starches; all ps<0.05). Cravings for fruits and vegetables, however, were increased at month 24 (p<0.05). Calorically restricted diets (regardless of their macronutrient composition) yielded significant reductions in cravings for fats, sweets, and starches whereas cravings for fruits and vegetables were increased.

Effect of diet composition on energy expenditure during weight loss: the POUNDS LOST Study

BACKGROUND

Weight loss reduces energy expenditure, but the contribution of different macronutrients to this change is unclear.

HYPOTHESIS

We tested the hypothesis that macronutrient composition of the diet might affect the partitioning of energy expenditure during weight loss.

DESIGN

A substudy of 99 participants from the Preventing Overweight Using Novel Dietary Strategies (POUNDS LOST) trial had total energy expenditure (TEE) measured by doubly labeled water, and resting energy expenditure (REE) measured by indirect calorimetry at baseline and repeated at 6 months in 89 participants. Participants were randomly assigned to one of four diets with either 15 or 25% protein and 20 or 40% fat.

RESULTS

TEE and REE were positively correlated with each other and with fat-free mass and body fat, at baseline and 6 months. The average weight loss of 8.1 ± 0.65 kg (least-square mean ± s.e.) reduced TEE by 120 ± 56  kcal per day and REE by 136 ± 18 kcal per day. A greater weight loss at 6 months was associated with a greater decrease in TEE and REE. Participants eating the high-fat diet (HF) lost significantly more fat-free mass (1.52 ± 0.55 kg) than the low-fat (LF) diet group (P<0.05). Participants eating the LF diet had significantly higher measures of physical activity than the HF group.

CONCLUSION

A greater weight loss was associated with a larger decrease in both TEE and REE. The LF diet was associated with significant changes in fat-free body mass and energy expenditure from physical activity compared with the HF diet.

Magnetic ordering in GdAgSb2

GdAgSb(2) has been studied using (155)Gd Mössbauer spectroscopy and neutron powder diffraction at a wavelength of 2.3672(1) Å. Commensurate antiferromagnetic order develops below T(N) = 13.8(4) K with the 6.2(3) μ(B) Gd moments lying in the ab-plane of the tetragonal cell. The magnetic ordering is characterized by a [½ 0 0] propagation vector (i.e. the magnetic cell is doubled along one of the crystallographic basal plane axes) with the Gd moments oriented perpendicular to the doubled direction. These results are fully consistent with an earlier determination by x-ray resonant magnetic exchange scattering.

Valence change and magnetic order in YbMn6Ge(6-x)Sn(x)

The YbMn(6)Ge(6-x)Sn(x) compounds (0 < x < 6) have been investigated using x-ray diffraction, magnetic measurements, neutron diffraction and (170)Yb Mössbauer spectroscopy. The YbMn(6)Ge(6-x)Sn(x) system comprises three solid solutions: (i) 0 < x ≤ 1.1, (ii) 3.2 ≤ x ≤ 4.6 and (iii) 5.3 ≤ x < 6, all of which crystallize in the hexagonal (P6/mmm) HfFe(6)Ge(6)-type structure. The substitution of Sn for Ge yields changes in the type of magnetic order (antiferromagnetic, helimagnetic, ferromagnetic, conical and ferrimagnetic), in the easy magnetization direction (from easy axis to easy plane) as well as in the valence state of Yb (from trivalent to divalent). The Mn moments order at or above room temperature, while magnetic ordering of the Yb sublattice is observed at temperatures up to 110 K. While Yb is trivalent for x ≤ 1.1 and divalent for x ≥ 5.3, both magnetic and (170)Yb Mössbauer spectroscopy data suggest that there is a gradual reduction in the average ytterbium valence through the intermediate solid solution (3.2 ≤ x ≤ 4.6), and that intermediate valence Yb orders magnetically, a very unusual phenomenon. Analysis of the (170)Yb Mössbauer spectroscopy data suggests that the departure from trivalency starts as early as x = 3.2 and the loss of ytterbium moment is estimated to occur at an average valence of ∼2.5+.

A study on the magnetic behaviour of polymorphic YbFe6Ge6

The intermetallic compound YbFe(6)Ge(6) adopts two very closely related hexagonal crystal structures, HfFe(6)Ge(6)-type and YCo(6)Ge(6)-type. In both structures the Fe sublattice orders antiferromagnetically at 485(2) K. The Yb sublattice does not order magnetically, down to 1.5 K. In the HfFe(6)Ge(6)-type structure, the Fe magnetic moments undergo a spin reorientation away from the C-axis upon cooling, commencing at around 60 K, whereas in the YCo(6)Ge(6)-type structure the Fe moments remain ordered along the C-axis, or quite close to it.

Neutron powder diffraction determination of the magnetic structure of Gd(3)Ag(4)Sn(4)

Natural gadolinium is the strongest neutron-absorbing element and neutron diffraction studies of Gd-containing materials rely on the use of either enriched Gd isotopes or short neutron wavelengths where the absorption is weaker but, unfortunately, the neutron flux is also weak. We have employed a new sample-mounting technique to obtain neutron powder diffraction patterns from the intermetallic compound Gd(3)Ag(4)Sn(4) containing natural Gd, at a neutron wavelength of ∼ 2.37 Å where there is much greater flux. Here, we report the magnetic structure of Gd(3)Ag(4)Sn(4). The magnetic ordering temperature is 28.8(2) K. At 2.8 K the Gd(4e) sublattice is antiferromagnetically ordered along the crystal c-axis, commensurate with the crystal lattice. The Gd(2d) sublattice is also ordered along the c-axis but its magnetic structure is incommensurate with the crystal lattice.

Structural transitions in RNi(10)Si(2) intermetallics

Intermetallic compounds of the type RFe(10)Si(2) and RCo(10)Si(2) crystallize in the ThMn(12) structure (space group I4/mmm) whilst the heavy rare earth series RNi(10)Si(2) crystallize in a maximal subgroup of I4/mmm, P4/nmm. Reported here are neutron powder diffraction investigations for TbNi(10)Si(2) and ErNi(10)Si(2) which show that the P4/nmm structure undergoes a high temperature order-disorder phase transition at approximately 930 °C above which the ordered Ni and Si fractions revert to a random distribution on 4d and 4e sites. The volume expansion has been tracked in detail via the temperature dependence of the lattice parameters, whilst the temperature dependence of the thermal expansion coefficients α(11), α(33) and α(volume) has been determined from the lattice parameters. Associated with the order-disorder transition is a transition associated with a displacement of the R ion along the c-axis. Both transitions are of second order and the critical exponent associated with the order-disorder and displacive transitions, β = 0.31, is in excellent agreement with the exponent determined for the three-dimensional Ising model.

Nanostructured materials for lithium-ion batteries: surface conductivity vs. bulk ion/electron transport

Lithium metal phosphates are amongst the most promising cathode materials for high capacity lithium-ion batteries. Owing to their inherently low electronic conductivity, it is essential to optimize their properties to minimize defect concentration and crystallite size (down to the submicron level), control morphology, and to decorate the crystallite surfaces with conductive nanostructures that act as conduits to deliver electrons to the bulk lattice. Here, we discuss factors relating to doping and defects in olivine phosphates LiMPO4 (M = Fe, Mn, Co, Ni) and describe methods by which in situ nanophase composites with conductivities ranging from 10(-4)-10(-2) S cm(-1) can be prepared. These utilize surface reactivity to produce intergranular nitrides, phosphides, and/or phosphocarbides at temperatures as low as 600 degrees C that maximize the accessibility of the bulk for Li de/insertion. Surface modification can only address the transport problem in part, however. A key issue in these materials is also to unravel the factors governing ion and electron transport within the lattice. Lithium de/insertion in the phosphates is accompanied by two-phase transitions owing to poor solubility of the single phase compositions, where low mobility of the phase boundary limits the rate characteristics. Here we discuss concerted mobility of the charge carriers. Using Mössbauer spectroscopy to pinpoint the temperature at which the solid solution forms, we directly probe small polaron hopping in the solid solution Li(x)FePO4 phases formed at elevated temperature, and give evidence for a strong correlation between electron and lithium delocalization events that suggests they are coupled.

Prediction of response to sibutramine therapy in obese non-diabetic and diabetic patients

BACKGROUND

Early weight loss is generally considered to predict long-term weight outcome in obese patients, and this is reflected in prescribing guidelines for antiobesity drugs. For example, the current prescribing guidelines for the antiobesity drug, sibutramine, indicate that if patients have not lost 2 kg (or 4 lb) in the first 4 weeks of treatment with sibutramine 10 mg, the physician should re-evaluate the therapy, which may result in increasing the dose to 15 mg or discontinuation. This regimen may deny treatment to a large group of patients who might otherwise benefit, particularly patients with type 2 diabetes who often find it more difficult to lose weight than non-diabetic obese individuals.

MATERIALS

We have re-analysed pooled data from seven randomized, controlled studies of sibutramine-induced weight loss and maintenance in which patients (n = 928; 75% female) had taken sibutramine 10 or 15 mg continuously for 12 months, in order to determine the predictors of success in weight loss (defined as loss of at least 5% of initial body weight at Month 12) in both diabetic and non-diabetic patients. Sensitivity and specificity analyses were used to calculate optimal predictive values.

RESULTS

In both diabetic and non-diabetic patients, weight loss of 4 kg at 3 months was identified as the optimal predictor for achieving at least 5% weight loss at 12 months. This target was associated with the best average values for sensitivity, specificity and accuracy, as well as high positive (78% vs. 84% for non-diabetics and 76% vs. 85% for diabetics, compared to existing guidelines target of 2 kg after 1 month treatment) and negative predictive values (63% vs. 71% for non-diabetics; 52% vs. 70% for diabetics).

CONCLUSION

Sibutramine, in conjunction with diet and exercise, should be continued for at least 3 months (providing there are no adverse effects) to determine whether or not patients are likely to achieve a clinically valid outcome at 1 year. This highlights the need to ensure that regulatory restrictions reflect the needs of clinical practice.

Field and temperature induced magnetic transition in Gd5Sn4: a giant magnetocaloric material

Gd5Sn4 exhibits a giant magnetocaloric effect comparable to that reported in the Gd5(Si,Ge)(4) system. The giant magnetocaloric effect is associated with a first-order change that occurs at approximately 82 K in zero field, and can be reversed by the application of an external field of a few Tesla. 119Sn Mössbauer spectroscopy shows that this material is magnetically inhomogeneous over a wide range of temperatures and fields.

The relation of gender, race and socioeconomic status to obesity and obesity comorbidities in a sample of US adults

OBJECTIVE

To examine the obesity-related chronic diseases in the US adult population according to gender, race and socioeconomic status.

METHODS

Data from the 1994-1996 Continuing Survey of Food Intakes by Individuals (1994-1996 CSFII) conducted by the US Department of Agriculture/Agricultural Research Service (USDA/ARS) were used in the analysis. Relevant data included self-reported weight and height, self-reported physician-diagnosed diabetes mellitus, hypertension, heart disease and high serum cholesterol. Analysis was conducted according to gender, race, income level and education level.

RESULTS

There was a graded increase in diabetes, hypertension and high serum cholesterol with increasing body weight in nearly all gender, racial and socioeconomic groups. Among the obese individuals, the prevalence of hypertension was higher in black subjects and the prevalence of diabetes, hypertension and heart disease was higher in individuals with lower education compared to their counterparts. The odds of having diabetes, hypertension, heart disease and high serum cholesterol increased with increasing body weight after adjusting for age, gender, race, income, education and smoking.

CONCLUSION

Although cross-sectional in nature, our results suggest that the disease burden associated with obesity in the population may be substantial. This burden increases with increasing severity of obesity. Our findings support the current opinion that, although the nature of obesity-related health risks is similar in all populations, the specific level of risk associated with a given level of obesity may be different depending on gender, race and socioeconomic condition.

Regulation of inherently autoreactive VH4-34 B cells in the maintenance of human B cell tolerance

The study of human B cell tolerance has been hampered by difficulties in identifying a sizable population of autoreactive B lymphocytes whose fate could be readily determined. Hypothesizing that B cells expressing intrinsically autoreactive antibodies encoded by the VH4-34 heavy chain gene (VH4-34 cells) represent such a population, we tracked VH4-34 cells in healthy individuals. Here, we show that naive VH4-34 cells are positively selected and mostly restricted to the follicular mantle zone. Subsequently, these cells are largely excluded from the germinal centers and underrepresented in the memory compartment. In healthy donors but not in patients with systemic lupus erythematosus (SLE), these cells are prevented from differentiating into antibody-producing plasma cells. This blockade can be overcome ex vivo using cultures of naive and memory VH4-34 cells in the presence of CD70, IL-2, and IL-10. VH4-34 cells may therefore represent an experimentally useful surrogate for autoantibody transgenes and should prove valuable in studying human B cell tolerance in a physiological, polyclonal environment. Our initial results suggest that both positive and negative selection processes participate in the maintenance of tolerance in autoreactive human B cells at multiple checkpoints throughout B cell differentiation and that at least some censoring mechanisms are faulty in SLE.

Overexpression of agouti protein and stress responsiveness in mice

Ectopic overexpression of agouti protein, an endogenous antagonist of melanocortin receptors' linked to the beta-actin promoter (BAPa) in mice, produces a phenotype of yellow coat color, Type II diabetes, obesity and increased somatic growth. Spontaneous overexpression of agouti increases stress-induced weight loss. In these experiments, other aspects of stress responsiveness were tested in 12-week-old male wild-type mice and BAPa mice. Two hours of restraint on three consecutive days produced greater increases in corticosterone and post-stress weight loss in BAPa than wild-type mice. In Experiment 2, anxiety-type behavior was measured immediately after 12 min of restraint. This mild stress did not produce many changes indicative of anxiety, but BAPa mice spent more time in the dark side of a light-dark box and less time in the open arms of an elevated plus maze than restrained wild-type mice. In a defensive withdrawal test, grooming was increased by restraint in all mice, but the duration of each event was substantially shorter in BAPa mice, possibly due to direct antagonism of the MC4-R by agouti protein. Thus, BAPa mice showed exaggerated endocrine and energetic responses to restraint stress with small differences in anxiety-type behavior compared with wild-type mice. These results are consistent with observations in other transgenic mice in which the melanocortin system is disrupted, but contrast with reports that acute blockade of central melanocortin receptors inhibits stress-induced hypophagia. Thus, the increased stress responsiveness in BAPa mice may be a developmental compensation for chronic inhibition of melanocortin receptors.

Increased dietary fat prevents sleep deprivation-induced immune suppression in rats

BACKGROUND AND PURPOSE

Fatty acid composition of rodent diets can affect baseline immune function as measured in vitro and in vivo. Stress, in a variety of forms, can also affect immune function. Possible interaction between diet and other stressors has not been fully explored. We examined the interaction between sleep deprivation stress and dietary fatty acid composition in altering lymphocyte responses to mitogen stimulation.

METHODS

Rats were fed diets containing various sources of fatty acids, then were subjected to sleep deprivation. Splenocytes were harvested and assayed for responsiveness to various mitogens, using a 72-h proliferation assay.

RESULTS

Rats subjected to sleep deprivation experienced significant suppression of in vitro proliferative response to various mitogens. This immune suppression was dependent on duration of sleep deprivation. Feeding sleep deprived rats a diet enriched in fatty acids abrogated the effect of sleep deprivation.

CONCLUSIONS

The fat content of rodent diets can have a marked effect on baseline and stress-modulated immune responses.

Spin dynamics in a frustrated magnet

180 degrees spin flips have been identified as the dominant fluctuation mechanism at the transverse spin freezing transition in partially frustrated a-Fe92Zr8. The form of the selective excitation double Mössbauer spectra, coupled with the perfect agreement with zero-field muon spin relaxation data, eliminates other relaxation forms.

Short-term dietary energy restriction reduces lean body mass but not performance in physically active men and women

We studied the effect of moderate, short-term energy restriction on physical performance in physically fit men (n = 13) and women (n = 11) in a controlled clinical research setting with a metabolic kitchen, exercise testing laboratory and training facility. The experiment consisted of a 10 d baseline period followed by either 2 wk of dietary energy restriction (750 kcal/d; n = 16) or energy balance (control; n = 8). During this 24 day study, exercise energy expenditure averaged 465 +/- 5.7 kcal/d in all subjects and was accomplished through treadmill running at a self-selected pace. Body weight was maintained in the control group (-0.36 +/- 0.24kg), but energy restriction resulted in weight loss of -1.29 +/- 0.16 kg (p < 0.001). There was a trend for lean body mass to decline more in the energy restriction group (p = 0.093), accounting for 61% of the weight loss, and urinary nitrogen excretion also tended to be higher in the energy restriction vs. control group (i.e., 13.2 +/- 1.1 vs. 11.2 +/- 1.0g/d; p = 0.089). Muscle strength (leg & shoulder press; 1 repetition maximum) was maintained or increased during the energy restriction period. Muscle endurance, assessed by leg squats to fatigue, and 5 mile run time improved following two weeks of energy restriction or balance. Anaerobic capacity (Wingate Test) increased slightly in the restriction (+ 368 +/- 219 joules) but declined in the control group 649 +/- 288 joules; p<0.05). We conclude that short-term (2 weeks) moderate energy restriction (approximately 750 kcal/d) results in weight loss but does not impair performance in physically fit young men and women.

Incorporating new recipes into the Armed Forces Recipe File: determination of acceptability

As part of a project of decrease fat, cholesterol, and sodium in soldiers' diets, new ethnic and breakfast items were developed and standardized for 100 portions. Acceptability data were collected after initial recipe development, during recipe validation at a collaborating university, and in an actual Army garrison. Acceptability was determined using a nine-point hedonic scale; products rating > or = 6.0 in initial tests were prepared in garrison. Acceptability data were compared among test settings, ethnic categories, and food type. When grouped by ethnic categories, acceptability ratings varied more than when grouped by food type. Ratings varied most between development and validation settings (7.2 vs. 6.6; p < 0.05) and least between validation and actual Army settings (6.6 vs. 6.6; not significant). Because acceptability ratings were similar between the validation site and the Army garrison, future recipe development may continue without additional testing at actual Army garrisons, leading to more timely armed forces recipe file additions.

Superparamagnetic spin dynamics studied using selective excitation double Mössbauer spectroscopy

A detailed study of spin dynamics in a 6 nm Fe3O4 ferrofluid using a substantially improved selective excitation double Mossbauer (SEDM) experimental technique has led to the unambiguous separation of static disorder, collective excitations, and moment reversals. Superparamagnetic spin flips have been observed through the appearance of an additional line in the SEDM spectrum, defining the energy transitions during relaxation, with frequencies of 2.5+/-0.3 MHz at 70 K to 9.7+/-1.0 MHz at 110 K. SEDM offers a precise window into the dynamics and blocking behavior of fine particle systems.

Identification of urocortin mRNA antisense transcripts in rat tissue

Urocortin (UCN) has 45% sequence homology with corticotropin releasing factor (CRF) and binds to CRF receptors. We used reverse-transcriptase-polymerase chain reaction to demonstrate the presence of UCN RNA in various brain regions and in peripheral tissues. Ribonuclease protection assay (RPA) using sense and antisense riboprobes demonstrated the presence of a naturally occurring antisense UCN RNA transcript in a number of tissues. Northern blot indicated that the antisense transcript was the same size as sense UCN. RPA, using probes that covered bases 1 to 560 of 579 bp sequence of rat UCN, indicated that the antisense sequence was complementary to sense UCN but did not contain an open reading frame. Sense and antisense UCN RNA were co-expressed in all tissues that contained levels of either transcript detectable by RPA. Sense RNA expression was greater than antisense in the midbrain, the two transcripts were expressed equally in the hypothalamus and antisense was expressed at higher levels than sense in the liver, heart, and skeletal muscle. Antisense RNA expression was stress responsive, suggesting that it may play a role in regulating transcription or translation of UCN mRNA.

Clinical evaluation of the overweight patient

Evaluation of an overweight patient is the first step in any therapeutic program. The syndromes of obesity can be classified in several ways. The first is an anatomic classification based on the size, number, and distribution of fat cells and fat tissue. The second is an etiologic classification based on identification of specific diseases and settings that produce obesity. Hypothalamic injury and endocrine disease such as Cushing's disease and the polycystic ovary syndrome are three identifiable causes of obesity. In this medicated society drugs are always candidates to produce weight gain. The most common causes, however, are stopping smoking, overconsumption of high-fat foods, a decrease in the level of activity, and aging. The natural history of obesity provides a useful framework in which to view both preventive and therapeutic strategies. Some individuals will never become overweight, but of those who do, about one-third will do so during the first two decades, and the remaining two-thirds will become overweight after age 20. A number of epidemiological and metabolic factors can serve as a guide to those individuals who are at high risk. Having overweight parents tops the list, but multiple births, cessation of smoking, and a sedentary lifestyle are additional factors. Therapeutic decisions should be based on risk-benefit decisions. The risk can be assessed from the body mass index, the distribution of fat in upper or lower body obesity, the rate of weight gain, and the degree of physical inactivity. After assessing risk, the therapeutic choices can be selected from the age category of the patient. With any therapeutic activity, involvement of the patient in a realistic approach to the treatment process is essential.

Use of sibutramine and other noradrenergic and serotonergic drugs in the management of obesity

Drugs that act through noradrenergic and serotonergic mechanisms have historically served as the mainstays of pharmacologic treatments for obesity. This review addresses the following three topics: a brief discussion of older weight loss medications approved for short-term use (benzphetamine, phendimetrazine, diethylpropion, mazindol, and phentermine), as well as over-the-counter adrenergic drugs (phenylpropanolamine and ephedrine); recent clinical studies documenting the safety and efficacy of a new medication for obesity treatment, sibutramine, recently approved by the Food and Drug Administration for long-term use; and recent studies characterizing the valvulopathy associated with fenfluramine and dexfenfluramine, serotonergic medications for obesity which have been removed from the markets.

Common apolipoprotein A-IV variants are associated with differences in body mass index levels and percentage body fat

OBJECTIVE

To determine the relationship between two common apoA-IV variants (Thr347-->Ser; Gln360-->His), and body mass index (BMI) and percentage body fat.

DESIGN

Cross-sectional study.

SUBJECTS

Eight-hundred and forty-eight subjects screened for participation in ongoing clinical studies.

MEASUREMENTS

ApoA-IV genotype, body mass index, waist-to-hip ratio and percentage body fat by bioelectric impedance.

RESULTS

Participants had an average age of 41+/-12 y and an average BMI of 28.2+/-5.5 kg/m2. Individuals homozygous for the Ser347 allele had higher BMI (32.3+/-6.6 vs 28.6+/-5.3 kg/m2; P<0.01) and percentage body fat (36.9+/-7.8 vs 31.0+/-9.6%; P<0.05) compared with individuals homozygous for Thr347. In contrast, the presence of at least one copy of the His360 allele was associated with lower BMI (27.2+/-5.0 vs 28.4+/-5.6 kg/m2; P<0.05) and percentage body fat (28.6+/-8.2 vs 30.7+/-9.1%; P<0.05). The genotype effects persisted after normalization of the data for the potential confounding effects of gender, age and race. When grouped by BMI percentile, the frequency of the Ser347/Ser347 genotype increased while the frequency of the His360 allele decreased with increasing BMI.

CONCLUSIONS

These data suggest a role for apoA-IV in fat storage or mobilization and that genetic variations in the apoA-IV gene may play a role in the development of obesity.

Magnetic nanostructured composites using alginates of different M/G ratios as polymeric matrix

Alginate extracted from Sargassum fluitans and Macrocystis pyrifera with different molecular weights and mannuronic/guluronic ratios, M/G, were used as gel matrixes in order to obtain magnetic nanostructured composites. Magnetic nanocrystalline particles of iron oxides were formed inside the alginate matrix by in situ alkaline oxidation of ferrous ions. The magnetic materials obtained were subjected to several oxidative cycles and the increment in iron content was determined after each cycle. X-ray diffraction, magnetometry and Mössbauer spectroscopy were used to examine the materials. The high magnetic response, the absence of hysteresis, and the centered paramagnetic doublet in the Mössbauer spectra indicate the presence of nanocrystalline particles with a superparamagnetic behavior. X-ray diffractograms show peaks that correspond to maghemite. After the first cycle, Sargassum had four times the magnetic response of Macrocystis, which had more than twice the M/G ratio.

Recent progress in obesity pharmacotherapy

Interest in obesity pharmacotherapy is intense, sparked by the public health threat of increases in obesity rates, as well as by increased knowledge of the biology underlying food intake and energy balance. After a hiatus of more than 20 years, three new medications approved by the US Food and Drug Administration for obesity treatment recently reached the marketplace. One of these, dexfenfluramine, has been withdrawn because of fenfluramine's and its isomer's association with valvular regurgitation. Sibutramine, a centrally acting reuptake inhibitor of monoamines, and orlistat, a pancreatic lipase inhibitor, have been approved for long-term obesity treatment. This review covers recent publications documenting clinical trial experience with these two agents and updates the evidence associating dexfenfluramine and fenfluramine with valvulopathy. As obesity rates increase throughout the world and as knowledge expands regarding the biology of obesity, an expansion of pharmacologic options for obesity treatment is certain.

Neuroleptic malignant syndrome after venlafaxine

A patient developed neuroleptic malignant syndrome after a single dose of venlafaxine with trifluoperazine treatment. A dopamine-inhibition effect induced by one dose of venlafaxine may have augmented dopamine-receptor inhibition by trifluoperazine.

Pharmaceutical cost savings of treating obesity with weight loss medications

OBJECTIVE

To evaluate, in compliant patients, the pharmaceutical costs of treating obesity with fenfluramine/mazindol, fenfluramine/phentermine, caffeine/ephedrine, or mazindol relative to the pharmaceutical costs of treating obesity-related comorbid conditions and reducing cardiovascular risk.

METHODS AND PROCEDURES

Subjects were between 18 and 60 years of age with a BMI of >30 kg/m2. Pharmaceutical costs were evaluated in 73 of 220 subjects taking medications for diabetes, hyperlipidemia, or hypertension before and after treatment using fenfluramine with mazindol or phentermine. The pharmaceutical cost of weight loss, cardiac risk reduction, and low-density lipoprotein (LDL) cholesterol reduction was calculated for fenfluramine with mazindol or phentermine, caffeine with ephedrine, or mazindol alone, and compared to approved lipid-lowering medications.

RESULTS

Losses of 6% to 10% of initial body weight reduced pharmacy costs $122.64/month for insulin treated diabetes, $42.92/month for sulfonylurea-treated diabetes, $61.07/month for hyperlipidemia treated with medication, and $0.20/month for hypertension treated with medication. Blood pressure and laboratory evidence of insulin resistance improved in all medication groups. Caffeine/ephedrine was most cost-effective of the three treatments in reducing weight, cardiac risk, and LDL cholesterol.

DISCUSSION

Obesity medications produced a substantial weight loss in compliant patients and resulted in a net pharmaceutical cost savings compared to treating obesity related comorbid conditions.

Treatment of chronic myelogenous leukemia with autologous bone marrow transplantation followed by roquinimex

Unmanipulated autologous bone marrow transplant (ABMT) offers patients with chronic myelogenous leukemia (CML) a long-term survival of 10%, at best. Immunotherapy has a role in the myeloid leukemias, and there is increasing evidence that of all hematopoietic neoplasms, CML may be the most susceptible to immune regulation. Roquinimex is known to enhance T cell, NK cell and macrophage activity. A phase II study was initiated in March 1992 to evaluate the role of roquinimex in Ph chromosome-positive CML post ABMT. Patients were conditioned with busulfan/ cyclophosphamide followed by reinfusion of unmanipulated Ph-positive bone marrow stem cells (>1 x 108 NBC/kg). When engraftment of neutrophils (ANC) reached 100/microl, patients received oral roquinimex twice weekly, escalating to a maximal dose of 0.2 mg/kg in 2 weeks. Seventeen patients have entered the study; 11 in first chronic phase (CP1); two in second chronic phase (CP2) and four in accelerated phase (AP). All required significant myelosuppressive therapy prior to ABMT to maintain stable blood counts and most had also received prior interferon therapy. All patients survived the transplant. Subsequent toxicity consisted mainly of musculoskeletal aches and peripheral edema. Additionally, specific skin changes were observed including graft-versus-host-like disease and eccrine sweat gland necrosis. Eight out of 17 patients are alive 28-60 months post ABMT. Of the nine patients who died, two were in CP2 and three in AP. All patients in CP1 went into a complete hematological remission post ABMT and seven of the 11 patients had at least a major cytogenetic response (greater than 65% Ph-negative metaphases) at 1 year or beyond and four of the 11 patients had a complete cytogenetic response at 2 years or beyond. Cytogenetic response post transplant often developed over time and did not simply represent post ABMT engraftment with Ph-negative cells. The clinical and cytogenetic data in these patients are encouraging and suggest that roquinimex may have significant activity when given post ABMT to patients with Ph-positive CML.

The effects of paradoxical sleep deprivation and valine on spatial learning and brain 5-HT metabolism

We have previously reported that rapid eye movement sleep deprivation (REMSD), induced by the flower pot technique, causes a deficit in reference spatial memory and increases rates of serotonin (5-HT) metabolism in the brain. In this study we used increased concentrations of dietary valine to inhibit tryptophan (TRP) transport across the blood-brain barrier in an attempt to modify the REMSD-induced increase of 5-HT metabolism. Rats were fed either a control diet or the same diet supplemented to 2% by weight valine, and were allocated to one of three experimental groups: cage control (CC), stress tank control (TC), or REMSD. Reference and working spatial memory of all rats was tested in a Morris water maze on Days 2, 3, and 4. REMSD produced a significant decrement in reference memory on Days 2 and 4, independent of dietary condition. The valine diet had a detrimental effect on the reference memory of TC rats on Day 2 but not Day 4. Measurements made on Day 4 indicated that the valine diet decreased brain TRP only in the CC rats. In contrast, the valine diet did not prevent increases in brain TRP or 5-HT metabolism in REMSD rats, and increased hypothalamic and brain stem TRP concentrations and the hippocampal 5-HIAA/5-HT ratio in TC rats. These results indicate that dietary valine does not prevent REMSD-induced changes in spatial memory or serotonin metabolism, although it does reduce brain TRP in nonstressed rats.

Sustained effects of repeated restraint stress on muscle and adipocyte metabolism in high-fat-fed rats

Repeated restraint stress 3 h/day for 3 days in rats causes a temporary hypophagia but a sustained weight loss. We investigated whether poststress changes in peripheral tissue metabolism contributed to these responses. One day after the last restraint, insulin sensitivity, measured by oral glucose tolerance test, was improved in restrained rats. Restraint and pair-fed rats weighed less than controls, but body fat content was the same in all groups. Muscle glucose uptake, measured in vitro, was not changed by treatment, whereas in vitro adipocyte glucose uptake was substantially inhibited only in restrained rats. Adipocytes from restrained rats had elevated rates of fatty acid oxidation but not fatty acid esterification, indicating a shift in energy supply from glucose to fatty acids. Five days after the last restraint, the reduced weight of restrained and pair-fed rats resulted from loss of both lean and fat tissue. These results demonstrate that restraint caused sustained, tissue-specific changes in metabolism that may contribute to changes in body composition and body weight of the rats.

Serial echocardiographic and clinical evaluation of valvular regurgitation before, during, and after treatment with fenfluramine or dexfenfluramine and mazindol or phentermine

OBJECTIVE

The prevalence of cardiac valvular regurgitation demonstrated by echocardiography in patients who took appetite-suppressant medication for weight loss has been assessed at 5%-30%. We studied 86 patients who had echocardiograms before treatment with appetite suppressants to determine the incidence of new cases and to evaluate the clinical implication of the echocardiographic findings.

RESEARCH METHODS AND PROCEDURES

We studied 69 men [Mean+/-Standard Deviation (S) age 49+/-8] and 17 women (mean+/-S age 50+/-7) who had 233 echocardiograms before, during, and after a weight-loss program that used predominantly fenfluramine (or dexfenfluramine) with mazindol (or phentermine). Mean drug exposure was 17 months. Blinded echocardiographic readings were performed to identify and grade aortic regurgitation (AR) or mitral regurgitation (MR).

RESULTS

Seven of 86 patients (8%) had pre-existing regurgitation with five (6%) meeting our case definition. Thirteen (16.5%) of initially normal patients developed valvular regurgitation and were new cases. Of the new cases, 12 were grade I/IV AR and one was both grade II/III MR and II/IV AR. All 13 patients were asymptomatic, and only two aortic insufficiency murmurs could be auscultated. There was significantly greater risk for developing valvulopathy for those who took medications longer than 6 months (p = 0.03), and no new cases were observed in patients exposed for less than 8 months. No increased risk associated with age, presence of hypertension, or exposure to fenfluramine-phentermine combination was demonstrated. Although there was a higher incidence of new regurgitation in women (31% vs. 13% for men), this was not statistically significant (p = 0.093).

DISCUSSION

Some patients who had normal echocardiograms at baseline developed cardiac valvular regurgitation after exposure to fenfluramine or dexfenfluramine with mazindol or phentermine. The development of valvulopathy was significantly correlated with duration of exposure. The clinical implications of echocardiographically demonstrated regurgitation are uncertain, since there were only two audible murmurs and no other clinically relevant signs or symptoms among the patients.

Flexible vs. Rigid dieting strategies: relationship with adverse behavioral outcomes

This study was designed to test the hypothesis that different types of dieting strategies are associated with different behavioral outcomes by investigating the relationship of dieting behaviors with overeating, body mass and mood. A sample of 223 adult male and female participants from a large community were studied. Only a small proportion of the sample (18%) was seeking weight loss treatment, though almost half (49.3%) of the subjects were significantly overweight (body mass index, BMI>30). Subjects were administered questionnaires measuring dietary restraint, overeating, depression and anxiety. Measurements of height and weight were also obtained in order to calculate BMI. Canonical correlation was performed to evaluate the relationship of dietary restraint variables with overeating variables, body mass, depression and anxiety. The strongest canonical correlation (r=0.65) was the relationship between flexible dieting and the absence of overeating, lower body mass and lower levels of depression and anxiety. The second strongest canonical correlation (r=0.59) associated calorie counting and conscious dieting with overeating while alone and increased body mass. The third canonical correlation (r=0.57) found a relationship between low dietary restraint and binge eating. The results support the hypothesis that overeating and other adverse behaviors and moods are associated with the presence or absence of certain types of dieting behavior.

Neuroautoantibody immunoreactivity in relation to aging and stress in apolipoprotein E-deficient mice

Progressive disruption of both the neuroendocrine and immune systems has been correlated with age-associated pathogenesis in patients with Alzheimer's disease and in mice lacking apolipoprotein E (ApoE). In this study, we examined neuroautoimmune and neuroendocrine activities in relation to aging and stress in ApoE-deficient mice. An elevated level of autoantibodies against brain antigens was found in sera from ApoE-deficient mice compared to that of wild-type mice as early as 7-8 weeks of age. However, there was no significant difference between the two genotypes at this age in the effect of stress on serum corticosterone or autoantibody titers. Higher titers of autoantibodies were observed in approximately 12-week-old ApoE-deficient mice, especially in those exposed to chronic stress. Based on Western analysis, sera from ApoE-deficient mice showed a strong immunoreactivity with approximately 78 kDa and approximately 40 kDa brain abundant polypeptides, approximately 58 kDa non-brain tissue abundant antigen, and others of approximately, 80-82 kDa in both the brain and non-brain tissues. Immunofluorescence confocal microscopy showed that the major cellular components recognized by the autoimmune sera from ApoE-deficient mice were associated with neuronal cell nuclei and fiber-like structures in different regions of the brain, including the frontal cortex, lateral cortex and hippocampus. These results suggest that neuroautoimmunity associated with the aging process and exposure to chronic stress may be involved in early development of neurodegeneration in mice with ApoE-deficiency.

Prevention of stress-induced weight loss by third ventricle CRF receptor antagonist

We previously reported that rats exposed to repeated restraint (3 h/day for 3 days) experience temporary hypophagia and a sustained reduction in body weight compared with nonrestrained controls. Studies described here determined the involvement of central corticotropin-releasing factor (CRF) receptors in the initiation of this chronic response to acute stress. In experiment 1, Sprague-Dawley rats were fitted with cannulas in the lateral ventricle and infused with 50 micrograms of alphahCRF-(9-41) or saline immediately before restraint on each of the 3 days of restraint. The receptor antagonist inhibited hypophagia and weight loss on day 1 of restraint but not on days 2 and 3. In experiment 2, 10 micrograms of alphahCRF-(9-41) or saline were infused into the third ventricle immediately before each restraint. The receptor antagonist totally blocked stress-induced hypophagia and weight loss. These results demonstrate that CRF receptors located in or near the hypothalamus mediate the acute responses to stress that lead to a permanent change in the hormonal or metabolic processes that determine body weight and body composition.