Cellular ionic effects of insulin in normal human erythrocytes: a nuclear magnetic resonance study

Summary Elevated erythrocyte cytosolic free calcium, and suppressed free magnesium and pH values are associated with the hyperinsulinaemia and insulin resistance of hypertension, obesity, and Type 2 (non-insulin-dependent) diabetes mellitus. To determine the role of insulin in this process, we utilized ¹⁹F- and ³¹P-nuclear magnetic resonance spectroscopy to study the cellular ionic effects of insulin in vitro on normal human erythrocytes. Insulin elevated cytosolic free calcium levels in a dose- and time-dependent manner. The effect began at 10 U/ml, peaked at 200 U/ml, and continued at both the 500 U/ml and 1000 U/ml doses. At 200 U/ml, free calcium levels rose from 24.6±2.5 nmol/l to a peak value at 120 min of 66.4±11 nmol/l (p<0.05 vs basal), levels remaining elevated throughout the incubation (45.7±5.6 nmol/l at 60 min, and 47.9±9.1 nmol/l at 180 min, p<0.05 vs basal, respectively). Similarly, insulin also increased intracellular free magnesium at all time points (basal: 177± 11 mol/l; 60 min: 209±19 mol/l; 120 min: 206±22 mol/l; and 180 min: 202±12 mol/l; p<0.05 vs basal at all times). No insulin-induced changes in pH were observed. We conclude (i) that insulin in physiological concentrations may participate in regulating divalent cations in the mature human erythrocyte, (ii) that insulin per se cannot account for the previously described cellular ionic lesions of hypertension and diabetes, and (iii) that future clinical studies of cell ion metabolism should be conducted in the fasting state, be controlled for ambient circulating insulin levels, or both.     

Pituitary gland growth during normal pregnancy: an in vivo study using magnetic resonance imaging

PURPOSE: Autopsy studies have shown that pregnancy results in physiologic pituitary enlargement. We used magnetic resonance imaging (MRI) to corroborate those findings in vivo. PATIENTS AND METHODS: Based on gestational age, 32 normal primigravid patients were divided into three groups: Group I (n = 10), less than 12 gestational weeks; Group II (n = 11), 13 to 26 gestational weeks; and Group III (n = 11), 27 gestational weeks or more. The pituitary dimensions and volumes in these groups were compared with those in 20 healthy nulliparous women (control group). RESULTS: MRI measurements showed a significant increase in pituitary volume in Groups I, II, and III when compared with the control group (p less than 0.001). Furthermore, there was an increase in pituitary volume between Groups I and II and between Groups II and III, although the former was not statistically significant (p greater than 0.05). At the end of pregnancy, the hypophysis had increased 2.6 mm in vertical, anteroposterior, and transversal dimensions, with an overall increase of 136 percent when compared with that of the control group. CONCLUSION: Baseline measurements of the normal enlargement of the pituitary gland that occurs during pregnancy could prove useful when evaluating pregnant patients with suspected pituitary tumors or lymphocytic hypophysitis.     

Proton nuclear magnetic resonance spectroscopic detection of oligomannosidic n glycans in alpha-mannosidosis: a method of monitoring treatment

In Alpha-mannosidosis (MIM 248500) the patients accumulate mainly unbranched oligosaccharide chains in the lysosomes in all body tissues, including the brain. With ensuing therapeutic modalities in man (BMT and ERT) non-invasive methods of monitoring the effect of treatment are needed. Paramount is the possible effect of the treatment on the brain, since this organ is regarded as difficult to reach because of the blood-brain barrier. We therefore performed proton nuclear magnetic resonance spectroscopy (MRS) of the brain in two untreated patients, and a 16-year-old patient treated with BMT at the age of 10 to assess whether this non-invasive method could be applied in the monitoring of the accumulation of abnormal chemicals in the brain of patients. We found an abnormal peak that was not present in the treated patient. A similar pattern was also found in MRS of urine from patients, reflecting the concentration of oligosaccharides in serum and tissues. We therefore conclude that MRS can be a useful method to monitor the effect of treatment for Alpha-Mannosidosis.     

The13C isotope and nuclear magnetic resonance: unique tools for the study of brain metabolism

As studies of brain metabolism grow in complexity, investigators turn increasingly to nuclear magnetic resonance spectroscopy combined with¹³C isotopic labeling. The unique ability to detect labeling non-destructively in specific carbon positions of individual compounds has opened the way to investigate brain metabolism in systems ranging from cellular preparations to the human brainin vivo. This review is written for investigators whose backgrounds do not include detailed knowledge of principles of nuclear magnetic resonance. Its purpose is to show the wide array of NMR techniques for¹³C detection that are available for application in different systems to study aspects of brain metabolism, such as metabolic compartmentation and measurements of the tricarboxylic acid cycle ratein vivo. Basic NMR concepts are explained, and, because each detection method possesses specific advantages to address the requirements of different experimental goals, basic explanations and examples are given for each technique. The review should provide readers with a basic understanding of the methods of¹³C detection by NMR and assess which of the methods are most applicable to the particular issues they may face in their own research.     

C and Hg nuclear magnetic resonance spectroscopic study of alkenemercurinium ions: Effect of methyl substituents on Hg chemical shifts

The long-lived ethylene, cyclohexene, and norbornenemercurinium ions prepared in superacidic, low-nucleophilic media have been studied by ¹³C and ¹⁹⁹Hg NMR spectroscopy. The norbornenemercurinium ion shows temperature-dependent ¹³C and ¹⁹⁹Hg NMR spectra, consistent with equilibration via rapid hydride and Wagner-Meerwin shifts. The ¹⁹⁹Hg NMR shifts of a series of alkylmercury bromides were also obtained in order to elucidate the effect of methyl substituents on ¹⁹⁹Hg NMR chemical shifts.     

Metabolism of normal skeletal muscle during dynamic exercise to clinical fatigue: in vivo assessment by nuclear magnetic resonance spectroscopy

In vivo nuclear magnetic resonance (NMR) spectroscopy was used to define several intracellular high energy phosphate variables of the gastrocnemius muscle of normal subjects during rest, graded plantar flexion exercise to exhaustion, and recovery. There were nine males and eight females with an average age of 34 +/- 8 years. At rest, pH averaged 7.09 +/- 0.03 and the energy cost index (ECI)--the ratio of inorganic phosphate to phosphocreatine--averaged 0.13 +/- 0.03. At peak exercise, the ECI increased markedly to 2.71 +/- 2.0 (P less than 0.001) and pH fell precipitately to 6.76 +/- 0.17 (P less than 0.001), indicating the high intensity of the exercise. Exercise endurance averaged 12 +/- 5 mins; it was not highly correlated with sex, age (r = 0.35), rest pH (r = 0.26), rest ECI (r = 0.38), peak exercise pH (r = 0.23) or peak exercise ECI (r = 0.38), nor exercise changes in pH (r = 0.17) and ECI (r = 0.28). At 23 mins post exercise all variables were similar to rest. Rest pH was the only variable different between males (7.10 +/- 0.03) and females (7.07 +/- 0.03) (P less than 0.05). Thus, dynamic exercise of large skeletal muscles in normal subjects was characterized by marked temporal changes in high energy phosphate profiles and very low pH at exhaustion. No single metabolic variable correlated highly with exercise endurance, suggesting that the intracellular pathophysiology of exhaustive muscle exercise and clinical fatigue may be multifactorial.     

Angiotensin-(1-7) in normal and preeclamptic pregnancy

Angiotensin-(1–7) (Ang-[1–7]) is a bioactive component of the renin-angiotensin system, which has depressor, vasodilatory, and antihypertensive actions. In normal pregnancy, we questioned whether the known rise in plasma angiotensin II (Ang II) is counterbalanced by an increase in plasma Ang-(1–7) and whether Ang-(1–7) levels are decreased in preeclampsia and may thus be a factor involved in the development of hypertension. Nulliparous preeclamptic subjects, third-trimester normotensive pregnant subjects, and a nonpregnant group were enrolled (n=15/group). Preeclamptic subjects had no previous history of hypertension or renal, connective-tissue, or metabolic disease, but at the time of delivery had significant hypertension (159±3/98±3 mmHg) and ≥3+ proteinuria. Plasma Ang-(1–7) was increased by 51% in normal pregnancy (p<0.05). Plasma Ang I, Ang II, and renin activity were also significantly elevated in normal pregnancy. In preeclamptic subjects, Ang-(1–7) was significantly decreased (p<0.01) compared with normal pregnant subjects. All other components of the renin-angiotensin-aldosterone system, except serum angiotensin-converting enzyme, were reduced in preeclamptic subjects compared with normal pregnant subjects; only plasma Ang II remained elevated in preeclamptic compared with nonpregnant subjects. These studies demonstrate, for the first time, increased plasma Ang-(1–7) in normal pregnant subjects compared with nonpregnant subjects and decreased Ang-(1–7) in preeclamptic subjects compared with normal pregnant subjects. In preeclampsia the decreased plasma Ang-(1–7) in the presence of elevated Ang II is consistent with the development of hypertension.     

Nuclear magnetic resonance as a tool to study brain metabolism

Nuclei which are most appropriate for nuclear magnetic resonance (NMR) spectroscopy in biological systems include, in decreasing sensitivity, 1H, 19F, 23Na, 31P, 13C and 15N. Proton NMR has achieved remarkable prominence in imaging of the brain, and though clinical 1H spectroscopy is still in its infancy, current developments indicate that it will provide interesting information on brain metabolism. The naturally abundant form of phosphorus (31P) has proved particularly useful in studies on energy metabolism in metabolically perturbed states in the brain in vivo and in vitro. Dynamic studies on turnover rates of ATP and creatine phosphate can be performed using saturation transfer techniques. The use of 13C to follow intermediary metabolism shows great potential, even though it is a relatively insensitive nucleus and has only 1% natural abundance. 19F is a highly sensitive and naturally abundant nucleus. When covalently attached to various chelators, it provides a most sensitive method for accurate measurement of many cations of biological importance, by virtue of the chemical shift of the 19F on binding of the cation to the chelator.     

Selective increase of brain lactate synthesis in experimental acute liver failure: results of a [H-C] nuclear magnetic resonance study

Acute liver failure (ALF) results in alterations of energy metabolites and of glucose-derived amino acid neurotransmitters in brain. However, the dynamics of changes in glucose metabolism remain unclear. The present study was undertaken using (1)H and (13)C nuclear magnetic resonance (NMR) spectroscopy to determine the rates of incorporation of glucose into amino acids and lactate via cell-specific pathways in relation to the severity of encephalopathy and brain edema in rats with ALF because of hepatic devascularization. Early (precoma) stages of encephalopathy were accompanied by significant 2- to 4.5-fold (P <.001) increases of total brain glutamine and lactate concentrations. More severe (coma) stages of encephalopathy and brain edema led to a further significant increase in brain lactate but no such increase in glutamine. Furthermore, (13)C isotopomer analysis showed a selective increase of de novo synthesis of lactate from [1-(13)C]glucose resulting in 2.5-fold increased fractional (13)C enrichments in lactate at coma stages. [2-(13)C]glutamine, synthesized through the astrocytic enzyme pyruvate carboxylase, increased 10-fold at precoma stages but showed no further increase at coma stages of encephalopathy. (13)C-label incorporation into [4-(13)C]glutamate, synthesized mainly through neuronal pyruvate dehydrogenase, was selectively reduced at coma stages, whereas brain GABA synthesis was unchanged at all time points. In conclusion, increased brain lactate synthesis and impaired glucose oxidative pathways rather than intracellular glutamine accumulation are the major cause of brain edema in ALF. Future NMR spectroscopic studies using stable isotopes and real-time measurements of metabolic rates could be valuable in the elucidation of the cerebral metabolic consequences of ALF in humans.     

分辨魔角旋转核磁共振波谱在大鼠慢性胰腺炎分级中的应用

目的 观察大鼠实验性慢性胰腺炎(CP)进展过程中胰腺组织代谢产物变化特征,探讨其在CP分级中的价值.方法 Wistar大鼠36只,经尾静脉注入二丁基二氯化物(dibutyltin dichloride,DBTC)溶液8 mg/kg体重制备CP模型.注射后即刻(对照组)及7、14、21、28、35 d分批取大鼠胰腺组织,小部分行病理检查,大部分液氮冷冻后置-80℃保存.应用高分辨魔角旋转核磁共振波谱(HRMAS NMR)法检测胰腺组织的代谢产物.以非正常结构、管状复合物、腺体萎缩、纤维化、水肿及炎细胞浸润程度等作为基本指标进行病理分级.结果 胰腺组织的病理损伤严重程度随造模时间的推移逐渐增加,造模后7、14 d大鼠胰腺改变为轻度CP,造模后21、28、35 d大鼠胰腺病理改变为重度CP.重度CP大鼠胰腺组织中甜菜碱(Bet)、胆碱(Cho)化合物含量较轻度CP组及对照组大鼠明显增多,而天冬氨酸盐(Asp)、乳酸(Lac)、脂肪酸(FA)、异亮氨酸/亮氨酸/缬氨酸(Ile/Leu/Val)的含量明显减少.轻度CP与对照组大鼠胰腺组织的代谢产物含量无明显差异.结论 应用HR-MAS NMR分析胰腺组织代谢产物有助于区分重度CP与轻度CP.     

31P nuclear magnetic relaxation studies of phosphocreatine in intact muscle: determination of intracellular free magnesium.

31P nuclear magnetic relaxation rates for phosphocreatine in intact frog gastrocnemius were compared with those observed in model solutions at 4 degrees, a temperature at which muscle maintains its physiological state for at least 5 hr. Both nuclear Overhauser effect and spin-lattice relaxation rate (1/T1) experiments indicate that dipole-dipole interactions from the dominant relaxation path for 31P in intact muscle and model solutions, independent of phosphocreatine and Mg concentrations. Spin-spin relaxation rates (1/T2) measured by modified Carr-Purcell-Melboom-Gill spin-echo experiments suggest the importance of scalar coupling modulated by chemical exchange with free Mg. From these results, we estimate the free intracellular Mg in intact muscle as 4.4 mM and demonstrate that 31P T2 experiments can be used as a tool for studying free Mg levels with minimum disturbance of the intact cell.     

The effect of low-molecular weight dextran on erythrocyte aggregation in normal and preeclamptic pregnancy

Erythrocyte aggregation was determined by a novel method enabling the quantification of the aggregation process in whole blood. Blood samples of 47 healthy pregnant women and 39 preeclamptic patients were examined. Subjects within each group were matched for the gestational age. It was found that RBC aggregation increases with the gestational age in healthy pregnancy and further increases in preeclampsia. Addition of low-molecular weight dextran (MW = 9300) to blood samples of both healthy pregnant women and preeclamptic patients reduces RBC aggregation in a concentration-dependent manner. The obtained results indicate alterations in plasma composition as the primary factor for the increased RBC aggregation in both normal and pathological pregnancy. It is suggested that adsorption of low-molecular weight dextran on the RBC membrane reduces the surface concentration of plasma bridging molecules thereby reducing RBC aggregation toward normal.     

Functional magnetic resonance imaging study of human olfaction and normal aging

BACKGROUND: The function of human olfaction declines with advancing age. An important question centers on whether functional alterations to olfactory brain structures accompany age-related behavioral changes. In the present study, we tested the hypothesis that aged adults have intact though reduced activity in the central olfactory system using functional magnetic resonance imaging (fMRI). METHODS: University of Pennsylvania Smell Identification Test (UPSIT) was used to test the smell function of 11 young (23.9 +/- 1.6 years) and 8 aged (66.4 +/- 4.4 years) healthy participants. Then, the participants received fMRI at 3.0 T with lavender and spearmint as stimulants. After fMRI, the participants provided ratings for the odorants' intensity and pleasantness. RESULTS: The average UPSIT score of the aged adults was 34.1 +/- 1.5, which was significantly lower than that of the young adults (37.3 +/- 1.1) (p =.0004). Both age groups showed significant activation in major olfactory brain structures, including the primary olfactory cortex, entorhinal cortex, hippocampus and parahippocampal cortex, thalamus, hypothalamus, orbitofrontal cortex, and insular cortex and its extension into the inferior lateral frontal region. The aged adults showed less brain activity in olfactory structures (p =.022), consistent with lower ratings of odor intensity and UPSIT scores. Activation intensity in bilateral primary olfactory cortex areas and right insular cortex was also comparatively weaker (p <.019). CONCLUSION: Results demonstrate that significant activation in aged adults can be observed in all the olfactory brain structures that are activated in young adults, but with lower activation volume and intensity. This finding provides a necessary baseline for further investigations in olfaction and aging.     

Processing of procorticotropin-releasing hormone (pro-CRH): molecular forms of CRH in normal and preeclamptic pregnancy

This study examined the different molecular forms of CRH in normal and preeclampsia maternal plasma and protease-blocked placental extracts using antibodies to different regions of the CRH precursor, pro-CRH. In the absence of protease inhibitors, chromatographed normal placental extracts contained four peaks of immunoreactivity corresponding to unprocessed approximately 19-kDa pro-CRH, its approximately 8-kDa intermediate metabolite, pro-CRH125-194, its approximately 2.8-kDa midportion fragment, pro-CRH125-151, and 4.75-kDa CRH1-41. However, if protease inhibitors were included in the extraction medium, only pro-CRH and pro-CRH125-194 were found. Pro-CRH processing was more extensive in protease-blocked preeclampsia placentas than in those from normal pregnancy, with three peaks corresponding to pro-CRH, proCRH125-194, and mature CRH1-41 peptide found. Using quantitative competitive PCR, the messenger ribonucleic acid levels of CRH precursor in preeclampsia placentas were 1.7-fold higher than those in normal placentas (37.83 +/- 3.48 vs. 21.83 +/- 2.59 attomoles/microg total ribonucleic acid, respectively; P < 0.005). Preeclampsia placentas contained significantly more CRH1-41 cross-reactivity (4.72 +/- 1.22 pmol/g) than normal term placentas (1.52 +/- 0.39 pmol/g; P < 0.048) extracted in medium containing protease inhibitors. The content of pro-CRH(125+/-151)-reactive species in these extracts followed the same pattern, with more immunoreactivity detected in preeclampsia placentas (4.23 +/- 1.39 pmol/g) than in those from normal term pregnancies (1.44 +/- 0.32 pmol/g; P < 0.01). Sequential plasma samples from 10 women with normal pregnancy and 5 women with preeclampsia were assayed for pro-CRH(125-151)- and CRH(1-41)-immunoreactive species In normal pregnancy, maternal plasma CRH(1-41) immunoreactivity rose with increasing gestational age, reaching 460 +/- 48 pmol/L at term. In women with preeclampsia, CRH(1-41) levels at each gestational age point were higher than those at the equivalent stage of normal pregnancy. In contrast, the levels of pro-CRH(125-151)-immunoreactive species remained barely detectable throughout normal and preeclamptic pregnancy. Both pro-CRH and CRH(1-41), but not pro-CRH(125-151), were shown to bind to the plasma CRH-binding protein. Our findings highlight the importance of protection of placental tissue from degrading enzymes during extraction and show that most of the CRH in the human placenta exists as unprocessed pro-CRH, with very little in the form of CRH(1-41) except in preeclampsia. Our studies using maternal plasma indicate that CRH(1-41) is the only one of the pro-CRH fragments studied to be maintained in significant amounts in the maternal circulation and also the only fragment studied for which a specific plasma binding protein exists.