Interactions of γ-immunoglobulins with lipid mono- or bilayers and liposomes. Existence of two conformations of γ-immunoglobulins of different hydrophobicities

Interactions between rabbit-γ-immunoglobulins and model membranes (lipid monalayers, planar lipid bilayers, liposomes) have been investigated. No significant interaction was observed with immunoglobulins. However, immunoglobulins dialysed first vs aqueous buffer having pH 2 or 3 and then dialysed against pH 7 buffer presumably adopt a new conformation which allows their bindings to model membranes. This binding is hydrophobic and the immunoglobulin region interacting with the lipid acyl chains is probably located in the heavy chain, as suggested by labelling in this region by a photosensitive probe previously incorporated into the lipid hydrophobic core. Cleavage at the hinge region by papain or pepsin, or heating above 38°C, induces the loss of the hydrophobic conformation responsible for hydrophobic bindings. The binding capacity of immunoglobulins heated above 38°C is restored after momentary dialysis at pH 2. The possible existence of two Ig isomers is discussed in relation to the mechanism of γ-immunoglobulin passage through the endoplasmic membrane and fixation into the plasma membrane.     

AMPK as a metabolic switch in rat muscle,liver and adipose tissue after exercise

An increasing body of evidence has revealed that activation of adenosine monophosphate (AMP)‐activated protein kinase (AMPK)‐activated protein kinase increases fatty acid oxidation by lowering the concentration of malonyl coenzyme A (CoA), an inhibitor of carnitine palmitoyl transferase 1. Studies carried out primarily in skeletal muscle suggest that AMPK modulates the concentration of malonyl CoA by concurrently phosphorylating and inhibiting acetyl CoA carboxylase (ACC), the rate limiting enzyme in malonyl CoA synthesis, and phosphorylating and activating malonyl CoA decarboxylase (MCD), an enzyme involved in its degradation. We have recently observed that AMPK and MCD activities are increased and ACC activity diminished in skeletal muscle, liver and, surprisingly, in adipose tissue 30 min following exercise (treadmill run) in normal rats. In liver and adipose tissue these changes were associated with a decrease in the activity of glycerol‐3‐phosphate acyltransferase (GPAT), which catalyses the first committed reaction in glycerolipid synthesis and, which like ACC, is phosphorylated and inhibited by AMPK. Similar changes in ACC, MCD and GPAT were observed following the administration of 5‐aminoimidazole 4‐carboxamide‐riboside (AICAR), further indicating that the exercise‐induced alterations in these enzymes were AMPK‐mediated. Conclusions: (1) AMPK plays a major role in regulating lipid metabolism in multiple tissues following exercise. (2) The net effect of its activation is to increase fatty acid oxidation and diminish glycerolipid synthesis. (3) The relevance of these findings to the regulation of muscle glycogen repletion in the post‐exercise state and to the demonstrated ability of AMPK activation to decrease adiposity and increase insulin sensitivity in rodents remains to be determined.     

Rapid molecular cytogenetic analysis of X-chromosomal microdeletions: Fluorescence in situ hybridization (FISH) for complex glycerol kinase deficiency

Diagnosis of X-chromosomal microdeletions has relied upon the traditional methods of Southern blotting and DNA amplification, with carrier identification requiring timeconsuming and unreliable dosage calculations. In this report, we describe rapid molecular cytogenetic identification of deleted DNA in affected males with the Xp21 contiguous gene syndrome (complex glycerol kinase deficiency, CGKD) and female carriers for this disorder. CGKD deletions involve the genes for glycerol kinase, Duchenne muscular dystrophy, and/or adrenal hypoplasia congenita. We report an improved method for diagnosis of deletions in individuals with CGKD and for identification of female carriers within their families, using fluorescence in situ hybridization (FISH) with a cosmid marker (cosmid 35) within the glycerol kinase gene. When used in combination with an Xq control probe, affected males demonstrate a single signal from the control probe, while female carriers demonstrate a normal chromosome with two signals, as well as a deleted chromosome with a single signal from the control probe. FISH analysis for CGKD provides the advantages of speed and accuracy for evaluation of submicroscopic X-chromosomal deletions, particularly in identification of female carriers. In addition to improving carrier evaluation, FISH will make prenatal diagnosis of CGKD more readily available. © 1995 Wiley-Liss, Inc.     

缺碘和氟中毒对大鼠甲状腺的协同作用

实验用Wistar大鼠212只,按饮食中碘和氟含量不同随机分为五组,实验期为7个月。结果显示:摄碘正常的大鼠长期饮用30ppm氟水后引起甲状腺功能和形态的严重损害,而饮用10ppm氟水的大鼠仅见甲状腺滤泡上皮超微结构的轻度异常变化;单纯性缺碘大鼠甲状腺肿大并伴有代偿性功能变化,缺碘并饮用10ppm氟水的大鼠在其甲状腺肿大的同时伴有明显的形态结构损伤及甲状腺代偿功能抑制,甚至功能低下。     

α-Adrenoceptor stimulation,but not muscarinic stimulation,increases cyclic AMP accumulation in brain slices due to protein kinase C mediated enhancement of adenosine receptor effects

In the present study, using rat hippocampal slices, we have further examined the stimulatory effect of α₁ adrenoceptors on the accumulation of cyclic AMP, which is known to depend on calcium and adenosine. The addition of noradrenaline (NA) stimulated the accumulation of [³H]inositol phosphates in [³H]inositol-treated slices. This effect was shared by carbachol (10–100 μmol l^-1) but not by the adenosine receptor agonist 2-chloroadenosine (100 μmol l^-1). The stimulatory effect of the α-agonists (phenylephrine or NA + propranolol) on cyclic AMP was shared by a diacylglycerol derivative, sn-1-oleyl-2-acetyl glycerol (OAG), and by the tumour-promoting phorbol esters phorboldibutyrate (PDiBu) and tetradecanoyl phorbol acetate (TPA). PDiBu caused a translocation of protein kinase C from soluble to particulate fractions. The effects of PDiBu and α-adrenoceptor stimulation on cyclic AMP were not additive. Surprisingly, carbachol (1–1000 μmol l^-1) did not stimulate cyclic AMP accumulation in rat hippocampal slices either in the presence or in the absence of an adenosine receptor agonist. The results are compatible with the opinion that a-adrenoceptor stimulating drugs enhance the formation of inositol phosphates and diacylglycerol, which synergistically activate protein kinase C, which in turn augments the stimulation of cyclic AMP formation. Thus, a neurotransmitter whose principal biological effect is to stimulate inositol phosphate formation can influence cyclic AMP formation by virtue of an interaction with the actions of the ubiquitous neuromodulator adenosine. The fact that the effect of the α-receptor stimulation was not mimicked by a muscarinic agonist could indicate that other factors besides activation of inositol phospholipid hydrolys are important for this receptor–receptor interaction.     

Penetration of teniposide (VM-26) into human intracerebral tumors

Thirty-four consenting patients received VM-26 50–100 mg/m² I.V. before surgical resection of intracerebral tumor, and drug was measured using a high pressure liquid chromatographic technique. Sufficient tumor for analysis was obtained from 29 patients. Brain metastases (13 patients) had higher concentrations of V M-26 than did gliomas (13 patients). Concentrations were comparable in brain metastases and meningiomas (3 patients). Prolonged (24 h) infusion of V M-26 did not appear to result in higher tumor drug concentrations in 5 patients than did rapid (1 h) infusion in 24 patients. Pretreatment with Amphotericin-B 10 mg/m² 12 h and 1 h before VM-26 did not appear to have any effect on VM-26 uptake into 4 intracerebral tumors, although data were limited, and VM-26 concentrations were very high in 1 metastasis. Pretreatment with oral glycerol 500 mg/kg 18 h, 12 h, 6 h, and immediately before I.V. VM-26 may have resulted in increased penetration of VM-26 into 9 tumors, although confirmation is required. Amphotericin-B, glycerol, and operative conditions did not appear to alter VM-26 plasma pharmacokinetics.VM-26 4-demethylepipodophyllotoxin 9-(4-6-O-thenylidene-B-D-glucopyranoside) - VP-16 4-demethylepipodophyllotoxin 9-(4-6-O-ethylidene-B-D-glucopyranoside) Presented in Part at the 74th Annual Meeting of the American Association for Cancer Research, San Diego, California, May 25–28, 183(1).     

Separation and determination of the two components of glycerol formal by high-performance liquid chromatography

The two isomeric components of glycerol formal, 1,3-dioxan-5-ol and 1,3-dioxolane-4-methanol, are marginally separated (R_s = 1.0) by polar-bonded-phase high-performance liquid chromatography (HPLC) on a cyanopropyl column with acetone—hexane as the eluent. Esterification of these components with 3,5-dinitrobenzoyl chloride produces derivatives which are, however, completely resolved (R_s > 2) by normal-phase HPLC on silica; derivatization has the added advantage of introducing an ultraviolet-absorbing chromophore into each component. Preparative scale chromatography is used to isolate each of the derivatives, which are characterized by their UV, NMR and mass spectral properties. These esters are used as reference standards for an analytical method based on derivatization and normal-phase chromatography. In this way a sample of glycerol formal is calibrated for use as a standard in the direct determination of the two components by polar-bonded-phase HPLC.     

131I的电离辐射对甲状腺功能早期影响的研究

目的探讨131I的电离辐射与甲状腺组织功能早期改变的关系,如血清TNF、IL-1β、IL-6、IL-8等细胞因子水平变化以及甲状腺组织本身的病理改变等.方法选用兔作动物实验(15只),分别在0、6、24、48、72h及1周时抽血做IL-1β、IL-8测定,并每次随机处死1～2只兔以做病理切片观察,1周时同时做甲功测定(TT3、TT4、FT3、FT4)并与0h比较.17例病情中及重度甲亢患者用治疗剂量的131I治疗(每人次用量146.2～469.9MBq,平均267.5MBq),治疗前和治疗后4～7天抽血做TNF、IL-1β、IL-6和IL-8测定.结果①使用131I6h后即可见兔血清IL-1β增高(P<0.05),IL-8于48h达高峰(P<0.01),两种细胞因子于1周时皆降低到0h水平(P>0.05).1周内兔血清甲状腺激素水平无明显变化(P>0.05).②甲亢患者131I治疗前后血清细胞因子的变化与兔有所不同,TNF无明显变化(P>0.05),IL-6和IL-8升高(P<0.05),而IL-1β反而降低,且差异显著(P<0.05).③摄取131I后兔甲状腺组织在不同时间内呈现不同的病理改变.结论①甲状腺组织摄取一定剂量的131I在不同时间内呈现不同的病理改变,但短期内甲状腺激素水平无明显变化.②某些细胞因子IL-1β、IL-6、IL-8等似可用作观察甲状腺组织对131I辐射效应反应的指标,但其临床价值有待于进一步探讨.     

玉米浆用量、渗透压和耗糖速率对甘油发酵的影响

Candida krusei发酵生产甘油过程中,菌体生长由玉米浆限制,菌体对玉米浆的得率为1．63g/g,培养其中玉米浆浓度相同时,增加渗透压或通过流加补料限制生长阶段的菌体生长,可使甘油生产阶段的比耗糖速率减慢,比耗糖速率保持在不很高的水平,可以因消耗的葡萄糖用于生长,维持,甘油和副产物形成所占比例的变化而提高甘油得率。     

Beta-blockade and lipolysis during endurance exercise

Summary Inhibition of adipose tissue lipolysis may be involved in the impairment of endurance capacity after administration of a -adrenoceptor blocker. During endurance exercise, no significant decrease in plasma glycerol and free fatty acid (NEFA) concentrations after -adrenoceptor blockade is found. However, the levels during recovery from exhaustion are lower after -adrenoceptor blockade. This study was designed to investigate whether the lower levels after exercise are due to -adrenoceptor blockade or to the shorter time to exhaustion after administration of a -adrenoceptor blocker.In a single-blind study, 11 well-trained male subjects (age 23 (0.9) y) performed a cycle ergometer test at 70% W_max until exhaustion 2 h after intake of 80 mg propranolol. One week later, the test was repeated after intake of placebo and was stopped at the time of exhaustion in the previous test. Average exercise time was 24 min. During exercise plasma glucose was lower, whereas plasma lactate and the respiratory exchange ratio were significantly higher when the subjects were on propranolol. Glycerol and NEFA concentrations during exercise were not significantly different between the two conditions. Despite an identical exercise time, glycerol and NEFA concentrations during recovery were significantly lower after propranol treatment.In conclusion, lipolysis is inhibited during exercise after propranolol, probably causing a shift from fat to carbohydrate combustion.