Generating CTLs against the subdominant EBV LMP antigens by transient expression of an A20 inhibitor with EBV LMP proteins in human DCs

Epstein-Barr virus (EBV) infection leads to Hodgkin’s disease (HD) in some immunocompetent hosts. The malignant Reed-Sternberg cells of HD only express a limited array of subdominant EBV antigens to evade preexisting immune responses to EBV. The EBV-encoded latent membrane proteins (LMP1 and LMP2), which are expressed by HD and various EBV-associated malignancies, have been proposed as a potential target for CTL-based therapy. However, the precursor frequency for LMP-specific CTL is generally low in healthy EBV-infected hosts, and immunotherapy based on these antigens is often compromised by the poor immunogenicity and the oncogenic potential. In the present study, we report that transitively expressing an inhibitor of A20, a key negative regulator of inflammatory signaling pathways, together with the LMP antigens (truncated LMP1 and full-length LMP2) greatly enhances maturation and cytokine production of human (h) monocyte-derived dendritic cells (DCs). As a consequence, LMP1/2-expressed, A20-silenced hDCs have an enhanced potency to prime LMP-specific T cell response. When the in vitro primed T cells are adoptively transferred into tumor-xenografted, severe combined immunodeficient (SCID) mice, some of the xenografted tumors approach complete regression. Thus, the study may provide an available resource of LMP-specific T cells for T cell immunotherapy.

Short term effects of energy restriction and dietary fat sub-type on weight loss and disease risk factors

BACKGROUND AND AIMS

Decreasing energy intake relative to energy expenditure is the indisputable tenet of weight loss. In addition to caloric restriction modification of the type of dietary fat may provide further benefits. The aim of the present study was to examine the effect of energy restriction alone and with dietary fat modification on weight loss and adiposity, as well as on risk factors for obesity related disease.

METHODS AND RESULTS

One-hundred and fifty overweight men and women were randomized into a 3month controlled trial with four low fat (30% energy) dietary arms: (1) isocaloric (LF); (2) isocaloric with 10% polyunsaturated fatty acids (LF-PUFA); (3) low calorie (LF-LC) (-2MJ); (4) low calorie with 10% PUFA (LF-PUFA-LC). Primary outcomes were changes in body weight and body fat and secondary outcomes were changes in fasting levels of leptin, insulin, glucose, lipids and erythrocyte fatty acids. Changes in dietary intake were assessed using 3day food records. One-hundred and twenty-two participants entered the study and 95 completed the study. All groups lost weight and body fat (P<0.0001 time effect for both), but the LC groups lost more weight (P=0.026 for diet effect). All groups reduced total cholesterol levels (P<0.0001 time effect and P=0.017 intervention effect), but the LC and PUFA groups were better at reducing triacylglycerol levels (P=0.056 diet effect). HDL increased with LF-LC and LF-PUFA but not with LF-PUFA-LC (0.042 diet effect). The LF and LF-LC groups reported greater dietary fat reductions than the two PUFA groups (P=0.043).

CONCLUSION

Energy restriction has the most potent effect on weight loss and lipids, but fat modification is also beneficial when energy restriction is more modest.

The effects of antipsychotic drugs administration on 5-HT1A receptor expression in the limbic system of the rat brain

Increasing evidence suggests that 5-HT1A receptors are involved in the pathophysiology and treatment of schizophrenia. This paper investigated 5-HT1A receptor mRNA expression and binding density in female rats treated with aripiprazole (2.25 mg/kg/day), olanzapine (1.5 mg/kg/day), haloperidol (0.3 mg/kg/day) or vehicle (control) orally three times/day for 1 or 12 weeks. Animals were sacrificed 48 h after the last administration. Aripiprazole significantly increased 5-HT1A receptor binding density by 33% in the CA1 region of the hippocampus and by 21% in the medial posterodorsal nuclei of posterior amygdala (MeP) compared to the control group after 1 week of treatment. Olanzapine significantly decreased 5-HT1A receptor binding density by 17-22% in Layers I-IV of the cingulate cortex after 1 week of treatment. Neither of these antipsychotic drugs affected 5-HT1A receptor binding density after 12 weeks drug treatment. As expected, haloperidol treatment did not have any significant effect on 5-HT1A binding density after 1 or 12 weeks of treatment. 5-HT1A receptor mRNA expression was not altered by antipsychotic treatment in any brain region. The results indicate that aripiprazole and olanzapine have differential effects on 5-HT1A receptor expression, which may contribute to their distinct profiles in improving negative symptoms and cognitive deficits in schizophrenia. Aripiprazole and olanzapine may produce adaptation and desensitization of 5-HT1A receptor expression after long term treatment.

Comparative study of gene expression during tooth eruption and orthodontic tooth movement in mice

OBJECTIVE

The aim of this study was to understand tooth eruption by comparing the gene expression during tooth eruption and orthodontic tooth movement (OTM).

MATERIALS AND METHODS

Orthodontic force was applied on maxillary molars for 2, 4, 7 and 14 days to study tooth movement. Mice at PN 0, 7, 10, 15 and 21 were fixed to observe tooth eruption. Comparative study of two procedures was assessed by haematoxylin and eosin, tartrate-resistant acid phosphatase staining and in situ hybridization for matrix metalloproteinase (Mmp)2, 13, bone sialoprotein (Bsp) and osteocalcin (Ocn).

RESULTS

Tartrate-resistant acid phosphatase activity and expression of Mmp2, 13 were obviously detectable in the compression region during OTM. They were also identified in the occlusal and apical region of alveolar bone during tooth eruption. Strong expression of Bsp and Ocn was detectable at the tension side during OTM. These genes were also expressed in the inner lateral region of alveolar bone adjacent to the tooth, but absent in the inner surface of the occlusal and root apical regions during tooth eruption.

CONCLUSION

The process of alveolar bone metabolism during developmental eruption and OTM shares the same mechanism. Internal force, as the orthodontic force for OTM, may be initiating factor for tooth eruption.

Association of vitamin D receptor gene polymorphisms in Chinese patients with generalized aggressive periodontitis

BACKGROUND AND OBJECTIVE

The clinical features suggest that genetic factors may have a strong influence on susceptibility to aggressive periodontitis. The aim of this study was to investigate the association of vitamin D receptor gene polymorphisms with generalized aggressive periodontitis in Chinese patients.

MATERIAL AND METHODS

A restriction fragment length polymorphism (RFLP) for 10,438,141 C to T (rs1544410, BsmI), 10,382,063 A to G (rs731236, TaqI), 10,382,143 C to A (rs7975232, ApaI) and 10,416,201 A to G (rs2228570, FokI) of vitamin D receptor gene was analysed by polymerase chain reaction, followed by digestion with restriction enzymes and gel electrophoresis. The genotypes of 51 generalized aggressive periodontitis patients and 53 periodontally healthy control subjects were analysed. The genotypic and allelic frequencies of each polymorphism site for the patients and control subjects were compared.

RESULTS

The distribution of vitamin D receptor FokI genotypes and alleles between the two groups was significantly different (p = 0.043 and p = 0.012, respectively). The F allele seemed to increase the susceptibility of aggressive periodontitis (odds ratio = 2.02, 95% confidence interval = 1.16-3.50) in Chinese patients. There was no significant difference in the genotype distribution or the allele frequencies of vitamin D receptor BsmI, ApaI and TaqI between two groups.

CONCLUSION

The study indicates that FokI polymorphism of vitamin D receptor gene might be associated with generalized aggressive periodontitis in Chinese patients. In addition, the carriage of F allele increases the risk of developing generalized aggressive periodontitis.

New self-limiting assembly model for Si quantum rings on Si(100)

We propose a new self-limiting assembly model for Si quantum rings on Si(100) where the ring's formation and evolution are driven by a growth-etching competition mechanism. The as-grown ring structure in a plasma enhanced chemical vapor deposition system has excellent rotational symmetry and superior morphology with a typical diameter, edge width, and height of 150-300, 10, and 5 nm, respectively. Based on this model, the size and morphology can be controlled well by simply tuning the timing procedure. We suggest that this growth model is not limited to certain material system, but provides a general scheme to control and tailor the self-assembly nanostructures into the desired size, shape, and complexity.

Decreased [(3)H]spiperone binding in the anterior cingulate cortex of schizophrenia patients: an autoradiographic study

Abnormalities in the anterior cingulate cortex have been reported in patients with schizophrenia, and have been implicated in the pathophysiology of this disorder. In the present study, we have examined antipsychotic-sensitive binding sites in the left anterior cingulate cortex of schizophrenia patients and controls. Using quantitative autoradiography and [(3)H]spiperone as a ligand, both saturation and competition experiments were performed in post-mortem brain tissue obtained from six schizophrenia and six control cases. Saturation experiments revealed that the maximum number of [(3)H]spiperone binding sites was significantly reduced by 31% in the schizophrenia group as compared to the control group (65.3+/-5.6 fmol/mg tissue versus 94.2+/-7.3 fmol/mg tissue). Increased dissociation constant was also observed in the schizophrenia group (2.2+/-0.4 nM versus 1.3+/-0.2 nM), but was not statistically significant (P=0.07). Competition experiments were performed in order to examine the pharmacological profile of [(3)H]spiperone binding, and revealed that: (i) displacement of [(3)H]spiperone binding by clozapine and mianserin was significantly reduced in the schizophrenia group as compared to the control group (-26% and -16% respectively); (ii) the order of displacement potency of the drugs tested was: haloperidol>mianserin>butaclamol approximately risperidone>clozapine>2-amino-6,7-dihydroxy-1,2,3,4-tetrahydronaphthalene. Our results suggest a reduction of antipsychotic-sensitive binding sites in the anterior cingulate cortex of patients with schizophrenia. Such abnormality could lead to an imbalance in neurotransmitter regulation in the anterior cingulate cortex which may contribute to the emergence of some symptoms of schizophrenia.

[Separation and determination of scandium, tin and aluminum by reversed-phase ion pair high performance liquid chromatography]

The reversed-phase ion pair high performance liquid chromatographic determination of scandium, tin and aluminum with diammonium stilbene-4,4'-bis(1-azo)-3,4-dihydroxybenzene-2,2'-disulfate as precolumn chelating reagent on Spherex C18 column has been investigated with the detection wavelength of 500 nm. Various parameters such as pH, reagent concentration, ion pair reagents, interference of foreign ions have been studied. The mobile phase was methanol-water (40:60, V/V) containing 20 mmol/L acetate buffer of pH 6.0 and 10 mmol/L sodium dodecyl sulfonate. Three complexes could be completely separated within 17 min. The method has been successfully used for the determination of the three metals in mineral samples, with recoveries of 98%, 101%, 103% respectively, and RSD was less than 3.6%. Beer's Law was obeyed over the concentration range 0.01 mg/L-3.80 mg/L, 0.06 mg/L-4.50 mg/L and 0.04 mg/L-3.40 mg/L respectively. The detection limits were 0.9 microgram/L, 1.0 microgram/L and 1.2 micrograms/L for scandium, tin and aluminum when the ratio of signal to noise was 3. Most of other metals did not interfere with the determination. The present method is sensitive and selective.

Gene structure, chromosomal localization and analysis of 3-ketosteroid reductase activity of the human 3(alpha-->beta)-hydroxysteroid epimerase

Following our previous characterization of the first human 3(alpha-->beta)hydroxysteroid epimerase (hHSE), we determined the genomic structure and chromosomal localization of the hHSE gene using fluorescent in situ hybridization (FISH) in this study. The gene spans 23 kb and contains five exons and four introns. FISH mapping assigned this gene to chromosome band 12q13. Primer extension analysis allowed the identification of a single transcription start site at 179 bp upstream from the ATG start codon. The 5'-flanking sequence lacks a typical TATA box in the proximal region of the transcription start site. However, analysis of the 2 kb promoter region revealed the presence of multiple potential transcription factor binding sites. Furthermore, we studied the 3-ketosteroid reductase activity demonstrated by hHSE in intact cells stably expressing the enzyme. It has been known that, in vitro, 3beta-hydroxysteroid dehydrogenase (3beta-HSD) shows both oxidative and reductive activity. Our results showed that hHSE catalyzes the reduction of 3-ketosteroids to form 3beta-hydroxysteroids while 3beta-HSD cannot catalyze this reaction in intact cells. However, hHSE showed 3-keto reductase activity in both microsomal fractions and intact cells. Since intact cells constitute a system which closely reflects in vivo intracellular conditions, we propose that hHSE might contribute to the cellular 3-ketosteroid reductase activity in the peripheral tissues.

Characterization of the oxidative 3alpha-hydroxysteroid dehydrogenase activity of human recombinant 11-cis-retinol dehydrogenase

11-cis-Retinol dehydrogenase catalyzes the oxidation of cis-retinols, a rate-limiting step in the biosynthesis of 9-cis-retinoic acid. It is also active toward 3alpha-hydroxysteroids, and thus might be involved in steroid metabolism. To better understand the role of this enzyme, we produced stable transfectants expressing 11-cis-retinol dehydrogenase in human embryonic kidney 293 cells. In vitro enzymatic assays have demonstrated that, with an appropriate exogenous cofactor, the enzyme catalyzes the interconversion of 5alpha-androstane-3alpha,17beta-diol and dihydrotestosterone and that of androsterone and androstanedione. However, using intact transfected cells, we found that the enzyme catalyzes reactions only in the oxidative direction. Thus, it is possible that 5alpha-androstane-3alpha,17beta-diol (an inactive androgen) can be converted into dihydrotestosterone, the most potent androgen, by the action of 11-cis-retinol dehydrogenase. This reaction could constitute a non-classical pathway of production of active androgens in the peripheral tissues. We also showed that all-trans-, 9-cis- and 13-cis-retinol inhibit the oxidative 3alpha-hydroxysteroid steroid activity of 11-cis-retinol dehydrogenase with similar K(i) values. Since all-trans-retinol is a precursor of cis-retinols, its inhibitory effect on the activity suggests that it could play an important role in modulating the formation of 9-cis-retinoic acid. In addition, we examined the effect of several known enzyme modulators, namely carbenoxolone, phenylarsine oxide and phosphatidylcholine, on 11-cis-retinol dehydrogenase activity. Taken together, our results suggest that, in humans, this enzyme might play a role in the biosynthesis of both 9-cis-retinoic acid and dihydrotestosterone.

Modulation of the androgenic response by recombinant human 11-cis retinol dehydrogenase

The 11-cis retinol dehydrogenase (11-cis-RoDH) enzyme catalyzes the oxidation of cis-retinols to their respective retinals, a rate limiting step in the formation of retinoic acids. Earlier, we have shown that the enzyme also exhibits an oxidative 3alpha-hydroxysteroid dehydrogenase (3alpha-HSD) activity that can convert 5alpha-androstane-3alpha,17beta-diol (3alpha-diol) into dihydrotestosterone (DHT), the most potent natural androgen. 11-cis-RoDH could thus control the formation of two active hormones, namely 9-cis retinoic acid and DHT. Therefore, depending upon the substrate availability in the various tissues, this enzyme could provide different metabolites for specific cell functions. To further investigate the role of 11-cis-RoDH in the formation of DHT from 3alpha-diol, we stably expressed the enzyme in the human embryonic kidney cell line 293 (HEK-293). The transformation of 3alpha-diol by these cells was evaluated by assays using both microsomal fractions and intact cultured cells stably expressing 11-cis-RoDH. The results show that in the intact cells 11-cis-RoDH only catalyzes the oxidation of 3alpha-diol into DHT whereas the microsomal fraction catalyzes both the oxidation and the reduction reactions depending upon whether NAD(+) or NADH is added. Furthermore, we examined the ability of 11-cis-RoDH, through the production from 3alpha-diol of the active androgen DHT, to activate the androgen-responsive promoter of the prostate-specific antigen (PSA) gene. The co-transfection of the pCMV expression vector containing 11-cis-RoDH (pCMV-11-cisRoDH), a luciferase reporter gene driven by a PSA promoter (pCMV-PSA-Luc) and an androgen receptor (pCMV-hAR) showed that, in the presence of 3alpha-diol, the expression of the PSA promoter is increased by five to six-fold. Moreover, this stimulatory effect is inhibited by hydroxyflutamide, a well-known antiandrogen. These results suggest that 11-cis-RoDH could be involved in a non-classical pathway of androgen formation and might play a role in the modulation of the androgenic response in some peripheral tissues.

Induction of vigorous helper and cytotoxic T cell as well as B cell responses by dendritic cells expressing a modified antigen targeting receptor-mediated internalization pathway

Efficient Ag presentation is essential to induce effective cellular and humoral immune responses. Thus, one central goal of current immunotherapy and vaccine development is to enhance Ag presentation to induce potent and broad immune responses. Here, a novel Ag presentation strategy is developed by transducing dendritic cells (DCs) to produce an Ag for presentation as an exogenous Ag to efficiently induce both humoral and cellular immunity. The principle of this strategy is illustrated by genetically modifying DCs to secrete a model hepatitis B virus Ag fused with a cell-binding domain and to process the fusion Ag as an exogenous Ag after receptor-mediated internalization for MHC class I and II presentation. Vigorous Ag-specific CD4(+) helper and CD8(+) cytotoxic T cell, as well as B cell, responses were induced by the transduced DCs in mouse models. Thus, this novel strategy uses a receptor-mediated internalization process to efficiently induce all arms of the adaptive immunity and may provide a powerful means to develop potent vaccines and immunotherapies.

Molecular characterization of a first human 3(alpha-->beta)-hydroxysteroid epimerase

In this report, we describe the isolation and characterization of a cDNA encoding an enzyme that exhibits catalytic characteristics of a 3(alpha-->beta)-hydroxysteroid epimerase (3(alpha-->beta)-HSE). The enzyme overexpressed in human 293 embryonic kidney cells transforms androsterone into epi-androsterone in two steps: the oxidation of androsterone to 5 alpha-androstane-3,17-dione, followed by the reduction of the latter to epi-androsterone. The reverse reaction, 3(beta-->alpha)-hydroxysteroid epimeration, is approximately 10-fold weaker. These results are confirmed by V(max)/K(m) determination, which shows that the enzyme catalyzes the oxidation of androsterone to 5 alpha-androstane-3,17-dione and the reduction of 5 alpha-androstane-3,17-dione to epi-androsterone more efficiently than the reverse reactions. The selective catalysis of the reaction following the 3(alpha-->beta) direction is also observed in intact transfected cells in culture, which better reflect physiological conditions. In vitro assays reveal that the recombinant enzyme prefers NAD(+) and NADH as cofactors and could recognize both C-19 and C-21 3 alpha-hydroxysteroids as substrates. DNA sequence analysis predicts a protein of 317 amino acids. Tissue distribution analysis using RT-PCR reveals that the mRNA of the enzyme is expressed in various tissues, including liver, brain, prostate, adrenal, and uterus, with the most abundant expression in the liver. Because active hydroxysteroids generally exert their effect in a stereo-specific manner, 3(alpha-->beta)-HSE could thus potentially play an important role in regulating the biological activities of various steroids.

Leptin receptor, NPY, POMC mRNA expression in the diet-induced obese mouse brain

A high fat diet leads to progressive development of obesity and leptin resistance in C57 mice with a middle stage of peripheral, but not central, leptin resistance. This stage is characterized by increased fat accumulation despite relative hypophagia. At a later stage central leptin resistance ensues along with hyperphagia, rapid weight and fat gain. The aim of this study is to characterize the mRNA levels of leptin receptor (LR), neuropeptide Y (NPY) and pro-opiomelanocortin (POMC) in high fat (HFF) and low fat (LFF) fed groups of mice. The hypothalamic arcuate nucleus (Arc) was investigated, as was the choroid plexus (ChP) in the case of the leptin receptor. No differences between groups were seen in LR, NPY or POMC mRNA levels after 1 week of feeding. After 8 and 19 weeks, the HFF mice, compared to LFF controls, demonstrated a +45% (P<0. 003) and +84% (P<0.0001) increase in the ratio of visceral fat to body weight and +223% (P<0.0001) and +468% (P<0.0001) elevation in plasma leptin levels, respectively. At 8 weeks, LR mRNA expression showed a +98% (P<0.016) and +66% (P<0.0001) increase in ChP and Arc, respectively, while Arc NPY mRNA showed down-regulation by -45% (P<0. 006). Arc POMC mRNA showed no significant changes between groups at 8 weeks. However, after long-term (19 weeks) feeding, the HFF mice displayed significantly -26% (P<0.039) and -33% (P<0.0015) reduced LR mRNA in the ChP and Arc, respectively, with Arc POMC and NPY mRNAs down by -55% (P<0.004) and -32% (P<0.009), respectively. The present results suggest that in the middle stage of development of high fat-induced obesity, when central leptin sensitivity is maintained, the increased leptin receptor expression may play a role to defend against obesity which is overwhelmed as central leptin insensitivity develops. In this later stage the down-regulation of the POMC system may be important in the final breakdown of weight homeostasis.

Androgen formation and metabolism in the pulmonary epithelial cell line A549: expression of 17beta-hydroxysteroid dehydrogenase type 5 and 3alpha-hydroxysteroid dehydrogenase type 3

Surfactant synthesis within developing fetal lung type II cells is affected by testosterone and 5alpha-dihydrotestosterone (5alpha-DHT). The pulmonary epithelial cell line A549, isolated from a human lung carcinoma, like normal lung type II cell, produces disaturated phosphatidylcholines and has been widely used for studying the regulation of surfactant production. Androgen receptor has been detected in A549 cells; however, the capacity of these cells for androgen synthesis and metabolism has not been investigated at molecular level. This study was undertaken to identify the steroidogenic enzymes involved in the formation and metabolism of androgens from adrenal C19 steroid precursors in A549 cells. When cultured in the presence of normal FCS, A549 intact cells converted DHEA to androstenediol, androstenedione principally to testosterone, and 5alpha-DHT to 5alpha-androstane 3alpha,17beta-diol. High levels of 17beta-hydroxysteroid dehydrogenase (HSD) and 3alpha-HSD activities were detected in both cytosol and microsomes isolated from homogenates. Analysis of A549 RNA indicated the presence of 17beta-HSD type 4 and type 5, and of 3alpha-HSD type 3 messenger RNAs. Very low levels of 3beta-HSD type 1 and 5alpha-reductase type 1 messenger RNAs and activities were detected. With regard to active androgen formation, there was little or no capacity for the conversion of DHEA to 5alpha-DHT. In contrast, androstenedione was rapidly transformed to testosterone. The pattern of steroid metabolism was not affected by the use of charcoal-stripped FCS or by the synthetic glucocorticoid dexamethasone. Together, our findings show that A549 cells express a pattern of steroid metabolism in which 17beta-HSD type 5 and 3alpha-HSD type 3 are the predominant enzymes. The level of androgens is regulated at the level of catalysis in intact cells such that the intracellular level of testosterone is stabilized, whereas 5alpha-DHT is rapidly inactivated by reduction to 3alpha,17beta-diol. This pattern of androgen metabolism has implications for the relative importance of testosterone and 5alpha-DHT in normal lung development and surfactant production.

Hypothalamic c-fos-like immunoreactivity in high-fat diet-induced obese and resistant mice

Some C57Bl/6 mice become obese, whereas others remain lean when raised on a high-fat diet. The mechanisms underlying this interindividual susceptibility to diet-induced obesity remain unknown. Because hypothalamus plays a major role in the regulation of body weight, this study was conducted to identify the differences of hypothalamic neuronal activity between diet-induced obese and diet-resistant mice. Using c-fos as a marker, this study showed that diet-induced obese mice significantly increased c-fos-like immunoreactive neurons in the dorsal part of lateral hypothalamus (+183%) and dorsomedial hypothalamic nucleus (+87.5%) compared with diet-resistant mice. Furthermore, switching from high fat to low fat, or high n-3 polyunsaturated fatty acid diet, significantly decreased body weight gain (-35.7% and -31.0%), overall fat storage (-63.4% and -59.6%), and c-fos-like immunoreactive neurons in the dorsal part of lateral hypothalamus (-76.5% and -64.7%) and dorsomedial hypothalamic nucleus (-73.3% and -56.7%) in diet-induced obese mice, respectively. The present study also showed that the ratio of serum leptin/fat mass was threefold higher in the diet-resistant mice than in the diet-induced obese mice, which may be responsible for the less fat storage in the diet-resistant mice. The current data further confirm that the increased neuronal activity in the key autonomic regulatory centers may contribute to the excessive fat storage in diet-induced obese mice. Moreover, both high-fat diet-induced excessive fat storage and the altered hypothalamic neuronal activity may be largely corrected by reducing dietary fat content or replacing it with non-obesogenic fat.

Development of high fat diet-induced obesity and leptin resistance in C57Bl/6J mice

OBJECTIVE

To investigate the development of high fat diet-induced obesity and leptin resistance.

DESIGN

Two experiments were carried out in this study. Firstly, we fed the mice with a high- or low-fat diet for up to 19 weeks to examine a progressive development of high fat diet-induced obesity. Secondly, we examined peripheral and central exogenous leptin sensitivity in mice fed high- or low-fat diets for 1, 8 or 19 weeks.

SUBJECTS

A total of 168 C57BL/6J mice (3 weeks old) were used in this study.

MEASUREMENTS

In the first experiment, we measured the body weight, energy intake, adipose tissue mass, tibia bone length, and plasma leptin in mice fed either a high- or low-fat diet for 1, 8, 15 and 19 weeks. In the second experiment, body weight change and cumulative energy intake were measured at 6 h intervals for 72 h after leptin injection in mice fed a high- or low-fat diet for 1, 8 or 19 weeks.

RESULTS

The results from the first experiment suggested that the development of high fat diet-induced obesity in mice could be divided into early, middle and late stages. Compared with the mice fed a low-fat diet, the mice fed a high-fat diet showed a gradually increased body weight (+5.2%), fat storage (epididymal plus perirenal; +6.7%) and plasma leptin (+18%) at 1 week; +11.4%, +68.1%, and +223%, respectively, at 8 weeks; and +30.5%, +141%, and +458%, respectively, at 19 weeks. Energy intake of high fat diet-fed mice was equal to that of low fat diet-fed controls for the first 3 weeks; it fell below control levels over the next 5 week period, but began to increase gradually after 8 weeks of high-fat diet feeding and then increased dramatically from 15 weeks to be 14% higher than that of controls after 19 weeks. The results from our second experiment showed that: (1) after 1 week of feeding, the mice fed a high-fat diet were sensitive to a 2 microg/g (body weight) intraperitoneal (i. p.) injection of leptin, with no differences in body weight change or cumulative energy intake post-injection; (2) after 8 weeks of feeding, the mice fed a high-fat diet were insensitive to 2 microg/g (body weight) i.p. leptin, but were sensitive to a 0.1 microg intracerebroventricular (i.c.v.) injection of leptin; (3) after 19 weeks of feeding, the mice fed a high-fat diet were insensitive to 0. 1 microg i.c.v. leptin, but were sensitive to a high dose of 2 microg i.c.v. leptin.

CONCLUSIONS

The present study demonstrated that the development of high fat diet-induced obesity (19 weeks) in C57 B1/6J mice could be divided into three stages: (1) an early stage in response to high-fat diet that mice were sensitive to exogenous leptin; (2) a reduced food intake stage when mice had an increase in leptin production and still retained central leptin sensitivity; and (3) an increased food intake stage, accompanied by a reduction of central leptin sensitivity.

[The role of somatostatin in area CA1 of rat hippocampus in experimental epilepy]

In area CA1, intrahippocampal microinjection of somatostatin(SS, 0.03 to 0.3 nmol) caused single or a series of spike-sharp waves in the cortex electroencephalogram (EEG), the spectrum average total power of which is increased dose-dependently from 0.006 to 0.15 nmol. Microinjection of SS into the hippocampal CA1 subregion brought out epileptic-like behavioral responses and aggregated kainic acid (KA)-induced epileptiform activity of rats. With extracellular recording technique, the effects of SS on 114 units epileptiform discharge were investigated in penicillin (PEN)-treated 95 rat hippocampal slices. In response to the application of SS (10(-10), 10(-8), 10(-6) mol/L), the burst frequency of area CA1 62/105 (59.05%) recorded unit discharges was increased significantly, while that of 23/105 (21.9%) was decreased. These results suggest that SS in hippocampal CA1 subregion mainly precipitates epileptiform discharge. The addition of anti-somatostatin antibody (1 1000) to the perfusate partly blocked the epileptiform bursts triggered by PEN perfusion, while this antiepileptic effect of SSAB was reversed by application of SS (10(-8) mol/L). These indicate that endogenous SS may be involved in epileptiform discharge in area CA1 of hippocampus.

Diet composition and insulin action in animal models

Critical insights into the etiology of insulin resistance have been gained by the use of animal models where insulin action has been modulated by strictly controlled dietary interventions not possible in human studies. Overall, the literature has moved from a focus on macronutrient proportions to understanding the unique effects of individual subtypes of fats, carbohydrates and proteins. Substantial evidence has now accumulated for a major role of dietary fat subtypes in insulin action. Intake of saturated fats is strongly linked to development of obesity and insulin resistance, while that of polyunsaturated fats (PUFAs) is not. This is consistent with observations that saturated fats are poorly oxidized for energy and thus readily stored, are poorly mobilized by lipolytic stimuli, impair membrane function, and increase the expression of genes associated with adipocyte profileration (making their own home). PUFAs have contrasting effects in each instance. It is therefore not surprising that increased PUFA intake in animal models is associated with improved insulin action and reduced adiposity. Less information is available for carbohydrate subtypes. Early work clearly demonstrated that diets high in simple sugars (in particular fructose) led to insulin resistance. However, again attention has rightly shifted to the very interesting issue of subtypes of complex carbohydrates. While no differences in insulin action have yet been shown, differences in substrate flux suggest there could be long-term beneficial effects on the fat balance of diets enhanced in slowly digested/resistant starches. A new area of major interest is in protein subtypes. Recent results have shown that rats fed high-fat diets where the protein component was from casein or soy were insulin-resistant, but when the protein source was from cod they were not. These are exciting times in our growing understanding of dietary factors and insulin action. While it has been clear for some time that 'oils ain't oils', the same is now proving true for carbohydrates and proteins.

Efficient glycosylation site utilization by intracellular apolipoprotein B. Implications for proteasomal degradation

The balance between the hepatic assembly of apolipoprotein B (apoB) and its presecretory degradation at the level of the endoplasmic reticulum (ER) may control the secretion of apoB-containing lipoproteins. In one model, apoB that fails to assemble with lipid undergoes translocation arrest, exposing the protein to the cytosolic proteasome. To examine apoB's translocation behavior under various metabolic conditions, glycosylation site utilization studies were performed. A 70-amino acid peptide containing three sites for N-linked glycosylation was appended to the C-terminus of apoB-50 (amino-terminal 50% of apoB) and expressed in both hepatic and nonhepatic cell lines. When the C-terminal reporter peptide was released by cyanogen bromide cleavage, all of the sites were glycosylated irrespective of cell type, labeling time, or assembly status. Similar peptide mapping of endogenous apoB-100 expressed in HepG2 cells was performed to monitor glycosylation at Asn residues 2752 (apoB-61), 2955 (apoB-65), and 3074 (apoB-68). N-linked glycosylation occurred at a minimum of two of the three sites, a frequency identical to that observed in apoB-100 recovered from cell media. Treatment of cells with proteasome inhibitors produced a 2. 5-fold increase in intracellular apoB but failed to cause accumulation of an unglycosylated form. These results indicate that 1) the efficient translocation of apoB into the ER occurs independently of microsomal triglyceride transfer protein and its assembly with lipid and 2) despite its large size and affinity for lipid, delivery of misassembled apoB to the proteasome requires retrograde translocation from the ER lumen to cytosol.

Influence of dietary fats on c-Fos-like immunoreactivity in mouse hypothalamus

The hypothalamus is a brain region of major importance in regulation of energy balance via autonomic nervous control of both intake and expenditure. There is substantial evidence that diets high in saturated fats lead to obesity while diets equally high in polyunsaturated fats (PUFAs) do not. Using c-Fos as a marker, this study aimed to investigate hypothalamic neuronal response in mice fed high fat diets (58% of calories as fat) emphasising saturated, n-3 or n-6 polyunsaturated fatty acids, or a low fat (10% of calories) diet over periods of 1 and 7 weeks. In addition, a 4-week "reversal" intervention with n-3 polyunsaturated or low fat diet was undertaken in saturated fat-fed mice. Food intake and body weight were measured over the feeding periods. At 1, 7 and 11 weeks mice were killed, epididymal fat pad were weighed and brains were removed for quantitation of hypothalamic c-Fos-like immunoreactive (FLI) neurons. Weight gain, and epididymal fat pad weight, were highest on the saturated fat diet and lowest on the n-3 diet despite similar food intakes (epididymal fat weight at week 7: saturated fat, 622+/-48 mg; n-6 fat 423+/-69; low fat 387+/-10, n-3 fat 225+/-26). Compared to a low fat diet, FLI neurons in the dorsal part of lateral hypothalamic (dLH) area was dramatically increased by saturated fat feeding (+367% at 1 week) while ventromedial hypothalamic (VMH) activity was decreased. In contrast with n-6 and n-3 feeding dLH FLI neuronal activity was unchanged but actually increased in the VMH. Paraventricular nucleus (PVN) FLI neurons increased in the high saturated group only at 7 and 11 weeks, after substantial fat accumulation. Substitution of saturated fat diet with the n-3 diet partially reversed (48%) the increase in FLI neurons in PVN of saturated fat-fed mice, while it significantly increase FLI neurons in arcuate nucleus (+400%). In summary, this study demonstrates that dietary saturated fat modulates hypothalamic neuronal activity in a pattern (high lateral, reduced ventromedial activity) consistent with its obesogenic effects. In contrast, diets equally high in PUFA (particularly of the n-3 class) neither increase adiposity nor derange the lateral/medial neuronal activity balance.

Disruption of disulfide bonds exhibits differential effects on trafficking of regulated secretory proteins

For several secretory proteins, it has been hypothesized that disulfide-bonded loop structures are required for sorting to secretory granules. To explore this hypothesis, we employed dithiothreitol (DTT) treatment in live pancreatic islets, as well as in PC-12 and GH(4)C(1) cells. In islets, disulfide reduction in the distal secretory pathway did not increase constitutive or constitutive-like secretion of proinsulin (or insulin). In PC-12 cells, DTT treatment caused a dramatic increase in unstimulated secretion of newly synthesized chromogranin B (CgB), presumably as a consequence of reducing the single conserved chromogranin disulfide bond (E. Chanat, U. Weiss, W. B. Huttner, and S. A. Tooze. EMBO J. 12: 2159-2168, 1993). However, in GH(4)C(1) cells that also synthesize CgB endogenously, DTT treatment reduced newly synthesized prolactin and blocked its export, whereas newly synthesized CgB was routed normally to secretory granules. Moreover, on transient expression in GH(4)C(1) cells, CgA and a CgA mutant lacking the conserved disulfide bond showed comparable multimeric aggregation properties and targeting to secretory granules, as measured by stimulated secretion assays. Thus the conformational perturbation of regulated secretory proteins caused by disulfide disruption leads to consequences in protein trafficking that are both protein and cell type dependent.

Altered hypothalamic c-Fos-like immunoreactivity in diet-induced obese mice

High-fat diet can induce obesity. However, it is not known if the neural activity of the hypothalamus is altered under high-fat diet. The aim of the present study is to search for the altered hypothalamic neuronal activity in C57BI/6J mice fed a high-fat diet for 15 weeks. Hypothalamic c-Fos-like immunoreactivity (FLI) and serum leptin were measured after mice were fed a high-fat diet for 15 weeks. Our results demonstrate that increased body weight and serum leptin are accompanied by an elevated neuronal c-Fos-like immunoreactivity in the lateral hypothalamus, the lateral part of the dorsomedial hypothalamic and perifornical nuclei of diet-induced obese mice. Fasting increases FLI neurons in the arcuate hypothalamic nucleus and decreases FLI neurons in the lateral hypothalamic area and dorsomedial hypothalamic nucleus of both diet-induced obese and lean mice. The current data suggest that constantly activated status of these neurons in the hypothalamus may be responsible for differences in body weight and serum leptin between obese and lean mice.

Xylene-induced effects on brain neurotransmitters, behavior and fos protein in rats

Male Sprague-Dawley rats administered xylene intraperitoneally on alternate days at a dose of 125 or 250 mg/kg for 30 days exhibited no marked changes in locomotor activity, learning and memory capacity. However in rats given xylene on alternate day at a dose of 500 mg/kg for 30 days, a significant decrease in locomotor activity, deficits in learning ability and memory loss were detected. These xylene-induced behavioral changes were associated with a decrease in beta-endorphin and leuenkaphlin concentrations in the pons-medulla. On the contrary, xylene at a dose of 500 mg/kg increased the beta-endorphin level in caudate and c-fos expression in hippocampus. These data suggest that the xylene-induced behavioral alterations might be associated with the expression of Fos protein in the hippocampus.

Simultaneous SPECT studies of pre- and postsynaptic dopamine binding sites in baboons

The central nervous system dopamine transporters (DATs) and dopamine D2/D3 receptors are implicated in a variety of neurological disorders. Both sites are also targets for drug treatment. With the successful development of [99mTc]TRODAT-1, single-isotope imaging studies using this ligand for DAT imaging can be complemented by additional use of 123I-labeled D2/D3 receptor ligand co-injected to assess both pre- and postsynaptic sites of the dopaminergic system simultaneously.

METHODS

Twelve SPECT scans of the brain were obtained in two baboons after intravenous administration of 740 MBq (20 mCi) [99mTc]-TRODAT-1 (technetium, [2-[[2-[[[3-(4-chlorophenyl)-8-methyl-8-azabicyclo[3,2,1]oct-2-yl]methyl ](2-mercaptoethyl) amino]ethyl]-amino]ethanethiolato (3-)]- oxo-[1R-(exo-exo)]) and 185 MBq (5 mCi) [123I]iodobenzamide or [123I]iodobenzofuran. SPECT data were acquired by a triple-head gamma camera equipped with ultra-high-resolution fanbeam collimators (scan duration = 210 min). Two sets of SPECT data were obtained using energy windows of 15% centered on 140 keV for 99mTc and 10% asymmetric with a lower bound at 159 keV for 123I. After coregistration with MRI, region-of-interest analysis was performed using predefined templates from coregistered MRI. In blocking studies, baboons were pretreated with N-methyl-2beta-carbomethoxy-3beta-(4-fluorophenyl)tropane (CFT, 14 mg) or raclopride (14 mg) to block DAT or D2/D3 binding site, respectively.

RESULTS

Image quality of dual-isotope studies was similar to that obtained from single-isotope studies. When one site was blocked with CFT or raclopride, the binding of the respective ligand to the other site was not affected.

CONCLUSION

This is the first example that clearly demonstrates the feasibility of simultaneous imaging of both pre- and postsynaptic sites of the dopaminergic system in baboons with dual-isotope SPECT studies. With or without corrections for cross-contamination of 123I into the 99mTc window, striatum-to-cerebellum ratios (target-to-nontarget) of dual-isotope experiments did not differ significantly from single-isotope experiments. This method may be a valuable and cost-effective tool for gaining comprehensive information about the dopaminergic system in one SPECT imaging session.

Localization of type 5 17beta-hydroxysteroid dehydrogenase, 3beta-hydroxysteroid dehydrogenase, and androgen receptor in the human prostate by in situ hybridization and immunocytochemistry

An important source of androgens in the human prostate are those synthesized locally from the inactive adrenal precursor dehydroepiandrosterone (DHEA) and its sulfated derivative DHEA-S. Three beta-HSD (hydroxysteroid dehydrogenase) converts DHEA into androstenedione (4-dione), whereas type 5 17beta-HSD catalyzes the reduction of 4-dione into testosterone in the human prostate and other peripheral intracrine tissues. In the present study, we have used two complementary approaches, namely in situ hybridization and immunocytochemistry, to identify the cells that contain the type 5 17beta-HSD messenger RNA and enzyme in human benign prostatic hyperplasia (BPH). Localization of 3beta-HSD and of the androgen receptor (AR) was also investigated by immunostaining in the same tissue. To find out whether there are any differences between BPH and normal prostate tissue, the localization of type 5 17beta-HSD was reexamined by immunocytochemistry in the normal human prostate samples and also in normal prostate epithelial cell line (PrEC). The in situ hybridization results obtained with a tritiated uridine triphosphate (3H-UTP)-labeled type 5 17beta-HSD riboprobe are in agreement with the immunostaining data obtained with a specific antibody to the enzyme. The immunostaining results obtained from normal prostate tissue and BPH were found to be similar. Thus, in the glandular epithelium, basal cells highly express the messenger RNA and the enzyme, whereas luminal cells show a much lower and variable level of expression. In the stroma and walls of blood vessels, fibroblasts and the endothelial cells lining the blood vessels show positive staining. Similar results are observed when the cellular distribution of 3beta-HSD is investigated. AR immunoreactivity, however, shows a different distribution because, in the epithelium, most of the nuclei of basal cells are negative, whereas the majority of nuclei of the luminal cells show positive staining. A strong reaction for AR is also found in most stromal cell nuclei and in the nuclei of most endothelial cells, as well as in some other cells of the walls of blood vessels. In conclusion, human type 5 17beta-HSD, as well as 3beta-HSD, are highly expressed, not only in the basal epithelial cells and stromal fibroblasts but also in the endothelial cells and fibroblasts of the blood vessels. AR, on the other hand, is highly expressed in the luminal cells. The present data suggest that DHEA is transformed in the basal cells of the glandular epithelium into 4-dione by 3beta-HSD and then into testosterone by type 5 17beta-HSD, whereas dihydrotestosterone is synthesized in the luminal cells after diffusion of testosterone from the underlying layer of basal cells. The potential role of androgen formation and action in blood vessels is unknown and opens new avenues of investigation for a better understanding of the multiple roles of androgens.

Apolipoprotein B in the rough endoplasmic reticulum: translation, translocation and the initiation of lipoprotein assembly

Apolipoprotein (apo) B and the microsomal triglyceride transfer protein are essential for the hepatic assembly and secretion of triglyceride-rich VLDL. To understand how apoB initiates the process of lipoprotein formation, interest has focused on the biogenesis of its amino terminal globular domain (alpha1 domain). When only this domain is expressed in hepatoma cells, no lipoprotein particle will form. However, proper folding of the alpha1 domain is essential for the internal lipophilic regions of apoB to engage in cotranslational lipid recruitment. The essential function of this domain may be related to its capacity to promote a specific physical interaction with the microsomal triglyceride transfer protein, necessary for apoB's proper folding and lipidation. Alternatively, this domain may promote an autonomous lipid recruitment step that nucleates microsomal triglyceride transfer protein-dependent lipid sequestration by apoB. Forms of apoB that fail to initiate particle assembly or forms associated with aberrant underlipidated particles are targeted for intracellular turnover. Two sites of apoB degradation have been identified. In hepatocarcinoma-derived cells, misassembled apoB may undergo progressive reverse translocation from the endoplasmic reticulum lumen to the cytosol, a process that is mechanistically coupled to polyubiquitination and proteasome-mediated degradation on the cytosolic side of the membrane. Alternatively, studies in primary hepatocytes reveal that apoB may undergo sorting to a post-endoplasmic reticulum compartment for presecretory degradation. In either case, the balance between assembly and presecretory degradation of apoB may represent a control point for the production of hepatic VLDL.

Characteristics of a highly labile human type 5 17beta-hydroxysteroid dehydrogenase

17Beta-hydroxysteroid dehydrogenases (17betaHSDs) play an essential role in the formation of active intracellular sex steroids. Six types of 17betaHSD have been described to date, which only share approximately 20% homology. Human type 5 17betaHSD complementary DNA is unique among the 17betaHSDs because it belongs to the aldo-keto reductase family, whereas the others are members of the short chain alcohol dehydrogenases. The characteristics of human type 5 17betaHSD were investigated in human embryonic (293) cells stably transfected with human and mouse type 5 17betaHSD, as well as human type 3 3alphaHSD. Using intact transfected cells, type 5 17betaHSD shows a substrate specificity pattern comparable to those of human type 3 17betaHSD and mouse type 5 17betaHSD. These enzymes catalyze more efficiently the transformation of androstenedione (4-dione) to testosterone, whereas the transformation of dihydrotestosterone to 5alpha-androstane-3alpha,17beta-diol is much lower. In contrast, type 3 3alphaHSD catalyzes more efficiently the transformation of dihydrotestosterone to 5alpha-androstane-3alpha,17beta-diol, whereas the transformation of 4-dione to testosterone represents only 7% of the 3alphaHSD activity. However, upon homogenization, human type 5 17betaHSD activity decreases to approximately 10% of the activity in intact cells and remains stable at this level together with the 3alphaHSD activity. Under the same conditions, however, the mouse enzyme is not altered by homogenization. Indeed, using purified human 17betaHSD overexpressed in Escherichia coli, we could confirm that a much greater amount of protein is required to produce activity similar to the enzymatic activity measured in intact transfected cells. The present data provide the answer to the question of why previous researchers could hardly detect type 5 17betaHSD activity. Indeed, all previous publications used cell or tissue homogenates or purified enzymes. Under such conditions, only the low level, but stable, 3alphaHSD and 17betaHSD activities could be measured, whereas the high level, but highly unstable, 17betaHSD activity could not be measured. As type 5 17betaHSD shares 84%, 86%, and 88% amino acid identity with types 1 and 3 3alphaHSD and 20alphaHSDs, respectively, Northern blot analysis used in previous studies could not provide unequivocal information. In this report, we used a more specific ribonuclease protection assay and could thus show that human type 5 17betaHSD is expressed in the liver, adrenal, and prostate; in prostatic cancer cell lines DU-145 and LNCaP; as well as in bone carcinoma (MG-63) cells. By analogy with type 3 17betaHSD, which is responsible for the formation of androgens in the testis, the expression of type 5 17betaHSD in the prostate and bone cells suggests that this enzyme is involved in the formation of active intracellular androgens in these tissues.

Localization by in situ hybridization of steroid 5alpha-reductase isozyme gene expression in the human prostate and preputial skin

PURPOSE

The synthesis of dihydrotestosterone is catalyzed by steroid 5alpha-reductase isozymes, designated as types 1 and 2. Controversial results have been reported on the identification of the cell types expressing each isozyme in the human prostate and genital skin. The objective of the present study was to clearly identify at the cellular level the cells containing each type of 5alpha-reductase isozyme.

MATERIALS AND METHODS

We used for the first time an in situ hybridization technique involving use of [35S]-labeled oligonucleotide probes to determine the cell type expression patterns of the two 5alpha-reductase isozymes in human prostate and preputial skin.

RESULTS

In the prostate, hybridization with types 1 and 2 5alpha-reductase antisense probes led to a positive reaction in both epithelial and stromal cells, while the sense probes did not generate any signal. The silver grain counts for both isozymes revealed a higher labeling in the epithelial cells. In fact, the ratio epithelial cells/stroma was around 2 for both 5alpha-reductase types 1 and 2. In the preputial skin, 5alpha-reductase type 1 was found to be highly expressed in all the layers of the epidermis with the exception of the stratum corneum while a lower labeling was observed in some fibroblasts as well as in the secretory cells of sebaceous glands and excretory duct cells of sweat glands. Type 2 5alpha-reductase showed a very similar pattern of distribution.

CONCLUSION

It appears that, in two human tissues, the two 5alpha-reductase isozymes mRNAs are expressed by the same cell types. This new observation should help clarify the physiological role of each type of 5alpha-reductase isozyme.

Altered c-fos expression in autonomic regulatory centers of genetically obese (ob/ob) mouse brain

This study examined c-fos-like immunoreactivity (FLI) in the brain of obese (ob/ob) and lean (+/+) mice during states of satiety and hunger. The results demonstrated that there is an altered neural activity primarily in the hypothalamus of the obese mouse brain. Most interestingly, only obese mice had an increased FLI in the dorsomedial and supramammillary nuclei. Conversely, only lean mice showed increase in FLI in the medial part of perifornical nucleus following food deprivation for 24 h.

Down-regulated NPY receptor subtype-5 mRNA expression in genetically obese mouse brain

Brain neuropeptide Y (NPY) subtype-5 (Y5 receptor) mRNA expression in lean (+/+) and obese (ob/ob) C57Bl/6 mice was examined using a non-radioactive in situ hybridization detection method. Significant decreases in Y5 receptor mRNA expression were found in the ventromedial, dorsomedial and arcuate hypothalamic nuclei, midline thalamic nuclei, piriform, cingulate and retrosplenial granular cortices of the obese mouse brain. There were minor changes in the amount of Y5 receptor mRNA expression in the hippocampal formation and medial habenular nucleus. Results indicated that Y5 receptor mRNA expression is downregulated in hereditary obese (ob/ob) mice. This is possibly due to over-expression of hypothalamic NPY which occurs in this phenotype.

Identification of cysteine pairs within the amino-terminal 5% of apolipoprotein B essential for hepatic lipoprotein assembly and secretion

There is growing evidence that the amino-terminal globular domain of apolipoprotein B (apoB) is essential for lipoprotein particle formation in the hepatic endoplasmic reticulum. To identify the structural requirements for its function in lipoprotein assembly, cysteine (Cys) pairs required to form the seven disulfide bonds within the amino-terminal 21% of apoB were replaced in groups or individually by serine. Substitution of Cys pairs required for formation of disulfide bonds 1-3 or 4-7 (numbered from amino to carboxyl terminus) completely blocked the secretion of apoB28 in transfected HepG2 cells. To identify the specific disulfide bonds required for secretion, Cys pairs were mutated individually. Substitution of Cys pairs required for disulfide bonds 1, 3, 5, 6, or 7 had little or no impact on apoB28 secretion or buoyant density. In contrast, individual substitution of Cys pair 2 (amino acid residues 51 and 70) or 4 (218 and 234) severely inhibited apoB28 secretion and its capacity to undergo intracellular assembly with lipid. The same assembly and secretion defects were observed when these mutations were expressed as part of apoB50. These studies provide direct evidence that the ability of the internal lipophilic regions of apoB to engage in the recruitment and sequestration of lipid during translation is critically dependent upon a structural configuration contained within or affected by the amino-terminal 5% of the protein.

Fasting increases leptin receptor mRNA expression in lean but not obese (ob/ob) mouse brain

Using a non-radioactive in situ hybridization detection method, we found that fasting up-regulated leptin receptor mRNA expression in the brain of C57 Bl/6 lean (+/+) but not obese (ob/ob) mice. After the lean mice were fasted for 24 h, increased leptin receptor mRNA expression was found in the arcuate and ventromedial hypothalamic nuclei, medial habenular nucleus and dentate gyrus of hippocampal formation. There was only a minor increase in mRNA expression of leptin receptor in the hippocampus proper while the piriform cortex remained unchanged. However, after the obese mice were fasted for 24 h, no detectable changes of leptin receptor mRNA expression could be found. These results indicated that leptin receptor gene expression was influenced by nutritional status. Further, genetically obese mice showed an inability to respond to nutritional change, probably due to the fact that obese mice lack leptin.

Polarized apical targeting directed by the signal/anchor region of simian virus 5 hemagglutinin-neuraminidase

To examine the possibility of independent cytoplasmic/transmembrane domain-based apical sorting, we have investigated paramyxovirus SV5 hemagglutinin-neuraminidase (HN), a type II membrane protein with a small N-terminal signal/anchor region. In SV5-infected Madin-Darby canine kidney (MDCK) cells, >90% of HN is found on the apical surface. We have expressed chimeric proteins in which the N terminus of HN, including its signal/anchor region, is attached to a (normally cytosolic) reporter pyruvate kinase (PK). PK itself expressed immediately downstream from a cleavable signal peptide was converted to a 58-kDa N-linked glycosylated form, which was secreted predominantly (80%) to the basolateral surface of MDCK cells. By contrast, stably expressed PK chimeras, now anchored as type II membrane proteins with either the first 48 or 72 amino acids of HN, received similar N-linked glycosylation, yet exhibited polarized transport with a preferentially (75%) apical distribution. These results suggest that the N-terminal signal/anchor region of HN contains independent sorting information for apical specific targeting in MDCK cells.

Phenotypic knockout of HIV type 1 chemokine coreceptor CCR-5 by intrakines as potential therapeutic approach for HIV-1 infection

A genetic defect in a CC-chemokine receptor (CCR)-5, the principal coreceptor for the macrophage-tropic HIV type 1 (HIV-1), recently was found to naturally protect CCR-5-defective, but healthy, individuals from HIV-1 infection. In this study, we mimic the natural resistance of the CCR-5-defective individuals by designing a strategy to phenotypically knock out CCR-5. The inactivation of the CCR-5 coreceptor is accomplished by targeting a modified CC-chemokine to the endoplasmic reticulum to block the surface expression of newly synthesized CCR-5. The lymphocytes transduced to express the intracellular chemokine, termed "intrakine," were found to be viable and resistant to macrophage-tropic HIV-1 infection. Thus, this gene-based intrakine strategy targeted at the conserved cellular receptor for the prevention of HIV-1 entry should have significant advantages over currently described approaches for HIV-1 therapy.

[Immunohistochemical detection of PCNA and p53 protein in the premalignant lesions and squamous cell carcinomas of the oral mucosa]

PCNA and p53 protein expression were detected by immunohistochemical technique in 39 oral premalignant and malignant lesion;which included 11 oral mucosal leukoplakia(LK),9 oral lichen planus (LP),7 in situ carcinomas(ISC) and 12 squamous cell carcinomas(SCC);in order to investigate the significance of PCNA and p53 Protein overexpression in predicting malignant transformation.The results showed that the gradual strong expression of PCNA and mutated p53 protein positive signal from premalignant to malignant lesions.The remarkable correlation were found on PCNA expression between LK and ISC; on p53 protein expression between SCC I grade and SCC II grade and on PCNA and p53 protein expression between premalignant and malignant lesions.The results imply that expression of PCNA and mutated p53 protein may be as indicators for potential malignant development in benign lesions of oral mucosa premalignant.

Upregulation of leptin receptor mRNA expression in obese mouse brain

Leptin receptor gene expression in the brains of lean (+/+) and obese (ob/ob) C57Bl/6 mice was examined using a non-radioactive in situ hybridization detection method. Significant increases in leptin receptor mRNA expression were found in the ventromedial and arcuate hypothalamic nuclei, piriform and olfactory cortices and medial habenular nucleus. There were very minor changes in the amount of leptin receptor mRNA expression in hippocampus proper (CA1-3). Results indicated that leptin receptor is upregulated when there is a lack of functional leptin, as in hereditary obese (ob/ob) mice. It is also suggested that leptin receptor may be an autoreceptor.

Molecular biological investigations into the role of the NMDA receptor in the pathophysiology of schizophrenia

OBJECTIVE

There is increasing acceptance that schizophrenia is associated with a generalised disorder in cortical neurodevelopment. The aim of this paper is to review the evidence that this disorder may be accounted for by abnormalities in mechanisms mediated by the main family of excitatory neuroreceptors in cortical brain systems, the N-methyl-D-aspartate (NMDA) glutamatergic receptors.

METHOD

The neurobiological evidence is presented for an abnormality in cortical development related to synaptic pathology in schizophrenia. The unique functions of the NMDA receptor in information processing are described, especially its role in learning and memory, and in neural plasticity and brain development. It is argued that the cellular and molecular mechanisms which underlie learning and memory also govern normal brain development. Studies examining abnormalities in glutamatergic transmission in schizophrenia are reviewed.

RESULTS

There is a substantial literature in support of the possibility that NMDA receptor abnormalities may be involved in the neurodevelopmental predisposition to schizophrenia, as well as in symptom production.

CONCLUSIONS

Research to determine the role of the NMDA receptor in the pathophysiology of schizophrenia is warranted and now feasible. To be successful, this research will require the application of molecular biology techniques to postmortem brain tissue studies, in addition to traditional histochemical approaches.

Molecular biology and the major psychoses

OBJECTIVE

To highlight the potential role of molecular biological studies in examining the expression of genes of interest in brain tissue to elucidate the pathophysiological basis of the major psychoses.

METHOD

To review the principles underlying the available techniques for expression studies.

RESULTS

Detection of messenger RNA by in situ hybridisation and quantitation by Northern analysis are powerful tools to detect abnormalities in gene expression in brain tissue.

CONCLUSION

The availability of simple techniques to examine the expression of RNA and protein products of individual genes, including examination at the level of individual cells, offers a clear opportunity to define the molecular basis of the major psychoses.

Potent antitumour activity of a new class of tumour-specific killer cells

Two approaches to the antibody-directed targeting of toxic or cytolytic activity and augmentation of cellular immune responses have been explored for tumour immunotherapy, but so far success has been limited. Obstacles facing immunotherapy are the limited accessibility of antibodies or antibody conjugates to solid tumours and the difficulty in obtaining tumour-specific cytotoxic lymphocytes. Here we generate a new class of tumour-specific killer cells by genetically modifying lymphocytes to produce and secrete a targeted toxin against an oncoprotein overexpressed on breast and other tumour cells. The transduced lymphocytes were shown to have potent and selective cytotoxicity to tumours in culture and nude mouse models. The potent in vivo antitumour activity is probably a result of the migration of the lymphocytes to tumours as a targeted toxin carrier, and production and accumulation of the targeted toxins inside tumours as a producer. Our approach, which has features of both antibody-directed and cell-mediated immunotherapy, may have application in a gene therapy context.

Localization of leptin receptor mRNA expression in mouse brain

The distribution of the leptin receptor in the brain of C57 mice was investigated using a non-radioactive in situ hybridization method. Leptin receptor mRNA expression was highest in the arcuate nucleus and median eminence of the hypothalamus, but it was also abundant in hippocampus, primarily in the dentate gyrus and CA1, and was detected at low levels in piriform cortex and the medial margin of the medial habenular nucleus. The localization of leptin receptor-containing neurones in the present study indicates the possibility that the leptin receptor is expressed on neuropeptide Y-containing neurones.

[Study on the enhancing effect of polyporus polysaccharide, mycobacterium polysaccharide and lentinan on lymphokine-activated killer cell activity in vitro]

The actions of Polyporus polysaccharide (PPS), mycobacterium polysaccharide (MPS) and lentinan (LEN) on lymphokine-activated killer (LAK) cell activity in vitro were investigated in this study. Human peripheral blood mononuclear cells (PBMC) were cultured for 96 hours with medium containing different concentrations of the above-mentioned drugs in combination with recombinant interleukin 2 (rIL-2). Then cell-mediated lysis was determined by 1H-TdR release assay including NK sensitive and NK resistant target cells. The results demonstrated that, when combined with rIL-2 in a certain concentration, all three kinds of polysaccharides could enhance the LAK activity by 42%-56.9%, and reduce the dose of rIL-2 by 50% (P < 0.05-0.01). It suggested that the PPS, MPS and LEN could be used as bioactivity regulators in LAK cell therapy in tumor treatment.

Human intermediate reticular zone: a cyto- and chemoarchitectonic study

The primary aim of this study was to provide a comprehensive account of the morphology, topography, and frequency of tyrosine hydroxylase- and substance P-like (TH-LI, SP-LI) immunoreactive neurons of the human intermediate reticular zone (IRt), the putative autonomic zone of the medullary reticular formation. A further aim is to examine the IRt from a three-dimensional perspective using computer reconstruction techniques and compare its relationship with other structures in the rest of the medullary reticular formation. Six adult human brains were obtained from individuals with no sign of cerebral disease and were perfusion fixed. Free-floating transverse sections were immunostained with monoclonal antibodies against tyrosine hydroxylase and substance P by the avidin-biotin-peroxidase technique. The entire IRt displays TH-LI cell bodies and fibers, and thus it is readily distinguishable from the neighbouring gigantocellular and parvicellular reticular nuclei. In contrast, SP-LI cells are restricted to the external part of the IRt that is found in the open medulla, while SP-LI fibers are more widely distributed. The IRt displays TH-LI neurons which are fusiform, oval, and round in shape. The SP-LI neurons of the IRt are primarily oval and fusiform. In preparations stained for Nissl substance, IRt cells were classified as pigmented and nonpigmented. A characteristic feature of the IRt is that its cells are larger (20 +/- 4 micrograms) than those of the laterally adjoining parvicellular (12 +/- 2 micrograms) and clearly smaller than those of the medially adjoining gigantocellular nuclei (33 +/- 6 micrograms). The shape of the IRt is in keeping with the radial organization of the medulla with zones emanating from the fourth ventricle. Three-dimensional computer reconstructions of the cell plots show that 1) TH-LI neurons extend through the entire IRt and densely packed in the rostral part of the ventrolateral IRt and 2) SP-LI neurons are found only in the rostral half of the medulla oblongata.

Intracellular transport of proinsulin in pancreatic beta-cells. Structural maturation probed by disulfide accessibility

In pancreatic islets, formation of beta-secretory granule cores involves early proinsulin homohexamerization and subsequent insulin condensation. We examined proinsulin conformational maturation by monitoring accessibility of protein disulfide bonds. Proinsulin disulfides are intact immediately upon synthesis, but are > or = 90% sensitive to in vivo reduction with 2 mM dithiothreitol; wash out of dithiothreitol leads to reoxidation, proinsulin transport, and conversion to insulin. With t1/2 approximately 10 min, newly synthesized proinsulin becomes resistant to disulfide reduction, correlating with endoplasmic reticulum (ER) export. However, inhibition of ER export with brefeldin A blocks acquisition of resistance to reduction, and once proinsulin arrives in the Golgi, it resists reduction despite brefeldin treatment. Moreover, in vivo, resistance of proinsulin disulfides is overcome after increasing [dithiothreitol] > 10-fold, or in vitro, in islets lysed in a zinc-free, but not a zinc-containing, medium. Employing 30 mM dithiothreitol in vivo, a further decrease in disulfide accessibility is observed following proinsulin conversion to insulin. Incubation of islets with chloroquine or zinc enhances and diminishes accessibility of insulin disulfides, respectively. We hypothesize that two major conformational changes culminating in granule core formation, proinsulin hexamerization and insulin condensation, are sensitive to zinc and occur upon ER exit and arrival in immature secretory granules, respectively.

Comparative distribution of receptors for amylin and the related peptides calcitonin gene related peptide and calcitonin in rat and monkey brain

The distribution of amylin receptors (125I-labelled rat amylin) in brains of rat and monkey were mapped and compared with the distribution of receptors for calcitonin (CT) (125I-labelled salmon CT) and calcitonin gene related peptide (CGRP) (rat, 125I-labelled rat CGRP alpha; monkey, 125I-labelled human CGRP alpha. In rat, amylin receptors were discretely distributed with the highest receptor densities found in mid-caudal accumbens nucleus, parts of the bed nucleus of the stria terminalis, amygdala, and hypothalamus. Moderate to high densities of binding also occurred in the area postrema, subfornical organ, vascular organ of the lamina terminalis, locus ceruleus, dorsal raphe, and caudal solitary tract nucleus. In monkey, the distribution of amylin binding sites was similar, although the highest densities of receptors were in the hypothalamus, with relatively fewer sites present in the accumbens nucleus. In rat, the distribution of amylin receptors formed a subset of the receptor distributions for 125I-labelled salmon CT and 125I-labelled rat CGRP alpha. In contrast, in monkey, although the amylin receptors again formed a subset of the binding sites identified with 125I-labelled salmon CT, there was very little overlap with the pattern of CGRP receptor distribution. This suggests that the specificity profile of amylin receptors in primates differs from that of amylin receptors in the rat, with CGRP alpha having relatively lower affinity for the primate amylin receptors.

Two Lactococcus lactis genes, including lacX, cooperate to trigger an SOS response in a recA-negative background

A 4.3-kb EcoRI fragment from a Lactococcus lactis genomic library alleviates the methyl methanesulfonate, mitomycin C, and UV sensitivities of an Escherichia coli recA mutant (M. Novel, X. F. Huang, and G. Novel, FEMS Microbiol. Lett. 72:309-314, 1990). It complements recA1 and delta recA mutations but not recA13. Three proteins (with molecular masses of 20, 35, and 23 kDa) were produced from this fragment in a T7-directed system, and three corresponding genes were detected by DNA sequencing, namely, ISS1CH;lacX, which is the distal gene of the lac operon; and a third open reading frame, named lacN, which encodes 211 amino acids. Mutations produced in either lacX or in lacN resulted in the loss of the resistance to DNA-damaging agents. Thus, these two genes appeared to be involved in this activity. Introduction of pUCB214 carrying the 4.3-kb fragment into a lexA+ delta recA306 sfiA::lacZ strain resulted in UV-inducible synthesis of beta-galactosidase. A uvrA strain or a lexA (Ind-) strain containing pUCB214 did not support any DNA repair. However, a lexA (Def-) strain carrying pUCB214 could partly repair UV damage. We discuss possible targets for LacX and LacN products, and we speculate that LacX and LacN may constitute a two-component regulatory system that is able to respond to SOS signals, and then to act in the SOS response, bypassing the RecA-activated function.