Metallothionein I+II expression as an early sign of chronic relapsing experimental autoimmune encephalomyelitis in rats

Metallothioneins (MTs) are small, cysteine-rich proteins which have been implicated in various forms of stress providing cytoprotective action against oxidative injury, DNA damage and apoptosis. Owing to their high affinity for physiological metals, such as zinc and copper MTs are also critical components of regulatory proteins involved in cell growth and multiplication, as well as in the maintenance of immune homeostasis. To elucidate the role of MTs in the pathomechanisms of autoimmune CNS disorders we estimated the expression of MT I+II proteins and the content of free Zn ions in the brain, spinal cord and in the liver early in the course of chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE) pathogenesis, i.e. before the onset of any clinical symptoms. Disease was induced in the genetically susceptible Dark Agouti (DA) rats by subcutaneous injection of bovine brain homogenate in CFA. Control animals were treated with CFA alone. The data, obtained by immuno-histochemistry and in situ fluorescent labeling of free zinc ions, have shown that in the presymptomatic phase of CR-EAE (on the seventh postimmunization day) MTs I+II were markedly upregulated in the cells that form blood-brain and blood-cerebrospinal fluid barriers, as well as in the cerebellar parenchyma and hippocampal dentate gyri. Furthermore, we found that the liver also becomes a site of extensive MTs I+II synthesis shortly after immunization. Simultaneously, tissue content of free zinc ions increased at the sites of MTs induction, reflecting their antioxidative activity. The data, described in this paper point to regulatory and neuroprotective role of MTs in the pathogenesis of CR-EAE.

Metallothioneins and trace elements dyshomeostasis induced by exposure to gasoline vapor in mice

To investigate the effects of air pollution related with the gasoline/petrochemical industry the expression of metallothionein I (MT-I) mRNA and tissue metals were analyzed in organs of mice, exposed to gasoline (G) vapor in laboratory conditions. Control groups consisted of intact mice and of those exposed in the metabolic chamber to fresh air. The data obtained by RT-PCR and inductively coupled plasma spectrometry have shown that exposure to G vapor leads to upregulation of MT-I mRNA in organs that receive a strong respiratory and olfactory input or participate in gasoline degradation and elimination (lungs, brain, kidney and liver). Besides, in the brain and in the lungs, kidney and liver a decreased tissue content of Zn²⁺ or Cu²⁺ and Mg²⁺ was found (p<0.001). Some of these changes were obtained also in mice closed in the metabolic chamber, pointing to the involvement of stress-induced mechanisms in the transcriptional regulation of MTs.

Metallothioneins I/II expression in rat strains with genetically different susceptibility to experimental autoimmune encephalomyelitis

OBJECTIVES

Compared to the Dark Agouti (DA), the Albino Oxford (AO) rat strain exhibits lower susceptibility to the induction of experimental autoimmune encephalomyelitis (EAE). Here, we investigated the potential contribution of the heavy metal-binding proteins metallothioneins (MTs) I/II to these effects.

METHODS

Rats were immunized with bovine brain homogenate emulsified in complete Freund's adjuvant or only with complete Freund's adjuvant. The expression patterns of MTs mRNA and proteins and tissue concentrations of Zn2+ and Cu2+ were estimated in the brain and in the liver on days 7 and 12 after immunization, by real-time PCR, immunohistochemistry and inductively coupled plasma spectrometry, respectively. Additionally, the hepatic transforming growth factor beta and nuclear factor kappa B immunoreactivities were tested.

RESULTS

Clinical signs of EAE were not induced in AO rats, but they upregulated the expression of MT I/II proteins in the brain (hippocampus and cerebellum) and in the liver, similarly as DA rats. The transcriptional activation of MT-I occurred, however, only in DA rats, which accumulated also more zinc in the brain and in the liver. In contrast, intact AO rats had greater hepatic MT-I mRNA immunoreactivity and more Cu2+ in the hippocampus. Besides, in immunized AO rats a high upregulation of transforming growth factor beta and nuclear factor kappa B immunoreactivities was found in several hepatic structures (vascular endothelium, Kupffer cells and hepatocytes).

CONCLUSIONS

Our data show that AO and DA rats differ in constitutive and inductive MT-I gene expression in the brain and in the liver, as well as in the hepatic cytokine profile, suggesting that these mechanisms may contribute to the discrepancy in the susceptibility to EAE.

Effects of temperature on sorption-desorption processes of imidacloprid in soils of Croatian coastal regions

Sorption-desorption behavior of imidacloprid in six soils collected from five coastal regions in Croatia at 20, 30 and 40°C was investigated using batch equilibrium technique. Isothermal data were applied to Freundlich, Langmuir and Temkin equations, and the thermodynamic parameters ΔH°, ΔG°, ΔS° were calculated. The sorption isotherm curves were non-linear and may be classified as L-type, suggesting a relatively high sorption capacity for imidacloprid. Our results showed that the K( sor ) ( F ) values decreased for all the tested soils as the temperature increased, indicating that the temperature strongly influences the sorption. Values of ΔG° were negative (-4.65 to -2.00 kJ/mol) indicating that at all experimental temperatures the interactions of imidacloprid with soils were spontaneous processes. The negative and small ΔH° values (-19.79 to -8.89 kJ/mol) were in the range of weak forces, such as H-bonds, consistent with interactions and partitioning of the imidacloprid molecules into soil organic matter. The ΔS° values followed the range of -57.12 to -14.51 J/molK, suggesting that imidacloprid molecules lose entropy during transition from the solution phase to soil surface. It was found that imidacloprid desorption from soil was concentration and temperature-dependent, i.e. at lower imidacloprid concentrations and temperature, lower desorption percentage occurred. Desorption studies revealed that hysteretic behavior under different temperature treatments existed, and it was more pronounced at 20°C in the soils with higher OC content. The study results emphasize the importance of thermodynamic parameters in controlling soil pesticide mobility in different geographical locations, seasons and greenhouse conditions.

Kinetics of tissue iron in experimental autoimmune encephalomyelitis in rats

To elucidate the role of iron in the pathomechanisms of autoimmune CNS disorders, we estimated the tissue concentrations of Fe(2+) in the brain, spinal cord, and liver in the chronic relapsing form of experimental autoimmune encephalomyelitis (EAE). The disease was induced in Dark Agouti (DA) strain of rats, by subcutaneous injection of bovine brain homogenate in complete Freund's adjuvant (CFA). Control rats consisted of unsensitized rats and of rats treated with CFA or saline. The data obtained by clinical assessment and by inductively coupled plasma spectrometry have shown that the attacks of disease (on the 12th and 22nd post-immunization day) were followed by high accumulation of iron in the liver. Additionally, during the second attack of disease, the decreased concentration of Fe(2+) was found in cervical spinal cord. The data point to regulatory effects of iron and hepatic trace elements regulating mechanisms in the pathogenesis of EAE.

Time-course expression of metallothioneins and tissue metals in chronic relapsing form of experimental autoimmune encephalomyelitis

To elucidate the role of metallothioneins (MTs) in the pathomechanisms of autoimmune CNS disorders we estimated the expression of MTs I+II and the tissue concentrations of Zn²+ and Cu²+ in the brain, spinal cord (SC) and in the liver during the periods of attacks and remissions in chronic relapsing experimental autoimmune encephalomyelitis (CR-EAE). Disease was induced in the genetically susceptible Dark Agouti (DA) rats by subcutaneous injection of bovine brain homogenate in CFA. Control rats were treated with CFA. The data, obtained by clinical assessment, immunohistochemistry and inductivity coupled plasma spectrometry, have shown that during the first attack (on the 12th day) MTs I+II were markedly upregulated in subarachnoid regions and perivascular space on astrocytes, microglia and on spinal neurons. Simultaneously, the concentrations of zinc in the SC and zinc and copper in the liver have found to be increased. During the second attack (on the 22nd day) a new overexpression of MTs was found in the cerebellum, in sulcus hippocampi, in spinal neurons and particularly in hepatocytes around the central vein. Concomitantly, in the brain and SC the concentration of copper increased. The data point to a neuroprotective role of MTs and to an important regulatory role of essential metals and hepatic MTs in the pathogenesis of CR-EAE.

Effect of olive oil on brain's lipid and calcium content after partial hepatectomy in mice

The aim of this study was to investigate the influence of olive oil (00) enriched diet on the lipid content of mice brain during the early phase of liver regeneration and to test a relationship of these changes with calcium content. C57BI mice were fed over 21 days with diet enriched with olive oil, containing predominantly oleic acid (18:1n-9). The animals were one-third partially hepatectomised (pHx) under aether anaesthesia. Total lipids were extracted from tissue samples with a chloroform-methanol (2:1, v/v) mixture according to Folch et al. Mineral concentration was determined by inductively coupled plasma atomic emission spectroscopy (ICP-AES) after microwave brain tissue digestion. The diet containing 00 increased both total lipid content and the calcium concentration in brain during the early phase of liver regeneration (12hrs post pHx), suggesting that monounsaturated oleic acid might interact with some metal-dependent activities that control changes in the brain during liver regeneration.

Professor Eugen Cerkovnikov (1904-1985): the founder of the Chemical and Biochemical Institute of the Rijeka University School of Medicine

Professor Eugen Cerkovnikov, PhD (Kamenska, Russia, 1904- Rijeka, Croatia 1985) graduated in chemical technology from the Faculty of Engineering in Zagreb in 1929. His first job was at the School of Medicine in Paris in 1930, and then he moved to Zagreb to the Department of Organic Chemistry of the Faculty of Engineering run by our Nobel Prize winner Vladimir Prelog (1935-1938). There he took his PhD degree with a dissertation on piperidine gamma derivatives. From 1938 to 1947 he was a research associate at an institute established by the pharmaceutical company Kastel (later Pliva). This is when he became a lecturer at the Faculty of Pharmacy in Zagreb and the first director of the Institute of Organic Chemistry, established in 1946/47. In 1948 he became reader, and in 1956 (full) professor. In 1957 he moved to the newly established School of Medicine in Rijeka, and set up the Institute of Chemistry and Biochemistry. He ran the Institute until retirement in 1975. He was the second dean of the Rijeka University School of Medicine and a pioneer of quantum chemistry and medical cybernetics in undergraduate and (post)graduate courses. His scientific work consists of over 200 papers published at home and abroad, 60 professional papers, 20 book reviews, three works of translation, and 27 volumes of lecture notes. In 1958, professor Cerkovnikov established the Croatian Chemical Society and the Rijeka and Istria branches of the nation's Association of Chemists and Chemical Engineers, chairing them until 1974. In addition, he was one of the founding fathers, and the first chair of the Health Culture Studies Association in Rijeka (that preceded today's Croatian Scientific Society for the History of Health Culture), established in 1965.

Dose- and time-dependent effects of luteolin on liver metallothioneins and metals in carbon tetrachloride-induced hepatotoxicity in mice

The aim of this study was to investigate the protective effect of luteolin on liver Ca, Mg, Zn, Cu, Fe, and Mn content in mice with carbon tetrachloride (CCl4)-induced hepatotoxicity. Additionally, liver metallothionein (MT) expression was studied. Luteolin was administered intraperitoneally (i.p.) as a single 5- or 50-mg/kg dose or once daily for two consecutive days, respectively. Two hours after the last injection, the mice were treated with CCl4 (20 mg/kg, i.p.). CCl4 injection reduced hepatic level of all metals except Ca, with an intense cytoplasmic staining pattern in hepatocytes located in periportal areas, indicating induction of MTs. Pretreatment with 50 mg/kg of luteolin for 2 days remarkably elevated metal content to control values (Mg and Cu) or even above them (Zn and Fe). Luteolin pretreatment increased pericentral MTs immunopositivity and histological architecture improvement in a time- and dose-dependent manner, being the most prominent in mice pretreated with 50 mg/kg for 2 days. The liver in this group showed pronounced MT expression in almost all hepatocytes throughout the liver parenchyma. In conclusion, these results suggest the protective effect of luteolin on CCl4-induced hepatotoxicity and an enhancement of hepatocyte proliferative capabilities.

Oxidative stress in mice: effects of dietary corn oil and iron

The aim of this study was to analyze the effect of high dietary Fe on liver antioxidant status in mice fed a corn-oil-enriched diet. Male Balb/c mice were fed for 3 wk with a standard diet enriched with 5% by weight of corn oil with adequate Fe (FCO diet) or supplemented with 1% carbonyl Fe (FCOFe diet). The control group was fed a standard diet. The high-Fe diet induced a twofold increase of hepatic Fe level. However, an increase of thymic Fe level has been induced solely by dietary fat. The hepatic copper (Cu) level slightly decreased in the FCO diet. In the spleen, the high-Fe diet-induced increase of Fe level was negatively correlated with the Cu level. The antioxidant status was influenced by both dietary fat and Fe. Mice fed corn-oil-enriched diets had a higher concentration of thiobarbituric acid-reactive substances (TBARS), with a greater increase in the FCOFe diet. Fatty acid analysis showed decreased n-3 and n-6/n-3 ratio, particularly in the FCOFe diet. Hepatic Cu/Zn superoxide dismutase (CuZn-SOD) activity was decreased in FCO diet, and Fe supplementation caused a further decrease in the enzyme activity. These results suggest that feeding with corn oil-enriched diet increases oxidative damage by decreasing antioxidant enzyme defense. The high-Fe diet additionally affects the antioxidant defense system, further increasing the tissue's susceptibility to lipid peroxidation. Additionally, both corn-oil- and Fe-enriched diets have increased the Cu requirement in mice.

Metallothionein expression and tissue metal kinetics after partial hepatectomy in mice

To better elucidate previous results showing that partial hepatectomy noticeably changes the tissue content of zinc, calcium, magnesium, and iron(II) ions in regenerating the liver, thymus, and spleen, we report on the correlation of these metal tissue kinetics in these organs with the expression of metallothionein-I+II (MT-I+II) proteins and MT-I mRNA in early postoperative period (1, 2, 6, 12, and 24 h) after one-third hepatectomy (pHx). The results showed that 2 h after pHx the regenerating liver accumulated Zn2+, Ca2+, Mg2+, and Fe2+ ions while decreasing the concentration of all these metals in the spleen and of Zn2+ in the thymus. On the 24th h, a new high accumulation of Zn2+ and Ca2+ was seen in the regenerating liver and of Zn2+, Ca2+, and Fe2+ in the spleen. Simultaneously, MT-I mRNA increased in the liver and spleen. In hepatocytes and on several spleen and thymus mononuclear lymphatic cells, the increased expression of MT proteins was found mainly in the cytoplasm and nuclei. The areas expressing MTs in regenerating liver inversely correlated with those containing apoptotic cells, suggesting that these proteins participate in tissue restoration through reduction or increase of metal ions after injury to the liver.

Liver fatty acid and element changes after partial hepatectomy in mice fed olive oil- and corn oil-enriched diets

The purpose of this study was to explore the effect of dietary fats on the hepatic fatty acid profile of mice liver after partial hepatectomy and to observe a correlation with changes in element content. Male Balb/C mice were divided into three groups: the control animals fed a standard diet (FSD), the FOO group fed a diet enriched with 5% olive oil, and the FCO group fed a diet enriched with 5% corn oil. Hepatic fatty acid and element content were analyzed within each group in intact animals and on d 1, 2, and 7 after partial hepatectomy. During the regenerative process, proportions of 18:1n-9 and 18:3n-6 substantially increased in the FSD diet, correlating with the Zn level. On the other hand, 20:4n-6 and 22:6n-3 decreased on d 1 and 2. Consequently, a significant increase in the n-6: n-3 ratio was found in these animals. In the FOO diet, a decreased polyunsaturated fatty acid/monounsaturated fatty acid (PUFA/MUFA) ratio was related to a significant decrease in PUFA content, mainly the result of decreased 20:3n-6 and 20:4n-6. The proportion of 18:1n-9 was highly increased when compared with other diets and remained high during the regeneration. Furthermore, the n-6: n-3 ratio was increased on d 2 and 7. Zn increased on d 1 and 2, and Fe increased on d 2. Feeding with corn oil generally induced an increase in the PUFA n-6 series, compared with other diets. The PUFA n-3 series decreased and the 18:1n-9 increased on d 1, compared to intact animals. Consequently, the n-6: n-3 ratio was elevated during the regeneration. Zn increased on d 1 and 2, whereas Fe remained unchanged until d 7, when it decreased. Decreased 20:4n-6 on d 1 and 2, as well as Cu on d 7, and increased Zn in the first 2 d were common to all three diets. These findings suggest that some significant signals transmitted during the regenerative process have induced alterations in the fatty acid composition and changes in the liver element content, which can be modified by the diet.

Effect of indomethacin on motor activity and spinal cord free fatty acid content after experimental spinal cord injury in rabbits

STUDY DESIGN

Determination of functional and biochemical parameters as well as the effect of specific therapies on these parameters, in the experimental model of neurotrauma in rabbits.

OBJECTIVE

To assess the effect of indomethacin (0.1-3.0 mg/kg for 9 days), a potent inhibitor of endogenous prostaglandin synthesis, on the motor activity and on the spinal cord tissue concentration of free palmitic, stearic, oleic, arachidonic and docosahexaenoic acids in an experimental model of a spinal cord injury in rabbits.

SETTING

Faculty of Medicine, University of Rijeka, Croatia.

METHODS

The animals were randomly divided into nine experimental groups, four sham and/or vehicle-treated and five indomethacin-treated (including one sham-operated and four injured groups). Laminectomy was followed by contusion of the spinal cord, using a modification of the technique of Albin. Motor activity was controlled daily during the course of the next nine postoperation days and scored using Tarlov's system. Spinal cord samples from the impact injury site were taken and frozen in liquid nitrogen. Total lipids were isolated and purified by a modification of the method of Folch. Free fatty acids (FFAs) were separated from the total lipid extract by preparative thin-layer chromatography, converted to the corresponding methyl esters and identified using gas chromatography, using nonadecanoic acid as the internal standard.

RESULTS

The concentrations of all analysed free fatty acids were increased in the spinal cord after neurotrauma, in comparison to control tissues. Treatment of injured rabbits with indomethacin resulted in a significant decrease in spinal cord FFAs and exerted a positive effect on neurotrauma-induced motor impairment.

CONCLUSION

These results indicate a mechanism whereby indomethacin protects rabbits from the sequellae of neuronal damage caused by trauma, and suggests that it may be beneficial in the therapy of neurotrauma.

SPONSORSHIP

This work was supported by the Croatian Ministry of Science and Technology (project 062019).

Metal tissue kinetics in regenerating liver, thymus, spleen, and submandibular gland after partial hepatectomy in mice

Liver regeneration after partial hepatectomy (pHx) is a well-defined process, which involves the concerted action of extra- and intracellular factors resulting in induction of cell replication and its inhibition at the time when the entire liver mass is restored. Concomitantly, the breakdown of previously maintained tolerance and the exposure of self-antigens lead to the activation of preimmune and immune repertoires, which participate in surveillance against aberrant cells and the re-establishment of previous morphostasis. Because, in these events, important biological function might have tissue minerals that are affecting the structural integrity and enzyme activities, transduction signals, transcription and replication factors during cell proliferation and apoptosis, as well as the development and maintenance of immune functions and cytokine production, in this study we analyzed tissue dynamics of zinc, iron, magnesium, and calcium in the liver, thymus, spleen, and submandibular gland in intact and pHx mice on the 1st, 2nd, 7th, and 15th d after one-third pHx, using microwave digestion and inductivity coupled plasma spectrometry. The data showed that pHx induces significant and interconnected changes in all of the estimated metals not only in the regenerating liver but also in the lymphatic tissues and submandibular gland, indicating their importance for the control of growth processes.

Gas chromatographic determination of fatty acids contained in different lipid classes after their separation by solid-phase extraction

A quick and successful procedure is presented for the separation of polar lipids, monoacylglycerols (MAGs), diacylglycerols and triacylglycerols (TAGs) and for fatty acid determination in the above-mentioned lipid fractions by gas chromatographic analysis, which was acceptable for physiological and nutrition studies. In the analysis of edible oils and biological tissue samples, lipid classes were separated and purified by solid-phase extraction (SPE) using an aminopropylsilica column. Fatty acids in the sn-2 position in edible oil TAGs were determined after previous 1,3-specific lipase hydrolysis and separation of 2-MAGs by SPE using an aminopropylsilica column. A preliminary study of the solid-phase extraction separation of lipid classes with stock standard solutions using styrene-divinylbenzene-methacrylate copolymer (Nexus), octadecylsilica (C18) and aminopropylsilica (NH2) was carried out and it was shown that NH2 was the best sorbent for the above-mentioned purpose.

Physico-chemical characteristics of olives and olive oil from two mono-cultivars during various ripening phases

The aim of this study was to find a correlation between the chemical and physical parameters in the pulp of the olive, in order to identify the optimum period during the 1998 harvesting period. For this reason various parameters have been monitored: the amount of oil in the pulp during the ripening phase obtained by solvent extraction with n-hexane, the acidity, the peroxide value, the composition of fatty acids and the saturated/unsaturated fatty acid ratio, the composition of the unsaponifiable fraction, the antioxidant capacity, the percentage of oil and the puncture test in two local Croatian olive cultivars. The chemical parameters change during the ripening, in order to control the oxidative changes of the cellular homeostasis of the whole lipophilic fraction that needs a stronger safeguard of the double bonds against the oxidative stress. The modification of the physical characteristics, observed with the puncture test, is related to the chemical changes which occur in the olive during the ripening period and the monitoring of these physical and chemical parameters can help to increase nutritional quality (as antioxidant capacity) and allow for an acceptable amount of oil.

Effect of olive oil- and corn oil-enriched diets on the tissue mineral content in mice

The mineral content (zinc, iron, magnesium, and calcium) in the liver, spleen, and thymus of male Balb/C mice was analyzed. Animals were fed, over 21 d, diets enriched with corn oil (FCO diet) or olive oil (FOO diet) (5% addition to standard pellet, w/w). Olive oil with predominant oleic acid (C18:1, n-9) had a quite different composition than corn oil, in which linoleic acid (C18:2, n-6) prevails. The zinc and magnesium tissue concentrations were not changed in either group. The calcium concentration in liver as well as the calcium concentration in spleen increased in mice fed both the FCO and FOO diets. Furthermore, mice fed both the FOO and FCO diets had increased spleen iron concentration. Mice fed the FCO diet had increased thymus calcium concentration compared to controls. The results show the effect of diets with unsaturated, particularly polyunsaturated fatty acids, on the calcium and iron concentration in some organs.

Effect of growth phase on the content and composition of ceramides of the hydrocarbon-assimilating yeast Candida lipolytica

Candida lipolytica yeast was grown batchwise on n-hexadecane as the carbon and energy source. Ceramides were quantitatively isolated from total lipids of exponential and stationary phase cells by a combination of column chromatography and preparative high-performance thin-layer chromatography. After acid methanolysis their composition was analyzed by gas-liquid chromatography. The ceramide content of the exponential phase cells was two times higher than the one of the stationary phase cells. The composition of long-chain base moiety of ceramides did not change significantly during the growth. In both growth phases 19-phytosphingosine was the major long-chain base. However, the fatty acid composition of ceramides changed greatly during the growth. In the exponential growth phase, ceramides contained predominantly fatty acids greater than 20 carbon atoms, while fatty acids shorter than 20 atoms predominated in ceramides of the stationary phase, 16:0 being the main one. In the exponential growth phase fatty acid moiety of ceramides was characterized by unusually high degree of unsaturation and relatively high proportion of odd-numbered fatty acids. However, the proportion of both, unsaturated and odd-numbered fatty acid decreased significantly in ceramides of the stationary phase. The unexpected finding was the absence of fatty acid hydroxylation of ceramides in the exponential phase cells and unusually low degree of hydroxylation in the stationary phase.

Tissue zinc dynamics during the immune reaction in mice

Owing to the importance of zinc for the functioning of the immune system, the role of endogenous Zn, located both in lymphoid and nonlymphoid organs, was investigated during the standard humoral and cellular types of immune response. For this purpose, the dynamics of hepatic, thymic, splenic, and renal Zn content was determined in mice sensitized with (a) sheep red blood cells and (b) semiallogeneic lymphocytes during the local host vs graft reaction (HVGR). The data obtained by ion-coupled plasma spectrometry revealed that the humoral type of immunity is characterized by a significant increase of Zn concentration in the liver and in the thymus. Simultaneously, linear regression analysis showed that the generation of plaque-forming cells in the individual mouse was highly positively correlated with Zn concentration in the liver (r=0.897), and spleen (r=0.833), and negatively with Zn concentration in the thymus (r=-0.624). Similar relationships between the intensity of local immune reaction and tissue Zn levels were found in local HVGR at the fifth day in the liver and spleen (r=0.861 and r=0.695, respectively), at the seventh day in the thymus (r=-0.797), and at the tenth day in the liver (r=-0.859). The data emphasize the necessity of Zn for the development of normal immune response and point to the existence of a Zn-dependent hepato-thymic axis during the humoral and cellular types of immune reactivity.

Zinc and metallothioneins on cellular immune effectiveness during liver regeneration in young and old mice

Partial hepatectomy in young mice (pHx) induces thymic atrophy, disregulation of thymocytes subsets and a strong accumulation of zinc in thymic tissue after 1-2 days of liver regeneration. Zinc is relevant for good immune functioning. Restoration of zinc into both the thymus and thymocytes subsets in the late period of liver regeneration is observed in young pHx mice. These findings have suggested a link between the thymus and the liver influencing T-cell functions and involving zinc. This kind of link could be relevant in aging because thymic involution, negative crude zinc balance and crippled immune functions are constant events. The preminence of a liver extrathymic T-cell pathway after pHx or during aging has been suggested. Thus the study of pHx in young and old mice may offer a good model to better understand the role played both by thymic involution and by liver extrathymic T-cell pathway and the role of zinc in these physiological processes during aging. Young pHx mice after 1-2 days of liver regeneration show: reduced thymic endocrine activity, increment of double negative (DN) thymocytes subsets, impairment of peripheral immune efficiency (PHA, NK activity and IL-2) and negative crude zinc balance, which are all restored in the late period of liver regeneration. By contrast the thymic and peripheral immune defects and the negative crude zinc balance, already present in old sham mice, are not modified during liver regeneration in old pHx mice. Circulating leukocytes and lymphocytes are not significantly modified both in young and old pHx mice as compared to respective sham controls. Zinc may also be crucial for extrathymic T-cells pathway, being preminent in aging, rather than in young age, due to its metallothioneins (MT) binding capacity. MT are significantly increased in young pHx and in aging inducing a low zinc-free quota for thymic and peripheral immune efficiency in young pHx mice, and for extrathymic T-cell pathway, in old age. Thus low zinc bioavailability, due to MT, may play a pivotal role, not only for thymocytes but also for liver extrathymic T-cell pathway.

Determination of standard zinc values in the intact tissues of mice by ICP spectrometry

The most commonly encountered difficulties for the quantitative measurement of zinc in biological samples are the limited sample amount, total and effective digestion of connective and fatty residues, and low zinc concentrations. These problems often lead to the determination of lower zinc values than actually present, so that the sample preparation, digestion, and analytical procedure deserve careful attention. In this short communication, a new method for microwave tissue disintegration is described. The authors have obtained consistent and reproducible results with tissue samples of 0.5 g or less.

Immunoregulating effects of peptidoglycan monomer linked with zinc in adult mice

Since it is well known that both zinc ions and bacterial immunostimulants influence the function of the immune system, in the present study we investigated the immunomodulating activity of a new analog of peptidoglycan monomer (PGM), in which the basic molecule was linked to zinc (PGM-Zn). Its effects in BALB/c mice, aged 10-12 months, were compared with the effects of equimolar doses of PGM and ZnCl2. The treatment lasted 26 days (one i.p. injection every fifth day). The results showed that PGM-Zn may markedly enhance antibody production to sheep red blood cells, as well as spontaneous and concanavalin A (ConA)-induced blastogenesis. The generation of plaque-forming cells in individual mouse was positively correlated with the expression of class II antigens in the liver and negatively correlated with the total quantity of hepatic proteins. PGM-Zn also induced the appearance of peritoneal macrophages, which in cocultures with syngeneic splenocytes were less able to enhance the spontaneous, and particularly the ConA-induced blastic transformation. The enhancing activities of PGM-Zn were in some respects more closely correlated with the action of PGM, whereas the induction of suppressive macrophages resembled more the activity of ZnCl2. The data emphasize that PGM-Zn may both stimulate and inhibit immunoregulative pathways by mechanisms which are not identical to those of PGM or ZnCl2.

Somatostatin promotes accumulation of phospholipids in regenerating liver tissue of rats

Effects of somatostatin (SOM) on tissue contents of proteins, total lipids and phospholipids were investigated in regenerating and intact liver tissue of Y-59 rats. Whereas SOM inhibited protein accumulation in regenerating liver, the hormone evoked an increase in total lipids, and specially in phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine (PS) and phosphatidylinositol (PI). Since the same effects were not seen when intact liver was analyzed, it is assumed that SOM acts primarily on tissue stimulated to rapid growth. The increase of PS + PI fractions indicates a specific effect of SOM on the metabolism of phosphatidylinositides. Such an effect might result from the interference of the hormone with the action of growth factors that accelerate phosphatidylinositol breakdown.