Proteolytic activity of opossum tooth extracts

Amelogenins are the main component of the developing enamel matrix. In placental mammals, amelogenins are rapidly cleaved following their secretion. HPLC fractionation of tooth extracts produces a complex chromatographic profile. The fractions are rich in amelogenin cleavage products that generally retain the amino-terminus of the parent protein but have varying lengths of peptide removed from the original carboxyl-terminus. In contrast, HPLC fractionation of opossum tooth extracts produces a simple profile with a single major chromatographic peak. SDS-and Western blot analyses demonstrated that most of the amelogenin consisted of a prominent protein band that migrated at 28 kDa. Mass spectroscopy confirmed the presence of two uncleaved, alternatively spliced forms of opossum amelogenin, Op202 and Op57, but did not detect major amelogenin cleavage products evident in tooth extracts from placental mammals. Amino acid composition analysis supported the conclusion that uncleaved amelogenin is the major component in the developing enamel matrix. Enzymogram analyses using gelatin, casein and recombinant amelogenin as substrates, comparing porcine, rat and opossum tooth extracts, suggested that fewer proteinases are present in opossum. These results identify potentially significant differences in the proteolytic processing of amelogenins between metatherian and eutherian mammals.

Derived protein and cDNA sequences of hamster amelogenin

Hamster enamel protein extracts were analyzed by RP-HPLC and the isolated fractions by SDS-and Western blotting using polyclonal antibodies against recombinant mouse amelogenin and anti-peptide antibodies against the mouse exon 4-encoded sequence. Total RNA was extracted from enamel organ epithelia and, using a 3' rapid amplification of cDNA ends (3' RACE) technique, the coding regions for three different amelogenin isoforms were cloned along with the 3' non-coding region. DNA sequencing revealed that the hamster amelogenin isoforms are 180, 73 and 59 amino acids in length, respectively. The 59-residue amelogenin corresponds to the leucine-rich amelogenin protein (LRAP), the 73-residue amelogenin corresponds to LRAP with the inclusion of the exon 4-encoded sequence, while the 180-residue amelogenin is the most abundant amelogenin isoform. Edman degradation was performed on purified hamster amelogenin, which provided the amino acid sequence in the region encoded by the 5' PCR amplification primer used in cloning. Therefore, the entire derived amino acid sequence of hamster amelogenin was revealed. The hamster amelogenin amino acid sequence was aligned with all its known homologues. Hamster differs from rat and mouse amelogenin at only three amino acid positions. Southern blot analysis using a panel of restriction enzymes gave the same pattern for hamster DNA obtained from males and females, suggesting that in hamster, as in mouse, amelogenin is expressed from a single gene located on the X chromosome.

[The effect of antisense human Fas RNA on activation induced apoptosis of T cell]

OBJECTIVE

To explore an approach to the reduction of activation induced apoptosis of T cell so as to maximize the number of CTL and enhance the tumor cytotoxicity.

METHODS

CD3-induced Jurkat cell line was used as the activated T cell apoptosis model,and the antisense Fas cDNA was introduced into Jurkat cells with retroviral vector.

RESULTS

The expression level of Fas protein in Jurkat cells transducted with the retroviral vector was decreased. Apoptosis was reduced in antisense Fas-transfected Jurkat cells after anti-CD3 or anti-Fas treatment.

CONCLUSION

Antisense blocking of Fas expression can partially inhibit Jurkat cell apoptosis induced by anti-CD3 or anti Fas.

Structural alterations far from the anticodon of the tRNAProGGG of Salmonella typhimurium induce +1 frameshifting at the peptidyl-site

A total of 12 Salmonella typhimurium mutants were selected with mutations in the minor tRNAProGGG which suppress a +1 frameshift mutation in the hisD gene. This tRNA normally has 1-methylguanosine (m1G37) next to and 3' of the anticodon (position 37). Since the presence of m1G37 prevents frameshifting, some of the +1 frameshift suppressor derivatives of tRNAProGGG had alterations in the primary sequence abolishing the formation of m1G37. However, several of the mutant tRNAProGGG species had a normal level of m1G37 and a normal-sized anticodon loop, showing that neither m1G37 deficiency, nor an oversized anticodon loop, is a prerequisite for +1 frameshifting. Moreover, base substitutions far from the anticodon, e.g. in the acceptor stem, DHU-loop and stem, and at the top of the anticodon stem, promoted +1 frameshifting. When the frameshifting site (CCC-Uaa; CCC is in the zero frame and a +1 frameshift moves the ribosome to the CC-U codon) is overlapped by a nonsense codon (UAA), the efficiency of frameshifting decreased when release factor 1 was over-expressed and increased at an elevated temperature in a mutant with a temperature-sensitive release factor 1. The frameshifting site (CCC-Uac) was also overlapped with the sense codon UAC, which is decoded by a tRNA species having a 2-methylthio-cis ribozeatin (ms2io6A) at position 37. Mutations in the miaA gene affect the formation of this modified nucleoside and result in an A instead of ms2io6A37 in the tRNA. Such an undermodified tRNA is very inefficient in translation and the efficiency of frameshifting increased in a miaA1 mutant. These results suggest that the frameshifting event occurs at the P-site, since the efficiency of frameshifting was sensitive to the decoding activity of the overlapping codon. We conclude that tRNA with mutations far from the anticodon, with a normal-sized anticodon loop and having m1G37 induce +1 frameshifting at the P-site.

Cloning and characterization of porcine enamelin mRNAs

Dental enamel forms by matrix-mediated biomineralization. The components of the developing enamel matrix are generally specific for that matrix. The primary structures of three enamel proteins-amelogenin, tuftelin, and sheathlin (ameloblastin/amelin)-have been derived from cDNA sequences. Here we report the cloning and characterization of mRNA encoding a fourth enamel protein: enamelin. The longest porcine enamelin cDNA clone has 3907 nucleotides, exclusive of the poly(A) tail. The primary structure of the secreted protein is 1104 amino acids in length. Without post-translational modifications, the secreted protein has an isotope-averaged molecular mass of 124.3 kDa and an isoelectric point of 6.5. Polymerase chain-reaction phenotyping of enamelin cDNA suggests that porcine enamelin transcripts are not alternatively spliced and use a single polyadenylation/cleavage site. Immunohistochemical and Western blot analyses with an affinity-purified antipeptide antibody specific for the enamelin carboxyl terminus demonstrate that enamelin is synthesized and secreted by secretory-phase ameloblasts. The parent protein is a 186-kDa glycoprotein that concentrates along the secretory face of the ameloblast Tomes' process. Intact enamelin and proteolytic cleavage products containing its carboxyl terminus are limited to the most superficial layer of the developing enamel matrix, while other enamelin cleavage products are observed in deeper enamel.

Gamma interferon is not essential in host defense against disseminated candidiasis in mice

In vitro studies have suggested a role for interferon gamma (IFN-gamma) in host defense against disseminated candidiasis, but in vivo studies are inconclusive. We utilized homozygous IFN-gamma knockout (GKO) mice to determine if the cytokine is essential in host defense against this disease. Genotypes of mice were determined by PCR with specific primers for the normal or disrupted IFN-gamma gene. The GKO status of the mice was confirmed by an enzyme-linked immunosorbent assay, which showed no detectable IFN-gamma produced by their splenocytes stimulated by concanavalin A. To test the susceptibility of GKO mice to candidiasis, the animals were infected either intravenously (i.v.) or intragastrically (i.g.) with Candida albicans. GKO mice infected i.v. survived as long as wild-type (WT) mice and showed no difference in Candida CFU counts in liver, spleen, or kidneys compared to those for WT mice. When animals were given Candida i.g., at 3 h or at 10 or 21 days after infection, there was no dissemination of Candida to the lung, liver, spleen, or kidneys for either GKO or WT mice. There was no difference in Candida CFU counts recovered from the stomach or intestines between GKO and WT mice. Histological examination of the stomach cardial-atrium fold, where the fungus was located, showed that GKO mice did not have evidence of more tissue damage or fungal invasion than WT mice. Finally, the jejunum for both types of mice showed no evidence of tissue damage or fungal invasion. These studies indicate that IFN-gamma is not essential in host defense against C. albicans that originates from a mucosal site or that is given directly into the bloodstream in a mouse model.

[In vitro reversal of homoharringtonine resistance by the combination of tamoxifen and verapamil]

OBJECTIVE

To investigate the reversal of homoharringtonine (HHT)-resistance by tamoxifen (TAM) or verapamil (VER) alone or in combination.

METHODS

The drug-sensitivity test was performed with semisolid agar culture.

RESULTS

The cytotoxicity of HHT to K562/S cells was not enhanced by TAM or VER alone or in combination,but HHT resistance in HHT resistant cells (K562/H20) was reversed by VER and TAM at nontoxic doses (4micromol/L or 8micromol/L). The IC50 of K562/H20 for HHT decreased from 446.8 +/- 0.08microg/L to 45.1 +/- 0.02microg/L in the presence of 4micromol/L of VER, to 22.4 +/- 0.03microg/L in 8micromol/L of VER, to 85.1 +/- 0.03microg/L in 4micromol/L of TAM and to 26.4 +/- 0.02microg/L in 8micromol/L of TAM. In the presence of combinations of 2micromol/L VER and 4micromol/L TAM and of 2micromol/L VER and 8micromol/L TAM, IC50 of K562/H20 decreased to 30.4 +/- 0.02microg/L and 4.3 +/- 0.04microg/L, respectively.

CONCLUSION

HHT-resistance could be reversed by VER or TAM alone, and the combination of the two drugs showed a synergistic effect.

Structural requirements for the formation of 1-methylguanosine in vivo in tRNA(Pro)GGG of Salmonella typhimurium

Maturation of tRNA and rRNA and the assembly of the ribosome in all organisms occurs in vivo in a complex pathway in which various proteins such as endo- and exonucleases, tRNA and rRNA modifying enzymes and ribosomal proteins, act concomitantly and temporarily during the maturation process. One class of RNA binding proteins are the tRNA modifying enzymes, which catalyse the formation of various modified nucleosides present in tRNA. Here we analyse the consequences of various alterations in a tRNA on the formation of modified nucleosides in the tRNA and the aminoacylation of it under true in vivo conditions, i.e. in a cell with normal amounts of the tRNA substrate and the tRNA binding protein. We have devised a selection method to obtain mutants of tRNA(Pro)GGG in Salmonella typhimurium that may no longer be a substrate inl vivo for the tRNA(m1G37)methyltransferase. These mutant tRNAs were purified from cells in balanced growth by a solid phase hybridisation technique and the presence of 1-methylguanosine (m1G) in position 37 next to the anticodon was monitored. Of 13 different mutant tRNA(Pro)GGG species analysed, eight of them had a drastically reduced level of m1G. Some of these mutant tRNA species had alterations far from the nucleotide G37 modified by the enzyme; e.g. base-pair disruptions in the first, fourth and eighth (last) base-pair of the acceptor stem, in the D-stem, and in the top of the anticodon stem. The structure of all the mutant tRNA(Pro)GGG species must deviate from the wild-type form, since they all induced +1 frameshifting. Still, tRNA(Pro)GGG from five of the mutants had normal levels of m1G. Thus, only a subset of mutations, all inducing an altered tRNA structure, resulted in m1G deficiency. However, those alterations in tRNA(Pro)GGG, which influenced the tRNA(m1G37)methyltransferase activity, did not affect in vivo the formation of four other modified nucleosides and the aminoacylation of tRNA(Pro)GGG, demonstrating the extreme dependence of the tRNA(m1G37)methyltransferase on an almost perfect three-dimensional structure of the tRNA. We discuss that the conformation of the anticodon loop may be a major determining element for the formation of m1G37 in vivo.

Determination of bromine and iodine in normal tissues from Beijing healthy adults

The contents of bromine and iodine in samples of heart, liver, spleen, lung, muscle, and hair from healthy adults living in Beijing, China, were determined using epithermal neutron activation analysis. The results indicate that the contents of bromine in lung and iodine in liver are higher than those in other tissues, except human hair. The bromine contents in Beijing human tissues are significantly lower than those in other countries. The contents of iodine are slightly lower than those in other countries, but the difference is not significant. Three biological standard reference materials were simultaneously determined with the samples, and our results agree well with the certified values.

Sheathlin: cloning, cDNA/polypeptide sequences, and immunolocalization of porcine enamel sheath proteins

Sheath proteins designate low-molecular-weight non-amelogenin enamel polypeptides and their parent protein, which concentrate in the sheath space separating rod and inter-rod enamel (Uchida et al., 1995). Two porcine sheath proteins, with apparent molecular weights of 13 and 15 kDa, are characterized by protein sequencing. The primary structures of these polypeptides match a portion of the derived amino acid sequences of clones isolated from a porcine enamel organ epithelia-specific cDNA library. Sheath protein RNA messages differ by the inclusion or deletion of a 45-nucleotide segment and by the use of three alternative polyadenylation/cleavage sites. The secreted proteins are 395 and 380 residues in length, with molecular masses of 42,358 and 40,279 Daltons and calculated isoelectric points of 6.3 and 6.7, respectively. Polyclonal antibodies were raised against a synthetic peptide having the sheathlin-specific sequence EHETQQYEYSGGC. Immunohistochemistry with this antibody demonstrates that the protein encoded by the sheathlin cDNA is preferentially localized in the sheath space. We propose that the porcine sheath proteins and their proteolytic cleavage products be designated "sheathlin".

Cloning, characterization, and heterologous expression of exon-4-containing amelogenin mRNAs

The formation of dental enamel is dependent upon amelogenins, a family of proteins constituting most of the developing enamel matrix. Depending upon the species, these enamel proteins are expressed from either one or two copies of the amelogenin gene. Each gene directs the synthesis of a variety of amelogenin isoforms through alternative splicing of their pre-mRNA transcript(s). Before the role of amelogenins in dental enamel formation can be better understood, one must know the isoforms that are secreted and their biochemical properties. Previously, we cloned and characterized 7 mouse amelogenin RNA messages generated by alternative splicing. The largest amelogenin cDNA encoded a 194-residue amelogenin isoform which was the only clone to contain the 42-nucleotide exon 4 segment. Anti-peptide antibodies raised against the derived translation of this exon revealed an unexpectedly diverse assortment of murine amelogenins, suggesting that additional splicing variants could contain the exon 4 coding region. Using exon-4-specific oligonucleotide primers, we have amplified, cloned, and characterized three different amelogenin RNA messages. These messages encode amelogenin polypeptides (exclusive of signal peptides) 194, 170, and 73 amino acids in length. The isotope-averaged molecular weights for the deduced, single-phosphorylated, proteins are 21,897.1, 19,113.9, and 8176.5 Daltons, respectively. Splice-site selection for the generation of these mRNAs was identical to that of the previously characterized messages for the M180, M156, and M59 except for the inclusion of exon 4. The exon-4-containing amelogenin isoforms were heterologously expressed in E. coli by means of the pET11 expression system (Novagen, Madison, WI).

The study of iodine in Chinese total diets

In this work, China was divided into four area groups according to their geographical positions and dietary habits. All foods were divided into 12 types and the iodine contents in various diets were determined using epithermal neutron activation analysis (NAA). The intakes for China were evaluated. The results indicate that the intakes of iodine in northern areas are slightly higher and in south areas lower than the lowest recommended intake, and the average intake in China is 166 micrograms/person per day, which is within the recommended range. In addition, one province were chosen from each area groups. The dietary intakes of iodine were investigated in different ages and sex using total mixed diet method. Our results indicate that the average iodine intake of four provinces was lower than the recommended value, which suggests that it is necessary to supplement iodine in foods in China.

Cloning, cDNA sequence, and alternative splicing of porcine amelogenin mRNAs

In mammals, the organic matrix of developing enamel is dominated by amelogenins. To investigate the expression of proteins secreted into the developing enamel matrix, we have constructed a porcine enamel organ epithelia-specific cDNA library. The amelogenin fraction of the cDNA library was characterized by the cloning of amelogenin-specific polymerase chain-reaction (PCR) amplification products, 5' and 3' rapid amplification of cDNA ends (RACE), and by helper phage rescue of unamplified clones. Clones were characterized that encode porcine amelogenin isoforms 173, 157, 56, 41, and 40 amino acids in length. The structure of the porcine amelogenin gene differs from that of any of those yet described. There are two homologous but distinct exons 1, 2, and 7. One of the two exon 7s can vary in length depending upon the selection of either of two polyadenylation signal/cleavage sites. As a rule, a given exon 1 always pairs with the same exon 2 but can be associated with either exon 7. Despite significant sequence divergence within these exons, no differences are observed in exons 3, 5, and 6. We interpret these findings as evidence of a single amelogenin gene expressed from two promoters; however, the results do not exclude the existence of a second amelogenin gene. The variability generated through the use of alternate promoters and exon 7s primarily affects the non-coding regions of the message. A given amelogenin isoform expressed from the two promoters displays four amino acid differences within the signal peptide, while the secreted proteins are identical. Similarly, the alternative use of exon 7 does not alter the structure of the protein products. The pattern of RNA splicing of amelogenin pre-mRNAs is different for the transcripts expressed from the two promoters. The 173- and the 56-residue amelogenins can be expressed from either promoter, while the 157-residue amelogenin is generated by only one of the two promoters.

Fluid resuscitation attenuates early cytokine mRNA expression after peritonitis

OBJECTIVE

To study the hypothesis that fluid resuscitation alters cytokine gene expression after experimental murine peritonitis.

MATERIALS AND METHODS

Mice underwent cecal ligation and puncture (CLP) to induce peritonitis and were randomized to receive variable amounts of normal saline (0, 0.25, 1.0 ml. subcutaneously) and serum (0 or 0.1 mL) after operation. Hepatic and small intestinal (ileal) tissue were harvested at 3 or 6 hours after CLP, and total tissue RNA was extracted. Reverse transcriptase polymerase chain reaction was used to provide relative quantitation of tumor necrosis factor-alpha and interleukin (IL)-1 beta messenger RNA (mRNA) compared with beta-actin.

RESULTS

CLP without resuscitation resulted in significant increases in hepatic tumor necrosis factor-alpha mRNA (1190% at 6 hours compared with normal animals), and IL-1 beta mRNA (1475%), and intestinal IL-1 beta mRNA (1243%). Volume administration attenuated cytokine expression at both 3 and 6 hours, and saline seemed to have more potent effects than serum. The volume of resuscitation correlated with survival at 18 hours. Survival in the saline (1 mL) + serum group was 90% at 18 hours compared with 20 to 40% in the groups with little or no resuscitation. Overall, there were no survivors at 30 hours.

CONCLUSIONS

Fluid resuscitation (amount, composition, timing) should be an important consideration in the utilization of experimental infection models. Furthermore, optimization of the patient's intravascular volume status during sepsis may have important effects on immune responses, in addition to improving hemodynamic variables.

Cloning, DNA sequence, and alternative splicing of opossum amelogenin mRNAs

The enamel layer that covers the surfaces of teeth is thickest and most highly mineralized in mammals. The durability of mammalian enamel may have allowed for selection against the lifelong replacement of teeth that is observed in other vertebrates. Variation in enamel structure among animals is thought to be the result of evolutionary changes in the constituents of the developing enamel matrix. In placental mammals, the principal component of this matrix is amelogenin. We have determined the complete primary structures of two opossum amelogenins through a combination of protein sequencing, cloning, and DNA sequencing. RNA messages were cloned that encode 202- and 57-residue amelogenins, which are presumed to be expressed from the same gene but differ due to alternative splicing of identical pre-mRNAs. Edman degradation of the larger amelogenin ran for 42 cycles and yielded the sequence: IPLPPHPGHPGYINFS YEVLTPLKWYQSMMRQQYPSYGYEPM. The derived 202-residue amelogenin, assuming that serine 16 is phosphorylated, has an isotope-averaged molecular mass of 23,023.75 Daltons and a pI of 6.2. This is the largest amelogenin yet characterized. The increase in length is due to the presence of a 30-residue tandem repeat of QP(I/M) in exon 6 in the same position as a similar, but shorter, repeat expressed from the bovine X-chromosome. The 57-residue amelogenin, which is known from other organisms as the leucine-rich amelogenin protein (LRAP), has an isotope-averaged molecular mass of 6764.75 Daltons and a pI of 5.5. The opossum enamel protein is highly homologous to those previously characterized in eutherians and demonstrates that amelogenins were refined structurally prior to the metatherian/eutherian divergence between 100 and 150 million years ago.

[Mechanisms of resistance to melphalan in leukemia cell line and reversal by interferon alpha]

OBJECTIVES

To study the mechanisms of resistance to alkylating agent melphalan (Mel) in leukemia cell and to investigate effect of modulation of resistance to Mel by IFN alpha.

METHODS

A Mel-resistant variant of the leukemic cell line (K562/Mel) was developed in vitro by continuous exposure to Mel. The level of expression of several resistance-related gene in K562/Mel and the effect of reversal of resistance to Mel by IFN alpha were observed.

RESULTS

K562/Mel was 8.0-fold resistant to Mel and also cross-resistant to nitrogen mustand and thiophosphoramide, but not to carmustine and doxorubicin. This enhanced Mel resistance was associated with increased level of GST alpha gene and total GST, but not with increased level of expression of GST pi, GST mu, MDR-1 and Top-II gene. IFN alpha, at 500 IU/ml, a noncytotoxic dosage significantly increased the cytotoxicity of Mel to K562/Mel. The reversal of Mel resistance is related to the decrease of the level of expression of GST alpha gene.

CONCLUSION

Resistance to Mel is associated with increased level of GST alpha gene and total GST in leukemic cell. IFN alpha can reverse Mel resistance.

[Detection of stromelysin mRNA expression in human hepatocellular carcinoma by in situ hybridization]

For the propose of detecting the significance of stromelysin (of matrix metalloproteinase family) mRNA expression in the invasion and metastasis process of liver cell carcinoma, 19 cases of human hepatocellular carcinoma (HCC) and their surrounding tissues were studied by in situ hybridization techniques. Nine cases of the HCC tissues were positive while all the tumor surrounding tissues were negative. The stromelysin expression levels were higher in those HCC complicated with portal tumor emboli or in those classified pathologically in II-IV degree. It is considered that portal cancer emboli is a characteristic event for intrahepatic and extrahepatic metastasis of HCC, and matrix metalloproteinase may be of importance for the tumor invasion and metastasis.

Human cytomegalovirus elevates levels of the cellular protein p53 in infected fibroblasts

Human cytomegalovirus (HCMV), like other DNA tumor viruses, induces morphological transformation of cells in vitro and stimulates host cell macromolecular synthesis in infected cells. Since other DNA tumor viruses, such as simian virus 40 and adenovirus, have previously been shown to interact with cellular protein p53, we investigated whether infection of cells by HCMV would modulate cellular p53 levels. Our results indicate that HCMV elevates cellular p53 levels on the order of 10- to 20-fold in infected fibroblasts. The induction of elevated p53 levels was dependent upon the presence of active virus and was prevented by neutralizing antibody. The induction of elevated p53 levels was determined not to be due to virus-receptor interactions or HCMV late events. The induction of elevated p53 levels commenced at immediate-early times of the HCMV multiplication cycle (6 h postinfection) and reached maximal levels by 24 h postinfection, before most of the HCMV DNA synthesis was initiated. HCMV immediate-early proteins were clearly shown to be responsible for elevating p53 levels in infected fibroblasts; expression of HCMV immediate-early region 1 and 2 proteins resulted in elevation of p53 levels in transfected human fibroblasts. This is the first report of increased p53 levels caused by HCMV in infected fibroblasts.

Elimination of mouse splenic macrophages correlates with increased susceptibility to experimental disseminated candidiasis

To evaluate the role of macrophages in experimental disseminated candidiasis, mouse splenic macrophages were eliminated by i.v. delivery of liposome-entrapped dichloromethylene diphosphonate (L-Cl2MDP). Splenic tissue sections that were immunoperoxidase-stained with mAbs against marginal zone macrophages (MONTS-4), red pulp macrophages (SK39), and neutrophils (SK208) showed that 3 days after L-Cl2MDP treatment, macrophages but not neutrophils were depleted, and circulating neutrophils responded normally to an irritated peritoneum and showed normal phagocytic ability. That is, in response to thioglycollate in the peritoneum, neutrophils migrated in normal numbers to the peritoneal cavity and expressed the normal activation phenotype of high Mac-1 and low Mel-14 Ag levels. These neutrophils also showed normal ability to ingest Candida albicans yeast cells in both in vitro and in vivo assays. However, the spleens from L-Cl2MDP-treated mice lost their ability to bind yeast, which agrees with our previous findings that yeast cells bind specifically to marginal zone macrophages. When macrophage-depleted were systemically challenged with C. albicans, clearance of viable fungal elements from blood was slower, their kidneys had higher recoverable CFU, and both BALB/cByJ and congenitally thymic-deficient (nude) mouse strains did not survive as long as control mice. Mice given L-Cl2MDP recovered most of their macrophage function by 56 days and became normal in their resistance to C. albicans. These results indicate that macrophages play an important role in host resistance to experimental disseminated candidiasis, but the mechanism does not appear to involve T cell functions.

Elimination of mouse splenic macrophages correlates with increased susceptibility to experimental disseminated candidiasis

To evaluate the role of macrophages in experimental disseminated candidiasis, mouse splenic macrophages were eliminated by i.v. delivery of liposome-entrapped dichloromethylene diphosphonate (L-Cl2MDP). Splenic tissue sections that were immunoperoxidase-stained with mAbs against marginal zone macrophages (MONTS-4), red pulp macrophages (SK39), and neutrophils (SK208) showed that 3 days after L-Cl2MDP treatment, macrophages but not neutrophils were depleted, and circulating neutrophils responded normally to an irritated peritoneum and showed normal phagocytic ability. That is, in response to thioglycollate in the peritoneum, neutrophils migrated in normal numbers to the peritoneal cavity and expressed the normal activation phenotype of high Mac-1 and low Mel-14 Ag levels. These neutrophils also showed normal ability to ingest Candida albicans yeast cells in both in vitro and in vivo assays. However, the spleens from L-Cl2MDP-treated mice lost their ability to bind yeast, which agrees with our previous findings that yeast cells bind specifically to marginal zone macrophages. When macrophage-depleted were systemically challenged with C. albicans, clearance of viable fungal elements from blood was slower, their kidneys had higher recoverable CFU, and both BALB/cByJ and congenitally thymic-deficient (nude) mouse strains did not survive as long as control mice. Mice given L-Cl2MDP recovered most of their macrophage function by 56 days and became normal in their resistance to C. albicans. These results indicate that macrophages play an important role in host resistance to experimental disseminated candidiasis, but the mechanism does not appear to involve T cell functions.

Total and methyl mercury levels in human scalp hairs of typical populations in China by NAA, GC(EC), and other techniques

The contents of total and methyl mercury in scalp hair samples of 1179 fishermen living in a typical Hg-polluted region in northeast China and 27 lying-in women and their newborns in Beijing have been determined by INAA, GC(EC), and other techniques. Only 18 of all fishermen had Hg contents above 5 micrograms/g, which indicates that the Hg pollution there has been substantially alleviated. The longitudinal Hg patterns of the lying-in women showed a gradually lowering tendency during pregnant period. Further, the Hg contents of the newborn babies generally were above or close to those of their mothers, confirming the mechanism that the methyl Hg, an organic species of Hg with high toxicity, is readily able to penetrate the placental barrier and to accumulate in the fetus. Thus, the mercury poison has occurred at the early stage of pregnancy.

Study of a low-selenium environment in China by INAA and Mössbauer spectrometry

The neutron activation analysis, gamma coincidence spectroscopy, nondispersive hydrogen flame atomic fluorescence spectroscopy, and Mössbauer spectrometry were used to study the low-selenium environment of the Exi Autonomous Prefecture, a well-known Keshan disease region. The Se contents in the soil samples there range from 0.075-0.18 mg/kg with the average of 0.13 mg/kg, whereas in the maize from 0.001-0.018 mg/kg with the average of 0.0099 mg/kg. The 57Fe Mössbauer spectrum of the soil indicates an anoxic environment. In addition to the FE3+ species the compounds containing low-valence iron e.g., goethite, and so forth, also exist. The rare earth element (REE) pattern obtained by NAA further confirms the reductive soil environment, which causes the selenium deficiency.