New and evolving concepts in the neurotoxicology of lead

Lead (Pb) is a xenobiotic metal with no known essential function in cellular growth, proliferation, or signaling. Decades of research characterizing the toxicology of Pb have shown it to be a potent neurotoxicant, especially during nervous system development. New concepts in the neurotoxicology of Pb include advances in understanding the mechanisms and cellular specificity of Pb. Experimental studies have shown that stress can significantly alter the effects of Pb, effects that could potentially be mediated through alterations in the interactions of glucocorticoids with the mesocorticolimbic dopamine system of the brain. Elevated stress, with corresponding elevated glucocorticoid levels, has been postulated to contribute to the increased levels of many diseases and dysfunctions in low socioeconomic status populations. Cellular models of learning and memory have been utilized to investigate the potential mechanisms of Pb-induced cognitive deficits. Examination of long-term potentiation in the rodent hippocampus has revealed Pb-induced increases in threshold, decreases in magnitude, and shorter retention times of synaptic plasticity. Structural plasticity in the form of adult neurogenesis in the hippocampus is also impacted by Pb exposure. The action of Pb on glutamate release, NMDA receptor function, or structural plasticity may underlie perturbations in synaptic plasticity and contribute to learning impairments. In addition to providing insight into potential mechanisms of Pb-induced cognitive deficits, cellular models offer an opportunity to investigate direct effects of Pb on isolated biological substrates. A target of interest is the 78-kDa molecular chaperone glucose-regulated protein (GRP78). GRP78 chaperones the secretion of the cytokine interleukin-6 (IL-6) by astrocytes. In vitro evidence shows that Pb strongly binds to GRP78, induces GRP78 aggregation, and blocks IL-6 secretion in astroglial cells. These findings provide evidence for a significant chaperone deficiency in Pb-exposed astrocytes in culture. In the long term, chaperone deficiency could underlie protein conformational diseases such as Alzheimer's Disease (AD). Lead exposure in early life has been implicated in subsequent progression of amyloidogenesis in rodents during old age. This exposure resulted in an increase in proteins associated with AD pathology viz., beta-amyloid precursor protein (beta-APP), and beta-amyloid (Abeta). These four new lines of research comprise compelling evidence that exposures to Pb have adverse effects on the nervous system, that environmental factors increase nervous system susceptibility to Pb, and that exposures in early life may cause neurodegeneration in later life.

New and evolving concepts in the neurotoxicology of lead

Lead (Pb) is a xenobiotic metal with no known essential function in cellular growth, proliferation, or signaling. Decades of research characterizing the toxicology of Pb have shown it to be a potent neurotoxicant, especially during nervous system development. New concepts in the neurotoxicology of Pb include advances in understanding the mechanisms and cellular specificity of Pb. Experimental studies have shown that stress can significantly alter the effects of Pb, effects that could potentially be mediated through alterations in the interactions of glucocorticoids with the mesocorticolimbic dopamine system of the brain. Elevated stress, with corresponding elevated glucocorticoid levels, has been postulated to contribute to the increased levels of many diseases and dysfunctions in low socioeconomic status populations. Cellular models of learning and memory have been utilized to investigate the potential mechanisms of Pb-induced cognitive deficits. Examination of long-term potentiation in the rodent hippocampus has revealed Pb-induced increases in threshold, decreases in magnitude, and shorter retention times of synaptic plasticity. Structural plasticity in the form of adult neurogenesis in the hippocampus is also impacted by Pb exposure. The action of Pb on glutamate release, NMDA receptor function, or structural plasticity may underlie perturbations in synaptic plasticity and contribute to learning impairments. In addition to providing insight into potential mechanisms of Pb-induced cognitive deficits, cellular models offer an opportunity to investigate direct effects of Pb on isolated biological substrates. A target of interest is the 78-kDa molecular chaperone glucose-regulated protein (GRP78). GRP78 chaperones the secretion of the cytokine interleukin-6 (IL-6) by astrocytes. In vitro evidence shows that Pb strongly binds to GRP78, induces GRP78 aggregation, and blocks IL-6 secretion in astroglial cells. These findings provide evidence for a significant chaperone deficiency in Pb-exposed astrocytes in culture. In the long term, chaperone deficiency could underlie protein conformational diseases such as Alzheimer's Disease (AD). Lead exposure in early life has been implicated in subsequent progression of amyloidogenesis in rodents during old age. This exposure resulted in an increase in proteins associated with AD pathology viz., beta-amyloid precursor protein (beta-APP), and beta-amyloid (Abeta). These four new lines of research comprise compelling evidence that exposures to Pb have adverse effects on the nervous system, that environmental factors increase nervous system susceptibility to Pb, and that exposures in early life may cause neurodegeneration in later life.

[Comparison observation on the mature alveolar of Echinococcus sibiricensis and Echinococcus multilocularis in the experimentally infected white mice]

The alveolar echinococcus is one of the most dangerous worm parasites in man. Rausch and Schiller reported a new species, Echinococcus sibiricensis n. sp. from arctic fox, Alpex logopus, on St. Lawrence Island of Alaska, USA. According to the view of Vogel, the sibiricensis form is only a geographical race or subspecies of Europe Echinococcus multilocularis. So far, the two names, Echinococcus multiocularis multilocularis and Echinococcus multilocularis sibiricensis, existed in many references and text books. We have found the adults of Echinococcus sibiricensis and Echinococcus multilocularis from sand foxes, Vulpes corsac and their larval stages (alveolar echinococcus) from field voles, Microtus brandti in the Hulunbeier Pasture of Inner Mongolia, northeastern China in 1985 and 1998-1999. Two types of metacestodes with quite different styles of early development of E. sibiricensis and E. multilocularis were found from field voles and laboratory experimental white mice. As one characteristic of alveolar E. multilocularis, the capsules are produced by the exogenous budding of germinal cell layer together with cyst wall. The protoscoleces grow from germinal cells on germinal cell layer. The peduncles of early protoscoleces attached to the germinal cell layer on the inner surface of capsule wall(Plate I, Figs. 1-2). Some protoscoleces in reticular structure were linked with the inner surface of capsule wall (Plate I, Fig. 3) in livers of mice in 9.5th month postinfection. In 14th month old alveolar multilocularis, large number of mature protoscoleces in reticular structure were still linked to the inner surface of capsule wall (Plate I, Figs. 4-8). The cavities of some capsules were filled with protoscoleces in meshes of reticular structure which were also linked around with the inner surface of capsule wall (Plate I, Fig. 9). The superficial surface of livers of positive field voles and experimental mice never showed any hyperemic phenomenon. The superficial surfaces of livers and lungs of positive field voles and experimental mice infected with alveolar E. sibiricensis were highly hyperemic. The metacestodes of E. sibiricensis composed of mother cyst, undifferentiated embryonic cysts and small brood capsules. Cavities of all cysts were fully filled with germinal cell masses. Host reaction appeared to be very strong, all cysts were surrounded by thick connective tissue and dense leukocytes (Plate II, Fig. 10). All alveolar vesicles were found located in lungs tissue of experimental mice. Large germinal cell masses metastasized out from undifferentiated embryonic cysts into host lung tissue, where germinal cell masses developed into accumulation of early protoscoleces (Plate II, Figs. 11-12). Early protoscoleces of alveolar E. sibiricensis were seen earliest in mice lung tissues on 101-104th days after infection. Many small capsules in different sizes and different shapes containing mature protoscoleces and reticular structure (Plate II, Figs. 13-15) were found in lungs of mice in 9th month after infection. Only in one experimental mouse infected with alveolar E. sibiricensis in 8.5th month postinfection, both its lung and liver existed alveolar cysts; the capsules in liver were surrounded by very thick connective tissue of the host, and there were some protoscoleces in their cavities (Plate II, Figs. 16-18).

[Expression and characterization of two kinds of recombinant snake neurotoxins]

The cDNA encoding the precursor of cobrotoxin was cloned from the venom gland of the Chinese continental cobra (Naja naja atra) by RT-PCR. Its deduced amino acid sequence analysis showed that the mature protein was identical to that identified from the Taiwan cobra (Naja naja atra) by protein sequencing technique. The cDNA encoding the mature protein was then subcloned into the expression vector pMAL-P2. The gene of CM11, which was formed by ligation of the fragments of the synthetic oligonucleotides, was also cloned into the expression vector pMAL-P2. After induction of IPTG, both of the neurotoxins were overexpressed as soluble fusion proteins which were confirmed by SDS-PAGE and western blotting. The expressed fusion proteins was purified by sepharose 6B-amylose affinity chromatography and DEAE-sepharose FF chromatography. Both of the recombinant proteins achieved after digestion by factor Xa showed the in vivo toxicity.

Preparation and cDNA sequence analysis of two novel monoclonal antibodies against magaininII

By using intrasplenic immunization and the conventional B lymphocyte hybridoma technique, we have established two novel hybridoma cell lines stably secreting specific monoclonal antibodies (MAbs) to magaininII, termed as 2D1 and 3F8, respectively. The two cell lines were then subjected to RNA extraction and the VH and VL segments were obtained by reverse transcription of RNA followed by polymerase chain reaction (RT-PCR) and characterized by nucleotide sequence analysis. The VH segments of 2D1 and 3F8 belong to the VH5 family and the VL segments of 2D1 and 3F8 belong to VK10 and VK1 groups, respectively. The two MAbs utilize different VL segments and have disparities in their HCDR3 regions, which may contribute to the different epitope recognition of the two antibodies.

cDNA sequence analysis of a novel member of the three loop protein family from the Chinese continental banded krait

The cDNA encoding a novel three loop protein was cloned from cellular RNA isolated from the venom gland of Bungarus multicinctus multicinctus by RT-PCR. The mature protein has 82 amino acid residues. It shared only 25-38% similarity with some cardiotoxins and did not have sequence similarity with neurotoxins, while its cDNA was about 70% similar to both the cDNAs encoding neurotoxins and the cDNAs encoding cardiotoxins.

cDNA cloning and sequence analysis of Lys-49 phospholipase A2 from Agkistrodon acutus

Total RNA was extracted from venom glands of Agkistrodon acutus. The cDNA encoding Lys-49 phospholipase A2 (PLA2) was amplified by reverse transcriptional polymerase chain reaction (RT-PCR). The cDNA was cloned into the pGEMT-vector and sequenced. The open reading frame (ORF) of Lys-49 PLA2 consists of 414 bp encoding 138 amino acids, which includes a signal peptide of 16 amino acids and a matured peptide of 122 amino acids. It shows 76% identity in amino acids with another reported Lys-49 PLA2. Because residue 49 in mature peptide is Lysine, it probably possesses myotoxicity. These results indicate there are at least two kinds of myotoxin in the venom of A. acutus.

Cloning, sequence analysis and expression in E. coli of the cDNA of the thrombin-like enzyme (pallabin) from the venom of Agkistrodon halys pallas

The cDNA of the thrombin-like enzyme (pallabin) from the venom of Agkistrodon halys pallas was cloned and sequenced. The length of the cDNA is 923bp which includes 120bp of noncoding region and 780bp of coding region. Pallabin was synthesized as a prozymogen with 260 amino acids, which includes a signal peptide of 18 amino acids, a proposed propeptide of 6 amino acids and a matured peptide of 236 amino acids. Pallabin exhibits a strong amino acid similarity to the serine proteases isolated from other snake venoms. It contains 12 cysteins which form 6 disulfide bridges. Like other serine proteases, it also has three conserved catalytically active sites: His41, Asp86 and Ser182. To our knowledge, this study is the first report concerning the cDNA of a thrombin-like enzyme from Agkistrodon halys pallas. The cDNA was cloned into the expression plasmid pT7ZZa and expressed in E.coli. The recombinant pallabin immunologically reacted with its specific antibody.

cDNA sequence analysis and expression of four long neurotoxin homologues from Naja naja atra

The novel cDNAs encoding four long neurotoxin homologues were firstly cloned from the venom gland of Naja naja atra by reverse transcriptase-polymerase chain reaction. Amino acid sequence comparison showed that they may come from two different evolutionary origins. The mature proteins were expressed as soluble fusion proteins in Escherichia coli and purified for immunoblotting. The results revealed that they displayed different immunochemical properties.

cDNA cloning and sequence analysis of six neurotoxin-like proteins from Chinese continental banded krait

The cDNAs encoding six neurotoxin-like proteins were cloned from the total RNA isolated from one venom gland of Bungarus multicinctus multicinctus by reverse transcription-polymerase chain reaction. Although they shared a high degree of nucleotide sequence homology, the deduced proteins displayed a rather low extent of identical residues with the exception that the 21 residue signal peptides were highly conserved. Each mature protein consisted of 65, 66 or 68 amino acids with four or five disulfide bonds respectively. Comparative sequence analyses showed that they were structurally related to neurotoxin homologues. Phylogenetic analyses implied that they might represent two different evolutionary branches.

[Effect of qigong on heart-qi deficiency and blood stasis type of hypertension and its mechanism]

Comparative study was performed on the Heart-Qi Deficiency and Blood Stasis type (HQDBS) of hypertensive patients treated with Qigong. The results showed that the clinical symptoms alleviated, cardiac morphology and function, hemorheology and erythrocyte deformity were improved. After one year of practicing Qigong, plasma histofibrinogen activation inhibitor (PAI) and VIII factor related antigen (VIII R: Ag) levels decreased, while plasma tissue fibrinolytic activator (t-PA) and anti-thrombogen III (AT-III) levels increased. Capillary blood velocity of nailfold microcirculation raised from 0.2940 +/- 0.0206 mm/s to 0.3045 +/- 0.0236 mm/s, the diameter and length of afferent limb tended to increase. The above data indicated that Qigong could benefit HQDBS. This might be the mechanism by which HQDBS type of hypertension was treated.

[The relationship between the number of S-100 protein positive cells in the regional lymph nodes of cardial carcinoma and the prognosis]

S-100 protein positive cells in the regional lymph nodes (LN) of cardial carcinoma were demonstrated with PAP method in 33 cases, and the number of positive cells were counted. The status of immune reaction combined with the number of positive cell in the LN and follow-up results were analysed. The results were as follows: 1. The average number (7.3) of S-100 protein positive cells in the group of deaths was significantly higher than that in the survival group (3.3). 2. The status of immune reaction of LN in the group of deaths was inactive or depressed, but in the survival group it was active. 3. In the group of deaths, 50% of detected LN harbored metastasis, but only 9.4% in the survival group had metastasis. 4. There was no difference in the positive cell numbers between the LN with and LN without metastasis in the group of deaths. It is considered that the number of S-100 protein positive cells is one of the criteria which is more important than carcinoma metastasis in judging the prognosis.

An endodermal sinus tumor in the cerebellopontine angle

Immunohistochemical and ultrastructural findings in a primary intracranial endodermal sinus tumor are reported in this paper. The tumor cells exhibited AFP, CEA and anti-alpha-1-trypsin positive immunoreactivity immunocytochemically. Aggregates of electron-dense material in the extra- and intracellular spaces and amorphous basement membrane-like substance were seen extracellularly by electron microscopy. The clinicopathological, immunocytochemical and ultrastructural features were consistent with the criteria for primary intracranial sinus tumor.