Differential interactions of Id proteins with basic-helix-loop-helix transcription factors

Dimerization of three Id proteins (Id1, Id2, and Id3) with the four class A E proteins (E12, E47, E2-2, and HEB) and two groups of class B proteins, the myogenic regulatory factors (MRFs: MyoD, myogenin, Myf-5 and MRF4/Myf-6), and the hematopoietic factors (Scl/Tal-1, Tal-2, and Lyl-1) were tested in a quantitative yeast 2-hybrid assay. All three Ids bound with high affinity to E proteins, but a much broader range of interactions was observed between Ids and the class B factors. Id1 and Id2 interacted strongly with MyoD and Myf-5 and weakly with myogenin and MRF4/Myf-6, whereas Id3 interacted weakly with all four MRFs. Similar specificities were observed in co-immunoprecipitation and mammalian 2-hybrid analyses. No interactions were found between the Ids and any of the hematopoietic factors. Each Id was able to disrupt the ability of E protein-MyoD complexes to transactivate from a muscle creatine kinase reporter construct in vivo. Finally, mutagenesis experiments showed that the differences between Id1 and Id3 binding map to three amino acids in the first helix and to a small cluster of upstream residues. The Id proteins thus display a signature range of interactions with all of their potential dimerization partners and may play a role in myogenesis which is distinct from that in hematopoiesis.

Novel regulation of the helix-loop-helix protein Id1 by S5a, a subunit of the 26 S proteasome

Id proteins negatively regulate the dimerization, DNA binding, and biological properties of basic helix-loop-helix proteins. In a search for novel factors that interact with Id1, we identified a component of the 26 S proteasome, S5a, that has previously been implicated only in the recognition of ubiquitinated polypeptides destined for proteolysis. S5a interacts strongly with Id1, less strongly with the basic helix-loop-helix proteins MyoD and E12, and not at all with other Id proteins. S5a restores DNA binding by MyoD-Id1 and E12-Id1 heterodimers, enhances DNA binding by MyoD and E12 homodimers, and reverses Id1-mediated repression of the muscle creatine kinase promoter during myogenic differentiation. Mutagenesis experiments showed that amino acids flanking the helix-loop-helix domain plus three residues in the first helix of Id1 impart S5a recognition. This requires only the NH2-terminal half of S5a. S5a thus appears to promote the positive regulation of myogenic genes through ubiquitin-independent mechanisms involving inhibition of Id1 and the enhancement of DNA binding by MyoD and E12. This latter property may permit the selection of novel promoter binding sites during myogenesis.

Analytical derivatizations of volatile and hydrophilic carbonyls from aqueous matrix onto a solid phase of a polystyrene-divinylbenzene macroreticular resin

Extraction and derivatization of carbonyls to benzyloximes, pentafluorobenzyloximes or 2,4-dinitrophenylhydrazones is simplified and reaction times are substantially reduced by simultaneous sorption and derivatization from aqueous solution onto a solid phase. In this reaction a macroreticular polystyrene-divinylbenzene resin acts as a sorbent and catalyst to allow simultaneous extraction and derivatization of hydrophilic and lipophilic aldehydes and ketones from simple as well as complex matrices including plasma. Conversion to the 2,4-dinitrophenylhydrazones or pentafluorobenzyloximation at ambient temperature requires 10 and 20 min, respectively. These reaction conditions correspond to at least a 6-fold reduction in reaction times for derivatization of the reactive aldelhydes and a 36-72-fold reduction for preparation of derivatives for the slower reacting ketones.

A simple method for enumerating bacteriophages in soil

A plaque technique that uses antibiotic-resistant bacteria growing on antibiotic-containing agar for the assay lawn resulted in significantly better recovery of bacteriophages P1 of Escherichia coli and F116 of Pseudomonas aeruginosa from nonsterile soil than standard membrane filtration or centrifugation techniques. Adsorption of the phages on soil particles appeared to be involved in their recovery and survival in soil.

[Clinical observation of TMJDS treated with pivot splint]

The pivot splint was applied to 50 patients with temporomandibular joint dysfunction syndrome that included 30 patients of anterior disc displacement without reduction, 12 patients of anteriordisc displacement with partial reduction and 8 patients of upward condyle displacement. The mouth opening and joint space of the TMJ tomographies before and after treatment were measured for each case. The results indicated that treatment with pivot splint was very effective for the patients with downward diplacemenr of the condyle. As a result, among 50 patients, 36 patients were cured (72%) and 14 patients were improved (28%). The results of 3 years follow-up indicated that original symptoms of the patients had no recurrence.

Differential determination of arsenic (III) and total arsenic with L-cysteine as prereductant using a flow injection non-dispersive atomic absorption device

Speciation of arsenic in environmental samples gains increasingly importance, as the toxic effects of arsenic are related to its oxidation state. A method was developed for the determination of trace amounts of arsenic (III) and total arsenic by flow injection hydride generation coupled with an in-house made non-dispersive AAS device. The total arsenic is determined after prereduction of arsenic (V) to arsenic (III) with L-cysteine in a low concentration of hydrochloric, acetic or nitric acid. The conditions for the prereduction, hydride generation and atomization were systematically investigated. A quartz tube temperature of 800 degrees C was found to be optimum in view of peak shape and baseline stability. Pb(II), Ni(II), Fe(III), Cu(II), Ag(I), Al(III), Ga(II), Se(IV), Bi(III) were checked for interfering with the 2 microg/L As(V) signal. A serious signal depression was only observed for Se(IV) and Bi(III) at a 150-fold excess. With the above system, arsenic was determined at a sampling frequency of about 1/min with a detection limit (3sigma) of 0.01 microg/L using a 0.5 mL sample. The reagent blank was 0.001+/-0.0003 absorbance units and the standard deviation of 10 measurements of the 2 microg/l As signal was found to be 1.2%. Results obtained for standard reference materials and water samples are in good agreement with the certified values and those obtained by ICP-MS

Molecular pathogenesis of peripheral neuropathy

Peripheral neuropathies can result from a failure to form or maintain the myelin internode or from autoimmune-mediated demyelination. Several gene defects responsible for the most common inherited human peripheral neuropathies referred to as Charcot-Marie-Tooth disease have been reported. These studies identified PMP-22 and connexin-32 as proteins that are essentiel for normal myelination. Point mutations in Po protein, PMP-22, and connexin-32 have been identified as causes of inherited peripheral neuropathies. In addition, studies indicated for the first time that alterations in PMP-22 gene dosage (trisomy and monosomy) can induce inherited peripheral neuropathies. Little is known, however, about how these gene defects cause myelin pathology. This report describes the distributions of proteins within the peripheral myelin internode and discusses how these molecules contribute to the pathogenesis of inherited and autoimmune peripheral neuropathy. A better understanding of the molecular composition of the myelin internode is essential for diagnosis and treatment of human peripheral neuropathies.

Mapping of preproenkephalin mRNA in brain of spontaneously hypertensive rats

AIM

To detect different expression of preproenkephalin mRNA (PPE mRNA) in 16-wk-old spontaneously hypertensive rat (SHR) and age-matched normotensive Wistar-Kyoto rat (WKY).

METHODS

Nonradioactive in situ hybridization was performed using digoxigenin-labeled RNA probe.

RESULTS

Compared with WKY rats, PPE mRNA levels of 16-wk-old SHR increased in hypothalamic nuclei (> 20), amygdaloid nuclei (> 23), ventrolateral central gray (21.2), reticular substantia nigra (21.5), interpeduncular nuclei (> 21), nucleus of the solitary tract (30.7), rostroventrolateral reticular nucleus (29.1), gigantocellular reticular nucleus (23.9) and thoracic spinal cord (> 30); decreased in dorsal central gray (22.7). No difference was found in compact substantia nigra (22.8), dentate gyrus (26.2) and CA1, CA2, CA3 of hippocampus (> 25).

CONCLUSION

PPE mRNA in brain regions involved in modulation of blood pressure may be associated with the genesis of spontaneous hypertension in SHR. Enkephalin, an endogenous ligand of opioid receptors, is important in the regulation of blood pressure (BP). Intracerebroventricular injection (icv) of mu agonist [D-Ala2-MePhe4-Gly5-ol]-enkephalin (DAGO) and delta agonist [D-Ala2, D-Leu5]-enkephalin (DADLE) increased the BP[1]. In situ hybridization study showed preproenkephalin mRNA was localized in hypothalamic nuclei, hippocampus, NTS, and spinal cord[2], where the cardiovascular regulation took place. The icv of mu agonist morphiceptin induced a pressor response in SHR but hypotension in WKY rat, and delta agonist Tyr-D-Thr-Gly-Phe-Leu-Thr (DTLET) icv decreased BP in SHR but increased BP in WKY[3]. Compared with WKY rats, SHR had greater concentration of methionine-enkephalin (Met-Enk) in cortex, pons, and medulla[4], but lower Leu-Enk in suprachiasmatic nucleus[5]. These studies imply that opiate system is disturbed in essential hypertension. The aim of this study is to determine whether the biosynthetic activity of CNS opiates in brain is altered in case of essential hypertension.

[Methylene blue staining in fiberoptic bronchoscopy in the diagnosis of bronchial tumors]

47 patients were stained by using methylene blue in fiberoptic bronchoscopy. Of these, 35 had central lung cancer, and 12 bronchitis. 40 patients with central lung cancer were detected by general fibreoptic endoscopy. The results demonstrated that normal bronchial mucosa was not stained, 97.14% central malignant bronchial tumors stained, and 8.33% bronchitis stained. X2test showed the marked difference. Positive diagnosis was 97.06% in biopsy specimens stained, it was higher than 77.05% in the general investigated (P < 0.05). Using methylene blue in fiberoptic bronchoscopy would help diagnose central lung cancer, determine tumors limits, permit accurate biopsy. The stain was not related to the pathological classification, differentiation of cancer cells, and classification of clinical pathology (P > 0.05).

Identification of an arginine residue in the dual coenzyme-specific glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides that plays a key role in binding NADP+ but not NAD+

Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides can utilize either NADP or NAD as coenzyme. The enzyme's three-dimensional structure has been solved (Rowland et al., 1994, Structure 2, 1073-1087) and shown to contain a conventional nucleotide binding domain. NADP+ was modeled into the structure by superimposing the beta alpha beta domain and that of coenzyme-bound 6-phosphogluconate dehydrogenase (Adams et al., 1994, Structure 2, 651-658), enabling us to identify Arg-46 as a potentially important residue for NADP+ binding. Using site-directed mutagenesis, we constructed mutant enzymes in which Arg-46 was replaced by glutamine (R46Q) and alanine (R46A) and examined their kinetic properties. The principal effects in these mutant enzymes were that the Km and Ki values for NADP+ increased by 2 to 3 orders of magnitude over those of the wild-type enzyme. No other kinetic constant was altered more than 6.5-fold. Changing this single amino acid leads to mutant glucose-6-phosphate dehydrogenases with coenzyme specificities that favor NAD+, whereas the wild-type enzyme prefers NADP+ as coenzyme. These results confirm that Arg-46 plays a key role in NADP+ binding by contributing a positively charged planar residue that interacts primarily with the 2'-adenosine phosphate. The Arg residue corresponding to Arg-46 in L. mesenteroides glucose-6-phosphate dehydrogenase is conserved in all glucose-6-phosphate dehydrogenases and, presumably, plays the same role in all these enzymes.

Identification of an arginine residue in the dual coenzyme-specific glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides that plays a key role in binding NADP+ but not NAD+

Glucose-6-phosphate dehydrogenase from Leuconostoc mesenteroides can utilize either NADP or NAD as coenzyme. The enzyme's three-dimensional structure has been solved (Rowland et al., 1994, Structure 2, 1073-1087) and shown to contain a conventional nucleotide binding domain. NADP+ was modeled into the structure by superimposing the beta alpha beta domain and that of coenzyme-bound 6-phosphogluconate dehydrogenase (Adams et al., 1994, Structure 2, 651-658), enabling us to identify Arg-46 as a potentially important residue for NADP+ binding. Using site-directed mutagenesis, we constructed mutant enzymes in which Arg-46 was replaced by glutamine (R46Q) and alanine (R46A) and examined their kinetic properties. The principal effects in these mutant enzymes were that the Km and Ki values for NADP+ increased by 2 to 3 orders of magnitude over those of the wild-type enzyme. No other kinetic constant was altered more than 6.5-fold. Changing this single amino acid leads to mutant glucose-6-phosphate dehydrogenases with coenzyme specificities that favor NAD+, whereas the wild-type enzyme prefers NADP+ as coenzyme. These results confirm that Arg-46 plays a key role in NADP+ binding by contributing a positively charged planar residue that interacts primarily with the 2'-adenosine phosphate. The Arg residue corresponding to Arg-46 in L. mesenteroides glucose-6-phosphate dehydrogenase is conserved in all glucose-6-phosphate dehydrogenases and, presumably, plays the same role in all these enzymes.

Distributions of mu and delta opioid receptors in central nervous system of SHR rats and normotensive WKY rats

AIM

To compare the distributions of opioid receptor subtypes in central nervous system of spontaneously hypertensive rat (SHR) and normotensive Wistar-Kyoto (WKY) rat.

METHODS

[3H] Ohmefentanyl (OMF), [3H]N-methyl-N-[7-(I-pyrrolidinyl)-1-oxaspiro (4,5)dec-8-yl] benzeneacetamide (U-69593) and [3H]etorphine after suppression of mu and kappa-sites by 15 mumol.L-1 each of unlabeled OMF and trans-(1R,2R)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl) cyclohexyl]-benzeneacetamide hydrochloride (U-50 488H) were used as ligands for mu, kappa, and delta opioid receptor subtypes in autoradiography, respectively.

RESULTS

Delta receptors had an increase in hypothalamic nuclei, periaqueductal gray, caudate and interpeduncular nuclei, and a decrease in substantia nigra in SHR than in those of WKY rat. Mu receptors were less concentrated in basolateral amygdaloid nucleus, habenular nuclei and nucleus of solitary tract of SHR than in those of WKY rats. Kappa receptor density was not checked out in the present study.

CONCLUSION

Distribution of opioid receptor subtypes is related to hypertension of SHR, and delta opioid receptor is more important than mu opioid receptor in the maintenance of hypertension in SHR.

Effect of polysialic acid on the behavior of retinal ganglion cell axons during growth into the optic tract and tectum

We have demonstrated previously that the polysialic acid (PSA) moiety of the neural cell adhesion molecule (NCAM) can regulate peripheral nerve branching during development. In particular, it was found that specific enzymatic removal of PSA from motor axons causes them to form tight fascicles that are less responsive to normal guidance cues. In the present study, the role of PSA in the behavior of axons in the central nervous system has been examined through an analysis of chick optic axons during development. Unlike peripheral axons, which generally grow in a PSA-free environment, PSA was found to be present both on retinal ganglion cell axons and their environment in the tract and tectum. Furthermore, the enzymatic removal of PSA from the optic axons caused them to defasciculate in the tract/tectal region. This response was morphologically similar to targeting corrections made by these axons at a later stage when PSA levels have decreased, suggesting that the PSA may serve to shield them from responding prematurely to some guidance cues in their target region.

Different distributions of opioid receptors in spontaneously hypertensive rats and Wistar-Kyoto rats

AIM

To compare the densities of opioid receptors in spontaneously hypertensive rats (SHR) with those of normotensive Wistar-Kyoto (WKY) rats in central nervous system which are related to the regulation of BP.

METHODS

[3H] Etorphine, a nonspecific opioid ligand, was used to determine the distributions of opioid receptors in 16-wk-old SHR and WKY rats by quantitative autoradiography.

RESULTS

The densities of [3H]etorphine in hippocampus (P < 0.01), periaqueductal gray, nucleus of the solitary tract, and thoracic (T4-6) spinal cord (P < 0.05) of SHR were lower than those of WKY rats. But in basolateral amygdaloid nucleus (P < 0.01), habenular nuclei (P < 0.05), and hypothalamic nuclei including arcuate nucleus (P < 0.01), higher densities of opioid receptors were found in SHR. No difference existed in interpeduncular nuclei between the 2 groups.

CONCLUSION

The difference in distributions of opioid receptors is related to the hypertension in SHR.

Mutation of the MXI1 gene in prostate cancer

The Mxi1 protein negatively regulates Myc oncoprotein activity and thus potentially serves a tumour suppressor function. MXI1 maps to chromosome 10q24-q25, a region that is deleted in some cases of prostate cancer. We have detected mutations in the retained MXI1 alleles in four primary prostate tumours with 10q24-q25 deletions. Two tumours contained inactivating mutations, whereas two others contained the identical missense mutation. Fluorescence in situ hybridization also demonstrated loss of one MXI1 allele in an additional tumour lacking chromosome 10 abnormalities. MXI1 thus displays allelic loss and mutation in some cases of prostate cancer that may contribute to the pathogenesis or neoplastic evolution of this common malignancy.

Phencyclidine receptors in brain and spinal cord of spontaneously hypertensive rats aged 4-16 wk

AIM

To study the relationship between the density of phencyclidine [1-(1-phenylcyclohexyl)piperidine hydrochloride, Phe] receptor binding sites in brain and thoracic spinal cord (T4-6) and the development of hypertension in spontaneously hypertensive rat (SHR).

METHODS

The density of Phe binding sites was determined by autoradiography using [3H]Phe in 4-, 8-, 12- and 16-wk-old rats.

RESULTS

There were fewer Phe binding sites in the hippocampus and dorsal horn of thoracic spinal cord of SHR at 12 and 16 wk (P < 0.01), when hypertension has established; while at 4 wk of age, before the development of hypertension, more Phe binding sites were found in SHR. As blood pressure began to rise at 8 wk, SHR had more Phe binding sites in hippocampus vs WKY, but no difference was seen between 2 strains in the dorsal horn of thoracic spinal cord.

CONCLUSION

Phe receptors might be involved in the genesis of SHR hypertension.

The effect of radix Salviae Miltiorrhizae Composita on peroxidation of low density lipoprotein due to copper dichloride

It is well known that plasma lipoprotein, particularly oxidized LDL, plays an important role in the pathogenesis of atherosclerosis and atherosclerotic diseases. We used oxidized LDL generated by incubating LDL from healthy persons with copper dichloride as a model to investigate the antioxidate property of Radix Salviae Miltiorrhizae Composita (RSMC). On photos, the spot X1 and the spot X2 were clearly found in the control group after the dialysis into copper dichloride for 24 and 48 hours, but they could not found in the RSMC group. The analysis of the constituents of lipids in LDL (by charring method) showed that after dialysis the percentages of the spot X1 and the spot X2 in the RSMC group were significantly lower than those in the control group (P < 0.01). The results suggest that RSMC plays a potential role in antioxidation of lipids or LDL.

Assignment of the human MAD and MXI1 genes to chromosomes 2p12-p13 and 10q24-q25

MAD and MXI1, two recently described members of the basic helix-loop-helix (bHLH) gene family, encode proteins that dimerize with and modulate the DNA binding of max. In turn, mad-max or mxi1-max heterodimers or max homodimers can compete for DNA binding sites with dimers formed between max and myc oncoproteins and antagonize the transcriptional activities of this latter class of proteins. Using a combination of somatic cell mapping and fluorescence in situ hybridization techniques, we have determined the chromosomal locations of the MAD and MXI1 genes. The MAD gene maps to chromosome 2p12-p13, a region involved in translocations and deletions in acute and chronic lymphocytic leukemias as well as non-lymphocytic leukemias and Hodgkin disease. The MXI1 gene localizes to chromosome 10q24-q25, a region involved in translocations and deletions in acute and chronic lymphocytic leukemias and prostatic carcinomas. The availability of genomic clones of MAD and MXI1 will permit an assessment of their involvement in these diseases at the molecular level.

Target determination of neurotransmitter phenotype in sympathetic neurons

While the majority of sympathetic neurons are noradrenergic, a minority population are cholinergic. At least one population of cholinergic sympathetic neurons arises during development by a target-dependent conversion from an initial noradrenergic phenotype. Evidence for retrograde specification has been obtained from transplantation studies in which sympathetic neurons that normally express a noradrenergic phenotype throughout life were induced to innervate sweat glands, a target normally innervated by cholinergic sympathetic neurons. This was accomplished by transplanting footpad skin containing sweat gland primordia from early postnatal donor rats to the hairy skin region of host rats. The sympathetic neurons innervating the novel target decreased their expression of noradrenergic traits and developed choline acetyltransferase (ChAT) activity. In addition, many sweat gland-associated fibers acquired acetylcholinesterase (AChE) staining and VIP immunoreactivity. These studies indicate that sympathetic neurons in vivo alter their neurotransmitter phenotype in response to novel environmental signals and that sweat glands play a critical role in the cholinergic and peptidergic differentiation of the sympathetic neurons that innervate them. The sweat gland-derived cholinergic differentiation factor is distinct from leukemia inhibitory factor and ciliary neurotrophic factor, two well-characterized cytokines that alter the neurotransmitter properties of cultured sympathetic neurons in a similar fashion. Recent studies indicate that anterograde signalling is also important for the establishment of functional synapses in this system. We have found that the production of cholinergic differentiation activity by sweat glands requires sympathetic innervation, and the acquisition and maintenance of secretory competence by sweat glands depends upon functional cholinergic innervation.

Vanadium as a modulator of cellular regulatory cascades and oncogene expression

Vanadium, a trace metal in the environment and in biological systems, influences the behavior of enzymes, mimics and regulates growth factor activity, is a potential mutagenic and carcinogenic agent, and regulates gene expression. The diverse biological actions of vanadium result from its capacity to function as an oxyanion, oxycation, or prooxidant. Vanadium is found in water, rocks, and soils in low concentration and in relatively high concentrations in coal and oil deposits. Vanadium compounds at much higher concentrations than are typically ingested are being considered in the treatment of diabetes mellitus. The actions of insulin and vanadium on the insulin receptor are similar, but the mechanisms are not identical. Vanadium modulates growth-factor-mediated signal transduction pathways. Vanadium promotes cell transformation and diminishes cell adhesion. Consistent with its mitogenic action and its capacity to mimic mitogenic growth factors, vanadium stimulates expression of protooncogenes. In particular, oxygen-derived active species are involved in the expression of the jun protooncogene in the presence of vanadium. The unique cellular activity of vanadium makes it a tool of unparalleled potential for studying mechanisms of cell growth, differentiation, and metabolism.

Vanadate-induced gene expression in mouse C127 cells: roles of oxygen derived active species

An underinvestigated aspect of the mitogenic and cell regulatory actions of vanadium is the regulation of gene expression. Among the fifteen cellular genes studied in cultured mouse C127 cells, vanadium (as 10 microM sodium vanadate) increased levels of mRNA of the actin and c-Ha-ras to four times control values. These increases represented de novo synthesis of mRNA, since they were inhibited by actinomycin D. Vanadate did not increase mRNA corresponding to c-src, c-mos, c-myc, p53, HSP70, pODC or RB genes, and expression of c-erb A, c-erb B, c-sis and c-fes genes was undetectable whether vanadium was present or not. Expression of a third gene affected by vanadium, c-jun, was augmented by addition of a reductant or oxidant together with the vanadate. Addition of NADH (marginally effective on its own) or H2O2 (effective alone) dramatically enhanced the effect of vanadate on c-jun gene expression. Catalase inhibited the effect of NADH partly. The vanadate-stimulated expression of actin and c-Ha-ras mRNA were unaffected by oxidants, reductants, metal chelators, or anti-oxidant enzymes. Evidently vanadate acts by two separate mechanisms on these two categories of genes. The alternate hypothesis that the actions of vanadate on actin and c-Ha-ras were mediated by a protein kinase cascade was inconsistent with the following observations. Neither insulin nor epidermal growth factor increased mRNA levels of c-Ha-ras or actin gene. Neither genistein (a tyrosine kinase inhibitor) nor pretreatment with 12-O-tetradecanoylphorbol-13-acetate blocked the actions of vanadate on these genes. Clearly the biological actions of vanadium depend in part on altered expression of genes. Since two of the genes are proto-oncogenes, this mechanism is potentially relevant to the mitogenic responses of cells to vanadium.

Intercellular space is affected by the polysialic acid content of NCAM

We have previously proposed that polysialic acid (PSA), which is attached to NCAM on the cell surface, can serve to regulate a variety of cell-cell interactions. The present study provides evidence that hydrated PSA influences a sufficiently large volume at the cell surface to exert broad steric effects, and that the removal of PSA in fact causes a detectable change in intercellular space. Using F11 neuron/neuroblastoma hybrid cells as a model system, the measured density and size of PSA suggests that a substantial fraction of the space between two apposed cell surface membranes could be sterically influenced by the presence of PSA. Specific enzymatic removal of PSA, which is similar in magnitude to changes that occur in many tissues during normal development, caused about a 25% decrease in the distance between two apposed cells. By contrast, removal of both heparan sulfate and chondroitin sulfate from the cells had no effect on this parameter. It is proposed that such changes in membrane-membrane distance could serve to alter selectively the efficiency of encounter between complementary receptors on apposing cells, and explain at least in part the broad biological influences of PSA.

Differential determination of chromium(VI) and total chromium in natural waters using flow injection on-line separation and preconcentration electrothermal atomic absorption spectrometry

A rapid, sensitive and selective method for the differential determination of CrIII and CrVI in natural waters is described. Chromium(vi) can be determined directly by flow injection on-line sorbent extraction preconcentration coupled with electrothermal atomic absorption spectrometry using sodium diethyldithiocarbamate as the complexing agent and C18 bonded silica reversed-phase sorbent as the column material. Total Cr can be determined after oxidation of CrIII to CrVI by potassium peroxydisulfate. Chromium(III) can be calculated by difference. The optimum conditions for sorbent extraction of CrVI and oxidation of CrIII to CrVI are evaluated. A 12-fold enhancement in sensitivity compared with direct introduction of 40 microliters samples was achieved after preconcentration for 60 s, giving detection limits of 16 ng l-1 for CrVI and 18 ng l-1 for total Cr (based on 3 sigma). Results obtained for sea-water and river water reference materials were all within the certified range for total Cr with a precision of better than 10% relative standard deviation in the range 100-200 ng l-1. The selectivity of the determination of CrVI was evaluated by analysing spiked reference materials in the presence of CrIII, resulting in quantitative recovery of CrVI.

[Quality of tuberous root of Liriope spicata (Thunb.) Lour. var. prolifera Y.T.Ma and Ophiopogon japonicus (L.F.) Ker-Gawl.--comparison of immune function]

This paper deals with comparative study on the immune function of the tuberous root of Liriope spicata var. prolifera and Ophiopogon japonicus. The results showed that the aqueous extract of both species mentioned above could increase obviously the spleen weight (immunity organ) of mice, enhance the clearance rate of iv charcoal particles in mice and antagonize remarkably the leukopenia caused by cyclophosphamide.

Microcapsules through polymer complexation. II. By complex coacervation of polymers containing a low charge density

Relationships between ionizable group content, structure and molecular weight, solubility and solution behaviour, and the efficacy of ionic complex formation through complex coacervation, have been established for a range of sparingly soluble synthetic weak polyelectrolyte polymers with low charge content, based on hydroxyalkyl methacrylates. Selected polymers containing methacrylic acid (acidic) and dimethylaminoethyl methacrylate (basic) functionality show promise as capsule-forming pairs for the entrapment of mammalian cells. The solubility of basic polymers and their ability to form microcapsules with structural integrity is enhanced through quaternization of the N-methyl functionality to the quaternary ammonium group. The survival of guinea-pig erythrocytes encapsulated for 4 d in this promising system was shown by the Drabkin's test to be about 41% of the control sample.

[Antimutagenicity screening of water extracts from 102 kinds of Chinese medicinal herbs]

Our observation shows that out of 102 kinds of Chinese medicinal herbs tested, 17 have remarkable antimutagenic effect on the mutation induced by aflatoxin B1, in Ames test. Among the 17 herbs Glycyrrhiza uralensis, Bupleurm chinense, Portulaca grandiflora and Cnidium monnieri have been found in other tests to be effective against mutagenesis induced by cyclophosphamide in mice.