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Metals in contaminated salt marshes are mainly locked in the anaerobic layer of sediments, where they are tightly bound as sulfides and organic complexes. Vascular plants survive in saturated soils in part by pumping O2 into their root zones, changing their microenvironment to an oxic one. This, along with chelating exudates, mobilizes metals, allowing uptake by the roots. We compared the common reed Phragmites australis and cordgrass Spartina alterniflora in lab and field studies for ways in which they handle trace metals. Both plants store most of their metal burden in their roots, but some is transported to aboveground tissues. Spartina leaves contain approximately 2-3 x more Cr, Pb, and Hg than Phragmites leaves, but equivalent Cu and Zn. Furthermore, Spartina leaves have salt glands, so leaf excretion of all metals is twice that of Phragmites. In-depth studies with Hg indicate that Hg excretion correlates with Na release but not with transpiration, which is 2.2 x higher in Phragmites; and that more Hg accumulates in early-appearing leaves than in upper (i.e. later) leaves in both species. Spartina thus makes more metals available to salt marsh ecosystems than Phragmites by direct excretion and via dead leaves which will enter the food web as detritus.

Cell viability requires accurate chromosome segregation at mitosis. The spindle checkpoint ensures that anaphase is not attempted until the sister chromatids of each chromosome are attached to spindle microtubules from opposite poles. The checkpoint mechanism involves a signal transduction cascade that is more complex than was originally envisioned.

We have investigated the effects of isoflurane anaesthesia on the motor evoked potential recorded in the extradural space during corrective spinal surgery in 15 patients. Isoflurane was added to a nitrous oxide in oxygen mixture supplemented with fentanyl and a neuromuscular blocking agent. Isoflurane was administered to achieve end-tidal concentrations of 2%, 1% and 0% in all patients, and also of 1.5% and 0.5% in nine patients. Transcranial electrical stimulation of the motor cortex was used to elicit descending volleys in corticospinal axons (the motor evoked potential). With stimuli of 450-750 V and no isoflurane, multiple I waves were always seen following the D wave. In all patients the number of I waves decreased and individual I waves became smaller in amplitude the greater the isoflurane concentration, but there were only minor changes in the D wave. The greatest depressant effect on I waves occurred at an end-tidal concentration of 0.5%. Given that I waves are an index of synaptic transmission, anaesthetic-induced changes in I waves may provide a useful model for the neuronal events underlying anaesthesia-induced unconsciousness.

The major sperm proteins (MSPs) are a family of closely related, small, basic proteins comprising 15% of the protein in Caenorhabditis elegans sperm. They are encoded by a multigene family of more than 50 genes, including many pseudogenes. MSP gene transcription occurs only in late primary spermatocytes. In order to study the genomic organization of transcribed MSP genes, probes specific for the 3' untranslated regions of sequenced cDNA clones were used to isolate transcribed genes from genomic libraries. These and other clones of MSP genes were located in overlapping cosmid clones by DNA fingerprinting. These cosmids were aligned with the genetic map by overlap with known genes or in-situ hybridization to chromosomes. Of 40 MSP genes identified, 37, including all those known to be transcribed, are organized into six clusters composed of 3 to 13 genes each. Within each cluster, MSP genes are not in tandem but are separated by at least several thousand bases of DNA. Pseudogenes are interspersed among functional genes. Genes with similar 3' untranslated sequences are in the same cluster. The six MSP clusters are confined to only three chromosomal loci; one on the left arm of chromosome II and two near the middle of chromosome IV. Additional sperm-specific genes are located in one cluster of MSP genes on chromosome IV. The multiplicity of MSP genes appears to be a mechanism for enhancing MSP synthesis in spermatocytes, and the loose clustering of genes could be a result of the mechanism of gene duplication or could play a role in regulation.

A new anion-exchange material has been developed which allows very rapid resolution of protein mixtures. The Microanalyzer MA7P matrix consists of small (7 micron), spherical, non-porous, polymethacrylate beads with polyethyleneimine (PEI) covalently coupled to the surface. When packed 30 X 4.6 mm I.D. columns, this matrix is particularly well suited for applications in which 1-300 micrograms of a protein mixture must be resolved in a minimum of time. Recoveries of injected proteins are usually quantitative, even when the amounts of individual proteins are in the submicrogram range. Chromatography on Microanalyzer MA7P columns is characterized by very narrow bandwidths, even at relatively high flow-rates. This is due to the combined effects of short column length, high selectivity, and the lack of velocity-dependent bandbroadening attributable to diffusion into and out of pores. These columns have no discernable gel filtration effects in the molecular weight range from 10(3) to 10(6) daltons. Columns are very rapidly equilibrated with new solvents, further reducing cycle-to-cycle times.

A new, weak cation exchanger (MA7C) is useful for the very rapid resolution of protein mixtures. MA7C columns (30 X 4.6 mm I.D.) are packed with non-porous spherical particles (7-micron in diameter) having carboxylic acid ion-exchange groups. These columns can readily separate human hemoglobin A1c from other hemoglobin species in 7 min. Quantitative results agree well with those of accepted techniques. Other separations are possible with flow-rates up to 5 ml/min. Chromatography on MA7C columns is characterized by very narrow bandwidths, even at high flow-rates.

Spasticity in man is presented as a disinhibition of spinal cord mechanisms, the responses to stretch depending on the interaction of the reflex effects of group Ia with those of group II afferent fibres. The reflex responses to muscle stretch and shortening in Parkinson's disease do not depend on an abnormality of spinal reflex mechanisms. The superimposition of physiological tremor or alternating tremor in rigidity produces the classical cog-wheel sensation. The phase lead of the action tonic stretch reflex was found to be reduced in patients with athetosis and cerebellar disease, thus diminishing damping of unwanted movements. The more complex transmission characteristics of the action tonic stretch reflex of normal man are absent in patients with spasticity and cerebellar lesions, presumably due to interference with long-loop pathways. In normal subjects gain of the reflex loop increases with voluntary contraction but in spasticity gain remains high irrespective of contraction level.

DNA fragments corresponding to genes encoding the MSP of Caenorhabditis elegans sperm have been isolated by recombinant DNA techniques. Analyses of individual genomic clones suggest that there are multiple MSP genes that are dispersed in the genome. From restriction enzyme digests of genomic DNA fractionated and hybridized with an MSP complementary DNA probe, there appear to be more than 30 MSP genes in the genome. Despite the occurrence of this large dispersed multigene family, the MSP messenger RNA from both males and hermaphrodites is homogene in size. There are at least three different proteins of identical molecular weight but different isoelectric point that cross-react with anti-MSP antisera. Each protein is a primary translation product with no detectable post-translational modifications, suggesting that at least three of the MSP genes are expressed.

Density gradient ultracentrifugation of low density lipoproteins (LDL) from 12 normal subjects showed multiple, distinct isopycnic bands. Densitometric scanning of the gradient tubes revealed that each band could be assigned to one of four density intervals and that the boundaries of these intervals were consistent among all the subjects. Analytic ultracentrifuge flotation (S(f)(0)) rates were assigned to the four density intervals, and there was a strong correlation between peak S(f)(0) rate and peak isopycnic banding position (R(f)) of the LDL in the 12 subjects. The S(f)(0) value corresponding to the boundary between the two most buoyant LDL density subgroups was 7.5. This value is close to that previously demonstrated to define two LDL subdivisions (S(f)(0) 0-7 and S(f)(0) 7-12) that were discriminated by differing concentrations in men and women, and differing statistical relationships with levels of HDL and VLDL in a normal population. Further delineation of distinct subspecies of LDL was afforded by electrophoresis in 2-16% gradient polyacrylamide gels. Densitometric scans of protein-stained gels revealed multiple peaks, and particle diameters were assigned to these peaks using calibration markers. Particles of diameter >/= 280 A included both IDL and Lp(a), the latter defined by pre-beta mobility on agarose electrophoresis and density > 1.050 g/ml. LDL particles with diameters 220-272 A could be grouped into seven size intervals defined by modes in the distribution of gradient gel electrophoretic peaks in LDL from a group of 68 healthy men and women. Particle diameters of the major peaks in each of seven density subfractions decreased with increasing density of the fractions. However, particles within each of the size groups were distributed across a range of densities. Use of a lipid-staining procedure allowed identification of electrophoretic bands in whole plasma which corresponded to those seen in isolated LDL, eliminating the possibility that ultracentrifugation was responsible for formation of the subspecies detected by the gradient gel procedure. The application of density gradient ultracentrifugation and gradient gel electrophoresis provides a means of characterizing LDL from normal humans in terms of multiple distinct subpopulations which may also prove to have differing metabolic and pathologic properties.-Krauss, R. M., and D. J. Burke. Identification of multiple subclasses of plasma low density lipoproteins in normal humans.