Decreased incidence of mycorrhizal root tips associated with soil heavy-metal enrichment

Mycorrhizal incidence was studied at two forested locations in south-central Virgina. At each location, one site with soil naturally enriched in copper, lead and zinc was designated as mineralized, and an adjacent site, with significantly lower levels of these metals, was used as a control. A total of 223 soil samples were collected during the summer of 1984 and assayed for active mycorrhizal tips. A reduced active mycorrhizal root tip count was found in those samples collected from the mineralized sites at both locations (P≤0.001).     

Dynamic compressive properties of human lumbar intervertebral joints: a comparison between fresh and thawed specimens

A comparison between the dynamic compressive properties of human lumbar intervertebral joints when fresh and after a period of deep frozen storage was made. Physiologically relevant loads of -750 +/- 250 N were applied in axial compression with the joint constrained against bending, over a frequency range of 0.01-10 Hz. Frozen storage was found not to affect the compressive stiffness or hysteresis of the seven joints. The magnitude of the observed changes in mean values were small, less than 1% decrease in the compressive stiffness and less than 1% increase in hysteresis after deep frozen storage.     

Drosophila basement membrane procollagen IV. I. Protein characterization and distribution

A collagen was isolated from Drosophila E85, Schneider line 2L and Kc cell cultures. The purified protein was characterized and antibodies were raised against it. Immunofluorescence microscopy locates this material to the regions of basement membranes of Drosophila embryos, larvae, and adults. The molecules are mostly, or entirely, homotrimers of one polypeptide chain linked by interchain disulfide bonds. The partial amino acid sequences of a cyanogen bromide cleavage product of this chain are identical with a part of the virtual translation product of the Drosophila pro alpha 1(IV) nucleotide sequence that is reported in the accompanying paper. This gene is at Drosophila chromosome location 25C and was identified by the high homology of one part of it with the noncollagenous carboxyl terminus (NC1) of vertebrate type IV basement membrane collagens (Blumberg, B., MacKrell, A. J., Olson, P. F., Kurkinen, M., Monson, J. M., Natzle, J. E., and Fessler, J. H. (1987) J. Biol. Chem. 262, 5947-5950). In the electron microscope each molecule appears as a thread with a knob at one end, which contains the carboxyl peptide domains. The variation of flexibility of the thread was mapped along its length. Pulse-chase labeling of cell cultures showed that these molecules associate into disulfide-linked dimers and higher oligomers that can be partly separated by velocity sedimentation and are resolved by sodium dodecyl sulfate-agarose gel electrophoresis. Dimers and higher oligomers formed by overlap of the amino ends of molecules were found. Mild pepsin digestion of Drosophila embryos and larvae solubilized the corresponding disulfide-linked collagen molecules, and Staphylococcus aureus V8 protease peptide maps showed the identity of the collagen derived from animals and from cell cultures. Individual, native molecules have a sedimentation coefficient s20,w = 4.1 S, the dichroic spectrum and amino acid composition of a collagen, and a Tm = 31 degrees C. Positive in situ hybridization with a specific probe for this collagen began 6-8 h after egg laying and showed message in the locations of embryos and larvae which reacted with the antibodies. This included some prominent individual cells in the hemolymph.     

Crystallization and preliminary diffraction data of Escherichia coli ADP glucose pyrophosphorylase

ADP glucose pyrophosphorylase from Escherichia coli has been crystallized from polyethylene glycol 8000 solutions. The crystals are: orthorhombic, a = 155(2), b = 153(2), c = 174(2) A, space group P2(1)2(1)2(1), four tetrameric molecules/unit cell. This gives a solvent fraction of about 75% consistent with the relatively poor diffraction quality of crystals (5.0-A resolution) and their sensitivity to x-ray exposure damage. Ways of circumventing the former and improving the latter are proposed.     

Phloem Loading and Transport of Endogenously or Exogenously Labelled Photo-Assimilate in Bean, Beet, Maize and Cucurbit

Transport of carbon-11 labelled photo-assimilate was monitoredin Phaseolus vulgaris. Beta vulgaris, Zea mays, and Cucwbitopepo. The region of leaf to be labelled was first abraded anda solution passed over it to gain access to its apoplast andmonitor changes in label therein. With PCMBS in the bathingsolution the rate of washout of label into the bathing solutionincreased, but the effect of phloem loading was very variablefor each species: on some occasions transport was hardly affected,on others it was halted. This was true even for Cucurbito pepo,where a symplastic pathway of loading has been widely acceptedand suggests that PCMBS affects symplastic transport or thatthere is an apoplastic step in Cucurbito pepo. Apoplastic pHhad little effect on transport or label washout unless a veryacid (pH 40) buffer was introduced, contrary to notions of hydrogenion co-transport for sugar uptake. Anoxia caused phloem loadingto decrease immediately and label washout to increase in allspecies. It is suggested that both symplastic and apoplasticpathways can operate in all species but that their proportionvaries according to species and ambient and/or growth conditions. Key words: Phloem loading, photo-assimilate transport     

Energetic mechanism of system A amino acid transport in normal and transformed mouse fibroblasts

Ouabain treatment (0.4 mM) of normal and transformed C3H-10T1/2 cells caused a progressive increase in 2-aminoisobutyrate (AIB) transport reaching a maximum after 16 to 18 h exposure. There was a virtually complete blockage of this stimulated rate when 3 microM cycloheximide (CHX) was added together with ouabain at T = 0. In the transformed cell, addition of CHX after 14 h had no effect; in the normal cell, it inhibited (ca. 50%) the final AIB transport rate achieved after 24 h. The t1/2 for reaching maximal activity (insensitive to CHX exposure) was thus shifted from 8 h in the transformed cell to 15 h in the normal cell. Since the rate of achieving maximal activity in the absence of CHX was about the same in the two cells, the shift in t1/2 in the presence of CHX suggests that the rate of degradation is more rapid in the normal cell. Following ouabain treatment, the apparent Km for Na+ was decreased in both cells. The Km returned to the basal level 1 h after ouabain removal in the normal cell, but remained low in the transformed cell during this time period. The stimulation of AIB transport following ouabain removal was largely abolished by a proton ionophore (1799), a lipophilic cation (tetraphenyl-phosphonium), or ouabain. These results suggest that, under the conditions of ouabain stress, there is a switch in the bioenergetic mechanism. The Na+/K+ pump and System A transporter appear to be linked and the membrane potential generated by the Na+/K+ pump activity becomes a major driving force for AIB uptake.     

Effect of individual and group rearing on age and size at maturity of male mosquitofish, Gambusia affinis

Age and size at sexual maturity were significantly greater for male mosquitofish, Gambusia affinis Baird and Girard, reared in sib-groups than for their sibs reared individually. Age at sexual maturity averaged 43.3 and 62.1 days for individually- and group-reared males, respectively, a 43% difference; final length and weight at maturity were 7.7 and 34.2% greater, respectively, for group-reared males than for their individually-reared sibs. The results were consistent among 30 families that represented the progeny of 30 wild-caught females. The observed differences may be attributable to behavioural interactions affecting the neuroendocrine control of the maturation process, as suggested by previous studies of Xiphophorus .     

Effect of a sprint training protocol on growth rate, conversion efficiency, food consumption and body composition of rainbow trout, Salmo gairdneri Richardson

Rainbow trout were sprint-trained (30 s duration) once or twice on alternate days for a period of 6 weeks. Swim speed for the first 10 s of a training bout averaged 11.4 bls for group 2 (trained once) and 10.2 bl s ⁻¹ for group 3 (trained twice). Food consumption, growth rate and conversion efficiency were measured over 2-week periods. Food consumption was 31-38% less for the trained groups than for the control group (group 1). The growth rates of control and trained fish increased gradually over the training period. The growth rate of trained fish was always significantly less (48-81%) than that of control fish. Although conversion efficiency was significantly less for group 3 at the beginning of training, no other significant differences in conversion efficiency were recorded. Maintenance rations were high in the initial period for all groups, but were lower than the initial values in the second and third periods. While condition factor was significantly lower for the trained groups, there were no differences in percent tissue protein, lipid, or moisture.     

Expression of C gamma 4 T cell receptors and lack of isotype exclusion by dendritic epidermal T cell lines

Although four murine C gamma gene segments (C gamma 1, 2, 3, and 4) are known to exist, the large majority of expressed gamma-chains have been shown to be of the C gamma 1 isotype and no evidence exists for the expression of more than one receptor by gamma delta TCR-bearing cells. We investigated the nature of the TCR expressed on a number of murine dendritic epidermal T cell-derived cell lines by using both Northern blot and immunoprecipitation analyses. One of these CD3+ cell lines (T195) expresses C gamma 4, V gamma 1, and delta mRNA, and its CD3-associated TCR complex can be precipitated by both anti-C gamma 4 and anti-delta sera, indicating that this receptor is a C gamma 4/delta heterodimer. Furthermore, we show that two cell lines (Y245, Y93) express two distinct TCR gamma-chains, one derived from the C gamma 4 locus, whereas the second gamma-chain is probably derived from the C gamma 2 locus. Together with the previous demonstration of C gamma 1/delta TCR on a number of dendritic epidermal T cell lines (DETC), these results indicate that such DETC are capable of expressing a variety of gamma delta TCR and that, in some DETC, isotype exclusion of gamma-chain expression does not occur.