Complement lysis: evidence for an amphiphilic nature of the terminal membrane C5b-9 complex of human complement

The terminal, membrane-derived C5b-9 complex of human complement (C) is an apparently hollow, cylindrical macromolecule vertically oriented on the target membrane. In the present study, an antiserum to the complex has been used to probe its immunobiochemical properties. "Neoantigenic" determinants characteristic of the complex have been detected, which are absent on native C5-C9 molecules. Evidence that the C5b-9 complex is an amphiphilic molecule that possesses apolar, detergent-binding surfaces has been obtained by using charge-shift crossed immunoelectrophoresis, and by direct demonstration of Triton X-100 binding to the complex in quantitative immunoelectrophoresis. By the same criteria, serum C5, C6, and C9 are hydrophilic molecules. The results indicate that assembly of C5-C9 into the terminal membrane C5b-9 complex is accompanied by conformational changes in the individual C components that lead to the exposure of apolar molecular regions in the complex. It is proposed that this constitutes the basis for the lipid-binding properties of the macromolecule, which enable it to become inserted into biologic and artificial lipid membranes with apparent generation of a transmembrane pore.     

Drilomermis leioderma n. gen., n. sp. (Mermithidae:Nematoda) parasitizing Cybister fimbriolatus (Say) (Dystiscidae-Coleoptera)

The nematode Drilomermis leioderma n. gen., n. sp. (Merrnithidae) is described from larvae of Cybister fimbriolatus (Say) (Dytiscidae: Coleoptera) in Louisiana. Diagnostic characters of the genus Drilomermis are: medium-sized nematodes with the cuticle appearing smooth (lacking cross fibers) under the light microscope, six cephalic papillae, without mouth papillae, six hypodermal cords at midbody, 2 extremely long spicules (longer than 10 times body width at anus) which are separate and parallel (not twisted), an S-shaped vagina, medium-sized amphids located near head papillae, and postparasitic juvenile with a tail appendage. D. leioderma possesses a ventrally displaced mouth, very long vagina, and male genital papillae arranged in 3 double rows in the vicinity of the cloacal opening. Even when containing multiple parasites, about 40% of the hosts sulwived emergence of the memithids and lived several more days. In nature, some of these hosts may be able to continue their development, which is unusual since most mermithid-parasitized hosts die soon after the nematode emerges.     

A comprehensive examination of protein sequences for evidence of internal gene duplication

Summary We have implemented a routine procedure for screening protein sequences for evidence of intragenic duplications. We tested 163 protein sequences representing 116 superfamilies of unrelated proteins. Twenty superfamilies contain proteins with internal gene duplications. The intragenic duplications detected can be divided into two major types. (1) One or more duplications of all or part of a gene produce a protein with two or several detectable regions of sequence homology. Sequences from 18 superfamilies contained this type of duplication. (2) Repeated reduplication of a small DNA segment can produce a protein that is repetitive over most of its length. Three superfamilies contain such repetitive sequences. We also investigated the limits of detection of ancient duplications using sequences derived by random mutation of a model sequence consisting of ten 10-residue repeats. The original repetitive nature of the sequence was usually detected after 250 point mutations even though the ancestral segment could not be accurately reconstructed.     

Studies on Tyzzer's disease in rats.

An outbreak of an epidemic disease occurred in a specified-pathogen-free (SPF) breeding colony of rats. The clinical signs and the post-mortem findings were characteristic for Tyzzer's disease. The causative agent, Bacillus piliformis, was demonstrated microscopically in ileum, liver and myocardium, and transmitted to mice where its pathogenicity appeared to be similar to that of another strain isolated from mice. B. piliformis from spontaneously-infected rats was demonstrated by indirect immunofluorescence technique. By means of the same technique it was found that the fluorescence antibody titre obtained of the individual sera from spontaneously-infected mice, rats and rabbits was the same, whether the antigen employed was organisms isolated from rats or mice. By testing sera from healthy rats in 3 different colonies by use of immunofluorescence technique, antibodies were found in several sera.     

Properties of a major α-globulin of rice endosperm

Globulin was isolated from milled rice (Oryza sativa, line IR480-5-9) by 5% NACl extraction and was precipitated by (NH₄)₂SO₂ or by dialysis against water. The extract was purified by repeated isoelectric precipitation at pH 4.5. The major globulin fraction (40%) exhibited one band by electrophoresis at pH 4.5 but two bands at pH 8.3. Similarly, one sharp peak was shown by sedimentation corresponding to 1.41S (α-globulin) in acetic acid (pH 2) and NaOH (pH 11.7) but a broad asymmetric peak was obtained at pH 6.7, 8.3 and 8.9. Gel filtration of the α-globulin at pH 6.5 exhibited 2 proteins with MW 20 000 and 98 000. The results suggest a pH dependent aggregation phenomenon. The two proteins could not be separated by DEAE-cellulose chromatography. SDS-polyacrylamide electrophoresis of α-globulin revealed one subunit with MW 18 000. This α-globulin is poorer in lysine and histidine but richer in cystine, methionine, arginine, tyrosine and glutamic acid than whole milled rice proteinfa]Taken part from the M.S. thesis of AAP from the University of the Philippine at Los Baños (1977).     

Leaf water potential,component potentials and relative water content in a xeric grass,Agropyron dasystachyum (Hook.) Scribn.

Summary Leaf water potential ( _l ), osmotic potential ( _s ), pressure potential ( _p , turgor pressure), relative water content (R) and their interrelationships were determined for a xeric grass (Agropyron dasystachyum) found in the grasslands of Canada. Thermocouple psychrometers were used to measure _l and _s ; _p was obtained by subtraction. _l dropped from near 0 bars to about-28 bars as R went from 90% to 75%. R greater than 90% was not observed, perhaps because of a systematic error in determination of turgid water content. R remained relatively high in A. dasystachyum, even at low _l . The slope of the _l -R relationship was similar to other species which are generally considered to be drought tolerant. _p as high as 14 bars was observed. Most of the decrease in _l was accounted for by a decline in _p . The ability of A. dasystachyum to adjust to fluctuating water stress over the growing season is probably as much related to changes in tissue structure and turgor relationships as to simple changes in osmotic potential.     

Evaluation of phosphorus in forest soils: Comparison of phosphorus uptake,extraction method and soil properties

Summary Phosphorus in soils from plantation of red pine (Pinus resinosa Ait.) was determined using six extractants: 0.002N H₂SO₄ (pH 3.0); 0.025N HCl+ +0.03N NH₄F; 0.5N NaHCO₃ (pH 8.5);N NH₄OAc (pH 4.8); anion exchange resin (Dower –2, Cl-form); H₂O. Correlations of extractable P with Al- and Al-+Fe-P indicated that these fractions are the dominant forms of inorganic P in most of the soils.Uptake of P by corn and Monterey pine seedlings grown in greenhouse culture was correlated with soil P extracted by the different methods. The most successful of the extractants for predicting P uptake was resin extractable P; the simple correlation coefficients were 0.811 and 0.609 for pine and corn respectively. P uptake by pine correlated significantly with 0.002N H₂SO₄ P (r=0.679),N NH₄OAc P (r=0.443), H₂O P (r=0.549) and Al-+Fe-P (r=0.532) while P uptake by corn correlated with 0.002N H₂SO₄ P (r=0.579), H₂O P (r=0.477) and organic P (r=0.460). Per cent P in pine seedling tops correlated significantly with 0.002N H₂SO₄, resin andN NH₄ OAc extractable P. Multiple regressions which included silt+clay and organic P improved correlations of some soil tests with P uptake in corn and pine seedlings respectively.Research supported by the School of Natural Resources, College of Agricultural and Life Sciences, Univ. of Wisconsin, Madison, the Wisconsin Department of Natural Resources and FAO Fellowship to the senior author.     

Effect of boron application on barley in a sierozem sandy soil

Summary In a pot culture experiment on a sierozem sandy soil (pH 8.2) rates of added B at 3 ppm although decreased root yield significantly but shoot and grain yield was unaffected even at 6 ppm added B, even though shoot B concentration was as high as 360 ppm and Ca/B ratio as low as 11. At 6 ppm applied B, shoot yield was increased by 18.5 per cent, whereas grain yield was at par with control. The results suggested that Ca/B ratio in barley straw was not a reliable index for determing the magnitude of B problem in the soil.     

Variabilin,a 6a-hydroxypterocarpan from Dalbergia variabilis

Bark and wood of the creeper Dalbergia variabilis contain the previously described friedelin, O-acetyl-oleanolic acid, formononetin, 8-O-methylretusin, (+)-vestitol, (±)-mucronulatol, (+)- and (±)-medicarpin, besides (+)-variabilin [(6aR,11aR)-6a-hydroxy-3,9-dimethoxypterocarpan]. This structure was confirmed by the conversion of (+)-variabilin into di-O-methylcoumestrol.     

The growth and nutrient uptake of winter wheat

Summary Measurements with an ion selective electrode under winter wheat and in adjacent fallow soil, from April to July 1976, showed that nitrate concentrations were high in the 0–25 cm zone and correspondingly lower at 50 cm, because of the extreme drying conditions. Maximum differences in nitrate concentrations between cropped and fallow soil occurred at Feekes' stages 6, 10, and 11.1 indicating periods of maximum uptake by the crop (cf Ref.⁴).Dry matter weight of wheat, sampled biweekly, was maximum 15 days before maturity. The foliage senesced and lost weight from Feekes' stage 10.1 onwards. Nutrient concentrations in the foliage decreased from Feekes' stage 4, but N, P and Mg concentrations in the ears increased during Feekes' stage 11. N, P and Mg accumulated in the ears at the expense of the foliage during stage 11, maximum uptake occurring at stages 11.3, 11.1 and 11.2 respectively. In contrast, K and Ca uptake ceased at stages 10.1 and 10.5 respectively and then both were lost from the foliage in heavy showers.Rates of N uptake and soil nitrate depletion correlated significantly, enabling N uptake to be deduced approximately from thesein situ soil nitrate measurements.