Trypsin inhibitor from the seeds of Acacia confusa.

A trypsin inhibitor (ACTI) was isolated and purified from the seeds of Acacia confusa by gel filtration, and trypsin-Sepharose 4B column affinity chromatography. The molecular weight of ACTI was found to be 21,000 +/- 1,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and amino acid composition analysis. ACTI contained four half-cystine and no methionine residues, and was rich in aspartic acid, glutamic acid, glycine, leucine, and lysine residues. The native trypsin inhibitor was composed of two polypeptide chains, and it inhibited trypsin and alpha-chymotrypsin stoichiometrically at the molar ratio of 1:1 and 2:1, respectively. The amino-terminal sequence analysis of the A. confusa trypsin inhibitor A and B chains revealed a more extensive homology with Acacia elata and silk tree trypsin inhibitors, and a less extensive homology with Kunitz soybean trypsin inhibitor.     

Bacterial DNA supercoiling and [ATP]/[ADP] ratio: changes associated with salt shock.

When Escherichia coli K-12 was shifted from a medium lacking salt to one containing 0.5 M NaCl, both the [ATP]/[ADP] ratio and negative supercoiling of plasmid DNA increased within a few minutes. After about 10 min both declined, eventually reaching a level slightly above that observed with cells growing exponentially in the absence of salt. Since in vitro the [ATP]/[ADP] ratio influences the level of supercoiling generated by gyrase (H. Westerhoff, M. O'Dea, A. Maxwell, and M. Gellert, Cell Biophys. 12:157-181, 1988), the physiological response of supercoiling to salt shock is most easily explained by the sensitivity of gyrase to changes in the intracellular [ATP]/[ADP] ratio. This raises the possibility that the [ATP]/[ADP] ratio is an important factor in the control of supercoiling.     

Drosophila topoisomerase II-DNA interactions are affected by DNA structure.

The binding of purified Drosophila topoisomerase II to the highly bent DNA segments from the SV40 terminus of replication and C. fasciculata kinetoplast minicircle DNA (kDNA) was examined using electron microscopy (EM). The probability of finding topoisomerase II positioned at or near the bent SV40 terminus and Crithidia fasciculata kDNA was two- and threefold higher, respectively, than along the unbent pBR325 DNA into which the elements had been cloned. Closer examination demonstrated that the enzyme bound preferentially to the junction between the bent and non-bent sequences. Using gel electrophoresis, a cluster of strong sodium dodecyl sulfate-induced topoisomerase II cleavage sites was mapped to the SV40 terminus DNA, and two weak cleavage sites to the C. fasciculata kDNA. As determined by EM, Drosophila topoisomerase II foreshortened the apparent length of DNA by only 15 base-pairs when bound, arguing that it does not wrap DNA around itself. When bound to pBR325 containing the C. fasciculata kDNA and the SV40 terminus, topoisomerase II often produced DNA loops. The size distribution was that predicted from the known probability of any two points along linear DNA colliding. In vitro mapping of topoisomerase II on DNA whose ends were blocked by avidin protein revealed that binding is enhanced at sites located near a blocked end as compared to a free end. These observations may contribute towards establishing a framework for understanding topoisomerase II-DNA interactions.     

Homozygous tyrosinase gene mutation in an American black with tyrosinase-negative (type IA) oculocutaneous albinism

We have identified a tyrosinase gene mutation in an American black with classic, tyrosinase-negative oculocutaneous albinism. This mutation results in an amino acid substitution (Cys----Arg) at codon 89 of the tyrosinase polypeptide. The proband is homozygous for the substitution, suggesting that this mutation may be frequently associated with tyrosinase-negative oculocutaneous albinism in blacks.     

Biotransformation of aflatoxin B1 and its conjugated metabolites by rat gastrointestinal microfloras.

Rat cecal microflora from high- and low-fiber-fed animals hydrolyzed aflatoxin conjugates to metabolites indistinguishable from aflatoxin B1 and aflatoxin P1, but aflatoxicol was not a transformation product.     

Hepatitis B surface antigen in pregnant women

Screening of HBsAg in 289 randomly selected normal pregnant women was done with counterelectrophoresis. Ten percent were found to be HBsAg positive. All of the 289 cord blood samples were HBsAg negative. Babies born to the HBsAg positive mothers were followed 2-8 months (average 3.5 months) after delivery and 37.5% were positive for HBsAg. Accordingly, the vertical transmission of HBsAg was postulated to occur during labor or after birth.     

CONTRIBUTION OF POLLEN MORPHOLOGY TO SYSTEMATICS OF COLLOMIA (POLEMONIACEAE)

Pollen morphology of 14 species of Collomia (Polemoniaceae) was examined by light microscopy, and by both scanning and transmission electron microscopy. Four distinct pollen types were observed which are based principally upon 1) shape, number and distribution of apertures, and 2) surface sculpturing: Type 1—zonocolporate with striate ridges; Type 2—zonocolporate with striato-reticulate ridges; Type 3—pantoporate with radiate ridges; Type 4—pantoporate with irregularly reticulate ridges. Evaluation of pollen morphology reveals considerable discrepancy with respect to presently accepted sectional classification. Collomia grandiflora of sect. Collomia has a pollen type similar to that of members of sect. Collomiastrum and is now interpreted as representing an independent evolutionary line derived from the latter section. Collomia diversifolia of sect. Courtoisia has a pollen morphology similar to that of sect. Collomia. whereas C. heterophylla of the same section possesses pollen unique within the genus. This last pollen type shows close similarity to the pollen of members of Polemonium, Gilia, Leptodactylon, and Ipomopsis. Pollen of C. tinctoria and C. tracyi of sect. Collomia are anomalous within Polemoniaceae. No significant difference in exine stratification was discernible among the four pollen types.     

Growth of Chaetomium cellulolyticum on Alkali-Pretreated Hardwood Sawdust Solids and Pretreatment Liquor

The treatment of a hardwood sawdust with 1% NaOH solution at 121°C dissolved 19.7% of the dry matter, mainly hemicellulose and lignin. Fermentation of the treated solids by Chaetomium cellulolyticum for 48 h gave a product containing 12.5% crude protein (total N × 6.25) on a dry weight basis. The in vitro rumen digestibility of the 48-h fermentation product was 30%, compared to 24% for the alkali-treated but unfermented sawdust. Growth was independent of sawdust particle size in the range 40 to 100 mesh. Fermentation of the pretreatment liquor gave a product containing up to 50% crude protein (dry weight basis) with an in vitro rumen digestibility of 65 to 76%. Approximately 6.7 g of crude protein was obtained from the treated solids and 2.2 g from the pretreatment liquor per 100 g of sawdust treated. The product from the pretreatment liquor fermentation has potential as a high-protein animal feed supplement but could not be produced economically without an outlet for the relatively indigestible product from the solids fermentation. Growth on the pretreatment liquor was strongly pH dependent; there was a considerable increase in the lag phase when the pH was lowered from 7.5 to 5.2. This effect appears to be due to an inhibitor whose toxicity is reduced at high pH.     

Anthraquinones in the biosynthesis of sterigmatocystin by Aspergillus versicolor.

14C-labeled averufin, versiconal hemiacetal acetate, and versicolorin A were efficiently converted to sterigmatocystin by Aspergillus versicolor, thus providing experimental evidence that these anthraquinones are biosynthetic precursors of sterigmatocystin, a xanthone.     

Case report. Cervical carcinoma with selective IgA deficiency

A patient with cervical carcinoma was found to have selective IgA deficiency. The intact cell-mediated immunity, normal levels of IgG and IgM, and the absence of serum and salivary IgA established the diagnosis. Contrary to those of normal persons, salivary IgM was elevated and salivary IgA was not detectable in this patient. The patient had no signs attributable to IgA deficiency, but she always had dryness of the mouth. The association between cervical carcinoma and selective IgA deficiency was discussed.