Cloning and structural analysis of integrated woodchuck hepatitis virus sequences from hepatocellular carcinomas of woodchucks

Woodchuck hepatitis virus (WHV), like the related hepatitis B virus, induces in its natural host hepatocellular carcinomas that contain integrated viral sequences. As a first step in determining whether and how the integrated sequences contribute to formation of the tumors in which they are found, we have cloned two such integrations of WHV and have determined their structure by restriction mapping and heteroduplex electron microscopy. The identity of the cloned sequences was confirmed by comparison of restriction sites in the clones with those located by Southern blot analysis of tumor DNA. Viral sequences in both integrations are extensively rearranged, and in neither were all parts of the viral genome represented. In this respect, the behavior of WHV in vivo is similar to that of other DNA tumor viruses that have been studied in vitro. We discuss the implications of these results in relation to possible mechanisms for tumor induction by WHV.     

Biochemical changes during germination and seedling growth in Cuscuta campestris

Changes in the contents of starch, protein, DNA, RNA, total phosphorus, acid soluble phosphorus and inorganic phosphorus, and in the activities of some enzymes of carbohydrate, amino acid, nucleic acid and phosphate metabolism were studied during the germination of Cuscuta campestris seeds. The results are expressed on per seed basis.
Starch content in Cuscuta seeds showed a steady decline with most of it depleted by the end of the eighth day of germination. Protein content increased with germination up to 48 h and then decreased. RNA and DNA contents increased to a maximal level on the fourth day of germination and then decreased. Total phosphorus in the seeds remained almost unchanged during the period of study. Both trichloroacetic acid soluble and inorganic phosphorus increased until the third day and then decreased. Phytin was rapidly hydrolyzed with little being detectable by the seventh day of germination. Glucose-6-phosphate dehydrogenase increased with germination, while fructose bisphosphate aldolase which is indispensable for glycolysis, decreased with germination. Ribonuclease and deoxyribonuclease increased till the third and fourth day, respectively, and then decreased. Aspartate and alanine aminotransferases showed a maximum on the second day and then decreased. Activities of alkaline fructose-1,6-bisphosphatase and phytase were absent in the dry seeds and appeared only on the second day of germination. Both α- and β-amylase activities were present in the dry seed.     

The influence of foraging benefits on association of cattle egrets (Bubulcus ibis) with cattle

Summary The degree of association between cattle egrets (Bubulcus ibis) and cattle was studied during one summer on Saint Catherines Island, Georgia, USA. Previous work by Grubb (1976) and others indicated that cattle egrets foraging with cattle require fewer steps and less time to catch prey than egrets foraging without cattle and single egrets catch prey at a higher rate than egrets foraging in groups of two or more with cattle. Accordingly, we predicted that when given a choice egrets should forage with cattle rather than alone, egrets should prefer to associate with standing rather than sitting cattle, and single egrets associated with cattle should be more common than expected by chance.In excess of two-thirds of the egrets accompanied cattle. Neither time of day nor month influenced the degree of association, but egrets in forest were more likely to be associated with cattle than egrets in pasture. Standing cattle were more likely to be accompanied by egrets than were sitting cattle. Single egrets occurred more frequently than expected by chance when accompanying standing cattle but not when associated with sitting cattle. Thus, cattle egrets usually distributed themselves among cattle in the way predicted by optimal foraging theory.We dedicate this paper to the memory of Michael D. Sabath     

Toward an Ecological Model of African Plio-Pleistocene Hominid Adaptations

What was the environmental complex in which the Plio-Pleistocene hominids were evolving? What situations selected f o r increasing variation in hominid morphology? A n ap-preciation of ecological dynamics is important to develop answers to those questions. The circumstances that accompany periodically more severe semiarid successions appear to have promoted a shqt in early australopithecine morphology toward hyper-robust forms. Successional dynamics (including ameliorated conditions) may have resulted in repeated sympat y of potentially competing lines. Through the process of character divergence, some earliergracile populations appear to have emerged more Homo-like by the end of the Pliocene. Palaeodemographic analysis combined with detailed ecological modeling offers new possibilities f o r explorato y retrodictions concerned with common and divergent hominid adaptations. [australopithecines. palaeoecology, early Homo]     

Differentiation of aflatoxins from territrems.

Three methods were adopted for differentiation of aflatoxins B1 and B2 from territrems A and B. They were as follows. (i) Then-layer chromatography coupled with chemical confirmation. A significant decrease in the Rf value of trifluoroacetic acid-treated aflatoxin B1 developed in chloroform-acetone (85:15, vol/vol) was satisfactory in differentiating this toxin from the other three. (ii) High-pressure liquid chromatography monitored synchronously at two wavelengths, 365 and 335 nm. The ratio derived from this double-wavelengh detection could serve as an indicator of the presence of each toxin. (iii) Velasco's flurotoxin meter method, which is used for the determination of aflatoxins within the range of 0 to 50 ng/ml, was not significantly affected by territrems even when they were present in quantities at the microgram-per-milliliter level.     

Carrier Protein-mediated Transport of Neutral Amino Acids into Mung Bean Mitochondria

The transport of neutral amino acids into mitochondria isolated from the hypocotyl of mung bean (Roxb.) was studied by the swelling technique. Isolated mitochondria swelled when added to an isosmotic solution of proline, serine, methionine, threonine, alanine, and glycine. The swelling was stereospecific in that it was faster in the l-amino acid than in the corresponding d-amino acid. Preincubation of the mitochondria with the sulfhydryl modifying reagents, p-mercuribenzoate and mersalyl, resulted in an inhibition of the swelling caused by proline, serine, threonine, and glycine. The swelling induced by alanine was inhibited only by mersalyl, whereas that by methionine was inhibited only by p-mercuribenzoate. In all cases, the inhibition caused by the sulfhydryl modifying reagents was readily reversible by the subsequent treatment of the mitochondria with dithiothreitol. N-Ethylmaleimide, another sulfhydryl-modifying reagent, did not cause any inhibition of the swelling. The findings indicate the existence of a protein mediated mechanism for the transport of neutral amino acids into plant mitochondria.     

Hydrazides of N-blocked amino acids as sole substrates with unique difunctional behavior under papain catalysis

Hydrazides of five N-acylamino acids have been used alone as substrates for papain catalysis to yield N¹,N²-diacylhydrazines. With the exception of N-(benzyloxycarbonyl)(Z)- -alanine hydrazide, they were very effective as both acylating agents of the enzyme and nucleophiles in attacking the enzyme-substrate intermediate. Although Z- -alanine hydrazide was a minimal acylating agent, it was a satisfactory nucleophile. The most favorable reaction involved Z- -alanine hydrazide in producing N¹,N²-bis(Z- -alanyl)hydrazine. When Z- -alanine hydrazide was the substrate, this same chiral diacylhydrazine was formed along with meso N¹-(Z- -alanyl)-N²-(Z- -alanyl)hydrazine. For the acylation step, the enzyme displayed powerful, essentially stereospecific, bias toward the enantiomer. Once the thioester intermediate was formed, little preference was detected for attack by the enantiomers as nucleophiles. The most direct procedure for synthesis of substrates was conversion of Z-amino acids to their esters by means of dry HCl in an absolute alcohol. Treatment with hydrazine produced the hydrazides in excellent yield.     

T lymphocytes responding to Mls-locus antigens are Lyt-1+, 2− andI-A restricted

We have investigated primary and secondary responses of mouse splenic T cells to strong mixed lymphocyte stimulating antigens controlled by theMls locus using MHC-identical mixtures of cells. Our studies show that strong primaryMls-locus specific responses involve recognition of self I-A antigens, since BUdR and light suicide or F1 into parent radiation bone-marrow chimeras both demonstrate a preference of unprimed F1 T cells to respond to Mis-locus antigens associated with one parent's MHC antigens. Furthermore, conventional anti-I-A antisera and monoclonal anti-I-A antibody both inhibitMls-locus responses in an MHC-specific manner. Finally, as is typical of T cells responding to I-A antigens or to nominal antigens associated with self I-A,Mlslocus responses are mediated by Lyt-1⁺, 2^– cells. One striking finding in these studies was the very high frequency of cells capable of responding to Mls-locus antigens, the highest being 1/300 splenic T cells. This plus evidence for recruitment during primaryMls-locus responses may account for reports of a lack ofI-A restriction in secondary anti-Mls locus responses to strong Mls-locus antigens, a finding with which we concur. The possibility that these secondary responses between noncongenic strains of mice may be directed at other genetic loci is also discussed. These experiments leave open the question of the biological role of theMls-locus and of the very large number of T cells reactive to it.Abbreviations used in this paper MHC Major histocompatibility complex - MIg Mouse immunoglobulin - MLC Mixed lymphocyte culture - TCGF T-cell growth factor     

Kidney Stones

The prevalence of kidney stones has steadily risen during this century; passage of a calculus and a positive family history increase the probability of recurrence. Findings from recent studies on the cause of renal calculi have stressed crystallization and crystal aggregation of stone minerals from supersaturated urine, rather than excessive organic matrix. Absence of normal urine inhibitors of calcium salts is also stressed. Formation of calcium oxalate stones is the major problem. Therapy with decreased calcium and oxalate intake, thiazides, phosphate salts and allopurinol in various combinations has substantially decreased the prevalence of recurrent stones. The rationale for the use of allopurinol is that uric acid salts enhance the tendency for calcium oxalate to crystallize from supersaturated urine. The hypercalciuria seen in 30 percent to 40 percent of patients with oxalate stones is usually caused by intestinal hyperabsorption of calcium. Although patients with uric acid calculi constitute only a small fraction of those in whom stones form, they represent a group in whom good medical therapy, based on sound physiologic principles, has proved extremely successful. Renal tubular syndromes lead to nephrocalcinosis and lithiasis through hypercalciuria, alkaline urine and hypocitraturia, the latter an inhibitor of calcium salt precipitation. Recent advances in surgical techniques are discussed, including the rationale for removing staghorn calculi. The ileal ureter and coagulum pyelolithotomy deserve special emphasis.