Extrahelical bases in duplex DNA

The two non-complementary synthetic DNAs, poly[d(G-G-A)] and poly[d(T-C)] can form a duplex structure at moderate ionic strengths in which every other T is extrahelical:

Only this structure is consistent with the stoichiometry of formation and with the production of C? photodimers on ultraviolet light irradiation. Further characterization with respect to melting temperature and interaction with nuclease or damage-recognizing proteins is described.     

Description and SEM Observations of Meloidogyne chitwoodi n. sp. (Meloidogynidae), a Root-knot Nematode on Potato in the Pacific Northwest

Meloidogyne chitwoodi n. sp. is described and illustrated from potato (Solanum tuberosum) originally collected from Quincy, Washington, USA. This new species resembles M. hapla, but its perineal pattern is basically round to oval with distinctive and broken, curled, or twisted striae around and above the anal area. The vulva is in a sunken area devoid of striae. Vesicles or vesicle-like structures are present in the median bulb of females. The larva tail, being short and blunt with a hyaline tail terminal having little or no taper to its rounded terminus, is distinctively different from M. hapla. SEM observations revealed the nature of the perineal pattern and details of the head of larvae and males, and showed the spicules to have dentate tips ventrally. Hosts for M. chitwoodi n. sp. include potato, tomato, corn, and wheat but not strawberry, pepper, or peanut. The latter three crops are excellent hosts for M. hapla. The known distribntion of this new root-knot species presently involves certain areas of Idaho, Washington, and Oregon. The common name "Columbia root-knot nematode" is proposed for M. chitwoodi n. sp.     

Minireview possible roles of dietary fats in carcinogenesis

Epidemiological data have implicated dietary fat as an important factor in the aetiology of various cancers in humans. This suggestion is supported by the results of experiments with animals which have shown that increased amounts of dietary fat, in particular polyunsaturated fat, increase the incidence of some spontaneous and induced tumours. The enhancement of carcinogenesis by dietary fats appears to be exerted at the promotional stage of carcinogenesis. Changes induced by dietary fats in several biological systems involved in carcinogenesis may well indicate the underlying mechanisms responsible for the results of these experiments. These include the effects of dietary fats on the metabolism of chemical carcinogens, the structure and function of membranes, immunocompetence, DNA repair potential and endocrine function.     

Carbon-13 nuclear magnetic resonance of heme carbonyls. Cytochrome c and carboxymethyl derivatives of cytochrome c.

Carbonyl complexes of horse cytochrome c and various carboxymethylated derivatives have been examined using 13C NMR (carbon-13 nuclear magnetic resonance) spectroscopy. The multiplicity and chemical shift of the 13CO resonance were found to be functions of pH and the extent of alkylation. Correlations have been made among prominent features of the chemical shift titration curves and changes in the environment of the heme. A simple model compatible with the bulk of previous observations has been suggested to account for the several carbonyl resonance peaks and the complex behavior of the chemical shift with changes in pH.     

Autocatalytic activation of the proenzyme form of the C1s subunit of the first component of complement.

The autocatalytic activation of the proenzyme form of the Cls subunit of the first component of complement is reported for the first time. Incubation of the purified proenzyme at 37° and pH 7.4 results in the evolution of esterolytic activity according to a second-order autocatalytic rate law. The lag phase portion of the sigmoidal activation curve can be shortened either by increasing the proenzyme concentration or by addition of the activated Cls subunit.     

Inuit myopia: an environmentally induced "epidemic"?

Among Inuit less than 30 years old the prevalence of myopia is far in excess of that of their elders. This is especially true for females. There seems to be little, if any, genetic contribution to this "epidemic" of myopia in the young. The age and sex distribution indicates the likelihood of an environmental factor, probably cultural, being responsible for the current pattern. Other data implicate school attendance as a possible etiologic factor.