Isolation and characterization of a type II restriction endonuclease from Streptococcus thermophilus

The alpha-toxin (phospholipase C) of Clostridium perfringens has been reported to contain catalytically essential zinc ions. We report here that histidine residues are essential for the co-ordination of these ion(s). Incubation of alpha toxin with diethylpyrocarbonate, a histidine modifying reagent, did not result in the loss of phospholipase C activity unless the protein was first incubated with EDTA, suggesting that zinc ions normally protect the susceptible histidine residues. When the amino acid sequences of three phospholipase C's were aligned, essential zinc binding histidine residues in the non-toxic B. cereus phospholipase C were found in similar positions in the toxic C. perfringens enzyme and the weakly toxic C. bifermentans phospholipase C.     

Striking difference in response to expanding brood parasites by birds in western and eastern Beringia

Two species of obligate brood‐parasitic Cuculus cuckoos are expanding their ranges in Beringia. Both now breed on the Asian side, close to the Bering Strait, and are found in Alaska during the breeding season. From May to July 2017, we used painted 3D‐printed model eggs of two cuckoo host‐races breeding in northeastern Siberia to test behavioral responses of native songbirds on both sides of the Bering Strait, with particular attention to species that are known cuckoo hosts in their Siberian range. Each host nest was tested after the second egg was laid and, if possible, again 4 days later with a model of a different type. Although our Siberian study site was also outside the known breeding ranges of the cuckoos, we found that Siberian birds had strong anti‐parasite responses, with 14 of 22 models rejected. In contrast, birds in Alaska had virtually no detectable anti‐parasite behaviors, with only one of 96 models rejected; the rejecters were Red‐throated Pipits (Anthus cervinus). Such differences suggest that the cuckoos might successfully parasitize naïve hosts and become established in North America whether or not their historic host species are widely available.     

Expression patterns of loricrin in various species and tissues

Abstract. In this study we analyzed the expression patterns of loricrin in various species and tissues using immunohistochemistry, immunoblotting and Northern blots. Loricrin is a glycine-, serine- and cysteine-rich protein expressed very late in epidermal differentiation in the granular layers of normal mouse and human epidermis. Later on in differentiation, loricrin becomes cross-linked as a major component into the cornified cell envelope by the formation of N^ɛ -(γ-glutamyl)lysine isopeptide bonds. This process either occurs directly or by the intermediate accumulation in L-keratohyaline granules of mouse epidermis and human acrosyringia. Loricrin was identified in all mammalian species analyzed by virtue of its highly conserved carboxy-terminal sequences revealing an electric mobility of ∼60 kDa in rodents, rabbit and cow and of ∼35 kDa in lamb and human on sodium dodecyl sulfate polyacrylamide gel electrophoresis. Loricrin is expressed in the granular layer of all mammalian orthokeratinizing epithelia tested including oral, esophageal and fore-stomach mucosa of rodents, tracheal squamous metaplasia of vitamin A deficient hamster and estrogen induced squamous vaginal epithelium of ovary ectomized rats. Loricrin is also expressed in a few parakeratinizing epithelia such as BBN [N-butyl-N-(4–hydroxybutyl)nitrosamine]-induced murine bladder carcinoma and a restricted subset of oral and single vaginal epithelial cells in higher mammals. Our results provide further evidence that the program of squamous differentiation in internal epithelia of the upper alimentary tract in rodents and higher mammals differ remarkably. In addition, we also have noted the distinct distribution patterns of human loricrin and involucrin, another major precursor protein of the cornified cell envelope.     

Toward an understanding of the economics of pastoralism: The balance of exchange between pastoralists and nonpastoralists in Western Iran, 1815–1975

It has become a theoretical commonplace among students of southwest Asian pastoralism that the balance of exchange between pastoralists and their settled neighbors has had a profound effect on pastoralists, strongly influencing household viability and, indeed, the viability of pastoralism as an adaptation. However, little attempt has been made to examine historical variation in the balance of exchange. Attempts to use transformations in the balance of exchange as a means of accounting for change among pastoralists thus remain largely impressionistic and underspecified. This paper examines variations in the balance of exchange between Iranian pastoralists and non-pastoralists from 1815 to 1977. It demonstrates that to the degree that there were long term shifts in the balance of exchange, they favored pastoralists, and it argues that this trend became stronger, rather than weaker in the 20th century. This suggests that pressures on pastoralists over this period were not directly economic and that variation in the balance of exchange itself cannot account for outcomes such as the increased settlement of Iranian pastoralists.     

Distribution of Fusarium wilt of Bambara nut (Vigna subterranea (L.) Verdc.) in farmers’ fields’ of Busia County in Western Kenya and its management using farmyard manure

A study was carried out to determine Fusarium wilt distribution in Bambara nut farmers’ fields and its management using farm yard manure (FYM). Four villages in Busia County were purposively sampled for the study. The data generated were subjected to analysis of variance and treatment means separated by least significant difference test. Fusarium wilt incidence in the fields ranged from 14.63 to 43.56%. In the greenhouse, FYM reduced the disease incidence by 10.2% and severity by 9.5% on the black landrace and 1.9 and 12.8%, respectively, on the red landrace. In the field, FYM reduced disease incidence by 9.1% and severity by 6.9% on the black landrace and 10.4 and 10.4%, respectively, on the red landrace. Farm yard manure had the lowest area under disease progress curve irrespective of the landrace. The study confirmed the presence of the pathogen in the fields and the ability to manage the disease using FYM.     

Hydrogen peroxide lethality is associated with a decreased ability to maintain positive DNA supercoiling

Hydrogen peroxide is more toxic to mammalian cells at 37 degrees C than 0 degree C at all concentrations studied. Histone-free nuclei (nucleoids) extracted from treated cells have a reduced ability to maintain positive DNA supercoiling, with the maximum effect at the higher temperature. Prior exposure of cells to sodium ascorbate at 0 degree C increased both toxicity and the inhibition of nuclear supercoil rewinding. After exposure at 0 degrees C, normal levels of supercoiling returned with both a fast and a slow component, kinetics characteristic of DNA single-strand break repair; the fast component was eliminated when cells were exposed at 37 degrees C due to in situ rejoining. At least a portion of the lethal lesions induced by hydrogen peroxide are DNA double-strand breaks (dsb) because the dsb repair-deficient mutant, xrs-5, is approximately two to three times more sensitive than wild-type cells over the initial portion of the survival curve. However, the increased toxicity found after exposure at 37 degrees C is observed equally in both cell lines, indicating that temperature-dependent cell killing is not directly linked to DNA dsb. It is suggested that cell killing at 37 degrees C is mediated through two linked processes. First, hydrogen peroxide may disrupt cation-stabilized nuclear supercoiling by direct ion oxidation. Second, as a part of the oxidation process, hydrogen peroxide will produce potentially cytotoxic free radicals close to the DNA-linked metal site, limited in extent only by the presence of chemicals capable of reducing metal ions prior to reoxidation.