The evolution of maximum body size of terrestrial mammals

The extinction of dinosaurs at the Cretaceous/Paleogene (K/Pg) boundary was the seminal event that opened the door for the subsequent diversification of terrestrial mammals. Our compilation of maximum body size at the ordinal level by sub-epoch shows a near-exponential increase after the K/Pg. On each continent, the maximum size of mammals leveled off after 40 million years ago and thereafter remained approximately constant. There was remarkable congruence in the rate, trajectory, and upper limit across continents, orders, and trophic guilds, despite differences in geological and climatic history, turnover of lineages, and ecological variation. Our analysis suggests that although the primary driver for the evolution of giant mammals was diversification to fill ecological niches, environmental temperature and land area may have ultimately constrained the maximum size achieved.     

Perineal urethrostomy in a brown capuchin monkey (Cebus apella).

A 14-yr-old male brown capuchin monkey (Cebus apella) was presented to the Veterinary Teaching Hospital of the Hebrew University of Jerusalem, Israel, with stranguria. The history included distal urethral obstruction and a previous surgical attempt to create a urinary diversion through the perineum. A perineal urethrostomy was performed. In a 17-mo follow-up period, neither stranguria nor dysuria was observed, and the monkey's social behavior appeared normal. Perineal urethrostomy appears to be a simple and practical procedure in primates with a compromised distal urethra.     

Segregation of axonal and somatic activity during fast network oscillations

In central neurons, information flows from the dendritic surface toward the axon terminals. We found that during in vitro gamma oscillations, ectopic action potentials are generated at high frequency in the distal axon of pyramidal cells (PCs) but do not invade the soma. At the same time, axo-axonic cells (AACs) discharged at a high rate and tonically inhibited the axon initial segment, which can be instrumental in preventing ectopic action potential back-propagation. We found that activation of a single AAC substantially lowered soma invasion by antidromic action potential in postsynaptic PCs. In contrast, activation of soma-inhibiting basket cells had no significant impact. These results demonstrate that AACs can separate axonal from somatic activity and maintain the functional polarization of cortical PCs during network oscillations.     

Effect of the Simultaneous Action of Zinc and Chromium on <Emphasis Type="Italic">Arthrobacter</Emphasis> spp.

Bacteria are regarded as the most effective in the detoxification of heavy metals, being environmental compatible. Metalloresistant bacteria are usually found in nature in highly contaminated environment where they interact with a combination of several toxic metals. For the present research, Arthrobacter oxydans and Arthrobacter globiformis have been isolated from the soil samples of the most polluted regions of Georgia, rich with manganese and iron, and contain co-produced toxic metals such as Cr, V, Zn, Ni, Pb, and Mo. We have studied the effects of the metals with different valence/charge on the metalloresistant Arthrobacter spp., the divalent cation—Zn(II) and the hexavalent anion—Cr(VI). The permanent presence of a nontoxic concentration of zinc alone or zinc together with the subtoxic concentration of chromium at the growth of A. oxydans and A. globiformis as batch culture causes the activation of the zinc primary uptake system transporters from the ZIP family (Zrt1). Chromium does not affect the process. The studied Arthrobacter spp. differ by the character of the activation of the antioxidant defense system. Chromium and zinc concomitant action causes the strongest oxidative stress in the case of A. globiformis that is demonstrated by the increased activity of superoxide dismutase (SOD) and catalase. In the case of A. oxydans, the zinc separate action, and the joint action of zinc and chromium decreases the activity of SOD and catalase. The antioxidant system is active in A. globiformis at the prolonged action of metals (96 h), whereas the cells of A. oxyidans activate the other defense mechanisms to survive.     

Searching a spring wheat mutation resource for correlations between yield,grain size,and quality parameters

To broaden genetic variation, an irradiated wheat (Triticum aestivum L.) M₅ population was generated in the background of spring wheat cv. Almaken. This resource was used to measure components of productivity, including grain number and grain weight (GW) per main spike, GW per plant (GWP), 1000-grain weight (TGW), grain size and grain shape, and some quality parameters. Some mutant lines, mostly in the 200-Gy-dosed germplasm, had 2–4 times higher grain iron and zinc concentrations and 7–11% higher protein content relative to the parent line. Some irradiated lines had significantly larger TGW, and grain area (GA), length, and width than the parent, cv. Almaken. The largest GA and grain length (GL) were 30–40% greater than those of the parent. Correlations for Zn concentration versus GA = 0.191, p ? 0.01, grain protein content (GPC) versus GA = 0.128, p ? 0.05, GPC versus GL = 0.113, p ? 0.05, and GPC versus grain width = 0.191, p?0.001 were observed in 200 Gy-dosed mutants. In 100 Gy-dosed mutants, correlations for Fe concentration versus GWP = 0.302, p ? 0.001 and Fe concentration versus TGW = 0.153, p ? 0.01 were found. The mutant lines showed the capacity to biofortify wheat grain without negatively impacting on crop productivity and this population offers promising donors for improving grain parameters such as GA, length, and width and quality. The data presented showed how the genetic variation generated through radiation could be used to test the linkage between various important grain parameters.     

Leaf Rust on Aegilops speltoides Caused by a New Forma Specialis of Puccinia triticina

ABSTRACT A leaf rust attacking Aegilops speltoides in its natural habitat is reported for the first time. It was found in two locations in northern and central Israel. The two collections from A. speltoides resemble wheat leaf rust, Puccinia triticina, in most spore dimensions, in the morphology of the substomatal vesicle of the urediniospore, and in DNA content in pycniospore nuclei. Similarly to P. triticina isolates from wheat, isolates taken from A. speltoides are compatible with Thalictrum speciosissimum as an aecial host and they are crossed easily with wheat leaf rust isolates. However, isolates from A. speltoides differ from wheat leaf rust in their telial host range. They are avirulent to cultivated wheat cultivars, but attack hundreds of A. speltoides accessions that were immune to wheat leaf rust. This distinct host preference justifies delineation of the newly found leaf rust as a forma specialis (f. sp. speltoides) within P. triticina.     

A new virulent strain of Puccinia hordei

Summary Four cultures of Puccinia hordei isolated from the alternate Ornithogalum hosts in Israel were virulent on seedlings of barley cultivars carrying resistance genes Pa, Pa2, Pa2 + Pa5, Pa2 + Pa6, Pa3, Pa4, and Pa7. Cultures with such a spectrum of virulence have never been reported. The cultures remained stable through 20 successive inoculation and isolation cycles. One of the cultures, T-40SS, retained its specific virulence after selfing on the alternate host. The evolution of virulent races of obligate parasites in the centers of origin of their hosts is discussed.