Morphological characteristics of testicular tissue in animals subjected to unilateral laser castration

In this paper, results of the morphological studies of mammalian testicular tissue after exposure of one of the testes to powerful laser radiation are reported. The results obtained are compared with those reported in the literature on the biological effect of penetrating radiation. No negative influence of powerful laser radiation is registered at the organism level. The criteria for estimation are the tissue response, morphological picture of spermatogenesis, and reproductive functions of exposed animals and of their progeny.     

Distinctions betweenHordeum bulbosum andH. murinum s.l. in seed and herbarium collections

It is sometimes necessary to identify eitherH. bulbosum orH. murinum on the basis of the inflorescence or seeds alone. The majority of taxonomic keys use the presence of swollen basal culms for the former against the annual habit for the latter. Confusion is due to similarities in inflorescences and spikelet morphology. Lodicules which always persist and are present beside the fruit in a mature caryopsis, and other characters such as the awns of the lemmas of the lateral spikelets enable conclusive distinction.     

Bacterially induced stolon settlement in the scyphopolyp ofAurelia aurita (Cnidaria,Scyphozoa)

Unsettled stoloniferous scyphopolyps ofAurelia aurita Lamarck were offered different substrates for settlement under defined conditions. On addition of different biogenic and abiotic substrates, a pure strain of bacteria, a species of Micrococcaceae, was observed to trigger the settlement of the stolon. The settlement reaction only takes place following direct contact with the bacteria; sterile filtrated culture medium of the same bacterial strain was not able to induce settlement. The bacteria were found to be effective on stolon settlement during the logarithmic growth phase, but not during the stationary phase.     

A review of the genetic effects of ethyl methanesulfonate

Ethyl methanesulfonate (EMS) is a monofunctional ethylating agent that has been found to be mutagenic in a wide variety of genetic test systems from viruses to mammals. It has also been shown to be carcinogenic in mammals. Alkylation of cellular, nucleophilic sites by EMS occurs via a mixed SN1/SN2 reaction mechanism. While ethylation of DNA occurs principally at nitrogen positions in the bases, because of the partial SN1 character of the reaction, EMS is also able to produce significant levels of alkylation at oxygens such as the O6 of guanine and in the DNA phosphate groups. Genetic data obtained using microorganisms suggest that EMS may produce both GC to AT and AT to GC transition mutations. There is also some evidence that EMS can cause base-pair insertions or deletions as well as more extensive intragenic deletions. In higher organisms, there is clear-cut evidence that EMS is able to break chromosomes, although the mechanisms involved are not well understood. An often cited hypothesis is that DNA bases ethylated by EMS (mostly the N-7 position of guanine) gradually hydrolyze from the deoxyribose on the DNA backbone leaving behind an apurinic (or possibly an apyrimidinic) site that is unstable and can lead to single-strand breakage of the DNA. Data also exist that suggest that ethylation of some chromosomal proteins in mouse spermatids by EMS may be an important factor in causing chromosome breakage.     

Nuclear DNA content in differentiated tissues of sunflower (Helianthus annuus L.)

Summary Scanning cytophotometry following Feulgen-staining was used to determine nuclear DNA content in many differentiated tissues of nine cultivars, hybrids or selfed lines ofHelianthus annuus. Apart from such ephemeral tissues as endosperm and anther tapetum, it was found that tissue differentiation in sunflower occurs in the diploid condition, cells being arrested in the DNA presynthetic phase (G₁). In certain cases, however, the nuclear DNA content of differentiated G₁ cells does not exactly match the 2C DNA content found in meristematic cells, but may be either higher or lower. In endosperm and anther tapetum cells, nuclear DNA content may be as high as 24 C and 32 C, respectively. Cytological and autoradiographic analyses after³H-thymidine incorporation reveal that polyploidy in the tapetal cells is due to chromosome endoreduplication. No detectable difference between male-fertile and male-sterile plants exists as far as occurrence and level of cell polyploidy are concerned. The results are discussed in the context of previous investigations on the nuclear condition of differentiatedHelianthus annuus tissue.     

Influence of carbohydrate side chains on activity of tissue-type plasminogen activator

When messenger RNA (mRNA) from both untreated and phorbol ester-treated melanoma cells is translated in simple reticulocyte lysates, tissue-type plasminogen activator can be immunoprecipitated by an affinity-purified antibody as a approximately 52,000 mol wt protein, with no detectable biological (plasminogen activating) activity. When the reticulocyte lysate system is supplemented with a preparation of microsomal membranes, biological activity becomes detectable and a 63,000 mol wt protein can be immunoprecipitated with the same antibody. Furthermore, when natural tissue-type plasminogen activator (mol wt approximately equal to 70,000) is incubated with different glycosidases, distinct alterations in the electrophoretic mobility of the molecules are observed, together with alterations in the level of biological activity. While treatment with neuraminidase and beta-galactosidase caused decreases in activity, alpha-mannosidase caused an increase. These results suggest that the carbohydrate part of the molecule can influence its biological behavior.     

Defined medium for Moraxella bovis

A defined medium (medium MB) for Moraxella bovis was formulated. Nineteen strains grew well on medium MB. One strain was auxotrophic for asparagine, and another was auxotrophic for methionine. Strains of M. equi and M. lacunata also grew on medium MB. All strains had an absolute requirement for thiamine and were stimulated by or actually required the other growth factors in the medium.     

Effects of dissolved oxygen concentration on biodegradation of 2,4-dichlorophenoxyacetic acid

Batch experiments were conducted to examine the effects of dissolved oxygen concentration on the degradation of 2,4-dichlorophenoxyacetic acid (2,4-D) by an enrichment culture of 2,4-D-utilizing bacteria. A modified Monod equation was found to describe the relationship between the specific growth rate and the concentrations of both the organic substrate and dissolved oxygen. Values for the maximum specific growth rate, yield, and Monod coefficient for growth on 2,4-D were 0.09 h-1, 0.14 g/g, and 0.6 mg/liter, respectively. The half-saturation constant for dissolved oxygen was estimated to be 1.2 mg/liter. These results suggest that dissolved oxygen concentrations below 1 mg/liter may be rate limiting for the biodegradation of chlorinated aromatic compounds such as 2,4-D, which have a requirement for molecular oxygen as a cosubstrate for metabolism.