Studies on preimplantation development of buffalo embryos

A total of 71 lactating and nonlactating buffalo-cows of the Murrah breed and F(1)-F(3) crossbreds of Murrah x Bulgarian buffalo were used for a year as donors of embryos after a preliminary treatment for superovulation induction with pregnant mare serum gonadotrophin (PMSG) or follicle stimulating hormone (FSH) in combination with prostaglandin F-2 alpha analog (PGF-2 alpha) according to general application procedures in cows. From 36 to 72 h following prostaglandin injection, the buffalo-cows were checked with the help of a teaser bull for detection of estrus. The animals in estrus were inseminated twice either naturally or artificially with frozen semen. Nonsurgical flushing of the uterine horns was done in 45 of the buffalo-cows between 108 and 162 h after the onset of estrus. After slaughter the uterine horns and oviducts of the other 26 animals were flushed separately between 74 and 108 h after the beginning of estrus. Seven late morulae and eight hatched blastocysts were recovered between 114 and 116 h from the onset of estrus as a result of nonsurgical flushing. All of the 40 embryos recovered after 117 h were in the hatched blastocyst stage. As a result of flushing the oviducts and the uterine horns of slaughtered donors between 74 and 100 h, eggs were obtained only from the oviducts, while flushing conducted between 102 and 108 yielded eggs from both the oviducts and the uterine horns.     

Radiology: angiographic diagnosis and therapy for impotence

The Scientific Board of the California Medical Association presents the following inventory of items of progress in radiology. Each item, in the judgment of a panel of knowledgeable physicians, has recently become reasonably firmly established, both as to scientific fact and important clinical significance. The items are presented in simple epitome, and an authoritative reference, both to the item itself and to the subject as a whole, is generally given for those who may be unfamiliar with a particular item. The purpose is to assist busy practitioners, students, research workers or scholars to stay abreast of these items of progress in radiology that have recently achieved a substantial degree of authoritative acceptance, whether in their own field of special interest or another.The items of progress listed below were selected by the Advisory Panel to the Section on Radiology of the California Medical Association and the summaries were prepared under its direction.     

Seasonal changes in inhibin activity in seminal plasma and serum concentrations of FSH, LH and testosterone in the male goat (Capra hircus)

Inhibin activity in goat seminal plasma was measured by in vitro assay throughout successive 9 months and its relationship with the serum FSH, LH and testosterone concentrations was investigated. Total inhibin activity (TIA) in seminal plasma gradually increased from spring to summer, reduced in autumn (P<0.05) and recovered toward winter (P<0.05). Serum FSH and LH reached a peak in mid-summer (P<0.01) and returned to the low levels in autumn. Serum testosterone also increased in mid-summer and kept the high levels until the early winter (P<0.05). Some positive correlation was found in monthly levels between seminal TIA and serum FSH (r=0.305; P<0.05). Results suggest that the summer increase of inhibin activity in seminal plasma relates with the mid-summer rise of serum FSH levels in the male goat.     

Hookworm antigens: the potential for vaccination

Hookworms rank with Ascaris as the most prevalent soil-transmitted helminths of man. Up to 1000 million people may be infected. Not all suffer the life-threatening anaemia that reflects heavy burdens of hookworms, but even mild iron-deficiency anaemia due to hookworms can lead to intellectual and growth retardation - especially among infected children. Health education, mass chemotherapy and the sanitary disposal of faeces have been the traditional mainstays of hookworm control, but more recently chemotherapy targeted only to heavily infected individuals who appear predisposed to hookworm anaemia has emerged as a realistic alternative. Ultimately, however, knowledge of the molecular immunology of hookworm infection may provide the basis for rational vaccine development. Although the evidence for acquired immunity to hookworms in man is not strong, work is now underway to identify and to characterize antigens from third and fourth larval stages and adults of Necator americanus and species of Ancylostoma (Table 1). As this article shows, the work provides real promise for improved immunodiagnosis and possible vaccination.     

Spatial scale and the determinants of plant species richness

Traditional ecological theory has stressed the importance of competitive interactions in regulating species richness. Recent research has transcended this viewpoint by considering the role of stochastic processes, mosaic phenomena and nonequilibrium conditions in the regulation of richness. This growing body of work indicates that the determinants of plant species richness may vary predictably over different spatial scales.     

Tn10 mutagenesis in Azotobacter vinelandii

Summary The tetracycline-resistant transposon Tn10 and its high-hopper derivative Tn10HH104 were introduced into the Azotobacter vinelandii genome using suicide conjugative plasmids derived from pRK2013. Several types of mutants induced by either of these elements are described. Nif^- mutants (deficient in nitrogen fixation) were easily isolated, whereas the isolation of other mutant types (auxotrophs, sugar non-users) required special selection conditions. The characterization of the mutations as transposon insertions was often complicated and sometimes required a combination of genetic and physical tests. A common source of complication, the existence of double inserts, was found among the mutants induced by Tn10HH104 but not among those induced by Tn10. Both the high-hopper and the wild-type element proved to undergo secondary transpositions, albeit at different frequencies. Another type of complication, the existence of heterozygotes, occurred because of the high level of redundancy of the A. vinelandii genome.     

Energization and activation of inorganic carbon uptake by light in cyanobacteria

The requirement of the inorganic carbon (C_i) transport system for light in cyanobacteria was investigated in Anabaena variabilis by the filtering centrifugation technique and in a mutant (E₁) isolated from Anacystis nidulans using a gas exchange system. C_i transport capability increased with time of preillumination and decreased following darkening. Full activity could not be obtained by operating either photosystem II (PSII) or photosystem I alone. 3(3,4 Dichlorophenyl)-1,1 dimethylurea strongly inhibited C_i uptake. Very low activity of PSII was sufficient to activate C_i uptake. However, in the presence of dithiothreitol PSII activity was not required. We conclude that light may be required to activate as well as to energize C_i uptake in cyanobacteria.     

Consequence of Absence of Nitrate Reductase Activity on Photosynthesis in Nicotiana plumbaginifolia Plants

Chlorate-resistant Nicotiana plumbaginifolia (cv Viviani) mutants were found to be deficient in the nitrate reductase apoprotein (NR⁻nia). Because they could not grow with nitrate as sole nitrogen source, they were cultivated as graftings on wild-type Nicotiana tabacum plants. The grafts of mutant plants were chlorotic compared to the grafts of wild type. Mutant leaves did not accumulate nitrogen and nitrate but contained less malate and more glutamine than wild leaves. They exhibited a slight increase of the proportion of the light-harvesting chlorophyll a/b protein complexes and a lowering of the efficiency of energy transfer between these complexes and the active centers. After a 3 second ¹⁴CO₂ pulse, the total ¹⁴C incorporation of the mutant leaves was approximately 20% of that of the control. The ¹⁴C was essentially recovered in ribulose bisphosphate in these plants. It was consistent with a decline of ribulose bisphosphate carboxylase activity observed in the mutant. After a 3 second ¹⁴CO₂ pulse followed by a 60 second chase with normal CO₂, ¹⁴C was mainly accumulated in starch which was labeled more in the mutant than in the wild type. These results confirm the observation that in the nitrate reductase deficient leaves, chloroplasts were loaded with large starch inclusions preceding disorganization of the photosynthetic apparatus.     

Osmotically induced proton extrusion from carrot cells in suspension culture

Addition of 200 mm of a polyol to anthocyanin containing carrot (Daucus carota L.) cells in suspension culture decreased turgor pressure to zero and induced hyperpolarization of the membrane potential and acidification of the medium due to H⁺ extrusion. These changes were shown to be slightly affected by vanadate. In parallel, a decrease in intracellular ATP and total adenylate concentrations were observed. However, when the osmoticum was NaCl acidification of the medium occurred in the absence of considerable changes in intracellular ATP concentration. These results are interpreted as indicating that a drop of turgor, by addition of a polyol, triggers a proton extrusion activity which is only slightly inhibited by vanadate but apparently ATP utilizing. The observed decrease in ATP level occurs without a change in respiration rate and is accompanied by a drop in total adenylate pool. However when NaCl is the osmoticum it is assumed that Δ_μH+ is enhanced through a Na⁺/H⁺ antiporter. The difference between the two types of osmotica as related to their ability to penetrate through the cellular membrane is discussed.