Successful transfer of embryos recovered from a cow with chronic cervicitis of mixed aerobic and anaerobic bacterial aetiology a case report

An imported 13-year-old Simmentaler cow was presented with severe purulent cervicitis and endometritis from which Corynebacterium pyogenes , Fusobacterium necrophorum , Bacteroides melaninogenicus and an untyped Clostridium perfringens were isolated. The endometritis responded to treatment but the cervix did not and remained fibrous, continuously patent and purulent. Natural pregnancy was considered unlikely and the cow was prepared as an embryo transfer donor. Eight embryos were recovered and six transferred, resulting in five confirmed pregnancies and four live births.     

Loading and translocation of assimilate in the fine veins of sunflower leaves

Abstract The time course of loading and transport of assimilate in sunflower leaves was examined by pulse labelling with ¹⁴CO₂, followed by freeze drying or freeze substitution, and dry autoradiography at both low and high resolution. The five classes of veins, V1-V5 (V5 being smallest), show a division of function: V5 and V4 are engaged in loading and short distance transport; V3 to V1, in long distance translocation. The first high concentration of ¹⁴C is found in two or three phloem parenchyma cells (intermediary cells) of V5 and V4 veins. The sieve elements of V5 and V4 veins do not show comparable concentrations of ¹⁴C at any time. Recently assimilated ¹⁴C is transported by the intermediary cells for distances of about 0.5 mm to the V3 veins. In V3 to V1 veins translocation is in the sieve tubes. Transport in V5 and V4 veins is in two directions, that in V3 to V1, in one direction towards the petiole. The high concentration of ¹⁴C formed in the intermediary cells does not increase further as the assimilate moves to the sieve tubes of the V3 veins, and so is probably the origin of the gradient that drives translocation.     

Appearance of a State 1 – State 2 transition during chloroplast development in the wheat leaf: Energetic and structural considerations

The ability of developing chloroplasts to dynamically regulate the distribution of excitation energy between photosystem 1 and photosystem 2, and thus perform a State 1 – State 2 transition, was examined from analyses of chlorophyll fluorescence kinetics in 4- and 8-day-old Triticum aestivum L. cv. Maris Dove leaves grown under a diurnal light regime. Chloroplasts at all stages of development in the two leaf systems could undergo a State 1 – State 2 transition, except those found in the basal 0.5 cm of the 4-day-old leaf. The ability to physiologically modify the excitation energy distribution between the chlorophyll matrices of the two photosystems developed after the development of mature, fully photochemically competent photosystem 2 units and the appearance of excitation energy transfer between photosystem 2 and photosystem 1. Also, changes in the degree of energetic interaction between the two photosystems, in vivo rates of electron transport and the chlorophyll a/b ratio could not be correlated with the appearance of a State 1 – State 2 transition. Ultrastructural studies demonstrated a 32% increase in the degree of thylakoid appression in chloroplasts at the base of the 8-day-old leaf compared to the situation in the basal 0.5 cm of the 4-day-old leaf. This difference in thylakoid stacking can account for the differing abilities of these two tissues to perform a State 1 – State 2 transition when considered in the context of the distribution of the two photosystems within appressed and non-appressed regions of thylakoid membranes.     

黄素氧还蛋白参与的固氮链电子传递

棕色固氮菌中电子载体Fld直接向固氮酶铁蛋白传递电子。Fld_(ox)至Fld_R是双电子二步还原反应,极谱半波电位分别为-210、-550 mV。Fld_(ox)至Fld_(SR)的中点电位为-280 mV,Fld_(SR)至Fld_R为-500mV。铁蛋白中点电位为-256mV,加MgATP后为-390 mV。Fld_R与铁蛋白ox组成的电池电动势为244mV,电子传递可自发进行,反应的J△G~o为-23KJ/摩尔,铁蛋白被Fld_R还原的K_a=1.3×120~4,加入MgATP后△G~o为-10.6KJ/摩尔,K_a=72。因此,未加入MgATP时电子传递反应更易进行。     

Mechanism of proton-pumping in the cytochrome b/f complex

Several models have been proposed to interpret the mechanism of proton-pumping associated with the electron transfer reactions in the cytochrome b/f complex. Energetics considerations suggest that the proton pump is coupled to the oxidation of cytochrome b by plastoquinone. Experiments performed in living cells under anaerobic conditions suggest that proton-pumping can occur through two independent mechanisms. When the two b cytochromes are reduced prior to a flash illumination i.e. after a long dark anaerobic incubation (>10 minutes), proton-pumping is very likely associated with the reduction of a semiquinone by cyt b which occurs at a site close to the inner face of the membrane. The electrogenic phase is associated with the tranfer of protons via a transmembrane channel. This process is not inhibited by 2-n-nonyl-4-hydroxyquinoline N-oxide (NQNO). Under repetitive-flash or under aerobic conditions, proton-pumping occurs according to a modified Q-cycle mechanism, which is inhibited by NQNO.Dedicated to Prof. L.N.M. Duysens on the occasion of his retirement     

Fermentative degradation of monohydroxybenzoates by defined syntrophic cocultures

From anaerobic freshwater enrichment cultures with 3-hydroxybenzoate as sole substrate, a slightly curved rod-shaped bacterium was isolated in coculture with Desulfovibrio vulgaris as hydrogen scavenger. The new isolate degraded only 3-hydroxybenzoate or benzoate, and depended on syntrophic cooperation with a hydrogenoxidizing methanogen or sulfate reducer. 3-Hydroxybenzoate was degraded via reductive dehydroxylation to benzoate. With 2-hydroxybenzoate (salicylate), short coccoid rods were enriched from anaerobic freshwater mud samples, and were isolated in defined coculture with D. vulgaris. This isolate also fermented 3-hydroxybenzoate or benzoate in obligate syntrophy with a hydrogen-oxidizing anaerobe. The new isolates were both Gram-negative, non-sporeforming strict anaerobes. They fermented hydroxybenzoate or benzoate to acetate, CO₂, and, presumably, hydrogen which was oxidized by the syntrophic partner organism. With hydroxybenzoates, but not with benzoate, Acetobacterium woodii could also serve as syntrophic partner. Other substrates such as sugars, alcohols, fatty or amino acids were not fermented. External electron acceptors such as sulfate, sulfite, nitrate, or fumarate were not reduced. In enrichment cultures with 4-hydroxybenzoate, decarboxylation to phenol was the initial step in degradation which finally led to acetate, methane and CO₂.     

Kinetic characterization of early intermediates in the folding of E. coli tryptophan-synthase beta 2 subunit

This report describes the use of fluorescence energy transfer between an intrinsic energy donor (tryptophan 177) and two chemically added acceptors to study intermediates in the folding of the beta 2 subunit of E. coli tryptophan-synthase. Two early folding steps are thus identified and characterized. One is very rapid (its rate constant at 12 degrees C is 0.02 sec-1) and corresponds to the folding of the N-terminal domain into a structure whose overall features approximate well those of the native domain. The second step is somewhat slower (its rate constant at 12 degrees C is 0.008 sec-1) and involves a conformational rearrangement of the N-terminal domain brought about by the interactions between the N- and C-terminal domains within a monomeric beta chain. This brings to five the number of intermediates which have been identified and ordered on the folding pathway of the dimeric beta 2 subunit.     

Toxoplasma gondii: decreased resistance to intracellular bacteria in mice

The effect of sublethal inocula of Toxoplasma gondii on the course of listeriosis and salmonellosis in mice was investigated. Intravenous injection of T. gondii 24 hr after inoculation of Listeria monocytogenes increased mortality from 16% (L. monocytogenes alone) to 68% (L. monocytogenes + T. gondii) (P less than 0.001). Multiplication of L. monocytogenes in spleens also was increased significantly in mice given T. gondii. By 3 days after infection, mice that had received T. gondii and L. monocytogenes had approximately 10 times the number of L. monocytogenes per spleen compared to mice receiving L. monocytogenes alone. Similarly, mortality and the number of bacteria in spleens were increased in mice injected with Salmonella typhimurium and then inoculated with T. gondii. An in vitro assay of macrophage listeriacidal activity was used to investigate the mechanism of this decreased resistance. Peritoneal macrophages from mice injected with T. gondii were less bactericidal than macrophages from uninfected mice. Delayed hypersensitivity responses to L. monocytogenes antigen were markedly suppressed in mice injected with T. gondii. T. gondii infection appears to suppress both macrophage and T-lymphocyte function and may result in decreased resistance to infections caused by intracellular bacteria.     

Isolation of a brain peptide identical to the intestinal PHI (peptide HI)

The isolation of a brain peptide identical to the intestinal peptide PHI (peptide HI) is described. The peptide was isolated from porcine brain extract using a chemical assay method based on its C-terminal isoleucine amide structure. The complete amino acid sequence of the peptide was found to be: His-Ala-Asp-Gly-Val-Phe-Thr-Ser-Asp-Phe-Ser-Arg-Leu-Leu-Gly-Gln-Leu-Ser-Ala- Lys-Lys-Tyr-Leu-Glu-Ser-Leu-Ile-NH2. This sequence is identical to the intestinal peptide thus demonstrating PHI to be a brain-gut peptide. The role of PHI in the central nervous system as a neurotransmitter or neuromodulator is discussed.     

The orientation of the magnetic axes of membrane-bound iron-sulfur clusters and a cytochrome b-559 in the green halophilic alga Dunaliella parva

Photosynthetic membrane fragments separated from whole cells of the green alga Dunaliella parva, were oriented by incorporation into multilayers on thin Mylar films. These partially dehydrated films were then examined by EPR spectroscopy for evidence of orientation of paramagnetic components. Five previously identified paramagnetic components, the reduced states of iron-sulfur clusters A and B, the intermediate acceptor X^?, the reduced Rieske iron-sulfur cluster, and oxidized cytochrome b-559, displayed EPR signals showing orientation. In addition, several previously unknown paramagnetic components were also observed to be oriented. Four components, previously characterized in spinach chloroplast preparations, the iron-sulfur clusters A and B, the intermediate acceptor X^?, and cytochrome b-559, were shown to be similar in the green alga, D. parva. The orientations of iron-sulfur clusters A and B, however, were determined unambiguously in this preparation; this was not possible in previous work with spinach. The heme plane orientation of cytochrome b-559 was found to be perpendicular to the membrane plane in agreement with the results in spinach preparations. A new photoinduced EPR signal with g values of 1.88, 1.97 and 2.12 was seen only in the oriented preparations and was indicative of a reduced iron-sulfur cluster with an orientation different from that of iron-sulfur cluster A or B. This suggests the existence of a previously unidentified acceptor in Photosystem I of green plants. These studies clearly show that the orientation of these components in bioenergetic membranes are conserved over a large span of evolutionary development and are, therefore, an important aspect of the mechanism of electron transfer.