Mitochondrial recombination in crosses of iso- and anisomitochondrial saccharomyces cerevisiae

Summary Mitochondrial mutants resistant to erythromycin, neomycin and monomycin were isolated. Mitochondria were transmitted from different natural strains to the cells of the same nuclear genotype. In bifactorial crosses of such isochromosomal and anisomitochondrial yeasts we tested random samples of diploid colonies. The distribution of mitochondrial markers in parent and recombinant classes has been shown to occur unequally. The asymmetry of parent and the polarity of recombinant classes were observed to differ in different mitochondrial mutants.Anisomitochondrial strain crosses proved that mitochondrial origin essentially influenced both the parent and recombinant classes distribution and the susceptibility of the transmission to the effect of mating type locus. One can distinguish between homo- and heterosexual cross combinations in terms of recombination polarity.The new type of mitochondria was found to occur with high frequency of transmission to the zygote progeny of markers resistant to erythromycin but not of markers resistant to neomycin. The problem of sex in mitochondria is discussed.     

Septic superficial thrombophlebitis: a major threat from a minor lesion

Sites of insertion of peripheral intravenous catheters remain an important but often overlooked source of hospital-acquired septicemia and the most important source of staphylococcal septicemia. Septic superficial thrombophlebitis is characterized by severe local pain and is readily evident clinically. Care of the intravenous line can prevent this complication. To be diagnosed, it must be suspected. Treatment consists of removal of the intravenous line and administration of heparin and antibiotics effective against penicillinase-producing organisms. Occasionally the vein must be ligated or, preferably, removed.     

Automated Chemical Synthesis of PNA and PNA-DNA Chimera on a Nucleic Acid Synthesizer

Abstract

Automated chemical synthesis of PNA and PNA-DNA chimera on a DNA synthesizer using the monomethoxytrityl/acyl protecting group strategy is described.     

Synthesis of Anti-Sense Phosphorothioate Analogues for Pharmacokinetic and Pre-Clinical Studies

Abstract

Nudease-resistant oligonucleotides (11 to 28-mers) containing stereorandom phosphorothioate linkages have been recently reported to exhibit potent anti-HIV III effects and sequence-specific inhibition of protein synthesis. Relatively large amounts (100 mg 1g) of these analogues. which are needed for further biological testing and initial pharmacokinetic and pre-clinical studies, were readily obtained by automated hydrogen phosphonate chemistry followed by reversed-phase HPLC and further processing. This chemistry features 1 -adamanetanecarbonyl chloride as the activator, capping with isopropyl phosphite, and more complete sulfurization in only one-step following chain assembly. An automated, quantitative. picomole method for analysis of the analogues in blood samples has been developed.     

The nature of different influence of Cd<Superscript>2+</Superscript> ions on the conformational equilibrium of triple-stranded polyribonucleotides poly(U)•poly(A)•poly(U) and poly(I)•poly(A)•poly(I) in aqueous solutions

The influence of Cd²⁺ ions on the conformational equilibrium of single-stranded (poly(U), poly(A), poly(I)) and triple-stranded polyribonucleotides (A2I, A2U) in aqueous solutions (0.1 M Na⁺ pH 7) has been investigated using difference UV spectroscopy and thermal denaturation. Analysis of the shape and intensity of the DUV spectra of poly(A), poly(I), and A2I has revealed the presence of two types of complex formed as a result of (i) interaction between Cd²⁺ and the N7 atoms of purines, producing macrochelates; and (ii) binding of Cd²⁺ to the N1 atoms of poly(A) and poly(I). Since Cd²⁺ ions are not bound to heteroatoms of the bases in A2U, the conformation of the structure remains stable up to 0.02 M Cd²⁺. There is a critical Cd²⁺ concentration (～1.5?10^?4 M) above which A2I assumes a new helical conformation with lower thermal stability. It is supposed that, upon the formation of the “metallized” A2I triplex, the Cd²⁺ ions are located inside the triple helix and form bridges between the hypoxanthine and adenine of the homopolynucleotide strands.     

Origin and diffusion of mtDNA haplogroup X

A maximum parsimony tree of 21 complete mitochondrial DNA (mtDNA) sequences belonging to haplogroup X and the survey of the haplogroup-associated polymorphisms in 13,589 mtDNAs from Eurasia and Africa revealed that haplogroup X is subdivided into two major branches, here defined as “X1” and “X2.” The first is restricted to the populations of North and East Africa and the Near East, whereas X2 encompasses all X mtDNAs from Europe, western and Central Asia, Siberia, and the great majority of the Near East, as well as some North African samples. Subhaplogroup X1 diversity indicates an early coalescence time, whereas X2 has apparently undergone a more recent population expansion in Eurasia, most likely around or after the last glacial maximum. It is notable that X2 includes the two complete Native American X sequences that constitute the distinctive X2a clade, a clade that lacks close relatives in the entire Old World, including Siberia. The position of X2a in the phylogenetic tree suggests an early split from the other X2 clades, likely at the very beginning of their expansion and spread from the Near East.     

The effect of low-molecular-weight heparin in the survival of a rabbit congested skin flap

Swelling and congestion of flaps are frequently seen postoperatively and can cause unexpected necrosis. According to previous reports, venous thrombosis seems to be a more frequent problem than arterial occlusion in both experimental and clinical surgery. Few satisfactory venous trauma models exist, and reports on experimental venous thrombosis are rare. The object of this study was to create a rabbit venous occlusion flap model and to evaluate the effect of low-molecular-weight heparin on this flap. Eight New Zealand rabbits were used in the pilot study, in which the ideal congested flap was investigated using a flap pedicle based on the central auricular artery with a skin pedicle 0, 1, 2, or 3 cm wide. The flap (3 x 6 cm) was designed on the central part of the left ear, and the central auricular vein and nerve, the former for venous return, were cut out at the base of the flap. The flaps with skin pedicles 0, 1, 2, or 3 cm wide showed mean necrosis length of 60.0, 9.3, 4.2, and 0.0 mm, respectively. The flaps with skin pedicles 0, 1, 2, or 3 cm wide showed mean necrosis of 100, 15.5, 7, and 0 percent, respectively. Therefore, the flap, based on a 1-cm-wide skin pedicle and the central auricular artery, was selected as an optimal congested flap model showing 15.5 percent necrosis. The congested flap was then elevated on the left ear of another 10 rabbits. Subcutaneous low-molecular-weight heparin (320 IU/kg) was administered immediately after surgery to five of the rabbits (the low-molecular-weight heparin group), and the remaining five were used as a control group. Fluorescein was injected 15 minutes after surgery to evaluate the circulatory territory of the flap, and the circulatory territory was measured 5 minutes after injection. The flaps were assessed 7 days after surgery by angiography, histology, and clinical findings. The circulatory territory was significantly greater in the low-molecular-weight heparin group (mean +/- SD, 39.2 +/- 3.0 mm) than the control group (mean +/- SD, 48.0 +/- 1.0 mm) (p < 0.001) assessed 7 days after surgery. The longest flap survival length in group A and group B ranged from 40 to 55 mm (mean +/- SD. 49.4 +/- 5.6 mm) and complete survival (mean +/- SD, 60.0 +/- 0.0 mm). The improvement in survival was statistically significant for group B compared with group A (p < 0.015). Histologic evaluation revealed moderate to severe venous congestion and inflammation in the control group, whereas there were minimal changes in the low-molecular-weight heparin group. Angiography of the flap revealed obvious venous occlusion in the periphery in the control group compared with the low-molecular-weight heparin group. The authors conclude that subcutaneous administration of low-molecular-weight heparin has a great potential to improve the survival length of a congested flap without major complications.     

Synthesis and preliminary analysis of a P-glycoprotein-specific [3H]-benzophenone photoaffinity label based on (-)-stipiamide

A benzophenone photoaffinity label 9 based on the polyene natural product (-)-stipiamide has been constructed using a diaminoethane spacer and the radioactive agent [3H]-BZDC (N-succinimidyl p-benzoyl-(2,3-3H)-dehydrocinnamate). Photoaffinity experiments show specific binding to human P-glycoprotein (Pgp) in the presence of cis-flupentixol but not with cyclosporin A.     

Maternal effort and joey growth in koalas (Phascolarctos cinereus)

The extent to which sex-biased maternal investment characterizes mammals is controversial, with less information available for evaluating patterns of maternal effort in marsupials than in placentals. Koalas Phascolarctos cinereus are size-dimorphic animals with a lengthy period of dependency and they reside in mating systems that might favour sex-biased maternal investment. We examined 18 years of data recorded from koalas living at the San Diego Zoo in order to examine how joey development and maternal condition might be connected. Koalas are pregnant for only 1 month, but joey emergence from the pouch does not occur until 32 weeks of age. Neither maternal condition nor age affected sex ratio at joey emergence, and both sexes had the same survivorship prospects. Koala dams transport and nurse joeys for close to 1 year, at which time the two sexes are size dimorphic. Given the poor-quality diet of koalas, combined with maternal transport of infants who are at least 25% of maternal mass, we suggest that infant rearing poses high energetic costs on koala females. We suggest that ecological and energetic constraints have moulded koala maternal strategies such that females maximize allocation of resources to offspring, regardless of sex, in order to increase prospects for joey survivorship.