The effect of cyclophosphamide on the centromere separation sequence in Chinese hamster spermatogonia

Summary The sequence of centromere separation in spermatogonial chromosomes of untreated and cyclophosphamide-treated Chinese hamsters is described.Centromeres of chromosome 1 and 2 separated much earlier than all other chromosomes, especially 6–8. Cyclophosphamide significantly inhibits the centromere separation in all chromosome groups but does not alter the sequence of separation.     

The regulation of the biosynthesis of ubiquinone in the rat.

The urinary excretion of p-hydroxybenzoate was not altered by ubiquinone feeding, but, although decreased considerably, was not eliminated in protein deficiency. The incorporation of p-hydroxy[U-14C]benzaldehyde into ubiquinone in vivo increased in cold-exposed and p-chlorophenoxyisobutyrate (clofibrate)-fed rats, and these changes were parallel with the changes in the incorporation of [2-14C]mevalonate under these conditions. Starvation, cholesterol feeding and cholic acid feeding resulted in the decreased incorporation of p-hydroxy[U-14C]benzaldehyde into ubiquinone, confirming the decreased ubiquinone synthesis. Feeding exogenous ubiquinone increased the hepatic ubiquinone concentration, but did not cause any decrease in the incorporation of p-hydroxy[U-14C]benzaldehyde into ubiquinone, indicating the absence of a feedback control.     

Prebiotic peptide-formation in the solid state

The reactions of benzoate ion and of glycine with adenosine 5-phosphorimidazolide have been investigated. Benzoate reacts first to give the anhydride, benzoyl-adenylate, which, in the presence of excess imidazole, reacts further to give the 2'- and 3'-esters of adenosine 5'-phosphate. Glycine also first attacks the imidazolide to give an anhydride, but this compound may react further either to give 2- and 3'-esters or to form peptides, depending on the reaction conditions.     

Presence and Measurement of Imidazoleacetic Acid, a γ-Aminobutyric Acid Agonist, in Rat Brain and Human Cerebrospinal Fluid

Imidazoleacetic acid (IAA) was unequivocally demonstrated in rat brain, human CSF, and human plasma by a gas chromatographic-mass spectrometric method that can reliably quantify as little as 8 pmol, i.e., 1 ng. Owing to tautomerism of the imidazole ring, IAA and [15N, 15N]IAA, the internal standard, each formed two chromatographically distinct isomers after derivatization of the ring nitrogens with either ethyl chloroformate or methyl chloroformate. The isomers of n-butyl(N-ethoxycarbonyl)imidazole acetate and n-butyl(N-methoxycarbonyl)imidazole acetate were identified by analysis with methane chemical ionization and electron impact ionization of molecular and fragment ions. The levels (mean +/- SEM) of free IAA were 140 +/- 14 pmol/g and 2.7 +/- 0.2 pmol/ml in brains of untreated rats and human lumbar CSF, respectively. Mean levels of IAA in brains of anesthetized rats, perfused free of blood, did not differ significantly from mean levels of anesthetized, nonperfused controls or from untreated rats. The source or sources of IAA in brain and CSF are unknown. Because IAA is a potent agonist at gamma-aminobutyrate receptors, it merits examination as a regulator in brain.     

Cytotoxic activity of lactobacilli isolated from plant and dairy sources

Forty four cultures of Lactobacilli isolated from their natural sources such as dahi, raw milk and fermenting rice-pulse doughs etc. along with four standard strains of Lactobacilli were assayed for their cytotoxic activity against three secondary tumour cell lines. Three cultures isolated from dahi samples and identified as Lactobacillus casei D-34, L. casei D-48a, L. plantarum D-70a along with one standard strain L. casei B 1922 exhibited significant cytotoxic activity in the range of 30 to 36%.     

Trade-off between iron uptake and protection against oxidative stress: deletion of cueO promotes uropathogenic Escherichia coli virulence in a mouse model of urinary tract infection

The periplasmic multicopper oxidase (CueO) is involved in copper homeostasis and protection against oxidative stress. Here, we show that the deletion of cueO in uropathogenic Escherichia coli increases its colonization of the urinary tract despite its increased sensitivity to hydrogen peroxide. The cueO deletion mutant accumulated iron with increased efficiency compared to its parent strain; this may account for its advantage in the iron-limited environment of the urinary tract.     

A novel method to label preformed liposomes with 64Cu for positron emission tomography (PET) imaging

Radiolabeling of liposomes with 64Cu (t(1/2)=12.7 h) is attractive for molecular imaging and monitoring drug delivery. A simple chelation procedure, performed at a low temperature and under mild conditions, is required to radiolabel preloaded liposomes without lipid hydrolysis or the release of the encapsulated contents. Here, we report a 64Cu postlabeling method for liposomes. A 64Cu-specific chelator, 6-[p-(bromoacetamido)benzyl]-1,4,8,11-tetraazacyclotetradecane-N,N',N',N'-tetraacetic acid (BAT), was conjugated with an artificial lipid to form a BAT-PEG-lipid. After incorporation of 0.5% (mol/mol) BAT-PEG-lipid during liposome formulation, liposomes were successfully labeled with 64Cu in 0.1 M NH4OAc pH 5 buffer at 35 degrees C for 30-40 min with an incorporation yield as high as 95%. After 48 h of incubation of 64Cu-liposomes in 50/50 serum/PBS solution, more than 88% of the 64Cu label was still associated with liposomes. After injection of liposomal 64Cu in a mouse model, 44+/-6.9, 21+/-2.7, 15+/-2.5, and 7.4+/-1.1 (n=4) % of the injected dose per cubic centimeter remained within the blood pool at 30 min, 18, 28, and 48 h, respectively. The biodistribution at 48 h after injection verified that 7.0+/-0.47 (n=4) and 1.4+/-0.58 (n=3) % of the injected dose per gram of liposomal 64Cu and free 64Cu remained in the blood pool, respectively. Our results suggest that this fast and easy 64Cu labeling of liposomes could be exploited in tracking liposomes in vivo for medical imaging and targeted delivery.