Archaeal histone tetramerization determines DNA affinity and the direction of DNA supercoiling

DNA binding and the topology of DNA have been determined in complexes formed by >20 archaeal histone variants and archaeal histone dimer fusions with residue replacements at sites responsible for histone fold dimer:dimer interactions. Almost all of these variants have decreased affinity for DNA. They have also lost the flexibility of the wild type archaeal histones to wrap DNA into a negative or positive supercoil depending on the salt environment; they wrap DNA into positive supercoils under all salt conditions. The histone folds of the archaeal histones, HMfA and HMfB, from Methanothermus fervidus are almost identical, but (HMfA)(2) and (HMfB)(2) homodimers assemble into tetramers with sequence-dependent differences in DNA affinity. By construction and mutagenesis of HMfA+HMfB and HMfB+HMfA histone dimer fusions, the structure formed at the histone dimer:dimer interface within an archaeal histone tetramer has been shown to determine this difference in DNA affinity. Therefore, by regulating the assembly of different archaeal histone dimers into tetramers that have different sequence affinities, the assembly of archaeal histone-DNA complexes could be localized and used to regulate gene expression.     

Curly bare (cub), a new mouse mutation on chromosome 11 causing skin and hair abnormalities,and a modifier gene (mcub) on chromosome 5

In the outcrossing of a new recessive mouse mutation causing hair loss, a new wavy-coated phenotype appeared. The two distinct phenotypes were shown to be alternative manifestations of the same gene mutation and attributable to a single modifier locus. The new mutation, curly bare (cub), was mapped to distal Chr 11 and the modifier (mcub) was mapped to Chr 5. When homozygous for the recessive mcub allele, cub/cub mice appear hairless. A single copy of the dominant Mcub allele confers a full, curly coat in cub/cub mice. Reciprocal transfer of full-thickness skin grafts between mutant and control animals showed that the skin phenotype was tissue autonomous. The hairless cub/cub mcub/mcub mice show normal contact sensitivity responses to oxazolone. The similarity of the wavy coat phenotype to those of Tgfa and Egfr mutations and the map positions of cub and mcub suggest candidate genes that interact in the EGF receptor signal transduction pathway.     

CCK-58 is the only detectable endocrine form of cholecystokinin in rat

CCK-58 differs from CCK-8 in patterns of expression of pancreatic secretion of fluid and amylase and gallbladder contraction. These differences have physiological relevance only if CCK-58 release is stimulated by nutrients entering the intestine and if CCK-58 circulates in sizeable amounts. In this study, we report that when radiolabeled CCK-58 is added to rat blood and plasma is formed, there is extensive loss and degradation of the radioactive peptide. Therefore, a new method was developed to minimize loss and degradation of this label. This method recovered >85% of the label with no detectable degradation. Furthermore, the optimized method recovered all unlabeled exogenous cholecystokinin molecular forms in >80% yields. Blood from fasted rats and rats in which cholecystokinin release was stimulated by the trypsin inhibitor camostat contained only CCK-58 (3.5 +/- 0.5 and 17 +/- 1.5 fmol/ml, respectively). Because CCK-58 predominates in the blood, this molecular form should be used in studies on the physiology and pathophysiology of cholecystokinin.     

The EEG Consistency Index as a Measure of ADHD and Responsiveness to Medication

The primary diagnostic procedure for Attention-Deficit/Hyperactivity Disorder (ADHD) is the clinical interview, because psychological, neuropsychological, and neurological tests to date have not had sufficient specificity. Currently, there is no objective means to measure severity of ADHD, or the extent to which it is benefited by various dosages of medication. We recently reported that a certain EEG profile, the Consistency Index, occurring during the transition between two easy cognitive tasks clearly differentiated ADHD from non-ADHD boys between the ages of 8 and 12. The current study replicated this with older males (19–25) using different tasks, and a double blind, placebo versus Ritalin® controlled crossover design. Seven ADHD subjects were found to have a significantly lower Consistency Index than 6 non-ADHD males while transitioning from 2 Simple tasks during placebo condition, while only the ADHD subjects demonstrated a significant improvement in their Consistency Index while on Ritalin®. Similar but nonsignificant trends were observed while transitioning across Hard tasks.     

Histones and nucleosomes in Archaea and Eukarya: a comparative analysis

Archaeal histones from mesophilic, thermophilic, and hyperthermophilic members of the Euryarchaeota have primary sequences, the histone fold, tertiary structures, and dimer formation in common with the eukaryal nucleosome core histones H2A, H2B, H3, and H4. Archaeal histones form nucleoprotein complexes in vitro and in vivo, designated archaeal nucleosomes, that contain histone tetramers and protect approximately 60 base pairs of DNA from nuclease digestion. Based on the sequence and structural homologies and experimental data reviewed here, archaeal nucleosomes appear similar, and may be homologous in evolutionary terms and function, to the structure at the center of the eukaryal nucleosome formed by the histone (H3+H4)₂ tetramer. Received: January 22, 1998 / Accepted: February 16, 1998     

Results of 12 years' treatment of chronic renal failure by dialysis and transplantation.

The survival of 305 patients with chronic renal failure treated at the Vancouver General Hospital by centre and home peritoneal dialysis, centre and home hemodialysis and cadaver renal transplantation over a 12-year period was analysed. There was decreasing survival with age except in patients undergoing home dialysis. Hypertension and analgesic nephropathy as primary causes of renal disease were associated with a poor prognosis. Hence age and diagnosis appear to be two of the main determinants of survival. Cardiovascular disease was the commonest cause of death but seven deaths were due to dialysis dementia. The results compare favourably with other published statistics.     

Relative bioactivities of cholecystokinins-8 and -33 on rat pancreatic acini

The relative potencies of cholecystokinin (CCK-33) and its carboxyl terminal octapeptide (CCK-8) for stimulation of amylase release from rat pancreatic acini was measured. Porcine CCK-33 and synthetic CCK-8 were initially subjected to high pressure liquid chromatography to assess purity. Concentrations of each peptide were determined by amino acid analysis. The relative immunoreactivities of CCK-33 and CCK-8 were compared using an antibody that recognizes the common carboxyl terminus of these forms. This antibody bound CCK-8 and CCK-33 with nearly equal affinity. The relative potencies of CCK-33 and CCK-8 were then measured by comparing their abilities to stimulate amylase release from isolated rat pancreatic acini. Statistical analysis of the relative potencies of the two hormones indicated that CCK-8 was 36% more potent than CCK-33 in this assay system. These data suggest that differences in biological activities between large and small forms of CCK are not as great as previously reported.     

Coppr deficiency in the rat. Relationship to chronic cyanide poisoning.

Daily administration of increasing doses intraperitoneally of 2.5-4.0 mg NaCN/kg to male Wistar rats for 5 weeks produced acute signs of poisoning immediately post-injection but no sign of chronic toxicity except lower final body weights than in control rats. CN-treated rats had less liver copper than controls, but not below the range of normality, and their liver mitochondrial membranes were 24% less able to bind adenine nucleotides than control membranes. No other biochemical or pathological sign of copper deficiency occurred. Liver cytochrome oxidase activity was normal after the 5 weeks of CN-administration, as was the ability of liver mitochondria to synthesize phospholipids. The ultrastructure of hepatocytes was normal without evidence of the enlarged, misshapen mitochondria produced by copper deficiency. Normal cytochrome oxidase activity of liver mitochondria, together with reduced liver copper levels and reduced binding affinity of mitochondrial membranes for adenine nucleotides, indicate that the membrane binding site for adenine nucleotides is not cytochrome oxidase per se but may involve copper, perhaps by virtue of its cationicity. With repeated exposure to CN- rats develop tolerance to acute poisoning. It is suggested that this may be due to the switch in glucose catabolism towards the pentose pathway at the expense of other pathways.