Exon skipping in the sterol 27-hydroxylase gene leads to cerebrotendinous xanthomatosis

We report a new mutation in the sterol 27-hydroxylase (CYP 27) gene in a Dutch family with cerebrotendinous xanthomatosis: a G→A transition in the splice donor site in intron 4. This mutation leads to skipping of exon 4, resulting in a loss of 66 amino acids in the CYP 27 enzyme molecule. Received: 15 March 1997 / Accepted: 26 March 1997     

Immunohistochemical localization of atrial natriuretic polypeptide (ANP) in human atrial and ventricular myocardiocytes

To date, there have been few immunohistochemical investigations of atrial natriuretic polypeptide (ANP) in human cardiac tissue, especially the ventricles. In this study, myocardial tissue was obtained from two sources: the bilateral atria and ventricles at autopsy; and biopsy tissues from the right auricle and left ventricle of a patient with myocardial infarction undergoing surgery. These tissues were examined by the avidin-biotin immunoperoxidase technique using three kinds of primary ANP-antibodies. ANP-immunoreactivity was observed in the perinuclear region of myocytes of all tissues examined. The intensity of the reaction was stronger in atrial tissue, weaker in ventricular tissue. In the later tissue, the positive-staining myocytes were not part of the pulse-conducting system. Although the tissues we studied were not obtained from normal hearts, our data demonstrates that ANP-reactivity can be detected in ventricular myocytes outside the pulse-conducting system.     

Immunohistochemical localization of atrial natriuretic polypeptide (ANP) in human atrial and ventricular myocardiocytes

Summary To date, there have been few immunohistochemical investigations of atrial natriuretic polypeptide (ANP) in human cardiac tissue, especially the ventricles. In this study, myocardial tissue was obtained from two sources: the bilateral atria and ventricles at autopsy; and biopsy tissues from the right auricle and left ventricle of a patient with myocardial infarction undergoing surgery. These tissues were examined by the avidin-biotin immunoperoxidase technique using three kinds of primary ANP-antibodies. ANP-immunoreactivity was observed in the perinuclear region of myocytes of all tissues examined. The intensity of the reaction was stronger in atrial tissue, weaker in ventricular tissue. In the later tissue, the positive-staining myocytes were not part of the pulse-conducting system. Although the tissues we studied were not obtained from normal hearts, our data demonstrates that ANP-reactivity can be detected in ventricular myocytes outside the pulse-conducting system.     

Induction of endoreduplication in Chinese hamsters V79 cells by cytosine arabinoside

Endoreduplication (ER) could be induced very effectively in Chinese hamster V79 cells exposed to cytosine arabinoside (1-β-D-arabinofuranosylcytosine; Ara-C). Cells were cultured for 48 hours in Ara-C containing medium. ER frequency increases rapidly after Ara-C release. About 60% of metaphase cells were endoreduplicated at 8–10 hours after release from Ara-C (5 μg/ml). Induction of ER also depends on Ara-C concentrations.     

Crystal structure of the self-complementary 5''-purine start decamer d(GCGCGCGCGC) in the Z-DNA conformation. I.

Alternating self-complementary oligonucleotides starting with a 5'-pyrimidine usually form left-handed Z-DNA; however, with a 5'-purine start sequence they form the right-handed A-DNA. Here we report the crystal structure of the decamer d(GCGCGCGCGC) with a 5'-purine start in the Z-DNA form. The decamer crystallizes in the hexagonal space group P6(5)22, unit cell dimensions a = b = 18.08 and c = 43.10 A, with one of the following four dinucleotide diphosphates in the asymmetric unit: d(pGpC)/d(GpCp)/d(pCpG)/d(CpGp). The molecular replacement method, starting with d(pGpC) of the isomorphous Z-DNA hexamer d(araC-dG)3 without the 2'-OH group of arabinose, was used in the structure analysis. The method gave the solution only after the sugar-phosphate conformation of the GpC step was manipulated. The refinement converged to a final R value of 18.6% for 340 unique reflections in the resolution range 8.0-1.9 A. A result of the sequence alternation is the alternation in the nucleotide conformation; guanosine is C3'-endo, syn, and cytidine is C2'-endo, anti. The CpG step phosphodiester conformation is the same as ZI or ZII, whereas that of the GpC step phosphodiester is "intermediate" in the sense that zeta (O3'-P bond) is the same as ZII but alpha (P-O5' bond) is the same as ZI. The duplexes generated from the dinucleotide asymmetric unit are stacked one on top of the other in the crystal to form an infinite pseudocontinuous helix. This renders it a quasi-polymerlike structure that has assumed the Z-DNA conformation further strengthened by the long inner Z-forming stretch d(CG)4. An interesting feature of the structure is the presence of water strings in both the major and the minor grooves. In the minor groove the cytosine carbonyl oxygen atoms of the GpC and CpG steps are cross-bridged by water molecules that are not themselves hydrogen bonded but are enclosed by the water rings in the mouth of the minor groove. In the major groove three independent water molecules form a zigzagging continuous water string that runs throughout the duplex.     

Evolution of the ATP-binding-cassette transmembrane transporters of vertebrates

The ATP-binding-cassette transmembrane transporters (ABC transporters) known from vertebrates belong to four major subfamilies: (1) the P- glycoproteins (Pgp); (2) the cystic fibrosis transmembrane conductance regulators (CFTR); (3) the Tap proteins encoded with the major histocompatibility complex of mammals; and (4) the peroxisomal membrane proteins. Both Pgp and CFTR have a structure suggesting a past internal gene duplication; a phylogenetic analysis indicated that these duplications occurred independently, while an independent tandem gene duplication occurred in the case of the Tap family. Both the Pgp and Tap proteins show evidence of relationship to bacterial ABC transporters lacking internal duplication, and both are significantly more closely related to the HlyB and MsbA families of transporters from purple bacteria than they are to ABC transporters from nonpurple bacteria. The simplest hypothesis to explain this observation is that eukaryotic Pgp and Tap genes are descended from a mitochondrial gene or genes that were subsequently translocated to the nuclear genome. The Pgp genes of eukaryotes are characterized by a remarkable degree of convergent evolution between the ATP-binding cassettes of their N- terminal and C-terminal halves, whereas no such convergence is seen between the two halves of CFTR genes or between the duplicated Tap genes. Exon 13 of the CFTR gene, which encodes a putative regulatory domain not found in other ABC transporters apart from CFTR, showed high levels of both synonymous and nonsynonymous difference in comparisons among different mammalian species, suggesting that this region is a mutational hot spot.      

Steroids and electrical activity in the brain

Corticosteroid hormones can enter the brain and bind to two receptor subtypes: the high affinity mineralocorticoid receptor (MR) and the glucocorticoid receptor (GR) with approximately 10-fold lower affinity. Under physiological conditions the degree of receptor occupation will range from a predominant MR occupation (at the beginning of the inactive period, under rest) to concurrent activation of MRs and GRs (at the circadian peak and after stress). With in vitro electrophysiological recording techniques we observed that neuronal excitability in the CA1 hippocampal field is under a long-term control of MR- and GR-mediated events. The predominant occupation of MRs is associated with a stable amino acid-carried synaptic transmission; calcium- and potassium-currents are small, as are the responses to biogenic amines. Occupation of GRs in addition to MRs results in a gradual failure of CA1 neurons to respond to repeated stimulation of amino acid-mediated input; ionic conductances and responses to biogenic amines are large. In general, electrical properties recorded when both MRs and GRs are unoccupied (i.e. after adrenalectomy) resemble the responses observed when both receptor types are activated. The corticosterone dependency of electrical properties is thus U-shaped. We conclude that MR occupation may be responsible for the maintenance of information processing in the CA1 field and the stability of the circuit. Additional activation of GRs will initially suppress synaptic activity, but may eventually result in an increased instability and even vulnerability of the neuronal networks.