Diurnal variation of corticotropin-releasing factor binding sites in the rat brain and pituitary

Summary 1. Corticotropin-releasing factor (CRF) is thought to be involved in the regulation of the diurnal activity of the hypothalamus-pituitary-adrenal (HPA) axis and to act as a neurotransmitter in the brain. To date it is unknown whether the binding sites of the central CRF system are subject to diurnal variations. 2. We measured the number of CRF binding sites over the course of a complete 24-hr light-dark cycle in the pituitary, amygdala, bed nucleus of the stria terminalis (BNST), cingulate cortex, visceral cortex, paraventricular nucleus of the hypothalamus, hippocampus, and locus ceruleus of rats byin vitro receptor autoradiography with iodinated ovine CRF. A 24-hr time course was also established for plasma CRF and corticosterone. 3. The diurnal pattern of plasma CRF does not correlate with the pattern of plasma corticosterone. Within the brain, CRF binding in the basolateral nucleus of the amygdala showed a U-shaped curve with maximum levels in the morning and a wide hallow between 1500 and 0100. A biphasic profile with a small depression in the afternoon and a more pronounced depression in the second half of the activity period is characteristic for the other brain areas and the pituitary. The profile for the pituitary correlates with those for the BNST and the area of the locus ceruleus. Furthermore, the diurnal pattern of CRF binding sites in the BNST correlates with that of the hippocampus, and the daytime pattern of the visceral cortex is similar to that of both the hippocampus and the BNST. 4. Since the CRF-binding profiles in the brain and the pituitary clearly differ from the profiles of both plasma CRF and corticosterone, one may assume that the diurnal pattern of central CRF binding sites is not directly coupled to the activity of the HPA axis.     

Expressed Peromyscus maniculatus (Pema) MHC class I genes: evolutionary implications and the identification of a gene encoding a Qa1-like antigen

To gain insight into the evolution of rodent major histocompatibility complex (MHC) class I genes and identify important (conserved) nonclassical class I (class Ib) gene products and residues in these proteins, sixPeromyscus maniculatus MHC (Pema) class I cDNA clones were isolated and sequenced. FivePema class I cDNAs appeared most similar to mouse and rat classical class I (class Ia) genes. One exhibited highest similarity to anH2 class Ib gene,H2-T23 (encoding the Qa1 antigen). Phylogenetic trees constructed withPema, RT1, andH2 class I sequences suggested that the lineages of some rodent class Ib genes (e.g.,T23 andT24) originated prior toMus andPeromyscus speciation [>50 million years (My) ago]. Sequences of four Qa1-like proteins from three species permitted the identification of ten Qa1-specific amino acids. On the basis of molecular modeling, three residues showed the potential to interact with T-cell receptors and three residues (all corresponding to polymorphic positions among H2 class Ia proteins) were predicted to influence antigen binding. The recognition of mouse Qa1 proteins by a subset of T-cells in influenced by a locus,Qdm, which encodes the H2-D leader peptide. One of thePema class I cDNA clones classified asH2-K, D/L-like (class Ia) is predicted to encode an identical peptide, implying that an antigen binding protein (Qa1) and the antigen to which it binds (the product ofQdm) has been conserved for over 50 My. The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers U12822 (Pm13), U12885 (Pm41), U12886 (Pm52), U12887 (Pm62), U16846 (Pm11), and U16847 (Pm53)     

The upper cretaceousLacazina limestone in the Basco-Cantabrian and Iberian basins of northern Spain: Cold-water grain associations in warm-water environments

Summary The Upper Santonian to Lower CampanianLacazina Limestone consists of massive, often amalgamated beds of packstones and grainstones which were deposited in a shallow marine environment. The most abundant skeletal components are miliolid foraminifera, echinoderm, bivalve and bryozoan fragments, peloids and sparse red algae. Small, solitary corals only occur sporadically. Hermatypic corals, sponges and green algae are missing. The series which reaches thicknesses between 60 m and 160 m, was sampled at intervals of 0.5 m at five localities. The petrographic features throughout the series are mainly a product of changing depositional energy. The limestones are well cemented. Diagenesis is characterized by a transition from marine phreatic to burial cementation. Syntaxial and blocky calcite cements predominate over early acicular to bladed and microgranular cements. The faunal association within theLacazina Limestone exhibits features typical for temperate water i.e.foramol carbonates. On the other hand, oxygen (δ¹⁸O =-1.7 to −6.3 ‰ PDB) and carbon (δ¹³C to 3.0‰ PDB) isotope values of diagentically unaltered bivalve shells indicate warm surface waters corresponding better to the palaeogeographical situation of theLacazina Limestone. Nutrient-surplus is proposed as a limiting factor preventing the development of reefs and finally ofchlorozoan sediments. In the sense of sequence stratigraphy, theLacazina Limestone is interpreted to contain transgressive and highstand systems tracts. This interpretation fits well into theHaq-Vail-curve. The series shows no visible high-frequency cyclicity in the field. Several cycles were found by means of principle component analysis and spectral analysis. Their relationships to the Milankovitch spectrum are discussed. The ammonite fauna of the unit and of preceding sediments (late Coniacian to early Campanian) is described and some inoceramids are figured. They permit—for the first time—the exact dating of theLacazina Limestone in the Basco-Cantabrian Basin (BCB) and throw light on a prominent faunal change at the Coniacian/Santonian boundary. The Cenomanian to Coniacian ammonite faunas which were dominated by endemic Tethyan pseudoceratitic faunas are replaced by cosmopolitan species dominated by Madagascan elements. This drastic change permits speculations about the installation of a new oceanic current system in the Santonian.     

H-2T24 and Pema T24: orthologous expressed MHC class Ib genes from mouse and Peromyscus maniculatus

The nucleotide sequence data reported in this paper have been submitted to the GenBank nucleotide sequence database and have been assigned the accession numbers U03104 and L22338.     

A new approach for rhizosphere research by X-ray microanalysis of microliter soil solutions

Lolium perenne growing with high root density on a fine nylon mesh (Kuchenbuch and Jungk, 1982) caused the development of element gradients in the rhizosphere below the mesh. Micro-liter soil solutions from 2-mg soil samples were sprayed onto Formvar-coated grids and analyzed by X-ray microanalysis in a transmission electron microscope. The results were comparable to those obtained by flame photometry and atomic absorption spectrometry (AAS) of conventional soil solutions from 1 g soil. X-ray microanalysis of micro-soil solutions allows the application of different extraction procedures to even small amounts of soil usually available from rhizosphere experiments. Information about soil buffering characteristics in the rhizosphere can thus be obtained. Aluminum accumulation in the rhizosphere of small segments of single Picea abies fine roots grown in undisturbed natural forest soil could be detected with this technique.     

Investigation of the role of the disulphide bond in the activity and structure of staphylococcal enterotoxin C1

The goal of this study was to Investigate the role of the disulphide bond of staphylococcal enterotoxin C1 (SEC1) in the structure and activity of the toxin. Mutants unable to form a disulphide bond were generated by substituting alanine or serine for cysteine at positions 93 and/or 110. Although we did not directly investigate the residues between the disulphide linkage, tryptic lability showed that significant native structure in the cystine loop is preserved in the absence of covalent bonding between residues 93 and 110. Since no correlation was observed between the behaviour of these mutants with regard to toxin stability, emesis and T cell proliferation, we conclude that SEC1 -induced emesis and T cell proliferation are dependent on separate regions of the molecule. The disulphide bond itself is not an absolute requirement for either activity. However, conformation within or adjacent to the loop is important for emesis. Although mutants with alanine substitutions were not emetic, those with serine substitutions retained this activity, suggesting that the disulphide linkage stabilizes a crucial conformation but can be replaced by residues which hydrogen bond.     

Comparison of techniques for measuring plasmid stability in yeasts

Summary Three techniques for measuring plasmid stability in yeasts are described and evaluated. The yeast used was aKluyveromyces lactis strain which was transformed with a plasmid, pCR1, to enable production of heterologous α-amylase. The techniques were based on plate counts on a selective antibiotic-containing medium and a non-selective medium, and on clearing zones on starch-supplemented plates for α-amylase detection. The plate ratio and clearing zones methods gave comparable results while the transfer colony method estimated much lower plasmid stabilities.