Hypophysiotrophic thyrotropin releasing hormone (TRH) synthesizing neurons. Ultrastructure, adrenergic innervation and putative transmitter action

The neuropeptide thyrotropin releasing hormone (TRH) is capable of influencing both neuronal mechanisms in the brain and the activity of the pituitary-thyroid endocrine axis. By the use of immunocytochemical techniques, first the ultrastructural features of TRH-immunoreactive (IR) perikarya and neuronal processes were studied, and then the relationship between TRH-IR neuronal elements and dopamine-beta-hydroxylase (DBH) or phenylethanolamine-N-methyltransferase (PNMT)-IR catecholaminergic axons was analyzed in the parvocellular subnuclei of the hypothalamic paraventricular nucleus (PVN). In control animals, only TRH-IR axons were detected and some of them seemed to follow the contour of immunonegative neurons. Colchicine treatment resulted in the appearance of TRH-IR material in parvocellular neurons of the PVN. At the ultrastructural level, immunolabel was associated with rough endoplasmic reticulum, free ribosomes and neurosecretory granules. Non-labelled axons formed synaptic specializations with both dendrites and perikarya of the TRH-synthesizing neurons. TRH-IR axons located in the parvocellular units of the PVN exhibited numerous intensely labelled dense-core and fewer small electron lucent vesicles. These axons were frequently observed to terminate on parvocellular neurons, forming both bouton- and en passant-type connections. The simultaneous light microscopic localization of DBH or PNMT-IR axons and TRH-synthesizing neurons demonstrated that catecholaminergic fibers established contacts with the dendrites and cell bodies of TRH-IR neurons. Ultrastructural analysis revealed the formation of asymmetric axo-somatic and axo-dendritic synaptic specializations between PNMT-immunopositive, adrenergic axons and TRH-IR neurons in the periventricular and medial parvocellular subnuclei of the PVN. These morphological data indicate that the hypophysiotrophic, thyrotropin releasing hormone synthesizing neurons of the PVN are directly influenced by the central epinephrine system and that TRH may act as a neurotransmitter or neuromodulator upon other paraventricular neurons.     

Comparison of genetic behaviour of the transposable element Tam3 at two unlinked pigment loci in Antirrhinum majus

Summary In Antirrhinum majus the transposable element Tam3 has been described at two unlinked loci pallida and nivea, both of which are required for the production of anthocyanin pigment in flowers. In each case the element is inserted in the promoter region and gives a variegated phenotype. We show that the rate of Tam3 excision at both loci is greatly affected by temperature, being approximately 1000-fold higher at 15°C compared with 25°C. Tam3 is also controlled by an unlinked gene Stabiliser, which considerably reduces excision rate. We show that the high degree of sensitivity to temperature and Stabiliser is an intrinsic property of Tam3 which is not shared by an unrelated element, Tam1. The Tam3 insertion at nivea gives rise to a series of alleles which confer reduced pigmentation, novel spatial patterns and changed instability. These are probably a result of imprecise excision and rearrangements of the Tam3 element.     

Demonstration of distinct corticotropin releasing factor--containing neuron populations in the bed nucleus of the stria terminalis. A light and electron microscopic immunocytochemical study in the rat

Immunocytochemical light and electron microscopic studies revealed two distinct populations of corticotropin releasing factor (CRF) - containing neurons, a dorsolateral and ventrolateral group, located in the bed nucleus of the stria terminalis (BST) of the rat brain. CRF neurons of the dorsolateral group had a smaller diameter and more primary dendrites than those of the ventrolateral group. CRF neurons in the dorsolateral BST had both somatic and dendritic spines, smooth contoured nuclei, and many dense and alveolate vesicles in their cytoplasm. Whereas, CRF neurons in the ventrolateral BST had only dendritic spines, irregularly-shaped indented nuclei and contained only alveolate vesicles in their cytoplasm. The only obvious difference in the type of unidentified afferents that synapsed on the CRF neurons of the BST could be attributed to the presence of the somatic spines on the CRF neurons of the dorsolateral population. Otherwise, the CRF neurons of the BST had a profuse innervation that included axosomatic, axospinous and axodendritic synapses. CRF-containing axons were distributed unevenly throughout the BST. The density of CRF axons was greatest in the lateral subdivisions of the BST, but the ventromedial BST contained many more CRF axons than the dorsomedial BST. The presence of these two CRF neuron populations in the BST suggests functional subdivision beyond previous proposals of a medial and lateral separation of function. Now there is additional morphological evidence to support the proposal of a dorsal and ventral separation of function within the BST.     

Upregulation ofE. coli 38kDa proteins induced by glutaraldehyde and formaldehyde

Exposure of the W3110 strain ofEscherichia coli K12 to low concentrations of glutaraldehyde or formaldehyde results in an unusual pattern of protein expression, as determined by high-resolution, two-dimensional polyacrylamide gel electrophoresis (2-D PAGE). A decline in total protein synthesis is accompanied by the upregulation of three proteins of approximate molecular weight 38 kDa. In the presence of 0.1 mM glutaraldehyde this response occurs within the first 5 min of incubation, and with 0.1 mM formaldehyde, within the first 30 min of incubation. The 38 kDa proteins continue to be expressed at high levels until cell death. Comparison of our 2-D PAGE patterns withE. coli gene-protein and plasmid indexes indicates that one of the proteins may be the major gene product of thepyrC locus. This pattern of protein synthesis may indicate a novelE. coli stress response.     

Survey of general practitioners' attitudes to AIDS in the North West Thames and East Anglian regions

As the numbers of people suffering from human immunodeficiency virus infection and the acquired immune deficiency syndrome (AIDS) increase, so will the contribution to care required from general practice. A postal questionnaire survey was therefore carried out among general practitioners in the North West Thames and East Anglian regions to determine their attitudes to AIDS and the issues it raises for them. One hundred and thirty seven questionnaires were returned (response rate 57%) and four factors underlying the doctors'' attitudes identified; these concerned disease control, general practitioner care, patient support, and perception of seriousness. There were wide divergencies of attitude among the general practitioners, younger doctors being more in line with specialist thinking on AIDS than older colleagues, and evidence of important gaps between policies advocated by AIDS specialists and bodies of opinion in general practice.Attitudes to AIDS in general practice may partly be a function of personal experience; further study is required.     

Tolerance to high concentrations of boron for the amphiploid of Triticum aestivum × Agropyron elongatum

The response to high concentrations of B in soil was compared for Triticum aestivum L. (vars. Chinese Spring and Halberd) and the amphiploid of Chinese Spring × Agropyron elongatum (Host). The tolerance of the three genotypes, with respect to yield at the high B treatments, was amphipolid>Halberd>Chinese Spring. The concentration of B in whole shoots was similar for the amphiploid and Halberd and significantly higher for Chinese Spring. The mechanism for tolerance to B appears to be the same for the amphiploid and wheat and is related to reduced accumulation of B in shoots.     

Genetic Analysis of a Mouse t Complex Locus That Is Homologous to a Kidney Cdna Clone

A mouse kidney cDNA clone, pMK174, identifies restriction fragment length polymorphisms (RFLPs) that map to two unlinked loci. One, designated D17Rp17, has been mapped near quaking, (qk), on chromosome 17 using three sets of recombinant inbred (RI) strains. A study of several t haplotypes resulted in the identification of t-specific alleles of D17Rp17 that map to the proximal half of the t complex. Neither t-specific nor wild-type D17Rp17 alleles are present in chromosomes carrying either the T Orleans (TtOrl) or the T hairpin tail (Thp) deletions. Comparison with other molecular markers indicates that pMK174 identifies a new proximal t complex locus, Rp17. The second locus identified by pMK174, termed D4Rp18, is tentatively assigned to chromosome 4 by mouse-Chinese hamster somatic cell hybrid analysis.