An overview of types of aggressive behaviour in dogs and methods of treatment

In 223 cases of dogs presented to a specialist behavioural clinic in Brisbane, Australia, 87 (39%) were for severe aggression. The classes of aggression included dominance (31.6%), territorial (29%), predatory (12.3%), intermale (12.3%), sibling rivalry (7.9%), fear biting (6%) and idiopathic rage (0.9%). The breeds most represented which attacked humans were the Bull Terrier (16%), German Shepherd and crosses (15%), Cattle dog breeds (Blue Heeler and crosses, 9.2%), Terrier breeds (9.2%), Labrador (8%), Poodle and Cocker Spaniel (both 5.7%) and Rottweiler (4.6%). The dangerous dog list put out by the local Brisbane City Council includes the first three breeds mentioned and the Rottweiler as the top four breeds causing aggression problems.

Hospital records in Victoria and Queensland confirm that most damage is caused to humans by Bull Terriers and German Shepherds. Many breeds similar to those in our study are also represented in American data on aggressive breeds.

Treatments included obedience training only, restraint only, obedience and restraint, synthetic progestins and obedience, castration, progestins and obedience, castration and obedience, use of chlorpromazine and as a last resort, euthanasia (12.6%). Entire males formed the largest group (44%), followed by castrated males and females (both 21%) and spayed females (15%).

Several breeds (Boxer, Briand, Samoyed and St. Bernard) only attacked other animals and birds.

This study reinforces evidence that social disruption is caused by aggressive dogs, but it also indicates that many responsible clients seek advice on how to deal with this behavioural problem.     

Transgenic animals as a tool for studying the effect of the c-myc proto-oncogene on cardiac development

Transgenic animals provide a model system to elucidate the role of specific proteins in development. This model is now being used increasingly in the cardiovascular system to study cardiac growth and differentiation. During cardiac myocyte development a transition occurs from hyperplastic to hypertrophic growth. In the heart the switch from myocyte proliferation to terminal differentiation is synchronous with a decrease in c-myc mRNA abundance. To determine whether c-myc functions to regulate myocyte proliferation and/or differentiation, we examined the in vivo effect of increasing c-myc expression during fetal development and of preventing the decrease in c-myc mRNA expression that normally occurs during myocyte development. The model system used was a strain of transgenic mice exhibiting constitutive expression of c-myc mRNA in cardiac myocytes throughout development. Increased c-myc mRNA expression is associated with both atrial and ventricular enlargement in the transgenic mice. This increase in cardiac mass is secondary to myocyte hyperplasia, with the transgenic hearts containing greater than twice as many myocytes as nontransgenic hearts. The results of this study indicate that constitutive expression of c-myc mRNA in the heart during development results in enhanced hyperplastic growth, and suggest a regulatory role for the c-myc protooncogene in cardiac myogenesis.     

A molecular genetic approach to the identification of isochromosomes of chromosome 21

Summary The largest class of de novo chromosomal rearrangements in Down syndrome are rea(21q21q). Classically, these rearrangements have been termed Robertsonian translocations, implying an attachment of two different chromosome 21 homologues. Additionally, a Robertsonian translocation between two chromosomes 21 cannot be distinguished from an isochromosome composed of genetically identical arms by cytogenetic analyses. Therefore, we have used molecular techniques to differentiate between true Robertsonian translocations and isochromosomes. Samples were obtained from 12 probands, ascertained for de novo rearrangements between homologous chromosomes 21 [11 rea(21q21q) and 1 rea (21;21)(q22;q22)], their parents (n = 24) and available siblings (n = 7). The parental origins of the de novo rearrangements were assigned using molecular and cytogenetic analyses. Although not statistically significant, there was a two-fold increase in the number of paternally derived de novo rearrangements (n = 8) as compared with maternally derived rearrangements (n = 4). To distinguish between rob(21q21q) and i(21q), we used restriction fragment length polymorphisms (RFLPs) spanning the length of chromosome 21. Using all informative and partially informative RFLPs, we used the method of maximum likelihood to assign the most likely rearrangement definition (i or rob) and parental origin in each family. The maximum likelihood estimates indicated that all rearrangements tested (n = 8) were isochromosomes. C-banding revealed two centromeres in three cases indicating that a U-type exchange occurred between sister chromatids in these rearrangements. Our results suggest that the majority of de novo rea(21q21q) are isochromosomes derived from a single parental chromosome 21.     

An ultrasensitive colorimetric assay for manganese

An ultrasensitive colorimetric assay for manganese is described. It is based upon the catalysis, by Mn(II), of the photochemical oxidation of o-dianisidine, sensitized by riboflavin. Catalase increases the Mn(II)-catalyzed rate of photosensitized oxidation of dianisidine to the bisazobiphenyl, while superoxide dismutase inhibits the rate. The mechanism appears to involve oxidation of Mn(II) by O2-, followed by oxidation of dianisidine by MnO2+ in equilibrium Mn(III). Cu(II) interferes, but Zn(II), Fe(II), Fe(III), Co(II), and Ni(II) do not. Chelating agents and thiol reductants also interfere. Interference by Cu(II) can be overcome by the addition of cyanide, while interference by organic compounds can be surmounted by wet ashing. This assay provides a linear response to Mn(II) over the range 10-2500 nM. The limit of detection was 5 nM Mn(II).     

Agalinis (Scrophulariaceae) in Peru and Bolivia

Chromosome numbers determined for ten species ofAgalinis from Peru and Bolivia are alln=16. Field observations have provided morphological data about habit, leaves, inflorescences, and flowers. A key to species in Peru and Bolivia is provided.     

Cyclic AMP-Dependent Protein Phosphorylation in Chemosensory Neurons: Identification of Cyclic Nucleotide-Regulated Phosphoproteins in Olfactory Cilia

Chemosensory dendritic membranes (olfactory cilia) contain protein kinase activity that is stimulated by cyclic AMP and more efficiently by the nonhydrolyzable GTP analog guanosine-5'-O-(3-thio)triphosphate (GTP gamma S). In control nonsensory (respiratory) cilia, the cyclic AMP-dependent protein kinase is practically GTP gamma S-insensitive. GTP gamma S activation of the olfactory enzyme appears to be mediated by a stimulatory GTP-binding protein (G-protein) and adenylate cyclase previously shown to be enriched in the sensory membranes. Protein kinase C activity cannot be detected in the chemosensory cilia preparation under the conditions tested. Incubation of olfactory cilia with [gamma-32P]ATP leads to the incorporation of [32P]phosphate into many polypeptides, four of which undergo covalent modification in a cyclic nucleotide-dependent manner. The phosphorylation of one polypeptide, pp24, is strongly and specifically enhanced by cyclic AMP at concentrations lower than 1 microM. This phosphoprotein is not present in respiratory cilia, but is seen also in membranes prepared from olfactory neuroepithelium after cilia removal. Cyclic AMP-dependent protein kinase and phosphoprotein pp24 may be candidate components of the molecular machinery that transduces odor signals.     

II. Selective accumulation of MPP+ in the substantia nigra: A key to neurotoxicity?

The neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is rapidly metabolized to a 1-methyl-4-phenylpyridinium species (MPP+) in the squirrel monkey. After administration of toxic doses of MPTP, the concentration of MPP+ in the substantia nigra appears to increase during the first 72 hours, reaching the highest concentration of any central nervous system (CNS) tissue studied. In contrast, the concentration of this compound in other brain areas suggested time dependent elimination during the same period. Pretreatment of animals with the monoamine oxidase (MAO) inhibitor pargyline blocks both the neurotoxic action and the biotransformation of MPTP. In animals given pargyline and MPTP, initial MPTP levels are much higher in all brain regions than in those not receiving pargyline, but by 12 hours, MPTP levels had fallen rapidly in all regions except the substantia nigra and the eye. It may be that the selective toxicity of MPTP is related in some way to the accumulation of its oxidized metabolite in the substantia nigra.     

Influence of δ-Opioid Receptors on Production of Labeled Methionine5-Enkephalin in Murine Neuroblastoma Cells

Synthesis of methionine5-enkephalin by intact cells of murine neuroblastoma clone N1E-115 has been demonstrated both immunocytochemically and biochemically. In addition, N1E-115 cells possess homogeneous enkephalin (delta) receptors which inhibit prostaglandin E1-induced intracellular cyclic AMP formation. An assay was developed for measuring de novo synthesis of methionine5-enkephalin by pulsing cells in culture with radioactive methionine and isolating this pentapeptide to radiochemical purity by a procedure that included immunoaffinity chromatography specific for oxidized methionine5-enkephalin. This assay indicated that production of radiolabeled-methionine5-enkephalin was increased upon lengthy exposure of intact N1E-115 cells in the late logarithmic phase of growth to a nonproteolyzable analog of methionine5-enkephalin. This increase in synthesis of intracellular methionine5-enkephalin relative to control cells was prevented by prior incubation of the clone with naloxone, indicating that the response was mediated by the delta receptor.     

Effects of ultraviolet-B radiation on plants during mild water stress. IV. The insensitivity of soybean internal water relations to ultraviolet-B radiation

The combined effects of ultraviolet-B (UV-B, 280–320 nm) radiation and water stress were investigated on the water relations of greenhouse grown soybean [ Glycine max (L.) Merr. cv. Essex]. On a weighted (Caldwell 1971), total daily dose basis, plants received either 0 or 3 000 effective J m² UV-B_BE supplied by filtered FS-40 sunlamps. The latter dose simulated the solar UV-B radiation anticipated at College Park, Maryland, U.S.A. (39°N latitude) in the event that the global stratospheric ozone column is reduced by 25%. Plants were either well-watered or preconditioned by drought stress cycles. Diurnal measurements of water potential and stomatal conductance were made on the youngest fully expanded leaf. Various internal water relations parameters were determined for detached leaves. Plants were monitored before, during and after water stress. There were no significant differences in leaf water potential or stomatal conductance between treatments before plants were preconditioned to water stress. However, drought stress resulted in significantly lower midday and afternoon leaf water potentials and lower leaf conductances as compared to well-watered plants. UV-B radiation had no additional effect on leaf water potential; however, UV did result in lower leaf conductances in plants preconditioned to water stress. Turgid weight:dry weight ratio, elastic modulus, bound water and relative water content were unaffected by UV-B radiation. Osmotic potentials at full and zero turgor were significantly lower in the drought stressed treatments as compared to well-watered plants.