A role for cAMP in angiotensin II mediated inhibition of cell growth in AT1A receptor-transfected CHO-K1 cells

G-protein coupled Angiotensin II receptors (AT1A), mediate cellular responses through multiple signal transduction pathways. In AT1A receptor-transfected CHO-K1 cells (T3CHO/AT1A), angiotensin II (AII) stimulated a dose-dependent EC50 = 3.3 nM) increase in cAMP accumulation, which was inhibited by the selective AT1, nonpeptide receptor antagonist EXP3174. Activation of protein kinase C, or increasing intracellular Ca2+ with ATP, the calcium ionophore A23187 or ionomycin failed to stimulate cAMP accumulation. Thus, AII-induced cAMP accumulation was not secondary to activation of a protein kinase C- or ca2+/calmodulin-dependent pathway. Since cAMP has an established role in cellular growth responses, we investigated the effect of the AII-mediated increase in cAMP on cell number and [3H]thymidine incorporation in T3CHOA/AT1A cells. AII (1 microM) significantly inhibited cell number (51% at 96 h) and [3H]thymidine incorporation of 68% at 24 h) compared to vehicle controls. These effects were blocked by EXP3174, confirming that these responses were mediated through the AT1 receptor. Forskolin (10 microM) and the cAMP analog dibutyryl-cAMP (1 mM) also inhibited [3H]thymidine incorporation by 55 and 25% respectively. We extended our investigation on the effect of AII-stimulated increases in cAMP, to determine the role for established growth related signaling events, i.e., mitogen-activated protein kinase activity an tyrosine phosphorylation of cellular proteins. AII-stimulated mitogen-activated protein kinase activity and phosphorylation of the 42 and 44 kD forms. These events were unaffected by forskolin stimulated increases in cAMP, thus the AII-stimulated mitogen-activated protein kinase activity was independent of cAMP in these cells. AII also stimulated tyrosine phosphorylation of a number of cellular proteins in T3CHO/AT1A cells, in particular at 127 kD protein. The phosphorylation of the 127 kD protein was transient, reaching a maximum at 1 min, and returning to basal levels within 10 min. The dephosphorylation of this protein was blocked by a selective inhibitor of cAMP dependent protein kinase A, H89-dihydrochloride and preexposure to forskolin prevented the AII-induced transient tyrosine phosphorylation of the 127 kD protein. These data suggest that cAMP, and therefore protein kinase A can contribute to AII-mediated growth inhibition by stimulating the dephosphorylation of substrates that are tyrosine phosphorylated in response to AII.

Molecular cloning and characterization of the type VII isoform of mammalian adenylyl cyclase expressed widely in mouse tissues and in S49 mouse lymphoma cells

We have isolated a 5199-nucleotide cDNA from a mouse library containing an open reading frame encoding the 1099-amino acid type VII adenylyl cyclase protein. The type VII protein is most closely related in primary structure to an unpublished human adenylyl cyclase clone (GenBank accession no. D25538) and type II adenylyl cyclase. Northern blot analysis demonstrates that the type VII mRNA is most abundant in mouse heart, spleen, and lung. cAMP content rises rapidly in HEK 293 cells overexpressing type VII adenylyl cyclase following treatment with phorbol ester, peaking by 4 min, while cells expressing the type II adenylyl cyclase reach peak accumulation only after 20 min. Increases in intracellular calcium through treatment of type VII-293 cells with either ATP or A23187 alone failed to increase intracellular cAMP content. Phorbol ester treatment acted synergistically with beta-adrenergic stimulation to increase cAMP content in type VII-transformed cells. Pretreatment of type VII-transformed cells with pertussis toxin fails to prevent phorbol ester potentiation of isoproterenol stimulation. Thus the ability of phorbol ester to increase basal and isoproterenol-stimulated type VII activity appears to be a direct effect on this adenylyl cyclase isoform and not the result of modification of the inhibitory G protein, Gi.

Role of angiogenesis in patients with cerebral ischemic stroke

BACKGROUND AND PURPOSE

Stroke is one of the most common causes of mortality and morbidity in the Western world. It results from the occlusion of a cerebral artery followed by severe disturbances in blood supply through microvessels to brain tissue. Despite an extensive literature its pathophysiology is poorly understood, and this has severely impeded the logical development of therapy.

METHODS

Brains were obtained from 10 patients aged 46 to 85 years with survival times of 5 to 92 days after their stroke. Infarcted areas and representative control tissues from the contralateral uninvolved brain hemisphere were collected. Microvessel density was measured microscopically. A total of 6520 microvessels were scored in 10,801 areas. The level of activation of the endothelial cells was studied by immunohistochemistry using three monoclonal antibodies, viz, E-9, raised against activated endothelial cells; IG11, recognizing vascular cell adhesion molecule-1; and anti-proliferating cell nuclear antigen. Angiogenic activity in tissue extracts was examined using an in vivo chicken chorioallantoic membrane assay.

RESULTS

There was a statistically significant increase in the number of microvessels (Wilcoxon log-rank test; P < or = .01) in 9 of 10 infarcted brain tissues when compared with their contralateral normal hemisphere. In these patients the higher blood vessel counts correlated with longer survival, as ascertained by Spearman's p analysis (P < .02). The number of microvessels filled with blood cells was significantly lower in the infarcted hemispheres (P < .01). In contrast, statistically significant increased numbers of empty microvessels occurred in infarcted tissues compared with the contralateral hemisphere. Monoclonal antibody E-9 reacted weakly with normal-brain vascular endothelial cells; anti-proliferating cell nuclear antigen and IG11 were virtually negative. All three antibodies strongly stained the blood vessels of stroke tissues. The stroke tissues contained angiogenic activity, as shown by the induction of new blood vessels in a chorioallantoic membrane assay.

CONCLUSIONS

We have shown that stroke causes active angiogenesis that is more developed in the penumbra. Further experiments are needed to determine if this angiogenesis has beneficial effect.

Type VIII adenylyl cyclase. A Ca2+/calmodulin-stimulated enzyme expressed in discrete regions of rat brain

A cDNA that encodes type VIII adenylyl cyclase has been isolated from two rat brain libraries. The open reading frame encodes a 1248-amino acid protein predicted to have two sets of six transmembrane spans and two putative nucleotide binding domains as is characteristic of other mammalian adenylyl cyclases. Two type VIII messages are detected in rat brain with estimated sizes of 5.5 and 4.4 kilobases. In situ hybridization indicates that the type VIII messages are most abundantly expressed in the granule cells of the dentate gyrus, the pyramidal cells of hippocampal fields CA1-CA3, the entorhinal cortex, and the piriform cortex. Hybridization is also detected in the neocortex, the amygdaloid complex, and regions of the thalamus and hypothalamus. Stable expression of the type VIII cDNA in human embryonal kidney cells leads to the appearance of a novel 165-kDa glycoprotein in the membrane fraction. Stimulation of these cells with agents that increase intracellular Ca2+ results in up to 43-fold increases in cAMP accumulation over that of control cells transfected with the expression vector. Addition of isoproterenol alone does not lead to type VIII-specific effects in intact cells. Adenylyl cyclase activity in membranes prepared from type VIII-transformed cells is stimulated up to 40-fold by the addition of Ca2+/calmodulin (EC50 = 53 nM calmodulin). The addition of activated recombinant alpha subunit of Gs synergistically increases the Ca2+/calmodulin-stimulated activity. A possible role for type VIII adenylyl cyclase in long-term potentiation is discussed.

Youth suicide in Victoria: a retrospective study

OBJECTIVE

To determine the trends in youth suicide in Victoria and Australia as a whole, and their relation to youth unemployment.

DESIGN

We used Australian Bureau of Statistics data to analyse suicide trends between 1907 and 1990 in young people aged 15-24 years and made an in-depth study of youth suicides between 1980 and 1990, for which computerised data are available.

RESULTS

There has been a steady increase in youth suicide both in Victoria and Australia as a whole since 1960 in males but not females. There were significant differences in age, sex and area of residence in both the rate and the method of suicide. The increase in youth suicide was not associated with the rise in unemployment. Male (not female) suicide rates were higher in non-metropolitan areas and areas of high youth unemployment. The reasons for the increase in youth suicide remain obscure.

CONCLUSIONS

There is a need for a prospective in-depth study to determine factors in the aetiology of youth suicide, with particular reference to possible areas for prevention.

A monoclonal antibody detects heterogeneity in vascular endothelium of tumours and normal tissues

A new murine monoclonal antibody (MAb), E-9, has been raised using tissue-cultured human umbilical vein endothelial cells. The antigen recognized by this MAb is a peptide of 170 kDa under non-reducing conditions and 96 kDa under reducing conditions. MAb E-9 showed marked heterogeneity in its distribution in various tissues. The antigen recognized by it was present in vascular endothelial cells of all tumours, foetal organs and in regenerating and inflamed tissues. It stained a few normal tissues. However, with the exception of tonsils, staining tended to be weak and limited to a few blood vessels, as revealed by double staining using pan-endothelial antibody (CD31) and antibody to von Willebrand factor, another marker of vascular endothelium. Surprisingly, blood vessels within the placental villi were completely negative. The function of the antigen recognized by MAb E-9 is not known, but its evaluation and use should increase our understanding of angiogenesis.

Molecular diversity in the adenylylcyclase family. Evidence for eight forms of the enzyme and cloning of type VI

The conservation of amino acid sequence among types I-IV adenylylcyclase has made it possible to apply the polymerase chain reaction to examine the extent of the molecular diversity within this family of enzymes. cDNA templates from rat heart, liver, kidney, guinea pig brain and testes, and mouse skeletal muscle were amplified with primers specific to adenylylcyclase sequences. Evidence was obtained for a total of eight distinct gene products divisible into five subfamilies. Five of the products correspond to regions from cloned forms of adenylylcyclase, while three are previously unidentified. As many as seven different adenylylcyclases are expressed in rat heart, liver, and kidney based on this analysis. Two newly identified polymerase chain reaction (PCR) products were utilized to screen a rat cDNA library from H35 Reuber hepatoma cells. A 6080-nucleotide cDNA contains an open reading frame encoding the 1166-amino acid type VI protein which has a predicted topography similar to that of other adenylylcyclases. The type VI message is abundantly expressed in rat heart, kidney, and brain. Human embryonal kidney cells stably expressing the cDNA showed an enhanced response to isoproterenol that could be inhibited by carbachol in intact cells. Increases in intracellular Ca2+ contribute to the inhibitory effect of carbachol.

Social psychiatry and sociology of mental health: a view on their past and future relevance

The origins of social psychiatry can be traced to the age of enlightenment and to the effects of the industrial revolution. Social psychiatry deals with social factors associated with psychiatric morbidity, social effects of mental illness, psycho-social disorders and social approaches to psychiatric care. Since the end of World War II up to the early seventies it has been claimed that social psychiatry should concentrate on the fight against war, poverty, racial discrimination, urban decay and all other social ills affecting people's mental health, and that the psychiatrist should be responsible for the mental health of the society. In contrast, sociology of mental health questioned the expertise of the psychiatrist and the very existence of mental illness, claiming that it covers deviant behaviour rejected by the society. The paper refutes this approach indicating that not the existence but the perception and presentation of psychiatric illness are socially determined. Acknowledging the contribution of sociology and social sciences to psychiatry, it is suggested that the heroic period of social psychiatry and the iconoclastic approach of sociology of mental health are over. However, social psychiatry, enriched by the use of epidemiological methods, has still much to offer to the daily practice of psychiatry.

Molecular cloning and characterization of a Ca2+/calmodulin-insensitive adenylyl cyclase from rat brain

Biochemical, immunological, and molecular cloning studies have suggested the existence of multiple forms of adenylyl cyclase (EC 4.6.1.1). An adenylyl cyclase cDNA clone (type II) was isolated from a rat brain library and found to encode a protein of 1090 amino acids that was homologous to but distinct from the previously described Ca2+/calmodulin-stimulated adenylyl cyclase from bovine brain. Expression of the type II cDNA in an insect cell line resulted in an increased level of adenylyl cyclase activity that was insensitive to Ca2+/calmodulin. Addition of activated Gs alpha protein to type II-containing membranes increased enzyme activity. The mRNA encoding the type II protein was expressed at high levels in brain tissue and at low levels in olfactory epithelium and lung. The existence of multiple adenylyl cyclase enzymes may provide for complex and distinct modes of biochemical regulation of cAMP levels in the brain.

The adenylyl cyclase family

Hormone-sensitive adenylyl cyclase is a model system for the study of receptor-mediated signal transduction. It is comprised of three types of components: 1) receptors for hormones that regulate cyclic AMP (cAMP) synthesis, 2) regulatory GTP binding proteins (G proteins), and 3) the family of enzymes, the adenylyl cyclases. Concentrations of cAMP are altered by at least 35 different stimulatory or inhibitory hormones and neurotransmitters. Other signalling pathways may also influence cAMP production through regulation of particular adenylyl cyclase subtypes. The second messenger, cAMP propagates the hormone signal through the effects of cAMP-dependent protein kinase. While structural information on the adenylyl cyclases is limited, a cDNA clone for a calmodulin-sensitive form of bovine brain adenylyl cyclase has been isolated. The amino acid sequence encoded by the Type I cDNA is approximately 40% identical to those specified by three other adenylyl cyclase cDNAs that have been cloned subsequently. This degree of structural variation implies that there must be functional differences between the adenylyl cyclases.

Expression and characterization of calmodulin-activated (type I) adenylylcyclase

A complementary DNA that encodes a bovine brain, calmodulin-sensitive (type I) adenylylcyclase has been inserted into the baculovirus genome under the control of the strong polyhedron promoter. Expression of the recombinant adenylylcyclase in Sf9 cells using recombinant baculovirus increases adenylylcyclase activity in cell membranes to 10-20 nmol.min-1.mg-1 (approximately 0.1% of membrane protein). The catalytic activity of the recombinant adenylylcyclase can be stimulated by Gs alpha, calmodulin, or forskolin, and it can be inhibited by adenosine analogs and by G protein beta gamma subunit. The specific activity of the purified recombinant protein approximates 5 mumol.min-1.mg-1. This is similar to that of the enzyme purified from bovine brain. Type I adenylylcyclase has a quasiduplicated structure. There are two membrane-spanning domains, each with six putative transmembrane helices, and there are two presumed nucleotide-binding domains that are about 55% similar to each other. No catalytic activity is detectable when each half of the adenylylcyclase molecule is expressed by itself. However, coexpression of the two halves results in considerable enzymatic activity. Interaction between the two halves of adenylylcyclase may be necessary for catalysis.

Adenylyl cyclase amino acid sequence: possible channel- or transporter-like structure

Complementary DNA's that encode an adenylyl cyclase were isolated from a bovine brain library. Most of the deduced amino acid sequence of 1134 residues is divisible into two alternating sets of hydrophobic and hydrophilic domains. Each of the two large hydrophobic domains appears to contain six transmembrane spans. Each of the two large hydrophilic domains contains a sequence that is homologous to a single cytoplasmic domain of several guanylyl cyclases; these sequences may represent nucleotide binding sites. An unexpected topographical resemblance between adenylyl cyclase and various plasma membrane channels and transporters was observed. This structural complexity suggests possible, unappreciated functions for this important enzyme.

Insulin-dependent phosphorylation of GTP-binding proteins in phospholipid vesicles

The involvement of GTP-binding proteins (G proteins) in insulin action has been investigated in an in vitro system. Insulin receptors that have been purified by wheat germ lectin chromatography and either tyrosine-agarose chromatography, sucrose density centrifugation, or insulin-Sepharose chromatography have been co-inserted into phospholipid vesicles with different purified G proteins. The results of these studies indicate that a specific insulin-promoted phosphorylation of two G proteins, Go and Gi, can occur in these phospholipid vesicles. Bovine retinal transducin is a poor substitute for Go and Gi, being only weakly phosphorylated by the insulin receptor, and bovine brain Gs is not a substrate. The phosphorylation of Gi and Go occurs primarily on the alpha-subunits. Under optimal conditions, about one alpha o- or alpha i-subunit is phosphorylated on a tyrosine residue for every two beta-subunits of the insulin receptor, suggesting a 1:1 interaction between these G proteins and the heterotetrameric (alpha 2 beta 2) insulin receptor molecular. The inactive (GDP-bound) form of the alpha-subunits appears to be the preferred substrate, with the phosphorylation being significantly reduced in alpha o and alpha i upon the binding of guanosine 5'-O-thiotriphosphate (GTP gamma S) and completely eliminated in the pure alpha-GTP gamma S complex of transducin. The Gi and Go proteins also cause an enhancement of the insulin-stimulated receptor autophosphorylation. This enhancement is a reflection of an increased incorporation of the insulin receptor into lipid vesicles which is induced by these G proteins. Taken together these results provide evidence for the interactions of G proteins with the insulin receptor in a lipid milieu.

Steady-state ATP synthesis by bacteriorhodopsin and chloroplast coupling factor co-reconstituted into asolectin vesicles

A method was developed for the co-reconstitution of bacteriorhodopsin and chloroplast coupling factor in asolectin vesicles. First, bacteriorhodopsin was reconstituted from a mixture of octyl glucoside, asolectin, and protein in the presence of ethylenediaminetetraacetic acid by passage through a Sephadex G-50 centrifuge column. Then, the purified coupling factor was reconstituted from a mixture of sodium cholate, bacteriorhodopsin vesicles, and coupling factor in the presence of Mg2+ by passage through the centrifuge column. Sucrose density-gradient centrifugation indicated a band of vesicles with slightly different positions in the gradient for maximum vesicle concentration, bacteriorhodopsin vesicle concentration, ATP synthesis, and ATP hydrolysis. The rate of light-driven ATP synthesis reaches a limiting value as the concentration of bacteriorhodopsin and the light intensity are increased. A steady-state rate of ATP synthesis of 1 mumol per mg of coupling factor X min-1 has been achieved. Apparently this rate is limited by the heterogeneity within the vesicle population and by the ability of bacteriorhodopsin to form a sufficiently large pH gradient.

Phase-lifetime spectrophotometry of deoxycholate-purified bacteriorhodopsin reconstituted into asolectin vesicles

A rapid reconstitution procedure has been developed to insert deoxycholate-purified bacteriorhodopsin (bR) into asolectin vesicles. The procedure relies on the ability of the hydrophobic resin Bio-Beads SM-2 to remove octyl glucoside from a mixture of deoxycholate-purified bR, asolectin, and the detergent. Light-dependent acidification of the vesicle interior is observed with the reconstituted preparations as judged by the fluorescence quenching of an entrapped pH indicator, pyranine. Inhibition of proton pumping by the addition of LaCl3 to the external medium indicates that approximately 90% of the bR is oriented such that it pumps protons into the vesicles. Phase-lifetime spectrophotometry was used to study the relaxation processes associated with the intermediate in the photocycle of the reconstituted bR which absorbs at 410 nm. Amplitude spectra indicate that these absorbance changes are associated with the M intermediate in the bR photocycle. Two relaxation processes are observed. One is characterized by a relaxation time of approximately 4 ms and is independent of pH over the range 4.4-9.4. The longer relaxation time varies from 4 to 200 ms in the same pH range. By digitization of transients, which are observable when the actinic source is modulated at a low frequency, information about the dependence of the slower process on the light intensity and carbonyl cyanide m-chlorophenylhydrazone was obtained. The results can be interpreted in terms of two different forms of the M intermediate that decay on parallel kinetic paths. To explain the pH dependence of the decay rate, the slower decaying form must have three coupled protonation states, each with a different decay rate.

Feasibility of discharge of chronic psychiatric patients

In a survey of all (2795) chronic psychiatric patients resident in Victorian Mental Health Division hospitals, charge nurses were asked to assess patients' levels of physical and psychological dependence on nursing care, aggressive and difficult behaviour and their preferred future placement. The vast majority were 'old' chronic patients and nurses considered the present placement as the most appropriate for two-thirds of the surveyed population. We adopted our own criteria of placement needs, such as level of physical and psychological dependence, behavioural problems and treatment received. Of the 2795 patients, one-quarter (682) would require continuing hospital care. The remainder could be transferred, depending on their characteristics, to intensive or general nursing care homes, hostels or special accommodation houses, provided that such facilities are available and the participation of patients in various therapeutic activities was ensured.

Multidisciplinary or nondisciplinary: evaluation of staff functioning in a community mental health centre

This paper describes the staffing aspects of an experimental community mental health centre (Melville Clinic). The different components of staff roles of members of a team consisting of different health professionals, crystallised during the three-year period with a shift from a 'nondisciplinary' to a 'multidisciplinary' approach, with preservation of 'generalised' and 'specialised', 'clinical' and 'community' roles of all staff members. The decision-making in the centre oscillated between group decisions by all staff members, and the acceptance of the leading role of the psychiatrist with the active multidisciplinary teamwork in community mental health centres.

Changing patterns of migration to Australia and their influence on the health of migrants

Whilst before World War II migration to Australia was almost entirely from the British Isles, over 60% of post-War II migrants came from other countries other than Britain. They arrived in Australia in distinct waves: Eastern European refugees were followed by migrants from Western Europe, who were later replaced by migrants from the Mediterranean Basin and finally by Asians, initially from the Indian subcontinent, afterwards from Lebanon and most recently from Indo-China. These patterns of migration were changing the numerical size, age distribution and length of residence in Australia of the different ethnic groups. The paper describes the influence of these changes on physical and mental health of the migrants. Physical morbidity was related to 'imported diseases', to the different physical and social environment and to differences and changes in eating and other habits. Psychiatric disorders were associated with traumatic experiences encountered prior to migration, and with stresses of migration and adjustment to the new country. Thus, in evaluating the health of immigrants, one has to take into account the sources from which the migrants were drawn, their situation in the host society, their numerical growth and age distribution, as well as acculturation to the country settlement.

Phase-lifetime spectrophotometry of membranes from ion flux mutants of Halobacterium halobium

Phase-lifetime spectrophotometry has been used to study the rate processes associated with intermediates in the photocycling pigments in membrane vesicles of mutant strains of Halobacterium halobium. Vesicles deficient in bacteriorhodopsin, but containing halorhodopsin, were monitored with light at 490 nm. Two relaxation processes, with kinetic parameters largely independent of pH over the range 6.2-7.8, were found to be associated with halorhodopsin photocycling in 4 M NaCl, 10 mM buffer at 23 degrees C. The average relaxation times are 0.94 and 11.4 ms. When vesicles deficient in both bacteriorhodopsin and halorhodopsin were monitored at 370 nm, a single relaxation process with an average relaxation time of 168 ms was detected. This process is independent of pH over the range 4.7-8.8. Examination of vesicles from ion flux mutants showed this slow process to be unrelated to halorhodopsin content and to derive from another photoreactive retinal pigment, possibly the recently described slow cycling pigment s-rhodopsin.