Targeted gene disruption of murine CD7

CD7 is a 40 kDa type I transmembrane glycoprotein member of the Ig superfamily. CD7 is a marker of mature human T cells and NK cells, and is expressed early in their development. Cross-linking CD7 positively modulates T cell and NK cell activity as measured by calcium fluxes, expression of adhesion molecules, cytokine secretion and proliferation. CD7 associates directly with phosphoinositol 3'-kinase, and CD7 ligation induces production of D-3 phosphoinositides and tyrosine phosphorylation. Severe combined immunodeficiency has been associated with a lack of lymphocyte surface CD7. The CD7 ligand is unknown. The murine CD7 homolog is encoded by a single gene on chromosome 11. In order to characterize the role of CD7 in lymphocyte development and function we have eliminated the CD7 gene by targeted disruption. CD7- deficient mice display normal histology of thymus and spleen, normal lymphocyte populations in primary and secondary lymphoid tissues, and normal serum Ig levels. Specific antibody responses after immunization with T-dependent and T-independent antigens are equivalent in wild-type and CD7 knockout mice. CD7-deficient lymphocytes respond normally to T cell mitogenic and allogeneic stimuli, and display normal NK cell cytotoxicity.      

Androgen receptor YAC transgenic mice carrying CAG 45 alleles show trinucleotide repeat instability

X-linked spinal and bulbar muscular atrophy (SBMA) is caused by a CAG repeat expansion in the first exon of the androgen receptor (AR) gene. Disease-associated alleles (37-66 CAGs) change in length when transmitted from parents to offspring, with a significantly greater tendency to shift size when inherited paternally. As transgenic mice carrying human AR cDNAs with 45 and 66 CAG repeats do not display repeat instability, we attempted to model trinucleotide repeat instability by generating transgenic mice with yeast artificial chromosomes (YACs) carrying AR CAG repeat expansions in their genomic context. Studies of independent lines of AR YAC transgenic mice with CAG 45 alleles reveal intergenerational instability at an overall rate of approximately 10%. We also find that the 45 CAG repeat tracts are significantly more unstable with maternal transmission and as the transmitting mother ages. Of all the CAG/CTG repeat transgenic mice produced to date the AR YAC CAG 45 mice are unstable with the smallest trinucleotide repeat mutations, suggesting that the length threshold for repeat instability in the mouse may be lowered by including the appropriate flanking human DNA sequences. By sequence-tagged site content analysis and long range mapping we determined that one unstable transgenic line has integrated an approximately 70 kb segment of the AR locus due to fragmentation of the AR YAC. Identification of the cis - acting elements that permit CAG tract instability and the trans -acting factors that modulate repeat instability in the AR YAC CAG 45 mice may provide insights into the molecular basis of trinucleotide repeat instability in humans.      

Prostaglandins, endotoxin and lipid A on body temperature in rats.

1. In unanaesthetized restrained rats kept at an ambient temperature of 21-23degrees C, rectal temperature was continuously monitored and the temperature effects of injections of prostaglandins, endotoxin from Salmonella abortus equi, lipid A, and antipyretics were examined. 2. Fever occurred when prostaglandin E1, E2, F1alpha or F2alpha (PGE1, PGE2, PGF1alpha, PGF2alpha) was injected into the cerebral ventricles in doses of 200 ng and 2 mug. PGE2 was the most potent prostaglandin followed in descending order by PGE1, PGF2alpha, and PGF1alpha. The fever produced by 2 mug of PGE1 and PGE2 was short and followed by a fall in temperature to below the pre-injection level. 3. I.V. injections of endotoxin and lipid A in doses of 3 or 10 mug usually caused a long lasting fall in temperature, but when injected into the cerebral ventricles in doses of 400 ng or 1 mug, they produced long lasting fevers. 4. Injected I.V. or I.P., indomethacin and paracetamol had a hypothermic action of their own. Indomethacin was more potent than paracetamol and both were more potent than injected I.P. 5. I.V. and I.P. injections of indomethacin and paracetamol did not reverse the hypothermia in response to I.V. endotoxin or lipid A, but the fever responses to their injection into the cerebral ventricles were prevented and abolished by the antipyretics. 6. It is concluded that in rats endotoxin and lipid A, or the endogenous pyrogens produced by them, do not readily pass through the blood-brain barrier into the brain tissue. If they do reach brain tissue, as when injected into the cerebral ventricles, they stimulate synthesis and release of prostaglandin in rats as they do in other species, and thereby produce fever. The hypothermia in response to I.V. endotoxin or lipid A, on the other hand, is thought to be independent of prostaglandin synthesis and to result from a direct toxic action on the skin vessels.     

Needle biopsy of renal allografts: comparison of two techniques

Two techniques for renal allograft biopsy were retrospectively evaluated to compare relative safety and efficacy. After ultrasound (US) localization of the kidney and biopsy with a hand-held 14-gauge cutting needle, an adequate specimen was obtained in 74 of 77 cases (96%). Major complications occurred in six of these 77 cases (8%). One hundred four biopsies were performed by using a smaller 18-gauge cutting needle with a spring-loaded biopsy "gun" and real-time US guidance. With this newer technique, specimens adequate for diagnosis were obtained in 99 biopsies (95%). There was a single major complication with this technique (1%). The 18-gauge needle with real-time US guidance yields comparably adequate specimens with a lower frequency of complications.     

Neurotensin stimulation of mast cell secretion is receptor-mediated, pertussis-toxin sensitive and requires activation of phospholipase C

Pretreatment of isolated rat serosal mast cells with U-73122, an aminosteroid inhibitor of phospholipase C, inhibited histamine secretion in response to neurotensin (NT). This inhibition reached a maximum after 1 h of pretreatment at 37 degrees C and was dependent upon the concentration of U-73122 (IC50 approximately 0.2 microM). The inactive analog, U-73343, had no effect on the secretory response to NT. Pretreatment of mast cells with U-73122 also blocked histamine secretion in response to substance P (SP), mastoparan (MP), compound 48/80, or amidated NT (NT-NH2). Stimulation of mast cells by NT was accompanied by a rise in the level of intracellular free calcium and a rapid (within seconds) increase in the level of inositol trisphosphate (IP3) which was inhibited by pretreatment of the cells with U-73122. Pretreatment of isolated mast cells with pertussis toxin (PTx) blocked histamine release in response to NT as well as to all peptides tested. PTx had no effect on histamine secretion elicited by anti-IgE stimulation of sensitized mast cells. Pretreatment of mast cells with SR 48692, a NT-receptor antagonist, had no effect on histamine release induced by MP. At a high concentration (100 nM) SR 48692 partially inhibited the response to NT-NH2. These results, together with our earlier findings with SR 48692, indicate that the signal transduction pathway in mast cells activated by NT requires a specific NT-receptor, the activation of phospholipase C, and the involvement of a PTx sensitive G protein. The peptides SP and MP, and compound 48/80, while also requiring the activation of PLC and a PTx sensitive G protein, are not inhibited by the NT-R antagonist, SR 48692, suggesting that they exert their actions either via a different mast cell receptor or via a receptor-independent mechanism.     

Proceedings of the Symposium ‘Angiotensin AT1 Receptors: From Molecular Physiology to Therapeutics’: PHYSIOLOGICAL ACTIONS OF ANGIOTENSIN II MEDIATED BY AT1 AND AT2 RECEPTORS IN THE BRAIN

• 1 Autoradiographic binding studies have shown that the AT₁ receptor is the predominant angiotensin II (AngII) receptor subtype in the central nervous system (CNS). Major sites of AT₁ receptors are the lamina terminalis, hypothalamic paraventricular nucleus, the lateral parabrachial nucleus, rostral and caudal ventrolateral medulla, nucleus of the solitary tract and the intermediolateral cell column of the thoraco-lumbar spinal cord.
• 2 While there are differences between species, AT₂ receptors are found mainly in the cerebellum, inferior olive and locus coeruleus of the rat.
• 3 Circulating AngII acts on AT₁ receptors in the subfornical organ and organum vasculosum of the lamina terminalis (OVLT) to stimulate neurons that may have a role in initiating water drinking.
• 4 Centrally administered AngII may act on AT₁ receptors in the median preoptic nucleus and elsewhere to induce drinking, sodium appetite, a sympathetic vasoconstrictor response and vasopressin secretion.
• 5 Recent evidence shows that centrally administered AT₁ antagonists inhibit dipsogenic, natriuretic, pressor and vasopressin secretory responses to intracerebroventricular infusion of hypertonic saline. This suggests that an angiotensinergic neural pathway has a role in osmoregulatory responses.
• 6 Central angiotensinergic pathways which include neural inputs to the rostral ventrolateral medulla may use AT₁ receptors and play a role in the function of sympathetic pathways maintaining arterial pressure.

     

Treatment of localized prostate cancer using a combination of high dose rate Iridium‐192 brachytherapy and external beam irradiation: Initial Australian experience

Combination high dose rate brachytherapy (HDRB) and external beam radiation therapy is technically and clinically feasible as definitive treatment for localized prostate cancer. We report the first large Australian experience using this technique of radiation dose escalation in 82 patients with intermediate‐ and high‐risk disease. With a median follow up of 3 years (156 weeks), complications were low and overall prostate‐specific antigen progression‐free survival was 91% using the American Society for Therapeutic Radiology and Oncology consensus definition. The delivery of hypofractionated radiation through the HDRB component shortens overall treatment time and is both biologically and logistically advantageous. As a radiation boost strategy, HDRB is easy to learn and could be introduced into most facilities with brachytherapy capability.