PAX5 expression correlates with increasing malignancy in human astrocytomas.

Rearrangements concerning chromosome 9p are a late event in the progression of human astrocytic tumors to their most malignant form. The expression of PAX5, which maps to chromosome 9p13, was studied in primary human brain tumors of astrocytic origin. Whereas murine Pax5 is not expressed in the forebrain at any stage, PAX5 expression was increased in a range of astrocytomas (WHO grades II-IV) which originated in the forebrain. Expression of PAX5 was limited to those cells which also expressed the oncogenes myc, fos, or jun singularly or in combination. The epidermal growth factor receptor was highly expressed in glioblastoma multiform tumors in areas which were also highly PAX5 positive. We conclude that the missappropriate expression of PAX5 may aid in promoting the progression of astrocytomal malignancy.

Effect of orthotopic liver transplantation and chemical denervation of the liver on the activities of hepatic monoamine oxidase and catechol-O-methyltransferase.

The denervation of some tissue is associated with a fall in the activities of monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT). Here we report on the effect of orthotopic liver transplantation and chemical denervation of the liver on the enzymes. Liver transplantation was performed on Lewis rats (n = 7). Denervation (n = 8) was by intraportal injection of 6-hydroxydopamine (75 mg/kg). A control group (n = 8) was also included. The norepinephrine content of the transplanted and denervated livers was reduced by greater than 99% (P < 0.001) and 95% (P < 0.001), respectively. The activity of hepatic COMT (substrate: catechol [5 mM] was not affected by transplantation or denervation. The activity of MAO with 0.1 mM 5-hydroxytryptamine (5-HT) (substrate for MAO-A) and with 0.01 mM 2-phenylethylamine (substrate for MAO-B) were not affected by denervation. In the transplanted liver, the activity of MAO with 5-HT and 2-phenylethylamine was increased by 26% (P < 0.05) and by 53% (P < 0.001), respectively. The ratios of the activities of the A to B forms of MAO (approximately 70% A to 30% B) was not affected by either procedure. Enzyme sensitivity for MAO inhibitors clorgyline and deprenyl were not significantly altered by transplantation. The concentration of plasma norepinephrine in the transplantation group was significantly lower than either the control (P < 0.001) or denervation groups (P < 0.05). We conclude from our results that the metabolism of circulating catecholamines by the liver is unlikely to be impaired after liver transplantation.

Redistribution of portal venous but not hepatic arterial flow is induced by hepatic nerve stimulation in the perfused rat liver.

The effects of hepatic nerve stimulation, norepinephrine and 6-hydroxydopamine (6-OHDA) on hepatic hemodynamics were investigated in rat livers perfused in situ via both the portal vein and hepatic artery. Nerve stimulation caused a significant fall in total liver blood flow and an increase in portal and arterial pressures. Norepinephrine and 6-OHDA in addition to causing a fall in flow caused significant pressure increases in the bed perfused (arterial or portal). Under basal conditions, the inter- and intra-lobar distribution of microspheres (113Sn- or 57Co-labelled) introduced via the portal vein or via the hepatic artery was homogeneous in all 6 liver lobes. During nerve stimulation, homogeneity of interlobular microsphere distribution was maintained. However, the intralobar distribution of microspheres introduced via the portal vein displayed a significant redistribution from the periphery to the core of each of the four largest lobes studied (p < 0.05). In contrast, when microspheres were introduced via the hepatic artery, there was no universal redistribution of microspheres with only one lobe demonstrating a significant decrease in flow to the periphery (p > 0.05). Infusion of norepinephrine (10(-8) M) or 6-OHDA (1 mg.kg-1 body weight) via either the hepatic artery or the portal vein was without effect on the intrahepatic distribution of the microspheres. We conclude from our results that during hepatic nerve stimulation there is a significant redistribution of portal venous but not hepatic arterial flow from the periphery to the core of the liver lobe. The persistence of hepatic arterial flow during nerve stimulation may represent a protective mechanism by which the periphery of the liver, especially the bile ducts, remains perfused during a reduction in total liver blood flow.

PAX genes: what's new in developmental biology and cancer?

PAX genes encode nuclear transcription factors which are rapidly becoming regarded as major controllers of developmental processes in both vertebrates and invertebrates. Mutations in murine Pax genes underlie three natural mouse alleles and two corresponding human syndromes. Murine Pax genes have been shown to be proto-oncogenes. Furthermore, human PAX genes have recently been demonstrated to play an influential part in some common human cancers. The diversity in effects of PAX genes reflects that of their structure. All encode a DNA-binding domain termed the paired domain and in addition some also encode a second binding domain--the paired type homeobox.

Loss of p53 function through PAX-mediated transcriptional repression.

Direct interactions between the genes that regulate development and those which regulate the cell cycle would provide a mechanism by which numerous biological events could be better understood. We have identified a direct role for PAX5 in the control of p53 transcription. In primary human diffuse astrocytomas, PAX5 expression inversely correlated with p53 expression. The human p53 gene harbours a PAX binding site within its untranslated first exon that is conserved throughout evolution. PAX5 and its paralogues PAX2 and PAX8 are capable of inhibiting both the p53 promoter and transactivation of a p53-responsive reporter in cell culture. Mutation of the identified binding site eliminates PAX protein binding in vitro and renders the promoter inactive in cells. These data suggest that PAX proteins might regulate p53 expression during development and propose a novel alternative mechanism for tumour initiation or progression, by which loss of p53 function occurs at the transcriptional level.

Interpretation of the laser Doppler flow signal from the liver of the rat.

It has been proposed that the laser Doppler flow (LDF) signal from the surface of the rat liver is almost exclusively a measure of hepatic arterial and not of total liver blood flow and therefore that LDF is not a suitable technique for the measurement of blood flow in the hepatic microcirculation. The objective of the present study was twofold: (i) to establish that liver blood flow is homogeneously distributed and (ii) to assess the behavior of the LDF signal during changes in hepatic perfusion. When 51Cr-labeled microspheres were injected into the portal vein (n = 12), no significant differences in the relative flow (cpm/lobe to cpm/liver) to each of the liver lobes were found nor was there any difference in the ratio of flow to the outer 1-2 mm of lobe as compared to that to the "core" of the liver. Temporary occlusion of the hepatic artery and the portal vein caused approximately 13% (n = 7, P < 0.001) and approximately 74% (n = 7, P < 0.001) fall in LDF signal, respectively. Diversion of flow from the anterior to the posterior lobes (n = 5) caused a 97.9 +/- 21.1% (SD, P < 0.001) rise in LDF signal in the posterior lobes. Zero-flow LDF signal was found to represent 13.0 +/- 4.1% of maximum. Hemorrhage (in 1.5-ml aliquots) was associated with a fall in mean arterial pressure (MAP) and LDF signals. A linear relationship between MAP and the LDF signal (r > 0.9) was found. Reinfusion of blood caused both MAP and the LDF signal to return to normal. We conclude that (i) blood flow in rat liver is homogeneously distributed; (ii) the LDF signal from the liver surface responds in a manner predicted by conventional theories of hepatic hemodynamics during alteration, either independent or combined, in hepatic arterial and portal venous blood flow; and (iii) LDF may be used to measure relative changes in hepatic perfusion but problems associated with zero-flow signal and intersite variability preclude its quantification in absolute flow units.

The expression of PAX5 in human transitional cell carcinoma of the bladder: relationship with de-differentiation.

OBJECTIVE: To investigate the expression of PAX genes, a family of developmental control genes (which encode nine nuclear transcription factors essential for embryogenesis and are proto-oncogenes in mice) in human transitional cell carcinoma (TCC) of the bladder. MATERIALS AND METHODS: PAX gene expression was assessed in three established bladder cancer cell lines and 29 primary tumours using the reverse transcriptase-polymerase chain reaction and Southern analysis. RESULTS: All three established TCC cell lines and 79% of primary TCCs expressed PAX5 mRNA. There was a significantly higher proportion of PAX5 expression in malignant than in benign urothelium (P=0.02, Fisher's exact test); nine of 12 pTa tumours (mucosa-confined), seven of eight pT1 (invading lamina propria) and eight of nine pT2 (invading muscle) expressed PAX5. A higher proportion of tumours with increasing de-differentiation expressed PAX5, which correlates well with the expression pattern of PAX5 in development. In well-differentiated tumours (grade 1), half expressed PAX5, compared with 84% of moderately to poorly differentiated tumours (grades 2/3). The odds ratio for PAX5 expression in malignancy suggests that it increases the risk of malignancy four-fold. CONCLUSION: These data support a role for the PAX family in oncogenesis, by identifying another human neoplasm in which they are inappropriately expressed. PAX5 expression in undifferentiated TCC cells may contribute to pathogenesis by supporting cellular proliferation in the de-differentiated state. Furthermore, the high incidence of PAX5 expression suggests its potential use as a diagnostic tool and therapeutic target in TCC.

Selective sympathectomy of the liver: a comparison of orthotopic liver transplantation and intraportal 6-hydroxydopamine injection.

1. Tissue noradrenaline (NA) levels correlate well with the extent of sympathetic innervation of that tissue. 2. In this study the distribution of NA throughout the different lobes of the rat liver was studied. The extent of sympathectomy by means of either orthotopic liver transplantation (OLT) (n = 7) or chemical denervation by intraportal administration of 6-hydroxydopamine (6-OH-DA) (n = 8) was examined. 3. In the normally innervated rat liver, NA was homogeneously distributed throughout the organ. Tissue NA was decreased both by OLT (> 99%) and 6-OH-DA (93%) (both P < 0.001 versus control). 4. Samples of the renal cortex and left ventricle were taken as reference tissues. OLT did not result in any change in reference tissue NA, however, 6-OH-DA decreased renal cortex NA by 93% and ventricular NA by 76%, respectively (both P < 0.01 versus OLT). 5. We conclude that OLT causes selective and complete hepatic sympathectomy but that 6-OH-DA causes incomplete denervation of the liver and significant denervation of other organs.

Effect of orthotopic transplantation and chemical denervation of the liver on hepatic hemodynamics in the rat.

The involvement of the sympathetic nervous system in the control of basal hepatic hemodynamics was investigated. Hepatic denervation was achieved by orthotopic transplantation or chemical denervation of the organ. In male Lewis rats, transplantation with rearterialization of the graft was performed. Chemical denervation was achieved by intraportal injection of 6-hydroxydopamine (75 mg/kg). Normal liver physiology was confirmed by histology and liver function tests. Four weeks post-transplantation and 7 days post-denervation, histological examination revealed no differences between transplanted, denervated and untreated or sham-operated control animals. Liver function measured by standard tests (e.g., plasma SGOT, bilirubin) was normal in all groups. The rate constants for aminopyrine breakdown in transplanted (0.015 +/- 0.005 min-1), denervated (0.015 +/- 0.0012 min-1) and control rats (0.015 +/- 0.001 min-1) were not significantly different. No significant difference in the rate of galactose breakdown was found. Total liver blood flow (measured by the 133Xe clearance technique in the anesthetized animal) was unaffected by transplantation (rate constant, 0.245 +/- 0.062 min-1; control 0.279 +/- 0.011 min-1). The interlobular distribution of portal blood flow was tested by intraportal injection of 51Cr-labelled microspheres. A linear relationship between flow to lobe and lobe size was confirmed in control (r = 0.95), denervated, (r = 0.99) and transplanted rats (r = 0.97) and the 'relative' flow to each lobe was not significantly different in the 3 groups. No significant differences in the 'core' to 'periphery' distribution of portal blood flow were found in the 3 groups. A small but significant portal systemic shunt was found in transplanted but not denervated or control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Targeted mutation of the murine goosecoid gene results in craniofacial defects and neonatal death.

The goosecoid gene encodes a homeodomain-containing protein that has been identified in a number of species and has been implicated in a variety of key developmental processes. Initially suggested to be involved in organizing the embryo during early development, goosecoid has since been demonstrated to be expressed during organogenesis-most notably in the head, the limbs and the ventrolateral body wall. To investigate the role of goosecoid in embryonic development, we have inactivated the gene by gene targeting to generate mice mutant for the goosecoid gene. Mice that are homozygous for the goosecoid mutation do not display a gastrulation phenotype and are born; however, they do not survive more than 24 hours. Analysis of the homozygotes revealed numerous developmental defects affecting those structures in which goosecoid is expressed during its second (late) phase of embryonic expression. Predominantly, these defects involve the lower mandible and its associated musculature including the tongue, the nasal cavity and the nasal pits, as well as the components of the inner ear (malleus, tympanic ring) and the external auditory meatus. Although the observed phenotype is in accordance with the late expression domains of goosecoid in wild-type embryos, we suggest that the lack of an earlier phenotype is the result of functional compensation by other genes.