Spatial Learning Deficits in Mice with a Targeted Glucocorticoid Receptor Gene Disruption

Previous studies in rats using the Morris water maze suggested that the processing of spatial information is modulated by corticosteroid hormones through mineralocorticoid and glucocorticoid receptors in the hippocampus. Mineralocorticoid receptors appear to be involved in the modulation of explorative behaviour, while additional activation of glucocorticoid receptors facilitates the storage of information. In the present study we used the water maze task to examine spatial learning and memory in mice homozygous and heterozygous for a targeted disruption of the glucocorticoid receptor gene. Compared with wild-type controls, homozygous and heterozygous mice were impaired in the processing of spatial but not visual information. Homozygous mutants performed variably during training, without specific platform-directed search strategies. The spatial learning disability was partly compensated for by increased motor activity. The deficits were indicative of a dysfunction of glucocorticoid receptors as well as of mineralocorticoid receptors. Although the heterozygous mice performed similarly to wild-type mice with respect to latency to find the platform, their strategy was more similar to that of the homozygous mice. Glucocorticoid receptor-related long-term spatial memory was impaired. The increased behavioural reactivity of the heterozygous mice in the open field points to a more prominent mineralocorticoid receptor-mediated function. The findings indicate that (i) the glucocorticoid receptor is of critical importance for the control of spatial behavioural functions, and (ii) mineralocorticoid receptor-mediated effects on this behaviour require interaction with functional glucocorticoid receptors. Until the development of site-specific, inducible glucocorticoid receptor mutants, glucocorticoid receptor-knockout mice present the only animal model for the study of corticosteroid-mediated effects in the complete absence of a functional receptor.     

Surge Capacity Associated with Restrictions on Nonurgent Hospital Utilization and Expected Admissions during an Influenza Pandemic: Lessons from the Toronto Severe Acute Respiratory Syndrome Outbreak

Background Current influenza pandemic models predict a surge in influenza‐related hospitalizations in affected jurisdictions. One proposed strategy to increase hospital surge capacity is to restrict elective hospitalizations, yet the degree to which this measure would meet the anticipated is unknown. Objectives To compare the reduction in hospitalizations resulting from widespread nonurgent hospital admission restrictions during the Toronto severe acute respiratory syndrome (SARS) outbreak with the expected increase in admissions resulting from an influenza pandemic in Toronto. Methods The authors compared the expected influenza‐related hospitalizations in the first eight weeks of a mild, moderate, or severe pandemic with the actual reduction in the number of hospital admissions in Toronto, Ontario, during the first eight weeks of the SARS‐related restrictions. Results Influenza modeling for Toronto predicts that there will be 4,819, 8,032, or 11,245 influenza‐related admissions in the first eight weeks of a mild, moderate, or severe pandemic, respectively. In the first eight weeks of SARS‐related hospital admission restrictions, there were 3,654 fewer hospitalizations than expected in Toronto, representing a modest 12% decrease in the overall admission rate (a reduction of 1.40 admissions per 1,000 population). Therefore, influenza‐related admissions could exceed the reduction in admissions resulting from restricted hospital utilization by 1,165 to 7,591 patient admissions, depending on pandemic severity, which corresponds to an excess of 0.44 to 2.91 influenza‐related admissions per 1,000 population per eight weeks, and an increase of 4% to 25% in the overall number of admissions, when compared with nonpandemic conditions. Conclusions Pandemic modeling for Toronto suggests that influenza‐related admissions would exceed the reduction in hospitalizations seen during SARS‐related nonurgent hospital admission restrictions, even in a mild pandemic. Sufficient surge capacity in a pandemic will likely require the implementation of other measures, including possibly stricter implementation of hospital utilization restrictions.     

Morphometric insights into nephrotic syndrome in children: Are we any wiser?

Summary: The present study was undertaken in the hope that conflicting opinions concerning interrelationships among minimal change disease (MCD), mesangial proliferative glomerulonephritis (MPG) and focal segmental glomeruloscierosis (FSGS) might be elucidated by morphometric methods performed by image analysis, as well as to study whether serum creatinine and changes in quantitatively analysed glomeruli could correlate with the interstitial fibrosis in these glomerulopathies. Fifteen renal biopsy specimens from children with MCD, 10 with primary MPG and 12 with FSGS for whom both light and electron microscopy as well as immunofluorescence microscopy and full clinical data were available, were examined quantitatively. As a control five biopsy and 10 autopsy specimens of the normal kidneys were used. Our quantitative study showed that in MCD, MPG and FSGS glomerular and interstitial values differed from normal. Morphometric differences between MPG and both MCD and FSGS groups were also shown. Although the mean values of total glomerular area and relative interstitial volume were increased in FSGS patients, in total glomerular cells per unit of glomerular area and mesangium (% of total glomerular area) were similar in both MCD and FSGS groups. In MPG strong positive correlations existed between interstitial volume and serum creatinine, interstitial volume and total glomerular cells per unit of glomerular area as well as between interstitial volume and glomerular mesangium (% of total glomerular area). In FSGS there was significant positive correlation between interstitial volume and serum creatinine. In the MCD group all correlations were weak and not significant. In conclusion, our morphometric studies suggest a close relationship between MCD and FSGS, and indicate that MPG is a separate morphologic entity in children.     

Isochromosome 18q in a girl with holoprosencephaly,DiGeorge anomaly,and streak ovaries

We report on the clinical and pathologic findings in a girl with isochromosome 18q (46, XX,i(18q)) who had combined manifestations of monosomy 18p and trisomy 18q. Major congenital anomalies included premaxillary agenesis, alobar holoprosenphaly, double Outlet right ventricle, DiGeorge anomaly and streak ovaries. The clinical spectrum in i(18q) is very broad. © 1993 Wiley-Liss, Inc.     

TNFα Inhibits Schwann Cell Proliferation, Connexin46 Expression, and Gap Junctional Communication

Schwann cell responses to nerve injury are stimulated, in part, by inflammatory cytokines. This study compares changes in the phenotype of cultured Schwann cells after exposure to the cytokine tumor necrosis factor (TNF)-α or the mitogen neu differentiation factor (NDF)-β. TNFα inhibited proliferation in a dose-dependent manner without altering Schwann cell survival. TNFα also reduced both gap junctional conductance and Lucifer yellow dye coupling between Schwann cells. Moreover, both P₀and glial fibrillary acidic protein (GFAP) immunoreactivity were reduced. By contrast, NDFβ initially had little effect on cell division although it reduced junctional coupling within 8 h. However, by 48 h, NDFβ stimulated proliferation with a concomitant increase in coupling. Dividing Schwann cells (BrdU⁺) were preferentially dye coupled compared to nondividing cells, indicating an association between proliferation and coupling. Moreover, cultured Schwann cells expressed connexin46 mRNA and protein, and changes in the levels of the protein correlated with the degree of proliferation and coupling. The data thus provide evidence for cytokine-induced modulation of Schwann cell antigenic phenotype, proliferation, and gap junction properties. These observations suggest that enhanced gap junctional communication among Schwann cells after nerve injury could help to coordinate cellular responses to the injury, and that TNFα may be a signal which terminates proliferation as well as junctional communication.     

Studies on the mechanism of 3-deazaguanine cytotoxicity in L1210-sensitive and -resistant cell lines

Summary 3-Deazaguanine (3-DG), a purine analogue, has unusual antitumor activity against experimental mammary tumor models and a number of other solid tumors. Others have shown that mutant CHO cells deficient in hypoxanthine guanine phosphoribosyl transferase (HGPRTase) or adenine phosphoribosyl transferase (APRTase) are resistant to 3-DG. We developed a L1210 cell line resistant to 3-DG, L1210/3-DG, by subculturing the parent L1210/0 cells in the presence of increasing concentrations of 3-DG. The IC₅₀ was 3.5 M and 620 M for L1210/0 and L1210/3-DG, respectively. Cytotoxicity studies proved the resistance to be stable. Examination of the baseline-specific activity of HGPRTase and APRTase showed that the former was 118-fold lower in L1210/3-DG than in L1210/0, and the latter demonstrated no difference. A 4-h treatment of the cell lines at IC₅₀ doses showed 48% and 23% reductions in IMP dehydrogenase in L1210/0 and L1210/3-DG, respectively. The rate of de novo purine biosynthesis was studied by using [¹⁴C]formic acid. Formate flux increased 2-fold in L1210/3DG in concert with the observed deficiency of HGPRTase in the cell line. 3-DG uptake was studied with [¹⁴C]-labelled compound. The total radioactivity was 9-fold higher in L1210/0 than in L1210/3-DG at 2 h. Subsequent chromatographic separation of radioactivity showed the 3-DG and 3-deazaguanosine pools of the drug to be equal in both lines. However, 3-DG nucleotide pools at 1 min and 2 h were 2.5-fold and 16-fold lower, respectively, in L1210/3-DG than in L1210/0. 3-DG incorporation studies with radiolabelled drug demonstrated that 3-deazaguanine is incorporated in the acid-insoluble fraction of the cell. These studies conclude that HGPRTase, and not APRTase, is required for the activation of drug. Inhibition of IMP dehydrogenase is partially responsible for antitumor activity of the drug. The incorporation of drug into nucleic acids may be a major mechanism for its antitumor activity. Further studies using a cloned cDNA probe for hypoxanthine guanine phosphoribosyltransferase (HGPRT) demonstrated no change in the DNA arrangements of the L1210/3-DG cell line, and Northern blot analysis showed approximately equal expression of mRNA in both cell lines.Abbreviations used APRTase adenine phosphoribosyltransferase - HGPRTase Hypoxanthine guanine phosphoribosyltransferase - IMPD Inosine mono-phosphate dehydrogenase - PRPP 5-Phosphorylribose-1-pyrophosphate - AOPCP , -Methyleneadenosine 5-diphosphate - NAD Nicotineamide dinucleotide - EDTA Ethylenediamine tetra acetic acid Presented at annual meeting of American Association of Cancer Research in May, 1986Supported in part by Warner-Lambert Company, Ann Arbor, Michigan     

Meta-analysis of four new genome scans for lipid parameters and analysis of positional candidates in positive linkage regions

Lipid levels in plasma strongly influence the risk for coronary heart disease. To localise and subsequently identify genes affecting lipid levels, we performed four genome-wide linkage scans followed by combined linkage/association analysis. Genome-scans were performed in 701 dizygotic twin pairs from four samples with data on plasma levels of HDL- and LDL-cholesterol and their major protein constituents, apolipoprotein AI (ApoAI) and Apolipoprotein B (ApoB). To maximise power, the genome scans were analysed simultaneously using a well-established meta-analysis method that was newly applied to linkage analysis. Overall LOD scores were estimated using the means of the sample-specific quantitative trait locus (QTL) effects inversely weighted by the standard errors obtained using an inverse regression method. Possible heterogeneity was accounted for with a random effects model. Suggestive linkage for HDL-C was observed on 8p23.1 and 12q21.2 and for ApoAI on 1q21.3. For LDL-C and ApoB, linkage regions frequently coincided (2p24.1, 2q32.1, 19p13.2 and 19q13.31). Six of the putative QTLs replicated previous findings. After fine mapping, three maximum LOD scores mapped within 1 cM of major candidate genes, namely APOB (LOD=2.1), LDLR (LOD=1.9) and APOE (LOD=1.7). APOB haplotypes explained 27% of the QTL effect observed for LDL-C on 2p24.1 and reduced the LOD-score by 0.82. Accounting for the effect of the LDLR and APOE haplotypes did not change the LOD score close to the LDLR gene but abolished the linkage signal at the APOE gene. In conclusion, application of a new meta-analysis approach maximised the power to detect QTLs for lipid levels and improved the precision of their location estimate.     

The composition of foetal and maternal blood during parturition in the ewe

1. Changes in the composition of foetal and maternal blood have been followed during the last 5-10 days of gestation and throughout parturition in the conscious sheep.2. Catheters were placed in the foetal inferior vena cava through a tarsal vein and in a maternal uterine vein in ten ewes under sodium pentobarbitone anaesthesia. In four of the foetuses blood pressure and heart rates were recorded before and during parturition from an arterial catheter.3. Foetal blood gas tensions, pH and PCV remained stable during the latter part of gestation and throughout labour until 15 min before delivery, when P(O) (2) and pH fell while PCV and P(CO) (2) rose in about 50% of the foetuses examined.4. Metabolite levels were also relatively stable at the end of gestation. Plasma glucose in both maternal and foetal blood rose during the hour before birth, while foetal plasma lactate was elevated as early as 4 hr before birth and was unrelated to any maternal changes. Foetal fructose levels were maintained until after delivery.5. Rises in foetal blood pressure before birth were associated with uterine contractions. Foetal heart rate changes during labour varied in different individuals. The heart rate either fell gradually before birth or there was little change until a sudden drop at delivery.6. The most striking changes in the lamb occurred at, or a few minutes after, birth; pH and P(O) (2) fell, P(CO) (2) and PCV rose, and bradycardia at delivery was succeeded by prolonged tachycardia. There were marked increases in plasma glucose and lactic acid at this time.7. P(O) (2) rose rapidly once respiration was established, while pH and P(CO) (2) levels were restored within (1/2)-1 hr. Plasma FFA levels rose rapidly in the lambs 10-30 min after birth and remained high, while plasma glucose, lactate and fructose concentrations declined slowly in the 1-2 hr after birth, although suckling raised the plasma glucose levels. Considerable individual variation in the metabolite levels was found in both ewes and lambs.8. In the majority of ewes delivery was associated with an abrupt maternal hyperglycaemia, with a much smaller rise in lactate and virtually no change in maternal blood gases or pH.9. These findings are discussed in relation to existing information on new-born lambs and the human infant during birth.