Effects of excess 1,25-dihydroxycholecalciferol in young rats

The oral administration for 5 days of excess 1h5520x4/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">,25-dihydroxychole-calciferol [1,25(OH)₂D₃] at doses of 1, 5, and 25 h5520x4/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">g/kg to rats, beginning at the age of 2 or 10 days, produced dose-dependent reductions in weight development and additional calcification near the skeleton. Alizarin red S stained skeleton revealed calcific deposits near the bones of the head, near the neural arches, between the ribs, along the bones both of the fore limbs and, to a lesser extent, of the hind limbs.Historically, the deposits appeared to be localized primarily in the subepithelial connective tissues. Starting treatment with 1,25(OH)₂D₃ (25 h5520x4/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">g/kg for 5 days) at the age of 20 days produced additional calcification in 1 of 8 rats at only 1 location (lower jaw). Additional calcification as described above could no longer be induced by 1,25(OH)₂D₃ in 30-day-old rats using doses up to 25 h5520x4/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">g/kg and 10 daily treatments. We conclude that the sensitivity of young rats to 1,25(OH)₂D₃-induced additional calcification, which differs in localization from that observed in adult rats, decreases with the maturation of the animals.     

Fetal Krabbe leukodystrophy

Summary Two new cases of Krabbe disease were diagnosed prenatally in a family with two previous affected children. The activity of galactosylceramide-h1084776426058n3/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-galactosidase was virtually absent in cultured amniotic cells.The prenatal diagnosis was confirmed enzymatically in cultured fibroblasts, brain, and visceral organs.Light and electron microscopy studies in both fetuses, 20 and 23 weeks of gestational age respectively, revealed the presence of typical globoid cells in the white matter of the spinal cord. Specific inclusions were also found in the brain stem and in peripheral nerves of the second fetus.A comparison with other Krabbe disease fetuses described in the literature contributes to the consensus that abnormal morphological findings can be expected in particular in the most actively myelinating areas of the nervous system.Although most of the cells containing the specific melusions are probably non-glial in nature, some of them could represent myelination glia.This work was supported by the FGWO (grants nos. 3.0033.77 and 3.0012.77), by the FRSM (grant no. 3.4542.79), and by the Baron Charles Bracht Foundation     

Lack of presynaptic modulation by isoprenaline of 3H-noradrenaline release from rabbit isolated ear artery

Summary The aim of the present investigation was to examine whether or not presynaptic facilitatory h125649/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-adrenoceptors are detectable on the postganglionic nerves in the rabbit isolated ear artery. Strips of rabbit central ear artery were incubated with ³H-noradrenaline (10^–7 mol/l; 30 min or 10^–6 mol/l; 60 min). Subsequently, they were washed repeatedly with physiological salt solution. The strips were subjected to electrical-field stimulation (S₁–S₈) and the resultant ³H-overflow was determined.When the ear artery was stimulated with 150 pulses (0.5 ms; 3 Hz; 225 mA), isoprenaline (10^–9–10^–6 mol/l) either alone or in the presence of either rauwolscine (10^–6 mol/l) or phentolamine (10^–6 mol/l) did not alter the stimulation-evoked ³H-overflow. This was also the case in the presence of rauwolscine (10^–6 mol/l) plus either the selective phosphodiesterase inhibitor ICI 63 197 (3 × 10^–5 mol/l) or forskolin (10^–6 mol/l). When the ear artery was stimulated with 300 pulses (1 ms; 5 Hz; 225 mA), isoprenaline had no effect on the stimulation-evoked ³H-overflow. This was also the case when phentolamine (10^–6 mol/l) was present. Propranolol (10^–7–10^–5 mol/l) did not alter the stimulation-evoked ³H-overflow. In some experiments, the stimulation current was reduced to 175 mA in order to obtain similar reference release (S₃) values despite the presence of rauwolscine (150 pulses; 0.5 ms; 3 Hz). Even then, isoprenaline (10^–9–10^–6 mol/l) did not change stimulation-evoked ³H-overflow. The results suggest that postganglionic sympathetic nerves in rabbit central ear artery do not possess presynaptic facilitatory h125649/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-adrenoceptors. Send offprint requests to J. Abrahamsen at the above address     

Prodrugs of Peptides. 9. Bioreversible N-α-Hydroxyalkylation of the Peptide Bond to Effect Protection Against Carboxypeptidase or Other Proteolytic Enzymes

Various N-h02v3574648068q2/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-hydroxyalkyl derivatives of N-acyl amino acids and di- and tripeptides were prepared by hydrolysis or aminolysis of N-acyl 5-oxazolidinones. The stability of these derivatives was studied in aqueous solution as a function of pH. The compounds were all degraded quantitatively to their parent N-acylated amino acid or peptide and aldehyde but with vastly different rates. At pH 7.4 and 37°C the half-lives of decomposition ranged from 4 min to 1500 hr. The structural factors influencing the stability included both steric and polar effects within the acyl and N-h02v3574648068q2/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-hydroxyalkyl moieties as well as within the amino acid attached to the N-h02v3574648068q2/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-hydroxyalkylated N-acyl amino acid. Whereas the N-benzyloxycarbonyl (Z) derivatives of the dipeptides Gly-L-Leu and Gly-L-Ala were readily hydrolyzed by carboxypeptidase A, the N-hydroxymethylated compounds, i.e., Z-Gly(CH₂OH)-Leu and Z-Gly(CH₂OH)-Ala, were resistant to cleavage by the enzyme as revealed by their similar rates of decomposition in the presence or absence of the enzyme at pH 7.4 and 37°C. The results suggest that N-h02v3574648068q2/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-hydroxyalkylation of a peptide bond protects not only this bond but also an adjacent peptide bond against proteolytic cleavage. Since the N-h02v3574648068q2/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">-hydroxyalkyl derivatives are readily bioreversible, undergoing spontaneous hydrolysis at physiological pH, this prodrug approach promises to overcome the enzymatic barrier to absorption of various peptides.     

Estimation of the biophase concentration of noradrenaline at presynaptic α2-adrenoceptors in brain slices

Summary The aim of the present study was to determine the local concentrations of noradrenaline existing at presynaptic h485l420r/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">₂-adrenoceptors during electrical pulse train stimulation of brain slices at different frequencies. The experiments are based on the assumption that the concentration of released noradrenaline at the h485l420r/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">₂-adrenoceptors exerting a certain autoinhibition should be equal to the concentration of exogenous noradrenaline causing the same inhibition under conditions in which any influence of the released transmitter is excluded. In order to avoid autoinhibition, hippocampus and cortex slices of the rabbit and the rat, prelabelled with [³H]noradrenaline and superfused in presence of an uptake inhibitor, were electrically stimulated using 4 pulses delivered at 100 Hz (POP stimulation). Exogenous noradrenaline diminished the overflow of tritium elicited by POP stimulation in a concentration-dependent manner. In rabbit brain tissues the EC₅₀ value and maximum inhibition of noradrenaline release were found to be approximately 6 nmol/l and more than 95%, respectively, whereas in rat tissues the corresponding values were between 20 and 30 nmol/l and approximately 90%. When electrical stimulation was performed with trains of 36 pulses delivered at 0.1, 0.3 or 3 Hz in absence or presence of an uptake inhibitor, the h485l420r/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0">₂-adrenoceptor antagonist yohimbine (1 or 10 h485l420r/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">mol/l) enhanced the evoked tritium overflow in a manner which was dependent on the frequency of stimulation and on blockade of the re-uptake mechanism. The facilitatory effects of yohimbine reflected an extent of autoinhibition which was between 53% (36 pulses/0.1 Hz, no uptake inhibitor) and 85% (36 pulses/3 Hz, uptake inhibitor present) in rabbit and between 16% (36 pulses/0.3 Hz, no uptake inhibitor) and 71% (36 pulses/3 Hz, uptake inhibitor present) in rat brain slices. Accordingly, the corresponding estimated biophase concentrations of noradrenaline were generally higher in rat than in rabbit tissues (they were between 32.5 and 74.5 or 5.1 and 51.6 nmol/l in the presence or absence of an uptake inhibitor, respectively, in the rat, and between 15 and 23.1 or 6.1 and 18.6 nmol/l in the rabbit). The observed frequency dependence of the effect of re-uptake blockade on the calculated biophase concentrations of noradrenaline would be compatible with the idea of a dependence of the effectiveness of the re-uptake mechanism on the firing rate of the neurone in being more effective at lower frequencies. Moreover, the stikingly low biophase concentrations of noradrenaline suggest that also in brain tissue noradrenaline causes lateral inhibition of release as has recently been shown for guinea-pig vas deferens. Send offprint requests to C. Allgaier at the above address     

Adrenoceptor-mediated effects on calcium channel currents are antagonized by 5′-(N-ethyl)-carboxamido-adenosine in guinea-pig atrial cells

Summary In guinea-pig atrial myocytes, the effects of the adenosine analogue 5h/xxlarge8242.gif" alt="prime" align="BASELINE" BORDER="0">-(N-ethyl)-carboxamido-adenosine (NECA) in the presence of isoprenaline (ISO) on Ca²⁺ channel activity were analyzed. Single Ca²⁺ channel currents were recorded from cell-attached patches by application of several hundred 100 ms depolarizing steps. Under control conditions, burstlike activity of channel openings during some depolarizing steps were followed by variably long periods of quiescence (blank sweeps). During superfusion with ISO (100 nmol/l), ensemble-averaged (mean) current was increased by about 150%. The underlying mechanism was found to be a significant increase in the channel availability, defined as the ratio of current-containing sweeps to the total number of sweeps. In addition, the ISO-induced reduction of blank sweeps was combined with slightly but not significantly higher values of the open probability in the current-containing sweeps. Open time and shut time histograms could be fitted by single and double exponential curves, respectively, which remained rather unaffected in the presence of ISO; accordingly, mean open time and mean shut time of the channel were not significantly changed by ISO. After the addition of NECA (1 h/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">mol/l) in the presence of ISO, the ISO-induced increase in mean current was abolished. This effect of NECA on mean current was due to a reduction of the channel availability and a slight decrease in the open probability. The purinoceptor blocking agent 8-phenyltheophylline (10 h/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">mol/l) antagonized the inhibitory action of NECA on the ISO-induced increase in Ca²⁺ channel activity. These results indicate that h/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">-adrenoceptor-induced changes in Ca²⁺ channel activity are counteracted by stimulation of, presumably, A₁ adenosine receptors. This may be explained by the fact that purinoceptors, beside their stimulating action on K⁺ channels, mediate an additional inhibitory effect on the adenylate cyclase system in the atrium. Subsequently, purinoceptor activation reverses the ISO-induced increase in Ca²⁺ channel activity due to a reduction in cAMP content leading to a decrease in the number of phosphorylated Ca²⁺ channels. Send offprint requests to U. Jahnel at the above address     

Effects of interleukin-1, tumor necrosis factor-β, and forskolin on tissue plasminogen activator activity in human osteoblastic osteosarcoma cells

Summary The effects of interleukin-1 (IL-1), forskolin, and tumor necrosis factor h3/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> (TNF-h3/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">) on tissue plasminogen activator (t-PA) activity were studied in the human osteoblastic osteosarcoma cell line, G292. t-PA activity was measured in the cell media using the chromogenic substrate, S-2251. After a 24 hour incubation period, IL-1 increased t-PA in a dose-dependent manner. The effect of IL-1 at 10.0 U/ml was partially inhibited in the presence of indomethacin. Forskolin (1.0 h3/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">M) increased t-PA activity after 24 hours with the effects of combined treatment of IL-1 (1.0 U/ml, 10.0 U/ml) and forskolin being apparently additive in nature. TNF-h3/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> (10^-8–10^-7 M) also produced increased t-PA activity in the cell medial after a 24 hour incubation period. These results suggest that the cytokines, IL-1 and TNF-h3/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0">, can increase t-PA activity in G292 cells and that there is both a cAMP-dependent as well as a cAMP-independent pathway involved in the regulation of this osteoblastic cell function.     

Tubular and interstitial factors in the progression of glomerulonephritis

All recent studies of the outcome of different forms of progressive glomerulonephritis concur that a major factor, apparently determining outcome, is the presence and severity of tubulointerstitial changes, and not the degree of glomerular alteration. Moreover, at the time of biopsy, tubulointerstitial changes correlate much better with the glomerular filtration rate. These at first surprising findings are not only useful clinically, but should make us think about our models of how progression takes place in so-called glomerular nephritides. In fact, a major tubulointerstitial infiltrate of immune-competent cells is present in all forms of progressive glomerulonephritis, and again correlates with outcome. In addition, it is now clear the tubular epithelium is capable of synthesising and secreting a number of factors important in fibrogenesis, and of displaying major histocompatibility complex class II antigens and leucocyte-adhesion molecules. Tubular cells could thus present peptides to T helper cells and amplify, or maybe even initiate, immune reactions. Finally, fibrogenesis within the kidney is at last being studied, long after studies have been performed on liver and lung. In the past, too much attention has been paid to reversible inflammation and not enough to irreversible cirrhosis of the kidney.Abbreviations used Ig immunoglobulin, e. g. IgA, IgG, IgM etc. - TBM tubular basement membrane - GBM glomerular basement membrane - WHO World Health Organization - MHC major histocompatibility complex - CD cluster determinant - NK natural killer - IL-1 interleukin-1 - IL-2 interleukin-2 - TNF-h62673411781m521/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> tumour necrosis factor alpha - ADCC antibody-dependent complement mediated cytolysis - ACE angiotensin-converting enzyme - mh62673411781m521/xxlarge934.gif" alt="PHgr" align="BASELINE" BORDER="0"> macrophage - ICAM-1 intercellular adhesion molecule-1 - ELAM-1 endothelial leucocyte adhesion molecule-1 - VCAM-1 vascular cell adhesion molecule-1 - LFA leucocyte function associated molecule, e. g. LFA-1, LFA-3 - C complement e. g. C3=third component of complement, etc. - TGF-h62673411781m521/xxlarge946.gif" alt="beta" align="MIDDLE" BORDER="0"> transforming growth factor beta - TGF-h62673411781m521/xxlarge945.gif" alt="agr" align="BASELINE" BORDER="0"> transforming growth factor alpha - PDGF platelet derived growth factor - PAS periodic acid Schiff - TCR T cell receptor - PTEC proximal tubular epithelial cell - GM-CSF granulocyte colony stimulating factor - M-CSF monocyte colony stimulating factor - FGF fibroblast growth factor     

Preliminary experience with the 1.32 μm neodymium-YAG laser in the treatment of tracheobronchial malignancy

Endoscopic laser treatment for tracheobronchial malignancy is usually given with the neodymium-YAG laser using the 1.064h23/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">m output beam. However, recent experimental work suggests that the 1.32h23/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">m output beam of this laser has more desirable tissue effects. We have now treated 55 patients with the 1.32h23/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">m Nd-YAG laser (MBB-Medizintechnic) under general anaesthesia, using power settings of 10–20 W and pulse durations of up to 1 s. The indications for treatment were localized airway obstruction in each case. Airway calibre was improved in 46 (84%) patients and this was associated with an improvement in symptoms of cough and breathlessness. Patients with tracheal and carinal obstruction exhibited the most striking clinical improvements with up to four-fold increases in peak expiratory flow. In patients with more peripheral endobronchial obstruction, treatment improved airway calibre less frequently and resulted in a smaller clinical improvement. Of 11 patients with obstruction of a main bronchus and lung collapse, treatment led to partial or complete re-expansion in 10 cases (91%). The 1.32h23/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">m wavelength allows treatment to be conducted efficiently and safely but at a considerably lower power than is required for the 1.064h23/xxlarge956.gif" alt="mgr" align="MIDDLE" BORDER="0">mwavelength. The ability to use low powers has the apparent advantage of generating only negligible quantities of smoke. Our experience with this new laser system demonstrates its considerable potential in the management of tracheobronchial malignancy.     

Biomonitoring lead exposure with δ-aminolevulinate dehydratase (ALA-D) activity ratios

Summary The occupational or environmental exposure of selected populations to lead, either alone or in combination with other metals, was monitored using ratios of the activity of the erythrocytic enzyme h65w7440xu460286/xxlarge948.gif" alt="delta" align="BASELINE" BORDER="0">-aminolevulinate dehydratase. The results obtained have reaffirmed earlier findings that this test affords several significant advantages over the use of the enzyme's activity value measured at a set pH value and other types of activity ratios to assess lead exposure. Furthermore, the activity ratios' proven sensitivity, reliability, reproducibility, specificity and stability warrant that they be considered as viable alternatives to the more widely accepted diagnostic criteria of lead intoxication namely zinc protoporphyrin and lead levels in blood.