Mixed glioneuronal tumour of the fourth ventricle with prominent rosette formation.

We describe three unusual tumours characterized by a mixture of glial and neuronal differentiation, involvement of the posterior fossa and formation of rosettes. Mixed glial-neuronal tumours of the posterior fossa are rare and poorly described neoplasms. However, several distinctive entities have appeared in the literature over recent years under a variety of different names. Our cases demonstrate the morphological features of the 'rosette-forming glioneuronal tumour of the fourth ventricle', a recently identified tumour characterised by its unique location, neurocytic pseudo-rosette formation and the presence of a low grade astrocytoma component. The long term prognosis of these tumours remains unclear. However, the clinical data available including the cases presented here, along with the histological features, suggest that these are low grade tumours with a good prognosis after surgical resection.

Direct effects of triiodothyronine on human internal mammary artery and saphenous veins.

OBJECTIVE: Thyroid hormone (3,5,3'-triiodo-L-thyronine is under investigation as a positive inotrope and vasodilator for patients undergoing cardiac surgery. This study determined the direct effects of triiodothyronine on human blood vessels. DESIGN: Prospective, controlled, in vitro study. SETTING: Laboratory facility in a university teaching hospital. PARTICIPANTS: Small excess segments of internal mammary arteries or saphenous veins were obtained from patients undergoing coronary artery bypass surgery. INTERVENTIONS: Vessel segments were cut into rings to measure isometric tension development in isolated tissue baths containing Krebs-Ringer bicarbonate solution at 37 degrees C. Rings were prestretched in vitro to resting tensions analogous to mean arterial or central venous pressures in vivo and then constricted with potassium or phenylephrine. Rings were exposed to increasing concentrations of triiodothyronine (4 x 10(-12) to 1 x 10(-4) mol/L) to obtain dose-response curves. MEASUREMENTS AND MAIN RESULTS: High concentrations (> or = 3.3 x 10(-5) mol/L) of trilodothyronine produced dose-dependent relaxation of preconstricted rings. The relaxation was not selective for arteries or veins at arterial resting tensions, and with either potassium or phenylephrine as a vasoconstrictor. Propranolol had little effect on subsequent triiodothyronine-induced relaxation of potassium-constricted rings at resting arterial tensions. CONCLUSIONS: Triiodothyronine, in supraphysiological and suprapharmacological concentrations, dilates preconstricted rings of human blood vessels in vitro; however, triiodothyronine had no demonstrable vasomotor effects on human internal mammary artery or saphenous vein in clinically relevant concentrations (10(-9) to 10(-8) mol/L). Triiodothyronine administration in vivo most likely has little direct effect on the tone of human vascular smooth muscle, particularly coronary artery bypass conduits.

Reversal of donor myocardial dysfunction by triiodothyronine replacement therapy.

Triiodothyronine deficiency after brain death can result in progressive deterioration of cardiac function in potential organ donors. We report on the use of triiodothyronine replacement in improving myocardial function, allowing the use of donor hearts that might have been considered unsuitable for transplantation. From July to September 1992, of 24 organ procurements and transplantations, six donors were receiving high doses of inotropes with elevated left-sided filling pressures. Donor characteristics were as follows: five were male donors and one was a female donor, with mean age 16.50 +/- 7.50 years (8 to 30 years), mean weight 49.17 +/- 13.64 kg (25 to 63 kg), average time from clinical brain death to procurement 94.50 +/- 73.53 hours (49 to 240 hours), and two donors had arrest periods of up to 10 minutes. Despite large inotrope infusions, echocardiograms showed depressed left ventricular function (mean ejection fraction 39.17 +/- 5.85) and hemodynamic instability was present with elevated ventricular filling pressures. Triiodothyronine replacement (maximal dose 0.6 microgram/kg) was initiated an average of 139.17 +/- 32.00 minutes (115 to 185 minutes) before procurement. At the time of procurement, ventricular filling pressures were lower, hemodynamic condition stabilized, and pressor requirements decreased. Hearts were preserved in University of Wisconsin solution with a mean ischemic time of 188.83 +/- 36.86 minutes (149 to 237 minutes).(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of the proto-oncogene c-jun by angiotensin II.

Angiotensin (Ang) II causes hypertrophy of rat aortic smooth muscle cells in culture and results in the rapid activation of c-fos. This study demonstrated that Ang II also activated c-jun and, in addition, could activate the AP-1 enhancer element. These data add support for a role of Ang II as an important mediator of vascular smooth muscle cell growth.

Studies of the initiation of myelination by Schwann cells.

The rapid morphologic changes in Schwann cells and in their relationships to axons during the transition from the premyelinating to the myelinating state have been known for more than 15 years. The sorting of axons by dividing Schwann cells, the establishment of a 1:1 relationship between a postmitotic Schwann cell, and the onset of myelin sheath formation have all been described in detail. However, the chain of molecular events and mechanisms by which these morphologic changes are regulated has not been elucidated. In this chapter we have reviewed results that strongly suggest that the adhesion molecule L1 is one of the important determinants that mediate the elongation of the Schwann cell along the axon, and the extension of Schwann processes to engulf axons. Thus, L1 functions to promote the spreading of the Schwann cell process over the surface of the axon. L1 does not appear to be exclusively involved in the adhesion of Schwann cells to axons, in the activation of Schwann cell proliferation by axons, or in the induction of synthesis of extracellular matrix proteins. The results from the anti-L1 blocking experiments further provided clues for an understanding of how the expression of GalC and MAG, which are both likely to be involved in the initiation of myelination, are regulated. These results imply that the overall regulation of expression of these early myelin components could require controls other than a single signaling mechanism derived from contact with axons. We propose that the deposition of basal lamina or one of its components could also be involved. Finally, the results from anti-GalC-blocking experiments indicated that GalC is involved in the mechanism of early growth of the myelin spiral.

Production of parathyroid hormone-related protein by a rat parathyroid cell line.

Parathyroid hormone-related protein (PTHrP), the peptide associated with humoral hypercalcemia of malignancy, has been identified in fetal and adult parathyroid glands. We here report a sub-clone of a rat parathyroid cell line which secretes a single peptide species corresponding in size to PTHrP(1-84). Biological activity of the secretion product was blocked by a specific antiserum against PTHrP, but not by parathyroid hormone (PTH) antiserum. Secretion of PTHrP by these cells was regulated by extracellular calcium in the physiological range. A single messenger RNA species for PTHrP was identified, though PTH mRNA could not be shown in these cells. Hybrid CAT genes containing 700-1000 bp of 5'-flanking DNA from the human PTH or PTHrP genes were transfected into these cells, and the PTHrP gene was expressed at 10-fold higher levels than the PTH gene. These cells thus provide a valuable model system for investigation expression of PTHrP in a non-transformed cell line.

Angiotensin II induces c-fos expression in smooth muscle via transcriptional control.

Angiotensin II (Ang II) has been shown to cause hypertrophy of cultured quiescent rat aortic smooth muscle cells. This observation along with the recent demonstration of angiotensinogen messenger RNA (mRNA) in the vessel wall has led us to postulate a role for Ang II in hypertensive smooth muscle hypertrophy. One of the earliest responses in a wide variety of cells in response to a growth-promoting agent is the induction of the proto-oncogene c-fos. To investigate the mechanism of the action of Ang II, we investigated the effect of Ang II on the expression of the c-fos gene in rat aortic smooth muscle cells that were made quiescent by being grown in a defined serum-free media for 48 hours. Ang II (10(-6)-10(-10) M) resulted in a dose-dependent increase in c-fos mRNA expression. This induction was angiotensin-receptor specific since it was completely abolished by the competitive inhibitor saralasin. Inhibition of protein synthesis did not block the rise in c-fos mRNA expression; it resulted in a superinduction and stabilization of the c-fos mRNA. Using a nuclear runoff transcription assay, we demonstrated that Ang II stimulated the transcription rate of the c-fos gene. This activation of c-fos gene expression may be an important mechanism in the angiotensin-induced smooth muscle hypertrophy.

Differentiation of axon-related Schwann cells in vitro: II. Control of myelin formation by basal lamina.

Several recent observations suggest that Schwann cell (SC) differentiation, including myelin formation, is dependent upon the development of basal lamina which characteristically surrounds each axon-SC unit in peripheral nerve. This dependence can be tested in a neuron-SC culture system developed in our laboratory in which SC differentiation, including basal lamina formation and myelination, is faithfully reproduced. The use of serum-free, defined medium (DM) with this culture system allows axon-driven SC proliferation but not basal lamina formation or myelination. We previously demonstrated that ascorbic acid, in the presence of a nondialyzable serum factor(s), stimulates basal lamina assembly and myelin formation with similar dose-response relationships (Eldridge et al., 1987). We hypothesized that ascorbic acid acts to promote SC myelination indirectly, by enabling the assembly of basal lamina. We now provide support for this hypothesis by demonstrating the following. (1) Pepsin-resistant triple-helical collagen molecules were produced only by SCs grown in the presence of ascorbic acid, suggesting that triple-helical type IV collagen may mediate the effect of ascorbic acid on basal lamina formation. (2) The formation of myelin by oligodendrocytes, which myelinate axons in the CNS without the concomitant deposition of basal lamina, was little affected by ascorbic acid, suggesting that the biosynthesis and assembly of myelin per se does not require ascorbic acid. (3) The provision of exogenous basal lamina matrix to SCs grown with neurons in DM without ascorbic acid promoted control levels of myelination (and basal lamina formation); the provision of exogenous fibrillar collagen matrix did not. (4) Purified laminin promoted control levels of myelination in the absence of ascorbic acid, but purified type IV collagen and heparan sulfate proteoglycan (HSPG) did not. Laminin caused SCs to assemble basal lamina-like structures that contained not only laminin but also HSPG and non-triple-helical type IV collagen. Thus, several types of experiments demonstrate that SC myelin formation can be controlled by regulating the ability of the SC to assemble basal lamina, illustrating that acquisition of basal lamina is a crucial prefatory step for further SC differentiation.

Thought for Food: Suggestions for a systematised approach to emergency food distribution operations.

The following paper is a synopsis of a longer report, under the same name, aimed at the people responsible for implementing relief food operations. The report attempts to fill a perceived need for a manual covering the organisation of relief operations from planning to evaluation stages. Following the initial planning phase, the distribution of relief food can be viewed as a logistics operation sandwiched between two phases of data acquisition - one before the distribution of relief to targetted destinations, and the other after the distribution, to assess its efficacy and to identify problems.

Structural analysis and expression of the human thrombospondin gene promoter.

We have isolated a 34-kilobase pair genomic thrombospondin clone and determined the sequence of 2033 base pairs of the 5'-flanking region, the first entirely untranslated exon and the first intron. A number of interesting regulatory motifs were identified. The transcription start site, determined by primer extension and S1 nuclease analysis, was shown to be 20-30 bases 3' of a TATA-like sequence, TTTAAAA. We have also shown that a thrombospondin promoter-bovine growth hormone fusion gene is transcribed in transiently transfected cells. We conclude that the genomic clone contains the transcriptional signals of the thrombospondin gene and will therefore be useful in the analysis of cis-acting elements that regulate the expression of this gene.

Effects of cis-4-hydroxy-L-proline, and inhibitor of Schwann cell differentiation, on the secretion of collagenous and noncollagenous proteins by Schwann cells.

The proline analog cis-4-hydroxy-L-proline (CHP) was previously shown to inhibit both Schwann cell (SC) differentiation and extracellular matrix (ECM) formation in cultures of rat SCs and dorsal root ganglion neurons. We confirmed that CHP inhibits basal lamina formation by immunofluorescence with antibodies to laminin, type IV collagen, and heparan sulfate proteoglycan. In order to test the hypothesis that CHP inhibits SC differentiation by specifically inhibiting the secretion of collagen, cultures grown in the presence or absence of CHP were metabolically labeled with [3H]leucine and the media were analyzed for relative amounts of (a) collagenous and noncollagenous proteins by assay with bacterial collagenase and by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), or (b) triple-helical collagen by pepsin digestion followed by SDS-PAGE. The results indicate that although CHP inhibited the accumulation of secreted collagen in the culture medium and disrupted collagen triple-helix formation, it also significantly inhibited the accumulation of secreted noncollagenous proteins in the medium. CHP had no significant effect on either total protein synthesis (medium plus cell layer) or cell number. We conclude that CHP does not act as a specific inhibitor of collagen secretion in this system, and thus data from these experiments cannot be used to relate SC collagen production to other aspects of SC differentiation. We discuss the evidence for and against specificity of CHP action in other systems.

Differentiation of axon-related Schwann cells in vitro. I. Ascorbic acid regulates basal lamina assembly and myelin formation.

Rat Schwann cells cultured with dorsal root ganglion neurons in a serum-free defined medium fail to ensheathe or myelinate axons or assemble basal laminae. Replacement of defined medium with medium that contains human placental serum (HPS) and chick embryo extract (EE) results in both basal lamina and myelin formation. In the present study, the individual effects of HPS and EE on basal lamina assembly and on myelin formation by Schwann cells cultured with neurons have been examined. Some batches of HPS were unable to promote myelin formation in the absence of EE, as assessed by quantitative evaluation of cultures stained with Sudan black; such HPS also failed to promote basal lamina assembly, as assessed by immunofluorescence using antibodies against laminin, type IV collagen, and heparan sulfate proteoglycan. The addition of EE or L-ascorbic acid with such HPS led to the formation of large quantities of myelin and to the assembly of basal laminae. Pretreatment of EE with ascorbic acid oxidase abolished the EE activity, whereas trypsin did not. Other batches of HPS were found to promote both basal lamina and myelin formation in the absence of either EE or ascorbic acid. Ascorbic acid oxidase treatment or dialysis of these batches of HPS abolished their ability to promote Schwann cell differentiation, whereas the subsequent addition of ascorbic acid restored that ability. Ascorbic acid in the absence of serum was relatively ineffective in promoting either basal lamina or myelin formation. Fetal bovine serum was as effective as HPS in allowing ascorbic acid (and several analogs but not other reducing agents) to manifest its ability to promote Schwann cell differentiation. We suggest that ascorbic acid promotes Schwann cell myelin formation by enabling the Schwann cell to assemble a basal lamina, which is required for complete differentiation.

Antithymocyte gamma globulin, low-dosage cyclosporine, and tapering steroids as an immunosuppressive regimen to avoid early kidney failure in heart transplantation.

Cyclosporine is a powerful immunosuppressive agent that unfortunately has significant renal toxicity. Two risk factors associated with a high incidence of kidney failure in patients receiving cyclosporine have been described in the literature. In an effort to decrease the possibility of renal toxicity with the use of cyclosporine, we use low-dosage cyclosporine, antithymocyte gamma globulin, and tapering dosages of steroids as an immunosuppressive regimen. Twenty-one patients had orthotopic heart transplants from January 1985 to January 1986. Sixteen of 21 patients or 70% had at least one high risk factor for kidney failure. There were no episodes of acute kidney failure, and the blood urea nitrogen and creatinine levels that were recorded over an average of 8.5 months per patient did not increase significantly from preoperative values. Seventeen of 21 or 81% of the patients are alive and functioning fully. The incidence of rejection per patient was 0.9, and there were no biopsy-proven severe rejections. One patient died at 5 months; the autopsy showed generalized moderate rejection. There were 0.24 episodes of infection per patient, with one patient who died from Pneumocystis pneumonia. With this immunosuppression protocol, early postoperative kidney dysfunction was avoided. The incidences of rejection and infection were within acceptable range, and the quality of life in the 17 survivors is excellent.

Basal lamina-associated heparan sulphate proteoglycan in the rat PNS: characterization and localization using monoclonal antibodies.

Cultured rat Schwann cells produce a basal lamina (BL)-associated heparan sulphate proteoglycan (HSPG). The HSPG has an apparent molecular weight of greater than 450 kD, is sensitive to both heparinase and heparitinase and contains a core protein of approximately 400 kD. Two independently derived monoclonal antibodies, B3 and C17, recognize this HSPG. Using B3 and C17, we found that this HSPG, or immunologically related material, is present in BLs throughout the body and in a small number of connective tissue sites without a formed BL. In the PNS it is present in BLs of Schwann cell-axon units, in synaptic and extrasynaptic portions of muscle fibre BL, and in the BLs of satellite cells that ensheath neurons in sympathetic and sensory ganglia. This HSPG is not detectable in the neuropil of the brain and spinal cord. Neurons, Schwann cells and fibroblasts cultured alone do not assemble a BL or accumulate immunocytochemically detectable amounts of this HSPG, but it is present in BLs assembled in myotube and in Schwann cell-neuron cultures. Thus, this HSPG is a component of most, if not all, BLs in the PNS.

Linkage between axonal ensheathment and basal lamina production by Schwann cells.

The availability of several methods for the preparation of SCs free of other cell types has allowed recent experimentation providing new insights into the capacity of SCs to synthesize, release, and organize extracellular matrix materials, particularly those of the basal lamina. When these SC populations are combined in tissue culture with pure populations of neurons capable of directing SC function (without fibroblasts), new aspects of interrelationships between these cell types have come to light. In this brief chapter we review the results from this experimental approach during the last decade, and suggest the implications these observations have for interpreting known differences in SC functional expression in various body regions as well as for understanding certain disease processes. Of particular note is the discovery of an apparently essential linkage between the function of the SCs in organizing and relating to basal lamina and their ability to ensheathe and myelinate axons. It now appears that SC functional expression requires an alliance not only with the nerve fiber but also with the ECM through the production and organization of a basal lamina.