Immune reactions associated with silicone-based ventriculo-peritoneal shunt malfunctions in children

The implantation of ventriculo-peritoneal (VP) shunting systems is the most commonly performed neurological procedure in children with hydrocephalus. Although the overall complication risk is low, the cumulative risk of shunt failure is high and unfortunately results in a high prevalence of revision surgeries. In this study, we explored the concept that some pediatric patients may develop an immune response to either the proteins attached to the silicone implant surface or to the biomaterial itself, and that this reaction may contribute to VP shunt failure in some individuals. The data displays that the sterile shunt malfunction group had a higher rate of protein deposition and increased levels of autoantibodies to the extracted surface proteins as compared to individuals with functioning shunting systems. The precise nature of the shunt-bound proteins that serve as antigens in this experiment have not yet been determined. The data also indicated that some individuals develop antibodies to polymeric substances that cross-react with partially polymerized acrylamide. The detection of significant amounts of shunt-bound protein, antibody responses to these proteins and to polymeric substances suggest that an immunological response to these proteins may play a role in the mechanism behind sterile shunt malfunctions.     

Potassium currents in primary cultured astrocytes from the rat corpus callosum

The corpus callosum (CC) is the main white matter tract in the brain and is involved in interhemispheric communication. Using the whole-cell voltage-clamp technique, a study was made of K⁺-currents in primary cultured astrocytes from the CC of newborn rats. These cells were positive to glial fibrillary acidic protein after culturing in Dulbecco’s Modified Eagle Medium (> 95% of cells) or in serum-free neurobasal medium with G5 supplement (> 99% of cells). Astrocytes cultured in either medium displayed similar voltage-activated ion currents. In 81% of astrocytes, the current had a transient component and a sustained component, which were blocked by 4-aminopyridine and tetraethylammonium, respectively; and both had a reversal potential of −66 mV, indicating that they were carried by K⁺ ions. Based on the Ba²⁺-sensitivity and activation kinetics of the K⁺-current, two groups of astrocytes were discerned. One group (55% of cells) displayed a strong Ba²⁺ blockade of the K⁺-current whose activation kinetics, time course of decay, and the current-voltage relationship were modified by Ba²⁺. This current was greatly blocked (52%) by Ba²⁺ in a voltage-dependent way. Another group (45% of cells) presented weak Ba²⁺-blockade, which was only blocked 24% by Ba²⁺. The activation kinetics and time course of decay of this current component were unaffected by Ba²⁺. These results may help to understand better the roles of voltage-activated K⁺-currents in astrocytes from the rat CC in particular and glial cells in general.     

Hybridization studies of cultured human pituitary prl and gh producing adenoma cells: Effects of thyrotropin-releasing hormone,somatostatin, and phorbol ester

The effects of the hypothalamic hormones, thyrotropin-releasing hormone (TRH), and somatostatin (SRIH), and of phorbol 12-myristate 13-acetate (PMA) on PRL and GH secretion and messenger RNA (mRNA) levels were analyzed in 10 GH and/or PRL producing adenomas after culturing the tumor cells in the presence of these secretagogues for 7 days. The expression of chromogranin A and B mRNAs was also examined. All four of the clinically diagnosed GH adenomas expressed or secreted both GH and PRL while four of six clinically diagnosed prolactinomas produced or secreted both PRL and GH. Prolactinomas had less than 10% of tumor cells expressing chromogranin A mRNA while more than 40% of the adenoma cells expressed chromogranin B mRNA. TRH stimulated PRL secretion and increased PRL mRNA levels while SRIH decreased GH secretion and mRNA expression in some cases. Unexpectedly, PMA stimulated PRL mRNA levels four- to sevenfold above control levels in two adenomas and generally stimulated chromogranin A and B mRNA expression but not GH mRNA, as determined by Northern hybridization and in situ hybridization analyses. These results indicate that cultured prolactinoma cells express significantly more chromogranin B mRNA than chromogranin A mRNA, and that PMA increases PRL mRNA expression in some prolactinomas, although the effect of PMA on various adenomas reflects the heterogeneity of these tumors with respect to protein kinase C stimulation.     

Towards cellular receptors for prions

Transmissible spongiform encephalopathies (TSE) are attributed to the conversion of the cellular prion protein (PrP(c)) into an abnormal isoform (PrP(sc)). This can be caused by the invasion of living organisms by infectious particles, or be inherited due to mutations on the PrP(c) gene. One of the most intriguing problems of prion biology is the inability to generate the infectious agent in vitro. This argues strongly that other cellular proteins besides those added in test tubes or found in cellular preparations are necessary for infection. Despite recent progress in the understanding of prion pathology, the subcellular compartments in which the interaction and conversion of PrP(c) into PrP(sc) take place are still controversial. PrP(c) interacts with various macromolecules at the cell membrane, in endocytic compartments and in the secretory pathway, all of which may play specific roles in the internalisation of PrP(sc) and conversion of PrP(c). A specific interacting protein required for the propagation of prions was originally proposed as a prion receptor, and later referred to as a ligand, a cofactor, protein X, or a partner. However, current studies indicate that PrP(c) associates with multi-molecular complexes, which mediate a variety of functions in distinct cellular compartments. It is proposed that a deeper understanding of the mechanics of such interactions, coupled to a better knowledge of the corresponding signalling pathways and ensuing cellular responses, will have a major impact on the prevention and treatment of TSE.     

Prognostic Significance of p27, Ki-67, and Topoisomerase lla Expression in Clinically Nonfunctioning Pancreatic Endocrine Tumors

Nonfunctioning islet cell tumors or pancreatic endocrine tumors are the most common type of malignant islet cell tumor. Although previously detected usually at an advanced stage because of mass effect, the early detection rate of small localized disease has been increasing. To date it has been difficult to predict the clinical behavior in localized regional nonfunctioning tumors. To investigate potential markers predicting malignancy and poor prognosis in nonfunctioning pancreatic endocrine tumors, we analyzed the expression of Ki-67, topoisomerase IIα (Topollα), and p27, as well as a variety of clinicopathologic parameters in 76 cases of nonfunctioning islet cell tumors (23 benign cases and 53 malignant cases). Ki-67, Topollα, and p27 labeling indices were significantly different between benign and malignant tumors. Expression of Ki-67, Topollα, and p27 were associated with survival in patients with a malignant tumor in a univariate setting. However, only p27 and Topollα were jointly associated with survival in multivariate analysis. Immunohistochemical staining for p27, Topollα, and Ki-67 can be helpful in the diagnosis of nonfunctioning pancreatic endocrine tumor. Analysis of p27 and Topollα may also have potential utility as prognostic factors for malignant tumors.     

Solubilization and immunological identification of presynaptic alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptors in the rat hippocampus

Alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors have been identified mostly as postsynaptic receptors mediating fast glutamatergic synaptic transmission. However, neurochemical studies based on the modulation of neurotransmitter release have suggested the existence of presynaptic AMPA receptors. We have used a recently described technique that allows a high-purity fractionation of the pre- and postsynaptic proteins of synaptic junctions to evaluate the distribution of the different AMPA receptor subunits in rat hippocampal synapses. Surprisingly, we found very high levels of GluR1- and GluR2/3-like immunoreactivity in the presynaptic fraction, but also in the postsynaptic and extrasynaptic fractions. GluR4-like immunoreactivity was much less abundant but was still detected, predominantly in the postsynaptic fraction. This methodology appears to be far more sensitive than the classical immunogold electron microscopy to determine the localization of synaptic receptors.     

DADOS-Survey: an open-source application for CHERRIES-compliant Web surveys

Background  

The Internet has been increasingly utilized in biomedical research. From online searching for literature to data sharing, the Internet has emerged as a primary means of research for many physicians and scientists. As a result, Web-based surveys have been employed as an alternative to traditional, paper-based surveys. We describe DADOS-Survey, an open-source Web-survey application developed at our institution that, to the best of our knowledge, is the first to be compliant with the Checklist for Reporting Results of Internet E-Surveys (CHERRIES). DADOS-Survey was designed with usability as a priority, allowing investigators to design and execute their own studies with minimal technical difficulties in doing so.     

Molecular cloning and characterization of actin genes from Echinococcus granulosus

An Echinococcus granulosus genomic library has been screened with a mouse β-actin cDNA probe. Two clones carrying DNA fragments of about 15 kb, possibly derived from the same genome region, have been isolated. This 15-kb genomic region includes 2 actin-related sequences (EgactI and EgactII) separated by about 4 kb. The nucleotide sequences of both genes were determined. The EgactI sequence presents no introns, but an intron of 591 bp was observed in the EgactII sequence. The genes potentially encode 375 and 376 amino-acid-long actins, respectively, with a homology of 85.3%. The deduced amino acid sequences from both genes were compared to the actin sequences from other organisms, showing similarities ranging from 63.5% to 90.6%. The nucleotide sequence of a partial actin cDNA clone has been determined. The deduced amino acids sequence showed a homology of 90.3% and 88.0% in relation to the EgactI and EgactII sequences respectively, suggesting the existence of at least one more actin gene in E. granulosus. This hypothesis is reinforced by the number of bands detected in the Southern blot analysis. Experiments based on the amplification of DNA segments using 3′-specific actin primers indicate that the EgactI gene is transcribed in protoscoleces.     

A study of frog muscle maintained in organ culture

1. Frog muscles are isolated and maintained in organ culture conditions for periods of up to 2 months. During the first 2 weeks, muscle fibres have normal resting membrane and action potentials. Subsequently the potentials decline in amplitude.2. Slow muscle fibres also survive in culture and retain their ability to give maintained contractures.3. Muscle sensory receptors continue to function in culture until the axon terminals degenerate at about 2 weeks.4. Neuromuscular transmission is normal during the first few days of culture, after which the motor endings degenerate. Transmission persists longer (up to 17 days) if a long segment of nerve is left attached to the muscle. With short-nerve preparations failure of transmission in vivo occurs at about the same time as in culture. With long-nerve preparations failure of transmission is delayed even further in culture.5. In short-nerve preparations miniature end-plate potentials disappear, in general, at about the time that transmission fails. In long-nerve preparations some end-plates continue to have miniature end-plate potential activity for a short time after nerve impulses cease to evoke any response; but eventually miniature potential activity disappears from all end-plates.6. After a few days of electrical silence, miniature end-plate potentials reappear at some of the denervated end-plates. The proportion of denervated end-plates which show miniature end-plate potentials in culture is smaller than in muscles denervated in situ.7. Electron microscopy shows that muscle structure is well preserved in culture, that the axons degenerate and that the Schwann cells move to occupy the space vacated by the axons. The Schwann cells are very probably the source of the acetylcholine which evokes miniature potentials in the denervated end-plates.