Brownian Ionic Channel Simulation

The simulation of ion transport in biological ion channels presents numerous interesting challenges. Since there are accurate structures for only a handful of channel proteins it is difficult to predict solely from the conformation how internal and external structure of the molecule will affect it's ionic transport characteristics. This problem is compounded by the fact that the electrostatics and dynamic behaviour of these molecules is, only now, beginning to be understood. We present an ion transport simulation methodology based on a self-consistent Brownian/Poisson technique, that is capable of resolving ion transport on ps-μs timescales including the effect of long range electric fields in complex dielectric structures. The results of the self-consistent Brownian simulation are compared against the commercial drift diffusion simulation package Taurus and experimental measurements of the ion conduction for the Kcsa bacterial ion channel protein.     

In vivo modulation of acetylcholine in the nucleus accumbens of freely moving rats: II. Inhibition by gamma-aminobutyric acid

Our earlier studies suggest dopamine and serotonin interact with acetylcholine (ACh) in the nucleus accumbens (NAC) as part of a system for motivation and reinforcement. The purpose of the present experiment was to characterize a possible link between GABA and acetylcholine in the nucleus accumbens using microdialysis in freely moving rats. Different doses of GABA, muscimol, baclofen, saclofen and bicuculline were locally infused into the nucleus accumbens through the microdialysis probe. GABA and its agonists dose-dependently decreased extracellular levels of acetylcholine in the nucleus accumbens. In contrast the GABAA antagonist, bicuculline, dose-dependently increased extracellular ACh while the GABAB antagonist, saclofen, was without effect. Co-infusion of bicuculline or saclofen was shown to block the decrease in recoverable ACh produced by muscimol or baclofen, respectively. The results demonstrate an inhibitory action of GABA on acetylcholine interneurones in the nucleus accumbens involving both GABAA and GABAB receptor subtypes. In addition a tonic inhibitory GABAergic tone is probably mediated through GABAA receptors.     

A Josephson-array calculable-waveform generator

This paper proposes a new method for using a Josephson array to create a voltage waveform with a root-mean-square value calculable to better than 2 in 10⁶ at frequencies below 50 Hz. A novel method of reliably switching the dc voltage from one known voltage step to another at precisely defined time intervals is investigated. In this method, transients in the microwave voltage driving the array are used to induce switching between steps. We consider two possible implementations of this concept. The first is for an array similar to that used in conventional dc voltage standards. The second uses the binary sequence of individually biased arrays introduced by Hamilton et al [1995]. Computer simulation and theoretical analysis are used to demonstrate that the uncertainties in switching times are potentially limited only by the speed of the available microwave attenuators, which is currently of the order of a nanosecond     

Cloning of p97/Gab2, the major SHP2-binding protein in hematopoietic cells, reveals a novel pathway for cytokine-induced gene activation

Several components in cytokine signaling remain unidentified. We report the cloning and initial characterization of one such component, p97, a widely expressed scaffolding protein distantly related to Drosophila DOS and mammalian Gab1. Upon cytokine, growth factor, or antigen receptor stimulation, p97 becomes tyrosyl phosphorylated and associates with several SH2 domain-containing proteins, including SHP2. Expression of p97 mutants unable to bind SHP2 blocks cytokine-induced c-fos promoter activation, inhibiting Elk1-mediated and STAT5-mediated transactivation. Surprisingly, such mutants do not inhibit MAPK activation. Our results identify p97 as an important regulator of receptor signaling that controls a novel pathway to immediate-early gene activation and suggest multiple functions for SHP2 in cytokine receptor signaling.     

Plasmacytomas of the head and neck

Plasmacytomas are rare tumors that often appear in the head and neck region and are characterized by a monoclonal proliferation of plasma cells. On both clinical presentation and pathologic examination these tumors may be confused with more common tumors of the head and neck. The purpose of this article is to review our experience with these rare neoplasms, with emphasis on clinical, pathologic, and therapeutic features. On retrospective chart review, we identified 20 patients with the diagnosis of plasmacytoma of the head and neck region at the Cleveland Clinic Foundation between 1976 and 1993. Records were reviewed with regard to initial symptoms, location of the neoplasm, diagnostic evaluation, treatment modalities, and survival. Of the 20 cases we identified, the tumor arose in the sinonasal/nasopharyngeal region in 11 (55%). Two cases (10%) represented medullary plasmacytomas, arising in the clavicle and presenting as supraclavicular masses. The mean follow-up was 60.2 months (range 6 to 131 months). In 15 of the 20 cases, immunohistochemistry staining for immunoglobulin light chain production was conducted. One of the two cases (50%) classified as medullary plasmacytoma demonstrated conversion to multiple myeloma, whereas only 2 of 18 cases of extramedullary plasmacytoma (11%) converted to multiple myeloma. The primary modality of treatment was radiation therapy with typical doses of 4500 to 6000 cGy. Kaplan-Meier survival estimates demonstrated 95% survival at 1 year, 82% survival at 5 years, and 10-year estimated survival of 72%. Plasmacytomas of the head and neck region are rare and on initial evaluation must be distinguished from multiple myeloma. The diagnostic evaluation includes appropriate radiologic and pathologic studies including immunohistochemistry. Despite the typical presentation as a locally destructive tumor, plasmacytomas are highly radiosensitive, and 70% to 80% survival may be obtained with the use of radiotherapy. Patients with plasmacytomas require long-term follow-up to detect conversion to multiple myeloma.     

Effect of some cooked food mutagens on unscheduled DNA synthesis in cultured precision-cut rat, mouse and human liver slices

The present study investigated the rates and perceived effects of past traumatic brain injury (TBI) and substance use in a prison population. Responses to a questionnaire indicated that 86.4% of the 118 respondents had sustained a TBI, with 56.7% reporting more than one, and rates of illicit substance use were higher than the general population. Maori reported 12% more TBI and more substance use than non-Maori. All those with TBI reported difficulties with general memory and socialization on a problem rating scale, but there was no relationship between level of difficulty and severity of TBI, problems with interpersonal relationships, family, and finances were associated with greater substance use.     

Influence of timing of morphine administration on postoperative pain and analgesic consumption

Flow cytometry was used to demonstrate that cultured human melanoma BRO cells expressed membrane-bound tumour necrosis factor-alpha (TNF-alpha) and were able to release TNF-alpha upon treatment with glucosaminylmuramyl dipeptide (GMDP). The released TNF-alpha was shown to prime melanoma cells, previously unable to respond to GMDP by increasing expression of melanoma-associated antigens, making them sensitive to GMDP treatment.     

The status of aggressive children and victims of aggression in school

A series of analogues of pentoxifylline metabolites were prepared in the purine, pteridine, [1,2,5]-thiadiazolo[3,4-d]pyrimidine, and quinazoline ring systems and evaluated for their ability to inhibit the production of tumor necrosis factor-alpha (TNF alpha) in human peripheral blood monocytes stimulated with bacterial lipopolysaccharide (LPS). The more active compounds were also tested for inhibition of cyclic AMP phosphodiesterase type IV (PDE IV) from human neutrophils in order to help determine their mechanism of action. Selected compounds which showed good activity in the in vitro TNF alpha assay were evaluated in an in vivo LPS-induced leukopenia model in mice. The most potent compounds in the TNF alpha assay, 6, 31, and 58, inhibited TNF alpha production at an IC50 of approximately 5 microM for each. Compound 58 was a very poor inhibitor of PDE IV but was the most active at preventing the leukopenia induced by TNF alpha in mice, providing more than 60% protection at 50 mg/kg. Thus, compounds such as 58, which are good inhibitors of TNF alpha production but are devoid of PDE IV inhibitory properties, may have potential as new antiinflammatory agents.