Persistent hyperendemicity of hepatitis C virus infection in Taiwan: the important role of iatrogenic risk factors

The purpose of this study was to investigate determinants of endemic hepatitis C virus (HCV) infection within communities in Taiwan. A two-phase study, including a seroprevalence survey and a prevalent case-control study at the first phase, which has been published previously, and a follow-up seroconversion determination and an incident case-control study during the second phase, was carried out to evaluate correlates of persistent endemic HCV infection. At the first phase, a total of 12,021 men and 1,819 women who were 30-64 years old and living in seven townships in Taiwan were tested for the seroprevalence of antibodies to HCV (anti-HCV). In addition, a prevalent case-control study involving 272 HCV-positive cases and 282 seronegative controls identified from the anti-HCV testing was conducted to investigate risk factors associated with HCV prevalence. During the second phase, a total of 2,728 men and 834 women who were seronegative at recruitment participated in the 1-year prospective study on anti-HCV seroconversion. Subsequently, an incident case-control study based on 39 seroconverters and 81 persistently seronegative controls were carried out to elucidate determinants of HCV seroconvertion. Antibodies to HCV were tested by the second-generation enzyme immunoassay. Information on risk factors of HCV infection was collected from subject interviews. The prevalence of anti-HCV consistently increased with age (range 2.9-5.4%), whereas no apparent age trend was observed for anti-HCV seroconversion rate (range 0.9-1.7%). A striking geographical variation in seroprevalence and seroconversion rates of anti-HCV was observed in the study townships. Furthermore, a significant geographical correlation between HCV seroprevalence and seroconversion rates was noted (r = 0.962, P = 0.001). From the results of both prevalent and incident case-control comparisons, medical injections were found to be the main mode to sustain the persistent endemic state of HCV infection within a community (odds ratios for prevalent and incident case-control studies were 2.5 (95% CI = 1.7-3.6) and 3.1 (95% CI = 1.4-7.1), respectively. The data indicate that the basis for HCV transmission has already been existed in study areas and the iatrogenic risk factor tended to be the major determinant for sustaining persistent endemicity within a community.

Cell cycle induction in post-mitotic neurons proceeds in concert with the initial phase of programmed cell death in rat

Neuronal programmed cell death (PCD) is increasingly becoming recognized as a dynamic process that may be amenable to resolution. Critical to this resolution is the identification of the cellular pathways that modulate the initial stages of apoptotic death. In this regard, we examined whether the activation of a latent cell cycle was associated with the initial phase of PCD. We demonstrate that free radical nitric oxide induced PCD results in the rapid generation of membrane phosphatidylserine residue exposure. This early phase of PCD functions in parallel with an untoward attempt to enter the cell cycle in the same population of post-mitotic neurons. We therefore offer an attractive molecular target to prevent or reverse neuronal PCD by elucidating a novel mechanism through which the majority of neurons meet their demise by attempting to enter a latent cell cycle.

UV-induced increase in RNA polymerase activity in Xanthomonas oryzae pathovar oryzae

UV radiation is thought to inhibit transcriptional elongation, as a result of the formation of pyrimidine dimers in the DNA template, as well as to activate specific transcription factors. However, the effect of UV radiation on the enzymatic activity of RNA polymerase has remained unknown. With the use of an in vitro assay, UV irradiation of Xanthomonas oryzae pathovar oryzae has now been shown to increase RNA polymerase activity. This effect was maximal at a UV dose of approximately 12 J m(-2) and at approximately 60 min after irradiation. It was also not inhibited by pretreatment of cells with chloramphenicol, an inhibitor of protein synthesis. Immunoprecipitation with antibodies to the RNA polymerase core enzyme revealed that exposure of the bacterial cells to UV radiation induced the association of the core enzyme with a protein of approximately 29 kDa. These results demonstrate that UV radiation increases the activity of RNA polymerase, and they suggest that this effect may be related to the repair of DNA damage.

Adsorption of hydrazoic acid from aqueous solution by macroreticular resin

Sodium azide is a key component in the automobile air bag. When dissolved in aqueous solution, it reacts rapidly with water to form hydrazoic acid which is a highly toxic chemical and is strongly regulated by government. In the present study, adsorption of hydrazoic acid from aqueous solution by macroreticular resin is investigated. This method can provides a convenient means for dealing with the toxic hydrazoic acid. Experimental tests of batch equilibrium adsorption and continuous column adsorption of hydrazoic acid were conducted and the test results were employed to establish adsorption isotherm and to evaluate the column adsorption efficiency. The test results revealed that the multilayer adsorption isotherms, like the modified Langmuir or Jossens model, are needed to adequately describe the hydrazoic acid adsorption equilibrium between the liquid and solid (resin) phases. In the column adsorption process, a theoretical model was adopted for representing the hydrazoic acid change in the aqueous solution exiting the column and the verified theoretical model significantly facilitates prediction of adsorption breakthroughs and column design. Regeneration of exhausted resin was investigated. Solution of 10% (w/w) NaCl was found to be a very efficient regenerant.

An improved method for determination of heavy metal bioavailability in contaminated soil

Bioavailability of heavy metal in contaminated soil is investigated. A general diffusion model for determining the heavy metal bioavailability in soil has been developed The bioavailability predictions based on the present model were more accurate than those based on a previous model. Experimental results obtained using cadmium-, copper-, zinc- and lead-contaminated soils were employed for model verification. The effects of soil pH, initial heavy metal concentration, temperature and soil type on the effective diffusion coefficient or bioavailability index were also examined experimentally. The theoretical model and experimental procedure proposed in the present study provide a convenient means for the determination of heavy metal or inorganic ion bioavailability in contaminated soil.

Signal transduction by the CEACAM1 tumor suppressor. Phosphorylation of serine 503 is required for growth-inhibitory activity

CEACAM1 is a cell-cell adhesion molecule that mediates homophilic cell adhesion. In addition, CEACAM1 was also shown to suppress the growth of prostate, breast, and colon tumors. Structural and functional analyses showed that the adhesion activity of CEACAM1 is mediated by its extracellular domain while its cytoplasmic domain is necessary and sufficient for growth-inhibitory activity. The signal pathways leading to CEACAM1-mediated growth suppression are not known. We studied the importance of phosphorylation of serine 503 in this growth-inhibitory signaling pathway. Full-length CEACAM1 was found to be phosphorylated in vivo in both tyrosine and serine residues. Mutation of tyrosine 488 to phenylalanine did not abolish the tumor-suppressive activity of CEACAM1, suggesting that phosphorylation at tyrosine 488 is not critical for CEACAM1's tumor-suppressive activity. Although expression of CEACAM1's cytoplasmic domain inhibited the growth of DU145 prostate cancer cells in vivo, mutation of serine 503 to alanine abolished the growth-inhibitory activity. In addition, the change of serine 503 to aspartic acid produced tumor-suppressive activity similar to that of the wild-type CEACAM1. These results suggested that phosphorylation at serine 503 is essential for CEACAM1's growth-inhibitory function in vivo.

Differences in tissue-specific and embryonic expression of mouse Ceacam1 and Ceacam2 genes

The intercellular adhesion molecule CEACAM1, also known as C-CAM1 (where CAM is cell-adhesion molecule), can function as a tumour suppressor in several carcinomas, including those of the prostate, breast, bladder and colon. This suggests that CEACAM1 may play an important role in the regulation of normal cell growth and differentiation. However, there is no direct evidence to support this putative function of CEACAM1. To elucidate its physiological function by targeted gene deletion, we isolated the Ceacam genes from a mouse 129 Sv/Ev library. Although there is only one Ceacam1 gene in humans and one in rats, two homologous genes (Ceacam1 and Ceacam2) have been identified in the mouse. Our sequence analysis revealed that the genes encoded nine exons and spanned approx. 16-17 kb (Ceacam1) and 25 kb (Ceacam2). The genes were highly similar (79.6%). The major differences in the protein-coding regions were located in exons 2, 5 and 6 (76.9%, 87.0% and 78.5% similarity respectively). In addition, introns 2, 5 and 7 were also significantly different, being 29.7%, 59.8% and 64.5% similar respectively. While most of these differences were due to nucleotide substitutions, two insertions of 418 and 5849 bp occurred in intron 2 of Ceacam2, and another two insertions of 1384 and 197 bp occurred in introns 5 and 7 respectively. To determine whether functional redundancy exists between Ceacam1 and Ceacam2, we examined their expression in 16 mouse tissues by using semi-quantitative reverse transcription-PCR. As in human and rat, in the mouse Ceacam1 mRNA was highly abundant in the liver, small intestine, prostate and spleen. In contrast, Ceacam2 mRNA was only detected in kidney, testis and, to a lesser extent, spleen. Reverse transcription-PCR using testis RNA indicated that Ceacam2 in the testis is an alternatively spliced form containing only exons 1, 2, 5, 6, 8 and 9. In the mouse embryo, Ceacam1 mRNA was detected at day 8.5, disappeared between days 9.5 and 12.5, and re-appeared at day 19. On the other hand, no Ceacam2 mRNA was detected throughout embryonic development. The different tissue expression patterns and regulation during embryonic development suggest that the CEACAM1 and CEACAM2 proteins, although highly similar, may have different functions both during mouse development and in adulthood.

Abnormal cardiovascular reflex tests are predictors of mortality in Type 2 diabetes mellitus

AIMS

To determine whether diabetic autonomic neuropathy is an important factor contributing to mortality in Type 2 diabetes mellitus.

METHODS

Between 1989 and 1993, 431 men and 181 women with Type 2 diabetes were given diabetic autonomic neuropathy cardiovascular reflex (CVR) tests. These subjects were followed for the subsequent 5--9 years to assess mortality rates.

RESULTS

The prevalence rate of abnormal CVR tests was 46.1% in patients with the history of diabetes less than 5 years and up to 69.4% when the history of diabetes exceeded 20 years. During the follow-up period from 1 January 1989 to 31 December 1997 (mean 7.7 years), a total of 135 participants died. The 8-year survival rate for patients with abnormal CVR tests was 63.6% in males and 76.4% in females, compared with 80.9 and 93.3% for patients with normal CVR tests. The results were grouped as: group 1, normal CVR tests without postural hypotension (PHT); group 2, normal CVR tests with PHT; group 3, abnormal CVR tests without PHT; and group 4, abnormal CVR tests with PHT. The 8-year survival rate was 85.4% in group 1, 80.9% in group 2, 74.5% in group 3 and 61.1% in group 4.

CONCLUSION

Type 2 diabetic patients with abnormal CVR tests may have increased mortality, and those combined with postural hypotension have higher mortality than those without. Abnormal CVR tests may be important predictors of mortality in Type 2 diabetes mellitus.

Novel neurotransmitters as natural ligands of orphan G-protein-coupled receptors

The "orphan" G-protein-coupled receptors (GPCRs) are cloned GPCRs that bind unknown ligands. Since 1995, nineteen orphan GPCRs have been used as targets to identify and isolate their natural ligands via the application of the "orphan receptor strategy". These ligands are peptides, lipids or biogenic amines, and act as transmitter molecules. One nucleotide-sugar derivative and six peptides or peptide families identified through this strategy are novel and have already enriched our understanding of various brain functions.

Purification and characterization of human cell--cell adhesion molecule 1 (C-CAM1) expressed in insect cells

The cell--cell adhesion molecule 1 (C-CAM1) plays an important role as a tumor suppressor for prostate cancer. Decreased expression of C-CAM1 was detected in prostate, breast, and colon carcinoma. Reexpression of C-CAM1 in prostate and breast cancer cell lines was able to suppress tumorigenicity in vivo. These observations suggest that C-CAM1 may be used as a marker for cancer detection or diagnosis. To generate monoclonal antibodies specific to C-CAM1, we have overexpressed full-length human C-CAM1 in Sf9 cells using a baculovirus expression system. The protein was purified 104-fold using nickel affinity chromatography. About 0.4 mg purified C-CAM1 was obtained from 200 mg of infected cells. When the purified protein was digested with peptidyl-N-glycosidase, the apparent mobility of the protein on SDS--PAGE changed from 90 to 58 kDa, which is close to the molecular weight predicted from the cloned cDNA sequence. This observation suggests that C-CAM1 was glycosylated on asparagine residues when expressed in Sf9 cells. Western blotting and internal protein sequencing analysis confirmed that the purified protein is human C-CAM1. Biochemical and functional assays indicate that this protein expressed in Sf9 cells displays characteristics similar to those of native protein, including adhesion function and glycosylation modification. Using this protocol, sufficient quantity of this protein can be produced with purity suitable for monoclonal antibody generation and biochemical study.

Hypokalaemia and paralysis

It is not uncommon for patients to present to the emergency room with severe weakness and a markedly low plasma potassium concentration. We attempted to identify useful clues to the diagnosis of hypokalaemic periodic paralysis (HPP), because its acute treatment aims are unique. We retrospectively reviewed charts over a 10-year period: HPP was the initial diagnosis in 97 patients. Mean patient age was 29+/-1.1 and the male:female ratio was 77:20. When the final diagnosis was HPP (n=73), the acid-base state was normal, the urine K(+) concentration was low, and the transtubular K(+) concentration gradient (TTKG) was <3. In patients with thyrotoxic periodic paralysis (TPP) (n=39), hypokalaemia was very commonly accompanied by hypophosphataemia (1.9+/-0.1 mg/dl). A clinical diagnosis of sporadic periodic paralysis (SPP) was made if hyperthyroidism and a family history of HPP were both absent (n=29). One subgroup of patients with HPP had a severe degree of hypernatraemia (167+/-5.0 mmol/l, n=3). There were only two patients with familial periodic paralysis (FPP). In 24 patients, the initial diagnosis was HPP, but subsequent studies failed to confirm this diagnosis. Each of these patients had an acid-base disorder, a high rate of renal K(+) excretion in the presence of hypokalaemia, and a TTKG of close to 7. With respect to therapy, much less K(+) was given to patients with HPP, yet 1:3 subsequently had a plasma K(+) concentration that eventually exceeded 5.0 mmol/l. Using plasma acid-base status, phosphate and K(+) excretion parameters allows a presumptive diagnosis of HPP with more confidence in the emergency room.

Propranolol rapidly reverses paralysis, hypokalemia, and hypophosphatemia in thyrotoxic periodic paralysis

Hypokalemia and hypophosphatemia are commonly encountered during paralysis in patients with thyrotoxic periodic paralysis (TPP) and may contribute to neuromuscular manifestations. Potassium and phosphate supplements have been recommended to hasten recovery and prevent cardiopulmonary complications. However, this recommendation has not yet proven efficacious. Hyperadrenergic activity has been implicated in the pathogenesis of TPP. We tested whether nonselective beta-blockers could terminate neuromuscular symptoms rapidly while reducing an intracellular shift of potassium and phosphate. We describe two patients who had an acute attack of TPP with characteristic hypokalemia and hypophosphatemia associated with low urinary potassium and phosphate excretion. After oral propranolol, 3 mg/kg, serum potassium and phosphate concentrations increased promptly in 2 hours in both patients, and there was complete amelioration of paralysis. No rebound hyperkalemia or hyperphosphatemia was detected. Given their efficacy in this pilot study, they should be considered as a first-line therapy for TPP.

The metabotropic glutamate receptor system protects against ischemic free radical programmed cell death in rat brain endothelial cells

As one of the key determinants of ischemic injury, cerebrovascular endothelial cell (EC) degeneration may be dependent upon the generation of the free radical nitric oxide (NO) and the subsequent induction of programmed cell death (PCD). Although the mechanisms that can prevent EC injury are most likely multifactorial in origin, the metabotropic glutamate receptor (mGluR) system may represent a novel therapeutic approach for ECs given the ability of the mGluR system to reverse neuronal cell injury. This study examined the modulation of individual subtypes of mGluRs during anoxia and NO toxicity in primary rat cerebrovascular ECs. Cell injury was determined through trypan blue dye exclusion, intracellular lactate dehydrogenase release, DNA fragmentation, membrane phosphatidylserine (PS) exposure, and cysteine protease activity. Anoxia, through the generation of NO, and exposure to exogenous NO were directly toxic to ECs. Exposure to NO rapidly decreased EC viability from 98% +/- 2% to 40% +/- 9%, increased DNA fragmentation from 2% +/- 2% to 61% +/- 9%, and increased membrane PS exposure from 3% +/- 3% to 66% +/- 6% over a 24-hour period. Activation of the mGluR system significantly increased EC survival through the prevention of NO-induced DNA fragmentation and cellular membrane PS residue exposure. In contrast, antagonism of the mGluR system failed to prevent PCD. Cytoprotection by the mGluR system was dependent, at least in part, upon the direct inhibition of NO-generated caspase 1- and caspase 3-like activities. Further investigation into the ability of the mGluR system to prevent PCD in ECs may open new therapeutic avenues for the treatment of cerebrovascular injury.

A comparison of insulin suppression tests performed with somatostatin and octreotide with particular reference to tolerability

To evaluate the tolerability of insulin suppression test (IST) using octreotide instead of somatostatin, we compared the steady-state plasma glucose (SSPG) values and the safety during and after the test in 17 normal volunteers. The subject received IST twice (with somatostatin or with octreotide) in random order. During the test, all subjects were infused with regular insulin and glucose simultaneously for 180 min. In addition, either somatostatin or octreotide was infused intravenously over the same period of time. Plasma glucose, insulin and C-peptide were measured. The subject response to the test was recorded during and one day after the test by a structured questionnaire. The SSPG and the steady-state plasma insulin (SSPI) values reached during IST were similar, irrespective of the use of somatostatin or octreotide. There was a positive correlation between the SSPG values obtained from both methods (r = 0.67, P = 0.003). However, the mean intra-individual coefficient of variation is 17.9% for SSPG. The SSPG levels, no matter from which method, correlated positively with the 2-h insulin after oral glucose challenge. Most adverse events (especially gastrointestinal discomfort) occurred after the test, and increased much more after using octreotide than somatostatin (P = 0.002 by chi 2 test). In conclusion, the SSPG values measured by IST using octreotide or somatostatin are similar in normal healthy subjects. Yet, the octreotide method has more adverse events after the test.

Group I metabotropic glutamate receptors prevent endothelial programmed cell death independent from MAP kinase p38 activation in rat

Activation of Group I metabotropic glutamate receptors (mGluRs) prevents neuronal programmed cell death (PCD), but the role of these receptors in the vascular endothelial cell (EC) system has not been defined. Since ECs are principal targets for ischemic free radical injury, we examined whether the mGluR system could modulate vascular PCD. Activation of the Group I mGluR system, but not antagonism, addressed two distinct pathways of PCD by preventing the destruction of genomic DNA and maintaining EC membrane asymmetry. The induction of nitric oxide (NO)-induced PCD in ECs paralleled the specific activation of the MAP kinase p38 pathway, but the vascular protection conferred by the Group I mGluR system appears to rely on more downstream cellular pathways. We provide initial evidence for Group I mGluRs to prevent NO-induced vascular injury and offer new directions for vascular disease treatment.

Expression of a truncated first exon BCR sequence in chronic myelogenous leukemia cells blocks cell growth and induces cell death

We have shown that a deletion mutant form of Bcr [Bcr(64-413)] is a strong inhibitor of the tyrosine kinase of Bcr-Abl in vitro and also inhibits its oncogenic growth effects (Liu et al., Cancer Res., 56: 5120-5124, 1996). To determine the effects of this Bcr-Abl kinase inhibitor on chronic myelogenous leukemia (CML) cells, we cloned BCR(64-413) into a recombinant, replication-defective adenovirus to express useful quantities of Bcr(64-413) in a wide variety of cells in culture. Infection of Cos1 cells with plaque-purified virus at a multiplicity of infection of 20-40 induced high expression of Bcr(64-413) as detected by Western blotting. Infection of hematopoietic cells at modest multiplicities of infection (20-40) required special conditions involving shifting cycling cells to a nongrowing condition involving serum starvation and cell crowding. Under these conditions, both Bcr-Abl-positive and -negative hematopoietic cells can be efficiently infected by adenovirus, as demonstrated by 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside staining of cells infected by beta-galactosidase (beta-GAL) adenovirus. We found that expression of Bcr(64-413) in Bcr-Abl-positive K562 and BV-173 cells, but not Bcr-Abl-negative SMS-SB cells, increased cell-cell clumping and inhibited cell growth. In contrast to the effects of the Bcr(64-413) adenovirus, the beta-GAL adenovirus, despite infecting both types of cells, did not block growth or increase cell-cell clumping of Bcr-Abl-positive and -negative hematopoietic cells. Expression of Bcr(64-413) protein in primary cultures of cells from CML patients with active disease interfered with cell growth, induced apoptosis (as measured by annexin staining), and increased cell-cell clumping, whereas the beta-GAL adenovirus and mock-infected cells lacked these effects. In contrast, normal marrow cells did not exhibit these effects on infection with Bcr(64-413) adenovirus. We conclude from these findings that Bcr(64-413) interferes with the oncogenic effects of Bcr-Abl and therefore has the potential for use in therapy of CML.

Preparation of Na,K-ATPase specifically modified on the anti-fluorescein antibody-inaccessible site by fluorescein 5'-isothiocyanate

Specific labeling is required for energy transfer measurements and to avoid artifacts in the use of fluorophores as reporter groups. Therefore, a method for specific modification by one of the most popular reagents for P-type ATPases (fluorescein 5'-isothiocyanate) has been developed. Sulfhydryl reagents protected against modification of cysteine residues, and treatment with dithiothreitol eliminated a slow doubling of the fluorescence of conventionally modified Na,K-ATPase upon dilution that is attributed to disappearance of self-energy transfer. Removal of nonspecifically bound fluorescein was also confirmed by titration of the modified Na, K-ATPase with anti-fluorescein antibody and by time resolution of the fluorescence change when the modified enzyme was mixed with Na(+) in a stopped-flow instrument. The only fluorescence change when specifically modified Na,K-ATPase was mixed with Na(+) was the signal from fluorescein at the antibody-inaccessible, substrate-protectable site that reports the conformational change in unphosphorylated enzyme. The magnitude of the fluorescence change reporting the conformational change increased from between 8 and 12% to between 25 and 30% without affecting the kinetic constants estimated from titrations with Na(+) and K(+). The method should be generally applicable to the preparation of specifically labeled P-type pumps for use in kinetic and equilibrium titrations or energy transfer measurements.

Coronary artery bypass grafting on the beating heart using the octopus method--a case report

A 74-year-old male was admitted due to chest tightness for one month. He had received percutaneous transilluminal coronary angioplasty (PTCA) because of single-vessel disease one year ago. Cardiac catheterization examination carried out during this admission revealed 90% stenosis of the left anterior descending coronary artery (LAD) and circumflex branch (CX). Because another attempt of PTCA was considered not optimal, the patient was advised to undergo surgical grafting to which he consented. After expediently balancing the merits and demerits of every practicable surgical procedure--the essential determinant in selection of which was that the patient's condition and criteria of indication of that procedure were in perfect harmony--we decided to carry out minimally invasive direct coronary artery bypass (MIDCAB) with the application of Octopus tissue stabilizer. We report the surgical course and anesthetic management of the patient and discourse some detail in MIDCAB.

Molecular cloning and characterization of a second human cysteinyl leukotriene receptor: discovery of a subtype selective agonist

The cysteinyl leukotrienes (CysLTs) are potent biological mediators in the pathophysiology of inflammatory diseases, in particular of airway obstruction in asthma. Pharmacological studies have suggested the existence of at least two types of CysLT receptors, designated CysLT(1) and CysLT(2). The CysLT(1) receptor has been cloned recently. Here we report the molecular cloning, expression, localization, and functional characterization of a human G protein-coupled receptor that has the expected characteristics of a CysLT(2) receptor. This new receptor is selectively activated by nanomolar concentrations of CysLTs with a rank order potency of LTC(4) = LTD(4) >> LTE(4). The leukotriene analog BAY u9773, reported to be a dual CysLT(1)/CysLT(2) antagonist, was found to be an antagonist at CysLT(1) sites but acted as a partial agonist at this new receptor. The structurally different CysLT(1) receptor-selective antagonists zafirlukast, montelukast, and MK-571 did not inhibit the agonist-mediated calcium mobilization of CysLT(2) receptors at physiological concentrations. Localization studies indicate highest expression of CysLT(2) receptors in adrenal glands, heart, and placenta; moderate levels in spleen, peripheral blood leukocytes, and lymph nodes; and low levels in the central nervous system and pituitary. The human CysLT(2) receptor gene is located on chromosome 13q14.12-21.1. The new receptor exhibits all characteristics of the thus far poorly defined CysLT(2) receptor. Moreover, we have identified BAY u9773 as a CysLT(2) selective agonist, which could prove to be of immediate use in understanding the functional roles of the CysLT(2) receptor.

Experimental observation of the slowdown of optical beams by a volume-index grating in a photorefractive LiNbO3 crystal

We investigate the group velocity of light in a one-dimensional volume-index grating inside a photorefractive LiNbO(3) crystal. The slowdown of the group electromagnetic propagation is observed experimentally by tuning of the wave number of the optical beam close to the outside edge of the forbidden bandgap. We obtain a large group index of up to 7.5 in a 3.5-cm crystal sample. The group index is compared with the result of a theoretical derivation. The results are presented and discussed.

Group I and group III metabotropic glutamate receptor subtypes provide enhanced neuroprotection

Neuroprotection by the metabotropic glutamate receptor (mGluR) system has been linked to the modulation of both the free radical nitric oxide (NO) and programmed cell death (PCD). Because the cellular mechanisms that ultimately determine neuronal PCD rely upon the independent pathways of genomic DNA degradation, externalization of membrane phosphatidylserine (PS) residues, and the activation of associated cysteine proteases, we investigated the ability of the individual mGluR subtypes to modulate the distinct pathways of NO-induced PCD in primary rat hippocampal neurons. Membrane PS residue externalization occurred within the initial 3 hr after exposure to the NO donors (300 microM SNP or 300 microM NOC-9), preceded genomic DNA fragmentation, and was present in 80 +/- 2% of the neurons within a 24-hr period. NO exposure also led to the rapid induction of both caspase 1-like and caspase 3-like activities that were determined to be necessary, at least in part, for the generation of NO-induced genomic DNA degradation, but distinct from the detrimental effects of intracellular acidification. Yet, only caspase 1-like activity was necessary for the modulation of PS residue externalization. Activation of group I mGluR subtypes utilized an effective, "upstream" mechanism for the inhibition of cysteine protease activity that offered an enhanced level of neuroprotection through both the preservation of genomic DNA integrity and the maintenance of PS membrane asymmetry. Group II and Group III mGluR subtypes maintained DNA integrity and group III mGluR subtypes additionally prevented PS residue externalization through mechanisms that were targeted below the level of caspase activation. Our work elucidates the independent nature of the mGluR subtypes to not only provide discrete levels of protection against neuronal PCD, but also offer robust therapeutic strategies for neurodegenerative disease.

Simulation of the wiener sausage

The volume of a region visited by a spherical Brownian particle for a time t, known as the Wiener sausage, is an important random variable characterizing Brownian motion. A Brownian dynamics simulation is used to study statistical properties of the Wiener sausage volume. We show that the probability density is closely approximated by a Gaussian distribution not only at asymptotically long times, but over a wide range of times as well. We also refine the expression for the dispersion by finding a correction term for the long-time asymptotic dependence.