Investigation of the role of tryptophan residues in cationic antimicrobial peptides to determine the mechanism of antimicrobial action

AIMS

To understand the effects of Trp residues in linear antimicrobial peptides with α-helical conformations on cell permeation ability and membrane transduction efficacy.

METHODS AND RESULTS

A series of L-K6 analogues were designed and synthesized by replacing Ile or Leu with Trp at different positions on the hydrophobic face of L-K6. The antimicrobial and haemolytic activity and secondary structure of the designed Trp-containing peptides were assessed. In addition, the role of Trp in membrane disruption for these designed peptides was investigated. I1W, I4W and L5W demonstrated stronger activity than the other peptides against both Gram-positive and Gram-negative bacteria. All of the tested peptides preferentially interacted with negatively charged vesicles composed of phosphatidylglycerol (PG)/cardiolipin (CL) or PG/CL/phosphatidylethanolamine, and, to a lesser extent, with zwitterionic vesicles. I1W, I4W and L5W caused calcein release at 2·5 μmol l(-1) .

CONCLUSIONS

The position of Trp, rather than the number of Trp residues, in these peptides was an important factor in the antimicrobial activity. Trp residues were deeply inserted into negatively charged membranes but were largely exposed in aqueous buffer solution.

SIGNIFICANCE AND IMPACT OF THE STUDY

These Trp-containing peptides may represent good candidates for new antibiotic agents and for use in new therapeutic approaches.

Progesterone-estrogen interactions in synaptic plasticity and neuroprotection

17ß-Estradiol and progesterone exert a number of physiological effects throughout the brain due to interactions with several types of receptors belonging to the traditional family of intracellular hormonal receptors as well as to membrane-bound receptors. In particular, both hormones elicit rapid modifications of neuronal excitability that have been postulated to underlie their effects on synaptic plasticity and learning and memory. Likewise, both hormones have been shown to be neuroprotective under certain conditions, possibly due to the activation of pro-survival pathways and the inhibition of pro-apoptotic cascades. Because of the similarities in their cellular effects, there have been a number of questions raised by numerous observations that progesterone inhibits the effects of estrogen. In this manuscript, we first review the interactions between 17ß-estradiol (E2) and progesterone (P4) in synaptic plasticity, and conclude that, while E2 exerts a clear and important role in long-term potentiation of synaptic transmission in hippocampal neurons, the role of P4 is much less clear, and could be accounted by the direct or indirect regulation of GABAA receptors. We then discuss the neuroprotective roles of both hormones, in particular against excitotoxicity. In this case, the neuroprotective effects of these hormones are very similar to those of the neurotrophic factor BDNF. Interestingly, P4 antagonizes the effects of E2, possibly through the regulation of estrogen receptors or of proteins associated with the receptors or interactions with signaling pathways activated by E2. Overall, this review emphasizes the existence of common molecules and pathways that participate in the regulation of both synaptic plasticity and neurodegeneration.

Risk of second primary cancer after treatment for esophageal cancer: a pooled analysis of nine cancer registries

The introduction of new treatments for esophageal cancer including surgery, chemotherapy, radiotherapy, or a combination of these modalities has not only improved patient survival, but may also increase the risk of the second primary cancers. The available evidence is conflicting with most risk estimates based on sparse numbers. Here we estimated standardized incidence ratios (SIRs) of second cancer among 24,557 esophageal cancer survivors (at least 2 months) in the Surveillance, Epidemiology, and End Results (SEER) Program between 1973 and 2007, who had been followed up for median 6.5 years (range 2 months-29.3 years). Second cancer risk was statistically significantly elevated (SIR = 1.34, 95% confidence interval [CI]= 1.25-1.42) among the survivors compared with the general population; the SIRs for cancers of oral and pharynx, stomach, small intestine, larynx, lung and bronchus, thyroid and prostate cancer were 8.64 (95% CI = 7.36-10.07), 2.87 (95% CI = 2.10-3.82), 3.80 (95% CI = 1.82-7.00), 3.19 (95% CI = 2.12-4.61), 1.68 (95% CI = 1.46-1.93), 2.50 (95% CI = 1.25-4.47), and 0.77 (95% CI = 0.65-0.90), respectively. Radiotherapy raised cancer risk of larynx (SIR = 3.98, 95% CI = 2.43-6.14) and thyroid (SIR = 3.57, 95% CI = 1.54-7.03) among all esophageal cancer survivors. For patients who had 5-9 years of follow up after radiotherapy, the SIR for lung cancer was 3.46 (95% CI = 2.41-4.82). Patients with esophageal cancer are at increased risks of second cancers of oral and pharynx, larynx, lung, and thyroid, while at a decreased risk for prostate cancer. These findings indicate that radiotherapy for esophageal cancer patients may increase risk of developing second cancers of larynx, lung, and thyroid. Thus, randomized clinical trials to address the association of radiotherapy and the risk of secondary cancer are warranted.

First-time donors responding to a national disaster may be an untapped resource for the blood centre

BACKGROUND

On 12 May 2008, a severe earthquake struck Sichuan in China. Many people donated blood for the first time, leading us to question whether these donors might become repeat donors in the future. The return pattern of post-earthquake first-time donors (PEFTD) was compared with that of first-time donors (FTD) in a comparable period.

METHODS

Demographic characteristics, transfusion-transmissible infection rates and 1-year return rates were compared between 5147 PEFTD (5/13-5/19, 2008) and 3176 FTD (5/13-5/19, 2009) from five Chinese blood centres using chi-squared tests. Adjusted logistic regression was used to detect earthquake effect on donor return.

RESULTS

Post-earthquake first-time donors were more frequently between 26 and 45 years, men, and better educated compared with the control group. Slightly higher but not statistically significant increased rates of hepatitis B virus surface antigen (HBsAg) (0·87% vs. 0·50%, P=0·054), hepatitis C virus (HCV) (0·70% vs. 0·63%, P=0·414), syphilis (0·9% vs. 0·7%, P=0·489) and lower rates of human immunodeficiency virus (HIV) (0·31% vs. 0·60%, P=0·078) reactivity were detected for PEFTD. The 1-year return rate for PEFTD was significantly lower than that of the controls (8·0% vs. 13·0%, P<0·001). After adjusting for demographic factors, donation volume and sites, the PEFTD were less likely to return in 1 year than the controls (OR: 0·520; 95% CI: 0·442, 0·611).

CONCLUSION

Post-earthquake first-time donors may be less likely to donate again without continuing motivation strategies. Further studies on PEFTD's lack of motivation to return for donation are needed to design recruitment strategies to convert PEFTD to become repeat donors to continuously replenish the blood supply.

Calpain-mediated regulation of stargazin in adult rat brain

Changes in AMPA receptors have been proposed to underlie changes in synaptic efficacy in hippocampus and other brain structures. Calpain activation has also been discussed as a potential mechanism to produce lasting modifications of synaptic structure and function. Stargazin is a member of the family of transmembrane AMPA receptor associated proteins (TARPs), which participates in trafficking of AMPA receptors and regulates their kinetic properties. We report here that preincubation of thin (20 μm) frozen rat brain sections with calcium changes the immunological properties of stargazin, an effect totally blocked by a calpain inhibitor. Immunocytochemistry indicates that in situ calpain activation produces a decreased immunoreactivity for stargazin in the neuropil throughout the brain, and Western blots confirmed that a similar treatment decreased stargazin levels. Interestingly, the same treatment did not modify the immunoreactivity for another TARP member, γ-8, although it increased immunoreactivity in cell bodies in hippocampus, an effect that was not blocked by calpain inhibition. These results strongly suggest the involvement of calpain in the regulation of AMPA receptor targeting and function through truncation of stargazin.

Simple and inexpensive method of wood pellets macro-porosity measurement

A novel simplified stereometric measurement method for determining the macro-porosity of wood pellets through geometrical approach was successfully developed and tested. The irregular ends of pellets of circular cross-section were sanded flat so that their geometry becomes cylinder and their volumes evaluated using mensuration formula. Such formed cylindrical pellets were loose or tap filled to selected volumes to evaluate the macro-porosity and the constant specific weight. The method was extended to evaluate actual wood pellets properties. Overall macro-porosity of actual wood pellets was determined as 41.0+/-2.5% and 35.5+/-2.7%, mean bulk density as 670+/-29 kg m(-3) and 731+/-31 kg m(-3), and classified as "Class-3:Medium" and "Class-3&4:Medium to Low" for loose and tapped fills, respectively. Hausner ratio and Carr's compressibility index classify wood pellets as "freely flowing." The developed stereometric method can be used as a handy inexpensive laboratory procedure to estimate the macro-porosity of different types and makes of wood pellets and other similar packaged materials.

Permeability of wood pellets in the presence of fines

Broken pellets and fines are produced when pellets are handled. The resistance to air flow was measured for clean pellets and for pellets mixed with 1-20% broken pellets (fines). A pellet diameter was 6mm. The lengths ranged from 6 to 12 mm. Clean pellets were defined as particles that remained on a 4mm screen. A typical sieve analysis showed 30% of the mass of particles that passed through the 4mm screen was smaller than 1mm. The airflow rates used in the experiment ranged from 0.004 to 0.357 ms(-1). The corresponding pressure drop ranged from 1.9 to 271 Pam(-1) for clean pellets, from 4.8 to 1100 Pam(-1) for 10% fines content, and from 7.9 to 1800 Pam(-1) for 20% fines content. Coefficients of Hukill and Ives' equation were estimated for clean pellets and a multiplier was defined to calculate pressure drop for pellets mixed with fines.

Identification of Interferon Regulatory Factor (IRF)-5 Tumor Suppressor Function in Human Breast Cancer

Background: Transcription factors of the IRF family participate in the early host response to pathogens, hematopoietic differentiation and immunomodulation. IRFs can regulate cell growth and apoptosis thereby affecting the susceptibility to and progression of cancer. IRF-1 was recently identified as a tumor suppressor in breast cancer. Early evidence from our lab and others suggests that IRF-5 may also have tumor suppressor activities. Although loss of IRF-5 expression has recently been shown to enhance transformation by Ha-ras, very little is known of IRF-5 tumor suppressor function(s).Material and Methods: Using paraffin-embedded formalin-fixed human breast tissue specimens from 64 patients with varying stages of ductal carcinoma, we analyzed and compared the expression of IRF-1 and IRF-5 by immunofluorescence (IF). Clinical data, such as histological subtype, stage, and receptor expression (ER, PR Her-2) were available for clinicopathological correlations. Protein levels were also determined in normal human breast epithelial MCF-10A, and -12A cells, and in cancer cell lines MCF-7, MDA-MB-231, -468, and T47D by immunoblot and IF. By retroviral infection, we overexpressed IRF-5 in breast cancer cell lines or knocked-down IRF-5 in normal MCF-10A and -12A cells and examined cell growth, apoptosis, metastasis and sensitivity to cytotoxic stress. In vivo tumor suppressor function was determined in NCr nu/nu mice inoculated with MCF-7 or MDA-MB-231 cells expressing or lacking IRF-5.Results: We confirmed recent data on IRF-1 revealing that it is expressed less frequently in tumor tissue of high-grade ductal carcinoma in situ (DCIS) or invasive DC compared with normal breast tissue. Data from patient samples indicate a significant difference between IRF-1 and IRF-5 expression that was distinctly associated with breast cancer disease stages, including early-to-late stage DCIS, suggesting their utilization as prognostic indicators.Similar findings were made in breast cancer cell lines. We demonstrate that forced expression of IRF-5 in breast cancer cells inhibits colony formation, sensitizes cells to cytotoxic stress-induced apoptosis, inhibits metastasis, and tumor formation in nude mice. Conversely, knockdown of IRF-5 in MCF-10A and -12A cells resulted in resistance to stress-induced cell death.Discussion: Data from this study strongly support a tumor suppressor function for IRF-5 in breast cancer. Ultimately, the study is expected to lead us to the identification of new prognostic indicators and therapeutic approaches for the treatment of breast cancer.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 3160.

Different pathways are involved in arsenic-trioxide-induced cell proliferation and growth inhibition in human keratinocytes

BACKGROUND

Arsenic is a carcinogen that is associated with an increased risk of human skin cancer. On the other hand, arsenic trioxide (As(2)O(3)) has potential anticancer activity against a wide range of carcinomas. The mechanisms involved in these two opposing processes remain unclear.

METHODS

We used normal human keratinocytes (NHK), the human keratinocyte HaCaT cell line and human epidermal carcinoma cells (A431 cell line) to investigate potential pathways involved in the effects on cell proliferation and growth inhibition by different concentrations of As(2)O(3).

RESULTS

At low concentrations (0.5-32 nM), As(2)O(3) enhanced keratinocyte proliferation and regulated the expression of about 172 genes. Among them, cell cycling pathway genes (including CDK4 and E2F1) were significantly upregulated. At high concentrations (0.5-10 microM), As(2)O(3) inhibited cell growth in NHK and HaCaT cells, but not in A431 cells. As(2)O(3) significantly induced NHK and HaCaT apoptosis through the activation of caspase-3, as well as cell cycle arrest at the G2-M phase.

CONCLUSION

Our data suggest that different pathways are involved in As(2)O(3)-mediated proliferation and growth inhibition. In addition, skin carcinoma cells were resistant to As(2)O(3)-induced cell growth inhibition and apoptosis when compared to NHK and HaCaT cells. Therefore, As(2)O(3) may not be appropriate for treatment of skin carcinomas.

Polyamine-based analogues as biochemical probes and potential therapeutics

The polyamines putrescine, spermidine and spermine are ubiquitous polycationic compounds that are found in nearly every cell type, and are required to support a wide variety of cellular functions. The existence of multiple cellular effector sites for naturally occurring polyamines implies that there are numerous targets for polyamine-based therapeutic agents. Through a programme aimed at the synthesis and evaluation of biologically active polyamine analogues, our laboratory has identified three distinct structural classes of polyamine derivatives that exhibit promising biological activity in vitro. We have synthesized more than 200 symmetrically and unsymmetrically substituted alkylpolyamines that possess potent antitumour or antiparasitic activity, depending on their backbone architecture and terminal alkyl substituents. Along similar lines, we have developed novel polyamino(bis)guanidines and polyaminobiguanides that are promising antitrypanosomal agents and that interfere with biofilm formation in the pathogenic bacterium Yersinia pestis. Finally, we recently reported a series of PAHAs (polyaminohydroxamic acids) and PABAs (polyaminobenzamides) that inhibit HDACs (histone deacetylases), and in some cases are selective for individual HDAC isoforms. These studies support the hypothesis that polyamine-based small molecules can be developed for use as biochemical probes and as potential therapies for multiple diseases.

The use of Medpor coated tear drainage tube in conjunctivodacryocystorhinostomy

PURPOSE

To analyse outcomes of lacrimal bypass surgery with the Medpor coated tear drainage tube.

METHODS

A total of 26 eyes in 26 patients with persistent epiphora who failed canaliculoanastomosis and dacryocystorhinostomy were treated by the lacrimal bypass surgery with the Medpor coated tear drainage tubes. Ten cases of severe obstruction of punctum and canaliculi and 16 cases with both upper system and lacrimal sac obstruction comprised this cohort of patients.

RESULTS

No tube extrusion or displacement was observed after 6-28 months of follow-up. Complete or significant resolution of epiphora was achieved in 23/26 cases (88.5%). Luminal obstruction by debris was noted in nine eyes, ocular discomfort in four, improper tube size selection in two, malposition in one, infection in one, diplopia in one, corneal abrasion in one, and reflux of intranasal secretion into fornix in another.

CONCLUSION

Medpor coated tear drainage tube offers tube stabilization in minimizing tube extrusion and displacement.

A novel method for determination of collagen orientation in cartilage by Fourier transform infrared imaging spectroscopy (FT-IRIS)

OBJECTIVE

The orientation of collagen molecules is an important determinant of their functionality in connective tissues. The objective of the current study is to establish a method to determine the alignment of collagen molecules in histological sections of cartilage by polarized Fourier transform infrared imaging spectroscopy (FT-IRIS), a method based on molecular vibrations.

METHODS

Polarized FT-IRIS data obtained from highly oriented tendon collagen were utilized to calibrate the derived spectral parameters. The ratio of the integrated areas of the collagen amide I/II absorbances was used as an indicator of collagen orientation. These data were then applied to FT-IRIS analysis of the orientation of collagen molecules in equine articular cartilage, in equine repair cartilage after microfracture treatment, and in human osteoarthritic cartilage. Polarized light microscopy (PLM), the most frequently utilized technique to evaluate collagen fibril orientation in histological sections, was performed on picrosirius red-stained sections for comparison.

RESULTS AND CONCLUSION

Thicknesses of each zone of normal equine cartilage (calculated based on differences in collagen orientation) were equivalent as determined by PLM and FT-IRIS. Comparable outcomes were obtained from the PLM and FT-IRIS analyses of repair and osteoarthritis tissues, whereby similar zonal variations in collagen orientation were apparent for the two methods. However, the PLM images of human osteoarthritic cartilage showed less obvious zonal discrimination and orientation compared to the FT-IRIS images, possibly attributable to the FT-IRIS method detecting molecular orientation changes prior to their manifestation at the microscopic level.

Uptake and pathogenic effects of amyloid beta peptide 1-42 are enhanced by integrin antagonists and blocked by NMDA receptor antagonists

Many synapses contain two types of receptors - integrins and N-methyl-D-aspartate (NMDA) receptors - that have been implicated in peptide internalization. The present studies tested if either class is involved in the uptake of the 42-residue form of amyloid beta peptide (Abeta1-42), an event hypothesized to be of importance in the development of Alzheimer's disease. Cultured hippocampal slices were exposed to Abeta1-42 for 6 days in the presence or absence of soluble Gly-Arg-Gly-Asp-Ser-Pro, a peptide antagonist of Arg-Gly-Asp (RGD)-binding integrins, or the disintegrin echistatin. Abeta uptake, as assessed with immunocytochemistry, occurred in 42% of the slices incubated with Abeta peptide alone but in more than 80% of the slices co-treated with integrin antagonists. Uptake was also found in a broader range of hippocampal subfields in RGD-treated slices. Increased sequestration was accompanied by two characteristics of early stage Alzheimer's disease: elevated concentrations of cathepsin D immunoreactivity and activation of microglia. The selective NMDA receptor antagonist D-(-)-2-amino-5-phosphonovalerate completely blocked internalization of Abeta, up-regulation of cathepsin D, and activation of microglia. Our results identify two classes of receptors that cooperatively regulate the internalization of Abeta1-42 and support the hypothesis that characteristic pathologies of Alzheimer's disease occur once critical intraneuronal Abeta concentrations are reached.

Evidence that integrins contribute to multiple stages in the consolidation of long term potentiation in rat hippocampus

Three structurally distinct groups of antagonists were used to test the hypothesis that integrin adhesion receptors play an essential role in consolidating (stabilizing) long term potentiation of the Schaffer collaterals in rat hippocampus. Comparisons were made of percent potentiation at antagonist-treated versus control sites within CA1 stratum radiatum of the same hippocampal slice. Function blocking antibodies against the alpha5 subunit of the fibronectin receptor had no effect on baseline responses or initial potentiation but resulted in a >30% reduction, relative to within-slice control long term potentiation, 45 min later. Larger reductions were recorded in separate experiments continued for 4 h after the induction of potentiation. Alpha(v) and alpha2 subunit antibodies did not reliably affect the stabilization of potentiation. An antagonist peptide with preference for beta1 integrins produced a slowly developing decline of the type seen with alpha5 antibodies. A cyclic peptide antagonist reduced potentiation within 10 min of induction and caused an almost 40% decrease over 45 min. Two disintegrins (snake toxins that potently block integrins) were very effective in preventing the consolidation of long term potentiation: echistatin reduced potentiation by >70%, while triflavin caused approximately 50% decrease. The suppressing effects of echistatin were concentration-dependent, obtained with treatment after induction, and much more rapid than the effects of antibodies. Rapid declines in potentiation were particularly evident when the two disintegrins were applied together. These results indicate that hippocampal fibronectin receptors (alpha5/beta1 integrin) contribute importantly to a slowly developing phase of long term potentiation consolidation. They also suggest that other integrins are critical to aspects of consolidation occurring in the first few minutes after induction.

Thermal stability and DPPC/Ca2+ interactions of pulmonary surfactant SP-A from bulk-phase and monolayer IR spectroscopy

Surfactant protein A (SP-A), the most abundant pulmonary surfactant protein, is implicated in multiple biological functions including surfactant homeostasis, biophysical activity, and host defense. SP-A forms ternary complexes with lipids and Ca2+ which are important for protein function. The current study uses infrared (IR) transmission spectroscopy to investigate the bulk-phase interaction between SP-A, 1,2-dipalmitoylphosphatidylcholine (DPPC), and Ca2+ ions along with IR reflection-absorption spectroscopy (IRRAS) to examine protein secondary structure and lipid orientational order in monolayer films in situ at the air/water interface. The amide I contour of SP-A reveals two features at 1653 and 1636 cm(-1) arising from the collagen-like domain and a broad feature at 1645 cm(-1) suggested to arise from the carbohydrate recognition domain (CRD). SP-A secondary structure is unchanged in lipid monolayers. Thermal denaturation of SP-A in the presence of either DPPC or Ca2+ ion reveals a sequence of events involving the initial melting of the collagen-like region, followed by formation of intermolecular extended forms. Interestingly, these spectral changes were inhibited in the ternary system, showing that the combined presence of both DPPC and Ca2+ confers a remarkable thermal stability upon SP-A. The ternary interaction was revealed by the enhanced intensity of the asymmetric carboxylate stretching vibration. The IRRAS measurements indicated that incorporation of SP-A into preformed DPPC monolayers at a surface pressure of 10 mN/m induced a decrease in the average acyl chain tilt angle from 35 degrees to 28 degrees. In contrast, little change in chain tilt was observed at surface pressures of 25 or 40 mN/m. These results are consistent with and extend the fluorescence microscopy studies of Keough and co-workers [Ruano, M. L. F., et al. (1998) Biophys. J. 74, 1101-1109] in which SP-A was suggested to accumulate at the liquid-expanded/liquid-condensed boundary. Overall these experiments reveal the remarkable stability of SP-A in diverse, biologically relevant environments.

[Studies on separation, purification and chemical structure of polysaccharide from Atractylodes macrocephala]

Separation and purification were done by column chromatographic fractionation; HPLC and 13C-NMR were used to determine the chemical structure of polysaccharide from Atractylodes macrocephala Koidz;, The molecular weight of the polysaccharide was estimated to be 1.36 x 10(5) (PSAM-1) and 1.04 x 10(5) (PSAM-2).

[Effect of methylmercury chloride on the c-fos expression in brain nerve cells of the rats]

OBJECTIVE

In order to study the mechanism of injury in the brain development caused by methylmercury chloride (MMC) and its effects on the c-fos expression in brain nerve cells of the rats with experiments in vitro and in vivo.

METHODS

In vitro, the effect of MMC on c-fos expression in the cultured nerve cells was observed by immunocytochemistry(SP method). In vivo, Wistar pregnant rats were administered 4 mg MMC per kg of body weight by a gastric tube from the 7th to the 10th gastational days. On the 1st, 3rd, 5th, 7th, 10th and 15th days after birth, the rats were killed and tissue sections were prepared from their brain, respectively. The expression of c-fos was detected by SP method.

RESULTS

The percentage of c-Fos-positive neuron in rats brain began to increase at 0.5 hours after being cultured in in vitro with 0.3 mumol/L MMC continuously, and increased gradually as length of the exposure to MMC prolonged. The percentage of c-Fos-positive of cultured nerve cells in vitro were (6.97 +/- 2.86)%, (66.86 +/- 5.32)% and (64.49 +/- 3.09)% in the experimental groups exposed to MMC for 10 min, 2 h and 6 h, respectively. In vivo, the percentage of Fos-positive neuron nuclei decreased with development of neonatal rats. The percentage of c-Fos-positive neuron in the experimental groups was higher than that in the control groups and decreased with length of development. The percentages of c-Fos-positive neuron were (47.01 +/- 3.79)% and (46.71 +/- 1.96)% in the experimental group 1 and 3 d, and (35.8 +/- 3.04)% and (33.35 +/- 1.06)% in the control group, respectively, with very significant difference.

CONCLUSIONS

It is concluded that MMC could induce c-fos over-expression in the nerve cells of the rat brain, which could explain the mechanism of injury to brain development caused by MMC.

Rapid induction of intraneuronal neurofibrillary tangles in apolipoprotein E-deficient mice

Cultured hippocampal slices prepared from apolipoprotein E-deficient mice were exposed to an inhibitor of cathepsins B and L and then processed for immunocytochemistry using antibodies against human paired helical filaments. Dense, AT8-immunopositive deposits were found in the subiculum, stratum oriens of hippocampal field CA1, and the hilus of the dentate gyrus. This distribution agrees with that described for tangles in Alzheimer's disease. The appearance of the labeled structures fell into categories that correspond to previously proposed stages in the progression of intraneuronal neurofibrillary tangles in human hippocampus. Electron microscopic analyses confirmed that microtubule disruption and twisted bundles of filaments were present in neurons in the affected areas. These results support the hypothesis that partial lysosomal dysfunction is a contributor to Alzheimer's disease and suggest a simple model for studying an important component of the disease.

Polarized distribution of alpha5 integrin in dendrites of hippocampal and cortical neurons

The distribution of immunoreactivity for the alpha5 subunit of the fibronectin receptor was evaluated in adult rat brain with particular interest in the cellular localization of immunostaining in the hippocampal formation and neocortex. Beyond localization to neuronal perikarya and short dendritic fragments within most brain areas, alpha5 immunoreactivity (-ir) was particularly dense within primary apical dendrites of pyramidal cells in both hippocampus and neocortex and within the dendritic arbors of cerebellar Purkinje cells. In hippocampal and cortical pyramidal cells, immunostaining was clearly polarized: alpha5-ir was not detectable in basal dendrites in hippocampal neurons and was limited to proximal arbors or absent from basal dendrites in pyramidal cells in superficial and deep layers of neocortex. Beyond this, alpha5-ir was distributed within the dendritic ramifications of the dentate gyrus granule cells and within perikarya and dendrites of occasional nonpyramidal neurons. Developmental studies demonstrated that, in both hippocampus and neocortex, alpha5-ir appears first within perikarya and is distributed to dendrites during the second postnatal week. These results are in accord with the broad hypothesis that integrins contribute to apical-basal differences in dendrites and that the integrin fibronectin (alpha5beta1) receptor, in particular, contributes to some late developing features of dendritic structure or function.

Regulated nuclear export of the homeodomain transcription factor Prospero

Subcellular distribution of the Prospero protein is dynamically regulated during Drosophila embryonic nervous system development. Prospero is first detected in neuroblasts where it becomes cortically localized and tethered by the adapter protein, Miranda. After division, Prospero enters the nucleus of daughter ganglion mother cells where it functions as a transcription factor. We have isolated a mutation that removes the C-terminal 30 amino acids from the highly conserved 100 amino acid Prospero domain. Molecular dissection of the homeo- and Prospero domains, and expression of chimeric Prospero proteins in mammalian and insect cultured cells indicates that Prospero contains a nuclear export signal that is masked by the Prospero domain. Nuclear export of Prospero, which is sensitive to the drug leptomycin B, is mediated by Exportin. Mutation of the nuclear export signal-mask in Drosophila embryos prevents Prospero nuclear localization in ganglion mother cells. We propose that a combination of cortical tethering and regulated nuclear export controls Prospero subcellular distribution and function in all higher eukaryotes.

Chromosomal boundaries in S. cerevisiae

Chromatin boundary elements or insulators in metazoans delimit distinct chromosomal domains of gene expression. Recently, DNA sequences with properties similar to boundary elements were also discovered in Saccharomyces cerevisiae. These sequences block the spread of transcriptionally silent chromatin, the yeast equivalent of metazoan heterochromatin, and are referred to as 'heterochromatin barriers'. These barriers share no sequence homology but all consist of multiple binding sites for various regulatory proteins. Current data suggest that barriers may function in yeast by recruiting a protein complex that precludes nucleosome assembly and thereby disrupts a contiguous array of nucleosomes required for the spread of silent chromatin.

[Effects of methyl mercury chloride on nuclear factor-kappa B DNA binding activities of nuclear protein extracts from developing rat cerebra and cerebella]

The effects of methyl mercury chloride (MMC) on DNA binding activities of nuclear factor kappa B(NF-kB) in developing rat cerebella and cerebra were investigated with electrophoretic mobility shift assays(EMSAs). The bindings of NF-kB in nuclei of rat cerebra and cerebella to kB probes showed two bands on gel shift in both control and experiment groups. NF-kB I and NF-kB II DNA binding activities of nuclear protein extracts from rat cerebra exposed to MMC in uterus, was lower than control groups on postnatal day 3 and 7, while that from rat cerebella was higher than control groups. The results suggested that the reactive abilities of neural cell to MMC between cerebra and cerebella were different. In binding reaction mixture, the quantities of MMC increased with the increase of NF-kB DNA binding activities of nuclear protein extracts.

Kinetic proofreading scanning models for eukaryotic translational initiation: the cap and poly(A) tail dependency of translation

Two simplified kinetic proofreading scanning (KPS) models were proposed to describe the 5' cap and 3' poly(A) tail dependency of eukaryotic translation initiation. In Model I, the initiation factor complex starts scanning and unwinding the secondary structure of the 5' untranslated region (UTR) from the 5' terminus of mRNA. In Model II, the initiation factor complex starts scanning from any binding site in the 5' UTR. In both models, following ATP hydrolysis, the initiation factor complex either dissociates from mRNA or continues to scan and unwind RNA secondary structure in the 5' UTR. This step repeats n times until the AUG codon is reached. These two models show very different cap and/or poly(A) tail dependency of translation initiation. The models predict that both cap and poly(A) tail dependencies of translation, and translatability of mRNAs are coupled with the structure of 5' UTR: the translation of mRNA with structured 5' UTR is strongly cap- and poly(A) tail-dependent; while translation of mRNA with unstructured 5' UTR is less cap- and poly(A) tail-dependent. We use these two models to explain: (1) the cap and poly(A) tail dependence of translation; (2) the effect of exogenous poly(A) on translation; (3) repression of host mRNA and translation of late adenovirus mRNA in the late phase of adenovirus infection; (4) repression of host mRNA and translation of Vaccinia virus mRNA in virus-infected cell; (5) heat shock repression of translation of normal mRNA and stimulation of translation of hsp mRNA; and (6) the synergistic effect of cap and poly(A) tail on stimulating translation. The kinetic proofreading scanning models provide a coherent interpretation of those phenomena.

Regionally selective changes in brain lysosomes occur in the transition from young adulthood to middle age in rats

The possibility that brain aging in rats exhibits regional variations of the type found in humans was studied using lysosomal chemistry as a marker. Age-related (two vs 12months; male Sprague-Dawley) differences in cathepsin D immunostaining were pronounced in the superficial layers of entorhinal cortex and in hippocampal field CA1, but not in neocortex and field CA3. Three changes were recorded: an increase in the intraneuronal area occupied by labeled lysosomes; clumping of immunopositive material within neurons; more intense cytoplasmic staining. Western blot analyses indicated that the increases involved the active forms of cathepsin D rather than their proenzyme. Shrinkage of cathepsin-D-positive neuronal cell bodies was observed in entorhinal cortex but not in neocortical sampling zones. Age-related lysosomal changes as seen with cathepsin B immunocytochemistry were considerably more subtle than those obtained with cathepsin D antibodies. In contrast, a set of glial and/or vascular elements located in a distal dendritic field of the middle-aged hippocampus was much more immunoreactive for cathepsin B than cathepsin D. The areas exhibiting sizeable changes in the present study are reported to be particularly vulnerable to aging in humans. The results thus suggest that aspects of brain aging common to mammals help shape neurosenescence patterns in humans.

Expression of N-myristoyltransferase inhibitor protein and its relationship to c-Src levels in human colon cancer cell lines

Earlier, we have reported that N-myristoyltransferase (NMT) activity is higher in colonic epithelial neoplasms than in normal appearing colonic tissue and that increase in NMT activity appears at an early stage in colonic carcinogenesis [Magnuson, B., Raju, R. V. S., Moyana, T. N., and Sharma, R. K. (1995) J. Natl. Cancer Inst. 87, 1630-1635]. In this study, we demonstrate increased NMT mRNA in well-differentiated adenocarcinomas. NMT and c-Src mRNA levels were generally elevated in a subset of human colon cancer cell lines. Western blotting analysis employing N-myristoyltransferase inhibitory protein (NIP(71)) antibody demonstrated low levels of NIP(71) in high-expressing c-Src cell lines and high levels of NIP(71) in low-expressing c-Src cell lines. Interestingly, down regulation of c-Src by antisense expression in the HT-29 cell line resulted in increased expression of NIP(71), suggesting c-Src may negatively regulate NIP(71) expression. Furthermore, this is the first study demonstrating the expression of NIP(71) in human colon cancer cell lines and a possible relationship to colon carcinogenesis.

[Meckel's diverticulum and its complications in children]

Seventy-two cases of Meckel's diverticulum were treated surgically in recent four years. There were 61 boys and 11 girls with a mean age of 5.2 years. Of the 65 symptomatic patients, 31(43%) had rectal bleeding, 16(23%) suffered from bowel obstruction and 17(24%) peritonitis. Patients with diverticulitis(8 cases) had acute abdominal pain in the periumbilical region or in the right lower quadrant compatible with appendicitis. Ectopic mucosa was found in 47 cases(65.3%). Gastric(36 cases) and pancreatic(11 cases) were the most common ectopic tissues. A nuclear medicine Meckel scan was positive in 26 of 31 patients(84%). It is emphasized that 99mmTcO4- scintiphoto is more specific in diagnosis of the Meckel's diverticulum. The best choice of the surgery is resection of the diverticulum and end-to-end intestinal anastomosis.

Wheat germ poly(A)-binding protein increases the ATPase and the RNA helicase activity of translation initiation factors eIF4A, eIF4B, and eIF-iso4F

Recent studies demonstrated that wheat germ poly(A)-binding protein (PABP) interacted with translation eukaryotic initiation factor (eIF)-iso4G and eIF4B, and these interactions increased the poly(A) binding activity of PABP (Le, H., Tanguay, R. L., Balasta, M. L., Wei, C. C., Browning, K. S., Metz, A. M., Goss, D. J., and Gallie, D. R. (1997) J. Biol. Chem. 272, 16247-16255) and the cap binding activity of eIF-iso4F (Wei, C. C., Balasta, M. L., Ren, J., and Goss, D. J. (1998) Biochemistry 37, 1910-1916). We report here that the interaction between PABP and eIF-iso4G has a substantial effect on the ATPase activity and RNA helicase activity of (eIF4A + eIF4B + eIF-iso4F) complex. ATPase kinetic assays show, in the presence of poly(U), PABP can increase the parameter (k(cat)/K(m)) by 3.5-fold with a 2-fold decrease of K(m) for the (eIF4A + eIF-iso4F) complex. In the presence of globin messenger RNA, the ATPase activity of the complex (eIF4A + eIF-iso4F) was increased 2-fold by the presence of PABP. RNA helicase assays demonstrated that the presence of PABP enhanced the RNA duplex unwinding activity of the initiation factor complex. These results suggest that, in terms of the scanning model of translation initiation, PABP may enhance the mRNA scanning rate of the complex formed by eIF4A, eIF4B, and eIF4F or eIF-(iso)4F and increase the rate of translation.

Wheat germ translation initiation factor eIF4B affects eIF4A and eIFiso4F helicase activity by increasing the ATP binding affinity of eIF4A

It has been proposed that, during translational initiation, structures in the 5' untranslated region of mRNA are unwound. eIF4A, a member of the DEAD box family of proteins (those that contain a DEAD amino acid sequence), separately or in conjunction with other eukaryotic initiation factors, utilizes the energy from ATP hydrolysis to unwind these structures. As a step in defining the mechanism of helicase activity in the wheat germ protein synthesis system, we have utilized direct fluorescence measurements, ATPase assays, and helicase assays. The RNA duplex unwinding activity of wheat germ eIF4A is similar to other mammalian systems; however, eIF4F or eIFiso4F is required, probably because of the low binding affinity of wheat germ eIF4A for mRNA. Direct ATP binding measurements showed that eIF4A had a higher binding affinity for ADP than ATP, resulting in a limited hydrolysis and procession along the RNA in the helicase assay. The addition of eIF4B resulted in a change in binding affinity for ATP, increasing it almost 10-fold while the ADP binding affinity was approximately the same. The data presented in this paper suggest that eIF4F or eIFiso4F acts to position the eIF4A and stabilize the interaction with mRNA. ATP produces a conformational change which allows a limited unwinding of the RNA duplex. The binding of eIF4B either prior to or after hydrolysis allows for increased affinity for ATP and for the cycle of conformational changes to proceed, resulting in further unwinding and processive movement along the mRNA.