[Interleukin-6 behaves as an autocrine growth stimulator for a human lung giant cell carcinoma cell line]

OBJECTIVE

To study the effect of interleukin-6 (IL-6) on the growth of human pulmonary giant cell carcinoma cell line PG in vitro.

METHODS

IL-6 mRNA level was detected by means of reverse transcriptase polymerase chain reaction (RT-PCR) and IL-6 receptor (IL-6R) mRNA was analyzed using Northern blotting hybridization. The production of IL-6 was detected by bioactive assay. The biological role of IL-6 produced by PG cells was assessed with anti-IL-6 neutralizing antibodies.

RESULTS

PG cells expressed IL-6R mRNA. Recombinant human IL-6 promoted the proliferation of PG cells. PG cells also expressed IL-6 mRNA and produced bioactive IL-6. Treatment of PG cells with anti-IL-6 antibodies resulted in reduced growth of PG cells.

CONCLUSION

The results indicate that IL-6 behaves as an autocrine growth stimulator for PG cells in vitro.

Adenine quantitation in yeast extracts and fermentation media and its relationship to protein expression and cell growth in adenine auxotrophs of Saccharomyces cerevisiae

We have described a method to reliably measure the free adenine content of yeast extract powders or the adenine concentrations found in chemically-defined and complex fermentation samples. This method relies on the selective precolumn derivatization of adenine with chloroacetaldehyde to form the fluorescent adenine adduct 1,N6-ethenoadenine. The derivatized adenine can then be resolved from other components found in samples with reverse phase HPLC and selectively monitored with fluorescence. This method was then used to study the adenine nutritional requirements of adenine auxotrophs of recombinant Saccharomyces cerevisiae. The adenine content of individual yeast extract powders was examined in relation to the cell mass (dry cell weight, DCW) achieved in culture media formulated with these powders. A general increase in DCW was observed with increasing adenine concentration in the yeast extract. Conversely, we observed that as adenine concentration increased in complex media the expression levels of a heterologous protein decreased. This method also allowed us to examine the adenine/DCW ratio in both steady-state continuous culture and batch culture. In both cases, the total in vivo adenine content as measured by the amount of adenine utilized from the culture media was estimated to be ca. 25-40 mg/g DCW. However, data suggest that this value is in excess of what is strictly required for cell growth and represents the quantity of adenine required to saturate intracellular pools of adenine or adenine metabolites. A minimum requirement for cell growth is at least as low as 12.5 mg of adenine/g of cells.

[Interleukin-6 functions as an autocrine growth stimulator for a human lung adenocarcinoma cell line PAa]

OBJECTIVE

To study the effect of interleukin-6(IL-6) on the growth of a human lung adenocarcinoma cell line PAa in vitro.

METHODS

IL-6 receptor (IL-6R) mRNA level was detected by means of reverse transcription polymerase chain reaction (RT-PCR) and IL-6 mRNA was analyzed using Northern blotting hybridization. The production of IL-6 was detected by bioassay. The biological effect of IL-6 released by PAa cells was assessed with anti-IL-6 neutralizing antibodies.

RESULTS

PAa cells expressed IL-6R mRNA. Recombinant human IL-6 stimulated the proliferation of PAa cells. PAa cells also expressed IL-6 mRNA and produced bioactive IL-6. Treatment of PAa cells with anti-IL-6 antibodies resulted in decreased growth of PAa cells.

CONCLUSION

These results demonstrate that IL-6 acts as an autocrine growth stimulator for PAa cells in vitro.

[Establishment of human amnion cell mutagenesis system by using a shuttle vector pS189]

Using transient shuttle vector pS189, we established a subclone human amnion cell (FL) mutagenesis detection system, and we detected the mutation specificity of N-methy-N'-nitro-N-nitrosoguanidine (MNNG) in this system. The spontaneous mutant frequency of target gene supF was 1.7 x 10(-5) and MNNG-induced mutant frequency was increased with dosage. The results from 0.8% agarose gel electrophoresis, PCR, PCR-single strand conformation polymorphism (PCR-SSCP) analysis showed that MNNG-induced 89% mutants were point mutants. These results indicated that this system can be used to detect and study the mutagenesis mechanism of potential mutagens.

Abnormally expressed low-voltage-activated calcium channels in beta-cells from NOD mice and a related clonal cell line

A macroscopic low-voltage-activated (LVA) inward current was found in pancreatic beta-cells isolated from NOD mice. However, this current was not present in nondiabetic prone mouse (e.g., Swiss-Webster) pancreatic beta-cells. We performed pharmacological analyses on this current in NOD insulinoma tumor cells (NIT-1). This cell line was developed from pancreatic beta-cells of a transgenic NOD mouse. The sodium-channel blocker, tetrodotoxin (TTX; 2 micromol/l) had no effect on this LVA current. The amplitudes of currents elicited by a -20 mV test pulse retained similarity when the extracellular sodium concentration was increased from 0 to 115 mmol/l; when the extracellular calcium concentration was decreased from 10 to 2 mmol/l, there was an approximate 50% reduction of this current elicited by a -30 mV test pulse. Neither the L-type calcium-channel blocker, nifedipine (3 micromol/l), nor the N-type calcium-channel blocker, omega-CgTx-GVIA (1 micromol/l), at -30 mV produced an appreciable effect. The T-type calcium-channel blockers, nickel (3 micromol/l) and amiloride (250 micromol/l), effectively reduced the peak of this current. In 2 mmol/l calcium external solution, the threshold of voltage-dependent activation of this calcium current was approximately -65 mV, and the peak current occurred at -20 mV. Half-maximum steady-state inactivation was around -43 mV. The mean time constant of slow deactivating tail currents generated by a preceding 20 mV pulse was 2.53 ms. The intracellular free calcium concentration was two- to threefold higher in NOD mouse pancreatic beta-cells compared with Swiss-Webster pancreatic beta-cells. We concluded that there are LVA calcium channels abnormally expressed in NOD mouse beta-cells. This LVA calcium channel may be factorial to the high cytosolic free calcium concentration observed in these cells, and thereby may contribute to the pathogenesis of NOD mouse beta-cells.

[The role of P53 gene in the development of oral squamous cell carcinoma: study of P53 gene mutation by silver staining polymerase chain reaction-single strand conformation polymorphism]

It is widely accepted that the inactivation of P53 tumor suppressor gene is related to the tumorigenesis of many cancers. The study on P53 tumor suppressor gene has become a hotspot in molecular oncology. But until now, the reports on the research of the role of P53 gene in the tumorigenesis and prognosis of oral squamous cell carcinoma are scarce. So, two studies have been carried out. (1) A silver staining method of polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis was established by detecting the mobility shifts of the DNA bands of the products of PCR of mutant P53 gene plasmid and the Sup F mutants which had been proved to have point mutation by DNA sequencing in shuttle vector plasmid pS 189 mutagenesised by N-methyl-N-nito-N-nitosoguanidine (MNNG). For the method is non-radiation with high sensitive, it has applicable value. (2) By silver staining PCR-SSCP system, tissues from normal oral mucoas membrane to metastatic oral squamous cell carcinoma (OSCC) were analyzed and the results showed that tissues from 53% oral precancerous lesions and 65% OSCC had abnormal SSCP bands and the abnormal frequency of metastatic cancers was higher than that of nonmetastatic ones. These suggest that P53 gene mutation plays some role on the process of initiation, development and metastasis of OSCC.

An easily constructed carbon fiber recording and microiontophoresis assembly

Traditional multibarreled pipette electrodes are still widely used in microiontophoresis studies. Although better electrodes have been introduced, they are difficult and time-consuming to make. Construction of a carbon fiber recording and microiontophoresis assembly is described here. The construction of a carbon fiber electrode assembly is easy and carbon fibers have excellent characteristics for recording extracellular single unit activity. Signal-to-noise ratio of the carbon fiber electrode is maintained when combined with microiontophoresis. The electrode assembly can be used repeatedly, if cleaned properly, and it can be used to make marking lesions upon completion of an experiment.

A comparison of continuous versus intermittent light exposure on apoptosis

PURPOSE

We recently found that continuous light exposure at a moderate intensity triggered apoptosis of photoreceptor cells. Since intermittent light exposure is known to cause more severe retinal damage than is continuous light exposure, we sought to determine if intermittent light exposure also triggered apoptosis of photoreceptor cells.

METHODS

Lewis albino rats were reared, for 2 weeks, in cyclic light and dark adapted for 24 hr before light exposure. Rats were exposed to intermittent light or continuous light for 6 or 9 hr, respectively. Light-exposed rats were killed by lethal injection at three timepoints: immediately after light exposure, after 6 hr of dark recovery following light exposure and after 24 hr of dark recovery following light exposure. Retinal damage after light exposure was evaluated by morphology, morphometry, the terminal transferase-mediated biotin dUTP nick end labeling (TUNEL) technique for identification of nicked/cleaved nuclear DNA and agarose gel electrophoresis of retinal DNA.

RESULTS

Evaluation of morphology confirmed that intermittent light exposure caused more photoreceptor cell damage than did continuous light exposure of the same duration and intensity. The TUNEL technique showed that photoreceptor nuclei contained nicked or cleaved DNA after either intermittent or continuous light exposure, although more TUNEL-positive nuclei were observed after intermittent exposure. Agarose gel electrophoresis of retinal DNA showed internucleosomal DNA fragmentation, which is associated with apoptosis in samples from intermittent light exposure.

CONCLUSIONS

These data demonstrated that intermittent light exposure triggered apoptosis in more photoreceptor cells than did continuous light exposure of the same intensity and duration.

[The role of p53 gene during the development of human oral malignant lesions: a comparative study of p53 gene mutation with P53 protein positive immunostaining]

In order to increase the sensitivity to immunostaining in formalinfixed, paraffin-embedded tissues, we developed an immunohistochemical method by microwave heating of tissue sections instead of trypsin digestion. The results of this study showed that there was no positive P53 protein reaction in normal and hyperplastic mucousa of human mouth, whereas 90% (27/30) of cases with dysplasia, 61% (30/49) of oral squamous cell carcinomas and 86% (13/15) of regional metastatic lymph nodes were positive. And all positive reactions were localized in nuclei. Comparison of these positive results of p53 gene mutation detected by silver staining method with the results by polymerase chain reaction-single strand conformation polymorphism analysis did not reveal matched results, especially during the precancerous period. The authors analysed the causes of difference not only by methodology, but also by cell groups which had different genetic changes in tissues of precancerous lesions.

RAGE and amyloid-beta peptide neurotoxicity in Alzheimer's disease

Amyloid-beta peptide is central to the pathology of Alzheimer's disease, because it is neurotoxic--directly by inducing oxidant stress, and indirectly by activating microglia. A specific cell-surface acceptor site that could focus its effects on target cells has been postulated but not identified. Here we present evidence that the 'receptor for advanced glycation end products' (RAGE) is such a receptor, and that it mediates effects of the peptide on neurons and microglia. Increased expressing of RAGE in Alzheimer's disease brain indicates that it is relevant to the pathogenesis of neuronal dysfunction and death.

Respiratory toxicity of direct lytic factor in the venom of the southern Chinese cobra (N. naja atra) in dogs

The effects of direct lytic factor (DLF) on respiratory ventilation, gas exchange as well as hemodynamics were studied in anesthetized dogs. After an intravenous DLF dose of 1 mg/kg, the initial manifestation of intoxication was observed as follows: (1) Increase in airway impedance characterized by slowed air flow rate and increased negative transpulmonary pressure. (2) Decrease in dynamic compliance. (3) Progressive increase in venoarterial shunt (Qs/Qt) and decrease in PaO2, (4) Elevation of pulmonary artery blood pressure and fall of mean systemic blood pressure and maximal left ventricular pressure. Above actions reached the peak values at 15 min and thereafter all respiratory functional parameters, except Qs/Qt and hypoxemia, returned gradually to approach the normal levels at 50 min. The tidal volume, PaCO2 and LVEDP remained unchanged until another DLF dose of 1.5 mg/kg was given. After a second dose of DLF (total 2.5 mg/kg), the respiratory functions and the cardiac performance deteriorated as follows: (1) Further increase in Qs/Qt and hypoxemia. (2) Appearance of hypercapnea and acidosis. (3) Fall of dP/dtmax and elevation of LVEDP, widening of QRS complex of ECG. (4) Blood pressure run a downhill course. From above experimental evidence, we came to the conclusion that as well as the basic cardiotoxicity, respiratory toxicity of DLF must be considered as the primary, because of broad spectrum of action of DLF and early effect on respiratory function.

Tissue transglutaminase in apoptosis of photoreceptor cells in rat retina

PURPOSE

The possible involvement of tissue transglutaminase (tTG) in apoptosis during photoreceptor degeneration was examined in retinal photic injury in rats and in retinal dystrophy of Royal College of Surgeons (RCS) rats.

METHODS

Retinal photic injury was induced in 48 male Lewis albino rats by exposure to green fluorescent light of 300 to 320 foot-candles. The retinal tTG was examined by enzyme assay, immunohistochemistry, and Western blot analysis after 9, 12, or 24 hours of exposure or at 6 or 24 hours of dark adaptation after 24 hours of light exposure. Retinas from RCS rats at various stages of degeneration also were examined with similar methods.

RESULTS

There was a progressive increase in retinal tTG activity after 300 to 320 ft-c of light exposure, reaching a peak after 24 hours of light exposure. In the RCS rats, tTG activity increased with age. Western blot analysis revealed an immunoreactive band at 80 kDa, which increased in accordance with the transglutaminase activity in both models. In normal rat retinas, tTG immunolabeling was present only in the outer segments. There was an increased number of immunolabeled photoreceptor nuclei from 12 hours of light exposure to 24 hours of light exposure. In the RCS rat, increasing numbers of immunopositive photoreceptor nuclei from 20 to 50 days of age were noted.

CONCLUSIONS

The data associated increased retinal tTG activity and enzyme levels with photoreceptor cells undergoing apoptosis. The tTG-dependent irreversible cross-linking of intracellular protein may play an important role in causing the structural changes in cells undergoing apoptosis in the retina.

Use of green fluorescent protein variants to monitor gene transfer and expression in mammalian cells

Two mutants of the green fluorescent protein (GFP), RSGFP4 and GFPS65T, have been recently created which differ from the wildtype GFP of A. victoria in their excitation maxima. Here we show that human fibroblasts transfected with either of the two mutant GFP genes emit a green fluorescence that is 18-fold brighter than the cells transfected with the wildtype GFP gene. Retroviral vectors expressing the improved GFP gene were also constructed to determine their suitability for stable gene transduction into mammalian cells. The inclusion of the RSGFP4 gene in a retroviral vector did not reduce the viral titer and resulted in a fluorescent signal in viable transduced cells detectable by both fluorescence microscopy and fluorescence-activated cell sorter (FACS) analysis. Therefore, the improved mutant GFP provides a vital marker for monitoring gene transfer and expression in mammalian cells.

Site-directed mutagenesis of residues in a conserved region of bovine aspartyl (asparaginyl) beta-hydroxylase: evidence that histidine 675 has a role in binding Fe2+

The roles in catalysis of several residues in bovine aspartyl (asparaginyl) beta-hydroxylase that are located in a region of homology among alpha-ketoglutarate-dependent dioxygenases were investigated using site-directed mutagenesis. Previous studies have shown that when histidine 675, an invariant residue located in this highly conserved region, was mutated to an alanine residue, no enzymatic activity was detected. A more extensive site-directed mutagenesis study at position 675 has been undertaken to define the catalytic role of this essential residue. The partial hydroxylase activity observed with some amino acid replacements for histidine 675 correlates with the potential to coordinate metals and not with size, charge, or hydrophobic character. Furthermore, the increase in Km for Fe2+ observed with the H675D and H675E mutant enzymes can account for their partial activities relative to wild type. No significant changes in the Km for alpha-ketoglutarate (at saturating Fe2+) or Vmax were observed for these mutants. These results support the conclusion that histidine 675 is specifically involved in Fe2+ coordination. Further site-directed mutagenesis of other highly conserved residues in the vicinity of position 675 demonstrates the importance of this region of homology in catalysis for Asp (Asn) beta-hydroxylase and, by analogy, other alpha-ketoglutarate-dependent dioxygenases.

Recombinant dengue type 1 virus NS5 protein expressed in Escherichia coli exhibits RNA-dependent RNA polymerase activity

The complete nonstructural NS5 gene of dengue type 1 virus, Singapore strain S275/90 (D1-S275/90) was expressed in Escherichia coli as a glutathione S-transferase (GST) fusion protein (126 kDa). The GST-NS5 fusion protein was purified and the recombinant NS5 protein released from the fusion protein by thrombin cleavage. The recombinant NS5 had a predicted molecular weight of 100 kDa and reacted with antiserum against D1-S275/90 virus in Western blot analysis. The purified recombinant NS5 protein possessed RNA-dependent RNA polymerase activity which was inhibited (>99%) by antibodies against the recombinant NS5 protein. The polymerase product was shown to be a negative-stranded RNA molecule, of template size, which forms a double-stranded complex with the template RNA.

Higher ploidy in Saccharomyces cerevisiae supports enhanced hepatitis B virus S cloned gene expression at the pilot scale

The effect of host strain ploidy on the production of hepatitis B surface antigen (HBsAg) in Saccharomyces cerevisiae was evaluated at the pilot scale (75 L). We found that the accumulation of HBsAg normalized to cell protein was 2-fold higher for the diploid strain compared to its isogenic haploid. No detectable differences in many fermentation parameters were observed (e.g., rate of fermentation, growth rate, final cell yield). However, the enhancement of productivity in the diploid strain appeared to be associated with a slower rate of plasmid shedding (2 microns element) and, thus, a higher average copy number (2-fold at stationary phase) compared to those of the haploid strain.

TEMPOL, a superoxide dismutase mimic, ameliorates light-induced retinal degeneration

The efficacy of 4-hydroxy-2,2,6,6-tetramethylpiperidine-l-oxyl (TEMPOL), a metal independent superoxide dismutase (SOD) mimic, in ameliorating light-induced retinal degeneration was investigated. Thirty-six Lewis albino rats were exposed to green fluorescent light (490-580 nm, 160-180 foot-candles) for 24 hr, after dark adaptation for 24 hr. The animals received six intraperitoneal (IP) injections of TEMPOL (100 mg/kg) or an equivalent volume of saline solution (vehicle-treated control groups) at 6 hr intervals starting 6 hr before the light exposure and ending 24 hr after light exposure. Another six rats were used as unexposed controls. The animals were killed at 6 hr, 6 days and 14 days after light exposure. Retinal damage was assessed by light and electron microscopy, measurements of outer nuclear layer (ONL) thickness and rhodopsin levels and counting of macrophages in the subretinal space. After light exposure, the TEMPOL-treated rats showed mild edema of the retinal pigment epithelium (RPE), less densified inner segments (IS) at 6 hr and better preserved photoreceptors at 6 days and 14 days compared with vehicle-treated control groups. Morphometrically the ONL was thicker in the TEMPOL-treated rats than in the vehicle-treated control at 6 days (p<0.01) and 14 days (p<0.05) but no significant difference occurred at 6 hr (p>0.05). Rhodopsin levels in the TEMPOL-treated rats were significantly higher at 6 days (p<0.05) but not at 6 hr (p>0.05) or 14 days (p>0.05). Our results demonstrated that TEMPOL ameliorated light-induced retinal degeneration in rats. These findings are consistent with the hypothesis that superoxide radicals may play a crucial role in mediating light-induced retinal degeneration.

Detection of MspI RFLP in human THY1 gene by the polymerase chain reaction

THY1 gene encodes a cell surface glycoprotein predominantly expressed in brain and peripheral nerves. Human THY1 gene region on chromosome 11q23 has been implicated in susceptibility to type 1 diabetes (Wong et al., 1991). Two primers derived from the sequences flanking the polymorphic MspI site in intron 2 of the human THY1 gene (Gatti et al., 1988) were selected for RCP to amplify a 566 bp fragment that spans the MspI polymorphism. Polymorphism was detected by MspI digestion of the PCR product.

Signal transduction by the receptors for thrombopoietin (c-mpL) and interleukin-3 in hematopoietic and nonhematopoietic cells

Antisense oligonucleotide to the translation initiation sequence of human c-mpI reduced the proliferation of human CD34+ bone marrow cells in response to interleukin-3 (IL-3) alone or to the combination of IL-3 and thrombopoietin (TPO). To investigate the molecular basis for these cytokine interactions, we analyzed the relationship between the receptor subunits for IL-3 and TPO and determined whether both receptors activate identical signal transduction pathways. The function of the receptor subunits was characterized in transiently transfected hepatoma cells and fibroblasts by the activation of gene expression via specific regulatory elements and by the stimulation of DNA-binding activity of STAT proteins. Although c-mpl and IL-3 receptor (IL-3R) reconstituted a qualitatively comparable gene regulatory response, there was no detectable functional interaction between their respective receptor subunits. By comparing the receptor action in different cell lines, we observed that in human hepatoma cells the signaling of c-mpI was 100-fold less sensitive to TPO than in rat hepatoma cells. However, IL-3R signaling was comparable between the two cell types, suggesting that c-mpI and IL-3R do not use identical signal transducing mechanisms. The cytoplasmic domains necessary for c-mpI signaling were determined by testing deletion mutants. The membrane-proximal box 1 sequence motif was critical for gene regulation and for STAT protein activation that seemed to involve the Janus kinase 2 (JAK2). Because IL-3R was less dependent on JAK2 than c-mpI, different levels of JAK2 expression may account, in part, for the quantitative difference in IL-3 and TPO response among various cell lines.

Non-enzymatically glycated tau in Alzheimer's disease induces neuronal oxidant stress resulting in cytokine gene expression and release of amyloid beta-peptide

Paired helical filament (PHF) tau is the principal component of neurofibrillary tangles, a characteristic feature of the neurodegenerative pathology in Alzheimer's disease (AD). Post-translational modification of tau, especially phosphorylation, has been considered a major factor in aggregation and diminished microtubule interactions of PHF-tau. Recently, it has been recognized that PHF-tau is also subject to non-enzymatic glycation, with formation of advanced glycation end products (AGEs). We now show that as a consequence of glycation, PHF-tau from AD and AGE-tau generate oxygen free radicals, thereby activating transcription via nuclear factor-kappa B, increasing amyloid beta-protein precursor and release of approximately 4 kD amyloid beta-peptides. These data provide insight into how PHF-tau disturbs neuronal function, and add to a growing body of evidence that oxidant stress contributes to the pathogenesis of AD.

The NSY mouse: a new animal model of spontaneous NIDDM with moderate obesity

The NSY (Nagoya-Shibata-Yasuda) mouse was established as an inbred strain of mouse with spontaneous development of diabetes mellitus, by selective breeding for glucose intolerance from outbred Jcl:ICR mice. NSY mice spontaneously develop diabetes mellitus in an age-dependent manner. The cumulative incidence of diabetes is 98% in males and 31% in females at 48 weeks of age. Neither severe obesity nor extreme hyperinsulinaemia is observed at any age in these mice. Glucose-stimulated insulin secretion was markedly impaired in NSY mice after 24 weeks of age. In contrast, fasting plasma insulin level was higher in male NSY mice than that in male C3H/He mice (545 +/- 73 vs 350 +/- 40 pmol/l, p < 0.05, at 36 weeks of age). Pancreatic insulin content was higher in male NSY mice than that in male C3H/He mice (76 +/- 8 vs 52 +/- 5 ng/mg wet weight, p < 0.05, at 36 weeks of age). Morphologically, no abnormal findings, such as hypertrophy or inflammatory changes in the pancreatic islets, were observed in NSY mice at any age. These data suggest that functional changes of insulin secretion in response to glucose from pancreatic beta cells may contribute to the development of non-insulin-dependent diabetes mellitus (NIDDM) in the NSY mouse. Although insulin sensitivity was not measured, fasting hyperinsulinaemia in NSY mice suggests that insulin resistance may also contribute to the pathogenesis of NIDDM. Since these findings are similar to the pathophysiologic features of human NIDDM patients, the NSY mouse is considered to be useful for investigating the pathogenesis and genetic predisposition to NIDDM.

Systemic hypertension exaggerates retinal photic injury

OBJECTIVE

To determine whether chronic systemic hypertension alters the response of photoreceptors to photic stress.

METHODS

Spontaneously hypertensive rats and strain-matched, normotensive Wistar-Kyoto rats were exposed to green fluorescent light (490 to 580 nm, 180 to 200 foot-candles) for 24 hours. Retinal changes were evaluated by histopathologic examination, morphometry of the outer nuclear layer, and rhodopsin levels.

RESULTS

Before light exposure, spontaneously hypertensive rats developed elevated systolic blood pressure and showed mild sclerosis of choroidal vasculature. After exposure, retinas of the spontaneously hypertensive rats revealed exaggerated light damage with increased loss of photoreceptor cells, more distortion, and shortening of the inner and outer segments relative to the normotensive Wistar-Kyoto rats. The outer nuclear layer thickness and rhodopsin level were significantly lower in spontaneously hypertensive rats than in the normotensive Wistar-Kyoto rats by day 14 after light exposure.

CONCLUSION

Photic injury to photoreceptor cells was exaggerated in spontaneously hypertensive rats. This may have clinical relevance given the association of both systemic hypertension and light exposure in patients with age-related macular degeneration.

Recent advances in the large scale fermentation of Neisseria meningitidis group B for the production of an outer membrane protein complex

The Outer Membrane Protein Complex (OMPC) of the bacterium Neisseria meningitidis group B has been used successfully as a protein carrier in a Haemophilus influenza type b (Hib) polysaccharide conjugate vaccine and a Streptococcus pneumoniae (Pn) polysaccharide conjugate vaccine to elicit antipolysaccharide immune responses in young infants. The OMPC carrier is derived by detergent extraction of whole cells and, thus, the consistent generation of suitable biomass is central to an effective production process. Therefore, we have developed a large-scale, high-cell density (5 g/L dry cell weight) fermentation process for the cultivation of N. meningitidis B11. Since current requirements for the production of human biologics mandate strict control of all aspects of the manufacturing process, several key features of the process, including a chemically defined medium and a rational event-based harvest criterion, support current good manufacturing practice (cGMP) and increased productivity.

Photorefractive two-beam coupling optimal thresholding filter for additive signal-dependent noise reduction

Computer simulations of photorefractive thresholding filters for the reduction of artifact or dust noise demonstrate an increase in signal-to-noise ratio (SNR) of 70% to 95%, respectively, of that provided by the Wiener filter for inputs with a SNR of approximately 3. These simple, nearly optimal filters use a spectral thresholding profile that is proportional to the envelope of the noise spectrum. Alternative nonlinear filters with either 1/ν or constant thresholding profiles increase the SNR almost as much as the noise-envelope thresholding filter.

The effect of aurintricarboxylic acid, an endonuclease inhibitor, on ischemia/reperfusion damage in rat retina

Apoptosis is a form of cell death distinct from necrosis showing distinctive morphologic features and may require energy. It is under various control mechanisms and may involve an endonuclease, which cleavages genomic DNA in the internucleosomal linker regions. Previously, we reported that ischemic/reperfusion injury to rat retina induced endonuclease mediated apoptosis of retinal neurons. In this study, we examined the effect of aurintricarboxylic acid (ATA), an endonuclease inhibitor, on ischemia/reperfusion damage in rat retina in our established rat model. A single intraperitoneal injection of ATA at 2 mg/kg given immediately after 60 minutes of ischemia to the retina showed no observable effect. At 10 mg/kg, there was notable beneficial effect morphologically but not morphometrically. ATA at 100 mg/kg showed significant effect both morphologically and morphometrically. This observation is consistent with the hypothesis that endonuclease mediated apoptosis may be involved in retinal cell loss after ischemia/reperfusion insult.

Purification and characterization of HIV-1 reverse transcriptase having a 1:1 ratio of p66 and p51 subunits

Wild-type and several mutant forms of recombinant human immunodeficiency virus type-1 reverse transcriptase were overexpressed as either the p66 or the p51 subunit in a protease-deficient strain of Escherichia coli. Immediately prior to cell lysis, p51 cell paste was mixed with cell paste containing the corresponding overexpressed p66 subunit in a ratio resulting in an excess of the smaller subunit with respect to the larger. During the subsequent chromatography steps stable heterodimer p66/p51 was purified to homogeneity. This protein was characterized by amino acid analysis, denaturing sodium dodecyl sulfate-polyacrylamide gel electrophoresis, analytical gel filtration HPLC, laser desorption mass spectroscopy, and isoelectric focusing. In addition, we were able to obtain crystals of the purified enzyme complexed with a quinazolinone class nonnucleoside inhibitor that diffracted to 3.2 A resolution. A potential application of this expression/purification methodology is the ability to alter specific amino acids residues, by site-directed-mutagenesis, of only one subunit of the RT-dimer.

The effectiveness of sponge-type intraoral applicators for applying topical fluorides in institutionalized older adults

Many older adults who reside in nursing homes have disabilities which limit their capacity to benefit from the usual protocols for prevention of dental caries. This is a report of a study of the effectiveness of an alternative method of applying topical fluoride in the institutionalized elderly. Fluoride gel (1.1% NaF) was applied to the facial tooth surfaces of 10 elderly nursing home residents using a sponge-type intraoral applicator (IA). Subsequently, the same subjects rinsed with a commercial fluoride solution (0.05% NaF). Salivary fluoride levels were then assessed by the Taves (1968) method. The IA with fluoride produced significantly higher salivary fluoride levels over a period of three hours compared with rinsing.

Phase-coding technique for one-way image transmission through aberrating media

We propose and demonstrate one-way image transmission through an aberrating medium. In contrast to previous techniques, which usually use exact phase compensation for correcting phase distortion, our technique uses the phase- or amplitude-coded form of the exact phase. This technique allows us to utilize a wide variety of spatial light modulators for image correction in one-way image transmission through aberrating media.

[Experimental study on oral candidiasis]

The successful rate in producing oral candidiasis of the animal is not high. By utilizing: (1) fresh cell-line isolated from the oral cavity of the patient suffering from oral candidiasis and passing twice in rabbits and re-isolated to increase its toxicity; and (2) expanding the area of examination, the authors successfully (100%) produced oral candidiasis in Wistar rats. The specimens are studied histologically on its nature of whether it is a precancerous lesion or not.

The Measurement and Uncertainty of a Calibration Standard for the Scanning Electron Microscope

Standard Reference Material 484 is an artifact for calibrating the magnification scale of a Scanning Electron Microscope (SEM) within the range of 1000 × to 20000 ×. Seven issues, SRM-484, and SRM-484a to SRM-484f, have been certified between 1977 and 1992. This publication documents the instrumentation, measurement procedures and determination of uncertainty for SRM-484 and illustrates with data from issues 484e and 484f.

A gene at 59 minutes on the Escherichia coli chromosome encodes a lipoprotein with unusual amino acid repeat sequences

We report a 1.432-kb DNA sequence at 59 min on the Escherichia coli chromosome that connects the published sequences of the pcm gene for the isoaspartyl protein methyltransferase and that of the katF or rpoS (katF/rpoS) gene for a sigma factor involved in stationary-phase gene expression. Analysis of the DNA sequence reveals an open reading frame potentially encoding a polypeptide of 379 amino acids. The polypeptide sequence includes a consensus bacterial lipidation sequence present at residues 23 to 26 (Leu-Ala-Gly-Cys), four octapeptide proline- and glutamine-rich repeats of consensus sequence QQPQIQPV, and four heptapeptide threonine- and serine-rich repeats of consensus sequence PTA(S,T)TTE. The deduced amino acid sequence, especially in the C-terminal region, is similar to that of the Haemophilus somnus LppB lipoprotein outer membrane antigen (40% overall sequence identity; 77% identity in last 95 residues). The LppB lipoprotein binds Congo red dye and has been proposed to be a virulence determinant in H. somnus. Utilizing a plasmid construct with the E. coli gene under the control of a phage T7 promoter, we demonstrate the lipidation of this gene product by the incorporation of [3H]palmitic acid into a 42-kDa polypeptide. We also show that treatment of E. coli cells with globomycin, an inhibitor of the lipoprotein signal peptidase, results in the accumulation of a 46-kDa precursor. We thus designate the protein NlpD (new lipoprotein D). E. coli cells overexpressing NlpD bind Congo red dye, suggesting a common function with the H. somnus LppB protein. Disruption of the chromosomal E. coli nlpD gene by insertional mutagenesis results in decreased stationary-phase survival after 7 days.

Beneficial effect of an ACTH-(4-9) analog (Org2766) in the treatment of experimental cortex lesion in rats

This paper reports that lesions of the medial frontal cortex (MFC) caused behavioral deficit in rats and that this deficit could be attenuated by a well formulated treatment with Org2766, an analog of ACTH-(4-9). Wistar rats were distributed in 3 groups: MFC lesion treated with saline (M-N); MFC lesion treated with Org2766 (M-O); and sham-operation treated with saline (S). Repeated Org2766 or saline injection commenced from the day of surgery and lasted for 13 days. After surgery, the rats were trained in a passive avoidance task and then in an active avoidance task. MFC lesions were found to be strongly associated with behavioral deficits. The M-N group rats displayed poor retention of the passive avoidance response and showed much slower learning of the active avoidance task as compared to S group rats. The result showed that chronic Org2766 administration improved the behavioral performance of both tasks in MFC lesioned rats. The also revealed that the superoxide dismutase (SOD) activity was significantly increased in the M-O group as compared to the M-N group 15 days after surgery. The possible mechanisms related to the beneficial effect of Org2766 on cortex damage are discussed.

Intravitreal delivery of ganciclovir in rabbits by transscleral iontophoresis

To avoid the side effects of systemic administration of ganciclovir (GCV) for the treatment of cytomegalovirus (CMV) retinitis, we studied transscleral iontophoresis of GCV into rabbit eyes. After a single application with 20% (w/w) aqueous solution of GCV at 1.0 mA for 15 min gave a vitreal/retinal level of GCV at 74 +/- 17 micrograms/ml at 2 hours as determined by HPLC. At 24 hours after iontophoresis the vitreal/retinal level was above therapeutic level at 4.2 +/- 0.6 micrograms/ml. At 72 hours, there was still detectable level in the vitreous/retina. Hence, transscleral iontophoresis is able to deliver effective dose of GCV into the vitreous. Multiple applications of iontophoresis should be examined as a possible means of CMV treatment.

Methylprednisolone therapy in laser injury of the retina

The efficacy of methylprednisolone in argon-laser-induced retinal injury in primates was evaluated by clinical, histopathologic, and morphometric criteria. Methylprednisolone was given with a loading dose of 30 mg/kg followed by 5.4 mg/kg per hour in three different regimens: (1) starting 24 h before laser and continuing for 4 days; (2) starting immediately after laser and continuing for 4 days; and (3) starting immediately after laser and continuing for 8 h. Fundus photography, fluorescein angiography, and histologic examination showed significant beneficial effects of all three treatments compared to controls. Morphometrically, at the center of the lesion, the width of disrupted outer nuclear layer, the width of the affected RPE, and the percentage of residual photoreceptor nuclei confirmed the efficacies of treatment regimens 1 and 2, but not treatment regimen 3.

Genotoxic effects of subacute treatments with wood dust extracts on the nasal epithelium of rats: assessment by the micronucleus and 32P-postlabelling

Human exposure to wood dust has been epidemiologically linked to a number of enhanced incidences of various neoplasias, including those of the nose. Among different suspected woods, long-term exposure to the dust of beech (Fagus silvatica) is strongly associated with development of these tumors. Experimentally, it has been shown that a simple alcoholic extract of beech wood dust is mutagenic toward some bacteria and tumorigenic on mouse skin. For the present study, different groups of male Wistar rats were treated with aqueous, ethanol, or methanol extract of untreated beech wood dust via nasal drip at three concentrations for 48 h. Animals were killed 24 h after the last treatment and the nasal tissues were isolated to be examined for possible induction of micronuclei and DNA adducts. A clear dose-dependent increase in the number of micronuclei (P < 0.01) was observed after treatment of rats with each alcoholic extract of wood dust. In contrast, no DNA adducts could be detected with these extracts using the 32P-postlabelling technique. No increased number of micronucleated cells was found with solvents alone or with aqueous extract of dust. These data might support the early hypothesis that wood dust per se contains some in vivo genotoxic and thus possibly carcinogenic components extractable by an alcohol.

Intelligence function in children with acute lymphoblastic leukemia after treatment

In order to evaluate the effects of chemotherapy and central nervous system prophylaxis on the intelligence function of children with acute lymphoblastic leukemia (ALL), 147 patients were divided into 2 groups according to their different treatment regimens. Group A included 75 patients with ALL who were diagnosed and treated from 1981 to 1986. Group B included 72 ALL patients diagnosed and treated from 1988 to 1990. A control group included 73 healthy children who shared the same education and environmental background with the patients. Chinese revisions of Wechsler measures of intelligence quotient were used to estimate verbal IQ, performance IQ and total IQ in the 3 groups. American-produced Systate software was used to analyze the data. Results showed that IQ distribution, verbal IQ, performance IQ and total IQ of group A were obviously lower than those in the control group. Verbal IQ and total IQ of group B were also reduced. Significant differences of verbal IQ and performance IQ as well as total IQ were also found between groups A and B. Multiple regression analysis showed negative correlations between IQ and cranial irradiation dosage, times of intrathecal MTX and time after irradiation.

[Bioassay of Lyso-PAF platelet activating factor and it's role in bronchial asthma]

Plasma and lung homogenate lyso-PAF were measured by using the method of bioassay in guinea pigs with allergic asthma and asthmatic patients. The results showed that Lyso-PAF levels were increased significantly in asthmatics, and it was positively correlated with TXB2 levels. It is suggested that PAF plays an important role in bronchial asthma, which may be correlated with TXA2. The method of bioassay of Lyso-PAF is stable, reliable and special instruments are not needed.

Fluoride concentrations in plaque, whole saliva, and ductal saliva after application of home-use topical fluorides [published eerratum appears in J Dent Res 1993 Jan;72(1):87]

It is now well-accepted that the primary anti-caries activity of fluoride (F) is via topical action. The retention of F in the mouth after topical fluoride treatment is considered to be an important factor in the clinical efficacy of F. The purpose of this study was to evaluate F levels in ductal saliva, whole saliva, and pooled plaque after treatment with topical F agents intended for home use. Ten consenting adults, mean (SD) age 31.0 (8.2) years, participated in all aspects of the study. Two days before each test, subjects received a professional tooth cleaning and subsequently abstained from all oral hygiene procedures to permit plaque to accumulate, and from the use of F-containing dental products. Treatments consisted of a placebo dentifrice (PD), fluoride dentifrice (FD; 0.24% NaF), fluoride rinse (FR; 0.05% NaF), and fluoride gel (FG; 1.1% NaF). Unstimulated whole saliva and pooled plaque were sampled at multiple points over a 24-hour period. In a separate experimental series, stimulated parotid saliva was sampled over a two-hour period after treatment. Fluoride levels generally followed the same pattern in whole saliva and pooled plaque samples, with FG > FR > FD > PD. Night-time F application resulted in prolonged F retention in whole saliva but not in plaque. Fluoride levels in parotid saliva were only slightly higher after F treatment and returned to baseline levels within two h. The results of this study indicate that the method of F delivery, the F concentration of the agent, and the time of application (daytime vs. night-time) are important factors influencing F levels in the mouth.(ABSTRACT TRUNCATED AT 250 WORDS)

Studies of fluoride retention by oral soft tissues after the application of home-use topical fluorides

Previous studies have focused on enamel and plaque as the primary sites of fluoride (F) retention in the mouth. The present study was undertaken to evaluate the role of oral soft tissue as a site of F retention by comparing an edentulous subject panel (n = 9) with a fully dentate panel (n = 10). Unstimulated whole saliva samples were collected by having subjects pool saliva for two min. Samples were collected over a 24-hour period after application of a placebo dentifrice (PD; 0.4 ppm F), fluoride dentifrice (FD; 1100 ppm F), fluoride rinse (FR; 226 ppm F), or fluoride gel (FG; 5000 ppm F) delivered in custom trays. There was no statistically significant difference in salivary flow rate between the two panels for any of the treatments. The edentulous panel had higher salivary F levels than the dentate panel, which reached statistical significance (p less than 0.05) for the FD and FG treatments. In a separate study involving the same treatments, F levels at specific soft-tissue sites were measured over a one-hour period by use of absorbent discs placed in different soft-tissue areas of the mouth. The tongue and lower posterior vestibule retained the highest F levels, followed by the upper posterior buccal vestibule and upper anterior labial vestibule, with the lowest F levels retained in the lower anterior vestibule and the floor of the mouth. There was a strong-to-moderate correlation between whole saliva F concentration and F levels at specific soft-tissue sites. This study establishes the importance of oral soft tissue as the major site of F retention in the mouth.

[Mutagenesis study of ethylmethane sulfonate with shuttle vector plasmid pZ189]

Shuttle vector plasmid pZ189 was used as a molecular tool and the SupF inserted in the plasmid was worked as a target gene for mutagenesis study. The host cells (E. coli MBM 7070) with pZ189 were treated with ethylmethane sulfonate (EMS) and plated on the selective media containing X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactoside) and IPTG (isopropyl-beta-D-thiogalactoside). The SupF and the LacZ amber mutant carried by the host cells complemented each other and thus made the colonies blue on the selective media. However the colonies derived from the SupF mutants changed the colour from blue to white. The mutant frequencies in a series of experiments with different concentrations of EMS were estimated. Furthermore, the DNA isolated from 5 SupF mutants was digested with restruiction enzyme Hha I. It suggests that the 214 bp Hha I fragments containing mutant SupF could be distinguished from their wild type counterparts by temperature-gradient gel electrophoresis under optimal conditions.

Escherichia coli host cell modifications in continuous culture affecting heterologous protein overproduction: a population dynamics study

There are many published studies of plasmid segregational instability in Escherichia coli in the literature. However, the formation of plasmid-free segregants can be controlled by the addition of selective chemical agents like antibiotics. This solution has become commonplace in both the laboratory and industry. On the other hand, host cell modifications, which result in low production of plasmid-encoded protein and lead to loss of culture productivity, have not been adequately addressed. Continuous culture of an inducible (ptac) Escherichia coli vector containing strain, RB791(pKN), was characterized by strong dynamic changes in the cell population and product (beta-lactamase) expression. Long-term cultivation resulted in the loss of high-level production of beta-lactamase. Loss of productivity was not due to the formation of plasmid-free cells or structural modifications to the plasmid; instead, continuous operation resulted in a culture dominated by irreversibly altered, low-producing cells. Two distinct classes of lac- mutants which inhibited induction were identified (Y- and I(s)).

Methylprednisolone ameliorates retinal photic injury in rats

Since lipid peroxidation induced by oxygen free radicals is believed to play an important role in retinal photic injury and high doses of certain steroids have been demonstrated to inhibit lipid peroxidation, we evaluated the effect of high-dose methylprednisolone sodium succinate on retinal injury inflicted by green light (490 to 580 nm, 160 to 180 foot-candles [1721.6 to 1936.8 lux]) for 24 hours in 36 rats. Animals received either intraperitoneal injections of the drug (80 mg/kg twice daily) or saline as a control, twice daily for 2 days, commencing with light exposure. The retinal photic injury was assessed 6 hours, 6 days, and 14 days after light exposure by light and electron microscopy, morphometric study of outer nuclear layer thickness and count of subretinal macrophages, and spectrophotometric measurement of rhodopsin. A beneficial effect of high-dose methylprednisolone was observed in retinal photic injury.

Full-length cDNA sequence of dengue type 1 virus (Singapore strain S275/90)

The complete nucleotide sequence and the deduced amino acid sequence of the genome of dengue virus type 1 (Singapore strain S275/90) were determined from cDNA clones. The single-stranded, positive-sense RNA is 10,718 nucleotides in length and contains a single long open reading frame of 10,188 nucleotides encoding a polyprotein of 3396 amino acids. The genomic size and organization were found to be similar to that of other dengue virus serotypes. Both the nucleotide and deduced amino acid sequences were compared with the partial sequence of DEN1 (Nauru Island) and complete sequences of DNE2 (Jamaica), DEN3 (H87), and DEN4 (Dominica) virus genomes.

Dexamethasone ameliorates retinal photic injury in albino rats

The effect of dexamethasone in two regimens on retinal photic injury was studied in Lewis albino rats that were exposed to 24 hr of continuous green fluorescent light. Under regimen 1, dexamethasone was given at a daily dosage of 1 mg kg-1 for 8 days, starting 6 days before light exposure. Under regimen 2, dexamethasone was given at the same daily dosage for 3 days, started 1 day before light exposure. Pathologic study of the light-exposed retina, morphometric evaluation of the photoreceptor cell loss, cell counts of the macrophages in the subretinal space, and measurements of rhodopsin levels were undertaken in the dexamethasone-treated and control retinas at various times. The administration of dexamethasone in both regimens did not produce pathologic changes in the retina before light exposure, but rhodopsin levels were significantly lowered in both treated groups when compared to corresponding vehicle treated control animals. Under regimen 1, at 6 hr after light exposure, both the treated and the control groups showed comparable loss of photoreceptor cells, degeneration of the photoreceptor elements and retinal pigment epithelium, but a significantly lowered level of rhodopsin in the treated group was noted. At 6 days after exposure, the outer nuclear layer thickness, and the outer and inner segments showed significant preservation in the treated group. Also in the treated group, the number of macrophages was significantly reduced and the retinal pigment epithelial (RPE) vacuolation was markedly less. However, there was no difference in rhodopsin levels. At 14 days after exposure, the outer nuclear layer thickness and rhodopsin levels of the treated rats had significantly higher values than the controls. Under regimen 2, however, at 6 days after exposure, an ameliorative effect in the RPE was observed but there were no differences of rhodopsin levels, the outer nuclear thickness and number of macrophages between the treated and control groups. Regimen 1 was associated with a significantly higher retinal level of dexamethasone when compared with regimen 2. The ameliorative effect of dexamethasone on rat retinal photic injury may be through inhibition of lipid peroxidation, in which a high retinal level of the steroid is required.

An improved intra-oral enamel demineralization test model for the study of dental caries

The intra-oral enamel demineralization test (IEDT) was introduced by Brudevold et al. (1984). This caries model involves human subjects wearing palatal appliances each holding eight bovine enamel blocks covered by a bacterial cell layer prepared by the harvesting of cultures of Streptococcus mutants (test plaque). The original model used the iodide permeability test for assessment of the extent of demineralization of bovine enamel blocks resulting from acid production by the test plaque after dietary substrate challenge. The IEDT model has been expanded and improved by us in the following ways: (1) Based on encouraging findings from an in vitro study (Zero et al., 1990), the surface microhardness test has been adopted to measure the extent of demineralization occurring at three sites on the enamel blocks corresponding to an area over which the effective plaque thickness is 0.5, 1.5, and 2.5 mm; (2) intra-oral pH of the test plaque is measured by means of a Beetrode miniature pH electrode at baseline, then at five, 10, 15, 30, and 45 min after the start of a test; (3) plaque samples are collected at the end of a test and analyzed for organic acid content by means of HPLC; (4) the bacterial test challenge has been expanded to include different cariogenic bacteria which are grown under various growth conditions. The improved model has the capability of studying fundamental aspects of the caries process, namely, the relationships among dietary substrate challenge, plaque pH change, plaque organic acid profiles, microbial virulence properties, and enamel demineralization. Furthermore, the model has the potential for use in more applied research on caries-preventive agents such as fluoride.