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.

[Experimental and clinical study of activated platelet in allergic asthma]

Twenty-five asthmatic Guinea pigs and fourteen asthmatic patients were included in this study. The results showed that the plasma concentration of lyso platelet activating-factor (lyso-PAF), B-thromboglobulin (B-TG), platelet factor 4 (PF4), TXB2, the ratio of TXB2/6-keto-PGF1a and the platelet aggregation rate (PAgT) were significantly increased (P less than 0.01) during acute attack, but the platelet count and plasma level of 6-keto-PGF1a were markedly decreased (P less than 0.01). During remission, the function of platelet gradually returned to normal. BN 52021 inhibited platelet aggregation and secretion and relieved the symptoms in seven asthmatic guinea pigs. We suggest that platelet may play an important role in allergic asthma and antiplatelet drugs may be used for prophylaxis and treatment.

A histopathologic study of retinal lesions inflicted by transscleral iontophoresis

In the present study, retinal lesions were induced by transscleral iontophoresis (1.5 mA) in rabbits. The size and severity of the lesions increased with the duration of application (2-25 min). No lesion was noted after less than 1 min application. Immediately after 5 min iontophoresis, the edematous retina exhibited necrotic retinal pigment epithelium (RPE), loss of outer segments, and thinning of the inner and outer nuclear layers. At 5 days after iontophoresis, there was a proliferation of RPE cells and macrophages in the subretinal space, with thinning of the inner and outer retinal layers continuing. By day 14, the retina had been reduced to a glial membrane. Immediately after 15 min iontophoresis, the damaged retina appeared in a mummified form containing no cellular elements. By day 5 thereafter, macrophages and actively proliferating RPE cells had been noted in the necrotic retina. By day 14, a glial membrane had formed.

Establishment of human myeloma cell line KM-2R and its preliminary application to human-human hybridoma research

The authors report the establishment of a human myeloma cell line--KM-2R--and its preliminary use in human-human hybridoma research. KM-2R cells are resistant to both 6-TG and ouabain. Their doubling time is about 30 h. They have a modal chromosome number of 81-85. Using ELISA and immunodiffusion techniques, gamma-heavy and kappa-light chains were detected in the concentrated cell culture supernatant. KM-2R cells are sensitive to HAT medium. When fusing with normal human spleen cells, tonsil cells, and B lymphoblasts transformed by EB virus, fusion frequencies of 20-60% resulted.

Use of an intra-oral model to evaluate 0.05% sodium fluoride mouthrinse in radiation-induced hyposalivation

The present study was undertaken to evaluate the effect of a twice-daily topical application of a 0.05% NaF mouthrinse on de- and remineralization in the oral cavities of subjects suffering from radiation-induced hyposalivation. Six subjects each wore a bonded intra-oral appliance containing a sound and a demineralized human enamel slab for four weeks. During that period, the subjects used 0.05% NaF rinses, twice daily, instead of the 1.1% NaF gel that had previously been a part of their preventive regimen. Salivary flow rates, plaque pH profiles following a 10% sucrose rinse, S. mutans and lactobacillus counts, fluoride clearance, and enamel microhardness were determined during the study. Sound enamel samples displayed no evidence of demineralization, and the previously demineralized enamel showed remineralization in the outer 50 microns in three of the six subjects. The results suggest that a twice-daily oral rinse with 0.05% NaF can prevent demineralization and enhance remineralization in subjects with radiation-induced hyposalivation.

Pressure-induced retinal ischemia in rats: an experimental model for quantitative study

The advent of treatment modalities with the potential to ameliorate retinal ischemic injury calls for methods allowing their quantitative assessment. We thus established a model of pressure-induced retinal ischemia/reperfusion injury in rats. The intraocular pressure (IOP) was raised to 110 mm Hg by cannulation of the anterior chamber for a duration of 0, 90 or 120 min. The eyes were reperfused for 3 or 7 days. Morphologically, retinal injury occurred in a pattern consistent with retinal and choroidal vascular occlusion. Damage increased in severity with prolonged durations of ischemia. Morphometric determination of the mean thickness of inner retinal layers (MTIRL) revealed significant differences between controls and the 90- or 120-min ischemia groups (p less than 0.05 and p less than 0.01, respectively). The difference in MTIRL between 3 and 7 days of reperfusion was not significant. Replacement of normal saline by a solution of 5% dextrose in the hydrostatic device used to increase the IOP led to a decrease in retinal injury after 120 min of ischemia (p less than 0.01). This model combines a relatively simple methodology, cost-effective execution and a fast, semicomputerized method of quantitation. Depletion of carbohydrates during ischemia may contribute to retinal injury in this model.

Strains from both Theiler's virus subgroups encode a determinant for demyelination

The GDVII strain and other members of the GDVII subgroup of Theiler's murine encephalomyelitis viruses (TMEV) cause an acute lethal neuronal infection in mice, whereas the DA strain and other members of the TO subgroup of TMEV cause a chronic demyelinating disease associated with a persistent virus infection. We used GDVII/DA chimeric infectious cDNAs to produce intratypic recombinant viruses in order to clarify reasons for the TMEV subgroup-specific difference in demyelinating activity. We found that both the GDVII and DA strains contain a genetic determinant(s) for demyelinating activity. No demyelination occurs following GDVII strain inoculation because this strain produces an early neuronal disease that kills mice before white matter disease and persistent infection can occur.

Collagen, proteoglycan and hyaluronidase activity in cultures from normal and scoliotic chicken fibroblasts

Connective tissue matrix components were investigated using skin fibroblasts from normal or inbred scoliotic lines of chickens. Specifically, the fibroblasts were obtained from either an isogenic line or a backcross, derived by crossing the isogenic line with a pure line of scoliotic birds. From the backcross, both affected (35-45%) and non-affected (55-65%) progeny were produced. The affected birds had spinal curves greater than 20 degrees. Several abnormalities of connective tissue were observed when cells from scoliotic chicks were grown in culture: increased collagen extractability, decreased aggregatability of proteoglycans under associative conditions and lower than normal levels of hyaluronic acid. There was also less collagen deposited in the cell layer with proportionately increased amounts of collagen secreted into the culture media by cells from scoliotic versus normal chick fibroblasts. Values for collagen matrix stability, as estimated by extractability and net deposition, were intermediate for cells from the backcrossed, but non-affected, birds. Moreover, hyaluronidase, an enzyme that degrades hyaluronic acid, was abnormally elevated in the fibroblast cultures from scoliotic chicks. It is proposed that the increase in hyaluronidase contributes to the abnormalities observed in extracellular matrix components and may be a factor in the expression of scoliosis in susceptible birds.

Comparison of the iodide permeability test, the surface microhardness test, and mineral dissolution of bovine enamel following acid challenge

The relationship among the iodide permeability (Ip) test, the surface microhardness (SMH) test, and enamel demineralization chemically analyzed as mineral loss was investigated using bovine enamel blocks. Demineralization periods of 0 (control) and 5, 15, 30, and 45 min using 0.05 mol/l lactate (pH 4.75) were chosen to approximate the acid challenge occurring during the intraoral enamel demineralization test. Mineral loss (Ca and PO4) was found to be directly proportional to dissolution time (r = 0.95). Changes (delta) in Ip and SMH each increased linearly over time (r = 0.58 and 0.64, respectively) and were similarly related to mineral loss (r = 0.60 and 0.65, respectively). The correlation between delta Ip and delta SMH was 0.55. When longer demineralization periods (60, 120, and 240 min) were included, the correlation between delta Ip and delta SMH was 0.68. We conclude that both the Ip test and the SMH test can be used as measures of the early stages of enamel dissolution.

Generation of monoclonal antibodies to prostatic acid phosphatase isoenzyme 2 and application in solid-phase enzyme immunoassay

Monoclonal antibodies specific to prostatic acid phosphatase (PAP) isoenzyme 2 were generated by using an improved hybridoma technique. After three subcutaneous immunizations and three intravenous boosters, cell fusion experiments were performed. The hybrid cells were first cultured in a semisolid medium containing methylcellulose and later transferred to a liquid medium for further subculture. Out of a total of 600 colonies recovered after two cell fusion experiments, 13 were shown to exhibit affinity to PAP isoenzyme 2 by radioimmunoassay. Nine hybrid cell lines which showed high affinity and specificity were established for further evaluation. Their immunoglobulin subclass was determined to be immunoglobulin G. The association constants between PAP isoenzyme 2 and each monoclonal antibody were determined by titration curve in radioimmunoassay (RIA). Three of them (PAP 1, PAP 03, and PAP 019) were shown to be over 1 X 10(9) M-1. From the results of a matrix cross-matching procedure, a pair of antibodies (PAP 03 and PAP 1) reacting with discrete antigenic determinants were identified for preparing a solid phase sandwich enzyme immunoassay (EIA) kit. The designed EIA procedure could be performed within 40 min in a one-stage incubation protocol. The assay time was shorter than that of other commercial RIA or EIA kits, and the sensitivity was 0.4 ng/ml which was comparable to that of RIA kits. The EIA kit was shown not to cross-react with human thyroid stimulating hormone, alpha-fetoprotein, carcinoembryonic antigen, and acid phosphatases derived from tissues other than prostate. Therefore, this design was a simple and rapid method with high sensitivity and specificity for determining PAP isoenzyme 2 in human serum.

Generation of monoclonal antibodies to alpha-fetoprotein and application in solid-phase enzyme immunoassay

By using an improved hybridoma technique, monoclonal antibodies specific to alpha-fetoprotein (AFP) were generated. After three subcutaneous immunizations and three intravenous boosters, cell fusion experiments were performed. The hybrid cells were initially cultured in a semisolid medium containing methylcellulose and later transferred to a liquid medium for subculture. Out of 800 colonies recovered after two cell fusion experiments, 16 were shown to exhibit affinity to AFP by radioimmunoassay. Six hybrid cell lines which showed high affinity and specificity were selected for further evaluation. From the results of a cross-matching procedure, two pairs of antibodies (AFP 3 and AFP 05; AFP 3 and AFP 013) reacting with discrete antigenic determinants were identified for preparing solid-phase sandwich enzyme immunoassay (EIA) kits. The association constants between AFP and these three antibodies (AFP 3, AFP 05, and AFP 013) were 2.0, 3.7, and 3.8 X 10(9) M-1, respectively. The immunoglobulin subclass of them was determined to be IgG1. The EIA procedure designed could be performed within 40 min in a one-stage incubation and 70 min in a two-stage incubation. The incubation time was shown to be equal to or shorter than that of any other known commercial kits and the sensitivity was less than 1 IU/ml. In order to avoid the high-dose hook effect which occurred in the one-stage incubation procedure, a two-stage incubation protocol was advised.