Effect of troglitazone (CS-045) and bezafibrate on glucose tolerance, liver glycogen synthase activity, and beta-oxidation in fructose-fed rats

To clarify the relationship between lipid and glucose metabolism abnormalities in fructose-fed rats, we examined whether an improvement of insulin sensitivity by troglitazone (CS-045) or a decrease in plasma lipids by bezafibrate affects the relationship between serum levels of lipid and glucose. In addition, we also examined changes in liver glycogen metabolism and beta-oxidation in fructose-fed rats. Troglitazone ameliorated fasting hyperlipidemia, hyperglycemia, and hyperinsulinemia. In addition, it augmented glycogen synthase activity by 53%, and decreased the mitochondrial palmitic acid beta-oxidation rate and ketone body production rate by 27% and 55%, respectively. However, hyperglycemia and liver glycogen synthase activity were not improved by bezafibrate treatment despite a marked reduction of serum triglyceride (TG) levels resulting from a 1.76-fold increase in mitochondrial oxidation and a 2.04-fold increase in hepatic ketone body production. These results suggest that abnormalities in glucose and lipid metabolism in fructose-fed rats, which are ameliorated by troglitazone, may be closely linked to reduced glycogen synthase activity in the liver.

Differentiation of photoreceptors, glia, and neurons in the retina of the cichlid fish Aequidens pulcher; an immunocytochemical study

Light-microscopic immunocytochemistry was carried out to investigate the developmental dynamics of several neurochemical markers in the retina of blue acara (Aequidens pulcher). As a rule, double-label experiments were performed in order to determine the absolute and relative timing of the appearance of these markers. The diameter of eye-ball (from 0.6 to 1.2 mm) and the body length (from 4.6 to 9.4 mm) enlarged in parallel during the observation period of 2 to 9 days after spawning (day 2-9); hatching took place usually on day 2. Immunoreactive proliferating cell nuclear antigen (ir-PCNA) was present in all neuroblasts (the embryonic homogeneous cell stage; day 1.0-2.0), but was lost progressively in a center-to-periphery and apparent proximal-to-distal sequence as the cells and layers differentiated. In late larvae and juveniles, ir-PCNA was confined to a ring of dividing neuroblasts at the retinal margin and to a population of scattered rod precursors in the outer nuclear layer. Immunoreactive structures of representative antigens progressively appeared after ir-PCNA had decayed. Around hatching, at the synaptic separation stage (day 2.0-2.5), luteinizing hormone-releasing hormone-ir centrifugal fibers, visinin-ir cones, glial fibrillary acidic protein-ir structures and gamma-aminobutyric acid-ir cell bodies appeared, which were followed by the emergence of rhodopsin-ir rods and tyrosine hydroxylase-ir interplexiform cells (on day 2.5-3.0) and serotonin-, neuropeptide Y- and substance P-ir amacrine cells (on day 3.0-4.0). The results indicate that photoreceptor cells, and especially rods start to differentiate at an earlier stage of retinogenesis than has previously been proposed. In addition, an extraretinal tissue in the brain identified as the prospective pineal organ was found to be visinin- and rhodopsin-immunoreactive on day 1.5-2.0 before these photoreceptor-specific antigens became positive in the retina.

Patterns of rod proliferation in deep-sea fish retinae

In a sample of 37 species of deep-sea fish species from the sea floor of the Porcupine Seabight and the Gobal spur (North Atlantic) we investigated the overall structure of the retina with special respect for the organization of rods, their length and their arrangement in multiple banks. Using an immunocytochemical marker for cell proliferation (PCNA) we studied the mechanisms of rod proliferation, and, by means of serial section reconstruction followed their integration into the existing population of rods. Furthermore, in three different species we have observed growth related changes in retinal thickness, rod density and proliferation activity. We found evidence for two different principles for the organization of rods in these deep-sea fish retinae. In the first group of species represented by Nematonurus armatus and Coryphaenoides guentheri we found rods to be rather short (20-30 microns) and arranged in three and more banks. In these species rod proliferation occurred in a single band of cells immediately vitread of the external limiting membrane, thus showing a high degree of spatial and temporal order. In these species, young rods are inserted just sclerad of the external limiting membrane and the older outer segments pushed away from the incoming light towards the back of the eye. This may be linked to a progressive loss of function of the older rods and might represent an alternative mechanism to the disk shedding in other vertebrates. In the second population (e.g. Conocara macroptera, Alepocephalus agassizii) we observed considerably longer rod outer segments (60-80 microns) forming no more than two layers. These retinae had rod precursors arranged in disseminated clusters throughout the outer nuclear layer indicating the lack of clear spatio-temporal order in mitotic activity along with a more statistical pattern of integration of the newly formed outer segments. In our sample of species both populations were of about equal size suggesting that the two mechanisms are equally effective and may have arisen independently.

Growth factors influence contractility and alpha-smooth muscle actin expression in bovine lens epithelial cells

PURPOSE

To determine whether basic fibroblast growth factor (bFGF) and transforming growth factor-beta 2 (TGF-beta 2) influence the contractile activity and the expression of alpha-smooth muscle actin (alpha-SMA) in bovine lens epithelial cells (LECs). To examine whether modulation of contractile activity by these growth factors depends on changes of alpha-SMA expression.

METHODS

Bovine LECs were cultured in collagen gel in MED 5 medium (F-12 nutrient mixture supplemented with 5% fetal bovine serum) with or without bFGF (1 to 100 ng/ml) or TGF-beta 2 (0.01 to 10 ng/ml). To evaluate collagen gel contraction, the longest and shortest diameters of the gels were measured daily for 7 days, and the area was determined. Detection of alpha-SMA in the gels was performed immunohistochemically using a mouse monoclonal antibody against alpha-SMA. The percentage of alpha-SMA-positive cells to the total number of cells was determined.

RESULTS

Control gels cultured with MED 5 medium alone contracted to 15.8% +/- 3.4% of their original area after 7 days. TGF-beta 2 significantly increased this contraction in a dose-dependent manner, whereas bFGF significantly decreased it. Approximately 30% of cells in the control gels were alpha-SMA positive. TGF-beta 2 significantly increased the alpha-SMA positivity dose dependently, whereas bFGF significantly decreased it. The percent positivity for alpha-SMA and the gel area showed a significant negative correlation.

CONCLUSIONS

TGF-beta 2 increased collagen gel contraction and alpha-SMA expression in bovine LECs, whereas bFGF decreased these parameters. Because collagen gel contraction was correlated with alpha-SMA expression, the modulation of LEC contractile activity by growth factors may be related to an effect on alpha-SMA.

The occurrence of dopaminergic interplexiform cells correlates with the presence of cones in the retinae of fish

Using light-microscopic immunocytochemistry against tyrosine hydroxylase, we have investigated the morphology of dopaminergic cells in 23 species of fishes representing various systematic classes and subclasses and which live in very different habitats. We have, for the first time, observed teleosts with dopaminergic amacrine cells. Thus, in both bony and cartilaginous fishes, dopaminergic cells are differentiated as interplexiform and amacrine cells. The differentiation of dopaminergic cells into amacrine or interplexiform cells in fishes correlates with the absence or presence of cones. In pure-rod retinae, they occur as amacrine cells, and in mixed rod/cone retinae, they occur as interplexiform cells. We conclude therefore that the differentiation of retinal dopaminergic cells in fish does not depend on the evolutionary or systematic classification of a given species. Rather, it is correlated with the occurrence of rods and/or cones, and thus linked more closely to the habitat. We argue that, in fish, the presence of cones and cone-specific horizontal cells may be responsible for inducing dopaminergic cells to differentiate as interplexiform cells. Possible functions of dopamine in all-rod retinae, which may not require adaptation, may include neuromodulation in the inner plexiform layer for the sensitization of the rod pathway, the shaping of biological rhythms, and the control of eye growth.

Induction of DNA recombination by activated 3-amino-1-methyl-5H-pyrido[4,3-b]indole

To investigate the genotoxic properties of a food-derived carcinogen, 3-amino-1-methyl-5H-pyrido-[4,3-b]indole (Trp-P-2), we have tested whether Trp-P-2 and its metabolically transformed products can induce DNA recombinations. Trp-P-2 is a strong mutagen and its activated form, the N-hydroxylated derivative, Trp-P-2(NHOH), is known to form DNA adducts and cause DNA chain cleavage. Using a system in which phage lambda undergoes recombination inside host Escherichia coli, we have found that Trp-P-2(NHOH), but not Trp-P-2 itself, can induce recombination. A nitroso derivative of Trp-P-2, Trp-P-2(NO), which can be reduced intracellularly to form Trp-P-2(NHOH), also induced recombination. Active oxygens are implicated in this recombinogenic action, since Trp-P-2(NHOH) is known to undergo spontaneous oxidative degradation, generating active oxygen radicals which can cause DNA chain cleavages. 4-Hydroxyaminoquinoline N-oxide and phenyl-hydroxylamine also showed recombinogenic actions in this assay system; hence, it is suspected that aromatic amine-type carcinogens have this property in common.

[Intermittent mini-dose vancomycin intravenous administration and closed continuous irrigation technique applied to mediastinitis caused by MRSA following mitral valve replacement]

Mediastinitis caused by MRSA (Methicillin-Resistant Staphylococcus aureus) remains an intractable infection producing high mortality even in these days of advanced chemotherapy. The authors report a case of mediastinitis due to MRSA complicated with acute renal failure following mitral valve replacement. The patient's mediastinum had been thoroughly cleaned with physiological saline solution with 0.2% povidone iodine, and underwent a chemotherapy regimen of mini-dose vancomycin. The patient made favorable progress and recovered completely. Our patient's progress confirmed that when chemotherapy using vancomycin is administered in a patient whose condition is complicated with acute renal failure, closely monitoring the vancomycin serum concentration is essential. Intermittent mini-dose intravenous administration is sufficient to maintain an effective vancomycin serum concentration. In our case, vancomycin serum concentration measured before and at completion of dialysis revealed no appreciable decline.

Spectra of superoxide-induced mutations in the lacI gene of a wild-type and a mutM strain of Escherichia coli K-12

We have analyzed the spectra of superoxide-induced mutations in the chromosomal lacI gene of a wild-type and a mutM strain of Escherichia coli K-12. The mutM strain is known to be deficient in removing 8-hydroxyguanine from DNA. An intracellular superoxide-generating agent, menadione, was used to cause the mutation. Analysis of the mutated DNA showed marked differences between the mutants from the wild type and those from the mutM strain. In the mutants from the wild type, all possible base-pair substitutions were present and their proportions were similar to each other, whereas in those from the mutM bacteria there was a 90% bias in favor of transversion. Furthermore, in the mutM strain GC-to-CG transversion rather than GC-to-TA was predominantly induced. 64% of the GC-to-CG transversions in the mutM strain occurred at the site of (CT/GC)GGC (mutated base underlined). The favorable mutation site, CTGGC, was the same as that of the UV- and sunlight-induced mutations previously reported: the mutations observed there were also G-to-C transversions. We speculate from these results that the superoxide in the cells may lead to production of a modified guanine that can pair with guanine and is subject to removal by the MutM protein.

Reciprocal changes in left ventricular collagen alpha 1 chain gene expression between types I and IV in spontaneously diabetic rats

The characteristic features of diabetic cardiomyopathy have been reported to be increased collagen formation associated with impairment of ventricular performance, based on experimental models of diabetes. The present study was therefore designed to clarify collagen gene expression in hearts obtained from female spontaneously diabetic BioBreeding Worcester Tokyo (BB/W@Tky) rats. Cardiac hypertrophy was observed as early as 14 weeks in diabetic BB/W@Tky rats, i.e. 4 weeks after the onset of diabetes. Left ventricular gene expression of collagen alpha 1 (I) was decreased to 10.6% of the control level. In 24-week-old diabetic rats, which had more marked cardiac hypertrophy, the level of alpha 1 Type I collagen mRNA was further decreased to 5.7% of the control level, whereas collagen alpha 1 (IV) mRNA demonstrated a 3-fold increase. As a result, a ratio of collagen alpha 1 (IV) to actin mRNA was positively correlated with plasma glucose concentration. These results suggest that hyperglycemia may alter the gene expression of extracellular matrix proteins, resulting in the morphological and functional changes seen in diabetic cardiomyopathy.

Nucleoside and nucleobase analog mutagens

Compounds with structures close to those of normal nucleosides or nucleobases may be incorporated into cells and then become constituents of their DNA. Proliferation of such cells could yield mutants. In this article, the current status of studies on such nucleoside and nucleobase analogs is described. Base mispairing mechanisms for these analogs are discussed in light of recent biochemical and biophysical findings.

Improvement of glucose tolerance by bezafibrate in non-obese patients with hyperlipidemia and impaired glucose tolerance

Glucose intolerance or diabetes mellitus, hyperlipidemia, obesity and hypertension may have a close interrelation based on insulin resistance. We selected 28 impaired glucose tolerance (IGT) patients with hyperlipidemia. The IGT patients demonstrated hypertriglyceridemia associated with hyperinsulinemia, a typical manifestation of insulin resistance. Administration of bezafibrate at 400 mg/day for 4 weeks to the IGT patients with hypertriglyceridemia resulted in an improvement of the plasma glucose level and insulin response to 75 g oral glucose loading associated with a concomitant decrease in non-esterified fatty acids. The ratio of the level of serum C-peptide to that of insulin after a 75 g oral glucose tolerance test (OGTT) was augmented after 4 weeks of bezafibrate administration. However, reduction of the cholesterol level with pravastatin did not alter these parameters. These results suggest that treatment to reduce the level of serum triglycerides, but not that of cholesterol, may have a beneficial effect for improving insulin resistance even in the non-obese subjects with IGT and decreasing the risk of coronary heart disease.

The effect of age on plasma level of setiptiline maleate in depressed patients

1. Setiptiline maleate (SPT) was administered orally to 45 subjects aged 22-86 years and steady state plasma levels were determined by mass fragment chromatography (GC-MF) to examine the effect of aging on those values. 2. There was a significant correlation between the plasma levels and daily dose. However, there was a wide interindividual variability. 3. Dose-corrected plasma level (DC-PL), or values corrected by dividing the plasma level by daily dose/body weight, was used as the systemic drug clearance parameter. 4. DC-PL was compared among 7 age groups of the subjects distributed in 10-year-intervals. DC-PL showed no difference among groups of subjects between the > 29 years bracket to the 70 years bracket, but showed significantly higher values in those in the > 80 bracket compared to all age groups and subjects in the < 79 bracket. 5. There was a significant correlation between the age of patients and DC-PL according to polynomial response curve analysis. Regression analysis yielded the equation y = -52.72 + 7.05 x -0.17 x2 + 0.01 x3 (n = 45, r = 0.49, p < 0.01).

[Efficacy and safety of electroshock therapy without convulsions under general anesthesia in senile depression]

We examined the efficacy and safety of electroshock therapy (EST) under general anesthesia in 26 depressed patients (9 males, 17 females, age range 55-79). The scores of the Hamilton Psychiatric Rating Scale for depression were significantly decreased after EST and clinical symptoms such as depressive mood. psychomotor retardation, anxiety, agitation, suicidal tendencies, hypochondria and sleeplessness improved in all of the patients. Complications included amnesia (16/26), delirium (3/26) and transient arrhythmia (1/26) after EST, but neither lethal nor lasting complications were observed. In summary, EST was an effective and convenient method of treatment for senile depression.

Effects of bromocriptine in Huntington chorea. Case report

1. The effects of bromocriptine (BC) on choreiform movement were compared with those of bromperidol (BP) and fluphenazine (FLZ) in a patient with Huntington disease. The patient (male, 42 years old) was treated with BP (15 mg/day, 4 weeks), FLZ (3 mg/day, 4 weeks), low dose of BC (5 mg/day, 4 weeks) and relatively high dose of BC (10 mg/day, 8 weeks). The CSF content of homovanilic acid (HVA) was assayed at last day of the each drug trial. The efficacy of the drugs was evaluated by electromyography. 2. Although BP and FLZ did not succeed to ameliorate the choreiform movement, both low dose and high dose BC showed rapid improvement of the involuntary movement. The CSF HVA concentration was 35.0 ng/ml before beginning treatment. Whereas FLZ and high dose of BC substantially increased the levels of HVA after the dosage (49.3 and 53.1 ng/ml, respectively), moderate increase of HVA (41.5 ng/ml) was observed when the low dose of BC was administered. These observations suggest that increase of CSF HVA might be necessary for clinical improvement of choreiform movement but not correlate with the degree of improvement and dopamine agonists could be useful drug for the treatment of choreiform movement which is refractory to the administration of neuroleptics.

Mutagenicity of 5-bromouracil and N6-hydroxyadenine studied by yeast oligonucleotide transformation assay

The mutagenicity of 5-bromouracil (BrU) and N6-hydroxyadenine (HA) was tested by means of the yeast oligonucleotide transformation procedure. BrU-containing oligonucleotide was not mutagenic; although two mutants (per 200 micrograms oligonucleotide) were obtained, they were attributed to base insertion or base substitution at positions different from BrU. This result supports the view that BrU mutagenesis is dependent on intracellular nucleotide pool imbalance. In contrast, HA-containing oligonucleotide was highly mutagenic; 56 mutants (per 140 micrograms oligonucleotide) were obtained. Of 21 induced mutants examined, 20 had G and one had C at the HA position, a result indicating that HA-->G changes took place. To provide back-up evidence, we carried out a general reversion assay for base HA using a set of yeast tester strains, and the results showed that HA induces exclusively AT-to-GC and GC-to-AT transitions. We conclude that in S. cerevisiae HA is a classic base analog mutagen, causing AT-to-GC and GC-to-AT transitions by ambiguous base pairing. The present work has clearly demonstrated the usefulness of the oligonucleotide transformation procedure for elucidating mutagenicity of modified bases.

8-Hydroxyguanine is not produced by permanganate oxidation of DNA

Single-stranded M13mp2 DNA was oxidized with 0.8 mM KMnO4 at pH 8.6 and 4 degrees C for 5 min. These are conditions used previously by Akman et al. (Arch. Biochem. Biophys., 1990, 282, 202) for the oxidation of a denatured DNA and the authors reported that 8-hydroxyguanine was formed in the DNA with this treatment. We decomposed the oxidized DNA with heating in formic acid and the resulting bases were analyzed by HPLC. No significant 8-hydroxyguanine formation was detected in this sample. We also investigated the consumption of KMnO4 by nucleosides. Under conditions in which thymidine consumed KMnO4 rapidly, very little consumption was found with deoxyguanosine (less than 1/100, in rate, compared to that by thymidine). These results show that the permanganate oxidation of DNA does not result in the formation of 8-hydroxyguanine.

Double-staining of horizontal and amacrine cells by intracellular injection with lucifer yellow and biocytin in carp retina

Horizontal and amacrine cells in the isolated carp retina were impaled with micropipette electrode, identified by their characteristic light responses, and injected iontophoretically with markers for morphological study. Both Lucifer Yellow CH and biocytin were injected simultaneously. Lucifer Yellow was seen by its own fluorescence while biocytin was visualized by binding with Texas Red-linked or horseradish peroxidase-conjugated avidin. For cone-connected horizontal cells, biocytin-coupled cells were found to be approximately five-times more numerous than Lucifer Yellow-coupled cells. Coupling for both tracers was consistently hampered by intravitreally applied dopamine. In untreated retinas, the injected Lucifer Yellow was restricted within one rod-connected horizontal cell, while biocytin revealed several coupled neighbors. Amacrine cells, labeled by the tracers, were morphologically grouped into eight types, based on our earlier classification. Among them, amacrine cells, belonging to three types (Fnd, Pmb or Pma), were confirmed to be Lucifer Yellow-coupled, and the number of biocytin-coupled cells was more numerous (about 2.5 times) than that of Lucifer Yellow-coupled cells. Most amacrine cells (i.e. Pwd, Fnb and Fna) showed biocytin-coupling with no Lucifer Yellow-coupling. A few classified (i.e. Pwb and Fwa) and unclassified cells did not show any coupling. Since the tracer coupling takes place via gap junctions, the majority of amacrine cells, belonging to certain homologous types, appear to be functionally coupled with each other in the inner plexiform layer. However, dopamine did not influence the range of tracer coupling between amacrine cells in the carp retina under the present experimental conditions.

5-Fluorouracil reduces proliferating cell nuclear antigen immunoreactive cells in goldfish retina

A pyrimidine analogue, 5-fluorouracil (5-FU), was injected intravitreally into one eye of the goldfish, either alone, or before or after injection of the same eye with the dopaminergic neurotoxin, 6-hydroxydopamine (6-OHDA). Effects of these agents were explored by measuring their actions on numbers of proliferating cell nuclear antigen-immunoreactive (PCNA-ir) cells, representing mitotically active rod precursor cells (RPCs) in normal conditions, in both treated and untreated retinas. At various intervals (5-45 days after the first injection of drug), the retinas (n = 6 for each treatment group) were isolated and processed as wholemounts by an indirect immunohistochemical method for PCNA. Some retinas were cryosectioned and processed for certain immunoreactive cells other than PCNA. Changes in the mean density of PCNA-ir cells, following intravitreal 5-FU (10 micrograms/2 microliter saline on 3 consecutive days) alone or in combination with intravitreal 6-OHDA (2.5 micrograms/2 microliter), were statistically compared for interval vs. day 0 (control from intact retinas) and for treated vs. contralateral (untreated or treated) retinas, in both outer and inner nuclear layers (ONL and INL, respectively). 5-FU at this dose drastically reduced the densities of endogenous and 6-OHDA-induced PCNA-ir cells in the ONL of treated retinas, but transiently increased them in the contralateral untreated retinas, probably reflecting an injury influence from the treated retina. The density of PCNA-ir cells at the retinal margin was also greatly reduced in treated retinas. Such changes peaked on days 10-15, and gradually disappeared over days 30-45.(ABSTRACT TRUNCATED AT 250 WORDS)

The relationship between early diabetic nephropathy and control of plasma glucose in non-insulin-dependent diabetes mellitus. The effect of glycemic control on the development and progression of diabetic nephropathy in an 8-year follow-up study

To clarify the relationship between early diabetic nephropathy and the glycemic control in non-insulin-dependent diabetes mellitus (NIDDM) without hypertension, excretion of urinary albumin was studied retrospectively for 8 years. The patients with early diabetic nephropathy were divided into two groups according to the initial urinary albumin index (UAI: mg/g.creatinine), namely, a normoalbuminuric (less than 15 mg/g.creatinine) and a microalbuminuric group (15 < or = UAI < 200 mg/g.creatinine). Comparisons of changes in UAI were made between good (HbA1 < 9.0% and fasting plasma glucose (FPG) < 140 mg/100 mL throughout the observation period) and poor glycemic control groups after 4 and 8 years. In the patients with normoalbuminuria at the initial determination, five of 11 patients (45.5%) with good glycemic control and 14 of 22 patients (63.6%) with poor glycemic control became microalbuminuric after 8 years, respectively (p < 0.05). In the microalbuminuric patients, five of ten patients (50%) with poor glycemic control became macroalbuminuric (UAI > or = 200 mg/g.creatinine), although only one case worsened of five patients with good glycemic control (p < 0.05). In conclusion, the development or progression of early diabetic nephropathy in NIDDM was significantly inhibited by good glycemic control (FPG < 140 mg/100 mL and HbA1 < 9.0%), independent of hypertension, and probably irrespective of the mode of therapeutic intervention.

Fibroblast growth factor induces proliferating cell nuclear antigen-immunoreactive cells in goldfish retina

New rod photoreceptors are added to mature teleost retinas throughout life by regulated proliferation of rod precursor cells (RPCs). In this study, candidate regulators of RPC proliferation, acidic and basic fibroblast growth factors (aFGF and bFGF; 0.1 microgram/eye), interleukin-6 (IL-6; 0.1 microgram) and phytohaemagglutinin (HA15; 1.0 microgram), were injected intravitreally into one eye of goldfish (body length 5-6 cm), and mitotic RPCs in both retinas were detected and counted 3-50 days later by immunohistochemistry for proliferating cell nuclear antigen (PCNA). Retinal integrity after treatment was assessed by immunohistochemistry for tyrosine hydroxylase (TH) and other retinal antigens. All the agents applied altered the density of PCNA-immunoreactive (ir) cells in the outer and inner nuclear layers (ONL and INL) in both retinas as soon as 2-3 days after unilateral injection. Initially (2-20 days after injection), particularly in the treated retina, PCNA-ir cells appeared in clusters accompanied by various numbers of scattered individual cells, but subsequently the clusters of PCNA-ir cells disappeared while the density of singly distributed cells increased until 30 days after injection. At the doses given, these effects were most striking with aFGF and bFGF and less with IL-6 and HA15. In radial cryosections, other cellular elements immunoreactive to markers such as TH, serotonin, neuropeptide Y, substance P, glutamine synthetase, glial fibrillary acidic protein and protein kinase C, were found normal in terms of morphology. In addition, a monoclonal antibody (NN-2) was found to label some non-neuronal structures (macrophages, microglia and blood vessels) inside and outside the retina intoxicated with 6-hydroxydopamine, a few NN-2-ir cells being PCNA-positive. However, clustered PCNA-ir and marginal neuroblast cells were NN-2-negative. These results indicate that FGFs may play an important role in stimulating the proliferation of RPCs, for example, in the regeneration of fish retinas following neurotoxic destruction.

Spectrum of mutations in single-stranded DNA phage M13mp2 exposed to sunlight: predominance of G-to-C transversion

Sunlight is regarded to be a cause of skin cancer, though the mechanisms underlying the causation are still unclear. The genotoxic effects of sunlight are believed to be induced by pyrimidine photoproducts produced by the action of the UV portion of sunlight. However, it is not clear whether these pyrimidine modifications are the sole sources for the mutations. In the present study, we have analyzed the mutagenic potential of sunlight on the lacZ alpha region of single-stranded DNA phage M13mp2 using an SOS-deficient recA- strain and an SOS-induced rec+ strain of Escherichia coli as hosts. Exposure to sunlight caused mutations; approximately 10-fold increases in the mutation frequency were observed with the use of both hosts. When SOS functions were induced in the host CSH50, the mutation frequencies increased another 10-fold over those obtained with the host lacking the SOS functions. DNA sequences of the mutants were analyzed by automated DNA sequencers. Sequence changes were identified in 53 mutants from the mutant DNAs obtained using NR9099 as host and in 78 mutant samples obtained using UV-treated CSH50. Most of the mutations were transversions of guanine, either G to C or G to T. Furthermore, 59% of the identified sequence changes in the SOS- host and 40% of those in the SOS-induced host were G-to-C transversions. These transversions may be caused by unidentified guanine damages or by the effects of damage at pyrimidines distal from guanines to be mutated.

Blockage of polymerase-catalyzed DNA chain elongation by chemically modified cytosine residues in templates and the release of blockage for readthrough

The Klenow fragment-mediated in vitro DNA elongation was inhibited by the presence of a class of modified cytosines in the template DNA, i.e., the N4-amino(and -methoxy)-5,6-dihydrocytosine-6-sulfonate residues. We have studied the mechanism of the blockage, using as templates bisulfite-hydrazine (and -methoxyamine)- modified single strand phage-M13mp2 DNA and synthetic oligonucleotides. Both N4-amino-5,6-dihydrocytosine-6-sulfonate and N4-methoxy-5,6-dihydrocytosine-6-sulfonate residues blocked the elongation at one nucleotide before these sites. In this blockage, the idling of polymerase at the lesion site due to its 3'-5' exonuclease action appears not to play a major role, because Sequenase that lacks the 3'-5' exonuclease activity still could not readthrough these sites. It seems possible that conformational distortion of the template near these sites is responsible for the blockage, because on conversion of this 5,6-dihydropyrimidine-6-sulfonate structure into a planar pyrimidine, a complete restoration of polymerase-readthrough resulted. In the presence of RecA and SSB proteins, the Klenow fragment was able to partially readthrough these sites. Since there was no decrease in the 3'-5' exonuclease activity during this readthrough, it seems that the binding of these proteins relaxes the distortion in the modified template to allow the polymerase to readthrough the lesion site. These sites on phage DNA can be lethal but also are capable of inducing C-to-T transitions. This observation suggests that these sites can be read by E. coli DNA polymerases in vivo with accompanying errors.

An immunohistochemical study of regenerating newt retinas

Light-microscopical examination was carried out to investigate the emergence and development of several classes of immunoreactive cells in regenerating retinas of the adult newt (Triturus pyrrhogaster) after total retinal ablation. Immunoreactive proliferating cell nuclear antigen (ir-PCNA, a marker for replicating cells) was present in nuclei of all neuroblasts in the early mono-layered to several-layered stages (15-20 days after retinal ablation; days 15-20), but was lost progressively in an intermediate-to-central/peripheral order as cells and layers increased (days 20-25). Cells, which had lost ir-PCNA, began to separate to form the outer nuclear, inner nuclear and ganglion cell layers around days 25-30 (the cell separation stage). Finally, the location of ir-PCNA was restricted to a band of neuroblast cells at the retinal margin (days 30-35) as seen in intact adult retinas. Visinin-immunoreactive (ir) cells, mainly destined to be cones, appeared first singly or as clusters at the most distal layer in the intermediate region of retinas multi-layered with PCNA-ir neuroblasts, which was followed by appearance of opsin-ir rod outer segments and tyrosine hydroxylase-ir amacrine cells around the cell separation stage. Shortly later, cells respectively immunoreactive to glutamic acid decarboxylase, neuropeptide Y, serotonin, glucagon, glutamine synthetase, glial fibrillary acidic protein, substance P and protein kinase C were found to emerge also in an intermediate-to-central/peripheral sequence. Some of the glucagon-ir cells appeared to be of an interplexiform type.