Monomodality versus Combined Therapy in Optic Pathway Gliomas—20-Year Experience from a Singapore Children’s Hospital

Introduction

The treatment of pediatric optic pathway gliomas (OPG) is challenging. At present, most centers provide individualized treatment to maximize progression free survival (PFS) and minimize morbidity. We aim to report our experience in the management of pediatric OPG, and investigate factors associated with an increased duration of remission after treatment.

Methods

This is a single-institution study approved by the hospital ethics board. A retrospective review of consecutive OPGs managed from 2000 to 2020 was performed. Patients were divided into those managed with monomodality treatment (MT) and those who received combined therapy (CT). MT included various forms of surgery, chemotherapy and radiotherapy given alone, while CT involves a combination of surgery and adjuvant chemotherapy and/or radiotherapy.

Results

Twenty-two patients were selected for this study. They had 40 treatment cycles; and a total follow up duration of 194.8 patient-years. Most of them were male (63.6%) and presented with visual deficits (72.7%). The mean age at initial presentation was 65 months and majority (86.4%) had their tumors arising directly from the optic chiasm, with 77.3% with hypothalamic extension. One patient had Neurofibromatosis type I (4.5%). The most common histological diagnosis was pilocytic astrocytoma (90.9%), followed by pilomyxoid astrocytoma (9.1%). The 5- and 10- year PFS were 46.2% and 36.4% respectively, while the 5- and 10-year OS were both 100%. When accounting for treatment type, there were 24 treatment cycles with MT (60.0%) and 16 CT (40.0%). After adjustment, treatments with MT were shown to have a shorter mean duration of remission (MT: 45 ± 49, CT: 84 ± 79 months; p = 0.007). Cox regression curve plotted after adjusting for patient’s age at treatment demonstrated a significantly longer PFS in the CT group (p = 0.037).

Conclusions

Our results suggest a significant survival benefit of CT over MT for affected patients due to the prolonged the duration of disease remission, for both primary and subsequent treatments. Nonetheless, we acknowledge that our study reflects the outcomes of treatment strategies that have evolved over time. We emphasize the need for collective efforts from a dedicated multidisciplinary team and international collaborations for better disease understanding.

A novel framework to compare the effectiveness of β-lactamase inhibitors against extended-spectrum β-lactamase-producing Enterobacteriaceae

OBJECTIVES

Extended-spectrum β-lactamases (ESBLs) present a serious challenge in the treatment of Gram-negative bacterial infections. ESBLs mediate resistance to most β-lactams, which may be reversed with the addition of an active β-lactamase inhibitor (such as tazobactam, relebactam and avibactam). However, various ESBLs may exhibit different susceptibilities to these inhibitors, which could impact efficacy. We proposed a framework for comparing the efficacy of these inhibitors when combined with the same β-lactam.

METHODS

Three clinical isolates of Klebsiella pneumoniae harbouring CTX-M-15 and one Escherichia coli isolate with SHV-12 were examined. Piperacillin MICs were determined by broth dilution using escalating concentrations of tazobactam, relebactam and avibactam. The resulting MICs were characterized as response to inhibitor concentrations using an inhibitory sigmoid E_max model. Using the best-fit parameter values, the model was conditioned with fluctuating inhibitor concentrations to simulate instantaneous MIC_i profiles for each isolate-inhibitor pair. Using a simulated exposure of 4 g piperacillin every 8 h, %fT > MIC_i was estimated for each piperacillin/inhibitor combination. A hollowfibre infection model was subsequently used to validate the predicted effectiveness of selected combinations.

RESULTS

In all scenarios, piperacillin MIC reductions were well characterized with increasing inhibitor concentrations. As predicted by %fT > MIC_i, combining piperacillin with avibactam (61.4%-73.6%) was found to be superior to tazobactam (13.5%-44.5%) for suppressing bacterial growth over time.

CONCLUSION

We illustrated a practical approach to compare the performance of different inhibitors. This platform may be used clinically to identify the optimal pairing of various β-lactams and β-lactamase inhibitors for individual isolates producing ESBLs.

C-Terminal Part of Glutamate-Ammonia-Ligase Adenyltransferase Gene Identified by RAPD-HRM with 3H Primer for E. Coli Screening

A single random oligonucleotide 3H primer has been previously applied in random-amplified- polymorphic-DNA (RAPD)-PCR to distinguish stocked bacteria E. coli within a cocktail mixture also containing Enterococcus faecalis, Bifidobacterium longum and Ruminococcus gnavus. In this study, we demonstrate that a 702 base pair (bp) gene fragment can be amplified as a unique pattern by RAPD-PCR using a 3H primer in human faeces containing E. coli. This unique 702 bp amplicon contained a 687 bp gene fragment identified as the C-terminal region of the glutamate-ammonia-ligase adenyltransferase (glnE) gene of E. coli. By high-resolution melt (HRM) analysis, a mean melt-curve temperature of this 702 bp amplicon was determined to be approximately 88.1 ± 0.22 degrees Celsius (°C). A combination of RAPD with HRM in one single reaction based on this amplicon can achieve semi-quantitative detection of up to 102 CFU/ml of E. coli. To increase the signal intensity of HRM, a primer pair capable of screening E. coli directly from fresh human faeces was re-designed from the 687 bp gene segment, giving a mean peak melt-curve temperature at 88.35 ± 0.11 °C. Finally, single-nucleotide polymorphisms of this 687 bp gene segment were analysed for pathogenic E. coli strains, including UMN026, O83:H1, O104:H4, O157:H7 and O169:H41. We conclude that this 687 bp segment of the glnE gene has a high potential for screening of human faecal E. coli, including pathogenic strains, in contaminated food and water.

Pharmacokinetics and tissue distribution of 3-((5-(6-methylpyridin-2-yl)-4-(quinoxalin-6-yl)-1H-imidazol-2-yl)methyl)benzamide; a novel ALK5 inhibitor and a potential anti-fibrosis drug

The authors investigated the pharmacokinetics and metabolism of 3-((5-(6-methylpyridin-2-yl)-4-(quinoxalin-6-yl)-1H-imidazol-2-yl)methyl)benzamide (IN-1130), a novel ALK5 inhibitor, which suppresses renal and hepatic fibrosis, and also exerts anti-metastatic effects on breast cancer-bearing MMTV-cNeu mice model. Plasma half-lives of orally administered IN-1130 were 62.6 min in mice, 76.6 +/- 10.6 min in dogs, 156.1 +/- 19.3 min in rats, and 159.9 +/- 59.9 min in monkeys. IN-1130 showed a high apparent permeability coefficient (P(app)) of (45.0 +/- 2.3) x 10(-6) cm s(-1) in in vitro permeability tests in a Caco-2 cell monolayer model. The bioavailability of orally administered IN-1130 was 84.9% in dogs and 34.4% in monkeys (oral dose, 5.5 mg kg(-1)), 11.4% in rats and 8.95% in mice (oral dose, 50.3 mg kg(-1)), respectively. Orally given IN-1130 was readily distributed into liver, kidneys and lungs. The major metabolite of IN-1130 (M1) was detected in the systemic circulation of rat and mouse and was purified and tentatively identified as 3-((4-(3-hydroxyquinoxaline-6-yl)-5-(6-methylpyridine-2-yl)-1H-imidazol-2-yl)methyl)benzamide or 3-((4-(2-hydroxyquinoxalin-6-yl)-5-(6-methylpyridine-2-yl)-1H-imidazol-2-yl)methyl)benzamide. The highest levels of M1 were found in liver. The results of this study suggest that IN-1130 has the potential to serve as an effective oral anti-fibrotic drug.

Comparison of the optical coherence tomographic features of choroidal neovascular membranes in pathological myopia versus age-related macular degeneration, using quantitative subanalysis

AIM

To compare the retinal morphological characteristics of eyes with choroidal neovascularisation (CNV) secondary to pathological myopia versus eyes with CNV secondary to age-related macular degeneration (AMD), using quantitative optical coherence tomography (OCT) subanalysis.

METHODS

Twenty-one eyes of 21 patients newly diagnosed as having CNV secondary to pathological myopia, and 43 consecutive cases of eyes with newly diagnosed subfoveal CNV secondary to AMD were retrospectively collected. In all patients, StratusOCT images and fluorescein angiograms (FA) were available for analysis. StratusOCT images were analysed using custom software (termed "OCTOR"), which allowed calculation of the thickness/volume of the neurosensory retina, subretinal fluid (SRF), subretinal tissue (SRT) and pigment epithelial detachments (PEDs). FA images were used to calculate CNV leakage area and CNV lesion size for each eye.

RESULTS

The total volume of neurosensory retina in the pathological myopia group was significantly less than in the AMD group (7.10 (SD 0.50) mm3 vs 7.76 (0.93) mm3, p = 0.004). The total volume of SRF in the pathological myopia group was less than in the AMD group, but the difference was not statistically significant (0.33 (1.38) mm3 vs 0.55 (0.82) mm3, p = 0.434). The total volume of SRT in the pathological myopia group was less than in the AMD group, but the difference was not statistically significant (0.16 (0.15) mm3 vs 0.36 (0.60) mm3, p = 0.144). The total volume of PED in the pathological myopia group was markedly less than in the AMD group (0.01 (0.03) mm3 vs 1.09 (1.89) mm3, p<0.001). On FA, the total leakage of CNV in the AMD group was significantly greater than in the pathological myopia group (4.17 (3.29) DAs vs 0.53 (0.58) DAs, p<0.001).

CONCLUSIONS

CNV lesions in pathological myopia were associated with considerably less retinal oedema, SRF and SRT compared with CNV associated with AMD. PEDs were almost negligible in myopic lesions compared with AMD. These findings are consistent with previous clinical and angiographic descriptions of myopic CNV as relatively small lesions with modest exudation.

The late-stage foetal liver microenvironment is essential for later sensitivity of B-lymphopoiesis to suppression by oestrogens

B-lymphopoiesis in FL differs notably from that of adult B-lymphopoiesis in being resistant to suppression by oestrogens due to the lack of expression of oestrogen receptors in B-cell progenitors and precursors. We have transplanted middle-stage FL cells (E14.5) to adult male mice and demonstrated that B-lymphopoiesis derived from FL cells remained resistant to suppression by exogenous oestrogen for several months compared to adult BM cells. This significant difference strongly suggests that the latestage FL environment exerts an inductive action on the haematopoietic stem cells and is mandatory for later sensitivity of B-lymphopoiesis to suppression by oestrogens. The results also provide the first in vivo functional confirmation of a differential responsiveness of FL- and adult BM-derived B-lymphopoiesis to suppression by oestrogens.

Intraductal papillary mucinous tumour of the pancreas: differentiation of malignancy and benignancy by CT

AIM

To retrospectively identify signs predictive of malignant intraductal papillary mucinous tumour (IPMT) of the pancreas on computed tomography (CT) images.

MATERIALS AND METHODS

Thirty-four benign and 21 malignant pancreatic IPMTs were evaluated. Preoperative helical CT images in these 55 cases of pathologically proven pancreatic IPMT were reviewed by two radiologists unaware of the histological grading. Tumour morphological types, locations, numbers and sizes of cystic lesions, maximum main pancreatic duct diameters, the presence of septa, mural nodule, wall thickening, and calcification in cysts, communication with the main pancreatic duct, peripancreatic haziness, protrusion of duodenal papilla, pancreatic atrophy, lymphadenopathy and distant metastasis were analysed using univariate and multivariate analysis.

RESULTS

Main duct IPMTs were more likely to be malignant (71%) than branch duct (23%) or combined type IPMTs (28%; p=0.002). Among the branch duct type and combined types, large cystic lesion (p=0.018), the presence of a mural nodule (p=0.018), a thickened wall (p=0.009), and peripancreatic haziness (p=0.039) were found to predict malignancy.

CONCLUSION

CT is helpful in the preoperative differentiation of malignant and benign pancreatic IPMT. The presence of a dilated main pancreatic duct, mural nodules, thickened wall and peripancreatic haziness may be used as independent predictive signs of malignancy.

Cytokine gene expression in regenerating haematopoietic tissues of mice after cyclophosphamide treatment

The goal of the study was to investigate changes in expression of selected growth factors tentatively involved in regeneration of haematopoietic tissues (bone marrow and spleen) following cyclophosphamide (CY) damage in the mouse. The bone marrow (BM) and spleen were examined separately, since the regenerating pattern for haematopoietic progenitor cells (HPC) markedly differs in these two haematopoietically active organs after CY. Cytokines assumed to have a stimulatory effect on HPC - stem cell factor (SCF), fetal liver tyrosine kinase 3-ligand (flt3-ligand), thrombopoietin (TPO), stromal cell-derived factor 1 (SDF-1), oncostatin M (OSM) -, a suppressive effect on HPC proliferation - macrophage inflammatory protein-1alpha (MIP-1alpha), transforming growth factor-beta1 (TGFbeta1), tumour necrosis factor-alpha (TNFalpha) - and to be involved in migration of HPC (SCF, flt3-ligand, MIP1alpha, SDF-1) were examined at the level of mRNA expression by means of real-time RT-PCR. The expression of a particular cytokine appears to be similar in both BM and spleen of untreated mice. CY administration changed the expression pattern of the studied genes in BM and spleen. In BM, the levels of mRNAs for SCF and SDF-1 were increased and that for TGFbeta1 decreased at time intervals at which HPC are known to proliferate intensively during BM regeneration. In contrast, stimulated proliferation of HPC in spleen was accompanied by increased expression of flt3-ligand and oncostatin M. Upon mobilization of HPC from BM into blood after CY, the expression of SCF, TPO, SDF-1 and TGFbeta1 tends to decrease in BM. Accumulation of HPC in spleen is accompanied by increased mRNA for flt3-ligand and OSM. Our findings demonstrate that different cytokines may be involved in the proliferation and mobilization/homing of HPC during recovery after CY damage in BM and spleen.

Voltage-gated channels block nicotinic regulation of CREB phosphorylation and gene expression in neurons

Synaptic activation of the transcription factor CREB and downstream gene expression usually depend on calcium influx aided by voltage-gated calcium channels. We find that nicotinic signaling, in contrast, activates CREB and gene expression in ciliary ganglion neurons both in culture and in situ only if voltage-gated channels are silent. The nicotinic response requires calcium influx and release from internal stores and acts through CaMK and MAPK pathways to sustain activated CREB. Voltage-gated channels mobilize CaMK to activate CREB initially, but they also enable calcineurin and PP1 to terminate the activation before transcription is affected. L-type voltage-gated channels dominate the outcome and block the effects of nicotinic signaling on transcription. This demonstrates a novel aspect of activity-dependent gene regulation.

Synaptically driven calcium transients via nicotinic receptors on somatic spines

Dendritic spines commonly receive glutamatergic innervation at postsynaptic densities and compartmentalize calcium influx arising from synaptic signaling. Recently, it was shown that a class of nicotinic acetylcholine receptors containing alpha7 subunits is concentrated on somatic spines emanating from chick ciliary ganglion neurons. The receptors have a high relative calcium permeability and contribute importantly to synaptic currents, although they appear to be excluded from postsynaptic densities. Here we show that low-frequency synaptic stimulation of the alpha7-containing receptors induces calcium transients confined to the spines. High-frequency stimulation induces a transient calcium elevation in the spines and a more sustained cell-wide elevation. The high-frequency transient elevation again depends on alpha7-containing receptors, whereas the sustained elevation can be triggered by other nicotinic receptors and depends on calcium release from internal stores and probably influx through voltage-gated L-type calcium channels as well. Retrograde axonal stimulation of the neurons at high frequency mimics synaptic stimulation in producing sustained cell-wide calcium increases that depend on L-type channels and release from internal stores, but it does not produce calcium transients in the spines. Thus frequent action potentials are sufficient to generate the cell-wide increases, but alpha7-containing receptors are needed for spine-specific effects. Patch-clamp recording indicates that alpha7-containing receptors preferentially desensitize at high-frequency stimulation, accounting for the inability of the stimulation to sustain high calcium levels in the spines. The spatial and temporal differences in the patterns of calcium elevation could enable the neurons to monitor their own firing histories for regulatory purposes.

Development of obesity in transgenic rats with low circulating growth hormone levels: involvement of leptin resistance

BACKGROUND

Human growth hormone (hGH) transgenic (TG) rats have been produced in our laboratory. These TG rats are characterized by low circulating hGH levels, virtually no endogenous rGH secretion, and massive obesity.

OBJECTIVE

To elucidate how energy balance and leptin sensitivity contributed to the establishment of this obesity.

DESIGN AND METHODS

Food intake, locomotor activity and leptin concentrations in serum and cerebrospinal fluid were measured in TG rats and their non-transgenic littermates (control). The effect of intraperitoneal and intracerebroventricular injection of leptin on food intake and body weight gain was also examined.

RESULTS

An increase in food intake and a decrease in locomotor activity were observed from 4 and 7 weeks of age, respectively, in the transgenic rats compared with control. Serum leptin concentrations of the transgenic rats were more than twice as high as those of control rats and were associated with an increased white adipose tissue mass and ob gene expression. Intraperitoneal injection of leptin significantly decreased food intake and body weight gain in control rats, but not in transgenic rats. Leptin concentration in the cerebrospinal fluid of transgenic rats was not different from that of control rats, and intracerebroventricular injection of leptin was similarly effective in reducing food intake and body weight gain as it was in control rats.

CONCLUSIONS

These results suggest that the transgenic rats, whose GH secretion is suppressed, develop obesity due to early onset of an increase in food intake and a decrease in locomotor activity with leptin resistance resulting from deteriorating leptin transport from peripheral blood to cerebrospinal fluid.

Expression of cysteine sulfinate decarboxylase mRNA in rat mammary gland

Our previous report demonstrated that high concentration of taurine is present in rat milk for the first few days of lactation and plays an important role in the body growth of rat pups. In the present study, gene expression of rate-limiting enzyme for taurine biosynthesis, cysteine sulfinate decarboxylase (CSD) were examined in rat mammary gland. By RT-PCR, CSD mRNA was found to be expressed in rat mammary gland like that in the liver. The expression level of CSD mRNA in the mammary gland was higher in the earlier lactational stage (days 1 and 6 of lactation) than that in the later lactational stage (day 14). CSD mRNA expression in the mammary gland of non-pregnant rats was only a trace level. By in situ hybridization analysis, CSD mRNA was demonstrated in the epithelial cells of the mammary gland. These results suggest that high concentrations of taurine in the milk are at least partially resulted from de novo synthesis of taurine in mammary gland epithelial cells and that the expression pattern of CSD mRNA may be responsible for the changes in taurine levels in the milk during a lactational period.

Interrelationships between cellular nucleotide excision repair, cisplatin cytotoxicity, HER-2/neu gene expression, and epidermal growth factor receptor level in non-small cell lung cancer cells

Nucleotide excision repair (NER) is a major repair mechanism for DNA lesions induced by cisplatin. Overexpressions of epidermal growth factor receptor (EGFR) and HER-2/neu have been reported to affect the sensitivity of certain human cancer cells to cisplatin, presumably by modification of DNA repair activity through interference with NER. Using an in vitro repair assay, we investigated NER activity of cisplatin-induced DNA lesions in a panel of 16 non-small cell lung cancer (NSCLC) cell lines. The interrelationships between NER activity, cisplatin sensitivity, HER-2/neu expression and EGFR level, were also analyzed. The results showed that high NER activity was closely correlated with cisplatin resistance and high levels of HER-2/neu expression (P<0.05). Analysis of the relationships between EGFR level and each of the other three parameters revealed no statistically significant correlations (all P values were >0.05 by Spearman rank correlation), but a trend of association (all the values of proportion of accordance were > or =62.5% by using a 2x2 contingency table). These results suggest that NER activity may play an important role in the cisplatin resistance of NSCLC cells and there may be an association between enhanced NER activity and high levels of p185neu and probably EGFR in NSCLC cells. The finding that high levels of EGFR showed very little influence on the relationship between p185neu and cisplatin resistance suggests that EGFR may be a less crucial factor in modulating the chemoresistance of NSCLC cells when compared with HER-2/neu.

Nicotinic acetylcholine receptors containing alpha7 subunits are required for reliable synaptic transmission in situ

Nicotinic acetylcholine receptors containing alpha7 subunits are widely expressed in the nervous system. The receptors are cation-selective, relatively permeable to calcium, and avid binders of alpha-bungarotoxin. Although the receptors can act both pre- and postsynaptically, their physiological significance is unclear. Using whole-cell patch-clamp analysis of chick ciliary ganglion neurons in situ, we show that the receptors are required for reliable synaptic transmission early in development. Stimulation of the presynaptic nerve root elicited a biphasic synaptic current, including a large rapidly decaying component generated by alpha7-containing receptors. Selective blockade of alpha7-containing receptors by perfusing the ganglion with alpha-bungarotoxin induced failures in synaptic transmission. One-half of the ciliary neurons that were tested failed when stimulated synaptically at 1 Hz, and two-thirds failed at 25 Hz. Failing cells missed, on average, 80% of the trials during a test train of stimuli. The ability to fire synaptically evoked action potentials after toxin treatment was correlated positively with the amplitude of the remaining synaptic current, suggesting that alpha7-containing receptors were needed to augment synaptic responses. Consistent with patch-clamp analysis, toxin blockade reduced the amplitude of the synaptically evoked compound action potential in the postganglionic nerve; it also desynchronized the firing of the remaining units. Methyllycaconitine, another antagonist of alpha7-containing receptors, mimicked alpha-bungarotoxin blockade. Toxin blockade had less impact on transmission in ganglia at the end of embryogenesis. The ability of the receptors to synchronize and sustain population firing, together with their ability to deliver calcium, may influence early developmental events such as target innervation and neuronal survival.

Effect of adsorbents coated with titanium dioxide on the photocatalytic degradation of propoxur

Photocatalytic oxidation of pesticides in aqueous media irradiated by UV light is a rapidly growing field of research. Therefore, the treatment technology for degradation of propoxur (an insecticide) using titanium dioxide coated on the supports such as activated carbon, zeolite, brick, quartz and glass beads, was performed in this research. Results show that GAC/TiO2 is the best complexing agent for oxidizing propoxur because of its adsorption properities. The others follow the sequence: plain TiO2 > glass beads > zeolite > brick > quartz. The degradation rate of propoxur with plain TiO2 is higher than that with TiO2/GAC complexing agent. But the mineralization rate of propoxur with plain TiO2 is lower than that with TiO2/GAC complexing agent. However, it can be concluded that using GAC as the support can improve the photocatalytic efficiency.

Presence of serum anti-p53 antibodies is associated with pleural effusion and poor prognosis in lung cancer patients

This study was designed prospectively to evaluate the development of anti-p53 antibodies (Abs) in lung cancer patients in relation to their clinical outcome. Sera, derived from 125 lung cancer patients, consisting of 14 small cell lung cancers (SCLC) and 111 non-SCLCs (NSCLC), were surveyed. The p53-null human NSCLC cell line, NCI-H1299, transfected with a human mutant p53 gene was prepared as the source of p53 antigen for immunoblotting analyses to detect the presence of serum anti-p53 Abs. The control group included sera from 10 healthy adults and 14 patients with benign pulmonary diseases. Clinical data including staging and survival were recorded for statistical analyses. The anti-p53 Abs were found in 8% (10 of 125) of the lung cancer patients studied (8.1% of NSCLC versus 7.1% of SCLC patients), whereas none of the control sera had detectable anti-p53 Abs. The presence of anti-p53 Abs was closely associated with malignant pleural effusions (P = 0.001). The p53 Ab-positive patients had a worse prognosis than the p53 Ab-negative patients (P < 0.02; median survival, 20 versus 41 weeks). In both univariate and multivariate analyses, the tumor extension and probably the presence of anti-p53 Abs were significant predictors for cancer death. The development of anti-p53 Abs (n = 9) was also a predictor for poor survival in patients with malignant effusions (n = 51). In conclusion, the presence of serum anti-p53 Abs is closely associated with malignant pleural effusions in lung cancer patients. It may serve as a negative prognostic factor for survival independent of malignant pleural effusions and tumor staging.

Obesity and insulin resistance in human growth hormone transgenic rats

A line of transgenic rats (heterozygotes) carrying a chimeric gene comprising a regulatory portion of murine whey acidic protein and a structural portion of human GH (hGH) genes developed severe obesity with age. To characterize physiological mechanisms that lead to fat accumulation, an array of parameters related to obesity were studied. Blood hGH levels were continuously low, endogenous rat GH secretion was suppressed, and the pulsatility in peripheral GH levels was absent. Plasma glucose, insulin, triglyceride, and FFA levels in the male transgenic rats significantly exceeded those in nontransgenic littermates at 12 and 17 weeks, but not at 7 weeks, of age. All symptoms except hyperlipidemia were restored to normal by treatment with an antidiabetic agent, thiazolidinedione (troglitazone), for 1 week from 17 weeks of age. As phenotypic expression of obesity was already evident before aberration of physiological parameters, it was assumed that animals had a condition in which obesity or hyperlipidemia caused hyperinsulinemia. Gene expression and enzymatic activity of lipoprotein lipase in the adipose tissue in the transgenic rats were not different from those in normal rats. In contrast, the gene expression level of glycerol-3-phosphodehydrogenase was markedly elevated, suggesting that glycerol synthesis was much enhanced in the adipocytes of the transgenic rats. In an i.p. glucose tolerance test, the transgenic rats were not hyperglycemic at 7 weeks of age; however, the animal became hyperglycemic at 15-17 weeks of age. Finally, treatment with recombinant hGH for 1 week to produce pulsatile secretion reduced the size of epididymal and kidney fat pads and restored normal weight gain. These observations suggest that continuously low peripheral GH levels with the lack of pulsatile secretion resulted in obesity and noninsulin-dependent diabetes mellitus.

The full agonistic effect of recombinant 20 kDa human growth hormone (hGH) on CHO cells stably transfected with hGH receptor cDNA

The agonistic effect of the recombinant 20 kilodalton human GH (20K-hGH) with authentic primary structure was studied using Chinese hamster ovary (CHO) cells stably transfected with hGH receptor (hGHR) cDNA and was compared with that of 22K-hGH. The binding affinities (dissociation constants) of 20K- and 22K-hGH were identical (0.41 +/- 0.11 nM and 0.41 +/- 0.04 nM, respectively). In addition, the two hGHs possessed the same potencies in activating the rat serine protease inhibitor (Spi) 2.1 gene promoter. 20K-hGH was similarly internalized as 22K-hGH but its internalization rate was a little slower than that of 22K-hGH. We also found that proliferation of CHO-hGHR cells stimulated by serum was remarkably inhibited by both hGHs to the same degree. In conclusion, both hGH isoforms exhibited the same binding affinities for hGHR and were potent enough to induce some hGHR-mediated cellular events. These suggest that 20K-hGH exerts a full agonistic activity for hGHR.

Equine inhibin/activin beta A-subunit mRNA is expressed in the endometrial gland, but not in the trophoblast, during pregnancy

The expression of both inhibin alpha- and inhibin/activin beta A-subunit mRNA was examined in equine uteroplacental tissues collected during pregnancy (days 90 to 300). Northern blot analysis revealed that 5 transcripts (7.0, 4.1, 3.4, 2.6, 1.5 kb) of beta A-subunit were present, and the most abundantly expressed transcript was the 1.5 kb one. Relatively high levels of the 1.5 kb transcript were seen in the second trimester of pregnancy compared to what was found in the third trimester. To identify the tissue localization of beta A-subunit mRNA, in situ hybridization was performed, and the positive signal was observed exclusively in the endometrial glands, but not in the fetal placental tissue (trophoblast) at days 150, 210, and 300 of pregnancy. On the other hand, inhibin alpha-subunit transcript could not be detected at any stage of pregnancy examined either by Northern blot analysis or in situ hybridization. Although the factor(s) regulating the gene expression of beta A-subunit in this equine tissue is currently unknown, these results suggest that activin, but not inhibin, is predominantly produced in the endometrial glands of the pregnant mare, and thus produced activin may play a paracrine or endocrine role during pregnancy in this species.

Different female reproductive phenotypes determined by human growth hormone (hGH) levels in hGH-transgenic rats

The effect of continuous human GH (hGH) secretion on female reproduction was studied in adult female transgenic rats expressing the hGH gene with a mouse whey acidic protein (mWAP) promoter. Two lines of transgenic female rats carrying the mWAP/hGH gene were established and used in the study. One was characterized by relatively high levels of serum hGH (high line), and the other had relatively low levels (low line). High-line female rats had recurring, pseudopregnancy-like estrous cycles accompanied by increased serum progesterone levels for 2 wk after ovulation, and they were fertile. In these rats, luteinization occurred spontaneously without cervical stimulation, probably due to high levels of serum hGH, which has prolactin (PRL)-like activity in the rat. Although low-line female rats had recurring, regular 4-day estrous cycles, they were sterile. In these rats, pseudopregnancy could not be induced by mating or by mechanical cervical stimulation. PRL surges following cervical stimulation were not detected, and PRL secretion was not induced by a dopamine antagonist, metoclopramide. The ovarian tissue in this line had a much higher number of corpora lutea and grew much heavier than in normal littermates, suggesting impairment of PRL-induced structural luteolysis. Suppression of PRL secretion in low-line rats was, at least in part, due to a marked decrease in the number of lactotrophs in the pituitary. The present study shows that the serum hGH level plays a crucial role in regulating luteal function in female transgenic rats expressing the hGH gene.

Formate bound to cytochrome oxidase can be removed by cyanide and by reduction

Using 14C-radiolabeled formate we have found that the rapid form of oxidized cytochrome oxidase can bind up to 1 mol of formate. Treatment of this formate-ligated enzyme with excess cyanide releases 97% of the radiolabel while reduction of formate-labeled enzyme with NADH+ruthenium releases 80-85% of the radioactivity. These data are most simply interpreted by assuming that formate binds to the heme iron of cytochrome a3.

Occurrence of deoxyribonucleic acid fragmentation during prolactin-induced structural luteolysis in cycling rats

We determined whether fragmentation of genomic DNA, one of the hallmarks of apoptosis, occurs during structural luteolysis in cycling rats. Corpora lutea (CL) were collected from rats at each estrous cycle stage (1800 h), and fragmented DNA was extracted. Only CL from rats at the proestrous stage showed distinct DNA fragmentation. To determine the period of occurrence of DNA fragmentation, CL were collected at several points between 1200 h on the day of proestrus and 0600 h on the day of estrus. Distinct DNA fragmentation was observed from 1800 h (proestrus) to 2400 h (proestrus), and the extent was significantly lower at 0600 h (estrus). It is known that prolactin (PRL) induces structural luteolysis in rats. To examine the role of PRL in luteal DNA fragmentation, 2-bromo-alpha-ergocryptine (BE) was used to suppress the PRL surge on the day of proestrus. CL collected at 1800 h from BE-treated rats did not show distinct DNA fragmentation, and PRL injection offset the effect of BE. Histochemical analysis with a 3'-end labeling technique confirmed the occurrence of DNA fragmentation in luteal tissue. These results suggest that apoptotic cell death occurs during PRL-induced structural luteolysis.

Enhancement of chemosensitivity by tyrphostin AG825 in high-p185(neu) expressing non-small cell lung cancer cells

The HER-2/neu gene product, p185(neu), is a membrane-bound receptor with tyrosine kinase activity. High levels of p185(neu) is correlated with intrinsic chemoresistance of non-small cell lung cancer (NSCLC) cell lines. We investigated the effects of tyrphostin AG825, a selective tyrosine kinase inhibitor preferentially inhibiting HER-2/neu kinase, on the chemosensitivities and on the drug-induced cell cycle changes of NSCLC cell lines that expressed different levels of p185(neu). Compared to the low-p185(neu) expressing cell lines, we found that the high-p185(neu) expressing cell lines were more resistant to doxorubicin, etoposide, and cis-diamminedichloroplatinum(II) but more sensitive to AG825. AG825 was able to significantly enhance the chemosensitivities of the high-p185(neu) expressing cell lines, whereas it had little effect on the chemosensitivities of the low-p185(neu) expressing cells, with a few exceptions in which minor antagonistic effects were observed. Although high concentrations of AG825 could reduce the drug-induced G(2) arrest that was accompanied by the activation of phosphorylated p34(cdc2), we failed to find any remarkably differential effects of AG825 on drug-induced G(2), arrest and the accompanying phosphorylation status of p34(cdc2) of the high- and and the low-p185(neu) expressing cell lines. In summary, tyrphostin AG825 can enhance chemosensitivity in high- but not in low-p185(neu) expressing NSCLC cell lines. This differential effect cannot be explained by the alterations of drug-induced cell cycle changes by AG825. Our results provide a rationale to develop p185(neu)- specific tyrphostin and to test them in combination with anticancer agents in vivo and in clinical trials.

Cytotoxic effects of gemcitabine-containing regimens against human non-small cell lung cancer cell lines which express different levels of p185neu

A novel pyrimidine analogue, gemcitabine, has been found to inhibit DNA replication and repair. We speculated that gemcitabine in combination with DNA-damaging agents might be more active against high- than low-p185neu expressing non-small cell lung cancer (NSCLC) cells because the high-p185neu expressors were proposed to posses a more effective DNA repair ability. We therefore compared the combination effects of gemcitabine plus cisplatin, gemcitabine plus etoposide, and cisplatin plus etoposide in a panel of 12 NSCLC cell lines. We also investigated the correlations between the level of p185neu and the cytotoxicities of each single agent and the three combinations. We found that as single agents the cytotoxicities of cisplatin and etoposide but not gemcitabine were significantly correlated with the level of p185neu. In contrast to the tight cross-resistance between cisplatin and etoposide, gemcitabine demonstrated little cross-resistance to either etoposide or cisplatin. Both gemcitabine-containing combinations demonstrated equivalent or more active cytotoxicities compared to cisplatin plus etoposide, with gemcitabine plus cisplatin showing a greater synergistic activity which was effect (dose) dependent. The effect of cisplatin plus etoposide was not p185neu related, whereas gemcitabine-containing regimens, especially gemcitabine plus cisplatin, had a greater cytotoxicity against the high- than the low-p185neu expressors. Our findings indicate that gemcitabine in combination with cisplatin is active against NSCLC cells in vitro. The gemcitabine-cisplatin interaction is more active than the etoposide-cisplatin interaction in cells with high-p185neu expression.

Correlations between intrinsic chemoresistance and HER-2/neu gene expression, p53 gene mutations, and cell proliferation characteristics in non-small cell lung cancer cell lines

Using a panel of 20 non-small cell lung cancer (NSCLC) cell lines established from previously untreated patients, we investigated the relationships between intrinsic chemoresistance (to four agents used commonly in the therapy of NSCLC) and HER-2/neu gene expression (which encodes glycoprotein p185neu), p53 gene mutations, and cell proliferation characteristics. Our results demonstrated that high p185neu expression was correlated with chemoresistance, low S-phase fractions, and long doubling times. By contrast, cell lines expressing relatively low levels of p185neu were relatively chemosensitive and had higher S-phase fractions and shorter doubling times. Although mutation of the p53 gene was a common event in this panel of cell lines (present in 18 of 20 lines), there was no relationship between mutations at any specific codon and chemoresistance or cell proliferation characteristics. Multivariate analysis revealed that the level of p185neu was the only independent predictor for chemoresistance to doxorubicin, etoposide, and probably cisplatin. Although intrinsic chemoresistance almost certainly is a multifactorial process, overexpression of p185neu may be an important factor in the chemoresistance of NSCLC.

Evaluation of the relative cytotoxic effects of anticancer agents in serum-supplemented versus serum-free media using a tetrazolium colorimetric assay

Most cell culture and in vitro drug sensitivity assays utilize serum-supplemented media (SSM). However, fully defined serum-free media (SFM) offer several advantages and are being used increasingly for initiation and maintenance of cell cultures. Because serum inhibits the in vitro cytotoxicity of certain antineoplastic agents, we investigated the inter-relationships between medium type, cell proliferation and cytotoxic effect. Twenty-four human lung cancer cell lines were tested with nine anticancer agents in both media types. A semi-automated tetrazolium (MTT) colorimetric assay was used for assaying cell survival. Cell lines initiated and maintained in SFM preferentially proliferated in that medium type or proliferated equally well in both media types. In contrast, cell lines established in SSM varied considerably in their medium of preference. There appeared to be a direct correlation or trend between cell proliferative rate and cytotoxicity of all drugs with the possible exceptions of methotrexate and carmustine. In general, the cell lines were more sensitive to anticancer agents when they were exposed in the culture medium in which they preferentially proliferated. Therefore, to determine the influence of culture media on cytotoxicity, we analyzed the data only from lines that replicated equally efficiently in both media. After correction for cell proliferative rate, SSM had a negative effect on the cytotoxic action of some drugs (especially methotrexate, 5-fluorouracil and, to a lesser extent, mitomycin-C). Our results demonstrate that fully defined SFM may be suitable for initiating cell lines and for use in in vitro cytotoxicity assays for selection of individualized therapy or for screening of new anti-neoplastic agents, and thus may increase the number of antineoplastic agents that can be tested satisfactorily.

Molecular cloning of DNA for inhibin alpha-subunit from equine ovary

cDNA encoding equine inhibin alpha-subunit precursor protein was isolated from an equine ovarian cDNA library. For screening, the DNA probe was amplified by the RT-PCR using primers designed based on the rat inhibin alpha-subunit cDNA sequence. Out of 1.2 x 10(5) plaques screened, 19 positive clones were isolated, and one of these clones (Eq-alpha-11) contained a complete open reading frame encoding 367 amino acids. The similarity of the deduced amino acid sequences of both equine inhibin alpha-subunit precursor protein and the mature protein were greater than 80% to those of other six mammalian species, including bovine, porcine, ovine, human, rat and mouse. Northern blot analysis revealed that a single major band at 1.5 kb was present in the RNA samples both from equine follicles and testes.

Molecular cloning of cDNA for equine ovarian inhibin/activin beta A subunit

cDNAs encoding equine inhibin/activin beta A subunit were isolated from an equine follicle cDNA library and characterized. Using primers based on the rat inhibin/activin beta A subunit cDNA sequence, a RT-PCR was performed to generate the probe for screening. Four positive clones were isolated. Analysis of the nucleotide sequence of these clones revealed that two pairs of identical clones were present, Eq-beta A-1 (0.9 kb) and Eq-beta A-2 (1.5 kb). Eq-beta A-2 clone contained a complete open reading frame encoding 426 amino acids. The deduced amino acid sequence of equine inhibin/activin beta A subunit showed high similarity (> 90%) to those of five other mammalian species. Northern blot analysis revealed that placenta from mare on day 180 of pregnancy contained a 1.5 kb inhibin/activin beta A subunit mRNA.

Chloromethyl ketones block induction of nitric oxide synthase in murine macrophages by preventing activation of nuclear factor-kappa B

N-alpha-tosyl-L-phenylalanine chloromethyl ketone (TPCK) and N-alpha-tosyl-L-lysine chloromethyl ketone (TLCK), serine protease inhibitors, block many cytotoxic functions of immune cells including superoxide anion production, cytokine release, cell-mediated cytolysis, and nitric oxide (NO)-related macrophage functions. IFN-gamma/LPS-induced NO production from murine peritoneal macrophages was inhibited by TPCK and TLCK in a dose-dependent manner (EC50s: approximately 20 microM for TPCK and approximately 30 microM for TLCK). Viability exceeded 91% with 25 microM TPCK and with 80 microM TLCK. When TPCK treatment was delayed until 1 h of activation, the inhibitory effect was markedly reduced. After 2 h of the activation, TPCK was not effective anymore. Addition of either TNF-alpha or conditioned media from IFN-gamma/LPS-activated macrophage culture did not prevent the inhibitory effect of TPCK. Neither TPCK nor TLCK reduced enzymatic NO production from macrophage lysates. Lysates from TPCK-treated cells did not generate NO even after supplementing necessary cofactors for NO synthase. Immunoblotting analysis showed that simultaneous treatment of TPCK with IFN-gamma/LPS abolished the NO synthase expression, whereas delayed addition of TPCK was either partially effective or not effective at all. Furthermore, TPCK treatment reduced the concentration of mRNA for NO synthase without decreasing mRNA stability. Thus, the serine protease inhibitors directly blocked an early event in expression of NO synthase. Electrophoretic mobility shift assay indicated that TPCK blocked the activation of nuclear factor-kappa B, a transcription factor necessary for NO synthase induction. TPCK also blocked disappearance of I kappa B from cytosolic fraction, and nuclear translocation of NF-kappa B subunits p50 and p65. Delaying the addition of TPCK by 10 min partially prevented the inhibition of the NF-kappa B activation process and allowed partial resuming of NO production. Thus, TPCK inhibited NO synthase induction by blocking NF-kappa B activation.

Chloromethyl ketones block induction of nitric oxide synthase in murine macrophages by preventing activation of nuclear factor-kappa B

N-alpha-tosyl-L-phenylalanine chloromethyl ketone (TPCK) and N-alpha-tosyl-L-lysine chloromethyl ketone (TLCK), serine protease inhibitors, block many cytotoxic functions of immune cells including superoxide anion production, cytokine release, cell-mediated cytolysis, and nitric oxide (NO)-related macrophage functions. IFN-gamma/LPS-induced NO production from murine peritoneal macrophages was inhibited by TPCK and TLCK in a dose-dependent manner (EC50s: approximately 20 microM for TPCK and approximately 30 microM for TLCK). Viability exceeded 91% with 25 microM TPCK and with 80 microM TLCK. When TPCK treatment was delayed until 1 h of activation, the inhibitory effect was markedly reduced. After 2 h of the activation, TPCK was not effective anymore. Addition of either TNF-alpha or conditioned media from IFN-gamma/LPS-activated macrophage culture did not prevent the inhibitory effect of TPCK. Neither TPCK nor TLCK reduced enzymatic NO production from macrophage lysates. Lysates from TPCK-treated cells did not generate NO even after supplementing necessary cofactors for NO synthase. Immunoblotting analysis showed that simultaneous treatment of TPCK with IFN-gamma/LPS abolished the NO synthase expression, whereas delayed addition of TPCK was either partially effective or not effective at all. Furthermore, TPCK treatment reduced the concentration of mRNA for NO synthase without decreasing mRNA stability. Thus, the serine protease inhibitors directly blocked an early event in expression of NO synthase. Electrophoretic mobility shift assay indicated that TPCK blocked the activation of nuclear factor-kappa B, a transcription factor necessary for NO synthase induction. TPCK also blocked disappearance of I kappa B from cytosolic fraction, and nuclear translocation of NF-kappa B subunits p50 and p65. Delaying the addition of TPCK by 10 min partially prevented the inhibition of the NF-kappa B activation process and allowed partial resuming of NO production. Thus, TPCK inhibited NO synthase induction by blocking NF-kappa B activation.

Correlation of intrinsic chemoresistance of non-small-cell lung cancer cell lines with HER-2/neu gene expression but not with ras gene mutations

BACKGROUND

At diagnosis, most small-cell lung cancers (SCLCs) are chemosensitive, whereas non-small-cell lung cancers (NSCLCs) are usually chemoresistant. Activation of ras genes and HER-2/neu genes (also known as ERBB2) is encountered in subpopulations of NSCLC but not in SCLC and has been linked to shortened survival. Therefore, activation of these genes may be associated with intrinsic chemoresistance in NSCLC. Studies have also suggested that the multidrug-resistant phenotype expressed by the MDR1 gene (also known as PGY1) does not correlate with the in vitro chemosensitivity of NSCLC cells or with clinical response to therapy and does not explain the spectrum of cross-resistance to drugs.

PURPOSE

The purpose of this study was to investigate the relationships between chemoresistance and the presence of ras gene point mutations and overexpression of the HER-2/neu gene in NSCLC cell lines, which indicates gene activation.

METHODS

Using a panel of 20 NSCLC cell lines established from untreated patients, we assessed the differences in HER-2/neu messenger RNA (mRNA) expression in the cell lines with or without ras mutations. We performed in vitro drug sensitivity testing by the tetrazolium-based MTT [i.e., 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H- tetrazolium bromide] assay with doxorubicin, carmustine, cisplatin, melphalan, mitomycin, and etoposide, and we determined the differences in IC50 values (i.e., the drug concentrations required to inhibit cell growth by 50%) for the cell lines.

RESULTS

We found a statistically significant correlation between the IC50 values for all six drugs and the degree of HER-2/neu gene expression in all 20 cell lines (r = .67-.86; P < .005) as well as in the subpopulation of eight cell lines with ras mutations (r = .83-.98; P < .05). The IC50 values for doxorubicin, carmustine, cisplatin, and melphalan were not significantly different in the cell lines with or without ras mutations, but the values for mitomycin and etoposide in lines with ras mutations were slightly lower than in those without ras mutations (borderline significance, P = .031). Levels of HER-2/neu expression in cell lines with ras mutations were lower than those without ras mutations, but the difference was not statistically significant.

CONCLUSION

Our findings indicate that overexpression of HER-2/neu is a marker for intrinsic multidrug resistance in NSCLC cell lines.

IMPLICATIONS

If the clinical relevance of our findings is confirmed, HER-2/neu gene expression can be used as a predictor of therapeutic failure in NSCLCs. The relationships between HER-2/neu gene expression, cell proliferation, and chemoresistance in NSCLC require further investigation.

Combination cytotoxic effects of cis-diamminedichloroplatinum(II) and 5-fluorouracil with and without leucovorin against human non-small cell lung cancer cell lines

Both cisplatin (CDDP) and leucovorin (LV) have been shown to enhance cytotoxicity of 5-fluorouracil (FUra) against murine and human neoplasms by increasing intracellular reduced folate concentrations. We were interested in their use in a combination to inhibit non-small cell lung cancer (NSCLC) cell growth and therefore conducted an in vitro study to investigate the cytotoxic activities of combinations of CDDP plus FUra, with and without LV (20 microM), against seven NSCLC cell lines. A tetrazolium assay with application of the classical isobole method was used to test drug combinations. We found that LV enhanced FUra but not CDDP cytotoxicity and that the degree of enhancement was negatively correlated with the effect of FUra. There was an overall additive combination effect of CDDP plus FUra, although there may be synergy at higher effect levels. There was synergy to a combination of CDDP, FUra, and LV, presumably primarily related to the synergistic effects of adding LV to FUra. In summary, LV and CDDP enhanced FUra cytotoxicity in a complementary fashion and there was clear synergy of a combination of CDDP, FUra, and LV against a panel of NSCLC cell lines. Our in vitro results provide a rationale for controlled clinical studies of this three-drug regimen in patients with NSCLC.

Characterization of two low-potential cytochromes from bean sprouts

Two cytochromes have been isolated from chlorophyll-free bean sprouts, purified and characterized. The more abundant cytochrome was purified to apparent homogeneity and exhibits visible region absorbance maxima at 416, 520 and 550 nm in the reduced form and at 410 and 530 nm in the oxidized form. Although Resonance Raman spectra of this cytochrome closely resemble those of c-type cytochromes, pyridine hemochromogen analysis suggests that this cytochrome may contain a variant of heme c as its prosthetic group. The cytochrome has an apparent molecular mass of 12.5 kDa, an isoelectric point > 9.0 and a midpoint oxidation-reduction potential (Em) of -130 mV at pH 8.0. The less abundant of the two cytochromes, which was not completely purified, exhibits absorbance maxima at 438 and 560 nm in the reduced form and at 411 nm in the oxidized form and was shown to contain heme c as a prosthetic group. This cytochrome, which may also contain FAD, has an apparent molecular mass of approx. 38 kDa, an isoelectric point > 9.0 and Em = -300 mV. Preliminary results indicate that both cytochromes can form electrostatically-stabilized complexes with ferredoxin, suggesting the possibility that one or both of the cytochromes may participate in low-potential, non-photosynthetic electron transfer pathways involving ferredoxin.

Monoclonal antibody studies of ferredoxin:NADP+ oxidoreductase

Eleven independent monoclonal antibodies, all IgG's, have been raised against the ferredoxin:NADP+ oxidoreductase of spinach leaves. All 11 monoclonal antibodies were able to produce substantial inhibition of the NADPH to 2,6-dichlorophenol indophenol (DCPIP) diaphorase activity of the enzyme, but none of the antibodies produced any significant inhibition of electron flow from NADPH to ferredoxin catalyzed by the enzyme. Spectral perturbation assays were used to demonstrate that antibody interaction with NADP+ reductase did not interfere significantly with the binding of either ferredoxin or NADP+ to the enzyme. Ultrafiltration binding assays were used to confirm that the monoclonal antibodies did not interfere with complex formation between ferredoxin and the enzyme. These results have been interpreted in terms of the likely presence of one or more highly antigenic epitopes at the site where the nonphysiological electron acceptor, DCPIP, binds to the enzyme. Furthermore, the results suggest that the site where DCPIP is reduced differs from both of the two separate sites at which the two physiological substrates, ferredoxin and NADP+/NADPH, are bound.

The interaction of ferredoxin and glutamate synthase: cross-linking and immunological studies

The water-soluble carbodiimide, N-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) serves as an effective reagent for cross-linking spinach leaf ferredoxin and the ferredoxin-dependent spinach leaf enzyme, glutamate synthase. The cross-linked complex was functional in the absence of added ferredoxin, suggesting that ferredoxin is cross-linked to glutamate synthase at the physiological binding site on the enzyme for this iron-sulfur protein electron donor. The ferredoxin:glutamate synthase stoichiometry of the cross-linked complex was estimated to be 2:1. The absorbance spectrum of the oxidized, cross-linked complex was very similar to that of an electrostatically stabilized, noncovalent, 2:1 complex of the two proteins. An antibody raised against spinach NADP+ reductase, which recognizes a ferredoxin-binding site on glutamate synthase, does not recognize the cross-linked ferredoxin-glutamate synthase complex. This implies that the ferredoxin-binding sites on the two enzymes are structurally similar enough so that an antibody raised against one of these ferredoxin-dependent enzymes recognizes an epitope at the ferredoxin-binding site of the second enzyme. Cross-linking of ferredoxin to its binding site on glutamate synthase renders this epitope inaccessible to the antibody.

Analysis and tracing of polycyclic aromatic hydrocarbons and mutagenicity of airborne particulates from the Taipei area

In a 3-year study, we determined the mutagenicity and polycyclic aromatic hydrocarbons (PAHs) of airborne particulates collected during December 1987-September 1988 (216 samples), October 1988-January 1989 (81 samples), and October 1989-April 1990 (52 samples) from 9 locations in the Taipei area. We found that dichloromethane extracts of all the samples were mutagenic to Salmonella typhimurium in the Ames test. Moreover, the mutagenicity was much higher in the presence of rat liver microsomal fraction (S9 mixture) than that observed in its absence, which indicates that airborne particulates contained both direct and indirect mutagens. The average mutagenicity of the samples collected in the 3-year period was 137, 127, and 118 histidine revertants/10 m3 air, respectively. On the other hand, we found that dichloromethane extracts of each airborne particulate sample contained 14 PAHs with wide variations in concentration and relative distribution. The levels of Pha, Flu, Pyr, and Ben were much higher than the PAHs with higher ring numbers such as BaP, BeP, Pr, IP, and DbA. The average PAH content was 8.0, 5.0, and 7.8 ng/m3 air for airborne particulates collected during December 1986-September 1987, October 1988-January 1989, and October 1989-April 1990, respectively. Among the 9 stations, Fu Hsing Elementary School and Chung Hsing University (Taipei campus), which are, respectively, located in the downtown area and a heavy traffic zone, had significantly higher levels of mutagenicity and PAHs than did the other stations. Moreover, comparative analysis of PAH levels of airborne particulates over the 3-year period revealed an interesting season-dependent change of PAH content in airborne particulates from the Taipei area. The concentrations of individual and total PAHs were consistently lower in the summer than those in the winter. A similar pattern of seasonal change was also observed in the mutagenicity of airborne particulate samples examined. It is worth mentioning that neither PAH level nor mutagenicity of airborne particulates showed significant yearly change over the 3-year period of study. As part of an effort to identify pollution sources, we examined the mutagenicity and PAH compounds of air particulates collected from the burning of garbage (14 samples) and motor-vehicle exhaust in the Hsin Hai Tunnel (17 samples), Taipei. The results showed that garbage burning gave rise to air particulates containing several hundred times higher levels of PAHs and about 20 times stronger mutagenicity, while the motor-vehicle exhaust contained about ten times higher PAH content and mutagenicity as compared with those of airborne particulates of the Taipei city.(ABSTRACT TRUNCATED AT 400 WORDS)

Amplification and expression of c-Ki-ras oncogene in human ovarian cancer

The amplification and expression of the cellular oncogene c-Ki-ras have been detected in twelve tissue specimens of human ovarian adenocarcinoma, one ascites of ovarian cancer and ovarian cancer cell line NIH: OVCAR-3. Four out of the twelve cancer tissue specimens, one specimen of cancer ascites cells and the NIH: OVCAR-3 cancer cell line showed elevated amplification of c-Ki-ras, as compared to the human fibroblast cell line FS4 and normal ovarian tissues. The amplification of the c-Ki-ras gene showed some correlation with clinical stages of ovarian cancer. The levels of c-Ki-ras specific RNA transcripts and ras gene product p21 were also elevated in these four cancer tissue specimens. Surprisingly, a discrepancy between amplification and expression of c-Ki-ras was noted in five of the other eight cancer tissue specimens, in which enhanced expression of c-Ki-ras was present without the accompanying elevated amplification of c-Ki-ras. The results do provide some clues to understanding the possible mechanisms of tumorigenesis in human ovarian cancer.

Characterization of a ferredoxin:NADP+ oxidoreductase from a nonphotosynthetic plant tissue

A flavoprotein with properties similar to those of ferredoxin:NADP+ oxidoreductases found in the leaves of higher plants has been purified to apparent homogeneity from bean sprouts, a nonphotosynthetic plant tissue. The absorbance and circular dichroism spectra of the bean sprout protein are similar to those of spinach leaf ferredoxin:NADP+ oxidoreductase and an antibody raised against the spinach enzyme recognized the bean sprout enzyme. The bean sprout enzyme catalyzed ferredoxin-dependent electron transfer from NADPH to equine cytochrome c at a high rate but, unlike the spinach enzyme, exhibited little NADPH to 2,6-dichlorophenol indophenol diaphorase activity. The bean sprout enzyme forms a 1:1 electrostatically stabilized complex with ferredoxins isolated from either bean sprouts or spinach leaves.

Mutagenicity and polycyclic aromatic hydrocarbons analysis of airborne particulate matters from Taipei City

The mutagenic activity of dichloromethane extracts of 147 air particulate samples collected from 8 stations during December 1986-June 1987 in Taipei city was consistently higher in S. typhimurium strain TA 98 than in strain TA 100 in the presence of S9 mixture. Among the 8 stations, Nan Kang Police Station, Fu Hsing Elementary School, and Chung Hsing University which were located in the industrial district, downtown area, and heavy traffic zone, respectively, had significantly higher levels of PAHs than the other stations. In contrast, the levels of PAHs were much lower in the suburban station, near Pei Tou Elementary School. However, PAH contents of the air particulate samples collected from these stations did not show good correlation with their mutagenicity. The air particulates collected at some stations on Sunday when the traffic changed from heavy to light showed lower mutagenicity and PAH contents as compared with the other weekdays at the same stations. On the contrary, the samples collected at Pei Tou station in a suburban area where the traffic changed from light to heavy on Sunday showed higher mutagenicity and PAH contents. The monthly average of PAHs of air particulate samples collected over a 7-month period from 8 stations in Taipei city was lower than the average in 1980. Moreover, when compared with other countries, such as U.S.A., the Netherlands, West Germany, Italy, Norway, and Japan, the levels of PAHs and mutagenicity of air particulate matters in Taipei city were similar or slightly lower. The mutagenicity and contents of PAHs of air particulates collected from burnt ABS were significantly higher than those of burnt PVC. One sample PT-6-3 was collected while a nearby garbage collection area was on fire. The mutagenicity of that sample increased 3 to 16 fold and contained an 11 to 33 times higher content of the six PAHs (BaP, BeP, BbF, BaA, Chr, and DbA) as compared with the other samples collected at the same location at a different time. The higher mutagenicity and PAH contents of that sample might be due to the pollution of the air from combustion of the garbage containing products made of ABS.