Nitroxide-mediated protection against X-ray- and neocarzinostatin-induced DNA damage.

The stable free radical Tempol (4-hydroxy-2,2,6,6-tetramethyl-piperidinyloxy) has been shown to protect against X-ray-induced cytotoxicity and hydrogen peroxide- or xanthine oxidase-induced cytotoxicity and mutagenicity. The ability of Tempol to protect against X-ray- or neocarzinostatin (NCS)-induced mutagenicity or DNA double-strand breaks (dsb) was studied in Chinese hamster cells. Tempol (50 mM) provided a protection factor of 2.7 against X-ray-induced mutagenicity in Chinese hamster ovary (CHO) AS52 cells, with a protection factor against cytotoxicity of 3.5. Using the field inversion gel electrophoresis technique of measuring DNA dsb, 50 mM Tempol provides a threefold reduction in DNA damage at an X-ray dose of 40 Gy. For NCS-induced damage, Tempol increased survival from 9% to 80% at 60 ng/mL NCS and reduced mutation induction by a factor of approximately 3. DNA dsb were reduced by a factor of approximately 7 at 500 ng/mL NCS. Tempol is representative of a class of stable nitroxide free radical compounds that have superoxide dismutase-mimetic activity, can oxidize metal ions such as ferrous iron that are complexed to DNA, and may also detoxify radiation-induced organoperoxide radicals by competitive scvenging. The NCS chromophore is reduced by sulfhydryls to an active form. Electron spin resonance (ESR) spectroscopy shows that 2-mercaptoethanol-activated NCS reacts with Tempol 3.5 times faster than does unactivated NCS. Thus, Tempol appears to inactivate the NCS chromophore before a substantial amount of DNA damage occurs.     

Evaluation of the leaf juice of some higher plants for their toxicity against soil borne pathogens

Out of the leaf juices of eighteen plant species screened, only Eupatorium cannabinum exhibited complete toxicity against Pythium debaryanum, Fusarium oxysporum, Rhizoctonia solani and Sclerotium rolfsii. Shade drying of the leaves had no adverse effect, while oven drying produced an adverse effect on the fungitoxicity of the leaves of E. cannabinum. The crude leaf juice of E. cannabinum successfully inhibited damping-off (Fusarium oxysporum) infection of Pisum sativum seedlings.     

Facial clefts in Saudi Arabia: an epidemiologic analysis in 179 patients

One hundred and seventy-nine consecutive cases of facial clefts that were treated at the King Khalid University Hospital, in Riyadh, Saudi Arabia, were analyzed for an epidemiologic study. Isolated cleft lip was present in 38 percent, cleft of lip and palate in 37.4 percent, and cleft of the posterior palate in only 22.4 percent. There was a male preponderance in all types. In cases of cleft lip with or without cleft palate, the more commonly affected side was the left, followed by bilateral cases. Associated malformations were present in 13.4 percent. A positive family history was found in 26.8 percent of cases. A significant number of patients (7.8 percent) were first seen at more than 10 years of age. The incidence of facial clefts at this hospital was 0.3 per 1000 live births, computed over a period of 6 years. This incidence is significantly lower than that reported from European and Far Eastern countries.     

Shift in product formation from acetate to ethanol using metabolic inhibitors inFusarium oxysporum

Summary Fusarium oxysporum 841 produces a mixture of ethanol and acetic acid from glucose, xylose or Avicel (microcrystalline cellulose) substrates. Some metabolic inhibitors viz. sodium azide, dinitrophenol and polyethylene glycol were used for shifting product formation from acetic acid to ethanol. Using these inhibitors 1.5- to 2- fold increase in ethanol production was achieved with significant repression (by 80 to 90%) of acetic acid. Almost theoretical yields of ethanol were obtained.     

In Vitro Propagation of Gladiolus: Optimisation of Conditions for Shoot Multiplication

Effect of some physical and chemical factors on in vitro shoot multiplication in Gladioius was investigated. A modified MS medium with NH₄NO₃ reduced to half strength, KH₂PO₄ replaced with 300 mg/l of NaH₂PO₄ 2 H₂O and Kl omitted completely, was found to be better than the original MS. BAP was better than either kinetin or 2iP. Of the various physical factors studied, the propagule size, light and container volume influenced the rate of shoot multiplication. On the modified medium containing 0.5 mg/l BAP in dark, the propagules bearing 20 buds showed 8-fold multiplication.     

Formation of acetic acid from cellulosic substrates byFusarium oxysporum

Summary Four strains of Fusarium oxysporum and a strain of Monilia brunnae were screened for their ability to convert cellulosic substrates into ethanol/acetic acid. These strains were found to utilize cellulose and produce extracellular cellulases. However, only F. oxysporum 841 was found to convert glucose, xylose, and cellulose into ethanol and acetic acid as major end-products under microaerobic conditions. Acetic acid at a level of 4.7 g/l resulted in a single-step process on potato pulp medium, indicating the potential of the strain for converting cellulosic substrates into acetic acid. Offprint requests to: K. Schügerl     

Molecular cloning,characterization and expression of a nitrofuran reductase gene ofescherichia coli

Mini-mu derivatives carrying plasmid replicons can be used to clone genesin vivo. This method was adopted to generate phasmid clones which were later screened for their ability of restore nitrofurantoin sensitivity of a nitrofuran-resistant host by eliciting nitroreductase activity. One phasmid-derived clone (pAJ101) resulted in considerable increase in nitroreductase activity when introduced into a nitrofurantoin-resistant mutant ofEscherichia coli with reduced nitroreductase activity. Subsequently, a 1.8 kb fragment obtained from pAJ101 by partial digestion with 5au3A, was subcloned into pUC18 to yield pAJ102. The nitroreductase activity attributable to pAJ102 was capable of reducing both nitrofurantoin and nitrofurazone. The polypeptides encoded by pAJ102 were identified by the minicell method. A large, well-defined band corresponding to 37 kDa and a smaller, less-defined band corresponding to 35 kDa were detected. Tnl000 mutagenesis was used to delineate the coding segment of the 1.8 kb insert of pAJ102. A 0.8 kb stretch of DNA was shown to be part of the nitroreductase gene. The gene was mapped at 19 min on theEscherichia coli linkage map.     

Regulation of phosphorylation of the c-erbB-2/HER2 gene product by a monoclonal antibody and serum growth factor(s) in human mammary carcinoma cells.

Monoclonal antibody (MAb) 4D5 was used to analyze the phosphorylation of p185HER2, the gene product of c-erbB-2/HER2, in SK-BR-3 cells. Culture in the continuous presence of 4D5 reduced the in vivo steady-state levels of p185HER2 phosphorylation by 80% in a dose-dependent manner, suggesting that MAb 4D5 may have interfered with the activation of phosphorylation of p185HER2. The observed MAb-mediated reduction of p185HER2 phosphorylation could not be completely accounted for by down-regulation. When cultures were grown under serum-free conditions, the steady-state levels of p185HER2 phosphorylation were reduced by 56%, and addition of 4D5 further inhibited phosphorylation to 20% of steady-state levels. With continuous exposure to increasing concentrations of newborn calf serum in these cultures, there was a linear increase in tyrosine-specific phosphorylation of p185HER2, reaching a 5.4-fold increase with 10% newborn calf serum. Phosphorylation of p185HER2 in the presence of newborn calf serum was not attributable to stimulation of the epidermal growth factor receptor by epidermal growth factor or by transforming growth factor-alpha. Extension of these observations to two other mammary carcinoma cell lines. MDA-MB-453 and BT-474, also demonstrated a significant capacity of serum to induce p185HER2 phosphorylation. The demonstration of antibody-mediated partial inhibition of phosphorylation under serum-free conditions suggests that mammary carcinoma cells may also produce and secrete a factor or factors which may activate p185HER2. Our observation that growth-inhibitory MAb 4D5 is able to reduce the phosphorylation of p185HER2 by newborn calf serum and by a cellular-derived factor(s) suggests the existence of a growth factor(s) which uses phosphorylation of p185HER2 as a signal transduction pathway to regulate cell proliferation.     

Role of Ca2+ ion on Leishmania-macrophage attachment

Summary Leishmania donovani, the etiological agent for the disease visceral leishmaniasis, attach themselves to the macrophages for initiation of the disease. The attachment process has been found to be regulated by Ca²⁺ ions. Verapamil, a Ca²⁺-channel blocker inhibits Leishmania-macrophage attachment. The inhibitory effect is increased with time. Nifedipine, another Ca²⁺-channel blocker exhibits the same effect. The attachment process is stimulated by Ca²⁺-ionophore alone. The inhibitory effects of the calcium channel blockers are reversed by the ionophore.